Utilizing hydrogen pressure energy by expansion machines – PEM fuel cells in mobile and other potential applications

Abstract

Hydrogen is an important energy carrier for a future without fossil fuels, but PEM fuel cell systems have to utilize the entire available energy as efficiently as possible. Hydrogen is typically stored at a maximum pressure of up to 700 bar and is supplied to the anode system at about 15 bar. Normally, a pressure reduction valve expands the hydrogen between 700 and 15 bar, but the pressure energy is unused during expansion. In this paper, different expansion machines are analyzed and the most attractive concepts are studied in detail to regain the expansion energy. Finally, a piston expansion system concept is designed with an estimated power output of 10 kW and a driving range increase of 2%, reflecting the high potential for efficiency improvement.