The Dearman Engine

At the heart of Dearman’s technology portfolio is 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 technology has a number of benefits compared to other low carbon technologies:

  • 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.
The Dearman Engine
100
No NOx emissions
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No particulates

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 engine.

The engine works as follows:

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

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