Design and technoeconomic performance analysis of a 1 MW solid oxide fuel cell polygeneration system for combined production of heat, hydrogen, and power

This work focuses on the design and performance estimation of a methane-fueled, 1 MW SOFC combined heat, hydrogen, and power (CHHP) system operating at steady-state. Two methods of hydrogen purification and recovery from the SOFC tail-gas are analyzed: pressure swing adsorption (PSA) and electrochemical hydrogen separation (EHS). The SOFC electrical efficiency at rated power is estimated at 48.8% (LHV) and the overall CHHP efficiency is 85.2% (LHV) for the EHS design concept. The EHS energy requirement of 2.7 kWh kg−1 H2 is found to be about three times lower than PSA in this system. Operating the system to produce additional hydrogen by flowing excess methane into the SOFC subsystem results in increased efficiency for both of the hydrogen separation design concepts. An economic analysis indicates that the expected cost of SOFC-based distributed hydrogen production (4.4 $ kg−1) is on par with other distributed hydrogen production technologies, such as natural gas reforming, electrolysis, and molten carbonate fuel cell CHHP systems. The study illustrates that ‘spark spreads’ (cost of electricity in ¢ kWh−1 minus cost of natural gas in $ MMBtu−1) of five or more offer near-zero or negative hydrogen production costs for distributed SOFC CHHP plants with total installed capital costs near 3950 $ kW.

► The amount of hydrogen recovery (85–90%) with EHS is higher than PSA.
► SOFC electrical efficiency of 48.8% (LHV) and best overall CHHP efficiency of 85.2% is achievable.
► Operating the system to produce excess hydrogen increases the CHHP efficiency for all concepts.
► Cost of distributed SOFC H2 production (4.4 $ kg−1) is on par with other distributed H2 production technologies.
► ‘Spark spreads’ of >five offer near-zero or negative H2 production costs for distributed SOFC plants.