ScienceDaily (Feb. 7, 2011) — Every time a car brakes, energy is generated. At present this energy is not used, but new research shows that it is perfectly possible to save it for later use in the form of compressed air. It can then provide extra power to the engine when the car is started and save fuel by avoiding idle operation when the car is at a standstill.
Air hybrids, or pneumatic hybrids as they are also known, are not yet in production. Nonetheless, electric cars and electric hybrid cars already make use of the brake energy, to power a generator that charges the batteries. However, according to Per Tunestål, a researcher in Combustion Engines at Lund University in Sweden, air hybrids would be much cheaper to manufacture. The step to commercialisation does not have to be a large one.
"The technology is fully realistic. I was recently contacted by a vehicle manufacturer in India which wanted to start making air hybrids," he says.
The technology is particularly attractive for jerky and slow driving, for example for buses in urban traffic.
"My simulations show that buses in cities could reduce their fuel consumption by 60 per cent," says Sasa Trajkovic, a doctoral student in Combustion Engines at Lund University who recently defended a thesis on the subject.