Polar Energy, continued

All Together Now

If one solar application is good in northern climates, two or more together can be even better. At Concordia University in Montreal, the new John Molson School of Business is making the most of solar in a large, cold-climate building.

The brainchild of Andreas Athienitis, scientific director for Canada’s Solar Buildings Research Network, the school integrates both photovoltaic and solar thermal technologies into its siding. As they generate electricity, the PV panels also capture heat. While fans blow warm air into the building, they cool the panels and make them operate more efficiently.

On the other side of the North Atlantic, University of Oslo physics professor John Rekstad is exploring boreal applications of solar thermal panels that produce domestic hot water and space heating—and look pretty, to boot.

“Short days and a sun only a few degrees above the horizon make it more feasible to place the collectors on a south-facing façade rather than on the roof,” says Rekstad. To enhance the aesthetics of such solar-paneled walls, he’s developing plastic collectors that come in a variety of colors.

“Our ambition is to [help] customers see solar thermal as a solution that is beneficial for them,” he says. “Hence, one needs to make solar systems appealing and ‘sexy.’”

Colorado inventor Sam Weaver is capitalizing on multiple applications, too. Founder of Cool Energy, Inc., Weaver is about to beta test a third-generation prototype of a system that uses sun-warmed mineral oil for space heating in winter, and for driving an electricity-generating Stirling engine during the off season. The system is ideal for northern climates, Weaver says, because that’s where demand for heat in winter and electricity in summer best balance out.

ICON, the U of M’s award-winning entry in the U.S. Department of Energy’s 2009 Solar Decathlon, takes yet another innovative approach to off-season solar heat. The student-designed and -built demonstration home uses excess solar hot water in summer to run a dehumidifier that cuts the need for air conditioning in half.

For ICON, heating and cooling are just the beginning. With passive solar, hot water and PV also part of the picture, this high-latitude house is literally run by the sun. In fact, it proved a net energy producer during the competition in Washington, D.C., this past October.

What makes ICON work so well? Solar integration team leader John Quinnell, a mechanical engineering graduate student, has a short answer that would make a good maxim for anyone hoping to exploit the sun’s energy at high latitudes.   

“Thinking,” he says. “Thinking about the climate and the solar resource.”

As reasons for letting go of conventional fuels grow, many expect solar energy applications in northern climates to grow as well. Exactly where and how quickly will depend on many variables, including the trajectory of technological advance and the availability of incentives to overcome innovation inertia.

But one thing seems clear: As sure as the sun will rise tomorrow, the future of solar looks bright for the northland.

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MARY HOFF is a science communicator specializing in the environment, natural resources and sustainability. A regular contributor to Minnesota Conservation Volunteer, she has also published in Science World, PLoS Biology and National Geographic Explorer, and has written nearly two dozen books for children on environmental and natural history topics.

Cold Calculations

ICON Solar House

Photo: Stephano Paltera

Does solar make sense in northern climates? Ask students who participated in the 2009 U.S. Department of Energy’s Solar Decathlon, and you’ll likely hear a resounding “yes.”

The biennial decathlon challenges 20 preselected teams of college students to build the most energy efficient and attractive solar home as rated in 10 categories. Of the top seven finishers in the 2009 event, five came from north of the 40th parallel, beating out participants from stereotypically sunny spots like Arizona and Spain. Among them: the University of Minnesota’s ICON solar house, with top ranking in both engineering and lighting design.

“What many people don’t know is that we have a great [solar] resource here in Minnesota,” says mechanical engineering grad student Josh Quinnell, who led the project’s solar integration team. “The biggest challenge here is that we have high heating loads. It isn’t the fact that we can’t collect enough solar energy. We can collect as much as in most places. The downside is, we need a lot in winter.”

The ICON is truly iconic of every aspect of cold-climate solar energy capture. The overall look emphasizes not only aesthetics but also passive solar benefits. The windows are strategically placed and shaded as needed to maximize winter light and heat gain (including what Quinnell estimates is an almost doubling effect of reflection from snow cover), while keeping out intense rays in the summer months. Building-integrated photovoltaics capture solar energy while providing structural integrity—and cleverly give off just enough heat to melt snow from their surface in winter.

To optimize photovoltaic output, the team used energy modeling software to calculate the perfect pitch for the roof that would meet competition parameters and also soak up bountiful sun in winter. Solar thermal flat-plate collectors on the south roof and walls heat a water-glycol mix, which in turn provides superheated water for radiant floor heating, domestic hot water, and interior-cooling dehumidification in summer.

The winning edge for the ICON solar house, says faculty advisor Ann Johnson, was its emphasis on being a good fit for the local climate all 12 months of the year. The house also scored high by including a broad spectrum of solar energy inputs. Topping it off was exceptional insulation to trap heat inside in winter and keep it outside in summer.

“That really was the key. You can’t design a house to just be insulating in the winter because then it doesn’t perform well in the summer,” says Johnson. “The students looked at it over the 12-month year and tried to achieve a balance.”