Driving on air

Research is taking place on both sides of the Atlantic into innovative air-hybrid engines that promise to be lighter, cheaper and more environmentally-friendly than existing electric-hybrids.

A collaborative project between researchers at

-which has a patent on the design - and car manufacturers

and

is to begin early next year to develop a prototype that could turn a conventional combustion engine into an air compressor.

The theory behind the design of an air-hybrid is not new but according to the project's leader, Prof Hua Zhao from the university's school of engineering and design, it has never been put into practice before.

An air-hybrid engine recovers the braking energy during deceleration by turning off the engine's combustion and using the valve timings to change the engine into an effective compressor that pumps highly-compressed air into a tank, where it is stored.

The engine compresses the air to a high temperature and pressure in the 20-30 litre air tank, which holds it until it can be used, according to Zhao.