Lund, Sweden -  Compressed air could one day provide power to assist a  vehicle’s gasoline engine, according to researchers at Sweden’s Lund University. The system would use energy generated by the brakes and stored as compressed air, which can provide extra power to the engine when the car is started.

Air hybrids, also called pneumatic hybrids, are not yet in production, but Per Tunestål, a combustion engine researcher at the university, said that air hybrids would be much cheaper to manufacture than battery hybrids. The technology is particularly attractive for jerky and slow driving, such as buses in urban traffic. “The technology is fully realistic,” Tunestål said. “I was recently contacted by a vehicle manufacturer in India which wanted to start making air hybrids.”

The research suggests that city buses could reduce their fuel consumption by 60 per cent, and that 48 per cent of brake energy, which is compressed and saved in a small air tank connected to the engine, could be reused later, matching the degree of reuse for electric hybrids. The engine does not require any expensive materials and the system, which works with gasoline, natural gas and diesel, takes up much less space than an electric hybrid engine.

The researchers said that Ford initially worked with the idea in the 1990s but lacked the necessary technology. Today, research is being conducted in Switzerland, France and Sweden. Scuderi, an American company, intends to invest in engines with air hybrid technology but their results so far have been from simulations, not from experiments.

The researchers in Lund hope to convert their research results from a single cylinder to a complete multi-cylinder engine, moving the concept a step closer to a real vehicle.