Say "steam power" and you conjure up images of Stevenson's rocket, Isambard Kingdom Brunel and the heyday of the Victorian railways – romantic, but hardly the stuff of a clean, cutting-edge technology.
But steam could be about to make a comeback, thanks to a company that is trying to make the internal combustion engine more efficient.

Clean Power Technologies, in Newhaven on the English south coast, is developing steam hybrid engines that claw back some of the immense amount of energy wasted by the internal combustion engine. Ultimately they aim to develop a car engine that runs partly on steam power.

"When you talk of steam people think you are going backwards," said Abdul Mitha, the company's CEO and president, "Anywhere where you are wasting a lot of heat, we can go in, capture the heat and turn it into energy savings... Steam has tremendous power. If it can drive a steam locomotive, why can't it drive an automotive engine?"

Mitha's company aims to target the wasted heat that is currently pumped out of the exhaust and convert it into useful power. Of the energy in your petrol tank, just 27% is converted into forward motion, 33% is spent cooling the engine, 4% is lost as friction and a whopping 36% is lost as exhaust heat. "There is a lot of heat that is created and totally wasted," said Mitha. Clean Power Technologies aims to recover 40% of this exhaust heat.

Dr Ralph Clague, a mechanical engineer at Imperial College London, thinks the strategy is a good one: "Recycling exhaust heat and energy that is rejected from the engine has got to be the way forward in the future." He said there has been little incentive to improve the efficiency of the internal combustion engine in the past. "A tank of petrol or a tank of diesel is such an incredibly good energy store that we have been able to afford to throw some of it away up until now."

Clean Power Technologies has developed an experimental set up in which engine exhaust at 750C – typical for a lorry – is run through a steam accumulator. This closed vessel allows water to be heated to 360C or hotter, creating high pressure steam that can then be used to provide useful power.

Ultimately, the aim is to pipe the steam back into the main engine and use it to drive some of the pistons, but the first step for the company is using it to run the refrigeration units on trucks that transport frozen goods. They are currently building a demonstration truck that will be finished by the end of October. They have links with Safeway supermarkets in the US and a haulage firm East-West Express Transportation in Calgary who are interested in fitting the technology to their vehicles. Currently each Safeway truck uses $10,000 to $15,000 (£5,400 to £8,000) worth of diesel per year to power the separate refrigeration unit.

Once the truck refrigeration units are up and running the company will concentrate on marine applications, such as providing power for air conditioning and electrics for boats. By the end of 2011 they aim to have created a steam hybrid car. "Any technology that can be gradually introduced like that is a very sensible idea. So I think they are doing exactly the right thing," said Clague.

He said that although similar ideas have floated around the engineering community for years, Clean Power Technologies appears to be furthest ahead in making them a commercial reality. "It's a perfectly feasible idea, certainly. It adds complexity to the engine and therefore cost and I think that's why we haven't seen it before," he said, "Obviously now with rising oil prices, etc., it becomes essential to extract more energy from the fuel you are putting in."

The Guardian