PEMFC-TTEG混合系统的特性研究

采用遗传算法构建一个与实验数据匹配的质子交换膜燃料电池(PEMFC)模型,提出一个利用PEMFC余热驱动双级半导体热电发电机(TTEG)的混合系统。推导出PEMFC电流密度与TTEG的无量纲电流密度之间的关系,确定混合系统中TTEG运行的工作电流区间。考虑混合系统中多种电化学损失和热损失,得出混合系统功率与效率的表达式,研究电池工作温度,热电元件的优值系数、导热率以及热电元件数目对混合系统性能的影响。     

基于生态学准则对MCFC/AR混合系统的优化分析

基于生态学准则对稳定状态下运行的熔融碳酸盐燃料电池(MCFC)与吸收式制冷机(AR)组成的混合系统进行优化,考虑系统存在的电化学和热力学不可逆性,导出混合系统等效输出功率、效率以及生态学性能系数(ECOP)的表达式。应用数值模拟分析混合系统性能,得到功率密度、效率以及ECOP分别与电流密度的基本关系,从而确定工作参数的优化区间。结果表明:混合系统运行时的输出功率和效率相比于燃料电池单独运行时有所提升,并且通过生态学优化能得到更为精确的优化工作区间。最后分析燃料电池的工作温度、工作压力以及制冷机内部不可逆性对混合系统生态学性能的影响。     

磷酸燃料电池-两级热电系统性能分析及负载匹配

建立一个利用磷酸燃料电池(PAFC)余热驱动两级半导体温差热电发电器(TTEG)的复合发电系统模型,考虑了PAFC电化学反应中的过电势损失、回热损失、热漏以及TTEG中的主要不可逆损失,导出PAFC,TTEG和复合系统的输出功率和效率的一般表达式,得到PAFC和TTEG电流密度之间的关系。确定系统的优化工作区间,分析主要参数对复合系统性能的影响,给出负载电阻的最佳匹配条件,所得结果可为实际的PAFC-TTEG复合发电系统的设计和优化运行提供理论依据。     

熔融碳酸盐燃料电池热启动过程的人工神经网络建模

熔融碳酸盐燃料电池(MCFC)是燃料电池研究领域的一个难点,其严格的热启动过程对电池性能和寿命的影响至关重要.针对这一问题,建立了基于人工神经网络的熔融碳酸盐燃料电池热启动过程模型,并详细给出了采用改进BP算法的熔融碳酸盐燃料电池热启动过程的模型结构、算法、训练和仿真.MATLAB仿真结果证明其快速准确,为熔融碳酸盐燃料电池热启动过程的控制提供了实际工程应用模型.     

非均质温差发电器的性能分析

建立非均质温差发电器（TEG）理论模型,考虑热电材料的非均质导热系数以及温差发电器与热源间的传热热阻的影响,分析非均质温差发电器的一般性能。讨论热电元件对数、热导率、高温热源温度对非均质温差发电器性能特性的影响。结果表明,相较于均质温差发电器,导热系数不均匀强度越大,非均质温差发电器的最大输出功率和最大效率越高;热电元件对数、热导率、高温热源温度的提高均可提升系统性能。     

氢能知识系列讲座(6)利用氢能的高效设备(二)——高温燃料电池

本讲将介绍高温燃料电池,即工作温度在500～1000℃的燃料电池,主要指工作温度在900～1000℃的固体氧化物燃料电池(SOFC)和工作温度在650℃左右的熔融碳酸盐燃料电池(MCFC)。     

燃料电池及其发展概况

概述了燃料电池原理并计算了氢氧型燃料电池可逆条件下电池电压和效率。介绍了国外熔融碳酸盐型燃料电池（MCFC）、固体氧化物型燃料电池（SOFC）和固体高分子型燃料电池（PEFC）的最新进展，国内的发展状况。     

计及电热耦合的多级温差发电建模和试验研究

为准确描述多级温差发电器实际工作时各级节点温度分布与通过热功率及其热电输出特性之间的关系,文章建立了计及电热耦合的多级温差发电数值分析模型。运用贪心算法(Greedy Algorithm)编程求解,以常见的Bi2Te3,PbTe和SiGe 3种半导体材料的发电片为例,通过试验验证了模型的正确性,并进一步研究了电热耦合效应对多级温差发电器的Seebeck电压、发电功率和热电转换效率的影响。模型的数值求解和实测结果对比表明:由于电热耦合效应的存在,多级温差发电器在实际工作时各级节点的温度上升,但冷、热端的温差值减小;电热耦合效应会使Seebeck电压、发电功率和热电转换效率明显降低,下降幅度随多级温差发电器热端温度的升高而增大,随发电器级数的增加而减小。     

应用温差发电器降低锅炉排烟热损失

锅炉是一种特殊结构部件，既可以为热电效应为基础的温差发电器提供热源，也可以为其提供冷源，这为应用温差发电器创造了条件。应用温差发电器可以降低排烟温度，减少排烟热损失。文章对应用温差发电器的可能性以及应用后的效率进行了分析，结论是可以提高锅炉效率；提出了如何应用温差发电器件的方法．并对锅炉应用温差发电器降低排烟损失应该考虑的问题进行了分析。     

ZT值温度依存性对温差发电器热电性能的影响

为了评估热电材料ZT值温度依存性对热电发电器性能的影响,基于HZ-20商用热电材料的热物性参数,分别采用定物性与变物性的计算方法,对温差发电器在具有不同热源温度下的工作性能进行理论研究。研究结果表明,当采用定物性方法计算时(即不考虑ZT值温度依存性),输出功率及相应转换效率的计算值都较采用变物性计算时存在一定的偏差。当半导体热端温度低于定物性计算时采用的定性温度值时,偏差很小,但随着半导体热端温度的继续增加,偏差则越来越大,高热端温度下计算得到的计算偏差达30%左右。因此,热电材料ZT值温度依存性对温差发电器热电性能的影响不容忽视。     

Maximum equivalent efficiency and power output of a PEM fuel cell/refrigeration cycle hybrid system

With the help of the current models of proton exchange membrane (PEM) fuel cells and three-heat-source refrigeration cycles, the general model of a PEM fuel cell/refrigeration cycle hybrid system is originally established, so that the waste heat produced in the PEM fuel cell may be availably utilized. Based on the theory of electrochemistry and non-equilibrium thermodynamics, expressions for the efficiency and power output of the PEM fuel cell, the coefficient of performance and cooling rate of the refrigeration cycle, and the equivalent efficiency and power output of the hybrid system are derived. The curves of the equivalent efficiency and power output of the hybrid system varying with the electric current density and the equivalent power output versus efficiency curves are represented through numerical calculation. The general performance characteristics of the hybrid system are discussed. The optimal operation regions of some parameters in the hybrid system are determined. The advantages of the hybrid system are revealed.     

An available method exploiting the waste heat in a proton exchange membrane fuel cell system

Based on the models of a proton exchange membrane (PEM) fuel cell working at steady state and a semiconductor thermoelectric generator, a hybrid system consisting of a PEM fuel cell, a semiconductor thermoelectric generator, and a regenerator is originally put forward. Expressions for the efficiencies and power outputs of the fuel cell, thermoelectric generator, and hybrid system are derived. The relation between the operating electric currents in the fuel cell and thermoelectric generator is obtained. The maximum power output of the hybrid system is numerically given. The optimally operating electric currents in the fuel cell and thermoelectric generator are calculated, and consequently, the optimal region of the hybrid system is determined. The results obtained here will provide some guidance for further understanding the performance and operation of practical PEM fuel cell-thermoelectric generator hybrid systems.     

Performance analysis of a pressurized molten carbonate fuel cell/micro-gas turbine hybrid system

This paper presents the work on the design and part-load operations of a hybrid power system composed of a pressurized molten carbonate fuel cell (MCFC) and a micro-gas turbine (MGT). The gas turbine is an existing one and the MCFC is assumed to be newly designed for the hybrid system. Firstly, the MCFC power and total system power are determined based on the existing micro-gas turbine according to the appropriate MCFC operating temperature. The characteristics of hybrid system on design point are shown. And then different control methods are applied to the hybrid system for the part-load operation. The effect of different control methods is analyzed and compared in order to find the optimal control strategy for the system. The results show that the performance of hybrid system during part-load operation varies significantly with different control methods. The system has the best efficiency when using variable rotational speed control for the part-load operation. At this time both the turbine inlet temperature and cell operating temperature are close to the design value, but the compressor would cross the surge line when the shaft speed is less than 70% of the design shaft speed. For the gas turbine it is difficult to obtain the original power due to the higher pressure loss between compressor and turbine.     

Molten-salt fuel cells—Technical and economic challenges

This paper presents a personal view of the status and research needs of the MCFC and other molten-salt fuel cells. After an overview of current MCFC performance, compared with performance and cost of other fuel cells, improvements in power density and lifetime as well as cost reduction are identified as key priorities to accelerate the commercialization of the MCFC. In spite of its unfavorable public image (compared to, in particular, PEMFC and planar SOFC) MCFC technology has progressed steadily and cost reduction has been significant. Large-scale commercialization, especially in the distributed generation and cogeneration market, remains a possibility but its chances are highly dependent on a forceful and consistent energy policy, for example taking into account the externalities associated with various modes of electric power production from fossil fuels. In spite of steady improvements in performance, important defects in fundamental knowledge remain about wetting properties, oxygen reduction kinetics, corrosion paths and control mechanisms. These must be addressed to stimulate further simplification of design and find solutions to lifetime issues. Recently, alternative concepts of molten-salt fuel cells have been capturing attention. The direct carbon fuel cell (DCFC), reviving an old concept, has caught the attention of energy system analysts and some important advances have been made in this technology. Direct CO and CH₄ oxidation have also been a focus of study. Finally, the potential of nanotechnology for high-temperature fuel cells should not be a priori excluded.     

Molten carbonate fuel cell (MCFC)-based hybrid propulsion systems for a liquefied hydrogen tanker

This study proposes a molten carbonate fuel cell (MCFC)-based hybrid propulsion system for a liquefied hydrogen tanker. This system consists of a molten carbonate fuel cell and a bottoming cycle. Gas turbine and steam turbine systems are considered for recovering heat from fuel cell exhaust gases. The MCFC generates a considerable propulsion power, and the turbomachinery generates the remainder of the power. The hybrid systems are evaluated regarding system efficiency, economic feasibility, and exhaust emissions. The MCFC with a gas turbine has higher system efficiency than that with a steam turbine. The air compressor consumes substantial power and should be mechanically connected to the gas turbine. Although fuel cell-based systems are less economical than other propulsion systems, they may satisfy the environmental regulations. When the ship is at berth, the MCFC systems can be utilized as distributed generation that is connected to the onshore-power grid.     

Performance model of molten carbonate fuel cell

A performance model of a molten carbonate fuel cell (MCFC), an electrochemical energy conversion device for electric power generation, is discussed. The presumptive ability of the MCFC model is improved and the impact of MCFC characteristics in fuel cell system simulations is investigated. Basic data are obtained experimentally by single-cell tests. A correlation formula based on the experimental data is derived for the cell voltage and the oxygen and carbon dioxide partial pressures. Three types of MCFC systems are compared. With regard to fuel utilization, system characteristics using the proposed correlation are very similar to those obtained using a previous model. However, the amount of decrease predicted by the proposed model with respect to system efficiency is larger than that obtained by the previous model at high air utilization     

Integration of molten carbonate fuel cell and looped multi-stage thermoacoustically-driven cryocooler for electricity and cooling cogeneration

Thermal management is essential for high-temperature molten carbonate fuel cell (MCFC) because the accumulated waste heat may degrade the durability. In this paper, looped multi-stage thermoacoustically-driven cryocooler (LMTC) is proposed to reuse the waste heat from MCFC for cooling production, which not only can tackle with the thermal management issue but also can provide additional usages. Accounting various irreversible dissipation, the models of MCFC, LMTC and MCFC-LMTC hybrid system are analytically formulated. Performance features of MCFC-LMTC hybrid system are revealed and the advantages are expounded via calculation examples. Calculations indicate that the maximum power density and corresponding efficiency of the hybrid system are 1688.9 W m^?2 and 39.7%, which are 11.4% and 1.3% bigger than that of the sole MCFC system, respectively. By comparing with other available systems, the superiority of using LMTC to recover MCFC waste heat for refrigeration is clearly demonstrated. Considerable parametric studies show that the heat-transfer coefficient of hot heat exchange for LMTC is not suggested to be greater than 2.5 × 10^?3 W m^?2 K^?1. In addition, an increase in the working temperature, working pressure of MCFC, reactant concentration or engine stage number of LMTC positively benefits the hybrid system performance, while an increase in the thermodynamic loss coefficient worsens the hybrid system performance. The obtained results may offer new insights into improving the performance of MCFCs through thermal management approaches.     

A theoretical study of molten carbonate fuel cell combined with a solar power plant and Cu–Cl thermochemical cycle based on techno-economic analysis

A novel power and hydrogen coproduction system is designed and analyzed from energetic and economic point of view. Power is simultaneously produced from parabolic trough collector power plant and molten carbonate fuel cell whereas hydrogen is generated in a three-steps Cu–Cl thermochemical cycle. The key component of the system is the molten carbonate fuel cell that provides heat to others (Cu–Cl thermochemical cycle and steam accumulator). A mathematic model is developed for energetic and economic analyses. A parametric study is performed to assess the impact of some parameters on the system performance. From calculations, it is deduced that electric energy from fuel cell, solar plant and output hydrogen mass are respectively 578 GWh, 25 GWh and 306 tons. The overall energy efficiency of the proposed plants is 46.80 % and its LCOE is 7.64 c€/kWh. The use of MCFC waste heat allows increasing the solar power plant efficiency by 2.15 % and reducing the annual hydrogen consumption by 3 %. Parametric analysis shows that the amount of heat recovery impacts the energy efficiency of fuel cell and Cu–Cl cycle. Also, current density is a key parameter that influences the system efficiency.     

Simulation and modeling of copper-chlorine cycle,molten carbonate fuel cell alongside a heat recovery system named regenerative steam cycle and electric heater with the incorporation of PID controller in MATLAB/SIMULINK

MCFC (molten carbonate fuel cell) is a relatively new kind of fuel cell that may be utilized in both local and large-scale energy distribution and generating systems. MCFCs are largely regarded as a viable source of renewable energy. Making an MCFC is a time-consuming and costly process. Mathematical modeling and efficiency simulations are essential to appropriately maximize its performance. Regenerative cycle, copper-chlorine cycle, and electric heater with PID controller is also studied to integrate them with MCFC to increase the efficiency of the overall system. Copper–Chlorine cycle is integrated to provide a stable stream of hydrogen and oxygen for the fuel cell. The Molten Carbonate fuel cell of stack 100 generates 1.203 MW of power at Voltage of 1.2 V each. Waste Heat recovery system is installed named regenerative Steam cycle which produces 2.94 MW of power. The total efficiency of system is 57% and the total extracted power is 4.143 MW. MATLAB/Simulink R2020a is used for modeling of multigeneration system with use of Engineering Equation Solver.     

Design analysis and tri-objective optimization of a novel integrated energy system based on two methods for hydrogen production: By using power or waste heat

Hydrogen is rapidly turning into one of the essential energy carriers for future sustainable energy systems. The main reason for this is the possibility of off-peak excess power production and storage of renewable stations such as wind farms, photovoltaic plants, etc. For hydrogen (itself) or its sub-productions methanol, ammonia, etc. Such energy systems are so-called power2X technologies. For hydrogen and other biogases, using a fuel cell is a promising method for returning the fuel to the power grid or electric cars in the form of electricity. In this paper, a novel hybrid energy system consisting of a molten carbonate fuel cell (MCFC) and different options to generate hydrogen from the waste heat of the MCFC is investigated. The system consists of two scenarios of weather using proton exchange membrane electrolyzer (PEME) of vanadium chloride (VCL) cycle. The article presents a comprehensive thermodynamic, economic, and environmental analysis of the system optimized by tri-objective optimization (as an innovative optimization) methods. The aim of the optimization task here is to minimize the costs and emissions while maximizing efficiency. A parametric study is conducted to see the effect of different design parameters on the system's performance. Results demonstrate that fuel utilization factor, stack temperature, and current density have the most critical effect on the system performance. In addition, the system coupled with the VCL cycle exhibits better performance than the system with PEME. In addition, at the optimized point, the efficiency, cost rate, and emission become 69.28%, 3.73 ($/GJ), and 1.16 kg/kWh, respectively. In addition, the produced hydrogen in VCL and PEME are 585 kg/day and 293 kg/day respectively.