[RE-wrenches] Tilt Racking vs. Roof Mount for Shedding snow
Ray Walters
ray at solarray.com
Fri Mar 27 10:27:03 PDT 2015
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 <dave at independentpowerllc.com
> <mailto:dave at independentpowerllc.com>> 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:re-wrenches-bounces at lists.re-wrenches.org
> <mailto:re-wrenches-bounces at lists.re-wrenches.org>] *On Behalf Of
> *dan at foxfire-energy.com <mailto:dan at foxfire-energy.com>
> *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" <dave at independentpowerllc.com
> <mailto:dave at independentpowerllc.com>>
> Date: Fri, March 27, 2015 10:32 am
> To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org
> <mailto:re-wrenches at lists.re-wrenches.org>>
>
> 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:re-wrenches-bounces at lists.re-wrenches.org_] *On
> Behalf Of *_dan at foxfire-energy.com_
> <mailto:dan at foxfire-energy.com>
> *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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