custom one-axis ground mount

manzanita2

I gave up on designing my own system and bought NAZ's solar kit with the 12kW Sol-Ark, 20kWh Pytes lithium battery bank and 6.7kW of REC 68.1"x44" panels. This part of the system seems fairly straight forward. I have a lot of reading to do though. My installation will be off-grid.

(A big thank you to BB for running the numbers for me several months ago when I said I was trying to design a system.)

This system is larger than I need, but I'm eager to have so much power available.

As usual, I'm introducing complications. Some years ago I cleared junk off a piece of property for a realtor. It included solar mounts that were apparently headed for a commercial installation before ending up stacked on the property.

The 5" diameter anodized aluminum tubes were originally 35' long with brackets every 41.5" execpt at the ends that are 39.5" spacing. The bad news is that I couldn't move anything that heavy and long so I had to cut them in half near the middle bracket.

They seem to be for a single axis tracking system, which I liked. I also have the ball shaped plastic bearings and clamps made to attach to vertical posts.

Unfortunately none of the brackets line up with these PV panels. But I'm doing a custom arrangement anyway. I am hoping to arrange the panels with their long axis parallel to the tube. With two parallel rows of panels on each tube. Using three tubes strung together in one line, I'd have a solar array approximately 89" by just short of 46'.

The critical part would be the 89" crossbeams attached to the tubes. They need to be strong enough not to bend in high winds. I haven't yet figured out the necessary cross-section. Four inch cross sections seem big, but may be near what I need.

The in ground posts will also be critical. I'm hoping to do two wood posts per 17' length of tube, but may have to do three. I haven't yet figured out the cross section and depth of the posts. I'm worried that I'll end up with 8x8 posts, but that's just a guess.

The next pieces would be 3 stringers across the cross braces for the entire 46 or so feet. Those stringers would hold the actual cross pieces (about 89" long) that would be attached to the PV panels according to REC's specs.

Does anyone have reccomendations on the type of metal I should use for the big cross beams? I'm guessing more anodized aluminum, but was hoping that I could use whatever metal I can get locally.

I don't have an automatic system for aligning the array to the sun. Initially, I'd be manually aligning the array, but linear actuators at each post would be much better.

I guess that this one axis ground mount goal just leads to craziness. It would be easier just to use standard ground mounts.

I'd appreciate any comments.

manzanita2

Oops. I forgot to mention there are 16 pv panels.

Wheelman55

Check this out. https://www.wattsun.com/products/accutrak-hzla-tracker

If your tubes look like the ones they use, you can use the same module clamps. 

These units use schedule 40 steel pipe to mount to the ground. 

manzanita2

Thanks for finding that. It is generally what I'm trying to do. It's good to see what they did.

But my hardware isn't the same. My tubes are 5" diameter, not square. And they have brackets already welded on.

I'll try to get a picture of the tube and hardware when I get home.

manzanita2

This is what the tubes look like. The tube is 5" in diameter and about 17' long. Most of the brackets are 41.5" center-to-center.

Wheelman55

5” OD or 5” ID?

Would you please attach pictures of the bearings and clamps?

When I return from the holidays I’ll snap pictures of the mounting hardware that we used for our HZLA tracker. 

Wheelman55

For attaching the solar modules. Just use a rail and clamp system compatible with your REC units. 

Rails running parallel with long dimension of tubes. Bolt two parallel sets of rails to the existing holes in the flat supports on the tubes. Use end and mid clamps to attach modules to rails. 

Talk to NAZ. They’ll help you find a solution. 

Wheelman55

Re: linear actuators. One actuator in the middle will be enough. 

Having multiple actuators would likely lead to sync issues. 

HZLA uses just one actuator. 

manzanita2

Problem: I can log in via my cellphone here at home,  but haven't been able to convince it to share an image with the Vanilla forum software. Obviously the problem is at my end.

:-(

manzanita2

Very sorry for the delay. Wasn't able to convince my cellphone to upload images. Not sure why.

This image shows some of the hardware that was included with the single axis tubes. In the center are the two plastic bearings and the 3-piece bracket that surrounds them. I believe the two small flanges on the right are to keep the bearing from shifting along the tube.

I don't know what the two pieces on the left are for.  The collection of hardware includes two 460/230V 3PH 60Hz 0.5HP worm gear drive motors built by Nord for Joyce Dayton Corp which I assume were used to align the single axis array. None of the hardware associated with controlling alignment was included.

Will I need to use stainless fasteners on the tubes and this hardware? I'm not used to working with aluminum.

manzanita2

I'm not sure how clear this is: the top half of the image shows how I plan to orient the 16 pv panels, each 68.1" by 44". 

The bottom half attempts to show what supports I'm planning. It's hard to see, but in the center of the lower image there is a black line representing the 5" dia aluminum tube that has brackets preinstalled. The red lines represent crossbeams attached to the tube's brackets. The spacing between bracket centers is usually 41.5" which does not match my panels. The 3 green lines run on top of the red crossbeams. Then the blue supports are lined up with where they need to be attached to the panels. At the far right is an attempt to show the end view of the assembly.

Not shown are the 6 or 9 posts into the ground.

WebPower

You could look at ironridge.com for some ground mount post ideas. Play with the design tools. Maybe use their rails mounted to the brackets? Only use posts at the ends of the tube setup. See what size/orientation of panels and how they lay out based on the panels you have or plan to use. At least it can figure loading for you. Maybe... Just some thoughts.

Dave Angelini

Wheelman55 said:

For attaching the solar modules. Just use a rail and clamp system compatible with your REC units. 

Rails running parallel with long dimension of tubes. Bolt two parallel sets of rails to the existing holes in the flat supports on the tubes. Use end and mid clamps to attach modules to rails. 

Talk to NAZ. They’ll help you find a solution. 

This is your weakest point, the module sail area ( big panels! ) is way up there! I would say start at the rails and not just a compatible rail and clamp but one that exceeds the panel requirement. 

Failure could occur if the modules are not secured over a large area on the rails. Example would be nuts bolts and washers. The washer needs alot more surface area than the rail width when you homebrew.

You do not want to see the pictures I have on the failures. Hopefully you are not in a really windy area!

Good Luck.

manzanita2

Thanks for the comments and info from last year. The wind can get strong here during storms. Not as bad as the Santa Ana winds in Southern California.

The Sol-Ark12 system from NAZ is running now. Only 6 of the 16 REC 420w panels are hooked up. I was getting by on a much smaller system and haven't discharged the 3 Pytes V5 batteries below 80% on this system.

I used to run a generator a lot as I was using more power than what two very abused Trojan T-105's could store. The new system solved that problem. The current setup completely recharges by 11am! Of course it's very sunny this time of year. And I'll find ways to use more power now that it's available.

The six PV panels are secured via the four 1/4" holes with bolts and washers, but I still need to install all 16 panels with a proper ground mount.

I appreciate the warning that securing panels better will help prevent failure in high winds. I hadn't thought of exceeding the Mfr's mounting suggestions. I did consider using less tilt than recommended for a 35 degree latitude to lessen wind loads.

JRHill

Question that I've pondered: Other than buying a single or multi axis OEM tracker is there a vendor that has a sensor with outputs for a DIY system?

littleharbor2

With my flat roof mounted array I've been through three minor hurricanes and numerous other high wind events and I haven't lost a single panel. Everything seems pretty secure and I believe it's most likely due to the Cedar dog eared fencing wall I put up behind the array it keeps the wind from getting up under the panels.
 I just noticed the shadows are pretty deceiving here it looks like my array is pointing the wrong direction. I actually laid this out to true solar S but this photo was taken early in the morning right around the first day of summer when the sun comes up in the northeast as opposed to the east.