Wal-Mart's 'greenest' store devours 45% less energy

Retail giant Wal-Mart today opened what it called it most energy efficient store ever - one that will use up to 45% less energy than its current Supercenters.

The building, in southwest Las Vegas, is engineered specifically for the region's desert climate, Wal-Mart said. Specifically, the store has heat-soaking floors that will help cool the 210,000-square-foot store's interior and pipes that run through the concrete floors every six inches, Wal-Mart says.

The pipes carry cold water from indirect evaporative coolers on the roof and keep the floor temperature at 67 degrees to 68 degrees. The system, which Wal-Mart calls an HE.5, reduces the temperature of water naturally by pumping it through roof-mounted cooling towers then runs the cold water underneath the retail floor to cool the shopping area. Unlike a typical retail store that needs up to 40 rooftop units to heat and cool the building, the HE.5 uses only 10 air handling units that bring in fresh outdoor air to maintain air quality. The reduction in rooftop units considerably reduces noise, raw materials and maintenance costs, Wal-Mart says.

The cooled water is also circulated to the water-source format refrigeration system to chill grocery and freezer cases. Even in the extreme desert climate, the store will stay cool and comfortable for customers and associates while saving energy.

Because water has approximately four times the heat carrying capacity of air, all of Wal-Mart's high efficiency prototypes were designed to use water for transfer between systems. The HE.5 store's indirect evaporative process is an even more efficient use of water that also optimizes electricity use.

Like most Wal-Mart stores, waste heat from the refrigeration system is used to heat domestic hot water for restrooms and kitchen areas. Nationwide, approximately 70% of the hot water needs for Wal-Mart Supercenters, Sam's Clubs and Neighborhood Markets are generated this way, saving enough energy to provide hot water for more than 30,000 U.S. homes per year, Wal-Mart says.

The store makes extensive use of LED lighting as well. LEDs last three to four times longer than fluorescent bulbs; stay cooler, which reduces the cooling load on the cases; perform better in cold environments; regenerate when turned off and contain no environmentally harmful mercury. The life span of LED lights is projected to be at least 10 years beyond conventional fluorescent lighting, which allows for a significant reduction in maintenance costs. LEDs with motion sensors use 70% less energy than industry standard fluorescent bulbs and can lower a Supercenter's overall energy use by approximately three percent, Wal-Mart says.

Wal-Mart execs told the Las Vegas Reviewjournal.com that the new energy conservation system will pay for itself through lower power bills within four years. Wal-Mart technicians will be monitoring the cooling and lighting systems at the new store remotely through computers in Bentonville, Ark.

The company will share data with the Department of Energy, the National Renewable Energy Lab in Denver and the University of California, Davis, the report said.

Layer 8 in a box

Check out these related stories:

Department of Energy shines $14 million on solar energy projects

GAO shines harsh light on advanced energy technology research

Department of Energy illuminates $21 million on advanced lighting research

General Motors turns down the heat, saves millions

Join the Network World communities on Facebook and LinkedIn to comment on topics that are top of mind.

Copyright © 2008 IDG Communications, Inc.

SD-WAN buyers guide: Key questions to ask vendors (and yourself)