While most car companies are racing to bring electric vehicles to the market, one startup company is skipping the high-tech electronics, making cars whose energy source is compressed air.
Zero Pollution Motors says its car, powered by a combination of compressed air and a small conventional engine, will be on the roads by 2011.
ZPM Chief Executive Shiva Vencat said the ultimate goal is a price tag between $US18,000 and $US20,000, fuel economy equivalent to 100 miles per gallon and a tailpipe that emits nothing but air at low enough speeds.
The French startup Motor Development International, which licensed the technology to ZPM, unveiled a new air-powered car at the Geneva Auto Show in March.
Engineering experts, however, are skeptical of the technology, saying compressing air is notoriously energy intensive. They point out air compressors are one of the least efficient machines to convert electricity to work.
According to Vencat, the “air cars” plug into a wall outlet, allowing an on-board compressor to pressurize the car’s air tank to 4,500lbs/in2.
It takes about four hours to get the tank to full pressure, then the air is then released gradually to power the car’s pistons.
At speeds less than 35mph, the car relies entirely on the air tank and emits only cold air. At faster speeds, a small conventionally fueled engine kicks in to run a heater that warms the air and speeds its release.
The engine also refills the air tank, extending the range and speed.
The technology behind the car was developed by the French race car engineer Guy Negre, head of Motor Development International.
Besides ZPM, Negre has licensed the technology to Indian car giant Tata Motors and others.
Many of the specifications of ZPM’s car are still speculative, but Vencat expects it to go about 20 miles on compressed air alone, and hundreds more after the engine kicks in, with a top speed of 96 mph.
The technology shouldn’t sound too outlandish, Vencat said. It’s similar to the internal-combustion engines in conventional cars — the main difference is the fuel.
“Every single car you see out there, except an electric car, is a compressed-air car,” he said.
“It takes air in the chamber and it pushes the piston, and the only way you push the piston is through pressure.”
Engineers point out that air compressors allow you to recover only 25 to 30 percent of the energy used to compress the air, the rest is lost through heat, air leakage and other forms of waste.
While that’s still slightly better than a petrol engine, it pales compared with the efficiencies of other alternative-fuel powertrains, like those in hybrid-electric cars, which have an efficiency closer to 80 percent.
A look at some of ZPM’s specifications illustrates the issue. With four hours of charging, the air car’s 5.5-kilowatt compressor would eat up 22 kilowatt-hours of electricity.
That means the same energy used to turn on 10 100-watt light bulbs for 22 hours would allow the car to travel 20 miles.
By comparison, General Motors Corp. has said its Chevrolet Volt will use about 8 kilowatt-hours of energy to fully charge, and it will be able to travel 40 miles on battery power alone.