Power Recovery by a Twin Screw Expander in a Fuel Cell Application

The fuel cell engine is being developed to be the future power source for transportation, gradually substituting the internal combustion engine.

For transportation both size and weight of components are very important. A common way of reducing size and weight of fuel cell engines is to use pressurized air systems. The stack, heat exchangers, pipes, valves etc. will be reduced in size and weight. There are also other advantages with pressurized systems: the response time when an increase in the power output is required is shortened, exhausting of the water continuously produced in stack is improved. Pressurized systems need an efficient, small, lightweight compressor. The Twin Screw compressor meets those requirements. By adding a Twin Screw Expander downstream the stack, 30-35% of the compressor input power can be recovered and the power output and the size and weight of the compressor drive motor reduced accordingly.

This paper will show possible improvement of the performance as well as different ways of integrating the compressor, the expander and the drive motor.