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How many watts of power does a fuel cell need to convert hydrogen into electricity?

I'm doing a science fair project. I'm trying to convert water into electricity. I already know how to separate the oxygen from the hydrogen and how to convert the hydrogen into electricity with the fuel cell, but how powerful does the fuel cell need to be to carry out this experiment. If I have the wrong idea about the fuel cell, please explain to me the right idea.


If it takes 2X worth of power to make hydrogen from water then you can expect to get about 1x of electricity from converting the hydrogen back into water. Efficiency might theoretically be improved to about 80% but the process will remain less efficient than storage batteries. Further most hydrogen for industrial purposes (96%) is made from fossil fuels and this is unlikely to change in the near future. Trying to legislate the supply chain would likely lead to a hydrogen black market for the cheaper source. Hydrogen only seems attractive for increasing the range for an otherwise electric vehicle. It would be far cheaper to electrify roadways and transmit power wirelessly to the EV giving unlimited range. But this would not play into the hands of the fossil fuel industry.
Jan 26, 2018
A real fuel cell is like a battery and would oxidize hydrogen with oxygen into CO2 and H2O. What you're talking about is the scam electrolysis products which uses electricity to produce hydrogen from water. It takes more watts to produce the hydrogen then you would get from burning the hydrogen. If a student did such a fuel cell as their science fair project, I would give them an F for falling for a scam project. The only way out of the F would be to demonstrate the calculations showing that the process loses energy.
Jan 26, 2018
Separating hydrogen from oxygen requires electricity (specifically, direct current, which you don't get from your wall outlet). The fuel cell doesn't need electricity to convert hydrogen and oxygen into electricity. It will yield a certain amount of energy given it's size and hydrogen input (which depends on the size of the cell in the first place), but it doesn't need electricity to do that. If you're using electricity to hydrolyze water, to burn in fuel cell to make electricity, you're designing a losing proposition. Just use (or store, with batteries) the electricity, and don't worry about transitioning it to other energy forms. That wastes energy. DK
Jan 26, 2018

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