Pneumatic Hybrid Engine Shows Promise

Swiss-developed engine uses compressed air instead of batteries to improve fuel economy by 30 percent on European test cycle.

Published: 01-Feb-2009

A pneumatic hybrid engine could be used to power vehicles in the future. The benefit of this technology: it is much cheaper than today’s electric hybrids and almost just as economical.

The Japanese automobile manufacturer Toyota has built a car, the “Prius”, which is seen as a concept for the future. It uses an electric hybrid engine to save fuel while still offering the usual drivability standards. However, this vehicle has a serious disadvantage. It is expensive and is unaffordable especially for consumers in up-and-coming countries such as China and India that are increasing rapidly their mobility demands. In addition, the battery needed by the electric hybrid as an energy storage device is heavy and expensive. Last but not least, the technology in the coupling between the gasoline engine and the electric drive is very complicated.
Simpler and cheaper

This is why Lino Guzzella, Professor of Thermotronics, does not think the electric hybrid is the only solution. As an experienced engineer, he therefore looked for an approach that was simpler than an electric hybrid but remained affordable even for people with less purchasing power. Guzzella explains that “The apple must be ripe but still hang just low enough to stay within reach.” The 'fruit' ripening in his group is the pneumatic hybrid drive. The concept is simpler than that of an electric hybrid: the new hybrid engine has a compressed air tank connected to the engine instead of a battery unit. When required, e.g. when starting from rest or after changing gear, compressed air flows into the engine through an electronically controlled valve. If fuel is also injected, the engine responds quickly. Although the system used to control the valve is also technologically complex, this challenge can be mastered nowadays thanks to powerful algorithms and computer systems.


It is the first vehicle from GM that combines an ethanol-capable engine with the two-mode hybrid system.

The hybrid-powered GMC Denali XT was produced at GM Holden's design centre at Port Melbourne.

The completed open wheel car which runs on the electric system and backed up by the Yamaha motorcycle engine.


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