This has been an issue on some of our systems, but strangely not most of
them. I have not figured out a correlation yet. We have dozens of pole
mount and roof systems that shed snow as soon as the sun comes out, and
then some that ice up and are a real mess all winter. The only
difference I seem to see is wind speed.
Has anyone ever tried insulating the backs of the modules in the
winter? (of course that would be removed in the Spring) Or what about
a black module backing that would pick up snow reflected light in the
winter, but not in the summer?
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 3/27/2015 11:11 AM, Kristopher Schmid wrote:
Ignoring the effect of roofing material friction and tilt angle, i
would surmise that the array being "open-backed" would reduce heat
build up and actually decrease the snow shedding ability.
On Fri, Mar 27, 2015 at 11:36 AM, Dave <[email protected]
<mailto:[email protected]>> wrote:
BTW Dan. I have designed and installed power sheds here in the
north with tilt up arrays using adjustable leg sets that allow up
to 80 degree tilt angles! Pretty ugly if it's staring you in the
face, but quite effective when the bottom of the array is directly
over the eave of the roof. Allow 18" or so distance from roof to
bottom of modules to allow the snow on the surface of the roof to
be cleaned occasionally with a roof rake. Adjustable legs will
allow experience to be your guide going forward on how much of a
tilt is needed (and tolerated appearance wise). Of course the wind
loads are severe with a design like this and must be managed.
Dave
*From:*RE-wrenches
[mailto:[email protected]
<mailto:[email protected]>] *On Behalf Of
*[email protected] <mailto:[email protected]>
*Sent:* Friday, March 27, 2015 12:00 PM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] Tilt Racking vs Roof Mount for
Shedding snow
My customers neighbor has 1.1k of 110W panels on a tilt up rack
set at about 45° (Some 20° from the roof). Her array pretty much
stayed clear all winter with minimal futzing. My customer has a
7.2k array (Four rows of six) in portrait, mounted on unirack
solar mount on an asphalt tile roof at around 45° (Off Grid), on
an unheated garage. My customers panels got a thin coat of ice on
the array early on that held some 12'' of snow all winter. We did
set it up so the bottom two rows were on their own CC and could be
cleared from the ground, but they never did totally clear. The
neighbor now wants to expand her system, is willing to build a
shed for the array, but wants me to elevate the array as far off
the roof as possible (and minimize costs). I'm working on my
diplomacey here. I suggested it might be a combination of factors
that contributed to my customers array not sheding, but the
neighbor insists it has something to do with the array being open
backed. I offered to put it out to the group for opinions. Thanks db
Dan Brown
Foxfire Energy Corp.
Renewable Energy Systems
(802)-483-2564 <tel:%28802%29-483-2564>
www.Foxfire-Energy.com <http://www.Foxfire-Energy.com>
NABCEP #092907-44
-------- Original Message --------
Subject: Re: [RE-wrenches] Tilt Racking vs Roof Mount for
Shedding snow
From: "Dave" <[email protected]
<mailto:[email protected]>>
Date: Fri, March 27, 2015 10:32 am
To: "'RE-wrenches'" <[email protected]
<mailto:[email protected]>>
Dan,
What do you mean by "tilt up racking". Would an example be a
rack that adds 15 degrees to a 5/12 roof? Good idea (as long
as wind load is taken care of) for cold snow country
(certainly for off grid) to get the tilt angle higher which
helps with snow shedding. BUT if it's super cold like this
winter here in northern New England nothing helps as much as a
snow rake.
On a side note. I had a couple of monitored grid tied systems
with second story roof top arrays that produced very little
power from January through second week of March. 80% less kWh
than similar first story roof top arrays where the homeowner
raked off snow. It was so cold that in one period this winter
that it did not get over 30 degrees F for 48 consecutive days
here, with many nights at 15 to 30 below zero. February was
the coldest on record (since 1886) with temps that were 15
degrees below average for the month. No snow shedding going on
at all.
On another type of array. My adjustable ground mount here set
at 90 degrees had a great winter as I regularly saw 1,750 to
1,950W out of my Apollo CC from a 1,440W array on sunny days
because of MPPT and the reflective bounce of sunlight off the
snow in front of the array. I never have to touch those
modules from mid November, when I tilt them to 90 degrees,
until after it stops snowing significantly (mid April usually).
Best,
Dave
David Palumbo
Independent Power LLC
462 Solar Way Drive
Hyde Park, VT 05655
802-888-7194 <tel:802-888-7194>
*From:*RE-wrenches
[_mailto:[email protected]_] *On
Behalf Of *[email protected]_
<mailto:[email protected]>
*Sent:* Friday, March 27, 2015 8:19 AM
*To:* RE-wrenches
*Subject:* [RE-wrenches] Tilt Racking vs Roof Mount for
Shedding snow
Hi Guys, I have a customer who seems convinced that tilt up
racking sheds snow better than conventional roof mounted
arrays (irregardless of angle or panel manufacturer). Anyone
else find this is true? Thanks db
Dan Brown
Foxfire Energy Corp.
Renewable Energy Systems
(802)-483-2564 <tel:%28802%29-483-2564>
_www.Foxfire-Energy.com_ <http://www.Foxfire-Energy.com>
NABCEP #092907-44
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Shine On!
Kris Schmid
Legacy Solar, LLC
864 Clam Falls Trail
Frederic, WI 54837
www.legacysolar.com <http://www.legacysolar.com/>
715-653-4295
NABCEP Certified PV Installer
Licensed Wisconsin Master Electrician
BSEE
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