Recent developments in the rapidly evolving food retailing business have made obsolete many of the underlying assumptions of the TEWI-3 study (“Energy and global warming impacts of HFC refrigerants and emerging technologies,” published in 1997).
The most significant change (which began about 10 years ago) is the increase in the size of the average supermarket that is being built, according to a new report, “Global comparative analysis of HFC and alternative technologies for refrigeration, air conditioning, foam, solvent, aerosol propellant, and fire protection applications,” prepared by Arthur D. Little, Inc.
From the average size of 25,000 sq ft for existing supermarkets cited in the TEWI-3 study, the average size of newly constructed supermarkets today is approaching 60,000 sq ft. Given the eight- to 10-year remodeling-renewal cycle of the industry, this will be the average store by the middle to late part of the next decade.
Based on an average of six recent Hussmann installations throughout the United States, a “typical” U.S. supermarket and its refrigeration system can be characterized by the following assumptions.
— Comparable or less for distributed systems; in essence, efficiency losses due to the heat transfer and pumping power of the heat-rejection loop are comparable in magnitude to the efficiency losses in the DX configuration due to low-side pressure drops (the long runs of suction line and EPR valves) and to suction line heat gain (i.e., non-useful superheat).
— The efficiency of secondary-loop systems is about 10% less than for DX systems due to the heat transfer and pumping power in the secondary loop, while being subject to heat gains in the secondary loop piping that are comparable to DX system suction line heat gains.
Based on this, representative refrigeration energy consumption in a typical, newly constructed supermarket is:
This is a representative level of energy consumption for comparing these alternatives as applied in a particular store. Obviously, many variables influence actual energy consumption.