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Re: PEM fuel cell efficiency

Subject: Re: PEM fuel cell efficiency
From: Don Lancaster
Date: Sat, 23 Jul 2005 14:56:43 -0700
Newsgroups: sci.energy.hydrogen
Don Lancaster wrote:
DE Pauley wrote:

This is only an indirect answer. MIT has a course on "Application of
Technology" in which fuel cells are analyzed. The 'theoretical' FC
efficiency depends on the load. In slide 9
(http://web.mit.edu/1.149/www/lecture21/lec21slides.pdf) the efficiency
varies from 100% at no load to 50% at full load. In slide 26 the
'typical' efficiency is given as 45%. This probably corresponds to a
range of load conditions encountered during driving, but I am not sure.
A tradeoff for higher efficiency vs larger FC size would be possible.
The optimum may be to increase the size to achieve an efficiency in the
60-75% range.


How can something be 100 percent efficient at no load?
The only possible efficiency at no load would be zero.


Also, there is no hydrogen fuel cell anything that can ever be over 83 percent efficient.

Hydrogen electrolysis is up to one-sixth endothermic.
Thus the reverse process has to be a minimum of one-sixth exothermic.

                                www.tinaja.com/glib/energfun.pdf">http://www.tinaja.com/glib/energfun.pdf



--
Many thanks,

Don Lancaster
Synergetics   3860 West First Street  Box 809  Thatcher, AZ 85552
voice: (928)428-4073 email: don@xxxxxxxxxx

Please visit my GURU's LAIR web site at                                 www.tinaja.com">http://www.tinaja.com

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