Part 2 of 2 By Tom Koppel Ph.D. and Jay Reynolds
There are six major types of fuel cells with potential for a variety of commercial applications.
The first to be fired into space was the proton exchange membrane (PEM) fuel cell, which was developed by GE and performed successfully on the Gemini orbital missions of the mid-1960s. Then it was abandoned, and GE’s patents gradually ran out. Ballard Power Systems, with Canadian government funding, began improving PEM in 1984, as told in the book by one of us, Powering the Future: The Ballard Fuel Cell and the Race to Change the World. Today, PEM is the main type being commercialized to power automobiles.
The Apollo moon missions used the alkaline fuel cell (AFC) developed by United Technologies Corporation. Now, under the aegis of its subsidiary, International Fuel Cells, a greatly improved version provides electrical power to the space shuttles. AFCs worked well in space, where the rocket was already supplied with extremely pure liquid hydrogen and oxygen. But it was not suited to operating on air and impure hydrogen.
By contrast, PEM had the potential to work on air and less pure hydrogen (such as gas that is “reformed” from a convenient liquid fuel like methanol). This makes PEMs more suitable than AFCs for use down here on earth. But the early PEM cells needed so much expensive platinum catalyst that this was prohibitive except for space and some military uses. (This has been solved by spreading such a thin layer of microscopic platinum particles on the electrodes that very little is now required.) Another plus for PEM is that it begins generating power at room temperature and attains its peak power at about 80
