Thermal Management of PEM Fuel Cells in Electric Vehicles

Abstract

The increasing number of fuel cell electric vehicles (FCEV) on the roads will considerably contribute to CO2 emission reduction and reduction of harmful air pollutants of the transport sector. FCEVs are seen as the future “long distance” and “all purpose” alternative to existing pure battery electric vehicles. The general objective in the FC development is to significantly reduce the costs and system degradation in order to increase the market penetration of FC vehicles. In addition to that, a critical issue represents an adequate thermal management and demand oriented cooling of FCEVs to avoid safety issues, degradation and a decrease in efficiency during operation. Proton exchange membrane fuel cell (PEMFC) can only tolerate a small temperature variation. Two factors are critical when designing a cooling system for PEMFCs. Firstly, the nominal operating temperature of a PEMFC is limited to roughly 80 °C. This means that the driving force for heat rejection is far less than in an internal combustion engine. Secondly, nearly the entire waste heat load must be removed by an ancillary cooling system because the exhaust streams contribute little to the heat removal. Several technical research publications and patents regarding effective cooling strategies are reviewed in this chapter. In the beginning, the thermodynamic characteristics of the heat generation and cooling requirements in a PEMFC stack are discussed. This is followed by outlined advantages, challenges and progresses of various cooling techniques with focus on liquid cooling. Finally, further research needs in this area are presented.