Energies

32 pages, 9360 KiB

Open AccessArticle

A Nature-Inspired Optimization-Based Optimum Fuzzy Logic Photovoltaic Inverter Controller Utilizing an eZdsp F28335 Board

by Ammar Hussein Mutlag, Azah Mohamed and Hussain Shareef

Energies 2016, 9(3), 120; https://doi.org/10.3390/en9030120 - 23 Feb 2016

Cited by 25 | Viewed by 7329

Abstract

Photovoltaic (PV) inverters essentially convert DC quantities, such as voltage and current, to AC quantities whose magnitude and frequency are controlled to obtain the desired output. Thus, the performance of an inverter depends on its controller. Therefore, an optimum fuzzy logic controller (FLC) [...] Read more.

Photovoltaic (PV) inverters essentially convert DC quantities, such as voltage and current, to AC quantities whose magnitude and frequency are controlled to obtain the desired output. Thus, the performance of an inverter depends on its controller. Therefore, an optimum fuzzy logic controller (FLC) design technique for PV inverters using a lightning search algorithm (LSA) is presented in this study. In a conventional FLC, the procedure for obtaining membership functions (MFs) is usually implemented using trial and error, which does not lead to satisfactory solutions in many cases. Therefore, this study presents a technique for obtaining MFs that avoids the exhaustive traditional trial-and-error procedure. This technique is implemented during the inverter design phase by generating adaptive MFs based on the evaluation results of the objective function formulated with LSA. The mean squared error (MSE) of the inverter output voltage is used as an objective function in this study. LSA optimizes the MFs such that the inverter provides the lowest MSE for the output voltage, and the performance of the PV inverter output is improved in terms of amplitude and frequency. First, the design procedure and accuracy of the optimum FLC are illustrated and investigated through simulations conducted in a MATLAB environment. The LSA-based FLC (LSA-FL) are compared with differential search algorithm (DSA)-based FLC (DSA-FL) and particle swarm optimization (PSO)-based FLC (PSO-FL). Finally, the robustness of the LSA-FL is further investigated with a hardware that is operated via an eZdsp F28335 control board. Simulation and experimental results show that the proposed controller can successfully obtain the desired output when different loads are connected to the system. The inverter also has a reasonably low steady-state error and fast response to reference variation. Full article

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12 pages, 1988 KiB

Open AccessArticle

On Variable Reverse Power Flow-Part I: Active-Reactive Optimal Power Flow with Reactive Power of Wind Stations

by Aouss Gabash and Pu Li

Energies 2016, 9(3), 121; https://doi.org/10.3390/en9030121 - 23 Feb 2016

Cited by 39 | Viewed by 9848

Abstract

It has recently been shown that using battery storage systems (BSSs) to provide reactive power provision in a medium-voltage (MV) active distribution network (ADN) with embedded wind stations (WSs) can lead to a huge amount of reverse power to an upstream transmission network [...] Read more.

It has recently been shown that using battery storage systems (BSSs) to provide reactive power provision in a medium-voltage (MV) active distribution network (ADN) with embedded wind stations (WSs) can lead to a huge amount of reverse power to an upstream transmission network (TN). However, unity power factors (PFs) of WSs were assumed in those studies to analyze the potential of BSSs. Therefore, in this paper (Part-I), we aim to further explore the pure reactive power potential of WSs (i.e., without BSSs) by investigating the issue of variable reverse power flow under different limits on PFs in an electricity market model. The main contributions of this work are summarized as follows: (1) Introducing the reactive power capability of WSs in the optimization model of the active-reactive optimal power flow (A-R-OPF) and highlighting the benefits/impacts under different limits on PFs. (2) Investigating the impacts of different agreements for variable reverse power flow on the operation of an ADN under different demand scenarios. (3) Derivation of the function of reactive energy losses in the grid with an equivalent-π circuit and comparing its value with active energy losses. (4) Balancing the energy curtailment of wind generation, active-reactive energy losses in the grid and active-reactive energy import-export by a meter-based method. In Part-II, the potential of the developed model is studied through analyzing an electricity market model and a 41-bus network with different locations of WSs. Full article

(This article belongs to the Special Issue Selected Papers from 15 IEEE International Conference on Environment and Electrical Engineering (EEEIC 2015))

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14 pages, 9744 KiB

Open AccessArticle

Enhanced Single-Sided Ventilation with Overhang in Buildings

by Jinsoo Park, Jung-Il Choi and Gwang Hoon Rhee

Energies 2016, 9(3), 122; https://doi.org/10.3390/en9030122 - 23 Feb 2016

Cited by 13 | Viewed by 6997

Abstract

Enhancing the ventilation performance of energy-efficient buildings with single-sided openings is important because their ventilation performance is poor and strongly depends on the wind conditions. We considered an overhang as a potential building façade for improving the single-sided ventilation performance. We performed numerical [...] Read more.

Enhancing the ventilation performance of energy-efficient buildings with single-sided openings is important because their ventilation performance is poor and strongly depends on the wind conditions. We considered an overhang as a potential building façade for improving the single-sided ventilation performance. We performed numerical simulations of three-dimensional unsteady turbulent flows over an idealized building with an overhang in order to investigate the effect of the overhang on the ventilation performance. Parametric studies were systematically carried out where the overhang length, wind speed, and wind direction were varied. The numerical results showed that the overhang drastically enhanced the ventilation rate in the windward direction regardless of the wind speed. This is because, for windward cases, the overhang produces a vortex with strong flow separation near the tip of the overhang, which promotes a net airflow exchange at the entrance and increases the ventilation rate. However, the ventilation rates for the leeward and side cases are slightly decreased with the overhang. Using an overhang with single-sided ventilation greatly reduces the local mean age of air (LMA) in the windward direction but increases it in the leeward direction. Full article

(This article belongs to the Special Issue Energy Efficient Building Design 2016)

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26 pages, 5582 KiB

Open AccessEditor’s ChoiceArticle

Parameter Sensitivity Analysis for Fractional-Order Modeling of Lithium-Ion Batteries

by Daming Zhou, Ke Zhang, Alexandre Ravey, Fei Gao and Abdellatif Miraoui

Energies 2016, 9(3), 123; https://doi.org/10.3390/en9030123 - 24 Feb 2016

Cited by 61 | Viewed by 8808

Abstract

This paper presents a novel-fractional-order lithium-ion battery model that is suitable for use in embedded applications. The proposed model uses fractional calculus with an improved Oustaloup approximation method to describe all the internal battery dynamic behaviors. The fractional-order model parameters, such as equivalent [...] Read more.

This paper presents a novel-fractional-order lithium-ion battery model that is suitable for use in embedded applications. The proposed model uses fractional calculus with an improved Oustaloup approximation method to describe all the internal battery dynamic behaviors. The fractional-order model parameters, such as equivalent circuit component coefficients and fractional-order values, are identified by a genetic algorithm. A modeling parameters sensitivity study using the statistical Multi-Parameter Sensitivity Analysis (MPSA) method is then performed and discussed in detail. Through the analysis, the dynamic effects of parameters on the model output performance are obtained. It has been found out from the analysis that the fractional-order values and their corresponding internal dynamics have different degrees of impact on model outputs. Thus, they are considered as crucial parameters to accurately describe a battery’s dynamic voltage responses. To experimentally verify the accuracy of developed fractional-order model and evaluate its performance, the experimental tests are conducted with a hybrid pulse test and a dynamic stress test (DST) on two different types of lithium-ion batteries. The results demonstrate the accuracy and usefulness of the proposed fractional-order model on battery dynamic behavior prediction. Full article

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21 pages, 2597 KiB

Open AccessArticle

Intentional Islanding Algorithm for Distribution Network Based on Layered Directed Tree Model

by Jian Su, Hao Bai, Pipei Zhang, Haitao Liu and Shihong Miao

Energies 2016, 9(3), 124; https://doi.org/10.3390/en9030124 - 24 Feb 2016

Cited by 5 | Viewed by 6105

Abstract

In this study, a novel intentional island model of a distribution system with distributed generations (DGs) is presented and the improved Dijkstra algorithm is used to solve this model. This paper abstracts the distribution network with DGs to the layered directed tree according [...] Read more.

In this study, a novel intentional island model of a distribution system with distributed generations (DGs) is presented and the improved Dijkstra algorithm is used to solve this model. This paper abstracts the distribution network with DGs to the layered directed tree according to its radial structure and power restoration process. In consideration of grade, controllability, capacity, level and electrical betweenness of load, the model weights load and maximizes total load weight in the island. The proposed model considers power balance, node voltage, phase angle and transmission capability of the branch, and network connectivity to meet practical engineering requirements. The improved Dijkstra algorithm formulates a search rule to select the load that can be divided into an island in descending order of the shortest path between the load node and DG node. An optimal island partition scheme is achieved through three stages: origin island, baby island and mature island. Meanwhile, scheme adjustment and constraint checking are used alternately to balance objective functions and constraints. The improved IEEE 43-bus distribution network is applied to verify the validity of the algorithm. A comparison of two island methods shows that the proposed algorithm can generate a reasonable scheme for island partitioning. Full article

(This article belongs to the Special Issue Microgrids 2016)

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19 pages, 965 KiB

Open AccessArticle

Public Engagement in Energy Research

by Jako Jellema and Henk A. J. Mulder

Energies 2016, 9(3), 125; https://doi.org/10.3390/en9030125 - 24 Feb 2016

Cited by 19 | Viewed by 7834

Abstract

Public Engagement in Research is a key element in “Responsible Research and Innovation”; a cross-cutting issue in current European research funding. Public engagement can advance energy R&D, by delivering results that are more in-line with society’s views and demands; and collaboration also unlocks [...] Read more.

Public Engagement in Research is a key element in “Responsible Research and Innovation”; a cross-cutting issue in current European research funding. Public engagement can advance energy R&D, by delivering results that are more in-line with society’s views and demands; and collaboration also unlocks societal skills and knowledge. This paper structures the ways to look at engagement, and gives some pointers on how to implement it in energy R&D, with various levels of intensity. The publics to engage with can be citizens, future users, affected persons, but also organisations that represent them. We have selected methods and tools that showcase a broad range of types of engagement that have been applied in The Netherlands or the UK. The cases are grouped based on the role of the researcher in the engagement process. These roles relate to discussing with, consulting, involving, collaborating with and supporting the various publics. This study shows that there is a diversity of tools and methods already available—open to variation, combinations and further development- that facilitate the participation of society in energy research. Not only for democratic reasons, but also for instrumental benefits in creating innovations to help solve the Grand Societal Challenge of the energy transition. Full article

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21 pages, 3633 KiB

Open AccessArticle

Effects of Inhomogeneities on Heat and Mass Transport Phenomena in Thermal Bridges

by Paola Iodice, Nicola Massarotti and Alessandro Mauro

Energies 2016, 9(3), 126; https://doi.org/10.3390/en9030126 - 26 Feb 2016

Cited by 9 | Viewed by 4519

Abstract

The interest of calculating the effects of thermal bridges in buildings energy consumption is growing, due to recent energy saving regulations applied in different countries. The widespread use of insulating materials to reduce energy requirements of buildings, often employed for intermediate insulation of [...] Read more.

The interest of calculating the effects of thermal bridges in buildings energy consumption is growing, due to recent energy saving regulations applied in different countries. The widespread use of insulating materials to reduce energy requirements of buildings, often employed for intermediate insulation of the building envelope, makes thermal bridges a crucial point in the energy analysis of building envelopes. Furthermore, heat losses through thermal bridges often lead to building pathologies due to moisture condensation. Therefore, thermal bridges need to be correctly characterized in the building design stage in order to reduce heat losses and avoid materials degradation. The authors numerically simulate, by using finite elements, the steady-state and dynamic three-dimensional (3D) heat and vapor transport in inhomogeneous thermal bridges and building envelopes. The aim of the present work is to show the importance of taking into account the presence of inhomogeneities (i.e., metal stud) in building materials for the calculation of actual heat losses and water condensation in 3D thermal bridges. The obtained heat transfer results are verified against the reference data of the technical standard UNI EN ISO 10211. The proposed microscopic approach is essential to calculate the actual heat losses of three-dimensional thermal bridges and building envelopes and to overcome condensation problems. Full article

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13 pages, 1254 KiB

Open AccessArticle

Distributed Energy Storage Using Residential Hot Water Heaters

by Linas Gelažanskas and Kelum A. A. Gamage

Energies 2016, 9(3), 127; https://doi.org/10.3390/en9030127 - 25 Feb 2016

Cited by 20 | Viewed by 6797

Abstract

This paper proposes and analyses a new demand response technique for renewable energy regulation using smart hot water heaters that forecast water consumption at an individual dwelling level. Distributed thermal energy storage has many advantages, including high overall efficiency, use of existing infrastructure [...] Read more.

This paper proposes and analyses a new demand response technique for renewable energy regulation using smart hot water heaters that forecast water consumption at an individual dwelling level. Distributed thermal energy storage has many advantages, including high overall efficiency, use of existing infrastructure and a distributed nature. In addition, the use of a smart thermostatic controller enables the prediction of required water amounts and keeps temperatures at a level that minimises user discomfort while reacting to variations in the electricity network. Three cases are compared in this paper, normal operation, operation with demand response and operation following the proposed demand response mechanism that uses consumption forecasts. The results show that this technique can produce both up and down regulation, as well as increase water heater efficiency. When controlling water heaters without consumption forecast, the users experience discomfort in the form of hot water shortage, but after the full technique is applied, the shortage level drops to nearly the starting point. The amount of regulation power from a single dwelling is also discussed in this paper. Full article

(This article belongs to the Special Issue Control of Energy Storage)

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16 pages, 1925 KiB

Open AccessArticle

New Aspects to Greenhouse Gas Mitigation Policies for Low Carbon Cities

by George Dalianis, Evanthia Nanaki, George Xydis and Efthimios Zervas

Energies 2016, 9(3), 128; https://doi.org/10.3390/en9030128 - 25 Feb 2016

Cited by 17 | Viewed by 5787

Abstract

Methane (CH₄) is an important greenhouse gas emitted by vehicles. This study provides estimates of emissions of this important and often not well characterized greenhouse gas (GHG) emission related to transportation energy use. It aims to assist urban community planners and [...] Read more.

Methane (CH₄) is an important greenhouse gas emitted by vehicles. This study provides estimates of emissions of this important and often not well characterized greenhouse gas (GHG) emission related to transportation energy use. It aims to assist urban community planners and policymakers to prioritize and choose implementation strategies for low carbon cities. The paper focuses on emissions of CH₄ from vehicles. Unlike emissions of CO₂, which are relatively easy to estimate, emissions of CH₄ are a function of many complex aspects of combustion dynamics and depend on the type of emission control systems used. In this context, they cannot be derived easily and instead must be determined through the use of published emission factors for each combination of fuel, end-use technology, combustion conditions, and emission control systems. Emissions of CH₄ play a significant role with regards to the relative CO₂–equivalent GHG emissions of the use of alternative transportation fuels, in comparison with the use of conventional fuels. By analyzing a database based on literature review this study analyzes all the factors affecting the creation of CH₄ emissions from different vehicle types. Statistical analysis indicated “r” values ranging from 0.10 to 0.85 for all vehicles. Full article

(This article belongs to the Special Issue Energy Efficient City)

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12 pages, 5064 KiB

Open AccessArticle

Shielding Effectiveness Simulation of Small Perforated Shielding Enclosures Using FEM

by Zdeněk Kubík and Jiří Skála

Energies 2016, 9(3), 129; https://doi.org/10.3390/en9030129 - 25 Feb 2016

Cited by 21 | Viewed by 6543

Abstract

Numerical simulation of shielding effectiveness (SE) of a perforated shielding enclosure is carried out, using the finite element method (FEM). Possibilities of model definitions and differences between 2D and 3D models are discussed. An important part of any simulation is verification of the [...] Read more.

Numerical simulation of shielding effectiveness (SE) of a perforated shielding enclosure is carried out, using the finite element method (FEM). Possibilities of model definitions and differences between 2D and 3D models are discussed. An important part of any simulation is verification of the model results—here the simulation result are verified in terms of convergence of the model in dependence on the degrees of freedom (DOF) and by measurements. The experimental method is based on measurement of electric field inside the enclosure using an electric field probe with small dimensions is described in the paper. Solution of an illustrative example of SE by FEM is shown and simulation results are verified by experiments. Full article

(This article belongs to the Special Issue Selected Papers from 15 IEEE International Conference on Environment and Electrical Engineering (EEEIC 2015))

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12 pages, 1294 KiB

Open AccessArticle

A Comparative Study of Open and Closed Heat-Engines for Small-Scale CHP Applications

by Ian W. Eames, Kieran Evans and Stephen Pickering

Energies 2016, 9(3), 130; https://doi.org/10.3390/en9030130 - 25 Feb 2016

Cited by 5 | Viewed by 5746

Abstract

In this paper the authors compare and contrast open and closed-cycle heat engines. First of all, by way of example and to aid discussion, the performance of proprietary externally heated closed-cycle Stirling engines is compared with that of internally heated open Otto cycle [...] Read more.

In this paper the authors compare and contrast open and closed-cycle heat engines. First of all, by way of example and to aid discussion, the performance of proprietary externally heated closed-cycle Stirling engines is compared with that of internally heated open Otto cycle engines. Both types of engine have disadvantages and merits and this suggested that in order to accommodate the best of both engine types an externally-heated open-cycle engine might offer a more satisfactory solution for small-scale combined heat and power (CHP) systems. To investigate this possibility further the paper goes on to compare the performance of externally-heated and recuperated Joule hot-air cycle engines with that of an externally-heated closed Stirling cycle engines. The results show that an externally heated recuperated open Joule cycle engine can exceed that of a closed cycle Stirling engine operating between the same heat source and sink temperatures when a variable temperature heat source is used. Full article

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14 pages, 5098 KiB

Open AccessArticle

A Co-Simulation Framework for Power System Analysis

by Seaseung Oh and Suyong Chae

Energies 2016, 9(3), 131; https://doi.org/10.3390/en9030131 - 25 Feb 2016

Cited by 11 | Viewed by 6573

Abstract

Power system electromagnetic transient (EMT) simulation has been used to study the electromagnetic behavior of power system components. It generally comprises detailed models of the study area and an equivalent circuit which represents an external part of the study area. However, a detailed [...] Read more.

Power system electromagnetic transient (EMT) simulation has been used to study the electromagnetic behavior of power system components. It generally comprises detailed models of the study area and an equivalent circuit which represents an external part of the study area. However, a detailed description of an external system that includes transmission or distribution system models is required to study the interaction among power system components because the number of high power converter based devices in a power grid have been increasing. Since detailed models of the system components are necessary to simulate a series of events such as cascading faults the computational burden of power system simulation has increased. Therefore a more effective and practical framework has been sought to handle this computational challenge. This paper proposes a co-simulation framework including a delay compensation algorithm to compensate the time delayed signals due to network segmentation and a fast and flexible simulation environment composed of non-real time power system EMT simulation on a general purpose computer with a multi core central processing unit (CPU), which is currently very popular owing to its performance. The proposed methods are applied to an AC/DC power system model. Full article

(This article belongs to the Special Issue Electric Power Systems Research)

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19 pages, 845 KiB

Open AccessReview

The Environmental Biorefinery: Using Microalgae to Remediate Wastewater, a Win-Win Paradigm

by Florian Delrue, Pablo David Álvarez-Díaz, Sophie Fon-Sing, Gatien Fleury and Jean-François Sassi

Energies 2016, 9(3), 132; https://doi.org/10.3390/en9030132 - 25 Feb 2016

Cited by 158 | Viewed by 12705

Abstract

Microalgae have been shown to be a source of multiple bio-based products ranging from high value molecules to commodities. Along with their potential to produce a large variety of products, microalgae can also be used for the depollution of wastewaters of different origins [...] Read more.

Microalgae have been shown to be a source of multiple bio-based products ranging from high value molecules to commodities. Along with their potential to produce a large variety of products, microalgae can also be used for the depollution of wastewaters of different origins (urban, industrial, and agricultural). This paper is focused on the importance of harnessing the bioremediation capacity of microalgae to treat wastewaters in order to develop the microalgae industry (especially the microalgae biofuel industry) and to find other alternatives to the classic wastewater treatment processes. The current research on the potential of microalgae to treat a specific wastewater or a targeted pollutant is reviewed and discussed. Then, both strategies of selecting the best microalgae strain to treat a specific wastewater or pollutant and using a natural or an artificial consortium to perform the treatment will be detailed. The process options for treating wastewaters using microalgae will be discussed up to the final valorization of the biomass. The last part is dedicated to the challenges which research need to address in order to develop the potential of microalgae to treat wastewaters. Full article

(This article belongs to the Special Issue Algae Fuel 2015)

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21 pages, 7557 KiB

Open AccessArticle

Technical, Economical and Social Assessment of Photovoltaics in the Frame of the Net-Metering Law for the Province of Salta, Argentina

by Luis Ramirez Camargo, Judith Franco, Nilsa María Sarmiento Babieri, Silvina Belmonte, Karina Escalante, Raphaela Pagany and Wolfgang Dorner

Energies 2016, 9(3), 133; https://doi.org/10.3390/en9030133 - 26 Feb 2016

Cited by 18 | Viewed by 6513

Abstract

Central and Northern Argentinean regions possess a high potential for the generation of solar energy. The realization of this potential is an alternative to alleviate the strong dependence on imports of fossil energy and to reduce the CO₂ emissions of the country. [...] Read more.

Central and Northern Argentinean regions possess a high potential for the generation of solar energy. The realization of this potential is an alternative to alleviate the strong dependence on imports of fossil energy and to reduce the CO₂ emissions of the country. However, the adoption of photovoltaics (PV) is still in an incipient state. It is undermined by a context of heavily subsidized electricity prices, high equipment and installation costs and a lack of information, training and experience in handling PV technology. This paper presents a techno-economical assessment of the application of the recently enacted net-metering law for promoting renewable energies (RE) in the Province of Salta (Northwest Argentina) for the case of PV. The assessment shows under which conditions and for which types of consumers it is profitable to adopt PV in the context of the law. This analysis is supported by a participatory planning approach as a study of stakeholders’ attitudes towards RE, intentions to adopt PV and their knowledge about the law. The results of this study and the economical analysis serve to provide recommendations aimed at increasing the level of PV adoption in the province. Full article

(This article belongs to the Special Issue Multi-Disciplinary Perspectives on Energy and Sustainable Development)

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15 pages, 5262 KiB

Open AccessArticle

A Dual-Consequent-Pole Vernier Memory Machine

by Hui Yang, Heyun Lin, Zi-Qiang Zhu, Shuhua Fang and Yunkai Huang

Energies 2016, 9(3), 134; https://doi.org/10.3390/en9030134 - 26 Feb 2016

Cited by 21 | Viewed by 7492

Abstract

This paper proposes a novel dual-consequent-pole Vernier memory machine (DCP-VMM) featuring alternatively arranged NdFeB and low coercive-force (LCF) magnet poles on the rotating and stationary sides, respectively. Due to the presence of LCF magnets that can be repetitively magnetized or demagnetized via a [...] Read more.

This paper proposes a novel dual-consequent-pole Vernier memory machine (DCP-VMM) featuring alternatively arranged NdFeB and low coercive-force (LCF) magnet poles on the rotating and stationary sides, respectively. Due to the presence of LCF magnets that can be repetitively magnetized or demagnetized via a simple current pulse, the extra-high torque density at low-speed, and excellent high-efficient high-speed flux-weakening performance can be simultaneously realized. The configuration and operating principle, as well as the design considerations of the proposed machine are introduced, respectively. The finite element method (FEM) coupled with a nonlinear analytical hysteresis model for LCF magnets is employed to investigate the electromagnetic performance of the machine, which verifies the effectiveness of machine design and the feasibility as a competent candidate for automotive applications. Full article

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15 pages, 3624 KiB

Open AccessArticle

Improved Sensorless Control of Interior Permanent Magnet Sensorless Motors Using an Active Damping Control Strategy

by Younghoon Cho

Energies 2016, 9(3), 135; https://doi.org/10.3390/en9030135 - 26 Feb 2016

Cited by 13 | Viewed by 5902

Abstract

This paper proposes the active damping control strategy for position sensorless operation of an interior permanent magnet (IPM) motor. The proposed method is applied to both the current controller and the position estimator to control damping characteristics of the IPM drive system. By [...] Read more.

This paper proposes the active damping control strategy for position sensorless operation of an interior permanent magnet (IPM) motor. The proposed method is applied to both the current controller and the position estimator to control damping characteristics of the IPM drive system. By actively increasing the damping characteristics of the system with the proposed method, the current control and the position estimation loops become immune to parameter variation of the stator resistance which may degrade the accuracy of the position estimator. To analyze the accuracy of the position estimator with and without the proposed method, a small-signal analysis is carried out for low speed operation where the effect of the parameter variation is relatively large due to a low signal-to-noise ratio (SNR). Additionally, an open-loop voltage to angular velocity transfer function including the electrical and the mechanical parameters is investigated. Since no hardware modifications are necessary, the proposed method can be easily implemented just in software routines. Both the simulations and the experimental validations in which the proposed active damping control strategy is incorporated with the existing extended electromotive force (EMF)- based sensorless algorithm are provided to support the effectiveness of the proposed method. Full article

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18 pages, 6202 KiB

Open AccessArticle

Closed Solar House with Radiation Filtering Roof for Transplant Production in Arid Regions: Energy Consumption

by Ahmed M. Abdel-Ghany, Ibrahim M. Al-Helal, Abdullah A. Alsadon, Abdullah A. Ibrahim and Mohamed R. Shady

Energies 2016, 9(3), 136; https://doi.org/10.3390/en9030136 - 26 Feb 2016

Cited by 1 | Viewed by 4818

Abstract

Under harsh weather conditions, closed transplant production systems (CTPS) are currently used to produce high quality transplants under artificial lighting. More than 70% of the electric energy consumed in the CTPS is for lighting. This article presents a simulation study to examine the [...] Read more.

Under harsh weather conditions, closed transplant production systems (CTPS) are currently used to produce high quality transplants under artificial lighting. More than 70% of the electric energy consumed in the CTPS is for lighting. This article presents a simulation study to examine the possibility of using an alternative closed solar house, with radiation filtering roof, for transplant production in hot sunny regions to replace the artificial lighting in the CTPS with sunlight. The sidewalls of the house were insulated as in the CTPS and the roof was transparent, and made from polycarbonate hollow-channeled structure. There was a liquid radiation filter (LRF) (1.5% CuSO₄–water solution) flowing in a closed loop through the roof channels to absorb the solar heat load (i.e., the near infra-red radiation, NIR: 700–2500 nm) and transmit the photosynthetically active radiation (PAR: 400–700 nm) for plant growth. The LRF inlet temperature was assumed to be 25 °C to prevent vapor condensation on the inner surface of the cover. The evapo-transpired water vapor was removed immediately to maintain the relative humidity inside the house at 70%. The results proved that this technique can offer an appropriate air temperature inside the house less than outside air temperature by around 8–10 °C in hot summer days, and the integrated electric energy consumption during the production period was estimated to be around 43% of the CTPS consumption. Full article

(This article belongs to the Special Issue Solar Heating & Cooling)

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15 pages, 6283 KiB

Open AccessArticle

Computational Fluid Dynamic Analysis of Co-Firing of Palm Kernel Shell and Coal

by Muhammad Aziz, Dwika Budianto and Takuya Oda

Energies 2016, 9(3), 137; https://doi.org/10.3390/en9030137 - 26 Feb 2016

Cited by 29 | Viewed by 7598

Abstract

The increasing global demand for palm oil and its products has led to a significant growth in palm plantations and palm oil production. Unfortunately, these bring serious environmental problems, largely because of the large amounts of waste material produced, including palm kernel shell [...] Read more.

The increasing global demand for palm oil and its products has led to a significant growth in palm plantations and palm oil production. Unfortunately, these bring serious environmental problems, largely because of the large amounts of waste material produced, including palm kernel shell (PKS). In this study, we used computational fluid dynamics (CFD) to investigate the PKS co-firing of a 300 MWe pulverized coal-fired power plant in terms of thermal behavior of the plant and the CO₂, CO, O₂, NO_x, and SO_x produced. Five different PKS mass fractions were evaluated: 0%, 10%, 15%, 25%, and 50%. The results suggest that PKS co-firing is favorable in terms of both thermal behavior and exhaust gas emissions. A PKS mass fraction of 25% showed the best combustion characteristics in terms of temperature and the production of CO₂, CO, and SO_x. However, relatively large amounts of thermal NO_x were produced by high temperature oxidation. Considering all these factors, PKS mass fractions of 10%–15% emerged as the most appropriate co-firing condition. The PKS supply capacity of the palm mills surrounding the power plants is a further parameter to be considered when setting the fuel mix. Full article

(This article belongs to the Special Issue Advances in Biomass for Energy Technology)

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15 pages, 3430 KiB

Open AccessArticle

An Automatic Switched-Capacitor Cell Balancing Circuit for Series-Connected Battery Strings

by Yuanmao Ye and Ka Wai Eric Cheng

Energies 2016, 9(3), 138; https://doi.org/10.3390/en9030138 - 27 Feb 2016

Cited by 58 | Viewed by 12309

Abstract

In this paper, a novel voltage equalizer is developed for series battery strings based on the two-phase switched capacitor technique. Different from the conventional voltage equalizers which are developed by switched-mode power converters, bulky magnetic components and complex monitoring and control system are [...] Read more.

In this paper, a novel voltage equalizer is developed for series battery strings based on the two-phase switched capacitor technique. Different from the conventional voltage equalizers which are developed by switched-mode power converters, bulky magnetic components and complex monitoring and control system are avoided in the proposed system. Just a pair of complementary pulse signals with constant switching frequency and fixed duty ratio are required to control all of switches employed in the proposed voltage equalizer, and charge transfers from the higher voltage battery cells to lower voltage ones automatically. The circuit configuration and operation principle are provided in this paper. The model of the proposed voltage equalizer is also derived. Comparison with other works indicates that the proposed method is superior to the conventional switched-capacitor (SC) voltage equalizer for the high stack of series battery strings. Experimental results demonstrate that the proposed voltage equalization system is capable of excellent voltage balancing performance with a simple control method. Full article

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14 pages, 2009 KiB

Open AccessArticle

Monte Carlo Evaluation of the Impact of Subsequent Strokes on Backflashover Rate

by Fabio Massimo Gatta, Alberto Geri, Stefano Lauria and Marco Maccioni

Energies 2016, 9(3), 139; https://doi.org/10.3390/en9030139 - 26 Feb 2016

Cited by 7 | Viewed by 5031

Abstract

The paper deals with the impact of subsequent strokes on the backflashover rate (BFR) of HV overhead transmission lines (OHLs), assessed by means of an ATP-EMTP Monte Carlo procedure. The application to a typical 150 kV Italian OHL is discussed, simulating several tower [...] Read more.

The paper deals with the impact of subsequent strokes on the backflashover rate (BFR) of HV overhead transmission lines (OHLs), assessed by means of an ATP-EMTP Monte Carlo procedure. The application to a typical 150 kV Italian OHL is discussed, simulating several tower grounding system arrangements. Subsequent strokes parameters are added to the statistical simulation variables: peak current, front time, time-to-half value, lightning polarity, line insulation withstand, lightning location and phase angle of the power frequency voltage. The input data are fed to an ATP-EMTP complete circuit model of the OHL, including line insulation, lightning representation and tower grounding system, the latter simulated by a pi-circuit model able to simulate the effects due to propagation and soil ionization, at modest computational costs. Numerical results evidence a non-negligible BFR increase (in relative terms) due to subsequent strokes: for spatially concentrated grounding systems the BFR increase approximatively vary in inverse proportion with the low frequency grounding resistance, whereas for spatially extended grounding systems the BFR increase depends on the grounding system behavior at high frequencies. Full article

(This article belongs to the Special Issue Selected Papers from 15 IEEE International Conference on Environment and Electrical Engineering (EEEIC 2015))

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19 pages, 2872 KiB

Open AccessArticle

Numerical Investigation of Influence of In-Situ Stress Ratio, Injection Rate and Fluid Viscosity on Hydraulic Fracture Propagation Using a Distinct Element Approach

by Bo Zhang, Xiao Li, Zhaobin Zhang, Yanfang Wu, Yusong Wu and Yu Wang

Energies 2016, 9(3), 140; https://doi.org/10.3390/en9030140 - 27 Feb 2016

Cited by 20 | Viewed by 7209

Abstract

Numerical simulation is very useful for understanding the hydraulic fracturing mechanism. In this paper, we simulate the hydraulic fracturing using the distinct element approach, to investigate the effect of some critical parameters on hydraulic fracturing characteristics. The breakdown pressure obtained by the distinct [...] Read more.

Numerical simulation is very useful for understanding the hydraulic fracturing mechanism. In this paper, we simulate the hydraulic fracturing using the distinct element approach, to investigate the effect of some critical parameters on hydraulic fracturing characteristics. The breakdown pressure obtained by the distinct element approach is consistent with the analytical solution. This indicates that the distinct element approach is feasible on modeling the hydraulic fracturing. We independently examine the influence of in-situ stress ratio, injection rate and fluid viscosity on hydraulic fracturing. We further emphasize the relationship between these three factors and their contributions to the hydraulic fracturing. With the increase of stress ratio, the fracture aperture increases almost linearly; with the increase of injection rate and fluid viscosity, the fracture aperture and breakdown pressure increase obviously. A low value of product of injection rate and fluid viscosity (i.e., Qμ) will lead to narrow fracture aperture, low breakdown pressure, and complex or dispersional hydraulic fractures. A high value of Qμ would lead wide fracture aperture, high breakdown pressure, and simple hydraulic fractures (e.g., straight or wing shape). With low viscosity fluid, the hydraulic fracture geometry is not sensitive to stress ratio, and thus becomes a complex fracture network. Full article

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20 pages, 7086 KiB

Open AccessArticle

Development and Simulation of a Type of Four-Shaft ECVT for a Hybrid Electric Vehicle

by Yong Zhang, Xuerui Ma, Chengliang Yin and Shifei Yuan

Energies 2016, 9(3), 141; https://doi.org/10.3390/en9030141 - 27 Feb 2016

Cited by 9 | Viewed by 8433

Abstract

In hybrid electric vehicles with power-split configurations, the engine can be decoupled from the wheel and operated with improved fuel economy, while the entire efficiency of the powertrain is affected by the circular electric power flow. Two planetary gear (2-PG) sets with adding [...] Read more.

In hybrid electric vehicles with power-split configurations, the engine can be decoupled from the wheel and operated with improved fuel economy, while the entire efficiency of the powertrain is affected by the circular electric power flow. Two planetary gear (2-PG) sets with adding brakes/clutches, namely a type of four shaft elelctric continuously variable transmission (ECVT) can provide multi-mode operation for the powertrain and extend the efficient area. First, a conventional 2-PG AT (Automatic Transmission) architecture is investigated. By analyzing and comparing the connection and operating modes based on the kinematic relationship and lever analogy, a feasible four-shaft ECVT architecture with two brakes and two simplified versions are picked. To make a trade-off between fuel economy and configuration complexity, an instantaneous optimal control strategy based on the equivalent consumption minimization strategy (ECMS) concept is then developed and employed as the unified optimization method in the simulations of three different configurations. Finally, the simulation results show that the simplified versions are suboptimal sets and the fuel economy is sacrificed by the limits of different modes. From the viewpoint of concept design, a multi-mode power-split configuration is more suitable for hybrid electric vehicles. This research applied a systematic methodology from concept design to energy management optimization, which can provide the guidelines for researchers to select a suitable multi-mode power-split hybrid powertrain. Full article

(This article belongs to the Special Issue Advances in Plug-in Hybrid Vehicles and Hybrid Vehicles)

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24 pages, 1549 KiB

Open AccessArticle

Smart Control of Multiple Evaporator Systems with Wireless Sensor and Actuator Networks

by Apolinar González-Potes, Walter A. Mata-López, Alberto M. Ochoa-Brust and Carlos Escobar-del Pozo

Energies 2016, 9(3), 142; https://doi.org/10.3390/en9030142 - 29 Feb 2016

Cited by 6 | Viewed by 7079

Abstract

This paper describes the complete integration of a fuzzy control of multiple evaporator systems with the IEEE 802.15.4 standard, in which we study several important aspects for this kind of system, like a detailed analysis of the end-to-end real-time flows over wireless sensor [...] Read more.

This paper describes the complete integration of a fuzzy control of multiple evaporator systems with the IEEE 802.15.4 standard, in which we study several important aspects for this kind of system, like a detailed analysis of the end-to-end real-time flows over wireless sensor and actuator networks (WSAN), a real-time kernel with an earliest deadline first (EDF) scheduler, periodic and aperiodic tasking models for the nodes, lightweight and flexible compensation-based control algorithms for WSAN that exhibit packet dropouts, an event-triggered sampling scheme and design methodologies. We address the control problem of the multi-evaporators with the presence of uncertainties, which was tackled through a wireless fuzzy control approach, showing the advantages of this concept where it can easily perform the optimization for a set of multiple evaporators controlled by the same smart controller, which should have an intelligent and flexible architecture based on multi-agent systems (MAS) that allows one to add or remove new evaporators online, without the need for reconfiguring, while maintaining temporal and functional restrictions in the system. We show clearly how we can get a greater scalability, the self-configuration of the network and the least overhead with a non-beacon or unslotted mode of the IEEE 802.15.4 protocol, as well as wireless communications and distributed architectures, which could be extremely helpful in the development process of networked control systems in large spatially-distributed plants, which involve many sensors and actuators. For this purpose, a fuzzy scheme is used to control a set of parallel evaporator air-conditioning systems, with temperature and relative humidity control as a multi-input and multi-output closed loop system; in addition, a general architecture is presented, which implements multiple control loops closed over a communication network, integrating the analysis and validation method for multi-loop control networks designed for multi-evaporator systems. Full article

(This article belongs to the Special Issue Energy Efficient Building Design 2016)

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15 pages, 7294 KiB

Open AccessArticle

Real-Time Occupant Based Plug-in Device Control Using ICT in Office Buildings

by Woo-Bin Bae, Sun-Hye Mun and Jung-Ho Huh

Energies 2016, 9(3), 143; https://doi.org/10.3390/en9030143 - 1 Mar 2016

Cited by 3 | Viewed by 4820

Abstract

The purpose of this study is to reduce the unnecessary plug loads used by computers, monitors, and computer peripheral devices, all of which account for more than 95% of the entire plug loads of an office building. To this end, an occupant-based plug-in [...] Read more.

The purpose of this study is to reduce the unnecessary plug loads used by computers, monitors, and computer peripheral devices, all of which account for more than 95% of the entire plug loads of an office building. To this end, an occupant-based plug-in device control (OBC-P) software was developed. The OBC-P software collects real-time information about the presence or absence of occupants who are connected to the access point through the Wifi and controls the power of monitors or computers, while a standby power off device controls computer peripheral devices. To measure the plug load saving of the occupant-based plug-in device control, an experiment was conducted, targeting 10 occupants of three research labs of the graduate school, for two weeks. The experiment results showed that it could save the plug loads of monitors and computer peripheral devices by 15% in the Awake mode, and by 26% in the Sleep mode. Full article

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13 pages, 2135 KiB

Open AccessArticle

Optimum Electric Boiler Capacity Configuration in a Regional Power Grid for a Wind Power Accommodation Scenario

by Da Liu, Guowei Zhang, Baohua Huang and Weiwei Liu

Energies 2016, 9(3), 144; https://doi.org/10.3390/en9030144 - 1 Mar 2016

Cited by 31 | Viewed by 6818

Abstract

Wind power generation reduces our reliance on fossil fuels and can thus reduce environmental pollution. However, rapid wind power development has caused various issues related to power grid restructuring. A high proportion of the generating capacity of northeast China is based on combined [...] Read more.

Wind power generation reduces our reliance on fossil fuels and can thus reduce environmental pollution. However, rapid wind power development has caused various issues related to power grid restructuring. A high proportion of the generating capacity of northeast China is based on combined heat and power (CHP), whose inflexible response to the peak regulation of power grids hinders the ability to accommodate wind power; thus, wind power curtailment is prevalent. Electric boilers can directly consume the excess wind power to supply heat during low load periods and thus mitigate the heat supply stress of CHP units. Therefore, electric boilers improve the power grid’s ability to accommodate additional wind power. From a regional power grid perspective, this paper discussed the feasibility of such a strategy for increasing the ability to accommodate wind power during the heat supply season. This paper analysed the optimum electric boiler capacity configuration of a regional power grid based on various constraint conditions, such as the heat-power balance, with the objective of maximising the associated social benefits. Using the Beijing-Tianjin-Hebei power grid as an example, the optimum electric boiler capacity of the studied power grid is approximately 1100 MW. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

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23 pages, 485 KiB

Open AccessArticle

Evaluating Internal Technological Capabilities in Energy Companies

by Mingook Lee and Sungjoo Lee

Energies 2016, 9(3), 145; https://doi.org/10.3390/en9030145 - 1 Mar 2016

Cited by 11 | Viewed by 6867

Abstract

As global competition increases, technological capability must be evaluated objectively as one of the most important factors for predominance in technological competition and to ensure sustainable business excellence. Most existing capability evaluation models utilize either quantitative methods, such as patent analysis, or qualitative [...] Read more.

As global competition increases, technological capability must be evaluated objectively as one of the most important factors for predominance in technological competition and to ensure sustainable business excellence. Most existing capability evaluation models utilize either quantitative methods, such as patent analysis, or qualitative methods, such as expert panels. Accordingly, they may be in danger of reflecting only fragmentary aspects of technological capabilities, and produce inconsistent results when different models are used. To solve these problems, this paper proposes a comprehensive framework for evaluating technological capabilities in energy companies by considering the complex properties of technological knowledge. For this purpose, we first explored various factors affecting technological capabilities and divided the factors into three categories: individual, organizational, and technology competitiveness. Second, we identified appropriate evaluation items for each category to measure the technological capability. Finally, by using a hybrid approach of qualitative and quantitative methods, we developed an evaluation method for each item and suggested a method to combine the results. The proposed framework was then verified with an energy generation and supply company to investigate its practicality. As one of the earliest attempts to evaluate multi-faceted technological capabilities, the suggested model can support technology and strategic planning. Full article

(This article belongs to the Special Issue Multi-Disciplinary Perspectives on Energy and Sustainable Development)

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25 pages, 8631 KiB

Open AccessArticle

Investigation of the Optimal Omni-Direction-Guide-Vane Design for Vertical Axis Wind Turbines Based on Unsteady Flow CFD Simulation

by Behzad Shahizare, Nik Nazri Bin Nik Ghazali, Wen Tong Chong, Seyed Saeed Tabatabaeikia and Nima Izadyar

Energies 2016, 9(3), 146; https://doi.org/10.3390/en9030146 - 2 Mar 2016

Cited by 15 | Viewed by 11362

Abstract

With soaring energy demands, the desire to explore alternate and renewable energy resources has become the focal point of various active research fronts. Therefore, the scientific community is revisiting the notion to tap wind resources in more rigorous and novel ways. In this [...] Read more.

With soaring energy demands, the desire to explore alternate and renewable energy resources has become the focal point of various active research fronts. Therefore, the scientific community is revisiting the notion to tap wind resources in more rigorous and novel ways. In this study, a two-dimensional computational investigation of the vertical axis wind turbine (VAWT) with omni-direction-guide-vane (ODGV) is proposed to determine the effects of this guide vane. In addition, the mesh and time step (dt) size dependency test, as well as the effect of the different turbulence models on results accuracy are investigated. Eight different shape ratios (R) of the omni-direction-guide-vane were also examined in this study. Further, the CFD model is validated by comparing the numerical results with the experimental data. Validation results show a good agreement in terms of shape and trend in CFD simulation. Based on these results, all the shape ratios, except two ratios including 0.3 and 0.4 at TSR of 1.3 to 3, have a positive effect on the power and torque coefficient improvement. Moreover, results show that the best case has a shape ratio of 0.55, which improves the power coefficient by 48% and the torque coefficient up to 58%. Full article

(This article belongs to the Special Issue Wind Turbine 2015)

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18 pages, 3841 KiB

Open AccessArticle

Efficient Photovoltaic System Maximum Power Point Tracking Using a New Technique

by Mehdi Seyedmahmoudian, Ben Horan, Rasoul Rahmani, Aman Maung Than Oo and Alex Stojcevski

Energies 2016, 9(3), 147; https://doi.org/10.3390/en9030147 - 2 Mar 2016

Cited by 55 | Viewed by 10664

Abstract

Partial shading is an unavoidable condition which significantly reduces the efficiency and stability of a photovoltaic (PV) system. When partial shading occurs the system has multiple-peak output power characteristics. In order to track the global maximum power point (GMPP) within an appropriate period [...] Read more.

Partial shading is an unavoidable condition which significantly reduces the efficiency and stability of a photovoltaic (PV) system. When partial shading occurs the system has multiple-peak output power characteristics. In order to track the global maximum power point (GMPP) within an appropriate period a reliable technique is required. Conventional techniques such as hill climbing and perturbation and observation (P&O) are inadequate in tracking the GMPP subject to this condition resulting in a dramatic reduction in the efficiency of the PV system. Recent artificial intelligence methods have been proposed, however they have a higher computational cost, slower processing time and increased oscillations which results in further instability at the output of the PV system. This paper proposes a fast and efficient technique based on Radial Movement Optimization (RMO) for detecting the GMPP under partial shading conditions. The paper begins with a brief description of the behavior of PV systems under partial shading conditions followed by the introduction of the new RMO-based technique for GMPP tracking. Finally, results are presented to demonstration the performance of the proposed technique under different partial shading conditions. The results are compared with those of the PSO method, one of the most widely used methods in the literature. Four factors, namely convergence speed, efficiency (power loss reduction), stability (oscillation reduction) and computational cost, are considered in the comparison with the PSO technique. Full article

(This article belongs to the Special Issue Solar Photovoltaics Trilemma: Efficiencey, Stability and Cost Reduction)

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16 pages, 5300 KiB

Open AccessArticle

Buck Converter with Soft-Switching Cells for PV Panel Applications

by Cheng-Tao Tsai and Wang-Min Chen

Energies 2016, 9(3), 148; https://doi.org/10.3390/en9030148 - 2 Mar 2016

Cited by 12 | Viewed by 14069

Abstract

In power conversion of photovoltaic (PV) energy, a hard-switching buck converter always generates some disadvantages. For example, serious electromagnetic interference (EMI), high switching losses, and stresses on an active switch (metal-oxide-semiconductor-field-effect-transistor, MOSFET), and high reverse-recovery losses of a freewheeling diode result in low [...] Read more.

In power conversion of photovoltaic (PV) energy, a hard-switching buck converter always generates some disadvantages. For example, serious electromagnetic interference (EMI), high switching losses, and stresses on an active switch (metal-oxide-semiconductor-field-effect-transistor, MOSFET), and high reverse-recovery losses of a freewheeling diode result in low conversion efficiency. To release these disadvantages, a buck converter with soft-switching cells for PV panel applications is proposed. To create zero-voltage-switching (ZVS) features of the active switches, a simple active soft-switching cell with an inductor, a capacitor, and a MOSFET is incorporated into the proposed buck converter. Therefore, the switching losses and stresses of the active switches and EMI can be reduced significantly. To reduce reverse-recovery losses of a freewheeling diode, a simple passive soft-switching cell with a capacitor and two diodes is implemented. To verify the performance and the feasibility of the proposed buck converter with soft-switching cells for PV panel applications, a prototype soft-switching buck converter is built and implemented by using a maximum-power-point-tracking (MPPT) method. Simulated and experimental results are presented from a 100 W soft-switching buck converter for PV panel applications. Full article

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22 pages, 9544 KiB

Open AccessEditor’s ChoiceArticle

Investigation of a High Head Francis Turbine at Runaway Operating Conditions

by Chirag Trivedi, Michel J. Cervantes and B. K. Gandhi

Energies 2016, 9(3), 149; https://doi.org/10.3390/en9030149 - 2 Mar 2016

Cited by 78 | Viewed by 11670

Abstract

Hydraulic turbines exhibit total load rejection during operation because of high fluctuations in the grid parameters. The generator reaches no-load instantly. Consequently, the turbine runner accelerates to high speed, runaway speed, in seconds. Under common conditions, stable runaway is only reached if after [...] Read more.

Hydraulic turbines exhibit total load rejection during operation because of high fluctuations in the grid parameters. The generator reaches no-load instantly. Consequently, the turbine runner accelerates to high speed, runaway speed, in seconds. Under common conditions, stable runaway is only reached if after a load rejection, the control and protection mechanisms both fail and the guide vanes cannot be closed. The runner life is affected by the high amplitude pressure loading at the runaway speed. A model Francis turbine was used to investigate the consequences at the runaway condition. Measurements and simulations were performed at three operating points. The numerical simulations were performed using standard k-ε, k-ω shear stress transport (SST) and scale-adaptive simulation (SAS) models. A total of 12.8 million hexahedral mesh elements were created in the complete turbine, from the spiral casing inlet to the draft tube outlet. The experimental and numerical analysis showed that the runner was subjected to an unsteady pressure loading up to three-times the pressure loading observed at the best efficiency point. Investigates of unsteady pressure pulsations at the vaneless space, runner and draft tube are discussed in the paper. Further, unsteady swirling flow in the blade passages was observed that was rotating at a frequency of 4.8-times the runaway runner angular speed. Apart from the unsteady pressure loading, the development pattern of the swirling flow in the runner is discussed in the paper. Full article

(This article belongs to the Special Issue Hydropower)

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22 pages, 5937 KiB

Open AccessArticle

Data Distribution Service-Based Interoperability Framework for Smart Grid Testbed Infrastructure

by Tarek A. Youssef, Ahmed T. Elsayed and Osama A. Mohammed

Energies 2016, 9(3), 150; https://doi.org/10.3390/en9030150 - 2 Mar 2016

Cited by 19 | Viewed by 8692

Abstract

This paper presents the design and implementation of a communication and control infrastructure for smart grid operation. The proposed infrastructure enhances the reliability of the measurements and control network. The advantages of utilizing the data-centric over message-centric communication approach are discussed in the [...] Read more.

This paper presents the design and implementation of a communication and control infrastructure for smart grid operation. The proposed infrastructure enhances the reliability of the measurements and control network. The advantages of utilizing the data-centric over message-centric communication approach are discussed in the context of smart grid applications. The data distribution service (DDS) is used to implement a data-centric common data bus for the smart grid. This common data bus improves the communication reliability, enabling distributed control and smart load management. These enhancements are achieved by avoiding a single point of failure while enabling peer-to-peer communication and an automatic discovery feature for dynamic participating nodes. The infrastructure and ideas presented in this paper were implemented and tested on the smart grid testbed. A toolbox and application programing interface for the testbed infrastructure are developed in order to facilitate interoperability and remote access to the testbed. This interface allows control, monitoring, and performing of experiments remotely. Furthermore, it could be used to integrate multidisciplinary testbeds to study complex cyber-physical systems (CPS). Full article

(This article belongs to the Special Issue Selected Papers from 15 IEEE International Conference on Environment and Electrical Engineering (EEEIC 2015))

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18 pages, 4220 KiB

Open AccessArticle

A Time-Frequency Analysis Method for Low Frequency Oscillation Signals Using Resonance-Based Sparse Signal Decomposition and a Frequency Slice Wavelet Transform

by Yan Zhao, Zhimin Li and Yonghui Nie

Energies 2016, 9(3), 151; https://doi.org/10.3390/en9030151 - 2 Mar 2016

Cited by 17 | Viewed by 6819

Abstract

To more completely extract useful features from low frequency oscillation (LFO) signals, a time-frequency analysis method using resonance-based sparse signal decomposition (RSSD) and a frequency slice wavelet transform (FSWT) is proposed. FSWT can cut time-frequency areas freely, so that any band component feature [...] Read more.

To more completely extract useful features from low frequency oscillation (LFO) signals, a time-frequency analysis method using resonance-based sparse signal decomposition (RSSD) and a frequency slice wavelet transform (FSWT) is proposed. FSWT can cut time-frequency areas freely, so that any band component feature can be extracted. It can analyze multiple aspects of the LFO signal, including determination of dominant mode, mode seperation and extraction, and 3D map expression. Combined with the Hilbert transform,the parameters of the LFO mode components can be identified. Furthermore, the noise in the LFO signal could reduce the frequency resolution of FSWT analysis, which may impact the accuracy of oscillation mode identification. Complex signals can be separated by predictable Q-factors using RSSD. The RSSD method can do well in LFO signal denoising. Firstly, the LFO signal is decomposed into a high-resonance component, a low-resonance component and a residual by RSSD. The LFO signal is the output of an underdamped system with high quality factor and high-resonance property at a specific frequency. The high-resonance component is the denoised LFO signal, and the residual contains most of the noise. Secondly, the high-resonance component is decomposed by FSWT and the full band of its time-frequency distribution are obtained. The 3D map expression and dominant mode of the LFO can be obtained. After that, due to its energy distribution, frequency slices are chosen to get accurate analysis of time-frequency features. Through reconstructing signals in characteristic frequency slices, separation and extraction of the LFO mode components is realized. Thirdly, high-accuracy detection for modal parameter identification is achieved by the Hilbert transform. Simulation and application examples prove the effectiveness of the proposed method. Full article

(This article belongs to the Special Issue Electric Power Systems Research)

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15 pages, 6511 KiB

Open AccessArticle

Statistical Analysis of Partial Discharges in SF₆ Gas via Optical Detection in Various Spectral Ranges

by Ming Ren, Ming Dong and Jialin Liu

Energies 2016, 9(3), 152; https://doi.org/10.3390/en9030152 - 2 Mar 2016

Cited by 44 | Viewed by 10766

Abstract

Partial discharge (PD) detection is essential to the operation of high-voltage systems. In this context, we investigate the basic characteristics of light emission during PDs in SF₆ gas from the perspective of insulation diagnosis. A synchronous system is constructed using three optical [...] Read more.

Partial discharge (PD) detection is essential to the operation of high-voltage systems. In this context, we investigate the basic characteristics of light emission during PDs in SF₆ gas from the perspective of insulation diagnosis. A synchronous system is constructed using three optical photoelectric instruments with separate wavelength responses in the ultraviolet (UV, 189–352 nm), visible (VIS, 381–675 nm), and near-infrared (NIR, 737–920 nm) spectral ranges and a wide-band PD current pulse detector with a response of 1 pC. The results indicate that light emission depends upon the type of insulation defect and discharge energy. An increase in PD charge gives rise to more components in the spectral range from UV to VIS, and the presence of an insulator surface in discharges yields a more complex VIS-to-NIR spectrum. The phase-resolved partial discharge pattern (PRPD) of UV light pulses can reasonably reflect the electroluminescence process in the presence of the insulator surface and weak corona at negative voltage points. The PRPD of VIS light describes the features of the actual PD pattern in most cases. In comparison with the other two spectral ranges, light intensity in the VIS range is more sensitive to changes in gas-pressure-normalized voltage (V_rms/p). The linear fitting analysis of the relationships between the light intensity and PD charge shows that UV light detection has a greater sensitivity to the PD charge and that UV detection exhibits a greater degree of linearity. NIR detection is applicable only to severe PDs. We believe that our findings can significantly aid in application of optical PD diagnosis in SF₆ gas insulated systems. Full article

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18 pages, 5305 KiB

Open AccessArticle

Constant Jacobian Matrix-Based Stochastic Galerkin Method for Probabilistic Load Flow

by Yingyun Sun, Rui Mao, Zuyi Li and Wei Tian

Energies 2016, 9(3), 153; https://doi.org/10.3390/en9030153 - 3 Mar 2016

Cited by 13 | Viewed by 6805

Abstract

An intrusive spectral method of probabilistic load flow (PLF) is proposed in the paper, which can handle the uncertainties arising from renewable energy integration. Generalized polynomial chaos (gPC) expansions of dependent random variables are utilized to build a spectral stochastic representation of PLF [...] Read more.

An intrusive spectral method of probabilistic load flow (PLF) is proposed in the paper, which can handle the uncertainties arising from renewable energy integration. Generalized polynomial chaos (gPC) expansions of dependent random variables are utilized to build a spectral stochastic representation of PLF model. Instead of solving the coupled PLF model with a traditional, cumbersome method, a modified stochastic Galerkin (SG) method is proposed based on the P-Q decoupling properties of load flow in power system. By introducing two pre-calculated constant sparse Jacobian matrices, the computational burden of the SG method is significantly reduced. Two cases, IEEE 14-bus and IEEE 118-bus systems, are used to verify the computation speed and efficiency of the proposed method. Full article

(This article belongs to the Special Issue Microgrids 2016)

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24 pages, 9584 KiB

Open AccessArticle

Direct Numerical Simulation of Supersonic Turbulent Boundary Layer with Spanwise Wall Oscillation

by Weidan Ni, Lipeng Lu, Catherine Le Ribault and Jian Fang

Energies 2016, 9(3), 154; https://doi.org/10.3390/en9030154 - 3 Mar 2016

Cited by 13 | Viewed by 6874

Abstract

Direct numerical simulations (DNS) of Mach = 2.9 supersonic turbulent boundary layers with spanwise wall oscillation (SWO) are conducted to investigate the turbulent heat transport mechanism and its relation with the turbulent momentum transport. The turbulent coherent structures are suppressed by SWO and [...] Read more.

Direct numerical simulations (DNS) of Mach = 2.9 supersonic turbulent boundary layers with spanwise wall oscillation (SWO) are conducted to investigate the turbulent heat transport mechanism and its relation with the turbulent momentum transport. The turbulent coherent structures are suppressed by SWO and the drag is reduced. Although the velocity and temperature statistics are disturbed by SWO differently, the turbulence transports of momentum and heat are simultaneously suppressed. The Reynolds analogy and the strong Reynolds analogy are also preserved in all the controlled flows, proving the consistent mechanisms of momentum transport and heat transport in the turbulent boundary layer with SWO. Despite the extra dissipation and heat induced by SWO, a net wall heat flux reduction can be achieved with the proper selected SWO parameters. The consistent mechanism of momentum and heat transports supports the application of turbulent drag reduction technologies to wall heat flux controls in high-speed vehicles. Full article

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10 pages, 882 KiB

Open AccessArticle

Adaptive Procurement Guidelines for Automatic Selection of Renewable Forest Energy Sources within a Sustainable Energy Production System

by Teijo Palander and Kalle Kärhä

Energies 2016, 9(3), 155; https://doi.org/10.3390/en9030155 - 3 Mar 2016

Cited by 3 | Viewed by 4140

Abstract

An automatic forest-stand selection method was developed that integrates the procurement of profitable energy sources within a sustainable energy production system. We tested the method using a forest harvester simulator. We found that site-specific estimates of forest characteristics are important when predicting the [...] Read more.

An automatic forest-stand selection method was developed that integrates the procurement of profitable energy sources within a sustainable energy production system. We tested the method using a forest harvester simulator. We found that site-specific estimates of forest characteristics are important when predicting the potential of an energy-wood stand as a renewable energy source. Further, tree parameters can be combined with automatic stem measurements from a multiple-tree harvester to predict the energy-wood biomass in the stands. The selection process uses data from profitability studies. The selection process also uses environmental criteria to ensure that sufficient soil organic matter is left behind and to protect the soil against erosion. The integrated system of the harvester automatically adapts the system’s models and stand-selection rules to account for various site-specific stand parameters. Predicting the profitable and environmentally acceptable yield of stand biomass has great potential in sustainable forest resource management, but managers must decide whether the operational procurement guidelines provided by the stand-selection method is acceptable under their local real-world wood procurement conditions. Full article

(This article belongs to the Special Issue Energy from Forest Biomass)

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15 pages, 1814 KiB

Open AccessArticle

An Efficiency Enhancement Technique for a Wireless Power Transmission System Based on a Multiple Coil Switching Technique

by Vijith Vijayakumaran Nair and Jun Rim Choi

Energies 2016, 9(3), 156; https://doi.org/10.3390/en9030156 - 3 Mar 2016

Cited by 38 | Viewed by 11045

Abstract

For magnetic-coupled resonator wireless power transmission (WPT) systems, higher power transfer efficiency can be achieved over a greater range in comparison to inductive-coupled WPT systems. However, as the distance between the two near-field resonators varies, the coupling between them changes. The change in [...] Read more.

For magnetic-coupled resonator wireless power transmission (WPT) systems, higher power transfer efficiency can be achieved over a greater range in comparison to inductive-coupled WPT systems. However, as the distance between the two near-field resonators varies, the coupling between them changes. The change in coupling would in turn vary the power transfer efficiency. Generally, to maintain high efficiency for varying distances, either frequency tuning or impedance matching are employed. Frequency tuning may not limit the tunable frequency within the Industrial Scientific Medical (ISM) band, and the impedance matching network involves bulky systems. Therefore, to maintain higher transfer efficiency over a wide range of distances, we propose a multiple coil switching wireless power transmission system. The proposed system includes several loop coils with different sizes. Based on the variation of the distance between the transmitter and receiver side, the power is switched to one of the loop coils for transmission and reception. The system enables adjustment of the coupling coefficient with selective switching of the coil loops at the source and load end and, thus, aids achieving high power transfer efficiency over a wide range of distances. The proposed technique is analyzed with an equivalent circuit model, and simulations are performed to evaluate the performance. The system is validated through experimental results that indicate for a fixed frequency (13.56 MHz) that the switched loop technique achieves high efficiency over a wider range of distances. Full article

(This article belongs to the Special Issue Energy Efficient Actuators and Systems)

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20 pages, 2485 KiB

Open AccessArticle

Optimal Site Selection of Electric Vehicle Charging Stations Based on a Cloud Model and the PROMETHEE Method

by Yunna Wu, Meng Yang, Haobo Zhang, Kaifeng Chen and Yang Wang

Energies 2016, 9(3), 157; https://doi.org/10.3390/en9030157 - 3 Mar 2016

Cited by 110 | Viewed by 11182

Abstract

The task of site selection for electric vehicle charging stations (EVCS) is hugely important from the perspective of harmonious and sustainable development. However, flaws and inadequacies in the currently used multi-criteria decision making methods could result in inaccurate and irrational decision results. First [...] Read more.

The task of site selection for electric vehicle charging stations (EVCS) is hugely important from the perspective of harmonious and sustainable development. However, flaws and inadequacies in the currently used multi-criteria decision making methods could result in inaccurate and irrational decision results. First of all, the uncertainty of the information cannot be described integrally in the evaluation of the EVCS site selection. Secondly, rigorous consideration of the mutual influence between the various criteria is lacking, which is mainly evidenced in two aspects: one is ignoring the correlation, and the other is the unconscionable measurements. Last but not least, the ranking method adopted in previous studies is not very appropriate for evaluating the EVCS site selection problem. As a result of the above analysis, a Preference Ranking Organization Method for Enrichment Evaluations (PROMETHEE) method-based decision system combined with the cloud model is proposed in this paper for EVCS site selection. Firstly, the use of the PROMETHEE method can bolster the confidence and visibility for decision makers. Secondly, the cloud model is recommended to describe the fuzziness and randomness of linguistic terms integrally and accurately. Finally, the Analytical Network Process (ANP) method is adopted to measure the correlation of the indicators with a greatly simplified calculation of the parameters and the steps required. Full article

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16 pages, 16865 KiB

Open AccessArticle

Rotor Design for an Efficient Single-Phase Induction Motor for Refrigerator Compressors

by Hyun-Jin Ahn, Kang-Won Kim, Joon-Ho Choi, Eui-Sun Kim and Young-Cheol Lim

Energies 2016, 9(3), 158; https://doi.org/10.3390/en9030158 - 3 Mar 2016

Cited by 6 | Viewed by 8908

Abstract

This article describes a rotor making technology for the production of high-efficiency single-phase induction motors (SPIMs) to be used in refrigerator compressors. Rotors can have different aluminum fill factors according to the fabrication method. In order to examine the association between the fill [...] Read more.

This article describes a rotor making technology for the production of high-efficiency single-phase induction motors (SPIMs) to be used in refrigerator compressors. Rotors can have different aluminum fill factors according to the fabrication method. In order to examine the association between the fill factor and the efficiency of the rotor, we analyzed the distribution of magnetic flux density using the finite element method (FEM). Next, we made prototype rotors by conventional casting methods and by the proposed casting method and compared their fill factors. In addition, SPIMs were made using the rotors, and their efficiencies were measured using a dynamometer. Moreover, the SPIMs were put to use in a compressor, for testing, and for each SPIM the refrigerating capacity of the compressor was measured with a calorimeter. Based on the results of the FEM analysis of the magnetic flux density and the experiments, the reliability and validity of the proposed method were proven. Full article

(This article belongs to the Special Issue Energy Saving Design for Manufacturing Process, Product, and System)

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14 pages, 2530 KiB

Open AccessArticle

Aggregator-Based Interactive Charging Management System for Electric Vehicle Charging

by Mingchao Xia, Qingying Lai, Yajiao Zhong, Canbing Li and Hsiao-Dong Chiang

Energies 2016, 9(3), 159; https://doi.org/10.3390/en9030159 - 4 Mar 2016

Cited by 37 | Viewed by 9319

Abstract

With the ongoing large-scale implementation of electric vehicles (EVs), the exploration of a more flexible approach to maintain fair interaction between EVs and the power grid is urgently required. This paper presents an aggregator-based interactive charging management scheme adopting interruptible load (IL) pricing, [...] Read more.

With the ongoing large-scale implementation of electric vehicles (EVs), the exploration of a more flexible approach to maintain fair interaction between EVs and the power grid is urgently required. This paper presents an aggregator-based interactive charging management scheme adopting interruptible load (IL) pricing, in which the EV aggregator will respond to the load control command of the grid in an EV interactive mode. Charging managements are carried out according to battery state-of-charge and the EV departure time in EV charging stations. A power-altering charging (PAC) control method is proposed to dispatch the EVs charging fairly in a station and guarantee EV owners’ preferences. The method does not require classical iterative procedures or heavy computations; furthermore, it is beneficial for EVs to depart earlier than expected for reasons beyond keeping homeostatic charging. The proposed scheme, which is tested to charge individual EVs well according to its preference, was implemented as part of an “EV Beijing” project. The proposed management scheme provides new insight into EV charging strategy and provides another choice to EV users. Full article

(This article belongs to the Special Issue Energy Storage Systems for Plug-in Electric Vehicles and Vehicle to Power Grid Integration)

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16 pages, 4155 KiB

Open AccessArticle

Development of a Mobile Application for Building Energy Prediction Using Performance Prediction Model

by Yu-Ri Kim and Hae Jin Kang

Energies 2016, 9(3), 160; https://doi.org/10.3390/en9030160 - 4 Mar 2016

Cited by 3 | Viewed by 5224

Abstract

Recently, the Korean government has enforced disclosure of building energy performance, so that such information can help owners and prospective buyers to make suitable investment plans. Such a building energy performance policy of the government makes it mandatory for the building owners to [...] Read more.

Recently, the Korean government has enforced disclosure of building energy performance, so that such information can help owners and prospective buyers to make suitable investment plans. Such a building energy performance policy of the government makes it mandatory for the building owners to obtain engineering audits and thereby evaluate the energy performance levels of their buildings. However, to calculate energy performance levels (i.e., asset rating methodology), a qualified expert needs to have access to at least the full project documentation and/or conduct an on-site inspection of the buildings. Energy performance certification costs a lot of time and money. Moreover, the database of certified buildings is still actually quite small. A need, therefore, is increasing for a simplified and user-friendly energy performance prediction tool for non-specialists. Also, a database which allows building owners and users to compare best practices is required. In this regard, the current study developed a simplified performance prediction model through experimental design, energy simulations and ANOVA (analysis of variance). Furthermore, using the new prediction model, a related mobile application was also developed. Full article

(This article belongs to the Special Issue Energy Conservation in Infrastructures)

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16 pages, 726 KiB

Open AccessArticle

A Biologically-Inspired Power Control Algorithm for Energy-Efficient Cellular Networks

by Hyun-Ho Choi and Jung-Ryun Lee

Energies 2016, 9(3), 161; https://doi.org/10.3390/en9030161 - 4 Mar 2016

Cited by 5 | Viewed by 5118

Abstract

Most of the energy used to operate a cellular network is consumed by a base station (BS), and reducing the transmission power of a BS can therefore afford a substantial reduction in the amount of energy used in a network. In this paper, [...] Read more.

Most of the energy used to operate a cellular network is consumed by a base station (BS), and reducing the transmission power of a BS can therefore afford a substantial reduction in the amount of energy used in a network. In this paper, we propose a distributed transmit power control (TPC) algorithm inspired by bird flocking behavior as a means of improving the energy efficiency of a cellular network. Just as each bird in a flock attempts to match its velocity with the average velocity of adjacent birds, in the proposed algorithm, each mobile station (MS) in a cell matches its rate with the average rate of the co-channel MSs in adjacent cells by controlling the transmit power of its serving BS. We verify that this bio-inspired TPC algorithm using a local rate-average process achieves an exponential convergence and maximizes the minimum rate of the MSs concerned. Simulation results show that the proposed TPC algorithm follows the same convergence properties as the flocking algorithm and also effectively reduces the power consumption at the BSs while maintaining a low outage probability as the inter-cell interference increases; in so doing, it significantly improves the energy efficiency of a cellular network. Full article

(This article belongs to the Special Issue Energy-Efficient and Sustainable Networking)

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19 pages, 2857 KiB

Open AccessArticle

Evaluation of the Fluid Model Approach for the Sizing of Energy Storage in Wave-Wind Energy Systems

by José A. Domínguez-Navarro and Elisabetta Tedeschi

Energies 2016, 9(3), 162; https://doi.org/10.3390/en9030162 - 4 Mar 2016

Cited by 2 | Viewed by 4851

Abstract

The application of energy storage in offshore renewable generation systems allows managing the intrinsic uncertainty of the resources and improving the utilization factor of the electrical network. Optimal storage design algorithms generally have to evaluate the behavior of the whole system thousands times [...] Read more.

The application of energy storage in offshore renewable generation systems allows managing the intrinsic uncertainty of the resources and improving the utilization factor of the electrical network. Optimal storage design algorithms generally have to evaluate the behavior of the whole system thousands times before converging to the optimal solution and the reliability of the results obviously depends on the quality of input data. On the other hand, the utilization of simplified storage models in the design stage can reduce the simulation time drastically, while still providing useful information. The goal of this paper is to evaluate the applicability of a methodology for sizing the energy storage system in a hybrid wind and wave farm, which is based on fluid models. The description and performance of this modeling approach will be introduced and compared to standard design procedures based on extensive simulations. Advantages and limitations of each approach will be underlined and the impact of input data quality will be discussed. Full article

(This article belongs to the Special Issue Tools and Techniques for Economic Delivery of Ocean Energy)

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18 pages, 3819 KiB

Open AccessArticle

Performance Analysis and Modeling of a Tubular Staggered-Tooth Transverse-Flux PM Linear Machine

by Shaohong Zhu, Ping Zheng, Bin Yu, Luming Cheng and Weinan Wang

Energies 2016, 9(3), 163; https://doi.org/10.3390/en9030163 - 8 Mar 2016

Cited by 5 | Viewed by 6329

Abstract

This paper investigates the performance analysis and mathematical modeling of a staggered-tooth transverse-flux permanent magnet linear synchronous machine (STTF-PMLSM), which is characterized by simple structure and low flux leakage. Firstly, the structure advantages and operation principle of the STTF-PMLSM are introduced, and a [...] Read more.

This paper investigates the performance analysis and mathematical modeling of a staggered-tooth transverse-flux permanent magnet linear synchronous machine (STTF-PMLSM), which is characterized by simple structure and low flux leakage. Firstly, the structure advantages and operation principle of the STTF-PMLSM are introduced, and a simplified one phase model is established to investigate the performance of the machine in order to save the computation time. Then, the electromagnetic characteristics, including no-load flux linkage, electromotive force (EMF), inductance, detent force and thrust force, are simulated and analyzed in detail. After that, the theoretical analysis of the detent force, thrust force, and power factor are carried out. And the theoretical analysis results are validated with 3-D finite-element method (FEM). Finally, an improved mathematical model of the machine based on d-q rotating coordinate system is proposed, in which inductance harmonics and coupling between d- and q-axis inductance is considered. The results from the proposed mathematical model are in accordance with the results from 3-D FEM, which proves the validity and effectiveness of the proposed mathematical model. This provides a powerful foundation for the control of the machine. Full article

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12 pages, 6489 KiB

Open AccessArticle

Francis Turbine Blade Design on the Basis of Port Area and Loss Analysis

by Zhenmu Chen, Patrick M. Singh and Young-Do Choi

Energies 2016, 9(3), 164; https://doi.org/10.3390/en9030164 - 4 Mar 2016

Cited by 17 | Viewed by 10264

Abstract

In this study, a Francis turbine with specific speed of 130 m-kW was designed on the basis of the port area and loss analysis. The meridional shape of the runner was designed focusing mainly on the combination of the guide vane loss analysis [...] Read more.

In this study, a Francis turbine with specific speed of 130 m-kW was designed on the basis of the port area and loss analysis. The meridional shape of the runner was designed focusing mainly on the combination of the guide vane loss analysis and experience. The runner blade inlet and outlet angles were designed by calculation of Euler’s head, while the port area of blade was modified by keeping constant angles of the blade at inlet and outlet. The results show that the effect of the port area of runner blade on the flow exit angle from runner passage is significant. A correct flow exit angle reduces the energy loss at the draft tube, thereby improving the efficiency of the turbine. The best efficiency of 92.6% is achieved by this method, which is also similar to the design conditions by the one dimension loss analysis. Full article

(This article belongs to the Special Issue Selected Papers from 5th Asia-Pacific Forum on Renewable Energy)

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11 pages, 3169 KiB

Open AccessArticle

An Effective Approach towards the Immobilization of PtSn Nanoparticles on Noncovalent Modified Multi-Walled Carbon Nanotubes for Ethanol Electrooxidation

by Xi Geng, Yinjie Cen, Richard D. Sisson and Jianyu Liang

Energies 2016, 9(3), 165; https://doi.org/10.3390/en9030165 - 4 Mar 2016

Cited by 8 | Viewed by 7010

Abstract

In this article, we describe an effective method to tether Pt and PtSn nanoparticles (NPs) on polyelectrolyte modified multi-walled carbon nanotubes (MWCNTs) for ethanol electrooxidation. By using a polymer wrapping technique, positively charged polyethyleneimine (PEI) was attached onto carbon nanotubes (CNTs) to provide [...] Read more.

In this article, we describe an effective method to tether Pt and PtSn nanoparticles (NPs) on polyelectrolyte modified multi-walled carbon nanotubes (MWCNTs) for ethanol electrooxidation. By using a polymer wrapping technique, positively charged polyethyleneimine (PEI) was attached onto carbon nanotubes (CNTs) to provide preferential linking sites for metal precursors. Well-dispersed Pt and PtSn nanocrystals (2–5 nm) were subsequently decorated on PEI-functionalized MWCNTs through the polyol reduction method. The successful non-covalent modification of MWCNTs was confirmed by Fourier transform infrared spectroscopy (FTIR) and Zeta potential measurements. Energy dispersive X-ray (EDX) spectrum indicates approximately 20 wt % Pt loading and a desirable Pt:Sn atomic ratio of 1:1. Electrochemical analysis demonstrated that the as-synthesized PtSn/PEI-MWCNTs nanocomposite exhibited improved catalytic activity and higher poison tolerance for ethanol oxidation as compared to Pt/PEI-MWCNTs and commercial Pt/XC-72 catalysts. The enhanced electrochemical performance may be attributed to the uniform dispersion of NPs as well as the mitigating of CO self-poisoning effect by the alloying of Sn element. This modification and synthetic strategy will be studied further to develop a diversity of carbon supported Pt-based hybrid nanomaterials for electrocatalysis. Full article

(This article belongs to the Special Issue Methanol and Alcohol Fuel Cells)

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25 pages, 5673 KiB

Open AccessArticle

Impacts of Climate Change and Anthropogenic Activities on the Ecological Restoration of Wetlands in the Arid Regions of China

by Haibo Wang and Mingguo Ma

Energies 2016, 9(3), 166; https://doi.org/10.3390/en9030166 - 5 Mar 2016

Cited by 22 | Viewed by 6896

Abstract

As an important part of the global ecosystem, wetlands and their dynamics greatly influence regional eco-environment systems. To understand the distributions, change processes and temporal-spatial characteristics of the wetlands of the inland river basin in an arid region (Heihe River Basin, HRB), this [...] Read more.

As an important part of the global ecosystem, wetlands and their dynamics greatly influence regional eco-environment systems. To understand the distributions, change processes and temporal-spatial characteristics of the wetlands of the inland river basin in an arid region (Heihe River Basin, HRB), this paper employed multi-source remote sensing data to facilitate multi-temporal monitoring of the HRB wetland using a wetland information extraction method. First, we performed monitoring of these wetlands for the years 2000, 2007, 2011 and 2014; then, we analyzed the variation characteristics of the spatial-temporal dynamics of the wetlands in the HRB over the last 15 years via the landscape dynamic change model and the transformation matrix. In addition, we studied the possible driving mechanisms of these changes. The research results showed that the total area of the HRB wetlands had decreased by 2959.13 hectares in the last 15 years (Since 2000), and the annual average loss was −1.09%. The dynamics characterizing the HRB wetlands generally presented a trend of slow increase after an initial decrease, which can be classified into three stages. From 2000 to 2007, the total wetland area rapidly decreased; from 2007 to 2011, the area slowly decreased; and from 2011 to 2014, the area gradually increased. The dynamic changing processes characterizing the wetland resources were ascribed to a combination of natural processes and human activities. The main driving mechanisms of wetland dynamic changes include climatic conditions, upper reach water inflows, population, water resources, cultivated area, and policy. The findings of this study can served as reference and support for the conservation and management of wetland resources in the HRB. Full article

(This article belongs to the Special Issue Large Scale LUCC, Ecosystem Service, Water Balance and Energy Use)

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11 pages, 1260 KiB

Open AccessArticle

Effect of the Coordinative Optimization of Interruptible Loads in Primary Frequency Regulation on Frequency Recovery

by Xia Zhou, Wei Li, Mengya Li, Qian Chen, Chaohai Zhang and Jilai Yu

Energies 2016, 9(3), 167; https://doi.org/10.3390/en9030167 - 5 Mar 2016

Cited by 6 | Viewed by 5183

Abstract

When faults and disturbances occur in power systems, backup power resources respond to maintain the system’s frequency, and the frequency recovery effect is related to the primary frequency regulation of the reserve capacity provided by and the response speeds of the system’s generating [...] Read more.

When faults and disturbances occur in power systems, backup power resources respond to maintain the system’s frequency, and the frequency recovery effect is related to the primary frequency regulation of the reserve capacity provided by and the response speeds of the system’s generating units and interruptible loads. The relationships between a system’s frequency and the frequency regulation capacity of the generating units and the interruptible loads are different. In this paper, an index for the frequency recovery effect is proposed based on the static frequency adjustment coefficient of the interruptible load and the adjustment coefficients of the generating units, and an optimization model of an interruptible load participating in primary frequency regulation is built with the objective of minimizing the cost of the primary frequency regulation reserve that uses the system’s frequency recovery effect as a constraint. The simulation results verify the validity of the model. Full article

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15 pages, 840 KiB

Open AccessArticle

Improved Spatio-Temporal Linear Models for Very Short-Term Wind Speed Forecasting

by Tansu Filik

Energies 2016, 9(3), 168; https://doi.org/10.3390/en9030168 - 7 Mar 2016

Cited by 20 | Viewed by 4817

Abstract

In this paper, the spatio-temporal (multi-channel) linear models, which use temporal and the neighbouring wind speed measurements around the target location, for the best short-term wind speed forecasting are investigated. Multi-channel autoregressive moving average (MARMA) models are formulated in matrix form and efficient [...] Read more.

In this paper, the spatio-temporal (multi-channel) linear models, which use temporal and the neighbouring wind speed measurements around the target location, for the best short-term wind speed forecasting are investigated. Multi-channel autoregressive moving average (MARMA) models are formulated in matrix form and efficient linear prediction coefficient estimation techniques are first used and revised. It is shown in detail how to apply these MARMA models to the spatially distributed wind speed measurements. The proposed MARMA models are tested using real wind speed measurements which are collected from the five stations around Canakkale region of Turkey. According to the test results, considerable improvements are observed over the well known persistence, autoregressive (AR) and multi-channel/vector autoregressive (VAR) models. It is also shown that the model can predict wind speed very fast (in milliseconds) which is suitable for the immediate short-term forecasting. Full article

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28 pages, 5705 KiB

Open AccessArticle

The Behaviour of Fracture Growth in Sedimentary Rocks: A Numerical Study Based on Hydraulic Fracturing Processes

by Lianchong Li, Yingjie Xia, Bo Huang, Liaoyuan Zhang, Ming Li and Aishan Li

Energies 2016, 9(3), 169; https://doi.org/10.3390/en9030169 - 7 Mar 2016

Cited by 47 | Viewed by 8472

Abstract

To capture the hydraulic fractures in heterogeneous and layered rocks, a numerical code that can consider the coupled effects of fluid flow, damage, and stress field in rocks is presented. Based on the characteristics of a typical thin and inter-bedded sedimentary reservoir, China, [...] Read more.

To capture the hydraulic fractures in heterogeneous and layered rocks, a numerical code that can consider the coupled effects of fluid flow, damage, and stress field in rocks is presented. Based on the characteristics of a typical thin and inter-bedded sedimentary reservoir, China, a series of simulations on the hydraulic fracturing are performed. In the simulations, three points, i.e., (1) confining stresses, representing the effect of in situ stresses, (2) strength of the interfaces, and (3) material properties of the layers on either side of the interface, are crucial in fracturing across interfaces between two adjacent rock layers. Numerical results show that the hydrofracture propagation within a layered sequence of sedimentary rocks is controlled by changing in situ stresses, interface properties, and lithologies. The path of the hydraulic fracture is characterized by numerous deflections, branchings, and terminations. Four types of potential interaction, i.e., penetration, arrest, T-shaped branching, and offset, between a hydrofracture and an interface within the layered rocks are formed. Discontinuous composite fracture segments resulting from out-of-plane growth of fractures provide a less permeable path for fluids, gas, and oil than a continuous planar composite fracture, which are one of the sources of the high treating pressures and reduced fracture volume. Full article

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17 pages, 2490 KiB

Open AccessArticle

Analysis of a Vertical Flat Heat Pipe Using Potassium Working Fluid and a Wick of Compressed Nickel Foam

by Geir Hansen, Erling Næss and Kolbeinn Kristjansson

Energies 2016, 9(3), 170; https://doi.org/10.3390/en9030170 - 7 Mar 2016

Cited by 10 | Viewed by 6196

Abstract

Heat at high temperatures, in this work 400–650 °C, can be recovered by use of cooling panels/heat pipes in the walls of aluminum electrolysis cells. For this application a flat vertical heat pipe for heat transfer from a unilateral heat source was analyzed [...] Read more.

Heat at high temperatures, in this work 400–650 °C, can be recovered by use of cooling panels/heat pipes in the walls of aluminum electrolysis cells. For this application a flat vertical heat pipe for heat transfer from a unilateral heat source was analyzed theoretically and in the laboratory, with special emphasis on the performance of the wick. In this heat pipe a wick of compressed nickel foam covered only the evaporator surface, and potassium was used as the working fluid. The magnitudes of key thermal resistances were estimated analytically and compared. Operating temperatures and wick performance limits obtained experimentally were compared to predictions. Thermal deformation due to unilateral heat flux was analyzed by the use of COMSOL Multiphysics^®. The consequences of hot spots at different locations on the wick were analyzed by use of a numerical 2D model. A vertical rectangular wick was shown to be most vulnerable to hot spots at the upper corners. Full article

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17 pages, 7496 KiB

Open AccessArticle

Design and Application of a Power Unit to Use Plug-In Electric Vehicles as an Uninterruptible Power Supply

by Gorkem Sen, Ali Rifat Boynuegri, Mehmet Uzunoglu, Ozan Erdinc and João P. S. Catalão

Energies 2016, 9(3), 171; https://doi.org/10.3390/en9030171 - 7 Mar 2016

Cited by 8 | Viewed by 9162

Abstract

Grid-enabled vehicles (GEVs) such as plug-in electric vehicles present environmental and energy sustainability advantages compared to conventional vehicles. GEV runs solely on power generated by its own battery group, which supplies power to its electric motor. This battery group can be charged from [...] Read more.

Grid-enabled vehicles (GEVs) such as plug-in electric vehicles present environmental and energy sustainability advantages compared to conventional vehicles. GEV runs solely on power generated by its own battery group, which supplies power to its electric motor. This battery group can be charged from external electric sources. Nowadays, the interaction of GEV with the power grid is unidirectional by the charging process. However, GEV can be operated bi-directionally by modifying its power unit. In such operating conditions, GEV can operate as an uninterruptible power supply (UPS) and satisfy a portion or the total energy demand of the consumption center independent from utility grid, which is known as vehicle-to-home (V2H). In this paper, a power unit is developed for GEVs in the laboratory to conduct simulation and experimental studies to test the performance of GEVs as a UPS unit in V2H mode at the time of need. The activation and deactivation of the power unit and islanding protection unit are examined when energy is interrupted. Full article

(This article belongs to the Special Issue Electric and Hybrid Vehicles)

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12 pages, 203 KiB

Open AccessReview

Reducing Energy Use and Carbon Emissions: A Critical Assessment of Small-Group Interventions

by Jill Fisher and Katherine Irvine

Energies 2016, 9(3), 172; https://doi.org/10.3390/en9030172 - 8 Mar 2016

Cited by 12 | Viewed by 4838

Abstract

Motivating individuals to decrease the environmental impact of their lifestyles could play an important role in reducing energy use and meeting carbon reduction commitments in developed countries. Few approaches which encourage voluntary changes in behaviour result in substantial reductions in energy use, however, [...] Read more.

Motivating individuals to decrease the environmental impact of their lifestyles could play an important role in reducing energy use and meeting carbon reduction commitments in developed countries. Few approaches which encourage voluntary changes in behaviour result in substantial reductions in energy use, however, particularly over the longer term. An exception to this general trend is small-group interventions which use group participation and which target collections of behaviours including energy use. Through a critical examination of published data this paper considers the energy and carbon emission reductions achieved by such initiatives, the durability of those reductions, and the common elements which may contribute to their success. Participants in small-group interventions reduced their energy use and carbon emissions by approximately 20% within a year. There is also some evidence that these reductions were lasting and that participants continued to make changes to their lifestyles after the end of the intervention. The reasonable person model (RPM) is proposed as a useful framework for understanding the success of these small-group interventions. Examination of small-group interventions suggests that they provide settings which are supportive of informational needs, and that this may be important to their success in promoting substantial and durable decreases in energy use. Full article

(This article belongs to the Special Issue Multi-Disciplinary Perspectives on Energy and Sustainable Development)

11 pages, 1486 KiB

Open AccessTechnical Note

Evaluation of Cell Disruption of Chlorella Vulgaris by Pressure-Assisted Ozonation and Ultrasonication

by Yuanxing Huang, Shengnan Qin, Daofang Zhang, Liang Li and Yan Mu

Energies 2016, 9(3), 173; https://doi.org/10.3390/en9030173 - 8 Mar 2016

Cited by 28 | Viewed by 6884

Abstract

This study evaluated the effectiveness of pressure-assisted ozonation (PAO) in Chlorella vulgaris (C. vulgaris) cell disruption, and compared the disruption result with that of the ultrasonication (US) by using four quantification indicators: cell counting, ultra violet (UV) absorbance, turbidity and visible [...] Read more.

This study evaluated the effectiveness of pressure-assisted ozonation (PAO) in Chlorella vulgaris (C. vulgaris) cell disruption, and compared the disruption result with that of the ultrasonication (US) by using four quantification indicators: cell counting, ultra violet (UV) absorbance, turbidity and visible light absorbance. It was found that under the condition of 0.8 MPa and 80 cycles, PAO treatment achieved cell rupture of 80.3%, with the power of 1080 W and treatment time of 60 min, US achieved cell rupture of 83.8%. Cell counting was a reliable indicator and applicable to both PAO and US treatments. Turbidity and visible light absorbance gave similar results and featured as the simplest operation. UV absorbance reflected the metabolite release due to cell breakage; however, it was less reproducible when it was applied to quantify the cell rupture by PAO. Its trend indicated that during cell disruption metabolite degradation occurred, especially after significant rupture in the case of excessive PAO treatment. The cellular morphology of C. vulgaris cells during PAO and US treatments was investigated by scanning electron microscope (SEM) which certified that the cells damage was caused by both physical and chemical attack. Full article

(This article belongs to the Special Issue Algae Fuel 2015)

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17 pages, 3231 KiB

Open AccessArticle

Application of the Extension Taguchi Method to Optimal Capability Planning of a Stand-alone Power System

by Meng-Hui Wang, Mei-Ling Huang, Zi-Yi Zhan and Chong-Jie Huang

Energies 2016, 9(3), 174; https://doi.org/10.3390/en9030174 - 8 Mar 2016

Cited by 8 | Viewed by 4725

Abstract

An Extension Taguchi Method (ETM) is proposed on the optimized allocation of equipment capacity for solar cell power generation, wind power generation, full cells, electrolyzer and hydrogen tanks. The ETM is based on the domain knowledge containing the product specifications and allocation levels [...] Read more.

An Extension Taguchi Method (ETM) is proposed on the optimized allocation of equipment capacity for solar cell power generation, wind power generation, full cells, electrolyzer and hydrogen tanks. The ETM is based on the domain knowledge containing the product specifications and allocation levels provided by suppliers and design factors since most of the renewable energy equipment available in the market comes with a specific capacity. A proper orthogonal array is used to collect 18 sets of simulation responses. The extension theory is introduced to determine the correlation function, and factor effects are used to identify the optimized capacity allocation. The hours of power shortage are simulated using Matlab for all capacity allocations at the lowest establishment cost and the optimized capacity allocation of loss of load probability (LOLP). Finally, the extension theory, extension AHP theory, ETM and Analytic Hierarchy Process (AHP) are used to determine the optimized capacity allocation of the system. Results are compared for the above four optimization simulation methods and verify that the proposed ETM surpasses the others on achieving the optimized capacity allocation. Full article

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17 pages, 1575 KiB

Open AccessEditor’s ChoiceArticle

Optimal Power Management Strategy for Energy Storage with Stochastic Loads

by Stefano Pietrosanti, William Holderbaum and Victor M. Becerra

Energies 2016, 9(3), 175; https://doi.org/10.3390/en9030175 - 9 Mar 2016

Cited by 23 | Viewed by 8413

Abstract

In this paper, a power management strategy (PMS) has been developed for the control of energy storage in a system subjected to loads of random duration. The PMS minimises the costs associated with the energy consumption of specific systems powered by a primary [...] Read more.

In this paper, a power management strategy (PMS) has been developed for the control of energy storage in a system subjected to loads of random duration. The PMS minimises the costs associated with the energy consumption of specific systems powered by a primary energy source and equipped with energy storage, under the assumption that the statistical distribution of load durations is known. By including the variability of the load in the cost function, it was possible to define the optimality criteria for the power flow of the storage. Numerical calculations have been performed obtaining the control strategies associated with the global minimum in energy costs, for a wide range of initial conditions of the system. The results of the calculations have been tested on a MATLAB/Simulink model of a rubber tyre gantry (RTG) crane equipped with a flywheel energy storage system (FESS) and subjected to a test cycle, which corresponds to the real operation of a crane in the Port of Felixstowe. The results of the model show increased energy savings and reduced peak power demand with respect to existing control strategies, indicating considerable potential savings for port operators in terms of energy and maintenance costs. Full article

(This article belongs to the Special Issue Control of Energy Storage)

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16 pages, 2427 KiB

Open AccessArticle

Distributed Renewable Generation and Storage System Sizing Based on Smart Dispatch of Microgrids

by Raji Atia and Noboru Yamada

Energies 2016, 9(3), 176; https://doi.org/10.3390/en9030176 - 9 Mar 2016

Cited by 23 | Viewed by 5794

Abstract

This paper considers the contribution of independent owners (IOs) operating within microgrids (MGs) toward green power generation in deregulated energy markets. An optimization scheme is introduced for sizing distributed renewable generation (DRG) and a distributed energy storage system (DESS) based on a novel [...] Read more.

This paper considers the contribution of independent owners (IOs) operating within microgrids (MGs) toward green power generation in deregulated energy markets. An optimization scheme is introduced for sizing distributed renewable generation (DRG) and a distributed energy storage system (DESS) based on a novel energy management system (EMS) that accounts for demand response (DR), DESS dispatch and performance degradation, dynamic pricing environments, power distribution loss and irregular renewable generation. The proposed EMS utilizes an iterative Newton-Raphson linear programming algorithm that schedules resources in order to minimize the objective function, to deal with the complicated nonlinear nature of the problem and to enable efficient long-term assessments. The EMS is used to evaluate candidate solutions that are generated by a genetic algorithm (GA) to determine the optimal combination of DRG and DESS. A case study for IEEE 34-bus distribution MG in Okinawa, Japan, is used for testing the algorithm and analyzing the potential for IO/MG investments and their strategies. Full article

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13 pages, 4848 KiB

Open AccessArticle

Impact of Urban Morphology on Infiltration-Induced Building Energy Consumption

by Andrius Jurelionis and Demetri G. Bouris

Energies 2016, 9(3), 177; https://doi.org/10.3390/en9030177 - 9 Mar 2016

Cited by 22 | Viewed by 7158

Abstract

External air movement within built neighborhoods is highly dependent on the morphological parameters of buildings and surroundings, including building height and street cavity ratios. In this paper, computational fluid dynamics (CFD) methods were applied to calculate surface pressure distributions on building surfaces for [...] Read more.

External air movement within built neighborhoods is highly dependent on the morphological parameters of buildings and surroundings, including building height and street cavity ratios. In this paper, computational fluid dynamics (CFD) methods were applied to calculate surface pressure distributions on building surfaces for three city models and two wind directions. Pressure differences and air change rates were derived in order to predict the heating load required to cover heat losses caused by air infiltration. The models were based on typical urban layouts for three cities, and were designed of approximately equal built volumes and equal air permeability parameters. Simulations of the three analyzed building layouts resulted in up to 41% differences in air change rates and heat losses caused by air infiltration. In the present study, wind direction did not have a significant impact on the relative difference between the models, however sideward wind direction caused higher air change rates and heat losses for all simulated layouts. Full article

(This article belongs to the Special Issue Energy Efficient City)

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13 pages, 4246 KiB

Open AccessArticle

Spent Nuclear Fuel Management: Levelized Cost of Electricity Generation and Analysis of Various Production Scenarios

by Laura Rodriguez-Penalonga, Beatriz Yolanda Moratilla Soria, Paula Ocaña-Pastor, Paula Martín-Cañas, Borja Belda-Sánchez, Natalia Cortes-Sanz, Mathilde Estadieu, José Ignacio Linares-Hurtado, José Manuel Vidal-Bernardez and Marta Niño-Serrano

Energies 2016, 9(3), 178; https://doi.org/10.3390/en9030178 - 10 Mar 2016

Cited by 5 | Viewed by 5409

Abstract

This article aims to analyze the results of an economic study carried out to compare the influence of nuclear production capacity in different countries. The analysis is based on LCOEs (levelized cost of electricity) for three back-end strategies: open cycle, closed cycle and [...] Read more.

This article aims to analyze the results of an economic study carried out to compare the influence of nuclear production capacity in different countries. The analysis is based on LCOEs (levelized cost of electricity) for three back-end strategies: open cycle, closed cycle and advanced closed cycle. The results show that costs are not a relevant criteria in order to select an energy policy for the spent nuclear fuel management. Full article

(This article belongs to the Special Issue Sustainable Future of Nuclear Power)

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18 pages, 6723 KiB

Open AccessArticle

A New Robust Decoupled Control of the Stator Active and Reactive Currents for Grid-Connected Doubly-Fed Induction Generators

by Ahmad Bashar Ataji, Yushi Miura, Toshifumi Ise and Hiroki Tanaka

Energies 2016, 9(3), 179; https://doi.org/10.3390/en9030179 - 9 Mar 2016

Cited by 4 | Viewed by 5661

Abstract

This paper addresses the grid-connected variable speed doubly-fed induction generator, and proposes a new decoupled control to replace the conventional decoupled active and reactive powers (P-Q) control. The proposed decoupled control is based on decoupling the stator active and reactive currents, in contrast [...] Read more.

This paper addresses the grid-connected variable speed doubly-fed induction generator, and proposes a new decoupled control to replace the conventional decoupled active and reactive powers (P-Q) control. The proposed decoupled control is based on decoupling the stator active and reactive currents, in contrast with the conventional decoupled P-Q control, which is based on decoupling the stator active and reactive powers by forcing the stator d- or q-voltage to zero. The proposed decoupled control has all the advantages of the conventional decoupled P-Q control such as constant switching frequency and robustness against slip angle inaccuracy, and it has some additional advantages: The proposed control requires less machine parameters; for the controller design, it requires the stator-to-rotor turns ratio only; for the online calculation, it does not requires any machine parameter. The proposed decoupled control is more flexible and robust since the control is independent of the grid voltage orientation. It is robust against variation in the grid voltage amplitude. Several experiments are carried out using a 1.1 kW doubly-fed induction generator (DFIG), and the results support the proposed decoupled control and demonstrate some of its advantages. Full article

(This article belongs to the Special Issue Microgrids 2016)

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15 pages, 9300 KiB

Open AccessArticle

A High-Gain Three-Port Power Converter with Fuel Cell, Battery Sources and Stacked Output for Hybrid Electric Vehicles and DC-Microgrids

by Ching-Ming Lai and Ming-Ji Yang

Energies 2016, 9(3), 180; https://doi.org/10.3390/en9030180 - 9 Mar 2016

Cited by 29 | Viewed by 8314

Abstract

This paper proposes a novel high-gain three-port power converter with fuel cell (FC), battery sources and stacked output for a hybrid electric vehicle (HEV) connected to a dc-microgrid. In the proposed power converter, the load power can be flexibly distributed between the input [...] Read more.

This paper proposes a novel high-gain three-port power converter with fuel cell (FC), battery sources and stacked output for a hybrid electric vehicle (HEV) connected to a dc-microgrid. In the proposed power converter, the load power can be flexibly distributed between the input sources. Moreover, the charging or discharging of the battery storage device can be controlled effectively using the FC source. The proposed converter has several outputs in series to achieve a high-voltage output, which makes it suitable for interfacing with the HEV and dc-microgrid. On the basis of the charging and discharging states of the battery storage device, two power operation modes are defined. The proposed power converter comprises only one boost inductor integrated with a flyback transformer; the boost and flyback circuit output terminals are stacked to increase the output voltage gain and reduce the voltage stress on the power devices. This paper presents the circuit configuration, operating principle, and steady-state analysis of the proposed converter, and experiments conducted on a laboratory prototype are presented to verify its effectiveness. Full article

(This article belongs to the Special Issue Energy Storage Systems for Plug-in Electric Vehicles and Vehicle to Power Grid Integration)

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19 pages, 6343 KiB

Open AccessArticle

A Study on Development of a Cost Optimal and Energy Saving Building Model: Focused on Industrial Building

by Hye Yeon Kim and Hae Jin Kang

Energies 2016, 9(3), 181; https://doi.org/10.3390/en9030181 - 12 Mar 2016

Cited by 12 | Viewed by 5503

Abstract

This study suggests an optimization method for the life cycle cost (LCC) in an economic feasibility analysis when applying energy saving techniques in the early design stage of a building. Literature and previous studies were reviewed to select appropriate optimization and LCC analysis [...] Read more.

This study suggests an optimization method for the life cycle cost (LCC) in an economic feasibility analysis when applying energy saving techniques in the early design stage of a building. Literature and previous studies were reviewed to select appropriate optimization and LCC analysis techniques. The energy simulation (Energy Plus) and computational program (MATLAB) were linked to provide an automated optimization process. From the results, it is suggested that this process could outline the cost optimization model with which it is possible to minimize the LCC. To aid in understanding the model, a case study on an industrial building was performed to outline the operations of the cost optimization model including energy savings. An energy optimization model was also presented to illustrate the need for the cost optimization model. Full article

(This article belongs to the Special Issue Energy Conservation in Infrastructures)

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17 pages, 4571 KiB

Open AccessArticle

A Half-Bridge Voltage Balancer with New Controller for Bipolar DC Distribution Systems

by Byung-Moon Han

Energies 2016, 9(3), 182; https://doi.org/10.3390/en9030182 - 10 Mar 2016

Cited by 20 | Viewed by 7809

Abstract

This paper proposes a half-bridge voltage balancer with a new controller for bipolar DC distribution systems. The proposed control scheme consists of two cascaded Proportional Integral (PI) controls rather than one PI control for balancing the pole voltage. In order to confirm the [...] Read more.

This paper proposes a half-bridge voltage balancer with a new controller for bipolar DC distribution systems. The proposed control scheme consists of two cascaded Proportional Integral (PI) controls rather than one PI control for balancing the pole voltage. In order to confirm the excellence of voltage balancing performance, a typical bipolar DC distribution system including a half-bridge voltage balancer with proposed controller was analyzed by computer simulations. Experiments with a scaled prototype were also carried out to confirm the simulation results. The half-bridge voltage balancer with proposed controller shows better performance than the half-bridge voltage balancer with one PI control for balancing the pole voltage. Full article

(This article belongs to the Special Issue Microgrids 2016)

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11 pages, 4045 KiB

Open AccessArticle

Thermal Stability of Hexamethyldisiloxane (MM) for High-Temperature Organic Rankine Cycle (ORC)

by Markus Preißinger and Dieter Brüggemann

Energies 2016, 9(3), 183; https://doi.org/10.3390/en9030183 - 10 Mar 2016

Cited by 70 | Viewed by 6926

Abstract

The design of efficient Organic Rankine Cycle (ORC) units for the usage of industrial waste heat at high temperatures requires direct contact evaporators without intermediate thermal oil circuits. Therefore, the thermal stability of high-temperature working fluids gains importance. In this study, the thermal [...] Read more.

The design of efficient Organic Rankine Cycle (ORC) units for the usage of industrial waste heat at high temperatures requires direct contact evaporators without intermediate thermal oil circuits. Therefore, the thermal stability of high-temperature working fluids gains importance. In this study, the thermal degradation of hexamethyldisiloxane (MM) is investigated in an electrically heated tube. Qualitative results concerning remarks on degradation products as well as quantitative results like the annual degradation rate are presented. It is shown that MM is stable up to a temperature of 300 °C with annual degradation rates of less than 3.5%. Furthermore, the break of a silicon–carbon bond can be a main chemical reaction that influences the thermal degradation. Finally, it is discussed how the results may impact the future design of ORC units. Full article

(This article belongs to the Special Issue Selected Papers from the 3rd International Seminar on ORC Power Systems)

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15 pages, 2222 KiB

Open AccessArticle

Comparisons of Modeling and State of Charge Estimation for Lithium-Ion Battery Based on Fractional Order and Integral Order Methods

by Renxin Xiao, Jiangwei Shen, Xiaoyu Li, Wensheng Yan, Erdong Pan and Zheng Chen

Energies 2016, 9(3), 184; https://doi.org/10.3390/en9030184 - 10 Mar 2016

Cited by 77 | Viewed by 6500

Abstract

In order to properly manage lithium-ion batteries of electric vehicles (EVs), it is essential to build the battery model and estimate the state of charge (SOC). In this paper, the fractional order forms of Thevenin and partnership for a new generation of vehicles [...] Read more.

In order to properly manage lithium-ion batteries of electric vehicles (EVs), it is essential to build the battery model and estimate the state of charge (SOC). In this paper, the fractional order forms of Thevenin and partnership for a new generation of vehicles (PNGV) models are built, of which the model parameters including the fractional orders and the corresponding resistance and capacitance values are simultaneously identified based on genetic algorithm (GA). The relationships between different model parameters and SOC are established and analyzed. The calculation precisions of the fractional order model (FOM) and integral order model (IOM) are validated and compared under hybrid test cycles. Finally, extended Kalman filter (EKF) is employed to estimate the SOC based on different models. The results prove that the FOMs can simulate the output voltage more accurately and the fractional order EKF (FOEKF) can estimate the SOC more precisely under dynamic conditions. Full article

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8 pages, 3950 KiB

Open AccessArticle

Shape Design of the Duct for Tidal Converters Using Both Numerical and Experimental Approaches (pre-2015)

by Chul H. Jo, Do Y. Kim, Su J. Hwang and Chan H. Goo

Energies 2016, 9(3), 185; https://doi.org/10.3390/en9030185 - 11 Mar 2016

Cited by 13 | Viewed by 5007

Abstract

Recently, focus has been placed on ocean energy resources because environmental concerns regarding the exploitation of hydrocarbons are increasing. Among the various ocean energy sources, tidal current power (TCP) is recognized as the most promising energy source in terms of predictability and reliability. [...] Read more.

Recently, focus has been placed on ocean energy resources because environmental concerns regarding the exploitation of hydrocarbons are increasing. Among the various ocean energy sources, tidal current power (TCP) is recognized as the most promising energy source in terms of predictability and reliability. The enormous energy potential in TCP fields has been exploited by installing TCP systems. The flow velocity is the most important factor for power estimation of a tidal current power system. The kinetic energy of the flow is proportional to the cube of the flow’s velocity, and velocity is a critical variable in the performance of the system. Since the duct can accelerate the flow velocity, its use could expand the applicable areas of tidal devices to relatively low velocity sites. The inclined angle of the duct and the shapes of inlet and outlet affect the acceleration rates of the flow inside the duct. In addition, the volume of the duct can affect the flow velocity amplification performance. To investigate the effects of parameters that increase the flow velocity, a series of simulations are performed using the commercial computational fluid dynamics (CFD) code ANSYS-CFX. Experimental investigations were conducted using a circulation water channel (CWC). Full article

(This article belongs to the Special Issue Selected Papers from 5th Asia-Pacific Forum on Renewable Energy)

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17 pages, 662 KiB

Open AccessArticle

Electric Vehicle Charging and Discharging Coordination on Distribution Network Using Multi-Objective Particle Swarm Optimization and Fuzzy Decision Making

by Dongqi Liu, Yaonan Wang and Yongpeng Shen

Energies 2016, 9(3), 186; https://doi.org/10.3390/en9030186 - 11 Mar 2016

Cited by 41 | Viewed by 8225

Abstract

This paper proposed a optimal strategy for coordinated operation of electric vehicles (EVs) charging and discharging with wind-thermal system. By aggregating a large number of EVs, the huge total battery capacity is sufficient to stabilize the disturbance of the transmission grid. Hence, a [...] Read more.

This paper proposed a optimal strategy for coordinated operation of electric vehicles (EVs) charging and discharging with wind-thermal system. By aggregating a large number of EVs, the huge total battery capacity is sufficient to stabilize the disturbance of the transmission grid. Hence, a dynamic environmental dispatch model which coordinates a cluster of charging and discharging controllable EV units with wind farms and thermal plants is proposed. A multi-objective particle swarm optimization (MOPSO) algorithm and a fuzzy decision maker are put forward for the simultaneous optimization of grid operating cost, CO₂ emissions, wind curtailment, and EV users’ cost. Simulations are done in a 30 node system containing three traditional thermal plants, two carbon capture and storage (CCS) thermal plants, two wind farms, and six EV aggregations. Contrast of strategies under different EV charging/discharging price is also discussed. The results are presented to prove the effectiveness of the proposed strategy. Full article

(This article belongs to the Special Issue Microgrids 2016)

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17 pages, 4947 KiB

Open AccessArticle

Catalytic Flash Pyrolysis of Biomass Using Different Types of Zeolite and Online Vapor Fractionation

by Ali Imran, Eddy A. Bramer, Kulathuiyer Seshan and Gerrit Brem

Energies 2016, 9(3), 187; https://doi.org/10.3390/en9030187 - 11 Mar 2016

Cited by 49 | Viewed by 7033

Abstract

Bio-oil produced from conventional flash pyrolysis has poor quality and requires expensive upgrading before it can be used as a transportation fuel. In this work, a high quality bio-oil has been produced using a novel approach where flash pyrolysis, catalysis and fractionation of [...] Read more.

Bio-oil produced from conventional flash pyrolysis has poor quality and requires expensive upgrading before it can be used as a transportation fuel. In this work, a high quality bio-oil has been produced using a novel approach where flash pyrolysis, catalysis and fractionation of pyrolysis vapors using two stage condensation are combined in a single process unit. A bench scale unit of 1 kg/h feedstock capacity is used for catalytic pyrolysis in an entrained down-flow reactor system equipped with two-staged condensation of the pyrolysis vapor. Zeolite-based catalysts are investigated to study the effect of varying acidities of faujasite Y zeolites, zeolite structures (ZSM5), different catalyst to biomass ratios and different catalytic pyrolysis temperatures. Low catalyst/biomass ratios did not show any significant improvements in the bio-oil quality, while high catalyst/biomass ratios showed an effective deoxygenation of the bio-oil. The application of zeolites decreased the organic liquid yield due to the increased production of non-condensables, primarily hydrocarbons. The catalytically produced bio-oil was less viscous and zeolites were effective at cracking heavy molecular weight compounds in the bio-oil. Acidic zeolites, H-Y and H-ZSM5, increased the desirable chemical compounds in the bio-oil such as phenols, furans and hydrocarbon, and reduced the undesired compounds such as acids. On the other hand reducing the acidity of zeolites reduced some of the undesired compounds in the bio-oil such as ketones and aldehydes. The performance of H-Y was superior to that of the rest of zeolites studied: bio-oil of high chemical and calorific value was produced with a high organic liquid yield and low oxygen content. H-ZSM5 was a close competitor to H-Y in performance but with a lower yield of bio-oil. Online fractionation of catalytic pyrolysis vapors was employed by controlling the condenser temperature and proved to be a successful process parameter to tailor the desired bio-oil properties. A high calorific value bio-oil having up to 90% organics was produced using two staged condensation of catalytic pyrolysis vapor. Zeolite-based acidic catalysts can be used for selective deoxygenation, and the catalytic bio-oil quality can be further improved with staged vapor condensation. Full article

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20 pages, 2621 KiB

Open AccessArticle

Measuring the Actual Energy Cost Performance of Green Buildings: A Test of the Earned Value Management Approach

by Luay N. Dwaikat and Kherun N. Ali

Energies 2016, 9(3), 188; https://doi.org/10.3390/en9030188 - 11 Mar 2016

Cited by 14 | Viewed by 8324

Abstract

Reduced energy consumption is a key aspect of the green building. Nonetheless, research indicates that there is a performance gap between the predicted and the actual energy performance once buildings are occupied, which implies a cost deviation from the anticipated energy cost performance. [...] Read more.

Reduced energy consumption is a key aspect of the green building. Nonetheless, research indicates that there is a performance gap between the predicted and the actual energy performance once buildings are occupied, which implies a cost deviation from the anticipated energy cost performance. However, the cost deviation also might result from lower or higher energy rates than expected. As an appropriate research methodology for existing theory testing, case study research strategy was adopted to empirically examine the earned value management (EVM) approach to measure the actual life cycle cost performance of energy in green buildings. With slight methodological and terminological adaptations, it is found that the EVM approach can be applied to conduct a holistic cost performance measurement of the actual energy consumption in green buildings. The strength of the earned value approach is that it allows for detecting whether the energy cost saving or overrun results from lower or higher energy consumption, or from actual energy rate variations. The earned value approach allows for quantifying each cost variance independently, which is a significant aspect of actual energy cost performance measurement in green buildings. Full article

(This article belongs to the Special Issue Energy Efficient Building Design 2016)

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17 pages, 4127 KiB

Open AccessFeature PaperArticle

Phenol-Formaldehyde Resin-Based Carbons for CO₂ Separation at Sub-Atmospheric Pressures

by Noelia Álvarez-Gutiérrez, María Victoria Gil, María Martínez, Fernando Rubiera and Covadonga Pevida

Energies 2016, 9(3), 189; https://doi.org/10.3390/en9030189 - 11 Mar 2016

Cited by 13 | Viewed by 6312

Abstract

The challenge of developing effective separation and purification technologies that leave much smaller energy footprints is greater for carbon dioxide (CO₂) than for other gases. In addition to its involvement in climate change, CO₂ is present as an impurity in [...] Read more.

The challenge of developing effective separation and purification technologies that leave much smaller energy footprints is greater for carbon dioxide (CO₂) than for other gases. In addition to its involvement in climate change, CO₂ is present as an impurity in biogas and bio-hydrogen (biological production by dark fermentation), in post-combustion processes (flue gas, CO₂-N₂) and many other gas streams. Selected phenol-formaldehyde resin-based activated carbons prepared in our laboratory have been evaluated under static conditions (adsorption isotherms) as potential adsorbents for CO₂ separation at sub-atmospheric pressures, i.e., in post-combustion processes or from biogas and bio-hydrogen streams. CO₂, H₂, N₂, and CH₄ adsorption isotherms at 25 °C and up to 100 kPa were obtained using a volumetric equipment and were correlated by applying the Sips model. Adsorption equilibrium was then predicted for multicomponent gas mixtures by extending the multicomponent Sips model and the Ideal Adsorbed Solution Theory (IAST) in conjunction with the Sips model. The CO₂ uptakes of the resin-derived carbons from CO₂-CH₄, CO₂-H₂, and CO₂-N₂ at atmospheric pressure were greater than those of the reference commercial carbon (Calgon BPL). The performance of the resin-derived carbons in terms of equilibrium of adsorption seems therefore relevant to CO₂ separation in post-combustion (flue gas, CO₂-N₂) and in hydrogen fermentation (CO₂-H₂, CO₂-CH₄). Full article

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23 pages, 12397 KiB

Open AccessArticle

An Improved Current Control Strategy for a Grid-Connected Inverter under Distorted Grid Conditions

by Ngoc Bao Lai and Kyeong-Hwa Kim

Energies 2016, 9(3), 190; https://doi.org/10.3390/en9030190 - 12 Mar 2016

Cited by 33 | Viewed by 8197

Abstract

This paper presents an improved current control strategy for a three-phase grid-connected inverter under distorted grid conditions. The main challenge associated with the grid-connected inverter in distributed generation (DG) systems is to maintain the harmonic contents in output current below the specified values [...] Read more.

This paper presents an improved current control strategy for a three-phase grid-connected inverter under distorted grid conditions. The main challenge associated with the grid-connected inverter in distributed generation (DG) systems is to maintain the harmonic contents in output current below the specified values even when the grid is subject to uncertain disturbances such as harmonic distortion. To overcome such a challenge, an improved current control scheme is proposed for a grid-connected inverter, in which the fundamental and harmonic currents are independently controlled by a proportional-integral (PI) decoupling controller and a predictive basis controller, respectively. The controller design approach is based on the model decomposition method, where the measured inverter currents and grid voltages are divided into the fundamental and harmonic components by means of moving average filters (MAFs). Moreover, to detect the angular displacement and angular frequency with better accuracy, even in the presence of the grid disturbance, the MAF is also introduced to implement an enhanced phase-lock loop (PLL) structure. Theoretical analyses as well as comparative simulation results demonstrate that the proposed control scheme can effectively compensate the uncertainties caused by the grid voltages with fast transient response. To validate the feasibility of the proposed scheme, the whole control algorithms are implemented on 2 kVA three-phase grid-connected inverter system using 32-bit floating-point DSP TMS320F28335. As a result, the proposed scheme is an attractive way to control a grid-connected inverter under adverse grid conditions. Full article

(This article belongs to the Special Issue Optimal and Neural Network Control for Renewables and Electric Power and Energy Systems)

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19 pages, 3546 KiB

Open AccessArticle

Climate Change and Increased Irrigation Demands: What Is Left for Hydropower Generation? Results from Two Semi-Arid Basins

by Tor Haakon Bakken, Christian Almestad, Jørgen Melhuus Rugelbak, Marisa Escobar, Steven Micko and Knut Alfredsen

Energies 2016, 9(3), 191; https://doi.org/10.3390/en9030191 - 14 Mar 2016

Cited by 9 | Viewed by 7061

Abstract

In this study, we have modelled the effect of climate change and increased irrigation withdrawals on the available water for hydropower production in two semi-arid river basins, i.e., Kizilirmak (Turkey) and Devoll (Albania), and the role of the reservoirs. The combined effect [...] Read more.

In this study, we have modelled the effect of climate change and increased irrigation withdrawals on the available water for hydropower production in two semi-arid river basins, i.e., Kizilirmak (Turkey) and Devoll (Albania), and the role of the reservoirs. The combined effect of climate change and extended irrigation withdrawals will overall lead to reduced runoff in the rivers, according to our simulations. The changes will be most dramatic at Kizilirmak, reducing the water available for hydropower production. The presence of the reservoirs will lead to extended water use/losses due to the provision of regulated flow, enabling larger irrigation withdrawals and increasing the evaporative losses from the reservoir surfaces. Comparing the water consumption losses at Kizilirmak, the irrigation losses are in the range of 2–4 times larger than the gross evaporation losses from reservoir surfaces. The reservoirs at Devoll will improve water availability for hydropower production during low flow periods, and the upstream irrigation represents presently a low risk to the downstream power producers. As the results are sensitive to specific river basin characteristics and the assumptions made, the results cannot be generalized to other river basins without taking these specifics into consideration. Full article

(This article belongs to the Special Issue Hydropower)

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28 pages, 10257 KiB

Open AccessArticle

Enhancement of Fire Safety of an Existing Green Building due to Natural Ventilation

by Hong Sheng Huang, Chung Hwei Su, Cheng Bang Li, Ching Yuan Lin and Chun Chou Lin

Energies 2016, 9(3), 192; https://doi.org/10.3390/en9030192 - 14 Mar 2016

Cited by 8 | Viewed by 7560

Abstract

In recent years, natural ventilation technology is extensively used in order to improve indoor environment quality and reduce power consumption of air-conditioning systems in green buildings. However, the effect of natural ventilation on fires needs to be evaluated carefully, and how to make [...] Read more.

In recent years, natural ventilation technology is extensively used in order to improve indoor environment quality and reduce power consumption of air-conditioning systems in green buildings. However, the effect of natural ventilation on fires needs to be evaluated carefully, and how to make these energy-saving buildings safe is a topic worth studying. This study uses Fire Dynamics Simulator on some fire safety enhancement measures for an existing green building without installation of a smoke exhaust system. Since the building is located on a school campus, it does not require a smoke exhaust system according to Taiwan fire regulations. Referential results, obtained after a series of improvement strategies are tested, show that kiln natural ventilation can generate a comfortable air flow. Unfortunately, due to the stack effect, hot air and fatal smoke are blown into the evacuation route area behind the room when a fire occurs. The findings showed that there are two feasible improvement measures, “controlling the off state of each air inlet” and “setting up an exhaust port in the rear of room”, which can effectively resolve the fire safety issues; the construction of which can be undertaken at a reasonable cost. Full article

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27 pages, 2542 KiB

Open AccessArticle

Medium-Term Probabilistic Forecasting of Extremely Low Prices in Electricity Markets: Application to the Spanish Case

by Antonio Bello, Javier Reneses and Antonio Muñoz

Energies 2016, 9(3), 193; https://doi.org/10.3390/en9030193 - 15 Mar 2016

Cited by 21 | Viewed by 6214

Abstract

One of the most relevant challenges that have arisen in electricity markets during the last few years is the emergence of extremely low prices. Trying to predict these events is crucial for market agents in a competitive environment. This paper proposes a novel [...] Read more.

One of the most relevant challenges that have arisen in electricity markets during the last few years is the emergence of extremely low prices. Trying to predict these events is crucial for market agents in a competitive environment. This paper proposes a novel methodology to simultaneously accomplish punctual and probabilistic hourly predictions about the appearance of extremely low electricity prices in a medium-term scope. The proposed approach for making real ex ante forecasts consists of a nested compounding of different forecasting techniques, which incorporate Monte Carlo simulation, combined with spatial interpolation techniques. The procedure is based on the statistical identification of the process key drivers. Logistic regression for rare events, decision trees, multilayer perceptrons and a hybrid approach, which combines a market equilibrium model with logistic regression, are used. Moreover, this paper assesses whether periodic models in which parameters switch according to the day of the week can be even more accurate. The proposed techniques are compared to a Markov regime switching model and several naive methods. The proposed methodology empirically demonstrates its effectiveness by achieving promising results on a real case study based on the Spanish electricity market. This approach can provide valuable information for market agents when they face decision making and risk-management processes. Our findings support the additional benefit of using a hybrid approach for deriving more accurate predictions. Full article

(This article belongs to the Special Issue Forecasting Models of Electricity Prices)

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17 pages, 2152 KiB

Open AccessEditor’s ChoiceArticle

Predictive Control Applied to a Solar Desalination Plant Connected to a Greenhouse with Daily Variation of Irrigation Water Demand

by Lidia Roca, Jorge A. Sánchez, Francisco Rodríguez, Javier Bonilla, Alberto De la Calle and Manuel Berenguel

Energies 2016, 9(3), 194; https://doi.org/10.3390/en9030194 - 14 Mar 2016

Cited by 30 | Viewed by 9144

Abstract

The water deficit in the Mediterranean area is a known matter severely affecting agriculture. One way to avoid the aquifers’ exploitation is to supply water to crops by using thermal desalination processes. Moreover, in order to guarantee long-term sustainability, the required thermal energy [...] Read more.

The water deficit in the Mediterranean area is a known matter severely affecting agriculture. One way to avoid the aquifers’ exploitation is to supply water to crops by using thermal desalination processes. Moreover, in order to guarantee long-term sustainability, the required thermal energy for the desalination process can be provided by solar energy. This paper shows simulations for a case study in which a solar multi-effect distillation plant produces water for irrigation purposes. Detailed models of the involved systems are the base of a predictive controller to operate the desalination plant and fulfil the water demanded by the crops. Full article

(This article belongs to the Special Issue Agriculture and Energy)

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19 pages, 1302 KiB

Open AccessArticle

On Scalability and Replicability of Smart Grid Projects—A Case Study

by Lukas Sigrist, Kristof May, Andrei Morch, Peter Verboven, Pieter Vingerhoets and Luis Rouco

Energies 2016, 9(3), 195; https://doi.org/10.3390/en9030195 - 14 Mar 2016

Cited by 32 | Viewed by 7696

Abstract

This paper studies the scalability and replicability of smart grid projects. Currently, most smart grid projects are still in the R&D or demonstration phases. The full roll-out of the tested solutions requires a suitable degree of scalability and replicability to prevent project demonstrators [...] Read more.

This paper studies the scalability and replicability of smart grid projects. Currently, most smart grid projects are still in the R&D or demonstration phases. The full roll-out of the tested solutions requires a suitable degree of scalability and replicability to prevent project demonstrators from remaining local experimental exercises. Scalability and replicability are the preliminary requisites to perform scaling-up and replication successfully; therefore, scalability and replicability allow for or at least reduce barriers for the growth and reuse of the results of project demonstrators. The paper proposes factors that influence and condition a project’s scalability and replicability. These factors involve technical, economic, regulatory and stakeholder acceptance related aspects, and they describe requirements for scalability and replicability. In order to assess and evaluate the identified scalability and replicability factors, data has been collected from European and national smart grid projects by means of a survey, reflecting the projects’ view and results. The evaluation of the factors allows quantifying the status quo of on-going projects with respect to the scalability and replicability, i.e., they provide a feedback on to what extent projects take into account these factors and on whether the projects’ results and solutions are actually scalable and replicable. Full article

(This article belongs to the Special Issue Optimal and Neural Network Control for Renewables and Electric Power and Energy Systems)

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14 pages, 4601 KiB

Open AccessArticle

Asymmetrical Fault Correction for the Sensitive Loads Using a Current Regulated Voltage Source Inverter

by Syed Sabir Hussain Bukhari, Shahid Atiq, Thomas A. Lipo and Byung-il Kwon

Energies 2016, 9(3), 196; https://doi.org/10.3390/en9030196 - 15 Mar 2016

Cited by 9 | Viewed by 6372

Abstract

Numerous industrial applications involve loads that are very sensitive to electrical supply instabilities. These instances involve various types of voltage imbalances as well as more serious disturbances such as symmetrical and asymmetrical faults. This paper proposes a cost-effective voltage imbalance and asymmetrical fault [...] Read more.

Numerous industrial applications involve loads that are very sensitive to electrical supply instabilities. These instances involve various types of voltage imbalances as well as more serious disturbances such as symmetrical and asymmetrical faults. This paper proposes a cost-effective voltage imbalance and asymmetrical fault correction solution for the three phase sensitive loads utilizing an industry-standard current regulated voltage source inverter by connecting it in parallel to the grid mains powering to the sensitive load. The inverter regulates the current for the load and never permits it to go beyond a prescribed value under any type of asymmetrical fault condition, which ensures high power regulating and conditioning capacities. Experimental results are obtained from a small laboratory size prototype to validate the operation of the proposed technique. Full article

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16 pages, 1739 KiB

Open AccessArticle

Improving the Eco-Efficiency of High Performance Computing Clusters Using EECluster

by Alberto Cocaña-Fernández, Luciano Sánchez and José Ranilla

Energies 2016, 9(3), 197; https://doi.org/10.3390/en9030197 - 14 Mar 2016

Cited by 7 | Viewed by 4935

Abstract

As data and supercomputing centres increase their performance to improve service quality and target more ambitious challenges every day, their carbon footprint also continues to grow, and has already reached the magnitude of the aviation industry. Also, high power consumptions are building up [...] Read more.

As data and supercomputing centres increase their performance to improve service quality and target more ambitious challenges every day, their carbon footprint also continues to grow, and has already reached the magnitude of the aviation industry. Also, high power consumptions are building up to a remarkable bottleneck for the expansion of these infrastructures in economic terms due to the unavailability of sufficient energy sources. A substantial part of the problem is caused by current energy consumptions of High Performance Computing (HPC) clusters. To alleviate this situation, we present in this work EECluster, a tool that integrates with multiple open-source Resource Management Systems to significantly reduce the carbon footprint of clusters by improving their energy efficiency. EECluster implements a dynamic power management mechanism based on Computational Intelligence techniques by learning a set of rules through multi-criteria evolutionary algorithms. This approach enables cluster operators to find the optimal balance between a reduction in the cluster energy consumptions, service quality, and number of reconfigurations. Experimental studies using both synthetic and actual workloads from a real world cluster support the adoption of this tool to reduce the carbon footprint of HPC clusters. Full article

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14 pages, 3293 KiB

Open AccessArticle

Comparing the Bio-Hydrogen Production Potential of Pretreated Rice Straw Co-Digested with Seeded Sludge Using an Anaerobic Bioreactor under Mesophilic Thermophilic Conditions

by Asma Sattar, Chaudhry Arslan, Changying Ji, Sumiyya Sattar, Irshad Ali Mari, Haroon Rashid and Fariha Ilyas

Energies 2016, 9(3), 198; https://doi.org/10.3390/en9030198 - 15 Mar 2016

Cited by 23 | Viewed by 6684

Abstract

Three common pretreatments (mechanical, steam explosion and chemical) used to enhance the biodegradability of rice straw were compared on the basis of bio-hydrogen production potential while co-digesting rice straw with sludge under mesophilic (37 °C) and thermophilic (55 °C) temperatures. The results showed [...] Read more.

Three common pretreatments (mechanical, steam explosion and chemical) used to enhance the biodegradability of rice straw were compared on the basis of bio-hydrogen production potential while co-digesting rice straw with sludge under mesophilic (37 °C) and thermophilic (55 °C) temperatures. The results showed that the solid state NaOH pretreatment returned the highest experimental reduction of LCH (lignin, cellulose and hemi-cellulose) content and bio-hydrogen production from rice straw. The increase in incubation temperature from 37 °C to 55 °C increased the bio-hydrogen yield, and the highest experimental yield of 60.6 mL/g VS_removed was obtained under chemical pretreatment at 55 °C. The time required for maximum bio-hydrogen production was found on the basis of kinetic parameters as 36 h–47 h of incubation, which can be used as a hydraulic retention time for continuous bio-hydrogen production from rice straw. The optimum pH range of bio-hydrogen production was observed to be 6.7 ± 0.1–5.8 ± 0.1 and 7.1 ± 0.1–5.8 ± 0.1 under mesophilic and thermophilic conditions, respectively. The increase in temperature was found useful for controlling the volatile fatty acids (VFA) under mechanical and steam explosion pretreatments. The comparison of pretreatment methods under the same set of experimental conditions in the present study provided a baseline for future research in order to select an appropriate pretreatment method. Full article

(This article belongs to the Special Issue Advances in Biomass for Energy Technology)

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12 pages, 706 KiB

Open AccessFeature PaperArticle

Measuring the Dynamic Characteristics of a Low Specific Speed Pump—Turbine Model

by Eve Cathrin Walseth, Torbjørn K. Nielsen and Bjørnar Svingen

Energies 2016, 9(3), 199; https://doi.org/10.3390/en9030199 - 15 Mar 2016

Cited by 31 | Viewed by 5862

Abstract

This paper presents results from an experiment performed to obtain the dynamic characteristics of a reversible pump-turbine model. The characteristics were measured in an open loop system where the turbine initially was run on low rotational speed before the generator was disconnected allowing [...] Read more.

This paper presents results from an experiment performed to obtain the dynamic characteristics of a reversible pump-turbine model. The characteristics were measured in an open loop system where the turbine initially was run on low rotational speed before the generator was disconnected allowing the turbine to go towards runaway. The measurements show that the turbine experience damped oscillations in pressure, speed and flow rate around runaway corresponding with presented stability criterion in published literature. Results from the experiment is reproduced by means of transient simulations. A one dimensional analytical turbine model for representation of the pump-turbine is used in the calculations. The simulations show that it is possible to reproduce the physics in the measurement by using a simple analytical model for the pump-turbine as long as the inertia of the water masses in the turbine are modeled correctly. Full article

(This article belongs to the Special Issue Hydropower)

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17 pages, 4911 KiB

Open AccessArticle

Solar Radiation Forecasting, Accounting for Daily Variability

by Roberto Langella, Daniela Proto and Alfredo Testa

Energies 2016, 9(3), 200; https://doi.org/10.3390/en9030200 - 15 Mar 2016

Cited by 4 | Viewed by 6542

Abstract

Radiation forecast accounting for daily and instantaneous variability was pursued by means of a new bi-parametric statistical model that builds on a model previously proposed by the same authors. The statistical model is developed with direct reference to the Liu-Jordan clear sky theoretical [...] Read more.

Radiation forecast accounting for daily and instantaneous variability was pursued by means of a new bi-parametric statistical model that builds on a model previously proposed by the same authors. The statistical model is developed with direct reference to the Liu-Jordan clear sky theoretical expression but is not bound by a specific clear sky model; it accounts separately for the mean daily variability and for the variation of solar irradiance during the day by means of two corrective parameters. This new proposal allows for a better understanding of the physical phenomena and improves the effectiveness of statistical characterization and subsequent simulation of the introduced parameters to generate a synthetic solar irradiance time series. Furthermore, the analysis of the experimental distributions of the two parameters’ data was developed, obtaining opportune fittings by means of parametric analytical distributions or mixtures of more than one distribution. Finally, the model was further improved toward the inclusion of weather prediction information in the solar irradiance forecasting stage, from the perspective of overcoming the limitations of purely statistical approaches and implementing a new tool in the frame of solar irradiance prediction accounting for weather predictions over different time horizons. Full article

(This article belongs to the Special Issue Forecasting Methods and Measurements of Forecasting Errors for Renewable Energy Sources)

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9 pages, 3903 KiB

Open AccessArticle

Catalytic Pyrolysis of Wild Reed over a Zeolite-Based Waste Catalyst

by Myung Lang Yoo, Yong Ho Park, Young-Kwon Park and Sung Hoon Park

Energies 2016, 9(3), 201; https://doi.org/10.3390/en9030201 - 15 Mar 2016

Cited by 10 | Viewed by 5566

Abstract

Fast catalytic pyrolysis of wild reed was carried out at 500 °C. Waste fluidized catalytic cracking (FCC) catalyst disposed from a petroleum refinery process was activated through acetone-washing and calcination and used as catalyst for pyrolysis. In order to evaluate the catalytic activity [...] Read more.

Fast catalytic pyrolysis of wild reed was carried out at 500 °C. Waste fluidized catalytic cracking (FCC) catalyst disposed from a petroleum refinery process was activated through acetone-washing and calcination and used as catalyst for pyrolysis. In order to evaluate the catalytic activity of waste FCC catalyst, commercial HY zeolite catalyst with a SiO₂/Al₂O₃ ratio of 5.1 was also used. The bio-oil produced from pyrolysis was analyzed using gas chromatography/mass spectrometry (GC/MS). When the biomass-to-catalyst ratio was 1:1, the production of phenolics and aromatics was promoted considerably by catalysis, whereas the content of oxygenates was affected little. Significant conversion of oxygenates to furans and aromatics was observed when the biomass-to-catalyst ratio of 1:10 was used. Activated waste FCC catalyst showed comparable catalytic activity for biomass pyrolysis to HY in terms of the promotion of valuable chemicals, such as furans, phenolics and aromatics. The results of this study imply that waste FCC catalyst can be an important economical resource for producing high-value-added chemicals from biomass. Full article

(This article belongs to the Special Issue Selected Papers from 5th Asia-Pacific Forum on Renewable Energy)

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28 pages, 3132 KiB

Open AccessArticle

Realistic Scheduling Mechanism for Smart Homes

by Danish Mahmood, Nadeem Javaid, Nabil Alrajeh, Zahoor Ali Khan, Umar Qasim, Imran Ahmed and Manzoor Ilahi

Energies 2016, 9(3), 202; https://doi.org/10.3390/en9030202 - 15 Mar 2016

Cited by 87 | Viewed by 9154

Abstract

In this work, we propose a Realistic Scheduling Mechanism (RSM) to reduce user frustration and enhance appliance utility by classifying appliances with respective constraints and their time of use effectively. Algorithms are proposed regarding functioning of home appliances. A 24 hour time slot [...] Read more.

In this work, we propose a Realistic Scheduling Mechanism (RSM) to reduce user frustration and enhance appliance utility by classifying appliances with respective constraints and their time of use effectively. Algorithms are proposed regarding functioning of home appliances. A 24 hour time slot is divided into four logical sub-time slots, each composed of 360 min or 6 h. In these sub-time slots, only desired appliances (with respect to appliance classification) are scheduled to raise appliance utility, restricting power consumption by a dynamically modelled power usage limiter that does not only take the electricity consumer into account but also the electricity supplier. Once appliance, time and power usage limiter modelling is done, we use a nature-inspired heuristic algorithm, Binary Particle Swarm Optimization (BPSO), optimally to form schedules with given constraints representing each sub-time slot. These schedules tend to achieve an equilibrium amongst appliance utility and cost effectiveness. For validation of the proposed RSM, we provide a comparative analysis amongst unscheduled electrical load usage, scheduled directly by BPSO and RSM, reflecting user comfort, which is based upon cost effectiveness and appliance utility. Full article

(This article belongs to the Special Issue Energy Efficient Building Design 2016)

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23 pages, 4858 KiB

Open AccessArticle

Quantifying the Impact of Feedstock Quality on the Design of Bioenergy Supply Chain Networks

by Krystel K. Castillo-Villar, Hertwin Minor-Popocatl and Erin Webb

Energies 2016, 9(3), 203; https://doi.org/10.3390/en9030203 - 16 Mar 2016

Cited by 17 | Viewed by 6268

Abstract

Logging residues, which refer to the unused portions of trees cut during logging, are important sources of biomass for the emerging biofuel industry and are critical feedstocks for the first-type biofuel facilities (e.g., corn-ethanol facilities). Logging residues are under-utilized sources of biomass for [...] Read more.

Logging residues, which refer to the unused portions of trees cut during logging, are important sources of biomass for the emerging biofuel industry and are critical feedstocks for the first-type biofuel facilities (e.g., corn-ethanol facilities). Logging residues are under-utilized sources of biomass for energetic purposes. To support the scaling-up of the bioenergy industry, it is essential to design cost-effective biofuel supply chains that not only minimize costs, but also consider the biomass quality characteristics. The biomass quality is heavily dependent upon the moisture and the ash contents. Ignoring the biomass quality characteristics and its intrinsic costs may yield substantial economic losses that will only be discovered after operations at a biorefinery have begun. This paper proposes a novel bioenergy supply chain network design model that minimizes operational costs and includes the biomass quality-related costs. The proposed model is unique in the sense that it supports decisions where quality is not unrealistically assumed to be perfect. The effectiveness of the proposed methodology is proven by assessing a case study in the state of Tennessee, USA. The results demonstrate that the ash and moisture contents of logging residues affect the performance of the supply chain (in monetary terms). Higher-than-target moisture and ash contents incur in additional quality-related costs. The quality-related costs in the optimal solution (with final ash content of 1% and final moisture of 50%) account for 27% of overall supply chain cost. Based on the numeral experimentation, the total supply chain cost increased 7%, on average, for each additional percent in the final ash content. Full article

(This article belongs to the Special Issue Applied Energy System Modeling 2015)

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19 pages, 3486 KiB

Open AccessArticle

Tunneling Horizontal IEC 61850 Traffic through Audio Video Bridging Streams for Flexible Microgrid Control and Protection

by Michael Short, Fathi Abugchem and Muneeb Dawood

Energies 2016, 9(3), 204; https://doi.org/10.3390/en9030204 - 16 Mar 2016

Cited by 13 | Viewed by 8214

Abstract

In this paper, it is argued that some low-level aspects of the usual IEC 61850 mapping to Ethernet are not well suited to microgrids due to their dynamic nature and geographical distribution as compared to substations. It is proposed that the integration of [...] Read more.

In this paper, it is argued that some low-level aspects of the usual IEC 61850 mapping to Ethernet are not well suited to microgrids due to their dynamic nature and geographical distribution as compared to substations. It is proposed that the integration of IEEE time-sensitive networking (TSN) concepts (which are currently implemented as audio video bridging (AVB) technologies) within an IEC 61850 / Manufacturing Message Specification framework provides a flexible and reconfigurable platform capable of overcoming such issues. A prototype test platform and bump-in-the-wire device for tunneling horizontal traffic through AVB are described. Experimental results are presented for sending IEC 61850 GOOSE (generic object oriented substation events) and SV (sampled values) messages through AVB tunnels. The obtained results verify that IEC 61850 event and sampled data may be reliably transported within the proposed framework with very low latency, even over a congested network. It is argued that since AVB streams can be flexibly configured from one or more central locations, and bandwidth reserved for their data ensuring predictability of delivery, this gives a solution which seems significantly more reliable than a pure MMS-based solution. Full article

(This article belongs to the Special Issue Microgrids 2016)

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18 pages, 5014 KiB

Open AccessArticle

Transient Numerical Simulation of the Melting and Solidification Behavior of NaNO₃ Using a Wire Matrix for Enhancing the Heat Transfer

by Martin Koller, Heimo Walter and Michael Hameter

Energies 2016, 9(3), 205; https://doi.org/10.3390/en9030205 - 16 Mar 2016

Cited by 18 | Viewed by 7340

Abstract

The paper presents the results of a transient numerical investigation of the melting and solidification process of sodium nitrate (NaNO₃), which is used as phase change material. For enhancing the heat transfer to the sodium nitrate an aluminum wire matrix is [...] Read more.

The paper presents the results of a transient numerical investigation of the melting and solidification process of sodium nitrate (NaNO₃), which is used as phase change material. For enhancing the heat transfer to the sodium nitrate an aluminum wire matrix is used. The numerical simulation of the melting and solidification process was done with the enthalpy-porosity approach. The numerical analysis of the melting process has shown that apart from the first period of the charging process, where heat conduction is the main heat transfer mechanism, natural convection is the dominant heat transfer mechanism. The numerical investigation of the solidification process has shown that the dominant heat transfer mechanism is heat conduction. Based on the numerical results, the discharging process has been slower than the charging process. The performance of the charged and discharged power has shown that the wire matrix is an alternative method to enhance the heat transfer into the phase change material. Full article

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12 pages, 2103 KiB

Open AccessArticle

The Evaluation of Energy Conservation Performance on Electricity: A Case Study of the TFT-LCD Optronics Industry

by Ven-Shing Wang, Cheng-Fong Sie, Ta-Yuan Chang and Keh-Ping Chao

Energies 2016, 9(3), 206; https://doi.org/10.3390/en9030206 - 17 Mar 2016

Cited by 15 | Viewed by 5532

Abstract

This study describes the performance evaluation of an energy management system, based on electricity consumption, for a Gen 6 Thin Film Transistor Liquid Crystal Display (TFT-LCD) panel plant. Of the various production lines and facility systems, the array system and the compressed dry [...] Read more.

This study describes the performance evaluation of an energy management system, based on electricity consumption, for a Gen 6 Thin Film Transistor Liquid Crystal Display (TFT-LCD) panel plant. Of the various production lines and facility systems, the array system and the compressed dry air consumed the most electricity of 21.8% and 19.8%, respectively, while the public utility used only 1.6% of the total electricity. The baseline electricity consumptions were correlated well (R² ≥ 0.77) to the monthly average wet-bulb temperatures of ambient air and the panel yield rates, which were determined by the product yield over the equipment available time index. After implementing the energy saving projects, the energy conservation performance was determined using a three-parameter change-point regression model incorporated with the panel yield rates. The post-retrofit monthly savings of the total electricity consumption for the panel manufacture were 5.35%–10.36%, with the efficiency of the electricity performance revealing an upswing trend following the implementation of the energy management system. Full article

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11 pages, 3437 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Progress on Low-Temperature Pulsed Electron Deposition of CuInGaSe₂ Solar Cells

by Massimo Mazzer, Stefano Rampino, Enos Gombia, Matteo Bronzoni, Francesco Bissoli, Francesco Pattini, Marco Calicchio, Aldo Kingma, Filippo Annoni, Davide Calestani, Nicholas Cavallari, Vimalkumar Thottapurath Vijayan, Mauro Lomascolo, Arianna Cretì and Edmondo Gilioli

Energies 2016, 9(3), 207; https://doi.org/10.3390/en9030207 - 16 Mar 2016

Cited by 25 | Viewed by 8063

Abstract

The quest for single-stage deposition of CuInGaSe₂ (CIGS) is an open race to replace very effective but capital intensive thin film solar cell manufacturing processes like multiple-stage coevaporation or sputtering combined with high pressure selenisation treatments. In this paper the most recent [...] Read more.

The quest for single-stage deposition of CuInGaSe₂ (CIGS) is an open race to replace very effective but capital intensive thin film solar cell manufacturing processes like multiple-stage coevaporation or sputtering combined with high pressure selenisation treatments. In this paper the most recent achievements of Low Temperature Pulsed Electron Deposition (LTPED), a novel single stage deposition process by which CIGS can be deposited at 250 °C, are presented and discussed. We show that selenium loss during the film deposition is not a problem with LTPED as good crystalline films are formed very close to the melting temperature of selenium. The mechanism of formation of good ohmic contacts between CIGS and Mo in the absence of any MoSe₂ transition layers is also illustrated, followed by a brief summary of the measured characteristics of test solar cells grown by LTPED. The 17% efficiency target achieved by lab-scale CIGS devices without bandgap modulation, antireflection coating or K-doping is considered to be a crucial milestone along the path to the industrial scale-up of LTPED. The paper ends with a brief review of the open scientific and technological issues related to the scale-up and the possible future applications of the new technology. Full article

(This article belongs to the Special Issue Key Developments in Thin Film Solar Cells)

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21 pages, 8288 KiB

Open AccessArticle

Multi-Train Energy Saving for Maximum Usage of Regenerative Energy by Dwell Time Optimization in Urban Rail Transit Using Genetic Algorithm

by Fei Lin, Shihui Liu, Zhihong Yang, Yingying Zhao, Zhongping Yang and Hu Sun

Energies 2016, 9(3), 208; https://doi.org/10.3390/en9030208 - 17 Mar 2016

Cited by 38 | Viewed by 9070

Abstract

With its large capacity, the total urban rail transit energy consumption is very high; thus, energy saving operations are quite meaningful. The effective use of regenerative braking energy is the mainstream method for improving the efficiency of energy saving. This paper examines the [...] Read more.

With its large capacity, the total urban rail transit energy consumption is very high; thus, energy saving operations are quite meaningful. The effective use of regenerative braking energy is the mainstream method for improving the efficiency of energy saving. This paper examines the optimization of train dwell time and builds a multiple train operation model for energy conservation of a power supply system. By changing the dwell time, the braking energy can be absorbed and utilized by other traction trains as efficiently as possible. The application of genetic algorithms is proposed for the optimization, based on the current schedule. Next, to validate the correctness and effectiveness of the optimization, a real case is studied. Actual data from the Beijing subway Yizhuang Line are employed to perform the simulation, and the results indicate that the optimization method of the dwell time is effective. Full article

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20 pages, 4460 KiB

Open AccessArticle

Pulse-Based Fast Battery IoT Charger Using Dynamic Frequency and Duty Control Techniques Based on Multi-Sensing of Polarization Curve

by Meng Di Yin, Jeonghun Cho and Daejin Park

Energies 2016, 9(3), 209; https://doi.org/10.3390/en9030209 - 17 Mar 2016

Cited by 45 | Viewed by 11886

Abstract

The pulse-based charging method for battery cells has been recognized as a fast and efficient way to overcome the shortcoming of a slow charging time in distributed battery cells, which is regarded as a connection of cells such as the Internet of Things [...] Read more.

The pulse-based charging method for battery cells has been recognized as a fast and efficient way to overcome the shortcoming of a slow charging time in distributed battery cells, which is regarded as a connection of cells such as the Internet of Things (IoT). The pulse frequency for controlling the battery charge duration is dynamically controlled within a certain range in order to inject the maximum charge current into the battery cells. The optimal frequency is determined in order to minimize battery impedance. The adaptation of the proposed pulse duty and frequency decreases the concentration of the polarization by sensing the runtime characteristics of battery cells so that it guarantees a certain level of safety in charging the distributed battery cells within the operating temperature range of 5–45 °C. The sensed terminal voltage and temperature of battery cells are dynamically monitored while the battery is charging so as to adjust the frequency and duty of the proposed charging pulse method, thereby preventing battery degradation. The evaluation results show that a newly designed charging algorithm for the implemented charger system is about 18.6% faster than the conventional constant-current (CC) charging method with the temperature rise within a reasonable range. The implemented charger system, which is based on the proposed dynamic frequency and duty control by considering the cell polarization, charges to about 80% of its maximum capacity in less than 56 min and involves a 13 °C maximum temperature rise without damaging the battery. Full article

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18 pages, 1542 KiB

Open AccessArticle

Spatial and Temporal Characteristics of PV Adoption in the UK and Their Implications for the Smart Grid

by J. Richard Snape

Energies 2016, 9(3), 210; https://doi.org/10.3390/en9030210 - 17 Mar 2016

Cited by 34 | Viewed by 6589

Abstract

Distributed renewable electricity generators facilitate decarbonising the electricity network, and the smart grid allows higher renewable penetration while improving efficiency. Smart grid scenarios often emphasise localised control, balancing small renewable generation with consumer electricity demand. This research investigates the applicability of proposed decentralised [...] Read more.

Distributed renewable electricity generators facilitate decarbonising the electricity network, and the smart grid allows higher renewable penetration while improving efficiency. Smart grid scenarios often emphasise localised control, balancing small renewable generation with consumer electricity demand. This research investigates the applicability of proposed decentralised smart grid scenarios utilising a mixed strategy: quantitative analysis of PV adoption data and qualitative policy analysis focusing on policy design, apparent drivers for adoption of the deviation of observed data from the feed-in tariff impact assessment predictions. Analysis reveals that areas of similar installed PV capacity are clustered, indicating a strong dependence on local conditions for PV adoption. Analysing time series of PV adoption finds that it fits neither neo-classical predictions, nor diffusion of innovation S-curves of adoption cleanly. This suggests the influence of external factors on the decision making process. It is shown that clusters of low installed PV capacity coincide with areas of high population density and vice versa, implying that while visions of locally-balanced smart grids may be viable in certain rural and suburban areas, applicability to urban centres may be limited. Taken in combination, the data analysis, policy impact and socio-psychological drivers of adoption demonstrate the need for a multi-disciplinary approach to understanding and modelling the adoption of technology necessary to enable the future smart grid. Full article

(This article belongs to the Special Issue Multi-Disciplinary Perspectives on Energy and Sustainable Development)

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18 pages, 4184 KiB

Open AccessArticle

Indices to Study the Electrical Power Signals in Active and Passive Distribution Lines: A Combined Analysis with Empirical Mode Decomposition

by Silvano Vergura, Roberto Zivieri and Mario Carpentieri

Energies 2016, 9(3), 211; https://doi.org/10.3390/en9030211 - 17 Mar 2016

Cited by 10 | Viewed by 4910

Abstract

The broad diffusion of renewable energy-based technologies has introduced several open issues in the design and operation of smart grids (SGs) when distributed generators (DGs) inject a large amount of power into the grid. In this paper, a theoretical investigation on active and [...] Read more.

The broad diffusion of renewable energy-based technologies has introduced several open issues in the design and operation of smart grids (SGs) when distributed generators (DGs) inject a large amount of power into the grid. In this paper, a theoretical investigation on active and reactive power data is performed for one active line characterized by several photovoltaic (PV) plants with a great amount of injectable power and two passive lines, one of them having a small peak power PV plant and the other one having no PV power. The frequencies calculated via the empirical mode decomposition (EMD) method based on the Hilbert-Huang transform (HHT) are compared to the ones obtained via the fast Fourier transform (FFT) and the wavelet transform (WT), showing a wider spectrum of significant modes mainly due to the non-periodical behavior of the power signals. The results obtained according to the HHT-EMD analysis are corroborated by the calculation of three new indices that are computed starting from the electrical signal itself and not from the Hilbert spectrum. These indices give the quantitative deviation from the periodicity and the coherence degree of the power signals, which typically deviate from the stationary regime and have a nonlinear behavior in terms of amplitude and phase. This information allows to extract intrinsic features of power lines belonging to SGs and this is useful for their optimal operation and planning. Full article

(This article belongs to the Special Issue Selected Papers from 15 IEEE International Conference on Environment and Electrical Engineering (EEEIC 2015))

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10 pages, 2610 KiB

Open AccessArticle

Exergy Flows inside a One Phase Ejector for Refrigeration Systems

by Mohammed Khennich, Mikhail Sorin and Nicolas Galanis

Energies 2016, 9(3), 212; https://doi.org/10.3390/en9030212 - 17 Mar 2016

Cited by 6 | Viewed by 5441

Abstract

The evaluation of the thermodynamic performance of the mutual transformation of different kinds of exergy linked to the intensive thermodynamic parameters of the flow inside the ejector of a refrigeration system is undertaken. Two thermodynamic metrics, exergy produced and exergy consumed, are introduced [...] Read more.

The evaluation of the thermodynamic performance of the mutual transformation of different kinds of exergy linked to the intensive thermodynamic parameters of the flow inside the ejector of a refrigeration system is undertaken. Two thermodynamic metrics, exergy produced and exergy consumed, are introduced to assess these transformations. Their calculation is based on the evaluation of the transiting exergy within different ejector sections taking into account the temperature, pressure and velocity variations. The analysis based on these metrics has allowed pinpointing the most important factors affecting the ejector’s performance. A new result, namely the temperature rise in the sub-environmental region of the mixing section is detected as an important factor responsible for the ejector’s thermodynamic irreversibility. The overall exergy efficiency of the ejector as well as the efficiencies of its sections are evaluated based on the proposed thermodynamic metrics. Full article

(This article belongs to the Special Issue Selected Papers from ECOS 2015—the 28th International Conference on Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems)

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13 pages, 3105 KiB

Open AccessArticle

An Actuator Control Unit for Safety-Critical Mechatronic Applications with Embedded Energy Storage Backup

by Sergio Saponara

Energies 2016, 9(3), 213; https://doi.org/10.3390/en9030213 - 17 Mar 2016

Cited by 4 | Viewed by 6656

Abstract

This paper presents an actuator control unit (ACU) with a 450-J embedded energy storage backup to face safety critical mechatronic applications. The idea is to ensure full operation of electric actuators, even in the case of battery failure, by using supercapacitors as a [...] Read more.

This paper presents an actuator control unit (ACU) with a 450-J embedded energy storage backup to face safety critical mechatronic applications. The idea is to ensure full operation of electric actuators, even in the case of battery failure, by using supercapacitors as a local energy tank. Thanks to integrated switching converter circuitry, the supercapacitors provide the required voltage and current levels for the required time to guarantee actuator operation until the system enters into safety mode. Experimental results are presented for a target application related to the control of servomotors for a robotized prosthetic arm. Mechatronic devices for rehabilitation or assisted living of injured and/or elderly people are available today. In most cases, they are battery powered with lithium-based cells, providing high energy density and low weight, but at the expense of a reduced robustness compared to lead-acid- or nickel-based battery cells. The ACU of this work ensures full operation of the wearable robotized arm, controlled through acceleration and electromyography (EMG) sensor signals, even in the case of battery failure, thanks to the embedded energy backup unit. To prove the configurability and scalability of the proposed solution, experimental results related to the electric actuation of the car door latch and of a robotized gearbox in vehicles are also shown. The reliability of the energy backup device has been assessed in a wide temperature range, from −40 to 130 °C, and in a durability test campaign of more than 10,000 cycles. Achieved results prove the suitability of the proposed approach for ACUs requiring a burst of power of hundreds of watts for only a few seconds in safety-critical applications. Alternatively, the aging and temperature characterizations of energy backup units is limited to supercapacitors of thousands of farads for high power applications (e.g., electric/hybrid propulsion) and with a temperature range limited to 70 °C. Full article

(This article belongs to the Special Issue Selected Papers from 15 IEEE International Conference on Environment and Electrical Engineering (EEEIC 2015))

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15 pages, 4912 KiB

Open AccessArticle

Application of Breathing Architectural Members to the Natural Ventilation of a Passive Solar House

by Kyung-Soon Park, Sang-Woo Kim and Seong-Hwan Yoon

Energies 2016, 9(3), 214; https://doi.org/10.3390/en9030214 - 17 Mar 2016

Cited by 10 | Viewed by 6024

Abstract

The efficient operation of a passive solar house requires an efficient ventilation system to prevent the loss of energy and provide the required ventilation rates. This paper proposes the use of “breathing architectural members” (BAMs) as passive natural ventilation devices to achieve much [...] Read more.

The efficient operation of a passive solar house requires an efficient ventilation system to prevent the loss of energy and provide the required ventilation rates. This paper proposes the use of “breathing architectural members” (BAMs) as passive natural ventilation devices to achieve much improved ventilation and insulation performance compared to mechanical ventilation. Considering the importance of evaluating the ventilation and insulation performances of the members, we also propose numerical models for predicting the heat and air movements afforded by the members. The numerical model was validated by comparison with experimental results. The effectiveness of the BAMs was also verified by installation in houses located in an area with warm climate. For this purpose, chamber experiments were performed using samples of the BAMs, as well as numerical simulations to assess natural ventilation and heat load. The main findings of the study are as follows: (1) the one-dimensional chamber experiments confirmed the validity of the numerical models for predicting the heat and air movements afforded by the BAMs. Comparison of the experimental and calculated values for the temperature of air that flowed into the room from outside revealed a difference of less than 5%; (2) observations of the case studies in which BAMs were installed in the ceilings and exterior walls of Tokyo model houses revealed good annual ventilation and energy-saving effects. When BAMs with an opening area per unit area of A = 0.002 m²/m² were applied to three surfaces, the required ventilation rate was 0.5 ACH (air changes per hour), and this was achieved consistently. Compared to a house with general insulation and conventional mechanical ventilation, heating load was reduced by 15.3%–40.2% depending on the BAM installation points and the differing areas of the house models. Full article

(This article belongs to the Special Issue Energy Efficient Actuators and Systems)

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23 pages, 8761 KiB

Open AccessArticle

Evaluation of a Mixed Method Approach for Studying User Interaction with Novel Building Control Technology

by Birgit Painter, Katherine N. Irvine, Ruth Kelly Waskett and John Mardaljevic

Energies 2016, 9(3), 215; https://doi.org/10.3390/en9030215 - 17 Mar 2016

Cited by 7 | Viewed by 6062

Abstract

Energy-efficient building performance requires sophisticated control systems that are based on realistic occupant behaviour models. To provide robust data for the development of these models, research studies in real-world settings are needed. Yet, such studies are challenging and necessitate careful design in terms [...] Read more.

Energy-efficient building performance requires sophisticated control systems that are based on realistic occupant behaviour models. To provide robust data for the development of these models, research studies in real-world settings are needed. Yet, such studies are challenging and necessitate careful design in terms of data collection methods and procedures. This paper describes and critiques the design of a mixed methods approach for occupant behaviour research. It reviews the methodology developed for a longitudinal study in a real-world office environment where occupants’ experience with a novel facade technology (electrochromic glazing) was investigated. The methodology integrates objective physical measurements, observational data and self-reported experience data. Using data from one day of the study, this paper illustrates how the different sources can be combined in order to derive an in-depth understanding of the interplay between external daylight conditions, characteristics of the facade technology, occupant interaction with the technology and the resulting occupant experience. It was found that whilst the individual methods may be affected by practical limitations, these can be partially offset by combining physical measurements and observations with self-reported data. The paper critically evaluates the individual techniques, as well as the benefits of their integration and makes recommendations for the design of future occupant behaviour studies in real-world settings. Full article

(This article belongs to the Special Issue Multi-Disciplinary Perspectives on Energy and Sustainable Development)

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42 pages, 7441 KiB

Open AccessArticle

A Multi-Objective Optimization Framework for Offshore Wind Farm Layouts and Electric Infrastructures

by Silvio Rodrigues, Carlos Restrepo, George Katsouris, Rodrigo Teixeira Pinto, Maryam Soleimanzadeh, Peter Bosman and Pavol Bauer

Energies 2016, 9(3), 216; https://doi.org/10.3390/en9030216 - 18 Mar 2016

Cited by 44 | Viewed by 17451

Abstract

Current offshore wind farms (OWFs) design processes are based on a sequential approach which does not guarantee system optimality because it oversimplifies the problem by discarding important interdependencies between design aspects. This article presents a framework to integrate, automate and optimize the design [...] Read more.

Current offshore wind farms (OWFs) design processes are based on a sequential approach which does not guarantee system optimality because it oversimplifies the problem by discarding important interdependencies between design aspects. This article presents a framework to integrate, automate and optimize the design of OWF layouts and the respective electrical infrastructures. The proposed framework optimizes simultaneously different goals (e.g., annual energy delivered and investment cost) which leads to efficient trade-offs during the design phase, e.g., reduction of wake losses vs collection system length. Furthermore, the proposed framework is independent of economic assumptions, meaning that no a priori values such as the interest rate or energy price, are needed. The proposed framework was applied to the Dutch Borssele areas I and II. A wide range of OWF layouts were obtained through the optimization framework. OWFs with similar energy production and investment cost as layouts designed with standard sequential strategies were obtained through the framework, meaning that the proposed framework has the capability to create different OWF layouts that would have been missed by the designers. In conclusion, the proposed multi-objective optimization framework represents a mind shift in design tools for OWFs which allows cost savings in the design and operation phases. Full article

(This article belongs to the Special Issue Techniques of Control for Energy Optimization in Actuators, Motors and Power Generation Systems)

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19 pages, 2691 KiB

Open AccessArticle

Modeling and Control of the Distributed Power Converters in a Standalone DC Microgrid

by Xiaodong Lu and Jiangwen Wan

Energies 2016, 9(3), 217; https://doi.org/10.3390/en9030217 - 18 Mar 2016

Cited by 13 | Viewed by 6611

Abstract

A standalone DC microgrid integrated with distributed renewable energy sources, energy storage devices and loads is analyzed. To mitigate the interaction among distributed power modules, this paper describes a modeling and control design procedure for the distributed converters. The system configuration and steady-state [...] Read more.

A standalone DC microgrid integrated with distributed renewable energy sources, energy storage devices and loads is analyzed. To mitigate the interaction among distributed power modules, this paper describes a modeling and control design procedure for the distributed converters. The system configuration and steady-state analysis of the standalone DC microgrid under study are discussed first. The dynamic models of the distributed converters are then developed from two aspects corresponding to their two operating modes, device-regulating mode and bus-regulating mode. Average current mode control and linear compensators are designed accordingly for each operating mode. The stability of the designed system is analyzed at last. The operation and control design of the system are verified by simulation results. Full article

(This article belongs to the Special Issue Distributed Renewable Generation)

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13 pages, 3679 KiB

Open AccessArticle

Advances in Thin-Film Si Solar Cells by Means of SiO_x Alloys

by Lucia V. Mercaldo, Iurie Usatii and Paola Delli Veneri

Energies 2016, 9(3), 218; https://doi.org/10.3390/en9030218 - 18 Mar 2016

Cited by 13 | Viewed by 5497

Abstract

The conversion efficiency of thin-film silicon solar cells needs to be improved to be competitive with respect to other technologies. For a more efficient use of light across the solar spectrum, multi-junction architectures are being considered. Light-management considerations are also crucial in order [...] Read more.

The conversion efficiency of thin-film silicon solar cells needs to be improved to be competitive with respect to other technologies. For a more efficient use of light across the solar spectrum, multi-junction architectures are being considered. Light-management considerations are also crucial in order to maximize light absorption in the active regions with a minimum of parasitic optical losses in the supportive layers. Intrinsic and doped silicon oxide alloys can be advantageously applied within thin-film Si solar cells for these purposes. Intrinsic a-SiO_x:H films have been fabricated and characterized as a promising wide gap absorber for application in triple-junction solar cells. Single-junction test devices with open circuit voltage up to 950 mV and ~1 V have been demonstrated, in case of rough and flat front electrodes, respectively. Doped silicon oxide alloys with mixed-phase structure have been developed, characterized by considerably lower absorption and refractive index with respect to standard Si-based films, accompanied by electrical conductivity above 10⁻⁵ S/cm. These layers have been successfully applied both into single-junction and micromorph tandem solar cells as superior doped layers with additional functionalities. Full article

(This article belongs to the Special Issue Key Developments in Thin Film Solar Cells)

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25 pages, 9609 KiB

Open AccessArticle

An Embedded System in Smart Inverters for Power Quality and Safety Functionality

by Rafael Real-Calvo, Antonio Moreno-Munoz, Juan J. Gonzalez-De-La-Rosa, Victor Pallares-Lopez, Miguel J. Gonzalez-Redondo and Isabel M. Moreno-Garcia

Energies 2016, 9(3), 219; https://doi.org/10.3390/en9030219 - 18 Mar 2016

Cited by 11 | Viewed by 8824

Abstract

The electricity sector is undergoing an evolution that demands the development of a network model with a high level of intelligence, known as a Smart Grid. One of the factors accelerating these changes is the development and implementation of renewable energy. In particular, [...] Read more.

The electricity sector is undergoing an evolution that demands the development of a network model with a high level of intelligence, known as a Smart Grid. One of the factors accelerating these changes is the development and implementation of renewable energy. In particular, increased photovoltaic generation can affect the network’s stability. One line of action is to provide inverters with a management capacity that enables them to act upon the grid in order to compensate for these problems. This paper describes the design and development of a prototype embedded system able to integrate with a photovoltaic inverter and provide it with multifunctional ability in order to analyze power quality and operate with protection. The most important subsystems of this prototype are described, indicating their operating fundamentals. This prototype has been tested with class A protocols according to IEC 61000-4-30 and IEC 62586-2. Tests have also been carried out to validate the response time in generating orders and alarm signals for protections. The highlights of these experimental results are discussed. Some descriptive aspects of the integration of the prototype in an experimental smart inverter are also commented upon. Full article

(This article belongs to the Special Issue Microgrids)

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11 pages, 2930 KiB

Open AccessArticle

Optimization of Shift Schedule for Hybrid Electric Vehicle with Automated Manual Transmission

by Wenchen Shen, Huilong Yu, Yuhui Hu and Junqiang Xi

Energies 2016, 9(3), 220; https://doi.org/10.3390/en9030220 - 19 Mar 2016

Cited by 29 | Viewed by 8446

Abstract

Currently, most hybrid electric vehicles (HEVs) equipped with automated mechanical transmission (AMT) are implemented with the conventional two-parameter gear shift schedule based on engineering experience. However, this approach cannot take full advantage of hybrid drives. In other words, the powertrain of an HEV [...] Read more.

Currently, most hybrid electric vehicles (HEVs) equipped with automated mechanical transmission (AMT) are implemented with the conventional two-parameter gear shift schedule based on engineering experience. However, this approach cannot take full advantage of hybrid drives. In other words, the powertrain of an HEV is not able to work at the best fuel-economy points during the whole driving profile. To solve this problem, an optimization method of gear shift schedule for HEVs is proposed based on Dynamic Programming (DP) and a corresponding solving algorithm is also put forward. A gear shift schedule that can be employed in real-vehicle is extracted from the obtained optimal gear shift points by DP approach and is optimized based on analysis of the engineering experience in a typical Chinese urban driving cycle. Compared with the conventional two-parameter gear shift schedule in both simulation and real vehicle experiments, the extracted gear shift schedule is proved to clearly improve the fuel economy of the HEV. Full article

(This article belongs to the Special Issue Energy Storage Systems for Plug-in Electric Vehicles and Vehicle to Power Grid Integration)

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20 pages, 4108 KiB

Open AccessArticle

Hybridizing DEMD and Quantum PSO with SVR in Electric Load Forecasting

by Li-Ling Peng, Guo-Feng Fan, Min-Liang Huang and Wei-Chiang Hong

Energies 2016, 9(3), 221; https://doi.org/10.3390/en9030221 - 19 Mar 2016

Cited by 47 | Viewed by 6938

Abstract

Electric load forecasting is an important issue for a power utility, associated with the management of daily operations such as energy transfer scheduling, unit commitment, and load dispatch. Inspired by strong non-linear learning capability of support vector regression (SVR), this paper presents an [...] Read more.

Electric load forecasting is an important issue for a power utility, associated with the management of daily operations such as energy transfer scheduling, unit commitment, and load dispatch. Inspired by strong non-linear learning capability of support vector regression (SVR), this paper presents an SVR model hybridized with the differential empirical mode decomposition (DEMD) method and quantum particle swarm optimization algorithm (QPSO) for electric load forecasting. The DEMD method is employed to decompose the electric load to several detail parts associated with high frequencies (intrinsic mode function—IMF) and an approximate part associated with low frequencies. Hybridized with quantum theory to enhance particle searching performance, the so-called QPSO is used to optimize the parameters of SVR. The electric load data of the New South Wales (Sydney, Australia) market and the New York Independent System Operator (NYISO, New York, USA) are used for comparing the forecasting performances of different forecasting models. The results illustrate the validity of the idea that the proposed model can simultaneously provide forecasting with good accuracy and interpretability. Full article

(This article belongs to the Special Issue Kernel Methods and Hybrid Evolutionary Algorithms in Energy Forecasting)

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22 pages, 8514 KiB

Open AccessArticle

Evaluation of Gas Production from Marine Hydrate Deposits at the GMGS2-Site 8, Pearl River Mouth Basin, South China Sea

by Yi Wang, Jing-Chun Feng, Xiao-Sen Li, Yu Zhang and Gang Li

Energies 2016, 9(3), 222; https://doi.org/10.3390/en9030222 - 21 Mar 2016

Cited by 39 | Viewed by 7251

Abstract

Natural gas hydrate accumulations were confirmed in the Dongsha Area of the South China Sea by the Guangzhou Marine Geological Survey 2 (GMGS2) scientific drilling expedition in 2013. The drilling sites of GMGS2-01, -04, -05, -07, -08, -09, -11, -12, and -16 verified [...] Read more.

Natural gas hydrate accumulations were confirmed in the Dongsha Area of the South China Sea by the Guangzhou Marine Geological Survey 2 (GMGS2) scientific drilling expedition in 2013. The drilling sites of GMGS2-01, -04, -05, -07, -08, -09, -11, -12, and -16 verified the existence of a hydrate-bearing layer. In this work gas production behavior was evaluated at GMGS2-8 by numerical simulation. The hydrate reservoir in the GMGS2-8 was characterized by dual hydrate layers and a massive hydrate layer. A single vertical well was considered as the well configuration, and depressurization was employed as the dissociation method. Analyses of gas production sensitivity to the production pressure, the thermal conductivity, and the intrinsic permeability were investigated as well. Simulation results indicated that the total gas production from the reference case is approximately 7.3 × 10⁷ ST m³ in 30 years. The average gas production rate in 30 years is 6.7 × 10³ ST m³/day, which is much higher than the previous study in the Shenhu Area of the South China Sea performed by the GMGS-1. Moreover, the maximum gas production rate (9.5 × 10³ ST m³/day) has the same order of magnitude of the first offshore methane hydrate production test in the Nankai Trough. When production pressure decreases from 4.5 to 3.4 MPa, the volume of gas production increases by 20.5%, and when production pressure decreases from 3.4 to 2.3 MPa, the volume of gas production increases by 13.6%. Production behaviors are not sensitive to the thermal conductivity. In the initial 10 years, the higher permeability leads to a larger rate of gas production, however, the final volume of gas production in the case with the lowest permeability is the highest. Full article

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Energies, Volume 9, Issue 3 (March 2016) – 104 articles

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