Polar Energy, continued

Improving PV

As useful as solar heat and light might be, they can’t run a computer, wash a load of laundry or charge electric cars. To do that demands transforming sun energy into electricity—the work of solar photovoltaics.

Currently, less than 1 percent of the electrical power generated in Minnesota comes from the sun. But interest in solar photovoltaic technology is growing across the Midwest and in other northern places. Germany, which sees less sun than Minnesota, is a global solar PV leader, thanks to strategically placed government incentives. And in far-flung locations at virtually any latitude, solar power is often the technology of choice.

NREL far-north representative Brian Hirsch has helped install solar photovoltaic systems throughout Alaska, including, in Arctic Village, what he believes is the most northerly, tribally-owned, dual-axis PV tracking system in the world. “Numerous remote ‘luxury’ lodges for hunting and fishing clients, and remote cabins and homes off any central grid use photovoltaic systems,” he says. “Remote telecommunications, government applications and other niche uses are present throughout Alaska.”

Photovoltaics do face a few unique challenges in upper latitudes, nevertheless. Snow, for instance, can block sun from PV collectors as quickly as it can bury one’s car in a mountain of white. But installers contend that, with the proper angle, panels can easily shed the load once the sun shines. Short day lengths are also capable of dramatically limiting PV’s power during winter months.

At the same time, cold and snow can have some positive implications.

“One of the wonderful characteristics of a photovoltaic module is that it actually operates more efficiently when it’s cold,” says Tim Hebrink, lead research specialist in solar photovoltaics for 3M. “And snow is a wonderful reflector, so if your photovoltaic module is facing a snow field or a snow-covered flat roof and you get reflection off that snow, the photovoltaic module will produce more power because of the additional light.”

Hebrink and colleagues are working to develop a number of products to improve the efficiency and reduce the price of solar PV and solar thermal. Tapes, adhesives and reflective films could make the technology less expensive and more reliable—both of which will benefit northern applications. They’re also working on ways to even out supply and demand over time, targeting research on improving batteries, fuel cells and capacitors for storing energy.

Other innovations that stand to boost the application of PV technology in northern climates include trackers that permit PV panels to follow the sun through its wide summer arc. Solar collectors that trap energy from diffuse, as well as direct, light also help make the most of the long days. In a 9.1 megawatt solar energy farm fired up in October, Canadian renewable energy developer SkyPower and solar company SunEdison used thin film technology rather than conventional PV, in part because of its ability to capture indirect solar energy.

At the U of M, chemical engineering and materials science professor Eray Aydil is trying to perfect a solar PV shingle that performs better in cold climates than in warm ones. The shingle is already on the market, but Aydil hopes “to increase the efficiency and long-term reliability.”

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Uncommon Cold

How do you know how well that solar panel is going to perform once it’s attached to your roof, not to mention Minnesota’s unpredictable theater of seasons?

In the past, solar devices installed in the state earned their efficiency, durability and other ratings at testing facilities in milder climates. Recognizing that things meant to be used in cold climates should be tested in them, too, Mike Reese—director of the University of Minnesota’s West Central Research and Outreach Center—is establishing a northern climate testing ground for solar and related energy technologies.

Cold, snow and ice bring many challenges, so the testing facility will look at many parameters. For solar thermal systems, which rely on fluid coursing reliably through their veins, “there are questions about the impact of the temperature change on fittings and pipes and on the liquid itself,” Reese says, as well as with the glass and lens that bring light to bear on them. Solar photovoltaic systems could present weather issues not only with the panels themselves, but also with the inverters needed to convert direct current into alternating current for household use.

Among the systems Reese plans to test is one that produces both space heating in winter and space cooling in summer. “That’s a challenge in an environment like Minnesota, where [conditions are] going from one extreme to the other.”

Does solar energy fit our climate? “It does in certain applications,” says Reese. “We’re going to find out.”