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

Eugene Leitl (
Fri, 4 Jun 1999 13:45:21 -0700 (PDT)

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.

> 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.

> 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.

> 50% of the bond energy due to reforming a fuel to hydrogen, we get better
> overall efficiency with the fuel cell. I just get itchy when ANY energy
> gets thrown away without a chance to do work.
> If I recall right, large methane fueled fuel cells were proposed for
> installation in New York City to generate power - and the waste heat could
> then be used for process or building heat. Does anyone know if this scheme
> was actually installed?
> Chuck Kuecker