Measurement of heat generation in a 40 Ah LiFePO4 prismatic battery using accelerating rate calorimetry

Accurate characterization of the heat generation behavior of a battery is crucial to a good design of its thermal management system. Concerning the thermal properties, much attention has been paid to small-sized batteries such as the 18650- or button-type and little information is available for large-capacity Li-ion prismatic cells under adiabatic conditions. In this work, heat generation of a commercial 40 Ah prismatic LiFePO₄/C battery is evaluated using an accelerating rate calorimeter under an adiabatic condition. The battery cell is charged or discharged at an initial temperature from ?12.5 to 40 °C and a current rate from 0.2C to 2C. The experiment results show that heat generated in the battery is highly dependent on its operating temperature, state of charge and current rate. Internal resistance and entropy coefficient of the battery cell are also determined by the Hybrid Pulse Power Characterization method and potentiometric method, respectively. Relationship between the internal resistance and the heat generation behavior is highlighted. Entropy coefficient and volumetric heat generation rate of the battery cell obtained in this work are compared with those of other Li-ion batteries reported in literature.     

Heat dissipation analysis and optimization of the pure electric bus lithium-ion battery pack based on CFD

针对某纯电动客车电池箱散热效果不佳的问题,本文基于CFD技术以该车的电池箱散热系统为研究对象,建立了估算锂离子电池生热速率数学模型,采用三维软件UG建立电池箱的几何模型,并利用软件Star-ccm+对该模型的速度场和温度场进行仿真和分析。通过添加导流板等措施,对电池箱的结构进行了优化改进,并进行了正交仿真实验,确定了电池箱导流散热的最优方案,结果表明,导流板能够降低电池箱内单体电池的最高温度,使电池组温度分布更加均匀。     

复杂热源下不可逆诺维科夫热机最大功率输出

考虑实际热机工作下的旁通热漏和内部耗散等不可逆因素,建立了包括连续均匀分布、三角形分布、二次分布和帕累托分布等四种不同的统计概率分布高温热源温度下的广义不可逆诺维科夫热机模型,导出了热机最大输出功率及相应的热效率和熵产率随高温热源温度、内部不可逆性等因素变化的关系式。结果表明：热漏和内部耗散分别对热机性能有着不同的影响,热漏使统计热源温度分布下最大功率输出对应的热效率减小,同时也增大了熵产率,但对热机的最大功率输出无影响;内部耗散不可逆性使热机的最大输出功率及相应热效率均明显减小,但使熵产率先增大后减小;熵产率随高温热源温度的标准差增大而减小。研究结果对太阳能发电厂性能提升具有一定理论指导意义。     

Thermal behavior of overcharged nickel/metal hydride batteries

This work provides a two-dimensional thermal model for cylinder Ni/MH battery. Thermal model is developed to analyze the thermal behavior of the battery when charged and overcharged. Quantity of heat and heat generation rate of the battery during charge and overcharge period are studied by quartz frequency microcalorimeter. Heat generation curve is fitted into a function, and heat transport equation is solved. Analysis with the model and experiment show that temperature rise is about 3 °C and difference between the model and the experiment is no more than 0.1 °C.     

Theoretical analysis of a thermodynamic cycle for power and heat production using supercritical carbon dioxide

A numerical study of a thermodynamic cycle is described: solar energy powered Rankine cycle using supercritical carbon dioxide as the working fluid for combined power and heat production. A model is developed to predict the cycle performance. Experimental data is used to verify the numerical formulation. Of interest in the present study is the thermodynamic cycle of 0.3–1.0 kW power generation and 1.0–3.0 kW heat output. The effects of the governing parameters on the performance are investigated numerically. The results show that the cycle has a power generation efficiency of somewhat above 20.0% and heat recovery efficiency of 68.0%, respectively. It is seen that the cycle performance is strongly dependent on the governing parameters and they can be optimized to provide maximum power, maximum heat recovery or a combination of both. The power generation and heat recovery are found to be increased with solar collector efficient area. The power generation is also increased with water temperature of the heat recovery system, but decreased with heat exchanging area. It is also seen that the effect of the water flow rate in the heat recovery system on the cycle performance is negligible.     

高温相变蓄热技术的研究进展

蓄热技术不仅能缓解环境污染和能源浪费的问题,还可以解决热能供给与需求失的矛盾.文中对高温相变蓄热技术的应用和研究现状做了一个综述,从蓄热材料的选择、蓄热器的数值模拟和数学建模、系统研究三个方面对高温相变蓄热技术的研究进展热点以及现状进行了总结.尤其对高温相变蓄热技术在太阳能热发电中的应用现状,并对高温相变蓄热技术在太阳能热发电中的应用进行了分析和展望.     

Performance of high-temperature heat exchangers in biomass fuel powered externally fired gas turbine systems

Recently, there has been wide-ranging research on the idea of biomass fuel powered externally firing micro gas turbines; but only a small subset of these studies has used experimental work to evaluate the systems. These systems have not yet been employed in Malaysia for applications in thermal energy or power generation. The objective of this study is to determine the performance of a stainless steel high-temperature heat exchanger, which was built to transfer thermal power from a biomass gasifier-combustor to the pure air turbine working fluid. The study is based on experimental work using different air blower capacities as an air supply. The heat exchanger achieved 694 °C turbine inlet temperature with an average effectiveness of 62.5%.     

变工况下直接空冷机组最佳真空的分析

为了提高直接空冷机组运行经济性,以冷端系统的变工况模型为基础,通过计算空冷凝汽器风机送风量增大时空冷机组发电功率与对应风机耗功功率的增量,得到直接空冷机组凝汽器最佳真空的确定方法．根据相似定律确定迎面风速对风机耗功的影响,并通过冷端系统数学模型的分析和简化得到机组背压与发电功率的关系,最终导出了不同环境温度和排汽热负荷下迎面风速对应的最佳真空．根据模型对某330Mw机组在变工况下的最佳真空进行了计算,结果表明：随着排汽量的增加或环境温度的升高,最佳真空及对应的风量都增加;当环境温度高于20℃时,环境温度对最佳真空的影响更加突出．     

Solar energy powered Rankine cycle using supercritical CO2

A solar energy powered Rankine cycle using supercritical CO₂ for combined production of electricity and thermal energy is proposed. The proposed system consists of evacuated solar collectors, power generating turbine, high-temperature heat recovery system, low-temperature heat recovery system, and feed pump. The system utilizes evacuated solar collectors to convert CO₂ into high-temperature supercritical state, used to drive a turbine and thereby produce mechanical energy and hence electricity. The system also recovers heat (high-temperature heat and low-temperature heat), which could be used for refrigeration, air conditioning, hot water supply, etc. in domestic or commercial buildings. An experimental prototype has been designed and constructed. The prototype system has been tested under typical summer conditions in Kyoto, Japan; It was found that CO₂ is efficiently converted into high-temperature supercritical state, of while electricity and hot water can be generated. The experimental results show that the solar energy powered Rankine cycle using CO₂ works stably in a trans-critical region. The estimated power generation efficiency is 0.25 and heat recovery efficiency is 0.65. This study shows the potential of the application of the solar-powered Rankine cycle using supercritical CO₂.     

Thermal simulation of high‐power Li‐ion battery with LiMn1/3Ni1/3Co1/3O2 cathode on cell and module levels

Thermal modeling of temperature rise in high‐power Li‐ion battery cells and modules is presented here. Simulation results are validated by experiments. Results indicate that entropy heat generation plays a significant role in heat generation of Li‐ion battery cells and should be included in simulation as a function of state of charge (SOC). Simulation results utilizing measured overpotential resistance and entropy heat generation provide the best fit when compared to experimental results. Resistance data provided by supplier shows significant difference compared with measured data and should be critically examined for any module design purposes. Copyright © 2013 John Wiley & Sons, Ltd.     

A review on lithium-ion power battery thermal management technologies and thermal safety

Lithium-ion power battery has become one of the main power sources for electric vehicles and hybrid electric vehicles because of superior performance compared with other power sources.In order to ensure the safety and improve the performance,the maximum operating temperature and local temperature difference of batteries must be maintained in an appropriate range.The effect of temperature on the capacity fade and aging are simply investigated.The electrode structure,including electrode thickness,particle size and porosity,are analyzed.It is found that all of them have significant influences on the heat generation of battery.Details of various thermal management technologies,namely air based,phase change material based,heat pipe based and liquid based,are discussed and compared from the perspective of improving the external heat dissipation.The selection of different battery thermal management (BTM) technologies should be based on the cooling demand and applications,and liquid cooling is suggested being the most suitable method for large-scale battery pack charged/discharged at higher C-rate and in high-temperature environment.The thermal safety in the respect of propagation and suppression of thermal runaway is analyzed.     

Three-dimensional thermal finite element modeling of lithium-ion battery in thermal abuse application

In order to better understand the thermal abuse behavior of high capacities and large power lithium-ion batteries for electric vehicle application, a three-dimensional thermal model has been developed for analyzing the temperature distribution under abuse conditions. The model takes into account the effects of heat generation, internal conduction and convection, and external heat dissipation to predict the temperature distribution in a battery. Three-dimensional model also considers the geometrical features to simulate oven test, which are significant in larger cells for electric vehicle application. The model predictions are compared to oven test results for VLP 50/62/100S-Fe (3.2 V/55 Ah) LiFePO₄/graphite cells and shown to be in great agreement.     

Lithium battery thermal management system for hybrid vehicles

为研究动力电池组的温度特性以及维持其工作在最佳的温度范围内,以锂离子电池为研究对象,设计了一种新型混合动力汽车的电池热管理系统,利用空调系统和发动机排气系统来调控电池组的温度。建立了锂电池组的三维瞬态产热数值模型,以电池组的三维尺寸和进风口流速为输入参数,以降低电池组的最大温升和提高电池组的温度均匀性为输出参数,利用FLUENT仿真软件和DesignXplorer模块进行联合优化设计了电池组的结构。优化后的电池组的温升比优化前降低了5.39 K,电池组温差降低了6.41 K。分析了恒倍率放电以及对流换热系数对单体电池温升的影响,研究表明：放电倍率越大电池温升越快,放电结束后电池的温度越高,在对流换热系数小于30 W/（m²·K）时,散热效果明显。对电池组在不同条件下加热或者冷却进行了仿真分析,验证了该电池热管理系统的可行性。     

Experimental study of hydrogen storage with reaction heat recovery using metal hydride in a totalized hydrogen energy utilization system

Experimental results for hydrogen storage tanks with metal hydrides used for load leveling of electricity in commercial buildings are described. Variability in electricity demand due to air conditioning of commercial buildings necessitates installation of on-site energy storage. Here, we propose a totalized hydrogen energy utilization system (THEUS) as an on-site energy storage system, present feasibility test results for this system with a metal hydride tank, and discuss the energy efficiency of the system. This system uses a water electrolyzer to store electricity energy via hydrogen at night and uses fuel cells to generate power during the day. The system also utilizes the cold heat of reaction heat during the hydrogen desorption process for air conditioning. The storage tank has a shell-like structure and tube heat exchangers and contains 50 kg of metal hydride. Experimental conditions were specifically designed to regulate the pressure and temperature range. Absorption and desorption of 5,400 NL of hydrogen was successfully attained when the absorption rate was 10 NL/min and desorption rate was 6.9 NL/min. A 24-h cycle experiment emulating hydrogen generation at night and power generation during the day revealed that the system achieved a ratio of recovered thermal energy to the entire reaction heat of the hydrogen storage system of 43.2% without heat loss.     

Optimization of Output Power and Thermal Efficiency of Solar‐Dish Stirling Engine Using Finite Time Thermodynamic Analysis

This paper presents an investigation on finite time thermodynamic (FTT) evaluation of a solar‐dish Stirling heat engine. FTTs has been applied to determine the output power and the corresponding thermal efficiency, exergetic efficiency, and the rate of entropy generation of a solar Stirling system with a finite rate of heat transfer, regenerative heat loss, conductive thermal bridging loss, and finite regeneration process time. Further imperfect performance of the dish collector and convective/radiative heat transfer mechanisms in the hot end as well as the convective heat transfer in the heat sink of the engine are considered in the developed model. The output power of the engine is maximized while the highest temperature of the engine is considered as a design parameter. In addition, thermal efficiency, exergetic efficiency, and the rate of entropy generation corresponding to the optimum value of the output power is evaluated. Results imply that the optimized absorber temperature is some where between 850 K and 1000 K. Sensitivity of results against variations of the system parameters are studied in detail. The present analysis provides a good theoretical guidance for the designing of dish collectors and operating the Stirling heat engine system.     

Simulation of a solar‐biogas hybrid energy system for heating,fuel supply,and power generation

Biogas production from organic wastes has been widely utilized for several decades, but maintaining right temperature for anaerobic bacteria is a challenge. In order to overcome the inhibition of the bacteria growth and biogas production due to the low temperature, a solar‐biogas hybrid energy system for heating, fuel supply, and power generation has been proposed for converting domestic garbage into biogas in a rural area of China. In this system, the solar energy has been included as one of the heating sources during an anaerobic digestion process. A mathematical model has been developed to evaluate the influence of system operating characteristics. Based on the simulation results, the biogas production rate, thermal efficiency, temperature of the digester, energy distributions in the system, optimal operating parameters, economic efficiency, and thermodynamic characteristics of the system were analyzed. The impact of solar irradiation on the efficiency of the system was also studied. According to the results, in cloudy days, the reactor volume and solar collector area greatly influenced the steady energy supply. In winter, the produced biogas is mostly utilized by the aided boiler to maintain the proper organic mixture temperature in the bioreactor. Heat loss from bioreactor dramatically increases the organic mixture volume. Per simulation, the longest return on the investment of this type of the biogas system is about 5.54 years, and the shortest return on the investment is less than 4 years if the battery is removed and the electric grid can be used. Therefore, in this study, the feasibility of a hybrid energy system for converting domestic garbage into energy has been validated. Copyright © 2017 John Wiley & Sons, Ltd.     

Development of a thermoelectric battery-charger with microcontroller-based maximum power point tracking technique

This article describes a battery charger, which is powered by thermoelectric (TE) power modules. This system uses TE devices that directly convert heat energy to electricity to charge a battery. The characteristics of the TE module were tested at different temperatures. A SEPIC dc–dc converter was applied and controlled by a microcontroller with the maximum power point tracking (MPPT) feature. The proposed system has a maximum charging power of 7.99 W: that is better than direct charging by approximately 15%. The objectives are to study the principle of TE power generation and to design and develop a TE battery charger that uses waste heat or another heat source as the direct input power.     

Microgrid composed of three or more SOFC combined cycles without accumulation of electricity

Large-scale centralization of the power supply system, consisting mainly of nuclear power generation and thermal power generation, has been adopted in Japanese electrical power system. Because Japan's centralized power supply system has little accommodation for changes in load, the amount of renewable energy that can be introduced is restricted substantially. The percentage of renewable energy introduced in Japan in 2012 was 1.6%; if this were to include hydraulic power generation, the percentage would be less than 10%. Accordingly, this study proposes the development of a microgrid that responds to the changes in output from a large-scale solar power system by using load from the operation of three or more solid oxide fuel cell hybrid power systems (PGSSs), and controlling the number of PGSS units in response to the magnitude of load. A storage battery is not used for the microgrid, developed in this study, for controlling the change in output from renewable energy. The proposal of a system with an introductory high rate of renewable energy is the purpose of this study. The study clarified the method of system operation and the rate at which renewable energy can be introduced at the time of distributed installation of the developed microgrid, using three or more PGSSs to supply all the cities in the Hokkaido region of Japan. From the results of the analysis, the control achieved with the PGSS units was confirmed to be effective. Furthermore, according to meteorological data and our proposed microgrid, the power supplied by renewable energy over the entire Hokkaido region in 2012 reached 48% on February 14 (winter), 49% on July 15 (summer), and 45% on October 15 (moderate season).     

Plate flat heat pipe and liquid‐cooled coupled multistage heat dissipation system of Li‐ion battery

A thermal management system with the capability of achieving excellent heat dissipation is essential to the development of battery pack for transportation devices. To meet the temperature uniformity requirements of the battery pack, the plate flat heat pipe and liquid‐cooled coupled multistage heat dissipation system had been introduced. In this article, the research status of thermal management systems in battery pack was introduced. And the heat generation and heating power of the Li‐ion cell were studied. Then, the structure model of plate flat heat pipe system was proposed. Finally, the enhanced heat conduction effect of the thermal management system proposed in this article was comprehensively analyzed. Through the analysis of the results, in high discharge rates, the thermal management system proposed in this article could meet the temperature uniformity requirements of battery pack; also, the internal difference would reduce by 30.20%.     

Geothermal electric power generation in Iceland for the proposedIceland/United Kingdom HVDC power link

A review is given of the geothermal electric power potential in Iceland which could economically be developed to supplement hydro power for the proposed HVDC power link to the United Kingdom and supply the power-intensive industries in Iceland which are currently envisioned for development. Technically harnessable energy for electricity generation, taking account of geothermal resources down to an assumed base depth, temperature distribution in the crust, probable geothermal recovery factor, and accessibility of the field, has been assessed. Nineteen known high-temperature fields and nine probable fields have been identified. Technically harnessable geoheat for various areas is indicated. Data on high-temperature fields suitable for geothermal electric power generation and on harnessable energy for electric power generation within volcanic zones are presented