Stuart Saville is a man of purpose. Charged with driving the sustainability agenda for Coles – one of the two dominant food retailers in Australia with Woolworths – Saville, national engineering refrigeration manager, is measured in his thoughts but knows he is onto a good thing.
Decked out with “all the bells and whistles,” Coles’ first CO2 transcritical booster installation at its recently opened flagship store in North Coburg, Melbourne, has so far performed above expectations. Management was hoping for energy reductions of 10%. But since the store opened in August 2015, the refrigeration system has so far seen an impressive 15% efficiency improvement (with a maximum of 22%) during the cooler months, compared to its baseline CO2/R134a systems.
It’s little wonder industry figures and rival retailers have been keeping their ears close to the ground for news on one of Australia’s five commercial transcritical installations, which include three at competitor Metcash IGA stores.
The transcritical installation is the result of Coles’ longtime use of subcritical CO2 systems at 120 of its 780 supermarkets. The chain is also testing other natural refrigerants, including propane in display cases at a Liquorland outlet adjacent to the North Coburg store, and one ammonia/CO2 cascade system.
Accelerate Australia was invited to see the bustling North Coburg store with Saville and Brian Toulson, senior project engineer for UK-based City Refrigeration Holdings, whose Australian arm, City Facilities Management, partners with Coles on all of its installations.
Described as a “concept store,” the 39,826-square-foot supermarket is Coles’ first attempt at an all-natural solution (only one back-up compressor is running on HFC R134a). Coles is eager to implement CO2 transcritical systems in two more stores as early as this year and is all but convinced that ejector technology will accompany one or both.
Meanwhile, the North Coburg installation encompasses not only refrigeration but also air conditioning and heating, making it one of the most versatile transcritical installations in the world. The booster system includes two Bitzer CO2 centralised racks supplying a load of 610kW; parallel compression; adiabatic cooling; hot gas defrost, 250kW of chilled water capacity to supply store air conditioning; heat reclaim supplying store hot water and heating; and four solar inverters generating up to 100kW.
Optimising energy – even on hot days
The transcritical system has performed well so far, even in warmer temperatures. Toulson, who has been in the engine room and seen the system under stable operation on a 43°C day, said no stone had been left unturned in ensuring the store was as advanced as possible. “We looked at everything that would help the energy profile and we really wanted to get rid of synthetic refrigerants and also to hit the optimum energy savings that we could.”
“On the 43°C day the operation of the [CO2 transcritical] system was very stable. We’ve got to the stage now where our mechanics and technicians don’t even bother coming here on the hot days; they go to the stores which have heat issues,” he said.
Coles has measured the transcritical system against one of its benchmark stores fitted with a CO2/R134a cascade system, using all the key metrics considered to be pertinent to get a true measure: overall refrigeration capacity, sales floor area, climatic region, and case length. “We were expecting to see in the vicinity of a 10% reduction in power consumption but after a full six-month period (August-January), we found that the consumption has actually come in at about 15% under one of our benchmark stores,” Saville said.
The next step is to measure the system’s efficiency during the upcoming summer months “so that we can clearly demonstrate what the savings have been,” Toulson said. “Hopefully then we can seek endorsement for two further stores.”
Avoiding the intricacies involved with installing any HVAC&R system is imperative for end users like Coles. The company ideally wants to use the technology as a template. “We’ll trial another couple of stores with transcritical, we’ll take the learnings that we’ve had, take some of the complexity out of what we’ve done here, and try to simplify it and drive down the capital cost,” Toulson said.
Bitzer and Danfoss were chosen as key suppliers due to their “experience and excellent track record in Europe,” Saville said. Bitzer and Danfoss helped both Coles and City Facilities Management with the design and installation. “We had buy-in from both of them [Bitzer and Danfoss] to ask for their assistance to ensure our technicians were fluent in installation, servicing and maintenance of the system.”
Indeed, European retailers considering investing in CO2 transcritical refrigeration systems for warmer regions would do well to hear from Coles’ experiences.