Efficiency Optimization of a Direct Liquid-Feed Fuel Cell Subject to Various Operating Variables

Energy density and power density are two of the most significant specifications for a fuel cell system. Generally speaking, energy density should be derived from the fuel cell efficiency. All these performance indices are closely correlated with the control variables of the balance of plant (BOP). The present paper proposes an optimization algorithm that maximizes the fuel cell efficiency. The strategy is based on the semi-empirical models of efficiency evaluation in our previous work. In this paper, the efficiency of a direct liquid-feed fuel cell is maximized subject to operating temperature, operating voltage, and fuel concentration as design variables in the feasible regions. Moreover, the power density in demand is considered as the constraint of the problem. The algorithm thereby serves as the basis of the controlling strategies of a direct methanol fuel cell system. Its feasibility is also verified on an instrument-based integrated testing platform. The well-designed controlling strategy not only ensures the safety of the system, but also enhances the performance of the fuel cell system.