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Integrated HVAC&R
Italian Supermarket Increases Efficiency of Transcritical CO2 System with Groundwater The groundwater condenses CO 2 , allowing the integrated system to run subcritically during the summer, says OEM Crea. ― By Tine Stausholm
An
Italian supermarket chain is using groundwater as a cooling fluid to condense the CO 2 in a transcritical system at a remodeled store in Milan, according to Italian OEM Crea, the system provider.
Since the reopening, the system has not shown “any kind of issues and it's working well,” said Emiliano Testa, technical engineer, Crea. “We and our retailer are very satisfied with this solution.”
This allows the integrated system to run subcritically in the warm summer months, and reduces the electricity consumption of the compressors, said Crea.
In the winter months the system is designed to run in transcritical mode to satisfy the supermarket’s need for hot water and space heating. To gain the needed heat, the system employs heat recovery, which can recover up to 42kW in the winter, equaling “total” heat recovery, and increasing the system’s COP to 4.2, according to Stefano Tortorici, Technical Engineer at Crea.
The groundwater used as a cooling fluid in the system is 15-20°C (59-68°F) year round. This allowed Crea to set a 25°C (77°F) condensing temperature in the system, using a plate heat exchanger. The use of groundwater, instead of air, to condense the CO 2 , allows the system to run in subcritical mode even during the hottest summer months when the ambient air temperature is 27-28°C (80.682.4°F) or more, Crea said. The 400m 2 (4,306ft 2) remodeled store was officially reopened in December 2019, after a two-month refurbishment period. Crea did not name the retailer.
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COP of 4.2
Crea experienced several challenges in designing the system, including limited space and local noise-level requirements. The store is located in a building in the historical center of Milan, near the Milan Cathedral, with a narrow technical room in the basement. The narrow space issue was solved via integration of air conditioning in the main rack. The high-temperature compressor
The technical room in the Milan store
used for air conditioning also doubles as a parallel compressor, disposing of flash gas accumulated in the receiver. The capacity of the Milan system is 30kW (8.5TR) for medium temperature, 6kW (1.7TR) for low temperature and 40kW (11.4TR) for high temperature (air conditioning). The system contains six Frascold compressors, three medium temperature, two low temperature and one high temperature. It has three Alfa Laval plate heat exchangers for the heat recovery, condenser and air conditioning. It also has a liquid receiver and Carel controls. Crea declined to comment on the cost or ROI of the system compared to an HFC system, saying that the client for whom the project was designed has worked with natural refrigerants for several years, and that a HFC system was never considered for this store. TS