Friday, November 21, 2014

Snow on Solar Panels in Toronto

3 in 12 roof (14.0deg)
8 in 12 roof (33.7 deg)
It snowed two days ago - We got the normal 2" of snow while Buffalo got the 50"! (1.5m of snow, in 24hr).
A neighbor recently installed solar on their roof, and there is a bit of snow covering the panels.  The two photos below are to indicate the tenacity of snow cover over the panels.  Their roof slope is 3 in 12 (14.0deg from horizontal).  Ours is at 8in12 (33.7 deg).  As I mentioned, the snow arrived two days ago on a cloudy day.  Temperatures yesterday were below freezing all day, with night time temperatures about -9 deg C and daytime about -3 peak.  Some sun yesterday.  Last night was similar, and the sun came out earlier today so at 10am (when both these photos were taken) it has risen to about -3 C already, and sunny.  You can see the roof angle makes a significant difference.  On the steeper roof, the snow was actively shedding and within about 1/2hr after the photo was taken, pretty much all the snow had slipped off the panels.  It is great when snow slides of panels - it has a cleaning effect due to the slight rubbing.  I'll be monitoring the snow over the next few hours and days and months and updating this posting.  There are is a lot of knowledge and data out there on how much sun solar panels receive based on their angle and local climate, but less information on how the panels shed snow or dust, which appears to be a bit more complex and difficult to figure out (due to a lack of experience).  One thing I can suggest for low-slope panel installations: frameless panels such as these from Lumos (photo from
 - these will probably shed the snow a little more easily, I suspect - but no real data, as far as I can tell.  But I would want this kind, just for the improved appearance.  A number of manufacturers offer them.

1 comment:

  1. Another complicating factor is the level of dust/dirt in the environment. Anyone living in Toronto will attest to the fact that pristine white snow quickly acquires the city's standard issue grey suit as grit and grime are deposited. The layer of dirt seems to hasten melting under the sun, perhaps due to a combination of increased solar energy absorption and salt-induced lowering of the melting temperature.

    If so, the snow cover on a low slope panel in the city may be shed more rapidly than it would in the country under otherwise identical conditions.