Energy and exergy analysis of a fuel cell based micro combined heat and power cogeneration system

Abstract

A fuel cell based micro combined heat and power (CHP) cogeneration system is a cost-effective means of meeting residential energy needs if capital cost targets can be met. The cogeneration system mainly consists of a fuel processing unit, a power generation unit and an auxiliary unit. The fuel-processing unit under investigation includes an autothermal reformer, high and low temperature shift reactors and a CO preferential oxidation reactor. Energy and exergy analysis of the system is useful to investigate the effects of key operating parameters on the system performance. A micro-CHP system that produces approximately 1kW of electricity is simulated with Aspen Plus. A typical case is analyzed and system energy and exergy loss break-down is studied. It is found that for the typical case, energy carried by unuseful streams accounts for the majority of the energy and exergy losses. Among all the components, proton exchange membrane fuel cell posses the least energy efficiency and exergy efficiency. Effects of steam to carbon ratio, air to carbon ratio, hydrogen utilization efficiency, power generation efficiency, and process methane feed variation on system performances are parametrically studied.