A modeling study on water and thermal management and cold startup of unmanned aerial vehicle fuel cell system

The water and thermal management of hydrogen/air proton exchange membrane fuel cell (PEMFC) system in a variable environment and its fast and efficient cold start at low temperature are the key issues in the practical design and integration of unmanned aerial vehicle (UAV) fuel cell power system. Herein, a complete mathematical model of fuel cell stack and balance of plant (BOP) is established, then the nonlinear relationship between cooling water flow rate, coolant bypass valve opening, and stack temperature at different flight altitudes is studied for a typical UAV configuration, and the safe working range of stack is pointed out. In addition, a cold-start model supporting operation at the high current density is proposed. After analyzing the cold start-up process of the fuel cell, it is found that a reduction of active reaction area caused by icing is the main reason for voltage loss. The optimal self-start current densities of the fuel cell at different low temperatures are detected by the galvanostatic method, as a result, a successful self-startup of the fuel cell is achieved at a temperature of 263.15 K. •A comprehensive mathematical model of UAV fuel cell system.•Safe working range of a typical UAV powertrain at different flight altitudes.•A cold-start model supporting operation at the high current density.•Mechanism analysis of performance loss caused by icing during cold start-up.•Optimal self-startup current density at different low ambient temperatures.