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The new roof at the 10-year-old Whole Foods Market in Berkeley, Calif., does more than protect the natural and organic products sold inside. Atop the roof membrane, 2,860 square feet of solar panels were installed to produce 33 kilowatts of electric power that is now the store's primary lighting power source.
"We're the nation's first major food retailer to take advantage of solar energy as the primary lighting source," said Ron Megahan, regional president for Austin, Texas-based Whole Foods Market Inc., a chain of 142 supermarkets specializing in organic foods. The decision to install a solar-powered lighting system "made sense both economically and environmentally for that Berkeley store," Megahan said.
Like many other California businesses, Whole Foods had watched its energy expenses rapidly spiral upward during last year's rise in the cost of electricity supplied by the state's utilities. When it was time to re-roof the Berkeley store, using energy from a renewable source like the sun to power its lighting appealed to Whole Foods management. The Berkeley store is approximately 26,000 square feet, about average for the chain.
Three firms collaborated with Whole Foods to plan and implement the system. Princeton Energy Systems of King of Prussia, Pa., prepared the financial analysis and detailed the technology required. PowerLight Corp. in Berkeley provided the solar tiles that are linked to power modules made by Nextek Power Systems Inc. of Sacramento, Calif. The modules feed 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," explained Patrick McLafferty, Nextek senior vice president. "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." McLafferty says his company's system to couple DC power directly to fluorescent or HID fixtures is 98-percent efficient.
More Efficient Connection
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. Last year, 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 said. "Now, the connection is made directly to the lighting system, resulting in more savings to the owner."
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 DC direct-connect system to power interior lighting fixtures. "We've completed installations in retailers' warehouses as well as manufacturing and office buildings," Bronez said.
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 says 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 said.
This article originally appeared in Display & Design Ideas, a sister publication of Convenience Store News