Posted by: nik | February 4, 2013

Solar experiment du jour

Regular readers of the Energy Freakshow will remember my recent post about clearing snow off our solar array. After conducting that experiment I started to wonder to myself, “When is worth it?” The short answer is; anytime there is a possibility to harvest more energy. But of course that answer just brings up more questions. If the sun is coming out, will it melt the snow off anyway? Am I totally wasting my time on something that will happen automatically if I just wait? And how long do I have to wait?

Well today I got a chance to find some answers to these questions. We received a light dusting of snow last night–probably less than an inch.


Light Dusting of Snow

I setup my trusty ladder and got out my new telescoping rubber squeegee. It worked like a charm to clear off the layer of dry fluff. I got to the last couple of panels just as the sun was starting to appear over the horizon. I decided to leave 2 modules covered to find out just how quickly–if at all–the snow would melt away.

Here are the results. By 9am the ambient temperature had only risen to about 15F and the snowy panel was totally clear. Here is the power chart for the snowy panel (green line) and the control panel (red) directly adjacent to it:

power chart 2013-02-04

Snowy panel in GREEN, Cleared control panel in RED

As you can see, the dusting of snow definitely had an effect on power production as we would expect. The cleared panel is outperforming the snowy panel by about 38% up until 9am. But by then the snow has melted and the power production from the 2 panels track within about 7% of each other for the rest of the day. Here’s a photo of the array at 10:51AM

totally cleared by late morning

totally cleared by late morning

Conclusion: if there is only a light dusting of snow, the sun will do the necessary work.


  1. Your blog is growing in leaps and bounds–really appreciate the tabbed contents!

  2. […] The dust and pollen have been building up on the solar panels so I decided to see if it actually has a measurable impact. As my luck would have it, the 2 lowest modules in the array have a very similar power production history. The panels are guaranteed by the factory to produce at least 250-watts under ideal conditions (also known at Standard Test Conditions) to within +5% or -0%. That is a very tight tolerance but these two control panels have been producing within about 0.5% of each other.  This makes it easy to see relatively small changes in output due to various conditions. (See entry about Solar experiment du jour.) […]

  3. I love good data!!! -N

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