Tips and tricks for pole mounts?

Re: Tips and tricks for pole mounts?

Scaffolding. 100% the way to go. It's way safer than a ladder and relatively cheap to rent. I put in a 6x8 array with my Dad. For the details here are some links to a few of my blog posts

part 1
part 2
part 3

I would recommend using heavy equipment unless someone else is going to dig the hole. The panels I put in have had no trouble surviving the infamous 30-year wind storm we got hit with this winter so we're fairly confidant it will hold up long term. We also mixed our own concrete and went a little heavy on the cement for our mix. Our ground is real heavy clay and the pole had steel bar welded in a 'X' shape to prevent the possible spinning in the wind. We tapered the concrete away from the pole in order to prevent water working its way down between the pole and concrete.

Your soil type will vary and it's seldom a bad idea to err on the side of caution when choosing hole size and rebar use.

Re: Tips and tricks for pole mounts?

jcgee88 wrote: »

Peter V,

You have an impressive installation and you get an
excellent harvest from it. I had a few pure curiousity
questions for you:

1. Why did you put gaps between the panels? Is that
to allow an escape path for wind, i.e., lessen the wind
load?
2. Do you have a sense for how much wind load your pole
mounted panels can sustain?
3. Why did you do a maximum of six panels/pole versus,
say, two poles with eight panels each?
4. Why did you do pole mounting instead of a roof mount?
It's true that you can't do tracking with a roof mount,
but classically, people compensate for that by being
able to buy additional PV panels with the money not
spent on tracking hardware.

John

They are on Zomeworks trackers. The pivot axle (part connected to the pole) sits above the main frame in order to get the COG as low as possible. This makes the tracker more stable in wind, etc.
Because of this the center panels have to be raised so they don't hit the axle. So the spacing is to keep the raised center panels from shading the edge panels in the early morning/ late evening.

The tracker is passive, no electronics or motors. It works by using a low boiling point fluid and the heat from the sun makes the fluid boil and the gas pressure moves the fluid from one side to the other, which changes the balance on the tracker so it tips and follows the sun.
The tracker only tips a total of 90 degrees, from 45 degrees one side to 45 the other. Hence the issue with possible shading in the morning/evening

The trackers are designed to handle a maximum of 120 sq feet, roughly 10 ft x 12 ft. 6 panels are all that fit within the limits of the trackers.
The small tracker is home made.

The trackers I bought, UTRF-120s, cost me about $1600 each last year. The next size up, UTRF-168 cost almost $1,000 more but only hold 2 more panels. The 168 needs a larger diameter pole, which has to be at least 4 feet taller and therefor deeper, and the footer had to be 3' foot diameter instead of only 2'
All and all the larger tracker was a lot more expensive.
So it was cheaper to buy two of the 120s and build a tracker than can handle 3-4 panels. I'm willing to gamble 3 panels on my DIY skills, but not 15 panels.

My roof faces southwest so that the house has a nice view of the nearby mountains. That coupled with the slope of the roof means that I would need approx 5 kw worth of roof mounted panels to equal my 3.4kw of pole top mounts. Either that or a fairly complicated (read expensive) adjustable angled roof mount with a bit over 4kw worth of panels.
The larger roof mounted array would actually cost more than the tracker mounted array.

Plus I'm not keen on roof mounts. Aside from the possibility(probability?) of leaks there is the whole issue of eventually having to replace the roofing tiles and having to pull off the array to facilitate that. Plus it's a hassle to climb up on the roof several times a year to clean the panels (it can get really dusty around here)

Finally I just think trackers are cool!

Re: Tips and tricks for pole mounts?

For mine, a small 3 panel install, I use schedule 20 steel pipe, buried 4' and in a hole 3' in diameter. The pole is 12' so 8' above ground. I "rebared" the hole in many directions to keep it from spinning and for strength AND pounded in the grounding rod next to the pole. I used sacrete style concrete and filled the hole plus some. Currently have 2 panels on the mount. going to add the 3rd this summer. We have some serious winds/gusts (60+mph) and the unit doesn't seem to move. No problems after 3 winters and summers.