“As a natural refrigerant, CO₂ is incredibly versatile, making it a highly attractive refrigerant for various applications, including refrigeration, air conditioning, and heating,” said Evan Aschow, lead engineer, Effecterra. “When properly designed and commissioned, CO₂ systems can exhibit high energy efficiency, contributing to cost savings and environmental sustainability. Considering all options, CO₂ is a well-rounded solution for diverse industrial, commercial, and residential refrigeration needs.”

CO₂’s Sustainability Assets

R-744 is a natural refrigerant with an ozone depletion potential (ODP) of zero and a global warming potential (GWP) of 1. These are key figures when considering the governmental regulations currently dictating the refrigerant landscape, which include the Kigali Amendment to the Montreal Protocol, a government-led phasedown of high-GWP hydrofluorocarbon (HFC) refrigerants, system efficiency qualifications, and more.

“CO₂ is incredibly environmentally friendly,” said Trevor Matthews, founder of Refrigerationmentor.com. “If you lose 1 pound of CO₂ refrigerant into the atmosphere, that’s 1 pound of GWP. However, if you’re working with 2,000 pounds of R-404A, and you lose it all, that’s almost 8 million pounds of GWP. With CO₂, 2,000 pounds of CO₂ is only 2,000 GWP. Thus, from an environmental standpoint, CO₂ is much less harmful than many common refrigerants.”

Additionally, the heat transfer characteristics of CO₂ are generally more attractive than synthetic refrigerants, which helps increase a system’s operational efficiency.

“CO₂ is excellent at moving heat – it’s one of the best,” said Matthews. “Whether it’s cooling products down or heating processes up, CO₂ has an excellent net refrigeration effect.”

Total Equivalent Warming Impact

The Total Equivalent Warming Impact (TEWI) is a metric used to assess the overall environmental impact of a refrigeration system, taking into account both direct and indirect contributions to global warming. It combines two main factors:

• Direct Impact (Direct TEWI): This component measures the direct emissions of refrigerants during their use in a refrigeration system. It includes the GWP of the refrigerant itself and any leakage or release of the refrigerant during operation.
• Indirect Impact (Indirect TEWI): This component considers the energy consumption of the refrigeration system over its entire life cycle, including the production, transportation, and disposal of the equipment as well as the energy consumed during operation. Indirect TEWI considers the emissions associated with electricity generation as well as any losses or inefficiencies in the refrigeration system.

By combining the direct and indirect components, TEWI provides a comprehensive measure of the environmental impact of a refrigeration system, considering both the direct emissions of refrigerants and the energy consumption associated with their use.

While a CO₂ refrigeration system’s TEWI can vary depending on various factors, such as the specific application, system design, operating conditions, and energy source used, most CO₂ refrigeration systems will have a much lower TEWI when compared to HFC or hydrochlorofluorocarbons (HCFCs).

In 2018, the Journal of Cleaner Production published a study exploring the TEWI of multiple refrigerant systems in warm cities. The research examined the performance of various refrigerant systems, including an R-744 multi-ejector refrigerant system with heating and air conditioning capabilities, an R-404A direct expansion system combined with an R-410A chiller for air conditioning purposes, and others.

The results showed that for locations with average yearly temperatures between 14.1°C (57.4°F) and 18.9°C (66°F), the R-744 multi-ejector solution achieved energy savings from 19.3% to 26.9% as well as a 53.2% to 90.9% reduction in TEWI.

While the study’s results differed based on the size and scope of the air conditioning system as well as the geographical location and climate, the R-744 solution integrated with air conditioning functionalities provided energy savings from 15.6% to 26.2% when compared to conventional HFC-based solutions.

“The nontoxic and nonflammable nature of CO₂ adds to its appeal, enhancing safety aspects in

comparison to some other refrigerants,” said Aschow. “CO₂ is well-suited to replace traditional synthetic refrigerants in small to large-sized refrigeration facilities across various sectors.”

In The Pole Position

CO₂ refrigeration systems are poised and ready to meet the present and future demands of the diverse HVACR applications across numerous applications, including supermarkets, distribution centers, cold storage facilities, food processing plants, ice rinks, data centers, and many more.

“Looking ahead, we anticipate an increased prevalence of CO₂ in HVAC applications as we integrate dew point coolers and other technology into heat pumps,” said Aschow. “This strategic deployment is aimed at delivering exceptional energy efficiency throughout both cooling and heating seasons. The evolving landscape of CO₂ technology positions it as a forward-thinking solution, particularly in enhancing the sustainability and efficiency of HVAC systems.”

As far as refrigerants are concerned, CO₂ is certainly in the pole position when it comes to sustainable, future-ready solutions.

“CO₂ is among the best options, if not the best, currently available,” said Aschow. “It’s emerged as a futureproof solution, aligning with regulatory trends and long-term environmental goals.”

The manifestation of CO₂ refrigerant is upon us, and its presence is only growing larger by the day.

“It’s only a matter of time before most, if not all, supermarkets are using CO₂,” said Matthews. “And cooling is only one aspect of CO₂’s reach. Right now, there are 5 million CO₂ water heaters operating in Japan. Those systems are quickly becoming more prevalent in North America. The refrigerant’s versatility makes it an incredibly valuable solution across multiple HVAC applications.”

Matthews summed it up very succinctly: “The CO₂ refrigeration conversation is growing. Now’s the time to start investing in yourself.”