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Tracking CO2 Refrigeration Trends in the U.S.

Andre Patenaude | Director – Solutions Strategy

Emerson’s Commercial and Residential Solution’s Business

Until recently, CO2 refrigeration systems in the U.S. have been perceived as exceptions to the rule in commercial refrigeration. But as corporate sustainability initiatives and refrigerant regulations continue to reshape refrigeration decisions, many supermarket retailers are exploring CO2’s long-term potential. I recently contributed an article for Supermarket News in which I examined the regulatory, market and technological trends behind its increased adoption in the U.S. To view the full article, click here.

To date, most CO2 installations in the U.S. have been deployed as proofs-of-concept. Although there are some sustainably-minded retailers that have made it the basis of their refrigeration strategy, CO2 hasn’t yet experienced the industry-wide acceptance we’ve seen in Europe. But that appears to be changing.

Among the environmental strategies identified to combat climate change, the greening of commercial and industrial refrigeration equipment has been recognized as an essential tactic of decarbonization plans and corporate sustainability initiatives. Food retail stakeholders are rethinking their approaches to refrigeration and transitioning away from legacy hydrofluorocarbon (HFC) refrigerants with high global warming potential (GWP). More than ever, retailers are evaluating long-term refrigeration strategies that support:

  • Environmental, social and governance (ESG) efforts
  • Energy efficiency and emissions reductions targets
  • Net-zero goals

Stage is set for wider adoption

With zero ozone depletion potential (ODP) and a GWP of 1, the natural refrigerant CO2 (aka R-744) is a proven alternative to higher-GWP HFC refrigerants. CO2’s inherent energy efficiency in most climates allows it to deliver direct and indirect emissions reductions — a lower total equivalent warming impact (TEWI). For more than a decade, CO2 refrigeration has become a leading sustainability strategy for European retailers. Today, that trend continues with adoption steadily increasing in the U.S. and other countries.

Per recent industry data, nearly 46,500 CO2 transcritical booster systems are currently installed worldwide.

  • 900 in the U.S. (1,400 in North America with the inclusion of Canada)
  • 40k in the E.U.
  • 5k in Japan

If CO2 growth trends continue as they have from 2020–2021, the U.S. commercial refrigeration industry can anticipate CO2 adoption to increase up to 50% by 2025. This trend is expected to follow a similar trajectory throughout the next decade, with the possibility that the U.S. could potentially mirror E.U. levels of adoption.

Regulations drive down GWP levels

Global, federal and state regulations are steering the industry away from HFCs and toward lower-GWP alternatives. Using the Kigali Amendment to the Montreal Protocol as a framework, the next step in the HFC production and consumption phasedown schedule will be a 40% reduction in 2024 (compared to the baseline established in 2011–2013).

The passing of the American Innovation and Manufacturing (AIM) Act in 2020 restored the Environmental Protection Agency’s (EPA) authority to enforce HFC mandates and establish sector-based guidelines. As the EPA follows the Kigali Amendment’s HFC phasedown, decreased supplies will continue to drive up HFC refrigerant prices.

The California Air Resources Board (CARB) continues its progressive efforts to phase down HFCs in the state of California. Under its recently adopted rule, all new refrigeration systems containing more than 50 pounds of refrigerant installed in new facilities must use refrigerants with less than 150 GWP. For existing installations with equipment greater than 50 pounds of refrigerant, retailers can take a fleet approach toward reducing their carbon footprint. CO2 refrigeration is becoming a leading option for achieving these regulatory targets.

Technological improvements and emerging applications

The proliferation of CO2 refrigeration systems around the globe has given equipment manufacturers opportunities to improve compression, controls and valve technologies. Emerson is at the forefront of efforts to simplify system management and help the industry transition from legacy high-GWP HFC systems.

Electronic system controllers

Emerson’s new Lumity™ E3 supervisory control for CO2 systems is designed to manage CO2’s high pressures and system volatilities, greatly simplifying commissioning and system management during standard operation. These improvements minimize system complexities, alleviate the burden from technicians, and provide peace of mind to end users.

Integrated CO2 transcritical booster system components

CO2 transcritical booster systems — where both medium- (MT) and low-temperature (LT) circuits run on R-744 — are the most widely adopted CO2 architectures in medium- to large-format food retail stores. Emerson is helping original equipment manufacturers (OEMs) and operators to ensure the system integration needed to maximize reliability and performance, including: compressors, electronic expansion valves (EEVs), high-pressure valves and an electronic controller.

Warm ambient strategies

CO2 transcritical booster systems are subject to declining efficiencies in warm ambient climates, but manufacturers have developed a variety of strategies to maintain efficiency levels.

  • Adiabatic gas coolers — keep the refrigerant below its critical point for as long as possible to maximize system efficiencies
  • Parallel compression — compresses excess flash gas at higher pressure via a dedicated intermediate- stage compressor, resulting in 8–10% annualized efficiency gains
  • Mechanical sub-cooling — provides increased refrigerant enthalpy
  • Gas ejectors, liquid ejectors — optimize efficiency
  • Low superheat of MT evaporators — delivers year-round efficiency improvements

Increasing our commitment to CO2 innovation

Emerson is expanding CO2 labs, testing facilities and development capabilities to further CO2 adoption and support our OEM and end user partners. As the market for CO2 refrigeration continues to expand, the proliferation of new products is creating economies of scale, which lower the costs and complexities of implementing CO2 technologies. To learn more about improving the efficiency, usability and simplicity of CO2 systems, please visit our CO2 resources hub.








[New Webinar] Spotlight on Emerging CO2 Refrigeration Technologies

Andre Patenaude | Director – Solutions Strategy

Emerson’s Commercial and Residential Solution’s Business

Emerson is pleased to announce our participation in the ATMO World Summit 2022 on March 30–31, when industry stakeholders will assemble virtually around the globe to discuss the future of cooling and heating technologies. This free, 24-hour event will feature a webinar at the top of every hour. At 3 p.m. EDT (12 p.m. PST) on March 30, Emerson’s Andre Patenaude, director of solutions strategy, and Emily Vilardi, product marketing manager, will explore how emerging natural refrigerant technologies are poised to deliver the next generation of refrigeration.

Today, corporate sustainability initiatives and refrigerant regulations are driving the increased adoption of natural refrigerants, such as CO2 (R-744), propane (R-290) and ammonia (R-717). Approved for use across a broad range of commercial refrigeration applications, these multipurpose refrigerants are among the lowest-global warming potential (GWP) alternatives available.

For more than a decade, Emerson has been developing natural refrigerant technologies to help support the transition away from high-GWP hydrofluorocarbons (HFCs). Our ATMO World Summit 2022 webinar — “Spotlight on Emerging CO2 Refrigeration Technologies” — will demonstrate how Emerson is simplifying the adoption of CO2 transcritical booster refrigeration via the seamless integration of key system components and technologies.

In addition to hearing the latest trends related to natural refrigerant adoption, attendees will learn about Emerson’s commitment to developing technologies that further CO2 refrigeration in the U.S. via:

  • Introducing electronic controls that simplify CO2 installation and system operation
  • Expanding our CO2 compressor lineup and system components
  • Increasing lab investments to create the next generation of natural refrigerant technologies
  • Releasing our next-generation CO2 mobile training unit to help fill the industry-wide training gapReleasing our next-generation CO2 mobile training unit to help fill the industry-wide training gap

Introducing Lumity™ E3 supervisory control for CO2

Among our many natural refrigerant-related product advancements, we’ll highlight how our new Lumity E3 supervisory control for CO2 reduces system start-up complexities, consolidates multiple functions into one easy-to-use interface, supports mobile connectivity for remote troubleshooting, and integrates with our new Lumity CC200 case controller for full system optimization.

Our webinar on March 30 is just one of 24 sessions that will be presented at the full-day ATMO World Summit 2022. Be sure to check the program’s schedule for other topics that may interest you. Registration for this free online event is now open and will be hosted by the Zoom Events platform.

To learn more about how Emerson is helping the commercial refrigeration industry adopt CO2 system technologies, register for this free webinar.




Beyond Trackers and Loggers: Optimizing the Cold Chain

Juliette Giles | Senior Product Manager, Software & Services

Cold Chain at Emerson

Cold chain monitoring has come a long way in recent years, thanks to devices that provide real-time visibility into perishable shipments. It’s now possible to get key transit information at any time, from a point of origin to final destinations, keeping all stakeholders accountable while minimizing rejected loads.

Now the perishable cold chain is becoming even stronger with the introduction of Oversight cargo services: a robust suite of monitoring, data analytics, and reporting capabilities that delivers detailed information about the real-time and historic performance of your shipments. This cloud-based portal offers many new capabilities — some available at no cost — to help you boost customer loyalty, optimize shipments, preserve your peace of mind, make better-informed cold chain decisions, and protect the integrity of your brand.

Oversight cargo services includes five modules, available individually or in any combination.

Track Your Shipment

If you’re using Emerson’s field-proven line of GO real-time trackers and loggers, you’ve already received a free upgrade with the launch of Oversight cargo services. The Track Your Shipment module — available at no cost with any of these devices — allows you to provide your customers real-time, in-transit shipment and temperature data.

By adding just a few lines of code, you can display a Track Your Shipment box on your website, customized to conform to your brand. Your customers and employees can access shipment data at any time, enhancing the value you provide.

Upgrade the platform with the following paid services:

Reports and Scorecards

Trackers and loggers can provide you with reams of data; but to make the most of it, you need to get the right information to the right people at the right time. Reports and Scorecards give you access to Emerson’s temperature monitoring dashboard, enabling you to identify patterns across multiple shipments and pinpoint the sources of recurring problems — such as whether a carrier, origin or destination is failing to maintain temperature compliance.

Data Integration

High volumes of data can be overwhelming, especially if you need multiple platforms to create new shipments or are constantly being bombarded with alerts. Data Integration allows you to see the information streams that matter most — such as location and temperature alerts — in a consolidated view. This benefits your operation by eliminating duplicate work, minimizing opportunities for error, and reducing your overhead costs. You’ll also have the option to consolidate shipment creation and purchase order (PO) entry processes into one convenient system.

Managed Services

Managed Services extends your in-house resources by outsourcing some (or all) of your monitoring tasks to an experienced team of cold chain specialists. This provides continuous monitoring whenever your shipments are on the road — no matter what time of day or day of the year. You can choose to get alerts when temperature abuse or light alerts happen in transit, and/or empower the Managed Services team to take immediate action in accordance with your preferred operating procedures.

Professional and Consultative Services

Sometimes the best solution to a challenging and complex issue is to get a fresh perspective. Emerson’s Professional and Consultative Services team can perform a comprehensive on-site consultation and analysis to identify gaps in your operation. This team-oriented approach gives you access to experienced cold chain specialists who can help you to identify and solve recurring issues.

Final thoughts

The new suite of Oversight cargo services has been developed by a skilled team of cold chain experts. Several members of the development team have backgrounds in logistics and designed it specifically to address challenges they’ve faced when working for organizations like yours. We’re excited about the portal’s potential to strengthen your perishable cold chain and welcome the opportunity to demonstrate its full value.

For more details, contact us today or download the Oversight cargo services brochure.

Learn More: Oversight Cargo Services at Your Fingertips (

CO2 Refrigeration Fundamentals: Energy Efficiency Strategies

Andre Patenaude | Director – Solutions Strategy

Emerson’s Commercial and Residential Solution’s Business

Welcome to the final installment of our CO2 Refrigeration Fundamentals blog series. So far, we’ve examined R-744’s unique properties, servicing tips, system operation and design strategies — all of which correspond with topics in our CO2 Chats educational videos. For our final blog, we’ll explore strategies for achieving CO2 transcritical booster system energy efficiencies in warm climates.

How do you achieve energy efficiency in a CO2 system?

The energy consumption of a refrigeration system is a key factor when evaluating its total cost of ownership (TCO). For a CO2 transcritical booster system, energy efficiency is dependent on many factors, including:

  • The ambient temperature range
  • The humidity of the region
  • The availability of and cost of water
  • The cost of peak demand charges

Among these factors, the goal of improving system energy efficiencies in warmer climates has become a major focus area for equipment manufacturers. Leading high ambient strategies include:

  • Adiabatic gas cooler
  • Parallel compression
  • Mechanical sub-cooling
  • Zero superheat control of medium-temperature (MT) evaporators
  • Ejector controls

Retailers must consider all of these variables and strategies when they work with their equipment suppliers and design engineers to specify a CO2 transcritical booster system — which also includes ensuring that qualified service technicians are available in their region to support CO2 refrigeration.

What is an adiabatic gas cooler used in CO2 systems?

An adiabatic gas cooler is very similar to a dry gas cooler, except that it uses adiabatic pre-cooling pads outside the condenser coils. When the ambient temperature reaches about 72 °F on a CO2 transcritical booster system, a water solenoid valve is energized, causing water to be sprayed along the top of the adiabatic pads. As the water trickles down the pads, a condenser pulls air through these wetted pads, causing moist, cooler air to hit the coils. In turn, the condenser reacts to this cooler air and drops the temperature and pressure, making the system significantly more energy-efficient by operating at lower pressures.

What is parallel compression in a CO2 system?

In a CO2 transcritical booster system, parallel compression refers to the practice of adding a separate suction group to the system. This could be confusing to service technicians, who may think we’re simply referring to a parallel rack used on a traditional hydrofluorocarbon (HFC)-based system.

The concept is relatively simple. A “parallel” compressor is added to the MT suction group, which essentially provides a separate suction group to the system. Thus, instead of the bypass gas circulating from the flash tank to the MT suction as in a standard transcritical booster system, the parallel compressor suction group compresses excess flash gas and circulates it to the gas cooler.

This allows the parallel compressor to operate at a suction pressure of about 550 psi (the same as the flash tank), instead of the MT suction of 425 psi. The net effect of leveraging the higher suction pressure is achieving higher compressor capacity for less effort, which translates into a lower heat of compression and reduces energy consumption. As a result, parallel compression is considered a leading high ambient strategy. When annualized in a typical environment, it can potentially save up to 10% in energy costs. Further, parallel compression can be used in combination with an adiabatic gas cooler to achieve additional energy efficiencies.

Thank you for following our CO2 Refrigeration Fundamentals blog series. To learn more about any topic discussed herein, please view the companion installments in our CO2 Chats video series. For more information about Emerson’s comprehensive CO2 products and capabilities, please visit






CO2 Refrigeration Fundamentals: System Design

Andre Patenaude | Director – Solutions Strategy

Emerson’s Commercial and Residential Solution’s Business

In the previous installment of our CO2 Refrigeration Fundamentals blog series, we explored how to manage CO2’s high pressures during normal operation and system shutdowns. Its unique properties also impact system design, resulting in CO2 refrigeration architectures that differ greatly from traditional hydrofluorocarbon (HFC)-based systems. In this blog, we’ll review two leading CO2 architectures and explore how to expand the potential of a CO2 system. Remember, you can also learn more about these CO2 topics in our new CO2 Chats video series.

What is a CO2 transcritical booster system, and how does it work?

A CO2 transcritical booster system is quite different than a standard HFC refrigeration rack. Medium-temperature (MT) compressors discharge into a stainless-steel discharge line designed to handle R-744’s high pressures and carry the refrigerant to a gas cooler. The pressure could reach 1,400 psi on a hot summer day, and refrigerant must be cooled before it can be condensed. So it circulates back into the building and is passed through a high-pressure valve, which drops the pressure to a useable pressure (550 psi) and deposits refrigerant inside the flash tank at 40 °F equivalent saturation.

Now the system circulates the 40 °F liquid through insulated liquid lines to feed all the MT and low-temperature (LT) cases and provide the cooling loads. The MT cases are equipped with an electronic expansion valve (EEV), and the MT suction gas feeds the three MT compressors. On the LT side, the liquid expansion valve and LT loads — which could be -20 °F — are supported by a separate set of LT compressors that discharge into the MT suction group.

In addition, the system utilizes a bypass line that’s designed to relieve the pressure on the flash tank. As ambient temperatures rise and fall, flash tank pressures can also fluctuate. Thus, the bypass line helps to release the flash tank pressure and stabilize the pressure at 550 psi. It is also designed to discharge into the MT suction group. In effect, the three MT compressors are being fed by three sources:

  • The total heat of rejection from the LT compressors
  • The MT suction from the evaporators
  • The bypass line with the excess flash gas from the flash tank

The system is called a booster system because the LT compressors are not going directly to the gas cooler, like they would on a typical HFC system. It’s called transcritical booster because the LT compressors discharge into the MT compressors, thereby allowing the MT compressors to boost the refrigerant to the gas cooler.

What is a CO2 cascade system, and how does it work?

A CO2 cascade system offers an alternate architecture for retailers who want to deploy a low-global warming potential (GWP) option but may not want a full CO2 transcritical booster system. In a CO2 cascade system, the high (MT) and low (LT) stages are completely independent of each other, except for one heat exchanger that connects them.

Typically, the high stage would use a lower-GWP, medium-pressure HFC such as R-513A. Not only does it serve the MT loads, but it is also used to condense the CO2 in the low stage. In the low stage, CO2 is discharged, condensed in a condenser, and then recirculated for LT loads. R-744 is a very effective refrigerant for LT loads; and with a GWP of 1, it contributes to a cascade architecture that could meet many retailers’ sustainability objectives.

Can you reclaim heat in a CO2 system?

CO2 systems are excellent candidates for heat reclamation strategies. In fact, many modern CO2 systems utilize some form of heat reclaim strategy — whether it’s for providing heated air, hot water, or even heating slabs beneath freezers. Rather than burning fossil fuel to generate heat, there are a variety of scenarios whereby the heat generated from a CO2 system can be leveraged.

Compared to HFC refrigerants, another advantage of CO2 is the fact the liquid quality of R-744 is not affected when head pressures are raised to generate more heating capacity. Instead, the flash tank or receiver is designed to keep refrigerant at a consistent pressure, even while head pressures may fluctuate.

How do you optimize the coefficient of performance (COP) in CO2 systems?

To understand how to optimize COP in a CO2 transcritical booster system, we must first evaluate the function of the gas cooler and the characteristics of R-744 as it enters the supercritical zone. R-744 has a low critical point of 87.8 °F, above which the refrigerant enters a supercritical phase where the relationship between pressure and temperature becomes unpredictable.

Below the critical point, the gas cooler acts like a condenser, where the liquid-vapor interface of R-744 exists in a state of saturation. At saturation, the temperature-pressure relationship is predictable: if you know the pressure, you can determine the temperature (and vice versa). Above 87.8 °F, the pressure can change without having an impact on the temperature (and vice versa). When optimizing COP, we can take advantage of this phenomenon.

Based on the gas cooler outlet temperature, technicians can adjust the pressure to achieve the most optimum COP — or the most efficient BTUs per watt input. This is done by modulating the high-pressure valve on the system, which connects the gas cooler to the flash tank. And since this can change throughout the day as ambient temperatures change, technicians may have to continually modulate pressure accordingly. If they need to increase or decrease the system’s head pressure, simply close off or open the high-pressure valve, respectively.

To learn more about the topic of CO2 system design, please view the companion installments in our CO2 Chats video series. The next installment of the CO2 Refrigeration Fundamentals blog series will focus on energy efficiency strategies in warm climates. For more information about Emerson’s comprehensive CO2 products and capabilities, please visit



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