[RE-wrenches] Clearing Snow From Modules

Sat Feb 4 08:15:14 PST 2017

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" <re-wrenches at lists.re-wrenches.org>

To:
"RE-wrenches" <re-wrenches at lists.re-wrenches.org>
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 <frenergy at psln.com [1]>
 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 [2] 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/

-------------------------

 [3] 

	 This email has been checked for viruses by Avast antivirus software.

www.avast.com [4]   

_______________________________________________
 List sponsored by Redwood Alliance

 List Address: RE-wrenches at lists.re-wrenches.org [5]

 Change listserver email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
[6]

 List-Archive:
http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html
[7]

 List rules & etiquette:
www.re-wrenches.org/etiquette.htm [8]

 Check out or update participant bios:
www.members.re-wrenches.org [9]

-- 

 [10] 

	 This email has been checked for viruses by Avast antivirus software.

www.avast.com [11]   

_______________________________________________
 List sponsored by Redwood Alliance

 List Address: RE-wrenches at lists.re-wrenches.org [12]

 Change listserver email address & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
[13]

 List-Archive:
http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html
[14]

 List rules & etiquette:
www.re-wrenches.org/etiquette.htm [15]

 Check out or update participant bios:
www.members.re-wrenches.org [16]

-- 
William Hoffer 

420 SE Wyers Street
P.O. Box 1823
White Salmon, WA 98672-1823
sunengser at gmail.com [17]

Links:
------
[1] mailto:frenergy at psln.com
[2] http://www.frenergy.net
[3]
https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient
[4]
https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient
[5] mailto:RE-wrenches at lists.re-wrenches.org
[6]
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
[7]
http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html
[8] http://www.re-wrenches.org/etiquette.htm
[9] http://www.members.re-wrenches.org
[10]
https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient
[11]
https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient
[12] mailto:RE-wrenches at lists.re-wrenches.org
[13]
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
[14]
http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html
[15] http://www.re-wrenches.org/etiquette.htm
[16] http://www.members.re-wrenches.org
[17] mailto:bhoffer at sunergyengineeringservices.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20170204/85e4e03e/attachment-0003.html>