Three-way maximized net power output from alkaline membrane fuel cell stacks

Abstract

This work uses an experimentally validated mathematical model to maximize alkaline membrane fuel cell (AMFC) stacks net power output. Temperature distribution, efficiency, polarization, and power output curves are obtained. Fundamental optimization opportunities exist for the internal and external structure, which led to a two-way optimized AMFC stack for maximized net power. After system optimization, a parametric analysis was carried out for electrolyte KOH mass fraction, stoichiometric ratios and total fuel cell stack size (volume). KOH content was shown to lead to a third optimum, i.e., 40 wt %. The three-way optimized AMFC stack (ξs=1.37×10−3, y = 40 wt% KOH)opt was shown to be independent of the stoichiometric ratio and stack size variation, but (ξy/ξx=ξz/ξx)opt was affected by total stack volume (or size). In fact, it was found that the three-way maximized dimensionless AMFC stack net power output rises as the stack volume rises in a path that is well correlated by W˜net,mmm×10−3=36.266V˜T0.74, which is similar to the allometric law of nature that correlates basal metabolic rate (BMR, W) and body mass (mb,kg) for living beings, i.e., BMR∼mb0.74, that could be understood as an indication that inanimate and animate systems follow the same evolution laws.