Bryan Kilgore, May 20, 2015. Image credit: Matt Reinbold
A zero-emissions refrigeration system for refrigerated trucks has been developed by Dearman, a UK company, and has begun vehicle testing. This novel technology replaces typical diesel-driven refrigeration units with a liquid nitrogen piston engine, the proprietary Dearman engine, and supplements the vapor-compression cooling with liquid nitrogen cooling. Dearman has indicated promising results of the initial testing, thanks to the Dearman system’s ability to cool the refrigerated trailer in less time than a diesel refrigeration unit.
Dearman’s refrigerated truck system includes a cryogenic storage tank with liquid nitrogen stored at pressures of approximately 3 bar (44 psi), a vapor-compression refrigeration system, the Dearman engine, and a pre-cooling heat exchanger. The liquid nitrogen is pumped from the tank up to 40 bar (580 psig) and it provides pre-cooling to the trailer through a heat exchanger. It is claimed that up to two-thirds of the cooling for the entire system is from this pre-cooling. The nitrogen is then supplied to the Dearman Engine and mixed with a specialized heat transfer fluid. The heat transfer fluid allows the liquid nitrogen to expand at near isothermal conditions, providing shaft power to the Dearman engine, which drives the refrigeration compressor. The rest of the cooling load is provided by the refrigeration system. The only emission from this system is nitrogen.
Zero emission transport refrigeration system trialled
Air Quality News, April 1, 2015
According to Dearman, conventional diesel refrigeration units emit up to six times as much nitrogen oxide and 29 times as many particulates as a Euro 6 diesel engine.
Transport refrigeration units account for up to 20% of the vehicle’s total diesel usage, and with global demand expected to grow for such units to 9.6 million, the firm claims its technology can help to reduce air pollution as well as carbon emissions while cutting operational vehicle costs.
Dearman said initial testing has been “promising” as the system is “already able to cool the chilled trailer more quickly than a conventional diesel refrigeration unit”.