Energies

Editorial

139 KiB

Open AccessEditorial

by Craig M. Jensen^1,*, Etsuo Akiba² and Hai-Wen Li³

¹ Department of Chemistry, University of Hawaii, Honolulu, HI 96822, USA

² Department of Mechanical Engineering, WPI International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan

³ International Research Center for Hydrogen Energy, WPI International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka 819-0395, Japan

Energies 2016, 9(4), 308; https://doi.org/10.3390/en9040308 - 22 Apr 2016

Viewed by 4371

Abstract

Both the Japanese and Hawaiian archipelagos are both completely devoid of petroleum resources.[...] Full article

(This article belongs to the Special Issue Hydrides: Fundamentals and Applications)

Research

Jump to: Editorial, Review

2145 KiB

Open AccessArticle

Integration of Microalgae-Based Bioenergy Production into a Petrochemical Complex: Techno-Economic Assessment

by Ana L. Gonçalves, Maria C. M. Alvim-Ferraz, Fernando G. Martins, Manuel Simões and José C. M. Pires^*

LEPABE, Departamento de Engenharia Química, Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, Porto 4200-465, Portugal

Energies 2016, 9(4), 224; https://doi.org/10.3390/en9040224 - 23 Mar 2016

Cited by 20 | Viewed by 6521

Abstract

The rapid development of modern society has resulted in an increased demand for energy, mainly from fossil fuels. The use of this source of energy has led to the accumulation of carbon dioxide (CO₂) in the atmosphere. In this context, microalgae [...] Read more.

The rapid development of modern society has resulted in an increased demand for energy, mainly from fossil fuels. The use of this source of energy has led to the accumulation of carbon dioxide (CO₂) in the atmosphere. In this context, microalgae culturing may be an effective solution to reduce the CO₂ concentration in the atmosphere, since these microorganisms can capture CO₂ and, simultaneously, produce bioenergy. This work consists of a techno-economic assessment of a microalgal production facility integrated in a petrochemical complex, in which established infrastructure allows efficient material and energy transport. Seven different scenarios were considered regarding photosynthetic, lipids extraction and anaerobic digestion efficiencies. This analysis has demonstrated six economically viable scenarios able to: (i) reduce CO₂ emissions from a thermoelectric power plant; (ii) treat domestic wastewaters (which were used as culture medium); and (iii) produce lipids and electrical and thermal energy. For a 100-ha facility, considering a photosynthetic efficiency of 3%, a lipids extraction efficiency of 75% and an anaerobic digestion efficiency of 45% (scenario 3), an economically viable process was obtained (net present value of 22.6 million euros), being effective in both CO₂ removal (accounting for 1.1 × 10⁴ t per year) and energy production (annual energy produced was 1.6 × 10⁷ kWh and annual lipids productivity was 1.9 × 10³ m³). Full article

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

▼ Show Figures

Graphical abstract

3695 KiB

Open AccessArticle

Electrochemical Mechanism for FeS₂/C Composite in Lithium Ion Batteries with Enhanced Reversible Capacity

by Shengping Wang^1,* and Jingxian Yu²

¹ Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan 430074, China

² ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP), School of Chemistry and Physics, The University of Adelaide, Adelaide, SA 5005, Australia

Energies 2016, 9(4), 225; https://doi.org/10.3390/en9040225 - 23 Mar 2016

Cited by 22 | Viewed by 7847

Abstract

Nanoscale FeS₂ was synthesized via a simple hydrothermal method and was decorated by hydrothermal carbonization (FeS₂@C). The structural properties of the synthesized materials detected by X-ray diffraction (XRD), together with the morphologies characterized by scanning electron microscopy (SEM) and transmission [...] Read more.

Nanoscale FeS₂ was synthesized via a simple hydrothermal method and was decorated by hydrothermal carbonization (FeS₂@C). The structural properties of the synthesized materials detected by X-ray diffraction (XRD), together with the morphologies characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the hydrothermal carbonization only had an impact on the morphology of pyrite. Additionally, the electrochemical performance of the coated pyrite in Li/FeS₂ batteries was evaluated by galvanostatic discharge-charge tests and electrochemical impedance spectroscopy (EIS). The results showed that the initial capacity of FeS₂@C was 799.2 mAh·g⁻¹ (90% of theoretical capacity of FeS₂) and that of uncoated FeS₂ was only 574.6 mAh·g⁻¹. XRD and ultraviolet (UV) visible spectroscopy results at different depths of discharge-charge for FeS₂ were discussed to clarify the electrochemical mechanism, which play an important part in Li/FeS₂ batteries. Full article

(This article belongs to the Special Issue Reacting Transport Phenomena in Electrochemical Cells)

▼ Show Figures

Figure 1

1991 KiB

Open AccessArticle

Thermo-Economic Analysis of Zeotropic Mixtures and Pure Working Fluids in Organic Rankine Cycles for Waste Heat Recovery

by Florian Heberle^* and Dieter Brüggemann

Institute of Engineering Thermodynamics (LTTT), Center of Energy Technology (ZET), University of Bayreuth, Bayreuth 95440, Germany

Energies 2016, 9(4), 226; https://doi.org/10.3390/en9040226 - 23 Mar 2016

Cited by 41 | Viewed by 6805

Abstract

We present a thermo-economic analysis of an Organic Rankine Cycle (ORC) for waste heat recovery. A case study for a heat source temperature of 150 °C and a subcritical, saturated cycle is performed. As working fluids R245fa, isobutane, isopentane, and the mixture of [...] Read more.

We present a thermo-economic analysis of an Organic Rankine Cycle (ORC) for waste heat recovery. A case study for a heat source temperature of 150 °C and a subcritical, saturated cycle is performed. As working fluids R245fa, isobutane, isopentane, and the mixture of isobutane and isopentane are considered. The minimal temperature difference in the evaporator and the condenser, as well as the mixture composition are chosen as variables in order to identify the most suitable working fluid in combination with optimal process parameters under thermo-economic criteria. In general, the results show that cost-effective systems have a high minimal temperature difference ΔT_PP,C at the pinch-point of the condenser and a low minimal temperature difference ΔT_PP,E at the pinch-point of the evaporator. Choosing isobutane as the working fluid leads to the lowest costs per unit exergy with 52.0 €/GJ (ΔT_PP,E = 1.2 K; ΔT_PP,C = 14 K). Considering the major components of the ORC, specific costs range between 1150 €/kW and 2250 €/kW. For the zeotropic mixture, a mole fraction of 90% isobutane leads to the lowest specific costs per unit exergy. A further analysis of the ORC system using isobutane shows high sensitivity of the costs per unit exergy for the selected cost estimation methods and for the isentropic efficiency of the turbine. Full article

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

▼ Show Figures

Figure 1

1299 KiB

Open AccessArticle

A Methodology for Constructing Marginal Abatement Cost Curves for Climate Action in Cities

by Nadine Ibrahim^*,†

and Christopher Kennedy^†

¹ Faculty of Applied Science and Engineering, University of Toronto, 35 St. George Street, Toronto, ON M5S 1A4, Canada

^† These authors contributed equally to this work.

Energies 2016, 9(4), 227; https://doi.org/10.3390/en9040227 - 23 Mar 2016

Cited by 35 | Viewed by 14562

Abstract

As drivers of climate action, cities are taking measures to reduce greenhouse gas (GHG) emissions, which if left unabated pose a challenge to meeting long-term climate targets. The economics of climate action needs to be at the forefront of climate dialogue to prioritize [...] Read more.

As drivers of climate action, cities are taking measures to reduce greenhouse gas (GHG) emissions, which if left unabated pose a challenge to meeting long-term climate targets. The economics of climate action needs to be at the forefront of climate dialogue to prioritize investments among competing mitigation measures. A marginal abatement cost (MAC) curve is an effective visualization of climate action that initiates a technical and economic discussion of the cost-effectiveness and abatement potential of such actions among local leaders, policy makers, and climate experts. More commonly demonstrated for countries, MAC curves need to be developed for cities because of their heterogeneity, which vary in their urban activities, energy supply, infrastructure stock, and commuting patterns. The methodology for constructing bottom-up MAC curves for cities is presented for technologies that offer fuel switching and/or energy efficiencies, while considering technology lifetimes, city-specific electricity and fuel prices, and emission intensities. Resulting MAC curves are unique to every city, and chart the pathway towards low-carbon growth by prioritizing measures based on cost-effectiveness. A case study of Toronto’s climate targets demonstrates the prioritization of select technologies. Leveraging MAC curves to support climate programs enables cities to strategically invest in financing climate action and designing incentives. Full article

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

▼ Show Figures

Figure 1

4565 KiB

Open AccessArticle

Performance Evaluation of Radiator and Radiant Floor Heating Systems for an Office Room Connected to a Ground-Coupled Heat Pump

by Ioan Sarbu^*

and Calin Sebarchievici

Department of Building Services Engineering, Polytechnic University Timisoara, Piata Victoriei, No. 2A, 300006 Timisoara, Romania

Energies 2016, 9(4), 228; https://doi.org/10.3390/en9040228 - 23 Mar 2016

Cited by 26 | Viewed by 8320

Abstract

A ground-coupled heat pump (GCHP) system used to provide the space heating for an office room is a renewable, high performance technology. This paper discusses vapour compression-based HP systems, briefly describing the thermodynamic cycle calculations, as well as the coefficient of performance (COP) [...] Read more.

A ground-coupled heat pump (GCHP) system used to provide the space heating for an office room is a renewable, high performance technology. This paper discusses vapour compression-based HP systems, briefly describing the thermodynamic cycle calculations, as well as the coefficient of performance (COP) and CO₂ emissions of a HP with an electro-compressor and compares different heating systems in terms of energy consumption, thermal comfort and environmental impact. It is focused on an experimental study performed to test the energy efficiency of the radiator or radiant floor heating system for an office room connected to a GCHP. The main performance parameters (COP and CO₂ emissions) are obtained for one month of operation of the GCHP system, and a comparative analysis of these parameters is presented. Additionally, two numerical simulation models of useful thermal energy and the system COP in heating mode are developed using the Transient Systems Simulation (TRNSYS) software. Finally, the simulations obtained from TRNSYS software are analysed and compared to the experimental data, showing good agreement and thus validating the simulation models. Full article

▼ Show Figures

Figure 1

3947 KiB

Open AccessArticle

Gas-Phase Mass-Transfer Resistances at Polymeric Electrolyte Membrane Fuel Cells Electrodes: Theoretical Analysis on the Effectiveness of Interdigitated and Serpentine Flow Arrangements

by Elisabetta Arato^*

, Marzia Pinna, Michela Mazzoccoli and Barbara Bosio

Department of Civil, Chemical and Environmental Engineering; University of Genoa, Via Opera Pia 15, Genoa -16145, Italy

Energies 2016, 9(4), 229; https://doi.org/10.3390/en9040229 - 23 Mar 2016

Cited by 4 | Viewed by 4189

Abstract

Mass transfer phenomena in polymeric electrolyte membrane fuel cells (PEMFC) electrodes has already been analyzed in terms of the interactions between diffusive and forced flows. It was demonstrated that the whole phenomenon could be summarized by expressing the Sherwood number as a function [...] Read more.

Mass transfer phenomena in polymeric electrolyte membrane fuel cells (PEMFC) electrodes has already been analyzed in terms of the interactions between diffusive and forced flows. It was demonstrated that the whole phenomenon could be summarized by expressing the Sherwood number as a function of the Peclet number. The dependence of Sherwood number on Peclet one Sh(Pe) function, which was initially deduced by determining three different flow regimes, has now been given a more accurate description. A comparison between the approximate and the accurate results for a reference condition of diluted reactant and limit current has shown that the former are useful for rapid, preliminary calculations. However, a more precise and reliable estimation of the Sherwood number is worth attention, as it provides a detailed description of the electrochemical kinetics and allows a reliable comparison of the various geometrical arrangements used for the distribution of the reactants. Full article

(This article belongs to the Special Issue Reacting Transport Phenomena in Electrochemical Cells)

▼ Show Figures

Figure 1

1390 KiB

Open AccessEditor’s ChoiceArticle

On the Front Lines of a Sustainable Transportation Fleet: Applications of Vehicle-to-Grid Technology for Transit and School Buses

by Tolga Ercan

, Mehdi Noori, Yang Zhao and Omer Tatari^*

Department of Civil, Environmental, and Construction Engineering, University of Central Florida, Orlando, FL 32816, USA

Energies 2016, 9(4), 230; https://doi.org/10.3390/en9040230 - 24 Mar 2016

Cited by 25 | Viewed by 9582

Abstract

The electricity generation/supply and transportation sectors are the two largest contributors to greenhouse gas (GHG) emissions in the U.S., and vehicle-to-grid (V2G) technology is a rapidly emerging solution to reduce these emissions with the adoption of battery-electric (BE) vehicles. Deployments of BE transit [...] Read more.

The electricity generation/supply and transportation sectors are the two largest contributors to greenhouse gas (GHG) emissions in the U.S., and vehicle-to-grid (V2G) technology is a rapidly emerging solution to reduce these emissions with the adoption of battery-electric (BE) vehicles. Deployments of BE transit and school buses are expected to have larger battery capacities than passenger vehicles, making them more feasible candidates for V2G service. Five electricity generation regions are considered for cash flow analysis of BE and diesel transit and school buses over their entire respective lifetimes with the allowance of V2G services’ net revenue. Besides, the environmental benefits of using the V2G system are studied in place of combustion power generation plants for the regulation services of each study region. Air emission externalities are another crucial issue for bus operations because buses are operated near highly populated areas, so these externalities are also studied in this research with the benefits of a V2G emission reduction potential taken into account. The analysis concluded that BE transit and school buses with V2G application have potential to reduce electricity generation related greenhouse-gas emissions by 1067 and 1420 tons of CO₂ equivalence (average), and eliminate $13,000 and $18,300 air pollution externalities (average), respectively. Full article

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

▼ Show Figures

Graphical abstract

3777 KiB

Open AccessArticle

Feasibility Study of a Scroll Expander for Recycling Low-Pressure Exhaust Gas Energy from a Vehicle Gasoline Engine System

by Xing Luo¹, Jihong Wang^1,2,*, Christopher Krupke¹ and Hongming Xu³

¹ School of Engineering, University of Warwick, Coventry CV4 7AL, West Midlands, UK

² School of Electrical & Electronic Engineering, Huazhong University of Science & Technology, Wuhan 430074, China

³ School of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT, UK

Energies 2016, 9(4), 231; https://doi.org/10.3390/en9040231 - 24 Mar 2016

Cited by 9 | Viewed by 7793

Abstract

The growing number of vehicles on the road has led to a rapid increase in fuel consumption and toxic gas emissions, so the challenges in fuel efficiency improvement and reduction of CO₂ and NO_x emissions have always been on the top [...] Read more.

The growing number of vehicles on the road has led to a rapid increase in fuel consumption and toxic gas emissions, so the challenges in fuel efficiency improvement and reduction of CO₂ and NO_x emissions have always been on the top agenda of the automotive industry. The paper presents a feasibility study of recovering the low-pressure exhaust gas energy via by-pass connection of a scroll expander to the engine system exhaust. The paper starts with the description of the proposed new exhaust energy recycling scheme and the mathematical modelling of the system. A feasibility study is carried out to investigate whether this new scheme can work with the engine operation conditions specified by the engine test data. The initial study indicated that the scroll expander structure needs to be modified; otherwise, it cannot be used for exhaust energy recovery. The experimental test and simulation results presented in this paper indicate that it is feasible to recover the low-pressure exhaust gas energy using a scroll expander with a modified structure. The proposed energy recovery system has the potential to produce over 400 W power output with over 90% of engine exhaust flow recycling. Full article

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

▼ Show Figures

Figure 1

5215 KiB

Open AccessArticle

Control and Optimization of a Variable-Pitch Quadrotor with Minimum Power Consumption

by Shouzhao Sheng^* and Chenwu Sun

College of Automation Engineering, Nanjing University of Aeronautics and Astronautics, 29 YuDao St., Nanjing 210016, China

Energies 2016, 9(4), 232; https://doi.org/10.3390/en9040232 - 24 Mar 2016

Cited by 39 | Viewed by 7091

Abstract

Recently, there has been a rapid growth of interest in quadrotors with electric variable-pitch propellers. The control and optimization of such propellers are important factors for improving the flight performance of the vehicles. Therefore, the steady-state identification method to estimate the parameters of [...] Read more.

Recently, there has been a rapid growth of interest in quadrotors with electric variable-pitch propellers. The control and optimization of such propellers are important factors for improving the flight performance of the vehicles. Therefore, the steady-state identification method to estimate the parameters of the mathematical model of the electric variable-pitch propeller is developed. The steady-state control and optimization scheme with minimum power consumption and the adaptive compensation scheme for the variable-pitch propeller are then proposed, based on which the response performance of the lift force produced by the variable-pitch propeller can be greatly improved by using a cascade compensation scheme. Furthermore, the direct lift-based flight control strategy is presented, which can significantly contribute to the improvement of the flight performance, precisely because the roll, pitch, yaw and vertical channels of the variable-pitch quadrotor are approximately linearized and completely decoupled from each other in this case. The experimental results demonstrate that both the endurance performance and the positioning accuracy of the variable-pitch quadrotor are improved simultaneously by using the proposed method with minimum power consumption. Full article

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

▼ Show Figures

Graphical abstract

4340 KiB

Open AccessArticle

Experiment on Bidirectional Single Phase Converter Applying Model Predictive Current Controller

by Gabriele D’Antona¹, Roberto Faranda¹

, Hossein Hafezi^1,*

and Marco Bugliesi²

¹ Politecnico di Milano, 20156 Milano, Italy

² Studio Progettazione Informatica Bugliesi (SpiB.it), 20877 Roncello, Italy

Energies 2016, 9(4), 233; https://doi.org/10.3390/en9040233 - 24 Mar 2016

Cited by 12 | Viewed by 4485

Abstract

A bidirectional converter able to manage storage is a basic power electronics device, and it is a major component of renewable energy sources, micro grid and also the smart grid concept. In this paper, single-phase bidirectional converter topology is discussed. The state space [...] Read more.

A bidirectional converter able to manage storage is a basic power electronics device, and it is a major component of renewable energy sources, micro grid and also the smart grid concept. In this paper, single-phase bidirectional converter topology is discussed. The state space model has been derived, and a simple model based predictive current controller has been utilized to control the inverter. Control block diagrams have been designed with MATLAB and simulation results are presented and compared with experimental ones, giving credibility to the derived model and the designed control method. Full article

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

▼ Show Figures

Figure 1

2124 KiB

Open AccessArticle

On Variable Reverse Power Flow-Part II: An Electricity Market Model Considering Wind Station Size and Location

by Aouss Gabash^* and Pu Li

Department of Simulation and Optimal Processes, Institute of Automation and Systems Engineering, Ilmenau University of Technology, Ilmenau 98693, Germany

Energies 2016, 9(4), 235; https://doi.org/10.3390/en9040235 - 25 Mar 2016

Cited by 22 | Viewed by 7017

Abstract

This is the second part of a companion paper on variable reverse power flow (VRPF) in active distribution networks (ADNs) with wind stations (WSs). Here, we propose an electricity market model considering agreements between the operator of a medium-voltage active distribution network (MV-ADN) [...] Read more.

This is the second part of a companion paper on variable reverse power flow (VRPF) in active distribution networks (ADNs) with wind stations (WSs). Here, we propose an electricity market model considering agreements between the operator of a medium-voltage active distribution network (MV-ADN) and the operator of a high-voltage transmission network (HV-TN) under different scenarios. The proposed model takes, simultaneously, active and reactive energy prices into consideration. The results from applying this model on a real MV-ADN reveal many interesting facts. For instance, we demonstrate that the reactive power capability of WSs will be never utilized during days with zero wind power and varying limits on power factors (PFs). In contrast, more than 10% of the costs of active energy losses, 15% of the costs of reactive energy losses, and 100% of the costs of reactive energy imported from the HV-TN, respectively, can be reduced if WSs are operated as capacitor banks with no limits on PFs. It is also found that allocating WSs near possible exporting points at the HV-TN can significantly reduce wind power curtailments if the operator of the HV-TN accepts unlimited amount of reverse energy from the MV-ADN. Furthermore, the relationships between the size of WSs, VRPF and demand level are also uncovered based on active-reactive optimal power flow (A-R-OPF). Full article

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

▼ Show Figures

Figure 1

1339 KiB

Open AccessArticle

Synergistic Optimization of Thermoelectric Performance in P-Type Bi_0.48Sb_1.52Te₃/Graphene Composite

by Dewen Xie^1,2, Jingtao Xu^1,*, Guoqiang Liu¹, Zhu Liu¹, Hezhu Shao¹, Xiaojian Tan¹, Jun Jiang^1,* and Haochuan Jiang¹

¹ Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China

² Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, China

Energies 2016, 9(4), 236; https://doi.org/10.3390/en9040236 - 25 Mar 2016

Cited by 33 | Viewed by 6820

Abstract

We report the synergistic optimization of the thermoelectric properties in p-type Bi_0.48Sb_1.52Te₃ by the additional graphene. Highly dense Bi_0.48Sb_1.52Te₃ + graphene (x wt%, x = 0, 0.05, 0.1 and 0.15) composites have been [...] Read more.

We report the synergistic optimization of the thermoelectric properties in p-type Bi_0.48Sb_1.52Te₃ by the additional graphene. Highly dense Bi_0.48Sb_1.52Te₃ + graphene (x wt%, x = 0, 0.05, 0.1 and 0.15) composites have been synthesized by zone-melting followed by spark plasma sintering. With the help of scanning electron microscopy, the graphene has been clearly observed at the edge of the grain in the composites. Due to the additional graphene, the composites show an improved power factor of 4.8 × 10⁻³ Wm⁻¹K⁻² with modified carrier concentration and suppressed lattice thermal conductivity. Consequently, synergistic optimization in electrical and lattice properties by additional graphene leads to a great improvement in the figure of merit ZT (1.25 at 320 K). Full article

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

▼ Show Figures

Figure 1

1123 KiB

Open AccessArticle

Cavitation Inception in Crossflow Hydro Turbines

by Ram Chandra Adhikari¹, Jerson Vaz^2,† and David Wood^1,*

¹ Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Dr NW, Calgary, AB T2N 1N4, Canada

² Faculty of Mechanical Engineering, Federal University of Pará –Av. Augusto Correa, N 1–Belém, PA 66075-900, Brazil

^† Current Address: Department of Mechanical and Manufacturing Engineering, University of Calgary, 2500 University Dr NW, Calgary, AB T2N 1N4, Canada

Energies 2016, 9(4), 237; https://doi.org/10.3390/en9040237 - 24 Mar 2016

Cited by 38 | Viewed by 9582

Abstract

Cavitation is a common flow phenomena in most hydraulic turbines and has the potential to cause vibration, blade surface damage and performance loss. Despite the fact that crossflow turbines have been used in small-scale hydropower systems for a long time, cavitation has not [...] Read more.

Cavitation is a common flow phenomena in most hydraulic turbines and has the potential to cause vibration, blade surface damage and performance loss. Despite the fact that crossflow turbines have been used in small-scale hydropower systems for a long time, cavitation has not been studied in these turbines. In this paper, we present the findings of a computational study on cavitation inception in crossflow turbines. Cavitation inception was assessed using three-dimensional (3D) Reynolds-Averaged Navier–Stokes (RANS) computations. A homogeneous, free-surface two-phase flow model was used. Pressure distributions on the blades were examined for different flow rates, heads and impeller speeds to assess cavitation inception. The results showed that cavitation occurs in the second stage of the turbine and was observed on the suction side near the inner edge of the blades. For the particular turbine studied, cavitation always occurred at shaft speeds greater than that, giving the maximum efficiency for each combination of flow rate and head. The implication is that the useful operating range of crossflow turbines is up to and including the maximum efficiency point. Full article

(This article belongs to the Special Issue Hydropower)

▼ Show Figures

Figure 1

3030 KiB

Open AccessArticle

Lightweight Borohydrides Electro-Activity in Lithium Cells

by Daniele Meggiolaro^1,2, Luca Farina¹, Laura Silvestri¹, Stefania Panero¹

, Sergio Brutti^2,3,*

and Priscilla Reale^4,*

¹ Chemistry Department, Sapienza University, Piazzale Aldo Moro 5, Rome 00185, Italy

² Istituto dei Sistemi Complessi, Consiglio Nazionale delle Ricerche (ISC-CNR), via dei Taurini, Rome 00185, Italy

³ Dipartimento di Scienze, Università della Basilicata, v.le Ateneo Lucano 10, Potenza 85100, Italy

⁴ Agenzia nazionale per le nuove tecnologie, l'energia e lo sviluppo economico sostenibile, ENEA, Centro Ricerche Casaccia, via Anguillarese 301, Rome 00123, Italy

Energies 2016, 9(4), 238; https://doi.org/10.3390/en9040238 - 25 Mar 2016

Cited by 13 | Viewed by 4855

Abstract

As a substitute for graphite, the negative electrode material commonly used in Li-ion batteries, hydrides have the theoretical potential to overcome performance limits of the current state-of-the-art Li-ion cells. Hydrides can operate through a conversion process proved for some interstitial hydrides like MgH [...] Read more.

As a substitute for graphite, the negative electrode material commonly used in Li-ion batteries, hydrides have the theoretical potential to overcome performance limits of the current state-of-the-art Li-ion cells. Hydrides can operate through a conversion process proved for some interstitial hydrides like MgH₂: M_xA_y + n Li = x M + y Li_mA, where m = n/y. Even if far from optimization, outstanding performances were observed, drawing the attention to the whole hydride family. Looking for high capacity systems, lightweight complex metal hydrides, such as borohydrides, deserve consideration. Capacities in the order of 2000–4000 mAh/g can be theoretically expected thanks to the very low formula unit weight. Although the potential technological impact of these materials can lead to major breakthroughs in Li-ion batteries, this new research field requires the tackling of fundamental issues that are completely unexplored. Here, our recent findings on the incorporation of borohydrides are presented and discussed. Full article

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

▼ Show Figures

Figure 1

4884 KiB

Open AccessArticle

Development of an ICE-Based Micro-CHP System Based on a Stirling Engine; Methodology for a Comparative Study of its Performance and Sensitivity Analysis in Recreational Sailing Boats in Different European Climates

by Guillermo Rey^1,*

, Carlos Ulloa¹, Jose Luis Míguez² and Elena Arce¹

¹ Defense University Center, Naval Academy, Marín 36920, Spain

² ETS Ingenieros Industriales, University of Vigo, Vigo 36310, Spain

Energies 2016, 9(4), 239; https://doi.org/10.3390/en9040239 - 25 Mar 2016

Cited by 12 | Viewed by 6697

Abstract

Micro combined heating and power (micro-CHP) systems are becoming more than important, and even essential, if we pretend to take full advantage of available energy. The efficiency of this kind of systems reaches 90% and important savings in energy transport processes can occur. [...] Read more.

Micro combined heating and power (micro-CHP) systems are becoming more than important, and even essential, if we pretend to take full advantage of available energy. The efficiency of this kind of systems reaches 90% and important savings in energy transport processes can occur. In this research, an internal combustion engine (ICE)-based micro-CHP system was developed and tested under specific constraints. The system uses a two cylinder Otto engine as prime mover, coupled to an electrical alternator, and it uses exhaust gases and engine cooling circuit heat. The micro-CHP system was developed to match the electrical power of a typical Stirling engine (SE)-based micro-CHP unit, in order to later compare both systems’ performance under similar circumstances. Different operating modes were tested under different engine speeds, in order to find the optimum operating point. A stand-alone portable application of this system was performed using recreational sailing boats as mobile homes. Specific considerations had to be taken, related to boundary conditions with sea water, and a transient simulation was performed, considering the boat under three different European climates. Results were compared for the different locations and the performance of the equipment shown. A comparative study with the SE-based micro-CHP system performance was done, and a sensitivity analysis of the influence of the battery size was carried out under the same conditions. The SE and ICE-based proposed micro-CHP system have similar behavior, except for the differences found due to the electric/thermal power ratios in both systems. Battery bank size sensitivity analysis reflects a limit in performance improvement. This limit is caused by the uniform distribution of electrical demand profile. Full article

(This article belongs to the Special Issue Simulation of Polygeneration Systems)

▼ Show Figures

Figure 1

2901 KiB

Open AccessArticle

Towards Renewable Iodide Sources for Electrolytes in Dye-Sensitized Solar Cells

by Iryna Sagaidak^1,3, Guillaume Huertas^1,2,3, Albert Nguyen Van Nhien^2,3 and Frédéric Sauvage^1,3,*

¹ Laboratoire de Réactivité et Chimie des Solides, Université de Picardie Jules Verne, CNRS UMR 7314, 33 rue Saint Leu, Amiens 80039, France

² Laboratoire de Glycochimie, des Antimicrobiens et des Agroressources, Université de Picardie Jules Verne, CNRS FRE3517, 33 rue Saint Leu, Amiens 80039, France

³ Institut de Chimie de Picardie, FR 3085 CNRS, UFR des Sciences, Université de Picardie Jules Verne, 33 rue Saint Leu, Amiens Cedex 1 80039, France

Energies 2016, 9(4), 241; https://doi.org/10.3390/en9040241 - 26 Mar 2016

Cited by 5 | Viewed by 5792

Abstract

A novel family of iodide salts and ionic liquids based on different carbohydrate core units is herein described for application in dye-sensitized solar cell (DSC). The influence of the molecular skeleton and the cationic structure on the electrolyte properties, device performance and on [...] Read more.

A novel family of iodide salts and ionic liquids based on different carbohydrate core units is herein described for application in dye-sensitized solar cell (DSC). The influence of the molecular skeleton and the cationic structure on the electrolyte properties, device performance and on interfacial charge transfer has been investigated. In combination with the C106 polypyridyl ruthenium sensitizer, power conversion efficiencies lying between 5.0% and 7.3% under standard Air Mass (A.M.) 1.5G conditions were obtained in association with a low volatile methoxypropionitrile (MPN)-based electrolyte. Full article

(This article belongs to the Special Issue Dye Sensitized Solar Cells)

▼ Show Figures

Graphical abstract

7389 KiB

Open AccessArticle

Optimization Design of an Inductive Energy Harvesting Device for Wireless Power Supply System Overhead High-Voltage Power Lines

by Wei Wang

, Xueliang Huang^*, Linlin Tan, Jinpeng Guo and Han Liu

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

Energies 2016, 9(4), 242; https://doi.org/10.3390/en9040242 - 26 Mar 2016

Cited by 48 | Viewed by 12594

Abstract

Overhead high voltage power line (HVPL) online monitoring equipment is playing an increasingly important role in smart grids, but the power supply is an obstacle to such systems’ stable and safe operation, so in this work a hybrid wireless power supply system, integrated [...] Read more.

Overhead high voltage power line (HVPL) online monitoring equipment is playing an increasingly important role in smart grids, but the power supply is an obstacle to such systems’ stable and safe operation, so in this work a hybrid wireless power supply system, integrated with inductive energy harvesting and wireless power transmitting, is proposed. The energy harvesting device extracts energy from the HVPL and transfers that from the power line to monitoring equipment on transmission towers by transmitting and receiving coils, which are in a magnetically coupled resonant configuration. In this paper, the optimization design of online energy harvesting devices is analyzed emphatically by taking both HVPL insulation distance and wireless power supply efficiency into account. It is found that essential parameters contributing to more extracted energy include large core inner radius, core radial thickness, core height and small core gap within the threshold constraints. In addition, there is an optimal secondary coil turn that can maximize extracted energy when other parameters remain fixed. A simple and flexible control strategy is then introduced to limit power fluctuations caused by current variations. The optimization methods are finally verified experimentally. Full article

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

▼ Show Figures

Graphical abstract

3864 KiB

Open AccessArticle

A Novel Secondary Control for Microgrid Based on Synergetic Control of Multi-Agent System

by Zhiwen Yu^1,*, Qian Ai¹, Jinxia Gong² and Longjian Piao¹

¹ School of Electronic Information and Electrical Engineering, Dongchuan Road, Shanghai Jiaotong University, Shanghai 200240, China

² Department of Electrical Power Engineering, Changyang Road, Shanghai University of Electrical Power, Shanghai 200240 China

Energies 2016, 9(4), 243; https://doi.org/10.3390/en9040243 - 26 Mar 2016

Cited by 20 | Viewed by 5835

Abstract

In power systems, the secondary control is a very useful way to restore the system frequency and voltage to the rated value. This paper tries to propose a secondary frequency and voltage control of islanded microgrids based on the distributed synergetic control of [...] Read more.

In power systems, the secondary control is a very useful way to restore the system frequency and voltage to the rated value. This paper tries to propose a secondary frequency and voltage control of islanded microgrids based on the distributed synergetic control of multi-agent systems. In the proposed control, since each distributed generation only requires its own information and that of the neighbors, the secondary control is fully distributed. The system is more reliable because the central controller and complex communication network are reduced in the distributed structure. Based on multi-agent systems, the dynamic model is established, and distributed synergetic control algorithms are given to design the secondary control of the islanded microgrid. Meanwhile, the system has globally asymptotic stability under the proposed control, which is proved by the direct Lyapunov method. Simulation results about a test microgrid are given to verify the effectiveness of the proposed control. Full article

(This article belongs to the Special Issue Microgrids 2016)

▼ Show Figures

Figure 1

2906 KiB

Open AccessArticle

The Performance of Surfactant-Polymer Flooding in Horizontal Wells Consisting of Multilayers in a Reservoir System

by Si Le Van

and Bo Hyun Chon^*

Department of Energy Resources Engineering, Inha University, Incheon 402-751, Korea

Energies 2016, 9(4), 244; https://doi.org/10.3390/en9040244 - 26 Mar 2016

Cited by 7 | Viewed by 8016

Abstract

Surfactant-polymer (SP) flooding has been demonstrated to be an effective method to recover oil in the enhanced oil recovery (EOR) stage when water flooding is no longer relevant. Theoretically, adding surfactant causes the reduction of the interfacial tension between oil and water in [...] Read more.

Surfactant-polymer (SP) flooding has been demonstrated to be an effective method to recover oil in the enhanced oil recovery (EOR) stage when water flooding is no longer relevant. Theoretically, adding surfactant causes the reduction of the interfacial tension between oil and water in pores, therefore reducing the residual oil saturation, whereas the sweep efficiency will be significantly improved by the polymer injection as a result of proper mobility control. With regard to the well patterns, water flooding has demonstrated a high productivity in horizontal wells. Recently, other EOR processes have been increasingly applied to the horizontal wells in various well patterns. In this study, the efficiency of SP flooding applied to horizontal wells in various well configurations is investigated in order to select the best EOR performance in terms of either a technical or economical point of view. Furthermore, the reservoir is assumed to be anisotropic with four different layers that have same porosity but different permeability between each layer. The study figures out that, the utilization of a horizontal injector and producer always gives a higher oil production in comparison with the reference case of a conventional vertical injector and producer; however, the best EOR performances that demonstrate the higher oil recovery and lower fluid injected volume than those of the reference case are achieved when the production well is located in bottom layers and parallel with the injection well at a distance. While the location of producer decides oil productivity, the location of injector yet affects the uniformity of fluids propagation in the reservoir. A predefined feasibility factor is also taken into consideration in order to reject the infeasible cases that might give a high oil production but require a higher injected volume than the reference case. This factor is used as an economic parameter to evaluate the success of the EOR performance. The simulation is carried out in a quarter five-spot pattern reservoir with the support of the Computer Modeling Group (CMG) simulator. Understanding the predominant EOR performance of SP flooding in horizontal wells will help to select the best plan to obtain the highest oil recovery when considering economic issues. Full article

▼ Show Figures

Figure 1

1367 KiB

Open AccessArticle

Sliding-Mode Control of a Charger/Discharger DC/DC Converter for DC-Bus Regulation in Renewable Power Systems

by Sergio Ignacio Serna-Garcés^1,*

, Daniel Gonzalez Montoya¹

and Carlos Andres Ramos-Paja²

¹ Departamento de Electrónica y Telecomunicaciones, Instituto Tecnológico Metropolitano, Carrera 31 No. 54-10, Medellín, Colombia

² Departamento de Energia Eléctrica y Automática, Universidad Nacional de Colombia, Carrera 80 No. 65-223-Facultad de Minas, Medellín, Colombia

Energies 2016, 9(4), 245; https://doi.org/10.3390/en9040245 - 29 Mar 2016

Cited by 41 | Viewed by 8006

Abstract

Stand-alone power systems based on renewable energy sources are used to replace generators based on fossil fuels. Those renewable power systems also require Energy Storage Devices (ESD) interfaced by a charger/discharger power converter, which consist of a bidirectional DC/DC converter, and a DC [...] Read more.

Stand-alone power systems based on renewable energy sources are used to replace generators based on fossil fuels. Those renewable power systems also require Energy Storage Devices (ESD) interfaced by a charger/discharger power converter, which consist of a bidirectional DC/DC converter, and a DC bus. This paper proposes a single sliding-mode controller (SMC) for the charger/discharger DC/DC converter to provide a stable DC bus voltage in any operation condition: charging or discharging the ESD, or even without any power exchange between the ESD and the DC bus. Due to the non-linear nature of the power converter, the SMC parameters are adapted on-line to ensure global stability in any operation condition. Such stability of the adaptive SMC is mathematically demonstrated using analytical expressions for the transversality, reachability and equivalent control conditions. Moreover, a design procedure for the adaptive SMC parameters is provided in order to ensure the dynamic response required for the correct operation of the load. Finally, simulations and experimental tests validate the proposed controller and design procedure. Full article

▼ Show Figures

Figure 1

6167 KiB

Open AccessArticle

Catalytic Intermediate Pyrolysis of Napier Grass in a Fixed Bed Reactor with ZSM-5, HZSM-5 and Zinc-Exchanged Zeolite-A as the Catalyst

by Isah Yakub Mohammed^1,6

, Feroz Kabir Kazi², Suzana Yusup³, Peter Adeniyi Alaba⁵, Yahaya Muhammad Sani⁵ and Yousif Abdalla Abakr^4,*

¹ Department of Chemical and Environmental Engineering, the University of Nottingham Malaysia Campus, Jalan Broga, Semenyih 43500, Darul Ehsan, Malaysia

² Department of Engineering and Mathematics, Sheffield Hallam University, City Campus, Howard Street, Sheffield S1 1WB, UK

³ Department of Chemical Engineering, Universiti Teknology Petronas (UTP) Bandar Seri Iskandar, Tronoh 31750, Malaysia

⁴ Department of Mechanical, Manufacturing and Material Engineering, the University of Nottingham Malaysia Campus, Jalan Broga, Semenyih 43500, Darul Ehsan, Malaysia

⁵ Department of Chemical Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia

⁶ Crops for the Future (CFF), the University of Nottingham Malaysia Campus, Jalan Broga, Semenyih 43500, Darul Ehsan, Malaysia

Energies 2016, 9(4), 246; https://doi.org/10.3390/en9040246 - 29 Mar 2016

Cited by 39 | Viewed by 8592

Abstract

The environmental impact from the use of fossil fuel cum depletion of the known fossil oil reserves has led to increasing interest in liquid biofuels made from renewable biomass. This study presents the first experimental report on the catalytic pyrolysis of Napier grass, [...] Read more.

The environmental impact from the use of fossil fuel cum depletion of the known fossil oil reserves has led to increasing interest in liquid biofuels made from renewable biomass. This study presents the first experimental report on the catalytic pyrolysis of Napier grass, an underutilized biomass source, using ZSM-5, 0.3HZSM-5 and zinc exchanged zeolite-A catalyst. Pyrolysis was conducted in fixed bed reactor at 600 °C, 30 °C/min and 7 L/min nitrogen flow rate. The effect of catalyst-biomass ratio was evaluated with respect to pyrolysis oil yield and composition. Increasing the catalyst loading from 0.5 to 1.0 wt % showed no significant decrease in the bio-oil yield, particularly, the organic phase and thereafter decreased at catalyst loadings of 2.0 and 3.0 wt %. Standard analytical methods were used to establish the composition of the pyrolysis oil, which was made up of various aliphatic hydrocarbons, aromatics and other valuable chemicals and varied greatly with the surface acidity and pore characteristics of the individual catalysts. This study has demonstrated that pyrolysis oil with high fuel quality and value added chemicals can be produced from pyrolysis of Napier grass over acidic zeolite based catalysts. Full article

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

▼ Show Figures

Figure 1

1046 KiB

Open AccessEditor’s ChoiceArticle

Biochar as Additive in Biogas-Production from Bio-Waste

by Daniel Meyer-Kohlstock^*

, Thomas Haupt, Erik Heldt, Nils Heldt and Eckhard Kraft

Biotechnology in Resources Management, Bauhaus-Universität Weimar, Coudraystr. 7, Weimar 99423, Germany

Energies 2016, 9(4), 247; https://doi.org/10.3390/en9040247 - 29 Mar 2016

Cited by 59 | Viewed by 11133

Abstract

Previous publications about biochar in anaerobic digestion show encouraging results with regard to increased biogas yields. This work investigates such effects in a solid-state fermentation of bio-waste. Unlike in previous trials, the influence of biochar is tested with a setup that simulates an [...] Read more.

Previous publications about biochar in anaerobic digestion show encouraging results with regard to increased biogas yields. This work investigates such effects in a solid-state fermentation of bio-waste. Unlike in previous trials, the influence of biochar is tested with a setup that simulates an industrial-scale biogas plant. Both the biogas and the methane yield increased around 5% with a biochar addition of 5%—based on organic dry matter biochar to bio-waste. An addition of 10% increased the yield by around 3%. While scaling effects prohibit a simple transfer of the results to industrial-scale plants, and although the certainty of the results is reduced by the heterogeneity of the bio-waste, further research in this direction seems promising. Full article

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

▼ Show Figures

Figure 1

12787 KiB

Open AccessArticle

A Novel DC-Bus Sensor-less MPPT Technique for Single-Stage PV Grid-Connected Inverters

by Mohamed A. Elsaharty¹, Hamdy A. Ashour¹

, Elyas Rakhshani²

, Edris Pouresmaeil^3,4,*

and João P. S. Catalão^3,4,5

¹ Department of Electrical and Control Engineering, College of Engineering and Technology, Arab Academy for Science, Technology & Maritime Transport, Alexandria 1029, Egypt

² Electrical Engineering Department, Technical University of Catalonia (UPC), Barcelona 08034, Spain

³ University of Beira Interior, R. Fonte do Lameiro, 6201-001 Covilhã, Portugal

⁴ INESC-ID, Inst. Super. Tecn., University of Lisbon, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal

⁵ INESC TEC and Faculty of Engineering of the University of Porto, R. Dr. Roberto Frias, 4200-465 Porto, Portugal

Energies 2016, 9(4), 248; https://doi.org/10.3390/en9040248 - 30 Mar 2016

Cited by 10 | Viewed by 6626

Abstract

Single-stage grid connected inverters are considered as an economic, compact and simple topology compared with multi-stage inverters. In photovoltaic (PV) grid connected systems, the major requirement is to achieve maximum output power from the source. Maximum Power Point Tracking (MPPT) techniques require measurements [...] Read more.

Single-stage grid connected inverters are considered as an economic, compact and simple topology compared with multi-stage inverters. In photovoltaic (PV) grid connected systems, the major requirement is to achieve maximum output power from the source. Maximum Power Point Tracking (MPPT) techniques require measurements on the DC side of the inverter connected to the PV in order to determine the current operating point on the power characteristics. Typically this is achieved by perturbing the reference output power and observe the change in the PV voltage, current or both. Based on the observation, it could be determined whether the current operating point is beyond or below maximum power. This paper presents an MPPT technique for a single-stage PV grid connected inverter where the MPPT algorithm determines the current operating point at different operating conditions based upon observing the inverter controller action. Such approach eliminates the requirement of sensing elements to be added to the converter which aids the advantages of the single-stage converter. Design of the utilized PV system is derived based on filter parameters, PV panel selection and controller parameters. Using simulation and practical implementation, the performance of the proposed MPPT technique is evaluated for the PV grid connected system. Full article

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

▼ Show Figures

Figure 1

7305 KiB

Open AccessArticle

Rock-Breaking Properties of Multi-Nozzle Bits for Tree-Type Drilling in Underground Coal Mines

by Yiyu Lu^1,2, Songqiang Xiao^1,2, Zhaolong Ge^1,2,*, Zhe Zhou^1,2

and Kai Deng^1,2

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

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

Energies 2016, 9(4), 249; https://doi.org/10.3390/en9040249 - 30 Mar 2016

Cited by 19 | Viewed by 5238

Abstract

Tree-type drilling is a new technique for drilling radial tree-type boreholes in coal seams in underground mines using water jets to break the coal. The aim is to drain gas from the coal seams in larger quantities and from larger areas than can [...] Read more.

Tree-type drilling is a new technique for drilling radial tree-type boreholes in coal seams in underground mines using water jets to break the coal. The aim is to drain gas from the coal seams in larger quantities and from larger areas than can be done by conventional gas drainage using single boreholes. The self-propelled drill bit is the most important component for this technique. The bit generates a self-propelling force to move forward, break coal, and form a borehole. This paper investigates the relationships between the physical parameters of the forward nozzles in the bit and the diameter and shape of the borehole drilled. The effect of different physical parameters on the rock-breaking efficiency is studied by conducting drilling experiments. The results show that the size, orientation and number of the nozzles significantly affect the rock-breaking efficiency of the bit. To obtain a better rock-breaking efficiency under the experimental conditions used for this paper, the axial angle for forward nozzles should be 15°, the radial angle 90°, and nozzles should be arranged 2.1 mm from the center of a 12 mm drill bit. The experimental results provide a reference for the design of multi-nozzle bits for many applications such as radial jet drilling (RJD) and bent pipe cleaning. Full article

▼ Show Figures

Figure 1

1444 KiB

Open AccessArticle

The Impact of Financial Crisis on Electricity Demand: A Case Study of North China

by Huiru Zhao¹, Haoran Zhao^1,*, Sen Guo^1,*, Fuqiang Li² and Yuou Hu²

¹ School of Economics and Management, North China Electric Power University, Beijing 102206, China

² North China Grid Company Limited, No. 482 Canton Avenue, Beijing Xuanwu District, Beijing 100053, China

Energies 2016, 9(4), 250; https://doi.org/10.3390/en9040250 - 30 Mar 2016

Cited by 18 | Viewed by 6208

Abstract

The electricity consumption and economic growth are highly correlated. The financial crisis in 2008 brought a negative effect on China’s economic growth, which also influenced the electricity consumption. The electricity demand of North China region was also greatly influenced by this financial crisis, [...] Read more.

The electricity consumption and economic growth are highly correlated. The financial crisis in 2008 brought a negative effect on China’s economic growth, which also influenced the electricity consumption. The electricity demand of North China region was also greatly influenced by this financial crisis, the whole social electricity consumption growth rate of which decreased by 14.31% in 2008 compared to that in 2007. In order to analyze the random impulse effect of the financial crisis on the demand of electricity in North China, the monthly data is decomposed into deterministic trend, stochastic impact effect, and periodic trend using the Beveridge-Nelson decomposition method. After comparatively analyzing the impulse effect of the financial crisis on electricity consumption of six provinces in North China, we can draw the conclusions: (1) the electricity consumption of the whole society and the secondary industry are under larger negative impacts, and the random impulse effect of the secondary industry is more intense; and (2) the impact of the financial crisis on the tertiary industry, which is mainly influenced by seasonal changes, is smaller. Finally, some policy implications are proposed. Full article

▼ Show Figures

Figure 1

2641 KiB

Open AccessArticle

Optimization of the Heating System Use in Aged Public Buildings via Model Predictive Control

by Edorta Carrascal^1,*

, Izaskun Garrido²

, Aitor J. Garrido² and José María Sala³

¹ Automatic Control Group, Department of Thermal Engineering, University of the Basque Country (UPV/EHU), Bilbao 48013, Spain

² Automatic Control Group, Department of Automatic Control and Systems Engineering, University of the Basque Country (UPV/EHU), Bilbao 48013, Spain

³ Enedi Research Group, Department of Thermal Engineering, University of the Basque Country (UPV/EHU), Bilbao 48013, Spain

Energies 2016, 9(4), 251; https://doi.org/10.3390/en9040251 - 30 Mar 2016

Cited by 15 | Viewed by 7115

Abstract

This work presents the implementation of a Model Predictive Control (MPC) scheme used to study the improvement of the thermal quality in aged residential buildings without any rehabilitation. The controller manages the heating system of an experimentally characterized model of a residential dwelling [...] Read more.

This work presents the implementation of a Model Predictive Control (MPC) scheme used to study the improvement of the thermal quality in aged residential buildings without any rehabilitation. The controller manages the heating system of an experimentally characterized model of a residential dwelling in a social block built during the decade of the 1960s located in the neighborhood of Otxarkoaga (Bilbao, Spain), so as to obtain an optimal energy efficiency performance. Due to the characteristics of the construction in those days, this kind of buildings suffer problems related to the use of awkward building materials and inefficient heating systems. A comparison with traditionally used ON-OFF hysteresis control is presented in order to demonstrate the energetic improvement provided by the MPC scheme. Besides, the variation of different parameters of the MPC is also studied to determine its influence over the energy consumption and comfort conditions. Full article

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

▼ Show Figures

Figure 1

881 KiB

Open AccessArticle

Pricing of Biomethane Products Targeted at Private Households in Germany—Product Attributes and Providers’ Pricing Strategies

by Carsten Herbes^1,*, Lorenz Braun^2,† and Dennis Rube^1,†

¹ Institute for International Research on Sustainable Management and Renewable Energy (ISR), Nuertingen-Geislingen University, Neckarsteige 6–10, Nuertingen 72622, Germany

² Faculty of Agriculture, Economics and Management (FAVM), Nuertingen-Geislingen University, Neckarsteige 6–10, Nuertingen 72622, Germany

^† These authors contributed equally to this work.

Energies 2016, 9(4), 252; https://doi.org/10.3390/en9040252 - 30 Mar 2016

Cited by 16 | Viewed by 5680

Abstract

In the effort to combat global warming, renewable energies play a key role. However, most efforts are still focused on the electricity market, so renewables remain underrepresented in the heat market. Biomethane derived from biogas is an intriguing option for using renewable energy [...] Read more.

In the effort to combat global warming, renewable energies play a key role. However, most efforts are still focused on the electricity market, so renewables remain underrepresented in the heat market. Biomethane derived from biogas is an intriguing option for using renewable energy to generate heat in residential homes. However, biomethane comes at a significantly higher cost than natural gas, meaning providers have to ask a price premium from consumers. Determining a pricing strategy is thus of crucial importance. Besides cost, providers have to consider consumers’ willingness-to-pay (WTP) for the product. We propose that they could draw on existing research on WTP for green electricity, albeit with some important modifications and scarce research on biomethane. To explore this proposition, we performed a first-of-its-kind analysis of providers’ pricing strategies for biomethane, using both providers’ published data and data provided in response to e-mail queries. Based on the features and prices of 165 biomethane-based gas products for private households in Germany, we find that features that could, according to existing research, elicit a higher WTP are not priced accordingly. As the consumer market for biomethane is still in its early development, our results suggest opportunities for providers to ask higher prices for certain biomethane-based gas products. Full article

(This article belongs to the Special Issue Economics of Bioenergy 2015)

▼ Show Figures

Figure 1

1338 KiB

Open AccessArticle

Ethanol Production from Sweet Sorghum Juice at High Temperatures Using a Newly Isolated Thermotolerant Yeast Saccharomyces cerevisiae DBKKU Y-53

by Sunan Nuanpeng^1,2, Sudarat Thanonkeo³, Mamoru Yamada⁴ and Pornthap Thanonkeo^2,5,*

¹ Graduate School, Khon Kaen University, Khon Kaen 40002, Thailand

² Department of Biotechnology, Faculty of Technology, Khon Kaen University, Khon Kaen 40002, Thailand

³ Walai Rukhavej Botanical Research Institute, Mahasarakham University, Maha Sarakham 44150, Thailand

⁴ Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan

⁵ Fermantation Research Center for Value Added Agricultural Products, Khon Kaen University, Khon Kaen 40002, Thailand

Energies 2016, 9(4), 253; https://doi.org/10.3390/en9040253 - 31 Mar 2016

Cited by 45 | Viewed by 7072

Abstract

Ethanol production at elevated temperatures requires high potential thermotolerant ethanol-producing yeast. In this study, nine isolates of thermotolerant yeasts capable of growth and ethanol production at high temperatures were successfully isolated. Among these isolates, the newly isolated thermotolerant yeast strain, which was designated [...] Read more.

Ethanol production at elevated temperatures requires high potential thermotolerant ethanol-producing yeast. In this study, nine isolates of thermotolerant yeasts capable of growth and ethanol production at high temperatures were successfully isolated. Among these isolates, the newly isolated thermotolerant yeast strain, which was designated as Saccharomyces cerevisiae DBKKU Y-53, exhibited great potential for ethanol production from sweet sorghum juice (SSJ) at high temperatures. The maximum ethanol concentrations produced by this newly isolated thermotolerant yeast at 37 °C and 40 °C under the optimum cultural condition were 106.82 g·L⁻¹ and 85.01 g·L⁻¹, respectively, which are greater than values reported in the literatures. It should be noted from this study with SSJ at a sugar concentration of 250 g·L⁻¹ and an initial pH of 5.5 without nitrogen supplementation can be used directly as substrate for ethanol production at high temperatures by thermotolerant yeast S. cerevisiae DBKKU Y-53. Gene expression analysis using real-time RT-PCR clearly indicated that growth and ethanol fermentation activities of the thermotolerant yeast S. cerevisiae DBKKU Y-53 at a high temperature (40 °C) were not only restricted to the expression of genes involved in the heat-shock response, but also to those genes involved in ATP production, trehalose and glycogen metabolism, and protein degradation processes were also involved. Full article

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

▼ Show Figures

Figure 1

3811 KiB

Open AccessArticle

How the Chlorine Treatment and the Stoichiometry Influences the Grain Boundary Passivation in Polycrystalline CdTe Thin Films

by Alessio Bosio¹, Greta Rosa^1,*, Daniele Menossi² and Nicola Romeo¹

¹ Thin Film Laboratory, Department of Physics and Earth Sciences, University of Parma, Parco area delle Scienze 7/A, Parma 43124, Italy

² Computer Science Department, University of Verona, Ca' Vignal 1, Strada Le Grazie 15, Verona 37134, Italy

Energies 2016, 9(4), 254; https://doi.org/10.3390/en9040254 - 31 Mar 2016

Cited by 15 | Viewed by 5479

Abstract

The absorption coefficient of CdTe is large enough to assure that all of the visible light is absorbed in a thickness on the order of 1 µm. High efficiency devices are fabricated by using close-spaced sublimation (CSS)-deposited CdTe films with a thickness in [...] Read more.

The absorption coefficient of CdTe is large enough to assure that all of the visible light is absorbed in a thickness on the order of 1 µm. High efficiency devices are fabricated by using close-spaced sublimation (CSS)-deposited CdTe films with a thickness in the range of 6–8 µm. In order to decrease the thickness of the CdTe film, a novel approach has been used. On top of the CdTe film, whose thickness is reduced to 2–3 μm, another CdTe layer is deposited by RF sputtering, with a thickness of 100–200 nm. The purpose of this approach is to fill up the voids, which tend to form when a low thickness-CdTe film is deposited by close-spaced sublimation. Using this CdTe double layer, solar cells, with an efficiency greater than 15%, were reproducibly obtained. Since the CdTe layer deposited by the CSS technique shows a p-type behavior, whereas the layer deposited by sputtering is n-type, it is supposed that the formation of a p-n junction into the grain boundaries, which makes a mirror for the charge carriers, increases their mean lifetime. In order to also have this system after the essential chlorine treatment of the CdTe layer, a special cadmium-free halogen treatment was developed. This process was especially tuned for very thin (≤3 µm) CdTe film thickness and for not making use of cadmium-based chlorine salt while, producing high efficiency devices, meets a better economic and environmental sustainability. Full article

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

▼ Show Figures

Graphical abstract

5313 KiB

Open AccessArticle

Analysis of a Battery Management System (BMS) Control Strategy for Vibration Aged Nickel Manganese Cobalt Oxide (NMC) Lithium-Ion 18650 Battery Cells

by Thomas Bruen^1,*, James Michael Hooper¹

, James Marco¹, Miguel Gama² and Gael Henri Chouchelamane²

¹ Warwick Manufacturing Group (WMG), University of Warwick, Coventry CV4 7AL, UK

² Jaguar Land Rover, Banbury Road, Warwick CV35 0XJ, UK

Energies 2016, 9(4), 255; https://doi.org/10.3390/en9040255 - 1 Apr 2016

Cited by 22 | Viewed by 9403

Abstract

Electric vehicle (EV) manufacturers are using cylindrical format cells as part of the vehicle’s rechargeable energy storage system (RESS). In a recent study focused at determining the ageing behavior of 2.2 Ah Nickel Manganese Cobalt Oxide (NMC) Lithium-Ion 18650 battery cells, significant increases [...] Read more.

Electric vehicle (EV) manufacturers are using cylindrical format cells as part of the vehicle’s rechargeable energy storage system (RESS). In a recent study focused at determining the ageing behavior of 2.2 Ah Nickel Manganese Cobalt Oxide (NMC) Lithium-Ion 18650 battery cells, significant increases in the ohmic resistance (R_O) were observed post vibration testing. Typically a reduction in capacity was also noted. The vibration was representative of an automotive service life of 100,000 miles of European and North American customer operation. This paper presents a study which defines the effect that the change in electrical properties of vibration aged 18650 NMC cells can have on the control strategy employed by the battery management system (BMS) of a hybrid electric vehicle (HEV). It also proposes various cell balancing strategies to manage these changes in electrical properties. Subsequently this study recommends that EV manufacturers conduct vibration testing as part of their cell selection and development activities so that electrical ageing characteristics associated with road induced vibration phenomena are incorporated to ensure effective BMS and RESS performance throughout the life of the vehicle. Full article

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

▼ Show Figures

Figure 1

6215 KiB

Open AccessArticle

An Experimental Study on the Potential Usage of Acetone as an Oxygenate Additive in PFI SI Engines

by Lei Meng^1,3, Chunnian Zeng¹, Yuqiang Li², Karthik Nithyanandan³, Timothy H. Lee³ and Chia-fon Lee^3,4,*

¹ School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China

² School of Energy Science and Engineering, Central South University, Changsha 410083, China

³ Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA

⁴ School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China

Energies 2016, 9(4), 256; https://doi.org/10.3390/en9040256 - 31 Mar 2016

Cited by 22 | Viewed by 6129

Abstract

To face the challenges of fossil fuel shortage and stringent emission norms, there is growing interest in the potential usage of alternative fuels such as bio-ethanol and bio-butanol in internal combustion engines. More recently, Acetone–Butanol–Ethanol (ABE), the intermediate product of bio-butanol fermentation, has [...] Read more.

To face the challenges of fossil fuel shortage and stringent emission norms, there is growing interest in the potential usage of alternative fuels such as bio-ethanol and bio-butanol in internal combustion engines. More recently, Acetone–Butanol–Ethanol (ABE), the intermediate product of bio-butanol fermentation, has been gaining a lot of attention as an alternative fuel. The literature shows that the acetone in the ABE blends plays an important part in improving the combustion performance and emissions, owing to its higher volatility. Acetone and ethanol are the low-value byproducts during bio-butanol production, so using acetone and ethanol as fuel additives may have both economic and environmental benefits. This study focuses on the differences in combustion, performance and emission characteristics of a port-injection spark-ignition engine fueled with pure gasoline (G100), ethanol-containing gasoline (E10 and E30) and acetone-ethanol-gasoline blends (AE10 and AE30 at A:E volumetric ratio of 3:1). The tests were conducted at 1200 RPM, under gasoline maximum brake torque (MBT) at 3 bar and 5 bar brake mean effective pressure (BMEP). Performance and emission data were measured under various equivalence ratios. Based on the comparison of combustion phasing, brake thermal efficiency, brake specific fuel consumption and various emissions of different fuels, it was found that using acetone as an oxygenate additive with the default ECU calibration (for gasoline) maintained the thermal efficiency and showed lower unburned HC emissions. Full article

▼ Show Figures

Graphical abstract

10184 KiB

Open AccessArticle

Control Strategies with Dynamic Threshold Adjustment for Supercapacitor Energy Storage System Considering the Train and Substation Characteristics in Urban Rail Transit

by Fei Lin^*, Xuyang Li, Yajie Zhao and Zhongping Yang

School of Electrical Engineering, Beijing Jiaotong University, No.3 Shangyuancun, Beijing 100044, China

Energies 2016, 9(4), 257; https://doi.org/10.3390/en9040257 - 31 Mar 2016

Cited by 28 | Viewed by 7737

Abstract

Recuperation of braking energy offers great potential for reducing energy consumption in urban rail transit systems. The present paper develops a new control strategy with variable threshold for wayside energy storage systems (ESSs), which uses the supercapacitor as the energy storage device. First, [...] Read more.

Recuperation of braking energy offers great potential for reducing energy consumption in urban rail transit systems. The present paper develops a new control strategy with variable threshold for wayside energy storage systems (ESSs), which uses the supercapacitor as the energy storage device. First, the paper analyzes the braking curve of the train and the V-I characteristics of the substation. Then, the current-voltage dual-loop control method is used for ESSs. Next, in order to achieve the best energy-saving effect, the paper discusses the selection principle of the charge and discharge threshold. This paper proposes a control strategy for wayside supercapacitors integrated with dynamic threshold adjustment control on the basis of avoiding the onboard braking chopper’s operation. The proposed control strategy is very useful for obtaining good performance, while not wasting any energy in the braking resistor. Therefore, the control strategy has been verified through simulations, and experimental tests, have been implemented on the Batong Line of Beijing subway using the 200 kW wayside supercapacitor energy storage prototype. The experimental results show that the proposed control is capable of saving energy and considerably reducing energy consumption in the braking resistor during train braking. Full article

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

▼ Show Figures

Graphical abstract

3682 KiB

Open AccessFeature PaperArticle

Performance of Natural Ester as a Transformer Oil in Moisture-Rich Environments

by Kapila Bandara¹

, Chandima Ekanayake^2,*, Tapan Saha¹

and Hui Ma¹

¹ School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia

² School of Engineering, Griffith University, Gold Coast, QLD 4222, Australia

Energies 2016, 9(4), 258; https://doi.org/10.3390/en9040258 - 31 Mar 2016

Cited by 45 | Viewed by 11541

Abstract

Interest has risen among utilities in using natural ester (NE) insulating oils in transformers as a substitute for conventional mineral oil. However, present understanding on aging behaviour of NE-paper composite insulation system and knowledge on application of existing condition monitoring tools for NE-based [...] Read more.

Interest has risen among utilities in using natural ester (NE) insulating oils in transformers as a substitute for conventional mineral oil. However, present understanding on aging behaviour of NE-paper composite insulation system and knowledge on application of existing condition monitoring tools for NE-based insulation are inadequate. This limits the cost effective and reliable field applications of NE insulating oil. To pave the way the application of NE-based insulation in transformers, a systematic study has been performed to compare the aging behaviour of transformer grade pressboard (PB) impregnated in NE and conventional mineral oil. Applicability of a number of chemical and physical parameters, including acidity value, dielectric dissipation factor (DDF), viscosity, and colour for assessing the quality of NE insulating oil is also discussed in this paper. Comparisons are made based on the limiting values provided in the related IEEE Standard and properties of mineral oil under similar aging conditions. Full article

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

▼ Show Figures

Figure 1

1610 KiB

Open AccessArticle

The Driving Forces of Changes in CO₂ Emissions in China: A Structural Decomposition Analysis

by Bowen Xiao^*, Dongxiao Niu and Xiaodan Guo

School of Economics and Management, North China Electric Power University, Hui Long Guan, Chang Ping District, Beijing 102206, China

Energies 2016, 9(4), 259; https://doi.org/10.3390/en9040259 - 31 Mar 2016

Cited by 32 | Viewed by 5253

Abstract

Understanding the drivers of changes in CO₂ emissions is vital for a range of stakeholders. Hence, this paper explores the main drivers of CO₂ emissions in China using structural decomposition analysis based on constant price and non-comparative input-output tables. The driving [...] Read more.

Understanding the drivers of changes in CO₂ emissions is vital for a range of stakeholders. Hence, this paper explores the main drivers of CO₂ emissions in China using structural decomposition analysis based on constant price and non-comparative input-output tables. The driving forces at both nationwide and industrial levels are divided into nine effects. To investigate the effects from an energy perspective, all nine effects are further decomposed into three kinds of fossil fuels. Our empirical results show that the energy intensity effect can significantly stimulate emission reduction. Though the energy structure effect is weak, the trend of which over time shows that the energy structure is shifting to low carbon. Additionally, among final demand effect, the urban consumption, investment, and export expansion effects predominantly overwhelm other effects and contribute significantly to CO₂ emissions. Although the short term Leontief effects fluctuate greatly, the total Leontief effect in 1997–2010 reveals that it can significantly contribute to CO₂ emissions. Finally, detailed and concrete policy implications for CO₂ emission reduction are provided. Full article

▼ Show Figures

Figure 1

3342 KiB

Open AccessArticle

Effects of Climate Change and LUCC on Terrestrial Biomass in the Lower Heihe River Basin during 2001–2010

by Haiming Yan^1,†, Jinyan Zhan^1,*,†, Feng Wu^2,3 and Huicai Yang⁴

¹ State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, China

² Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

³ Center for Chinese Agricultural Policy, Chinese Academy of Sciences, Beijing 100101, China

⁴ College of Water Sciences, Beijing Normal University, Beijing 100875, China

^† These authors contributed equally to this work.

Energies 2016, 9(4), 260; https://doi.org/10.3390/en9040260 - 1 Apr 2016

Cited by 13 | Viewed by 5094

Abstract

Ecosystem services are tightly coupled with availability of solar energy and its partition into energy fluxes, and biomass accumulation, which represents the energy flux in ecosystems, is a key aspect of ecosystem services. This study analyzed the effects of climate change and land [...] Read more.

Ecosystem services are tightly coupled with availability of solar energy and its partition into energy fluxes, and biomass accumulation, which represents the energy flux in ecosystems, is a key aspect of ecosystem services. This study analyzed the effects of climate change and land use and land cover change (LUCC) on the biomass accumulation change in the Lower Heihe River Basin during 2001–2010. Biomass accumulation was represented with net primary productivity (NPP), which was estimated with the C-Fix model, and scenario analysis was carried out to investigate effects of climate change and LUCC on biomass accumulation change in a spatially explicit way. Results suggested climate change had an overall positive effect on biomass accumulation, mainly owning to changes in CO₂ concentration and temperature. LUCC accounted for 70.61% of biomass accumulation change, but primarily owning to fractional vegetation change (FVCC) rather than land conversion, and there is a negative interactive effect of FVCC and climate change on biomass accumulation, indicating FVCC resulting from water diversion played a dominant in influencing biomass accumulation. These results can provide valuable decision support information for the local ecosystem managers and decision makers to guarantee sustainable provision of essential ecosystem services. Full article

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

▼ Show Figures

Figure 1

2055 KiB

Open AccessArticle

Wind Power Generation Forecasting Using Least Squares Support Vector Machine Combined with Ensemble Empirical Mode Decomposition, Principal Component Analysis and a Bat Algorithm

by Qunli Wu and Chenyang Peng^*

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

Energies 2016, 9(4), 261; https://doi.org/10.3390/en9040261 - 1 Apr 2016

Cited by 48 | Viewed by 5472

Abstract

Regarding the non-stationary and stochastic nature of wind power, wind power generation forecasting plays an essential role in improving the stability and security of the power system when large-scale wind farms are integrated into the whole power grid. Accurate wind power forecasting can [...] Read more.

Regarding the non-stationary and stochastic nature of wind power, wind power generation forecasting plays an essential role in improving the stability and security of the power system when large-scale wind farms are integrated into the whole power grid. Accurate wind power forecasting can make an enormous contribution to the alleviation of the negative impacts on the power system. This study proposes a hybrid wind power generation forecasting model to enhance prediction performance. Ensemble empirical mode decomposition (EEMD) was applied to decompose the original wind power generation series into different sub-series with various frequencies. Principal component analysis (PCA) was employed to reduce the number of inputs without lowering the forecasting accuracy through identifying the variables deemed as significant that maintain most of the comprehensive variability present in the data set. A least squares support vector machine (LSSVM) model with the pertinent parameters being optimized by bat algorithm (BA) was established to forecast those sub-series extracted from EEMD. The forecasting performances of diverse models were compared, and the findings indicated that there was no accuracy loss when only PCA-selected inputs were utilized. Moreover, the simulation results and grey relational analysis reveal, overall, that the proposed model outperforms the other single or hybrid models. Full article

(This article belongs to the Special Issue Energy Time Series Forecasting)

▼ Show Figures

Figure 1

5807 KiB

Open AccessArticle

A Model for the Assessment of Different Net-Metering Policies

by Georgios C. Christoforidis^1,*

, Ioannis P. Panapakidis¹, Theofilos A. Papadopoulos²

, Grigoris K. Papagiannis³, Ioannis Koumparou⁴, Maria Hadjipanayi⁴ and George E. Georghiou⁴

¹ Department of Electrical Engineering, Western Macedonia University of Applied Sciences, 50100 Kozani, Greece

² Department of Electrical & Computer Engineering, Democritus University of Thrace, 67100 Xanthi, Greece

³ School of Electrical and Computer Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece

⁴ FOSS Research Centre for Sustainable Energy, PV Technology, Department of Electrical and Computer Engineering, University of Cyprus, 1678 Nicosia, Cyprus

Energies 2016, 9(4), 262; https://doi.org/10.3390/en9040262 - 1 Apr 2016

Cited by 48 | Viewed by 6501

Abstract

The photovoltaic market has recently experienced an enormous expansion, mainly due to the generous Feed-in-Tariffs (FiTs) adopted by many countries. However, in the recent years FiTs have been considerably reduced or even disappeared as their role in the PV deployment has ended. One [...] Read more.

The photovoltaic market has recently experienced an enormous expansion, mainly due to the generous Feed-in-Tariffs (FiTs) adopted by many countries. However, in the recent years FiTs have been considerably reduced or even disappeared as their role in the PV deployment has ended. One of the alternatives is the Net-Metering (NEM) policy, which has attracted the interest of stakeholders as it provides a basis for the efficient collaboration between generation and the consumption profiles of the consumer. Currently, there is a lack of a universal policy harmonizing the respective legislations of the E.U. member countries. This paper proposes a novel generalized methodology for the techno-economic assessment of different NEM policies in terms of profitability for the prosumer. The methodology is tested in a formulated case study based on the current NEM policy in Greece. The method proposed uses as inputs the averaged load profiles constructed from real measurements collected from 31 consumers in the Thessaloniki area and evaluated PV production. The current NEM policy and four alternatives are examined, using as additional input the average system marginal prices of the year 2013. The results show that the proposed methodology is capable of evaluating a wide variety of NEM policies and can lead to suggestions for policy adaptation in order to establish a win-win contract between all interested stakeholders. Full article

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

▼ Show Figures

Figure 1

362 KiB

Open AccessArticle

Towards Highly Energy-Efficient Roadway Lighting

by Adam Sȩdziwy^*

and Leszek Kotulski

Department of Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland

Energies 2016, 9(4), 263; https://doi.org/10.3390/en9040263 - 1 Apr 2016

Cited by 24 | Viewed by 5171

Abstract

The reports presented by consulting firms show that annual energy costs generated by 340 million streetlights are expected to reach $23.9 to $42.5 billion by 2025. Those numbers reveal a motivation behind the research aiming at optimizing outdoor lighting energy efficiency. They show [...] Read more.

The reports presented by consulting firms show that annual energy costs generated by 340 million streetlights are expected to reach $23.9 to $42.5 billion by 2025. Those numbers reveal a motivation behind the research aiming at optimizing outdoor lighting energy efficiency. They show that even a small unit improvement can yield large benefits due to the effect of scale. The development of solid state lighting solutions enables highly effective modernization of street lighting installations. It allows obtaining power saving not only by replacing high pressure lamps with LEDs but also by improving a design quality and by introducing a dynamic street lighting control. Both methods, however, are not feasible for industry-standard software tools due to the significant complexity related to a configuration optimization, especially for large-scale projects. The goal of this article is presenting the workaround to the complexity issue, which is based on application of graph methods. They enable optimizing lighting installations in the scale of a city by providing a scalable computational environment. The presented case study shows that, thanks to applying the proposed method, one can design a lighting system which has the energy consumption reduced by up to 70%. Full article

▼ Show Figures

Figure 1

9874 KiB

Open AccessArticle

Design and Analysis of Jacket Substructures for Offshore Wind Turbines

by I-Wen Chen, Bao-Leng Wong, Yu-Hung Lin, Shiu-Wu Chau

and Hsin-Haou Huang^*

Department of Engineering Science and Ocean Engineering, National Taiwan University, Taipei 106, Taiwan

Energies 2016, 9(4), 264; https://doi.org/10.3390/en9040264 - 2 Apr 2016

Cited by 35 | Viewed by 19117

Abstract

This study focused on investigating various existing types of offshore jacket substructures along with a proposed twisted-tripod jacket type (modified jacket (MJ)-structures). The architectures of the three-leg structure, as well as the patented twisted jacket structure motivated the design of the proposed MJ-structures. [...] Read more.

This study focused on investigating various existing types of offshore jacket substructures along with a proposed twisted-tripod jacket type (modified jacket (MJ)-structures). The architectures of the three-leg structure, as well as the patented twisted jacket structure motivated the design of the proposed MJ-structures. The dimensions of the structures were designed iteratively using static stress analysis to ensure that all structures had a similar level of load-carrying capability. The numerical global buckling analyses were performed for all structures after the validation by the scaled-down experiments. The local buckling strength of all compressive members was analyzed using the NORSOK standard. The results showed that the proposed MJ-structures possess excellent structural behavior and few structural nodes and components competitive with the patented twisted jacket structures, while still maintaining the advantages of low material usage similar to the three-leg jacket structures. This study provides alternatives for the initial selection and design of offshore wind turbine substructures for green energy applications. Full article

▼ Show Figures

Figure 1

3270 KiB

Open AccessArticle

A Novel Power-Saving Transmission Scheme for Multiple-Component-Carrier Cellular Systems

by Yao-Liang Chung

Department of Communications, Navigation and Control Engineering, National Taiwan Ocean University, Keelung City 20224, Taiwan

Energies 2016, 9(4), 265; https://doi.org/10.3390/en9040265 - 2 Apr 2016

Cited by 5 | Viewed by 4383

Abstract

As mobile data traffic levels have increased exponentially, resulting in rising energy costs in recent years, the demand for and development of green communication technologies has resulted in various energy-saving designs for cellular systems. At the same time, recent technological advances have allowed [...] Read more.

As mobile data traffic levels have increased exponentially, resulting in rising energy costs in recent years, the demand for and development of green communication technologies has resulted in various energy-saving designs for cellular systems. At the same time, recent technological advances have allowed multiple component carriers (CCs) to be simultaneously utilized in a base station (BS), a development that has made the energy consumption of BSs a matter of increasing concern. To help address this concern, herein we propose a novel scheme aimed at efficiently minimizing the power consumption of BS transceivers during transmission, while still ensuring good service quality and fairness for users. Specifically, the scheme utilizes the dynamic activation/deactivation of CCs during data transmission to increase power usage efficiency. To test its effectiveness, the proposed scheme was applied to a model consisting of a BS with orthogonal frequency division multiple access-based CCs in a downlink transmission environment. The results indicated that, given periods of relatively light traffic loads, the total power consumption of the proposed scheme is significantly lower than that of schemes in which all the CCs of a BS are constantly activated, suggesting the scheme’s potential for reducing both energy costs and carbon dioxide emissions. Full article

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

▼ Show Figures

Figure 1

3396 KiB

Open AccessArticle

Energy Conservation and Emissions Reduction in China’s Power Sector: Alternative Scenarios Up to 2020

by Jiahai Yuan^1,*

, Chunning Na^1,2, Zheng Hu^3,* and Ping Li²

¹ School of Economics and Management, North China Electric Power University, 2# Beinong Road, Changping District, Beijing 102206, China

² School of Physics and Electrical Information Engineering, Ningxia University, 217# Wencui Road, Xixia District, Yinchuan 750021, Ningxia, China

³ School of Engineering and Applied Sciences, Harvard University, 29 Oxford St, Cambridge, MA 02138, USA

Energies 2016, 9(4), 266; https://doi.org/10.3390/en9040266 - 4 Apr 2016

Cited by 9 | Viewed by 6431

Abstract

This paper discusses energy conservation and emissions reduction (ECER) in China’s power sector. To better understand China’s successes and failures on energy conservation in the electricity industry, first it is important to know the status of China’s power sector, and the key energy [...] Read more.

This paper discusses energy conservation and emissions reduction (ECER) in China’s power sector. To better understand China’s successes and failures on energy conservation in the electricity industry, first it is important to know the status of China’s power sector, and the key energy conservation actions, as well as the achievements in the past years. Second, two ECER scenarios are constructed to probe the 2020 energy conservation potential. Results show that the potential is estimated to be more than 240 million tons of coal equivalent (Mtce). Third, the improvement of coal power operations, structures and technologies, and ambitious deployment of energy conservation measures are proposed to fully explore the potential of China’s power industry. Fourth, great challenges for China’s ECER and some suggested policies are summed up. The lessons learnt from China will provide a valuable reference and useful inputs for other emerging economies. Full article

(This article belongs to the Special Issue Energy Policy and Climate Change 2016)

▼ Show Figures

Figure 1

6670 KiB

Open AccessArticle

Waste Heat Recovery of a PEMFC System by Using Organic Rankine Cycle

by Tianqi He¹, Rongqi Shi¹, Jie Peng^1,*, Weilin Zhuge² and Yangjun Zhang²

¹ School of Aerospace Engineering, Tsinghua University, Beijing 100084, China

² Department of Automotive Engineering, Tsinghua University, Beijing 100084, China

Energies 2016, 9(4), 267; https://doi.org/10.3390/en9040267 - 5 Apr 2016

Cited by 32 | Viewed by 8501

Abstract

In this study, two systems are brought forward to recover the waste heat of a proton exchange membrane fuel cell (PEMFC), which are named the organic Rankine cycle (ORC), and heat pump (HP) combined organic Rankine cycle (HPORC). The performances of both systems [...] Read more.

In this study, two systems are brought forward to recover the waste heat of a proton exchange membrane fuel cell (PEMFC), which are named the organic Rankine cycle (ORC), and heat pump (HP) combined organic Rankine cycle (HPORC). The performances of both systems are simulated on the platform of MATLAB with R123, R245fa, R134a, water, and ethanol being selected as the working fluid, respectively. The results show that, for PEMFC where operating temperature is constantly kept at 60 °C, there exists an optimum working temperature for each fluid in ORC and HPORC. In ORC, the maximal net power can be achieved with R245fa being selected as the working fluid. The corresponding thermal efficiency of the recovery system is 4.03%. In HPORC, the maximal net power can be achieved with water being selected in HP and R123 in ORC. The thermal efficiency of the recovery system increases to 4.73%. Moreover, the possibility of using ORC as the cooling system of PEMFC is also studied. The heat released from PEMFC stack is assumed to be wholly recovered by the ORC or HPORC system. The results indicate that the HPORC system is much more feasible for the cooling system of a PEMFC stack, since the heat recovery ability can be promoted due to the presence of HP. Full article

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

▼ Show Figures

Figure 1

5848 KiB

Open AccessArticle

Decentralized Renewable Hybrid Mini-Grids for Sustainable Electrification of the Off-Grid Coastal Areas of Bangladesh

by Majbaul Alam¹ and Subhes Bhattacharyya^2,*

¹ School of Engineering and Sustianable Development, De Montfort University, Leicester LE1 9BH, UK

² Institute of Energy and Sustainable Development, De Montfort University, Leicester LE1 9BH, UK

Energies 2016, 9(4), 268; https://doi.org/10.3390/en9040268 - 6 Apr 2016

Cited by 48 | Viewed by 10992

Abstract

Lack of access to energy is considered as a serious bottleneck for the socio-economic development of Bangladesh. Despite earning recognition for promoting solar home systems, most of the rural areas and remote islands of the country still remain non-electrified due to very high [...] Read more.

Lack of access to energy is considered as a serious bottleneck for the socio-economic development of Bangladesh. Despite earning recognition for promoting solar home systems, most of the rural areas and remote islands of the country still remain non-electrified due to very high unit cost and low quality of electricity from solar home systems (SHS) coupled with only few hours of restricted usages in the evening. Considering the resource potential and demand characteristics at the local level, the present study investigates the hybrid renewable mini-grid approach as a possible solution for universal electricity access in the country. Using Hybrid Optimisation of Multiple Energy Resources (HOMER) simulation model, the study, covering the whole coastal region of Bangladesh, shows that it is possible to offer a much better quality electricity for 12 h to 18 h a day for as low as USD 0.29–USD 0.31/kWh. Hybrid models suggested in this study can be replicated along the coastal belt and remote islands to obtain maximum diffusion of this technology and hence universal electrification. Full article

(This article belongs to the Special Issue Microgrids 2016)

▼ Show Figures

Figure 1

4686 KiB

Open AccessArticle

Thermal Efficiency of Cogeneration Units with Multi-Stage Reheating for Russian Municipal Heating Systems

by Evgeny Lisin¹, Alexander Sobolev², Wadim Strielkowski^3,4,* and Ivan Garanin¹

¹ Department of Economics in Power Engineering and Industry, National Research University “Moscow Power Engineering Institute”, Krasnokazarmennaya street 14, Moscow 111250, Russia

² Department of Thermal Power Plants, National Research University “Moscow Power Engineering Institute”, Krasnokazarmennaya street 14, Moscow 111250, Russia

³ J.E. Cairnes School of Business and Economics, National University of Ireland Galway, Ireland

⁴ Institute of Mathematics, Economics and Informatics, Irkutsk State University, Gagarin Blvd. 20, Irkutsk 664003, Russia

Energies 2016, 9(4), 269; https://doi.org/10.3390/en9040269 - 5 Apr 2016

Cited by 39 | Viewed by 6975

Abstract

This paper explores the layout of an optimum process for supplying heat to Russian municipal heating systems operating in a market environment. We analyze and compare the standard cogeneration unit design with two-stage reheating of service water coming from controlled extraction locations and [...] Read more.

This paper explores the layout of an optimum process for supplying heat to Russian municipal heating systems operating in a market environment. We analyze and compare the standard cogeneration unit design with two-stage reheating of service water coming from controlled extraction locations and layouts that employ three in-line reheaters with heat the supply controlled by a rotary diaphragm and qualitative/quantitative methods (so-called “uncontrolled extraction”). Cogeneration unit designs are benchmarked in terms of their thermal efficiency expressed as a fuel consumption rate. The specific fuel consumption rate on electricity production is viewed as a key parameter of thermal efficiency. Full article

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

▼ Show Figures

Figure 1

3152 KiB

Open AccessArticle

Optimal Siting of Charging Stations for Electric Vehicles Based on Fuzzy Delphi and Hybrid Multi-Criteria Decision Making Approaches from an Extended Sustainability Perspective

by Huiru Zhao¹ and Nana Li^1,2,*

¹ School of Economics and Management, North China Electric Power University, Beijing 102206, China

² School of Natural Resources and Environment, University of Michigan, Ann Arbor, MI 48108-1041, USA

Energies 2016, 9(4), 270; https://doi.org/10.3390/en9040270 - 6 Apr 2016

Cited by 110 | Viewed by 9682

Abstract

Optimal siting of electric vehicle charging stations (EVCSs) is crucial to the sustainable development of electric vehicle systems. Considering the defects of previous heuristic optimization models in tackling subjective factors, this paper employs a multi-criteria decision-making (MCDM) framework to address the issue of [...] Read more.

Optimal siting of electric vehicle charging stations (EVCSs) is crucial to the sustainable development of electric vehicle systems. Considering the defects of previous heuristic optimization models in tackling subjective factors, this paper employs a multi-criteria decision-making (MCDM) framework to address the issue of EVCS siting. The initial criteria for optimal EVCS siting are selected from extended sustainability theory, and the vital sub-criteria are further determined by using a fuzzy Delphi method (FDM), which consists of four pillars: economy, society, environment and technology perspectives. To tolerate vagueness and ambiguity of subjective factors and human judgment, a fuzzy Grey relation analysis (GRA)-VIKOR method is employed to determine the optimal EVCS site, which also improves the conventional aggregating function of fuzzy Vlsekriterijumska Optimizacijia I Kompromisno Resenje (VIKOR). Moreover, to integrate the subjective opinions as well as objective information, experts’ ratings and Shannon entropy method are employed to determine combination weights. Then, the applicability of proposed framework is demonstrated by an empirical study of five EVCS site alternatives in Tianjin. The results show that A3 is selected as the optimal site for EVCS, and sub-criteria affiliated with environment obtain much more attentions than that of other sub-criteria. Moreover, sensitivity analysis indicates the selection results remains stable no matter how sub-criteria weights are changed, which verifies the robustness and effectiveness of proposed model and evaluation results. This study provides a comprehensive and effective method for optimal siting of EVCS and also innovates the weights determination and distance calculation for conventional fuzzy VIKOR. Full article

▼ Show Figures

Figure 1

2791 KiB

Open AccessArticle

Preparation and Characterization of Tetra-Imidazolium Hydroxide Polyphenylene Membranes via Nickel Catalyzed C–C Coupling Polymerization

by Hohyoun Jang¹, Soonho Lee¹, Jaeseong Ha¹, Kunyoung Choi¹, Taewook Ryu¹, Kyunghwan Kim¹, Heung-Seok Jeon² and Whangi Kim^1,*

¹ Department of Applied Chemistry, Konkuk University, Chungju 380-701, Korea

² Department of Computer Engineering, Konkuk University, Chungju 380-701, Korea

Energies 2016, 9(4), 271; https://doi.org/10.3390/en9040271 - 6 Apr 2016

Cited by 3 | Viewed by 5063

Abstract

Imidazolium hydroxide anion exchange membranes functionalized with conjugated tetraphenylethylene moieties were synthesized via Ni(0) catalyzed polymerization by sequential chloromethylation, substitution with imidazoliums and ion exchange. Moreover, with their pendant benzoyl groups the copolymers showed high molecular weight, durability, thermo-oxidative stability, high solubility in [...] Read more.

Imidazolium hydroxide anion exchange membranes functionalized with conjugated tetraphenylethylene moieties were synthesized via Ni(0) catalyzed polymerization by sequential chloromethylation, substitution with imidazoliums and ion exchange. Moreover, with their pendant benzoyl groups the copolymers showed high molecular weight, durability, thermo-oxidative stability, high solubility in polar aprotic solvents and strong chemical and thermal stability in comparison to alkyl quaternary ammonium-functionalized polymers. The proposed polymer membranes, without ether linkages, demonstrated improved performance in ion exchange capacity, water uptake, ion conductivity, and thermal stability. The polymer membranes were studied by ¹H-NMR (Nuclear Magnetic Resonance) spectroscopy, thermogravimetric analysis, water uptake, ion exchange capacity and ion conductivity. Surface morphologies were assessed by atomic force microscope (AFM). The synthesized polymers may have applications as fuel cell membranes because of their excellent ion conductivity. Full article

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

▼ Show Figures

Figure 1

4316 KiB

Open AccessArticle

Critical Filler Concentration in Sulfated Titania-Added Nafion™ Membranes for Fuel Cell Applications

by Mirko Sgambetterra¹

, Sergio Brutti^2,3,*

, Valentina Allodi⁴, Gino Mariotto⁴

, Stefania Panero¹

and Maria Assunta Navarra¹

¹ Chemistry Department, University of Roma La Sapienza, P.le Aldo Moro 5, 00185 Rome, Italy

² Insitute for Complex Systems, National Research Council (ISC-CNR), via dei Taurini, 00185 Rome, Italy

³ Science Department, University of Basilicata, v.le Ateneo Lucano 10, 85100 Potenza, Italy

⁴ Informatics Department, University of Verona, Strada le Grazie 15, 37134 Verona, Italy

Energies 2016, 9(4), 272; https://doi.org/10.3390/en9040272 - 6 Apr 2016

Cited by 11 | Viewed by 5174

Abstract

In this communication we present a detailed study of Nafion™ composite membranes containing different amounts of nanosized sulfated titania particles, synthesized through an optimized one-step synthesis procedure. Functional membrane properties, such as ionic exchange capacity and water uptake (WU) ability will be described [...] Read more.

In this communication we present a detailed study of Nafion™ composite membranes containing different amounts of nanosized sulfated titania particles, synthesized through an optimized one-step synthesis procedure. Functional membrane properties, such as ionic exchange capacity and water uptake (WU) ability will be described and discussed, together with thermal analysis, atomic force microscopy and Raman spectroscopy data. Also electrochemical properties such as proton conductivity and performances in hydrogen fuel cells will be presented. It has been demonstrated that a critical concentration of filler particles can boost the fuel cell performance at low humidification, exhibiting a significant improvement of the maximum power and current density delivered under 30% low-relative humidity (RH) and 70 °C with respect to bare Nafion™-based systems. Full article

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

▼ Show Figures

Figure 1

349 KiB

Open AccessArticle

Agricultural Business Strategy: Theory and Methods for Cost-Effectiveness Investment Analysis in Agro-Energy Production

by Sonia Prestamburgo^1,*

and Mario Prestamburgo²

¹ Department of Engineering and Architecture, University of Trieste, V. Valerio 6/1, 34127 Trieste, Italy

² Department of Economic Sciences, Business, Mathematical and Statistical Sciences, University of Trieste, V. Valerio 4/1, 34127 Trieste, Italy

Energies 2016, 9(4), 273; https://doi.org/10.3390/en9040273 - 6 Apr 2016

Cited by 4 | Viewed by 5439

Abstract

Environmental change is currently considered a high-priority matter, both in the scientific community at large and at the institutional level of national and international governing bodies. Actually, an all-out effort seeks to investigate and advance viable solutions to deal with the global emergencies [...] Read more.

Environmental change is currently considered a high-priority matter, both in the scientific community at large and at the institutional level of national and international governing bodies. Actually, an all-out effort seeks to investigate and advance viable solutions to deal with the global emergencies regarding to anthropic climate change; increasing demands for renewable sources of energy, technological innovation and energy-saving systems, ecological and environmental sustainability of natural resources and land. At the core of this worldwide endeavour an increasingly significant role seems destined to the agricultural sector and to agro-energy production systems for the potential benefits in terms of production costs. In fact, the interest in unconventional and low-impact energy sources mandates thorough investigation not only into the advantages, in terms of availability and affordability, but also into the impact on the environment and the quality of the landscape, as well as the aspects regarding the overall measures that need be adopted so as to enable the supply on the market. Given this scenario, the wide-ranging agro-energy question would be incomplete without extensive economic sustainability analyses, serving as operational decision-support tools to measure cost-effectiveness regarding investments in agro-energy production and its use. Full article

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

▼ Show Figures

Figure 1

5867 KiB

Open AccessArticle

Analysis and Optimization of Three-Resonator Wireless Power Transfer System for Predetermined-Goals Wireless Power Transmission

by Jin Zhang¹

and Chonghu Cheng^2,*

¹ College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China

² College of Communications and Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China

Energies 2016, 9(4), 274; https://doi.org/10.3390/en9040274 - 7 Apr 2016

Cited by 10 | Viewed by 5297

Abstract

Three-resonator wireless power transfer (WPT) systems have been proposed to improve the power transfer efficiency (PTE) and power delivered to the load (PDL) in recent years. However, analysis formulas of a three-resonator WPT system are complicated, and the parameters for clarifying the transfer [...] Read more.

Three-resonator wireless power transfer (WPT) systems have been proposed to improve the power transfer efficiency (PTE) and power delivered to the load (PDL) in recent years. However, analysis formulas of a three-resonator WPT system are complicated, and the parameters for clarifying the transfer characteristics of this system are difficult to extract. In this paper, concise formulas for analyzing PTE and PDL of the three-resonator system are derived by introducing three factors. Diagram discriminance based on the derived formulas is proposed to obtain the frequency splitting criterions of PTE and PDL in this system. Further, at the transfer distances, where the PTE and PDL are low at original frequency due to frequency splitting phenomenon, the two predetermined-goals of maximizing PTE and PDL are achieved by optimizing coupling strength between the three resonators. The third predetermined-goal of obtaining a constant amount of PDL transfer at maximum PTE is also implemented based on basic algorithms in numerical software. Finally, Simulation and measurement results verify the correctness of analyzing the transfer characteristics of three-resonator WPT system using the presented concise formulas and discriminance. Moreover, effectiveness of realizing the three predetermined-goals via the proposed optimization method is confirmed with experiments. Full article

▼ Show Figures

Figure 1

9540 KiB

Open AccessArticle

Effect of Guide Vane Clearance Gap on Francis Turbine Performance

by Ravi Koirala^1,2, Baoshan Zhu^1,*

and Hari Prasad Neopane²

¹ State Key Laboratory of Hydroscience and Engineering, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China

² Turbine Testing Lab, Kathmandu University, P.O. Box 6250, Dhulikhel, Nepal

Energies 2016, 9(4), 275; https://doi.org/10.3390/en9040275 - 11 Apr 2016

Cited by 37 | Viewed by 11298

Abstract

Francis turbine guide vanes have pivoted support with external control mechanism, for conversion of pressure to kinetic energy and to direct them to runner vanes. This movement along the support is dependent on variation of load and flow (operating conditions). Small clearance gaps [...] Read more.

Francis turbine guide vanes have pivoted support with external control mechanism, for conversion of pressure to kinetic energy and to direct them to runner vanes. This movement along the support is dependent on variation of load and flow (operating conditions). Small clearance gaps between facing plates and the upper and lower guide vane tips are available to aid this movement, through which leakage flow occurs. This secondary flow disturbs the main flow stream, resulting performance loss. Additionally, these increased horseshoe vortex, in presence of sand, when crosses through the gaps, both the surfaces are eroded. This causes further serious effect on performance and structural property by increasing gaps. This paper discusses the observation of the severity in hydropower plants and effect of clearance gaps on general performance of the Francis turbine through computational methods. It also relates the primary result with the empirical relation for leakage flow prediction. Additionally, a possible method to computationally estimate thickness depletion has also been presented. With increasing clearance gap, leakage increases, which lowers energy conversion and turbine efficiency along with larger secondary vortex. Full article

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

▼ Show Figures

Figure 1

223 KiB

Open AccessArticle

Exploring Local and Community Capacity to Reduce Fuel Poverty: The Case of Home Energy Advice Visits in the UK

by Andrew Reeves

Institute of Energy and Sustainable Development, De Montfort University, Leicester LE1 9BH, UK

Energies 2016, 9(4), 276; https://doi.org/10.3390/en9040276 - 8 Apr 2016

Cited by 14 | Viewed by 5142

Abstract

Local delivery of support to householders to reduce the exposure to, and impacts of, fuel poverty is attracting increasing policymaker interest, but there is a dearth of empirical research that describes and evaluates local support schemes. Community organisations are viewed as having great [...] Read more.

Local delivery of support to householders to reduce the exposure to, and impacts of, fuel poverty is attracting increasing policymaker interest, but there is a dearth of empirical research that describes and evaluates local support schemes. Community organisations are viewed as having great potential to aid this delivery, but research on how this could be achieved is scarce. The research presented in this paper responds to these needs through an exploratory study of the delivery of home energy advice visits in the UK. Data were collected through interviews and supporting documents from twelve projects and analysis examined the inter-relationships between the process, delivered outputs and impacts of each project. The research findings suggest that long-term local professional initiatives appear to be most effective at reaching and providing support to fuel poor households across a local area. Community organisations appear to have some potential to fill gaps in local provision and can assist professional initiatives, particularly through signposting, but a lack of volunteer capacity ultimately constrains their impact. Issues identified for further study include: how local support services can be resourced and delivered nationwide; trade-offs between pursuing climate change and fuel poverty agendas; a need for more robust evidence of impacts. Full article

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

8469 KiB

Open AccessArticle

Short-Circuit Calculation in Distribution Networks with Distributed Induction Generators

by Niancheng Zhou¹, Fan Ye^1,*

, Qianggang Wang^1,2

, Xiaoxuan Lou^1,3 and Yuxiang Zhang²

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

² School of Electricaland Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore

³ Department of Electrical Engineering, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA

Energies 2016, 9(4), 277; https://doi.org/10.3390/en9040277 - 9 Apr 2016

Cited by 5 | Viewed by 5696

Abstract

This paper presents an improved current source equivalent model method to determine the short-circuit current of a distribution system with multiple fixed-speed and variable-speed induction generators (IGs). The correlation coefficients of flux components between stator and rotor under the unsymmetrical fault are analyzed [...] Read more.

This paper presents an improved current source equivalent model method to determine the short-circuit current of a distribution system with multiple fixed-speed and variable-speed induction generators (IGs). The correlation coefficients of flux components between stator and rotor under the unsymmetrical fault are analyzed using the positive and negative sequence steady-state equivalent circuits of an IG. The terminal voltage and current responses of fixed-speed and variable-speed IGs with and without the rotor slip changes under different penetration levels are compared to investigate the coupling relation between the short-circuit currents of IGs and the nodal voltages in the distribution network. Then the transient equivalent potential of an IG at the grid fault instant is derived. Sequence components of the short-circuit current in the network can be determined using the proposed technique. The correctness of the proposed method is verified using dynamic simulation. Full article

▼ Show Figures

Figure 1

8187 KiB

Open AccessArticle

Robust Optimization-Based Scheduling of Multi-Microgrids Considering Uncertainties

by Akhtar Hussain

, Van-Hai Bui and Hak-Man Kim^*

Department of Electrical Engineering, Incheon National University, 12-1 Songdo-dong, Yeonsu-gu, Incheon 406-840, Korea

Energies 2016, 9(4), 278; https://doi.org/10.3390/en9040278 - 9 Apr 2016

Cited by 92 | Viewed by 9128

Abstract

Scheduling of multi-microgrids (MMGs) is one of the important tasks in MMG operation and it faces new challenges as the integration of demand response (DR) programs and renewable generation (wind and solar) sources increases. In order to address these challenges, robust optimization (RO)-based [...] Read more.

Scheduling of multi-microgrids (MMGs) is one of the important tasks in MMG operation and it faces new challenges as the integration of demand response (DR) programs and renewable generation (wind and solar) sources increases. In order to address these challenges, robust optimization (RO)-based scheduling has been proposed in this paper considering uncertainties in both renewable energy sources and forecasted electric loads. Initially, a cost minimization deterministic model has been formulated for the MMG system. Then, it has been transformed to a min-max robust counterpart and finally, a traceable robust counterpart has been formulated using linear duality theory and Karush–Kuhn–Tucker (KKT) optimality conditions. The developed model provides immunity against the worst-case realization within the provided uncertainty bounds. Budget of uncertainty has been used to develop a trade-off between the conservatism of solution and probability of unfeasible solution. The effect of uncertainty gaps on internal and external trading, operation cost, unit commitment of dispatchable generators, and state of charge (SOC) of battery energy storage systems (BESSs) have also been analyzed in both grid-connected and islanded modes. Simulations results have proved the robustness of proposed strategy. Full article

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

▼ Show Figures

Graphical abstract

6971 KiB

Open AccessArticle

Modeling and Experimental Validation of a Volumetric Expander Suitable for Waste Heat Recovery from an Automotive Internal Combustion Engine Using an Organic Rankine Cycle with Ethanol

by José Galindo¹, Vicente Dolz^1,*,‡

, Lucía Royo-Pascual^1,‡

, Regine Haller² and Julien Melis³

¹ CMT-Motores Térmicos, Polytechnic University of Valencia, 6D Building, Camino de Vera s/n, Valencia 46022, Spain

² Valeo Systèmes Thermiques, 8, rue Louis Lormand, La Verrière 78321, France

³ Exoès S.A.S., 6, avenue de la Grande Lande, Gradignan 33170, France

^‡ These authors contributed equally to this work.

Energies 2016, 9(4), 279; https://doi.org/10.3390/en9040279 - 9 Apr 2016

Cited by 20 | Viewed by 7838

Abstract

Waste heat recovery (WHR) in exhaust gas flow of automotive engines has proved to be a useful path to increase the overall efficiency of internal combustion engines (ICE). Recovery potentials of up to 7% are shown in several works in the literature. However, [...] Read more.

Waste heat recovery (WHR) in exhaust gas flow of automotive engines has proved to be a useful path to increase the overall efficiency of internal combustion engines (ICE). Recovery potentials of up to 7% are shown in several works in the literature. However, most of them are theoretical estimations. Some present results from prototypes fed by steady flows generated in an auxiliary gas tank and not with actual engine exhaust gases. This paper deals with the modeling and experimental validation of an organic Rankine cycle (ORC) with a swash-plate expander integrated in a 2 L turbocharged petrol engine using ethanol as working fluid. A global simulation model of the ORC was developed with a maximum difference of 5%, validated with experimental results. Considering the swash-plate as the main limiting factor, an additional specific submodel was implemented to model the physical phenomena in this element. This model allows simulating the fluid dynamic behavior of the swash-plate expander using a 0D model (Amesim). Differences up to 10.5% between tests and model results were found. Full article

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

▼ Show Figures

Graphical abstract

3141 KiB

Open AccessArticle

Simultaneous Fault Detection and Sensor Selection for Condition Monitoring of Wind Turbines

by Wenna Zhang^1,2,* and Xiandong Ma²

¹ College of Mechatronics and Automation, National University of Defense Technology, Changsha 410073, China

² Engineering Department, Lancaster University, Bailrigg, Lancaster LA1 4YW, UK

Energies 2016, 9(4), 280; https://doi.org/10.3390/en9040280 - 12 Apr 2016

Cited by 21 | Viewed by 5923

Abstract

Data collected from the supervisory control and data acquisition (SCADA) system are used widely in wind farms to obtain operation and performance information about wind turbines. The paper presents a three-way model by means of parallel factor analysis (PARAFAC) for wind turbine fault [...] Read more.

Data collected from the supervisory control and data acquisition (SCADA) system are used widely in wind farms to obtain operation and performance information about wind turbines. The paper presents a three-way model by means of parallel factor analysis (PARAFAC) for wind turbine fault detection and sensor selection, and evaluates the method with SCADA data obtained from an operational farm. The main characteristic of this new approach is that it can be used to simultaneously explore measurement sample profiles and sensors profiles to avoid discarding potentially relevant information for feature extraction. With K-means clustering method, the measurement data indicating normal, fault and alarm conditions of the wind turbines can be identified, and the sensor array can be optimised for effective condition monitoring. Full article

▼ Show Figures

Figure 1

1196 KiB

Open AccessArticle

Vibration Durability Testing of Nickel Cobalt Aluminum Oxide (NCA) Lithium-Ion 18650 Battery Cells

by James Michael Hooper^1,*

, James Marco¹, Gael Henri Chouchelamane², Christopher Lyness² and James Taylor¹

¹ Warwick Manufacturing Group (WMG), University of Warwick, Coventry CV4 7AL, UK

² Jaguar Land Rover, Banbury Road, Warwick CV35 0XJ, UK

Energies 2016, 9(4), 281; https://doi.org/10.3390/en9040281 - 12 Apr 2016

Cited by 27 | Viewed by 8567

Abstract

This paper outlines a study undertaken to determine if the electrical performance of Nickel Cobalt Aluminum Oxide (NCA) 3.1 Ah 18650 battery cells can be degraded by road induced vibration typical of an electric vehicle (EV) application. This study investigates if a particular [...] Read more.

This paper outlines a study undertaken to determine if the electrical performance of Nickel Cobalt Aluminum Oxide (NCA) 3.1 Ah 18650 battery cells can be degraded by road induced vibration typical of an electric vehicle (EV) application. This study investigates if a particular cell orientation within the battery assembly can result in different levels of cell degradation. The 18650 cells were evaluated in accordance with Society of Automotive Engineers (SAE) J2380 standard. This vibration test is synthesized to represent 100,000 miles of North American customer operation at the 90th percentile. This study identified that both the electrical performance and the mechanical properties of the NCA lithium-ion cells were relatively unaffected when exposed to vibration energy that is commensurate with a typical vehicle life. Minor changes observed in the cell’s electrical characteristics were deemed not to be statistically significant and more likely attributable to laboratory conditions during cell testing and storage. The same conclusion was found, irrespective of cell orientation during the test. Full article

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

▼ Show Figures

Figure 1

2170 KiB

Open AccessArticle

Study on the Performance of the “Pendulor” Wave Energy Converter in an Array Configuration

by Sudath Prasanna Gunawardane^1,*, Chathura Jayan Kankanamge¹ and Tomiji Watabe²

¹ Department of Mechanical Engineering, Faculty of Engineering, University of Peradeniya, Peradeniya 20400, Sri Lanka

² T-Wave Consultant Volunteer, 5-23-3, Misono, Noboribetsu, Hokkaido 059-0036, Japan

Energies 2016, 9(4), 282; https://doi.org/10.3390/en9040282 - 12 Apr 2016

Cited by 14 | Viewed by 9069

Abstract

For over three decades the “Pendulor” wave energy device has had a significant influence in this field, triggering several research endeavours. It includes a top-hinged flap propelled by the standing waves produced in a caisson with a back wall on the leeward side. [...] Read more.

For over three decades the “Pendulor” wave energy device has had a significant influence in this field, triggering several research endeavours. It includes a top-hinged flap propelled by the standing waves produced in a caisson with a back wall on the leeward side. However, one of the main disadvantages which impedes its progress is the enormous expense involved in the construction of the custom made typical caisson structure, about a little more than one-quarter of the wave length. In this study, the influence of such design parameters on the performance of the device is investigated, via numerical modelling for a device arranged in an array configuration, for irregular waves. The potential wave theory is applied to derive the frequency-dependent hydrodynamic parameters by making a distinction in the fluid domain into a separate sea side and lee side. The Cummins equation was utilised for the development of the time domain equation of motion while the transfer function estimation methods were used to solve the convolution integrals. Finally, the device was tested numerically for irregular wave conditions for a 50 kW class unit. It was observed that in irregular wave operating conditions, the caisson chamber length could be reduced by 40% of the value estimated for the regular waves. Besides, the device demonstrated around 80% capture efficiency for irregular waves thus allowing provision for avoiding the employment of any active control. Full article

(This article belongs to the Special Issue Numerical Modelling of Wave and Tidal Energy)

▼ Show Figures

Graphical abstract

2430 KiB

Open AccessArticle

The Effect of Biomass Physical Properties on Top-Lit Updraft Gasification of Woodchips

by Arthur M. James R.¹, Wenqiao Yuan^2,* and Michael D. Boyette²

¹ Department of Mechanical Engineering, Universidad Tecnológica de Panamá, Apartado 0819-07289, El Dorado, Panamá City, Panama

² Department of Biological and Agricultural Engineering, North Carolina State University, Campus Box 7625, Raleigh 27695, NC, USA

Energies 2016, 9(4), 283; https://doi.org/10.3390/en9040283 - 12 Apr 2016

Cited by 42 | Viewed by 7626

Abstract

The performance of a top-lit updraft gasifier affected by biomass (pine wood) particle size, moisture content and compactness was studied in terms of the biochar yield, biomass burning rate, syngas composition and tar content. The highest biochar yield increase (from 12.2% to 21.8%) [...] Read more.

The performance of a top-lit updraft gasifier affected by biomass (pine wood) particle size, moisture content and compactness was studied in terms of the biochar yield, biomass burning rate, syngas composition and tar content. The highest biochar yield increase (from 12.2% to 21.8%) was achieved by varying the particle size from 7 to 30 mm, however, larger particles triggered tar generation that reached its maximum of 93.5 g/m³ syngas at 30-mm biomass particles; in contrast, the hydrogen content in syngas was at its minimum of 2.89% at this condition. The increase in moisture content from 10% to 22% reduced biochar yield from 12% to 9.9%. It also reduced the tar content from 12.9 to 6.2 g/m³ which was found to be the lowest range of tar content in this work. Similarly, the carbon monoxide composition in syngas decreased to its minimum of 11.16% at moisture content of 22%. Finally, the biomass compactness increased biochar yield up to 17% when the packing mass was 3 kg. However, the addition of compactness also increased the tar content in syngas, but little effect was noticed in syngas composition. Full article

▼ Show Figures

Figure 1

3716 KiB

Open AccessEditor’s ChoiceArticle

Impact of Biodiesel Blends and Di-Ethyl-Ether on the Cold Starting Performance of a Compression Ignition Engine

by Adrian Clenci^1,2,*

, Rodica Niculescu¹, Amélie Danlos², Victor Iorga-Simăn¹ and Alina Trică³

¹ Department Automobiles and Transport, University of Pitesti, 1, Tg. din Vale street, Pitești 110040, Romania

² Le Cnam Paris, Laboratoire de génie des procédés pour l’environnement l’énergie et la santé, 292 rue St. Martin, Paris 75003, France

³ Renault Technologie Roumanie, 2, Bd. Pipera, Voluntari, Ilfov 077190, Romania

Energies 2016, 9(4), 284; https://doi.org/10.3390/en9040284 - 18 Apr 2016

Cited by 23 | Viewed by 6657

Abstract

The use of biodiesel fuel in compression ignition engines has the potential to reduce CO₂, which can lead to a reduction in global warming and environmental hazards. Biodiesel is an attractive fuel, as it is made from renewable resources. Many studies [...] Read more.

The use of biodiesel fuel in compression ignition engines has the potential to reduce CO₂, which can lead to a reduction in global warming and environmental hazards. Biodiesel is an attractive fuel, as it is made from renewable resources. Many studies have been conducted to assess the impact of biodiesel use on engine performances. Most of them were carried out in positive temperature conditions. A major drawback associated with the use of biodiesel, however, is its poor cold flow properties, which have a direct influence on the cold starting performance of the engine. Since diesel engine behavior at negative temperatures is an important quality criterion of the engine’s operation, one goal of this paper is to assess the starting performance at −20 °C of a common automotive compression ignition engine, fueled with different blends of fossil diesel fuel and biodiesel. Results showed that increasing the biodiesel blend ratio generated a great deterioration in engine startability. Another goal of this study was to determine the biodiesel blend ratio limit at which the engine would not start at −20 °C and, subsequently, to investigate the impact of Di-Ethyl-Ether (DEE) injection into the intake duct on the engine’s startability, which was found to be recovered. Full article

▼ Show Figures

Figure 1

5179 KiB

Open AccessArticle

Optimal Design of an Axial-Flux Permanent-Magnet Motor for an Electric Vehicle Based on Driving Scenarios

by Yee Pien Yang^1,2,* and Guan Yu Shih³

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

² Mechanical and Systems Research Labortories, Industrial Technology Research Institute, 195, Section 4, Chung Hsing Road, Hsinchu 310, Taiwan

³ CADMEN, Taiwan Auto-Design Corporation, 11 F, No. 68, Section 2, Xianmin Boulevard, New Taipei City 220, Taiwan

Energies 2016, 9(4), 285; https://doi.org/10.3390/en9040285 - 13 Apr 2016

Cited by 30 | Viewed by 15551

Abstract

This paper proposes a driving-scenario oriented optimal design of an axial-flux permanent-magnet (AFPM) motor for an electric vehicle. The target torque and speed (TN) curve is defined as three operation zones-constant torque, maximum direct current, and maximum voltage—based on the driving scenario. The [...] Read more.

This paper proposes a driving-scenario oriented optimal design of an axial-flux permanent-magnet (AFPM) motor for an electric vehicle. The target torque and speed (TN) curve is defined as three operation zones-constant torque, maximum direct current, and maximum voltage—based on the driving scenario. The AFPM motor is designed to minimize energy consumption based on the motor weight and the frequent operating points of a driving cycle. The final result shows that the electric vehicle driven by the proposed AFPM motor consumes about 15% less energy than motors designed using traditional methods. Full article

▼ Show Figures

Figure 1

1578 KiB

Open AccessArticle

A Method for Estimating Annual Energy Production Using Monte Carlo Wind Speed Simulation

by Birgir Hrafnkelsson^1,*, Gudmundur V. Oddsson²

and Runar Unnthorsson²

¹ Faculty of Physical Sciences, Department of Mathematics, University of Iceland, Reykjavik IS-107, Iceland

² Faculty of Industrial Engineering, Mechanical Engineering and Computer Science, Centre for Productivity, Performance and Processes, University of Iceland, Hjardarhagi 6,107, Reykjavik IS-107, Iceland

Energies 2016, 9(4), 286; https://doi.org/10.3390/en9040286 - 13 Apr 2016

Cited by 22 | Viewed by 6944

Abstract

A novel Monte Carlo (MC) approach is proposed for the simulation of wind speed samples to assess the wind energy production potential of a site. The Monte Carlo approach is based on historical wind speed data and reserves the effect of autocorrelation and [...] Read more.

A novel Monte Carlo (MC) approach is proposed for the simulation of wind speed samples to assess the wind energy production potential of a site. The Monte Carlo approach is based on historical wind speed data and reserves the effect of autocorrelation and seasonality in wind speed observations. No distributional assumptions are made, and this approach is relatively simple in comparison to simulation methods that aim at including the autocorrelation and seasonal effects. Annual energy production (AEP) is simulated by transforming the simulated wind speed values via the power curve of the wind turbine at the site. The proposed Monte Carlo approach is generic and is applicable for all sites provided that a sufficient amount of wind speed data and information on the power curve are available. The simulated AEP values based on the Monte Carlo approach are compared to both actual AEP and to simulated AEP values based on a modified Weibull approach for wind speed simulation using data from the Burfell site in Iceland. The comparison reveals that the simulated AEP values based on the proposed Monte Carlo approach have a distribution that is in close agreement with actual AEP from two test wind turbines at the Burfell site, while the simulated AEP of the Weibull approach is such that the P50 and the scale are substantially lower and the P90 is higher. Thus, the Weibull approach yields AEP that is not in line with the actual variability in AEP, while the Monte Carlo approach gives a realistic estimate of the distribution of AEP. Full article

▼ Show Figures

Figure 1

629 KiB

Open AccessArticle

Load Concentration Factor Based Analytical Method for Optimal Placement of Multiple Distribution Generators for Loss Minimization and Voltage Profile Improvement

by Mohsin Shahzad^1,*,†

, Ishtiaq Ahmad^1,†, Wolfgang Gawlik^2,†

and Peter Palensky^3,†

¹ Energy Department, AIT Austrian Institute of Technology, Vienna 1210, Austria

² Institute of Energy Systems and Electrical Drives, TU Wien, Wien 1040, Austria

³ Department Electrical Sustainable Energy, TU Delft, Delft 2628 CD, The Netherlands

^† These authors contributed equally to this work.

Energies 2016, 9(4), 287; https://doi.org/10.3390/en9040287 - 14 Apr 2016

Cited by 31 | Viewed by 6726

Abstract

This paper presents novel separate methods for finding optimal locations, sizes of multiple distributed generators (DGs) simultaneously and operational power factor in order to minimize power loss and improve the voltage profile in the distribution system. A load concentration factor (LCF) is introduced [...] Read more.

This paper presents novel separate methods for finding optimal locations, sizes of multiple distributed generators (DGs) simultaneously and operational power factor in order to minimize power loss and improve the voltage profile in the distribution system. A load concentration factor (LCF) is introduced to select the optimal location(s) for DG placement. Exact loss formula based analytical expressions are derived for calculating the optimal sizes of any number of DGs simultaneously. Since neither optimizing the location nor optimizing the size is done iteratively, like existing methods do, the simulation time is reduced considerably. The exhaustive method is used to find the operational power factor, and it is shown with the results that the losses are further reduced and voltage profile is improved by operating the DGs at operational power factor. Results for power loss reduction and voltage profile improvement in IEEE 37 and 119 node radial distribution systems are presented and compared with the the loss sensitivity factor (LSF) method, improved analytical (IA) and exhaustive load flow method (ELF). The comparison for operational power factor and other power factors is also presented. Full article

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

▼ Show Figures

Figure 1

7111 KiB

Open AccessArticle

A High-Performance Adaptive Incremental Conductance MPPT Algorithm for Photovoltaic Systems

by Chendi Li¹, Yuanrui Chen¹, Dongbao Zhou¹, Junfeng Liu^2,* and Jun Zeng¹

¹ School of Electric Power, South China University of Technology, Guangzhou 510640, China

² School of Automation Science and Engineering, South China University of Technology, Guangzhou 510640, China

Energies 2016, 9(4), 288; https://doi.org/10.3390/en9040288 - 15 Apr 2016

Cited by 65 | Viewed by 11057

Abstract

The output characteristics of photovoltaic (PV) arrays vary with the change of environment, and maximum power point (MPP) tracking (MPPT) techniques are thus employed to extract the peak power from PV arrays. Based on the analysis of existing MPPT methods, a novel incremental [...] Read more.

The output characteristics of photovoltaic (PV) arrays vary with the change of environment, and maximum power point (MPP) tracking (MPPT) techniques are thus employed to extract the peak power from PV arrays. Based on the analysis of existing MPPT methods, a novel incremental conductance (INC) MPPT algorithm is proposed with an adaptive variable step size. The proposed algorithm automatically regulates the step size to track the MPP through a step size adjustment coefficient, and a user predefined constant is unnecessary for the convergence of the MPPT method, thus simplifying the design of the PV system. A tuning method of initial step sizes is also presented, which is derived from the approximate linear relationship between the open-circuit voltage and MPP voltage. Compared with the conventional INC method, the proposed method can achieve faster dynamic response and better steady state performance simultaneously under the conditions of extreme irradiance changes. A Matlab/Simulink model and a 5 kW PV system prototype controlled by a digital signal controller (TMS320F28035) were established. Simulations and experimental results further validate the effectiveness of the proposed method. Full article

▼ Show Figures

Figure 1

5608 KiB

Open AccessArticle

High Pressure Oxydesulphurisation of Coal Using KMnO₄—Effect of Coal Slurry Concentration, pH and Alkali

by Moinuddin Ghauri^1,*, Khurram Shahzad^2,*, Abrar Inayat³, Zulfiqar Ali⁴ and Keith R. Cliffe⁵

¹ Department of Chemical Engineering, COMSATS Institute of Information Technology, Defence Road, Off Raiwind Road, Lahore 54000, Pakistan

² Centre for Coal Technology, University of the Punjab, Lahore 54000, Pakistan

³ Department of Sustainable & Renewable Energy Engineering, University of Sharjah, Sharjah 27272, UAE

⁴ Department of Mining Engineering, University of Engineering and Technology, Lahore 54000, Pakistan

⁵ Department of Mechanical and Process Engineering, University of Sheffield, Sheffield S10 2TN, UK

Energies 2016, 9(4), 289; https://doi.org/10.3390/en9040289 - 16 Apr 2016

Cited by 6 | Viewed by 5756

Abstract

A high pressure oxydesulphurisation technique was investigated to reduce sulphur content, especially at ambient temperature. Prince of Wales coal was chosen for this study. The focus of the study was on the reduction of both pyritic and organic sulphur. The effects of pressure, [...] Read more.

A high pressure oxydesulphurisation technique was investigated to reduce sulphur content, especially at ambient temperature. Prince of Wales coal was chosen for this study. The focus of the study was on the reduction of both pyritic and organic sulphur. The effects of pressure, coal slurry concentration, pH and KOH concentration in a fixed time interval on sulphur removal were studied with a series of experimental runs at ambient temperature. Heating value recovery was found to be increased with decreased pressure and with increased coal slurry concentration. It was found that sulphur removal was enhanced with an increase in pressure, with a more significant effect on the organic sulphur. With increase in the coal slurry concentration reduction, sulphur was found to be decreased. Full article

▼ Show Figures

Figure 1

4413 KiB

Open AccessArticle

Robust Longitudinal Speed Control of Hybrid Electric Vehicles with a Two-Degree-of-Freedom Fuzzy Logic Controller

by Jau-Woei Perng and Yi-Horng Lai^*

Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan

Energies 2016, 9(4), 290; https://doi.org/10.3390/en9040290 - 16 Apr 2016

Cited by 11 | Viewed by 5842

Abstract

This paper proposes a new robust two-degree-of-freedom (DoF) design method for controlling the nonlinear longitudinal speed problem of hybrid electric vehicles (HEVs). First, the uncertain parameters of the HEV model are described by fuzzy α-cut representation, in which the interval uncertainty and [...] Read more.

This paper proposes a new robust two-degree-of-freedom (DoF) design method for controlling the nonlinear longitudinal speed problem of hybrid electric vehicles (HEVs). First, the uncertain parameters of the HEV model are described by fuzzy α-cut representation, in which the interval uncertainty and the possibility can be simultaneously indicated by the fuzzy membership function. For the fuzzy parametric uncertain system, the maximum uncertainty interval can be translated into the weighting matrix Q of the linear quadratic tracking problem to guarantee that the designed feedback controller is robust. Second, the fuzzy forward compensator is incorporated with a robust feedback controller to enhance the system tracking response. The simulation results demonstrate that the proposed controller has higher tracking performance compared to the single-DoF self-tuning fuzzy logic controller or conventional optimal H_∞ controller. Full article

(This article belongs to the Special Issue Power Management for Hybrids and Vehicle Drivetrains)

▼ Show Figures

Figure 1

4603 KiB

Open AccessArticle

Study on the System Design of a Solar Assisted Ground Heat Pump System Using Dynamic Simulation

by Min Gyung Yu¹, Yujin Nam^1,*, Youngdong Yu² and Janghoo Seo³

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

² Research Institute of Industrial Science & Technology, Incheon 406-840, Korea

³ Department of Architecture, Kookmin University, Seoul 501-759, Korea

Energies 2016, 9(4), 291; https://doi.org/10.3390/en9040291 - 16 Apr 2016

Cited by 12 | Viewed by 7155

Abstract

Recently, the use of hybrid systems using multiple heat sources in buildings to ensure a stable energy supply and improve the system performance has gained attention. Among them, a heat pump system using both solar and ground heat was developed and various system [...] Read more.

Recently, the use of hybrid systems using multiple heat sources in buildings to ensure a stable energy supply and improve the system performance has gained attention. Among them, a heat pump system using both solar and ground heat was developed and various system configurations have been introduced. However, establishing a suitable design method for the solar-assisted ground heat pump (SAGHP) system including a thermal storage tank is complicated and there are few quantitative studies on the detailed system configurations. Therefore, this study developed three SAGHP system design methods considering the design factors focused on the thermal storage tank. Using dynamic energy simulation code (TRNSYS 17), individual performance analysis models were developed and long-term quantitative analysis was carried out to suggest optimum design and operation methods. As a result, it was found that SYSTEM 2 which is a hybrid system with heat storage tank for only a solar system showed the highest average heat source temperature of 14.81 °C, which is about 11 °C higher than minimum temperature in SYSTEM 3. Furthermore, the best coefficient of performance (COP) values of heat pump and system were 5.23 and 4.32 in SYSYEM 2, using high and stable solar heat from a thermal storage tank. Moreover, this paper considered five different geographical and climatic locations and the SAGHP system worked efficiently in having high solar radiation and cool climate zones and the system COP was 4.51 in the case of Winnipeg (Canada) where the highest heating demand is required. Full article

▼ Show Figures

Figure 1

5212 KiB

Open AccessArticle

Modeling and Simulation of the Thermal Runaway Behavior of Cylindrical Li-Ion Cells—Computing of Critical Parameters

by Andreas Melcher^*, Carlos Ziebert, Magnus Rohde and Hans Jürgen Seifert

Institute for Applied Materials-Applied Materials Physics, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz-1, Eggenstein-Leopoldshafen 76344, Germany

Energies 2016, 9(4), 292; https://doi.org/10.3390/en9040292 - 16 Apr 2016

Cited by 69 | Viewed by 11693

Abstract

The thermal behavior of Li-ion cells is an important safety issue and has to be known under varying thermal conditions. The main objective of this work is to gain a better understanding of the temperature increase within the cell considering different heat sources [...] Read more.

The thermal behavior of Li-ion cells is an important safety issue and has to be known under varying thermal conditions. The main objective of this work is to gain a better understanding of the temperature increase within the cell considering different heat sources under specified working conditions. With respect to the governing physical parameters, the major aim is to find out under which thermal conditions a so called Thermal Runaway occurs. Therefore, a mathematical electrochemical-thermal model based on the Newman model has been extended with a simple combustion model from reaction kinetics including various types of heat sources assumed to be based on an Arrhenius law. This model was realized in COMSOL Multiphysics modeling software. First simulations were performed for a cylindrical 18650 cell with a

L i C o O_{2}

-cathode to calculate the temperature increase under two simple electric load profiles and to compute critical system parameters. It has been found that the critical cell temperature

T_{crit}

, above which a thermal runaway may occur is approximately

400 K

, which is near the starting temperature of the decomposition of the Solid-Electrolyte-Interface in the anode at

393.15 K

. Furthermore, it has been found that a thermal runaway can be described in three main stages. Full article

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

▼ Show Figures

Figure 1

6557 KiB

Open AccessArticle

Influence of Droplet Size on Exergy Destruction in Flow of Concentrated Non-Newtonian Emulsions

by Rajinder Pal

Department of Chemical Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada

Energies 2016, 9(4), 293; https://doi.org/10.3390/en9040293 - 16 Apr 2016

Cited by 5 | Viewed by 6183

Abstract

The influence of droplet size on exergy destruction rate in flow of highly concentrated oil-in-water emulsions was investigated experimentally in a cone and plate geometry. The oil concentration was fixed at 74.5% by volume. At this dispersed-phase (oil) concentration, two different droplet size [...] Read more.

The influence of droplet size on exergy destruction rate in flow of highly concentrated oil-in-water emulsions was investigated experimentally in a cone and plate geometry. The oil concentration was fixed at 74.5% by volume. At this dispersed-phase (oil) concentration, two different droplet size emulsions were prepared: fine and coarse emulsions. The fine and coarse emulsions were mixed in different proportions to vary the droplet size distribution. Although the dispersed and matrix phases of the emulsions were Newtonian in nature, the emulsions exhibited a non-Newtonian (shear-thinning) behavior due to the high droplet concentration. The shear stress—shear rate data of the emulsions could be described adequately by a power law model. At low shear rates, the exergy destruction rate per unit volume of emulsion exhibited a minimum at a fine emulsion proportion of 35%. The results from the cone and plate geometry were used to simulate exergy loss in pipeline flow of emulsions. The pumping of emulsions becomes more efficient thermodynamically upon mixing of fine and coarse emulsions provided that the flow regime is maintained to be laminar and that the Reynolds number is kept at a low to moderate value. In the turbulent regime, the exergy loss generally increases upon mixing the fine and coarse emulsions. Full article

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

▼ Show Figures

Figure 1

1896 KiB

Open AccessArticle

How Can the Context Affect Policy Decision-Making: The Case of Climate Change Mitigation Policies in the Greek Building Sector

by Niki-Artemis Spyridaki

, Anastasia Ioannou and Alexandros Flamos^*

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

Energies 2016, 9(4), 294; https://doi.org/10.3390/en9040294 - 18 Apr 2016

Cited by 8 | Viewed by 5834

Abstract

The influence of context dynamics in the course of the climate change mitigation policy instruments’ (PIs) deployment cycle, usually causes a need for policy adaptation mechanisms to ensure that policies can meet the sector needs efficiently and effectively. In this paper, we argue [...] Read more.

The influence of context dynamics in the course of the climate change mitigation policy instruments’ (PIs) deployment cycle, usually causes a need for policy adaptation mechanisms to ensure that policies can meet the sector needs efficiently and effectively. In this paper, we argue that important contextual factors are the ones that are perceived to have a great impact over policy effectiveness by key related actors. By examining more thoroughly those effects over PIs, as perceived by policy and market actors, useful feedback on observed policy adaptations can be highlighted. In this context, the aim of this paper is to present a conceptual framework which seeks to investigate the impact of key external factors on policy decision-making. This framework is then applied to policies intended to foster sustainability in the Greek building sector. Contextual parameters that are influential over the effectiveness of the national energy conservation measures are identified through a stakeholder survey. Cluster analysis is then employed for the elicitation of three distinct decision-making priorities’ scenarios. General macroeconomic trends, energy costs, characteristics of the building sector and socio-institutional factors are prioritized differently from various types of actors and induce certain types of PI changes. Distinguishing among the different types of PI change can help explain better under which contextual circumstances policy adaptations occur and provide guidance to other policy makers when found in similar decisional contexts. Full article

(This article belongs to the Special Issue Energy Policy and Climate Change 2016)

▼ Show Figures

Figure 1

5719 KiB

Open AccessArticle

Decomposition Analysis in Decoupling Transport Output from Carbon Emissions in Guangdong Province, China

by Yalan Zhao^1,2,3

, Yaoqiu Kuang^1,2,* and Ningsheng Huang¹

¹ Sustainable Development Research Center, Guangzhou Institute of Geochemistry, Chinese Academic of Sciences, 511 Kehua Street, Guangzhou 510640, Guangdong, China

² Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences, Guangzhou 510640, Guangdong, China

³ University of Chinese Academic of Sciences, Yuquan Road, Beijing 100049, China

Energies 2016, 9(4), 295; https://doi.org/10.3390/en9040295 - 19 Apr 2016

Cited by 32 | Viewed by 5665

Abstract

With a continuously growing share of the world’s overall energy consumption, the transport sector has been acknowledged as one of the most important contributors to global carbon emissions. This paper applies a complete decomposition and decoupling analysis to investigate and quantitatively analyze the [...] Read more.

With a continuously growing share of the world’s overall energy consumption, the transport sector has been acknowledged as one of the most important contributors to global carbon emissions. This paper applies a complete decomposition and decoupling analysis to investigate and quantitatively analyze the main factors influencing the energy-related carbon emissions of the transport (TCE) sector during 1995–2012 in Guangdong, the richest and most populated province in China. Results showed that decoupling level between transport output and TCE was relatively low, especially when compared with year 1995, in which case it remained as expansive coupling. Optimization of tertiary industry structure was the main factor inhibiting TCE increase. However the rapid growth of GDP per capita and population was more powerful at boosting TCE, resulting in elasticity index rising directly. 2005 was a turning point when environmental friendly policies took action, after which decoupling state improved significantly, achieving weak decoupling when comparing adjacent years. By studying TCE and its components, we found that the National 5-Year Plan policy impacts TCE tremendously, which leads to a 5-year periodic pattern of fluctuations. This highlights policy as potentially the most important factor behind Guangdong’s decoupling effort, dwarfing the impact from energy and other inner-drivers. Full article

▼ Show Figures

Figure 1

10477 KiB

Open AccessArticle

Aerodynamic Analysis and Three-Dimensional Redesign of a Multi-Stage Axial Flow Compressor

by Tao Ning^1,2,*, Chun-Wei Gu^1,2, Wei-Dou Ni^1,2, Xiao-Tang Li³ and Tai-Qiu Liu³

¹ Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing 100084, China

² Collaborative Innovation Center of Advanced Aero-Engine, Beijing 100191, China

³ Shenyang Engine Design and Research Institute (SEDRI), Shenyang 110000, China

Energies 2016, 9(4), 296; https://doi.org/10.3390/en9040296 - 16 Apr 2016

Cited by 8 | Viewed by 8952

Abstract

This paper describes the introduction of three-dimension (3-D) blade designs into a 5-stage axial compressor with multi-stage computational fluid dynamic (CFD) methods. Prior to a redesign, a validation study is conducted for the overall performance and flow details based on full-scale test data, [...] Read more.

This paper describes the introduction of three-dimension (3-D) blade designs into a 5-stage axial compressor with multi-stage computational fluid dynamic (CFD) methods. Prior to a redesign, a validation study is conducted for the overall performance and flow details based on full-scale test data, proving that the multi-stage CFD applied is a relatively reliable tool for the analysis of the follow-up redesign. Furthermore, at the near stall point, the aerodynamic analysis demonstrates that significant separation exists in the last stator, leading to the aerodynamic redesign, which is the focus of the last stator. Multi-stage CFD methods are applied throughout the three-dimensional redesign process for the last stator to explore their aerodynamic improvement potential. An unconventional asymmetric bow configuration incorporated with leading edge re-camber and re-solidity is employed to reduce the high loss region dominated by the mainstream. The final redesigned version produces a 13% increase in the stall margin while maintaining the efficiency at the design point. Full article

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

▼ Show Figures

Figure 1

3580 KiB

Open AccessArticle

Multi-Objective Predictive Balancing Control of Battery Packs Based on Predictive Current

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

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

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

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

Energies 2016, 9(4), 298; https://doi.org/10.3390/en9040298 - 19 Apr 2016

Cited by 15 | Viewed by 4636

Abstract

Various balancing topology and control methods have been proposed for the inconsistency problem of battery packs. However, these strategies only focus on a single objective, ignore the mutual interaction among various factors and are only based on the external performance of the battery [...] Read more.

Various balancing topology and control methods have been proposed for the inconsistency problem of battery packs. However, these strategies only focus on a single objective, ignore the mutual interaction among various factors and are only based on the external performance of the battery pack inconsistency, such as voltage balancing and state of charge (SOC) balancing. To solve these problems, multi-objective predictive balancing control (MOPBC) based on predictive current is proposed in this paper, namely, in the driving process of an electric vehicle, using predictive control to predict the battery pack output current the next time. Based on this information, the impact of the battery pack temperature caused by the output current can be obtained. Then, the influence is added to the battery pack balancing control, which makes the present degradation, temperature, and SOC imbalance achieve balance automatically due to the change of the output current the next moment. According to MOPBC, the simulation model of the balancing circuit is built with four cells in Matlab/Simulink. The simulation results show that MOPBC is not only better than the other traditional balancing control strategies but also reduces the energy loss in the balancing process. Full article

▼ Show Figures

Figure 1

7421 KiB

Open AccessArticle

Numerical Study on the Formation of Shear Fracture Network

by Zhaobin Zhang and Xiao Li^*

Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

Energies 2016, 9(4), 299; https://doi.org/10.3390/en9040299 - 20 Apr 2016

Cited by 14 | Viewed by 5631

Abstract

Shear fracture network is important to the hydraulic fracturing treatment of a shale gas reservoir. In this paper, the formation of shear fracture network is investigated by a Displacement Discontinuity Method (DDM) based model. The results show that the sliding of fracture surface [...] Read more.

Shear fracture network is important to the hydraulic fracturing treatment of a shale gas reservoir. In this paper, the formation of shear fracture network is investigated by a Displacement Discontinuity Method (DDM) based model. The results show that the sliding of fracture surface is irreversible but may change significantly after fluid pressure dissipates. The final sliding distance is different for natural and hydraulic fractures. Most of the shear fractures are natural fractures while the newly formed hydraulic fractures tend to be totally closed after pressure dissipates. The effects of in situ stress are investigated. The affected area reaches its maximum value when the maximum principle stress direction is perpendicular to the principal fracture direction. The effects of the injection rate are also investigated. The increasing of the injection rate is helpful in increasing the fracture aperture, but has no effect on the final sliding distance. Moreover, the effects of the injection rate on the affected area depend on the connectivity of natural fractures. The affected area increases with the injection rate when the connectivity is poor but decreases slightly with injection rate when the connectivity is good. Full article

▼ Show Figures

Figure 1

5979 KiB

Open AccessArticle

Preliminary Development of a Free Piston Expander–Linear Generator for Small-Scale Organic Rankine Cycle (ORC) Waste Heat Recovery System

by Gaosheng Li^1,2, Hongguang Zhang^1,2,*, Fubin Yang^1,2, Songsong Song^1,2, Ying Chang^1,2, Fei Yu^1,2, Jingfu Wang^1,2 and Baofeng Yao^1,2

¹ College of Environmental and Energy Engineering, Beijing University of Technology, Pingleyuan No. 100, Beijing 100124, China

² Collaborative Innovation Center of Electric Vehicles in Beijing, Pingleyuan No. 100, Beijing 100124, China

Energies 2016, 9(4), 300; https://doi.org/10.3390/en9040300 - 20 Apr 2016

Cited by 47 | Viewed by 10572

Abstract

A novel free piston expander-linear generator (FPE-LG) integrated unit was proposed to recover waste heat efficiently from vehicle engine. This integrated unit can be used in a small-scale Organic Rankine Cycle (ORC) system and can directly convert the thermodynamic energy of working fluid [...] Read more.

A novel free piston expander-linear generator (FPE-LG) integrated unit was proposed to recover waste heat efficiently from vehicle engine. This integrated unit can be used in a small-scale Organic Rankine Cycle (ORC) system and can directly convert the thermodynamic energy of working fluid into electric energy. The conceptual design of the free piston expander (FPE) was introduced and discussed. A cam plate and the corresponding valve train were used to control the inlet and outlet valve timing of the FPE. The working principle of the FPE-LG was proven to be feasible using an air test rig. The indicated efficiency of the FPE was obtained from the p–V indicator diagram. The dynamic characteristics of the in-cylinder flow field during the intake and exhaust processes of the FPE were analyzed based on Fluent software and 3D numerical simulation models using a computation fluid dynamics method. Results show that the indicated efficiency of the FPE can reach 66.2% and the maximal electric power output of the FPE-LG can reach 22.7 W when the working frequency is 3 Hz and intake pressure is 0.2 MPa. Two large-scale vortices are formed during the intake process because of the non-uniform distribution of velocity and pressure. The vortex flow will convert pressure energy and kinetic energy into thermodynamic energy for the working fluid, which weakens the power capacity of the working fluid. Full article

▼ Show Figures

Graphical abstract

9667 KiB

Open AccessArticle

Code-to-Code Validation and Application of a Dynamic Simulation Tool for the Building Energy Performance Analysis

by Annamaria Buonomano

DII (Department of Industrial Engineering), University of Naples Federico II, P.le Tecchio 80, Naples I-80125, Italy

Energies 2016, 9(4), 301; https://doi.org/10.3390/en9040301 - 21 Apr 2016

Cited by 34 | Viewed by 7187

Abstract

In this paper details about the results of a code-to-code validation procedure of an in-house developed building simulation model, called DETECt, are reported. The tool was developed for research purposes in order to carry out dynamic building energy performance and parametric analyses by [...] Read more.

In this paper details about the results of a code-to-code validation procedure of an in-house developed building simulation model, called DETECt, are reported. The tool was developed for research purposes in order to carry out dynamic building energy performance and parametric analyses by taking into account new building envelope integrated technologies, novel construction materials and innovative energy saving strategies. The reliability and accuracy of DETECt was appropriately tested by means of the standard BESTEST validation procedure. In the paper, details of this validation process are accurately described. A good agreement between the obtained results and all the reference data of the BESTEST qualification cases is achieved. In particular, the obtained results vs. standard BESTEST output are always within the provided ranges of confidence. In addition, several test cases output obtained by DETECt (e.g., dynamic profiles of indoor air and building surfaces temperature and heat fluxes and spatial trends of temperature across walls) are provided. Full article

(This article belongs to the Special Issue Simulation of Polygeneration Systems)

▼ Show Figures

Figure 1

5260 KiB

Open AccessArticle

Power Quality Improvement and LVRT Capability Enhancement of Wind Farms by Means of an Inductive Filtering Method

by Yanjian Peng¹, Yong Li^1,*

, Zhisheng Xu², Ming Wen², Longfu Luo¹, Yijia Cao¹ and Zbigniew Leonowicz³

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

² Hunan Electrical Power Corporation Economical & Technical Research, Changsha 410004, China

³ Department of Electrical Engineering, Wroclaw University of Technology, Wroclaw 50370, Poland

Energies 2016, 9(4), 302; https://doi.org/10.3390/en9040302 - 20 Apr 2016

Cited by 6 | Viewed by 5135

Abstract

Unlike the traditional method for power quality improvement and low-voltage ride through (LVRT) capability enhancement of wind farms, this paper proposes a new wind power integrated system by means of an inductive filtering method, especially if it contains a grid-connected transformer, a static [...] Read more.

Unlike the traditional method for power quality improvement and low-voltage ride through (LVRT) capability enhancement of wind farms, this paper proposes a new wind power integrated system by means of an inductive filtering method, especially if it contains a grid-connected transformer, a static synchronous compensator (STATCOM) and fully-tuned (FT) branches. First, the main circuit topology of the new wind power integrated system is presented. Then, the mathematical model is established to reveal the mechanism of harmonic suppression and the reactive compensation of the proposed wind power integrated system, and then the realization conditions of the inductive filtering method is obtained. Further, the control strategy of STATCOM is introduced. Based on the measured data for a real wind farm, the simulation studies are carried out to illustrate the performance of the proposed new wind power integrated system. The results indicate that the new system can not only enhance the LVRT capability of wind farms, but also prevent harmonic components flowing into the primary (grid) winding of the grid-connected transformer. Moreover, since the new method can compensate for reactive power in a wind farm, the power factor at the grid side can be improved effectively. Full article

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

▼ Show Figures

Figure 1

7714 KiB

Open AccessArticle

Responses of Ecosystem Service to Land Use Change in Qinghai Province

by Ze Han^1,2, Wei Song^1,*

and Xiangzheng Deng^1,3

¹ Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China

² College of Architecture and Urban Planning, Chongqing Jiaotong University, Chongqing 400041, China

³ Center for Chinese Agricultural Policy, Chinese Academy of Sciences, Beijing 100101, China

Energies 2016, 9(4), 303; https://doi.org/10.3390/en9040303 - 21 Apr 2016

Cited by 66 | Viewed by 7050

Abstract

Qinghai Province has a very fragile ecological environment and is an important component of the Qinghai-Tibet Plateau. To understand the disturbance caused by human activities to the local ecological system, it is necessary to evaluate the response of ecological service functions to land [...] Read more.

Qinghai Province has a very fragile ecological environment and is an important component of the Qinghai-Tibet Plateau. To understand the disturbance caused by human activities to the local ecological system, it is necessary to evaluate the response of ecological service functions to land use change in Qinghai Province and to uncover the sensitivity of ecological service functions to land use change. This study uses a proxy-based method and proposes a sensitivity index to describe the degree of ecological service function response to the land use change in Qinghai Province. The findings were as follows. (1) From 1988 to 2008, the area of cultivated land, construction land and water in Qinghai Province increased, and forest land and grassland continuously decreased. The agricultural economy and the development of urbanization are the main driving factors in land use change in this area. Policies and eco-environmental engineering, such as the grain-for-green project, the Three-North shelterbelt project and the natural forest protection project, have certain effects on controlling the expansion of cultivated land. (2) The value of ecosystem services in Qinghai Province was 157.368 billion yuan, 157.149 billion yuan and 157.726 billion yuan in 1988, 2000 and 2008, respectively, decreasing and then increasing again. (3) The average sensitivity index values of ecological services in Qinghai Province for the periods 1988–2000 and 2000–2008 was 0.693 and 1.137, respectively. This means that for every 1% increase in land use change, the ecological service value fluctuated by 0.693% and 1.137% in those periods. Full article

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

▼ Show Figures

Figure 1

9376 KiB

Open AccessArticle

Decreasing NO_x of a Low-Speed Two-Stroke Marine Diesel Engine by Using In-Cylinder Emission Control Measures

by Liyan Feng

, Jiangping Tian, Wuqiang Long^*, Weixin Gong, Baoguo Du, Dan Li and Lei Chen

Institute of Internal Combustion Engine, Dalian University of Technology, Dalian 116024, China

Energies 2016, 9(4), 304; https://doi.org/10.3390/en9040304 - 21 Apr 2016

Cited by 33 | Viewed by 10924

Abstract

The authors applied one-dimensional (1-D) simulation and 3-D Computational Fluid Dynamics (CFD) simulation to evaluate the potential of in-cylinder control methods on a low-speed 2-stroke marine engine to reach the International Maritime Organization (IMO) Tier 3 NO_x emissions standards. Reducing the combustion [...] Read more.

The authors applied one-dimensional (1-D) simulation and 3-D Computational Fluid Dynamics (CFD) simulation to evaluate the potential of in-cylinder control methods on a low-speed 2-stroke marine engine to reach the International Maritime Organization (IMO) Tier 3 NO_x emissions standards. Reducing the combustion temperature is an important in-cylinder measure to decrease NO_x emissions of marine diesel engines. Miller-cycle and Exhaust Gas Recirculation (EGR) are effective methods to reduce the maximum combustion temperature and accordingly decrease NO_x emissions. The authors’ calculation results indicate that with a combination of 2-stage turbocharging, a mild Miller-cycle and 10% EGR rate, the NO_x emissions can be decreased by 48% without the increased Specific Fuel Oil Consumption (SFOC) penalties; with a medium Miller-cycle and 10% EGR, NO_x can be decreased by 56% with a slight increase of SFOC; with a medium Miller-cycle and 20% EGR, NO_x can be decreased by 77% and meet IMO Tier 3 standards, but with the high price of a considerable increase of SFOC. The first two schemes are promising to meet IMO Tier 3 standards with good fuel economy if other techniques are combined. Full article

(This article belongs to the Special Issue Combustion and Propulsion)

▼ Show Figures

Figure 1

1879 KiB

Open AccessArticle

Parametric Analysis of a Rotary Type Liquid Desiccant Air Conditioning System

by M. Mujahid Rafique¹

, Shafiqur Rehman^2,*

, Luai M. Alhems² and Aref Lashin^3,4

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

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

Energies 2016, 9(4), 305; https://doi.org/10.3390/en9040305 - 21 Apr 2016

Cited by 12 | Viewed by 6338

Abstract

Now days, air conditioning systems are a must for almost every commercial and residential building to achieve comfortable indoor conditions. The increasing energy demand, and increasing oil prices and pollution levels raise the need for alternative air conditioning systems which can efficiently utilize [...] Read more.

Now days, air conditioning systems are a must for almost every commercial and residential building to achieve comfortable indoor conditions. The increasing energy demand, and increasing oil prices and pollution levels raise the need for alternative air conditioning systems which can efficiently utilize renewable energy resources. The liquid desiccant-based air conditioning method is pollution free and thermal energy-based cooling techniques can use low grade thermal energy resources like solar energy, waste heat, etc. These systems have an additional advantage of cleaning bacteria and fungi from the air. In this paper, a newly proposed rotary liquid desiccant air conditioning system has been investigated theoretically. Most direct contact liquid desiccant cooling systems have the problem of desiccant carryover which can be eliminated using the proposed system. The effects of various key parameters and climatic conditions on the performance of the system have been evaluated. The results showed that if the key parameters of the system are controlled effectively, the proposed cooling system has the ability to achieve the desired supply air conditions. The system can achieve high coefficient of performance (COP) under different conditions. The dehumidifier has a sensible heat ratio (SHR) in the range of 0.3–0.6 for different design, climatic, and operating conditions. The system can remove latent load efficiently in applications which require good humidity control. Full article

▼ Show Figures

Graphical abstract

5527 KiB

Open AccessArticle

Interaction and Coordination among Nuclear Power Plants, Power Grids and Their Protection Systems

by Guoyang Wu^1,*, Ping Ju¹, Xinli Song², Chenglong Xie³ and Wuzhi Zhong²

¹ School of Energy and Electrical Engineering, Hohai University, Nanjing 210098, China

² China Electric Power Research Institute, Beijing 100192, China

³ China Nuclear Power Operation Technology Co. Ltd., Wuhan 430223, China

Energies 2016, 9(4), 306; https://doi.org/10.3390/en9040306 - 21 Apr 2016

Cited by 14 | Viewed by 7564

Abstract

Nuclear power plants (NPPs) have recently undergone rapid development in China. To improve the performance of both NPPs and grids during adverse conditions, a precise understanding of the coordination between NPPs and grids is required. Therefore, a new mathematical model with reasonable accuracy [...] Read more.

Nuclear power plants (NPPs) have recently undergone rapid development in China. To improve the performance of both NPPs and grids during adverse conditions, a precise understanding of the coordination between NPPs and grids is required. Therefore, a new mathematical model with reasonable accuracy and reduced computational complexity is developed. This model is applicable to the short, mid, and long-term dynamic simulation of large-scale power systems. The effectiveness of the model is verified by using an actual NPP full-scope simulator as a reference. Based on this model, the interaction and coordination between NPPs and grids under the conditions of over-frequency, under-frequency and under-voltage are analyzed, with special stress applied to the effect of protection systems on the safe operation of both NPPs and power grids. Finally, the coordinated control principles and schemes, together with the recommended protection system values, are proposed for both NPPs and grids. These results show that coordination between the protection systems of NPPs and power networks is a crucial factor in ensuring the safe and stable operation of both NPPs and grids. The results can be used as a reference for coordination between NPPs and grids, as well as for parameter optimization of grid-related generator protection of NPPs. Full article

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

▼ Show Figures

Graphical abstract

8931 KiB

Open AccessArticle

An Optimal Integrated Control Scheme for Permanent Magnet Synchronous Generator-Based Wind Turbines under Asymmetrical Grid Fault Conditions

by Dan Wang, Chongru Liu^* and Gengyin Li

State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Changping District, Beijing 102206, China

Energies 2016, 9(4), 307; https://doi.org/10.3390/en9040307 - 22 Apr 2016

Cited by 9 | Viewed by 5812

Abstract

In recent years, the increasing penetration level of wind energy into power systems has brought new issues and challenges. One of the main concerns is the issue of dynamic response capability during outer disturbance conditions, especially the fault-tolerance capability during asymmetrical faults. In [...] Read more.

In recent years, the increasing penetration level of wind energy into power systems has brought new issues and challenges. One of the main concerns is the issue of dynamic response capability during outer disturbance conditions, especially the fault-tolerance capability during asymmetrical faults. In order to improve the fault-tolerance and dynamic response capability under asymmetrical grid fault conditions, an optimal integrated control scheme for the grid-side voltage-source converter (VSC) of direct-driven permanent magnet synchronous generator (PMSG)-based wind turbine systems is proposed in this paper. The optimal control strategy includes a main controller and an additional controller. In the main controller, a double-loop controller based on differential flatness-based theory is designed for grid-side VSC. Two parts are involved in the design process of the flatness-based controller: the reference trajectories generation of flatness output and the implementation of the controller. In the additional control aspect, an auxiliary second harmonic compensation control loop based on an improved calculation method for grid-side instantaneous transmission power is designed by the quasi proportional resonant (Quasi-PR) control principle, which is able to simultaneously restrain the second harmonic components in active power and reactive power injected into the grid without the respective calculation for current control references. Moreover, to reduce the DC-link overvoltage during grid faults, the mathematical model of DC-link voltage is analyzed and a feedforward modified control factor is added to the traditional DC voltage control loop in grid-side VSC. The effectiveness of the optimal control scheme is verified in PSCAD/EMTDC simulation software. Full article

▼ Show Figures

Graphical abstract

Review

Jump to: Editorial, Research

7061 KiB

Open AccessReview

S-Rich CdS_1−yTe_y Thin Films Produced by the Spray Pyrolysis Technique

by Shadia J. Ikhmayies

Faculty of Science, Department of Physics, Al Isra University, Amman 11622, Jordan

Energies 2016, 9(4), 234; https://doi.org/10.3390/en9040234 - 24 Mar 2016

Cited by 5 | Viewed by 5157

Abstract

Understanding the properties of CdSTe ternary alloys is important because they always form at the interface between the CdS window layer and CdTe absorber layer in CdS/CdTe solar cells due to the intermixing. This interdiffusion is necessary because it improves the device performance. [...] Read more.

Understanding the properties of CdSTe ternary alloys is important because they always form at the interface between the CdS window layer and CdTe absorber layer in CdS/CdTe solar cells due to the intermixing. This interdiffusion is necessary because it improves the device performance. Experimental work has been devoted to studying Te rich p-type CdS_xTe_1−x alloys, but there is a lack of studies on S-rich n-type CdS_1−yTe_y solid solutions. In this work, a review of the structure, morphology, and optical properties of the S-rich n-type CdS_1−yTe_y thin films produced by the spray pyrolysis technique on glass substrates is presented. Full article

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

▼ Show Figures

Figure 1

6887 KiB

Open AccessReview

Progress in Heat Pump Air Conditioning Systems for Electric Vehicles—A Review

by Qinghong Peng^1,2 and Qungui Du^1,*

¹ School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510641, China

² Department of Mechanical and Electrical Engineering, Shunde Polytechnic, Foshan 528333, China

Energies 2016, 9(4), 240; https://doi.org/10.3390/en9040240 - 25 Mar 2016

Cited by 80 | Viewed by 24159

Abstract

Electric vehicles have become increasingly popular in recent years due to our limited natural resources. As a result, interest in climate control systems for electric vehicles is rising rapidly. According to a variety of research sources, the heat pump air conditioning system seems [...] Read more.

Electric vehicles have become increasingly popular in recent years due to our limited natural resources. As a result, interest in climate control systems for electric vehicles is rising rapidly. According to a variety of research sources, the heat pump air conditioning system seems to be a potential climate control system for electric vehicles. In this paper, an extensive literature review has been performed on the progress in heat pump air conditioning systems for electric vehicles. First, a review of applications of alternative environmentally friendly refrigerants in electric vehicles is introduced. This is followed by a review of other advanced technologies, such as the inverter technology, innovative components and the system structure of the heat pump air conditioning system for electric vehicles. Lastly, recent developments in multiple source heat pump systems are presented. The use of these advanced technologies can provide not only sufficient refrigerating capacity for the electric vehicle, but also higher climate control system efficiency. We believe that ideal practical air conditioning for electric vehicles can be attained in the near future as the mentioned technical problems are gradually resolved. Full article

▼ Show Figures

Figure 1

1827 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Smart Distribution Systems

by Yazhou Jiang¹

, Chen-Ching Liu^1,2 and Yin Xu^1,*

¹ School of Electrical Engineering and Computer Science, Washington State University, Pullman, WA 99164, USA

² School of Mechanical and Materials Engineering, University College Dublin, Belfield, Dublin 4, Ireland

Energies 2016, 9(4), 297; https://doi.org/10.3390/en9040297 - 19 Apr 2016

Cited by 30 | Viewed by 9798

Abstract

The increasing importance of system reliability and resilience is changing the way distribution systems are planned and operated. To achieve a distribution system self-healing against power outages, emerging technologies and devices, such as remote-controlled switches (RCSs) and smart meters, are being deployed. The [...] Read more.

The increasing importance of system reliability and resilience is changing the way distribution systems are planned and operated. To achieve a distribution system self-healing against power outages, emerging technologies and devices, such as remote-controlled switches (RCSs) and smart meters, are being deployed. The higher level of automation is transforming traditional distribution systems into the smart distribution systems (SDSs) of the future. The availability of data and remote control capability in SDSs provides distribution operators with an opportunity to optimize system operation and control. In this paper, the development of SDSs and resulting benefits of enhanced system capabilities are discussed. A comprehensive survey is conducted on the state-of-the-art applications of RCSs and smart meters in SDSs. Specifically, a new method, called Temporal Causal Diagram (TCD), is used to incorporate outage notifications from smart meters for enhanced outage management. To fully utilize the fast operation of RCSs, the spanning tree search algorithm is used to develop service restoration strategies. Optimal placement of RCSs and the resulting enhancement of system reliability are discussed. Distribution system resilience with respect to extreme events is presented. Test cases are used to demonstrate the benefit of SDSs. Active management of distributed generators (DGs) is introduced. Future research in a smart distribution environment is proposed. Full article

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

▼ Show Figures

Figure 1

Journal Menu

Journal Browser

Energies, Volume 9, Issue 4 (April 2016) – 85 articles

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI