Like many products of scientific endeavour, the fuel-cell arose from a chance observation. William Grove, an English amateur scientist, was one of the early students of electrolysis – that’s the process of splitting water into hydrogen and oxygen by applying an electric current. One day in 1839, having disconnected his experimental apparatus, he noticed that the process also appeared to work in reverse… releasing energy. It is this discovery that led Grove to the fuel-cell.
Despite extensive scientific research on the fuel-cell, it has remained essentially in the laboratory for over a hundred years. It was only in the 1960s that fuel-cell technology was used to obtain power for spacecraft, beginning with the US Gemini space programme and being used extensively from the Apollo programme onwards. In one mission, water – the only by-product of the fuel-cell process – was collected and used as drinking water for the astronauts.
Fuel-cells have also been used in some specialised applications for power generation but they have required bulky facilities comparable to a container. They have also been expensive for widespread commercial applications.
Fuel-cell technology has been of interest to automakers for some time but various problems have prevented the technology from becoming practical for daily use. However, since California announced tough forthcoming regulations that would require vehicles to have either zero emissions (ZEV) or ultra-low emissions (ULEV), the industry has been galvanized into finding solutions quickly.
One major problem has been storage of hydrogen, the fuel. This gas is abundant in the atmosphere but it takes up a lot of space so a tank would have to be very large and bulky; even if it is compressed, the volume needed would mean that we would have to drive petrol tanker-shaped vehicles around!
One approach tried for storage was liquefication which required dropping the gas temperature to -253 degrees C. But to store liquid hydrogen would require a specially insulated container which would be very heavy. And just as NGV stations are not easy to set up, stations storing liquid hydrogen would be even more rare!
Researchers have looked at two approaches: either tackle the problem of on-board storage, or develop a process that could produce hydrogen as an ongoing chemical reaction. The former would be truly emission-free but the latter would generate some carbon dioxide and some other gases (but at very low levels).
The most promising solution is the proton exchange membrane (PEM) fuel-cell which was first used in Gemini spacecraft in the 1960s. The PEM fuel-cell features supply channels for the hydrogen fuel, a thin membrane through which protons must travel, and a catalyst coating on the membrane that induces protons to pass through the membrane.
To make such fuel-cells operate efficiently, the first obstacle that had to be overcome was to reduce the amount of catalyst needed. A US government project successfully reduced this by a factor of 40 and by 1993, reductions in the expensive catalyst had dropped to a level which made the PEM fuel-cell commercially viable.
The size too was reduced and with main technological hurdles passed, the race has been on to develop a practical prototype vehicle using a fuel-cell. Some manufacturers have declared that they can offer models using fuel cells before the middle of this decade.