Energies

20 pages, 797 KiB

Open AccessArticle

Life is Short: The Impact of Power States on Base Station Lifetime

by Luca Chiaraviglio^*

, Marco Listanti and Edoardo Manzia

Department of Information, Electronics and Telecommunications, University of Rome Sapienza, Rome 00185, Italy

Energies 2015, 8(12), 14407-14426; https://doi.org/10.3390/en81212435 - 19 Dec 2015

Cited by 8 | Viewed by 4944

Abstract

We study the impact of power state transitions on the lifetime of base stations (BSs) in mobile networks. In particular, we propose a model to estimate the lifetime decrease/increase as a consequence of the application of power state changes. The model takes into [...] Read more.

We study the impact of power state transitions on the lifetime of base stations (BSs) in mobile networks. In particular, we propose a model to estimate the lifetime decrease/increase as a consequence of the application of power state changes. The model takes into account both hardware (HW) parameters, which depend on the materials used to build the device, and power state parameters, that instead depend on how and when power state transitions take place. More in depth, we consider the impact of different power states when a BS is active, and one sleep mode state when a BS is powered off. When a BS reduces the power consumption, its lifetime tends to increase. However, when a BS changes the power state, its lifetime tends to be decreased. Thus, there is a tradeoff between these two effects. Our results, obtained over universal mobile telecommunication system (UMTS) and long term evolution (LTE) case studies, indicate the need of a careful management of the power state transitions in order to not deteriorate the BS lifetime, and consequently to not increase the associated reparation/replacement costs. Full article

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

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27 pages, 3551 KiB

Open AccessArticle

Integrated Assessment of Carbon Capture and Storage (CCS) in South Africa’s Power Sector

by Peter Viebahn^*

, Daniel Vallentin and Samuel Höller^†

¹ Wuppertal Institute for Climate, Environment and Energy, Döppersberg 19, Wuppertal 42103, Germany

^† Current address: German Federal Environment Agency, Bismarckplatz 1, Berlin 14193, Germany

Energies 2015, 8(12), 14380-14406; https://doi.org/10.3390/en81212432 - 18 Dec 2015

Cited by 26 | Viewed by 8649

Abstract

This article presents an integrated assessment conducted in order to explore whether carbon capture and storage (CCS) could be a viable technological option for significantly reducing future CO₂ emissions in South Africa. The methodological approach covers a commercial availability analysis, an analysis [...] Read more.

This article presents an integrated assessment conducted in order to explore whether carbon capture and storage (CCS) could be a viable technological option for significantly reducing future CO₂ emissions in South Africa. The methodological approach covers a commercial availability analysis, an analysis of the long-term usable CO₂ storage potential (based on storage capacity assessment, energy scenario analysis and source-sink matching), an economic and ecological assessment and a stakeholder analysis. The findings show, that a reliable storage capacity assessment is needed, since only rough figures concerning the effective capacity currently exist. Further constraints on the fast deployment of CCS may be the delayed commercial availability of CCS, significant barriers to increasing the economic viability of CCS, an expected net maximum reduction rate of the power plant’s greenhouse gas emissions of 67%–72%, an increase in other environmental and social impacts, and low public awareness of CCS. One precondition for opting for CCS would be to find robust solutions to these constraints, taking into account that CCS could potentially conflict with other important policy objectives, such as affordable electricity rates to give the whole population access to electricity. Full article

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

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Graphical abstract

19 pages, 7465 KiB

Open AccessArticle

Investigation of a Co-Axial Dual-Mechanical Ports Flux-Switching Permanent Magnet Machine for Hybrid Electric Vehicles

by Wei Hua^* and Ling Kang Zhou

School of Electrical Engineering, Southeast University, Nanjing 210096, China

Energies 2015, 8(12), 14361-14379; https://doi.org/10.3390/en81212434 - 18 Dec 2015

Cited by 13 | Viewed by 6948

Abstract

In this paper, a co-axial dual-mechanical ports flux-switching permanent magnet (CADMP-FSPM) machine for hybrid electric vehicles (HEVs) is proposed and investigated, which is comprised of two conventional co-axial FSPM machines, namely one high-speed inner rotor machine and one low-speed outer rotor machine and [...] Read more.

In this paper, a co-axial dual-mechanical ports flux-switching permanent magnet (CADMP-FSPM) machine for hybrid electric vehicles (HEVs) is proposed and investigated, which is comprised of two conventional co-axial FSPM machines, namely one high-speed inner rotor machine and one low-speed outer rotor machine and a non-magnetic ring sandwiched in between. Firstly, the topology and operation principle of the CADMP-FSPM machine are introduced; secondly, the control system of the proposed electronically-controlled continuously-variable transmission (E-CVT) system is given; thirdly, the key design specifications of the CADMP-FSPM machine are determined based on a conventional dual-mechanical ports (DMP) machine with a wound inner rotor. Fourthly, the performances of the CADMP-FSPM machine and the normal DMP machine under the same overall volume are compared, and the results indicate that the CADMP-FSPM machine has advantages over the conventional DMP machine in the elimination of brushes and slip rings, improved thermal dissipation conditions for the inner rotor, direct-driven operation, more flexible modes, lower cogging torque and torque ripple, lower total harmonic distortion (THD) values of phase PM flux linkage and phase electro-motive force (EMF), higher torque output capability and is suitable for the E-CVT systems. Finally, the pros and cons of the CADMP-FSPM machine are highlighted. This paper lays a theoretical foundation for further research on CADMP-FSPM machines used for HEVs. Full article

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

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15 pages, 1878 KiB

Open AccessArticle

Wind Power Grid Connected Capacity Prediction Using LSSVM Optimized by the Bat Algorithm

by Qunli Wu and Chenyang Peng^*

Department of Economics and Management, North China Electric Power University, Baoding 071003, China

Energies 2015, 8(12), 14346-14360; https://doi.org/10.3390/en81212428 - 18 Dec 2015

Cited by 16 | Viewed by 5754

Abstract

Given the stochastic nature of wind, wind power grid-connected capacity prediction plays an essential role in coping with the challenge of balancing supply and demand. Accurate forecasting methods make enormous contribution to mapping wind power strategy, power dispatching and sustainable development of wind [...] Read more.

Given the stochastic nature of wind, wind power grid-connected capacity prediction plays an essential role in coping with the challenge of balancing supply and demand. Accurate forecasting methods make enormous contribution to mapping wind power strategy, power dispatching and sustainable development of wind power industry. This study proposes a bat algorithm (BA)–least squares support vector machine (LSSVM) hybrid model to improve prediction performance. In order to select input of LSSVM effectively, Stationarity, Cointegration and Granger causality tests are conducted to examine the influence of installed capacity with different lags, and partial autocorrelation analysis is employed to investigate the inner relationship of grid-connected capacity. The parameters in LSSVM are optimized by BA to validate the learning ability and generalization of LSSVM. Multiple model sufficiency evaluation methods are utilized. The research results reveal that the accuracy improvement of the present approach can reach about 20% compared to other single or hybrid models. Full article

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16 pages, 1959 KiB

Open AccessArticle

Optimal Operation of Combined Heat and Power System Based on Forecasted Energy Prices in Real-Time Markets

by Chenghong Gu¹, Da Xie^2,*, Junbo Sun², Xitian Wang² and Qian Ai²

¹ Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK

² Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China

Energies 2015, 8(12), 14330-14345; https://doi.org/10.3390/en81212427 - 18 Dec 2015

Cited by 23 | Viewed by 5398

Abstract

This paper develops a discrete operation optimization model for combined heat and powers (CHPs) in deregulated energy markets to maximize owners’ profits, where energy price forecasting is included. First, a single input and multi-output (SIMO) model for typical CHPs is established, considering the [...] Read more.

This paper develops a discrete operation optimization model for combined heat and powers (CHPs) in deregulated energy markets to maximize owners’ profits, where energy price forecasting is included. First, a single input and multi-output (SIMO) model for typical CHPs is established, considering the varying ratio between heat and electricity outputs at different loading levels. Then, the energy prices are forecasted with a gray forecasting model and revised in real-time based on the actual prices by using the least squares method. At last, a discrete optimization model and corresponding dynamic programming algorithm are developed to design the optimal operation strategies for CHPs in real-time. Based on the forecasted prices, the potential operating strategy which may produce the maximum profits is pre-developed. Dynamic modification is then conducted to adjust the pre-developed operating strategy after the actual prices are known. The proposed method is implemented on a 1 MW CHP on a typical day. Results show the optimized profits comply well with those derived from real-time prices after considering dynamic modification process. Full article

(This article belongs to the Special Issue Advanced Heating and Cooling Techniques)

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19 pages, 736 KiB

Open AccessArticle

Optimization of Train Operation in Multiple Interstations with Multi-Population Genetic Algorithm

by Youneng Huang^1,2,4,*, Xiao Ma^1,2, Shuai Su^1,2 and Tao Tang^3,4

¹ School of Electronics and Information Engineering, Beijing Jiaotong University, Haidian District, Beijing 100044, China

² National Engineering Research Center of Rail Transportation Operation and Control System, Beijing Jiaotong University, Haidian District, Beijing 100044, China

³ State Key Lab of Rail Traffic Control and Safety, Beijing Jiaotong University, Haidian District, Beijing 100044, China

⁴ Beijing Lab of Rail Traffic, Beijing Jiaotong University, Haidian District, Beijing 100044, China

Energies 2015, 8(12), 14311-14329; https://doi.org/10.3390/en81212433 - 18 Dec 2015

Cited by 54 | Viewed by 6529

Abstract

Subway systems consume a large amount of energy each year. How to reduce the energy consumption of subway systems has already become an issue of concern in recent years. This paper proposes an energy-efficient approach to reduce the traction energy by optimizing the [...] Read more.

Subway systems consume a large amount of energy each year. How to reduce the energy consumption of subway systems has already become an issue of concern in recent years. This paper proposes an energy-efficient approach to reduce the traction energy by optimizing the train operation for multiple interstations. Both the trip time and driving strategy are considered in the proposed optimization approach. Firstly, a bi-level programming model of multiple interstations is developed for the energy-efficient train operation problem, which is then converted into an integrated model to calculate the driving strategy for multiple interstations. Additionally, the multi-population genetic algorithm (MPGA) is used to solve the problem, followed by calculating the energy-efficient trip times. Finally, the paper presents some examples based on the operation data of the Beijing Changping subway line. The simulation results show that the proposed approach presents a better energy-efficient performance than that with only optimizing the driving strategy for a single interstation. Full article

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13 pages, 1965 KiB

Open AccessArticle

Study of the Impact of Initial Moisture Content in Oil Impregnated Insulation Paper on Thermal Aging Rate of Condenser Bushing

by Youyuan Wang¹, Kun Xiao^1,*, Bijun Chen^1,2 and Yuanlong Li¹

¹ State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing University, Chongqing 400044, China

² State Grid Tianjin Electric Power Supply Company, Tianjin 300457, China

Energies 2015, 8(12), 14298-14310; https://doi.org/10.3390/en81212429 - 18 Dec 2015

Cited by 16 | Viewed by 6280

Abstract

This paper studied the impact of moisture on the correlated characteristics of the condenser bushings oil-paper insulation system. The oil-impregnated paper samples underwent accelerated thermal aging at 130 °C after preparation at different initial moisture contents (1%, 3%, 5% and 7%). All the [...] Read more.

This paper studied the impact of moisture on the correlated characteristics of the condenser bushings oil-paper insulation system. The oil-impregnated paper samples underwent accelerated thermal aging at 130 °C after preparation at different initial moisture contents (1%, 3%, 5% and 7%). All the samples were extracted periodically for the measurement of the moisture content, the degree of polymerization (DP) and frequency domain dielectric spectroscopy (FDS). Next, the measurement results of samples were compared to the related research results of transformer oil-paper insulation, offering a theoretical basis of the parameter analysis. The obtained results show that the moisture fluctuation amplitude can reflect the different initial moisture contents of insulating paper and the mass ratio of oil and paper has little impact on the moisture content fluctuation pattern in oil-paper but has a great impact on moisture fluctuation amplitude; reduction of DP presents an accelerating trend with the increase of initial moisture content, and the aging rate of test samples is higher under low moisture content but lower under high moisture content compared to the insulation paper in transformers. Two obvious “deceleration zones” appeared in the dielectric spectrum with the decrease of frequency, and not only does the integral value of dielectric dissipation factor (tan δ) reflect the aging degree, but it reflects the moisture content in solid insulation. These types of research in this paper can be applied to evaluate the condition of humidified insulation and the aging state of solid insulation for condenser bushings. Full article

(This article belongs to the Special Issue Power Transformer Diagnostics, Monitoring and Design Features)

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11 pages, 753 KiB

Open AccessArticle

Efficient Parallelization of the Stochastic Dual Dynamic Programming Algorithm Applied to Hydropower Scheduling

by Arild Helseth^1,* and Hallvard Braaten²

¹ SINTEF Energy, Sem Sælands vei 11, Trondheim 7465, Norway

² Department of Mathematical Sciences, The Norwegian University of Science and Technology, Trondheim 7491, Norway

Energies 2015, 8(12), 14287-14297; https://doi.org/10.3390/en81212431 - 18 Dec 2015

Cited by 14 | Viewed by 6786

Abstract

Stochastic dual dynamic programming (SDDP) has become a popular algorithm used in practical long-term scheduling of hydropower systems. The SDDP algorithm is computationally demanding, but can be designed to take advantage of parallel processing. This paper presents a novel parallel scheme for the [...] Read more.

Stochastic dual dynamic programming (SDDP) has become a popular algorithm used in practical long-term scheduling of hydropower systems. The SDDP algorithm is computationally demanding, but can be designed to take advantage of parallel processing. This paper presents a novel parallel scheme for the SDDP algorithm, where the stage-wise synchronization point traditionally used in the backward iteration of the SDDP algorithm is partially relaxed. The proposed scheme was tested on a realistic model of a Norwegian water course, proving that the synchronization point relaxation significantly improves parallel efficiency. Full article

(This article belongs to the Special Issue Hydropower)

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15 pages, 8223 KiB

Open AccessArticle

Multi-Agent System-Based Microgrid Operation Strategy for Demand Response

by Hee-Jun Cha¹, Dong-Jun Won^1,*, Sang-Hyuk Kim², Il-Yop Chung² and Byung-Moon Han³

¹ Department of Electrical Engineering, Inha University, 100, Inha-ro, Nam-gu, Incheon 402-751, Korea

² School of Electrical Engineering, Kookmin University, Jeongneung-ro, Seongbuk-gu, Seoul 136-702, Korea

³ Department of Electrical Engineering, Myongji University, 116, Myongji-ro, Cheoin-gu, Yongin-si, Gyeonggi-do 449-728, Korea

Energies 2015, 8(12), 14272-14286; https://doi.org/10.3390/en81212430 - 18 Dec 2015

Cited by 35 | Viewed by 6870

Abstract

The microgrid and demand response (DR) are important technologies for future power grids. Among the variety of microgrid operations, the multi-agent system (MAS) has attracted considerable attention. In a microgrid with MAS, the agents installed on the microgrid components operate optimally by communicating [...] Read more.

The microgrid and demand response (DR) are important technologies for future power grids. Among the variety of microgrid operations, the multi-agent system (MAS) has attracted considerable attention. In a microgrid with MAS, the agents installed on the microgrid components operate optimally by communicating with each other. This paper proposes an operation algorithm for the individual agents of a test microgrid that consists of a battery energy storage system (BESS) and an intelligent load. A microgrid central controller to manage the microgrid can exchange information with each agent. The BESS agent performs scheduling for maximum benefit in response to the electricity price and BESS state of charge (SOC) through a fuzzy system. The intelligent load agent assumes that the industrial load performs scheduling for maximum benefit by calculating the hourly production cost. The agent operation algorithm includes a scheduling algorithm using day-ahead pricing in the DR program and a real-time operation algorithm for emergency situations using emergency demand response (EDR). The proposed algorithm and operation strategy were implemented both by a hardware-in-the-loop simulation test using OPAL-RT and an actual hardware test by connecting a new distribution simulator. Full article

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12 pages, 1909 KiB

Open AccessArticle

Research on and Design of a Self-Propelled Nozzle for the Tree-Type Drilling Technique in Underground Coal Mines

by Yiyu Lu^1,2, Zhe Zhou^1,*

, Zhaolong Ge^1,2,*, Xinwei Zhang^1,2 and Qian Li^1,2

¹ State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China

² National & Local Joint Engineering Laboratory of Gas Drainage in Complex Coal Seam, Chongqing University, Chongqing 400044, China

Energies 2015, 8(12), 14260-14271; https://doi.org/10.3390/en81212426 - 17 Dec 2015

Cited by 31 | Viewed by 5876

Abstract

Due to the increasing depths of coal mines and the low permeability of some coal seams, conventional methods of gas drainage in underground mines are facing many problems. To improve gas extraction, a new technique using water jets to drill tree-type boreholes in [...] Read more.

Due to the increasing depths of coal mines and the low permeability of some coal seams, conventional methods of gas drainage in underground mines are facing many problems. To improve gas extraction, a new technique using water jets to drill tree-type boreholes in coal seams is proposed. A self-propelled water-jet drilling nozzle was designed to drill these boreholes. The configuration of the self-propelled nozzle was optimized by conducting drilling experiments and self-propelling force measurements. Experimental results show that the optimal self-propelled nozzle has a forward orifice axial angle at 25°, a radial angle at 90°, a center distance of 1.5 mm, and backward pointing orifices with an axial angle of 25°. The self-propelling force generated by the jets of the nozzle with 30 MPa pump pressure can reach 29.8 N, enough to pull the hose and the nozzle forward without any external forces. The nozzle can drill at speeds up to 41.5 m/h with pump pressures at 30 MPa. The radial angles of the forward orifices improve the rock breaking performance of the nozzle and, with the correct angle, the rock breaking area of the orifices overlap to produce a connecting hole. The diameter of boreholes drilled by this nozzle can reach 35.2 mm. The nozzle design can be used as the basis for designing other self-propelled nozzles. The drilling experiments demonstrate the feasibility of using the tree-type drilling technique in underground mines. Full article

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16 pages, 2313 KiB

Open AccessArticle

A Study on Maximum Wind Power Penetration Limit in Island Power System Considering High-Voltage Direct Current Interconnections

by Minhan Yoon¹, Yong-Tae Yoon¹ and Gilsoo Jang^2,*

¹ Department of Electrical & Computer Engineering, Seoul National University, Gwanakero 599, Gwanakegu, Seoul 151-742, Korea

² School of Electrical Engineering, Korea University, Anam-dong, Sungbuk-gu, Seoul 136-713, Korea

Energies 2015, 8(12), 14244-14259; https://doi.org/10.3390/en81212425 - 17 Dec 2015

Cited by 30 | Viewed by 7384

Abstract

The variability and uncontrollability of wind power increases the difficulty for a power system operator to implement a wind power system with a high penetration rate. These are more serious factors to consider in small and isolated power systems since the system has [...] Read more.

The variability and uncontrollability of wind power increases the difficulty for a power system operator to implement a wind power system with a high penetration rate. These are more serious factors to consider in small and isolated power systems since the system has small operating reserves and inertia to secure frequency and voltage. Typically, this difficulty can be reduced by interconnection with another robust power system using a controllable transmission system such as a high-voltage direct current (HVDC) system. However, the reliability and stability constraints of a power system has to be performed according to the HVDC system implementation. In this paper, the method for calculation of maximum wind power penetration in an island supplied by a HVDC power system is presented, and the operational strategy of a HVDC system is proposed to secure the power system reliability and stability. The case study is performed for the Jeju Island power system in the Korean smart grid demonstration area. Full article

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

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25 pages, 7658 KiB

Open AccessFeature PaperArticle

Wave Energy Resource along the Coast of Santa Catarina (Brazil)

by Pasquale Contestabile, Vincenzo Ferrante and Diego Vicinanza^*

Department of Civil Engineering, Design, Building and Environment, Second University of Naples, Via Roma 29, Aversa 81031, Caserta, Italy

Energies 2015, 8(12), 14219-14243; https://doi.org/10.3390/en81212423 - 17 Dec 2015

Cited by 79 | Viewed by 7938

Abstract

Brazil has one of the largest electricity markets in South America, which needs to add 6000 MW of capacity every year in order to satisfy growing the demand from an increasing and more prosperous population. Apart from biomass, no other renewable energy sources, [...] Read more.

Brazil has one of the largest electricity markets in South America, which needs to add 6000 MW of capacity every year in order to satisfy growing the demand from an increasing and more prosperous population. Apart from biomass, no other renewable energy sources, besides hydroelectricity, play a relevant role in the energy mix. The potential for wind and wave energy is very large. Brazil's Santa Catarina state government is starting a clean energy program in the state, which is expected to bring more than 1 GW of capacity. Assessment of wave energy resources is needed along the coastline. This work studied the potential wave energy along the north-central coasts of Santa Catarina, in Southern Brazil, by analysis of the hindcast data from the European Centre for Medium-Range Weather Forecasts (ECMWF). The annual offshore wave power was found to be equal to 15.25 kW/m, the bulk of which is provided by southeastern waves. The nearshore energetic patterns were studied by means of a numerical coastal propagation model (Mike21 SW). The mean wave power of 20 m isobaths is 11.43 kW/m. Supplementary considerations are drawn on realistic perspectives for wave energy converters installations. Full article

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

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22 pages, 2231 KiB

Open AccessArticle

Designing an Incentive Contract Menu for Sustaining the Electricity Market

by Ying Yu^1,*, Tongdan Jin² and Chunjie Zhong¹

¹ School of Mechatronics Engineering and Automation, Shanghai University, Shanghai 200072, China

² Ingram School of Engineering, Texas State University, San Marcos, TX 78666, USA

Energies 2015, 8(12), 14197-14218; https://doi.org/10.3390/en81212419 - 16 Dec 2015

Cited by 7 | Viewed by 4731

Abstract

This paper designs an incentive contract menu to achieve long-term stability for electricity prices in a day-ahead electricity market. A bi-level Stackelberg game model is proposed to search for the optimal incentive mechanism under a one-leader and multi-followers gaming framework. A multi-agent simulation [...] Read more.

This paper designs an incentive contract menu to achieve long-term stability for electricity prices in a day-ahead electricity market. A bi-level Stackelberg game model is proposed to search for the optimal incentive mechanism under a one-leader and multi-followers gaming framework. A multi-agent simulation platform was developed to investigate the effectiveness of the incentive mechanism using an independent system operator (ISO) and multiple power generating companies (GenCos). Further, a Q-learning approach was implemented to analyze and assess the response of GenCos to the incentive menu. Numerical examples are provided to demonstrate the effectiveness of the incentive contract. Full article

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

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15 pages, 3799 KiB

Open AccessArticle

Waste-to-Energy in China: Key Challenges and Opportunities

by Dongliang Zhang^1,2

, Guangqing Huang^1,*, Yimin Xu³ and Qinghua Gong¹

¹ Guangzhou Institute of Geography, Guangzhou 510070, China

² Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China

³ South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China

Energies 2015, 8(12), 14182-14196; https://doi.org/10.3390/en81212422 - 16 Dec 2015

Cited by 90 | Viewed by 18471

Abstract

China—the largest developing country in the world—is experiencing both rapid economic maturation and large-scale urbanization. These situations have led to waste disposal problems, and the need to identify alternative energy sources. Waste-to-energy (WTE) conversion processes, a source of renewable energy, are expected to [...] Read more.

China—the largest developing country in the world—is experiencing both rapid economic maturation and large-scale urbanization. These situations have led to waste disposal problems, and the need to identify alternative energy sources. Waste-to-energy (WTE) conversion processes, a source of renewable energy, are expected to play an increasingly important role in China’s sustainable management of municipal solid waste (MSW). The purpose of this research is to investigate the key problems and opportunities associated with WTE, to provide recommendations for the government. This paper begins by describing China’s current MSW management situation and analyzing its waste disposal problems. The major challenges associated with China’s WTE incineration are then discussed from economic, environmental and social points of view. These include the high costs associated with constructing necessary facilities, the susceptibility of facilities to corrosion, the lower heating value of China’s MSW, air pollutant emissions and especially public opposition to WTE incineration. Since discarded waste can be used to produce energy for electricity and heat—thus reducing its volume and the production of greenhouse gas (GHG) emissions—with government policies and financial incentives, the use of WTE incineration as a renewable energy source and part of a sustainable waste management strategy will be of increasing importance in the future. The paper concludes by summarizing the management, economic and social benefits that could be derived from developing the country’s domestic capacity for producing the needed incineration equipment, improving source separation capabilities, standardizing regulatory and legal responsibilities and undertaking more effective public consultation processes. Full article

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

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14 pages, 18410 KiB

Open AccessArticle

High Resolution Modeling of the Impacts of Exogenous Factors on Power Systems—Case Study of Germany

by Antriksh Singh

, Patrick Eser, Ndaona Chokani^* and Reza Abhari

Laboratory for Energy Conversion, Swiss Federal Institute of Technology, Sonneggstrasse 3, Zurich CH-8092, Switzerland

Energies 2015, 8(12), 14168-14181; https://doi.org/10.3390/en81212424 - 16 Dec 2015

Cited by 6 | Viewed by 6705

Abstract

In order to reliably design the planning and operation of large interconnected power systems that can incorporate a high penetration of renewables, it is necessary to have a detailed knowledge of the potential impacts of exogenous factors on individual components within the systems. [...] Read more.

In order to reliably design the planning and operation of large interconnected power systems that can incorporate a high penetration of renewables, it is necessary to have a detailed knowledge of the potential impacts of exogenous factors on individual components within the systems. Previously, the assessment has often been conducted with nodes that are aggregated at the country or regional scale; this makes it impossible to reliably extrapolate the impact of higher penetration of renewables on individual transmission lines and/or power plants within an aggregated node. In order to be able to develop robust power systems this study demonstrates an integrated framework that employs high resolution spatial and temporal, physical modeling of power generation, electricity transmission and electricity demand, across the scale of a continent or country. Using Germany as a test case, an assessment of the impacts of exogenous factors, including local changes in ambient weather conditions, effect of timely implementation of policy, and contingency for scenarios in 2020 are demonstrated. It is shown that with the increased penetration of renewables, while the power production opportunities of conventional power plants are reduced, these power plants are required during periods of low renewables production due to the inherent variability of renewables. While the planned reinforcements in Germany, including high voltage direct current lines, reduce congestion on the grid and alleviate the differentials in power price across the country, on the other hand the reinforcements make the interconnected transmission system more vulnerable as local perturbations have a more widespread impact. Full article

(This article belongs to the Special Issue Resilience of Energy Systems)

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17 pages, 3043 KiB

Open AccessArticle

Optimal Design of an Axial-Flux Permanent-Magnet Middle Motor Integrated in a Cycloidal Reducer for a Pedal Electric Cycle

by Yee-Pien Yang^*,† and Jia-Ming Jiang^†

¹ Department of Mechanical Engineering, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei 106, Taiwan

^† These authors contributed equally to this work.

Energies 2015, 8(12), 14151-14167; https://doi.org/10.3390/en81212421 - 16 Dec 2015

Cited by 9 | Viewed by 22036

Abstract

This paper proposes an optimal design of a middle motor integrated into a mid-drive unit for pedal electric cycles. This middle motor is an axial-flux permanent magnet brushless DC motor with a stator plate. Facing this plate is a rotor plate that acts [...] Read more.

This paper proposes an optimal design of a middle motor integrated into a mid-drive unit for pedal electric cycles. This middle motor is an axial-flux permanent magnet brushless DC motor with a stator plate. Facing this plate is a rotor plate that acts as an eccentric component of a cycloidal reducer next to the stator. Both the middle motor and cycloidal reducer are easily installed on the same axle of the bike crankset. In the preliminary design, driving requirements are used to make the middle motor specifications. The numbers of stator slots and magnet poles on the rotor were chosen to achieve the best winding factor, and the winding layout was determined accordingly. A one-dimensional magnetic circuit model of the middle motor was built, and its shape was optimized utilizing a multifunctional optimization system tool. Finally, the resulting design was verified and refined by a finite element analysis. A prototype of the middle motor was fabricated with a stator made of a soft magnetic composite and integrated with a cycloidal reducer. Experimental results show that the motor has a sinusoidal back electromotive force. Additionally, it is easily controlled by sinusoidal currents with acceptable torque and speed curves. Full article

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

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15 pages, 4217 KiB

Open AccessArticle

Optimization of Biodiesel-Diesel Blended Fuel Properties and Engine Performance with Ether Additive Using Statistical Analysis and Response Surface Methods

by Obed M. Ali^1,*, Rizalman Mamat^1,†, Gholamhassan Najafi^2,*,†, Talal Yusaf^3,*,† and Seyed Mohammad Safieddin Ardebili⁴

¹ Faculty of Mechanical Engineering, University Malaysia Pahang, Pekan 26600, Pahang, Malaysia

² Mechanics of Biosystems Engineering Department, Tarbiat Modares University, Tehran 14115-111, Iran

³ Faculty of Engineering and Surveying, University of Southern Queensland University, Toowoomba, QLD 4350, Australia

⁴ Department of Biosystems Engineering, Shahid Chamran University of Ahvaz, Ahvaz 6135583151, Iran

^† These authors contributed equally to this work.

Energies 2015, 8(12), 14136-14150; https://doi.org/10.3390/en81212420 - 16 Dec 2015

Cited by 78 | Viewed by 9055

Abstract

In this study, the fuel properties and engine performance of blended palm biodiesel-diesel using diethyl ether as additive have been investigated. The properties of B30 blended palm biodiesel-diesel fuel were measured and analyzed statistically with the addition of 2%, 4%, 6% and 8% [...] Read more.

In this study, the fuel properties and engine performance of blended palm biodiesel-diesel using diethyl ether as additive have been investigated. The properties of B30 blended palm biodiesel-diesel fuel were measured and analyzed statistically with the addition of 2%, 4%, 6% and 8% (by volume) diethyl ether additive. The engine tests were conducted at increasing engine speeds from 1500 rpm to 3500 rpm and under constant load. Optimization of independent variables was performed using the desirability approach of the response surface methodology (RSM) with the goal of minimizing emissions and maximizing performance parameters. The experiments were designed using a statistical tool known as design of experiments (DoE) based on RSM. Full article

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

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18 pages, 4604 KiB

Open AccessArticle

Energetic and Exergetic Analysis of Combined Cycle Power Plant: Part-1 Operation and Performance

by Abdulrahman Almutairi^1,*

, Pericles Pilidis¹ and Nawaf Al-Mutawa²

¹ Power and Propulsion Department, School of Aerospace, Transport and Manufacturing, Cranfield University, Cranfield, Bedfordshire MK43 0AL, UK

² Mechanical Engineering Department, College of Engineering and Petroleum, Kuwait University, Al Asimah, P.O. Box 5969 Safat 13060, Khalidiya 72301, Kuwait

Energies 2015, 8(12), 14118-14135; https://doi.org/10.3390/en81212418 - 14 Dec 2015

Cited by 41 | Viewed by 10212

Abstract

Energetic and exergetic analyses are conducted using operating data for Sabiya, a combined cycle power plant (CCPP) with an advanced triple pressure reheat heat recovery steam generator (HRSG). Furthermore, a sensitivity analysis is carried out on the HRSG using a recent approach to [...] Read more.

Energetic and exergetic analyses are conducted using operating data for Sabiya, a combined cycle power plant (CCPP) with an advanced triple pressure reheat heat recovery steam generator (HRSG). Furthermore, a sensitivity analysis is carried out on the HRSG using a recent approach to differentiate between the sources of irreversibility. The proposed system was modelled using the IPSEpro software and further validated by the manufacturer’s data. The performance of the Sabiya CCPP was examined for different climatic conditions, pressure ratios, pinch point temperatures, high-pressure steam, and condenser pressure values. The results confirmed that 60.9% of the total exergy destruction occurs in the combustion chamber, which constitutes the main source of irreversibilities within a system. The exergy destruction was significantly affected by both the pressure ratio and the high-pressure steam, where the relation between them was seen to be inversely proportional. The high-pressure stage contributes about 50% of the exergy destruction within the HRSG compared to other stages and the reheat system, due to the high temperature difference between the streams and the large number of components, which leads to high energy loss to the surroundings. Numerous possibilities for improving the CCPP’s performance are introduced, based on the obtained results. Full article

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20 pages, 13535 KiB

Open AccessArticle

Provision of Supplementary Load Frequency Control via Aggregation of Air Conditioning Loads

by Lei Zhou, Yang Li^*, Beibei Wang, Zhe Wang and Xiaoqing Hu

Department of Electrical Engineering, Southeast University, No. 2 Sipailou, Nanjing 210096, Jiangsu, China

Energies 2015, 8(12), 14098-14117; https://doi.org/10.3390/en81212417 - 14 Dec 2015

Cited by 15 | Viewed by 6182

Abstract

The integration of large-scale renewable energy poses great challenges for the operation of power system because of its increased frequency fluctuations. More load frequency control (LFC) resources are demanded in order to maintain a stable system with more renewable energy injected. Unlike the [...] Read more.

The integration of large-scale renewable energy poses great challenges for the operation of power system because of its increased frequency fluctuations. More load frequency control (LFC) resources are demanded in order to maintain a stable system with more renewable energy injected. Unlike the costly LFC resources on generation side, the thermostatically controlled loads (TCLs) on the demand side become an attractive solution on account of its substantial quantities and heat-storage capacity. It generally contains air conditioners (ACs), water heaters and fridges. In this paper, the supplementary LFC is extracted by the modeling and controlling of aggregated ACs. We first present a control framework integrating the supplementary LFC with the traditional LFC. Then, a change-time-priority-list method is proposed to control power output taking into account customers’ satisfaction. Simulations on a single-area power system with wind power integration demonstrate the effectiveness of the proposed method. The impact of ambient temperature changes and customer preferences on room temperature is also involved in the discussion. Results show that the supplementary LFC provided by ACs could closely track the LFC signals and effectively reduce the frequency deviation. Full article

(This article belongs to the Special Issue Microgrids 2016)

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20 pages, 4514 KiB

Open AccessArticle

Modelling of Evaporator in Waste Heat Recovery System using Finite Volume Method and Fuzzy Technique

by Jahedul Islam Chowdhury

, Bao Kha Nguyen^* and David Thornhill

School of Mechanical and Aerospace Engineering, Queen’s University Belfast, Belfast BT9 5AH, UK

Energies 2015, 8(12), 14078-14097; https://doi.org/10.3390/en81212413 - 12 Dec 2015

Cited by 32 | Viewed by 9584

Abstract

The evaporator is an important component in the Organic Rankine Cycle (ORC)-based Waste Heat Recovery (WHR) system since the effective heat transfer of this device reflects on the efficiency of the system. When the WHR system operates under supercritical conditions, the heat transfer [...] Read more.

The evaporator is an important component in the Organic Rankine Cycle (ORC)-based Waste Heat Recovery (WHR) system since the effective heat transfer of this device reflects on the efficiency of the system. When the WHR system operates under supercritical conditions, the heat transfer mechanism in the evaporator is unpredictable due to the change of thermo-physical properties of the fluid with temperature. Although the conventional finite volume model can successfully capture those changes in the evaporator of the WHR process, the computation time for this method is high. To reduce the computation time, this paper develops a new fuzzy based evaporator model and compares its performance with the finite volume method. The results show that the fuzzy technique can be applied to predict the output of the supercritical evaporator in the waste heat recovery system and can significantly reduce the required computation time. The proposed model, therefore, has the potential to be used in real time control applications. Full article

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

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14 pages, 1706 KiB

Open AccessArticle

Strategies for Reducing the Start-up Operation of Microbial Electrochemical Treatments of Urban Wastewater

by Zulema Borjas¹, Juan Manuel Ortiz², Antonio Aldaz², Juan Feliu² and Abraham Esteve-Núñez^1,3,*

¹ IMDEAWATER Institute, Scientific-Technological Park of Alcalá, Madrid 28805, Spain

² Institute of Electrochemistry, University of Alicante, Alicante 03690, Spain

³ Department of Chemical Engineering, University of Alcalá, Madrid 28871, Spain

Energies 2015, 8(12), 14064-14077; https://doi.org/10.3390/en81212416 - 12 Dec 2015

Cited by 26 | Viewed by 7994

Abstract

Microbial electrochemical technologies (METs) constitute the core of a number of emerging technologies with a high potential for treating urban wastewater due to a fascinating reaction mechanism—the electron transfer between bacteria and electrodes to transform metabolism into electrical current. In the current work, [...] Read more.

Microbial electrochemical technologies (METs) constitute the core of a number of emerging technologies with a high potential for treating urban wastewater due to a fascinating reaction mechanism—the electron transfer between bacteria and electrodes to transform metabolism into electrical current. In the current work, we focus on the model electroactive microorganism Geobacter sulfurreducens to explore both the design of new start-up procedures and electrochemical operations. Our chemostat-grown plug and play cells, were able to reduce the start-up period by 20-fold while enhancing chemical oxygen demand (COD) removal by more than 6-fold during this period. Moreover, a filter-press based bioreactor was successfully tested for both acetate-supplemented synthetic wastewater and real urban wastewater. This proof-of-concept pre-pilot treatment included a microbial electrolysis cell (MEC) followed in time by a microbial fuel cell (MFC) to finally generate electrical current of ca. 20 A·m⁻² with a power of 10 W·m⁻² while removing 42 g COD day⁻¹·m⁻². The effective removal of acetate suggests a potential use of this modular technology for treating acetogenic wastewater where Geobacter sulfurreducens outcompetes other organisms. Full article

(This article belongs to the Special Issue Microbial Fuel Cells: Power-up, Cost Reduction and Practical Application)

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15 pages, 1551 KiB

Open AccessArticle

Solar Dryer Application for Olive Oil Mill Wastes

by Irene Montero^*

, María Teresa Miranda

, Francisco José Sepúlveda

, José Ignacio Arranz

, Carmen Victoria Rojas and Sergio Nogales

Department of Mechanical Engineering, Energy and Materials, Industrial Engineering School, University of Extremadura, Av. Elvas s/n, 06006 Badajoz, Spain

Energies 2015, 8(12), 14049-14063; https://doi.org/10.3390/en81212415 - 12 Dec 2015

Cited by 26 | Viewed by 6148

Abstract

Global waste production has raised recently due to numerous agricultural and industrial activities. Among other actions devoted to waste reduction, revaluation seems to be the most advantageous one from an environmental and economic point of view. In the olive oil sector, by-product management [...] Read more.

Global waste production has raised recently due to numerous agricultural and industrial activities. Among other actions devoted to waste reduction, revaluation seems to be the most advantageous one from an environmental and economic point of view. In the olive oil sector, by-product management (namely olive pomace, olive mill wastewater, and sludge residue) poses serious problems for companies, with the energy use of these wastes being a feasible option to solve these problems. Due to their high moisture content, drying constitutes the main stage for a possible bio-fuel conversion. This research work deals with the analysis of drying for the three main wastes from olive oil by using a prototype dryer. This equipment has different working regimes depending on the kind of convection (natural or forced for passive and active mode, respectively), the incidence of solar radiation on the product (indirect or mixed type) and the use of an additional system for energy supply (hybrid type). From the results, it could be said that all the wastes were suitable for solar drying. However, drying conditions were different for each case. Olive pomace and olive mill wastewater showed promising results for solar drying application in mixed active mode. Concerning sludge residue, its special physical structure could employ the use of turners for drying, in order to improve heat transfer to the product. Moreover, hybrid active mode enabled a considerable reduction in drying time, being an aspect to take into account for its use during low solar radiation or at night time. Full article

(This article belongs to the Special Issue Organic Waste/Resources to Energy and Value added Product)

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9 pages, 1517 KiB

Open AccessArticle

Characteristics of Biochar Obtained by Hydrothermal Carbonization of Cellulose for Renewable Energy

by Daegi Kim¹

, Kunio Yoshikawa² and Ki Young Park^1,*

¹ Department of Civil and Environmental System Engineering, Konkuk University, 120 Neungdong-ro, Gwangjin-gu, Seoul 143-701, Korea

² Department of Environmental Science and Technology, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503, Japan

Energies 2015, 8(12), 14040-14048; https://doi.org/10.3390/en81212412 - 11 Dec 2015

Cited by 72 | Viewed by 9127

Abstract

The effect of hydrothermal carbonization on the properties of cellulose present in lignocellulosic biomass was investigated for converting it into a renewable energy resource with high energy recovery efficiency. The biochar obtained from cellulose subjected to hydrothermal carbonization showed a significant increase in [...] Read more.

The effect of hydrothermal carbonization on the properties of cellulose present in lignocellulosic biomass was investigated for converting it into a renewable energy resource with high energy recovery efficiency. The biochar obtained from cellulose subjected to hydrothermal carbonization showed a significant increase in its carbon content and a calorific value. ¹³C NMR spectroscopy showed that when raw cellulose was subjected to hydrothermal carbonization above 220 °C, the resulting biochar had more aromatic and aliphatic fractions than those in raw cellulose. The resulting composition of the biochars was comparable to that of solid fuels and was between that of lignite and sub-bituminous coal. Therefore, cellulose, the main component of lignocellulosic biomass, was used to investigate the effects of varying the reaction temperature during hydrothermal carbonization. The energy recovery efficiency calculations showed that the optimum reaction temperature for the transformation of a mixture of cellulose was approximately 220 °C. Full article

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14 pages, 1948 KiB

Open AccessArticle

Pareto-Optimal Evaluation of Ultimate Limit States in Offshore Wind Turbine Structural Analysis

by Michael Muskulus

Department of Civil and Transport Engineering, Norwegian University of Science and Technology, Høgskoleringen 7A, 7491 Trondheim, Norway

Energies 2015, 8(12), 14026-14039; https://doi.org/10.3390/en81212414 - 11 Dec 2015

Cited by 6 | Viewed by 7015

Abstract

The ultimate capacity of support structures is checked with extreme loads. This is straightforward when the limit state equations depend on a single load component, and it has become common to report maxima for each load component. However, if more than one load [...] Read more.

The ultimate capacity of support structures is checked with extreme loads. This is straightforward when the limit state equations depend on a single load component, and it has become common to report maxima for each load component. However, if more than one load component is influential, e.g., both axial force and bending moments, it is not straightforward how to define an extreme load. The combination of univariate maxima can be too conservative, and many different combinations of load components can result in the worst value of the limit state equations. The use of contemporaneous load vectors is typically non-conservative. Therefore, in practice, limit state checks are done for each possible load vector, from each time step of a simulation. This is not feasible when performing reliability assessments and structural optimization, where additional, time-consuming computations are involved for each load vector. We therefore propose to use Pareto-optimal loads, which are a small set of loads that together represent all possible worst case scenarios. Simulations with two reference wind turbines show that this approach can be very useful for jacket structures, whereas the design of monopiles is often governed by the bending moment only. Even in this case, the approach might be useful when approaching the structural limits during optimization. Full article

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

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17 pages, 879 KiB

Open AccessArticle

Voltage Control Method Using Distributed Generators Based on a Multi-Agent System

by Hyun-Koo Kang¹, Il-Yop Chung^2,* and Seung-Il Moon³

¹ Korea Electric Power Research Institute (KEPRI), Korea Electric Power Company (KEPCO), 105 Munji-Ro, Yuseong-Gu, Daejeon 34056, Korea

² School of Electrical Engineering, Kookmin University, Seoul 136-702, Korea

³ School of Electrical Engineering and Computer Scirnce, Seoul National University, Gwanak-ro, Gwanak-gu, Seoul 151-744, Korea

Energies 2015, 8(12), 14009-14025; https://doi.org/10.3390/en81212411 - 11 Dec 2015

Cited by 14 | Viewed by 7135

Abstract

This paper presents a voltage control method using multiple distributed generators (DGs) based on a multi-agent system framework. The output controller of each DG is represented as a DG agent, and each voltage-monitoring device is represented as a monitoring agent. These agents cooperate [...] Read more.

This paper presents a voltage control method using multiple distributed generators (DGs) based on a multi-agent system framework. The output controller of each DG is represented as a DG agent, and each voltage-monitoring device is represented as a monitoring agent. These agents cooperate to accomplish voltage regulation through a coordinating agent or moderator. The moderator uses the reactive power sensitivities and margins to determine the voltage control contributions of each DG. A fuzzy inference system (FIS) is employed by the moderator to manage the decision-making process. An FIS scheme is developed and optimized to enhance the efficiency of the proposed voltage control process using particle swarm optimization. A simple distribution system with four voltage-controllable DGs is modeled, and an FIS moderator is implemented to control the system. Simulated data show that the proposed voltage control process is able to maintain the system within the operating voltage limits. Furthermore, the results were similar to those obtained using optimal power flow calculations, even though little information on the power system was required and no power flow calculations were implemented. Full article

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

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13 pages, 4782 KiB

Open AccessArticle

Design and Optimization of Permanent Magnet Brushless Machines for Electric Vehicle Applications

by Weiwei Gu, Xiaoyong Zhu^*, Li Quan and Yi Du

School of Electrical and Information Engineering, Jiangsu University, Zhenjiang 212013, China

Energies 2015, 8(12), 13996-14008; https://doi.org/10.3390/en81212410 - 10 Dec 2015

Cited by 38 | Viewed by 10971

Abstract

In this paper, by considering and establishing the relationship between the maximum operating speed and d-axis inductance, a new design and optimization method is proposed. Thus, a more extended constant power speed range, as well as reduced losses and increased efficiency, especially [...] Read more.

In this paper, by considering and establishing the relationship between the maximum operating speed and d-axis inductance, a new design and optimization method is proposed. Thus, a more extended constant power speed range, as well as reduced losses and increased efficiency, especially in the high-speed region, can be obtained, which is essential for electric vehicles (EVs). In the first step, the initial permanent magnet (PM) brushless machine is designed based on the consideration of the maximum speed and performance specifications in the entire operation region. Then, on the basis of increasing d-axis inductance, and meanwhile maintaining constant permanent magnet flux linkage, the PM brushless machine is optimized. The corresponding performance of the initial and optimal PM brushless machines are analyzed and compared by the finite-element method (FEM). Several tests are carried out in an EV simulation model based on the urban dynamometer driving schedule (UDDS) for evaluation. Both theoretical analysis and simulation results verify the validity of the proposed design and optimization method. Full article

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

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11 pages, 2875 KiB

Open AccessArticle

Combustion of Microalgae Oil and Ethanol Blended with Diesel Fuel

by Saddam H. Al-lwayzy^1,* and Talal Yusaf²

¹ National Centre for Engineering in Agriculture (NCEA), University of Southern Queensland, Toowoomba, QLD 4350, Australia

² School of Mechanical and Electrical Engineering, Faculty of Health, Engineering and Sciences (HES), University of Southern Queensland, Toowoomba, QLD 4350, Australia

Energies 2015, 8(12), 13985-13995; https://doi.org/10.3390/en81212409 - 10 Dec 2015

Cited by 16 | Viewed by 8494

Abstract

Using renewable oxygenated fuels such as ethanol is a proposed method to reduce diesel engine emission. Ethanol has lower density, viscosity, cetane number and calorific value than petroleum diesel (PD). Microalgae oil is renewable, environmentally friendly and has the potential to replace PD. [...] Read more.

Using renewable oxygenated fuels such as ethanol is a proposed method to reduce diesel engine emission. Ethanol has lower density, viscosity, cetane number and calorific value than petroleum diesel (PD). Microalgae oil is renewable, environmentally friendly and has the potential to replace PD. In this paper, microalgae oil (10%) and ethanol (10%) have been mixed and added to (80%) diesel fuel as a renewable source of oxygenated fuel. The mixture of microalgae oil, ethanol and petroleum diesel (MOE20%) has been found to be homogenous and stable without using surfactant. The presence of microalgae oil improved the ethanol fuel demerits such as low density and viscosity. The transesterification process was not required for oil viscosity reduction due to the presence of ethanol. The MOE20% fuel has been tested in a variable compression ratio diesel engine at different speed. The engine test results with MOE20% showed a very comparable engine performance of in-cylinder pressure, brake power, torque and brake specific fuel consumption (BSFC) to that of PD. The NO_x emission and HC have been improved while CO and CO₂ were found to be lower than those from PD at low engine speed. Full article

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

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14 pages, 5779 KiB

Open AccessArticle

Electromagnetic Performance Analysis of Novel Flux-Regulatable Permanent Magnet Machines for Wide Constant-Power Speed Range Operation

by Yunchong Wang, Shuangxia Niu^* and Weinong Fu

Department of Electrical Engineering, The Hong Kong Polytechnic University, Hong Kong, China

Energies 2015, 8(12), 13971-13984; https://doi.org/10.3390/en81212407 - 10 Dec 2015

Cited by 9 | Viewed by 5566

Abstract

Two novel structures of permanent magnet (PM) machine, namely a hybrid excitation flux modulation machine (HEFMM) and a variable flux memory machine (VFMM), which have excellent field-weakening capability, are presented in this paper. The HEFMM incorporates the advantages of parallel hybrid excitation structure [...] Read more.

Two novel structures of permanent magnet (PM) machine, namely a hybrid excitation flux modulation machine (HEFMM) and a variable flux memory machine (VFMM), which have excellent field-weakening capability, are presented in this paper. The HEFMM incorporates the advantages of parallel hybrid excitation structure and flux modulation structure, so as to increase the torque density as well as increase the constant-power speed range. Inspired by the HEFMM, aiming to further improve the efficiency of machine, the VFMM with aluminum-nickel-cobalt (AlNiCo) PMs in the inner stator which can be magnetized by the current pulse of the direct current (DC) windings is developed. With double-stator structure, flux modulation effect in both machines can be employed to realize the hybrid excitation and regulate the air-gap flux density readily. The operation principle is illustrated and the static and steady performances of the machines are analyzed and compared with time stepping finite element analysis, which validates the effectiveness of the proposed designs. Full article

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

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11 pages, 3816 KiB

Open AccessArticle

TOPSIS Multi-Criteria Decision Modeling Approach for Biolubricant Selection for Two-Stroke Petrol Engines

by Masoud Dehghani Soufi¹, Barat Ghobadian^1,*, Gholamhassan Najafi¹, Mohammad Reza Sabzimaleki¹ and Talal Yusaf²

¹ Biosystems Engineering Department, Tarbiat Modares University, Jalal Ale Ahmad Highway, P.O.Box 14115-111, Tehran 11732, Iran

² Faculty of Engineering and Surveying, University of Southern Queensland, Toowoomba, QLD 4350, Australia

Energies 2015, 8(12), 13960-13970; https://doi.org/10.3390/en81212408 - 9 Dec 2015

Cited by 33 | Viewed by 8109

Abstract

Exhaust pollutants from two-stroke petrol engines are a problem for the environment. Biolubricants are a new generation of renewable and eco-friendly vegetable-based lubricants, which have attracted a lot of attention in recent years. In this paper, the applicability of the Technique for Order [...] Read more.

Exhaust pollutants from two-stroke petrol engines are a problem for the environment. Biolubricants are a new generation of renewable and eco-friendly vegetable-based lubricants, which have attracted a lot of attention in recent years. In this paper, the applicability of the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) method to support the process of building the scoring system for selecting an appropriate two-stroke lubricant has been analyzed. For this purpose, biolubricants (TMP-triesters) based on castor oil, palm oil, and waste cooking oil were produced and then utilized in a 200 cc two-stroke gasoline engine to investigate their effects on its performance and exhaust emissions. The results obtained from the use of the entropy technique in the TOPSIS algorithm showed that palm oil-based lubricant took up the greatest distance from the Negative Ideal Solution (NIS) and was selected as the most optimal lubricant for these types of engines. Full article

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

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7 pages, 1282 KiB

Open AccessTechnical Note

A Simple Expression for the Tortuosity of Gas Transport Paths in Solid Oxide Fuel Cells’ Porous Electrodes

by Wei Kong^*,†, Qiang Zhang^†, Xiuwen Xu^† and Daifen Chen^†

¹ School of Energy and Power Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China

^† These authors contributed equally to this work.

Energies 2015, 8(12), 13953-13959; https://doi.org/10.3390/en81212406 - 9 Dec 2015

Cited by 22 | Viewed by 6110

Abstract

Based on the three-dimensional (3D) cube packing model, a simple expression for the tortuosity of gas transport paths in solid oxide fuel cells’ (SOFC) porous electrodes is developed. The proposed tortuosity expression reveals the dependence of the tortuosity on porosity, which is capable [...] Read more.

Based on the three-dimensional (3D) cube packing model, a simple expression for the tortuosity of gas transport paths in solid oxide fuel cells’ (SOFC) porous electrodes is developed. The proposed tortuosity expression reveals the dependence of the tortuosity on porosity, which is capable of providing results that are very consistent with the experimental data in the practical porosity range of SOFC. Furthermore, for the high porosity (>0.6), the proposed tortuosity expression is also accurate. This might be helpful for understanding the physical mechanism for the tortuosity of gas transport paths in electrodes and the optimization electrode microstructure for reducing the concentration polarization. Full article

(This article belongs to the Special Issue Solid Oxide Fuel Cells)

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