a simple fuel cell that uses a solar panel to get the energy to electrolyze water and use the hydrogen to power a small fan.what would be the best way?
There are 4 sources of efficiency here: the solar cell, the electrolyzer, the fuel cell and the fan (also the propeller if you want to consider that, too). The easiest way to determine the total effeciency would be to measure each one individually and multiply the efficiencies. There are a lot fo equations for all of this, but basically you would need voltmeters for the solar cell and fuel cell, an ampmeter for the motor, a calorimeter or gas chromatograph for the fuel cell, and a wind speed detector if you want to measure the fan's efficiency.
