Home Sizing the System The Structure The PV panels Field Wiring Tilt Angle

The Structure


I researched various ways to support the PV structure but decided against the commercial racking offerings. Instead I applied fencepost technology to produce a heavily fortified structure with adjustable declination.


I developed the layout with DesignCAD and uploaded coordinates to my laser theodolite. Then I used this instrument to locate the holes and posts. The galvanized pipe was purchased cut to length and threaded to my specifications.


I recruited help with the really tough job of boring holes in the hard decomposed granite soil. Here is Dave, a local fencing contractor, doing what he does best. Dave and his partner Bucky assembled most of the pipe structure while I stepped away to take a few pictures.


993.jpg (105613 bytes)
When the support row of pipe was erect, but before the concrete was poured, my wife commented on how much it intruded on our panoramic southerly view. I had to agree, so work stopped and I spent several hours that night at the computer. I had the answer in time to dismantle and start over the next morning.


1055.jpg (72293 bytes)
The structure, shortened by three feet from the original design, was erected again. We used some of the steel struts to brace every other post to an iron stake as we proceeded.


I then spent the next two days with my instruments aligning and refining, straightening and plumbing, and finally got the structure tweaked to perfection and fully braced. In fact, the 100-ft long horizontal axle pipe was so straight and level you could look in one end and see the full opening at the other end. It was almost time to pour the concrete.


The original design height provided space to mount the inverters, whose bottom must be at least three feet above the ground. That space was lost in the height reduction exercise, so I dug four cavities in the bank and formed slabs with posts for the inverter mounts. The concrete was pumped to the holes and slabs and a few days later I built the retaining walls.


1121.jpg (101735 bytes) I spent two more weeks removing the temporary bracing and completing the structure. The structural members are hot-dipped galvanized steel, but all of the fasteners are 316 stainless steel. The stainless U-bolts had to be custom-made.


1122.jpg (65216 bytes)
At last, the structure was cast in stone. The anchor posts in the rear were left long and will eventually support a decorative fence. Or maybe some type of view-enhancing hedge or vine will be planted on the north side.

The next step was to place the inverters and install the PV panels.