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Liquid-nitrogen engine could be an alternative to batteries

A new design for a liquid-nitrogen-powered vehicle engine could provide an emissions-free alternative to batteries and fuel cells.

The engine, which is driven by the pressure created as liquid nitrogen (LN2) returns to its gas form, could provide a way of powering a vehicle without producing carbon-dioxide tailpipe emissionsbut with a longer range and faster refuelling than a battery.

A proof-of-concept model, which its developers said is far more efficient than any previous design for a LN2 engine, has already been used to power a car at more than 30mph with only cold air in the exhaust.

‘Our product is likely to be, on a cost-base, more competitive to a piston engine than a battery, and piston engines are massively cheaper’

Toby Peters, director, DEC

The firm behind the idea, the Dearman Engine Company (DEC), now plans to develop a commercial prototype and is working with engineering consultancy Ricardo and several UK academics to assess its feasibility and develop a business strategy.

Speaking exclusively to The Engineer, DEC director Toby Peters said the company was looking at forklift trucks as a first potential route to market.

‘We’re looking at the application not just the technology,’ he said. ‘Because of regulations and emissions, [forklift trucks] already have a high penetration of battery technology, around 60 per cent.

‘The reason we’ve identified that market as a potential start-point is that you’re not looking for emotive reasons for buying low-carbon power vehicles. If you want to operate a fork-lift truck inside a building it needs to be zero-emission.

‘Our product is likely to be, on a cost-base, more competitive to a piston engine than a battery, and piston engines are massively cheaper.’

Inventor Peter Dearman demonstrates his liquid-nitrogen engine, which has since been developed under a four-year PhD programme and is about to be the subject of an industry-led feasibility study.

LN2-powered vehicles are not a new idea and a car developed by researchers at the University of Washington in 2000, the LN2000, reached speeds of 22mph.

But Peters said the engine invented by company co-founder Peter Dearman operated in a different way that produced much more power.

‘He invented a process whereby you inject a heat-exchange fluid such as anti-freeze and water into the head of the piston just before you inject the liquid nitrogen.

‘You keep the liquid nitrogen liquid right the way up to the piston. The result of that is that all the expansion takes place inside the cylinder.

‘And because you’ve got this volume of heat-exchange fluid, it’s isothermal expansion, so it keeps the temperature the same, which is far more efficient.’

Using LN2 as a fuel has the advantage of relying on an existing distribution infrastructure as many industrial companies use it for cooling. It could be particularly efficient as fuel for refrigerated delivery trucks.

But it could also be generated in remote places using renewable energy sources and a small liquefaction plant, possibly even as a solution for military bases, said Peters.

The firm was spun out of Highview Power Storage, which last week won The Engineer’s Technology and Innovation Awards Grand Prix for its utility-scale liquid-air energy-storage system.

DEC has raised enough feed capital for the feasibility study and now hopes to secure a few million pounds in private equity and grants to develop the technology commercially from 2013.

Peters said the key engineering challenge was optimising the injection of liquid nitrogen into the cylinder but that all the technologies involved, including the LN2 storage tanks, were mature enough not to be showstoppers.

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Readers' comments (18)

  • Operating nitrogen driven vehicles in-house may have limitations as nitrogen emission can easily reduce oxygen percentage in enclosed space below permitted level.

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  • There are multitudinous ways of getting piston engines to turn. The problem with most is the energy density of the fuel source and LN2 turning to N2 has a pretty poor energy content.
    In the war the busses round oxford used to pull a small trailer with a coke burner on it to make the gas that the buses ran on. I can see a tanker trailer being necessary for a significant mileage, even on a fork truck.

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  • Endorsing the first comment, in an enclosed space elevated nitrogen levels are deadlier than elevated carbon dioxide as nitrogen does not cause respiratory distress.

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  • Well, at least it's not as pointless and damaging as electric and fuel cell (preferably called "futile cells") cars are at the moment. Probably not going to lead to a massive impact for the reasons discussed above, but compared with the billions poured into pointless electric and fuel cell "ignorant rich nimby mobiles", definitely worth the effort.

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  • Hi guys,

    For indoor applications it is a fair comment about monitoring Nitrogen levels, but all that is required is awareness and appropriate regulation, a simple alarm could easily be installed.

    Most warehouses that need a fork lift contain a large volume of air and are often ventilated, or partially open to the elements.

    The bigger questions are system useability and cost (even for warehouse or local operations). What are the installation and running costs of the micro production plant referred to in the article? What is its production rate? Could such a plant be run at low power levels via an inverter and 12v battery fed from a renewable energy source?
    What is the energy conversion cycle efficiency?

    It sounds good, but there are key figures missing from the article.

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  • You are absolutely correct about nitrogen being an asphyxiant; however the engine would commercially use liquid air; we simply use liquid nitrogen at this stage as a commercially product available in small quantities for testing - given air is 78% nitrogen, broadly same characteristics. As to energy density, yes, zero emission solutions are poor compared to hydrocarbons; but our energy density is similar to advanced batteries but much cheaper, faster refuelling and long life and much better than for example compressed air (without the need for high pressure tankage).

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  • Anything that reduces harmful emissions and our reliance on imported fuels must be beneficial to our environment and therefore long term health and also our economy. It's early days yet, but oak trees and acorns come to mind. Good luck to them.

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  • Whilst I welcome the development of this engine, anything that moves us forward technologically should always be welcomed when it also advances knowledge, I wonder why the engine is not used to turn an alternator for electrical production, this would seem ideal within the bulk of a Fork Truck. Further, is it that difficult to extract and compress Oxygen from the air and then "burn" this in pistons as all that gets produced will be air!!

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  • In the video, sounded to me as if the lack of power was being compensated for by very high revs and a low gear. No grunt !
    Therfore it is going to be of limited use?
    How cheap is it to produce the fuel, how much energy required? Stack that against the water engine and cracking off the hydrogen?
    Qvestions, alvays ze qvestions!

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  • This is an ingenious product, and I assume makes use of the higher carnot efficiencies enabled by the low temperature, to give good energy storage.

    So Dearman can get descent energy storage levels but it seems power is the problem - it could be limited by how much warm air you can bring in.And power levels would fall on very cold days.

    If this ever takes off though it solves the issues of intermittent power production from renewables. And distribution - you could have solar plants making liquid air in the deserts and shipping it in tankers to northern markets.

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