On Aug 1, 2008, at 2:28 PM, Michel Jullian wrote:
A very good point!
Making the efficiency rise from 65% to almost 100% as calculated by
Horace is also a very important progress, if confirmed. It would
make it possible to consider a "water battery" consisting in an
electrolysis cell plus H2 storage plus fuel cell, if fuel cells
happened to also be very efficient (which I don't know)
Michel
Yes they are pretty good for cars, and even generators (compared to,
say, diesel powered generators) even now. They are not limited by a
Carnot cycle efficiency. See:
http://en.wikipedia.org/wiki/Fuel_cell#Efficiency
"The tank-to-wheel efficiency of a fuel cell vehicle is about 45% at
low loads and shows average values of about 36% when a driving cycle
like the NEDC (New European Driving Cycle) is used as test procedure.
[14] The comparable NEDC value for a Diesel vehicle is 22%."
I expect batteries might be better for short term storage and power
management, and hydrogen for covering overnight, multiple day
periods, and possibly even transmission provided sufficient storage
and distribution facilities become available.
The main problem with fuel cells I think is price. A new Australian
technology has just been announced that makes similar price gains
(though not efficiency gains) in the fuel cell arena as was made by
Nocera and Kanan for electrolysers.
See:
http://www.abc.net.au/news/stories/2008/08/02/2322139.htm
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
