During a technical visit to one of the world’s first CO2-only booster systems participants could gain first-hand experience with a highly reliable and cost-effective solution for supermarket refrigeration.
On Tuesday, a technical tour led participants to the SuperBest supermarket in Solrød – host of a newly developed CO2 transcritical refrigeration unit. The innovative standard design covers both low and medium temperature as a replacement for R404a and secondary fluids. Since its installation in autumn 2007 the R744 system has not only been operating reliably, but has also led to significant increases in energy efficiency compared to traditional systems. Most importantly, the CO2 system is one of the most cost-efficient alternative to HFC-based cooling systems now subject to high taxes and bans in Scandinavian countries.
The technical visit, part of the Gustav Lorentzen Conference on Natural Working Fluids, was preceded by a short introduction by Danish manufacturer Advansor, supplier of the CO2-only booster system at SuperBest. Torben Hansen from Advansor gave an overview of the system’s fundamental design and main advantages, covering, among others, low noise, easy installation and servicing, as well as a remarkably compact design. Hansen stressed that the “compSUPER” model is the result of more than 10 years of dedicated development, combining the most advanced components optimised for Scandinavian and Northern climate applications. Advansor’s system, soon to be presented on R744.com, is available as a sub- and transcritical option.
The CO2 transcritical booster system
Following Advansor’s introductory speech, participants could convince themselves of the R744 system’s reliable operation on site. At SuperBest Solrød, industry experts and academics had free access to the shop and machinery room hosting the system with a cooling capacity of 130 kW and 35KW at -12°C and -35°C. Designed by Advansor and installed by Super Køl A/S, the unit integrates semi-hermetic compressors by Dorin and components by Danfoss. The chosen welded carbon steel and all elastomers are suitable for CO2, ensuring a safe and reliable operation. Moreover, the SuperBest installation includes suction gas filters, filter driers to remove water from the system, an advanced oil management, and a suction manifold with integrated oil cooler. A high energy efficiency is achieved through an optimized compressor and gas cooler design, the adiabatic humidification of the gas cooler, and the absence of an internal heat exchanger. Metal- and Teflon hoses for connections to the compressor, an oil-refill during operation, as well as changeable oil-filters and filter-driers ensure an easy maintenance. Due to the CO2-only system’s high Coefficient of System Performance (COSP) and low energy consumption, operation costs have decreased significantly.
However, in his introduction, Hansen lamented the still existing lack of knowledge regarding CO2 systems and their components’ performance, and the scarcity of measurement and simulation tools available to suppliers of R744 technology. Especially the need for fitting components would impede a more accelerated spread of CO2 systems, where “home-made” solutions would still have to bridge the gap between demand and supply.