Solar-powered retail lighting

The new roof at the 10-year-old Whole Foods Market store in Berkeley, Calif., does more than protect the natural and organic products sold inside. Atop the new roof membrane, 2,860 sq. ft. of solar panels were installed to produce 33kW of electric power that is now the store's primary lighting power source.

The fuel cells turn the sun's energy into usable power transmitted by interconnected power modules. High-quality DC power is directly fed to the market's retrofitted interior lighting system. "We're the nation's first major food retailer to take advantage of solar energy as the primary lighting source," says Ron Megahan, regional president for Whole Foods Market Inc., Austin, Texas. The decision to install a solar-powered lighting system "made sense both economically and environmentally for the 3000 Telegraph Avenue store," Megahan says.

The Whole Foods chain of 125 supermarkets in the United States last year topped $2.3 billion in annual sales. The company, founded 22 years ago, is the top natural foods retailer in the world.

Like other California businesses, Whole Foods had watched its energy expenses rapidly spiral upward during the recent rise in the cost of electricity supplied by the state's electric public utilities. When it was time to re-roof the Berkeley store, utilizing energy from a renewable source like the sun to power its lighting appealed to Whole Foods management. The Berkeley store is approximately 26,000 sq. ft., the average size of the chain's units.

Three firms collaborated with Whole Foods to plan and implement the system. Princeton Energy Systems, King of Prussia, Pa., prepared the financial analysis and detailed the technology required for the project. PowerLight Corp., Berkeley, Calif., provided the solar tiles that are linked to power modules made by Nextek Power Systems Inc., Sacramento, Calif. The modules feed DC power to the store's retrofitted DC lighting system. Existing lighting fixtures were fitted with new ballasts from Nextek to handle the direct energy source.

"Typically, the electricity supplied to a store for lighting purposes is DC [direct current] that is inverted to AC [alternating current] and then back to DC," explains Patrick McLafferty, senior vice president of Nextek. "This results in a loss of up to one-third of the power, and because 30 to 40 percent of energy used by supermarkets and other stores goes to lighting, the loss of power is significant and expensive." According to McLafferty, his company's system to couple DC power directly to fluorescent or HID fixtures is 98 percent efficient.

Each Nextek power module generates 1000 watts (one kilowatt), sufficient to operate 16 two-lamp T8 fluorescent ballasts, McLafferty says. Energy not expended on running the store's lights is stored in batteries linked to the emergency and security lights. The system is designed to be blended into the local utility's power grid if the solar output isn't sufficient. "Daylighting and occupancy sensors work in conjunction with our technology, and together they give owners the best value and return on their investment in a solar power installation," McLafferty says. "A single-story supermarket that has generous roof space, not shrouded by surrounding high-rise buildings, is an ideal structure for this application."

Mark Bronez, vice president of sales for PowerLight, worked with Whole Foods and with Lunardi's, a family-owned and operated six-store supermarket company in the San Francisco Bay area. In May, Lunardi's completed a retrofit to light its Burlingame store using the same team that handled the Berkeley project for Whole Foods. "Previously, large rooftop solar energy systems had to be connected to the electric power of the building," he says. "Now, the connection is made directly to the lighting system, resulting in more savings to the owner."

Bronez points out additional benefits of a solar tile-covered roof: extension of the roof's life, lower roof maintenance, reduced heating and cooling loads and lower initial roof cost because less roofing insulation is required. The firm's PowerGuard photovoltaic roofing tiles are lightweight. "They weigh five pounds per square inch and can be installed on new or existing roofs," he says.

Retailers are showing increased interest in solar power for lighting and other energy uses. "There is less difference than most people would assume in the amount of sunlight needed to efficiently run a solar energy system," Bronez says. Areas of the country where utility-supplied electricity is relatively expensive, such as New York, New Jersey, California and Hawaii, are prime candidates for the direct DC connect system to power interior lighting fixtures. "We've completed installations in retailers' warehouses as well as manufacturing and office buildings," says Bronez.

Payback is calculated in years, depending on the size of the system. PowerLight offers assistance to customers to secure long-term financing from sources such as commercial banks and investor groups specializing in this market. Nextek's McLafferty advises that retailers can qualify for substantial tax credits and rebates, depending on their area's legislation. In parts of California, he says, a subsidy of up to $6 per watt can be applied for initial installations. Federal and state investment tax credits are also available. "Together, they can add up to 60 to 70 percent of the cost of a typical installation," he says.

McLafferty reveals that jobs similar to the Whole Foods Berkeley installation are pending with a major national big-box retailer, starting with three stores in California, and with two other large supermarket chains.

Lamps from any supplier will operate on the power supplied by the DC solar energy system, says Peter Kassay, vice president of engineering for Intrepid Lighting Manufacturing, a Bohemia, N.Y., lighting fixture maker. ILM, which often teams with Nextek and PowerLight, builds fluorescent fixtures adapted to Nextek's ballasts, which are approximately one-third smaller than typical ballasts.

ILM distributors service national retail chains. To date, Kassay says that retail customers include Sears Roebuck warehouses in the Southeast and Puerto Rico, P.C. Richards & Son stores, plus a discount chain, a multi-unit book store, and clothing and sporting goods chains. He applauds Nextek's technology as "a fantastic way to light a retail store." A new product in ILM's line developed for a King Kullen supermarket on Long Island is scheduled for prototype testing later this summer. Solar energy is becoming a viable alternative power source for retail lighting.





PROJECT FILE

whole Foods Market Inc.

Austin, Texas

John Mackey, president

Lunardi's

Burlingame, Calif.

Paul Lunardi, president

Analysis

Princeton Energy Systems King of Prussia, Pa.

David J. Smith, president

Solar Tiles

PowerLight Corp. Berkeley, Calif.

Mark Bronez, vice president/sales

Power Modules

Nextek Power Systems Inc. Sacramento, Calif.

Patrick McLafferty, senior vice president

Ronkonkoma, N.Y.

Dave Mandell, business development manager



Information in the Project File is provided by the retailer and/or designer.