Thermo-economic assessment of molten carbonate fuel cell hybrid system combined between individual sCO2 power cycle and district heating

Abstract

A molten carbonate fuel cell (MCFC) is a high-performance electric power generation system, but much research is still required to develop technologies to enhance its power efficiency, because the exhaust gases of an MCFC contain sensible energy. The high level of heat energy in the exhaust gases leads to a poor performance, with an increased electricity rate and decreased efficiency. This study investigated the supercritical carbon dioxide cycle with three different configurations as a bottoming cycle using the exhaust gases of an MCFC stand-alone system and compared the supercritical carbon dioxide cycle with a combined heat and power system in terms of economical operational strategies. The thermodynamic characteristics of each cycle were determined by varying the turbine inlet pressure and isentropic efficiency of the turbomachinery. The results of an analysis found that optimal discharge pressure of compressor, are remarkable parameter for supercritical carbon dioxide cycle. Furthermore, the net power efficiency was increased (3.41%–4.6%) compared to that of the MCFC stand-alone system. In addition, the levelized cost of electricity values for the supercritical carbon dioxide cycle and combined heat and power system were calculated, and sensitivity analyses were conducted for factors such as the heating cost and major equipment cost. The results showed that using the supercritical carbon dioxide cycle as the MCFC bottoming cycle was more economical when the heating cost was less than $28/Gcal and the printed circuit heat exchanger cost was less than $100/kW.