Energies

11 pages, 2967 KiB

Open AccessArticle

Cathode Assessment for Maximizing Current Generation in Microbial Fuel Cells Utilizing Bioethanol Effluent as Substrate

by Guotao Sun, Anders Thygesen^*

and Anne S. Meyer

Center for BioProcess Engineering, Department of Chemical and Biochemical Engineering, Technical University of Denmark, Søltofts Plads 229, DK-2800 Kgs. Lyngby, Denmark

Energies 2016, 9(5), 388; https://doi.org/10.3390/en9050388 - 20 May 2016

Cited by 5 | Viewed by 6562

Abstract

Implementation of microbial fuel cells (MFCs) for electricity production requires effective current generation from waste products via robust cathode reduction. Three cathode types using dissolved oxygen cathodes (DOCs), ferricyanide cathodes (FeCs) and air cathodes (AiCs) were therefore assessed using bioethanol effluent, containing 20.5 [...] Read more.

Implementation of microbial fuel cells (MFCs) for electricity production requires effective current generation from waste products via robust cathode reduction. Three cathode types using dissolved oxygen cathodes (DOCs), ferricyanide cathodes (FeCs) and air cathodes (AiCs) were therefore assessed using bioethanol effluent, containing 20.5 g/L xylose, 1.8 g/L arabinose and 2.5 g/L propionic acid. In each set-up the anode and cathode had an electrode surface area of 88 cm², which was used for calculation of the current density. Electricity generation was evaluated by quantifying current responses to substrate loading rates and external resistance. At the lowest external resistance of 27 Ω and highest substrate loading rate of 2 g chemical oxygen demand (COD) per L·day, FeC-MFC generated highest average current density (1630 mA/m²) followed by AiC-MFC (802 mA/m²) and DOC-MFC (184 mA/m²). Electrochemical impedance spectroscopy (EIS) was used to determine the impedance of the cathodes. It was thereby confirmed that the FeC-MFC produced the highest current density with the lowest internal resistance for the cathode. However, in a setup using bioethanol effluent, the AiC-MFC was concluded to be the most sustainable option since it does not require ferricyanide. The data offer a new add-on option to the straw biorefinery by using bioethanol effluent for microbial electricity production. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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18 pages, 4033 KiB

Open AccessArticle

Online Diagnosis for the Capacity Fade Fault of a Parallel-Connected Lithium Ion Battery Group

by Hua Zhang^1,2, Lei Pei¹, Jinlei Sun¹, Kai Song¹, Rengui Lu¹, Yongping Zhao¹, Chunbo Zhu^1,* and Tiansi Wang¹

¹ School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China

² College of Electronic Science, Northeast Petroleum University, Daqing 163318, China

Energies 2016, 9(5), 387; https://doi.org/10.3390/en9050387 - 20 May 2016

Cited by 31 | Viewed by 7510

Abstract

In a parallel-connected battery group (PCBG), capacity degradation is usually caused by the inconsistency between a faulty cell and other normal cells, and the inconsistency occurs due to two potential causes: an aging inconsistency fault or a loose contacting fault. In this paper, [...] Read more.

In a parallel-connected battery group (PCBG), capacity degradation is usually caused by the inconsistency between a faulty cell and other normal cells, and the inconsistency occurs due to two potential causes: an aging inconsistency fault or a loose contacting fault. In this paper, a novel method is proposed to perform online and real-time capacity fault diagnosis for PCBGs. Firstly, based on the analysis of parameter variation characteristics of a PCBG with different fault causes, it is found that PCBG resistance can be taken as an indicator for both seeking the faulty PCBG and distinguishing the fault causes. On one hand, the faulty PCBG can be identified by comparing the PCBG resistance among PCBGs; on the other hand, two fault causes can be distinguished by comparing the variance of the PCBG resistances. Furthermore, for online applications, a novel recursive-least-squares algorithm with restricted memory and constraint (RLSRMC), in which the constraint is added to eliminate the “imaginary number” phenomena of parameters, is developed and used in PCBG resistance identification. Lastly, fault simulation and validation results demonstrate that the proposed methods have good accuracy and reliability. Full article

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

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24 pages, 13674 KiB

Open AccessArticle

Modelling, Testing and Analysis of a Regenerative Hydraulic Shock Absorber System

by Ruichen Wang^*, Fengshou Gu

, Robert Cattley and Andrew D. Ball

School of Computing and Engineering, University of Huddersfield, Queensgate, Huddersfield HD1 3DH, UK

Energies 2016, 9(5), 386; https://doi.org/10.3390/en9050386 - 19 May 2016

Cited by 48 | Viewed by 13026

Abstract

To improve vehicle fuel economy whilst enhancing road handling and ride comfort, power generating suspension systems have recently attracted increased attention in automotive engineering. This paper presents our study of a regenerative hydraulic shock absorber system which converts the oscillatory motion of a [...] Read more.

To improve vehicle fuel economy whilst enhancing road handling and ride comfort, power generating suspension systems have recently attracted increased attention in automotive engineering. This paper presents our study of a regenerative hydraulic shock absorber system which converts the oscillatory motion of a vehicle suspension into unidirectional rotary motion of a generator. Firstly a model which takes into account the influences of the dynamics of hydraulic flow, rotational motion and power regeneration is developed. Thereafter the model parameters of fluid bulk modulus, motor efficiencies, viscous friction torque, and voltage and torque constant coefficients are determined based on modelling and experimental studies of a prototype system. The model is then validated under different input excitations and load resistances, obtaining results which show good agreement between prediction and measurement. In particular, the system using piston-rod dimensions of 50–30 mm achieves recoverable power of 260 W with an efficiency of around 40% under sinusoidal excitation of 1 Hz frequency and 25 mm amplitude when the accumulator capacity is set to 0.32 L with the load resistance 20 Ω. It is then shown that the appropriate damping characteristics required from a shock absorber in a heavy-haulage vehicle can be met by using variable load resistances and accumulator capacities in a device akin to the prototype. The validated model paves the way for further system optimisation towards maximising the performance of regeneration, ride comfort and handling. Full article

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18 pages, 3033 KiB

Open AccessArticle

A Study on Price-Based Charging Strategy for Electric Vehicles on Expressways

by Lixing Chen^*, Zhong Chen, Xueliang Huang and Long Jin

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

Energies 2016, 9(5), 385; https://doi.org/10.3390/en9050385 - 19 May 2016

Cited by 20 | Viewed by 6115

Abstract

With the large-scale adoption of electric vehicles (EVs) on expressways, the exploration of a guiding-based charging method to effectively adjust interactions between EVs and the fast charging stations (CSs) is urgently needed. This paper proposes a status-of-use (SOU) price-based charging strategy that can [...] Read more.

With the large-scale adoption of electric vehicles (EVs) on expressways, the exploration of a guiding-based charging method to effectively adjust interactions between EVs and the fast charging stations (CSs) is urgently needed. This paper proposes a status-of-use (SOU) price-based charging strategy that can motivate users to charge in advance. A queuing model for a CS cluster was established to verify the effectiveness of the strategy, and then a simulation of traveling and charging conditions of 12,000 pure EVs on the road network from 0:00 to 24:00 was performed according to the related data and using the Monte Carlo method, the Floyd-Warshall algorithm, and the queuing algorithm proposed in this paper. Compared to unordered charging (UC), SOU price-based charging can not only reduce the charging cost and waiting time for users, but also increase the utilization ratio of charging facilities in a CS cluster and thus lower their influence on the power grid and expressway traffic. SOU price-based charging can effectively adjust interactions between EVs and CSs. Full article

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

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22 pages, 3279 KiB

Open AccessEditor’s ChoiceReview

Cobalt-Based Electrolytes for Dye-Sensitized Solar Cells: Recent Advances towards Stable Devices

by Federico Bella^1,*

, Simone Galliano², Claudio Gerbaldi¹ and Guido Viscardi²

¹ GAME Lab, CHENERGY Group, Department of Applied Science and Technology—DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy

² Department of Chemistry and NIS Interdepartmental Centre, Università degli Studi di Torino, Via Pietro Giuria 7, 10125 Torino, Italy

Energies 2016, 9(5), 384; https://doi.org/10.3390/en9050384 - 19 May 2016

Cited by 104 | Viewed by 12711

Abstract

Redox mediators based on cobalt complexes allowed dye-sensitized solar cells (DSCs) to achieve efficiencies exceeding 14%, thus challenging the emerging class of perovskite solar cells. Unfortunately, cobalt-based electrolytes demonstrate much lower long-term stability trends if compared to the traditional iodide/triiodide redox couple. In [...] Read more.

Redox mediators based on cobalt complexes allowed dye-sensitized solar cells (DSCs) to achieve efficiencies exceeding 14%, thus challenging the emerging class of perovskite solar cells. Unfortunately, cobalt-based electrolytes demonstrate much lower long-term stability trends if compared to the traditional iodide/triiodide redox couple. In view of the large-scale commercialization of cobalt-based DSCs, the scientific community has recently proposed various approaches and materials to increase the stability of these devices, which comprise gelling agents, crosslinked polymeric matrices and mixtures of solvents (including water). This review summarizes the most significant advances recently focused towards this direction, also suggesting some intriguing way to fabricate third-generation cobalt-based photoelectrochemical devices stable over time. Full article

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

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15 pages, 3719 KiB

Open AccessArticle

An Intelligent Sensor for the Ultra-High-Frequency Partial Discharge Online Monitoring of Power Transformers

by Jian Li¹, Xudong Li¹, Lin Du^1,*, Min Cao² and Guochao Qian²

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

² Yunnan Electric Power Research Institute, Kunming 650217, China

Energies 2016, 9(5), 383; https://doi.org/10.3390/en9050383 - 19 May 2016

Cited by 23 | Viewed by 7926

Abstract

Ultra-high-frequency (UHF) partial discharge (PD) online monitoring is an effective way to inspect potential faults and insulation defects in power transformers. The construction of UHF PD online monitoring system is a challenge because of the high-frequency and wide-frequency band of the UHF PD [...] Read more.

Ultra-high-frequency (UHF) partial discharge (PD) online monitoring is an effective way to inspect potential faults and insulation defects in power transformers. The construction of UHF PD online monitoring system is a challenge because of the high-frequency and wide-frequency band of the UHF PD signal. This paper presents a novel, intelligent sensor for UHF PD online monitoring based on a new method, namely a level scanning method. The intelligent sensor can directly acquire the statistical characteristic quantities and is characterized by low cost, few data to output and transmit, Ethernet functionality, and small size for easy installation. The prototype of an intelligent sensor was made. Actual UHF PD experiments with three typical artificial defect models of power transformers were carried out in a laboratory, and the waveform recording method and intelligent sensor proposed were simultaneously used for UHF PD measurement for comparison. The results show that the proposed intelligent sensor is qualified for the UHF PD online monitoring of power transformers. Additionally, three methods to improve the performance of intelligent sensors were proposed according to the principle of the level scanning method. Full article

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

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9 pages, 6880 KiB

Open AccessArticle

Comparative Study of the Subsurface Thermal Structure in Northern Honshu, Japan, Based on Normalized Temperature Data and Solute Geothermometers

by Yota Suzuki^1,*, Seiichiro Ioka² and Hirofumi Muraoka²

¹ Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo-cho, Hirosaki, Aomori 036-8561, Japan

² North Japan Research Institute for Sustainable Energy, Hirosaki University, 2-1-3 Matsubara, Aomori 030-0813, Japan

Energies 2016, 9(5), 382; https://doi.org/10.3390/en9050382 - 19 May 2016

Cited by 2 | Viewed by 4926

Abstract

To promote geothermal development in Aomori Prefecture, Japan, this study compiled a database of the geothermal resources of the prefecture, which included chemical data for 786 hot springs, temperature data for 26 natural springs, and subsurface temperature data for 35 wells. A map [...] Read more.

To promote geothermal development in Aomori Prefecture, Japan, this study compiled a database of the geothermal resources of the prefecture, which included chemical data for 786 hot springs, temperature data for 26 natural springs, and subsurface temperature data for 35 wells. A map of the activity index distribution for the entire prefecture was also developed using the Aomori Prefecture Geothermal Resource database, and its efficiency was discussed by comparison with the distribution of Quaternary volcanoes and the temperature distribution map calculated using quartz and Na-K solute geothermometers. The activity index distribution map for the entire prefecture showed a good fit with both the distribution map of a region with a sharp eastern edge of low-velocity zones in the mantle wedge and the volcanic front, as well as the temperature distribution map calculated using the quartz and Na-K geothermometers. This reflected the effectiveness of the developed map, which indicated the Hakkoda-san and Hiuchi-dake areas as promising for geothermal development. Given that the activity index distribution map is easy to use, it could become a method of assessment, in conjunction with temperature distribution maps calculated using solute geothermometers, for detecting promising areas in the early stages of geothermal exploration. Full article

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24 pages, 923 KiB

Open AccessArticle

An Event-Triggered Online Energy Management Algorithm of Smart Home: Lyapunov Optimization Approach

by Wei Fan, Nian Liu^*

and Jianhua Zhang

School of Electrical and Electronic Engineering, North China Electric Power University, Beijing 102206, China

Energies 2016, 9(5), 381; https://doi.org/10.3390/en9050381 - 19 May 2016

Cited by 39 | Viewed by 8337

Abstract

As an important component of the smart grid on the user side, a home energy management system is the core of optimal operation for a smart home. In this paper, the energy scheduling problem for a household equipped with photovoltaic devices was investigated. [...] Read more.

As an important component of the smart grid on the user side, a home energy management system is the core of optimal operation for a smart home. In this paper, the energy scheduling problem for a household equipped with photovoltaic devices was investigated. An online energy management algorithm based on event triggering was proposed. The Lyapunov optimization method was adopted to schedule controllable load in the household. Without forecasting related variables, real-time decisions were made based only on the current information. Energy could be rapidly regulated under the fluctuation of distributed generation, electricity demand and market price. The event-triggering mechanism was adopted to trigger the execution of the online algorithm, so as to cut down the execution frequency and unnecessary calculation. A comprehensive result obtained from simulation shows that the proposed algorithm could effectively decrease the electricity bills of users. Moreover, the required computational resource is small, which contributes to the low-cost energy management of a smart home. Full article

(This article belongs to the Special Issue Smart Home Energy Management)

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23 pages, 10779 KiB

Open AccessArticle

Analysis and Minimization of Output Current Ripple for Discontinuous Pulse-Width Modulation Techniques in Three-Phase Inverters

by Gabriele Grandi^1,*

, Jelena Loncarski² and Milan Srndovic¹

¹ Department of Electrical, Electronic, and Information Engineering, University of Bologna, Viale Risorgimento 2, Bologna 40136, Italy

² Department of Engineering Sciences, Ångström Laboratory, Uppsala University, Lägerhyddsvägen 1, Box 534, Uppsala S-751 21, Sweden

Energies 2016, 9(5), 380; https://doi.org/10.3390/en9050380 - 19 May 2016

Cited by 5 | Viewed by 9927

Abstract

This paper gives the complete analysis of the output current ripple in three-phase voltage source inverters considering the different discontinuous pulse-width modulation (DPWM) strategies. In particular, peak-to-peak current ripple amplitude is analytically evaluated over the fundamental period and compared among the most used [...] Read more.

This paper gives the complete analysis of the output current ripple in three-phase voltage source inverters considering the different discontinuous pulse-width modulation (DPWM) strategies. In particular, peak-to-peak current ripple amplitude is analytically evaluated over the fundamental period and compared among the most used DPWMs, including positive and negative clamped (DPWM+ and DPWM−), and the four possible combinations between them, usually named as DPWM0, DPWM1, DPWM2, and DPWM3. The maximum and the average values of peak-to-peak current ripple are estimated, and a simple method to correlate the ripple envelope with the ripple rms is proposed and verified. Furthermore, all the results obtained by DPWMs are compared to the centered pulse-width modulation (CPWM, equivalent to the space vector modulation) to identify the optimal pulse-width modulation (PWM) strategy as a function of the modulation index, taking into account the different average switching frequency. In this way, the PWM technique providing for the minimum output current ripple is identified over the whole modulation range. The analytical developments and the main results are experimentally verified by current ripple measurements with a three-phase PWM inverter prototype supplying an induction motor load. Full article

(This article belongs to the Special Issue Power Electronics Optimal Design and Control)

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18 pages, 3491 KiB

Open AccessArticle

Adaptive Protection Scheme for a Distribution System Considering Grid-Connected and Islanded Modes of Operation

by Yavuz Ates¹, Ali Rifat Boynuegri¹, Mehmet Uzunoglu^1,*, Abdullah Nadar², Recep Yumurtacı¹, Ozan Erdinc^1,3, Nikolaos G. Paterakis⁴ and João P. S. Catalão^3,5,6

¹ Department of Electrical Engineering, Faculty of Electric-Electronics, Yildiz Technical University Davutpasa Campus, Esenler, Istanbul 34220, Turkey

² Marmara Research Center, The Scientific and Technological Research Council of Turkey, Energy Institute, Ankara Branch 06800, Turkey

³ Instituto de Engenharia de Sistemas e Computadores - Investigação e Desenvolvimento (INESC-ID), Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais, 1, Lisbon 1049-001, Portugal

⁴ Department of Electrical Engineering, Eindhoven University of Technology (TU/e), 5600 MB Eindhoven, The Netherlands

⁵ Instituto de Engenharia de Sistemas e Computadores - Tecnologia e Ciência (INESC-TEC) and Faculty of Engineering of University of Porto, R. Dr. Roberto Frias, Porto 4200-465, Portugal

⁶ The Centre for Mechanical and Aerospace Science and Technologies (C-MAST), University of Beira Interior, R. Fonte do Lameiro, Covilhã 6201-001, Portugal

Energies 2016, 9(5), 378; https://doi.org/10.3390/en9050378 - 18 May 2016

Cited by 47 | Viewed by 11142

Abstract

The renewable energy-based distributed generation (DG) implementation in power systems has been an active research area during the last few decades due to several environmental, economic and political factors. Although the integration of DG offers many advantages, several concerns, including protection schemes in [...] Read more.

The renewable energy-based distributed generation (DG) implementation in power systems has been an active research area during the last few decades due to several environmental, economic and political factors. Although the integration of DG offers many advantages, several concerns, including protection schemes in systems with the possibility of bi-directional power flow, are raised. Thus, new protection schemes are strongly required in power systems with a significant presence of DG. In this study, an adaptive protection strategy for a distribution system with DG integration is proposed. The proposed strategy considers both grid-connected and islanded operating modes, while the adaptive operation of the protection is dynamically realized considering the availability of DG power production (related to faults or meteorological conditions) in each time step. Besides, the modular structure and fast response of the proposed strategy is validated via simulations conducted on the IEEE 13-node test system. Full article

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

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17 pages, 8631 KiB

Open AccessArticle

A Novel Single Winding Structure and Closed Loop Control of the Suspension Force Vector of Bearingless Permanent Magnet Synchronous Motors

by Huangqiu Zhu, Jianfei Yuan^* and Jintao Jv

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

Energies 2016, 9(5), 377; https://doi.org/10.3390/en9050377 - 18 May 2016

Cited by 5 | Viewed by 5450

Abstract

At present, because of their advantages of simple structure, low cost, low power consumption and high efficiency, single winding bearingless permanent magnet synchronous motors (SBPMSMs) have become one of the research hotspots in the bearingless technology field. However, a high motional-electromotive force (EMF) [...] Read more.

At present, because of their advantages of simple structure, low cost, low power consumption and high efficiency, single winding bearingless permanent magnet synchronous motors (SBPMSMs) have become one of the research hotspots in the bearingless technology field. However, a high motional-electromotive force (EMF) is generated by rotor rotation in the single winding, which already has side-effects on the normal suspension force current, and the suspension force response can be delayed. Because the method of double torque current inverse injection in the symmetrical winding allows the motional-EMFs of the corresponding phase windings to offset each other in the opposite direction, with no adverse effects on original performance, a T-shaped single winding configuration is proposed to realize precisely that effect. In this paper, the analytical expressions of the radial suspension force and torque are deduced and the motional-EMF and performance are analyzed by finite element method using the Ansys-Maxwell software. In addition, a suspension force vector closed loop control strategy is proposed to improve the suspension performance. The complete control strategy of torque and suspension force is designed based on the above motor winding configuration. Finite element analysis (FEA) is used to verify the T-shaped winding structure. The control strategy is demonstrated by software (MATLAB) simulation and an experimental prototype. These results show that the winding structure and the control strategy can achieve the desired effect, improving the radial suspension force. Full article

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11 pages, 3019 KiB

Open AccessArticle

Fabrication and Characterization of CH₃NH₃PbI_3−x−yBr_xCl_y Perovskite Solar Cells

by Atsushi Suzuki^*

, Hiroshi Okada and Takeo Oku

Department of Materials Science, the University of Shiga Prefecture, 2500 Hassaka, Hikone, Shiga 522-8533, Japan

Energies 2016, 9(5), 376; https://doi.org/10.3390/en9050376 - 17 May 2016

Cited by 29 | Viewed by 12496

Abstract

Fabrication and characterization of CH₃NH₃PbI_3−x−yBr_xCl_y perovskite solar cells using mesoporous TiO₂ as electron transporting layer and 2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene as a hole-transporting layer (HTL) were performed. The purpose of the [...] Read more.

Fabrication and characterization of CH₃NH₃PbI_3−x−yBr_xCl_y perovskite solar cells using mesoporous TiO₂ as electron transporting layer and 2,2′,7,7′-tetrakis-(N,N-di-4-methoxyphenylamino)-9,9′-spirobifluorene as a hole-transporting layer (HTL) were performed. The purpose of the present study is to investigate role of halogen doping using iodine (I), bromine (Br) and chlorine (Cl) compounds as dopant on the photovoltaic performance and microstructures of CH₃NH₃PbI_3−x−yBr_xCl_y perovskite solar cells. The X-ray diffraction identified a slight decrease of crystal spacing in the perovskite crystal structure doped with a small amount of I, Br, and Cl in the perovskite compounds. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) showed the perovskite crystal behavior depended on molar ratio of halogen of Pb, I, Br and Cl. Incorporation of the halogen doping into the perovskite crystal structure improved photo generation, carrier diffusion without carrier recombination in the perovskite layer and optimization of electronic structure related with the photovoltaic parameters of open-circuit voltage, short-circuit current density and conversion efficiency. The energy diagram and photovoltaic mechanisms of the perovskite solar cells were discussed in the context of the experimental results. Full article

(This article belongs to the Special Issue Nano-Structured Solar Cells)

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35 pages, 2051 KiB

Open AccessReview

Telecommunication Technologies for Smart Grid Projects with Focus on Smart Metering Applications

by Nikoleta Andreadou^*, Miguel Olariaga Guardiola and Gianluca Fulli

Energy Security, Systems and Markets Unit, Institute of Energy and Transport, Joint Research Centre, Ispra 21027, Italy

Energies 2016, 9(5), 375; https://doi.org/10.3390/en9050375 - 17 May 2016

Cited by 102 | Viewed by 17502

Abstract

This paper provides a study of the smart grid projects realised in Europe and presents their technological solutions with a focus on smart metering Low Voltage (LV) applications. Special attention is given to the telecommunications technologies used. For this purpose, we present the [...] Read more.

This paper provides a study of the smart grid projects realised in Europe and presents their technological solutions with a focus on smart metering Low Voltage (LV) applications. Special attention is given to the telecommunications technologies used. For this purpose, we present the telecommunication technologies chosen by several European utilities for the accomplishment of their smart meter national roll-outs. Further on, a study is performed based on the European Smart Grid Projects, highlighting their technological options. The range of the projects analysed covers the ones including smart metering implementation as well as those in which smart metering applications play a significant role in the overall project success. The survey reveals that various topics are directly or indirectly linked to smart metering applications, like smart home/building, energy management, grid monitoring and integration of Renewable Energy Sources (RES). Therefore, the technological options that lie behind such projects are pointed out. For reasons of completeness, we also present the main characteristics of the telecommunication technologies that are found to be used in practice for the LV grid. Full article

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14 pages, 651 KiB

Open AccessArticle

Chemical Analysis of Different Parts of Date Palm (Phoenix dactylifera L.) Using Ultimate, Proximate and Thermo-Gravimetric Techniques for Energy Production

by Ramadan A. Nasser^1,2,*, Mohamed Z. M. Salem^2,*

, Salim Hiziroglu³, Hamad A. Al-Mefarrej¹, Ahmed S. Mohareb^2,4, Manawwer Alam⁵ and Ibrahim M. Aref¹

¹ Plant Production Department, Food and Agricultural Sciences College, King Saud University, Riyadh 11451, Saudi Arabia

² Forestry and Wood Technology Department, Faculty of Agriculture (El-Shatby), Alexandria University, Alexandria 2154, Egypt

³ Department of Natural Resource Ecology and Management, Oklahoma State University, Stillwater, OK 74078, USA

⁴ College of Science, Dammam University, Dammam 31433, Saudi Arabia

⁵ Research Center, College of Science, King Saud University, Riyadh 11451, Saudi Arabia

Energies 2016, 9(5), 374; https://doi.org/10.3390/en9050374 - 16 May 2016

Cited by 141 | Viewed by 10258

Abstract

The objective of the study was to analyze chemical structure of date palm (Phoenix dactylifera L.) by employing ultimate, proximate and thermo-gravimetric techniques. Samples from different anatomical parts of date palm, namely trunk, frond base, frond midrib, leaflets, coir, fruit stem, date [...] Read more.

The objective of the study was to analyze chemical structure of date palm (Phoenix dactylifera L.) by employing ultimate, proximate and thermo-gravimetric techniques. Samples from different anatomical parts of date palm, namely trunk, frond base, frond midrib, leaflets, coir, fruit stem, date stone, and fruit empty bunches were considered for the experiments. Based on the findings in this work palm leaflet samples gave the highest amount of extractives content (32.9%), followed by date palm stone specimens with 31.5%. Cellulose content values of 32.8% and 47.5% were obtained for date palm stone and palm coir samples, respectively. Overall the hemicellulose contents of all samples were relatively similar to those of typical wood or non-wood lignocellulosic materials with the two exceptions of palm coir and palm leaflets. Both palm coir and palm leaflet specimens had 12.6% and 16.1% hemicellulose content. Volatile matter values of 74.3% and 87.5% were determined for leaflets and fruit empty bunch samples. The ash content of the samples ranged from 1.4% for date stone to 15.2% for palm leaflet samples. The thermal decomposition was completed below a temperature of 500 °C with an exception of those samples taken from palm leaflets. Taken together the data indicate that date palm stone and palm coir revealed could be more viable for renewable energy production than the other specimens considered in this work. Full article

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32 pages, 8216 KiB

Open AccessEditor’s ChoiceReview

Nanostructured p-Type Semiconductor Electrodes and Photoelectrochemistry of Their Reduction Processes

by Matteo Bonomo

and Danilo Dini^*

Department of Chemistry, University of Rome “La Sapienza”, 00139 Rome, Italy

Energies 2016, 9(5), 373; https://doi.org/10.3390/en9050373 - 16 May 2016

Cited by 51 | Viewed by 15880

Abstract

This review reports the properties of p-type semiconductors with nanostructured features employed as photocathodes in photoelectrochemical cells (PECs). Light absorption is crucial for the activation of the reduction processes occurring at the p-type electrode either in the pristine or in a [...] Read more.

This review reports the properties of p-type semiconductors with nanostructured features employed as photocathodes in photoelectrochemical cells (PECs). Light absorption is crucial for the activation of the reduction processes occurring at the p-type electrode either in the pristine or in a modified/sensitized state. Beside thermodynamics, the kinetics of the electron transfer (ET) process from photocathode to a redox shuttle in the oxidized form are also crucial since the flow of electrons will take place correctly if the ET rate will overcome that one of recombination and trapping events which impede the charge separation produced by the absorption of light. Depending on the nature of the chromophore, i.e., if the semiconductor itself or the chemisorbed dye-sensitizer, different energy levels will be involved in the cathodic ET process. An analysis of the general properties and requirements of electrodic materials of p-type for being efficient photoelectrocatalysts of reduction processes in dye-sensitized solar cells (DSC) will be given. The working principle of p-type DSCs will be described and extended to other p-type PECs conceived and developed for the conversion of the solar radiation into chemical products of energetic/chemical interest like non fossil fuels or derivatives of carbon dioxide. Full article

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

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14 pages, 5693 KiB

Open AccessArticle

Black Start Strategy for PV-ESS Multi-Microgrids with Three-Phase/Single-Phase Architecture

by Zhirong Xu^1,2, Ping Yang^1,2,3, Zhiji Zeng^1,*, Jiajun Peng¹ and Zhuoli Zhao¹

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

² Guangdong Key Laboratory of Clean Energy Technology, Guangzhou 511458, China

³ National-Local Joint Engineering Laboratory for Wind Power Control and Integration Technology, South China University of Technology, Guangzhou 511458, China

Energies 2016, 9(5), 372; https://doi.org/10.3390/en9050372 - 16 May 2016

Cited by 23 | Viewed by 8031

Abstract

With the rapid development of microgrids (MGs) in recent years, it is anticipated that combinations of multiple microgrids—multi-microgrids (MMGs)—will gradually become a new form of power grid. A safe and efficient black start strategy for MMGs is in urgent demand because of their [...] Read more.

With the rapid development of microgrids (MGs) in recent years, it is anticipated that combinations of multiple microgrids—multi-microgrids (MMGs)—will gradually become a new form of power grid. A safe and efficient black start strategy for MMGs is in urgent demand because of their complicated structure and control systems. In this paper, first, we analyze the topology and control system of residential-type MMGs with three-phase/single-phase (TP/SP) architecture. Second, a black start strategy based on a hierarchical control scheme is presented, including the selection strategy for the main power supply and master microgrid, the stand-alone operation strategy, and the grid-connected operation strategy. After the selection of the main power supplies, the master MG is determined. Hereby, all sub-microgrids (SMGs) execute the stand-alone algorithm. When the synchronous connection condition is satisfied, the slave SMGs connect to the master MG who provides the voltage and frequency support. Meanwhile, the control algorithm transfers to the grid-connected algorithm, with the grid dispatching value set to zero. Finally, experimental results from the MMG experimental setup in the Clean Energy Technology Laboratory (CETLAB) are presented to verify the effectiveness and feasibility of the proposed black start strategy. Full article

(This article belongs to the Special Issue Microgrids 2016)

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18 pages, 11952 KiB

Open AccessArticle

Experimental Attempts to Investigate the Influence of Petrographic Properties on Drying Characteristics of Lignite in Superheated Steam Atmosphere

by Anna Sciazko¹, Yosuke Komatsu^2,3,*, Marcin Zakrzewski¹, Taro Akiyama³, Akira Hashimoto³, Naoki Shikazono³, Shozo Kaneko³, Shinji Kimijima^3,4, Janusz S. Szmyd¹

and Yoshinori Kobayashi³

¹ AGH University of Science and Technology, Department of Fundamental Research in Energy Engineering, Krakow 30-059, Poland

² Shibaura Institute of Technology, Division of Regional Environment Systems, Saitama 337-8570, Japan

³ The University of Tokyo, Institute of Industrial Science, Tokyo 153-8505, Japan

⁴ Shibaura Institute of Technology, Department of Machinery and Control Systems, Saitama 337-8570, Japan

Energies 2016, 9(5), 371; https://doi.org/10.3390/en9050371 - 16 May 2016

Cited by 7 | Viewed by 5548

Abstract

A superheated steam fluidized bed dryer (SSFBD) in a self-heat recuperative configuration has a great potential of improving thermal efficiency of a lignite-fired power plant by recovering both of latent heat of vaporization of water kept in the fuel and part of sensible [...] Read more.

A superheated steam fluidized bed dryer (SSFBD) in a self-heat recuperative configuration has a great potential of improving thermal efficiency of a lignite-fired power plant by recovering both of latent heat of vaporization of water kept in the fuel and part of sensible heat during the fuel processing. However, the optimal design of the dryer requires the fundamental knowledge of drying characteristics in respect to the individual properties of the utilized fuel. Experimental investigation to determine the correlation between a specific coal properties originated from geological background and its drying characteristics is thus the major concern in this paper. The investigated lignite is a representative of Turoszow deposit in Poland. Experimental attempts unveiling drying kinetics were carried out for 5 mm and 10 mm diameter spherical samples in the superheated steam atmosphere in the temperature range of 110 °C–170 °C. Simultaneous and continuous measurements of changes in weight, surface and interior temperatures and appearance on each tested sample were carried out for describing drying behavior. Analytical investigation was applied to explain the drying characteristics, which are strongly affected by the individual properties of coal and the inherent ash composition. Full article

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

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16 pages, 2536 KiB

Open AccessArticle

A Multi-Period Framework for Coordinated Dispatch of Plug-in Electric Vehicles

by Yinuo Huang¹, Chuangxin Guo^1,*, Yi Ding¹, Licheng Wang², Bingquan Zhu³ and Lizhong Xu³

¹ College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China

² School of Information Technology and Electrical Engineering, The University of Queensland, Brisbane 4067, Australia

³ State Grid Zhejiang Electric Power Company, Hangzhou 310007, China

Energies 2016, 9(5), 370; https://doi.org/10.3390/en9050370 - 16 May 2016

Cited by 9 | Viewed by 5023

Abstract

Coordinated dispatch of plug-in electric vehicles (PEVs) with renewable energies has been proposed in recent years. However, it is difficult to achieve effective PEV dispatch with a win-win result, which not only optimizes power system operation, but also satisfies the requirements of PEV [...] Read more.

Coordinated dispatch of plug-in electric vehicles (PEVs) with renewable energies has been proposed in recent years. However, it is difficult to achieve effective PEV dispatch with a win-win result, which not only optimizes power system operation, but also satisfies the requirements of PEV owners. In this paper, a multi-period PEV dispatch framework, combining day-ahead dispatch with real-time dispatch, is proposed. On the one hand, the day-ahead dispatch is used to make full use of wind power and minimize the fluctuation of total power in the distribution system, and schedule the charging/discharging power of PEV stations for each period. On the other hand, the real-time dispatch arranges individual PEVs to meet the charging/discharging power demands of PEV stations given by the day-ahead dispatch. To reduce the dimensions of the resulting large-scale, non-convex problem, PEVs are clustered according to their travel information. An interval optimization model is introduced to obtain the problem solution of the day-ahead dispatch. For the real-time dispatch, a priority-ordering method is developed to satisfy the requirements of PEV owners with fast response. Numerical studies demonstrate the effectiveness of the presented framework. Full article

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

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16 pages, 8100 KiB

Open AccessArticle

Effects of Different Factors on Electrical Equipment UV Corona Discharge Detection

by Zhenyu Li^1,*, Licheng Li^1,2, Xingliang Jiang¹, Jianlin Hu¹, Zhijin Zhang¹ and Wei Zhang¹

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

² School of Electric Power, South China University of Technology, Guangdong 5010640, China

Energies 2016, 9(5), 369; https://doi.org/10.3390/en9050369 - 16 May 2016

Cited by 30 | Viewed by 6848

Abstract

As a non-contact discharge detection method, ultraviolet (UV) imaging can rapidly, directly, and securely detect corona discharges. Therefore, UV imaging has been widely applied to power systems. To study the influences of different factors on UV corona discharge detection, two typical types of [...] Read more.

As a non-contact discharge detection method, ultraviolet (UV) imaging can rapidly, directly, and securely detect corona discharges. Therefore, UV imaging has been widely applied to power systems. To study the influences of different factors on UV corona discharge detection, two typical types of UV imagers (DayCor^®Superb and CoroCAM^®6D) were utilized. Results show that the observation angle has little impact on UV detection if no obstacles block the detection line of sight. Given that different UV imagers have different optimal imager gains, photon numbers under different gains could be calibrated to the values under optimal gains in accordance with the gain correction formula. Photon numbers decrease with the increase in the square of observation distance. Detection results under different observation distances could be corrected to the contrast distance after the detection of electrical equipment. The photon numbers of different UV imager types could be corrected in accordance with the instrumental correction factor. The results of this study can provide references to improve the applications and standardizations of UV imaging technology in corona discharge detection. Full article

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11 pages, 789 KiB

Open AccessArticle

Assessment of the Variability of Biogas Production from Sugar Beet Silage as Affected by Movement and Loss of the Produced Alcohols and Organic Acids

by Ali Heidarzadeh Vazifehkhoran^1,*, Jin Mi Triolo¹, Søren Ugilt Larsen², Kasper Stefanek³ and Sven G. Sommer¹

¹ Institute of Chemical Engineering, Biotechnology and Environmental Technology, Faculty of Engineering, University of Southern Denmark, Campusvej 55, Odense M 5230, Denmark

² Danish Technological Institute, Agro Food Park 15, Skejby, Aarhus N 8200, Denmark

³ HedeDanmark, Jens Juuls Vej 16, Viby 8260, Denmark

Energies 2016, 9(5), 368; https://doi.org/10.3390/en9050368 - 16 May 2016

Cited by 19 | Viewed by 6484

Abstract

The biochemical methane potential and composition of sugar beet pulp silage were investigated using samples taken from six different depths in both open and closed silos (height 3.6 m). The biochemical methane potential (BMP) of pulp silage in open silos ranged from 337 [...] Read more.

The biochemical methane potential and composition of sugar beet pulp silage were investigated using samples taken from six different depths in both open and closed silos (height 3.6 m). The biochemical methane potential (BMP) of pulp silage in open silos ranged from 337 to 420 normal litre (NL) CH₄/kg volatile solids (VS), while the BMP of pulp silage in closed silos varied between 411 and 451 NL CH₄/kg VS. The biochemical methane potential peaked at a depth of 1.45 m with 420 NL CH₄/kg VS for open silos and 451 NL CH₄/kg VS for closed silos. The ethanol concentration and biochemical methane potential showed the same trend with depth throughout the silos. The energy loss correlated to the loss of volatile solids, and the depths described a linear relationship between them for both the open and closed silos (R² = 0.997 for the open silo and R² = 0.991 for the closed silo). The energy potentials and composition of beet pulp silage were highly stratified and there was a risk that the silage samples were not representative in investigations of biomass quality for energy production. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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13 pages, 1217 KiB

Open AccessArticle

How Much Detail Should We Use to Compute Societal Aggregated Exergy Efficiencies?

by Miguel Palma^*

, Tânia Sousa^* and Zeus Guevara

Maretec, Environment and Energy Scientific Area, DEM, Instituto Superior Técnico (IST), Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

Energies 2016, 9(5), 364; https://doi.org/10.3390/en9050364 - 16 May 2016

Cited by 10 | Viewed by 4614

Abstract

The current method used for calculating societal aggregated exergy efficiencies is reviewed. Cooling is introduced as an end-use category; conversion efficiencies for heating processes are obtained for each energy carrier; and electricity shares per end-use are retrieved for each sector, improving the accuracy [...] Read more.

The current method used for calculating societal aggregated exergy efficiencies is reviewed. Cooling is introduced as an end-use category; conversion efficiencies for heating processes are obtained for each energy carrier; and electricity shares per end-use are retrieved for each sector, improving the accuracy of the estimated values of aggregated exergy efficiencies. We show that: (1) cooling uses are a relevant end-use in Portugal and that their introduction decreased overall efficiency by 3.4% in 2009; and (2) disaggregating the heating second law efficiencies for each energy carrier has a significant effect on the aggregated efficiencies of the country, decreasing aggregated efficiency by 1.3% in 2009. We studied two other factors that showed no significant impact on aggregated exergy efficiency: a technological lag of 10 years in the efficiency of stationary mechanical drive devices and the use of a year-specific ambient temperature to compute exergy efficiencies of heating processes. Full article

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29 pages, 864 KiB

Open AccessEditor’s ChoiceReview

Review of Physicochemical-Based Diagnostic Techniques for Assessing Insulation Condition in Aged Transformers

by Janvier Sylvestre N’cho¹, Issouf Fofana^2,*

, Yazid Hadjadj² and Abderrahmane Beroual³

¹ Département Génie Électrique et Électronique, Institut National Polytechnique Houphouët Boigny (INP-HB), BP 1093 Yamoussoukro, Ivory Coast

² Research Chair on the Aging of Power Network Infrastructure (ViAHT), Université du Québec à Chicoutimi, 555 Boulevard de l’Université, Chicoutimi, QC G7H 2B1, Canada

³ Ecole Centrale de Lyon, Université de Lyon, Ampère CNRS UMR 5005, 36 Avenue Guy de Collongue, 69134 Ecully, France

Energies 2016, 9(5), 367; https://doi.org/10.3390/en9050367 - 13 May 2016

Cited by 204 | Viewed by 12778

Abstract

A power transformer outage has a dramatic financial consequence not only for electric power systems utilities but also for interconnected customers. The service reliability of this important asset largely depends upon the condition of the oil-paper insulation. Therefore, by keeping the qualities of [...] Read more.

A power transformer outage has a dramatic financial consequence not only for electric power systems utilities but also for interconnected customers. The service reliability of this important asset largely depends upon the condition of the oil-paper insulation. Therefore, by keeping the qualities of oil-paper insulation system in pristine condition, the maintenance planners can reduce the decline rate of internal faults. Accurate diagnostic methods for analyzing the condition of transformers are therefore essential. Currently, there are various electrical and physicochemical diagnostic techniques available for insulation condition monitoring of power transformers. This paper is aimed at the description, analysis and interpretation of modern physicochemical diagnostics techniques for assessing insulation condition in aged transformers. Since fields and laboratory experiences have shown that transformer oil contains about 70% of diagnostic information, the physicochemical analyses of oil samples can therefore be extremely useful in monitoring the condition of power transformers. Full article

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

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23 pages, 6447 KiB

Open AccessArticle

A Large-Eddy Simulation Study of Vertical Axis Wind Turbine Wakes in the Atmospheric Boundary Layer

by Sina Shamsoddin and Fernando Porté-Agel^*

Wind Engineering and Renewable Energy Laboratory (WIRE), École Polytechnique Fédérale de Lausanne (EPFL), EPFL-ENAC-IIE-WIRE, Lausanne 1015, Switzerland

Energies 2016, 9(5), 366; https://doi.org/10.3390/en9050366 - 13 May 2016

Cited by 70 | Viewed by 9547

Abstract

In a future sustainable energy vision, in which diversified conversion of renewable energies is essential, vertical axis wind turbines (VAWTs) exhibit some potential as a reliable means of wind energy extraction alongside conventional horizontal axis wind turbines (HAWTs). Nevertheless, there is currently a [...] Read more.

In a future sustainable energy vision, in which diversified conversion of renewable energies is essential, vertical axis wind turbines (VAWTs) exhibit some potential as a reliable means of wind energy extraction alongside conventional horizontal axis wind turbines (HAWTs). Nevertheless, there is currently a relative shortage of scientific, academic and technical investigations of VAWTs as compared to HAWTs. Having this in mind, in this work, we aim to, for the first time, study the wake of a single VAWT placed in the atmospheric boundary layer using large-eddy simulation (LES). To do this, we use a previously-validated LES framework in which an actuator line model (ALM) is incorporated. First, for a typical three- and straight-bladed 1-MW VAWT design, the variation of the power coefficient with both the chord length of the blades and the tip-speed ratio is analyzed by performing 117 simulations using LES-ALM. The optimum combination of solidity (defined as

N c / R

, where N is the number of blades, c is the chord length and R is the rotor radius) and tip-speed ratio is found to be 0.18 and 4.5, respectively. Subsequently, the wake of a VAWT with these optimum specifications is thoroughly examined by showing different relevant mean and turbulence wake flow statistics. It is found that for this case, the maximum velocity deficit at the equator height of the turbine occurs 2.7 rotor diameters downstream of the center of the turbine, and only after that point, the wake starts to recover. Moreover, it is observed that the maximum turbulence intensity (TI) at the equator height of the turbine occurs at a distance of about 3.8 rotor diameters downstream of the turbine. As we move towards the upper and lower edges of the turbine, the maximum TI (at a certain height) increases, and its location moves relatively closer to the turbine. Furthermore, whereas both TI and turbulent momentum flux fields show clear vertical asymmetries (with larger magnitudes at the upper wake edge compared to the ones at the lower edge), only slight lateral asymmetries were observed at the optimum tip-speed ratio for which the simulations were performed. Full article

(This article belongs to the Collection Wind Turbines)

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12 pages, 1879 KiB

Open AccessArticle

Energy Performance of Verandas in the Building Retrofit Process

by Rossano Albatici^1,*, Francesco Passerini¹ and Jens Pfafferott²

¹ Department of Civil Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento, Italy

² Department of Mechanical and Process Engineering and Institute of Energy System Technology, Offenburg University of Applied Sciences, Badstraße 24, 77652 Offenburg, Germany

Energies 2016, 9(5), 365; https://doi.org/10.3390/en9050365 - 13 May 2016

Cited by 9 | Viewed by 6075

Abstract

Passive solar elements for both direct and indirect gains, are systems used to maintain a comfortable living environment while saving energy, especially in the building energy retrofit and adaptation process. Sunspaces, thermal mass and glazing area and orientation have been often used in [...] Read more.

Passive solar elements for both direct and indirect gains, are systems used to maintain a comfortable living environment while saving energy, especially in the building energy retrofit and adaptation process. Sunspaces, thermal mass and glazing area and orientation have been often used in the past to guarantee adequate indoor conditions when mechanical devices were not available. After a period of neglect, nowadays they are again considered as appropriate systems to help face environmental issues in the building sector, and both international and national legislation takes into consideration the possibility of including them in the building planning tools, also providing economic incentives. Their proper design needs dynamic simulation, often difficult to perform and time consuming. Moreover, results generally suffer from several uncertainties, so quasi steady-state procedures are often used in everyday practice with good results, but some corrections are still needed. In this paper, a comparative analysis of different solutions for the construction of verandas in an existing building is presented, following the procedure provided by the slightly modified and improved Standard EN ISO 13790:2008. Advantages and disadvantages of different configurations considering thermal insulation, windows typology and mechanical ventilation systems are discussed and a general intervention strategy is proposed. The aim is to highlight the possibility of using sunspaces in order to increase the efficiency of the existing building stock, considering ease of construction and economic viability. Full article

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

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13 pages, 4171 KiB

Open AccessFeature PaperArticle

Hydropower Production in Future Climate Scenarios: The Case for Kwanza River, Angola

by Byman H. Hamududu^1,*

and Ånund Killingtveit²

¹ Norwegian Water Resources and Energy Directorate (NVE), Department of Hydrology, Middelthuns gate 29, Oslo 0301, Norway

² Norwegian University of Science and Technology (NTNU), Department of Hydraulic and Environmental Engineering, S.P. Andersens Vei. 5, Trondheim 7491, Norway

Energies 2016, 9(5), 363; https://doi.org/10.3390/en9050363 - 12 May 2016

Cited by 11 | Viewed by 7929

Abstract

Climate change is altering hydrological processes with varying degrees in various regions of the world and remains a threat to water resources projects in southern Africa. The likely negative impacts of changes in Africa may be worse than in most other regions of [...] Read more.

Climate change is altering hydrological processes with varying degrees in various regions of the world and remains a threat to water resources projects in southern Africa. The likely negative impacts of changes in Africa may be worse than in most other regions of the world. This study is an evaluation of the possible impacts of climate change on water resources and hydropower production potential in Kwanza River Basin, Angola. The regional climate data, the basis for future climate scenarios, is used in the hydrological model HBV to assess climate change impacts on water resources in the Kwanza River Basin. Evaluation of changes in hydropower production potential is carried out using an energy model. The simulations show that annual rainfall in 2080 would increase by approximately 16% with increasing inter-annual variability of rainfall and dry season river flow and later onset of the rainy season. The simulation results show that for the Kwanza River Basin the effects as a result of changes in the future climate, in general, will be positive. Consequently, the increase in water resources will lead to increased hydropower production potential in the basin by up to 10%. Full article

(This article belongs to the Special Issue Hydropower)

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14 pages, 3074 KiB

Open AccessArticle

Dynamic Equivalent Modeling for Small and Medium Hydropower Generator Group Based on Measurements

by Bowei Hu¹, Jingtao Sun¹, Lijie Ding², Xinyu Liu¹ and Xiaoru Wang^1,*

¹ School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China

² Sichuan Electric Power Research Institute, Chengdu 610072, China

Energies 2016, 9(5), 362; https://doi.org/10.3390/en9050362 - 12 May 2016

Cited by 9 | Viewed by 6330

Abstract

At present, the common practice in the power system of China is to represent the small and medium hydropower generator group as a negative load. This paper presents a method to build a dynamic equivalent model of the hydropower generator group using a [...] Read more.

At present, the common practice in the power system of China is to represent the small and medium hydropower generator group as a negative load. This paper presents a method to build a dynamic equivalent model of the hydropower generator group using a 3rd order generator model and a static characteristic load model. Based on phasor measurements in the tie line which connects to the modeled hydropower generator group, the dynamic multi-swarm particle swarm optimizer (DMS-PSO) algorithm is used to obtain parameters of the equivalent model. The proposed method is verified in the small and medium hydropower generator group of Sichuan power grid with both simulation and actual data. The results show that the dynamic responses and the transient stability are consistent before and after the equivalence. The proposed method can be used for modeling a group of small and medium hydropower generators whose structures and parameters are unknown. Full article

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

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13 pages, 1592 KiB

Open AccessArticle

Techno-Economic Analysis of Integrating First and Second-Generation Ethanol Production Using Filamentous Fungi: An Industrial Case Study

by Karthik Rajendran^1,2,*

, Sreevathsava Rajoli¹ and Mohammad J. Taherzadeh¹

¹ Swedish Centre for Resource Recovery, University of Borås, 50190 Borås, Sweden

² Department of Molecular Biosciences and Bioengineering, University of Hawai’i at Mānoa, Honolulu, HI 96822, USA

Energies 2016, 9(5), 359; https://doi.org/10.3390/en9050359 - 12 May 2016

Cited by 30 | Viewed by 10029

Abstract

The 2nd generation plants producing ethanol from lignocelluloses demand risky and high investment costs. This paper presents the energy- and economical evaluations for integrating lignocellulose in current 1st generation dry mill ethanol processes, using filamentous fungi. Dry mills use grains and have mills, [...] Read more.

The 2nd generation plants producing ethanol from lignocelluloses demand risky and high investment costs. This paper presents the energy- and economical evaluations for integrating lignocellulose in current 1st generation dry mill ethanol processes, using filamentous fungi. Dry mills use grains and have mills, liquefactions, saccharifications, fermentation, and distillation to produce ethanol, while their stillage passes centrifugation, and evaporation to recycle the water and dry the cake and evaporated syrup into animal feed. In this work, a bioreactor was considered to cultivate fungi on the stillage either before or after the centrifugation step together with pretreated lignocellulosic wheat bran. The results showed that the integrated 1st and 2nd generation ethanol process requires a capital investment of 77 million USD, which could yield NPV of 162 million USD after 20 years. Compared to the fungal cultivation on thin stillage modified 1st generation process, the integrated process resulted in 53 million USD higher NPV. The energy analysis showed that the thin stillage modified 1st generation process could reduce the overall energy consumption by 2.5% and increase the ethanol production by 4%. Such modifications in the 1st generation processes and integration concepts could be interesting for the ethanol industries, as integrating lignocelluloses to their existing setup requires less capital investment. Full article

(This article belongs to the Collection Bioenergy and Biofuel)

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19 pages, 6605 KiB

Open AccessArticle

A Study on the Efficiency Improvement of Multi-Geothermal Heat Pump Systems in Korea Using Coefficient of Performance

by Young-Ju Jung¹, Hyo-Jun Kim², Bo-Eun Choi², Jae-Hun Jo³ and Young-Hum Cho^4,*

¹ Green Building Center, Korea Productivity Center Quality Assurance, 32 Saemoonan 5th street, Jongno-gu, Seoul 03170, Korea

² Department of Architectural Engineering, Graduate School of Yeungnam University, 280 Daehak-Ro, Gyeongsan, Gyeongbuk 38541, Korea

³ Department of Architectural Engineering, Inha University, 100 Inha-ro, Nam-gu, Incheon 22212, Korea

⁴ School of Architecture, Yeungnam University, 280 Daehak-Ro, Gyeongsan, Gyeongbuk 38541, Korea

Energies 2016, 9(5), 356; https://doi.org/10.3390/en9050356 - 12 May 2016

Cited by 14 | Viewed by 6205

Abstract

The Korean government is fostering a renewable energy industry as a means of handling the energy crisis. Among the renewable energy systems available, geothermal energy has been highlighted as highly efficient, safely operable and relatively unaffected by outdoors air conditions. Despite the increasing [...] Read more.

The Korean government is fostering a renewable energy industry as a means of handling the energy crisis. Among the renewable energy systems available, geothermal energy has been highlighted as highly efficient, safely operable and relatively unaffected by outdoors air conditions. Despite the increasing use of renewable energy, the devices using renewables may not be operating appropriately. This study examined current problems in the operation of a geothermal heat pump (GHP) system. The efficiency of a geothermal heat pump system to studied to maximize the operation plan. Our study modelled the target building and analyzed the energy using TRNSYS, which is a dynamic energy simulation tool, to apply the coefficient of performance (COP) and evaluate the operation method. As a result, the GHP total energy consumption from the COP control method was reduced by 46% compared to the current operation. The proposed control method was evaluated after applying the system to a building. The results showed that efficient operation of a geothermal heat pump system is possible. Full article

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

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16 pages, 2436 KiB

Open AccessArticle

Foliage and Grass as Fuel Pellets–Small Scale Combustion of Washed and Mechanically Leached Biomass

by Jan Hari Arti Khalsa^1,*

, Frank Döhling¹ and Florian Berger²

¹ Deutsches Biomasseforschungszentrum gemeinnützige GmbH (DBFZ)/German Biomass Research Center, Leipzig 04347, Germany

² florafuel AG, München 81829, Germany

Energies 2016, 9(5), 361; https://doi.org/10.3390/en9050361 - 11 May 2016

Cited by 32 | Viewed by 8064

Abstract

The high contents of disadvantageous elements contained in non-woody biomass are known to cause problems during small and large scale combustion, typically resulting in a higher risk of slagging, corrosion, and increased emissions. Mechanically leaching the respective elements from the biomass through a [...] Read more.

The high contents of disadvantageous elements contained in non-woody biomass are known to cause problems during small and large scale combustion, typically resulting in a higher risk of slagging, corrosion, and increased emissions. Mechanically leaching the respective elements from the biomass through a sequence of process steps has proven to be a promising solution.The florafuel process used here is comprised of size reduction followed by washing and subsequent mechanical dewatering of the biomass. Densification of the upgraded biomass into standardized pellets (Ø 6mm) enables an application in existing small-scale boilers. The presented combustion trials investigated the performance of pellets made from leached grass, foliage and a mixture of both in two small-scale boilers (<100 kWth) with slightly different technology (moving grate versus water-cooled burner tube) during a 4-h measurement period. Emissions were in accordance with German emissions standards except for NO_x (threshold is 0.50 g/m³) in the case of pure grass pellets (0.51 g/m³) and particulate matter (PM) in all but one case (foliage, 13–16 mg/m³). An electrostatic precipitator (ESP) unit installed with one of the boilers successfully reduced PM emission of both the grass and mixture fuel below the threshold of 20 mg/m³ (all emission values refer to 13 vol.% O₂, at standard temperature and pressure (STP)). Bottom ash composition and grate temperature profiles were analyzed and discussed for one of the boilers. Full article

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

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23 pages, 19740 KiB

Open AccessArticle

Lithium Ion Batteries—Development of Advanced Electrical Equivalent Circuit Models for Nickel Manganese Cobalt Lithium-Ion

by Alexandros Nikolian^*, Yousef Firouz, Rahul Gopalakrishnan, Jean-Marc Timmermans

, Noshin Omar, Peter Van den Bossche and Joeri Van Mierlo

Department Mobility, Logistics and Automotive Technology Research Centre, Vrije Universiteit Brussels, Pleinlaan 2, Brussels 1050, Belgium

Energies 2016, 9(5), 360; https://doi.org/10.3390/en9050360 - 11 May 2016

Cited by 82 | Viewed by 12331

Abstract

In this paper, advanced equivalent circuit models (ECMs) were developed to model large format and high energy nickel manganese cobalt (NMC) lithium-ion 20 Ah battery cells. Different temperatures conditions, cell characterization test (Normal and Advanced Tests), ECM topologies (1st and 2nd Order Thévenin [...] Read more.

In this paper, advanced equivalent circuit models (ECMs) were developed to model large format and high energy nickel manganese cobalt (NMC) lithium-ion 20 Ah battery cells. Different temperatures conditions, cell characterization test (Normal and Advanced Tests), ECM topologies (1st and 2nd Order Thévenin model), state of charge (SoC) estimation techniques (Coulomb counting and extended Kalman filtering) and validation profiles (dynamic discharge pulse test (DDPT) and world harmonized light vehicle profiles) have been incorporated in the analysis. A concise state-of-the-art of different lithium-ion battery models existing in the academia and industry is presented providing information about model classification and information about electrical models. Moreover, an overview of the different steps and information needed to be able to create an ECM model is provided. A comparison between begin of life (BoL) and aged (95%, 90% state of health) ECM parameters (internal resistance (R_o), polarization resistance (R_p), activation resistance (R_p2) and time constants (τ) is presented. By comparing the BoL to the aged parameters an overview of the behavior of the parameters is introduced and provides the appropriate platform for future research in electrical modeling of battery cells covering the ageing aspect. Based on the BoL parameters 1st and 2nd order models were developed for a range of temperatures (15 °C, 25 °C, 35 °C, 45 °C). The highest impact to the accuracy of the model (validation results) is the temperature condition that the model was developed. The 1st and 2nd order Thévenin models and the change from normal to advanced characterization datasets, while they affect the accuracy of the model they mostly help in dealing with high and low SoC linearity problems. The 2nd order Thévenin model with advanced characterization parameters and extended Kalman filtering SoC estimation technique is the most efficient and dynamically correct ECM model developed. Full article

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

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