mount panels on top of a 40 ft container

[Mike90250]

I would not rely on panel frames as the mount. The proper rails and clamps are a much better way and retain the warranty.

[J.P.M.]

Excellent points, thank you. What you are basically saying is that it would have to be connected to the edges of container which is where the beef is ?

You're welcome. I'm not saying use the edges or that welding is a good idea at all. What I am saying is that if you weld, use your head and make sure you think about what you are doing.

I'd also add, that if it was me, I probably wouldn't be welding anything to the roof of a shipping container. Nuts and bolts are easier on the roof than welding. Done correctly, it can also be pretty leak tight. It's also more easily modified if/when you get more informed and aware of what a good PV design entails.

[geekwithoutacause]

I once had a new (recent) graduate M.E. (EIT) designing a set of lifting lugs to be welded to the wall of a pressure vessel. The vessel was a low pressure design and the wall thickness was 7 ga. (~ 0.187" thickness). The engineer did a good design on the lug, using the correct vessel dry weight and also did a thorough and acceptable design on the welds, all fit for purpose with correct weld procedures and PQR's (procedure qualification record) for the material and service requirements. Unfortunately, he neglected what the weight of the lift would do to the vessel wall. The lug would have separated from the vessel wall in any way the rigging could have been done. Fortunately, as happens in any well run engineering outfit of any size, everyone was always checking everyone else's work before it got to a fabricator.

To the OP: Know the design loads on the welds (probably wind loadings) as well as how and in what form those loads will be transferred to what the weldment is attached to.

Example : A seriously bodacious lifting lug attached by serious welding to the roof of a 5,000 lbm vehicle will lift and leave the car behind.

Attach the panels to something more substantial than an or under reinforced roof.

Excellent points, thank you. What you are basically saying is that it would have to be connected to the edges of container which is where the beef is ?

[J.P.M.]

Not everyone has welding skills ? I don't...
It's not thick metal on top, unless you weld it to the corners which is very thick.

I once had a new (recent) graduate M.E. (EIT) designing a set of lifting lugs to be welded to the wall of a pressure vessel. The vessel was a low pressure design and the wall thickness was 7 ga. (~ 0.187" thickness). The engineer did a good design on the lug, using the correct vessel dry weight and also did a thorough and acceptable design on the welds, all fit for purpose with correct weld procedures and PQR's (procedure qualification record) for the material and service requirements. Unfortunately, he neglected what the weight of the lift would do to the vessel wall. The lug would have separated from the vessel wall in any way the rigging could have been done. Fortunately, as happens in any well run engineering outfit of any size, everyone was always checking everyone else's work before it got to a fabricator.

To the OP: Know the design loads on the welds (probably wind loadings) as well as how and in what form those loads will be transferred to what the weldment is attached to.

Example : A seriously bodacious lifting lug attached by serious welding to the roof of a 5,000 lbm vehicle will lift and leave the car behind.

Attach the panels to something more substantial than an or under reinforced roof.

[geekwithoutacause]

Welding to the metal skin :
Damages existing inner & outer paint, which must be cleaned and repaired (lots of labor)
CORTEN steel may not weld well because of it's alloy
Any heat treatment will be gone after welding, so it may require reinforcement
I'm a great microelectronics solderer, but I can't weld and have seen bad welds fail.

If it was I, I'd liquid nails 2x4's to the inside, drill pilot holes into them, bolt on, with rubber & stainless washers and roof glop over the completed fitting and hope it works

Yeah, that kind of what I was thinking. The 2x4's on the inside will be a frame along the walls and along the roof. I think that should be beefy enough.Probably have 4 supports per panel (2 top , 2 bottom).
I will use superstrut for the frames. Do you think I can rely on the solarpanels frame itself and only attach the top and bottom of the panel to the superstrut frame? so basically have 4 legs only ?

[Mike90250]

Welding to the metal skin :
Damages existing inner & outer paint, which must be cleaned and repaired (lots of labor)
CORTEN steel may not weld well because of it's alloy
Any heat treatment will be gone after welding, so it may require reinforcement
I'm a great microelectronics solderer, but I can't weld and have seen bad welds fail.

If it was I, I'd liquid nails 2x4's to the inside, drill pilot holes into them, bolt on, with rubber & stainless washers and roof glop over the completed fitting and hope it works

[geekwithoutacause]

Hey Mike,

I am curious as to why you don't recommend welding to the storage containers?

As long as you have a competent welder, I can't think of a downside. Competent is key.........

Not everyone has welding skills ? I don't...
It's not thick metal on top, unless you weld it to the corners which is very thick.

[PNW_Steve]

I would not weld to the container. SS Thru bolts with SS & rubber washers outside are likely a better solution.

Hey Mike,

I am curious as to why you don't recommend welding to the storage containers?

As long as you have a competent welder, I can't think of a downside. Competent is key.........

[geekwithoutacause]

This depends on a number of factors, among them are how tall the front row is standing (angle) and your latitude. 12 feet away and sitting higher, sounds like you should be safe unless you are in the arctic circle.

No, I am in sw Colorado so that shouldn't be an issue. They are 77 inches high.
Probably make them adjustable so the snow will slide off in winter, like Bruce Roe said. This winter we had some serious snow here. Would help a lot to not have to clear that as well.

If I am going to use both containers anyways, I might as well spread them out evenly among the 2. Would be easy to expand the panels at some point as well.

[geekwithoutacause]

I would not weld to the container. SS Thru bolts with SS & rubber washers outside are likely a better solution.

Ok, I thought of that too but was a bit concerned w leaks. Would have to drill thru the roof part and not the corner/edge parts. The roof isn't very thick. You think that would be sufficient? Or should I frame the inside w 2x4 ? (which I was going to do anyways so I can build shelves and stuff).
So that brings me to the next question, what kind of metal should I use for it.....

[littleharbor]

Or would the first set block too much light?

This depends on a number of factors, among them are how tall the front row is standing (angle) and your latitude. 12 feet away and sitting higher, sounds like you should be safe unless you are in the arctic circle.

[Mike90250]

I would not weld to the container. SS Thru bolts with SS & rubber washers outside are likely a better solution.

[geekwithoutacause]

Yep, 72 cell panels. 12 panels probably easiest would be 12 in a single row.

ok. I have a 2nd container which is 12 ft behind it, parallel, and it also sits a little bit higher up (maybe a foot, or 2). I could mount the rest on there.? Or would the first set block too much light?
What materials should I use and how many mount points? Anyone done this ?

[littleharbor]

The panel sizes are 39 x 77 inches.

Yep, 72 cell panels. 12 panels probably easiest would be 12 in a single row.

[geekwithoutacause]

The panel sizes are 39 x 77 inches.