Fuel cell vehicles work by combining pure hydrogen and oxygen to produce electricity, which is then used to power an electric motor. Essentially, fuel cells combine the long range of a petroleum-powered car with the efficiency of an electric car. Unlike hybrid vehicles, they also have the potential to run without using fossil fuels, a huge step in slowing and reversing the greenhouse effect.
Fuel cells work by letting hydrogen flow through a stack of cells, each of which contains a proton exchange membrane. These cells oxidize the hydrogen by way of a catalyst (platinum) and create electricity (for more info, see sources).
The only byproducts of the electricity creation process are heat (though not nearly as much as internal combustion engines) and water vapor (H20). As a result, fuel cells are completely free of the harmful green house gases which make fossil fuels so undesirable.
Fuel cells have the potential to achieve much greater efficiency (energy produced vs. energy inputs) than internal combustion engines. The DOE is shooting for 60% efficiency by 2010; internal combustion engines get half that or less.
Besides the unfinished technology, a main drawback to fuel cells is price. The cells utilize platinum as a catalyst, which is expensive, but new technologies are lowering the prices. Nonetheless, subsidies would be required to bring the price low enough to produce vehicles competitive with today’s internal combustion engines. To improve the technology, President Bush recently allocated $1.6 billon to fuel cell research.
The other main problem with fuel cells is the use of hydrogen. Unlike gasoline, the US currently lacks a hydrogen distribution network. Making such a network would require new filling stations or retrofitting existing ones, delaying any widespread use of fuel cells. But steps are being taken: a hydrogen filling station recently opened in California.
Finally, there is no easy source of pure hydrogen in nature (even though hydrogen is the most abundant element in the universe). Potential sources for hydrogen are gasoline, natural gas, propane, and ethanol, but extracting hydrogen from these requires energy and creates harmful emissions. Hydrogen can also be extracted from water through electrolysis, but that also requires a large amount of energy input. Using energy derived from fossil fuels to pull hydrogen from water would still result in a rise in CO2 emissions. Unless a renewable source of electricity is developed, electrolysis will only push the emissions further up the chain towards the power plants. Any widespread use of fuel cell technology appears to be years in the future.