It was Jules Verne that first predicted a transportation system based on compressed air – he portrayed a picture of Paris in the 21st Century where this had become a reality. Today it is science fact and not science fiction, with clean running compressed air prototype cars having been tested for use as private transport in both India and the US.
Compressed air as a vehicle fuel is a fundamentally clean technology – the only exhaust is simply naturally occurring atmospheric gases. In theses engines there is no combustion, so the only engine heat comes from friction this means that the engine can be made primarily from lightweight aluminum. In the current designs the only energy consumption for the prototype cars is firstly during manufacture and from re-fueling on compressed air. High speed compression devices are powered by electricity – usually from the main electricity grid. Currently this energy may be taken from fossil fuels – but in the future it is conceivable that these will be from renewable sources. Achieving this would make this one of the cleanest cars in the world.
It was Guy Negre of Motor Development International (MDI) that first set about designing an engine that could run cleanly on compressed air. His innovative technology can potentially be paired in two, four, or six cylinder engine configurations this makes it more appealing to companies who would wish to put it into commercial production. This would allow them to produce anything from short distance economy class cars through to high performance sports models and industrial use trucks and vans.
The air engine works by having a small piston with a conventional connecting rod for turning the crankshaft. A neighboring, larger piston uses a newly designed rocker arm configuration with the connecting rod. This design allows the large piston to pause at top-dead-center for 70 degrees of crankshaft rotation while metered air pressure builds in a pre-chamber as the small piston keeps the crank turning during its power stroke. The large piston then turns the crankshaft with greater power as the pair combine to produce power over 270 degrees of crankshaft rotation. What all this means is that the cars that have been developed can have an impressive top speed of 70 mph and a range of 125 miles before requiring a refill. By offering compressor refill stops at most service stations these vehicle become a viable clean transport option.
In India the Tata Motor company is reviewing options to install a MDI air engine in an existing budget model of car called the Nano. The addition of air power to an already inexpensive and efficient model would be quite appealing in the Indian market along with other countries where personal transportation is in growing demand. In these developing areas, air pollution could present a serious challenge as demand for cars is now expanding exponentially. Solutions that eliminate toxic emissions will be key to transport infrastructure development in the near future and the compressed air engine will most certainly play a major role.
In the United States, a company called Zero Pollution Motors (ZPM) has recognised the environmental appeal of the design and has licensed the rights to produce the MDI design. Based in New Platz, New York, ZPM has an ambitious goal of rolling out a North American compressed air vehicle later this year with a view of going into full production in 2011. The company most recently unveiled MDI’s newest car at the Automotive X-Prize exhibit at the New York Auto Show – on view were its six seat, four door prototype in the mainstream class, and the three seat, two door economy-utility model in the alternative class demonstrating the range of potential for this latest green car engine.
Images: Main – Tata Car courtesy of the Tata Motor Company.
Insert ZMP artist impression four door prototype.