If you're looking for the car of the future, look no further than Peter Dearman's rusty, 25-year-old Vauxhall Nova.
A beer keg sits in the messy trunk. Pipes run through the middle of the car, which is littered with wrenches and loose bolts. Under the hood, a red, plastic garbage can holds anti-freeze that spills over the sides and a piece of wood holds, well, everything else together.
But look beyond the homemade at what's not there: no gas, no batteries. The Dearman engine -- which sounds like a high pitched golf cart -- is powered only by liquid air. This may be the greenest car on the planet.
"We're starting to run out of fossil fuels now. We've got to do something," said Dearman, a full-time inventor. "Hopefully this offers a solution."
Dearman's car works like a steam engine, except instead of steam, he uses very cold air. Air turns into a liquid at minus 300 degrees. In Dearman's car, the liquid air is held in the beer keg before it flows into the engine. As it warms up and begins to boil, it expands back into a gas, pumping the pistons.
All of that has been done before. But what Dearman has added is incredible efficiency and a vision for a totally sustainable car that can be both manufactured and driven with almost zero effect on the environment.
"It won't produce any emissions because it's only air we're using," the 61-year-old explained on his makeshift test track, a farm outside of London. "We're not burning anything. We're just using heat from the atmosphere and liquid air."
Starting with a traditional steam engine, Dearman introduced heat exchange fluid -- in this case, anti-freeze -- and has essentially turned a traditional engine on its head. Instead of creating energy inside the engine, his engine absorbs energy from the atmosphere to power the car.
"It's been done before in the past -- many times, actually," he said. "The secret to [my engine] is that once you warm the liquid air, you have to be able to keep it warm as it expands. If you let it cool, it shrinks and you lose all the efficiency."
So in his engine, he said, "the liquid air boils and creates a pressure that forces the piston down. As the piston goes down, the gas expands and cools -- but it's able to absorb more heat from the heat exchange fluid, making it much more efficient."
By choosing liquid air, Dearman believes he has created one of the most sustainable cars on the planet. His engine is very light, allowing manufacturers to build a car that could be made cheaply, and, perhaps, out of plastic -- no metal required. And by not using any batteries, manufacturers can avoid using any scarce materials.
Dearman also chose liquid air because it's convenient. Whereas battery powered cars can take hours to recharge, a car powered by air can be refilled in the same time as a gas-powered car.
"Everything that's used in here can be recycled very easily," he said. "Very little energy goes into actually producing the car. So the car is very cheap."
Dearman recently invited an ABC News crew to watch him test the car at a barn near his home, northeast of London. On a cold, grey morning, the car belched what appeared to be steam (it was actually the liquid air expanding back into a gas). It did a few circles at about 20 to 30 miles an hour. Its range is no more than 3 miles.
To turn the car off, he disconnects two wires.