In recent years, many under-developed technologies have re-emerged as potential alternatives to petroleum fuel. Compressed air is not given much consideration as an automotive fuel in the United States, but examples of compressed air or pneumatic technology can be found in a handful of countries. Though the technology is mostly experimental, France in particular is currently a forerunner in developing this technology, with some models in production today.
Efficiency and environmental impact
The impact depends on the source of the energy used to compress the air. This is only a green form of transport if the energy derives from a sustainable source, and reasonable efficiency is achieved in delivering energy to the road.
History
A pneumatic vehicle is an automobile powered by the expansion of compressed air instead of traditional petroleum fuel. Pneumatic vehicles have been given more consideration in recent years as a petroleum alternative, though it cannot be considered a new technology. The earliest concepts of this technology can be traced back to the 17th century, and a functioning prototype was built in France in 1839, but abandoned. The 1870s saw important advances in compressed-air vehicle technology with the development of the “Mekarski” pneumatic motor, the first recorded use of a pneumatic motor for street transit and locomotive lines. During this time, several were imported to the United States, primarily for mining applications. Because they didn't require combustion or spark, pneumatic motors were a safer alternative in gaseous mine tunnels.
The technology appeared again in the 1920s in the United States when a man named Lee Barton Williams retrofitted a gasoline-burning motor to run primarily on compressed air. In the following decade, several more air-petrol hybrids were developed, but the technology was suppressed heavily by the petroleum industry, which has a reputation for silencing pesky inventors. The gas crisis of the 70s and 80s brought out a multitude of designs from inventors all over the world, all claiming to have developed machines that could run for months on a single tank of air. Despite the widespread development and interest, none apparently made it to production/distribution on the consumer level.
Technology
A pneumatic automobile is powered by the expansion of compressed air from the atmosphere. Similar technology is commonly seen in the pneumatic motors used in air tools, etc. Current models such as those produced by French company Motor Development international (MDI) generally consist of a high-pressure carbon fiber air tank, filled initially at a high speed dedicated filling station, or filled over a few hours while parked using the vehicle's on-board air compressor. The vehicle is then propelled by the release of air from the tank. At high speeds a small motor fueled by a traditional fuel is often required in order to heat the air before delivery and compress more air while running to increase the vehicle's range between filling. Regenerative braking is also used in modern pneumatic vehicles. Pneumatic motors often produce cold air as exhaust, which can then be used to air-condition the car. Some companies claim their exhaust air is cleaner than the air in earth's atmosphere, creating “negative pollution”.
Downside
The technology is still very experimental and generally considered impractical for highway use. Critics claim that the compressed air car actually requires more total energy to fuel once all the factors (such as energy cost of air compression, etc.) are taken into consideration. Many believe that the compressed air vehicle is not practical enough to consider seriously as an alternative fuel. MDI's “Air Car” still needs to be re-filled more frequently than traditionally-fueled automobiles, and has little application today aside from a secondary “grocery getter.” Many designers, however, claim to have built designs that will run for months on a single tank of air, and compressed air, though experimental, may still prove useful as a petroleum alternative.
References
http://www.motorauthority.com/news/1033303_zero-pollution-motors-plans-2011-u-s-launch-for-106mpg-air-powered-car www.eduplace.com/science/hmsc/4/f/cricket/ckt_4f.shtml www.rexresearch.com/negre/negre.htm www.aircarfactories.com › Air Cars www.guynegre.net/index-eng.php