Search Results

This paper compares the merits of operating a direct-hydrogen fuel cell (DHFC) system using a high-pressure air supply (compressor) versus one using a low-pressure air supply (blower). Overall, for the system modeled, it is shown that there is no inherent performance advantage for either mode of operation at the DHFC stack level. However, in practical applications, as will be shown in this paper, a systems analysis (stack and air supply) of power and efficiency needs to be performed. Equivalent PEM DHFC stack peak power values can be obtained using both high-pressure and low-pressure air supply systems. For each air supply configuration, air mass flow and pressure operating conditions can be found that result in an equal value of the oxygen partial pressure at the cathode catalyst layer surface. However, at the system level, the required air supply power needed to achieve the same DHFC stack performance values can be drastically different for high and low pressure operation.

This paper addresses the critical need to incorporate realistic models of the air supply sub-system in fuel cell system performance analysis. The paper first presents the dominant performance issues involved with the air supply operation in the fuel cell system. The report then goes on to propose a methodology for an air supply model that addresses many of the performance issues. Most importantly, a model is needed with a defined set of performance criteria and data input format, one that can accommodate multiple air supply configurations, and one that realistically and accurately simulates the air supply operation and its effect on the system power and efficiency. The paper concludes that it is possible to compare alternative air supply components under the constraint of maximizing the instantaneous net fuel cell system efficiency for a dynamic vehicle driving cycle under various ambient conditions.