Clean cold and power specialist Dearman is planning to set up a factory to produce up to 20,000 liquid air engines a year, having been emboldened by early trials of its technology fitted to a refrigerated truck.
The trials, being carried out at the Mira test facility, comprise a Dearman heat engine using liquid nitrogen as ‘fuel’, providing a refrigerated truck with zero-emission cooling and power. Early-stage assessment has shown that the system has met all modelling predictions.
“We’re getting commercially viable performance off our first laboratory-designed and built engine,” said Toby Peters, senior group managing director at Dearman. “That’s pretty unheard of. But it hasn’t surprised me because we have a very good team of engineers who have done their homework and designed and built a very good engine. It all goes back to very robust and well-known mechanical and thermal engineering.”
The Dearman transport refrigeration system stores liquid nitrogen at 3bar in a cryogenic vessel. This is pumped to 40bar and transferred to a vaporising heat exchanger where it provides cooling for the chilled compartment. The cryogenic gas is fed into the Dearman engine, where after being combined with heat exchange fluid it expands, producing shaft power.
This is used to support ancillary systems such as feed pumps, an alternator and fans for air circulation, and to drive the compressor of a vapour compression refrigeration cycle that provides additional cooling. 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. The heat exchange fluid is reused in the engine. The only emission back to the atmosphere is air or nitrogen.
“It’s a critical balance,” said Nick Owen, chief technology officer at Dearman. “Can we pump enough heat out of the fridge system to provide the Dearman engine with the heat that it needs? The news, which has now been validated during the Mira tests, is that that balance is achievable.”
Owen said that the trials would likely lead to refinement of the Dearman transport technology. “We’ve got a lot of hours accumulated in the lab but until you actually go out there and hang it on a truck, and leave it outside for the night, you haven’t really validated it. We think we can do more optimisation: the basic engine will be more efficient, the cryogenic handling system can be made simpler, and the refrigeration system can be made neater. That’s why we are doing this testing,” he said.
The Mira trials will run until the autumn. Then Dearman plans to fit its technology to a commercial vehicle in the UK, building up to 15 vehicles by the middle of next year. “By the end of next year we will have between 60 and 100 engines in operation,” said Peters. “Some will be operating in places like Spain and the Netherlands, while others will be outside Europe.”
Peters said that ultimately Dearman wanted to start producing its engines in a manufacturing facility. “We plan to be producing between 10,000 and 20,000 engines by 2018. They will be commercially priced plug-and-play zero-emissions transport refrigeration systems. That plant will absolutely be in the UK, probably in the Midlands.”
Meanwhile, a consortium led by Dearman has been awarded £850,000 by Innovate UK to develop a zero-emissions auxiliary engine for lorries and buses, so that cooling can be provided with a surplus of electrical power to run the vehicle’s auxiliary systems, such as electric doors, lighting and power steering.
Peters said: “Traditional diesel auxiliary engines are under-regulated, inefficient and often highly polluting. Zero-emission liquid air technology can significantly improve the efficiency of both buses and refrigerated vehicles, reducing diesel consumption and thereby cutting harmful emissions of CO2, NOx and particulates.
“At a time when concern is growing about the health effects of air pollution on our city streets, and global demand for air-conditioned buses and refrigerated vehicles is rising rapidly, this technology can play an invaluable role.”
Finally, Dearman has announced that it has recruited Dr Tim Fox, the IMechE’s head of energy and environment, to the role of global ambassador as it looks to access overseas markets. Peters said the recruitment of Fox showed that it was a company with real ambition that was growing fast. “We employ 47 people at the moment, and that will rise to 70 by the year end.”
Cool solution: Dearman’s engine offers zero-emissions truck refrigeration