Energies

5882 KiB

Open AccessArticle

Arrhenius Equation-Based Cell-Health Assessment: Application to Thermal Energy Management Design of a HEV NiMH Battery Pack

by Yalian Yang, Xiaosong Hu, Datong Qing and Fangyuan Chen

Energies 2013, 6(5), 2709-2725; https://doi.org/10.3390/en6052709 - 22 May 2013

Cited by 50 | Viewed by 8603

Abstract

This paper presents a model-based cell-health-conscious thermal energy management method. An Arrhenius equation-based mathematical model is firstly identified to quantify the effect of temperature on the cell lifetime of a Nickel Metal Hydride (NiMH) battery pack. The cell aging datasets collected under multiple [...] Read more.

This paper presents a model-based cell-health-conscious thermal energy management method. An Arrhenius equation-based mathematical model is firstly identified to quantify the effect of temperature on the cell lifetime of a Nickel Metal Hydride (NiMH) battery pack. The cell aging datasets collected under multiple ambient temperatures are applied to extract the Arrhenius equation parameters. The model is then used as an assessment criterion and guidance for the thermal management design of battery packs. The feasibility and applicability of a pack structure with its cooling system, is then evaluated, and its design problems are studied by a computational fluid dynamics (CFD) analysis. The performance and eligibility of the design method is validated by both CFD simulations and experiments. Full article

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325 KiB

Open AccessArticle

Energy-Exergy, Environmental and Economic Criteria in Combined Heat and Power (CHP) Plants: Indexes for the Evaluation of the Cogeneration Potential

by Marco F. Torchio

Energies 2013, 6(5), 2686-2708; https://doi.org/10.3390/en6052686 - 22 May 2013

Cited by 17 | Viewed by 6681

Abstract

In the first part of this work, combined heat and power (CHP) criteria pertaining to energy, exergy, environmental (pollutant emission) and economic aspects, have been investigated and compared. Although the constraints in legislation usually refer to energy efficiency, primary energy savings and greenhouse [...] Read more.

In the first part of this work, combined heat and power (CHP) criteria pertaining to energy, exergy, environmental (pollutant emission) and economic aspects, have been investigated and compared. Although the constraints in legislation usually refer to energy efficiency, primary energy savings and greenhouse gas savings, other criteria should also be taken into account in order to obtain a better evaluation of a cogeneration plant. Here particular attention has been paid to saving indexes for both an individual CHP-unit and for a CHP-system, that is the complete system with all the cogeneration units and the auxiliary plants necessary to cover the users’ demand. Five indexes, named potential indexes, have been introduced to evaluate the cogeneration potential: one for energy saving, one for exergy, two for environmental aspects (global and local scale) and one for economic aspects. Finally, some indexes analysed in the paper have been applied to a case study concerning a district heating cogeneration system, and the different behaviour of the energy-exergy, environmental and economic aspects has been discussed. Full article

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292 KiB

Open AccessArticle

Energy and Environmental Implications of Hybrid and Electric Vehicles in China

by Jianlei Lang, Shuiyuan Cheng, Ying Zhou, Beibei Zhao, Haiyan Wang and Shujing Zhang

Energies 2013, 6(5), 2663-2685; https://doi.org/10.3390/en6052663 - 22 May 2013

Cited by 40 | Viewed by 8500

Abstract

The promotion of hybrid and electric vehicles (EVs) has been proposed as one promising solution for reducing transport energy consumption and mitigating vehicular emissions in China. In this study, the energy and environmental impacts of hybrid and EVs during 2010–2020 were evaluated through [...] Read more.

The promotion of hybrid and electric vehicles (EVs) has been proposed as one promising solution for reducing transport energy consumption and mitigating vehicular emissions in China. In this study, the energy and environmental impacts of hybrid and EVs during 2010–2020 were evaluated through an energy conversion analysis and a life cycle assessment (LCA), and the per-kilometer energy consumptions of gasoline, coal, natural gas (NG), oil, biomass, garbage and electricity for EVs and HEVs were estimated. Results show that the EVs and HEVs can reduce the energy consumption of vehicles by national average ratios of 17%–19% and 30%–33%, respectively. The study also calculated the detailed emission factors of SO₂, NO_X, VOC, CO, NH₃, PM₁₀, PM_2.5, OC, EC, CO₂, N₂O, CH₄, Pb and Hg. It is indicated that the HEVs can bring significant reductions of NO_X, VOC and CO emissions and lesser decreases of SO₂ and CO₂ for a single vehicle. The EVs could decrease many of the VOC, NH₃, CO and CO₂ emissions, but increase the SO₂, NO_X and particles by 10.8–13.0, 2.7–2.9 and 3.6–11.5 times, respectively. In addition, the electricity sources had significant influence on energy consumption (EC) and emissions. A high proportion of coal-fired energy resulted in large ECs and emission factors. The total energy consumption and pollutants emission changes in 2015 and 2020 were also calculated. Based on the energy use and emission analysis of HEVs and EVs, it is suggested that EVs should be promoted in the regions with higher proportions of hydropower, natural gas-fired power and clean energy power, while HEVs can be widely adopted in the regions with high coal-fired power ratios. This is to achieve a higher energy consumption reduction and pollutant emission mitigation. Moreover, the results can also provide scientific support for the total amount control of regional air pollutants in China. Full article

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443 KiB

Open AccessArticle

Life Cycle GHG of NG-Based Fuel and Electric Vehicle in China

by Xunmin Ou, Xiliang Zhang, Xu Zhang and Qian Zhang

Energies 2013, 6(5), 2644-2662; https://doi.org/10.3390/en6052644 - 22 May 2013

Cited by 53 | Viewed by 8725

Abstract

This paper compares the greenhouse gas (GHG) emissions of natural gas (NG)- based fuels to the GHG emissions of electric vehicles (EVs) powered with NG-to-electricity in China. A life-cycle model is used to account for full fuel cycle and use-phase emissions, as well [...] Read more.

This paper compares the greenhouse gas (GHG) emissions of natural gas (NG)- based fuels to the GHG emissions of electric vehicles (EVs) powered with NG-to-electricity in China. A life-cycle model is used to account for full fuel cycle and use-phase emissions, as well as vehicle cycle and battery manufacturing. The reduction of life-cycle GHG emissions of EVs charged by electricity generated from NG, without utilizing carbon dioxide capture and storage (CCS) technology can be 36%–47% when compared to gasoline vehicles. The large range change in emissions reduction potential is driven by the different generation technologies that could in the future be used to generate electricity in China. When CCS is employed in power plants, the GHG emission reductions increase to about 71%–73% compared to gasoline vehicles. It is found that compressed NG (CNG) and liquefied NG (LNG) fuels can save about 10% of carbon as compared to gasoline vehicles. However, gas-to-liquid (GTL) fuel made through the Fischer-Tropsch method will likely lead to a life-cycle GHG emissions increase, potentially 3%–15% higher than gasoline, but roughly equal to petroleum-based diesel. When CCS is utilized, the GTL fueled vehicles emit roughly equal GHG emissions to petroleum-based diesel fuel high-efficient hybrid electric vehicle from the life-cycle perspective. Full article

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404 KiB

Open AccessArticle

Short-Term Power Forecasting Model for Photovoltaic Plants Based on Historical Similarity

by Claudio Monteiro, Tiago Santos, L. Alfredo Fernandez-Jimenez, Ignacio J. Ramirez-Rosado and M. Sonia Terreros-Olarte

Energies 2013, 6(5), 2624-2643; https://doi.org/10.3390/en6052624 - 22 May 2013

Cited by 99 | Viewed by 9628

Abstract

This paper proposes a new model for short-term forecasting of electric energy production in a photovoltaic (PV) plant. The model is called HIstorical SImilar MIning (HISIMI) model; its final structure is optimized by using a genetic algorithm, based on data mining techniques applied [...] Read more.

This paper proposes a new model for short-term forecasting of electric energy production in a photovoltaic (PV) plant. The model is called HIstorical SImilar MIning (HISIMI) model; its final structure is optimized by using a genetic algorithm, based on data mining techniques applied to historical cases composed by past forecasted values of weather variables, obtained from numerical tools for weather prediction, and by past production of electric power in a PV plant. The HISIMI model is able to supply spot values of power forecasts, and also the uncertainty, or probabilities, associated with those spot values, providing new useful information to users with respect to traditional forecasting models for PV plants. Such probabilities enable analysis and evaluation of risk associated with those spot forecasts, for example, in offers of energy sale for electricity markets. The results of spot forecasting of an illustrative example obtained with the HISIMI model for a real-life grid-connected PV plant, which shows high intra-hour variability of its actual power output, with forecasting horizons covering the following day, have improved those obtained with other two power spot forecasting models, which are a persistence model and an artificial neural network model. Full article

(This article belongs to the Special Issue Hybrid Advanced Techniques for Forecasting in Energy Sector)

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864 KiB

Open AccessArticle

Exploring Ventilation Efficiency in Poultry Buildings: The Validation of Computational Fluid Dynamics (CFD) in a Cross-Mechanically Ventilated Broiler Farm

by Eliseo Bustamante, Fernando-Juan García-Diego, Salvador Calvet, Fernando Estellés, Pedro Beltrán, Antonio Hospitaler and Antonio G. Torres

Energies 2013, 6(5), 2605-2623; https://doi.org/10.3390/en6052605 - 21 May 2013

Cited by 62 | Viewed by 10420

Abstract

Broiler production in modern poultry farms commonly uses mechanical ventilation systems. This mechanical ventilation requires an amount of electric energy and a high level of investment in technology. Nevertheless, broiler production is affected by periodic problems of mortality because of thermal stress, thus [...] Read more.

Broiler production in modern poultry farms commonly uses mechanical ventilation systems. This mechanical ventilation requires an amount of electric energy and a high level of investment in technology. Nevertheless, broiler production is affected by periodic problems of mortality because of thermal stress, thus being crucial to explore the ventilation efficiency. In this article, we analyze a cross-mechanical ventilation system focusing on air velocity distribution. In this way, two methodologies were used to explore indoor environment in livestock buildings: Computational Fluid Dynamics (CFD) simulations and direct measurements for verification and validation (V&V) of CFD. In this study, a validation model using a Generalized Linear Model (GLM) was conducted to compare these methodologies. The results showed that both methodologies were similar in results: the average of air velocities values were 0.60 ± 0.56 m s⁻¹ for CFD and 0.64 ± 0.54 m s⁻¹ for direct measurements. In conclusion, the air velocity was not affected by the methodology (CFD or direct measurements), and the CFD simulations were therefore validated to analyze indoor environment of poultry farms and its operations. A better knowledge of the indoor environment may contribute to reduce the demand of electric energy, increasing benefits and improving the thermal comfort of broilers. Full article

(This article belongs to the Special Issue Energy Efficient Building Design 2013)

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443 KiB

Open AccessArticle

Online Semiparametric Identification of Lithium-Ion Batteries Using the Wavelet-Based Partially Linear Battery Model

by Dazhong Mu, Jiuchun Jiang and Caiping Zhang

Energies 2013, 6(5), 2583-2604; https://doi.org/10.3390/en6052583 - 21 May 2013

Cited by 13 | Viewed by 7048

Abstract

Battery model identification is very important for reliable battery management as well as for battery system design process. The common problem in identifying battery models is how to determine the most appropriate mathematical model structure and parameterized coefficients based on the measured terminal [...] Read more.

Battery model identification is very important for reliable battery management as well as for battery system design process. The common problem in identifying battery models is how to determine the most appropriate mathematical model structure and parameterized coefficients based on the measured terminal voltage and current. This paper proposes a novel semiparametric approach using the wavelet-based partially linear battery model (PLBM) and a recursive penalized wavelet estimator for online battery model identification. Three main contributions are presented. First, the semiparametric PLBM is proposed to simulate the battery dynamics. Compared with conventional electrical models of a battery, the proposed PLBM is equipped with a semiparametric partially linear structure, which includes a parametric part (involving the linear equivalent circuit parameters) and a nonparametric part [involving the open-circuit voltage (OCV)]. Thus, even with little prior knowledge about the OCV, the PLBM can be identified using a semiparametric identification framework. Second, we model the nonparametric part of the PLBM using the truncated wavelet multiresolution analysis (MRA) expansion, which leads to a parsimonious model structure that is highly desirable for model identification; using this model, the PLBM could be represented in a linear-in-parameter manner. Finally, to exploit the sparsity of the wavelet MRA representation and allow for online implementation, a penalized wavelet estimator that uses a modified online cyclic coordinate descent algorithm is proposed to identify the PLBM in a recursive fashion. The simulation and experimental results demonstrate that the proposed PLBM with the corresponding identification algorithm can accurately simulate the dynamic behavior of a lithium-ion battery in the Federal Urban Driving Schedule tests. Full article

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1716 KiB

Open AccessArticle

Characteristics of the Operational Noise from Full Scale Wave Energy Converters in the Lysekil Project: Estimation of Potential Environmental Impacts

by Kalle Haikonen, Jan Sundberg and Mats Leijon

Energies 2013, 6(5), 2562-2582; https://doi.org/10.3390/en6052562 - 21 May 2013

Cited by 24 | Viewed by 9338

Abstract

Wave energy conversion is a clean electric power production technology. During operation there are no emissions in the form of harmful gases. However there are unsolved issues considering environmental impacts such as: electromagnetism; the artificial reef effect and underwater noise. Anthropogenic noise is [...] Read more.

Wave energy conversion is a clean electric power production technology. During operation there are no emissions in the form of harmful gases. However there are unsolved issues considering environmental impacts such as: electromagnetism; the artificial reef effect and underwater noise. Anthropogenic noise is increasing in the oceans worldwide and wave power will contribute to this sound pollution in the oceans; but to what extent? The main purpose of this study was to examine the noise emitted by a full scale operating Wave Energy Converter (WEC) in the Lysekil project at Uppsala University in Sweden. A minor review of the hearing capabilities of fish and marine mammals is presented to aid in the conclusions of impact from anthropogenic sound. A hydrophone was deployed to the seabed in the Lysekil research site park at distance of 20 and 40 m away from two operational WECs. The measurements were performed in the spring of 2011. The results showed that the main noise was a transient noise with most of its energy in frequencies below 1 kHz. These results indicate that several marine organisms (fish and mammals) will be able to hear the operating WECs of a distance of at least 20 m. Full article

(This article belongs to the Special Issue Energy from the Ocean - Wave and Tidal Energy)

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1270 KiB

Open AccessArticle

Coordinated Control of a DFIG-Based Wind-Power Generation System with SGSC under Distorted Grid Voltage Conditions

by Jun Yao, Qing Li, Zhe Chen and Aolin Liu

Energies 2013, 6(5), 2541-2561; https://doi.org/10.3390/en6052541 - 17 May 2013

Cited by 16 | Viewed by 6864

Abstract

This paper presents a coordinated control method for a doubly-fed induction generator (DFIG)-based wind-power generation system with a series grid-side converter (SGSC) under distorted grid voltage conditions. The detailed mathematical models of the DFIG system with SGSC are developed in the multiple synchronous [...] Read more.

This paper presents a coordinated control method for a doubly-fed induction generator (DFIG)-based wind-power generation system with a series grid-side converter (SGSC) under distorted grid voltage conditions. The detailed mathematical models of the DFIG system with SGSC are developed in the multiple synchronous rotating reference frames. In order to counteract the adverse effects of the voltage harmonics upon the DFIG, the SGSC generates series compensation control voltages to keep the stator voltage sinusoidal and symmetrical, which allows the use of the conventional vector control strategy for the rotor-side converter (RSC), regardless of grid voltage harmonics. Meanwhile, two control targets for the parallel grid-side converter (PGSC) are identified, including eliminating the oscillations in total active and reactive power entering the grid or suppressing the fifth- and seventh-order harmonic currents injected to the grid. Furthermore, the respective PI-R controller in the positive synchronous reference frame for the SGSC voltage control and PGSC current control have been developed to achieve precise and rapid regulation of the corresponding components. Finally, the proposed coordinated control strategy has been fully validated by the simulation results of a 2 MW DFIG-based wind turbine with SGSC under distorted grid voltage conditions. Full article

(This article belongs to the Special Issue Wind Turbines 2013)

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410 KiB

Open AccessArticle

Activity Sectors and Energy Intensity: Decomposition Analysis and Policy Implications for European Countries (1991–2005)

by Gustavo A. Marrero and Francisco J. Ramos-Real

Energies 2013, 6(5), 2521-2540; https://doi.org/10.3390/en6052521 - 16 May 2013

Cited by 41 | Viewed by 6848

Abstract

This paper studies the change in Energy Intensity (EI) of the main economic activities in the EU15 countries, which represents approximately 45% of their final energy consumption. The purpose is, first, to measure the different patterns between the countries by establishing [...] Read more.

This paper studies the change in Energy Intensity (EI) of the main economic activities in the EU15 countries, which represents approximately 45% of their final energy consumption. The purpose is, first, to measure the different patterns between the countries by establishing differentiated typologies, and second, to investigate those reasons that explain the different trends by country. To attain our objective, the changes in EI are decomposed into their structural and efficiency components for EU15 countries for the period 1991–2005. Results reveal four different typologies for this set of countries, and show the importance of identifying those economic activities which, due to their special impact, are key to reducing energy consumption. The changes in the structural component are due mainly to a transformative process in which the importance of industry in the economy as a whole drops, while the opposite holds for services. However, the changes in the efficiency component do not seem to be linked to this same process. It does not appear as though the services sector resulted in a more efficient use of final energy. We have detected significant evidence of convergence for EI in the service sector that would help to understand the recent worsen evolution of EI in this sector (and in overall EI) of Southern European countries. It can also be concluded that an analysis of global EI change without distinguishing among its components can result in misleading conclusions and in improperly conceived Energy Policies. Full article

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Final Energy Intensity (TOE/thousands Euro) decomposition in activity sectors in EU15 excluding transports and households: 1991–2005. (a) Austria; (b) Belgium; (c) Denmark; (d) Germany; (e) Italy; (f) France; (g) Finland; (h) The Netherlands; (i) Greece; (j) Spain; (k) Portugal; (l) Ireland; (m) Sweden; (n) United Kingdom. Full article ">Figure 1 Cont.
Final Energy Intensity (TOE/thousands Euro) decomposition in activity sectors in EU15 excluding transports and households: 1991–2005. (a) Austria; (b) Belgium; (c) Denmark; (d) Germany; (e) Italy; (f) France; (g) Finland; (h) The Netherlands; (i) Greece; (j) Spain; (k) Portugal; (l) Ireland; (m) Sweden; (n) United Kingdom. Full article ">Figure 2
(a) Structural component and the GVA in the industry sector; (b) Structural component and the GVA in the service sector. Full article ">Figure 3
(a) Efficiency component and the GVA in the industry sector; (b) Efficiency component and the GVA in the service sector. Full article ">Figure 4
The relationship between EI changes and initial levels in activity sectors in EU15. Full article ">Figure 5
(a) Structural component and the Energy Intensity in the industry; (b) Efficiency component and the Energy Intensity in the industry. Full article ">

865 KiB

Open AccessArticle

Development and Evaluation of an Aerodynamic Model for a Novel Vertical Axis Wind Turbine Concept

by Andrew Shires

Energies 2013, 6(5), 2501-2520; https://doi.org/10.3390/en6052501 - 15 May 2013

Cited by 39 | Viewed by 7876

Abstract

There has been a resurgence of interest in the development of vertical axis wind turbines which have several inherent attributes that offer some advantages for offshore operations, particularly their scalability and low over-turning moments with better accessibility to drivetrain components. This paper describes [...] Read more.

There has been a resurgence of interest in the development of vertical axis wind turbines which have several inherent attributes that offer some advantages for offshore operations, particularly their scalability and low over-turning moments with better accessibility to drivetrain components. This paper describes an aerodynamic performance model for vertical axis wind turbines specifically developed for the design of a novel offshore V-shaped rotor with multiple aerodynamic surfaces. The model is based on the Double-Multiple Streamtube method and includes a number of developments for alternative complex rotor shapes. The paper compares predicted results with measured field data for five different turbines with both curved and straight blades and rated powers in the range 100–500 kW. Based on these comparisons, the paper proposes modifications to the Gormont dynamic stall model that gives improved predictions of rotor power for the turbines considered. Full article

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1012 KiB

Open AccessArticle

Stochastic Rating of Storage Systems in Isolated Networks with Increasing Wave Energy Penetration

by Elisabetta Tedeschi, Jonas Sjolte, Marta Molinas and Maider Santos

Energies 2013, 6(5), 2481-2500; https://doi.org/10.3390/en6052481 - 15 May 2013

Cited by 12 | Viewed by 6112

Abstract

The future success of wave energy in the renewable energy mix depends on the technical advancements of the specific components and systems, on the grid access availability and, ultimately, on the economical profitability of the investment. Small and remote islands represent an ideal [...] Read more.

The future success of wave energy in the renewable energy mix depends on the technical advancements of the specific components and systems, on the grid access availability and, ultimately, on the economical profitability of the investment. Small and remote islands represent an ideal framework for wave energy exploitation, due both to resource availability and to the current high cost of electricity that mostly relies on diesel generation. Energy storage can be the enabling technology to match the intermittent power generation from waves to the energy needs of the local community. In this paper real data from La Palma, in the Canary Islands, are used as a basis for the considered test case. As a first step the study quantifies the expected power production from Wave Energy Converter (WEC) arrays, based on data from the Lifesaver point absorber developed by Fred. Olsen. Then, a stochastic optimization approach is applied to evaluate the convenience of energy storage introduction for reducing the final cost of energy and to define the corresponding optimal rating of the storage devices. Full article

(This article belongs to the Special Issue Energy from the Ocean - Wave and Tidal Energy)

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349 KiB

Open AccessArticle

Similarity Analysis in Scaling a Gas Hydrates Reservoir

by Yi Wang, Chun-Gang Xu, Xiao-Sen Li, Gang Li and Zhao-Yang Chen

Energies 2013, 6(5), 2468-2480; https://doi.org/10.3390/en6052468 - 13 May 2013

Cited by 6 | Viewed by 7212

Abstract

A complete set of scaling criteria for gas hydrate reservoir of five-spot well system case is derived from the 3D governing equations, involving the mass balance equation, the energy balance equation, the kinetic model, the endothermic model and the phase equilibrium model. In [...] Read more.

A complete set of scaling criteria for gas hydrate reservoir of five-spot well system case is derived from the 3D governing equations, involving the mass balance equation, the energy balance equation, the kinetic model, the endothermic model and the phase equilibrium model. In the scaling criteria, the key parameters of the experiment are the water/gas production rates, the water injection rate, and the production time. By using the scaling criteria, the experimental results can be enlarged to a field scale. Therefore, the experimental results and the scaling criteria could be used to evaluate the hydrate dissociation strategies and the gas production potential of the hydrate reservoir. Full article

(This article belongs to the Special Issue Natural Gas Hydrate 2013)

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1310 KiB

Open AccessArticle

Analysis and Assessments of Combined Cooling, Heating and Power Systems in Various Operation Modes for a Building in China, Dalian

by Miao Li, Hailin Mu and Huanan Li

Energies 2013, 6(5), 2446-2467; https://doi.org/10.3390/en6052446 - 8 May 2013

Cited by 25 | Viewed by 6148

Abstract

Combined Cooling, Heating and Power (CCHP) systems have been widely used in different kinds of buildings to make better use of fuels because of their high overall efficiency. This paper presents a mathematical analysis of a CCHP system in comparison to a Heating, [...] Read more.

Combined Cooling, Heating and Power (CCHP) systems have been widely used in different kinds of buildings to make better use of fuels because of their high overall efficiency. This paper presents a mathematical analysis of a CCHP system in comparison to a Heating, Ventilation and Air Conditioning (HVAC) system. The operation strategies following electric load (FEL), thermal load (FTL) and a hybrid electric-thermal load (FHL) are proposed and investigated in this study. Criteria, namely primary energy saving (PES), exergy efficiency (η_exergy), and CO₂ emission reduction (CER) are defined to evaluate the performances of CCHP systems for a hypothetical building located in Dalian (China). The results indicate that: (1) a new mathematical foundation is established to find whether the recovered thermal energy and the amount of electricity generated by the power generation unit (PGU) are enough to provide the energy required; (2) the CCHP system does not always perform better than a HVAC system from an instantaneous perspective, especially in FTL mode; (3) the CCHP system in FEL operation mode can be seen as a suitable energy system in Dalian from the annual performance perspective. Furthermore, a sensitivity analysis is presented in order to show how the performances vary due to the changes of various technical variables. Full article

(This article belongs to the Special Issue Energy Efficient Building Design 2013)

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657 KiB

Open AccessArticle

Analysis of Fuel Cell Driven Ground Source Heat Pump Systems in Community Buildings

by Jae-Ki Byun, Dong-Hwa Jeong, Young-Don Choi and Jong-Keun Shin

Energies 2013, 6(5), 2428-2445; https://doi.org/10.3390/en6052428 - 7 May 2013

Cited by 5 | Viewed by 7155

Abstract

In the present study, a fuel cell driven ground source heat pump (GSHP) system is applied in a community building and heat pump system performance is analyzed by computational methods. Conduction heat transfer between the brine pipe and ground is analyzed by TEACH [...] Read more.

In the present study, a fuel cell driven ground source heat pump (GSHP) system is applied in a community building and heat pump system performance is analyzed by computational methods. Conduction heat transfer between the brine pipe and ground is analyzed by TEACH code in order to predict the performance of the heat pump system. The predicted coefficient of performance (COP) of the heat pump system and the energy cost were compared with the variation of the location of the objective building, the water saturation rate of the soil, and the driven powers of the heat pump system. Compared to the late-night electricity driven system, a significant reduction of energy cost can be accomplished by employing the fuel cell driven heat pump system. This is due to the low cost of electricity production of the fuel cell system and to the application of the recovered waste heat generated during the electricity production process to the heating of the community building. Full article

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371 KiB

Open AccessArticle

Greening Public Buildings: ESCO-Contracting in Danish Municipalities

by Jesper Ole Jensen, Susanne Balslev Nielsen and Jesper Rohr Hansen

Energies 2013, 6(5), 2407-2427; https://doi.org/10.3390/en6052407 - 6 May 2013

Cited by 26 | Viewed by 7335

Abstract

This paper presents current research on Danish municipalities’ use of Energy Service Companies (ESCO) as a way to improve the standard of public buildings and to increase energy efficiency. In recent years more and more municipalities have used ESCO-contracts to retrofit existing public [...] Read more.

This paper presents current research on Danish municipalities’ use of Energy Service Companies (ESCO) as a way to improve the standard of public buildings and to increase energy efficiency. In recent years more and more municipalities have used ESCO-contracts to retrofit existing public buildings, and to make them more energy efficient. At the moment 30 municipalities (of the 98 municipalities in Denmark) are involved in, or preparing, ESCO contracts. Nevertheless, ESCO-contracting still faces many challenges on the Danish market, as there is a widespread skepticism towards the concept amongst many stakeholders. The purpose of this paper is to discuss the various experience gained so far by municipalities use of ESCO-contracting, the different approached to ESCO-contracting being used in practice, as well as the different viewpoints drivers and barriers behind the development. The strong growth in ESCO-contracts reflects that the ESCO-concept fits well with a number of present problems that municipalities are facing, as well as a flexible adaptation to the local context in different municipalities. Full article

(This article belongs to the Special Issue Energy Efficient Buildings and Green Buildings)

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2129 KiB

Open AccessArticle

Evaluation of Structural Changes in the Coal Specimen Heating Process and UCG Model Experiments for Developing Efficient UCG Systems

by Faqiang Su, Takuya Nakanowataru, Ken-ichi Itakura, Koutarou Ohga and Gota Deguchi

Energies 2013, 6(5), 2386-2406; https://doi.org/10.3390/en6052386 - 3 May 2013

Cited by 40 | Viewed by 7020

Abstract

In the underground coal gasification (UCG) process, cavity growth with crack extension inside the coal seam is an important phenomenon that directly influences gasification efficiency. An efficient and environmentally friendly UCG system also relies upon the precise control and evaluation of the gasification [...] Read more.

In the underground coal gasification (UCG) process, cavity growth with crack extension inside the coal seam is an important phenomenon that directly influences gasification efficiency. An efficient and environmentally friendly UCG system also relies upon the precise control and evaluation of the gasification zone. This paper presents details of laboratory studies undertaken to evaluate structural changes that occur inside the coal under thermal stress and to evaluate underground coal-oxygen gasification simulated in an ex-situ reactor. The effects of feed temperature, the direction of the stratified plane, and the inherent microcracks on the coal fracture and crack extension were investigated using some heating experiments performed using plate-shaped and cylindrical coal specimens. To monitor the failure process and to measure the microcrack distribution inside the coal specimen before and after heating, acoustic emission (AE) analysis and X-ray CT were applied. We also introduce a laboratory-scale UCG model experiment conducted with set design and operating parameters. The temperature profiles, AE activities, product gas concentration as well as the gasifier weight lossess were measured successively during gasification. The product gas mainly comprised combustible components such as CO, CH₄, and H₂ (27.5, 5.5, and 17.2 vol% respectively), which produced a high average calorific value (9.1 MJ/m³). Full article

(This article belongs to the Special Issue Coal Combustion and Gasification)

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2362 KiB

Open AccessArticle

Banki-Michell Optimal Design by Computational Fluid Dynamics Testing and Hydrodynamic Analysis

by Vincenzo Sammartano, Costanza Aricò, Armando Carravetta, Oreste Fecarotta and Tullio Tucciarelli

Energies 2013, 6(5), 2362-2385; https://doi.org/10.3390/en6052362 - 29 Apr 2013

Cited by 131 | Viewed by 13063

Abstract

In hydropower, the exploitation of small power sources requires the use of small turbines that combine efficiency and economy. Banki-Michell turbines represent a possible choice for their simplicity and for their good efficiency under variable load conditions. Several experimental and numerical tests have [...] Read more.

In hydropower, the exploitation of small power sources requires the use of small turbines that combine efficiency and economy. Banki-Michell turbines represent a possible choice for their simplicity and for their good efficiency under variable load conditions. Several experimental and numerical tests have already been designed for examining the best geometry and optimal design of cross-flow type machines, but a theoretical framework for a sequential design of the turbine parameters, taking full advantage of recently expanded computational capabilities, is still missing. To this aim, after a review of the available criteria for Banki-Michell parameter design, a novel two-step procedure is described. In the first step, the initial and final blade angles, the outer impeller diameter and the shape of the nozzle are selected using a simple hydrodynamic analysis, based on a very strong simplification of reality. In the second step, the inner diameter, as well as the number of blades and their shape, are selected by testing single options using computational fluid dynamics (CFD) simulations, starting from the suggested literature values. Good efficiency is attained not only for the design discharge, but also for a large range of variability around the design value. Full article

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Open AccessArticle

The Effect of Free-Atmosphere Stratification on Boundary-Layer Flow and Power Output from Very Large Wind Farms

by Mahdi Abkar and Fernando Porté-Agel

Energies 2013, 6(5), 2338-2361; https://doi.org/10.3390/en6052338 - 29 Apr 2013

Cited by 107 | Viewed by 10865

Abstract

Large-eddy simulation is used to study the influence of free-atmosphere stratification on the structure of atmospheric boundary-layer flow inside and above very large wind farms, as well as the power extracted by the wind turbines. In the simulations, tuning-free Lagrangian scale-dependent dynamic models [...] Read more.

Large-eddy simulation is used to study the influence of free-atmosphere stratification on the structure of atmospheric boundary-layer flow inside and above very large wind farms, as well as the power extracted by the wind turbines. In the simulations, tuning-free Lagrangian scale-dependent dynamic models are used to model the subgrid-scale turbulent fluxes, while the turbine-induced forces are parameterized with an actuator-disk model. It is shown that for a given surface cover (with and without turbines) thermal stratification of the free atmosphere reduces the entrainment from the flow above compared with the unstratified case, leading to lower boundary-layer depth. Due to the fact that in very large wind farms vertical energy transport associated with turbulence is the only source of kinetic energy, lower entrainment leads to lower power production by the wind turbines. In particular, for the wind-turbine arrangements considered in the present work, the power output from the wind farms is reduced by about 35% when the potential temperature lapse rate in the free atmosphere increases from 1 to 10 K/km (within the range of values typically observed in the atmosphere). Moreover, it is shown that the presence of the turbines has significant effect on the growth of the boundary layer. Inspired by the obtained results, a simple one-dimensional model is developed to account for the effect of free-atmosphere stability on the mean flow and the power output from very large wind farms. Full article

(This article belongs to the Special Issue Wind Turbines 2013)

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Open AccessArticle

Decomposition Analysis of Energy-Related Industrial CO₂ Emissions in China

by Liang Chen, Zhifeng Yang and Bin Chen

Energies 2013, 6(5), 2319-2337; https://doi.org/10.3390/en6052319 - 25 Apr 2013

Cited by 48 | Viewed by 7744

Abstract

Based on the logarithmic mean Divisia index (LMDI) approach, this paper presents a decomposition analysis of China’s energy-related industrial CO₂ emissions from 1985 to 2007, as well as a comparative analysis of differential influences of various factors on six sectors. Via the [...] Read more.

Based on the logarithmic mean Divisia index (LMDI) approach, this paper presents a decomposition analysis of China’s energy-related industrial CO₂ emissions from 1985 to 2007, as well as a comparative analysis of differential influences of various factors on six sectors. Via the decomposition, five categories of influencing factors are included: (1) Per capita GDP (PCG) was the largest positive driving factor for industrial CO₂ emissions growth for all sectors in China, with the largest cumulative contribution value; Population (P), economic structure (YS) and energy structure (ES) also played a positive driving role, but with weak contributions. As the only negative inhibiting factor, energy intensity (EI) significantly reduced the energy-related CO₂ emissions from industrial sectors. Meanwhile, CO₂ emissions reduction based on the efficiency of energy use still held a large space. (2) Various influencing factors imposed differential impacts on CO₂ emissions of six sectors. Full article

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Energies, Volume 6, Issue 5 (May 2013) – 20 articles , Pages 2319-2725

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