Mixed combustion–electrochemical energy conversion for high-efficiency, transportation-scale engines

Abstract

This article discusses an approach to exceeding current peak exergy efficiencies of approximately 50% for transportation-scale engines. A detailed model was developed for an internal combustion engine and a fuel cell, where the internal combustion engine is operated under fuel-rich conditions to produce a hydrogen-rich exhaust gas as a fuel for the fuel cell. The strategy of using combustion and electrochemical energy conversion processes has been shown to reduce reaction-related exergy losses while providing the balance of plant necessary to achieve efficient thermal management. Prior approaches which used internal combustion engines downstream of the fuel cell have shown exergy efficiencies near 70%. The system architecture developed for this article, in addition to achieving exergy efficiencies near 70%, provides further advantages. The internal combustion engine, producing work in addition to generating synthesis gas, enables a quick-start approach to this mixed strategy and the ability to use a range of fuels. Therefore, the proposed architecture supplies a very efficient starting point for the development of a quick-start, hybridized system for transportation-scale applications.