Fuel Cell Efficiency: Average Output for Cars, Homes, & More

[Savage1701]

I understand that generating the hydrogen that powers a typical fuel cell is (prohibitively?) energy intensive at this point, but I was curious about the following:

Assuming a sufficiently efficient catalyst was obtained that allowed large-scale production of pure hydrogen without environmentally damaging by-products, what is the efficiency, on average, of a hydrogen fuel cell on the scale that would power a car, motorcycle, or even provide most of the electrical needs of the average home?

Just curious. Not a homework question, and I hope I have the correct forum area to be posting this question into.

Thank you in advance for any help in answering this question for me.

 

[russ_watters]

Fuel cells operate on the 50-80% efficiency range.

 

[mheslep]

The maximum theoretical efficiency in terms only of electrical energy output per joule of hydrogen chemical energy presented to the cell is limited by the http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/helmholtz.html#c2". I am unaware of any production cell coming anywhere close to that point so far. If the rejected heat of the fuel cell reaction is somehow captured and used to do more work, then the theoretical overall system efficiency can be higher than 83%.

 

[Savage1701]

Thank you both for your time and replies.

And yes, I should have been more specific. I was asssuming electrical output only, not non-recapturable and/or unuseable heat loss or further conversion loss when that electrical output drives a motor in a vehicle or lights a bulb, etc.

Again, thank you for your time answering a rather poorly posed question.