Cold start capability is one of remaining major challenges in realizing PEMFC (Proton Exchange Membrane Fuel Cell) technology for automotive applications. Gas purge is a common and integral shutdown procedure of a PEMFC automotive in subzero temperature. A dryer membrane electrode assembly (MEA) can store more water before it gets saturated and ice starts to penetrate in the open pores of porous media, thus enhancing cold start capability of a PEMFC. Therefore, gas purge is always performed prior to fuel cell shutdown to minimize residual water in a PEMFC. In the hope of improving effectiveness of purge in a PEMFC vehicle, two important purge parameters are evaluated including purge time and energy requirement. In practice, an optimized gas purge protocol should be developed with minimal parasitic energy, short purge duration and no degradation of components. To conclude, the cold start capability and performance can be consolidated by proper design of gas purge strategies.
Despite of its paramount importance, gas purge is not studied in detail and no known efforts have been made to review in detail. This paper begins with a fundamental understanding of gas purge mechanism. Thereafter, the paper reviews the current state of art in gas purge numerical and experimental investigations by different researchers. The most recently applied different gas purge methods are summarized and compared (i.e. pressure reduction for water removal, pressure gradient for discharge method, addition of hydrogen on the cathode side). It is suggested that gas purge strategies should remove residual water from the fuel cell after it shutdowns in shortest possible period of time for practical purpose and energy conservation point of view.