I have 4 rows of solar panels (330 watts) of 40 pieces for each row. How can i calculate the metal structure , metal thickness.Structure, the design should be like in the picture . 

I know only one way, and it is the way used by most farmers. Oversize it to such an extent that you simply cannot be wrong.

(I'm kidding of course. I think the correct answer is to employ a structural engineer).

Probably the most critical thing is that the structure must be able to withstand wind without flying off into the sunset. The panels themselves are not heavy (About 20Kg for a 300W panel)

 

That is a serious amount of panels, 120 panels.

I agree, for that investment it is probably better to get a structural engineer.

18 hours ago, plonkster said:

Oversize it to such an extent that you simply cannot be wrong.

you joke .. i ended up using galvanized square tubing (100mmx100mm*2.1mm) for my frames... and there are thee panels per frame 🤣🤣 ... we do have wind up rooting trees here though.

@Pavel 

Some basics use concrete for compression.

You haven't got much weight to deal with, you just have make sure there enough grip and weight that the wind can't pull up the footings.

And use steel for tension.

And how do you do that?

You use triangles.

That beam across the bottom isn't really adding much that the concrete footings aren't already doing, and you've got a four sided shape in the steel.

That's no good, a four-side shape has little resistance to changing shape because two "hinges" can move, you can't do that with a triangle.

You'd be better off using the steel in that beam elsewhere, maybe cut it and make a triangle shape at the top and bottom.

There are also no triangles to give it lateral strength, it looks like dominoes from the side.

(I mean in the direction of the row, a bump with a bakkie and the whole row will bend).

Sure use fence posts and you'd give it lateral strength, but the point is you can get away with a lot less material if you do it right.

Another thing to consider is the back of the front row panels will be sheltered from the wind by the back row panels and vice versa.

So the two rows will face forces their wind forces from different directions respectively, so their designs should be asymmetrical.

Save money on the protected inner rows and spend it on the exposed outer rows.

As far as beam size, that was too long ago for me to remember.

Edited January 22, 20197 yr by phil.g00

Maybe the triangle wasn't clear, basically your design should be such that you can't compress a triangle without trying to stretch another.

And because you cant easily stretch steel, that makes it difficult to compress the other steel in the structure.

Steel by itself bends easily under compression ( when compared to concrete).

It follows then that something as bendy steel wire under compression, can make a structure incredibly strong when used as diagonals for its tensile strength.

Unfortunately in South Africa you need to consider theft as well. I have welded mine into steel channel so they can't be removed without a lot of cutting. I have seen other anti theft ideas like paining the back of the panel bright orange with a message like 'STOLEN FROM XXXXX Contact 0123456789 for reward." 

12 hours ago, phil.g00 said:

bendy steel wire

Essentially the way you brace windmills (when we still used those). 8mm steel rod bolted on one end and with a thread on the other so it can be tensioned. By criss-crossing them you can make that entire tower rock-solid, even though the rods actually bend quite easily.