Drake, Regarding snow cover being a "major problem", ...are you only referring to off-grid or also grid-tie systems? 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.
Here is a link to a great ongoing project that is assessing the effects of module tilt and snow cover..... https://solaralberta.ca/content/alberta-solar-performance-data Benn Kilburn SkyFire Energy Inc. 780-906-7807 > On Feb 4, 2017, at 9:15 AM, [email protected] wrote: > > Bill, > > 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. > > 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. > > 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. > > Drake > > > > ----- Original Message ----- > From: > "RE-wrenches" <[email protected]> > > To: > "RE-wrenches" <[email protected]> > Cc: > > Sent: > Wed, 1 Feb 2017 20:31:58 -0800 > Subject: > Re: [RE-wrenches] Clearing Snow From Modules > > > Drake > > 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! > > Bill Hoffer > >> On Wed, Feb 1, 2017 at 6:19 PM, frenergy <[email protected]> wrote: >> Drake, >> >> 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. >> >> 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. >> >> 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. >> >> 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. >> >> Bill >> >> Feather River Solar Electric >> Bill Battagin, Owner >> 4291 Nelson St. >> Taylorsville, CA 95983 >> 530.284.7849 >> CA Lic 874049 >> www.frenergy.net >> On 2/1/2017 11:13 AM, Drake wrote: >> Hi Wrenches, >> >> 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. >> >> 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? >> >> Maybe this would even work on a sunny day when the temperatures were colder? >> Could a module break? Anyone ever try this? >> >> Thanks, >> >> Drake >> >> Drake Chamberlin >> Athens Electric LLC >> OH License 44810 >> CO License 3773 >> NABCEP Certified Solar PV >> 740-448-7328 >> http://athens-electric.com/ >> >> >> >> >> This email has been checked for viruses by Avast antivirus software. >> www.avast.com >> >> >> >> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> List Address: [email protected] >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> List-Archive: >> http://www.mail-archive.com/[email protected]/maillist.html >> >> List rules & etiquette: >> www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> www.members.re-wrenches.org >> >> >> -- >> >> >> >> This email has been checked for viruses by Avast antivirus software. >> www.avast.com >> >> >> >> _______________________________________________ >> List sponsored by Redwood Alliance >> >> List Address: [email protected] >> >> Change listserver email address & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> List-Archive: >> http://www.mail-archive.com/[email protected]/maillist.html >> >> List rules & etiquette: >> www.re-wrenches.org/etiquette.htm >> >> Check out or update participant bios: >> www.members.re-wrenches.org >> >> > > > > -- > William Hoffer > 420 SE Wyers Street > P.O. Box 1823 > White Salmon, WA 98672-1823 > [email protected] > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/[email protected]/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org >
_______________________________________________ List sponsored by Redwood Alliance List Address: [email protected] Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/[email protected]/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
