Solar and the snow

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Solar is slowly but surely making its way further from the equator and into regions that might not be thought to offer significant solar irradiation.

While both technological improvements and increased acceptance have driven solar’s push into colder climes, plenty of challenges remain to operating a PV system in these environments. Not least among these is dealing with snowfall: keeping panels clear and able to absorb sunlight, ensuring the weight of snowfall doesn’t cause permanent damage, and many other issues.

Since snowy regions are new ground for solar installations, little data is available to help system operators make the best decision. Looking to remedy this, Sandia National Laboratories has begun a project, Snow as a Factor in Photovoltaic Performance and Reliability, to quantify the effects of snow on a PV system, conducting field research at four sites spread across the U.S.

Challenge and opportunity

A paper written as part of the project notes that thanks to its very high albedo, snow presents an opportunity as well as a challenge to solar, particularly in systems featuring bifacial modules. The paper, Performance of Bifacial Photovoltaic Modules on a Dual-Axis Tracker in a High-Latitude, High-Albedo Environment, published in the Proceedings of the IEEE PVSC-46 Conference, examines two years of performance data from experimental systems featuring bifacial modules on dual-axis trackers, located in Vermont.

These data show that the bifacial modules overall produced 14% more energy than monofacial modules, in addition to the estimated 35% to 40% boost provided by the dual-axis tracker. During peak winter months, the bifacial modules performed as much as 40% better than single-sided panels. The results also showed a 41% increase in energy yield for bifacial + dual-axis tracker, compared to bifacial fixed-tilt installation.

The study suggests a significant yield gain from dual-axis tracking thanks to the sun’s low angle in northern latitudes. These trackers, however, are generally thought too expensive in most settings, and the analysis does not take into account economic factors.

The study also found that low temperatures in the region increased the system’s operating efficiency, while slightly increased temperature, thanks to the rear side irradiance, as well as the high tilt angle and use of frameless modules, assisted with effective snow shedding.

“Our work suggests there is an underrecognized opportunity to deploy bifacial dual-axis tracking systems in regions of the world that see abundant snow in winter and are also experiencing significant growth in PV capacity,” concludes the paper. “It is also noteworthy that snow-covered terrain— unlike artificial substrates— adds no additional cost to a project and is constantly refreshed throughout the winter, thus retaining a high albedo for five to six months a year.”

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The February 2020 edition of pv magazine takes an in-depth at PV’s growth in northern latitudes, in Europe’s Nordic nations, and in the remote settlements of the Canadian Arctic. Click here to subscribe