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Doug & Todd,<br>
<br>
We install here in Fairbanks, AK and I'm a big believer in a really
steep tilt angle. 85 degrees or more. One reason is that it's got
to be steep enough to shed snow. If you're array is under snow
you're not going to get much performance if any. Second is we get
most of our sunshine in the springtime. We get more hours of
possible sunshine in the summer but as a rule summers are cloudier,
so if you miss out on the spring sun you lose a lot. Third is
during snow season you definitely get some benefit from snow
reflection. I personally have seen a 10% boost but some have told
me they've seen higher.<br>
<br>
We have some pretty cold temperatures so even if it's sunny out it
can be well below 0. Our snow doesn't melt off the panels fast like
it must in some warmer climes. I like pole mounts as well because
they're easy to clean, easy to adjust and will never cause a roof to
leak. Of course there are places where they just don't fit for one
reason or another. <br>
<br>
If you have a pole mount with plenty of room under it for snow (or
someone who's good with a snow shovel), you can do really well in
the winter with snow reflection and then adjust as needed for the
summer months. If you're going to put something high on a pole you
want to make sure your foundation and the pole can handle the extra
stress. Using a structural engineer is better than guesting and
you'll sleep a lot better during wind storms.<br>
<br>
Last, I don't know how they stand up to heavy loads but Sharp
NU-U240F1 (240 watt panel) has two beams that kind of separates the
panel in to 3rds. This should make it stronger since structurally
it's closer to 3 - 80 watt modules than one 240 watt panel<br>
<br>
Best,<br>
<br>
Greg Egan<br>
NABCEP Certified PV<br>
Remote Power Inc.<br>
Fairbanks, AK<br>
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Hi Doug,
I had a customer's roof mount system break modules this spring after yet another record Mount Shasta snow event. This one brought 8' in 10 days.
The situation here was 15 Evergreen 190 watt modules (rated for 80#/sq ft), on a DP&W power rail mount, on a 6/12 pitch, comp roof. Ice dams were not removed so the bottom edge of 5 module's frames were peeled off the glass... without the frame's support, 2 of the module's glass broke. Evergreen did not warranty the damage.
>From Evergreen:
"The observed damage is attributable to weather related effects, not manufacturing or workmanship issues with the panels.
You are correct, we do guarantee our panels for up to 80 pounds / sq. ft. However, that is for a uniform load. The installation manual, page 3 (attached), has the following warning:
The maximum permissible loads apply to uniformly distributed
wind or snow loading. Care should be taken to avoid mounting
panels in areas that are prone to drifting snow, icicle and/or ice dam
formation."
I have come to the conclusion that the only real way to mount PV modules in heavy snow country is on a pole mount with a steep winter angle and enough ground clearance (minimum 6' from the bottom edge of the array to the ground) to allow the snow to keep sliding off the array all winter. A roof mount might still work, but it would need to be greater than ~8/12 pitch (not so good for summer production) and accessible to manual snow removal in those critical situations like we had here a couple of weeks ago.
One of my most difficult challenges is trying to design my installations to mitigate winter snow damage. I realize very few list members have to deal with these kinds of severe conditions, but any feedback on my empirical conclusions would be welcome.
Todd
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<pre wrap="">Wrenches,
Can anyone recommend a panel that is built with more strength or
ability to handle greater load.
I am installing on a shallow pitched roof and am concerned about snow
build up in this particular location.
I know you guys out in the Sierra's get a lot more snow than we do.
What modules are up to the challenge?
Are there any new military spec modules like the old MSX 120's?
Any experience or guidance is appreciated.
Doug Wells
Morrisville, VT 05661
NABCEP Certified PV
Vermont Solar Partner
The Solar Specialists
<a class="moz-txt-link-abbreviated" href="http://www.thesolarspecialists.com">www.thesolarspecialists.com</a>
802-498-5856
_______________________________________________
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