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Snow and Grid Tied Solar Electric System Production

Canadian winters are synonymous with snow so it is important that consideration be given for the effects of snow on winter and year round energy production from solar electric and solar thermal systems.  Although clearing the snow from a solar array can help you squeeze a few more kiloWatt-hours (kWh) from your solar PV system, this blog entry will hopefully prove to you that this isn’t worth the hassle or the risk!  We do not recommend that any of our customers get up on their roof to clear the solar modules (panels) of snow during the winter months – this is extremely dangerous and not necessary.

With a grid-connected solar electric system, the total annual energy production from the system is most important.  The majority of the energy produced by a solar electric system in Canada is produced from March to October.  Lost energy production due to snow during the darker months of November to February is not as important.

With all that said, solar electric and solar thermal systems will actually clear themselves of snow!  There are a number of factors that affect when and how quickly this will happen such as:

  • ambient temperature – the warmer the better
  • amount of sunlight (insolation) – the snow isn’t usually cleared on a cloudy day but the energy production from a cloudy winters day is negligible anyways
  • angle and orientation of the solar array – the steeper the angle, the quicker the snow clears; facing directly South or slightly West of South helps with snow clearing
  • solar module backing colour (dark or black modules will get hotter) – black solar modules might clear snow faster but solar modules actually produce less energy when hot, more when they are cold so their are tradeoffs here
  • How much snow is on the modules – the sun can penetrate a couple of inches of snow to heat up the modules but penetrating through 6 inches of snow or more is less likely – a big dump of snow might stick to the modules until the wind blows some of it off or until warmer weather moves in

 

To help illustrate this point, we recorded a time lapse video showing the snow clear from our Calgary office’s solar array after a snow storm blew through.  The roughly 6cm of snow was cleared by 2:30pm the day after the snow storm.

 

 

The solar array in this case is at 35 degrees, which is a good angle for year round production while limiting the ‘sail’ affect and structural concerns of a more upright solar array. This system uses Enphase Energy microinverters which allow for energy monitoring of each individual module.  We can see the effect of the snow cover on the bottom of the solar array reflected online.  The photo and the monitoring screen shot both show conditions at 1:15pm the day after the blizzard:

 

Solar PV snow melting

 

Solar PV snow melting Enphase monitoring

Any questions?