A Quebec supermarket has realized thousands of dollars in energy savings per month using a transcritical CO2 system rack system with heat recovery, according to a case study presented by Arneg Canada during the online ATMOsphere America 2020 conference on October 20.

“In January and February, right in the heating season, the customer is seeing an average of CA$6,000 [of savings per month] at CA$0.06 per kWh – right into June and July where they are averaging CA$4,000 of energy savings,” said Phillip Walker, Refrigeration Solutions Director for Arneg Canada.

ATMOsphere America, organized by shecco, publisher of this website, was held online on October 20 and 21 and concludes with a Latin America-focused program in Spanish on October 22.

The savings, Walker explained, are a result of recovering and reusing heat generated from the supermarket’s transcritical CO2 rack system for melting snow on the path for delivery trucks as well as for space, hot water, floor and warehouse heating.

The CO2 system has a single heat exchanger which is connected to a closed glycol loop. The glycol loop is then connected to the store’s snow melting module, boiler, space heaters and HVAC modules. 

The control system, Walker explained, plays an important role in designing the heat recovery system.

The Quebec store has 13 independent heat recovery zones and “we can’t simultaneously heat all 13 zones at once,” he said. “The control system is used to prioritize the zones depending upon the time of year and the temperatures required in each zone.”

Annual heat recovery

Regarding the heat used for the HVAC modules, Walker emphasized that a long heating season is not needed to fully take advantage of the heat recovered from the transcritical CO2 system. “We’re doing a lot of annual heat recovery,” said Walker. 

For example, the store uses “available heat from the transcritical [CO2] refrigeration system to temper the air stream so we’re delivering a much more neutral air temperature throughout the dehumidification season,” Walker said.

“As we [move] into the heating season, that becomes a full-blown heating coil so we’re maximizing our useful heat to heat the supermarket.”

“[With heat reclaim from a transcritical CO2 system], in January and February, right in the heating season, the customer is seeing an average of CA$6,000 [of savings per month] at CA$0.06 per kWh – right into June and July where they are averaging CA$4,000 of energy savings.”

Phillip Walker, Arneg Canada.

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