Pneumatic Hybrid Eliminates Need For Batteries, Motors

Researchers at the Swiss Federal Institute of Technology have developed a hybrid drive system for vehicles that eliminates the need for batteries and motors. The design, created by Lino Guzzella, uses compressed air to power the vehicle. The developer says that the engine costs about 20 percent more to manufacture than a conventional gasoline engine and reduces overall fuel consumption by about one-third. This fuel economy puts the engine in range of today's gas-electric hybrid vehicles.

While the designs still have major drawbacks – compressed air has a relatively low energy density, and the pneumatic engines are not very efficient – the new design uses automated controls to improve the overall fuel economy of the engine. With the new hybrid design, regenerative braking doesn't play as large a role in recapturing wasted energy, though it is still incorporated into the system. The design does use pneumatics to improve the efficiency of the gasoline engine.

The design calls for a very small gasoline engine – 750-ml – which is used to provide power to the vehicle at cruising speed. Compressed air used for acceleration in a process called supercharging. Supercharging burns more fuel than normal during the acceleration phase and according to the designer, is free from the lag drivers typically experience with a turbocharger. The system also features a stop-start mechanism that cuts the gasoline engine when the vehicle is idling.

Guzzella will show his design at the Society For Automotive Engineer's Congress in April 2009. Most of his efficiency figures come from computer modeling, and he will continue to tweak the model to achieve greater efficiencies. He has built a basic, functional prototype of the system as well. One of the major advantages of Guzzella's design is that it does not require major modifications to a conventional gasoline-powered drive train. While it's not precisely a drop-in substitution, the design does lend itself easily to conversion.

Source: Technology Review
Photo Credit: Lucas Pettinati, via Flickr