Snow Drift
Snow Drift
(OP)
A client of ours is considering covering most of his (150,000 sq.ft.) flat warehouse roof with solar collector panels. The building is in Toronto, Canada and the roof live load in this area is for about 20" of snow. The base of the panels are 1'-0 off the roof and they are sloped at 45 degrees, total vertical height would be 6'-0. We originally designed the building and of course did not allow for this type of additional snow drift. My thought is that if I raise the base at least 3'-0 off the roof the wind would tend to scour the snow below and minimize (eliminate?) drift.
Any thoughts?
Thanks,
Peter
Any thoughts?
Thanks,
Peter






RE: Snow Drift
RE: Snow Drift
Dik
RE: Snow Drift
Mike McCann
MMC Engineering
RE: Snow Drift
You'd have the weight of the panels and their racks + the orignal weight of the (potential 20") of snow + the weight of the snow accumulating under (not melted and wind-blown and melted->refrozen back into ice) the panels. At least wind load would not be increased too much: the panels will be somewhat sheltered by the raised edges around the existing flat roof. Wind load won't be reduced at all, but it won't be increased too much, that is.
What's the angle of the panels? (Aimed for best summer reception of the rays, I hope) At Toronto's latitude of 43 degrees, that would be 43 degree nominal; for summer reception use 43 deg (up from horizontal) + 13 degrees = 56 degrees. So snow will fall around and between the panels, plus accumulate on the total area panels themselves. (Of course, some will eventually fall of of the panels, sliding down tot he roof. )
So potential snow accumulation surface has to account for MORE area: the original flat roof area plus the extra panel area angled at that 56 degrees.
RE: Snow Drift
Mike McCann
MMC Engineering
RE: Snow Drift
Think Cook. In summer, they need to use 43 deg (up from horizontal) MINUS 13 degrees (since the sun is higher in summer) = 30 degrees final angle.
So final area covered by snow = (original roof area covered by panels)/.866 = 1.15 original roof area.
RE: Snow Drift
RE: Snow Drift
1. spread them out enough that additional drift will be negligible (as others have suggested)
2. put them all in a single area and stiffen the supporting members locally.
No free lunch I am afraid.
RE: Snow Drift
DaveAtkins