Building my frame for solar tracker

solarcory · January 2017

Hey guys, first post here.

Ive got a home solar project that I am learning with, its a single panel, with battery, inverter that I use to power my home pc and some other small gadgets. Its been running for about two years and its doing well.

Ive bought a Ebay solar tracker motor and solar sensor, and Ive built a large frame out of aluminum to just have this sitting on the ground and not cemented. The issue I have, is how do I allow the solar panel to pivot? I mean, I have the lower frame built, and I can figure out how to wire in the solar tracker, but Im not sure what to use for the solar panel pivot mechanism.

What are you guys using? Anyone have any useful input? Maybe when I get home I can attach some photos.

dexter12353 · June 2017

Try gate hinges...That's what I am using. These are the ones, and they can easily be welded to a steel plate that can screw into your aluminum frame.

These specific hinges are probably overkill for your single panel application, however, I have 4ea 250 watt solar panels on my rack and since they are well balanced they move with just a finger. I then installed a linear actuator with a tracker I got off Amazon to make them follow the sun. My system is a prototype right now, because I'm not sure how it will react to the wind, but if it works we have about 30 more panels we can rack up to make us some power, we just dont want the wind to pick the whole thing up and throw it across the hill....

MichaelK · August 2017

Here's a pic of the tracking arrays I build for my own system. For the main post, I used a 3.5" steel pipe sunk 4' into concrete. On top of this I slipped a 4" pipe, 4' long. The array frame is made of welding unistruts, with re-enforcing trusses incorporated into all 3 axes. The trusses are either 7/8 unistruts, or rebar, with the rebar passing through the unistruts.

They can be rotated either left to right to track the daily sun, and tilled up and down for seasonal tracking. It's not motorized though. I refer to it as hillbilly tracking.

MichaelK · October 2017

Here's what the finished frames look like with the Renogy panels.

Image: https://us.v-cdn.net/6024911/uploads/editor/jc/574kiifa86cr.jpg

Ocean · October 2017

Nice Build!

just starting · March 2018

How much was each array? Would it have been cheaper to add 1/2 more panels to gain 40% ?

Dave Angelini · March 2018

Probably on the edge already for durability/wind/snow. Going larger would be a 6 inch pipe if you expect it to last.

MichaelK · April 2018

Dave Angelini said:

Probably on the edge already for durability/wind/snow. Going larger would be a 6 inch pipe if you expect it to last.

Well, that's your opinion. What I can say is that my frames as constructed have already gone through a winter with storms that have knocked down 18" oaks (I just chopped one up last weekend for firewood). They're all in perfect condition with no problems whatsoever.

I can also add the Missouri Wind and Solar markets a 4" steel pipe frame designed to hold eight 250W panels, so it appears that my design may be too conservative.

https://www.youtube.com/watch?v=2k5XaPImhK0

Let's see some pics of your wonderfully overbuild tracker?

MichaelK · April 2018

just starting said:

How much was each array? Would it have been cheaper to add 1/2 more panels to gain 40% ?

I spent about 750$ total to build all 5 frames, so call it 150$ each. That cost includes the purchase of 10lbs of flux-core MIG wire. I got all the unistruts at half price off of Craigslist, so that cost was significantly lower. I didn't add additional panels because only three would fit onto a standard 120" unistrut with my original design. Keep in mind that these arrays are already BIG, about 9' tall.

I am now in the design phase of my second generation tracking frame. It will be using sections of 4" pipe as slip bearings on a 3.5" pipe rather than using hinges. I think this will be a more robust design that will handle four 250W grid-tie panels instead of the original three 300W. Just the round steel for that cost 230$, and I haven't picked up any inexpensive unistruts yet, but the total price for the next array is likely to be ~300$

Photowhit · April 2018

MichaelK said:
I can also add the Missouri Wind and Solar markets a 4" steel pipe frame designed to hold eight 250W panels, so it appears that my design may be too conservative.

I can't think of any solar site/business I have less respect for!

I think you have a very nice design for 3 panels! I would prefer a 2 different direction arrays but looks like these should hold up well. It also looks like you have some trees and ground clutter that will help with any straight line winds from behind.

Estragon · April 2018

Lots of details that matter in pipe size. Schedule 40? 80? Back/side guys/bracing? Design wind load? Local climate. Length of pipe above pier. Corrosion prevention, especially where the pipe meets concrete pier.

Conservative can be a good thing. There was an early-ish storm at my cabin this fall, in which a lot of freezing rain and wet snow was followed by much colder temps and high winds. The wind blew the ice-weighted tops off lots of trees large and small, and a few down entirely. Fortunately none hit arrays, and the racking itself held up fine. Not something that happens every year, but often enough to be conservative.

Dave Angelini · April 2018

Estragon said:

Lots of details that matter in pipe size. Schedule 40? 80? Back/side guys/bracing? Design wind load? Local climate. Length of pipe above pier. Corrosion prevention, especially where the pipe meets concrete pier.

Conservative can be a good thing. There was an early-ish storm at my cabin this fall, in which a lot of freezing rain and wet snow was followed by much colder temps and high winds. The wind blew the ice-weighted tops off lots of trees large and small, and a few down entirely. Fortunately none hit arrays, and the racking itself held up fine. Not something that happens every year, but often enough to be conservative.

It really is conformance to requirements and engineering to back it up. Meeting and exceeding local codes, even if not inspected, goes a long way for durability over time.

Estragon · April 2018

Quite true. I normally start with code and add from there. There's the odd case where I deliberately disregard, but that's the exception.

An example exception is how I plan to wire some kitchen duplex outlets. Code calls for a split circuit with top outlets on a different circuit than bottom ones to avoid overload with two high watt loads plugged into the same duplex. Of course, it can still overload the circuit with two loads on the top outlet of adjacent duplexes. Maybe the idea is the breaker protects wire, but doesn't properly protect a double loaded single duplex? I plan to use GFCI duplex near wet areas (which I believe is code is other areas, but incompatible with split circuit wiring).

The thing about code for structure is it doesn't address ongoing maintenance required. The local (public owned) electric utility has been lax in repainting steel streetlighting standards. Aside from bad cosmetics, the poles are corroding at the bases - some now with >1" rust perforations. If not replaced soon, I suspect they'll start coming down in windstorms. Someone probably got a nice bonus for saving $10 on paint though.

BB. · April 2018

In Pacifica (just south of San Francisco on the coast), the minimum wire AWG is 12 (nominal NEC code is 14 AWG). Gives contractors fits as they wire up lighting and switches in over crowded junction boxes (now that we use LED lights, which use less power, use larger AWG cable....).

Regarding wiring two circuits to one duplex receptacle (in the US, you can separate the upper and lower receptacle by breaking off the bus tabs), I guess that they support using the waffle iron and toaster oven at the some time next too each other.

Regarding falling lamp poles, the URL describes it all (year 2015):

https://www.sfgate.com/bayarea/article/City-lamp-post-falls-and-urine-was-a-factor-6424634.php

-Bill

Estragon · April 2018

Yup, must be the dog pee, not neglect

Isn't the maximum number of a given size of conductors in a box also a code item?

Dave Angelini · April 2018

BB. said:

In Pacifica (just south of San Francisco on the coast), the minimum wire AWG is 12 (nominal NEC code is 14 AWG). Gives contractors fits as they wire up lighting and switches in over crowded junction boxes (now that we use LED lights, which use less power, use larger AWG cable....).

Regarding wiring two circuits to one duplex receptacle (in the US, you can separate the upper and lower receptacle by breaking off the bus tabs), I guess that they support using the waffle iron and toaster oven at the some time next too each other.

Regarding falling lamp poles, the URL describes it all (year 2015):

https://www.sfgate.com/bayarea/article/City-lamp-post-falls-and-urine-was-a-factor-6424634.php

-Bill

My old chinese sailboat had outlets with a 120vac and a 12vdc in the manner you describe Bill. They don't do that anymore

Building my frame for solar tracker

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