Philip Thornton looks at a vehicIe that is leading the way to a post-petroleum future for the motor car

With oil prices surging through $70 a barrel on their way to $100, and petrol nearing a pound a litre, one would hope the alternative energy industry is in overdrive in the search to find new motor fuels.

But if you want to get a view of life beyond petroleum, you will have to take the bus. To be precise, you will have to hang around in central London for one of three hydrogen-powered vehicles currently running through the capital's streets.

The Mercedes Citaro bendybuses ply a tourist route between the Tower of London and Covent Garden known as the RV1. London is one of nine cities taking part in a trial of fuel cell buses, making it collectively the largest project of its type anywhere in the world.

The project is the result of an alliance of some 40 organisations, including seven in the UK - BP, BOC, DaimlerChrysler, First, the bus operator Transport for London (TfL), the Energy Saving Trust and the European Union.

In what seems like magic, the buses run by combining hydrogen gas with oxygen to make water, producing electricity in the process. The only emission from the engine - known as a fuel cell - is water that emerges as a vapour cloud as it leaves the exhaust and enters the environment. Too good to be true? Not necessarily - but certainly too expensive to be economically viable, at the moment at least.

The project organisers Clean Urban Transport for Europe (CUTE) in July announced that the 33 buses had collectively covered 760,000km - equivalent to a return trip between the Earth and the Moon. A decision whether to continue the two-year trial that ends in January will be taken later this autumn and so far the signs are positive.

London has the largest bus fleet - in terms of buses per people - of any major developed city. This is where economies of scale come in. While the technology may be in place, manufacturers will only go ahead with production when they believe people will buy the products. At the same time, consumers will only part with their cash when they are confident that the investment is in place to ensure their vehicles can be maintained and refuelled. So, which comes first - the supply or the demand?

As such a major player London Buses, TfL's bus authority, could have a major impact. If it decides to open up more of its tendered services to fuel cell buses, it will create more demand, and encourage the private sector to continue with its research.

In London, the buses come to a depot at Hornchurch to be filled up. The refuelling station is the first in Europe to use underground storage of liquid hydrogen for transport use. Paul Page, a spokesman for BOC, said: "The feeling of whether it makes economic sense is gathering momentum. These things were not on our radar screen a few years ago, but they are now an integral feature of what we are doing."

The hope is that fuel cell buses could provide the first commercial market for application of the technology, if the trials are seen as a success. However, according to Fuel Cell Today, an independent website which is supported by the chemicals giant Johnson Matthey, the current market price of a single fuel cell bus is well over $1m (£555,000) - this is well over double the cost of a top-of-the-range diesel bus.

The hope is that the political value of having clean buses will encourage policymakers such as the Greater London Authority, to directly support fuel cells.

"When this is coupled with technology such as the hydrogen fuel cell combination that addressed environmental issues, governments could potentially be a major early adopter, speeding up adoption issues," said Kerry-Ann Adamson, Fuel Cell Today's deputy editor, in a report published last year.

TfL says: "The results [of the trial] will help European governments assess what contribution fuel cell technology can make towards commitments given in the Kyoto protocol and help industry partners add to their knowledge in operating this technology in real-life conditions."

But how long it will take for the RV1's fuel cell to end up in your own modest car is another question. A recent survey of carmakers found that most saw commercialisation only beginning in 2010, with DaimlerChrysler forecasting fuel market penetration in 2020 at the earliest. Honda has experimental fuel cell cars that are operating with public authorities in the US, however.

General Motors, the beleaguered US motor giant, has pledged to become the first company to sell a million fuel cell vehicles.

But even the behemoth of Motown acknowledges the economic challenges. "The change from an oil-based - gasoline, natural gas - infrastructure to one based on hydrogen cannot happen overnight," it says.

"It will require a transition period to ease society out of the familiar and comfortable oil-based economy and into the new one based on hydrogen."

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