The use of CO2 as a refrigerant has grown in recent years, thanks to market demand spurred by a combination of environmental regulatory actions and technology advances in microprocessor controls and valve design.

While CO2 systems are still more expensive than conventional refrigerants in the commercial world, proponents of CO2 say the technology is ready to be embraced by retailers and end users alike as a way to alleviate regulatory and corporate pressure to find an environmentally friendly alternative to refrigerants with high global warming potential.

“Because of pressure to meet environmental goals, the market, and our industry is looking at how we can use natural refrigerants like CO2 again in the mainstream,” said Scott Martin, Director of Sustainable Technologies for Hillphoenix.

“There is a real movement in our industry to seriously consider CO2 ,” said Dan O’Brien, Vice President of Sales and Marketing for Zero Zone. “As big global companies have said they’re going to be green – and utilize refrigerants with low global warming potential – credibility for CO2 is building.”

Both Hillphoenix and Zero Zone manufacture CO2 systems for the commercial and industrial markets, where each company said they’re seeing an increased interest in CO2 projects in sectors as varied as grocery, pharmaceutical and cold storage.

U.S. companies, Target, Coca Cola, Nestlé and Red Bull, as well as Canadian food retailers Sobeys and Loblaws, are among several retailers who have made formal corporate commitments to natural refrigerants.

As costs mount for retailers caught in a seemingly never-ending cycle of system upgrades or replacements – to accommodate new phase-outs of refrigerants deemed environmentally unfriendly by the EPA – CO2 is emerging as an attractive solution with the potential of solving operational challenges.

“In my career, R12 and 502 has been replaced by 22, which has been replaced by 404A, which was replaced by 407 and now 407 is about to be replaced by a new series of refrigerants released later this year. That’s five sets of refrigerants, and each one of those changes comes with development work you have to do to make them work in a system,” said Martin. “Supermarkets are building stores every day, so all of a sudden, you have this large install base, and you’re starting to look at . . . when do I convert this store to a next generation refrigerant that takes me out of this cycle?”

“That’s where CO2 comes in. It’s a refrigerant that is never going to be taxed or regulated because it’s environmentally benign,” he said.

Expense is still a major decision factor for this type of customer, but other factors, such as the potential to deal with regulatory pressure and boost corporate environmental image, are also starting to play a big role in the decision making process, said O’Brien.

“Our customers are now at the point where they’re making decisions according to factors that justify natural refrigerants, and even though CO2 may mean investing a little bit more money, the other payoffs are attractive,” he said. “In some cases, company policy and philosophy is outweighing and becoming more important than the initial cost of building these systems.”

“In the commercial market, we’re seeing customers trying CO2 . Among large grocery retailers in the U.S., they want to do one or two stores. They’re not making a large commitment yet, but they want to understand it and be ready.”

That’s a sentiment echoed by Bent Wiencke, Manager, Refrigeration Engineering for Nestlé USA. “There’s a lot of end user interest in CO2 and the end user market is absolutely assessing CO2 as a viable alternative to conventional ammonia systems. But this needs to be evaluated on a caseby-case basis and weighed against other technical solutions providing a high degree of safety and possibly less complexity. An example is, low charge ammonia systems and the use of brines as a secondary refrigerant.”

“CO2 technology still has its challenges finding its marketplace in smaller applications where it’s competing with commercial HVAC and chiller equipment,” he said. “This is predominantly here in the U.S. and Canada where we see a significantly lower price level of commercial equipment when compared to Europe, and currently no legislative pressure exists to phase out HFC refrigerants” at the same level as in Europe.

Wiencke added that, “Purely from a cost standpoint, CO2 systems still have a long journey ahead before they can compete. Without legislative pressure or corporate mandates to switch to natural refrigerants, [that journey] may even get a tad longer.”

As for what it will take to spur widespread adoption, only time will tell, as the sector works towards a critical mass of projects that it hopes will increase the pool of suppliers, and buyers, enough to bring manufacturing costs down. To see what could happen in the U.S. CO2 market may mean looking no further than Europe.

Momentum behind the use of CO2 as a refrigerant started building there as early as 2000, when European countries began imposing taxes on HFCs and HCFCs to deter their use, said Andre Patenaude, the director of CO2 business development for Emerson Climate Technologies, a refrigeration engineering and design consultant.

The taxes drove the commercial supermarket sector to look for and start developing technology that would make CO2 a good option for modern systems and requirements, and it has been growing for several years, he added.

“Three years ago there were about 1,000 transcritical CO2 systems in Europe; about a year ago there were 3,000, and now there are probably 5,000 to 6,000 systems,” he said. “It’s growing there, and I believe it’s safe to say the U.S. will have a similar pattern, depending, of course, on how much legislation drives it. But it’s already in supermarkets without creating major issues, so I think it’s a trend that’s taking off,” he said.

To realize that kind of growth here in the United States, the market will need more component suppliers and an update to the codes and standards that describe CO2 systems and their use.

While the pool of CO2 component suppliers is increasing in the U.S., it still hasn’t gotten big enough, or specialized enough, to start bringing down the cost of manufacturing the systems, a hurdle many see as the last big barrier to growth in this country.

“There are more suppliers than there used to be that are making components that we use for CO2 systems, but a lot of the components we use are unique and special for CO2 ,” said Hillphoenix’s Martin. “In the beginning there were only one or two suppliers, but now that number has tripled or more, and that’s driving down the cost of components, which is driving down the cost of systems.”

“There’s just starting to be enough volume now to make CO2 systems efficient enough to produce,” he said. “This sector is hitting its stride, but it took this long for volume to build to the point that this even looks economically feasible.”

From that perspective, growth may be a volume game, but it’s also a complexity game, said Zero Zone’s O’Brien.

“One of the things we’ve seen in systems we’ve built is that we end up dealing with the reality that a lot of equipment manufacturers haven’t optimized the equipment they’re selling specifically for CO2 systems,” he said. “We don’t have a lot of equipment available yet that is designed to address the unique properties of CO2 . That means we’re not able to take full advantage of the capabilities of CO2 systems [as an industry] as we may in the future. It will take an investment from the equipment manufacturers and others that are building these systems to truly realize the potential of CO2 .”

Such an investment could be seen as one that would benefit the industry in general, as industrial refrigeration looks to the codes and standards that have the potential to spur growth for all natural refrigerants.

“Our regulations here still impose some pretty significant requirements around pressure” in CO2 systems, said Mark Dutton, Segment Manager for Cold Storage, Heatcraft Kysor/ Warren. “We look forward to the opportunity to harmonize U.S. standards with the broader international standards driven from Europe. That will help reduce system cost and improve component availability.”

Heatcraft Kysor/ Warren manufactures CO2 systems and components for the commercial and industrial markets.

IIAR President Dave Rule agreed with Dutton, saying, “The lack of updated CO2 standards has the potential to hinder the growth of CO2 in the U.S. market.” Rule added that IIAR will focus attention on the development of standards for CO2 systems in the coming year.

And that effort will be a big step forward for CO2 system manufacturers, especially in the commercial applications world, said Zero Zone’s O’Brien, adding that new standards will also facilitate the development of better training resources to help solve another growth problem faced by the sector – the shortage of operators who know and are comfortable with CO2 systems.

“What’s exciting at this stage is that for so long CO2 has been discussed as an attractive technology option, and for so long, the standard response for not putting CO2 out there in the systems we use today has been: ‘we don’t have the people who know how to handle CO2 , or we don’t have the components to build the systems.’ That’s not necessarily the case anymore,” he said.

“Those problems are becoming less and less of a reality as more of these systems are being installed. We’re seeing CO2 systems gaining a foothold in new applications and we’re installing them in places we haven’t commonly used them before. The growth of CO2 is just a matter of time and project volume.”