The sun is the “Big Power Source” and here are some of the recent photovoltaic installations I have worked on with Bruce Erickson of Mendocino Solar Service.
6.27 Kilowatts, Big river, California, 2008.
I do the structural calculations and support designs, and Bruce and his crews design the electrical systems and do the installations.
Most of the structural stresses on these installations come from wind “uplift” trying to rip the panels off the roof in a storm. There must be enough fasteners into the roof structure to resist the wind, and the existing roof structure has to be strong enough to take the added forces.
Sometimes it is necessary to strengthen the roof framing from below.
The job in Little River (top photo) with the pipe framing supports was unusual and there are more photos of it at the bottom of the page.
This is the “before” photo of a photovoltaic site at Little River, California. The building has a flat roof due to zoning height restrictions, and it has membrane roofing. The site has NO shading at all. Bruce Erickson of Mendocino Solar Service surveys the location.
Here is a photo of the pipe supports before the photovoltaic panels were installed on them. We used 1-1/2 inch nominal diameter schedule 40 galvanized steel pipe, with floor flanges threaded to the bottom of the vertical pipes, and lagged into the ceiling beams below. The roofer sealed all the penetrations and the tops of the pipes were capped. Once the vertical pipes were installed, the rest of the pipes were held in place with “Kee Klamps” which are very versatile & strong. Kee Klamps attach with set screws, so there was no welding.
Once the pipe frames were established, we used a standard Kee Klamp fitting to bridge to the “Uni Rack” support system which is the usual hardware for holding the photovoltaic panels in place.
A view of the completed installation. The pipe frames probably add strength to the existing roof although I did not calculate for that effect, and instead made sure that the roof could support the completed solar array as an added load, which it could. I also arranged a load test on the roof before I gave the go ahead.
Joe Ødegård, Architect
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