Snow on solar panels (in Canada)

The reality of solar panels in the Canadian winter is that they face the same ice and snow that our cars, our houses and we, ourselves, face. How this affects you – the solar panel owner – depends on whether you have a rooftop installation or ground-mounted panels.

If you have rooftop solar panels, mounted on your house or barn, they will face the same challenges that the roof faces. The steeper the roof, the more likely the snow is to clear itself. If your slope is less steep, you might face the choice:

  • No solar power for a few months.
  • Clearing snow manually in somewhat precarious (slippery) circumstances.
  • Partially clearing with a ladder and whatever you can reach from the ladder.

Even if your roof is quite steep, you might find that snow does not always clear. Solar panels are generally black, so they absorb the sun’s heat and melt the snow – but that also depends on whether the snow completely covers the black surface. This is one reason that it might be worth climbing a ladder to remove at least the lower, more accessible parts of the panels

Given the uneven patterns of snow and melting, you might find that your rooftop panels generate power for certain parts of the winter and not for others.

I will relate my experience with ground-mounted solar panels, which will be of interest even if yours are roof-top mounted.

If you have ground-mounted solar panels, mounted with a tracking system, you *should* never have to worry about snow. Of course, “should” and “reality” often disagree on the details.

Our installation has this little platform that detects when snow is accumulating. It sends a signal to the position controls to raise the panels to their most upright position. The snow would of course slide right off and clear the panels.

Of course.

Snow never sticks.

Ha! You can’t escape the realities of winter that easily. It is already January, and already snow has stuck three times. Twice it was an inch deep.

In theory, that is not a big deal, because the sun will melt it and before long the snow is gone. But with no black surface, on a cold day, you could easily miss two-thirds of your generating time before the panels are mostly clear. And imagine if the panels are already upright facing the west from last night’s sunset, and are then covered with snow in the night. The sun won’t even shine on them directly until the afternoon.

In theory, that is not an issue, because the tracker should tell the positioning controls to rotate the panels to face the sun. But covered by an inch of snow and facing away from the sun (and let’s say the sun is weak that morning), several hours could pass before enough solar radiation breaks through the snow and kicks in the system.

So a broom is a worthwhile investment. I am short, but I can clear half the snow with a regular broom.

Below are a couple photos. The “before” photo shows the panels mostly covered in snow. This was the day that the snow was not an inch thick, but still mostly covering the panels. There was no sun that day; the sky was about as overcast as it could get. Each post was generating 54 watts per hour when I checked, which is about 1.1 percent capacity. Interesting that even with no sun and almost covered in snow they were generating a tiny amount of electricity.

I then cleared half the snow, as much as I could reach with my broom. Power generation jumped to 151 watts per hour, or about three percent of capacity. You can see here the first one cleared of snow, while the other remained covered.

Here is some interesting math:

Given the top of the panels had a bit more snow than the bottom, let’s say that the top was generating 24 watts, while the bottom was generating 30 (total of 51 watts).

After clearing the snow, the top was still generating 24 watts, but the bottom was generating 127 watts (151 – 24 = 127).

So clearing snow increased the efficiency of the panels by five times. The snow-covered panels were generating 20% of the power they would have been generating without snow cover. Clearing the snow was worthwhile – and if the snow had been thicker, as it had been on the two previous occasions, the benefits would have been even greater.

Sure, the sun would eventually clear the panels, but how much lost power generation would you miss out on in the meantime?

If I had cleared the top, I would have generated 270 watts per hour, or 5.4 percent of capacity, even on the most overcast of days. On A less-overcast day, with a thicker snow cover – as the two other days were – I could have increased my power generation from 20 watts to 2000 watts per hour by clearing all the snow.

Conclusion: I’m buying a longer broom.

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One Response to Snow on solar panels (in Canada)
  1. Darius
    January 16, 2012 | 8:57 am

    Thanks for your suggestions and comments on removing snow from solar panels.

    Darius
    UNFCCC consultant on climate change



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