The idea is not new. Compressed air has powered trams and trains for decades, starting in the late 19th century. As long ago, the first recorded compressed-air vehicle in France was built by Frenchmen Andraud and Tessie of Motay. A car ran on a test track at Chaillot on the 9th of and worked well, but the idea was not pursued further.

It's only in recent times with rising oil prices and the environment becoming an issue, that compressed air-powered powerpacks for automotive use have once again caught the fancy of engineers and inventors. And Tata Motor's compressed air technologies are big news these days. A little over a year ago, French technology company Moteur Development International (MDI) signed up with Tata Motors, allowing them the use of the technology for the Indian marketplace and now there is talk that an air-powered Tata car will soon be on the road, something that Tata spokes men are not confirming.

MDI have been developing the technology since, and it is protected by more than 30 international patents. And MDI have been actively seeking licensees, and a dozen-odd, other than the one with Tata, have apparently been signed already. Although revolutionary in potential the technology really isn't that complicated. What a compressed-air car does is use the force of super-compressed air to move the engine's pistons up and down, as opposed to explosions produced from injecting a small amount of fuel.

To get things moving on compressed air, weight reduction is a top priority. MDI's aluminium-based engine is half the weight of a normal engine, and the frame is also built out of lightweight materials essentially fibreglass and a bonded aluminium spaceframe. The compressed air (some 90 cubic metres of it) is stored in carbon fibre tanks at very high pressure. Carbon fibre tanks are used for safety reasons since they tend to split open (as opposed to explode) when punctured and so there is no shrapnel.

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The expansion of air pushes the pistons and creates the movement. The atmospheric temperature is used to re-heat the engine and increase road coverage. The aircon system makes use of the expelled cold air. Due to the absence of combustion and the fact that there is no pollution, oil change is only necessary every 50,000km. Compressed air from the tanks runs directly to the engine under speeds of 55kph. At higher speeds the engine burns a small amount of fuel to create more compressed air, sort of like how a plug-in hybrid produces on-the-fly electricity. The hybrid air-car setup should be able to use any number of fuels petrol, diesel, propane, ethanol.

The car's compressed-air tank can be refilled in about three minutes at a service station. To fill it up at home the car would need to be plugged in, and an onboard compressor would refill the tank in about four hours. And even when the engine is working, the car emits about half the C02 per kilometre as a Toyota Priusl MDI propose a whole range of body styles, and depending on powerpack options, max speeds vary from 110 to 140kph. OneCATS is a 3.4-metre three to-six-seater that is proposed for 'developing' markets, with typical semi-offroad open-top 'rural' thinking. MDI hint that this could be what Tata would make in India. We understand that this won't be so.

In fact, the Nano will, in all likelihood, be developed to take on a compressed air powertrain, and that could very well be the first 'aircar' in production. But we don't see that happening by the end of this year. Tata have their hands full getting the petrol engined Nano into series production. The diesel engine that Tata is developing is certainly next in line. Tata is also working on a pure electric version, plus hybdrids. The compressed-air version could be just another option.