There are a
number of different kinds of fuel cells, but the one that has everyone excited today is
the Direct Methanol Fuel Cell.
Fuel cells have to have hydrogen to react with oxygen and produce an
electrical current. But we all know the problems of storing hydrogen. Normally
it has to be contained in a high pressure vessel, or in a cryogenic state as a super-cold
liquid, or using some other technically challenging method. But theres more
hydrogen in a gallon of liquid methanol than in a gallon of pure cryogenic hydrogen.
So methanol turns out to be a very good carrier fuel for the hydrogen that fuel
cells need. All thats required is a way to get the methanol to give up its
hydrogen, and it turns out that methanol does this very easily.
In the past, methanol PEM cells have used a separate reformer to release
the hydrogen from liquid methanol, then the pure hydrogen is fed into the fuel cell
stack. But in the last couple of years, weve discovered a way to feed a
methanol/water mix directly into a slightly modified PEM cell and release the hydrogen to
do its work internally - without a separate reformer. This tremendously simplifies
the fuel cell, and holds the promise of a cheap, highly efficient replacement for the
internal combustion engine. Perfected direct methanol fuel cell are only about 5
years away.
On the downside, however, when hydrogen is removed from methanol, carbon is released in
the process. So when methanol is made from natural gas, there is a net gain of CO2
emissions. Not as much as with a gasoline car, but the emissions do exist. In
contrast, pure hydrogen fuel cells have no CO2 emissions, and bio-ethanol or bio-methanol
fuel cells result in a zero net gain of CO2 emissions.