A compressed air car is a car that uses a motor powered by compressed air. The car can be powered solely by air, or combined (as in a hybrid electric vehicle) with gasoline, diesel, ethanol, or an electric plant with regenerative braking. History
Compressed air has been used since the 19th century to power mine locomotives and trams in cities such as Paris (via a central, city-level, compressed air energy distribution system), and was previously the basis of naval torpedo propulsion. In 1903, the Liquid Air Company located in London, England manufactured a number of compressed-air and liquefied-air cars. The major problem with these cars and all compressed-air cars is the lack of torque produced by the "engines" and the cost of compressing the air. Recently several companies have started to develop compressed air cars, although none have been released to the public, or have been tested by third parties. Technology
Compressed air cars are powered by motors fueled with compressed air, which is stored in a tank at high pressure such as 30 MPa (4500 psi or 300 bar). Rather than driving engine pistons with an ignited fuel-air mixture, compressed air cars use the expansion of compressed air, in a similar manner to the expansion of steam in a steam engine. Storage tanks
In contrast to hydrogen's issues of damage and danger involved in high-impact crashes, air, on its own, is non-flammable. It is know that carbon-fiber is brittle and can split under sufficient stress, but creates no shrapnel when it does so. Carbon-fiber tanks safely hold air at a pressure somewhere around 4500 psi, making them comparable to steel tanks. The cars are designed to be filled up by a high-pressure pump. Energy density
Compressed air has relatively low energy density. Air at 30 MPa (4,500 psi) contains about 50 Wh of energy per litre. For comparison, gasoline contains about 9411 Wh per litre; however, a typical gasoline engine with 18% efficiency can only...