Q:Several television and magazine stories over the last five years have talked about compressed-air cars as an answer to our fuel and pollution problems. Is this a genuine technology we are going to see on a big scale, or another gimmick? Jim D., Minneapolis
A:It's a genuine technology in the sense that several companies have been developing it and there are vehicles in the world operating on compressed air. The advantages manufacturers of this engine type stress are that air is abundant and that pushing mechanical parts with air does not produce any toxic exhaust.
The pollution hitch here is comparable to the one with electric cars, however. Neither of these technologies eliminates pollution, because you have to generate the electricity and you have to compress the air. If you can do this purely with a waterfall or wind, rather than burning a fossil fuel such as coal, then yes, in those limited circumstances, you aren't generating much pollution (parts still wear out, etc., so there's always some small amount of pollution generated). But the electrical grid in this country is far from being powered solely by water or wind or the sun.
Power plants generate pollution in proportion to the amount of energy they generate: if they have to work harder to create more electricity for electric cars or to compress air for this technology, there is a pollution output, even though it comes at the power plant and not each vehicle's tailpipe. That has meaning in the grand scheme, but does not eliminate the utility of vehicles with no tailpipe emissions. In a large enclosed space - like a huge factory, for example - having a compressed-air vehicle you can operate indoors without generating toxic fumes is a real advantage.
Several variations on the compressed air concept include the piston-engine design, a rotary design, and versions that can run on petroleum-based fuels as well as compressed air. The rotary design's manufacturers claim it is the most efficient, but all of them are limited in top speed - and the faster you go, the quicker you drain the air tank. The compressed-air vehicles in use are mainly in urban or industrial settings operating at slow and stop-and-go speeds. Since cities have the biggest vehicle pollution problems, that's OK.
All alternative-fuel vehicles face acceptance and distribution problems. The public has to accept them and an infrastructure needs to be created to refuel them. Refueling a big compressed air tank requires an industrial-sized compressor. To use compressed air vehicles on a large scale, these compressors would have to be distributed much the same way gas pumps are today. Can we expect this in 10 or even 20 years? Doesn't seem probable.
Technological changes occur most swiftly when the new device is vastly superior to the old one. Computers are much more powerful and capable than typewriters. Cell phones are a lot handier than land lines. A compressed-air car, or an electric one for that matter, doesn't perform better than a gasoline car. It just does it differently, creating a different set of pollution and fuel-distribution challenges. Where the technology is superior, in urban areas and enclosed spaces with strong pollution concerns, they'll probably make headway. As a widespread replacement for our everyday automobiles, any market expansion they make in that regard will be much slower.
