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By Samuel R. Avro on Feb 26, 2012 with 13 responses

How Not To Go Solar

On a recent trip to Canada, I passed through Kingston, Ontario — home to Canadian Forces Base Kingston (CFB Kingston). A solar power installation just off the roadway — inside the perimeter of the base — caught my attention. Unfortunately, the reason it captured my attention was because the solar panels looked like the side of a trash can.

The picture tells the story.

dirty-solar-panels

Look at the contrast between the above photo (click to enlarge) and the one of clean solar panels below.

So how much can unmonitored and dirty solar panels affect output? A study conducted for the U.S. Department of Energy suggests that unmonitored solar panels can degrade by up to 10% in a year, and according to another study from the National Renewable Energy Laboratories (NREL) “the reduction in power from shading half of one cell is equivalent to removing a cell active area 36 times the shadow’s actual size.”

According to Google, when they cleaned their flat solar panels 15 months after installation they noticed its output double overnight. Eight months later it went up 37% after the panels were cleaned once again. The Google study did note, however, that “rain does a sufficient job of cleaning the tilted solar panels,” so perhaps the fine folks at CFB Kingston are just waiting for a good rain.

  1. By Russ Finley on February 26, 2012 at 12:36 pm

    That guy needs a better way to clean solar panels …

    Seattle has some of the cleanest solar panels around, which is a good thing considering that we average four sunny days a month for about eight months in the winter ; )

    Although it would probably be a good idea to clean them at least once a summer when we get most of our sunshine.

    Solar panels require maintenance. My guess is that the window washing industry will benefit from this.

    This is also why a home designed to optimize the use of solar should facilitate the cleaning of the panels with a roof slope that isn’t too steep, along with anchors for ropes, and paths between panels for access.

    Most people don’t hire window washers today. This would be an added expense and hassle, like oil changes on a car.

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  2. By josephdietrich on February 26, 2012 at 1:28 pm

    Uh, those look like hot-water thermal solar panels (see the pipes), while both the studies you cite and the Google blog post talk about photovoltaic panels. Those are different beasts. It seems to me that thermal panels would be far less susceptible to dirt and grime (although I would expect some level of albedo).

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    • By Robert Rapier on February 26, 2012 at 1:39 pm

      It seems to me that thermal panels would be far less susceptible to dirt and grime (although I would expect some level of albedo).


      I have a solar hot water heater, and I have heard the numbers, but you definitely lose efficiency as the dirt builds up. It is recommended to clean them every six months.

      RR
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      • By josephdietrich on February 26, 2012 at 1:47 pm

        Thanks Robert. I was curious about that.

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    • By Samuel R. Avro on February 26, 2012 at 3:03 pm

      Fair point. Most of the studies on the subject of efficiency loss I could find were for PV, but as Robert mentioned, solar thermal will also be affected by dirt — and especially crusty dirt and grime that cover the panel in the case of CFB Kingston — and should be cleaned every six months (more or less, depending on the specific area and case).

      The main point of this post was to highlight something that goes under reported — namely, that projected output is only as good as the maintenance that goes into the project in order to keep it going at a high level of efficiency.

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  3. By Maury Markowitz on February 26, 2012 at 5:32 pm

    Older solar thermal systems often used enclosed boxes similar to greenhouses, and are highly susceptible to condensation. I believe that is what is effecting these panels. I have seen this installation, but it was long enough that I don’t really recall. Many systems here in Toronto, like the system on the Post Office on Oakwood or the building at the top of avenue road show this problem. Modern evacuated tube systems do not have this problem, are more efficient and generally cooler too.

    Now speaking of bad installs in Kingston, there’s a microFIT on the main route from downtown to the 401 that looks terrible. Panels everywhere, no pattern, Ugg.

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  4. By Bert Beirinckx on February 27, 2012 at 3:42 am

    You might want to take the chimney in the background into the equation… 

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  5. By Mike on February 27, 2012 at 9:59 am

    Youre trying to compare apes and oranges. The first, supposedly dirty panels are solar thermal panels while the “clean” ones are photovoltaic. hot water ie thermal modules are not impacted in the same way PV modules are , in fact they are minimally impacted. A misleading article

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    • By Anatoli Naoumov on February 27, 2012 at 12:09 pm

      From the photo we do not even know if the collectors (and these are indeed solar thermal collectors, not solar PV panels) are dirty. Commonly collectors are covered with low reflective glass, which the unaware author of this article confused for dirt.

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  6. By Moiety on February 27, 2012 at 10:16 am

    There used to be a alrge bank of solar PV cells in the company that I used to work . These were only cleaned once every six months despite a large marine population of the avian variety. Efficiencies were not affected much over that period.

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  7. By Deb French on February 27, 2012 at 1:31 pm

    I’d pull the article until the actual facts on this installation are researched adequately.

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  8. By Ralph on February 28, 2012 at 12:51 am

    Good old natural rain must help some…. Also, I wonder how much of the particulates are from gasoline, coal and oil pollutants? As more consumer owned solar rooftops are put into place, the less cleaning they may need. Also, as far as efficiency, most warranties are for 25 years, what would the output of the panels be at 35 or 40 years? I know there are some pretty old sources out there still producing electricity from sunshine for free, but what is the actual “lifetime”, even at a lower efficiency?

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  9. By S'toon on May 17, 2013 at 1:03 pm

    I’ve been posted to that base, and others across Canada. Those aren’t photo-voltaic cells, they are solar water heating, which the Canadian Forces have been using since the ’70s. Believe me, the water gets HOT. I’ve been scalded.

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