Modular Stack-Internal Air Humidification Concept-Verification in a 1 kW Stack

The analysis of the complete H(2)/air polymer electrolyte fuel cell system shows that process air humidification is one of the biggest obstacles for a high performance portable system in the kW range. Therefore, a new concept, with passive process air humidification integrated into the stack, has been developed. Humidification in each cell makes the process independent from the number of cells and the operation mode, thus making the concept fully scalable. Without external humidification the system is simpler, smaller, and cheaper. The humidification of the process air is achieved by transfer of product water from the exhaust air, through part of the membrane, to the dry intake air. Tests have shown that cells using the concept of internal humidification and operated with dry air at 70 degrees C have almost the same performance as when operated with external humidification. A 42-cell stack with this internal humidification concept was built and integrated into a portable 1 kW power generator system.