Tata Motors, India largest automotive company, on Feb. 5, 2007 announced that it has signed an agreement with Moteur Development International (MDI) of France, inventors of the car, to develop a car that runs on compressed air, thus making it very economical to run and be almost totally pollution free. This article in Rediff India Abroad and the MDI website gives further details.
The air engine has 4 two-stage pistons, i.e. 8 compression and/or expansion chambers on one crankshaft. The pistons work in two stages: one motor stage and one intermediate stage of compression/expansion. They have two functions: to compress ambient air and refill the storage tanks; and to make successive expansions (reheating air with ambient thermal energy) thereby approaching isothermic expansion. It has injection similar to normal engines, but uses a special crankshaft and pistons, which remain at top dead center for about 70 degrees of the crankshaft's cycle; this allows more power to be developed in the engine. The engine is powered by compressed air, stored in a carbon-fiber tank containing 90 cubic meters (3178 cubic feet) of air at 30 MPa (4500 psi).
The expansion of this air pushes the pistons and creates movement. The atmospheric temperature is used to re-heat the engine and increase the range.
The cars have the following characteristics:
- Are light weight vehicle that can reach speeds up to 220 kmph.
- MDI's vehicle's have fiberglass bodies which makes them light, silent urban car.
- The vehicles do not have normal speed gages. Instead, they will have a small computer screen
- Both ends of the seat belt are anchored to the vehicles floor for greater safety.
- The vehicle's uses a patented electric system that makes the car 20 kilos lighter and considerably quieter.
- There are no keys - just an access card that can be read by the car from your pocket.
- In the single energy mode MDI cars consume around US$1.00 (Rs 45) every 60 miles (100 km).
- There is no pollution from the car.
- The vehicle's driving range is close to twice that of the most advanced electric cars (from 200 to 180 miles (300 km) or 8 hours of operation).
- The recharging of the car will be done at gas stations in 2 to 3 minutes at a price of Rs 90, once the market is developed.
- The car also has a small compressor that can be connected to an electrical network (220V or 380V) and will recharged the tanks completely in 3 or 4 hours.
- The car's oil (a liter of vegetable) only needs to be changed every 50,000 km.
- The temperature of the exhaust is between 0 and 15 degrees below zero and can be used for air conditioning of the car.
The hybrid has been conceived as much for the city as the open road and will be available in all MDI vehicles. The engines will work exclusively with compressed air while it is running under 50 km/h in urban areas. But when the car is running at speeds over 50 km/h, the engines will switch to fuel mode. The engine will be able to use gasoline, biodiesel, natural gas, LNG, alcohol, etc. It was not clear whether the air engine would also be used as an ICE or whether two engines would be employed in the hybrid.
Engines will be available with 2, 4 and 6 cylinders. When the air tanks are empty the driver will be able to switch to fuel mode.
The car -- MiniCAT -- could cost around US$8,000 (Rs 350,000) in India and would have a range of around 180 miles (300 km) between refuels. The cost of a refill would be about US$2.00 (Rs 90).
The smallest and most innovative: three seats, minimal dimensions.
- Airbag, air conditioning, ABS, 3 seats, 1.5 m3.
- Dimensions: 2.65m, 1.62m, 1.64m
- Weight: 750 kg
- Maximum speed: 110 kmh
- Mileage: 200 - 300 km
- Maximum load: 270 Kg
- Recharging time: 4 hours (Mains connector)
- Recharge: 3 minutes (Air station)
A more spacious car with seats which can face different directions. The vehicle's design is based on the needs of a typical family.
- Airbag, air conditioning, 6 seats.
- Dimensions: 3.84m, 1.72m, 1.75m
- Weight: 750 kg
- Maximum speed: 110 kmh
- Mileage: 200 - 300 km
- Max load: 500 Kg
- Recharge time: 4 hours (Mains connector)
- Recharge time: 3 minutes (Air station)
Although there is no official word on when the car will be commercially manufactured for India, reports say that it will be sooner than later.
The MDI headquarters are located in Luxembourg while the prototype factory is in the south of France, where 60 people are employed. According to the MDI website "At the moment the construction of the first serial production factory is being completed, at the same location."
Currently licenses for manufacture and distribution have been sold to companies in Spain, Portugal, Brazil, South Africa, India, Great Briton, France and the United States. ZevCAT has the license in the US.
This technology competes with the electric car. The claimed advantage of compressed air over electric storage is that it is less expensive, has a faster recharge time and pressure vessels have a longer lifetime compared to batteries. Both technologies have hurdles to overcome, demonstrating that the air engine/compressed air system is as light, efficient and cheap as available electric motors/batteries. The main issues to me are that the air engine has not been proven to be dependable and advanced batteries are still too expensive. According to Gizmag the signing of the Tata agreement has made the prospects of very cost-effective mass production are now a distinct possibility. According to Wikepedia: as of March 2007 the Air car is not in production; they have been said to be going into production "soon" since at least 1998. In 2003 Wired had a fairly negative article on the company. An Australian rotary air engine, the Di Pietro Rotary Air Engine, appears to be further along in development and they have a small demonstration vehicle in use. In retrospect it appears that I should have written this piece about the DiPetro engine, but maybe a later post.
A discussion of the energy efficiencies of an air engine vehicle vs an electric vehicle would breakdown into the efficiency of the air compressor and air engine vs the efficiency of batteries and motors in the electric car, which I am sure the electric car would win. However because of the potentially low initial cost, low maintence cost and low operating cost compared to a fossil fueled vehicle the "air car" could find a niche market if it could be marketed before low cost batteries are available.