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Dearman and Hubbard Products form technology partnership for zero-emission transport refrigeration

Dearman, the developer of the liquid air Dearman Engine—an innovative heat engine that uses liquid air (or liquid nitrogen) as a “fuel” and emits cold air as exhaust(earlier post)—has formed a technology partnership with Hubbard Products, Europe’s leading designer, manufacturer and supplier of commercial cooling equipment.

Both companies work together to further develop and bring to market a highly efficient and cost-effective zero-emission transport refrigeration system based around the Dearman engine. In September, Dearman presented an analysis showing that the 1 million transport refrigeration units currently on European streets have the equivalent impact on air pollution as up to 56 million diesel cars.

Dearman and Hubbard have worked together for a number of years and are both members of an Innovate UK funded consortium to develop zero-emission auxiliary power units for buses and heavy-duty goods vehicles (HGVs). (Earlier post.)

This agreement cements their relationship and confirms that both companies will work together, not only to continue to develop technology, but also to bring it to market in multiple countries.

Revolution is crucial for the future of Transport Refrigeration, for a long while the refrigeration industry has relied on improving old technologies. We believe that approach is a compromise too far and is now irrelevant to the needs of the future. The fresh thinking that Dearman has brought to the table has been revelatory. New ideas create huge opportunities, and the Dearman Hubbard partnership is a chance to create a cost-effective, cleaner and more sustainable environment.

—Pat Maughan, Managing Director of Hubbard Products

The Dearman-powered Hubbard transport refrigeration system will build upon on-vehicle trials already conducted by Dearman and extensive lab testing. Commercial trials of the system will begin in the UK later this year, with extended international trials to begin in 2016.

The system is highly efficient, offering both operational performance benefits, including a rapid pull down, and providing significant savings for operators.

Crucially, it is also zero emission, eliminating all of the PM and NOx emissions associated with diesel. This is a significant improvement, as existing transport refrigeration units can emit up to 29 times more potentially carcinogenic particulate matter and six times more NOx than far larger, modern diesel truck engines, and up to 165 times as much particulate matter and 93 times as much NOx as the latest diesel cars, according to Dearman research.

Until now, nobody has given transport refrigeration units a thought. We all shop at food stores, eat in restaurants or have chilled and frozen food delivered, but the impact of transport refrigeration units has never been investigated, let alone addressed. They are unregulated, use out-dated, fossil-fueled technology and are disproportionately polluting. What’s worse, their pollution is concentrated on city streets where it does the most damage to our health.

With 400,000 people dying prematurely every year in the EU as a result of air pollution, we simply cannot afford to ignore these hidden polluters any longer. Awareness is growing and the policy landscape is just beginning to change, but action is needed now to prevent further environmental damage.

—Professor Toby Peters, Chair in Power and Cold Economy, University of Birmingham and CEO of Dearman

Dearman research presented in the September report also found that pollution from transport refrigeration units could cost EU countries €22 billion (US$25 billion) over the next decade, as the EU fleet grows by 20% to 1.2 million by 2025. If nothing is done, the environmental and health impact of emissions will impose an annual burden of €2.5 billion (US$2.8 billion) by 2025.

This year alone, the cooling of refrigerated vehicles in the EU will emit 13 million tonnes of CO2e; 40,000 tonnes of NOx; and 5,000 tonnes of particulate matter—equivalent to the emissions from 56 million diesel cars.

The report projections were based on a conservative assumption that the refrigerated vehicle fleet will grow by 1.5% per year. However, other studies have predicted that annual cold chain market growth could be as much as 12% YoY.

Dearman engine. The Dearman engine is a novel piston engine that harnesses the rapid expansion of liquid air (or liquid nitrogen) to produce zero-emission power and cooling for a range of applications, including transportation, buildings and food distribution.

The Dearman Engine operates by the vaporization and expansion of cryogenic fluids. Ambient or low grade waste heat is used as an energy source with the cryogen providing both the working fluid and heat sink. The Dearman Engine process involves the heat being introduced to the cryogenic fluid through direct contact heat exchange with a heat exchange fluid (HEF) inside the engine.


Prior cryogenic expansion engines have worked on an open Rankine cycle—i.e., similar to a traditional steam engine but operating across a different temperature range. In this approach, the cryogenic fluid is pumped to operating pressure and vaporized through a heat exchanger, before expansion in the engine cylinder.

This approach has a number of drawbacks, Dearman says, as the heat exchanger must be large enough to cope with the heat transfer rates and heavy to withstand the high pressure. Additionally, little heat transfer occurs in the expansion stage (near adiabatic expansion) reducing the work output.

The Dearman Engine instead uses the heat exchange fluid to facilitate extremely rapid rates of heat transfer within the engine. This allows injection of the liquid cryogen directly into the engine cylinder whereupon heat transfer occurs via direct contact mixing with the HEF. The heat transfer on injection generates very rapid pressurization in the engine cylinder.

Direct contact heat transfer continues throughout the expansion stroke giving rise to a more efficient near-isothermal expansion. With the pressurization process taking place in the cylinder, the amount of pumping work required to reach a given peak cylinder pressure is reduced.

After each expansion cycle the heat exchange fluid is recovered from the exhaust and reheated to ambient temperature via a heat exchanger similar to a conventional radiator.

Direct contact heat transfer continues throughout the expansion stroke giving rise to a more efficient near-isothermal expansion. With the pressurization process taking place in the cylinder, the amount of pumping work required to reach a given peak cylinder pressure is reduced.

After each expansion cycle the heat exchange fluid is recovered from the exhaust and reheated to ambient temperature via a heat exchanger similar to a conventional radiator.

The Dearman transport refrigeration system works as follows:

  1. Liquid nitrogen is stored at ~3 bar in a cryogenic vessel.

  2. Liquid nitrogen is then pumped to ~40 bar and transferred to a vaporizing heat exchanger where it provides cooling for the chilled compartment. Approximately two thirds of the total cooling supplied comes from this source.

  3. The cryogenic gas is fed into the Dearman Engine, where after being combined with heat exchange fluid it expands, producing shaft power, which is used to:

    • Support ancillary systems such as feed pumps, an alternator and fans for air circulation.
    • Drive the compressor of a vapor compression refrigeration cycle that provides additional cooling, a third of the total cooling supplied comes from this source.

  4. The heat exchange fluid is then reclaimed and used to harvest heat from the condenser of the refrigeration cycle, which has the advantage of approximately doubling its efficiency.

  5. The heat exchange fluid is re-used in the engine. The only emission back to the atmosphere is air or nitrogen.




Who knew conventional refrigeration units had this bad of emissions? Sort of like gas lawn mowers... Sounds like an innovative, no emissions solution. I am guessing fleet use first due to the need to store and dispense liquid air or nitrogen which is probably not available at the average truck stop like diesel fuel.


Terrific gains for the environment but it will have to be mandated and/or fully regulated to forced current polluters to progressively upgrade their heavy vehicles?

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