Optimization of Set Points of State Variables in Air and Coolant Systems of Fuel Cell Systems

Numerous simulators have been developed to improve the performance and expand the applications of fuel cell (FC) systems. However, many of them are too simple to accurately reproduce the dynamic behaviors of FC systems. Besides, it is too laborious to identify the optimal operating condition, which varies with changes in applications and material properties, by trial and error. In this study, a method for simultaneously optimizing the set points of the state variables in air supply and thermal management systems is developed. In the developed method, a comprehensive FC system simulator “FC-DynaMo” developed by Hasegawa et al. is used. To confirm the usefulness of the method, the simulations with different thicknesses of the gas diffusion layer (GDL) in the fuel cell stack were conducted. As a result of optimization by the proposed method, system net efficiency was improved by an average of 6% compared to the base case. In addition, it was confirmed that the optimal operating condition was successfully found for each thickness of GDL. This is because the optimal operating condition was identified by taking into account the tradeoff between water activity in the cathode catalyst layer and air compressor power consumption.