By Jim Reed
Newsbeat motoring reporter
Classic British carmaker Morgan has made a hydrogen-powered car
Just a couple of years ago, "green" cars were something eccentric inventors played with in their spare time.
Then came global warming and oil at more than $100 a barrel.
Road tax, parking fees and the congestion charge have all combined to make owning a gas guzzler a bit like paying a second mortgage.
Suddenly low emission vehicles like the Prius are all the rage and politicians are starting to talk about a nationwide network of hydrogen refuelling stations.
So it's no surprise that car makers, from the American and Japanese giants, right down to niche British sporting brands, are falling over themselves to push their green credentials.
The Sexy Green Car Show, which opens on 23 May at the Eden Project in Cornwall, gives them a platform to do just that.
Now in its second year, the show attracts all the big name brands from Ford and Volkswagen through to Honda and Fiat.
But don't expect too many weird and wonderful ideas from the mainstream players.
There are the usual smattering of electric/petrol hybrids, mainly coming from the Japanese car makers.
Transport is the third largest source of CO2 emissions in the UK
The Europeans and Americans are more concerned with getting the most out of their traditional combustion engines.
Ford is launching its new Focus ECOnetic with better aerodynamic performance, a new gearbox and a 1.6 litre engine.
It claims to reduce CO2 emissions from 184 g/km for the standard five-door Focus down to 115 g/km.
Fuel economy rises from 58 to 66 mpg.
Carbon fibre body
But, for the more ambitious ideas, you have to turn to the smaller British manufacturers.
Axon Automotive is showing off what it says is the UK's first 100 mpg family car.
The unnamed two-door, due to enter production in 2010, is made from lightweight carbon fibre.
Eleven different car manufacturers are exhibiting eco-friendly vehicles
Axon's boss, Steve Cousins, said: "Rather than focus on hybrids, we've made the car light and safe with good aerodynamics.
"Then a small 500 cc twin-cylinder engine gives you reasonable acceleration and top speed."
Axon claims it has engineered the car to meet UK and European crash safety standards.
But space is squeezed in the back with room for either two child seats or luggage but not both.
Classic British carmaker Morgan, meanwhile, is really throwing the rulebook out with its LIFECar.
It has worked with technology start-up RiverSimple on a concept you can imagine Al Capone driving in a Batman movie.
Turning off air conditioning can improve fuel consumption by 5-10%
Powered by a hydrogen-fuel cell, its makers claim energy consumption equivalent to 150 mpg.
It can reach 0-60 mph in seven seconds, has a top speed of 85 mph and an average range before refuelling of 250 miles.
The catch? It's just a prototype and the LIFECar hasn't a chance of entering full production.
The technology behind it is now being put to use in RiverSimple's next project, a more realistic city vehicle.