Snow Tolerant PV Mounting

[Kingram]

I live in Phoenix what is this Snow you talk of ?? Seriously you have a nice set up and it looks like you have put a lot of thought into your Solar with the tilt and ground clearance and I think the 8 inch gap is a game changer so congrats.

[bcroe]

PV owners who live with snow every winter, soon discover it is devastating
to production. For roof mounted panels not much can be done, but
ground mounts are another story.

Snow often falls in the night, so clearing the panels at sunrise can promote
production for the next few days. But the classic SW desert array design is
not set up for convenient snow management. Below are some changes
to remedy this, which I have tested in real snow. Sn6gap2.JPG





The first change is to leave a gap between upper and lower panels, for snow
to slide into and drop down. Experiments showed that a 4 inch gap was not
wide enough for snow to drop through freely. A 6 inch gap was generally
sufficient, but still a bit tight for a 6 inch snow fall. The decision was made to
go for a nominal 8 inch gap. Sn6gap1.JPG
Sn8gap.JPG





The gap was found to greatly encourage snow to slide off on its own, since
it only needed to slide half as far as before. The wider gap absorbed a greater
fraction of the snow. When manually clearing remaining snow, the snow could
be pushed or pulled to the nearest opening, only half as far away, and with
much less physical effort to move half as much snow at a time. After a heavy
storm my clearing time was reduced from 90 minutes to 40 minutes.

In addition a greater amount of snow fell under the array instead of down to
the front. This saved more snow moving, because a buildup at the base can
block the bottom panel cells and kill production. A 20 inch ground clearance
was found to require snow blower passes to move snow farther away.

The next change is to mount panels in landscape orientation. This has been
recommended before, so that blockage at the bottom would cause bypass
operation of only 1/3 of a panel, instead of all of it. But my motivation is to
reduce the distance and effort, and the vertical amount of snow, that must be
moved to the nearest opening.

My next change is an array for which the tilt can EASILY and QUICKLY be
changed on a seasonable basis. Changes were POSSIBLE on my first array,
but NOT PRACTICAL. The new design has placed the pivot near the array
center of gravity, so very little force is needed to move even a 24 panel array.
Use of 6061 aluminum held with 18-8 stainless hardware minimizes weight
and avoids corrosion problems of a steel support. Actual machine roller
bearings avoid friction, 6 used in this case to improve support.

For snow months the panels would be set straight up, for a minimum of snow
accumulation. This may not completely keep any snow from sticking, but
experience is that just a TAP on a panel may be enough to clear it and even
several others adjacent. For that period in the snow latitudes, the production
is not much less than for the optimum tilt. And sun reflected off
ground snow favors this position.

Finally a lot of ground clearance is needed to keep the panels higher than
accumulating snow. I have mounted panels 40 inches above the ground, hugely
reducing the chance of needing to move snow farther away.

With big ground clearance and a snow gap, 2 landscape panels are approaching
10 feet in height. Stacking more rows than this makes wind stress much greater,
a problem for any easily tiltable array. And more height is a problem to reach for
clearing. So my design is only 2 panels high. This in general WILL NOT increase
the ground space needed for an array, but more or longer rows may be needed.

To steady the array during storm stress, I have added several adjustable braces.
These are easily removed from the ground, while making a seasonable tilt change. SnBrace.JPG






Bruce Roe