Environmental Effort Enters 2nd Generation
June 2, 2008
Wal-Mart Stores new Supercenter in Las Vegas is a second-generation, high-efficiency (HE.2) store designed to use 25 percent less energy than a baseline Supercenter and significantly reduce the carbon footprint by lowering refrigerant charge by 75 percent. The Las Vegas store, which opened in March, is the one of five Supercenter stores to feature greener, more sustainable refrigeration systems using new Second Nature technologies by Hill Phoenix, a designer and manufacturer of commercial refrigeration systems based in Conyers, Ga.
“This technology was developed uniquely for Wal-Mart, and, as far as we know, it’s a first for the supermarket industry,” said Scott Martin, director of sustainable technologies for Hill Phoenix.
“Sustainable initiatives have long been a focus at Hill Phoenix and we’re excited to have developed this technology with Wal-Mart’s engineering team. This is further recognition of our efforts in creating sustainable technologies that are viable answers to industry issues and truly make a difference.”
Besides the 195,000-square-foot Las Vegas store, the other four HE.2 stores opening in 2008 are in Romeoville, Ill.; Wichita, Kan.; Garland, Texas; and Bernalillo, N.M. By combining the knowledge learned from the first-generation (HE.1) stores, the new stores mark advances in energy efficiency and reduction of greenhouse gas emissions, said officials.
“We’ve learned a lot since we opened our first HE.1 store one year ago and we are excited to put what have learned into practice with the HE.2,” said Charles Zimmerman, vice president of prototype and new format development at Wal-Mart.
REDUCTION OF REFRIGERANT, SYSTEM SIMPLIFICATIONAccording to Hill Phoenix, the two biggest advantages of the new system are the decrease in refrigerant charge and the overall simplification of the system.
The medium-temperature Second Nature system installed at Las Vegas uses different-sized modular chillers that refrigerate food products by using a secondary refrigeration loop combined with an advanced water-source heating, cooling, and refrigeration system.
In typical secondary refrigeration systems, a parallel rack is tied to chillers. In the new system, modular chillers are tied to individual compressors on the same glycol loop, eliminating refrigerant receivers, oil reservoirs, oil separators, oil floats, and other components. Having less oil and refrigerant in the system has enabled Hill Phoenix to reduce the medium-temperature refrigerant charge by 82 percent over Wal-Mart’s HE.1 stores and by 90 percent over a prototypical Wal-Mart store, Martin said.
The units also have variable-frequency drives that allow for precise capacity control throughout the rack. By producing only the refrigerant capacity each refrigerated unit needs, excess cooling is eliminated, officials said.
Another advantage of the technology is the utilization of a proprietary superheat management system. According to Martin, “This system uses the Hill Phoenix SmartValve™ Superheat Management system on the direct expansion (DX) side of the glycol chiller, which is another new application.
“In the past, we’ve used the SmartValve System in DX display cases, but with our new proprietary system, we’re now able to utilize SmartValve technology on the chillers in our Second Nature systems.”
Additionally, the Las Vegas store is the first HE store to include the addition of an advanced heat reclaim loop. Wal-Mart officials estimated the store will realize a natural gas savings of 10,000 therms per year utilizing the new system design. Heat reclaim condensers have been added to each refrigeration rack to recover the thermal heat rejection during the heating season.
The heat reclaim condensers are equipped with holdback valves to increase the amount of heat available for recovery. The fluid side of the heat reclaim condensers is piped in series to get small lifts in temperature at each refrigeration system rack.
For example, 71°F water enters systems B and D and exits at 78°; the 78° water enters system C and exits at 88°; the 88° water enters systems A and E and exits at 93°. The 93° water is sent to the coils in the rooftop units for heating areas of the store. A 22° temperature lift is achieved through the three-stage heat reclaim design.
DISTRIBUTED APPROACHHill Phoenix WeatherPac Distributed Systems are placed on the roof over the area containing the refrigerated and frozen food cases being serviced. The installation of the systems at the five new HE.2 stores marks the first distributed rooftop Second Nature secondary coolant systems installed in the United States. These systems, which replace the typical Wal-Mart outdoor mechanical center, serve to reduce copper piping and eliminate refrigerant charges associated with longer copper pipelines.
For example, there is approximately 11,350 lineal feet of copper refrigeration piping installed at the Las Vegas Wal-Mart. Previous stores that utilize a prototypical machine house utilized an average of 24,170 lineal feet of copper refrigeration pipe.
Several of the new HE.2 SuperCenters feature Georg Fischer engineered ABS piping that has been substituted in place of copper refrigeration pipe. The Georg Fischer system further reduces copper piping.
“Because copper mining and smelting are large producers of greenhouse gases in the production of copper piping materials, the use of engineered ABS pipe at several of the new HE.2 stores, as well as other Wal-Mart stores, has a significantly overall lower environmental impact than copper,” Martin said.
In fact, a recent study showed that the Hill Phoenix WeatherPac System installed at the new Romeoville store used 4,325 less feet of medium-temperature copper piping than the HE.1 project, and 7,575 feet less copper piping than typically found in a prototypical Wal-Mart store.
A SUCCESSFUL PARTNERSHIPHill Phoenix has been involved in store planning and design for Wal-Mart since 1988 and has created a variety of refrigeration and electrical distribution systems for the retail chain.
In 2006, the Sam’s Club in Savannah, Ga., became the first Sam’s Club to utilize Second Nature technology in medium-temperature systems using a secondary fluid composed of 35 percent aqueous propylene glycol and 65 percent water. By using Second Nature technology, the Savannah Sam’s Club reduced the initial R-404a charge by 34 percent.
The store also was the site of North America’s first installation of Second Nature Advance LT Refrigeration System that operates with R-744 (CO2) as the secondary heat transfer fluid.
For more information, visit www.hillphoenix.com, or www.walmartfacts.com.
Publication Date: 06/02/2008