Snow on panels - A picture is worth 1000 words

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peakbagger

Minister of Fire
Jul 11, 2008
8,845
Northern NH
I took this picture yesterday for another site but thought it may be of interest as it illustrates several phenomena. NCM_0070.JPG

I have three PV arrays, one on the second floor roof, my original wall mount and a pole mount not in the picture. The snow piled up on the wood pile happened in the last week. The wood pile is overflow from a particularly good year of cutting, the primary wood storage is in the side yard and backyard The panels to the left on the roof with the small PV panel are solar hot water panels with a DC solar pump for circulation. The chimney in the center is the one that my wood boiler is hooked to. Off to the side you can see my cold climate mini split under a small shed roof, I run it anytime the temps over 15 degrees. The truck is far enough from the house that snow slides wont catch it and the wall mount PVs are set at a 30 degree angle and any snow sliding from the roof misses the bottom edge (but not by much). Unless I get the extension ladder out, I can only reach the bottom edge of the roof with a 4 section snow rake. My approach to the roof array is clear off the asphalt shingles and the bottom edge of the array and heat from the sun normally works up under the panels and the snow and eventually it lets loose. The roof was clear in that spot just a few minutes before I took the picture and already some snow had slid down.

The icicles are interesting, they line up with the chimney that runs through an unheated attic equipped with soffit vents, The house has ridge vents but as you can see the ridge is covered with snow. There are also gable end vents so there is air flow up through the soffits and proper vents to channel the air flow. The icicles are caused by snow melt from the area around the chimney running down the roof. Note the snow is not as thick around the chimney. The entire roof is covered with storm shield underlayment, so no worry about water backing up under the shingles.

The SHW panels in winter are interesting, snow piles up on them but very soon in the morning the top edge get exposed. Once the water on the roof is hotter than the storage tank, the pump start to circulate. Snow slides down the panel but at some point the interior of the panels are not warm enough to melt the snow. Therefore a big lump of snow forms on the roof in front of the panel until a warm stretch. In winter I use my wood boiler for hot water and just use the panels for preheat so its not a major issue. The wood and the PV pretty well cover year round heating demands, I have an oil boiler but still working off what is left in the tanks from 4 years ago.
 
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I actually raked the wall mounts before I took the picture, it slides off quicker but still can snow covered.
 
Is there a film covering the lower windows? They look kind of greyed out.
 
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Window Screens, The lower double hungs have outside screens, the upper casements are internal screens. Too lazy to take out the external screens so I leave them in year round.