STEAM power may soon be making a comeback鈥攊n a high street near you.
Fred Bayley has designed a hybrid car that combines diesel and steam power. The
trick is to store exhaust heat in a form that can be used later.
Hybrid cars reduce emissions, particularly during city driving. They have
both an internal combustion engine fuelled by petrol or diesel and an electric
motor powered by a rechargeable battery or a hydrogen fuel cell. The engine
powers the vehicle on motorways, where it runs cleanest. In urban areas, the
conventional engine either switches off or idles while the electric motor takes
over.
But hybrids would be even less polluting if they used steam power instead of
batteries, according to Bayley, an automotive engineer from Brighton. He told a
vehicle technology conference in Brighton last month that diesel/steam hybrids
could be nearly 70 per cent more efficient for city driving than a
diesel/battery hybrid. They will let you drive for up to 40 minutes on steam
alone.
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Bayley has designed a 鈥渟team accumulator鈥� based on a wrought aluminium
pressure vessel containing 100 litres of water. During diesel-powered driving,
the water is heated by the 500 掳C exhaust gases until it reaches a pressure
of 100 atmospheres (10 megapascals). In town, the diesel engine switches off and
a pressure valve opens. This releases a superheated steam jet that drives a
turbine, which in turn drives the wheels. The waste steam is condensed and
pumped back into the pressure vessel.
Bayley says his system will increase the distance driven on a litre of fuel
from the 29.4 kilometres achieved by diesel/battery hybrids to 49.5 kilometres,
equivalent to 140 miles per gallon. This improvement can be achieved because
鈥渃harging鈥� the steam storage system does not take power away from the diesel
engine. 鈥淐urrent hybrids run the internal combustion engine to charge the
electric battery,鈥� explains Bayley. 鈥淏ut this design doesn鈥檛 ask the internal
combustion engine to do anything except power the vehicle. The accumulator gets
its energy from the hot exhaust gases鈥攅nergy which is usually chucked out
of the tailpipe.鈥�
He dreamed up his design three years ago but has been rebuffed by motor
manufacturers. Now Richard Stobart, head of automotive engineering at Sussex
University, is helping him find development funding.
Steam accumulators were used in the 20th century on railway locomotives, says
Roger Waller, chief engineer at DLM in Switzerland, which makes modern steam
locos. They minimised the hazard from the firebox in environments such as
chemical plants. 鈥淚t鈥檚 an old principle but it needs to be developed,鈥� says
Waller. 鈥淭he problem is convincing people that steam has its place. It鈥檚 a
forgotten technology.鈥�