Thermo-economic analysis of Phosphoric Acid Fuel-Cell (PAFC) integrated with Organic Ranking Cycle (ORC)

Hydrogen produced from renewable resources has been gaining attention and its use is encouraged, as an effort of emission control. Consequently, the development of hydrogen production methods allows for fuel cell technologies to be developed in parallel. As a clean system for generating electricity, the reaction between hydrogen and oxygen occurring in a fuel cell produces only water and heat. By recovering heat release, thermal energy can be converted to mechanical work or electric power, improving performance and profitability of the system. This work studies the process integration of a 300 kW Phosphoric Acid Fuel-Cell (PAFC) and the Organic Ranking Cycle (ORC); a combined heat recovery process for generating additional electricity. A thermo-economic analysis is performed to determine the optimal working fluid with minimum payback time and net profit of PAFC/ORC integration. Among 15 working fluids examined, utilizing ammonia for ORC increased additional electricity produced by 6.64%, showing the greatest net profit, approximately 149 K€, and the payback time is reached after 3.3 years. Examined fluids with high critical temperature were water, benzene, and toluene, and obtained great efficiency improvement (about 9–11%) but they were unable to results to profit during 10 years of fuel cell lifetime.