Performance analysis on various system layouts for the combination of an ambient pressure molten carbonate fuel cell and a gas turbine

This study analyses hybrid systems combining a molten carbonate fuel cell (MCFC) operating at ambient pressure and a gas turbine. Various possible system layouts, with the major difference among these layouts being the heating method of the turbine inlet gas, are proposed and their design performances are simulated and comparatively analyzed. Power of the MCFC in the hybrid system is explained in terms of the cathode inlet air temperature. Power of the gas turbine differs among various layouts because of large difference in the turbine inlet temperature. The direct firing in front of the turbine allows far higher turbine inlet temperature, and thus greater gas turbine power than the indirect heating of the inlet gas. The optimum pressure ratio of the directly fired system is higher than that of the indirectly fired system. The directly fired system allows not only much larger system power and higher optimum efficiency but also greater flexibility in the selection of the design pressure ratio of the gas turbine. In addition, the directly fired system can better accommodate the specifications of both current micro gas turbines and advanced gas turbines than the indirectly fired system.     

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.     

Influence of multiple irreversible losses on the performance of a molten carbonate fuel cell-gas turbine hybrid system

In this study, a new molten carbonate fuel cell-gas turbine hybrid system, which consists of a fuel cell, three heat exchangers, a compressor, and a turbine, is established. The multiple irreversible losses existing in real hybrid systems are taken into account by the models of a molten carbonate fuel cell and an open Brayton cycle with a regenerative process. Expressions for the power outputs and efficiencies of the subsystems and hybrid system are derived. The maximum power output and efficiency of the hybrid system are numerically calculated. It is found that compared with a single molten carbonate fuel cell, both the power output and efficiency of the hybrid system are greatly enhanced. The general performance characteristics of the hybrid system are evaluated and the optimal criteria of the main performance parameters are determined. The effects of key irreversibilities on the performance of the hybrid system are investigated in detail. It is found that the use of a regenerator in the gas turbine can availably improve the power output and efficiency of the system. The results obtained here are significant and may be directly used to discuss the optimal performance of the hybrid system in special cases.     

An advanced integrated biomass gasification and molten fuel cell power system

Biomass has recently received considerable attention as a potential substitute for fossil fuels in electric power production. Renewable biomass crops, industrial wood residues, and municipal wastes as fuels for production of electricity allow substantial reduction of environmental impact. High reactivity of biomass makes it relatively easy to convert solid feedstocks into gaseous fuel for subsequent use in a power cycle.So far most of the studies were focused on investigating performance and economics of biomass gasifiction–gas turbine systems. A general conclusion resulting from these studies is that the combination of biomass gasifiers, hot gas cleanup systems, and advanced gas turbines is promising for cost competitive electric power generation[1, 2]. In this paper another concept of biomass fueled power systems is considered, namely biomass gasification with a molten carbonate fuel cell (MCFC). Comparison between two concepts is made in terms of efficiency, feasibility, and process requirements. As an example of such a system, a highly efficient novel power cycle consisting of the Battelle gasification process, a molten carbonate fuel cell, and a steam turbine is introduced. The calculated efficiency is around 53%, which exceeds efficiencies of traditional designs[1, 3] considerably. Finally, an economic analysis and electricity cost projection are performed for a power plant consuming 2000 tons of biomass per day. Results are compared with those for more traditional integrated biomass gasification/gas turbine systems and for coal fueled cycles.     

Characteristics and economic evaluation of a CO2-capturing repowering system with oxy-fuel combustion for utilizing exhaust gas of molten carbonate fuel cell (MCFC)

A scale of 2.4 MW molten carbonate fuel cell (MCFC) was taken to construct a high-efficiency and economic power generation system without CO₂ emission for utilizing its exhaust gas. A conventional steam turbine power generation system (STPS) is evaluated and the net generated power (NGP) is estimated to be only 131 kW and the STPS is not economically feasible. A CO₂-caputuring repowering system is proposed, where low temperature steam produced at heat recovery steam generator (HRSG) by using the MCFC exhaust gas is utilized as a main working fluid of a gas turbine, and the temperature of the steam is raised by combusting fuel in a combustor by using pure oxygen, not the air. It is estimated that NGP of the proposed system is 253 kW, and CO₂ reduction amount is 583 t-CO₂/y, compared to 302 t-CO₂/y for the STPS and that the proposed system becomes economically feasible if a CO₂ emission credit higher than 20 $/t-CO₂ can be granted. It is also estimated, when its turbine inlet temperature is increased from 850 °C to 1000 °C, CO₂-capturing is not cost-consuming but becomes to be profitable, owing to improved power generation characteristics.     

A methodology for improving the performance of molten carbonate fuel cell/gas turbine hybrid systems

In the present article a molten carbonate fuel cell (MCFC) system has been developed, modeled and implemented in Matlab language. It enables definition of the optimal operating conditions of the fuel cell, in terms of electrical and thermal performance, when it is a part of a hybrid plant composed of an MCFC system, a gas turbine and a possible heat recovery system. The thermal energy, which is recoverable from the adequately treated anodic exhaust gases, is utilized in a gas turbine plant to reduce its fuel consumption. Therefore, in the present article a methodology is illustrated to calculate the optimal values of some parameters characterizing the MCFC/gas turbine integrated system in terms of the electrical, first law and equivalent efficiencies. A choice is made among the sets of values of parameters investigated to improve the performance of the same integrated system according to its use (for the production of electric energy only or for the contemporary production of electric and thermal energy). Copyright © 2010 John Wiley & Sons, Ltd.     

Electrical and electrical–thermal power plants with molten carbonate fuel cell/gas turbine‐integrated systems

In this article the calculation tool further developed and implemented in Matlab language by the authors was used to determine some optimal operating conditions in electrical and thermal or electrical terms for two different types of hybrid systems: molten carbonate fuel cells (MCFC)/gas turbine with their heat recovery system and the hybrid systems operating in these optimal conditions were analyzed. In the heat recovery system, in both cases, a part of the thermal energy of these gases is used to produce the steam necessary for the MCFC system. The remaining thermal energy is used, in one case, for the production of steam at various levels of pressure and temperature, which feeds a steam bottom plant to produce additional electric energy; in the other case, the same thermal energy is used to produce steam for cogenerative use. The heat recovery system was suitably designed according to the circumstances and the performances and the specific CO₂ emissions of the hybrid systems were evaluated. Copyright © 2010 John Wiley & Sons, Ltd.     

Study of molten carbonate fuel cell—microturbine hybrid power cycles

The interaction realized by fuel cell—microturbine hybrids derive primarily from using the rejected thermal energy and combustion of residual fuel from a fuel cell in driving the gas turbine. This leveraging of thermal energy makes the high temperature molten carbonate fuel cells (MCFCs) ideal candidates for hybrid systems. Use of a recuperator contributes to thermal efficiency by transferring heat from the gas turbine exhaust to the fuel and air used in the system.Traditional control design approaches, consider a fixed operating point in the hope that the resulting controller is robust enough to stabilize the system for different operating conditions. On the other hand, adaptive control incorporates the time-varying dynamical properties of the model (a new value of gas composition) and considers the disturbances acting at the plant (load power variation).     

Carbon dioxide separation from high temperature fuel cell power plants

High temperature fuel cell technologies, solid oxide fuel cells (SOFCs) and molten carbonate fuel cells (MCFCs), are considered for their potential application to carbon dioxide emission control. Both technologies feature electrochemical oxidisation of natural gas reformed fuels, avoiding the mixture of air and fuel flows and dilution with nitrogen and oxygen of the oxidised products; a preliminary analysis shows how the different mechanism of ion transport attributes each technology a specific advantage for the application to CO₂ separation. The paper then compares in the first part the most promising cycle configurations based on high efficiency integrated SOFC/gas turbine “hybrid” cycles, where CO₂ is separated with absorption systems or with the eventual adoption of a second SOFC module acting as an “afterburner”. The second part of the paper discusses how a MCFC plant could be “retrofitted” to a conventional fossil-fuel power station, giving the possibility of draining the majority of CO₂ from the stack exhaust while keeping the overall cycle electrical efficiency approximately unchanged.     

Thermodynamic and economic optimization of a MCFC-based hybrid system for the combined production of electricity and hydrogen

In this paper, a biogas fuelled power generation system is considered. The system is based on a molten carbonate fuel cell (MCFC) stack integrated with a micro gas turbine for electricity generation, coupled with a pressure swing absorption system (PSA) for hydrogen production.     

Comparative feasibility study of combined cycles for marine power system in a large container ship considering energy efficiency design index (EEDI)

This study investigates an appropriate combined cycle as the electric propulsion system in a large container ship. A gas turbine combined cycle and molten carbonate fuel cell-steam turbine cycle are considered; the gas turbine uses LNG or hythane fuels. Because it is difficult to choose an appropriate propulsion system from only one perspective, comprehensive and unbiased analyses refer to the system performance, eco-efficiency, and economic feasibility for three configurations. An LNG-fueled COGES (combined gas turbine and steam integrated electric drive system) seems to be a promising alternative with regards to economic feasibility as well as a greenhouse gas regulation. The following alternative is the molten carbonate fuel cell-steam turbine cycle. A hythane-fueled COGES has a relatively low economic feasibility but will be the sole propulsion system if the regulation of greenhouse gas emission from shipping is stringent. On the other hand, the carbon taxation and implementation of an incentive for hydrogen fuel may facilitate a greener shipping environment; the additional eco-friendly policy for the shipping industry needs to be provided, shortly soon.     

Exergoeconomic analysis and determination of power cost in MCFC – steam turbine combined cycle

A novel combined molten carbonate fuel cell – steam turbine based system is proposed herein. In this cycle, steam is produced through the recovery of useful heat of an internal reforming MCFC and operates as work fluid in a Rankine cycle. Exergoeconomic analysis was performed, in order to verify the technical feasibility, including which components could be improved for greater efficiencies, as well as the cost of the power generated by the plant. A 10 MW MCFC was initially proposed, when the system reached 54.1% of thermal efficiency, 8.3% higher than MCFC alone, 11.9 MW of net power, 19% higher than MCFC alone, and an energy cost of 0.352 $/kWh. A sensitivity analysis was carried out and the parameters that most influenced on the cost were pointed out. The analysis pointed to the MCFC generation as the most impactful factor. By manipulating these values, it could be noted a significant power cost decrease, reaching satisfactory values to become economically feasible. The concept of economy of scale could be noticed in the proposed system, proving that a large-scale plant could be the focus of investment and public policies.     

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.     

Exergy based performance analysis of a solid oxide fuel cell and steam injected gas turbine hybrid power system

This paper presents exergy analysis of a hybrid solid oxide fuel cell and gas turbine (SOFC/GT) system in comparison with retrofitted system with steam injection. It is proposed to use hot gas turbine exhaust gases heat in a heat recovery steam generator to produce steam and inject it into gas turbine. Based on a steady-state model of the processes, exergy flow rates are calculated for all components and a detailed exergy analysis is performed. The components with the highest proportion of irreversibility in the hybrid systems are identified and compared. It is shown that steam injection decreases the wasted exergy from the system exhaust and boosts the exergetic efficiency by 12.11%. Also, 17.87% and 12.31% increase in exergy output and the thermal efficiency, respectively, is demonstrated. A parametric study is also performed for different values of compression pressure ratio, current density and pinch point temperature difference.     

MCFC-并联TTEG混合系统的性能优化

为有效回收熔融碳酸盐燃料电池产生的余热,提出一种由熔融碳酸盐燃料电池(MCFC)、两级并联温差发电器(TTEG)和回热器组合而成的混合系统模型。考虑MCFC电化学反应中的过电势损失和混合系统中的不可逆损失,通过数值分析得出混合系统的输出功率和效率的数学表达式,获得混合系统的一般性能特征,讨论MCFC电流密度与温差发电器的无量纲电流之间的关系,确定混合系统的优化工作电流区间。结果表明,该混合系统的功率密度和效率分别比单一的MCFC系统提高46.9%和35.0%。此外,考虑了热电材料性能指标等对热电能量转换的影响,为进一步开展燃料电池与两级温差发电器的混合系统的研究提供参考。     

Economic and environmental impact assessments of hybridized aircraft engines with hydrogen and other fuels

Hybridized engines have become the focus of research nowadays in order to update the existing engines in different transportation sectors. This paper presents a hybridized aircraft engine consisting of a molten carbonate fuel cell system and a commercial turbofan system. The MCFC units are connected to a steam reforming and a water gas shift system. Also, five clean fuels are selected, such as dimethyl ether, hydrogen, ethanol, methane, and methanol, which are combined with different mass ratios to form five different fuel blends. The hybridized aircraft is investigated using three approaches: exergy analysis, exergoeconomic analysis, and exergoenvironmental analysis. It is found that the proposed engine has an average exergetic efficiency of 88% and an average exergy destruction ratio of 12%. The specific exergetic cost of electricity of the engine has an average value of 710 $/GJ for the high-pressure turbine and 230$/GJ for the intermediate and low-pressure turbines, as well as 50 $/GJ for the MCFC. The average specific exergoenvironmental impact of electricity is 14 mPt/MJ for turbines and 4 mPt/MJ for the MCFC. In addition, a blend of ethanol and hydrogen appears to be a viable option economically and environmentally.     

高温燃料电池_燃气轮机混合发电系统性能分析

针对 高温燃料电池系统的高效率、环保性以及排气废热的巨大利用潜能，将其与燃气轮机组成混合装置进行发电是未来分布式发电的一种极有前景的方案。文中对高温燃料电池及混合循环系统作了简介，并对两种典型的高温燃料电池－燃气轮机混合循环发电系统进行了性能分析，这将为我国高温燃料电池－燃气轮机混合循环系统的研制提供参考。     

Molten carbonate fuel cell and gas turbine hybrid systems as distributed energy resources

Molten carbonate fuel cell (MCFC)/gas turbine (GT) hybrid system has attracted a great deal of research effort due to its higher electricity efficiency. However, its technology has remained at the conceptual level due to incomplete examination of the related issues, challenges and variables. To contribute to the development of system technology, the MCFC/GT hybrid system is analyzed and discussed herein. A qualitative comparison of the two kinds of MCFC/GT hybrid system, indirect and direct, is hindered by the many variables involved. However, the indirect system may be preferred for relatively small-scale systems with the micro-GT. The direct system can be more competitive in terms of system efficiency and GT selection due to the optionality of system layouts as well as even higher GT inlet temperature. System layout is an important factor influencing the system efficiency. The other issues such as GT selection, system pressurization and part-load operation are also significant.     

燃料电池_燃气轮机混合动力系统中催化燃烧室特性分析

对熔融碳酸盐燃料电池/微型燃气轮机(MCFC/MGT)混合动力系统中的催化燃烧室进行了实验和理论分析,确定了燃烧室入口温度、燃料浓度对燃料转化率的影响,在非设计工况下运行时催化燃烧室入口条件会发生变化,应用数学模型分析了各主要因素对催化燃烧室运行特性的影响。结果表明,计算结果与实验结果的最大误差在4%以内。在混合动力系统的运行范围内催化燃烧室入口温度高于770K时燃料转化率达99%以上,而入口流速和燃料浓度的变化对转化率的影响不明显。     

固体氧化物燃料电池与燃气轮机混合发电的发展及甲烷蒸汽重整的研究

燃料电池与燃气轮机混合发电系统有着很高的能量利用效率,是能量转换的重要研究方向。而固体氧化物燃料电池的蒸汽重整技术为该联合提供了重要的技术支持。本文设计了固体氧化物燃料电池的结构,并进行甲烷蒸汽重整的模拟计算,计算结果显示燃料电池排气温度达到1380K左右时,有很高的能量利用价值。