Carbon dioxide as a refrigerant
Carbon dioxide (CO2; R744) is a natural refrigerant that is commonly used in commercial and is rapidly emerging in the industrial refrigeration systems. A brief background information about this technology is provided here.
History
The history of CO2 can be divided into two parts. The first is part is during the 19th and 20th centuries when systems evolved and developed. This era ended when the interest in CO2 virtually disappeared in the 1950s since synthetic refrigerants were introduced and took over.
At the end of the 1980s, Norwegian professor Gustav Lorentzen brought up the idea of using CO2 again, which introduced the second era of the history of CO2. He investigated how CO2 technology could be used in different applications and published many articles. In 1993 he stated that “CO2 is as close to the ideal refrigerant as it is possible to come….” One aspect of CO2 that he discussed was how heat may be reclaimed, as well as the associated control strategies to optimize the process.
CO2 is one of the first refrigerants used.
Picture: An advertisement for CO2 systems originating from the early 20th century
Properties
Carbon dioxide is a natural, non-flammable, and non-toxic substance that offers technical advantages when compared to other natural alternatives. Regarding toxicity, codes such as the European corresponding EN378 do impose certain safety measures in order to use CO2 as refrigerant, nevertheless, safety measures are simple and do not impose a high cost.
The historical challenge with CO2 basically stems from the fact that it has high pressures in the system, reaching 120 bar. Because of the rapid CO2 technology development since the 1990s, today high pressures are no longer a valid argument against the favor to CO2.
Actually, it is the opposite - the unique characteristics of CO2 offer significant advantages over other refrigerants, such as smaller components and effective evaporators. A special advantage is when there are simultaneous cooling and heating demands, where CO2 heat reclaim offers high-temperature grade heating energy. In some applications, 100% of the heating demand can be covered with heat generated by the refrigeration system.
Trend
Throughout the last decade, a growing interest to use CO2 as a refrigerant in many applications has been seen, especially in the commercial sector. The energy efficiency improvements that are achieved with CO2 refrigeration combined with heat recovery is becoming more and more attractive for a wide variety of applications. Since a few years back this trend has entered the industrial sector as well which has considerable implications for the business.
*Source: Shecco (2020)
Naturally energy efficient by EKA
EKA is specialised in refrigeration engineering with a focus on natural refrigerants and especially CO2 technology, also being a member of R744.com to showcase the company’s expertise. EKA’s first CO2 project dates to 2004, where CO2 was used as a secondary fluid. Ten years later EKA designed Europe’s first full CO2 ice arena which became self-sufficient with heat from its own heat recovery system. A more recent EKA project to highlight is the NSSO Speed Skating Oval for Beijing Olympics 2022, which is also a 100% CO2 ice arena.