To demonstrate the system efficacy of a transcritical CO2 technology in a higher ambient climate, U.S. OEM Zero Zone installed its transcritical CO2 booster system, equipped with components from U.S. manufacturer Emerson, at a food retail outlet in Joplin, Missouri (U.S.)
Concerns over operating pressures, maintenance levels and energy have prompted end users like supermarkets to conduct “thorough evaluations” to comprehend “the true cost” of CO2 system ownership, said Andre Patenaude, Director, Solution Strategy, Cold Chain, for Emerson Commercial & Residential Solutions.
Zero Zone and Emerson partnered to “address the challenges presented by installing CO2 transcritical booster systems in warm climates,” said Patenaude.
In the case of the Joplin store, it “is operating efficiently and effectively on the Zero Zone CO2 transcritical system,” he said.
With experiences like this In the U.S., added Patenaude, the view of end users toward transcritical CO2 booster systems “is shifting from hesitancy toward wider acceptance.”
The Zero Zone transcritical rack features three Copeland transcritical CO2 semi-hermetic compressors for medium-temperature cases (dairy, produce and meat) and two Copeland ZO scroll compressors for freezers, including a digital scroll compressor with 20–100% variable capacity control.
In addition, the lead CO2 transcritical compressor operates with the assistance of a variable frequency drive (VFD) for capacity modulation. In May, Emerson launched Copeland Commercial Variable Frquency Drives (VFDs), designed for use in a wide variety of commercial and industrial refrigeration applications, including with Emerson’s natural refrigerant compressors.
Both compressor models were designed “to manage CO2’s high-pressure requirements and benefit from its thermodynamic properties,” said Patenaude.
Seamless integration of controls
Emerson’s E2 supervisory control was installed to oversee the operation of the system, including management of Emerson’s Dixell XM Series case controls in each of 12 cases.
The E2 system also manages suction-pressure variations as well as temperature differences on the gas cooler and provides visibility into the operation of the high-pressure controller. It also controls oil management and building HVAC.
“All the controls are designed to integrate seamlessly with each other and with the system’s electronic expansion valves (EEVs), enabling real-time visibility of their operational status,” said Patenaude.
All Joplin store compressors were equipped with diagnostics, protection and communications technologies, controlled by the E2 system, that allow technicians to make “faster, more accurate decisions, resulting in improved compressor performance and reliability,” said Patenaude.
Another key feature is an adiabatic gas cooler, which helps the transcritical system to operate efficiently in high ambient temperatures. The E2 system controls the variable speed of the fans on the adiabatic gas cooler in response to operating conditions
With these advances in system technology and architecture, CO2 refrigeration “could not only be more widely adopted, but could be considered a game changer for retailers seeking to improve energy efficiencies, achieve sustainability targets, and meet regulatory compliance requirements,” Patenaude said.
“The store is operating efficiently and effectively on the Zero Zone CO2 transcritical system.”
Andre Patenaude, Emerson
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