ADDITION OF HIGHLY EFFICIENT BOTTOMING CYCLES FOR THE NTH-GENERATION MOLTEN-CARBONATE FUEL-CELL POWER-PLANT

An intermediate scale (2.0 MW gross) molten carbonate fuel cell (MCFC) power plant recently began operating in Santa Clara, California. The goal of the project is to demonstrate the possibility of long-term ope ration of MCFC stacks. The fuel cell stacks are the only source of ele ctricity, which means a simple power plant system, and relatively low capital costs. This, however, results in substantial work losses in th e plant, most of which come from the hot exhaust gas discharge. The pr edicted efficiency is a respectable 50 percent. In this paper, an exer gy analysis is performed in order to study if a future plant's efficie ncy can be improved. It is shown that for the future plant of this typ e it would be worthwhile to consider the addition of a steam bottoming cycle as well as changing the configuration of the top cycle. This ca n lead to improving the efficiency to close to 70 percent. The modifie d power plant requires additional equipment, such as steam turbines, h eat exchangers, condensers; thus, the capital cost of the plant change s substantially A cost analysis of the modified plant was performed an d a comparison of the cost of electricity between the two cycles is ma de. Finally, a Kalina cycle as one option for a bottoming cycle is con sidered as well.