Seed funding promises a cool alternative engine23 December 2011

A zero emission powertrain looks more likely, following successful first round seed funding (which closed more than 30% oversubscribed) for engine technology developer Dearman Engine Company (DEC).

DEC has now started development work on its novel piston engine technology – which uses liquid air as the working fluid – working with UK engineering consultancy Ricardo UK and several UK academics.

Company founder Toby Peters explains that with this patented engine design, the exhaust is cold air, which can be harnessed for cooling. He also says that the powertrain has similar energy density to batteries, but potentially significant advantages, specifically including weight, operational life, capital cost and refuelling times.

The engine has been the subject of a four year PhD at Queen Mary University of London and has been subject to independent analysis at the University of Leeds.

Peters says that a proof-of-concept model has also been lab tested and proven to be far more efficient than previous designs for cryogenic engines – and that it powered a car at more than 30mph with only cold air in the exhaust.

"The work to date has delivered and validated a proof of concept engine, which produces positive power, and confirmed that there are a number of suitable applications," states Peters.

"The next stage is engineering to optimise the sub-systems and produce a commercial demonstrator. Our work to date has confirmed there are currently no show-stoppers."

Cryogenic-powered vehicles are not a new idea, but, as Peters explains, the engine invented by Peter Dearman is novel, operating in a different way to its predecessors and producing considerably more power.

"You inject a heat-exchange fluid, such as anti-freeze and water, into the head of the piston just before you inject liquid nitrogen. The result is that all the expansion takes place inside the cylinder. And because you've got this volume of heat exchange fluid, it is isothermal expansion – so it keeps the temperature the same, which is far more efficient."

Peters believes the engine is likely to be suitable for a broad range of applications, from fork-lift trucks to inland waterway boats and, longer term, also on-road commercial vehicles, particularly refrigerated delivery trucks that could harnessing the cold air for cooling.

He also notes that using liquid air or liquid nitrogen as a fuel has the advantage of relying on the existing industrial gases distribution infrastructure. Additionally, the fuel could be generated remotely, using renewable energy sources and a small liquefaction plant, possibly even as a solution for power and cooling.

For Peters, the key remaining engineering challenge is around optimising the injection of liquid nitrogen into the cylinder. However, he insists that all the technologies, including on-vehicle fuel storage, are mature.

The company is now working with Ricardo and a team of researchers from Loughborough, Brighton, Leeds and Queen Mary Universities, as well as the STFC Rutherford Appleton Laboratory.

The programme is expected to take 20 months including testing.

Brian Tinham

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