Compressed air tank

Several companies claim to have been developing compressed air cars for public use, since about 1990, but none are available yet. Typically the main advantages are claimed to be: no roadside emissions, low cost technology, engine uses food oil for lubrication, and integrated air conditioning.

The tanks must be designed to safety standards appropriate for a pressure vessel, such as ISO 11439.

The storage tank may be made of:
 * carbon-fiber in order to reduce its weight while achieving the necessary strength.
 * kevlar.

Compressed air is a heavy way of storing fuel, 300l air at 300 bar only amounts to about 12kWh (the equivalent of 1.4 liter (0.37 gallons) of gasoline). During rupture testing, the tank cracks, but does not break up, producing no splinters or fragments.

All four major manufacturers who are developing air cars have designed safety features into their containers as opposed to hydrogen's issues of damage and danger involved in high-impact crashes. Air, on its own, is also non-flammable. Though no company has yet demonstrated the effectiveness of an imploding engine (ZAP) vs a quick release (MDI) standard, and other safety designs; it is expected that large-scale production may lead specific governments to set their own standards. It was reported on Discovery's Beyond Tomorrow that on its own carbon-fiber is brittle and splits; but creates no shrapnel.

The tanks may be refilled at a service station (using volume transfer), or in a few hours at home or in parking lots plugging the car into the electric grid via an on-board compressor. The cost of driving such car is typically projected to be around €0.75 per 100 km, with a complete refill at the "tank-station" at about US$3.

Safety
As with most technologies, compressed air has safety concerns, mainly the catastrophic rupture of the tank. Rigid safety codes make this a rare occurrence at the cost of weight: codes may require the working pressure to less than 40% of the rupture pressure for steel bottles and less than 20% for fiber-wound bottles. High pressure bottles are fairly strong so that they stay unruptured in crashes and follows the ISO 11439 standard.

Carbon tanks
Airhog provides 4,500 PSI carbon tanks.

Specifications:


 * Model# - 6109
 * Capacity - 550 cu inch
 * Pressure - 4500 psi
 * Diameter - 6.97''
 * Length - 21''
 * Weight - 11.5 lbs.
 * Price about $1k


 * Model# - 62803A
 * Capacity - 1624 cu in
 * Pressure - 4500 PSI
 * Diameter - 9.81''
 * Length - 30.83''
 * Weight - 30lbs
 * Price about $2k

Bigger tank to special order in lots of 30.