Snow accumulation question

[garybeck]

I have a customer who is concerned about snow accumulation on her panels. My original design was to use a roof mount with seasonal adjustment that would put their panels at 60 degrees in the winter and minimize snow accumulation. However I have had trouble finding a rack that offers convenient seasonal adjustments.

We're looking at the Unirac roof mounts with tilt legs, which are not really adjustable. And unfortunately there's a gap in tilt angle options... they offer 3 lengths of tilt legs. The short ones go up to a max of 39 degrees effective tilt angle including the roof pitcth. The next step up, the medium length legs, offer a minimum of 50 degress tilt angle.

Given that the summer produces more power and the year-round average for 39 is better than 50 (according to PV Watts), I'm recommending to mount her panels at 39 degrees.

She's worried that the snow will accumulate at this angle. I'm wondering if there are any studies out there or personal accounts from users here in this forum on what angle prevents snow build up. I think if we had seasonally adjustable racks and could go up to 60 degrees in the winter we'd be pretty well off. But 39 degress... I don't know.

Before I order this rack for her I want to see if there's any feedback or studies on snow. Oh yeah, this is Vermont where there is plenty of snow and the concern is valid. I have a friend with flush mounted panels and he's always complaining about his panels being covered in snow.

Any info is appreciated!

Thanks
Gary Beckwith

[garybeck]

OK, I'm answering my own question here, but in case anyone's interested, I had forgotten that while Unirac's mounts are not seasonally adjustable, another company called Direct Power and Water makes adjustable mounts. They go up to 60 degrees and down to 30 degrees. This, along with standoffs on the mounts to allow some accumulation of snow on the roof without impacting the panels, is a good plan for roof mounts in a snow climate.

[peakbagger]

I have a pole mounted array in Northern NH. I adjust for 60 degrees in winter and still have snow build up if the snow conditions are right. They do melt off a lot quicker at the steep angle but it could be a day or two.

I also have DHW panels at close to 60 degrees on a 30 degree pitch roof. The biggest problem I see is that the snow slides down the panel and builds up at the base where it intersects the shallower roof pitch. Not a majro issue with hot water but it sure would shut down a PV array, unless individual panel mounted inverters would work. My friend has a 45 pitch array on his barn roof and it can take a couple of days to melt off, he has a long roof rake for such occasions.

[bighoss]

Check out a product called Rain-X if the panels have glass surfaces. I havent tried it on polycarbonate. The stuff sheds ice n water from windshields very well.

[radio2]

I have used Pam cooking spray for my sat dish and the snow just slid off.