(561d) Temperature Dynamics and Control of a Fuel Cell Stack System

Hydrogen-powered fuel cells are of current interest as an alternative source of energy for both mobile as well as stationary applications.  While there are multiple theoretical models available for a fuel cell stack, they only consider the dynamics of the reaction itself inside of the cell and assume that the stack temperature can be maintained at the desired set-point via natural air convection.  However, when the power requirements are high, it may be necessary to use a water-cooled system to maintain a desired stack temperature.  In this research, a time-varying proportional-integral (PI) controller is designed for controlling the temperature of a water-cooled 5 kW hydrogen fuel cell stack.  This controller is designed using a mathematical model for a Ballard Mark V PEM fuel cell stack, which is derived using basic chemical engineering material and energy balances.  The controller affects the stack temperature by changing the flow rate of cooling water that passes across the stack.  The model is then analyzed using a number of realiastic power demand profiles to determine the effectiveness of the controller. In particular a power profile from experimental data from a residential house is used to test the efficacy of the controller. The results show that a time-varying PI controller is adequate for maintaining the stack temperature within 5 K of the target point.