The Selective Zero Emission Power Systems Between NaBH4-Based Fuel Cells and Solar Cells for UAVs

The selective zero emission power system using fuel and solar cells is tested on the ground to evaluate if this system can provide continuous power for UAVs. The sodium borohydride (NaBH4) solution with two catalysts, Co/gamma-Al(2)O(3)and Co-P/Ni foam catalyst, is adopted as a hydrogen source for the fuel-cell system, so that the volume of required hydrogen gas is readily produced in accordance with hydrogen-consumption rates from the fuel-cell stack by controlling NaBH(4)solution flow rates. Thus, two catalysts play a major role to promote the hydrogen production speed. The solar-cell system is formed with a maximum power-point tracking device (MPPT), solar modules, and a lithium-polymer battery. Thus, the power generated from solar arrays flows through the MPPT to the electric load or to the battery simultaneously, charging mode if extra energy is available. The selective power system between two different power sources is achieved using power relays which can allow one system to function, while the other is on standby. In consequence, the selective electric power system can offer continuous power for the high-endurance operation.