Many inland areas in California, Oregon, and Washington are 85 mph
zones. I think that's the lowest requirement anywhere in the U.S. I
can't imagine designing for 185 mph winds.
Doesn't that just blow the glass out of the modules?
Kent Osterberg
Blue Mountain Solar, Inc.
www.bluemountainsolar.com
On 3/24/2012 2:07 PM, Jason Szumlanski wrote:
Oh, to have 85 mph winds. Code changes just brought us up to 180 mph
design wind speeds in Southwest Florida. Yay.
Jason Szumlanski
Fafco Solar
On Mar 24, 2012, at 5:05 PM, Kent Osterberg<[email protected]> wrote:
William,
There are auger mounted systems that don't require any concrete. For locations
with suitable soil, they probably save some time and are a little less
expensive than concrete. But it takes a substantial structure to withstand 85
mph, or greater, winds. There's no getting around the physics of that.
Oregon also requires PV mounting structures to be engineered unless they meet
conditions prescribed in the solar installation code. The prescriptive rules
only apply to roof mounted systems, so ground mounts require a structural
engineer to sign off on the construction plans.
Kent Osterberg
Blue Mountain Solar, Inc.
www.bluemountainsolar.com
On 3/24/2012 10:29 AM, William Miller wrote:
Daryl:
Thanks for the photos and description of the mounts you are installing. We
have installed many of the DPW ground mount systems in similar configurations.
http://millersolar.com/MillerSolar/Portfolio/ground-mount/engineered_ground_mount.jpg
We are realizing two things:
1. Concrete footings of any type are expensive. The cost of excavation,
forming and concrete really adds up.
2. For off-grid, when the module tilt angle increases to 45 degrees, the
foundations need to be substantial. During one install we had our heavy PV
trailer blow over due to high winds. We decided to have the foundations
reviewed by an engineer and when we received the results, we had to go back and
double our piers and strut. We had bid the job so the updates came out of our
pocket. See:
http://millersolar.com/MillerSolar/Portfolio/ground-mount/full_size_photos/engineered_ground_mount.JPG
We are now required by the AHJ to provide a wet stamp from a structural
engineer for every PV structure over 6 feet in height. This means every
off-grid. We know the engineers will require massive foundations which will
cost a lot. I am looking for a cheaper way to install these racks. I have not
found it yet.
Thanks for your input.
William Miller
At 04:37 AM 3/24/2012, you wrote:
William,
I'm attaching a picture of a system we just completed in Eleuthera
using DPW racks on concrete pilings. We tied the pilings and rebar
reinforcement into the limestone bedrock with rebar down 16 inches and
used 12 inch sono tubes as forms.
We do a lot of ground mounting since our summer work is mostly in New
England and snow removal is always a factor. I have two pole mounted
arrays at my home, but it is the most expensive option, and therefore
do a lot of this type of ground mounting. We also have an economical
"cribworks" type structure made from solid railroad ties and weighing
in at about 2800 lbs each that we will sometimes offer to customers in
off grid situations.
Daryl
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