There's snow on my modules!

Ahh winter!  Cold, snowy and diffenetly less sun.

In December the most power I had generated was 9.39 Kw, while the worse day was .106..just enough to light a 100 watt light bulb for 1 hour.  Toronto winters can be dull!.

Power generation was not great but considering it is winter and there is less light up here in the northern hemisphere; I can’t complain.  It has been less sunny than last year, but then again last year we had an exceptional winter; in fact I can’t really remember it as winter so much as a prolonged slightly colder fall with lots of sunlight. Yes this is Canada, but our weather in Toronto is moderated by Lake Ontario. The lake retains the heat from the summer for quite some time.  We don’t get much snow up on our side of the lake unlike Buffalo N.Y or Niagara Falls.  This is called the lake effect....and of course there is climate change to blame as well.  But what does this have to do with generating solar electricity?  Not much really aside from the fact that when it does snow, the snow can sit on the modules for some time, especially when it is very cold outside.  Some electricity will be generated depending upon the coverage, depth of snow and the amount of sun hitting the panels.  The cold temperatures also make the generation of power from the modules more efficient than at much warmer termperatures.  

The other aspect which is a factor to consider, is what happens when the panel is only partially covered with snow.  If you have a an Optimizer that would help because that panel will not affect the rest of the string, however if you do not, the snow on just the one panel will affect your entire string and reduce your total energy harvest.  

Random patches of snow covering the panels

I have noticed that my Solaredge installation is doing quite a bit better in some cases than a 10 kw Powerone install a few kilometres away.  For example today (Jan 2 at approx. 4 pm) the 10 Kw install has generated a total of 398 Whr of electricity while my 6.24 Kw system has generated 2.42 Kw. I really don't have an explanation except possible there is a lot of snow on the panels.   I have also compared my system to a 5.5 Kw system in the neighborhood and during sunny summertime it is generating more power.  Remember, I have an “inefficient” install. That is, I have panels on the West, South and East gables of my house.  But the inefficient approach works efficiently in this instance for a number of reasons I suspect.  Some of my panels are facing sunlight at some point in the day when there is sun or intermittent cloud. Panels that are partially covered in snow don’t bring the whole string down because of the Optimizer, so I produce power most of the time. My roof has different angles so while one side may have snow on the panels that other side doesn’t.  So I get a benefit.  Mind you it is a small benefit compared to having a completely south facing system but at least over the 20 year contract, there is some payback.

Meanwhile, up here in Canada, in the wintertime you would not want to depend upon solar to handle all of your energy needs.