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Hypothetical question

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msquared48

msquared48

Structural
Aug 7, 2007
14,745
The subject is snow/ice loading on a solar panel array sloping bete=ween 10 to 45 degrees to the horizontal...

It is a fact that solar panels produce power as well as heat during the power generation process. My question is if the panels will generate any hea=eat to melt a small snowfall 0 say 3 to 4" before it forme into ice. As the snow layer gets deeper, the heat generated would get less, also due to the cloud layer abo9ve. That's well and good. But when the clouds clear, and it is still bel;ow freezing with the sun shining, will the snow be memted more by the sun on the snow and sublimation, or by any improbable heat generated from the panels?

I doubt that there is any information on this, so I'm tempeted to coat these panels with an inch of ice as well as the 20 psf or so of snow by code here to be safe.

Mike McCann
MMC Engineering
 
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Are the panels even producing anything with an inch of snow/ice over them?

TTFN
faq731-376
7ofakss
 
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Not icing, but they do mention snow load of 1 PSF on page 10/11.

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7ofakss
 
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The other citation mentions shorting out the panel to dump heat into the ice, but there's a lot of undefined parameters, namely, ambient temperature, wind, ice thickness, etc. SAE AIR 1168-4 Ice, Rain, Fog, and Frost Protection may be worth reading, if you do this more often. Unfortunately, it doesn't really cover a stationary object, so some of this is guesswork. Extrapolating from the airborne de-icing requirements, you'd need no more than 0.2 W/in^2 to de-ice for ~25ºF ambient. This would be about 300 W/m^2, which would be pretty much everything that one might reasonably expect from the panel under ice.

TTFN
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7ofakss
 
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IR:

Snow load will be a lot more than that (25 psf here). I think what you are looking at are the ASD load combinations to be used with other loadings.

Mike McCann
MMC Engineering
 
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When I go into TIA222-G, which does not really control here but can be used as a guide nevertheless, the minimum ice loading is 1/4" for the county involved, and that would cover not only the panels, but any f=steel framing.

In recent years, we have had to deal with freezing rain and ice fog. Not the norm by any means for this region, but someting to consider. Prior to 10 years ago, I had never seen or heard of either phenomenon in the area.

Mike McCann
MMC Engineering
 
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Freezing rain and ice fog are fairly common in my locale and the temperature can get pretty cold, so I don't think I would want to rely on solar panels melting any snow or ice. But, under the right conditions, it might work.

BA
 
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I haven't relied on any melting from the solar panel for my calcs. Just doesn't seam intuitive that the panel would be hot enough to melt the snow. Seams it would be counter productive from an energy standpoint.

I have also ALWAYS considered snow loads on the framing systems for the solar panels I have designed.
 
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I have always wondered about sliding snow with regards to panels. If the pitch were sufficient enough, would you be allowed reduce your snow load in accordance with the Cs charts accounting for Ct=1.2?
 
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SteelPE:

If the slope is 70 degrees or better, you can assume all the snow slides off, but for most solar panel applications, that will not be the case.

And, yes, I'm looking at Ct = 1.2 with Cs = about .6.

Mike McCann
MMC Engineering
 
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msquared48

So by your statement, I would assume that you reduced your Pg by the Cs factor of 0.6?
 
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