A Swedish researcher claims that energy released when a car brakes can be harnessed for later use in the form of compressed air.

The energy saved can be put to better use, to turn the engine on for example, and will make hybrids cheaper in the long run.

Per Tunestål, a researcher in Combustion Engines at Lund University in Sweden, said: “The technology is fully realistic. I was recently contacted by a vehicle manufacturer in India which wanted to start making air hybrids. The technology is particularly attractive for jerky and slow driving, for example for buses in urban traffic.”

Electric cars and electric hybrid cars already make use of brake energy, to power a generator that charges the batteries.

Sasa Trajkovic, a doctoral student in Combustion Engines at Lund University said: “My simulations show that buses in cities could reduce their fuel consumption by 60 per cent”