Monday, November 29, 2010

Effect of Partial Snow Cover on PV Panel Output

This is a quick test to see how much a thin layer of snow covering a part of a PV panel effects the output.

In other words, should you bother to get out there and clean off the PV panels when they are only partly covered by a light snow?

We had a snowstorm yesterday that covered all the panels with about an inch of snow.  By mid morning today, the tops had cleared off, but the bottoms still had the inch of snow.

I was curious how much this affected the output, so I cleared off 5 of the panels and left the other 5 with the snow on them.  Like this:

Half of panels cleared, half with partial snow cover.

  The effect of power output is shown below:

The effect is pretty dramatic, the panels that were cleared of snow are producing nearly ten times as much power as the uncleared panels. 

While its certainly true that only a small amount of shading can cut a PV panels output considerably, I was a bit surprised by this in that snow lets a lot of light through.

So, I guess the moral is -- get out there and clean off those panels!

All the details on this test here...

All the details on the PV system here...


Note - the reason that the panel report above does not show the 5 cleared panels on the left and the 5 snow covered panels on the right is that apparently the panel map I turned into Enphase had some panels in the wrong position -- have to send them a new map.
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