From: Kent Spaulding (kents@trajecta.com)
Date: Fri May 18 2001 - 07:36:27 PDT
Er, I should have explicitly said that gasoline consuming cells are not
efficient enough in terms of pollutants, $, and mpg right now - not that
they can't be. I didn't mean to claim (nor did I) that they never will
be. Every once in a while it would serve you well, Eugene, to give an
author the benefit of the doubt. You're right though, one should not make
ambiguous blanket statements.
more below.
At 09:03 AM 5/18/01 +0200, Eugene.Leitl@lrz.uni-muenchen.de wrote:
>kents@trajecta.com wrote:
> >
> > 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).
Okay, see below.
>
> > 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.
Yes - current generation.
>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
>probably zero.
>
>So mentioning platinum group metals as "pollutants" in fuel cell
>context is very, very misleading.
Granted. The last time I looked (5 yrs ago), these cells used some small
amount of 'heavy' metals, in addition to platinum and palladium. It is
those metals generally considered to be pollutants. They too are
expensive. Perhaps they are no longer used.
Regardless, providing enough platinum and palladium for a billion cars is
not a slam-dunk. Consider the pollution from mining these metals, if you
want to pick nits.
> > 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.
I'm going to give you the benefit of the doubt and assume you are not
calling me an idiot.
As for 'production of methonal scaling' and the 'current infrastructure
being potentially useful' - I doubt it. It's not about the technology
being available. This is the real world. You have to include the cost of
convincing the oil industry to move away from gasoline for cars in your
analysis of whether or not the infrastructure is reusable. They are the
infrastructure - moving them to methanol should be a slam-dunk. As if.
As for Stirling engines, there is research at Los Alamos on engines that
use specially shaped wave chambers to amplify sound. The amplified
resonating waves can then be used to generate power, rather
efficiently. You get the initial sound from a small explosion, you know,
spark some gasoline and air vapor. Is this or this not a form of the
Stirling engine? It is really what I had in mind. These engines may be an
option in vehicles - given more development. I seem to recall there may be
a prototype bus running on this technology.
And finally, I am not arguing that we don't need to replace the current
means of powering our cars - I'm just saying that given the investment in
gasoline distribution that has occurred over the last century, fuel-cells
that burn gasoline might be fine option as a gap solution. Sound-wave
and/or Stirling engines might also serve us well as a gap solution until we
get to an ultra-clean and efficient means of powering cars.
Chau,
--Kent
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