Recent research suggests that alternative forms of regenerative braking could store the same amount of energy as current systems and further increase fuel efficiency.Systems using an electric motor and generator to harness a vehicle’s kinetic energy and convert it into electricity that is then fed into the vehicle’s battery pack for storage are the most widely used applications of regenerative braking. However, Gizmag.com says new research suggests that air hybrids that store energy as compressed air would be cheaper to produce than current electric vehicles and battery-electric hybrids. Alternatives such as mechanical and hydraulic systems exist, but it is believed pneumatic systems that store energy as compressed air, or air hybrid systems, can be used to create cars that are more fuel efficient than the current selection of alternative-fuel driven vehicles. EXTRA POWER, ZERO IDLINGGizmag refers to the work of Sasa Trajkovic, a doctoral student in combustion engines at Lund University in Sweden, who did his doctoral thesis on pneumatic hybrid vehicles. Trajkovic says that the compressed air could be used to provide extra power to the vehicle on start up and save fuel by avoiding idling. And Trajkovic calculated that 48 percent of the brake energy compressed and stored in a small air tank could be reused, similar to the regenerative braking systems seen on current petrol-electric hybrid cars. SMALLER AND CHEAPERGizmag says the air hybrid engine would work with petrol, diesel and natural gas engines, would be cheaper to manufacturer than battery packs and would take up less space than an electric hybrid engine. While the idea of a pneumatic motor is not new, most of the work thus far has been theoretical, Gizmag says. Following their findings with the single-cylinder air hybrid engine, the researchers at Lund University are now hoping to expand their work to a multi-cylinder engine.