Sometimes humanity really pulls together and solves problems.  One example is the 1987 Montreal Protocol, an agreement among countries to ban ozone-hole creating refrigerants. The hole in the ozone layer of Earth’s atmosphere is now shrinking. Nations succeeding together! 

Another “success story in the making” has been emerging over the last decade.  Again, it comes from the refrigeration world.  The industry is showing great promise with retail store and warehouse refrigeration systems that work with natural refrigerants.  At the February 2020 AHR Expo, North America’s biggest heating, cooling and refrigeration industry event, the top innovation award went to a new carbon dioxide-based system from Danfross.


The world’s biggest retailers and food and beverage manufacturers have been testing natural refrigerants since the early 2000s, and since approximately 2010 they have moved beyond pilot projects, undertaking mass rollouts of successful natural refrigerant systems.

Three trends have taken hold in retail settings:

• R290 propane based standalone refrigeration cases

• Carbon dioxide (C02) – based transcritical systems for supermarket rack refrigeration

• Energy recovery, also for rack refrigeration.


During the UN climate Summit in New York in September 2019, Thomas Lingard, Global Sustainability Leader from Unilever updated delegates on his company’s longstanding alliance with Pepsi and Coke and their widespread global use of plug and play cabinets that use natural R290 propane refrigerant. Target and Walmart have also begun using them.

In 2016 Guillaume Grolier, a commercial director for AHT Cooling Systems in France said, “We’re recording better energy efficiency results than with HFCs.” His comment was based on the installation of about 10,000 R290 cabinets each year in Europe, with a total, at that time, of about 70,000 in France alone.


Writing on in 2019 Pega Hrnjak president of Creative Thermal Solutions, and research professor at the University of Illinois said; “Hydrocarbons, notably R290, have also become…adopted by chains like McDonald’s and Starbucks, as well as brands like PepsiCo, Red Bull (using isobutane) and Coca-Cola.”


Target has deployed such cases in more than 1,000 of its 1,800 U.S. stores, while Whole Foods has them in 500 stores, according to the Energy Information Administration of the US Department of Energy. They are self-contained display cases at the checkout or in spot merchandising locations, with a maximum charge of 150 grams.

“More recently, some U.S. supermarkets have begun installing R290 cases in partial or whole-store configurations, creating an alternative to centralized rack systems. One example is Hannaford, a Maine-based grocer, which is testing R290 in complete frozen-food lineups in some new stores, with heat removed by a glycol loop.”

H.E. Butt Grocery, is a Texas chain that became an early US adopter of R290 cases in 2013. Hannaford and H.E. Butt are using R290 cases from Hussmann, which recently unveiled a new line of R290 self-contained, glycol-cooled cases called MicroDS. Hannaford also began using transcritical CO2 rack refrigeration from Quebec’s Carnot, in July 2013.


Vincent Grass, Global Refrigeration Leader for Nestlé, told the attendees at the 2019 ATMOsphere Europe Conference in Poland that becoming “fully transferred to natural refrigerants” ties into the company’s plans to become net-zero. At the end of 2018, the firm’s emissions were down by 22%.

Nestlé is known for its food and beverage products, but it also operates 21 supermarkets in Switzerland. Since 2016, the company has only used hydrocarbons in its ice cream freezers, (Propane R-290, Isobutane R-600a, and Propylene R-1270),and it started employing transcritical CO2 for refrigeration in its supermarkets six to seven years ago, according to Grass.


Walmart opened its first store in the USA using C02 refrigeration in 2009 and has been adding stores since. In 2013 the Environmental Investigation Agency said Walmart was using a secondary loop refrigeration system that combines either carbon dioxide or glycol and HFCs in about 125 stores. In 2016 Walmart built a store in Guelph, Ontario and installed a C02 refrigeration system, heat reclaim and geothermal heating and cooling. It saves about $130,000 on energy each year compared to comparable Walmart stores.

Around the same time, Walmart built a 450,000 square foot refrigerated distribution center near Calgary with a modern ammonia refrigeration system and a handful of other clean energy technologies. It saves about a million dollars on energy each year.


The ALDI U.S. supermarket chain operates more than 320 stores using transcritical CO2 refrigeration.  ALDI’s main transcritical system supplier has been Conyers, Ga.-based Hillphoenix, which has been a leading provider of CO2 technology to U.S. food retailers.


Whole Foods, Albertsons and Raley’s are also operating successful ammonia/ C02 systems. Whole Foods has at least 20 installations.

In 2015 Piggly Wiggly opened a 36,000-square-foot store in Columbus, Georgia using an ammonia/C02 refrigeration system. It employed an ultra-low 53 pounds ammonia charge and a CO2 charge of 1,400 lbs. It also saves about 25% on energy. As long ago as 2009 Tesco in the UK and Metro in Germany each had five grocery stores using C02 refrigeration.


Some of the earliest Transcritical CO2 refrigeration systems in North America were installed in approximately 2008, in the Sobeys supermarket chain. Sobeys now has an estimated 140 stores equipped with the technology, many supplied by Carnot or Lesage-LMP Inc. Other Canadian chains, like Loblaw and Longo’s, have followed suit.

One of the key features of these systems is that they recapture heat from the refrigeration system and use it for space heating in the store. In many regions including some cold places in Canada, the result is an abundance of heat available, and no other heating system is needed.


As mentioned, Walmart’s modern ammonia system at its 450,000 square foot refrigerated distribution center near Calgary saves about one million dollars on energy each year, compared to similar facilities using conventional refrigeration.

For warehouses and production facilities, Nestlé also utilizes ammonia and ammonia/ CO2 for refrigeration. For large and medium-sized systems, and for processing, the go-to solution is ammonia/CO2; the latest example of this is being built for a large factory in Mexico.

Most of the Nestlé factories have now transitioned from HFCs to natural refrigerants. “Not many” are left to convert, according to Vincent Grass, Global Refrigeration Leader.

OEMs like Evapco, Azane and NXTCOLD (marketed by Hillphoenix), among others, have unveiled low-charge packaged systems and contractors like CIMCO and Stellar have begun installing them. Low-charge central systems have also emerged in the last few years.


Here are some excerpts from a piece in by Chuck Taylor and Todd Allsup on the reasons this technology is emerging as a top solution:

The CO2, used on the low stage, is distributed to the evaporators throughout the facility. Ammonia, used on the high stage, is completely contained in the machine room. This configuration facilitates the use of two of the most energy-efficient refrigerants on the market while minimizing the risk of distributing large charges of ammonia throughout the facility. For industrial applications, this is an excellent solution.


The real advantage of using CO2 is mitigating risk. For example, a typical 200,000-square-foot refrigerated warehouse using a conventional central station ammonia system will have a refrigerant charge in the neighborhood of 40,000 lbs of ammonia. The same facility using CO2 on the low stage and ammonia on the high stage will have a refrigerant charge of less than 7,000 lbs. This level of charge is below the threshold limit that triggers requirements with OSHA for compliance to Process Safety Management (PSM) and with the Department of Homeland Security for compliance with the Chemical Facility Anti-Terrorism Standards (CFATS) program.

From a pure theoretical standpoint, CO2 is slightly less efficient than ammonia, but this difference decreases as the evaporator temperature drops. But because CO2 is a very dense gas, the size of the equipment needed to provide the same refrigeration effect is significantly smaller.

A compressor running with a -40 °F saturated suction temperature (SST) on CO2 is almost 10 times smaller than the same compressor for ammonia. This facilitates the use of reciprocating compressors, which have a better part load efficiency than standard screw compressors—and they’re cheaper.

Since most refrigeration systems operate in some form of part loading over the year, the CO2 system’s efficiencies are very competitive with ammonia systems and in some cases even more efficient, especially at lower temperatures.

From an initial cost standpoint, CO2/NH3 cascade systems have historically cost 10 to 15 percent more than conventional two-stage ammonia systems. However, as manufacturers have started bringing a complete line of standard products for CO2 to market and as more engineers and contractors become comfortable with providing these systems, the cost is becoming very competitive with a typical ammonia system. And for applications where the evaporator temperatures are below -40 °F, the systems are becoming less expensive.

A comprehensive peer-reviewed report was published by and Shecco in 2019, aimed at identifying the underlying trends for low-charge ammonia technology in different parts of the world.


According to R290 propane systems offer 30% operating savings compared with now obsolete HFC systems. For rack refrigeration C02/Ammonia systems have a higher up front cost than HFC systems, but they also have lower operating costs resulting in a 3-5 year payback on the investment.

Jim Knudson of the North American Sustainable Refrigeration Council prepared the following notes in 2016, which is already dated information in the context of the quickly changing natural refrigerants landscape. The trend since then has been continuously more efficient natural refrigeration systems at competitive costs, including up front cost.


Some physical properties of CO2, such as high working pressures and relative performance through the heat rejection and expansion process, pose inherent challenges to its efficiency as a refrigerant, but these disadvantages can be mitigated through system design.

Other properties of CO2 contribute to its efficiency in food retail applications, including excellent volumetric efficiency (more than six times the cooling effect per volume as R22); low compression ratio (the ratio between inlet and outlet pressures at the compressor); and low viscosity (making it easier to pump).

Saving Energy: High-efficiency HFC vs. High-efficiency CO2

Certain technologies typically used on CO2 systems, such as electronic expansion valves with case controllers, variable speed drives, and heat reclamation, can also be applied with great effect…Several new CO2-specific technologies squeeze even more efficiency into a CO2 system’s design.

As the table below illustrates, transcritical CO2 technology is being developed to be deployed in nearly any climate and can provide substantial environmental and financial benefits. So why invest more upfront for CO2? Simply put, not only are the environmental benefits significantly greater with CO2; over time, the energy savings achieved with CO2 make it the better choice.


Colin James, Service Manager and technician for Mayekawa, a Japanese compressor manufacturer says more innovative designs are emerging as technicians become familiar with natural refrigerants. He describes an installation in a northeast seafood plant that uses a large volume of hot water in its operations. There is no gas service in the region, so the plant was using very expensive oil-fired water heaters.

“It already had a regular ammonia system for making solid ice blocks. We took the gas from that system before it is rejected outside and increased it to 450 pounds pressure, using a heat exchanger and ammonia and two 125 horsepower electric compressors. Now they have plenty of far less expensive hot water at 158oF without fossil fuels.”

James has been working on the large systems for 24 years and says his company and others are creating big systems, including one at a brewery, with much lower ammonia charges and with heat exchangers and secondary loops of C02, brine or food grade glycol.

“The ammonia doesn’t have to come in contact with the building or the product, but the added heat exchanger does increase the system cost.” This also means the ammonia charge is small, which seems to be the current trend. I haven’t been seeing brand new systems with massive ammonia charges.”

The bottom line on natural refrigerants is that they have come of age, and there is no longer any reason to use HFCs and blends, most of which will soon be banned all over the world and cost more. Some natural refrigerant systems still have higher up front costs, but this is changing quickly. In addition they all offer significantly lower operating costs with payback periods now compressed to a few short years. Efficiencies and safety concerns have been addressed and natural refrigerant systems are now in widespread use.

TripleWin Advisory develops sustainable business cases and supports strategic decision-making through value-chain mapping and Scope 3 inventories of companies’ greenhouse gas emissions. In so doing, it unlocks opportunities for greater profitability, relevancy, and longevity for businesses. Learn more.        

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