Fuel cells

The vision of a world without oil or other fossil fuels is both surreal and at the same time seductive as a solution to current concerns over climate change and oil availability. It is also, to some extents, an irrelevant one for fuel cells. Rather than being an energy source they provide a mechanism for transforming one form of energy (chemical) to another (typically electricity or heat). In this way, they resemble batteries, internal combustion engines, and even steam engines. The key to their value is really their efficiency: they are able to carry out this transformation cleanly and efficiently. Fuel cells are not yet fully developed. The technology and the fuel cell effect were discovered in 1839 by, depending on your point of view, William Grove or Christian Schoenbein (Sanstede et al., 2003). For a long time after this, the technology was essentially dormant until the 1940s when Francis Bacon started working on it and the 1950s when Allis-Chalmers built the first application of the technology (a fuel cell powered tractor). Research and development accelerated when fuel cells were chosen as power sources for space missions in the 1960s and the 1970s oil price shocks increased interest in other technologies, but the real impetus came in the 1990s when DaimlerChrysler examined the proton exchange membrane fuel cell and decided that it could be used to power a vehicle. Considerable effort is still to be expended on improving fuel cell technology in terms of cost and performance. Ancillary questions like the best method of fuelling and of carrying fuel still remain to be solved. However, we have begun to see fuel cells entering the commercial marketplace and the coming years and decades should see this accelerate. A simple definition of a fuel cell might be ‘a device that reacts a fuel and an oxidant, without combustion, producing heat and electricity’. The best-known case, that of a proton exchange membrane (PEM) fuel cell (PEMFC), is illustrated in Fig. 11.1. In a PEM fuel cell, the fuel is hydrogen, the oxidant is oxygen and the only chemical product is water, as described in reaction (1): . . . 2H2 + O2 ⇒ 2H2O + heat + electricity (11.1) . . .