Supermarkets are one of the most energy-intensive types of commercial buildings. Supermarket refrigeration systems consume the significant amount of energy to maintain freezing temperatures for a variety of items intended for human consumption on a 24 hours a day, seven days a week basis, which implies that the refrigeration equipment is never shut off. In a typical supermarket, sales area of 1000m² consumes around 300.000kWh annually for refrigeration, including the power consumed by compressors, condensers, coolers, and evaporator defrosting.
In 2017, Kaltra specialists developed high-efficient and environment-safe refrigeration system for its client located in Spain. The primary objectives of Hipercor in Madrid were to minimize the energy consumption to cut costs and reduce the amount of refrigerant used in the primary loops.
Secondary loop system proposed by Kaltra implies two refrigeration circuits where the brine solution in the secondary circuits is cooled by heat exchange with the HFC refrigerant in the primary circuit. Secondary circuits provide the circulation of brine solution to the cooling coils located inside the display cases and cold stores. Secondary loop solution has a set of advantages over traditional systems, including homogenous cooling, minimization of refrigerant charges and thereby also the leakages of refrigerant.
The proposed refrigeration solution employed the chillers with integrated pumps located in a plant room and connected to low- and high-temperature loops to refrigerate a brine solution (propylene glycol mixture) to -8°C and -2°C, respectively, and pump it to the cold stores and display cases specifically designed for the use of brine. The chillers utilize multiple parallel compressors for capacity control and heat rejection accomplished with remote evaporative condensers to achieve lowest condensing temperatures.
Use of evaporative condensers was the principal driver for energy savings for the system: the energy consumption was reduced by about 15% when evaporative condensers were substituted for the air-cooled condensers. Installed evaporative condensers also feature high-efficient, low-charge microchannel heat exchangers that enabled the reduction of refrigerant charge over previous refrigeration system by one fourth.