Technology pushes fuel-cell vehicle development
To satisfy consumer needs, fuel cell powered vehicles must have the same, or better, performance than those driven by a conventional internal combustion engine. Sufficient power also needs to be generated in the fuel cell to power all the functions demanded by today's motorists - air conditioning, power steering and brakes, and in-car entertainment.
Current hydrogen-powered fuel cell vehicles, like those produced by Mercedes, have a range of 170 to 250 miles with 0-60mph acceleration times of 12-16 seconds. But up to twice the range, 300 miles, and half the 0-60 mph acceleration time of current fuel cell powered vehicles, less than 10 seconds, was the claim made by General Motors for its new Sequel concept vehicle at its launch in January at the North American International Auto Show in Detroit.
The extended range is due to advances made in high-pressure hydrogen storage that enables the vehicle to carry 8 kg of hydrogen at a pressure of 700 bar in three lightweight carbon composite tanks. According to GM, this represents the world's first 700 bar tank system to be certified by the inspection organisation, TUV, to German and international guidelines.
The acceleration improvement has been achieved through the develop-ment of a 25 per cent more powerful fuel cell module. Greater component simplicity has helped to reduce the design costs of the fuel cell module, which produces 73 kW of high-voltage electricity to drive the electric motors in its wheel hubs, power the ventilation and air-conditioning, the electronic controls and recharge the on-board battery.
The cell has a sandwich- like structure; an electrolytic polymer foil, or proton exchange membrane, separates two gas-permeable electrodes of graphite paper. Since a single cell produces a very small electrical potential, a number of individual cells must be connected in series to form a fuel cell stack or module to produce sufficient power.
Ford and BMW, however, believe that fuel cells are still for the future and have taken a different path, using modified internal combustion engines that run on hydrogen. BMW has hedged its bets even further by developing a bi-fuel version of its 700 series saloon, modified to run on both hydrogen and gasoline.