Don Lancaster wrote in news:4l4oggF8btoU1
@individual.net:

(Don originally wrote)

You have to recognize that converting water vapor to liquid
consumes energy and has to be charged against the fuel cell
efficiency budget.

(snip in between)

What is the context about the statement "converting water vapor to
liquid consumes energy". That statement is in fact backwards. Water
vapor contains more energy than liquid water - about 9.8 kcal/mole, if
memory serves me.

The energy IS consumed and charged against the fuel cell.

The energy isn't consumed, unless you are stating that the fuel cell
originally produces liquid water and then subsequently turns it into
vapor - which AFAIK is not what happens.

Conceivably, if the fuel cell system output liquid water, it would be
more efficient by the latent heat difference.

Which is one reason why stationary fuel cells are potentially a good
solution for some applications - e.g. hospitals that need heat, need a
backup source of power, and use enough energy to repay capital costs. I
say potentially because current stationary fuel cells are way too
expensive to repay the investment. And no, I don't think the fuel is
going to be hydrogen, at least not anytime soon.


Throwing away the heat --- throws it away.

Agreed, but it isn't charged against the fuel cell budget, it just isn't
credited to the budget. This might be considered a quibble, but there is
enough nonsense on this newsgroup without adding to the confusion by
stating that "converting water vapor to liquid consumes energy".


Yours,

Bill Morse