CAMAS, Wash. -- Fred Meyer Inc. is projecting a 15% to 20% reduction in refrigeration costs as a result of switching to a new-generation coolant and a two-stage compressor system at a store here.
If successful, the system could serve as a model for future installations at the chain, said David Wright, mechanical engineer at Fred Meyer, Portland, Ore.
The chain's new 165,000-square-foot supercenter is pairing the hydrofluorocarbon coolant R-507 with two-stage compressors to maximize cooling capacity of its low- and medium-temperature cases, Wright said.
But it is in the low-temperature arena that the chain expects to realize the greatest efficiency gains by using compressors that will deliver cooling power in two stages rather than in a single step, as is the more common set-up in supermarkets, he said.
The compressor equipment design and the R-507 gas sufficiently cool freezer cases at the first stage of compression through a subcooler, which requires less power. The two-stage compressors can also be used with R-22 coolant, a hydrofluorochlorocarbon gas, but R-507 delivers higher energy efficiency, Wright said.
Although pleased with the system's initial performance results, the chain is "holding our ground to see how this particular store progresses, and could make some decisions based on that. We have three or four stores in line that could be changed based on the performance of the Camas store," Wright said.
In addition to the potential for reducing energy costs, the chlorine-free HFC system delivers environmental benefits by not damaging the Earth's ozone layer. The system also qualifies for a one-time energy rebate from the local utility's Energy Smart Design program.
Fred Meyer is now in the process of planning how to eliminate the use of chlorofluorocarbons at all its stores. By January 1996, all production of CFCs will be banned, as mandated by the Montreal Protocol, the international convention governing the phase-out of ozone-depleting gases.
"We still have a lot of stores that have the R-12 and R-502 [CFC coolants], which we are phasing out during the course of remodels," Wright said.
The refrigeration system at the new store includes compressors manufactured by Carlyle Compressor, Syracuse, N.Y., and Genetron AZ-50 coolant, a mixture of two HFC gases, known as R-507, manufactured by AlliedSignal, Morristown, N.J.
"Primarily, we're excited with the results of the AZ-50 and the reduction of horsepower because it gives us a little more leverage with our design," Wright explained. With the added efficiency of the new system, future stores may be able to reduce the number of compressors required, yielding even more savings in equipment costs and floor space.
"We feel, environmentally, we're moving in the right direction, and we're able to then reap the benefits of using less power, saving our own company money with the energy savings."
The refrigeration system at the Camas store today is not the one the chain originally envisioned when work on the design was begun by Wright and Dick Byrd of Tyler Refrigeration, Milwaukee, Ore. Initial plans called for use of R-22 coolant and single-stage compressors. But tests indicated that R-507 coolant and two-stage compressors could cool freezer cases at a mid-range power level, rather than running at full tilt. While the original plan with R-22 called for single-stage compressors to operate at 45 horsepower, the new system called for two-stage compressors to run at 25 hp, resulting in energy savings.
The ability to deliver cooling power at a lower energy level is attributed to R-507's high cooling capacity and to a subcooling function inherent in two-stage compressors, a newer generation of equipment that entered the marketplace around 1990, explained a refrigeration engineer. "The two-stage cooler allows you to use the first-stage pressure of the compressor to drive a subcooler. What that does, in effect, is improve the efficiency of the compressor."
While a single-stage compressor raises the pressure of vapors in all eight cylinders, a two-stage compressor first raises the pressure level in just four cylinders. "That intermediate pressure is what drives the subcooler" for freezer cases, he added. "You've got an industry that's been relatively happy with single-stage compressors and basic refrigerants," said an industry source. "They are now thrust into all kinds of change" with the advent of alternative refrigerants, the phase-out of CFCs and new compression technologies.
