By Roger Harrabin
Environment analyst, BBC News
An engineer has promised that within a year he will start selling a car in India that runs on compressed air, producing no emissions at all in towns.
The Aircar can be filled with air in just three minutes
The OneCAT will be a five-seater with a glass fibre body, weighing just 350kg and could cost just over £2,500.
The project is being backed by the Indian conglomerate, Tata for an undisclosed sum. It says the technology may also be used for power generation.
The car will be driven by compressed air stored in carbon-fibre tanks.
The tanks, built into the chassis, can be filled with air from a compressor in just three minutes - much quicker than a battery car.
Alternatively, it can be plugged into the mains for four hours and an on-board compressor will do the job.
For long journeys the compressed air driving the pistons can be boosted by a fuel burner which heats the air so it expands and increases the pressure on the pistons. The burner will use all kinds of liquid fuel.
The designers say on long journeys the car will do the equivalent of 120mpg. In town, running on air, it will be cheaper than that.
Analysts say the fact that the project has the backing of an internationally well known company such as Tata makes the idea much more marketable.
The Indian company - which will put the finishing touches to the engine - says it is even considering using the technology for power generation.
Parts of the country are desperately short of electricity supplies. On Tuesday officials announced that Delhi and Moscow had finalised plans for Russia to build four new nuclear power stations in India.
"The first buyers [of the compressed air car] will be people who care about the environment," says French inventor Guy Negre.
"It also has to be economical."
Mr Negre has been promising for more than a decade to be on the verge of a breakthrough.
The compressed air is stored in carbon-fibre tanks
Tata is the only big firm he'll license to sell the car - and they are limited to India. For the rest of the world he hopes to persuade hundreds of investors to set up their own factories, making the car from 80% locally-sourced materials.
"This will be a major saving in total emissions," he says.
"Imagine we will be able to save all those components travelling the world and all those transporters."
He wants each local factory to sell its own cars to cut out the middle man and he aims for 1% of global sales - about 680,000 per year.
Terry Spall from the Institution of Mechanical Engineers says: "I really hope he succeeds. It is a really brave experiment in producing a sustainable car."
But he said he was interested to see how the car would fare with safety tests and how much it would appeal to a public conditioned to expect luxury fittings adding to the weight of the vehicle.
Mr Negre says there's no issue with safety - if the air-car crashes the air tanks won't shatter - they will split with a very loud bang. "The biggest risk is to the ears."