Refrigerated Cases

Aug. 1, 2002
SUPERMARKET REFRIGERATION By Marc Sandofsky, contributing editor Supermarket refrigeration systems have gone through dramatic changes in recent years

SUPERMARKET REFRIGERATION By Marc Sandofsky, contributing editor Supermarket refrigeration systems have gone through dramatic changes in recent years with the emergence of technologies such as electronic and wireless controls, distributed systems, secondary coolant systems, rotary compressors, and environmentally friendly refrigerants. In an industry noted more for evolution than revolution, the speed and magnitude of this transformation is extremely noteworthy. While many of these changes have come about to satisfy environmental issues, manufacturers have never lost sight of their customers' desire to lower energy costs while increasing the reliability and longevity of their refrigeration equipment. After so many years of steady improvement, incremental changes might reasonably be expected. After all, refrigeration systems are made up of components supplied by often-unrelated manufacturers. Even if one vendor should make a breakthrough discovery, it stands to reason that will only affect one portion of the system, and the impact on the overall energy use will not be nearly so great. Recently though, refrigerated cases have experienced a quantum leap forward in performance. In some instances, manufacturers have been able to improve efficiencies by 25% or more through a combination of their own innovations and others provided by component suppliers. Because of the large amount of energy consumed refrigerating these cases, this performance improvement has the potential to yield a major reduction in the overall energy use of supermarkets. As an example of one technological improvement making an impact, Carl Roberts, a mechanical engineer for Zero Zone of North Prairie, WI, points to the PSC (permanent split capacitor) fan motors being employed today in Zero Zone's Maximizer cases. While other types of high-efficiency fan motors have been available for some time, reliability and cost issues have limited their use. "The old shaded pole motors were reliable and inexpensive," says Roberts. "Then, electronic fan motors were introduced, and they were very efficient but also costly. Now we have PSC fan motors. They provide the reliability of the shaded pole motors, and are almost as efficient as electronic fan motors, but their cost is lower so the payback is much faster." Roberts calculates that at eight cents per kWh, a PSC fan motor will typically pay for itself in 1.1 years. "PSC fan motors save money two ways. They use less electricity to operate, and they introduce less heat to the cases. Because less heat is put in the cases, less energy has to be spent on refrigeration to remove it." Roberts says the Electronic Lighting System(ELS) by Anthony International Zero Zone is using now provides savings in a similar fashion: it consumes less energy and gives off less heat, so there's less heat to remove. "It’s a highly efficient T-8 lighting system with a prism lens," he explains. Roberts adds that ELS lighting is a mature technology, noting that there were lighting ballast failures and even fires when high-efficiency lighting systems for refrigerated cases were first introduced. "It sometimes takes time to work out the problems with new technologies, so it's important that they be time-tested and mature. With PSC fan motors and ELS lighting, we're beyond the testing stage. We know they work." The most obvious energy-saving feature being used in Maximizer cases is a low technology type: insulation. Zero-Zone claims to provide the industry's thickest insulation while simultaneously providing the greatest usable interior space. While vendors have supplied many of the innovations Zero Zone is using now, the company has developed others on its own. For instance, Zero Zone spent a great deal of time developing its S-Coil, a high-efficiency evaporator with sinusoidal fins and smaller tubes that increase the velocity of the refrigerant. "This coil provides a temperature differential of as low as 3F," says Roberts. "That increases the COP by allowing the evaporator to run at a higher saturated temperature. At the same time, it reduces the refrigeration requirement. In the end, every BTU saved translates into reduced energy use." Roberts sees the new glass doors and frames being offered on today's refrigerated cases having the greatest energy saving potential. Although there are several manufacturers of these, he mentioned the Eliminaator by Anthony International of San Fernando, CA. He described the Eliminaator as having an argon-filled glass pack with panes of glass spaced further apart than normal. "The Eliminaator also falls under the category of a mature, proven technology," says Roberts. "Depending on the application, the payback from these doors can be less than one year, and it's often less than seven months." Anthony advertises the Eliminaator as the most energy-efficient door and frame system in the industry today, noting that the frame heaters, glass packs, and door rails are energy-free "in conforming environments." In other words, under the right relative humidity/temperature conditions, little or no energy will be used, although that is specific to the application and locality. The Eliminaator also has an enhanced door profile engineered to improve its utility, retrofits to many refrigerated cases, is reversible, and may qualify for energy conservation rebates, depending on the utility John Camp, vice president of sales for Anthony, explains that much of the savings with the Eliminaator is derived from no longer having to heat the glass. "Over the years, refrigerated case doors have required a large amount of heat to prevent condensation from forming on the glass. We've redesigned the door now so the glass is energy free. When a store has 150 doors, that amounts to a lot of energy savings." Camp described Anthony's innovations as coming from the "latest technology available." He points out that the company has re-engineered the door and frame to reduce the required heat. "In areas where heat is still necessary, it has been reduced. The heater loom wire in the frame has been moved to a specific location that minimizes the heating requirements." Camp says that energy savings vary depending on a number of factors. "The manufacturer of the case has a lot to do with its efficiency. For instance, airflow has a major impact. The case temperature is also very important. The savings also will vary according to the location, application, and user requirements." In other words, it is virtually impossible to establish a savings figure that would apply universally. Still, Camp says Anthony has measured savings of more than 25% on some installations put in 18 months ago. Among the customers for the Eliminaator, Anthony lists OEMs like Zero Zone, Tyler, Hill Phoenix, and Kysor/Warren. Zero Zone uses the Eliminaator in its Maximizer line to achieve one of the most energy efficient cases in the industry today. Perhaps the most notable user of the Maximizer is Wal-Mart of Bentonville, AR. With annual sales of more than $191 billion, Wal-Mart operates more than 2,600 discount stores, Supercenters and Neighborhood Markets, and more than 480 Sam's Clubs in the United States while employing 962,000 people. Internationally, Wal-Mart operates more than 1,080 stores and employs 282,000 people. Steve Burcham, director of mechanical services for Wal-Mart, points to the Maximizer's high efficiencies and large interior capacity as reasons for Wal-Mart using Maximizer cases. Burcham says they typically have to defrost the Maximizer only one time per day. "We terminate the defrost based on temperature, and use time as a failsafe," he says. "Based on past experience, we set the defrost time for one hour, but the Maximizer defrost usually runs for only about 45 minutes. That's a savings of 15 minutes per defrost." Burcham notes that the reduced defrost time extends product life and reduces shrinkage, which translates into additional savings. "With the Maximizer's large capacity, it merchandises very well," Burcham adds. "This allows us to cut down labor and stocking costs." Burcham has no knowledge of the actual savings attributable to the Maximizer, stating those numbers fall under the domain of Wal-Mart's energy department, but he believes the savings are substantial. Brookshire Brothers of Lufkin, TX, is one of Zero Zone's newest customers. That chain has some 70 locations spread out from Louisiana to Central Texas. Once family-owned, about 67% of Brookshire Brothers is now owned by employees. Almost all Brookshire Brothers stores sell Conoco gasoline. In fact, it is one of Conoco's largest distributors worldwide. Most stores also have "tobacco barns", which are set up in a drive-through configuration and sell all types of tobacco products, and sometimes beer. Brookshire Brothers construction manager John Newell says that Zero Zone low temperature cases are presently being installed into two new Texas stores, one in Montgomery, and the other in Livingston. He has no data yet on the relative efficiencies of the cases, but he is quite familiar with the Maximizer's energy saving features and expects the cases to meet his expectations. At the same time, Newell points out that with energy prices coming down in recent months, efficiency gains have become "academic" unless they are very substantial. "Don't get me wrong," he says, "we want all the savings we can get, but the energy reductions we see from more efficient equipment is dwarfed by the credits we're seeing on our utility bills as the cost of gas and electricity has come down." Newell expects additional energy cost reductions in Texas in the coming months since the state has only recently deregulated its electric utility industry. Despite Newell’s preference for lower utility prices over greater efficiencies, he was excited when talking about the results of an energy test Brookshire Brothers recently completed on its own. "We took two almost identical stores, 40 miles apart, and installed a heat reclaim coil in one, and left it out of the other. During the colder months, the gas bill for the store with heat reclaim was about $600. At the store without heat reclaim, it was $4,000. That's a savings of $3,400 per month, which is very meaningful."