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The Dearman Engine – power from thin air

22nd Oct 2018

Those of you who have children have no doubt found yourself saying “I can’t make something from thin air!” when asked for the thirteenth time in a car journey whether there is something to eat. But Peter Dearman did make something from thin air, the ability to power an engine while producing no pollution, and he did so in his shed. If that sounds like madness, you’re in good company because that’s more or less what Sir Alan Sugar (as he was then) thought when Peter approached him 17 years ago. Fast-forward to the present day, Dearman Engine Company has 70 or so employees, and Peter Dearman has just been honoured at a dinner by the Royal Society with Lord Sugar congratulating him on his success. A full article on the dinner can be found here.

When Peter Dearman approached Sir Alan he had just invented his engine which is based on the Rankine cycle, the same principle that steam engines are based on. However, instead of steam, the Dearman engine, which uses a reciprocating piston in a cylinder much like an internal combustion engine, uses liquefied air. The process begins with the piston at top dead centre when the liquefied air is injected into the cylinder. The liquefied air mixes with a heat exchange fluid (injected into the cylinder during the return stroke of the piston) which causes a rapid temperature rise causing the air to boil and expand pushing the piston down generating work; this expansion process is near isothermal. At bottom dead centre the mixture of air and heat exchange fluid leaves the cylinder, the air being exhausted to atmosphere, the heat exchange fluid being re-heated and re-used in a closed cycle.

The result is output shaft power, plus a source of “cold” which can be used to cool, for example, goods during transport. There are of course caveats here, air is not a primary energy source, merely a means for energy storage. That energy is stored as “cold”, the air (or nitrogen) being liquefied by chilling it to -196 deg. C. Although off-peak, or renewable, energy can be used to liquefy the air (or nitrogen) this requires about 400 Wh/kg, whereas the theoretical maximum specific energy available from liquid nitrogen is only about 214 Wh/kg. Despite these inefficiencies, the zero-emissions at the point of use and ability to store energy generated off-peak, provides significant advantages.

So that’s the technology, what about the IP?

We’ve just heard that the engine was developed in a shed, did Peter fall into the classic trap for lone-inventors and start-ups to not protect their innovation early enough? As we know, any patent application must be filed before the invention is made public, but lack of budget and a desire to get investors on-board, can mean that many inventors fall foul of this requirement.

Looking at the patent databases, it seems that a patent application was sought early, back in 2000, and that patent application eventually led to granted patents in a number of countries. One of those patents was granted in Europe, and the breadth of the granted claim, re-produced below, goes to show the originality of the invention:


An engine comprising an expansion chamber, inlet means for admitting to the chamber a drive fluid comprising a refrigerated, liquefied gas, and also for admitting to the chamber a heat-exchange liquid, outlet means for withdrawing the heat-exchange liquid, in a cooled state, from the chamber and a heat exchanger for increasing the temperature of the withdrawn heat-exchange liquid prior to re-circulation of the heat-exchange liquid through the chamber, in use the drive fluid expanding to a gaseous state in the chamber and the heat-exchange liquid giving up heat energy to the expanding drive fluid, the expansion of the drive fluid causing the generation of shaft power by the engine, wherein the drive fluid is liquefied nitrogen, liquefied air, liquefied carbon dioxide or a mixture thereof.” [emphasis added]


The only structural requirements are an engine having an inlet and an outlet, and that the drive fluid is liquefied nitrogen, air, or carbon dioxide, all other limitations are functional and so provide broad protection for the general concept.

Since that early, broad patent filing, no doubt used to secure funding for further research & development, a number of other patent families have been filed, with an acceleration in those filings in the past few years.

This filing strategy is often seen for deep technology such as this, where an initial proof of concept, both in terms of the technology and patentability, is essential to gain sufficient investment and buy-in to turn that deep technology into a commercial reality. Once those initial challenges have been overcome, the development programme and the patent strategy accelerate hand-in-hand leading to rapid growth.

I’ve followed Dearman for years now, never quite sure if the invention, borne of no doubt long nights spent in a shed, would ever make it to a commercial reality. So I was pleased to see that the acceleration of the patent filing programme did indeed point to a commercial offering. Just a few years ago a major supermarket chain began to use the TRU (Transport Refrigeration Unit) variant of the Dearman engine, and more have followed suit in the following years. The TRU is seemingly the perfect initial commercial offering, making use of the cooling effect of liquid nitrogen, together with the output shaft power from the Dearman engine to power a conventional chiller unit. Onwards and upwards for a great British success story.

This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.

Paul Loustalan
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Would you like to know more? You can talk to Paul Loustalan who will be able to help. Call +44 (0)20 7242 0901


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