Refuelling sounds like a problem. I suppose petrol stations will have to be converted to store hydrogen?
A fuel-cell vehicle can get its fuel from two main sources. Ideally it would carry liquefied hydrogen on-board, and refill from a network of hydrogen stations. But there's another method that uses an on-board chemical plant called a 'reformer' to create hydrogen from another fuel - either petrol or natural gas.
If the manufacturers opt for the first solution, all the world's petrol stations will have to add hydrogen pumps, which will be very costly and take years to implement - experts reckon it'll be 2020 before liquid hydrogen is widely available. But the alternative is less than ideal, too: on-board reformers are hugely complex, unreliable and will add massively to the cost of each vehicle.
The car makers and fuel companies have currently got their heads together, trying to find a way forward and a means of dividing the costs of developing a whole new infrastructure. The medium-term solution might be to fit out petrol stations with their own medium-scale reformers to create hydrogen at a local level using petrol or natural gas as the energy source. That would give the oil companies time to move over gradually to the hydrogen economy.
Where will all this hydrogen come from?
Today the world makes 50m tonnes of hydrogen a year, according to Matthias Altmann, a hydrogen expert at consultants L-B Systemtechnik of Germany. That would be enough to power all the cars in Europe, the US and Asia, but at the moment it's used to make fertiliser and to strip out sulphur in the production of low-sulphur petrol and diesel. Ninety per cent of this hydrogen, however, is made by reforming natural gas - one of the fossil fuels that will eventually run out. So in the long term, the world will have to find other methods.
Hydrogen can be made by electrolysis of water, but that requires huge quantities of electricity. Today just one per cent of hydrogen is made by electrolysis. Hydro-electric and geo-thermal power offer huge hopes for the future, although the large-scale dams needed for hydro-power are controversial for ecological reasons. A greener method is 'biomass', using microbes to rot specially-grown crops. Altmann predicts that no one method will be prevalent: 'There will not be just one method, but always several in use simultaneously.'
Richard Stobart, a fuel-cell expert at Cambridge Consultants, describes this picture as a 'patchwork network', in which different countries will adopt different methods of hydrogen production - natural gas, thermal, hydro-power and biomass - but will all be working towards 2020 when every fuel station around the world will have a hydrogen pump alongside the petrol and diesel.
