Hydrogen fired PAFCs: an experimental investigation into the optimal utilization of impure, recycled hydrogen

Phosphoric acid fuel cells (PAFCs) had been developed for cogeneration plants based on natural gas as fuel. Operation of phosphoric acid fuel cells on hydrogen requires recycling of unspent hydrogen from the anode exhaust for obtaining highest efficiency. But recycling rates are limited due to accumulation of inert gases. Theoretical calculations and experimental data on optimizing this operation mode with respect to highest electrical energy efficiency are compared. The results are verified in a 100 cm2 PAFC unit. From the data obtained with a Fuji 2 kW PAFC, the performance of large units with hydrogen recycling is predicted.