Conceptual design and life cycle assessment of decentralized power generation by HT-PEMFC system with sorption enhanced water gas shift loop

Abstract

In this work, the decentralized power generation system consisting of a biomass gasifier, high-temperature proton exchange membrane fuel cells (HT-PEMFCs), and a sorption enhanced water gas shift reactor (SE-WGS) is investigated. With very low CO2 and CO concentrations in the reformate gas, the unconsumed fuel at the anode outlet stream of HT-PEMFC is possibly recirculated to the sorption enhanced water gas shift reactor to improve the performance and overall system efficiency without an increase in the problematic CO poisoning. The effects of CaO/C ratio, fuel utilization, and anode split ratio are analysed. With the anode recirculation, the operation at higher fuel utilization and anode split ratio improves the hydrogen efficiency and the system efficiency. The environmental impacts of the biomass gasification integrated with the SE-WGS and HT-PEMFCs are analysed and compared to the different decentralized HT-PEMFC systems fuelled by biomass using life cycle assessment methodology. The CaO production process is found to be the main cause of global warming impact and damage to human health and ecosystem quality, and no negative effect on resource depletion is observed for all studied power generation systems fuelled by biomass. The implementation of CO2 capture into the decentralized HT-PEMFC systems to enhance the hydrogen purity and efficiency significantly increases the environmental impact of the systems. Compared to the Thai Mixed Electricity Grid, better global warming impact of power generation from all studied HT-PEMFC systems is observed due to the environmental benefit obtained from the electricity produced from biomass. © 2018 Elsevier Ltd