"Robert Clark" wrote in
ups.com:
wrote:
...
Batteries would not give you *liquid* water while carrying 1/8th
the
weight of the water in fuel. That's an important part of my
application.
Bob Clark
Why not just dump the water vapor to the atmosphere (global warming
gas! ack! haha) and just load up on liquid water, somewhere else,
later on?
Otherwise, as someone else mentioned, you have to invest in a heavy,
expensive condensing solution (for example, a radiator or heat
exchanger).
Michael
Proton exchange membrane fuel cells (PEFC) might work since they
condense the water automatically.
From reading some references they appear to have some problem with the
liquid water clogging the membranes, impeding hydrogen flow.
I want to get as much water exhaust out as possible for my
application. Still the PEFC cells might be sufficient for my purposes.
I'm sure you can imagine scenarios where neither fresh water nor
electrical power is freely available. The commonly stated "8 glasses a
day" water per person amounts to 2 liters, or 2 kilos, about 4 1/2
pounds. Over a 10 day trek or a 10 day period without power or fresh
water, that would be 45 pounds that would have to be carried along or
transported to an effected area per person.
There would be significant weight savings if that could be reduced to
5 pounds of hydrogen that had to be carried by each person or
transported to an effected area for a large number of people,
especially if the hydrogen also could provide electrical power,
assuming the fuel cells could be made lightweight.
That raises the question, how lightweight can the fuel cells be made
per electrical power output, not including the hydrogen?
Not very.
In almost all environments save space and maybe the Sahara desert, it is
easier to get water from local sources and purify it, no matter what the
power needs. There are methods for producing water by condensation using
day-night differences in temperature in the desert.
If weight is an overriding concern and volume is not a problem, you could
transport the hydrogen by balloon, and use the balloon to carry the fuel
cells - and you could also use the balloon to carry water.
To summarize, I am having difficulty in seeing any reason to use fuel
cells to produce water.
Yours,
Bill Morse