Re: [pf] Fuel cells.

At 22:53 26/09/99 +0800, Pang Yiu Kai wrote:
>Dear David, Tully,
>       A fuel cell emits virtually no pollutant except "heat"
>( this can become an environmental hazard when in great excess) 
>when using hydrogen as fuel. H2 can be stored in liquid state in room temp.
>inside pressurized containers. The principle of operation of a fuel cell is
>some what similar to the respiration process of a human cell. 
>Pls see the attached files downloaded from a fuel cell site. 
>      Can this be used in cars to solve the environmental problem caused 
>by 
>driving cars? So you don't need to consider riding horses instead. 
>Pang, Yiu Kai

**  Sorry, Yiu Kai; I think you've confused the two ways of storing H2.

**  The method that can use relatively light storage tanks has the H2
adsorbed onto the surface of a specialised medium (a metal alloy?) inside
the fairly thin-walled tank, at room temperature; you raise the temperature
to get it out again.

**  Hydrogen has an extremely low boiling-point, below -252 deg. Celsius at
atmospheric pressure; I know of only helium with a lower boiling point. It
can be liquified by pressure alone if it is first cooled below -234 deg. C. 

**  I believe storing liquid H2 requires a combination of: a pressure-tank,
excellent insulation, and a powerful refrigeration system (depending on how
good the insulation and how strong the pressure tank are). Quite heavy,
though there was some investigation a decade or two ago into using hydrogen
as fuel for an aircraft; from memory there was almost no room for 
passengers.

**  My information could be out-of-date, but hydrogen is a very special
gas, so I suspect it's as I've described and any claims to the contrary
should be looked at with suspicion.

**  Using a carbon atom to trap 4 hydrogen atoms seems to me an eminently
sensible way to deal with hydrogen storage. (the CNG of my previous post.)


** Your general question, whether hydrogen or natural-gas fuel cells could
be used in cars to solve the environmental problem, implies a "technical
fix" to let us continue our current profligate ways; there are many more
faults with the car culture than how much CO2-and-'pollutants' is emitted,
and personally I think some of them are more serious, at least while coal
is used in electric power stations. Yes, fuel cells will be a part of the
solution, but no, they won't "solve the environmental problem".

David. (If I sound like a professor, that's because I was one.)
(David MacClement) d1v9d @ bigfoot.com (remove spaces)
http://www.emucities.com.au/member/davd/index.html#top
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