3.4 Marked Growth of Transcritical CO2 in Industrial Refrigeration

While transcritical CO2 refrigeration was first used in supermarkets, it has gradually become a major option in the industrial space in cold storage, food processing and other applications, competing with ammonia and other refrigerants in all major markets.

In fact, CO2 has emerged as a particularly strong refrigerant for low-temperature applications in cold storage and food processing. It is seen as a way of avoiding the safety protocols associated with ammonia refrigeration while still using a natural refrigerant. On the other hand, it represents a new technology for an industry that has long been accustomed to using ammonia.

Transcritical CO2 systems were originally regarded as most suited to small- and medium-capacity industrial applications, but in the past few years transcritical CO2 installations have been specified for larger installations as well, with cooling capacities of up to 4 MW (1,137 TR) being achieved.75 This was helped along by CO2 specific components, such as semi-hermetic reciprocating compressors in particular, being scaled to industrial sizes by manufacturers.76

Evidence of the growth of transcritical CO2 in the industrial sphere comes from a survey of manufacturers, contractors, consultants/engineers and others working with the technology about their primary market sectors.77 The data revealed that while the majority of these respondents are active in the commercial HVAC&R supermarket sector (41%), a further 30% are active in the industrial HVAC&R sector, including cold storage, food processing, pharmaceutical industry, chemical industry, etc.

Another sign of CO2’s relevance to the industrial sector is the publication in August 2021 of the International Institute of Ammonia Refrigeration’s (IIAR’s) ANSI-approved Safety Standard for Closed-Circuit Carbon Dioxide Refrigeration Systems.78 IIAR has traditionally produced safety standards for industrial ammonia applications, but the trade group has recognized the growing use of transcritical CO2 by industrial end users, and the need for standards to address CO2.

This year, manufacturers on both sides of the Atlantic have been noting the significant progress of CO2 in industrial applications.

For example, Maurice Robinson, Technical Support Team Leader for German OEM TEKO, said at the ATMO World Summit on March 31 that TEKO’s inquiries for industrial CO2 systems above 250kW (71.1TR) went from seven inquiries in 2017 to 185 in 2021.79 For industrial applications above 500kW (142.2TR), the company went from a single inquiry in 2017 to 38 in 2021.

He pointed out that several compressor manufacturers have invested in research and development to produce larger-capacity CO2 compressors, and this has been a major driver of CO2’s increasing use in industrial refrigeration. Instead of 10 or 15 compressors in an industrial CO2 rack, six are possible.

U.S. component manufacturer Colmac Coil has seen a move away from both ammonia and synthetics towards CO2 in evaporators for industrial applications, with CO2's share of the company’s output increasing from 5% in 2019 to 30% in 2022, said Jeremy Olberding, its VP of Sales, at the IIAR conference in March.80

One of the reasons for the move towards CO2 is that it allows the removal of ammonia from the occupied space. Quoting what customers have told him,