Also, when you're calculating snow load, the load is decreased when
on an angle. Simple Trig, the snow load is straight down(gravity), so
if the panel is at an angle it only sees the portion of the load
straight down. Same as you would figure wind loading with an array.
I'll send anyone interested a sheet on how to calculate this, if
you're not seeing it.
R. Walters
Solarray.com
NABCEP # 04170442
On Jul 28, 2009, at 8:57 AM, Greg Egan wrote:
My solution to snow load issues is to install modules on racks so
they can tilt to 90 degrees when it's snow season. I guess it
depends on where you are but in the areas of Alaska where we work
we tell people to tilt your array to 90 in the fall and kick it
back to lat-15 in the late spring. They gain some from snow
reflection and lose some because they're not always at the best
angle but they make a lot more power than modules installed under
the snow.
We like top of pole mounts that allow for an 85 or 90 degree
setting for the snowy season. We've done some installs of modules
on the s side of buildings where we leave them basically plumb
during snow season and kick them out like an awning the rest of the
year. Sometimes there's a nice 2' overhang on the roof that keeps
the snow off the wall mounted array even if it's kicked out maybe
to 75 degrees or so. Roof installs are our least favorite for a
number of reasons.
I know the architects among us love to not see those ugly modules
but I generally try to convince my clients that their neighbors
will think they're stupid if they see their PV panels under the snow.
Believe it or not we get most of our annual sunshine in the
spring. It's clear and cool. June has more "possible" sun hours
but is generally cloudier so the NREL 30 yr averages show spring to
be the most productive for us. Don't want to miss out on that
power if we can help it!
Best,
Greg
Greg Egan
Remote Power Inc.
981 Gold Mine Trail
Fairbanks, AK 99712
P. 907.457.4299
U.S.Distributor for Outback Power Systems and other premium power
equipment.
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