making modern living possible

Transcritical refrigeration comes one step closer

Jørn Westermann, Senior Vice President and General Manager

reFrigeraTion &air CondiTioning division

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New legislation in Denmark that limits the charge of refrigerants in systems moves transcritical refrigeration one step closer to commercial availability.

The supermarket chain rema 1000 is part of a danish team-up that in 2006 will build and test a full sized transcritical Co2 system for use in small supermarkets. legislation is constantly pushing for natural refrigerants, and developers and end users alike are begin-ning to look harder at transcritical refrigeration as a safe and cost efficient means of keeping food cool.

“everyone can see that this is the future. denmark, norway and sweden are among the first to heavily tax and ban HFC refrigerants. We have heard a lot of talk about transcritical systems, but nobody was actually doing anything,” says Jørgen modvig, who is technical manager at rema 1000 about the decision to take part in the project.

Together with knudsen køling (cabinets and contractor), alu Heat exchanger (heat exchangers), bock (compressors), danish Techno-logical institute (testing and know-how) and danfoss (controls, valves, know-how), the aim is to test a technology that is expected to become widespread in the coming years. The project is partly funded by the eU liFe-environment programme.

“it is extremely important in our business to reduce running costs and there is no doubt that this is the way to go. This project gives us the opportunity to gain an overview of the economy in transcritical systems, and if the project goes well we hope to install a transcritical system in one of our supermarkets sometime next year,” he continues.

Head startThe søborg branch of the superbest supermarket chain was the first supermarket in denmark to take a step towards refrigeration systems using only Co2 as refrigerant. The system installed is a cas-cade system where a subcritical system part handles the low tem-perature cooling demands and a transcritical part handles the medium temperature cooling demands.

The system was installed by knudsen køling who was eager to get a head start before danish legislation from January 1 2007 severely limits the use of HFC refrigerants in systems to a maximum of 10 kg. but one of the main challenges of being at the front line of devel-oping new refrigeration systems is finding the right components to install.

“Components for transcritical systems are few and far between, and those that are commercially available are very expensive. How-ever, new legislation keeps pushing for lasting solutions and we wanted to get started and gain experience when the opportunity arose,” says Torben olsen, technical director at knudsen køling.

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www.danfoss.com

Maturing technologymany of the components used in the system are specially devel-oped prototypes that can withstand the high pressures required by carbon dioxide systems. danfoss participated with technical know-how and a range of valves, electronic controls and mechanical products for the system that in some cases were specially modified prototypes.

“Transcritical systems are particularly attractive in the region of northern europe due to the fact that ambient temperatures most of the summer season stay below 25oC, enabling a subcritical op-eration mode with high energy efficiency. although capacity and energy efficiency drops for the few hours when the ambient tem-perature rises above 25oC, and the system goes into the transcritical operation mode, it does not outweigh the benefits coming from the period with the subcritical operation mode”, says bjarne dindler rasmussen, refrigeration specialist at danfoss.

“a transcritical system will relatively effortlessly be able to live up to the new refrigerant legislation and, with the right type of controls and valves, is a safe and reliable choice that can reduce energy costs and running expenses for owners,” says mr. rasmussen who points out that when the technology is tested and ready, transcritical systems may offer owners a better balance of cost efficient running costs and environmental impact.

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