Re: Fuel cells (was Re: jeff's cyborg cells)

Michael S. Lorrey (
Fri, 04 Jun 1999 17:27:03 -0400

Eugene Leitl wrote:

> Chuck Kuecker writes:
> > Looks to me that all current fuel cells work only with hydrogen - the
> No, you _can_ use alcohols, especially methanol in low temperature
> cells. People have recently been talking about using alcohol fuel
> cells to power portable computers. Interesting how this would compare
> to MEMS microturbine generators, powered by butane.

The turbines that the Army is testing for use by infantry are something like 10 watts per cubic inch. I wonder how the will compete with those new radioactive powder plasma/dielectric batteries which supposedly have phenomenal power densities.

> > carbon bonds, if any, are wasted as CO2 without contributing to the
> > electrical output. Perhaps in the high temperature cell, this energy helps
> In a way, the energy is not wasted. Fuel reforming is supposed to work in the
> following way:
> CH4+2H2O->catalyzed reforming->CO2+4H2
> This is how the bulk of hydrogen is produced today. CO2 are scrubbed
> using organic bases -- for high purity the gas can be passed though a
> heated Pd/Ag alloy membrane, which is selective to hydrogen.

I though the reformation process preferred producing carbon monoxide. Maybe I'm thinking of the old coal reformation process...

> > Fuel cells are about 50% efficient, if I recall rightly - so even losing
> Oh, a non-production room temperature cells could have well
> beyond 90%. And electrical motors with 98% efficiencies are not
> unheard of. Notice that Carnot machines will never make more
> than 37%. A real-world car does much, much worse.

Actually, current econo-speck car engines are at least 46% efficient, but the transmission and rolling and aerodynamic drag will drop it down to the 14-24% efficiency range. Even an electric car, all told, has a 30-45% efficiency.