The result should be a cell that will, weight for weight, put out as much power as a diesel engine.

ECONOMIST: Clean living in Iceland

Although this is impressive, America's Department of Energy has calculated that carbon materials will need to be able to store 6.5% of their own weight of hydrogen in order to make fuel-cell cars practical (defined as having a range of 500km, or 310 miles, between refuelling stops).

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RFLKT's sleek profile and lowly 2 ounce weight, make it virtually unnoticeable when mounted, while the coin cell operated battery has a life of over one year and requires no charging.

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But until recently they have suffered from a low power-to-weight ratio, unlike the other sort of room-temperature fuel cell, the temperamental and costly proton-exchange-membrane device, which several firms hope soon to use in motor cars.

ECONOMIST: Clean living in Iceland