Potential global warming impact of 1 kW polymer electrolyte membrane fuel cell system for residential buildings on operation phase

This study established global warming potential(GWP) emission factors through a life cycle assessment on the operation phases of two different 1 kW polymer electrolyte membrane fuel cell (PEMFC) systems for residential buildings (NG-PEMFC, fed with hydrogen from natural gas reforming; WE-PEMFC, fed with hydrogen from photovoltaics-powered water electrolyzer). Their effectiveness was also compared with conventional power grid systems in Korea, specifically in the area of greenhouse gas emissions. The operation phases of the NG-PEMFC and the WE-PEMFC were divided into burner, reformer, and stack, and into water electrolysis and stack, respectively. The functional unit of each fuel cell system was defined as 1 kWh of electricity production. In the case of NG-PEMFC, the GWP was 3.72E-01 kg-CO2eq/kWh, the embodied carbon emissions due to using city gas during the life cycle process was about 20.87 %, the carbon emission ratio according to the reformer's combustion burner was 6.07 %, and the direct carbon emission ratio of the air emissions from the reformer was 73.06 %, indicating that the carbon emission from the reformer contributed over 80 % of the total GWP. As for the WE-PEMFC, the GWP was 1.76E-01 kg-CO2eq/kWh, and the embodied carbon emissions from photovoltaic power generation during the life cycle process contributed over 99 % of the total GWP.