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Fuel Cells: Intermediate and High Temperature
Published in Brian D. Fath, Sven E. Jørgensen, Megan Cole, Managing Air Quality and Energy Systems, 2020
Xianguo Li, Gholamreza Karimi, Kui Jiao
The MCFC operates at higher temperature than all the fuel cells described so far. The operating temperature of the MCFC is generally around 600–700°C, typically 650°C. Such high temperature produces high-grade waste heat that is suitable for fuel processing, cogeneration, or combined cycle operation, leading to higher electric efficiency. It also yields the possibility of utilizing carbonaceous fuels (especially natural gas) directly, through internal reforming to produce the fuel (hydrogen) ultimately used by the fuel cell electrochemical reactions. This results in simpler MCFC systems (i.e., without external reforming or fuel processing subsystem), less parasitic load, and less cooling power requirements, hence higher overall system efficiency as well. The high operating temperature reduces voltage losses due to reduced activation and ohmic and mass transfer polarization. The activation polarization is reduced to such an extent that it does not require expensive catalysts as low-temperature fuel cells do, such as PAFCs and PEMFCs. It also offers great flexibility in the use of available fuels, say, through in situ reforming of fuels. It has been estimated that the MCFC can achieve an energy conversion efficiency of 52%–60% (from chemical energy to electrical energy) with internal reforming and natural gas as the primary fuel. Some studies have indicated that the MCFC efficiency of methane to electricity conversion is the highest attainable by any fuel cell or other single pass/simple cycle generation scheme.
Fuel Cells
Published in D. Yogi Goswami, Frank Kreith, Energy Conversion, 2017
The MCFC operates at higher temperature than all the fuel cells described so far. The operating temperature of the MCFC is generally around 600°C–700°C, typically 650°C. Such high temperature produces high-grade waste heat, which is suitable for fuel processing, cogeneration, or combined cycle operation, leading to higher electric efficiency. It also yields the possibility of utilizing carbonaceous fuels (especially natural gas) directly, through internal reforming to produce the fuel (hydrogen) ultimately used by the fuel cell electrochemical reactions. This results in simpler MCFC systems (i.e., without external reforming or fuel processing subsystem), less parasitic load, and less cooling power requirements, hence higher overall system efficiency as well. The high operating temperature reduces voltage losses due to reduced activation, ohmic, and mass transfer polarization. The activation polarization is reduced to such an extent that it does not require expensive catalysts as low-temperature fuel cells do, such as PAFCs and PEMFCs. It also offers great flexibility in the use of available fuels, say, through in situ reforming of fuels. It has been estimated that the MCFC can achieve an energy conversion efficiency of 52%–60% (from chemical energy to electrical energy) with internal reforming and natural gas as the primary fuel. Some studies have indicate that the MCFC efficiency of methane to electricity conversion is the highest attainable by any fuel cell or other single-pass/simple cycle generation scheme.
Electrochemical Energy Systems and Efficient Utilization of Abundant Natural Gas
Published in Sheila Devasahayam, Kim Dowling, Manoj K. Mahapatra, Sustainability in the Mineral and Energy Sectors, 2016
Manoj K. Mahapatra, Boxun Hu, Prabhakar Singh
In PEFC, hydrogen is oxidized in the anode and the protons (H+) conducts through electrolyte and combines with oxygen at the cathode to produce water. In MCFC, carbonate ion forms at the cathode, conducts through molten carbonate electrolyte, and oxidizes fuel at the anode. Carbon dioxide produced in the anode can be streamed to the cathode. In SOFC, oxygen ion forms at the cathode, conducts through solid electrolyte, and oxidizes fuel at the anode. Proton conducting electrolyte is also being developed for SOFC. The working principle and the electrochemical reactions of the fuel cells are shown in Figure 27.1 (EG&G Technical Services, Inc., 2004). The characteristics of the different kinds of fuel cells are given in Table 27.4 (EG&G Technical Services, Inc., 2004; Stambouli, 2011; Mahapatra and Singh, 2013; Kalmula and Kondapuram, 2015).
Optimal design and performance evaluation of a cogeneration system based on a molten carbonate fuel cell and a two-stage thermoelectric generator
Published in International Journal of Ambient Energy, 2022
Xinru Guo, Houcheng Zhang, Jiapei Zhao, Fu Wang, Jiatang Wang, He Miao, Jinliang Yuan
Different from the traditional fuel-fired power plants, fuel cells are capable of converting the chemical energy of a fuel into electrical power without intermediate energy conversion processes (Xie et al. 2018; Kirubakaran, Jain, and Nema 2009; Sharaf and Orhan 2014). Among various kinds of fuel cells, molten carbonate fuel cell (MCFC) is the available off-the-shelf equipment up to MW scale. Furthermore, MCFC is also one of the most prospective high-temperature devices for stationary power generation (Açıkkalp 2017a; Kim, Kim, and Park 2018). To date, MCFC has been developed in a large scale by many countries including USA, Germany, Japan, Italy and South Korea (Hu et al. 2014). In addition, it has been reported that 90% of the produced can be captured in a combined system composed of MCFC, IGCC and CO2 capture system (Mehrpooya, Rahbari, and Moosavian 2017). For example, Luca, Stefano, and Jack (2018) proposed an SOFC-MCFC poly-generation plant that has achieved near-zero emissions using electrochemical carbon separation. It is indicated that MCFC has potential for greenhouse gas emission reduction and climate change mitigation.