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18 pages, 4934 KiB

Open AccessArticle

Aerodynamic and Structural Integrated Optimization Design of Horizontal-Axis Wind Turbine Blades

by Jie Zhu^1,2,*, Xin Cai² and Rongrong Gu²

¹ College of Civil Engineering and Architecture, Jiaxing University, Jiaxing 314001, China

² College of Mechanics and Materials, Hohai University, Nanjing 210098, China

Energies 2016, 9(2), 66; https://doi.org/10.3390/en9020066 - 22 Jan 2016

Cited by 25 | Viewed by 10030

Abstract

A procedure based on MATLAB combined with ANSYS is presented and utilized for the aerodynamic and structural integrated optimization design of Horizontal-Axis Wind Turbine (HAWT) blades. Three modules are used for this purpose: an aerodynamic analysis module using the Blade Element Momentum (BEM) [...] Read more.

A procedure based on MATLAB combined with ANSYS is presented and utilized for the aerodynamic and structural integrated optimization design of Horizontal-Axis Wind Turbine (HAWT) blades. Three modules are used for this purpose: an aerodynamic analysis module using the Blade Element Momentum (BEM) theory, a structural analysis module employing the Finite Element Method (FEM) and a multi-objective optimization module utilizing the non-dominated sorting genetic algorithm. The former two provide a sufficiently accurate solution of the aerodynamic and structural performances of the blade; the latter handles the design variables of the optimization problem, namely, the main geometrical shape and structural parameters of the blade, and promotes function optimization. The scope of the procedure is to achieve the best trade-off performances between the maximum Annual Energy Production (AEP) and the minimum blade mass under various design requirements. To prove the efficiency and reliability of the procedure, a commercial 1.5 megawatt (MW) HAWT blade is used as a case study. Compared with the original scheme, the optimization results show great improvements for the overall performance of the blade. Full article

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

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18 pages, 4595 KiB

Open AccessArticle

The Concept, Design and Performance of a Novel Rotary Kiln Type Air-Staged Biomass Gasifier

by Huiyuan Shi^1,*,†

, Wen Si^2,† and Xi Li¹

¹ Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, China

² College of Information and Computer Science, Shanghai Business School, Shanghai 200235, China

^† These authors contributed equally to this work.

Energies 2016, 9(2), 67; https://doi.org/10.3390/en9020067 - 22 Jan 2016

Cited by 37 | Viewed by 12144

Abstract

Tar formation is the main bottleneck for biomass gasification technology. A novel rotary kiln type biomass gasification process was proposed. The concept design was based on air staging and process separation. This concept was demonstrated on a pilot scale rotary kiln reactor under [...] Read more.

Tar formation is the main bottleneck for biomass gasification technology. A novel rotary kiln type biomass gasification process was proposed. The concept design was based on air staging and process separation. This concept was demonstrated on a pilot scale rotary kiln reactor under ambient pressure and autothermic conditions. The pilot scale gasifier was divided into three different reaction regions, which were oxidative degradation, partial oxidation and char gasification. A series of tests was conducted to investigate the effect of key parameters. The results indicate that under optimum operating conditions, a fuel gas with high heat value of about 5500 kJ/Nm³ and gas production rate of 2.32 Nm³/kg could be produced. Tar concentration in the fuel gas could be reduced to 108 mg/Nm³ (at the gasifier outlet) and 38 mg/Nm³ (after gas conditioning). The cold gas efficiency and carbon conversion rate reached 75% and 78%, respectively. The performance of this gasification system shows considerable potential for implementation in distributed electricity and heat supply projects. Full article

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

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10 pages, 1937 KiB

Open AccessArticle

Device Performance Improvement of Double-Pass Wire Mesh Packed Solar Air Heaters under Recycling Operation Conditions

by Chii-Dong Ho^*, Hsuan Chang, Chun-Sheng Lin, Chun-Chieh Chao and Yi-En Tien

Energy and Opto-Electronic Materials Research Center, Department of Chemical and Materials Engineering, Tamkang University, Tamsui, New Taipei 251, Taiwan

Energies 2016, 9(2), 68; https://doi.org/10.3390/en9020068 - 22 Jan 2016

Cited by 2 | Viewed by 5487

Abstract

The improvement of device performance of a recycling solar air heater featuring a wire mesh packing was investigated experimentally and theoretically. The application of the wire mesh packing and recycle-effect concept to the present study were proposed aiming to strengthen the convective heat-transfer [...] Read more.

The improvement of device performance of a recycling solar air heater featuring a wire mesh packing was investigated experimentally and theoretically. The application of the wire mesh packing and recycle-effect concept to the present study were proposed aiming to strengthen the convective heat-transfer coefficient due to increased turbulence. Comparisons were made among different designs, including the single-pass, flat-plate double-pass and recycling double-pass wire mesh packed operations. The collector efficiency of the recycling double-pass wire mesh packed solar air heater was much higher than that of the other configurations for various recycle ratios and mass flow rates scenarios. The power consumption increment due to implementing wire mesh in solar air heaters was also discussed considering the economic feasibility. A fairly good agreement between theoretical predictions and experimental measurements was achieved with an analyzed error of 1.07%–9.32%. Full article

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

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23 pages, 6523 KiB

Open AccessArticle

An Innovative Control Strategy to Improve the Fault Ride-Through Capability of DFIGs Based on Wind Energy Conversion Systems

by Vandai Le^1,2,*

, Xinran Li¹, Yong Li¹

, Tran Le Thang Dong³ and Caoquyen Le⁴

¹ College of Electrical and Information Engineering, Hunan University, Changsha 410082, China

² Faculty of Electrical Engineering, Industrial University of Ho Chi Minh City, Ho Chi Minh 700000, Vietnam

³ Duy Tan University, Da Nang 550000, Vietnam

⁴ Power Engineering Consulting Joint Stock Company 4, Nha Trang 650000, Vietnam

Energies 2016, 9(2), 69; https://doi.org/10.3390/en9020069 - 25 Jan 2016

Cited by 21 | Viewed by 7234

Abstract

An innovative control strategy is proposed for enhancing the low voltage ride-through (LVRT) capability of a doubly fed induction generator based on wind energy conversion systems (DFIG-WECS). Within the proposed control method, the current control loops of the rotor side converter (RSC) are [...] Read more.

An innovative control strategy is proposed for enhancing the low voltage ride-through (LVRT) capability of a doubly fed induction generator based on wind energy conversion systems (DFIG-WECS). Within the proposed control method, the current control loops of the rotor side converter (RSC) are developed based on passivity theory. The control scheme for the grid side converter (GSC) is designed based on a two-term approach to keep the DC-link voltage close to a given value. The first term based on the maximal voltage of GSC is introduced in the GSC control loops as a reference reactive current. The second one reflecting the instantaneous unbalanced power flow between the RSC and GSC is also introduced in the GSC control loops as a disturbance considering the instantaneous power of the grid filter to compensate the instantaneous rotor power. The effectiveness of the proposed control strategy is verified via time domain simulation of a 2.0 MW-575 V DFIG-WECS using PSCAD/EMTP. Simulation results show that the control of the DFIG with the proposed approach can improve the LVRT capability better than with the conventional one. Full article

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13 pages, 514 KiB

Open AccessArticle

Electric Load Forecasting Based on a Least Squares Support Vector Machine with Fuzzy Time Series and Global Harmony Search Algorithm

by Yan Hong Chen¹, Wei-Chiang Hong^2,3,*

, Wen Shen¹ and Ning Ning Huang¹

¹ School of Information, Zhejiang University of Finance & Economics, Hangzhou 310018, China

² School of Economics & Management, Nanjing Tech University, Nanjing 211800, China

³ Department of Information Management, Oriental Institute of Technology, 58 Sec. 2, Sichuan Road, Panchiao, Taipei 220, Taiwan

Energies 2016, 9(2), 70; https://doi.org/10.3390/en9020070 - 26 Jan 2016

Cited by 95 | Viewed by 8076

Abstract

This paper proposes a new electric load forecasting model by hybridizing the fuzzy time series (FTS) and global harmony search algorithm (GHSA) with least squares support vector machines (LSSVM), namely GHSA-FTS-LSSVM model. Firstly, the fuzzy c-means clustering (FCS) algorithm is used to calculate [...] Read more.

This paper proposes a new electric load forecasting model by hybridizing the fuzzy time series (FTS) and global harmony search algorithm (GHSA) with least squares support vector machines (LSSVM), namely GHSA-FTS-LSSVM model. Firstly, the fuzzy c-means clustering (FCS) algorithm is used to calculate the clustering center of each cluster. Secondly, the LSSVM is applied to model the resultant series, which is optimized by GHSA. Finally, a real-world example is adopted to test the performance of the proposed model. In this investigation, the proposed model is verified using experimental datasets from the Guangdong Province Industrial Development Database, and results are compared against autoregressive integrated moving average (ARIMA) model and other algorithms hybridized with LSSVM including genetic algorithm (GA), particle swarm optimization (PSO), harmony search, and so on. The forecasting results indicate that the proposed GHSA-FTS-LSSVM model effectively generates more accurate predictive results. Full article

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

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15 pages, 3389 KiB

Open AccessArticle

A Large Scale Daylighting System Based on a Stepped Thickness Waveguide

by Ngoc Hai Vu

and Seoyong Shin^*

Department of Information and Communication Engineering, Myongji University, San 38-2 Nam-dong, Yongin 449728, Korea

Energies 2016, 9(2), 71; https://doi.org/10.3390/en9020071 - 26 Jan 2016

Cited by 29 | Viewed by 7338

Abstract

This paper presents a study on the use of optical fiber and a solar concentrator for a building daylighting system. Daylighting is essential for improving indoor environments and reducing electric lighting power consumption in office buildings. Traditionally, optical fiber daylighting systems were implemented [...] Read more.

This paper presents a study on the use of optical fiber and a solar concentrator for a building daylighting system. Daylighting is essential for improving indoor environments and reducing electric lighting power consumption in office buildings. Traditionally, optical fiber daylighting systems were implemented only on a small scale. More complicated technologies are required for more amounts of daylight over further distance via a smaller light guider. The proposed solar lighting system with optical fiber is composed of an array of linear Fresnel lenses and a stepped thickness waveguide. The linear Fresnel lenses collect light into the stepped thickness waveguide. The stepped-thickness waveguide is an optical component which redirects focused sunlight from the vertical direction to the horizontal direction, and it guides light to the attached optical fiber. Simulation models were developed using commercial optical simulation tools (LightTools™). The optical efficiency and angular tolerance of the system are analyzed. The overall system cost is also estimated. Some considerations on the economic expansion of the system in terms of efficiency and estimated annual average energy saving are discussed. The results show that the presented optical fiber daylighting system is a strong candidate for low-price and highly efficient solution for solar energy application to building energy savings. Full article

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18 pages, 1593 KiB

Open AccessEditor’s ChoiceArticle

Effects of Reynolds Number on the Energy Conversion and Near-Wake Dynamics of a High Solidity Vertical-Axis Cross-Flow Turbine

by Peter Bachant and Martin Wosnik^*

Center for Ocean Renewable Energy, University of New Hampshire, 24 Colovos Rd., Durham, NH 03824, USA

Energies 2016, 9(2), 73; https://doi.org/10.3390/en9020073 - 26 Jan 2016

Cited by 129 | Viewed by 14831

Abstract

Experiments were performed with a large laboratory-scale high solidity cross-flow turbine to investigate Reynolds number effects on performance and wake characteristics and to establish scale thresholds for physical and numerical modeling of individual devices and arrays. It was demonstrated that the performance of [...] Read more.

Experiments were performed with a large laboratory-scale high solidity cross-flow turbine to investigate Reynolds number effects on performance and wake characteristics and to establish scale thresholds for physical and numerical modeling of individual devices and arrays. It was demonstrated that the performance of the cross-flow turbine becomes essentially R e -independent at a Reynolds number based on the rotor diameter R e_D ≈ 10⁶ or an approximate average Reynolds number based on the blade chord length R e_c ≈ 2 × 10⁵ . A simple model that calculates the peak torque coefficient from static foil data and cross-flow turbine kinematics was shown to be a reasonable predictor for Reynolds number dependence of an actual cross-flow turbine operating under dynamic conditions. Mean velocity and turbulence measurements in the near-wake showed subtle differences over the range of R e investigated. However, when transport terms for the streamwise momentum and mean kinetic energy were calculated, a similar R e threshold was revealed. These results imply that physical model studies of cross-flow turbines should achieve R e_D ∼ 10⁶ to properly approximate both the performance and wake dynamics of full-scale devices and arrays. Full article

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

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13 pages, 3495 KiB

Open AccessArticle

Analysis of a Solar Cooling System for Climatic Conditions of Five Different Cities of Saudi Arabia

by M. Mujahid Rafique¹

, Shafiqur Rehman^2,*

, Aref Lashin^3,4

and Nassir Al Arifi⁵

¹ Department of Mechanical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

² Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia

³ College of Engineering, Petroleum and Natural Gas Engineering Department, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia

⁴ Faculty of Science, Geology Department, Benha University, P.O. Box 13518, Benha 345629, Egypt

⁵ College of Science, Geology and Geophysics Department, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia

Energies 2016, 9(2), 75; https://doi.org/10.3390/en9020075 - 27 Jan 2016

Cited by 18 | Viewed by 8079

Abstract

Air high in humidity leads to uncomfortable conditions and promotes the growth of different fungi and bacteria, which may cause health problems. The control of moisture content in the air using traditional air conditioning techniques is not a suitable option due to large [...] Read more.

Air high in humidity leads to uncomfortable conditions and promotes the growth of different fungi and bacteria, which may cause health problems. The control of moisture content in the air using traditional air conditioning techniques is not a suitable option due to large consumption of primary energy and hence emission of greenhouse gases. The evaporative cooling technology is a cost effective and eco-friendly alternative but can provide thermal comfort conditions only under low humidity conditions. However, the evaporative cooling method can be used effectively in conjunction with desiccant dehumidifiers for better control of humidity. Such systems can control the temperature and humidity of the air independently and can effectively utilize the low-grade thermal energy resources. In this paper, the theoretical analysis of desiccant based evaporative cooling systems is carried out for five cities in Saudi Arabia (Jeddah, Jazan, Riyadh, Hail, and Dhahran). It has been observed that the coefficient of performance (COP) of the system varies from 0.275 to 0.476 for different locations. The water removal capacity of the desiccant wheel is at its maximum for the climatic conditions of Jazan and at its minimum for Hail. The effect of climatic conditions of five cities on regeneration temperature, air mass flow rate, and potential of solar energy has been evaluated using RET Screen software. Full article

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20 pages, 4531 KiB

Open AccessArticle

Economic Viability Study of an On-Road Wireless Charging System with a Generic Driving Range Estimation Method

by Aditya Shekhar^1,*,‡

, Venugopal Prasanth^1,‡

, Pavol Bauer¹ and Mark Bolech²

¹ Electrical Sustainable Energy, Delft Institute of Technology, Mekelweg 4, Delft 2628 CD, The Netherlands

² The Netherlands Organisation for Applied Scientific Research (TNO), Van Mourik Broekmanweg 6, Delft 2628 XE, The Netherlands

^‡ These authors contributed equally to this work.

Energies 2016, 9(2), 76; https://doi.org/10.3390/en9020076 - 26 Jan 2016

Cited by 54 | Viewed by 11763

Abstract

The economic viability of on-road wireless charging of electric vehicles (EVs) strongly depends on the choice of the inductive power transfer (IPT) system configuration (static or dynamic charging), charging power level and the percentage of road coverage of dynamic charging. In this paper, [...] Read more.

The economic viability of on-road wireless charging of electric vehicles (EVs) strongly depends on the choice of the inductive power transfer (IPT) system configuration (static or dynamic charging), charging power level and the percentage of road coverage of dynamic charging. In this paper, a case study is carried out to determine the expected investment costs involved in installing the on-road charging infrastructure for an electric bus fleet. Firstly, a generic methodology is described to determine the driving range of any EV (including electric buses) with any gross mass and frontal area. A dynamic power consumption model is developed for the EV, taking into account the rolling friction, acceleration, deceleration, aerodynamic drag, regenerative braking and Li-ion battery behavior. Based on the simulation results, the linear dependence of the battery state of charge (SoC) on the distance traveled is proven. Further, the impact of different IPT system parameters on driving range is incorporated. Economic implications of a combination of different IPT system parameters are explored for achieving the required driving range of 400 km, and the cost optimized solution is presented for the case study of an electric bus fleet. It is shown that the choice of charging power level and road coverage are interrelated in the economic context. The economic viability of reducing the capacity of the on-board battery as a trade-off between higher transport efficiency and larger on-road charging infrastructure is presented. Finally, important considerations, like the number of average running buses, scheduled stoppage time and on-board battery size, that make on-road charging an attractive option are explored. The cost break-up of various system components of the on-road charging scheme is estimated, and the final project cost and parameters are summarized. The specific cost of the wireless on-road charging system is found to be more expensive than the conventional trolley system at this point in time. With decreasing battery costs and a higher number of running buses, a more economically-viable system can be realized. Full article

(This article belongs to the Special Issue Wireless Power Transfer)

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12 pages, 1221 KiB

Open AccessArticle

A Sectoral Micro-Economic Approach to Scenario Selection and Development: The Case of the Greek Power Sector

by Alexandros Flamos

Department of Industrial Management and Technology, University of Piraeus, Karaoli & Dimitriou 80, Piraeus 18534, Greece

Energies 2016, 9(2), 77; https://doi.org/10.3390/en9020077 - 27 Jan 2016

Cited by 12 | Viewed by 5062

Abstract

Generating policy-relevant scenarios is instrumental for understanding and developing policy measures. These are especially relevant to the power sector. Practitioners have been working on policy-relevant scenarios for the ex-ante assessment of policy measures in a meaningful way for end-users related to climate change [...] Read more.

Generating policy-relevant scenarios is instrumental for understanding and developing policy measures. These are especially relevant to the power sector. Practitioners have been working on policy-relevant scenarios for the ex-ante assessment of policy measures in a meaningful way for end-users related to climate change mitigation and adaptation strategies. This paper presents a method for generating such policy relevant scenarios by focusing on the actor-contingent elements of the scenarios, i.e., the developments that are within the control of system actors to change or bring about. Several scenario techniques focusing on systematic-formalized or quantitative approaches have been published on this front over the past few years. Here, we introduce a methodology that is best suited for the assessment of the expected effect of different policy measures on the involved stakeholders’ behavior as well as for the analysis of the interactions between different policy measures as reflected on their impact on the strength and direction of the provided incentives. The applicability of our methodology is demonstrated for the case of the Greek power market. It was further evaluated in view of the challenges related to the issues of generation capacity adequacy and increased fiscal deficit. The strategic implications of the proposed approach concern the demonstration of the benefits from adopting a policy assessment methodology that focus on stakeholder expectations and interactions. Full article

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

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18 pages, 2229 KiB

Open AccessArticle

A Systematic Study of Separators in Air-Breathing Flat-Plate Microbial Fuel Cells—Part 1: Structure, Properties, and Performance Correlations

by Sona Kazemi^1,2,*, Madjid Mohseni¹ and Khalid Fatih²

¹ Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC V6T 1Z3, Canada

² National Research Council Canada, Vancouver, BC V6T 1W5, Canada

Energies 2016, 9(2), 78; https://doi.org/10.3390/en9020078 - 27 Jan 2016

Cited by 11 | Viewed by 5325

Abstract

Passive air-breathing microbial fuel cells (MFCs) are a promising technology for energy recovery from wastewater and their performance is highly dependent on characteristics of the separator that isolates the anaerobic anode from the air-breathing cathode. The goal of the present work is to [...] Read more.

Passive air-breathing microbial fuel cells (MFCs) are a promising technology for energy recovery from wastewater and their performance is highly dependent on characteristics of the separator that isolates the anaerobic anode from the air-breathing cathode. The goal of the present work is to systematically study the separator characteristics and its effect on the performance of passive air-breathing flat-plate MFCs (FPMFCs). This was performed through characterization of structure, properties, and performance correlations of eight separators in Part 1 of this work. Eight commercial separators were characterized, in non-inoculated and inoculated setups, and were examined in passive air-breathing FPMFCs with different electrode spacing. The results showed a decrease in the peak power density as the oxygen and ethanol mass transfer coefficients in the separators increased, due to the increase of mixed potentials especially at smaller electrode spacing. Increasing the electrode spacing was therefore desirable for the application of diaphragms. The highest peak power density was measured using Nafion^®117 with minimal electrode spacing, whereas using Nafion^®117 or Celgard^® with larger electrode spacing resulted in similar peak powers. Part 2 of this work focuses on numerical modelling of the FPMFCs based on mixed potential theory, implementing the experimental data from Part 1. Full article

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

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16 pages, 2197 KiB

Open AccessArticle

Systematic Study of Separators in Air-Breathing Flat-Plate Microbial Fuel Cells—Part 2: Numerical Modeling

by Sona Kazemi^1,2,*, Melissa Barazandegan¹, Madjid Mohseni¹ and Khalid Fatih²

¹ Department of Chemical and Biological Engineering, The University of British Columbia, Vancouver, BC V6T 1Z3, Canada

² National Research Council Canada, Vancouver, BC V6T 1W5, Canada

Energies 2016, 9(2), 79; https://doi.org/10.3390/en9020079 - 27 Jan 2016

Cited by 8 | Viewed by 5043

Abstract

The separator plays a key role on the performance of passive air-breathing flat-plate MFCs (FPMFC) as it isolates the anaerobic anode from the air-breathing cathode. The goal of the present work was to study the separator characteristics and its effect on the performance [...] Read more.

The separator plays a key role on the performance of passive air-breathing flat-plate MFCs (FPMFC) as it isolates the anaerobic anode from the air-breathing cathode. The goal of the present work was to study the separator characteristics and its effect on the performance of passive air-breathing FPMFCs. This was performed partially through characterization of structure, properties, and performance correlations of eight separators presented in Part 1. Current work (Part 2) presents a numerical model developed based on the mixed potential theory to investigate the sensitivity of the electrode potentials and the power output to the separator characteristics. According to this numerical model, the decreased peak power results from an increase in the mass transfer coefficients of oxygen and ethanol, but mainly increasing mixed potentials at the anode by oxygen crossover. The model also indicates that the peak power is affected by the proton transport number of the separator, which affects the cathode pH. Anode pH, on the other hand, remains constant due to application of phosphate buffer solution as the electrolyte. Also according to this model, the peak power is not sensitive to the resistivity of the separator because of the overshadowing effect of the oxygen crossover. Full article

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

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14 pages, 1109 KiB

Open AccessArticle

Multi-Objective Demand Response Model Considering the Probabilistic Characteristic of Price Elastic Load

by Shengchun Yang^1,2,*, Dan Zeng², Hongfa Ding¹, Jianguo Yao², Ke Wang² and Yaping Li²

¹ School of Electrical & Electronic Engineering, Huazhong University of Science and Technology, Wuhan 430074, Hubei, China

² China Electric Power Research Institute-Nanjing Branch, Nanjing 210003, Jiangsu, China

Energies 2016, 9(2), 80; https://doi.org/10.3390/en9020080 - 27 Jan 2016

Cited by 25 | Viewed by 5192

Abstract

Demand response (DR) programs provide an effective approach for dealing with the challenge of wind power output fluctuations. Given that uncertain DR, such as price elastic load (PEL), plays an important role, the uncertainty of demand response behavior must be studied. In this [...] Read more.

Demand response (DR) programs provide an effective approach for dealing with the challenge of wind power output fluctuations. Given that uncertain DR, such as price elastic load (PEL), plays an important role, the uncertainty of demand response behavior must be studied. In this paper, a multi-objective stochastic optimization problem of PEL is proposed on the basis of the analysis of the relationship between price elasticity and probabilistic characteristic, which is about stochastic demand models for consumer loads. The analysis aims to improve the capability of accommodating wind output uncertainty. In our approach, the relationship between the amount of demand response and interaction efficiency is developed by actively participating in power grid interaction. The probabilistic representation and uncertainty range of the PEL demand response amount are formulated differently compared with those of previous research. Based on the aforementioned findings, a stochastic optimization model with the combined uncertainties from the wind power output and the demand response scenario is proposed. The proposed model analyzes the demand response behavior of PEL by maximizing the electricity consumption satisfaction and interaction benefit satisfaction of PEL. Finally, a case simulation on the provincial power grid with a 151-bus system verifies the effectiveness and feasibility of the proposed mechanism and models. Full article

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

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20 pages, 1691 KiB

Open AccessArticle

The Health Costs of Revised Coal Mining Limits in Northern Bohemia

by Vojtěch Máca^* and Jan Melichar

Charles University Environment Center, Jose Martiho 2, 160 00 Prague 6, Czech Republic

Energies 2016, 9(2), 81; https://doi.org/10.3390/en9020081 - 27 Jan 2016

Cited by 15 | Viewed by 5935

Abstract

Brown coal has been the major source of energy for more than 150 years for the Czech economy, but its role in the coming decades is nowadays the source of heated debate. Many of the recurring discussions address the coal reserves that were [...] Read more.

Brown coal has been the major source of energy for more than 150 years for the Czech economy, but its role in the coming decades is nowadays the source of heated debate. Many of the recurring discussions address the coal reserves that were set aside in 1991 in order to halt the massive destruction of the landscape and the unprecedented deterioration of the human environment in Northern Bohemia. We study the proposed variants of the revised mining limits using the impact-pathway approach in order to quantify and monetize the health effects of airborne emissions from coal mining and the use of extracted coal for the production of electricity and heat. We find that the dominant health impacts associated with the revision of the limits, estimated to be up to 7 billion euros over the 2015–2050 period, will stem from the use of coal for the production of electricity and heat and that a large part of the impact will be borne by populations outside the Czech Republic. Full article

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22 pages, 6802 KiB

Open AccessArticle

Numerical Investigation of a Tuned Heave Plate Energy-Harvesting System of a Semi-Submersible Platform

by Kun Liu^1,2,*, Haizhi Liang³

and Jinping Ou^1,2,4

¹ School of Civil Engineering, Harbin Institute of Technology, Harbin 150090, China

² Key Lab of Structures Dynamic Behavior and Control of the Ministry of Education (Harbin Institute of Technology), Harbin 150090, China

³ Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, China

⁴ State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China

Energies 2016, 9(2), 82; https://doi.org/10.3390/en9020082 - 28 Jan 2016

Cited by 17 | Viewed by 7948

Abstract

A novel tuned heave plate energy-harvesting system (THPEH) is presented for the motion suppressing and energy harvesting of a semi-submersible platform. This THPEH system is designed based on the principle of a tuned mass damper (TMD) and is composed of spring supports, a [...] Read more.

A novel tuned heave plate energy-harvesting system (THPEH) is presented for the motion suppressing and energy harvesting of a semi-submersible platform. This THPEH system is designed based on the principle of a tuned mass damper (TMD) and is composed of spring supports, a power take-off system (PTO) and four movable heave plates. The permanent magnet linear generators (PMLG) are used as the PTO system in this design. A semi-submersible platform operating in the South China Sea is selected as the research subject for investigating the effects of the THPEH system on motion reduction and harvesting energy through numerical simulations. The numerical model of the platform and the THPEH system, which was established based on hydrodynamic analysis, is modified and validated by the results of the flume test of a 1:70 scale model. The effects of the parameters, including the size, the frequency ratio and the damping ratio of the THPEH system, are systematically investigated. The results show that this THPEH system, with proper parameters, could significantly reduce the motions of the semi-submersible platform and generate considerable power under different wave conditions. Full article

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

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19 pages, 12128 KiB

Open AccessArticle

The Chaotic-Based Control of Three-Port Isolated Bidirectional DC/DC Converters for Electric and Hybrid Vehicles

by Zheng Wang^1,*, Bochen Liu¹, Yue Zhang¹, Ming Cheng¹

, Kai Chu¹ and Liang Xu²

¹ School of Electrical Engineering, Southeast University, Nanjing 210096, China

² Aviation Key Laboratory of Science and Technology on Aerospace Electromechanical System Integration, No. 33 Shuige Road, Jiangning District, Nanjing 210061, China

Energies 2016, 9(2), 83; https://doi.org/10.3390/en9020083 - 27 Jan 2016

Cited by 13 | Viewed by 10133

Abstract

Three-port isolated (TPI) bidirectional DC/DC converters have three energy ports and offer advantages of large voltage gain, galvanic isolation ability and high power density. For this reason this kind of converters are suitable to connect different energy sources and loads in electric and [...] Read more.

Three-port isolated (TPI) bidirectional DC/DC converters have three energy ports and offer advantages of large voltage gain, galvanic isolation ability and high power density. For this reason this kind of converters are suitable to connect different energy sources and loads in electric and hybrid vehicles. The purpose of this paper is to propose chaotic modulation and the related control scheme for TPI bidirectional DC/DC converters, in such a way that the switching harmonic peaks can be suppressed in spectrum and the conducted electromagnetic interference (EMI) is reduced. Two chaotic modulation strategies, namely the continuously chaotic modulation and the discretely chaotic modulation are presented. These two chaotic modulation strategies are applied for TPI bidirectional DC/DC converters with shifted-phase angle based control and phase-shifted PWM control. Both simulation and experiments are given to verify the validity of the proposed chaotic modulation-based control schemes. Full article

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

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24 pages, 2466 KiB

Open AccessArticle

Environmental Analysis of Petrol, Diesel and Electric Passenger Cars in a Belgian Urban Setting

by Nils Hooftman^*,†, Luis Oliveira^*,†, Maarten Messagie, Thierry Coosemans and Joeri Van Mierlo

¹ Electrotechnical Engineering and Energy Technology, MOBI Research Group, Vrije Universiteit Brussel, Pleinlaan 2, Brussels 1050, Belgium

^† These authors contributed equally to this work.

Energies 2016, 9(2), 84; https://doi.org/10.3390/en9020084 - 29 Jan 2016

Cited by 121 | Viewed by 32408

Abstract

The combustion of fossil fuels in the transport sector leads to an aggravation of the air quality along city roads and highways. Urban air quality is a serious problem nowadays as the number of vehicles increases on a yearly basis. With stricter Euro [...] Read more.

The combustion of fossil fuels in the transport sector leads to an aggravation of the air quality along city roads and highways. Urban air quality is a serious problem nowadays as the number of vehicles increases on a yearly basis. With stricter Euro emission regulations, vehicle manufacturers are not meeting the imposed limits and are also disregarding the non-exhaust emissions. This paper highlights the relevance of non-exhaust emissions of passenger vehicles, both conventional (diesel and petrol) or electric vehicles (EV), on air quality levels in an urban environment in Belgium. An environmental life cycle assessment was carried out based on a real-world emission model for passenger cars and fuel refinery data. A cut-off was applied to the models to highlight what emissions, both from the refinery to the exhaust and electricity production for EV, do actually occur within Belgium’s borders. Results show that not much progress has been made from Euro 4 to 6 for conventional vehicles. Electric vehicles pose the best alternative solution as a more environmentally friendly means of transportation. The analysis results target policy makers with the intention that regulations and policies would be developed in the future and target the characterization of non-exhaust emissions from vehicles. These results indicate that EVs offer a valid solution for addressing the urban air quality issue and that non-exhaust emissions should be addressed in future regulatory steps as they dominate the impact spectrum. Full article

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

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25 pages, 11174 KiB

Open AccessArticle

Implementing a Novel Hybrid Maximum Power Point Tracking Technique in DSP via Simulink/MATLAB under Partially Shaded Conditions

by Shahrooz Hajighorbani^1,2,*, Mohd Amran Mohd Radzi^1,2

, Mohd Zainal Abidin Ab Kadir¹

, Suhaidi Shafie¹ and Muhammad Ammirrul Atiqi Mohd Zainuri^1,2

¹ Department of Electrical and Electronic Engineering, Faculty of Engineering, Universiti Putra Malaysia, Serdang 43400, Selangor, Malaysia

² Centre for Advanced Power and Energy Research, Faculty of Engineering, University Putra Malaysia, Serdang 43400, Malaysia

Energies 2016, 9(2), 85; https://doi.org/10.3390/en9020085 - 28 Jan 2016

Cited by 11 | Viewed by 6389

Abstract

This paper presents a hybrid maximum power point tracking (MPPT) method to detect the global maximum power point (GMPP) under partially shaded conditions (PSCs), which have more complex characteristics with multiple peak power points. The hybrid method can track the GMPP when a [...] Read more.

This paper presents a hybrid maximum power point tracking (MPPT) method to detect the global maximum power point (GMPP) under partially shaded conditions (PSCs), which have more complex characteristics with multiple peak power points. The hybrid method can track the GMPP when a partial shadow occurs either before or after acquiring the MPP under uniform conditions. When PS occurs after obtaining the MPP during uniform conditions, the new operating point should be specified by the modified linear function, which reduces the searching zone of the GMPP and has a significant effect on reducing the reaching time of the GMPP. Simultaneously, the possible MPPs are scanned and stored when shifting the operating point to a new reference voltage. Finally, after determining the possible location of the GMPP, the GMPP is obtained using the modified P&O. Conversely, when PS occurs before obtaining the MPP, the referenced MPP should be specified. Thus, after recognizing the possible location of the GMPP, the modified P&O can be used to obtain the GMPP. The simulation and experimental implementations for the proposed algorithm are performed with different scenarios of shadowing under different irradiations, which clearly indicate that the proposed method is robust and has a fast tracking speed. Moreover, this work presents the load sizing method for PSCs to avoid controller failure when detecting the GMPP. Additionally, in this paper, the user-friendly method for programming the digital signal processing (DSP) via Simulink/MATLAB is presented in detail. Full article

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21 pages, 591 KiB

Open AccessArticle

Electric Vehicles in Logistics and Transportation: A Survey on Emerging Environmental, Strategic, and Operational Challenges

by Angel Alejandro Juan^1,*

, Carlos Alberto Mendez², Javier Faulin³

, Jesica De Armas¹ and Scott Erwin Grasman⁴

¹ Computer Science Department, Internet Interdisciplinary Institute, Open University of Catalonia, 08018 Barcelona, Spain

² Instituto de Desarrollo Tecnológico para la Industria Química, Universidad Nacional del Litoral, CONICET, 3000 Santa Fe, Argentina

³ Statistics and Operations Research Department, Public University of Navarre, 31006 Pamplona, Spain

⁴ Industrial and Systems Engineering, Rochester Institute of Technology, Rochester, NY 14623, USA

Energies 2016, 9(2), 86; https://doi.org/10.3390/en9020086 - 28 Jan 2016

Cited by 175 | Viewed by 28493 | Correction

Abstract

Current logistics and transportation (L&T) systems include heterogeneous fleets consisting of common internal combustion engine vehicles as well as other types of vehicles using “green” technologies, e.g., plug-in hybrid electric vehicles and electric vehicles (EVs). However, the incorporation of EVs in L&T activities [...] Read more.

Current logistics and transportation (L&T) systems include heterogeneous fleets consisting of common internal combustion engine vehicles as well as other types of vehicles using “green” technologies, e.g., plug-in hybrid electric vehicles and electric vehicles (EVs). However, the incorporation of EVs in L&T activities also raise some additional challenges from the strategic, planning, and operational perspectives. For instance, smart cities are required to provide recharge stations for electric-based vehicles, meaning that investment decisions need to be made about the number, location, and capacity of these stations. Similarly, the limited driving-range capabilities of EVs, which are restricted by the amount of electricity stored in their batteries, impose non-trivial additional constraints when designing efficient distribution routes. Accordingly, this paper identifies and reviews several open research challenges related to the introduction of EVs in L&T activities, including: (a) environmental-related issues; and (b) strategic, planning and operational issues associated with “standard” EVs and with hydrogen-based EVs. The paper also analyzes how the introduction of EVs in L&T systems generates new variants of the well-known Vehicle Routing Problem, one of the most studied optimization problems in the L&T field, and proposes the use of metaheuristics and simheuristics as the most efficient way to deal with these complex optimization problems. Full article

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13 pages, 3944 KiB

Open AccessArticle

Influence of Fine Metal Particles on Surface Discharge Characteristics of Outdoor Insulators

by Yong Liu^1,*

, Bowen Xia¹, Boxue Du¹ and Masoud Farzaneh²

¹ Key Laboratory of Smart Grid of Ministry of Education (Tianjin University), School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China

² Canada Research Chair on Engineering of Power Network Atmospheric Icing (INGIVRE), Université du Québec à Chicoutimi, 555, Boulevard de l'Université, Chicoutimi, QC G7H 2B1, Canada

Energies 2016, 9(2), 87; https://doi.org/10.3390/en9020087 - 29 Jan 2016

Cited by 11 | Viewed by 5435

Abstract

Focusing on the influence of fine metal particles on the insulation characteristics of outdoor insulators, spherical micrometer-level iron powders were used to represent fine metal particles of different parameters on a polymer insulator specimen surface. Dynamic movement and lift-off behavior of fine particles, [...] Read more.

Focusing on the influence of fine metal particles on the insulation characteristics of outdoor insulators, spherical micrometer-level iron powders were used to represent fine metal particles of different parameters on a polymer insulator specimen surface. Dynamic movement and lift-off behavior of fine particles, as well as the triggered surface discharges under AC voltage were investigated in a uniform electric field under different experimental conditions. The results reveal that the inception, propagation and intensity of surface discharges are significantly affected by the particle parameters, including particle size, amount and distributing characteristic. Based on the measurement of light emission during the flashover process using a high-speed camera, the process of surface discharge to flashover triggered by the fine metal particles were investigated to obtain a relationship between flashover voltage, discharge light intensity and particle parameters. It is suggested that particle size smaller than 28 µm and particle amount more than 40 mg in contact with the non-uniform distribution can cause a significant distortion and intensification of the electric field resulting in a higher risk of surface discharges leading to flashover. Such investigations can enhance the operating reliability of outdoor insulators subjected to these conditions. Full article

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14 pages, 5571 KiB

Open AccessArticle

Field Experiments on 10 kV Switching Shunt Capacitor Banks Using Ordinary and Phase-Controlled Vacuum Circuit Breakers

by Wenxia Sima¹, Mi Zou^1,*

, Qing Yang¹, Ming Yang¹ and Licheng Li²

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

² School of Electric Power, South China University of Technology, Guangdong 510640, China

Energies 2016, 9(2), 88; https://doi.org/10.3390/en9020088 - 30 Jan 2016

Cited by 8 | Viewed by 9628

Abstract

During the switching on/off of shunt capacitor banks in substations, vacuum circuit breakers (VCBs) are required to switch off or to switch on the capacitive current. Therefore, the VCBs have to be operated under a harsh condition to ensure the reliability of the [...] Read more.

During the switching on/off of shunt capacitor banks in substations, vacuum circuit breakers (VCBs) are required to switch off or to switch on the capacitive current. Therefore, the VCBs have to be operated under a harsh condition to ensure the reliability of the equipment. This study presents a complete comparison study of ordinary and phase-controlled VCBs on switching 10 kV shunt capacitor banks. An analytical analysis for switching 10 kV shunt capacitor banks is presented on the basis of a reduced circuit with an ungrounded neutral. A phase selection strategy for VCBs to switch 10 kV shunt capacitor banks is proposed. Switching on current waveforms and switching off overvoltage waveforms with, and without, phase selection were measured and discussed by field experiments in a 110 kV substation in Chongqing, China. Results show that the operation of phase-controlled VCBs for 10 kV switching shunt capacitor banks is stable, and phase-controlled VCBs can be used to implement the 10 kV switching on/off shunt capacitor banks to limit the transient overvoltage and overcurrent. The values of overvoltage and inrush current using phase-controlled VCBs are all below those with ordinary VCBs. Full article

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

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22 pages, 3244 KiB

Open AccessArticle

Field Study on Humidification Performance of a Desiccant Air-Conditioning System Combined with a Heat Pump

by Koichi Kawamoto¹, Wanghee Cho^2,*

, Hitoshi Kohno³, Makoto Koganei⁴, Ryozo Ooka⁵ and Shinsuke Kato⁵

¹ Kawamoto Engineering, 3-1-11 Kami-Ikebukuro, Toshimaku, Tokyo 170-0012, Japan

² Department of Architecture, Faculty of Engineering, Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, Yokohama 221-8686, Japan

³ Research and Development Center, Asahi Kogyosha Co., Ltd., 6-17-16 Higashi-Narashino, Narashino, Chiba 275-0001, Japan

⁴ Department of Architectural Design and Engineering, Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan

⁵ Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan

Energies 2016, 9(2), 89; https://doi.org/10.3390/en9020089 - 30 Jan 2016

Cited by 19 | Viewed by 6812

Abstract

A desiccant air-conditioning system was developed as a latent-load-processing air conditioner in a dedicated outdoor air system during the summer. This study investigated the application of this air-conditioning system to humidification during the winter without using make-up water, thereby eliminating the cause of [...] Read more.

A desiccant air-conditioning system was developed as a latent-load-processing air conditioner in a dedicated outdoor air system during the summer. This study investigated the application of this air-conditioning system to humidification during the winter without using make-up water, thereby eliminating the cause of microbial contamination in air-conditioning systems. The experiments were conducted with a system used for summer applications to determine the feasibility of adsorbing vapor from outdoor air and supplying it to an indoor space. The humidification performance, energy efficiency, and operating conditions were examined. Although the conditions were subpar because the experiments were performed with an actual dedicated outdoor air system, the results showed that it is possible to supply air with a minimum humidity ratio of 5.8 g/kg dry air (DA) when the humidity ratio of outdoor air ranges from 1.8 to 2.3 g/kg DA. The minimum humidification performance required for a dedicated outdoor air system was achieved by increasing the airflow rate of the moisture-adsorption side to 2–3 times that of the humidification side. In addition, air leaking from the moisture-adsorption side to the humidification side, improving the mechanical structure, such as by the insulation of the moisture-adsorption side, and an efficient operating method were examined for humidification during the winter. Full article

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18 pages, 4402 KiB

Open AccessArticle

Optimization of Fuel Consumption and Emissions for Auxiliary Power Unit Based on Multi-Objective Optimization Model

by Yongpeng Shen^1,*, Zhendong He¹, Dongqi Liu² and Binjie Xu²

¹ College of Electric and Information Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China

² College of Electric and Information Engineering, Hunan University, Changsha 4100822, China

Energies 2016, 9(2), 90; https://doi.org/10.3390/en9020090 - 2 Feb 2016

Cited by 10 | Viewed by 9325

Abstract

Auxiliary power units (APUs) are widely used for electric power generation in various types of electric vehicles, improvements in fuel economy and emissions of these vehicles directly depend on the operating point of the APUs. In order to balance the conflicting goals of [...] Read more.

Auxiliary power units (APUs) are widely used for electric power generation in various types of electric vehicles, improvements in fuel economy and emissions of these vehicles directly depend on the operating point of the APUs. In order to balance the conflicting goals of fuel consumption and emissions reduction in the process of operating point choice, the APU operating point optimization problem is formulated as a constrained multi-objective optimization problem (CMOP) firstly. The four competing objectives of this CMOP are fuel-electricity conversion cost, hydrocarbon (HC) emissions, carbon monoxide (CO) emissions and nitric oxide (NO x ) emissions. Then, the multi-objective particle swarm optimization (MOPSO) algorithm and weighted metric decision making method are employed to solve the APU operating point multi-objective optimization model. Finally, bench experiments under New European driving cycle (NEDC), Federal test procedure (FTP) and high way fuel economy test (HWFET) driving cycles show that, compared with the results of the traditional fuel consumption single-objective optimization approach, the proposed multi-objective optimization approach shows significant improvements in emissions performance, at the expense of a slight drop in fuel efficiency. Full article

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

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15 pages, 748 KiB

Open AccessArticle

Probability Density Function Characterization for Aggregated Large-Scale Wind Power Based on Weibull Mixtures

by Emilio Gómez-Lázaro^1,*

, María C. Bueso²

, Mathieu Kessler²

, Sergio Martín-Martínez¹

, Jie Zhang³, Bri-Mathias Hodge⁴ and Angel Molina-García⁵

¹ Renewable Energy Research Institute and DIEEAC/EDII-AB, Universidad de Castilla-La Mancha, Albacete 02071, Spain

² Department of Applied Mathematics and Statistics, Universidad Politécnica de Cartagena, Cartagena 30202, Spain

³ Department of Mechanical Engineering, The University of Texas at Dallas, Richardson, TX 75080, USA

⁴ National Renewable Energy Laboratory, Golden, CO 80401, USA

⁵ Department of Electrical Engineering, Universidad Politécnica de Cartagena, Cartagena 30202, Spain

Energies 2016, 9(2), 91; https://doi.org/10.3390/en9020091 - 2 Feb 2016

Cited by 28 | Viewed by 7262

Abstract

The Weibull probability distribution has been widely applied to characterize wind speeds for wind energy resources. Wind power generation modeling is different, however, due in particular to power curve limitations, wind turbine control methods, and transmission system operation requirements. These differences are even [...] Read more.

The Weibull probability distribution has been widely applied to characterize wind speeds for wind energy resources. Wind power generation modeling is different, however, due in particular to power curve limitations, wind turbine control methods, and transmission system operation requirements. These differences are even greater for aggregated wind power generation in power systems with high wind penetration. Consequently, models based on one-Weibull component can provide poor characterizations for aggregated wind power generation. With this aim, the present paper focuses on discussing Weibull mixtures to characterize the probability density function (PDF) for aggregated wind power generation. PDFs of wind power data are firstly classified attending to hourly and seasonal patterns. The selection of the number of components in the mixture is analyzed through two well-known different criteria: the Akaike information criterion (AIC) and the Bayesian information criterion (BIC). Finally, the optimal number of Weibull components for maximum likelihood is explored for the defined patterns, including the estimated weight, scale, and shape parameters. Results show that multi-Weibull models are more suitable to characterize aggregated wind power data due to the impact of distributed generation, variety of wind speed values and wind power curtailment. Full article

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11 pages, 956 KiB

Open AccessArticle

Potential Biogas Production from Artichoke Byproducts in Sardinia, Italy

by Fabio De Menna^1,*

, Remo Alessio Malagnino¹, Matteo Vittuari¹

, Giovanni Molari¹

, Giovanna Seddaiu^2,3

, Paola A. Deligios²

, Stefania Solinas³ and Luigi Ledda^2,3

¹ Department of Agricultural and Food Sciences, University of Bologna, Viale Giuseppe Fanin 50, Bologna 40127, Italy

² Department of Agricultural Sciences, University of Sassari, Viale Italia 39, Sassari 07100, Italy

³ Desertification Research Centre—NRD, University of Sassari, Viale Italia 39, Sassari 07100, Italy

Energies 2016, 9(2), 92; https://doi.org/10.3390/en9020092 - 2 Feb 2016

Cited by 31 | Viewed by 6492

Abstract

The paper aims at evaluating the potential biogas production, both in terms of CH₄ and theoretical energy potential, from globe artichoke agricultural byproducts in Sardinia. Field data about the productivity of byproducts were collected on five artichoke varieties cultivated in Sardinia, to [...] Read more.

The paper aims at evaluating the potential biogas production, both in terms of CH₄ and theoretical energy potential, from globe artichoke agricultural byproducts in Sardinia. Field data about the productivity of byproducts were collected on five artichoke varieties cultivated in Sardinia, to assess the biomethane production of their aboveground non-food parts (excluding the head). Moreover, secondary data from previous studies and surveys at regional scale were collected to evaluate the potential biogas production of the different districts. Fresh globe artichoke residues yielded, on average, 292.2 Nm³·t_DOM⁻¹, with dissimilarities among cultivars. Fresh samples were analyzed in two series: (a) wet basis; and (b) wet basis with catalytic enzymes application. Enzymes proved to have some beneficial effects in terms of anticipated biomethane availability. At the regional level, ab. 20 × 10⁶ Nm³ CH₄ could be produced, corresponding to the 60% of current installed capacity. However, districts potentials show some differences, depending on the specific biomass partitioning and on the productivity of cultivated varieties. Regional assessments should encompass the sensitiveness of results to agro-economic variables and the economic impacts of globe artichoke residue use in the current regional biogas sector. Full article

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27 pages, 1542 KiB

Open AccessArticle

Quantitative Model and Metrics of Electrical Grids’ Resilience Evaluated at a Power Distribution Level

by Alexis Kwasinski

Department of Electrical and Computer Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA

Energies 2016, 9(2), 93; https://doi.org/10.3390/en9020093 - 3 Feb 2016

Cited by 126 | Viewed by 11325

Abstract

This paper presents a framework to systematically measure and assess power grids’ resilience with a focus on performance as perceived by customers at the power distribution level. The proposed framework considers an analogous measure of availability as a basic metric for resilience and [...] Read more.

This paper presents a framework to systematically measure and assess power grids’ resilience with a focus on performance as perceived by customers at the power distribution level. The proposed framework considers an analogous measure of availability as a basic metric for resilience and defines other key resilience-related concepts and metrics, such as resistance and brittleness. This framework also provides a measurement for the degree of functional dependency of loads on power grids and demonstrates how the concepts of resilience and dependency are inherently related. It also discusses the implications of considering human-centered processes as fundamental constituting components of infrastructure systems. Thanks to its quantitative nature, the proposed resilience framework enables the creation of tools to evaluate power grids’ performance as a lifeline and to assess the effects of plans for optimal electrical power infrastructure deployment and operation. The discussion is supported by practical examples and empirical records from field damage assessments conducted after recent notable natural disasters. Full article

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

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16 pages, 6658 KiB

Open AccessArticle

Simulation of Wind Speed in the Ventilation Tunnel for Surge Tanks in Transient Processes

by Jiandong Yang¹, Huang Wang^1,2, Wencheng Guo^1,3,*, Weijia Yang⁴ and Wei Zeng¹

¹ State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China

² Changjiang Institute of Survey, Planning, Design and Research Co. Ltd., Wuhan 430010, China

³ Maha Fluid Power Research Center, Department of Agricultural and Biological Engineering, Purdue University, West Lafayette, IN 47907, USA

⁴ Department of Engineering Sciences, Uppsala University, Uppsala SE-751 21, Sweden

Energies 2016, 9(2), 95; https://doi.org/10.3390/en9020095 - 3 Feb 2016

Cited by 5 | Viewed by 6126

Abstract

Hydroelectric power plants’ open-type surge tanks may be built in mountains subject to the provision of atmospheric air. Hence, a ventilation tunnel is indispensable. The air flow in the ventilation tunnel is associated with the fluctuation of water-level in the surge tank. There [...] Read more.

Hydroelectric power plants’ open-type surge tanks may be built in mountains subject to the provision of atmospheric air. Hence, a ventilation tunnel is indispensable. The air flow in the ventilation tunnel is associated with the fluctuation of water-level in the surge tank. There is a great relationship between the wind speed and the safe use and project investment of ventilation tunnels. To obtain the wind speed in a ventilation tunnel for a surge tank during transient processes, this article adopts the one-dimensional numerical simulation method and establishes a mathematical model of a wind speed by assuming the boundary conditions of air discharge for a surge tank. Thereafter, the simulation of wind speed in a ventilation tunnel, for the case of a surge tank during transient processes, is successfully realized. Finally, the effective mechanism of water-level fluctuation in a surge tank and the shape of the ventilation tunnel (including length, sectional area and dip angle) for the wind speed distribution and the change process are discovered. On the basis of comparison between the simulation results of 1D and 3D computational fluid dynamics (CFD), the results indicate that the one-dimensional simulation method as proposed in this article can be used to accurately simulate the wind speed in the ventilation tunnel of a surge tank during transient processes. The wind speed fluctuations can be superimposed by using the low frequency mass wave (i.e., fundamental wave) and the high frequency elastic wave (i.e., harmonic wave). The water-level fluctuation in a surge tank and the sectional area of the ventilation tunnel mainly affect the amplitude of fundamental and harmonic waves. The period of a fundamental wave can be determined from the water-level fluctuations. The length of the ventilation tunnel has an effect on the period and amplitude of harmonic waves, whereas the dip angle influences the amplitude of harmonic waves. Full article

(This article belongs to the Special Issue Hydropower)

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16 pages, 10081 KiB

Open AccessArticle

Elimination of the Inrush Current Phenomenon Associated with Single-Phase Offline UPS Systems

by Syed Sabir Hussain Bukhari

, Shahid Atiq and Byung-il Kwon^*

Deptartment of Electronic Systems Engineering, Hanyang University ERICA, Ansan 426-791, Korea

Energies 2016, 9(2), 96; https://doi.org/10.3390/en9020096 - 4 Feb 2016

Cited by 14 | Viewed by 8058

Abstract

Critical load applications always rely on UPS systems to uphold continuous power during abnormal grid conditions. In case of any power disruption, an offline UPS system starts powering the load to avoid blackout. However, this process can root the momentous inrush current for [...] Read more.

Critical load applications always rely on UPS systems to uphold continuous power during abnormal grid conditions. In case of any power disruption, an offline UPS system starts powering the load to avoid blackout. However, this process can root the momentous inrush current for the transformer installed before the load. The consequences of inrush current can be the reduction of output voltage and tripping of protective devices of the UPS system. Furthermore, it can also damage the sensitive load and decrease the transformer’s lifetime. To prevent the inrush current, and to avoid its disruptive effects, this research suggests an offline UPS system based on a current regulated inverter that eliminates the inrush current while powering the transformer coupled loads. A detailed comparative analysis of the conventional and proposed topologies is presented and the experiment was performed by using a small prototype to validate the performance, and operation of the proposed topology. Full article

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10 pages, 1618 KiB

Open AccessArticle

Performance Evaluation of Palm Oil-Based Biodiesel Combustion in an Oil Burner

by Abdolsaeid Ganjehkaviri^*, Mohammad Nazri Mohd Jaafar, Seyed Ehsan Hosseini and Anas Basri Musthafa

Faculty of Mechanical Engineering, Universiti Teknologi Malaysia (UTM), 81310 UTM Skudai, Johor, Malaysia

Energies 2016, 9(2), 97; https://doi.org/10.3390/en9020097 - 4 Feb 2016

Cited by 56 | Viewed by 8238

Abstract

This paper presents an experimental investigation of the combustion characteristics of palm methyl ester (PME), also known as palm oil-based biodiesel, in an oil burner system. The performance of conventional diesel fuel (CDF) and various percentages of diesel blended with palm oil-based biodiesel [...] Read more.

This paper presents an experimental investigation of the combustion characteristics of palm methyl ester (PME), also known as palm oil-based biodiesel, in an oil burner system. The performance of conventional diesel fuel (CDF) and various percentages of diesel blended with palm oil-based biodiesel is also studied to evaluate their performance. The performance of the various fuels is evaluated based on the temperature profile of the combustor’s wall and emissions, such as nitrogen oxides (NO_x) and carbon monoxide (CO). The combustion experiments were conducted using three different oil burner nozzles (1.25, 1.50 and 1.75 USgal/h) under lean (equivalence ratio (Φ) = 0.8), stoichiometric (Φ = 1) and rich fuel (Φ = 1.2) ratio conditions. The results show that the rate of emission formation decreases as the volume percent of palm biodiesel in a blend increases. PME combustion tests present a lower temperature inside the chamber compared to CDF combustion. High rates of NO_x formation occur under lean mixture conditions with the presence of high nitrogen and sufficient temperature, whereas high CO occurs for rich mixtures with low oxygen presence. Full article

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14 pages, 4446 KiB

Open AccessArticle

A Study on the Power Generation Capacity of Piezoelectric Energy Harvesters with Different Fixation Modes and Adjustment Methods

by Zhixiang Li^1,2,†, Gongbo Zhou^1,2,*,†, Zhencai Zhu^1,2 and Wei Li^1,2

¹ School of Mechanical and Electrical Engineering, China University of Mining & Technology, Xuzhou 221116, Jiangsu, China

² Jiangsu Key Laboratory of Mine Mechanical and Electrical Equipment, China University of Mining & Technology, Xuzhou 221116, Jiangsu, China

^† These authors contributed equally to this work.

Energies 2016, 9(2), 98; https://doi.org/10.3390/en9020098 - 19 Feb 2016

Cited by 20 | Viewed by 6345

Abstract

The power generation capacity of piezoelectric energy harvesters (PEHs) is not only related to the properties of the piezoelectric material, the vibration magnitude and the subsequent conditioning circuit, but also to the fixation modes and adjustment methods. In this paper, a commercial piezoelectric [...] Read more.

The power generation capacity of piezoelectric energy harvesters (PEHs) is not only related to the properties of the piezoelectric material, the vibration magnitude and the subsequent conditioning circuit, but also to the fixation modes and adjustment methods. In this paper, a commercial piezoelectric ceramic plate (PCP) in simply supported beam fixation mode and cantilever beam fixation mode were analyzed through finite element simulations and experiments, and furthermore, two ways of adjusting the natural frequency of PCP are studied and compared. As a result, some guidelines are proposed for the application of PCPs according to the simulation and experimental results which showed that: (1) the simply supported beam fixation mode is suitable for environments in which the exciting frequency exceeds 50 Hz, while the cantilever beam fixation mode fits the circumstance where the exciting frequency is below 50 Hz; (2) the maximum generation power a PCP produces in simply supported beam fixation mode is larger than that in cantilever beam fixation mode; (3) adjusting the weight of the mass block affixed on the PCP can change the natural frequency of PCP more efficiently than length-width ratio does. Full article

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

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21 pages, 3471 KiB

Open AccessArticle

One-Dimensional Modeling of an Entrained Coal Gasification Process Using Kinetic Parameters

by Moonkyeong Hwang, Eunhye Song

and Juhun Song^*

School of Mechanical Engineering, Pusan National University, Pusan 46241, Korea

Energies 2016, 9(2), 99; https://doi.org/10.3390/en9020099 - 6 Feb 2016

Cited by 12 | Viewed by 5975

Abstract

A one-dimensional reactor model was developed to simulate the performance of an entrained flow gasifier under various operating conditions. The model combined the plug flow reactor (PFR) model with the well-stirred reactor (WSR) model. Reaction kinetics was considered together with gas diffusion for [...] Read more.

A one-dimensional reactor model was developed to simulate the performance of an entrained flow gasifier under various operating conditions. The model combined the plug flow reactor (PFR) model with the well-stirred reactor (WSR) model. Reaction kinetics was considered together with gas diffusion for the solid-phase reactions in the PFR model, while equilibrium was considered for the gas-phase reactions in the WSR model. The differential and algebraic equations of mass balance and energy balance were solved by a robust ODE solver, i.e., an semi-implicit Runge–Kutta method, and by a nonlinear algebraic solver, respectively. The computed gasifier performance was validated against experimental data from the literature. The difference in product gas concentration from the equilibrium model, and the underlying mechanisms were discussed further. The optimal condition was found after parameter studies were made for various operating conditions. Full article

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16 pages, 3638 KiB

Open AccessArticle

Joint Estimation of the Electric Vehicle Power Battery State of Charge Based on the Least Squares Method and the Kalman Filter Algorithm

by Xiangwei Guo^1,2,3, Longyun Kang^1,2,*, Yuan Yao^1,2, Zhizhen Huang^1,2 and Wenbiao Li^1,2

¹ New Energy Research Center of Electric Power College, South China University of Technology, Guangzhou 510640, China

² Guangdong Key Laboratory of Clean Energy Technology, South China University of Technology, Guangzhou 510640, China

³ College of Electrical Engineering and Automation, Henan Polytechnic University, Jiaozuo 454000, China

Energies 2016, 9(2), 100; https://doi.org/10.3390/en9020100 - 8 Feb 2016

Cited by 74 | Viewed by 8293

Abstract

An estimation of the power battery state of charge (SOC) is related to the energy management, the battery cycle life and the use cost of electric vehicles. When a lithium-ion power battery is used in an electric vehicle, the SOC displays [...] Read more.

An estimation of the power battery state of charge (SOC) is related to the energy management, the battery cycle life and the use cost of electric vehicles. When a lithium-ion power battery is used in an electric vehicle, the SOC displays a very strong time-dependent nonlinearity under the influence of random factors, such as the working conditions and the environment. Hence, research on estimating the SOC of a power battery for an electric vehicle is of great theoretical significance and application value. In this paper, according to the dynamic response of the power battery terminal voltage during a discharging process, the second-order RC circuit is first used as the equivalent model of the power battery. Subsequently, on the basis of this model, the least squares method (LS) with a forgetting factor and the adaptive unscented Kalman filter (AUKF) algorithm are used jointly in the estimation of the power battery SOC. Simulation experiments show that the joint estimation algorithm proposed in this paper has higher precision and convergence of the initial value error than a single AUKF algorithm. Full article

(This article belongs to the Special Issue Electrochemical Energy Storage - 2015)

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20 pages, 3314 KiB

Open AccessEditor’s ChoiceArticle

Design and Analysis of Electrical Distribution Networks and Balancing Markets in the UK: A New Framework with Applications

by Vijayanarasimha Hindupur Pakka^*

and Richard Mark Rylatt

Institute of Energy & Sustainable Development, Faculty of Technology, De Montfort University, The Gateway, Leicester LE1 9BH, UK

Energies 2016, 9(2), 101; https://doi.org/10.3390/en9020101 - 9 Feb 2016

Cited by 13 | Viewed by 10332

Abstract

We present a framework for the design and simulation of electrical distribution systems and short term electricity markets specific to the UK. The modelling comprises packages relating to the technical and economic features of the electrical grid. The first package models the medium/low [...] Read more.

We present a framework for the design and simulation of electrical distribution systems and short term electricity markets specific to the UK. The modelling comprises packages relating to the technical and economic features of the electrical grid. The first package models the medium/low distribution networks with elements such as transformers, voltage regulators, distributed generators, composite loads, distribution lines and cables. This model forms the basis for elementary analysis such as load flow and short circuit calculations and also enables the investigation of effects of integrating distributed resources, voltage regulation, resource scheduling and the like. The second part of the modelling exercise relates to the UK short term electricity market with specific features such as balancing mechanism and bid-offer strategies. The framework is used for investigating methods of voltage regulation using multiple control technologies, to demonstrate the effects of high penetration of wind power on balancing prices and finally use these prices towards achieving demand response through aggregated prosumers. Full article

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

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13 pages, 4677 KiB

Open AccessArticle

Analysis of the Potential for Use of Floating Photovoltaic Systems on Mine Pit Lakes: Case Study at the Ssangyong Open-Pit Limestone Mine in Korea

by Jinyoung Song and Yosoon Choi^*

Department of Energy Resources Engineering, Pukyong National University, Busan 608-737, Korea

Energies 2016, 9(2), 102; https://doi.org/10.3390/en9020102 - 10 Feb 2016

Cited by 114 | Viewed by 11668

Abstract

Recently, the mining industry has introduced renewable energy technologies to resolve power supply problems at mines operating in polar regions or other remote areas, and to foster substitute industries, able to benefit from abandoned sites of exhausted mines. However, little attention has been [...] Read more.

Recently, the mining industry has introduced renewable energy technologies to resolve power supply problems at mines operating in polar regions or other remote areas, and to foster substitute industries, able to benefit from abandoned sites of exhausted mines. However, little attention has been paid to the potential placement of floating photovoltaic (PV) systems operated on mine pit lakes because it was assumed that the topographic characteristics of open-pit mines are unsuitable for installing any type of PV systems. This study analyzed the potential of floating PV systems on a mine pit lake in Korea to break this misconception. Using a fish-eye lens camera and digital elevation models, a shading analysis was performed to identify the area suitable for installing a floating PV system. The layout of the floating PV system was designed in consideration of the optimal tilt angle and array spacing of the PV panels. The System Advisor Model (SAM) by National Renewable Energy Laboratory, USA, was used to conduct energy simulations based on weather data and the system design. The results indicated that the proposed PV system could generate 971.57 MWh/year. The economic analysis (accounting for discount rate and a 20-year operational lifetime) showed that the net present value would be $897,000 USD, and a payback period of about 12.3 years. Therefore, we could know that the economic effect of the floating PV system on the mine pit lake is relatively higher than that of PV systems in the other abandoned mines in Korea. The annual reduction of greenhouse gas emissions was analyzed and found to be 471.21 tCO₂/year, which is twice the reduction effect achieved by forest restoration of an abandoned mine site. The economic feasibility of a floating PV system on a pit lake of an abandoned mine was thus established, and may be considered an efficient reuse option for abandoned mines. Full article

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

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13 pages, 1549 KiB

Open AccessArticle

Maximum Power Point Tracking and Harmonic Reducing Control Method for Generator-Based Exercise Equipment

by Meng-Hui Wang¹, Mei-Ling Huang^2,*

and Wei-Jhe Jiang¹

¹ Department of Electrical Engineering, National Chin-Yi University of Technology, No.57, Section 2, Chung-Shan Road, Taiping District, Taichung City 41170, Taiwan

² Department of Industrial Engineering & Management, National Chin-Yi University of Technology, No.57, Section 2, Chung-Shan Road, Taiping District, Taichung City 41170, Taiwan

Energies 2016, 9(2), 103; https://doi.org/10.3390/en9020103 - 11 Feb 2016

Cited by 5 | Viewed by 4960

Abstract

This study uses a sliding mode control (SMC) in a generator-based exercise equipment (GBEE) with nonlinear P-V characteristic curves. A P-V characteristics curve can be influenced by varying the pedaling speed of the generator. The traditional maximum power point [...] Read more.

This study uses a sliding mode control (SMC) in a generator-based exercise equipment (GBEE) with nonlinear P-V characteristic curves. A P-V characteristics curve can be influenced by varying the pedaling speed of the generator. The traditional maximum power point tracking (MPPT) control method is used with perturb and observe algorithms (P&O), extremum seeking control (ESC), etc. However, these control methods are not robust enough for control. SMC is created by two pattern methods for robustness control, approaching and sliding conditions. However, SMC allows infinite high-frequency switching of the sign function. If the sign function is used to switch the converter, it will cause the converter and switch life to be cut short, and also to form high frequency noise. Therefore, this study proposes an extension theory for an intelligent control method that will effectively improve conversion efficiency and responsiveness. This study compares generator input current waveforms for fast Fourier transform (FFT) for three different control methods. Finally, using simulation validates the stability and FFT analysis with power simulation (PSIM) software. The results of upgrading overall efficiency are about a 5% increase in efficiency and a faster response speed of about 0.5 s. The amount of generator input current harmonic is greatly reduced. Full article

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12 pages, 730 KiB

Open AccessArticle

Influence of Electrode Density on the Performance of Li-Ion Batteries: Experimental and Simulation Results

by Jelle Smekens^*, Rahul Gopalakrishnan, Nils Van den Steen

, Noshin Omar, Omar Hegazy, Annick Hubin and Joeri Van Mierlo

Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Elsene, Belgium

Energies 2016, 9(2), 104; https://doi.org/10.3390/en9020104 - 12 Feb 2016

Cited by 56 | Viewed by 17333

Abstract

Lithium-ion battery (LIB) technology further enabled the information revolution by powering smartphones and tablets, allowing these devices an unprecedented performance against reasonable cost. Currently, this battery technology is on the verge of carrying the revolution in road transport and energy storage of renewable [...] Read more.

Lithium-ion battery (LIB) technology further enabled the information revolution by powering smartphones and tablets, allowing these devices an unprecedented performance against reasonable cost. Currently, this battery technology is on the verge of carrying the revolution in road transport and energy storage of renewable energy. However, to fully succeed in the latter, a number of hurdles still need to be taken. Battery performance and lifetime constitute a bottleneck for electric vehicles as well as stationary electric energy storage systems to penetrate the market. Electrochemical battery models are one of the engineering tools which could be used to enhance their performance. These models can help us optimize the cell design and the battery management system. In this study, we evaluate the ability of the Porous Electrode Theory (PET) to predict the effect of changing positive electrode density in the overall performance of Li-ion battery cells. It can be concluded that Porous Electrode Theory (PET) is capable of predicting the difference in cell performance due to a changing positive electrode density. Full article

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

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19 pages, 973 KiB

Open AccessArticle

Evaluation of Strategies to Reducing Traction Energy Consumption of Metro Systems Using an Optimal Train Control Simulation Model

by Shuai Su^*, Tao Tang and Yihui Wang

State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University, No.3, Shangyuncun, Haidian District, Beijing 100044, China

Energies 2016, 9(2), 105; https://doi.org/10.3390/en9020105 - 12 Feb 2016

Cited by 89 | Viewed by 13030

Abstract

Increasing attention is being paid to the energy efficiency in metro systems to reduce the operational cost and to advocate the sustainability of railway systems. Classical research has studied the energy-efficient operational strategy and the energy-efficient system design separately to reduce the traction [...] Read more.

Increasing attention is being paid to the energy efficiency in metro systems to reduce the operational cost and to advocate the sustainability of railway systems. Classical research has studied the energy-efficient operational strategy and the energy-efficient system design separately to reduce the traction energy consumption. This paper aims to combine the operational strategies and the system design by analyzing how the infrastructure and vehicle parameters of metro systems influence the operational traction energy consumption. Firstly, a solution approach to the optimal train control model is introduced, which is used to design the Optimal Train Control Simulator(OTCS). Then, based on the OTCS, the performance of some important energy-efficient system design strategies is investigated to reduce the trains’ traction energy consumption, including reduction of the train mass, improvement of the kinematic resistance, the design of the energy-saving gradient, increasing the maximum traction and braking forces, introducing regenerative braking and timetable optimization. As for these energy-efficient strategies, the performances are finally evaluated using the OTCS with the practical operational data of the Beijing Yizhuang metro line. The proposed approach gives an example to quantitatively analyze the energy reduction of different strategies in the system design procedure, which may help the decision makers to have an overview of the energy-efficient performances and then to make decisions by balancing the costs and the benefits. Full article

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8 pages, 921 KiB

Open AccessEditor’s ChoiceArticle

Recovery of Bio-Oil from Industrial Food Waste by Liquefied Dimethyl Ether for Biodiesel Production

by Kiyoshi Sakuragi, Peng Li^*, Maromu Otaka and Hisao Makino

Energy Engineering Research Laboratory, Central Research Institute of Electric Power Industry, Yokosuka, Kanagawa 240-0196, Japan

Energies 2016, 9(2), 106; https://doi.org/10.3390/en9020106 - 17 Feb 2016

Cited by 38 | Viewed by 10050

Abstract

The development of new energy sources has become particularly important from the perspective of energy security and environmental protection. Therefore, the utilization of waste resources such as industrial food wastes (IFWs) in energy production is expected. The central research institute of electric power [...] Read more.

The development of new energy sources has become particularly important from the perspective of energy security and environmental protection. Therefore, the utilization of waste resources such as industrial food wastes (IFWs) in energy production is expected. The central research institute of electric power industry (CRIEPI, Tokyo, Japan) has recently developed an energy-saving oil-extraction technique involving the use of liquefied dimethyl ether (DME), which is an environmentally friendly solvent. In this study, three common IFWs (spent coffee grounds, soybean, and rapeseed cakes) were evaluated with respect to oil yield for biodiesel fuel (BDF) production by the DME extraction method. The coffee grounds were found to contain 16.8% bio-oil, whereas the soybean and rapeseed cakes contained only approximately 0.97% and 2.6% bio-oil, respectively. The recovered oils were qualitatively analysed by gas chromatography-mass spectrometry. The properties of fatty acid methyl esters derived from coffee oil, such as kinematic viscosity, pour point, and higher heating value (HHV), were also determined. Coffee grounds had the highest oil content and could be used as biofuel. In addition, the robust oil extraction capability of DME indicates that it may be a favourable alternative to conventional oil extraction solvents. Full article

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16 pages, 6609 KiB

Open AccessArticle

Coordinated Voltage Control in Distribution Network with the Presence of DGs and Variable Loads Using Pareto and Fuzzy Logic

by José Raúl Castro^1,2,*, Maarouf Saad^3,†, Serge Lefebvre^4,†, Dalal Asber^4,† and Laurent Lenoir^4,†

¹ Departamento de Ciencias de la Computación y Electrónica, Universidad Técnica Particular de Loja, Loja 11-01-608, Ecuador

² Power Electronics and Industrial Control Research Group (GREPCI), Ecole de technologie supérieure, Montréal, QC H3C 1K3, Canada

³ Department of Electrical Engineering, Ecole de technologie supérieure, 1100, Notre–Dame Ouest, Montréal, QC H3C 1K3, Canada

⁴ Hydro-Québec’s research institute (IREQ), 1800, boul. Lionel-Boulet, Varennes, QC J3X 1S3, Canada

^† These authors contributed equally to this work.

Energies 2016, 9(2), 107; https://doi.org/10.3390/en9020107 - 17 Feb 2016

Cited by 12 | Viewed by 5730

Abstract

This paper presents an efficient algorithm to solve the multi-objective (MO) voltage control problem in distribution networks. The proposed algorithm minimizes the following three objectives: voltage variation on pilot buses, reactive power production ratio deviation, and generator voltage deviation. This work leverages two [...] Read more.

This paper presents an efficient algorithm to solve the multi-objective (MO) voltage control problem in distribution networks. The proposed algorithm minimizes the following three objectives: voltage variation on pilot buses, reactive power production ratio deviation, and generator voltage deviation. This work leverages two optimization techniques: fuzzy logic to find the optimum value of the reactive power of the distributed generation (DG) and Pareto optimization to find the optimal value of the pilot bus voltage so that this produces lower losses under the constraints that the voltage remains within established limits. Variable loads and DGs are taken into account in this paper. The algorithm is tested on an IEEE 13-node test feeder and the results show the effectiveness of the proposed model. Full article

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

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13 pages, 6080 KiB

Open AccessArticle

Performance and Feasibility Study of a Standing Column Well (SCW) System Using a Deep Geothermal Well

by Jeong-Heum Cho¹, Yujin Nam^1,* and Hyoung-Chan Kim²

¹ Department of Architectural Engineering, Pusan National University, 2 Busandaehak-ro 63, Geomjeong-gu, Busan 609-735, Korea

² Division of Geologic Environment, Korea Institute of Geoscience and Mineral Resources, 124, Gahang-no, Yuseong-gu, Daejeon 305-350, Korea

Energies 2016, 9(2), 108; https://doi.org/10.3390/en9020108 - 17 Feb 2016

Cited by 12 | Viewed by 7652

Abstract

Deep geothermal heat pump systems have considerable energy saving potential for heating and cooling systems that use stable ground temperature and groundwater as their heat sources. However, deep geothermal systems have several limitations for real applications such as a very high installation cost [...] Read more.

Deep geothermal heat pump systems have considerable energy saving potential for heating and cooling systems that use stable ground temperature and groundwater as their heat sources. However, deep geothermal systems have several limitations for real applications such as a very high installation cost and a lack of recognition as heating and cooling systems. In this study, we performed a feasibility assessment of a Standing Column Well (SCW) system using a deep geothermal well, based on a real-scale experiment in Korea. The results showed that the temperature of the heat source increased up to 42.04 °C in the borehole after the heating experiment, which is about 30 °C higher than that of normal shallow geothermal wells. Furthermore, the coefficient of performance (COP) of the heat pump during 3 months of operation was 5.8, but the system COP was only 3.6 due to the relatively high electric consumption of the pump. Moreover, the payback period of the system using a deep well for controlled horticulture in a glass greenhouse was calculated as 6 years compared with using a diesel boiler system. Full article

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15 pages, 778 KiB

Open AccessArticle

Wind Speed Prediction Using a Univariate ARIMA Model and a Multivariate NARX Model

by Erasmo Cadenas¹, Wilfrido Rivera^2,†, Rafael Campos-Amezcua^2,*,†

and Christopher Heard^3,†

¹ Facultad de Ingenieria Mecanica, Universidad Michoacana de San Nicolas de Hidalgo, Santiago Tapia No. 403, Col. Centro, CP 58000 Morelia, Michoacan, Mexico

² Instituto de Energias Renovables, Universidad Nacional Autonoma de Mexico, Apartado postal 34, CP 62580 Temixco, Morelos, Mexico

³ Division de Ciencias de la Comunicacion y Diseno, Departamento de Teoria y Procesos del Diseno, Diseno Ambiental, Universidad Autonoma Metropolitana Unidad Cuajimalpa, Torre III, 5to. piso, Av. Vasco de Quiroga 4871, Col. Santa Fe Cuajimalpa, Del. Cuajimalpa, Mexico D.F. 11850, Mexico

^† These authors contributed equally to this work.

Energies 2016, 9(2), 109; https://doi.org/10.3390/en9020109 - 17 Feb 2016

Cited by 265 | Viewed by 14228

Abstract

Two on step ahead wind speed forecasting models were compared. A univariate model was developed using a linear autoregressive integrated moving average (ARIMA). This method’s performance is well studied for a large number of prediction problems. The other is a multivariate model developed [...] Read more.

Two on step ahead wind speed forecasting models were compared. A univariate model was developed using a linear autoregressive integrated moving average (ARIMA). This method’s performance is well studied for a large number of prediction problems. The other is a multivariate model developed using a nonlinear autoregressive exogenous artificial neural network (NARX). This uses the variables: barometric pressure, air temperature, wind direction and solar radiation or relative humidity, as well as delayed wind speed. Both models were developed from two databases from two sites: an hourly average measurements database from La Mata, Oaxaca, Mexico, and a ten minute average measurements database from Metepec, Hidalgo, Mexico. The main objective was to compare the impact of the various meteorological variables on the performance of the multivariate model of wind speed prediction with respect to the high performance univariate linear model. The NARX model gave better results with improvements on the ARIMA model of between 5.5% and 10. 6% for the hourly database and of between 2.3% and 12.8% for the ten minute database for mean absolute error and mean squared error, respectively. Full article

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

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18 pages, 2873 KiB

Open AccessArticle

Dynamic Analysis of Wind Turbine Gearbox Components

by Mingming Zhao^* and Jinchen Ji

School of Electrical, Mechanical and Mechatronic Systems, University of Technology Sydney, Sydney 2000, Australia

Energies 2016, 9(2), 110; https://doi.org/10.3390/en9020110 - 17 Feb 2016

Cited by 36 | Viewed by 9568

Abstract

This paper studies the dynamic response of a wind turbine gearbox under different excitation conditions. The proposed 4 degree-of-freedom (DOF) dynamic model takes into account the key factors such as the time-varying mesh stiffness, bearing stiffness, damping, static transmission error and gear backlash. [...] Read more.

This paper studies the dynamic response of a wind turbine gearbox under different excitation conditions. The proposed 4 degree-of-freedom (DOF) dynamic model takes into account the key factors such as the time-varying mesh stiffness, bearing stiffness, damping, static transmission error and gear backlash. Both the external excitation due to wind and the internal excitation due to the static transmission error are included to represent the gearbox excitation conditions. With the help of the time history and frequency spectrum, the dynamic responses of wind turbine gearbox components are investigated by using the numerical integration method. This paper explains under which conditions the fretting corrosion, as one of the wind turbine gearbox failure modes, may occur. Furthermore, it is observed that the external excitation fluctuation has large influence on the dynamic responses of both the gears and bearings. Full article

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16 pages, 1951 KiB

Open AccessArticle

Feasibility Assessment of Using Power Plant Waste Heat in Large Scale Horticulture Facility Energy Supply Systems

by Min Gyung Yu and Yujin Nam^*

Department of Architectural Engineering, Pusan National University, 2 Busandaehak-ro 63, Geomjeong-gu, Busan 609-735, Korea

Energies 2016, 9(2), 112; https://doi.org/10.3390/en9020112 - 18 Feb 2016

Cited by 14 | Viewed by 6734

Abstract

Recently, the Korean government has been carrying out projects to construct several large scale horticulture facilities. However, it is difficult for an energy supply to operate stably and economically with only a conventional fossil fuel boiler system. For this reason, several unused energy [...] Read more.

Recently, the Korean government has been carrying out projects to construct several large scale horticulture facilities. However, it is difficult for an energy supply to operate stably and economically with only a conventional fossil fuel boiler system. For this reason, several unused energy sources have become attractive and it was found that power plant waste heat has the greatest potential for application in this scenario. In this study, we performed a feasibility assessment of power plant waste heat as an energy source for horticulture facilities. As a result, it was confirmed that there was a sufficient amount of energy potential for the use of waste heat to supply energy to the assumed area. In Dangjin, an horticultural area of 500 ha could be constructed by utilizing 20% of the energy reserves. In Hadong, a horticulture facility can be set up to be 260 ha with 7.4% of the energy reserves. In Youngdong, an assumed area of 65 ha could be built utilizing about 19% of the energy reserves. Furthermore, the payback period was calculated in order to evaluate the economic feasibility compared with a conventional system. The initial investment costs can be recovered by the approximately 83% reduction in the annual operating costs. Full article

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

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16 pages, 2426 KiB

Open AccessArticle

Ice Storage Air-Conditioning System Simulation with Dynamic Electricity Pricing: A Demand Response Study

by Chi-Chun Lo^1,2,†, Shang-Ho Tsai^1,† and Bor-Shyh Lin^3,*

¹ Institute of Electrical and Control Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan

² Department of Engineering and Maintenance, Chang Gung Memorial Hospital, Kaosiung 83301, Taiwan

³ Institute of Imaging and Biomedical Photonics, National Chiao Tung University, Tainan 71150, Taiwan

^† These authors contributed equally to this work.

Energies 2016, 9(2), 113; https://doi.org/10.3390/en9020113 - 18 Feb 2016

Cited by 40 | Viewed by 8170

Abstract

This paper presents an optimal dispatch model of an ice storage air-conditioning system for participants to quickly and accurately perform energy saving and demand response, and to avoid the over contact with electricity price peak. The schedule planning for an ice storage air-conditioning [...] Read more.

This paper presents an optimal dispatch model of an ice storage air-conditioning system for participants to quickly and accurately perform energy saving and demand response, and to avoid the over contact with electricity price peak. The schedule planning for an ice storage air-conditioning system of demand response is mainly to transfer energy consumption from the peak load to the partial-peak or off-peak load. Least Squares Regression (LSR) is used to obtain the polynomial function for the cooling capacity and the cost of power consumption with a real ice storage air-conditioning system. Based on the dynamic electricity pricing, the requirements of cooling loads, and all technical constraints, the dispatch model of the ice-storage air-conditioning system is formulated to minimize the operation cost. The Improved Ripple Bee Swarm Optimization (IRBSO) algorithm is proposed to solve the dispatch model of the ice storage air-conditioning system in a daily schedule on summer. Simulation results indicate that reasonable solutions provide a practical and flexible framework allowing the demand response of ice storage air-conditioning systems to demonstrate the optimization of its energy savings and operational efficiency and offering greater energy efficiency. Full article

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17 pages, 7197 KiB

Open AccessArticle

A New Fluctuation Index: Characteristics and Application to Hydro-Wind Systems

by Xianxun Wang^1,2

, Yadong Mei^1,2,*

, Hao Cai^1,2 and Xiangyu Cong³

¹ State Key Laboratory of Water Resource and Hydropower Engineering Science, Wuhan University, Wuhan 430072, Hubei, China

² Hubei Collaborative Innovation Center for Water Resources Security, Wuhan 430072, Hubei, China

³ POWERCHINA Kunming Engineering Corporation Limited, Kunming 650051, Yunnan, China

Energies 2016, 9(2), 114; https://doi.org/10.3390/en9020114 - 18 Feb 2016

Cited by 30 | Viewed by 7120

Abstract

Hydro-wind system output fluctuations are the primary factors used to assess the effects of hydropower on power companies compensating for wind power intermittency. Considering that most fluctuation indices can only characterize one aspect of fluctuations, namely, the quantitative or contour variations, we present [...] Read more.

Hydro-wind system output fluctuations are the primary factors used to assess the effects of hydropower on power companies compensating for wind power intermittency. Considering that most fluctuation indices can only characterize one aspect of fluctuations, namely, the quantitative or contour variations, we present a new index that uses the standard deviation (SD) and rotation angle to detect the quantitative variations and contour changes, respectively. Herein, the new index is compared with commonly used indices, specifically, the first-order difference, SD, and Richards-Baker flashiness indices. The results of tests performed using various processes and disposals show that: (1) when dealing with the process by moving average, repeating or overlay disposal, the new index performs comparably to the other indices, while when dealing with the process by zooming disposal, it more fully describes the fluctuation characteristics by taking both quantitative and contour variations into consideration; (2) when the new index is used to characterize the hydro-wind output fluctuations with different resources and capacities, the outcomes coincide with the mechanisms of hydro-wind systems. This study presents a new way to characterize the fluctuation of hydro-wind output. Full article

(This article belongs to the Special Issue Hydropower)

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11 pages, 4098 KiB

Open AccessArticle

Synthesis and Characterization of Sulfonated Poly(Phenylene) Containing a Non-Planar Structure and Dibenzoyl Groups

by Hohyoun Jang

, Sabuj Chandra Sutradhar, Jiho Yoo, Jaeseong Ha, Jaeseung Pyo, Chaekyun Lee, Taewook Ryu and Whangi Kim^*

Department of Applied Chemistry, Konkuk University, Chungju 380-701, Korea

Energies 2016, 9(2), 115; https://doi.org/10.3390/en9020115 - 18 Feb 2016

Cited by 19 | Viewed by 6159

Abstract

Polymers for application as sulfonated polyphenylene membranes were prepared by nickel-catalyzed carbon-carbon coupling reaction of bis(4-chlorophenyl)-1,2-diphenylethylene (BCD) and 1,4-dichloro-2,5-dibenzoylbenzene (DCBP). Conjugated cis/trans isomer (BCD) had a non-planar conformation containing four peripheral aromatic rings that facilitate the formation of π–π interactions. 1,4-Dichloro-2,5-dibenzoylbenzene was synthesized [...] Read more.

Polymers for application as sulfonated polyphenylene membranes were prepared by nickel-catalyzed carbon-carbon coupling reaction of bis(4-chlorophenyl)-1,2-diphenylethylene (BCD) and 1,4-dichloro-2,5-dibenzoylbenzene (DCBP). Conjugated cis/trans isomer (BCD) had a non-planar conformation containing four peripheral aromatic rings that facilitate the formation of π–π interactions. 1,4-Dichloro-2,5-dibenzoylbenzene was synthesized from the oxidation reaction of 2,5-dichloro-p-xylene, followed by Friedel-Crafts reaction with benzene. DCBP monomer had good reactivity in polymerization affecting the activity of benzophenone as an electron-withdrawing group. The polyphenylene was sulfonated using concentrated sulfuric acid. These polymers without any ether linkages on the polymer backbone were protected from nucleophilic attack by hydrogen peroxide, hydroxide anion, and radicals generated by polymer electrolyte membrane fuel cell (PEMFC) operation systems. The mole fraction of the sulfonic acid groups was controlled by varying the mole ratio of bis(4-chlorophenyl)-1,2-diphenylethylene in the copolymer. In comparison with Nafion 211^® membrane, these SBCDCBP membranes showed ion exchange capacity (IEC) ranging from 1.04 to 2.07 meq./g, water uptake from 36.5% to 69.4%, proton conductivity from 58.7 to 101.9 mS/cm, and high thermal stability. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membrane Fuel Cells 2016)

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17 pages, 1080 KiB

Open AccessArticle

The Value of Lost Load for Sectoral Load Shedding Measures: The German Case with 51 Sectors

by Aaron Praktiknjo

School of Business and Economics, RWTH Aachen University, Mathieustr. 10, 52074 Aachen, Germany

Energies 2016, 9(2), 116; https://doi.org/10.3390/en9020116 - 19 Feb 2016

Cited by 24 | Viewed by 9383

Abstract

The transition of the German electricity system towards a renewable, nuclear free and increasingly fluctuating power generation raises concerns about supply security. A possible contribution to solve this issue might lie in demand response or load shedding measures. The goal of our work [...] Read more.

The transition of the German electricity system towards a renewable, nuclear free and increasingly fluctuating power generation raises concerns about supply security. A possible contribution to solve this issue might lie in demand response or load shedding measures. The goal of our work is to monetarily quantify the consequences of power interruptions. The focus lies on power interruption costs in 51 economic sectors. Two input-output models are proposed to estimate the Value of Lost Load for each sector. The first does not take inter-linkages of the sectors and possible cascading effects on interruption costs into account. The second model is a new and innovative approach which is based on the Ghosh Input-Output model and which accounts for these effects. We assume that the first model is adequate to assess shorter power interruptions, whereas the second model might be more appropriate when estimating costs of longer interruptions. Full article

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

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12 pages, 2427 KiB

Open AccessArticle

Performance Analysis of a Grid-connected High Concentrating Photovoltaic System under Practical Operation Conditions

by Zhe Mi^1,†, Jikun Chen^2,*,†, Nuofu Chen^1,3,*, Yiming Bai¹

, Wenwang Wu⁴, Rui Fu¹ and Hu Liu⁵

¹ State Key Laboratory of Alternate Electrical Power System with Renewable Energy Source, North China Electric Power University, Beijing 102206, China

² School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China

³ Yunnan Lincang Xinyuan Germanium Co. Ltd., Kunming 650503, China

⁴ State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, China

⁵ Department of Mathematics and Physics, Shijiazhuang Tiedao University, Shijiazhuang 050043, China

^† These authors contributed equally to this work.

Energies 2016, 9(2), 117; https://doi.org/10.3390/en9020117 - 19 Feb 2016

Cited by 13 | Viewed by 5382

Abstract

High concentrating photovoltaic (HCPV) is a promising technique for the practical commercial utilization of solar energy. However, the performance of a HCPV system is significantly influenced by environmental parameters such as solar direct normal irradiance (DNI) level and environmental temperature. This paper analyzes [...] Read more.

High concentrating photovoltaic (HCPV) is a promising technique for the practical commercial utilization of solar energy. However, the performance of a HCPV system is significantly influenced by environmental parameters such as solar direct normal irradiance (DNI) level and environmental temperature. This paper analyzes the performance of a 9 kW_p grid-connected HCPV system in Kunming (Yunnan, China), during practical field operations over an entire year, and discusses how the environmental parameters influence the performance from both the energy conversion and power inversion perspective. Large variations in the performance of the HCPV system have been observed for different months, due to the respective changes in the environmental parameters. The DNI level has been found to be a dominant parameter that mainly determines the amount of energy production as well as the performance ratio of the HCPV system. The environmental temperature and wind velocity have less influence on the system performance ratio than expected. Based on the performance of the present HCPV system, a quantified correlation between the output power and the direct normal irradiance has been derived, which provides guidelines for both the cogent application and the modeling of HCPV techniques for grid-connected power generation. Full article

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20 pages, 35703 KiB

Open AccessArticle

Structural Reliability of Plain Bearings for Wave Energy Converter Applications

by Simon Ambühl^1,*

, Morten Kramer^1,2 and John Dalsgaard Sørensen¹

¹ Department of Civil Engineering, Aalborg University, Sofiendalsvej 11, Aalborg SV 9200, Denmark

² Wave Star A/S, Park Allé, Brøndby 2605, Denmark

Energies 2016, 9(2), 118; https://doi.org/10.3390/en9020118 - 19 Feb 2016

Cited by 4 | Viewed by 6716

Abstract

The levelized cost of energy (LCOE) from wave energy converters (WECs) needs to be decreased in order to be able to become competitive with other renewable electricity sources. Probabilistic reliability methods can be used to optimize the structure of WECs. Optimization is often [...] Read more.

The levelized cost of energy (LCOE) from wave energy converters (WECs) needs to be decreased in order to be able to become competitive with other renewable electricity sources. Probabilistic reliability methods can be used to optimize the structure of WECs. Optimization is often performed for critical structural components, like welded details, bolts or bearings. This paper considers reliability studies with a focus on plain bearings available from stock for the Wavestar device, which exists at the prototype level. The Wavestar device is a point absorber WEC. The plan is to mount a new power take-off (PTO) system consisting of a discrete displacement cylinder (DDC), which will allow different hydraulic cycles to operate at constant pressure levels. This setup increases the conversion efficiency, as well as decouples the electricity production from the pressure variations within the hydraulic cycle when waves are passing. The new PTO system leads to different load characteristics at the floater itself compared to the actual setup where the turbine/generator is directly coupled to the fluctuating hydraulic pressure within the PTO system. This paper calculates the structural reliability of the different available plain bearings planned to be mounted at the new PTO system based on a probabilistic approach, and the paper gives suggestions for fulfilling the minimal target reliability levels. The considered failure mode in this paper is the brittle fatigue failure of plain bearings. The performed sensitivity analysis shows that parameters defining the initial crack size have a big impact on the resulting reliability of the plain bearing. Full article

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15 pages, 4630 KiB

Open AccessArticle

Exploitation Contradictions Concerning Multi-Energy Resources among Coal, Gas, Oil, and Uranium: A Case Study in the Ordos Basin (Western North China Craton and Southern Side of Yinshan Mountains)

by Xiaowei Feng¹, Nong Zhang^1,*, Xiaoting Chen², Lianyuan Gong³, Chuangxin Lv⁴ and Yu Guo¹

¹ Key Laboratory of Deep Coal Resource Mining, Ministry of Education of China, China University of Mining and Technology, Xuzhou 221116, China

² Faculty of economics and business, University Malaysia Sarawak, Kota Samarahan 94300, Malaysia

³ Key Laboratory of Coal Processing and Efficient Utilization, Ministry of Education of China, School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221116, China

⁴ Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Kowloon 999077, Hong Kong, China

Energies 2016, 9(2), 119; https://doi.org/10.3390/en9020119 - 19 Feb 2016

Cited by 23 | Viewed by 9276

Abstract

The particular “rich coal, meager oil, and deficient gas” energy structure of China determines its high degree of dependence on coal resources. After over 100 years of high-intensity mining activities in Northeast China, East Region, and the Southern Region, coal mining in these [...] Read more.

The particular “rich coal, meager oil, and deficient gas” energy structure of China determines its high degree of dependence on coal resources. After over 100 years of high-intensity mining activities in Northeast China, East Region, and the Southern Region, coal mining in these areas is facing a series of serious problems, which force China’s energy exploitation map to be rewritten. New energy bases will move to the western and northern regions in the next few years. However, overlapping phenomena of multiple resources are frequently encountered. Previous exploitation mainly focused on coal mining, which destroys many mutualistic and accompanying resources, such as uranium, gas, and oil. Aiming at solving this unscientific development mode, this research presents a case study in the Ordos Basin, where uranium, coal, and gas/oil show a three-dimensional overlapping phenomenon along the vertical downward direction. The upper uranium and lower coal situation in this basin is remarkable; specifically, coal mining disturbs the overlaying aquifer, thus requiring the uranium to be leached first. The technical approach must be sufficiently reliable to avoid the leakage of radioactive elements in subsequent coal mining procedures. Hence, the unbalanced injection and extraction of uranium mining is used to completely eradicate the discharged emissions to the environment. The gas and oil are typically not extracted because of their deep occurrence strata and their overlapping phenomenon with coal seams. Use of the integrated coal and gas production method is recommended, and relevant fracturing methods to increase the gas migrating degree in the strata are also introduced. The results and recommendations in this study are applicable in some other areas with similarities. Full article

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17 pages, 1396 KiB

Open AccessReview

Quantifying the Water-Energy-Food Nexus: Current Status and Trends

by Yuan Chang^1,*, Guijun Li¹, Yuan Yao², Lixiao Zhang³ and Chang Yu⁴

¹ School of Management Science and Engineering, Central University of Finance and Economics, Beijing 100081, China

² McCormick School of Engineering and Applied Science, Northwestern University, Evanston, IL 60208, USA

³ State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China

⁴ School of Economics and Management, Beijing Forestry University, Beijing 100083, China

Energies 2016, 9(2), 65; https://doi.org/10.3390/en9020065 - 22 Jan 2016

Cited by 204 | Viewed by 21865

Abstract

Water, energy, and food are lifelines for modern societies. The continuously rising world population, growing desires for higher living standards, and inextricable links among the three sectors make the water-energy-food (WEF) nexus a vibrant research pursuit. For the integrated delivery of WEF systems, [...] Read more.

Water, energy, and food are lifelines for modern societies. The continuously rising world population, growing desires for higher living standards, and inextricable links among the three sectors make the water-energy-food (WEF) nexus a vibrant research pursuit. For the integrated delivery of WEF systems, quantifying WEF connections helps understand synergies and trade-offs across the water, energy, and food sectors, and thus is a critical initial step toward integrated WEF nexus modeling and management. However, current WEF interconnection quantifications encounter methodological hurdles. Also, existing calculation results are scattered across a wide collection of studies in multiple disciplines, which increases data collection and interpretation difficulties. To advance robust WEF nexus quantifications and further contribute to integrated WEF systems modeling and management, this study: (i) summarizes the estimate results to date on WEF interconnections; (ii) analyzes methodological and practical challenges associated with WEF interconnection calculations; and (iii) points out opportunities for enabling robust WEF nexus quantifications in the future. Full article

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

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14 pages, 1307 KiB

Open AccessReview

Visualization of International Energy Policy Research

by Xiaoling Wang^1,2,*

, Jatin Nathwani^3,† and Chunyou Wu^2,†

¹ Donlinks School of Economics and Management, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing 100083, China

² Faculty of Management and Economics, Dalian University of Technology, Dalian 116023, China

³ Department of Management Science, Faculty of Engineering, Waterloo Institute of Sustainable Energy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada

^† These authors contributed equally to this work.

Energies 2016, 9(2), 72; https://doi.org/10.3390/en9020072 - 26 Jan 2016

Cited by 13 | Viewed by 5817

Abstract

The complexity of policy decision making is well recognized. It is not clear, however, what role academic policy research has played in influencing the directions of policy outcomes and how the research has intertwined with notable issues globally. Given the importance of energy [...] Read more.

The complexity of policy decision making is well recognized. It is not clear, however, what role academic policy research has played in influencing the directions of policy outcomes and how the research has intertwined with notable issues globally. Given the importance of energy choices on sustainable development, we have developed a comprehensive and powerful visualization of the research trends worldwide in energy policy studies over the past five decades using the literature metrology theory and its techniques. The analytical framework provides a visual tracking of research activity, directional flow and a robust basis for judging progress. The emergent findings are an aid to decision makers drawing insights from specific policy studies within a fully transparent view of the historical context on a global scale. Full article

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24 pages, 9983 KiB

Open AccessEditor’s ChoiceReview

Experimental and Numerical Studies of a High-Head Francis Turbine: A Review of the Francis-99 Test Case

by Chirag Trivedi^1,*

, Michel J. Cervantes^1,2 and Ole G. Dahlhaug¹

¹ Department of Energy and Process Engineering, Norwegian University of Science and Technology, Trondheim 7491, Norway

² Department of Engineering Sciences and Mathematics, Luleå University of Technology Sweden, Luleå 97187, Sweden

Energies 2016, 9(2), 74; https://doi.org/10.3390/en9020074 - 26 Jan 2016

Cited by 80 | Viewed by 13050

Abstract

Hydraulic turbines are widely used to meet real-time electricity demands. Computational fluid dynamic (CFD) techniques have played an important role in the design and development of such turbines. The simulation of a complete turbine requires substantial computational resources. A specific approach that is [...] Read more.

Hydraulic turbines are widely used to meet real-time electricity demands. Computational fluid dynamic (CFD) techniques have played an important role in the design and development of such turbines. The simulation of a complete turbine requires substantial computational resources. A specific approach that is applied to investigate the flow field of one turbine may not work for another turbine. A series of Francis-99 workshops have been planned to discuss and explore the CFD techniques applied within the field of hydropower with application to high-head Francis turbines. The first workshop was held in December 2014 at the Norwegian University of Science and Technology, Norway. The steady-state measurements were conducted on a model Francis turbine. Three operating points, part load, best efficiency point, and high load, were investigated. The complete geometry, meshing, and experimental data concerning the hydraulic efficiency, pressure, and velocity were provided to the academic and industrial research groups. Various researchers have conducted extensive numerical studies on the high-head Francis turbine, and the obtained results were presented during the workshop. This paper discusses the presented numerical results and the important outcome of the extensive numerical studies on the Francis turbine. The use of a wall function assuming equilibrium between the production and dissipation of turbulence is widely used in the simulation of hydraulic turbines. The boundary layer of hydraulic turbines is not fully developed because of the continuously-changing geometry and large pressure gradients. There is a need to develop wall functions that enable the estimation of viscous losses under boundary development for accurate simulations. Improved simulations and results enable reliable estimation of the blade loading. Numerical investigations on leakage flow through the labyrinth seals were conducted. The volumetric efficiency and losses in the seals were determined. The seal leakage losses formulated through analytical techniques are sufficient. Full article

(This article belongs to the Special Issue Hydropower)

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17 pages, 3611 KiB

Open AccessReview

Overcoming the Fundamental Limit: Combustion of a Hydrogen-Oxygen Mixture in Micro- and Nano-Bubbles

by Vitaly Svetovoy^1,2,*, Alexander Postnikov^2,†, Ilia Uvarov^2,†, Remco Sanders^1,† and Gijs Krijnen^1,†

¹ MESA⁺ Institute for Nanotechnology, University of Twente, PO 217, Enschede 7500 AE, The Netherlands

² Yaroslavl Branch of the Institute of Physics and Technology, RAS, Yaroslavl 150007, Russia

^† These authors contributed equally to this work.

Energies 2016, 9(2), 94; https://doi.org/10.3390/en9020094 - 3 Feb 2016

Cited by 21 | Viewed by 9829

Abstract

Combustion reactions quench in small volumes due to fast heat escape via the volume boundary. Nevertheless, the reaction between hydrogen and oxygen was observed in nano- and micro-bubbles. The bubbles containing a mixture of gases were produced in microsystems using electrochemical decomposition of [...] Read more.

Combustion reactions quench in small volumes due to fast heat escape via the volume boundary. Nevertheless, the reaction between hydrogen and oxygen was observed in nano- and micro-bubbles. The bubbles containing a mixture of gases were produced in microsystems using electrochemical decomposition of water with a fast switching of voltage polarity. In this paper, we review our experimental results on the reaction in micro- and nano-bubbles and provide their physical interpretation. Experiments were performed using microsystems of different designs. The process was observed with a stroboscope and with a vibrometer. The latter was used to measure the gas concentration in the electrolyte and to monitor pressure in a reaction chamber covered with a flexible membrane. Information on the temperature was extracted from the Faraday current in the electrolyte. Since the direct observation of the combustion is complicated by the small size and short time scale of the events, special attention is paid to the signatures of the reaction. The mechanism of the reaction is not yet clear, but it is obvious that the process is surface dominated and happens without significant temperature increase. Full article

(This article belongs to the Special Issue Micro Combustor)

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27 pages, 3191 KiB

Open AccessFeature PaperEditor’s ChoiceReview

A Review of Modeling Bioelectrochemical Systems: Engineering and Statistical Aspects

by Shuai Luo^1,†, Hongyue Sun^2,†, Qingyun Ping¹, Ran Jin^2,* and Zhen He^1,*

¹ Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA

² Grado Department of Industrial and Systems Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA

^† These authors contributed equally to this work.

Energies 2016, 9(2), 111; https://doi.org/10.3390/en9020111 - 18 Feb 2016

Cited by 68 | Viewed by 12339

Abstract

Bioelectrochemical systems (BES) are promising technologies to convert organic compounds in wastewater to electrical energy through a series of complex physical-chemical, biological and electrochemical processes. Representative BES such as microbial fuel cells (MFCs) have been studied and advanced for energy recovery. Substantial experimental [...] Read more.

Bioelectrochemical systems (BES) are promising technologies to convert organic compounds in wastewater to electrical energy through a series of complex physical-chemical, biological and electrochemical processes. Representative BES such as microbial fuel cells (MFCs) have been studied and advanced for energy recovery. Substantial experimental and modeling efforts have been made for investigating the processes involved in electricity generation toward the improvement of the BES performance for practical applications. However, there are many parameters that will potentially affect these processes, thereby making the optimization of system performance hard to be achieved. Mathematical models, including engineering models and statistical models, are powerful tools to help understand the interactions among the parameters in BES and perform optimization of BES configuration/operation. This review paper aims to introduce and discuss the recent developments of BES modeling from engineering and statistical aspects, including analysis on the model structure, description of application cases and sensitivity analysis of various parameters. It is expected to serves as a compass for integrating the engineering and statistical modeling strategies to improve model accuracy for BES development. Full article

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