Home Built Solar Mount
In my first attempt, I had built six solar panels that were mounted to a framework of treated 2 X 4's constructed in a fashion that resembled a child's swing set. Each end had two legs that supported a cross piece to which three panels were attached. I wanted to be able to raise and lower the bottom edge of the panels as the sun gets higher and lower in the sky with the seasons. The idea was effective with just one itsy bitsy little problem.
During a spring wind storm, they tipped over. Fortunately the panels survived, but I didn't want to tempt fate a second time. I built the much more substantial mount shown in the photos.
A foundation consisting of six concrete piers will hopefully hold this mount down in a wind storm. I used treated 2x4's to fabricate a truss-like structure, tied and braced together, and bolted down to the piers.
The six solar panels are once again screwed on their top edges to 2 x 4's that are fastened to the trusses using 3.5 inch hinges spaced approximately 36 inches apart. I plan to install threaded rods through cross pieces that support the bottom edges of the solar panels. The threaded rods will allow me to adjust the elevation of the panels to match the sun's elevation. Six more panels will be installed soon.
The triangle shape of the trusses is based on a 30-60-90 degree triangle. The vertical height is 9 feet 4 inches. The base is 7 feet 0 inches, and the hypotenuse, the side that holds the panels, is 12 feet long. Screws and truss plates were used to fasten the members.
The smaller array in the foreground was a venture into building a polar mount that would track the sun during the day. My inverter and four lead-acid batteries are housed in the insulated compartment under these two panels.
Cable Tie-Downs Added July 3, 2005: To further ensure that a high wind will not tip the structure over, I installed 40 inch long steel earth anchors, three behind and two in front. 1/4 inch steel cable ties the structure to the anchors. With and eye on one end and a helix on the other, the anchors are designed to be turned into the soil.
It was hard going because we have such rocky soil. I found that I could free an anchor that got jammed on a rock by striking it with a hammer.
Hopefully, the tiedowns will prevent catastrophe when the inevitable "noreaster" storms its way into New England.
UPDATE 12/30/2007
In the intervening period, the mount has experienced four severe wind storms with gusts of 85 mph and above. The mount still stands, however the original homemade panels did not. They were hinged on the top edge to allow tilting the panels to match the seasonal sun angle. During one particularly harsh October storm the wind lifted the panels to the horizontal, like a flag in a breeze, and then dropped them back down onto the frame. A day of this was too much for the cells and most of them cracked and shattered.
Now the installation has been rebuilt. New manufactured panels are bolted down to the original wood frame. This new configuration has withstood two blizzards so far with 80+ mph winds. Follow this link to see details of the grid-interactive system with its ten 165 watt solar panels.
I don't think your 6 concrete piers are enough weight to hold the array in
a strong wind. I found a spreadsheet at US WINDTURBINES that might help.
My copy can be found at http://groups.yahoo.com/group/alternatepower/files/
Hi Dan. Thanks for your comment. I was not able to access the spreadsheet
you referenced, but I did find some other data on the web that suggests
there could be as much as 6800 pounds of lifting force on on a roof
measuring 12 x 16 feet in hurricane force winds. There are 17 80-pound bags
of concrete mix in the foundation so you may be right. I may be short about
5000 pounds. I have ordered six earth anchors to bolster the concrete
piers. These are 40 inch steel rods with a 6 inch diameter helix welded to
one end. They are designed to be twisted into the ground. They should add
substantial holding power.
This is really great. Do you have any way to adjust it for winter and
summer sun?
I have plans to raise and lower the panels to better match the sun's angle
during the seasons using threaded rods. That is on tap for the coming
summer.
This project now has six more solar panels beneath the ones in the photo.
It is capable of delivering 50 amps into the 12 volt battery bank, midday,
sunny weather. Thus, it is 600 watts of power.
I built a number of solar mounts, one like the one you made. Wind was a
real problem and I too found that solar panels can survive a huge crash.
Then I made wooden pole mounts. This worked for 2 years, but the poles
rocked in the wind and broke the mounts. Trees popping up were also a
problem. Now I am making roof mounts using Veranda composite decking. I
learn more as I go. Mounting is very important!