U.S.-based manufacturer Emerson, in collaboration with British retailer Co-op and U.K.-based OEM Artic Circle, has unveiled an initiative to increase the adoption of CO2 (R744) refrigeration technology in smaller retail stores by simplifying systems, making them more affordable.
The three companies shared details of the initiative during the ATMOsphere Europe conference, which took place online September 28-29. ATMOsphere Europe was organized by ATMOsphere (formerly shecco), publisher of R744.com.
“We want to bring CO2 technology to the next level of adoption for the smaller size supermarkets,” said Olivier Liegeois, Marketing Director for Refrigeration at Emerson. “To achieve this we want [to] minimize the installation cost by providing a system that is less complex and has less components, and also by using the new vapor injection technology.”
One way to reduce cost is, of course, to improve efficiency, especially with energy prices rising all over the world. To achieve this, the project has developed a system with a simpler design that uses fewer and more compact compressors.
Two of the design changes are an improved compressor scroll design and a new dynamic vapor injection 2-in-1 technology, where the parallel compression is included in the compressor. The project has also looked at high standstill pressures and improved “smart” controls.
“We want to bring CO2 technology to the next level of adoption for the smaller size supermarkets, to achieve this we want [to] minimize the installation cost by providing a system that is less complex and has less components, and also by using the new vapor injection technology.”Olivier Liegeois, Emerson.
New scrolls and dynamic vapor injection
The benefit of scroll technology is that the scroll is “a continuous compression process, meaning it is a very good choice for vapor injection,” Liegeois said. “Scroll technology is also rotating much faster than the semi-hermetic piston compressors, so we are able to deliver more capacity per unit of volume.”
Addressing how parallel compression not only increases system efficiency but also makes it more complex, Liegeois said that the new dynamic vapor injection 2-in-1 design takes “the flash gas from the tank and injects it directly into the compressor, and this is where the scroll has an advantage because you can easily inject the vapor inside the scroll.”
After some seasonal efficiency simulations, the team concluded that, compared to a standard CO2 system, the new scroll system achieved 4% more efficiency in a cold climate, 6% more efficiency in a medium climate, and 8% more efficient in a warm climate, with cold represented by Helsinki, Finland, medium by Strasbourg, France, and warm by Athens, Greece. The applied cost also substantially decreased by 9%, Liegeois explained.
When compared to a booster system with traditional parallel compression, the efficiency gains are less: 2%, 3% and 2% for Helsinki, Strasbourg and Athens, respectively. The applied cost, however, is much lower, saving 14% due to the simpler system setup.
Another benefit of the scroll design is that it’s 50% lighter than traditional semi-hermetic compressors and can reduce a system’s weight by up to 10%, Liegeois added.
The project model assumptions have been validated by field test data obtained since 2019 at a 750m2 (8,073ft2) Co-op store in Malmesbury, U.K. The refrigeration system has been running reliably for two years, even through a 38°C (100.4°F) heat wave. Co-op is pleased with the system and is planning to implement it in other stores.
Emerson unveiled the Copeland CO2 scroll compressors for both medium- and low-temperature applications in September. Commercial scale production is expected to start early next year, Liegeois said.
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