Date: Fri May 18 2001 - 00:03:17 PDT
> Not ALL fuel cells run on hydrogen - however, since one can
> crack gasoline and get hydrogen, cells that use hydrogen sound like
> are a great idea for vehicles. We already have a distribution
> infrastructure for gasoline.
It's a good start, but as I said, higher alcanes are difficult
to reform (not crack, reforming uses water coming from fuel
cell exhaust as another reaction educt), since they soot up
the catalyst so quickly.
Lower alcanes (ethane, propane, butane) are easier to reform,
but their source and distribution infrastructure is limited.
In principle methanol (despite its energy density being almost
half of gasoline) would be best, but it is more corrosive towards
steel and gaskets, so you might have to upgrade the infrastructure.
Also, methanol is fully mixable with water, and is fully biodegradable,
and doesn't burn quite like napalm if spilled during a car accident.
And it can be made from about anything, including oil, coal, methane,
biomass and even electrosynthetically from carbon dioxide (and one
could in principle make a an artificial photosynthetic center that
does synthesize methanol photosynthetically, but R&D for this can
take decades -- the point is that methanol scales).
> But there are downsides. The cells need to be more efficient
> than internal combustion engines, in terms of dollars, pollutants, and
> mpg. They aren't. The main issue is that the catalysts used in the
Blanket assertions like that trouble me. MPG is a problem of
efficiency -- electrochemical energy sources can in theory be
almost 100% efficient, while Carnot machines are maximally 40%
efficient (before your movable parts can't take the heat anymore),
and in reality big installations manage something like 32% and
vehicular systems something like 20%. Real-world efficiencies
of fuel cells are right now what? >40%? Of course the fuel
reformer drags you down a bit, since draining some of the juice
to heat the reactor, but I very much doubt the total efficiency
is under 30%. And that's of course *current* generation. No
reason not to suspect you can ramp up to 50, maybe even 60%
in near future.
Plus, there are unexploited synergisms available for electrical
propulsion, which make the whole system perform much better as
soon as you design fo rit. Fuel cells are flat stacks which can
be integrated into the vehicle floor. Their power density/weight
can become much better than car engines', which allows you to
reduce vehicle weight. If combined with composite (carbon/epoxy
honeycomb) as car body structural elements and smart in-hub
electromotors plus regenerative braking and spike cache you suddenly
get quiet zero emission speed demons which accelerate like demented
when you floor the pedal and run on 1-2 l fuel/100 km.
> cells are rare (i.e. expensive) and some can be considered to be
> pollutants in and of themselves.
Bowllllshit. Right, platinum group metals are expensive. But
platinum group metals used in fuel cells are not just platinum
and palladium, and the platinum content of fuel cells is dropping
with R&D. Pt group metals are eminently recyclable, and there is
already enough platinum in car catalysts present (which *do*
spew it into environment) so the net amount vs. a fuel cell is
So mentioning platinum group metals as "pollutants" in fuel cell
context is very, very misleading.
> Using methanol-based cells has advantages, like the catalysts are
> easier to come by and the cells are lighter. But then there's the
> tricky issue of producing and distributing enough methanol.
Producing is a non issue, as methanol is made from synthesis gas
on a colossal scale already, and since you won't power the entire
world vehicle fleet with methanol overnight, ramping up the production
is trivial. Whether one can use existing gasoline infrastructure for
methanol distribution needs some looking into. I think if we do, we
find the problem to be very solvable.
> So what's the right policy? Maybe it's the Stirling engine?
Our problem is not the technology. Our problem are the idiots.
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