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10 Years Energies - Horizon 2028

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A special issue of Energies (ISSN 1996-1073).

Deadline for manuscript submissions: closed (31 December 2018) | Viewed by 383435

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Special Issue Editors

Prof. Dr. Enrico Sciubba

E-Mail Website
Guest Editor

Department of Mechanical and Aerospace Engineering, University of Roma Sapienza, Via Eudossiana 18, 00184 Roma, Italy
Interests: turbomachinery CFD; turbulence modelling; exergy analysis of complex systems; engineering applications of AI to thermal conversion processes
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Paul Stewart

E-Mail Website
Guest Editor

Institute for Innovation in Sustainable Engineering, University of Derby, Lonsdale House, Derby DE1 3EE, UK
Interests: complex system simulation, design and optimization; engineering applications of artificial intelligence; advanced control systems; power and energy architectures; electrical machines, drives and systems; energy conversion and storage; remote monitoring and sensing; prognostics and diagnostics; low carbon and low emissions operations
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Thomas E. Amidon

E-Mail Website
Guest Editor

Department of Paper and Bioprocess Engineering, College of Environmental Science and Forestry, State University of New York, 1 Forestry Drive, Syracuse, NY 13210, USA
Interests: biorefineries; biofuels; bioenergy; bio-based materials and chemicals; nanocellulose; pulp and paper; pellets; forest and biomass resources; process development; novel bio-based products; cell wall deconstruction; hot water extraction; cellulosic bioproducts; improved fiber-based products; biomass productivity
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. K. T. Chau

E-Mail Website
Guest Editor

Department of Electrical and Electronic Engineering, The Hong Kong Polytechnic University, Hong Kong, China
Interests: electric vehicle technologies; renewable energy systems; machines and drives; power electronics
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Abdul-Ghani Olabi

E-Mail Website
Guest Editor

1. Department of Sustainable and Renewable Energy Engineering, University of Sharjah, Sharjah P.O. Box 27272, United Arab Emirates
2. Mechanical Engineering and Design, School of Engineering and Applied Science, Aston University, Aston Triangle, Birmingham B4 7ET, UK
Interests: renewable energy; energy storage systems, sustainability; CAD and design; smart materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Energies (ISSN 1996-1073; CODEN: ENERGA) https://www.mdpi.com/journal/energies) has reached a milestone: it is now 10 years since our journal was launched.

In celebration of this special occasion, the Energies editorial team have decided to publish a special issue called "10 Years of Energies – Horizon 2028". We would like to invite you to contribute a comprehensive review article or an original research paper for peer-review and possible publication. The details for this special issue can be found at:

https://www.mdpi.com/journal/energies/special_issues/A_Decade_of_Horizon_2028

The last ten years of technological and theoretical advancements in Energies have been extraordinary. We now want to look to the future. For example, with the development and application of new materials, Big Data analytics, Industry 4.0, Internet of Things and AI being applied to the Energy sector and its relationship to areas such as electric vehicle design, charging infrastructure and renewable energy networks, we predict the pace of change in the next ten years to be even greater

The purpose of this special issue is to publish a set of articles that typify the very best insightful and influential investigations or theories that will form the foundation of the next ten year’s technological change. We would like to include articles that will form the new benchmark against which other articles are measured; this benchmark is, of course, a moving target as Energies continues to advance to new frontiers. We expect these articles to be widely read and highly influential within the field.

There is no restriction on the subject areas for this special issue. Energies readers and authors are encouraged to send their very best work to be showcased. The key criteria for manuscript acceptance will be novelty and the potential breadth and contribution to the field. Manuscripts with experimental implementation and empirical proofs are also encouraged.

Prof. Dr. Enrico Sciubba
Prof. Dr. Paul Stewart
Prof. Dr. Thomas E. Amidon
Prof. Dr. K.T. Chau
Prof. Dr. Abdul-Ghani Olabi
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Renewables
Distribution
Electric Transportation
Generation
Smart Grid
Machines and Drives
Prognostics and Diagnostics
Power Architectures
Energy Conversion and Storage
Low Carbon

Published Papers (54 papers)

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Research

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20 pages, 2284 KiB

Open AccessArticle

A Novel Correlation Model for Horizontal Axis Wind Turbines Operating at High-Interference Flow Regimes

by Anurag Rajan and Fernando L. Ponta

Energies 2019, 12(6), 1148; https://doi.org/10.3390/en12061148 - 25 Mar 2019

Cited by 1 | Viewed by 3864

Driven by economics-of-scale factors, wind-turbine rotor sizes have increased formidably in recent years. Larger rotors with lighter blades of increased flexibility will experiment substantially higher levels of deformation. Future turbines will also incorporate advanced control strategies to widen the range of wind velocities [...] Read more.

Driven by economics-of-scale factors, wind-turbine rotor sizes have increased formidably in recent years. Larger rotors with lighter blades of increased flexibility will experiment substantially higher levels of deformation. Future turbines will also incorporate advanced control strategies to widen the range of wind velocities over which energy is captured. These factors will extend turbine operational regimes, including flow states with high interference factors. In this paper we derive a new empirical relation to both improve and extend the range of Blade Element Momentum (BEM) models, when applied to high interference-factor regimes. In most BEM models, these flow regimes are modeled using empirical relations derived from experimental data. However, an empirical relation that best represents these flow states is still missing. The new relation presented in this paper is based on data from numerical experiments performed on an actuator disk model, and implemented in the context of a novel model of the BEM family called the DRD-BEM (Dynamic Rotor Deformation—BEM), recently introduced in Ponta, et al., 2016. A detailed description of the numerical experiments is presented, followed by DRD-BEM simulation results for the case of the benchmark NREL-5MW Reference Wind Turbine with this new polynomial curve incorporated. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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19 pages, 10608 KiB

Open AccessFeature PaperArticle

Rotor Loading Characteristics of a Full-Scale Tidal Turbine

by Magnus Harrold and Pablo Ouro

Energies 2019, 12(6), 1035; https://doi.org/10.3390/en12061035 - 17 Mar 2019

Cited by 21 | Viewed by 4753

Tidal turbines are subject to highly dynamic mechanical loading through operation in some of the most energetic waters. If these loads cannot be accurately quantified at the design stage, turbine developers run the risk of a major failure, or must choose to conservatively [...] Read more.

Tidal turbines are subject to highly dynamic mechanical loading through operation in some of the most energetic waters. If these loads cannot be accurately quantified at the design stage, turbine developers run the risk of a major failure, or must choose to conservatively over-engineer the device at additional cost. Both of these scenarios have consequences on the expected return from the project. Despite an extensive amount of research on the mechanical loading of model scale tidal turbines, very little is known from full-scale devices operating in real sea conditions. This paper addresses this by reporting on the rotor loads measured on a 400 kW tidal turbine. The results obtained during ebb tidal conditions were found to agree well with theoretical predictions of rotor loading, but the measurements during flood were lower than expected. This is believed to be due to a disturbance in the approaching flood flow created by the turbine frame geometry, and, to a lesser extent, the non-typical vertical flow profile during this tidal phase. These findings outline the necessity to quantify the characteristics of the turbulent flows at sea sites during the entire tidal cycle to ensure the long-term integrity of the deployed tidal turbines. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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18 pages, 4765 KiB

Open AccessFeature PaperArticle

Designing a Large-Scale Lake Cooling System for an Ultra-Deep Mine: A Canadian Case Study

by Ali Fahrettin Kuyuk, Seyed Ali Ghoreishi-Madiseh, Agus P. Sasmito and Ferri Hassani

Energies 2019, 12(5), 811; https://doi.org/10.3390/en12050811 - 01 Mar 2019

Cited by 7 | Viewed by 5013

Subsurface mining operations are continuously getting deeper and more complex due to depletion of shallow deposits. This fact inevitably brings more expensive, high-tech oriented and most importantly energy intensive subsurface mining operations to come alive. Accordingly, while big mining companies are developing sensible [...] Read more.

Subsurface mining operations are continuously getting deeper and more complex due to depletion of shallow deposits. This fact inevitably brings more expensive, high-tech oriented and most importantly energy intensive subsurface mining operations to come alive. Accordingly, while big mining companies are developing sensible extraction methods to exploit orebodies located at great depths, they are also seeking to cut down their costs and carbon footprint. A large percentage of the energy needed by a subsurface mine is due to the mine ventilation and air conditioning reasons. In fact, for mines deeper than 2 km, mine air conditioning becomes a must. Yet, as there are not many alternatives developed, most of the modern mines are subjected to deploy tens of megawatts worth of cooling plants using massive refrigeration units. This does not only create a large financial burden during the project stage but also results in heavy energy demands during the operation. This paper aims to investigate a natural, alternative deep-mine lake cooling system by providing a detailed ‘front-end-loading’ design conducted for a real-life, Canadian example. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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22 pages, 14590 KiB

Open AccessArticle

Heat Recovery for a Textile Stenter: CFD Analysis of Air Curtain Benefits

by Lorenzo Ciappi, Daniele Fiaschi, Giampaolo Manfrida, Simone Salvadori, Jacek Smolka and Lorenzo Talluri

Energies 2019, 12(3), 482; https://doi.org/10.3390/en12030482 - 02 Feb 2019

Cited by 5 | Viewed by 5502

Modern textile stenters are designed to reduce the inefficiency of the process and to recover the flow stream, which still contains a relatively high energetic value. In recent years, research has focused on the recovery of the energy content of the low-temperature exhaust [...] Read more.

Modern textile stenters are designed to reduce the inefficiency of the process and to recover the flow stream, which still contains a relatively high energetic value. In recent years, research has focused on the recovery of the energy content of the low-temperature exhaust flow; nonetheless, another important aspect that may increase the efficiency of the process is the reduction of the ambient air suction. In the present research, an innovative way to improve both machine insulation and energy savings, by using preheated air, was numerically evaluated. The proposed solution utilizes an air stream transverse to the fabric (generally called air curtain), either preheated or not, to create soft gates both at the inlet and at the outlet section of the drying machine. Several valuable advantages can be listed when using this solution: reduction of the dispersion of heat and humid polluted air to the work environment, limitation of air ingestion from outside, and effective heat recovery coupled to a uniform temperature profile around the textile fabric. To analyze the insulation capability of the air curtains in terms of mass and energy transfer, a two-dimensional CFD model of the machine was realized. A test matrix including three possible fabric speeds (20, 40 and 60 m/min), three tilt angles (−15°, 0° and 15°), four mass flow rates (0% with no air curtains and 3%, 5% and 7% of the total flow rate through the machine, where the 5% case is equivalent to the flow rate ingested from the ambient) and two temperatures (15 °C and 70 °C) of the plane jets exiting from the air curtains was considered, thus covering a wide range of possible practical applications. The obtained results demonstrate that warm air curtains at both the inlet and outlet are very effective in a fabric speed range up to 40 m/min; at higher fabric speed, entrainment of warm gases from inside the machine at the fabric outlet becomes relevant, and the adoption of a cold air curtain (capable of better insulation) can be recommended in this position. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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20 pages, 691 KiB

Open AccessArticle

Stochastic Planning of Distributed PV Generation

by Mohammadhafez Bazrafshan, Likhitha Yalamanchili, Nikolaos Gatsis and Juan Gomez

Energies 2019, 12(3), 459; https://doi.org/10.3390/en12030459 - 31 Jan 2019

Cited by 10 | Viewed by 3068

Recent studies by electric utility companies indicate that maximum benefits of distributed solar photovoltaic (PV) units can be reaped when siting and sizing of PV systems is optimized. This paper develops a two-stage stochastic program that serves as a tool for optimally determining [...] Read more.

Recent studies by electric utility companies indicate that maximum benefits of distributed solar photovoltaic (PV) units can be reaped when siting and sizing of PV systems is optimized. This paper develops a two-stage stochastic program that serves as a tool for optimally determining the placing and sizing of PV units in distribution systems. The PV model incorporates the mapping from solar irradiance to AC power injection. By modeling the uncertainty of solar irradiance and loads by a finite set of scenarios, the goal is to achieve minimum installation and network operation costs while satisfying necessary operational constraints. First-stage decisions are scenario-independent and include binary variables that represent the existence of PV units, the area of the PV panel, and the apparent power capability of the inverter. Second-stage decisions are scenario-dependent and entail reactive power support from PV inverters, real and reactive power flows, and nodal voltages. Optimization constraints account for inverter’s capacity, PV module area limits, the power flow equations, as well as voltage regulation. A comparison between two designs, one where the DC:AC ratio is pre-specified, and the other where the maximum DC:AC ratio is specified based on historical data, is carried out. It turns out that the latter design reduces costs and allows further reduction of the panel area. The applicability and efficiency of the proposed formulation are numerically demonstrated on the IEEE 34-node feeder, while the output power of PV systems is modeled using the publicly available PVWatts software developed by the National Renewable Energy Laboratory. The overall framework developed in this paper can guide electric utility companies in identifying optimal locations for PV placement and sizing, assist with targeting customers with appropriate incentives, and encourage solar adoption. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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17 pages, 4737 KiB

Open AccessArticle

Artificial Neural Network Based Reinforcement Learning for Wind Turbine Yaw Control

by Aitor Saenz-Aguirre, Ekaitz Zulueta, Unai Fernandez-Gamiz, Javier Lozano and Jose Manuel Lopez-Guede

Energies 2019, 12(3), 436; https://doi.org/10.3390/en12030436 - 30 Jan 2019

Cited by 73 | Viewed by 6718

This paper introduces a novel data driven yaw control algorithm synthesis method based on Reinforcement Learning (RL) for a variable pitch variable speed wind turbine. Yaw control has not been extendedly studied in the literature; in fact, most of the currently considered developments [...] Read more.

This paper introduces a novel data driven yaw control algorithm synthesis method based on Reinforcement Learning (RL) for a variable pitch variable speed wind turbine. Yaw control has not been extendedly studied in the literature; in fact, most of the currently considered developments in the scope of the wind energy are oriented to the pitch and speed control. The most important drawbacks of the yaw control are the very large time constants and the strict yaw angle change rate constraints due to the high mechanical loads when the wind turbine angle is changed in order to adequate it to the wind speed orientation. An optimal yaw control algorithm needs to be designed in order to adapt the rotor orientation depending on the wind turbine dynamics and the local wind speed regime. Consequently, the biggest challenge of the yaw control algorithm is to decide the moment and the quantity of the wind turbine orientation variation to achieve the highest quantity of power at each instant, taking into account the constraints derived from the mechanical limitations of the yawing system and the mechanical loads. In this paper, a novel based algorithm based on the RL Q-Learning algorithm is introduced. The first step is to obtain a model of the power generated by the wind turbine (a real onshore wind turbine in this paper) through a power curve, that in conjunction with a conventional proportional regulator will be used to obtain a dataset that explains the actual behaviour of the real wind turbine when a variety of different yaw control commands are imposed. That knowledge is then used to learn the best control action for each different state of the wind turbine with respect to the wind direction represented by the yaw angle, storing that knowledge in a matrix Q(s,a). The last step is to model that matrix through a MultiLayer Perceptron with BackPropagation (MLP-BP) Artificial Neural Network (ANN) to avoid large matrix management and quantification problems. Once that the optimal yaw controller has been synthetized, its performance has been assessed using a number of wind speed realizations obtained using the software application TurbSim, in order to analyze how the introduced novel algorithm deals with different wind speed scenarios. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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27 pages, 12429 KiB

Open AccessArticle

A Parametric Study and Performance Evaluation of Energy Retrofit Solutions for Buildings Located in the Hot-Humid Climate of Paraguay—Sensitivity Analysis

by Fabiana Silvero, Fernanda Rodrigues and Sergio Montelpare

Energies 2019, 12(3), 427; https://doi.org/10.3390/en12030427 - 29 Jan 2019

Cited by 7 | Viewed by 3858

Nowadays, awareness concerning the need to use energy efficiently is increasing significantly worldwide, thus, improving the energy efficiency levels in the building sector has acquired high importance because of their energy saving potential. However, several intervention options are available to achieve high energy [...] Read more.

Nowadays, awareness concerning the need to use energy efficiently is increasing significantly worldwide, thus, improving the energy efficiency levels in the building sector has acquired high importance because of their energy saving potential. However, several intervention options are available to achieve high energy efficiency levels in buildings, and the choice must be made considering the efficiency of the solution and the costs involved. Considering this, the present research aimed to develop a parametric study of several energy retrofit solutions for buildings located in the hot-humid climate of Paraguay, in order to analyse their efficiency in terms of comfort rates and cooling energy needs. Furthermore, the Analytic Hierarchy Process (AHP) is employed as a decision-making method to choose the most suitable intervention considering the investment costs required. Thus, threshold values of thermal transmittance for the building thermal envelope components are established through a parametric study and sensitivity analysis of the simulations results. Considering that Paraguay does not have national building energy codes, the outcomes of this research will constitute a support and contribute for the thermal parameters regulation of buildings aiding to improve the energy efficiency of Paraguayan buildings. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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23 pages, 696 KiB

Open AccessFeature PaperArticle

Defining and Evaluating Use Cases for Battery Energy Storage Investments: Case Study in Croatia

by Ivan Pavić, Zora Luburić, Hrvoje Pandžić, Tomislav Capuder and Ivan Andročec

Energies 2019, 12(3), 376; https://doi.org/10.3390/en12030376 - 24 Jan 2019

Cited by 21 | Viewed by 6773

Battery energy storage systems (BESS) and renewable energy sources are complementary technologies from the power system viewpoint, where renewable energy sources behave as flexibility sinks and create business opportunities for BESS as flexibility sources. Various stakeholders can use BESS to balance, stabilize and [...] Read more.

Battery energy storage systems (BESS) and renewable energy sources are complementary technologies from the power system viewpoint, where renewable energy sources behave as flexibility sinks and create business opportunities for BESS as flexibility sources. Various stakeholders can use BESS to balance, stabilize and flatten demand/generation patterns. These applications depend on the stakeholder role, flexibility service needed from the battery, market opportunities and obstacles, as well as regulatory aspects encouraging or hindering integration of storage technologies. While developed countries are quickly removing barriers and increasing the integration share of BESS, this is seldom the case in developing countries. The paper identifies multiple case opportunities for different power system stakeholders in Croatia, models potential BESS applications using real-world case studies, analyzes feasibility of these investments, and discusses financial returns and barriers to overcome. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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23 pages, 2726 KiB

Open AccessArticle

Simulation-Based Evaluation and Optimization of Control Strategies in Buildings

by Georgios D. Kontes, Georgios I. Giannakis, Víctor Sánchez, Pablo De Agustin-Camacho, Ander Romero-Amorrortu, Natalia Panagiotidou, Dimitrios V. Rovas, Simone Steiger, Christopher Mutschler and Gunnar Gruen

Energies 2018, 11(12), 3376; https://doi.org/10.3390/en11123376 - 02 Dec 2018

Cited by 28 | Viewed by 5977

Over the last several years, a great amount of research work has been focused on the development of model predictive control techniques for the indoor climate control of buildings, but, despite the promising results, this technology is still not adopted by the industry. [...] Read more.

Over the last several years, a great amount of research work has been focused on the development of model predictive control techniques for the indoor climate control of buildings, but, despite the promising results, this technology is still not adopted by the industry. One of the main reasons for this is the increased cost associated with the development and calibration (or identification) of mathematical models of special structure used for predicting future states of the building. We propose a methodology to overcome this obstacle by replacing these hand-engineered mathematical models with a thermal simulation model of the building developed using detailed thermal simulation engines such as EnergyPlus. As designing better controllers requires interacting with the simulation model, a central part of our methodology is the control improvement (or optimisation) module, facilitating two simulation-based control improvement methodologies: one based in multi-criteria decision analysis methods and the other based on state-space identification of dynamical systems using Gaussian process models and reinforcement learning. We evaluate the proposed methodology in a set of simulation-based experiments using the thermal simulation model of a real building located in Portugal. Our results indicate that the proposed methodology could be a viable alternative to model predictive control-based supervisory control in buildings. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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17 pages, 4360 KiB

Open AccessArticle

Cross-Border Energy Exchange and Renewable Premiums: The Case of the Iberian System

by Juan Manuel Roldan-Fernandez, Catalina Gómez-Quiles, Adrien Merre, Manuel Burgos-Payán and Jesús Manuel Riquelme-Santos

Energies 2018, 11(12), 3277; https://doi.org/10.3390/en11123277 - 24 Nov 2018

Cited by 9 | Viewed by 3800

In 2002, the European Union set a target of 10% electricity interconnection capacity for 2020: a target that has been further extended to 15% by 2030. Cross-border interconnection of regional/national electricity systems will allow the EU to enhance its security of supply and [...] Read more.

In 2002, the European Union set a target of 10% electricity interconnection capacity for 2020: a target that has been further extended to 15% by 2030. Cross-border interconnection of regional/national electricity systems will allow the EU to enhance its security of supply and to integrate more renewables into energy markets. Although the EU has a common renewable directive, every Member State has its own renewable support policy. For the case of Spain, consumers pay the renewable premium in their electricity bills; however, consumers would not be overburdened if premiums were counter-balanced with the energy-cost reduction due to the merit-order effect of renewables. When two markets are interconnected, the energy exchange through the interconnection yields certain expected rent transfers due to the market rules. However, this exchange is also accompanied by other unforeseen rent transfers related to the regional/national policies on renewables. To the authors’ knowledge, the identification and quantification of these indirect rent transfers has not been previously addressed. This paper analyses and quantifies how the premiums on regional/national renewables are distributed between neighbouring countries through cross-border exchanges. The analysis focuses on the Iberian/Spanish system and its neighbours, although the methodology could be extended to other systems. To this end, data on the market and premiums has been considered, as well as the exchanges between France, Spain, Portugal, and Morocco, for the years 2015–2017. The main finding of this work is that the Spanish system, due to the lack of a coordinated/harmonized renewable premium policy, has been “importing” about 40 M€/year of renewable premium from France and 17 M€/year from Portugal while “exporting” about 66 M€/year towards the Moroccan systems. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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17 pages, 1574 KiB

Open AccessArticle

Participation as a Key Aspect for Establishing Wastewater as a Source of Renewable Energy

by Florian Kretschmer, Georg Neugebauer, Gernot Stoeglehner and Thomas Ertl

Energies 2018, 11(11), 3232; https://doi.org/10.3390/en11113232 - 21 Nov 2018

Cited by 15 | Viewed by 4627

Climate change is one of the great challenges of our times. In the search for renewable energy sources, wastewater has received increasing attention in recent years. This is due to the fact that it can serve as a source of electricity and heat [...] Read more.

Climate change is one of the great challenges of our times. In the search for renewable energy sources, wastewater has received increasing attention in recent years. This is due to the fact that it can serve as a source of electricity and heat supply, as well as a substitute for natural gas. The current literature frequently addresses more technical aspects from a mostly sanitary engineering-orientated perspective. Social aspects related to the energetic use of wastewater still appear to be underrepresented. To support the closure of existing knowledge gaps and to contribute to the development in this field, this article addresses two issues: it defines and characterises key stakeholder groups required to catalyse broader energetic usage of wastewater, and it proposes a participatory approach to support successfully establishing wastewater as a commonly accepted source of renewable energy to best support the ongoing energy transition. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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21 pages, 2080 KiB

Open AccessArticle

Computational Modelling of Three Different Sub-Boundary Layer Vortex Generators on a Flat Plate

by Ruben Gutierrez-Amo, Unai Fernandez-Gamiz, Iñigo Errasti and Ekaitz Zulueta

Energies 2018, 11(11), 3107; https://doi.org/10.3390/en11113107 - 10 Nov 2018

Cited by 20 | Viewed by 4221

Flow separation is the source of several problems in a wind turbine including load fluctuations, lift losses, and vibrations. Vortex generators (VGs) are passive flow control devices used to delay flow separation, but their implementation may produce overload drag at the blade section [...] Read more.

Flow separation is the source of several problems in a wind turbine including load fluctuations, lift losses, and vibrations. Vortex generators (VGs) are passive flow control devices used to delay flow separation, but their implementation may produce overload drag at the blade section where they are placed. In the current work, a computational model of different geometries of vortex generators placed on a flat plate has been carried out throughout fully meshed computational simulations using Reynolds Averaged Navier-Stokes (RANS) equations performed at a Reynolds number of

R e_{θ}

= 2600 based on local boundary layer (BL) momentum thickness

θ

= 2.4 mm. A flow characterization of the wake behind the vortex generator has been done with the aim of evaluating the performance of three vortex generator geometries, namely Rectangular VG, Triangular VG, and Symmetrical VG NACA0012. The location of the primary vortex has been evaluated by the vertical and lateral trajectories and it has been found that for all analyzed VG geometries the primary vortex is developed below the boundary layer thickness

δ

= 20 mm for a similar vorticity level (

w x_{m a x}

). Two innovative parameters have been developed in the present work for evaluating the vortex size and the vortex strength: Half-Life Surface

S_{05}

and Mean Positive Circulation

Γ_{05}^{+}

. As a result, an assessment of the VG performance has been carried out by all analyzed parameters and the symmetrical vortex generator NACA0012 has provided good efficiency in energy transfer compared with the Rectangular VG. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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16 pages, 507 KiB

Open AccessArticle

Energy Commodity Price Forecasting with Deep Multiple Kernel Learning

by Shian-Chang Huang and Cheng-Feng Wu

Energies 2018, 11(11), 3029; https://doi.org/10.3390/en11113029 - 05 Nov 2018

Cited by 12 | Viewed by 3442

Oil is an important energy commodity. The difficulties of forecasting oil prices stem from the nonlinearity and non-stationarity of their dynamics. However, the oil prices are closely correlated with global financial markets and economic conditions, which provides us with sufficient information to predict [...] Read more.

Oil is an important energy commodity. The difficulties of forecasting oil prices stem from the nonlinearity and non-stationarity of their dynamics. However, the oil prices are closely correlated with global financial markets and economic conditions, which provides us with sufficient information to predict them. Traditional models are linear and parametric, and are not very effective in predicting oil prices. To address these problems, this study developed a new strategy. Deep (or hierarchical) multiple kernel learning (DMKL) was used to predict the oil price time series. Traditional methods from statistics and machine learning usually involve shallow models; however, they are unable to fully represent complex, compositional, and hierarchical data features. This explains why traditional methods fail to track oil price dynamics. This study aimed to solve this problem by combining deep learning and multiple kernel machines using information from oil, gold, and currency markets. DMKL is good at exploiting multiple information sources. It can effectively identify the relevant information and simultaneously select an apposite data representation. The kernels of DMKL were embedded in a directed acyclic graph (DAG), which is a deep model and efficient at representing complex and compositional data features. This provided a solid foundation for extracting the key features of oil price dynamics. By using real data for empirical testing, our new system robustly outperformed traditional models and significantly reduced the forecasting errors. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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14 pages, 417 KiB

Open AccessArticle

Crop Characteristics of Aquatic Macrophytes for Use as a Substrate in Anaerobic Digestion Plants—A Study from Germany

by Lucie Moeller, Aline Bauer, Harald Wedwitschka, Walter Stinner and Andreas Zehnsdorf

Energies 2018, 11(11), 3016; https://doi.org/10.3390/en11113016 - 02 Nov 2018

Cited by 16 | Viewed by 4288

Several thousand metric tonnes of aquatic biomass are removed from water bodies every year, so that these waters can continue to be used for ship and boat traffic and for leisure activities. The mowed material is generally disposed off without any further use. [...] Read more.

Several thousand metric tonnes of aquatic biomass are removed from water bodies every year, so that these waters can continue to be used for ship and boat traffic and for leisure activities. The mowed material is generally disposed off without any further use. Therefore, the crop properties of samples from 39 weed control measures all over Germany were examined to assess the suitability of aquatic plant biomass as a substrate for anaerobic digestion systems. Analysis of the crop samples consisted of the identification of plant species and the evaluation of sediment contents and concentrations of macroelements. The methane yield was determined for selected aquatic plants. Analysis revealed a carbon/nitrogen ratio (C/N) of between 10 and 20 in 74% of samples. The concentrations of nitrogen and phosphorous in the samples were comparable to grass silages. With regard to heavy metal concentrations, the threshold values for biowaste for nickel, zinc, and cadmium were exceeded in three samples. There were no significant seasonal differences in substrate characteristics and qualities. The specific methane yields of individual aquatic plants were between 142 and 372 L_CH4/kg volatile solids (VS). The results of this study showed that aquatic macrophytes can be used as substrates in anaerobic digestion plants without any restrictions. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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17 pages, 6556 KiB

Open AccessArticle

Dual Frequency Regulation in Pumping Mode in a Wind–Hydro Isolated System

by José Ignacio Sarasúa, Guillermo Martínez-Lucas, Carlos A. Platero and José Ángel Sánchez-Fernández

Energies 2018, 11(11), 2865; https://doi.org/10.3390/en11112865 - 23 Oct 2018

Cited by 28 | Viewed by 4837

Frequency control is one of the most critical tasks in isolated power systems, especially in high renewable penetration scenarios. This paper presents a new hydropower pumped-storage dual control strategy that combines variable-speed-driven pumps and fixed-speed-driven pumps. A possible case for implementation of such [...] Read more.

Frequency control is one of the most critical tasks in isolated power systems, especially in high renewable penetration scenarios. This paper presents a new hydropower pumped-storage dual control strategy that combines variable-speed-driven pumps and fixed-speed-driven pumps. A possible case for implementation of such a control scheme is described based on El Hierro Island’s power system. This isolated power system consists of a hybrid wind pumped-storage hydropower plant and diesel generators. The pumped-storage power plant is divided into a hydropower plant equipped with four Pelton turbines and a pump station equipped with both fixed- and variable-speed pumps. According to the proposed control scheme, frequency regulation will be provided by a dual controller: a continuous controller for the variable-speed pumps and a discrete controller for the fixed-speed pumps. The Pelton units, which operate as synchronous condensers, also supply the power system inertia. Therefore, diesel units may be disconnected, decreasing generation costs and greenhouse gas emissions. Owing to the combination of both controllers and the inertia of the Pelton units, an acceptable frequency regulation can be achieved. This technique has been validated through computer simulations. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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18 pages, 1953 KiB

Open AccessArticle

Legal and Regulatory Development of Nuclear Energy in Bangladesh

by Ridoan Karim, Firdaus Muhammad-Sukki, Mohammad Ershadul Karim, Abu Bakar Munir, Imtiaz Mohammad Sifat, Siti Hawa Abu-Bakar, Nurul Aini Bani and Mohd Nabil Muhtazaruddin

Energies 2018, 11(10), 2847; https://doi.org/10.3390/en11102847 - 21 Oct 2018

Cited by 6 | Viewed by 5915

The adequacy of legal and regulatory framework relating to nuclear energy in Bangladesh has sparked many questions since the government took the formal decision to establish a nuclear power plant (NPP) at Rooppur. Consequently, the government has taken some measures to make a [...] Read more.

The adequacy of legal and regulatory framework relating to nuclear energy in Bangladesh has sparked many questions since the government took the formal decision to establish a nuclear power plant (NPP) at Rooppur. Consequently, the government has taken some measures to make a comprehensive and robust framework to ensure safe and secure nuclear energy production in the country. Even though these initiatives are highly appreciable, there remain certain regulatory concerns which this paper has attempted to reflect. Therefore, the objective of this paper is to showcase the recent legal and regulatory development of Bangladesh in relation to nuclear energy and to recommend further developments. The study was based on secondary sources where a doctrinal research was carried out to solve particular research questions. The safety and security of the Rooppur Nuclear Power Plant will frankly rely on how the government of Bangladesh plans and learns to implement, design, safeguard, exchange and further develop nuclear energy related knowledge and talent around the country. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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24 pages, 5473 KiB

Open AccessArticle

Optimization of Control Variables and Design of Management Strategy for Hybrid Hydraulic Vehicle

by Branimir Škugor and Joško Petrić

Energies 2018, 11(10), 2838; https://doi.org/10.3390/en11102838 - 20 Oct 2018

Cited by 6 | Viewed by 4380

The article deals with optimization of control variables and design of management strategy for a hybrid hydraulic vehicle in parallel configuration. Conventionally driven delivery truck with experimentally verified data from the previous research is taken as a starting base and benchmark for comparison [...] Read more.

The article deals with optimization of control variables and design of management strategy for a hybrid hydraulic vehicle in parallel configuration. Conventionally driven delivery truck with experimentally verified data from the previous research is taken as a starting base and benchmark for comparison of the benefits of hybridization. Optimization of control variables is carried out using dynamic programming (DP) algorithm to gain insight into optimum operation of the driveline and minimum possible fuel consumption for five different driving cycles. Two rule based management strategies are given and compared, one of which is improved and innovative, based on the knowledge gained from DP results. Hybrid driveline can reduce fuel consumption from 5% to 30% depending on the driving cycle. More dynamic cycles with lot of "stop-and-go" events score greater reduction. Innovative management strategy has achieved a similar distribution of internal combustion engine (ICE) operating points as DP optimization but this did not result in a consistent reduction of fuel consumption compared to basic management strategy for all cycles. That is explained by the state of charge (SoC) behaviour and reducing the potential for recovery of regenerative braking energy. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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14 pages, 2628 KiB

Open AccessArticle

Environmentally Friendly Compact Air-Insulated High-Voltage Substations

by Maurizio Albano, A. Manu Haddad, Huw Griffiths and Paul Coventry

Energies 2018, 11(9), 2492; https://doi.org/10.3390/en11092492 - 19 Sep 2018

Cited by 12 | Viewed by 5752

This paper investigates the possible options for achieving a substantial reduction in a substation footprint using air-insulated switchgear as a more environmentally-friendly alternative to gas-insulated substations that use SF₆ gas. Adopting a new approach to surge arrester location and numbers, International Electrotechnical [...] Read more.

This paper investigates the possible options for achieving a substantial reduction in a substation footprint using air-insulated switchgear as a more environmentally-friendly alternative to gas-insulated substations that use SF₆ gas. Adopting a new approach to surge arrester location and numbers, International Electrotechnical Commission (IEC) minimum clearances can be successfully selected instead of the maximum clearances as currently adopted by many utilities, as is the case in the UK. In addition, innovative alternative compact busbar arrangements using vertical and delta configurations have been proposed by the authors. A further opportunity for compaction is offered by the application of compact and integrated technology offered from several manufacturers. The full overvoltage control within the entire substation under any surge condition is a key aspect of the feasibility of this type of substation. This work demonstrates that the new design option can be an attractive alternative for future substation configuration with minimum footprint. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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28 pages, 14272 KiB

Open AccessArticle

Nonlinear Temperature-Dependent State Model of Cylindrical LiFePO₄ Battery for Open-Circuit Voltage, Terminal Voltage and State-of-Charge Estimation with Extended Kalman Filter

by Cheng Siong Chin, Zuchang Gao, Joel Hay King Chiew and Caizhi Zhang

Energies 2018, 11(9), 2467; https://doi.org/10.3390/en11092467 - 17 Sep 2018

Cited by 25 | Viewed by 4907

Ambient temperature affects the performance of a battery power system and its accuracy in state-of-charge (SOC) estimation for electric vehicles and smart grid systems. This paper proposes a battery model that considered ambient temperature, cell temperature, hysteresis voltage and thermal aging [...] Read more.

Ambient temperature affects the performance of a battery power system and its accuracy in state-of-charge (SOC) estimation for electric vehicles and smart grid systems. This paper proposes a battery model that considered ambient temperature, cell temperature, hysteresis voltage and thermal aging on capacity due to multiple charging and discharging. The SOC is then estimated using an extended Kalman filter. Several forms of validation were tested on an actual cell battery under specific ambient temperatures to verify the battery cell model, terminal voltage and SOC estimation performance. The SOC estimation results show an improvement in root-mean-squared error as compared to Extended Kalman Filter (EKF) without considering the temperature dependency. The proposed battery temperature-dependent model gave a smaller root-mean square error in SOC and terminal voltage at 5 °C, 15 °C and 45 °C. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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18 pages, 2710 KiB

Open AccessArticle

Implementation Strategy of Convolution Neural Networks on Field Programmable Gate Arrays for Appliance Classification Using the Voltage and Current (V-I) Trajectory

by Darío Baptista, Sheikh Shanawaz Mostafa, Lucas Pereira, Leonel Sousa and Fernando Morgado-Dias

Energies 2018, 11(9), 2460; https://doi.org/10.3390/en11092460 - 17 Sep 2018

Cited by 30 | Viewed by 4525

Specific information about types of appliances and their use in a specific time window could help determining in details the electrical energy consumption information. However, conventional main power meters fail to provide any specific information. One of the best ways to solve these [...] Read more.

Specific information about types of appliances and their use in a specific time window could help determining in details the electrical energy consumption information. However, conventional main power meters fail to provide any specific information. One of the best ways to solve these problems is through non-intrusive load monitoring, which is cheaper and easier to implement than other methods. However, developing a classifier for deducing what kind of appliances are used at home is a difficult assignment, because the system should identify the appliance as fast as possible with a higher degree of certainty. To achieve all these requirements, a convolution neural network implemented on hardware was used to identify the appliance through the voltage and current (V-I) trajectory. For the implementation on hardware, a field programmable gate array (FPGA) was used to exploit processing parallelism in order to achieve optimal performance. To validate the design, a publicly available Plug Load Appliance Identification Dataset (PLAID), constituted by 11 different appliances, has been used. The overall average F-score achieved using this classifier is 78.16% for the PLAID 1 dataset. The convolution neural network implemented on hardware has a processing time of approximately 5.7 ms and a power consumption of 1.868 W. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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10 pages, 1668 KiB

Open AccessArticle

Optimisation of Tray Drier Microalgae Dewatering Techniques Using Response Surface Methodology

by Ruth Chinyere Anyanwu, Cristina Rodriguez, Andy Durrant and Abdul Ghani Olabi

Energies 2018, 11(9), 2327; https://doi.org/10.3390/en11092327 - 04 Sep 2018

Cited by 14 | Viewed by 4782

The feasibility of the application of a tray drier in dewatering microalgae was investigated. Response surface methodology (RSM) based on Central Composite Design (CCD) was used to evaluate and optimise the effect of air temperature and air velocity as independent variables on the [...] Read more.

The feasibility of the application of a tray drier in dewatering microalgae was investigated. Response surface methodology (RSM) based on Central Composite Design (CCD) was used to evaluate and optimise the effect of air temperature and air velocity as independent variables on the dewatering efficiency as a response function. The significance of independent variables and their interactions was tested by means of analysis of variance (ANOVA) with a 95% confidence level. Results indicate that the air supply temperature was the main parameter affecting dewatering efficiency, while air velocity had a slight effect on the process. The optimum operating conditions to achieve maximum dewatering were determined: air velocities and temperatures ranged between 4 to 10 m/s and 40 to 56 °C respectively. An optimised dewatering efficiency of 92.83% was achieved at air an velocity of 4 m/s and air temperature of 48 °C. Energy used per 1 kg of dry algae was 0.34 kWh. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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15 pages, 1170 KiB

Open AccessArticle

Determining Equipment Capacity of Electric Vehicle Charging Station Operator for Profit Maximization

by Se Hoon Baik, Young Gyu Jin and Yong Tae Yoon

Energies 2018, 11(9), 2301; https://doi.org/10.3390/en11092301 - 01 Sep 2018

Cited by 24 | Viewed by 4177

Related to global efforts to reduce greenhouse gases, numerous electric vehicles (EVs) are expected to be integrated to the power grid. However, the introduction of EVs, particularly in Korea, is still marginal due to the lack of EV charging infrastructure, even though various [...] Read more.

Related to global efforts to reduce greenhouse gases, numerous electric vehicles (EVs) are expected to be integrated to the power grid. However, the introduction of EVs, particularly in Korea, is still marginal due to the lack of EV charging infrastructure, even though various supportive policies exist. To address this shortage of EV charging stations, the EV charging business needs to be profitable. As with any business, the profitability of the EV charging business is significantly affected by the initial capital investment related to EV chargers and auxiliary equipment such as power conditioning system (PCS), battery energy storage system (BESS), and on-site photovoltaic (PV) generation system. Thus, we propose a formulation to determine the number of EV chargers and the capacity of auxiliary equipment with the objective of a charging station operator (CSO) maximizing profit under regulatory, economic, and physical constraints. The effectiveness of the proposed method is verified with simulations considering various EV charging patterns. The study results will help improve the EV charging infrastructure by encouraging individuals and companies to participate in EV charging business. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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21 pages, 1964 KiB

Open AccessArticle

An Indicator-Based Approach for Analysing the Resilience of Transitions for Energy Regions. Part II: Empirical Application to the Case of Weiz-Gleisdorf, Austria

by Romano Wyss, Susan Mühlemeier and Claudia R. Binder

Energies 2018, 11(9), 2263; https://doi.org/10.3390/en11092263 - 28 Aug 2018

Cited by 8 | Viewed by 3886

In this paper, we apply an indicator-based approach to measure the resilience of energy regions in transition to a case study region in Austria. The indicator-based approach allows to determine the resilience of the transition of regional energy systems towards higher shares of [...] Read more.

In this paper, we apply an indicator-based approach to measure the resilience of energy regions in transition to a case study region in Austria. The indicator-based approach allows to determine the resilience of the transition of regional energy systems towards higher shares of renewables and potentially overall higher sustainability. The indicators are based on two core aspects of resilience, diversity and connectivity. Diversity is thereby operationalized by variety, disparity and balance, whereas connectivity is operationalized by average path length, degree centrality and modularity. In order to get a full picture of the resilience of the energy system at stake throughout time, we apply the measures to four distinct moments, situated in the pre-development, take-off, acceleration and stabilization phase of the transition. By contextually and theoretically embedding the insights in the broader transitions context and empirically applying the indicators to a specific case, we derive insights on (1) how to interpret the results in a regional context and (2) how to further develop the indicator-based approach for future applications. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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13 pages, 4163 KiB

Open AccessArticle

Design, Development and Implementation of a Weather Station Prototype for Renewable Energy Systems

by Carlos Morón, Jorge Pablo Diaz, Daniel Ferrández and Pablo Saiz

Energies 2018, 11(9), 2234; https://doi.org/10.3390/en11092234 - 26 Aug 2018

Cited by 14 | Viewed by 4475

The production of energy at the global level is conditioned by the use of fossil fuels that have a great environmental impact. In the last decades, renewable energy production systems have been implemented, and networks of nearly zero-energy buildings have been created, with [...] Read more.

The production of energy at the global level is conditioned by the use of fossil fuels that have a great environmental impact. In the last decades, renewable energy production systems have been implemented, and networks of nearly zero-energy buildings have been created, with a consequent complexity in the design phase in order to optimize the results. In this way, electronic prototype development methods like the one that is proposed in this paper improve the tasks of design and modelling. Thus, a new weather station based on an Arduino platform has been developed to collect and store ambient temperature, relative humidity, barometric pressure, wind speed and air quality data, comparing the obtained data to those obtained using a validation station containing commercial sensors. The results show how the use of low cost Arduino sensors allow one to obtain similar values to those collected by more professional meteorological stations with insignificant scatter between both technologies. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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17 pages, 8059 KiB

Open AccessArticle

The Effect of a Wave Energy Farm Protecting an Aquaculture Installation

by Dina Silva, Eugen Rusu and C. Guedes Soares

Energies 2018, 11(8), 2109; https://doi.org/10.3390/en11082109 - 13 Aug 2018

Cited by 21 | Viewed by 4486

This paper assesses the impact of a farm of wave energy converters on a nearby offshore aquaculture installation and on the nearshore dynamics. The coastal area targeted is Aguçadoura, located in the north of Portugal, where the world’s first wave farm operated in [...] Read more.

This paper assesses the impact of a farm of wave energy converters on a nearby offshore aquaculture installation and on the nearshore dynamics. The coastal area targeted is Aguçadoura, located in the north of Portugal, where the world’s first wave farm operated in 2008. The study is focused mainly on the evaluation of the sheltering effect provided by the wave farm to the aquaculture cages. Furthermore, the possible impact on the coastal wave climate of such an energy park is also evaluated. These objectives are accomplished by performing simulations, corresponding to the wave conditions, which are more often encountered in that coastal environment. The SWAN model (Simulating WAves Nearshore) was adopted for this. Various transmission scenarios are considered to account for the impact of different types of wave converter farms on the downwave conditions. The results show that such a wave energy park might have a clear positive impact on the wave conditions fish farm installed downwave and it might also have a beneficial influence on shoreline dynamics from the perspective of coastal protection. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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16 pages, 2969 KiB

Open AccessArticle

Site Selection of Hybrid Offshore Wind and Wave Energy Systems in Greece Incorporating Environmental Impact Assessment

by Eva Loukogeorgaki, Dimitra G. Vagiona and Margarita Vasileiou

Energies 2018, 11(8), 2095; https://doi.org/10.3390/en11082095 - 12 Aug 2018

Cited by 29 | Viewed by 5536

This paper presents a methodological framework for evaluating marine areas in Greece for the purpose of identifying the most adequate sites for Hybrid Offshore Wind and Wave Energy Systems (HOWiWaES), with special focus on the HOWiWaES’ environmental impact assessment evaluation. Nine evaluation criteria [...] Read more.

This paper presents a methodological framework for evaluating marine areas in Greece for the purpose of identifying the most adequate sites for Hybrid Offshore Wind and Wave Energy Systems (HOWiWaES), with special focus on the HOWiWaES’ environmental impact assessment evaluation. Nine evaluation criteria that reflect various environmental, economic, technical and socio-political aspects are considered, including Wind Velocity (WV), Wave Energy Potential (WEP), Water Depth (WD), Distance from Shore (DS), Connection to Local Electrical Grid (CLEG), Population Served (PS), Shipping Density (SD), Distance from Ports (DP) and Environmental Performance Value (EPV). Analytical Hierarchy Process (AHP) is performed to hierarchically rank twelve predefined siting alternatives. Questionnaires are used to collect information on pairwise comparisons of the evaluation criteria from a group of stakeholders/experts. Geographic Information Systems (GIS) are used as a metric tool for pairwise comparisons of each siting alternative with respect to the first eight evaluation criteria, while the last criterion is assessed through the development of an innovative environmental impact assessment tool. The results indicate that WV, WEP and EPV present the evaluation criteria with the highest relative significance, while PS, DP and SD correspond to less influencing criteria. The proposed methodology can be easily applied to other countries worldwide for supporting socially accepted siting of HOWiWaES. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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19 pages, 6118 KiB

Open AccessArticle

Computational Modeling of Gurney Flaps and Microtabs by POD Method

by Unai Fernandez-Gamiz, Macarena Gomez-Mármol and Tomas Chacón-Rebollo

Energies 2018, 11(8), 2091; https://doi.org/10.3390/en11082091 - 11 Aug 2018

Cited by 34 | Viewed by 5053

Gurney flaps (GFs) and microtabs (MTs) are two of the most frequently used passive flow control devices on wind turbines. They are small tabs situated close to the airfoil trailing edge and normal to the surface. A study to find the most favorable [...] Read more.

Gurney flaps (GFs) and microtabs (MTs) are two of the most frequently used passive flow control devices on wind turbines. They are small tabs situated close to the airfoil trailing edge and normal to the surface. A study to find the most favorable dimension and position to improve the aerodynamic performance of an airfoil is presented herein. Firstly, a parametric study of a GF on a S810 airfoil and an MT on a DU91(2)250 airfoil was carried out. To that end, 2D computational fluid dynamic simulations were performed at Re = 10⁶ based on the airfoil chord length and using RANS equations. The GF and MT design parameters resulting from the computational fluid dynamics (CFD) simulations allowed the sizing of these passive flow control devices based on the airfoil’s aerodynamic performance. In both types of flow control devices, the results showed an increase in the lift-to-drag ratio for all angles of attack studied in the current work. Secondly, from the data obtained by means of CFD simulations, a regular function using the proper orthogonal decomposition (POD) was used to build a reduced order method. In both flow control cases (GFs and MTs), the recursive POD method was able to accurately and very quickly reproduce the computational results with very low computational cost. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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22 pages, 4204 KiB

Open AccessArticle

Effect of Zonal Hydraulics on Energy Consumption and Boom Structure of a Micro-Excavator

by Abinab Niraula, Shuzhong Zhang, Tatiana Minav and Matti Pietola

Energies 2018, 11(8), 2088; https://doi.org/10.3390/en11082088 - 10 Aug 2018

Cited by 14 | Viewed by 6065

This paper investigates the effect of extra weight caused by the Direct Driven Hydraulics (DDH) in a micro-excavator. These projects are investigating the implementation of zonal or decentralized hydraulics for non-road mobile machinery (NRMM) and stationary industrial applications. The benefit of DDH is [...] Read more.

This paper investigates the effect of extra weight caused by the Direct Driven Hydraulics (DDH) in a micro-excavator. These projects are investigating the implementation of zonal or decentralized hydraulics for non-road mobile machinery (NRMM) and stationary industrial applications. The benefit of DDH is the combination of electric and hydraulic technologies in a compact package compared to conventional hydraulics, which enables a reduction of potential leakage points, flexible tubing, and boosting of the system efficiency due to switching to direct pump control instead of a loss-generating conventional valve-based control. In order to demonstrate these benefits for the excavator case, this paper proposes a system model approach to assess and predict energy consumption of the zonal hydraulics approach implemented with DDH in various working cycles, complemented by a structural analysis. The finite element analysis utilized for this demonstrated that the extra weight and selected location of DDH units do not negatively affect the structure of the excavator. Simulation results demonstrated that the energy consumption is approximately 15% higher with extra weight added by the three DDH units. Although approximately 20% more regeneration energy is produced, taking into account the regeneration energy, the increases in energy consumption are about 12%. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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9 pages, 1006 KiB

Open AccessArticle

BiPAD: Binomial Point Process Based Energy-Aware Data Dissemination in Opportunistic D2D Networks

by Seho Han, Kisong Lee, Hyun-Ho Choi and Howon Lee

Energies 2018, 11(8), 2073; https://doi.org/10.3390/en11082073 - 09 Aug 2018

Viewed by 3185

In opportunistic device-to-device (D2D) networks, the epidemic routing protocol can be used to optimize the message delivery ratio. However, it has the disadvantage that it causes excessive coverage overlaps and wastes energy in message transmissions because devices are more likely to receive duplicates [...] Read more.

In opportunistic device-to-device (D2D) networks, the epidemic routing protocol can be used to optimize the message delivery ratio. However, it has the disadvantage that it causes excessive coverage overlaps and wastes energy in message transmissions because devices are more likely to receive duplicates from neighbors. We therefore propose an efficient data dissemination algorithm that can reduce undesired transmission overlap with little performance degradation in the message delivery ratio. The proposed algorithm allows devices further away than the k-th furthest distance from the source device to forward a message to their neighbors. These relay devices are determined by analysis based on a binomial point process (BPP). Using a set of intensive simulations, we present the resulting network performances with respect to the total number of received messages, the forwarding efficiency and the actual number of relays. In particular, we find the optimal number of relays to achieve almost the same message delivery ratio as the epidemic routing protocol for a given network deployment. Furthermore, the proposed algorithm can achieve almost the same message delivery ratio as the epidemic routing protocol while improving the forwarding efficiency by over

103 %

when

k \geq 10

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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22 pages, 972 KiB

Open AccessArticle

A Simple Assessment of Housing Retrofit Policies for the UK: What Should Succeed the Energy Company Obligation?

by Luciana Maria Miu, Natalia Wisniewska, Christoph Mazur, Jeffrey Hardy and Adam Hawkes

Energies 2018, 11(8), 2070; https://doi.org/10.3390/en11082070 - 08 Aug 2018

Cited by 9 | Viewed by 5730

Despite the need for large-scale retrofit of UK housing to meet emissions reduction targets, progress to date has been slow and domestic energy efficiency policies have struggled to accelerate housing retrofit processes. There is a need for housing retrofit policies that overcome key [...] Read more.

Despite the need for large-scale retrofit of UK housing to meet emissions reduction targets, progress to date has been slow and domestic energy efficiency policies have struggled to accelerate housing retrofit processes. There is a need for housing retrofit policies that overcome key barriers within the retrofit sector while maintaining economic viability for customers, funding organizations, and effectively addressing UK emission reductions and fuel poverty targets. In this study, we use a simple assessment framework to assess three policies (the Variable Council Tax, the Variable Stamp Duty Land Tax, and Green Mortgage) proposed to replace the UK’s current major domestic retrofit programme known as the Energy Company Obligation (ECO). We show that the Variable Council Tax and Green Mortgage proposals have the greatest potential for overcoming the main barriers to retrofit policies while maintaining economic viability and contributing to high-level UK targets. We also show that, while none of the assessed schemes are capable of overcoming all retrofit barriers on their own, a mix of all three policies could address most barriers and provide key benefits such as wide coverage of property markets, operation on existing financial infrastructures, and application of a “carrot-and-stick” approach to incentivize retrofit. Lastly, we indicate that the specific support and protection of fuel-poor households cannot be achieved by a mix of these policies and a complementary scheme focused on fuel-poor households is required. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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18 pages, 5204 KiB

Open AccessArticle

Indicator-Based Methodology for Assessing EV Charging Infrastructure Using Exploratory Data Analysis

by Alexandre Lucas, Giuseppe Prettico, Marco Giacomo Flammini, Evangelos Kotsakis, Gianluca Fulli and Marcelo Masera

Energies 2018, 11(7), 1869; https://doi.org/10.3390/en11071869 - 18 Jul 2018

Cited by 20 | Viewed by 6108

Electric vehicle (EV) charging infrastructure rollout is well under way in several power systems, namely North America, Japan, Europe, and China. In order to support EV charging infrastructures design and operation, little attempt has been made to develop indicator-based methods characterising such networks [...] Read more.

Electric vehicle (EV) charging infrastructure rollout is well under way in several power systems, namely North America, Japan, Europe, and China. In order to support EV charging infrastructures design and operation, little attempt has been made to develop indicator-based methods characterising such networks across different regions. This study defines an assessment methodology, composed by eight indicators, allowing a comparison among EV public charging infrastructures. The proposed indicators capture the following: energy demand from EVs, energy use intensity, charger’s intensity distribution, the use time ratios, energy use ratios, the nearest neighbour distance between chargers and availability, the total service ratio, and the carbon intensity as an environmental impact indicator. We apply the methodology to a dataset from ElaadNL, a reference smart charging provider in The Netherlands, using open source geographic information system (GIS) and R software. The dataset reveals higher energy intensity in six urban areas and that 50% of energy supplied comes from 19.6% of chargers. Correlations of spatial density are strong and nearest neighbouring distances range from 1101 to 9462 m. Use time and energy use ratios are 11.21% and 3.56%. The average carbon intensity is 4.44 gCO_2eq/MJ. Finally, the indicators are used to assess the impact of relevant public policies on the EV charging infrastructure use and roll-out. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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12 pages, 1857 KiB

Open AccessArticle

A Simple Pseudo-Homogeneous Reversible Kinetic Model for the Esterification of Different Fatty Acids with Methanol in the Presence of Amberlyst-15

by Mauro Banchero and Giuseppe Gozzelino

Energies 2018, 11(7), 1843; https://doi.org/10.3390/en11071843 - 13 Jul 2018

Cited by 33 | Viewed by 8370

Fatty acid esterification with alcohols is a crucial step in biodiesel synthesis. Biodiesel consists of long-chain alkyl esters that derive from the transesterification or hydro-esterification of the triglycerides that are contained in vegetable oils. In the first route, the esterification of the free [...] Read more.

Fatty acid esterification with alcohols is a crucial step in biodiesel synthesis. Biodiesel consists of long-chain alkyl esters that derive from the transesterification or hydro-esterification of the triglycerides that are contained in vegetable oils. In the first route, the esterification of the free fatty acids is an important pretreatment of the feed; in the second, it is the main reaction of the industrial process. Knowledge of appropriate kinetic models for the catalytic esterification of fatty acids with alcohols is critical in the design of biodiesel synthesis processes. In this work, the kinetic behavior of the reversible esterification of lauric, myristic, palmitic and stearic acid, which are the most common saturated fatty acids that are contained in triglyceride feedstocks for biodiesel, with methanol at different temperatures (70–150 °C) and molar ratios of the reactants (1:1–1:2–1:5) was investigated in a batch laboratory basket reactor both in the presence and absence of Amberlyst-15 as the catalyst. Results obtained with Amberlyst-15 were fitted through a ready-to-use pseudo-homogeneous reversible model suitable for process design. The kinetic model was compared with that obtained in a previous work with niobium oxide as the catalyst. With respect to the results that were obtained with niobium oxide, the influence of the chain length of the acid on the kinetic behavior was strongly reduced in the presence of Amberlyst-15. This phenomenon was ascribed to a different catalytic mechanism. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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20 pages, 487 KiB

Open AccessArticle

Energy Revolution for Our Common Future: An Evaluation of the Emerging International Renewable Energy Law

by Md Ershadul Karim, Abu Bakar Munir, Mohammad Ataul Karim, Firdaus Muhammad-Sukki, Siti Hawa Abu-Bakar, Nazmi Sellami, Nurul Aini Bani and Mohamad Zaki Hassan

Energies 2018, 11(7), 1769; https://doi.org/10.3390/en11071769 - 05 Jul 2018

Cited by 21 | Viewed by 7763

Climate change poses profound threats to the Earth and its people. Its mitigation, therefore, demands common but differentiated actions with comprehensive and coordinated approach. The global community has pledged to mitigate various greenhouse gases in some international soft law instruments. Exploitation of renewables [...] Read more.

Climate change poses profound threats to the Earth and its people. Its mitigation, therefore, demands common but differentiated actions with comprehensive and coordinated approach. The global community has pledged to mitigate various greenhouse gases in some international soft law instruments. Exploitation of renewables to generate energy and produce electricity is simultaneously suggested for the last couple of decades as a viable alternative in mitigating climate change. This gets momentum with the adoption of the historical and universally ratified Paris Agreement in 2016 where energy is placed at the heart of the Agreement. Energy, where renewable energy is a branch, is generally regulated and governed domestically and so, international legal regime is still evolving in this regard. In the absence of any specific and direct international instrument on energy and renewable energy, published literatures have considered this topic from different directions ranging from climate change to the principle of national sovereignty, economic, trade and investment issues. In this backdrop, this paper aims to introduce various renewable sources, prospects and challenges in their promotion that may help to mitigate the adverse effects of climate change. Relevant international law provisions have been evaluated, performances of the relevant regional and international organizations active in this sector are highlighted and some of the disputes in this area considered in international forums are duly addressed. It is revealed that strong political will of the global community in fulfilling their commitments made so far in different international forums is the key to transforming the world into a better one for the future generation. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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15 pages, 468 KiB

Open AccessArticle

Nuclear Energy Development in Bangladesh: A Study of Opportunities and Challenges

by Ridoan Karim, Mohammad Ershadul Karim, Firdaus Muhammad-Sukki, Siti Hawa Abu-Bakar, Nurul Aini Bani, Abu Bakar Munir, Ahmed Imran Kabir, Jorge Alfredo Ardila-Rey and Abdullahi Abubakar Mas’ud

Energies 2018, 11(7), 1672; https://doi.org/10.3390/en11071672 - 27 Jun 2018

Cited by 28 | Viewed by 8745

It is a challenging task for Bangladesh to meet its increasing demand of energy while its economy is rapidly growing. Though prices of oil, coal, and fossil fuels around the world have been volatile, the price trend in Bangladesh demonstrates a persistent rise [...] Read more.

It is a challenging task for Bangladesh to meet its increasing demand of energy while its economy is rapidly growing. Though prices of oil, coal, and fossil fuels around the world have been volatile, the price trend in Bangladesh demonstrates a persistent rise in the immediate past. This is further exacerbated by depleting reserves of natural gas. Cumulatively, these two effects heighten Bangladesh’s energy needs. Bangladesh presently mitigates her energy requirements predominantly through natural gas, supplemented by a handful of coal and furnace oil plants. Consequently, due to scarcity of natural gas, oil and coal resources, nuclear power surfaces as a palatable strategic option for Bangladesh’s future development agenda. However, a successful nuclear power program entails an extensive infrastructure. Just like the other nuclear energy-producing countries, Bangladesh also face challenges to safeguard the health and security of nuclear reactors, the proper management for nuclear waste treatment and the security concerns over the safe usage of nuclear materials. Additionally, the development of nuclear energy is also bewildered because of the complex nature of fission technology, lack of efficient human resources, and non-existence of proper legal instruments to guide safe nuclear power production. Moreover, the further challenges include the questions, for example: whether the nuclear power plant project is supported by the mass people or not? What are the strategies for nuclear waste disposal? Whether the recent initiatives for nuclear energy production is necessary or the country should more concern with renewable sources? This paper evaluates the nuclear energy development in Bangladesh. It operates under qualitative methodological framework and utilises secondary sources for analysis. We advance several recommendations in this paper to remedy the highlighted issues: (1) creating a comprehensive legal and regulatory system; (2) fortifying home-based technology of nuclear development and simultaneously localising of foreign-based technology; (3) reducing the cost of nuclear energy production; (4) fast-tracking the procedure of efficient development of nuclear technology; (5) accelerating the procedure of switching to more efficient reactor and nuclear fuel cycle, and (6) conducting effective profile-raising activities to generate greater awareness and spur common acceptance. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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14 pages, 1384 KiB

Open AccessArticle

The Influence of Imports and Exports on the Evolution of Greenhouse Gas Emissions: The Case for the European Union

by Laia Pié, Laura Fabregat-Aibar and Marc Saez

Energies 2018, 11(7), 1644; https://doi.org/10.3390/en11071644 - 24 Jun 2018

Cited by 16 | Viewed by 3472

Part of a country’s emissions are caused by producing goods for export to other countries, while a country’s own needs also generate emissions in other parts of the world that are associated with the products they import. Our interest was to evaluate the [...] Read more.

Part of a country’s emissions are caused by producing goods for export to other countries, while a country’s own needs also generate emissions in other parts of the world that are associated with the products they import. Our interest was to evaluate the influence of imports and exports of goods and services on greenhouse gas (GHG) emissions in a data panel composed of 30 countries over 21 years. We included as control variables the gross domestic product per capita, employment, an indicator of the economic crisis and a non-linear trend and inferences were performed using a Bayesian framework. The results showed that it was the exports and imports of goods, rather than services, that were related to CO₂-equivalent levels. Exports and imports of goods were very inelastic, albeit less so in the case of the index. In summary, the more a country imports, the higher their GHG emission levels are. However, it is important to point out that when employment rates are higher more energy is consumed and GHG emissions are greater. In richer countries, GDP per capita is the factor that best explains why their emissions are so high. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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17 pages, 3825 KiB

Open AccessArticle

Design, Fabrication, and Performance Test of a 100-W Helical-Blade Vertical-Axis Wind Turbine at Low Tip-Speed Ratio

by Dowon Han, Young Gun Heo, Nak Joon Choi, Sang Hyun Nam, Kyoung Ho Choi and Kyung Chun Kim

Energies 2018, 11(6), 1517; https://doi.org/10.3390/en11061517 - 11 Jun 2018

Cited by 24 | Viewed by 16750

A 100-W helical-blade vertical-axis wind turbine was designed, manufactured, and tested in a wind tunnel. A relatively low tip-speed ratio of 1.1 was targeted for usage in an urban environment at a rated wind speed of 9 m/s and a rotational speed of [...] Read more.

A 100-W helical-blade vertical-axis wind turbine was designed, manufactured, and tested in a wind tunnel. A relatively low tip-speed ratio of 1.1 was targeted for usage in an urban environment at a rated wind speed of 9 m/s and a rotational speed of 170 rpm. The basic dimensions were determined through a momentum-based design method according to the IEC 61400-2 protocol. The power output was estimated by a mathematical model that takes into account the aerodynamic performance of the NACA0018 blade shape. The lift and drag of the blade with respect to the angle of attack during rotation were calculated using 2D computational fluid dynamics (CFD) simulation to take into account stall region. The average power output calculated by the model was 108.34 W, which satisfies the target output of 100 W. The manufactured wind turbine was tested in a large closed-circuit wind tunnel, and the power outputs were measured for given wind speeds. At the design condition, the measured power output was 114.7 W, which is 5.9% higher than that of the mathematical model. This result validates the proposed design method and power estimation by the mathematical model. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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Review

Jump to: Research

25 pages, 2201 KiB

Open AccessReview

A Review of the Energy Efficiency Improvement in DC Railway Systems

by Mihaela Popescu and Alexandru Bitoleanu

Energies 2019, 12(6), 1092; https://doi.org/10.3390/en12061092 - 21 Mar 2019

Cited by 61 | Viewed by 7122

This study is focused on the topical issue of increasing the energy efficiency in DC railway systems, in the context of global concerns for reducing the CO₂ emissions by minimizing the energy consumption and energy loss. The main achievements in this complex [...] Read more.

This study is focused on the topical issue of increasing the energy efficiency in DC railway systems, in the context of global concerns for reducing the CO₂ emissions by minimizing the energy consumption and energy loss. The main achievements in this complex issue are synthesized and discussed in a comprehensive review, emphasizing the implementation and application of the existing solutions on concrete case studies. Thus, all specific subtopics related to the energy efficiency are covered, starting with power quality conditioning and continuing with the recovery of braking energy, of which a large part is lost in the classic DC-traction substations. The solutions of onboard and wayside storage systems for the braking energy are discussed and compared, and practical examples are given. Then, the achievements in transforming the existing DC-traction substations in reversible substations with capabilities of power quality improvement are systematically reviewed by illustrating the main results of recent research on this topic. They include the equipment available on the market and solutions validated through implementations on experimental models. Through the results of this extensive review, useful reference and support are provided for the research and development focused on energy efficient traction systems. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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23 pages, 10214 KiB

Open AccessReview

Occurrence and Characterization of Paraffin Wax Formed in Developing Wells and Pipelines

by Marwa M. El-Dalatony, Byong-Hun Jeon, El-Sayed Salama, Mohamed Eraky, Won Beom Kim, Jihoon Wang and Taewoong Ahn

Energies 2019, 12(6), 967; https://doi.org/10.3390/en12060967 - 13 Mar 2019

Cited by 62 | Viewed by 9775

Deposition and precipitation of paraffin wax in pipelines are major problems in the production, transfer, storage, and processing of crude oil. To prevent complete clogging, it is necessary to minimize and remove deposited wax in pipelines and tubing. Significant research has been done [...] Read more.

Deposition and precipitation of paraffin wax in pipelines are major problems in the production, transfer, storage, and processing of crude oil. To prevent complete clogging, it is necessary to minimize and remove deposited wax in pipelines and tubing. Significant research has been done addressing the mechanisms of wax formation and its composition. In this review, the status of research and perspectives on the occurrence and characterization of the paraffin wax that forms in crude oil developing wells and pipelines has been critically reviewed. Several approaches for detecting paraffin wax and managing wax formation damage during oil recovery were discussed. This review also highlighted the effects of temperature and crude oil type on wax formation. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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21 pages, 1691 KiB

Open AccessReview

Comprehensive Review of Islanding Detection Methods for Distributed Generation Systems

by Min-Sung Kim, Raza Haider, Gyu-Jung Cho, Chul-Hwan Kim, Chung-Yuen Won and Jong-Seo Chai

Energies 2019, 12(5), 837; https://doi.org/10.3390/en12050837 - 04 Mar 2019

Cited by 140 | Viewed by 7449

The increased penetration of distributed generation (DG), renewable energy utilization, and the introduction of the microgrid concept have changed the shape of conventional electric power networks. Most of the new power system networks are transforming into the DG model integrated with renewable and [...] Read more.

The increased penetration of distributed generation (DG), renewable energy utilization, and the introduction of the microgrid concept have changed the shape of conventional electric power networks. Most of the new power system networks are transforming into the DG model integrated with renewable and non-renewable energy resources by forming a microgrid. Islanding detection in DG systems is a challenging issue that causes several protection and safety problems. A microgrid operates in the grid-connected or stand-alone mode. In the grid-connected mode, the main utility network is responsible for a smooth operation in coordination with the protection and control units, while in the stand-alone mode, the microgrid operates as an independent power island that is electrically separated from the main utility network. Fast islanding detection is, therefore, necessary for efficient and reliable microgrid operations. Many islanding detection methods (IdMs) are proposed in the literature, and each of them claims better reliability and high accuracy. This study describes a comprehensive review of various IdMs in terms of their merits, viability, effectiveness, and feasibility. The IdMs are extensively analysed by providing a fair comparison from different aspects. Moreover, a fair analysis of a feasible and economical solution in view of the recent research trend is presented. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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28 pages, 728 KiB

Open AccessReview

A Survey on Power System Blackout and Cascading Events: Research Motivations and Challenges

by Hassan Haes Alhelou, Mohamad Esmail Hamedani-Golshan, Takawira Cuthbert Njenda and Pierluigi Siano

Energies 2019, 12(4), 682; https://doi.org/10.3390/en12040682 - 20 Feb 2019

Cited by 369 | Viewed by 29343

Power systems are the most complex systems and have great importance in modern life. They have direct impacts on the modernization, economic, political and social aspects. To operate such systems in a stable mode, several control and protection techniques are required. However, modern [...] Read more.

Power systems are the most complex systems and have great importance in modern life. They have direct impacts on the modernization, economic, political and social aspects. To operate such systems in a stable mode, several control and protection techniques are required. However, modern systems are equipped with several protection schemes with the aim of avoiding the unpredicted events and power outages, power systems are still encountering emergency and mal-operation situations. The most severe emergencies put the whole or at least a part of the system in danger. If the emergency is not well managed, the power system is likely to have cascading failures that might lead to a blackout. Due to the consequences, many countries around the world have research and expert teams who work to avoid blackouts on their systems. In this paper, a comprehensive review on the major blackouts and cascading events that have occurred in the last decade are introduced. A particular focus is given on the US power system outages and their causes since it is one of the leading power producers in the world and it is also due to the ready availability of data for the past events. The paper also highlights the root causes of different blackouts around the globe. Furthermore, blackout and cascading analysis methods and the consequences of blackouts are surveyed. Moreover, the challenges in the existing protective schemes and research gaps in the topic of power system blackout and cascading events are marked out. Research directions and issues to be considered in future power system blackout studies are also proposed. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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20 pages, 890 KiB

Open AccessReview

100 Years of Symmetrical Components

by Gianfranco Chicco and Andrea Mazza

Energies 2019, 12(3), 450; https://doi.org/10.3390/en12030450 - 31 Jan 2019

Cited by 25 | Viewed by 6104

28 June 2018 was the 100th anniversary of the first presentation on symmetrical components made by Charles LeGeyt Fortescue at the 34th Annual Convention of the American Institute of the Electrical Engineers in Atlantic City (NJ, USA). The introduction of the symmetrical component [...] Read more.

28 June 2018 was the 100th anniversary of the first presentation on symmetrical components made by Charles LeGeyt Fortescue at the 34th Annual Convention of the American Institute of the Electrical Engineers in Atlantic City (NJ, USA). The introduction of the symmetrical component concept was immediately seen as a milestone for electrical system studies, and many applications have been developed during the ensuing years. Today, refined or advanced contributions to conceptual and practical aspects of electrical applications are still being proposed based on the powerful structure of symmetrical components. This paper recalls the most significant steps made in the electrical engineering field after the introduction of the symmetrical component theory, and indicates recent developments concerning the studies on electrical machines, harmonics and interharmonics in different applications, and the operation of power and distribution systems with distributed energy resources. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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13 pages, 589 KiB

Open AccessReview

Technology is not a Barrier: A Survey of Energy System Technologies Required for Innovative Electricity Business Models Driving the Low Carbon Energy Revolution

by Christoph Mazur, Stephen Hall, Jeffrey Hardy and Mark Workman

Energies 2019, 12(3), 428; https://doi.org/10.3390/en12030428 - 29 Jan 2019

Cited by 19 | Viewed by 5140

Energy system decarbonisation and changing consumer behaviours will create and destroy new markets in the electric power sector. This means that the energy industry will have to adapt their business models in order to capture these pools of value. Recent work explores how [...] Read more.

Energy system decarbonisation and changing consumer behaviours will create and destroy new markets in the electric power sector. This means that the energy industry will have to adapt their business models in order to capture these pools of value. Recent work explores how changes to the utility business model that include digital, decentralised or service-based offers could both disrupt the market and accelerate low carbon transitions. However, it is unclear whether these business models are technologically feasible. To answer this question, we undertook an expert panel study to determine the readiness levels of key enabling technologies. The result is an analysis of what technologies may hinder electricity business model innovation and where more research or development is necessary. The study shows that none of the business models that are compatible with a low carbon power sector are facing technology barriers that cannot be overcome, but there is still work to be done in the domain of system integration. We conclude that, especially in the field of energy system coordination and operation, there is a need for comprehensive demonstration trials which can iteratively combine and test information and communications technology (ICT) solutions. This form of innovation support would require a new approach to energy system trials. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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45 pages, 5001 KiB

Open AccessReview

A State-of-the-Art Literature Review on Capacitance Resistance Models for Reservoir Characterization and Performance Forecasting

by Rafael Wanderley de Holanda, Eduardo Gildin, Jerry L. Jensen, Larry W. Lake and C. Shah Kabir

Energies 2018, 11(12), 3368; https://doi.org/10.3390/en11123368 - 01 Dec 2018

Cited by 64 | Viewed by 8542

Capacitance resistance models (CRMs) comprise a family of material balance reservoir models that have been applied to primary, secondary and tertiary recovery processes. CRMs predict well flow rates based solely on previously observed production and injection rates, and producers’ bottomhole pressures (BHPs); i.e., [...] Read more.

Capacitance resistance models (CRMs) comprise a family of material balance reservoir models that have been applied to primary, secondary and tertiary recovery processes. CRMs predict well flow rates based solely on previously observed production and injection rates, and producers’ bottomhole pressures (BHPs); i.e., a geological model and rock/fluid properties are not required. CRMs can accelerate the learning curve of the geological analysis by providing interwell connectivity maps to corroborate features such as sealing faults and channels, as well as diagnostic plots to determine sweep efficiency and reservoir compartmentalization. Additionally, it is possible to compute oil and water rates by coupling a fractional flow model to CRMs which enables, for example, optimization of injected fluids allocation in mature fields. This literature review covers the spectrum of the CRM theory and conventional reservoir field applications, critically discussing their advantages and limitations, and recommending potential improvements. This review is timely because over the last decade there has been a significant increase in the number of publications in this subject; however, a paper dedicated to summarize them has not yet been presented. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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28 pages, 5795 KiB

Open AccessReview

Evaluating the Effect of Metal Bipolar Plate Coating on the Performance of Proton Exchange Membrane Fuel Cells

by Oluwatosin Ijaodola, Emmanuel Ogungbemi, Fawwad Nisar. Khatib, Tabbi Wilberforce, Mohamad Ramadan, Zaki El Hassan, James Thompson and Abdul Ghani Olabi

Energies 2018, 11(11), 3203; https://doi.org/10.3390/en11113203 - 18 Nov 2018

Cited by 74 | Viewed by 9586

Environmental concerns of greenhouse gases (GHG) effect from fossil commodities and the fast increase in global energy demand have created awareness on the need to replace fossil fuels with other sources of clean energy. PEM fuel cell (PEMFC) is a promising source of [...] Read more.

Environmental concerns of greenhouse gases (GHG) effect from fossil commodities and the fast increase in global energy demand have created awareness on the need to replace fossil fuels with other sources of clean energy. PEM fuel cell (PEMFC) is a promising source of energy to replace fossil fuels. The commercialization of the cell depends on its price, weight and mechanical strength. Bipolar plates are among the main components of PEMFC which perform some significant functions in the fuel cell stack. Metal bipolar plate is considered by the research community as the future material for fuel cells. However, surface coating is required for metals to enhance its corrosion resistance, hydrophilicity and interfacial contact resistance (ICR) in PEM fuel cells. Open pore cellular metal foam (OPCMF) materials have been used to replace the conventional flow field channel in recent times due to its low electrical resistance, high specific area and high porosity; however, it endures the same corrosion problem as the metallic bipolar plate. This investigation offers an overview on different types of bipolar plates and techniques in coating metallic bipolar platse and open pore metal foam as flow field channel materials to improve the corrosion resistance which will eventually increase the efficiency of the fuel cell appreciably. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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34 pages, 7960 KiB

Open AccessReview

A Review of the Energy Performance and Life-Cycle Assessment of Building-Integrated Photovoltaic (BIPV) Systems

by Tiantian Zhang, Meng Wang and Hongxing Yang

Energies 2018, 11(11), 3157; https://doi.org/10.3390/en11113157 - 14 Nov 2018

Cited by 115 | Viewed by 13966

Building integrated photovoltaic (BIPV) technology provides an aesthetical, economic, and technical solution for electricity self-sufficiency in buildings. As one of the most promising technologies for solar energy harvesting in urban areas, BIPV technology provides multiple benefits for buildings, including power generation from renewable [...] Read more.

Building integrated photovoltaic (BIPV) technology provides an aesthetical, economic, and technical solution for electricity self-sufficiency in buildings. As one of the most promising technologies for solar energy harvesting in urban areas, BIPV technology provides multiple benefits for buildings, including power generation from renewable energy resources, the replacement of traditional wall cladding, daytime lighting, heating/cooling load reduction, etc. This paper systematically reviews the progress of recent research on the electrical, thermal, optical, and overall energy performances of BIPV systems. Furthermore, based on the literature review on the energy payback time and the greenhouse-gas emission of various BIPV technologies, the research progress of the life-cycle assessment of BIPV systems is also discussed. It is anticipated that the review results can provide meaningful reference and support for the research and development of BIPV technology. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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21 pages, 651 KiB

Open AccessReview

A Review of Commercial Biogas Systems and Lessons for Africa

by Francis Kemausuor, Muyiwa S. Adaramola and John Morken

Energies 2018, 11(11), 2984; https://doi.org/10.3390/en11112984 - 01 Nov 2018

Cited by 67 | Viewed by 9627

Many African countries have vast biomass resources that could serve as feedstock for methane production through the adoption of commercial biogas plants. However, due to many inhibiting factors, these resources are under-utilised. This article reviews commercial biogas systems that treat organic waste from [...] Read more.

Many African countries have vast biomass resources that could serve as feedstock for methane production through the adoption of commercial biogas plants. However, due to many inhibiting factors, these resources are under-utilised. This article reviews commercial biogas systems that treat organic waste from municipalities, large livestock farms, large plantations/crop farms, food/beverage production facilities, and other industries, to identify essential lessons which African countries could use to develop/disseminate such biogas systems. The review identified the critical barriers to commercial biogas development to be high initial capital costs, weak environmental policies, poor institutional framework, poor infrastructure and a general lack of willpower to implement renewable energy policies and set challenging targets. In African countries where feed-in-tariffs, quota obligations and competitive bidding programmes have been instituted, implementation has been poor, and most state-owned utilities have been unsupportive. Using knowledge from more experienced countries such as Germany and China, some key lessons have were identified. Among the key lessons is the need to institute and enforce environmental management policies to ensure that waste from medium and large livestock farms and industries are not disposed of indiscriminately, a tool China has recently used to promote commercial biogas plants to a high degree of success. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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38 pages, 6136 KiB

Open AccessFeature PaperReview

Urban and Extra-Urban Hybrid Vehicles: A Technological Review

by Roberto Capata

Energies 2018, 11(11), 2924; https://doi.org/10.3390/en11112924 - 26 Oct 2018

Cited by 41 | Viewed by 9802

Pollution derived from transportation systems is a worldwide, timelier issue than ever. The abatement actions of harmful substances in the air are on the agenda and they are necessary today to safeguard our welfare and that of the planet. Environmental pollution in large [...] Read more.

Pollution derived from transportation systems is a worldwide, timelier issue than ever. The abatement actions of harmful substances in the air are on the agenda and they are necessary today to safeguard our welfare and that of the planet. Environmental pollution in large cities is approximately 20% due to the transportation system. In addition, private traffic contributes greatly to city pollution. Further, “vehicle operating life” is most often exceeded and vehicle emissions do not comply with European antipollution standards. It becomes mandatory to find a solution that respects the environment and, realize an appropriate transportation service to the customers. New technologies related to hybrid–electric engines are making great strides in reducing emissions, and the funds allocated by public authorities should be addressed. In addition, the use (implementation) of new technologies is also convenient from an economic point of view. In fact, by implementing the use of hybrid vehicles, fuel consumption can be reduced. The different hybrid configurations presented refer to such a series architecture, developed by the researchers and Research and Development groups. Regarding energy flows, different strategy logic or vehicle management units have been illustrated. Various configurations and vehicles were studied by simulating different driving cycles, both European approval and homologation and customer ones (typically municipal and university). The simulations have provided guidance on the optimal proposed configuration and information on the component to be used. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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26 pages, 1493 KiB

Open AccessReview

Intelligent Systems for Building Energy and Occupant Comfort Optimization: A State of the Art Review and Recommendations

by Abhinandana Boodi, Karim Beddiar, Malek Benamour, Yassine Amirat and Mohamed Benbouzid

Energies 2018, 11(10), 2604; https://doi.org/10.3390/en11102604 - 29 Sep 2018

Cited by 49 | Viewed by 6175

Today, buildings consume more than 40% of primary energy in and produce more than 36% of CO₂. So, an intelligent controller applied to the buildings for energy and comfort management could achieve significant reduction in energy consumption while improving occupant’s comfort. [...] Read more.

Today, buildings consume more than 40% of primary energy in and produce more than 36% of CO₂. So, an intelligent controller applied to the buildings for energy and comfort management could achieve significant reduction in energy consumption while improving occupant’s comfort. Conventional on/off controllers were only able to automate the tasks in building and were not well suited for energy optimization tasks. Therefore, building energy management has become a focal point in recent years, promising the development of various technologies for various scenarios. This paper deals with a state of the art review on recent developments in building energy management system (BEMS) and occupants comfort, focusing on three model types: white box, black box, and gray box models. Through a comparative study, this paper presents pros and cons of each model. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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24 pages, 793 KiB

Open AccessReview

Prosumer Communities and Relationships in Smart Grids: A Literature Review, Evolution and Future Directions

by Eunice Espe, Vidyasagar Potdar and Elizabeth Chang

Energies 2018, 11(10), 2528; https://doi.org/10.3390/en11102528 - 21 Sep 2018

Cited by 146 | Viewed by 11795

Smart grids are robust, self-healing networks that allow bidirectional propagation of energy and information within the utility grid. This introduces a new type of energy user who consumes, produces, stores and shares energy with other grid users. Such a user is called a [...] Read more.

Smart grids are robust, self-healing networks that allow bidirectional propagation of energy and information within the utility grid. This introduces a new type of energy user who consumes, produces, stores and shares energy with other grid users. Such a user is called a “prosumer.” Prosumers’ participation in the smart grid is critical for the sustainability and long-term efficiency of the energy sharing process. Thus, prosumer management has attracted increasing attention among researchers in recent years. This paper systematically examines the literature on prosumer community based smart grid by reviewing relevant literature published from 2009 to 2018 in reputed energy and technology journals. We specifically focus on two dimensions namely prosumer community groups and prosumer relationships. Based on the evaluated literature, we present eight propositions and thoroughly describe several future research directions. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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23 pages, 7879 KiB

Open AccessReview

Review of Reactors with Potential Use in Thermochemical Energy Storage in Concentrated Solar Power Plants

by Gabriel Zsembinszki, Aran Solé, Camila Barreneche, Cristina Prieto, A. Inés Fernández and Luisa F. Cabeza

Energies 2018, 11(9), 2358; https://doi.org/10.3390/en11092358 - 06 Sep 2018

Cited by 65 | Viewed by 6829

The aim of this study is to perform a review of the state-of-the-art of the reactors available in the literature, which are used for solid–gas reactions or thermal decomposition processes around 1000 °C that could be further implemented for thermochemical energy storage in [...] Read more.

The aim of this study is to perform a review of the state-of-the-art of the reactors available in the literature, which are used for solid–gas reactions or thermal decomposition processes around 1000 °C that could be further implemented for thermochemical energy storage in CSP (concentrated solar power) plants, specifically for SPT (solar power tower) technology. Both direct and indirect systems can be implemented, with direct and closed systems being the most studied ones. Among direct and closed systems, the most used configuration is the stacked bed reactor, with the fixed bed reactor being the most frequent option. Out of all of the reactors studied, almost 70% are used for solid–gas chemical reactions. Few data are available regarding solar efficiency in most of the processes, and the available information indicates relatively low values. Chemical reaction efficiencies show better values, especially in the case of a fluidized bed reactor for solid–gas chemical reactions, and fixed bed and rotary reactors for thermal decompositions. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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21 pages, 2695 KiB

Open AccessReview

Parameter Identification of Inverter-Fed Induction Motors: A Review

by Jing Tang, Yongheng Yang, Frede Blaabjerg, Jie Chen, Lijun Diao and Zhigang Liu

Energies 2018, 11(9), 2194; https://doi.org/10.3390/en11092194 - 22 Aug 2018

Cited by 48 | Viewed by 5500

Induction motor parameters are essential for high-performance control. However, motor parameters vary because of winding temperature rise, skin effect, and flux saturation. Mismatched parameters will consequently lead to motor performance degradation. To provide accurate motor parameters, in this paper, a comprehensive review of [...] Read more.

Induction motor parameters are essential for high-performance control. However, motor parameters vary because of winding temperature rise, skin effect, and flux saturation. Mismatched parameters will consequently lead to motor performance degradation. To provide accurate motor parameters, in this paper, a comprehensive review of offline and online identification methods is presented. In the implementation of offline identification, either a DC voltage or single-phase AC voltage signal is injected to keep the induction motor standstill, and the corresponding identification algorithms are discussed in the paper. Moreover, the online parameter identification methods are illustrated, including the recursive least square, model reference adaptive system, DC and high-frequency AC voltage injection, and observer-based techniques, etc. Simulations on selected identification techniques applied to an example induction motor are presented to demonstrate their performance and exemplify the parameter identification methods. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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11 pages, 523 KiB

Open AccessFeature PaperReview

Li-Ion Battery Fire Hazards and Safety Strategies

by Lingxi Kong, Chuan Li, Jiuchun Jiang and Michael G. Pecht

Energies 2018, 11(9), 2191; https://doi.org/10.3390/en11092191 - 22 Aug 2018

Cited by 213 | Viewed by 20209

In the past five years, there have been numerous cases of Li-ion battery fires and explosions, resulting in property damage and bodily injuries. This paper discusses the thermal runaway mechanism and presents various thermal runaway mitigation approaches, including separators, flame retardants, and safety [...] Read more.

In the past five years, there have been numerous cases of Li-ion battery fires and explosions, resulting in property damage and bodily injuries. This paper discusses the thermal runaway mechanism and presents various thermal runaway mitigation approaches, including separators, flame retardants, and safety vents. The paper then overviews measures for extinguishing fires, and concludes with a set of recommendations for future research and development. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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34 pages, 16926 KiB

Open AccessReview

A Review on Recent Advances and Future Trends of Transformerless Inverter Structures for Single-Phase Grid-Connected Photovoltaic Systems

by Kamran Zeb, Imran Khan, Waqar Uddin, Muhammad Adil Khan, P. Sathishkumar, Tiago Davi Curi Busarello, Iftikhar Ahmad and H. J. Kim

Energies 2018, 11(8), 1968; https://doi.org/10.3390/en11081968 - 28 Jul 2018

Cited by 51 | Viewed by 11564

°CThe research significance of various scientific aspects of photovoltaic (PV) systems has increased over the past decade. Grid-tied inverters the vital elements for the effective interface of Renewable Energy Resources (RER) and utility in the distributed generation system. Currently, Single-Phase Transformerless Grid-Connected Photovoltaic [...] Read more.

°CThe research significance of various scientific aspects of photovoltaic (PV) systems has increased over the past decade. Grid-tied inverters the vital elements for the effective interface of Renewable Energy Resources (RER) and utility in the distributed generation system. Currently, Single-Phase Transformerless Grid-Connected Photovoltaic (SPTG-CPV) inverters (1–10 kW) are undergoing further developments, with new designs, and interest of the solar market. In comparison to the transformer (TR) Galvanic Isolation (GI)-based inverters, its advantageous features are lower cost, lighter weight, smaller volume, higher efficiency, and less complexity. In this paper, a review of SPTG-CPV inverters has been carried out. The basic operational principles of all SPTG-CPV inverters are presented in details for positive, negative, and zero cycles. A comprehensive analysis of each topology has been deliberated. A comparative assessment is also performed based on weaknesses, strengths, component ratings, efficiency, total harmonic distortion (THD), semiconductor device losses, and leakage current of various SPTG-CPV inverters schemes. Typical PV inverter structures and control schemes for grid connected three-phase system and single-phase systems are also discussed, described, and reviewed. Comparison of various industrial grids-connected PV inverters is also performed. Loss analysis is also performed for various topologies at 1 kW. Selection of appropriate topologies for their particular application is thoroughly presented. Then, discussion and forthcoming progress are emphasized. Lastly, the conclusions are presented. More than 100 research publications on the topic of SPTG-CPV inverter topologies, configurations, and control schematics along with the recent developments are thoroughly reviewed and classified for quick reference. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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14 pages, 1989 KiB

Open AccessReview

Voltage Correction Factors for Air-Insulated Transmission Lines Operating in High-Altitude Regions to Limit Corona Activity: A Review

by Jordi-Roger Riba, William Larzelere and Johannes Rickmann

Energies 2018, 11(7), 1908; https://doi.org/10.3390/en11071908 - 21 Jul 2018

Cited by 18 | Viewed by 7184

Nowadays there are several transmission lines projected to be operating in high-altitude regions. It is well known that the installation altitude has an impact on the dielectric behavior of air-insulated systems. As a result, atmospheric and voltage correction factors must be applied in [...] Read more.

Nowadays there are several transmission lines projected to be operating in high-altitude regions. It is well known that the installation altitude has an impact on the dielectric behavior of air-insulated systems. As a result, atmospheric and voltage correction factors must be applied in air-insulated transmission systems operating in high-altitude conditions. This paper performs an exhaustive literature review, including state-of-the-art research papers and International Standards of the available correction factors to limit corona activity and ensure proper performance when planning air-insulated transmission lines intended for high-altitude areas. It has been found that there are substantial differences among the various correction methods, differences that are more evident at higher altitudes. Most high-voltage standards were not conceived to test samples to be installed in high-altitude regions and, therefore, most high-voltage laboratories are not ready to face this issue, since more detailed information is required. It is proposed to conduct more research on this topic so that the atmospheric corrections and altitude correction factors found in the current International Standards can be updated and/or modified so that high-voltage components to be installed in high-altitude regions can be tested with more accuracy, taking into account their insulation structure. Full article

(This article belongs to the Special Issue 10 Years Energies - Horizon 2028)

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