Compressed-air vehicle

A compressed-air vehicle (CAV) is a transport mechanism fueled by tanks of pressurized atmospheric gas and propelled by the release and expansion of the gas within a pneumatic motor.

CAV's have found application in torpedoes, locomotives used in situations where standard locomotives are a hazard, and early prototype submarines.

Compressed-air vehicles operate according to a thermodynamic process in which air cools down when expanding and heats up when being compressed, resulting in unwanted energy losses. However, with recent developments in isothermal compressed air energy storage (ICAES) plants, compressed air storage has reached 3.6 MJ/m³ and four times the capacity factor of lithium-ion batteries with 2.7 MJ/kg.^[1] In 2020 there were developments published by Dr. Reza Alizade Evrin from Ontario Tech University^[2][3] with an isothermal compressed-air vehicle prototype that uses low-pressure air tanks and exhaust air recovery to power a paraffin heat exchanger system with a global energy efficiency of 74% and a driving range of 140 km (87 mi). This efficiency and range can be increased by using storage tanks as vehicle structure, high-pressure tanks, new rotary engines, and a more efficient heat exchanger.

Compressed-air propulsion may also be incorporated in hybrid systems, such as with battery electric propulsion. This kind of system is hybrid pneumatic–electric propulsion. Regenerative braking can also be used in such systems.