Over two conference days, June 18-19, ATMOsphere America 2014 held parallel case study sessions covering the latest in CO2 innovation for centralised commercial refrigeration systems. The presentations summarised below by Hillphoenix, Systemes LMP, Carel, SandenVendo, Danfoss, SCM Frigo, Micro Thermo, Emerson, KAV Consulting, Zero Zone, and DC Engineering, touch on topics such as cost, technological improvements, serviceability and best practice; as well as give installation examples at major food retail stores and the latest performance results.

Small footprint CO₂ technology for commercial refrigeration

CO₂ technology is rapidly becoming a mainstream technology. According to Michael Englebright, Global Key Accounts Manager for Retail, Carel these systems have almost achieved cost parity with traditional HFC systems, with only a 5% difference between the two. However, whereas the European market for CO₂ racks and plug-in and self-contained systems has evolved rapidly, for small footprint systems barriers remain in terms of initial upfront costs, usability for installers and system complexity.

The advent of smaller footprint CO₂ units developed on the basis of traditional condensing units, a technology already used in Japan, is beginning to change the situation. In the US, Roche pharmaceuticals has already invested in this technology, and by the end of 2014, Englebright said that 18 such systems were planned for completion.

From SandenVendo, Mike Weisser, VP Marketing and Sales also discussed small footprint CO₂ refrigeration systems, and the significant market opportunity that the convenience store market represents. In North America for example, retailer CVS has 150,000 stores, adding 5000-7000 stores per year, in addition to which store remodels can be expected every 15 years. Overall, this represents a market of 15,000 – 17,000 stores for small footprint CO₂ systems.

New technologies open door for efficient CO₂ use in hot climates

Jeff Newel, Director of Research and Development Hillphoenix, presented an industry first, the company’s pioneering installation of a CO₂ booster system in a warm ambient climate at a Sprouts Farmers Market store in Dunwoody Georgia. Here, a standard Advansor CO₂ booster system with 4 MT compressors and 3 LT compressors was installed together with an adiabatic gas cooler (operated dry in cooler weather and with wet pads for pre-cooling in warmer weather), minimising the CO₂ temperature leaving the gas cooler and thereby reducing energy consumption by 6%.

From Systemes LMP, Xavier Marle, Director of Operations and North American Sales Representative, discussed the advantages of mechanical sub-cooling, a technology that can reduce energy consumption by 17%, improve the Energy Efficiency Rating (EER) by 35%, and decrease the number of refrigeration compressors needed to keep systems in a positive temperature mode. This lowers the energy costs associated with CO₂ transcritical systems, enabling them to operate efficiently at high ambient temperatures.

Klass Visser, owner of KAV Consulting presented the application of CO₂ evaporative condensers and gas coolers. Visser believes that CO₂ transcritical refrigeration can be used throughout the United States when combined with an evaporative condenser and gas cooler. This combination provides a suitable alternative technology for the conversion of existing HFC/CO₂ cascade systems.

SCM Frigo’s Technical Director Mirko Birnabei presented another case study illustrating the successful installation of CO2 technology in a warmer climate. Bernabei looked at an installation in a meat factory in France, in a location with a similar climate to the United States. The installation, comprised of a CO₂ booster MT and LT with parallel compression and total heat recovery, provides both cooling and heating in one unit. Parallel compression maximises the efficiency of the system when the weather is hot or during heat recovery mode in wintertime, which decreases power consumption compared with a traditional booster unit.

Accurate CO₂ system controls

Peter Dee, Sales & Service Director, Danfoss North America, one of several manufacturers that supply mechanical and electronic rack controls and case controls, presented his company’s involvement in one of the first CO₂ transcritical supermarket installations in the US, at a Whole Foods store in Brooklyn, New York. The 56,000 ft2 (5,203 m2) store features a CO₂ trancritical refrigeration system, combined heat and power (CHP), and air handling units (AHU) with hot and chiller water. One of the most significant successes of the project was strong industry collaboration and contractor training.

Also speaking from the perspective a leading controller and component manufacturer was Louis Morris, Applied Engineering Manager at Micro Thermo Technologies a subsidiary of the Parker Hannifin Corporation. Micro Thermo Technologies has worked on 80 locations that use CO₂ as a refrigerant, and focuses on providing a holistic, system approach that ensures none of an installation’s heating and cooling systems are competing each other. To illustrate this approach Morris described the way in which all of the subsystems in an IGA store in Terrebonee, Québec, Canada are interconnected, so that the condensers, RTU (rooftop units), lighting, racks and cases influence each other. The 40,000 ft2 (3,716m2) store has 105 cases, 15 coolers/freezers, one centralised CO₂ trancritical system with heat reclaim. The installed Micro Thermo Technologies control system collects all the data needed to provide efficient case control, such as ambient temperature, humidity, dewpoint, liquid temperature, and liquid pressure. In turn, the system enables the cases to provide important information to the interconnected systems relating to defrost and emergency situations. The goal is for the system to be predictive.

CO₂ booster system advantage versus R404A DX

In his presentation Andre Patenaude Director - CO₂ Business Development Emerson presented a Life Cycle Climate Performance (LCCP) comparison of a CO₂ booster system and an R404A DX system. Compared to the latter a CO₂ transcritical booster system has a 64.5% lower carbon footprint at 70°F (21°C). Patenaude also discussed the lower compression ratio of a 15HP CO₂ compressors compared to a 15 HP CO₂ compressor: 2.9:1 versus 3.5:1, which is explained by the higher CO₂ suction pressures. Emerson manufactures a variety of compressor operating envelopes, all of which come equipped with CoreSense electrical controls, reducing maintenance costs, increasing system uptime, and which records a history of all trips, alarms run our and starts.

Also presenting on the advantages of CO₂ systems versus HFC DX systems were Tom Wolgamot, Principal Engineer / Branch Manager, DC Engineering, and Dan O-Brian, Vice President of Zero Zone, who compared three similar sized Whole Foods stores, one with a CO₂/R407A system, one with a DX LT/Glycol system, and one with a distributed system. In terms of monthly store main feed usage the CO₂/R407A installation had the best results.