<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Drake, </div><div>Regarding snow cover being a "major problem", ...are you only referring to off-grid or also grid-tie systems? </div><div>For off-grid, I'd agree, however, for grid-tied systems around here (Edmonton, Alberta) we've found that snow is not a great concern, when considering its effect on a systems annual production. </div><div><br></div><div>Here is a link to a great ongoing project that is assessing the effects of module tilt and snow cover.....</div><div><a href="https://solaralberta.ca/content/alberta-solar-performance-data">https://solaralberta.ca/content/alberta-solar-performance-data</a><br><br><div><span style="background-color: rgba(255, 255, 255, 0);">Benn Kilburn</span><div><span style="background-color: rgba(255, 255, 255, 0);">SkyFire Energy Inc. </span></div><div><span style="background-color: rgba(255, 255, 255, 0);">780-906-7807</span></div></div></div><div><br>On Feb 4, 2017, at 9:15 AM, <a href="mailto:drake.chamberlin@redwoodalliance.org">drake.chamberlin@redwoodalliance.org</a> wrote:<br><br></div><blockquote type="cite"><div>Bill,<br><br>The thermal shock is what I'm concerned about. On the other hand, snow covered modules can melt out with ice covering part of the module and hot sun on the exposed portions. <br><br>What is the effect on the border between ice and illuminated module? There could easily be a 70 degree or greater temperature differential in a fraction of an inch. There must be pretty good tolerance for thermal shock. <br><br>It does appear that Bill Battagin has washed snow off modules without noticeable negative effect. Due to your warning, I'm hesitant to do it. It would be good if some testing were done on this, as snow coverage is a major problem.<br><br>Drake <br><br><br><blockquote><br>----- Original Message -----<br><div id="origionalMessageFromField" style="width:100%;background:rgb(228,228,228);"><div style="font-weight:bold;">From:</div> "RE-wrenches" <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>></div><br><div id="origionalMessageToField" style="font-weight:bold;">To:</div>"RE-wrenches" <<a href="mailto:re-wrenches@lists.re-wrenches.org">re-wrenches@lists.re-wrenches.org</a>><br><div id="origionalMessageSentField" style="font-weight:bold;">Cc:</div><br><div style="font-weight:bold;">Sent:</div>Wed, 1 Feb 2017 20:31:58 -0800<br><div id="origionalMessageSubjectField" style="font-weight:bold;">Subject:</div>Re: [RE-wrenches] Clearing Snow From Modules<br><br><br><div dir="ltr">Drake<div><br></div><div>Thermal shock is not a good thing at all for modules and it is the way we verify test them for life cycling and bankability. Yes I saw someone on a hot day during a solar drag race hit the modules with a fire extinguisher to cool them down in the hot sun and they survived for the race. Unknown what damage to the longer term life of the module can be done with all those layers with very different thermal coefficients of expansion is hard to say. By the way they still lost to our team because we had a superior variable drive transmission! I am most concerned about tempered glass, especially since they are getting thinner and thinner these days. I have seen tempered glass break much easier then you would think, almost for looking wrong at it or a very small insignificant pressure in the wrong spot. Happens randomly every once in awhile on the module manufacturing floor. Of course modules are thermally cycled as part of their qualifications and also for Bankability, but you would never risk putting these modules into field service cause you just do not know how much damage was done...even if they still meet specifications. As long as you are washing modules with a water temperature that is close to the module temperature you should be OK. IMHO modules may be cheap put not cheap enough to risk thermal shock, so they should still be treated with the respect and care they deserve as a product meant to last 20 years at 80% output! If a module manufacturer knew you thermal shocked them washing them off I am sure that they would find a clause in their warranty to weasel out of it!</div><div><br></div><div>Bill Hoffer</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Feb 1, 2017 at 6:19 PM, frenergy <span dir="ltr"><<a href="mailto:frenergy@psln.com">frenergy@psln.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div>
<p>Drake,</p>
<p> I am no expert, BUT, about a year ago I covered an
older not-in-service PV with a foot of snow on a 25 degree day and
then hooked up a hose to a hot water faucet. With a pistol grip
sprayer I directed a solid stream of hot water at the PV. It only
took a second for that hot water to reach the PV's glass, no doubt
cold from the snow. I kept it there in one area for about 30
seconds, slowly widening the area of 'impact', much of the snow
melting of course.</p>
<p> Afterwards I carefully visually inspected the PV (it
was an older Kyo) and could not find/see anything out of the
ordinary, still tested to label specs (slight de-rating due to
age) when placed in direct sun.</p>
<p> Another note, several times I have sprayed cool tap
water (around 45 degrees, F) on my in-service array on my shop to
eliminate the snow. It's a 12:12 pitch but it still took a good
15 minutes to clear it off. The array is 22, 60 cell PVs. I have
not any decrease in performance to date.</p>
<p> Conclusion? None really, I can't imagine 'washing'
snowy PVs off with cool water could do any harm. Whereas the hot
water test, intuitively probably not smart.</p>
<p>Bill<br></p>
Feather River Solar Electric <br>
Bill Battagin, Owner<br>
4291 Nelson St.<br>
Taylorsville, CA 95983<br><a>530.284.7849</a><br>
CA Lic 874049<br><a class="m_-2947649340024530204moz-txt-link-abbreviated" href="http://www.frenergy.net">www.frenergy.net</a>
<div class="m_-2947649340024530204moz-cite-prefix">On 2/1/2017 11:13 AM, Drake wrote:<br></div>
<blockquote>
Hi Wrenches,<br><br>
We have a lot of border line temperatures here that will not quit
melt
the snow off an array. We can lose production on a semi sunny, 28
degree
day. During such a day, I was looking at my frost free water
faucet and
my array. Humm, I could easily hose the snow off.<br><br>
Is there a reason not to do that? Any ice or slush would not
present a
problem. Is there a danger to the modules from doing that? <br><br>
Maybe this would even work on a sunny day when the temperatures
were
colder? Could a module break? Anyone ever try this?<br><br>
Thanks,<br><br>
Drake <br><br><a name="m_-2947649340024530204__MailAutoSig"></a>Drake Chamberlin<br><i>Athens Electric LLC<br>
OH License 44810<br>
CO License 3773<br>
NABCEP Certified Solar PV <br><a>740-448-7328</a><br></i><a href="http://athens-electric.com/">http://athens-electric.com/<br><br></a>
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