The Dearman Engine at the heart of everything we do

The Dearman engine – a novel piston engine driven by the expansion of liquid nitrogen or liquid air, to produce clean cold and power.

Liquid nitrogen expands 710 times between liquid and gas phases and this expansion is used to drive the pistons of an engine. Dearman engines operate like high-pressure steam engines, but the low boiling temperature of liquid nitrogen means that low-grade or ambient heat can be used as a heat source, eliminating the need for a traditional fuel.

A unique feature of Dearman engines is the use of heat exchange fluid (warm water). When it mixes with the extremely cold nitrogen, this fluid enables a quasi-isothermal (near constant) expansion and significantly increases the engine’s efficiency.

Crucially, the only emission from a Dearman engine is air or nitrogen, with no emissions of NOx, CO2 or particulates.

Dearman engine has a number of benefits compared to other low carbon technologies:

The Dearman Engine
  • Cost competitive &  low embedded carbon – Dearman engines are made from conventional materials, using methods known to the engine manufacturing industry.
  • Fast refuelling – liquid air can be transferred between vessels at high rates, the industrial gas industry has developed filling systems capable of >100 litre/min transfer rates.
  • Significant existing infrastructure – the industrial gas industry is established and global. There is sufficient spare liquid nitrogen production capacity to supply thousands of Dearman engines.
  • Mature fuel production process – liquefaction of air is a 100-year-old process and the only requirements are air and electricity. Production facilities can be operated flexibly, during off-peak times or used to harness wrong-time renewable energy to minimise costs.
No NOx emissions
No particulates
How the Dearman engine works

How it works

The Dearman engine builds upon understood and industry tested piston engine technology, but includes proprietary heat exchange techniques, which significantly increase the efficiency, applicability and cost benefits of the Dearman engine.

The Dearman engine works as follows:

  • Heat exchange fluid is pumped into the Dearman engine filling nearly all of the cylinder’s volume;

  • Cryogenic nitrogen is then introduced to the cylinder, coming into contact with the heat exchange fluid where it begins to expand;

  • Heat from the exchange fluid is absorbed by the expanding gas, causing near-isothermal expansion;

  • The piston is forced down, the exhaust valve opens and a mixture of gas and heat exchange fluid is exhausted from the Dearman engine;

  • The heat exchange fluid is reclaimed, reheated and reused, while the nitrogen or air is released back to the atmosphere.

Dearman Engine Generations

With each generation of Dearman engine there has been improvements in durability, efficiency and power gains and the current Dearman engine has formed the foundations of the Dearman industrialisation programme and the platform to support the development of other applications.


  • Developed under the InnovateUK supported IDP8 Cool-E Project
  • Dearman engine used numerous donor parts for proof of concept for lab and controlled environment testing to prove core Dearman technology principals
  • Dearman Engine was integrated into a transport refrigeration unit mule as part of a project with Loughborough University, Horiba-MIRA and Air Products which formed first validation of Transport Refrigeration Unit (TRU) application

Dearman Engine Generation 1


  • Benefitted from support from the APC Technology Development Accelerator Programme and InnovateUK supported IDP11-AuxPAC project
  • Delivered target of 30% smaller package and 30% efficiency gains
  • First engine fully designed by Dearman
  • Dearman Engine operated in world first Sainsbury’s TRU trial

Dearman Engine Generation 2.3



  • Under development within the APC5 Project CEMZEP
  • Dearman Engine delivers step change durability improvement through bottom end upgrades alongside further power and efficiency gains
  • Packaging integration developed with Hubbard a refrigeration OEM’s input
  • Unit undergoing trials with customers in UK and Europe
  • Dearman Engine will be the basis of the Dearman industrialisation programme and platform to support applications diversification programme

Dearman Engine Generation 2.3


Dearman Engine Applications

Dearman have a number of applications in development. These systems harness the unique properties of liquid nitrogen and the revolutionary Dearman Engine to offer a completely new approach to cooling and power generation.

The Dearman-Hubbard transport refrigeration units (TRUs) are the world’s first to overcome the big four environmental downsides of diesel TRUs – noise, waste heat, greenhouse gases, exhaust emissions of nitrogen oxides (NOx) and particulate matter (PM) and setting new industry performance standards for temperature control and emissions with a cost-effective clean alternative and powered by the Dearman Engine.

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Dearman partners with Unilever to conduct successful trial of groundbreaking technology

Dearman is developing a genset based on the Dearman engine, which will perform the same functions as a diesel system, including providing emergency backup power, reducing the owner’s energy costs and providing reserve services to the grid. What’s more, the Dearman genset would provide ‘free’ cooling, making it particularly advantageous for applications such as supermarkets and data centres, which require extensive cooling.

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Dearman Built Environment - Data Centre


The Dearman auxiliary power system would be a cost effective enhancement to a vehicle’s systems, utilising the unique properties of an engine powered by liquid nitrogen to provide efficient cooling and also sufficient power for the vehicle’s electrified braking, steering assistance, electric doors, lighting etc

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Auxiliary Power Unit


Hybrid systems can increase fuel efficiency in urban areas by up to 30%. The most common hybrid systems seek to harness braking energy in kinetic or electrical recovery systems, and then use it when the primary engine would be operating inefficiently. Hybrid systems for large vehicles are expensive, hard to retrofit, and without subsidy the economics are insufficiently attractive for them to be deployed.

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Dearman Horiba MIRA Hybrid Bus


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