Anybody implemented the "Projects by Everyday Dave" bifacial ground mount?

[AlaskanNoob]

If so, how far down did you put the I-beams, did you use concrete, and how has it been in the wind? I'm thinking about doing five arrays of seven doing the same thing Dave did with the same beams and same Renogy brackets, but with a couple differences.

Some differences in my setup (other than seven panels instead of two):

1. I would mount the panels so all panel fronts face the same direction (instead of alternating them as Dave did).



2. While Dave put his beams two foot down without concrete, my I-beams would be three feet in the ground with concrete (for now planning on 6" sonotube, 3 foot down, filled with concrete).

3. My panels would be about two feet higher off the ground (11 foot I-beams, buried 3 foot in the ground).

4. My panels are the same dimensions as Dave's, but they are 13 pounds lighter.

My only concern is wind. Dave at 2:35 into the video says he's seen 60mph winds and they hold up alright. But as he shows, the beams are definitely not rigid. Mine would be two foot higher up so I would think would be even more affected by the wind. But my posts would be a foot deeper in the ground with concrete. That wouldn't keep the beams from bending with the wind though. But what's the worst that could happen? If the aluminum bends, I'd just bend it back I would think.

I'll probably send the plan to an engineer before I order these beams though, in case I need to go a size up.

 

[kommando]

It's not the strength of the wind that is the issue but the back and forth bending, you risk fatigue cracks appearing and then propagating. This is likely to appear at the point of entry into the ground. Best solution is another beam running from the top at an angle to the ground on the shaded side to triangulate the beams, this does not need to be the same strength of the vertical beam.

 

[AlaskanNoob]

It's not the strength of the wind that is the issue but the back and forth bending, you risk fatigue cracks appearing and then propagating. This is likely to appear at the point of entry into the ground. Best solution is another beam running from the top at an angle to the ground on the shaded side to triangulate the beams, this does not need to be the same strength of the vertical beam.

I'm not sure if they make beams smaller than the ones here. Running it at an angle would mean doubling the I-beams and then some (since I would imagine with the angle it would need to be longer than the vertical beams).

Probably cheaper (and less shading) to just increase the size of the vertical I-beams until they become rigid, no?

Or maybe not every beam needs a triangle? Maybe on an array of 7 I could have two extra beams (one on each end) to stabilize the whole thing?

 

[kommando]

A lot of it comes down to resonance, certain wind speeds will create a rapid back and forward swing if the posts are of a certain length. Bridge engineers have software to predict what windspeed, direction etc will get the deck swinging dangerously and change the profile of the deck until the software tells them the swing is gone. There is no software for vertical fences (which is what you have) that I know of, it may be fine but if the swing starts then when the wind drops you need to get in their and brace it before the next similar wind appears.

 

[Q-Dog]

Don't overthink this. You are building a fence out of solar panels, and your posts are about 40" apart, not 6' or 8' apart.

 

[AlaskanNoob]

Don't overthink this. You are building a fence out of solar panels, and your posts are about 40" apart, not 6' or 8' apart.

Ha, I can assure you that I'm not overthinking it. I'm too ignorant to really have much in the way of thoughts. But based on your comment I'm guessing you think the design should be fine? Makes sense to think of it from a fence perspective with the posts, but the difference is those solar panels make a bit of a wind sail, no?

I just sent my CAD plan to our engineer and if he gives me a reasonable quote I'll get his thoughts and share them. Otherwise if inflation shows up in his quote, I'll probably just wing it and build it. But it's 35 bifacial panels we're putting up, so I'd sure hate to be making a mistake...