17-10-2017, 11:19 AM
A compressed air vehicle (ACV) is powered by an air motor, using compressed air, which is stored in a tank. Instead of mixing the fuel with air and burning it in the engine to drive the pistons with hot expansion gases, vehicles with compressed air use the expansion of compressed air to drive the pistons. A manufacturer claims to have designed an engine that is 90% efficient.Compressed air propulsion can also be incorporated into hybrid systems, such as with the electric propulsion of the battery. This type of system is called hybrid-pneumatic electric propulsion. In addition, regenerative braking can also be used in conjunction with this system.
Tanks must be designed to the appropriate safety standards for a pressure vessel, such as ISO 11439. The storage tank may be made of metal or composite materials. Fiber materials are considerably lighter than metals, but are generally more expensive. Metal tanks can withstand a large number of pressure cycles, but should be periodically checked for corrosion.
One company stores air in tanks at 4,500 pounds per square inch (about 30 MPa) and holds about 3,200 cubic feet (about 90 cubic meters) of air. Tanks can be filled at a service station equipped with heat exchangers, or in a few hours at home or in parking lots, by connecting the car to the mains power supply through an on-board compressor. The cost of driving a car of this type is typically around € 0.75 per 100 km, with a full recharge at the "tank station" of approximately $ 3.
Compressed air has a low energy density. In containers of 300 bar, it can reach approximately 0.1 MJ / L and 0.1 MJ / kg, comparable to the electrochemical lead-acid batteries. While the batteries can keep their voltage down a bit during their discharge and the chemical fuel tanks provide the same power densities from the first to the last liter, the pressure of the compressed air tanks decreases as it withdraws the air. A consumer car of conventional size and shape typically consumes 0.3-0.5 kWh (1.1-1.8 MJ) on the transmission shaft per mile of use, although unconventional sizes can operate significantly less.