Hybrid technology propels most fuel-efficient vehicles currently on sale in the U.S., but with costly battery packs and not-so-easy-on-the-wallet pricing; Are gas-electric hybrids long for this world? Could pneumatic hybrids be a cost-effective replacement?

According to UK-based Economist they can. The idea of a pneumatic hybrid system is an old one. That's because it's very simple when you break it down to the core contributors. Firstly, this is not a car that runs strictly on air, but instead utilizes a gasoline or diesel internal combustion engine mated with an electric engine-replacing, compressed air tank.

The electric motor and battery pack within a hybrid vehicle merely act as a boost mechanism when excess power is needed beyond the scope of the internal combustion engine and gains its charge through a processes such as regenerative braking. A regenerative braking system converts the kinetic energy produced while stopping the vehicle into a storeable energy form, rather than allowing it to dissipate as heat, which is the case in conventional braking systems. This energy is then re-routed into the battery packs, which in turn provides power to the electric motor that then supplements the main drive engine.


The difference with a pneumatic hybrid system is that instead of gathering kinetic energy through the brake system, it would instead be gained by utilizing the internal combustion engine. Under braking, the fuel supply would be shut off and the vehicle would slow via engine (compression) braking, but rather than lose the air that would be compressed by the pistons in the cylinders, it would then be collected. In this case the internal combustion engine acts as the air compressor for the system, then stores it in a high compression storage tank for a quick burst of additional energy when deemed necessary.

The disadvantage of this system is that compressed air has an extremely low energy density making it fairly inefficient during long strides of freeway driving, but put this system into an urban environment and now we're talking. The constant stop and go of city traffic would allow the system to quickly build up, store and dispense the compressed air in regular cycles, making the system all but invisible to the driver. The fuel consumption hovers around a 32% gain over a normal internal combustion engine according to Swiss Federal Institute of Technology professor, Lino Guzzella, and offers roughly 80% of the of the fuel savings offered by current gas-electric hybrids, but at a much lower price.


Could this be the system of the future or is it just another gimmicky foray into laboratory science that'll never see the light of day on our public road systems? Tell us what you think in the comments below. [via Economist, graphic via evconvert]