A project near Slayton, Minn., will test whether the alternative energy sources can complement each other, increase reliability.
Wind power needs a breeze. Solar power relies on sun rays. And they don't always occur at the same time.
So a renewable energy developer is putting Minnesota's largest solar power array in the heart of the state's wind-farm region in hopes of answering a question:
Could one intermittent power source complement another and produce electricity more reliably?
Ecos Energy of Mendota Heights said Wednesday that construction of a 13-acre solar array near Slayton, in southwest Minnesota, will begin in April and should be completed by July.
Xcel Energy, the Minneapolis-based electric utility that serves 1.1 million customers in the state, said it has agreed to purchase all of the solar array's power, and will study how its output compares with that of three nearby wind farms.
Southwest Minnesota is home to more than 70 wind farms whose total output equals that of the state's largest power plant. But the turbines spin intermittently, with peak output generally in the spring and fall. In addition, wind often is stronger at night than by day.
Chris Little, director of development for Ecos, said he hopes the project answers the question: "Could you fill that gap with another energy resource that might complement the wind?"
The Slayton project, at 2 megawatts, is not big enough to fill the gap by itself. It should provide roughly the output of a single wind turbine, equivalent to the power used by 340 homes.
Even so, it will be the largest solar array in Minnesota, slightly bigger than the one that retailer Ikea has said it will install on the roof its Bloomington store this year.
Jim Alders, Xcel's director of regulatory administration, said Xcel has no current plans for more solar arrays among Minnesota wind farms, partly because solar energy remains more expensive that wind power.
"It is more fact finding and data gathering at this stage of the game," he said.
But Xcel isn't the only company looking at the possible benefits of co-locating wind and solar power generators. Last week, GE announced it would supply solar panels for a 23-megawatt solar farm to be built adjacent to a wind farm owned by renewable energy developer Invenergy in La Salle County, Ill. It will be the largest solar project in the Midwest.
Whether solar generation can fill in some of the peaks and valleys of wind power is an open question. Solar panels generate the most power on long days of summer, less in winter and nothing at night.
"Solar can be even more variable than wind," said Beth Soholt, director of Wind on the Wires, a wind energy trade group in St. Paul. "I think it will be very interesting to see what comes out of this."
Little said the Slayton solar project won't be on the same property as the wind farms, but it will be close enough to test whether there's a benefit to locating two renewable energy sources near each other. One potential savings of such an arrangement is that only a single connection might be needed to the power grid, he said.
"You could bring on more renewable energy without enhancing the transmission system in the rural parts of Minnesota," he said.
But the data analysis probably will take several years.
The terms of Xcel's 20-year power purchase agreement were not disclosed. But regulatory filings suggest that the project will cost about $7 million to build, with $2 million covered by a grant from Xcel's Renewable Development Fund. The state-mandated fund gets its money from utility ratepayers.
Ecos Energy is a sister company to Outland Energy Services of Canby, Minn., which operates and maintains wind farms. It proposed the solar project in 2008, near Jeffers, Minn., also in southwest Minnesota, but transmission lines in that area couldn't handle it.
That left the fate of the project uncertain for about three years, as the developer looked for a new site. During the delay, the price of solar panels dropped significantly, helping to cut the project's cost by 50 percent, regulatory filings say.
The chosen location, Slayton, population about 2,200, is served by Xcel, and the solar-generated electricity will go directly on the utility's local distribution grid.
Unlike other utility-scale solar projects, Xcel will buy all the power from the Slayton solar array. By contrast, Ikea plans to use most of its rooftop solar power in its store.
David Shaffer • 612-673-7090