Another thing that makes a big difference here in Colorado is to use dark colored frames and cells as opposed to silver frames and lighter colored cells. We get a lot of cold but clear days and dark color makes a huge difference in how quickly shedding will occur. This same phenomenon will work against you in the summer but for off-grid our design day is mid-winter typically.
We prefer pole mounts where snow can be broomed off and tilts optimized throughout the winter. Cheers On Fri, Mar 27, 2015 at 10:15 AM, Dave <[email protected]> wrote: > I will back up your opinion that open back has not a lot to do with it. I > have several arrays that I care for here in my off grid neighborhood and > some are tilted 20 degrees off of roofs to 45 degree array angle and one is > a TPM that is set at 60 degrees for winter and all of these experience > severe snow cover problems unless it warms up for a significant amount of > time, or the roof rake is used. > > > > As you know, building the rack far off of the roof AND minimize costs do > not go together. Extra material and extra strength for wind loads. > > > > Dave > > > > *From:* RE-wrenches [mailto:[email protected]] *On > Behalf Of *[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 > 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]> > Date: Fri, March 27, 2015 10:32 am > To: "'RE-wrenches'" <[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 > > > > > > > > *From:* RE-wrenches [*mailto:[email protected]* > <[email protected]>] *On Behalf Of * > *[email protected]* <[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 > *www.Foxfire-Energy.com* <http://www.Foxfire-Energy.com> > NABCEP #092907-44 > > > ------------------------------ > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: *[email protected]* > <[email protected]> > > Change listserver email address & settings: > *http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org* > <http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org> > > List-Archive: > *http://www.mail-archive.com/[email protected]/maillist.html* > <http://www.mail-archive.com/[email protected]/maillist.html> > > List rules & etiquette: > *www.re-wrenches.org/etiquette.htm* > <http://www.re-wrenches.org/etiquette.htm> > > Check out or update participant bios: > *www.members.re-wrenches.org* <http://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 > > > -- Mac Lewis *"Yo solo sé que no sé nada." -Sócrates*
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