Car run by Air coming soon to India by TATA motors

A compressed air car is an alternative fuel 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 electric plant and regenerative braking.

Tata Motors signed an agreement with MDI to continue research on air powered motors and cars. The time line for bringing their compressed air car, the Tata OneCAT, to market has been said to be in 2008 or 2009. Other companies are also working on air cars.
The compressed air car has been mentioned in Popular Mechanics as being the true car of tomorrow, with a range comparable to an electric vehicle or fuel-cell car. It does not offer zero emissions at the tailpipe without batteries or hydrogen fuel.
Compressed air cars are powered by engines fueled by compressed air, which is stored in a tank at high pressure such as 30 MPa (4500 psi or 300 bar). The storage tank is likely to be made of carbon-fiber in order to reduce its weight while achieving the necessary strength. Instead of mixing fuel with air and burning it to drive pistons with hot expanding gases; compressed air cars use the expansion of compressed air to drive their pistons.
The idea is not new. There have been prototype cars since the 1920s and compressed air has been used in torpedo propulsion as well.
Compressed air is a heavy way of storing fuel, 300 litres (11 cu ft) air at 30 MPa (4,500 psi) contains about 16 kWh of energy (the equivalent of 1.7 liters  of gasoline, assuming a 100% efficiency of the engine). During rupture testing, the tank cracks, but does not break up, producing no splinters or fragments.
All four major manufacturers that are developing air cars have designed safety features into their containers. In contrast to hydrogen's issues of damage and danger involved in high-impact crashes, air, on its own, is non-flammable. It was reported on Discovery's Beyond Tomorrow that on its own, 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 4500psi, which is good when compared with steel tanks.
Emission output
Due to this reason, a compressed air car's emission output can vary both with location and time. Different regions can have very different sources of power, ranging from high-emission power sources such as coal to zero-emission power sources such as wind. A given region can also update its electrical power sources with time, thereby improving or worsening emissions output.

Advantages
The principal advantages of an air powered vehicle are:
* Refueling can be done at home using an air compressor or at service stations. The energy required for compressing air is produced at large centralized plants, making it less costly and more effective to manage carbon emissions than from individual vehicles.

* Reduced vehicle weight is the principal efficiency factor of compressed-air cars. Furthermore, they are mechanically more rudimentary than traditional vehicles as many conventional parts of the engine may be omitted. Some plans include motors built into the hubs of each wheel, thereby removing the necessity of a transmission, drive axles and differentials. A four passenger vehicle weighing less than 800 pounds (360 kg) is a reasonable design goal.
* One manufacturer promises a range of 200 kilometres (120 mi) by the end of the year at a cost of € 1.50 per fill-up.
* Compressed air engines reduce the cost of vehicle production by about 20%, because there is no need to build a cooling system, spark plugs, transmission, axles, starter motor, or mufflers.
* Most compressed air engines do not need a transmission, only a flow control.
* The rate of self-discharge is very low opposed to batteries that deplete their charge slowly over time. Therefore, the vehicle may be left unused for longer periods of time than electric cars.
* Lower initial cost than battery electric vehicles when mass produced. One estimate is €3,000 less.
* Expansion of the compressed air lowers in temperature; this may be exploited for use as air conditioning.
* Compressed-air vehicles emit no pollutants.
* Air turbines, closely related to steam turbines, is a technology over 50 years old. It is simple to achieve with low tech materials. This would mean that developing countries, and rapidly growing countries like China and India, could easily implement a less polluting means of personal transportation than an internal combustion engine automobile.
* Possibility to refill air tank at home (using domestic power socket).
* Lighter vehicles would result in less wear on roads.
* The price of fueling air powered vehicles may be significantly cheaper than current fuels. Some estimates project $3.00 for the cost of electricity for filling a tank.
* Reduction or elimination of hazardous chemicals such as gasoline or battery acids/metals
Disadvantages
Like the modern car and most household appliances, the principle disadvantage is the indirect use of energy. Energy is used to compress air, which - in turn - provides the energy to run the motor. Any conversion of energy between forms results in loss. For conventional combustion motor cars, the energy is lost when oil is converted to usable fuel - including drilling, refinement, labor, storage, eventually transportation to the end-user. For compressed-air cars, energy is lost when electrical energy is converted to compressed air.

* When air expands, as it would in the engine, it cools dramatically (Charles law) and must be heated to ambient temperature using a heat exchanger similar to the Intercooler used for internal combustion engines. The cooling is necessary in order to obtain a significant fraction of the theoretical energy output. The heat exchanger can be problematic. While it performs a similar task to the Intercooler, the temperature difference between the incoming air and the working gas is smaller. In heating the stored air, the device gets very cold and may ice up in colder climates.
* Refueling the compressed air container using a home or low-end conventional air compressor may take as long as 4 hours though the specialized equipment at service stations may fill the tanks in only 3 minutes.
* Early tests have demonstrated the limited storage capacity of the tanks; the only published test of a vehicle running on compressed air alone was limited to a range of 7.22 km.
* A 2005 study demonstrated that cars running on lithium-ion batteries out-perform both compressed air and fuel cell vehicles more than three-fold at same speeds. MDI has recently claimed that an air car will be able to travel 140km in urban driving , and have a range of 80 km with a top speed of 110km/h on highways, when operating on compressed air alone.
Crash Safety Unproven
North American crash testing has not yet been conducted, and skeptics question the ability of an ultralight vehicle assembled with adhesives to produce acceptable crash safety results. Shiva Vencat, vice president of MDI and CEO of Zero Pollution Motors, claims the vehicle would pass crash testing and meet U.S. safety standards. He insists that the millions of dollars invested in the AirCar would not be in vain. To date, there has never been a lightweight, 100-plus mpg car which passed North American crash testing. Technological advances may soon make this possible, but the AirCar has yet to prove itself, and collision safety questions remain.
The key to achieving an acceptable range with an air car is reducing the power required to drive the car, so far as is practical. This pushes the design towards minimizing weight. In a collision the occupants of a heavy vehicle will, on average, suffer fewer and less serious injuries than the occupants of a lighter vehicle. An accident in a 2000 lb (900 kg) vehicle will on average cause about 50% more injuries to its occupants than a 3000 lb (1350 kg) vehicle. Air cars may use low rolling resistance tires, which typically offer less grip than normal tires. In addition, the weight (and price) of safety systems such as airbags, ABS and ESC may encourage manufacturers not to include them.

MDI and Tata Motors
MDI proposes a range of vehicles developed on an identical concept, made up of MiniCATs and CityCATs.
The MDI MiniCat has a range of up to 1000 miles when fitted with an internal combustion engine, but that drops to 30 miles when used in ZEV mode at low speeds in cities. OneCAT, priced in a range ($5,100 to $7,800) within reach of consumers in a developing economy, such as India.
The ultralight bodies of the vehicles would be made of glued-together fiberglass and injected foam, and the aluminum chassis would also be glued, not welded, to simplify manufacturing.
The engine is available in two versions. The Mono Energy air engine is a true air engine. The Dual Energy engines are Internal combustion engines, which use hydrocarbon fuels.
They have licensed 12 factories : 5 in Mexico, 3 in Australia and New Zealand, 1 in South Africa and 3 in France. MDI Andina S.A is going to sell the car in Colombia, Peru, Ecuador and Panama. MDI has entered into an agreement with Tata Motors, to produce air cars in India. Zero Pollution Motors will be the first company to manufacture and sell a car in the U.S. called the "Air Car" using MDI technology. ZPM will begin taking reservations in early 2009 for US deliveries in early 2010.