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We too are suddenly faced with a requirement for an engineer's stamp
on foundation drawings for pole-top racks. This new requirement just
rankles my craw (an expression from our great-grandfathers'
time...). This is even though DP&W (our preferred pole top rack
manufacturer) supplies drawings of pole length and foundation,
specific to the slope, soil type, array size and wind load, upon
request. These aren't good enough.<br>
<br>
I still prefer to install seasonally-adjustable racks for off-grid,
which the array in your link, while beautifully executed as usual,
decidedly isn't. <br>
<br>
But I'm starting to reconsider. Who has read Christopher Freitas'
excellent article on large battery banks in the preceding SolarPro?
One of his latter points in the article, which I understand was
highly edited, was that with battery prices rising and PV prices
falling, our off-grid designs ought to move toward substantially
larger arrays and smaller battery banks. I believe he's right, and
it will be a fundamental shift in our design approach. The same may
prove relevant to racking as well: larger fixed arrays, with less
emphasis on seasonal adjustment when other factors work against it.<br>
Allan<br>
<br>
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<font face="Times New Roman, Times, serif"><b>Allan Sindelar</b></font><br>
<small><a href="mailto:Allan@positiveenergysolar.com"><font
color="#000099" face="Times New Roman, Times, serif"><u>Allan@positiveenergysolar.com</u></font></a></small><font
face="Times New Roman, Times, serif"><br>
<span style="font-size: 10pt;">NABCEP Certified Photovoltaic
Installer<br>
NABCEP Certified Technical Sales Professional<br>
New Mexico EE98J Journeyman Electrician<br>
<b>Positive Energy, Inc.</b><br>
3201 Calle Marie<br>
Santa Fe, New Mexico 87507<br>
<b>505 424-1112</b><br>
<a href="http://www.positiveenergysolar.com/" target="_blank"><u>www.positiveenergysolar.com</u></a><o:p></o:p></span></font>
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<br>
On 3/24/2012 11:29 AM, William Miller wrote:
<blockquote
cite="mid:6.0.1.1.2.20120324101925.051bd9b0@millersolar.com"
type="cite">Daryl:
<br>
<br>
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.
<a class="moz-txt-link-freetext" href="http://millersolar.com/MillerSolar/Portfolio/ground-mount/engineered_ground_mount.jpg">http://millersolar.com/MillerSolar/Portfolio/ground-mount/engineered_ground_mount.jpg</a><br>
<br>
We are realizing two things:
<br>
<br>
1. Concrete footings of any type are expensive. The cost of
excavation, forming and concrete really adds up.
<br>
<br>
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:
<a class="moz-txt-link-freetext" href="http://millersolar.com/MillerSolar/Portfolio/ground-mount/full_size_photos/engineered_ground_mount.JPG">http://millersolar.com/MillerSolar/Portfolio/ground-mount/full_size_photos/engineered_ground_mount.JPG</a><br>
<br>
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.
<br>
<br>
Thanks for your input.
<br>
<br>
William Miller
<br>
<br>
<br>
At 04:37 AM 3/24/2012, you wrote:
<br>
<blockquote type="cite">William,
<br>
I'm attaching a picture of a system we just completed in
Eleuthera
<br>
using DPW racks on concrete pilings. We tied the pilings and
rebar
<br>
reinforcement into the limestone bedrock with rebar down 16
inches and
<br>
used 12 inch sono tubes as forms.
<br>
We do a lot of ground mounting since our summer work is
mostly in New
<br>
England and snow removal is always a factor. I have two pole
mounted
<br>
arrays at my home, but it is the most expensive option, and
therefore
<br>
do a lot of this type of ground mounting. We also have an
economical
<br>
"cribworks" type structure made from solid railroad ties and
weighing
<br>
in at about 2800 lbs each that we will sometimes offer to
customers in
<br>
off grid situations.
<br>
<br>
Daryl
<br>
</blockquote>
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