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Mounting solar panels on a 40 foot container?

Calvin98

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Looking at filling a vertical wall on a 40 foot high cube container with solar panels. Has anyone done anything like that? How did they mount them? Attaching two by fours to the container and then attaching the panels to that is the cheapest, but not sure how strong it would be. Unistrut would cost like over 600 bucks just for the rail. You need about 160 feet of rail to cover the wall. You could just mount the panels directly to the container but then you’d be drilling hundreds of holes in the wall which could lead to leaking.
 
Do you live in the north pole or are you just willing to accept the compromise for a simpler install than an angled array?
 
The container wall is facing west, and I want to take advantage of the afternoon/evening sun.
 
The container wall is facing west, and I want to take advantage of the afternoon/evening sun.
Yeah I am building a due west array. There's a lot of debate there but leaving that aside, try using pvwatts to compare the production at 90 degree tilt vs. 20, 40, etc. I think it's a pretty big hit.
 
It is. 50% less production. I checked. But with new panels under $0.30/watt, you can't really go wrong. The roof is already covered with panels. Just want to get more power during the 4-9pm peak rate time and see how it works.

A vertical N-S wall of vertical bifacial panels is also interesting. You can get early AM power as well as late PM power from the other side. You don't even need 2 sets of panels back to back anymore.
 
But if you are already going to figure out how to secure some mounting rails to the top of the container, couldn't you build one row of footers out away from it to kick it out 45 degrees?

But also, I don't disagree with doing something unique anyways, big solar cube look with 90 degrees.
 
I might do that. Now I'm thinking of making a frame out of 10' or 12' 2x4's and attaching to the top and other side. Container is 9 /12' tall. No holes required that way. Can be 90 deg vertical and will allow for some air behind the panels. Have plenty of power at noon. If it does not work, can always choose a different mounting. Just wondering if anyone else did anything similar and how they did it. Another benefit of panels on the wall might be that it keeps the inside of the container a bit cooler in the summer since the sun is not hitting it directly anymore.
 
Well, it’s mostly done. Interesting experiment. West facing wall at this time of year in April puts out about 50% of the power of south facing polemount panels. It does seem to give me at least one extra hour of full solar power in the evening, and of course it evens out the duck curve. Most of the production is from three or 4 PM all the way to six or seven. Will be interesting to see how this does over the course of a full year. This is 19 panels at 320w each. Two strings. One string of 10 and one string of nine. Split into a North string and South string. With solar panels being priced so low and low cost inverters, something like this is practical. 20 years ago this would’ve been cost prohibitive.
 

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Quick Update: The peak production of West facing panels is about 5:30pm. For comparison, top-of-pole South facing panels peak at about 12:00pm and they pretty much end production at 6:30pm (500 W). At 6:30 pm the West panels are approaching their peak power output. So as one set of panels is producing almost nothing worth while, the other is approaching peak output (4.4KW). Also, the West panels make power all the way until 7:45pm now. At 7:30pm they are still putting out 1kw of power. All in all, at this time of year they put out an extra 10kwh during peak hours. In a day, they are making about 21kwh now. South facing pole mounts make about 40kwh. A bifacial vertical E-W facing wall could get early AM power as well as evening power. For the future, the West panels could replace/offset/avoid several kwh of battery storage potentially and get you an extra few hrs of solar production during peak hours.
 

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Quick Update: The peak production of West facing panels is about 5:30pm. For comparison, top-of-pole South facing panels peak at about 1:30pm and they pretty much end production at 6:30pm (500 W). At 6:30 pm the West panels are approaching their peak power output. So as one set of panels is producing almost nothing worth while, the other is approaching peak output (4.4KW). Also, the West panels make power all the way until 7:45pm now. At 7:30pm they are still putting out 1kw of power. All in all, at this time of year they put out an extra 10kwh during peak hours. In a day, they are making about 21kwh now. South facing pole mounts make about 40kwh. A bifacial vertical E-W facing wall could get early AM power as well as evening power. For the future, the West panels could replace/offset/avoid several kwh of battery storage potentially and get you an extra few hrs of solar production during peak hours.
Nice. I just started up my 270 degree (due west) array as well. But mine is angled at 25 degrees.
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In the winter, there's going to be more of a penalty. In the summer though, it's a good curve especially with our peak rates being 4-9pm.
 
Great! Right. In Winter this is not go great, but I am trying to get some of the "higher hanging fruit" so to speak. When panels cost $4.50/watt this was too expensive to do. So people did a lot of pole top mounts that could be seasonally adjusted. With panels costing $0.10 to $0.20/watt it is easy to just throw some panels out there and see what happens. 20 yrs ago, this would have cost $28,800 just in panels. Now it cost about $2,400 in panels. Big difference. It could have cost $1,200 had I been able to get them on sale.

We do have some trees that will shade the panels at some point, but you can't have everything. We have them on 2 strings so that hopefully the shading will happen on different strings at different times of the day and year. One string should always be without shade. The panels might shade the container wall also and maybe keep things cooler inside in the summer.

Angling the panes is possible, but this mount was super easy and cheap. Just 2x4's and no holes drilled into the container (just a few at the bottom to hold a 4x4). The panels are also all removable individually. Will see how it does over time.
 
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How much is that riser pipe hurting your production? It is blocking one half of the bifacials, my guess is it bypasses 1/3 of 1 panel given the string length
 
I'm also a little bit wondering if your retaining boards are shading the top half inch of the cells. Supposedly it can quite significantly limit production if that happens.
 
The bottom solar panels have the boards perpendicular to the presumed cell strings. The top solar panels have the boards parallel.

Was this gamed out beforehand?

For the top panels, the MPPT bypass option is to drop 1/3 or 2/3 of the voltage (and the half-cut structure is irrelevant in this orientation). Because the boards are parallel to the strings so it is lined up with how the bypass diodes work.

For the bottom panels, the half-cut structure will allow the top and bottom half currents to be decoupled from each other. However the boards are perpendicular to the strings so 2 cells in EVERY bypass diode zone will be affected equally. Those cells will bottleneck the panel and there is no away around it via bypassing.

The amount of shading impact on the cells also depends on the orientation geometry of the shadow vs the way the cell is oriented\. Parallel is better than perpendicular. I think the top panels are parallel and the bottom panels are perpendicular but it is hard to tell with black on black cells.

Now if those retaining boards do not block the sun at all, then ignore all that.
 
Very observant! Yes, the boards could be thinner or beveled a bit. Thin metal strip could solve that. Pipe will be shortened. Yes, all things to consider. Will see how I can improve it. Work in progress...
 
Any ideas for thin bar stock that would work? Need something 3" wide ideally. 3" steel 40' + 40' (top and bottom) costs $1,000 at Home depot. Metal supply should be cheaper, but that is still a lot. Metal roofing edging is less, but also a lot thinner. If I used 2" x 2" x 10' edging, it would cost $60. Beveling the wood gets rid of the shading, but also weakens the wood at that area.
 
Quick Update: The peak production of West facing panels is about 5:30pm. For comparison, top-of-pole South facing panels peak at about 1:30pm and they pretty much end production at 6:30pm (500 W). At 6:30 pm the West panels are approaching their peak power output. So as one set of panels is producing almost nothing worth while, the other is approaching peak output (4.4KW). Also, the West panels make power all the way until 7:45pm now. At 7:30pm they are still putting out 1kw of power. All in all, at this time of year they put out an extra 10kwh during peak hours. In a day, they are making about 21kwh now. South facing pole mounts make about 40kwh. A bifacial vertical E-W facing wall could get early AM power as well as evening power. For the future, the West panels could replace/offset/avoid several kwh of battery storage potentially and get you an extra few hrs of solar production during peak hours.

Pretty good amount of power from 4:00 to 7:00, which is within my peak time of use.

21 kWh vs. 40 kWh for South facing, is that for same total panel wattage rating?
How does peak wattage (that inverter has to process) of West facing array compare to South facing?
 
My other idea would be using clamps somehow, screwed into wood. If you shop around they can get pretty cheap. This is just an example I found at first glance. But it is a lot of panels so would probably still add up.

Yes, I looked at those. Trying to keep a small gap between the panels for air flow, but not so big so as to let mice build nests behind the panels. The ideal material would be 3" black anodized flat aluminum bar. But it is way too expensive. Need 80' of it.
 
Yes, I looked at those. Trying to keep a small gap between the panels for air flow, but not so big so as to let mice build nests behind the panels. The ideal material would be 3" black anodized flat aluminum bar. But it is way too expensive. Need 80' of it.
Could you cut the flat bar into little 1-2" "clamps" in the same profile you are picturing, instead of a long continuous bar?
 
Pretty good amount of power from 4:00 to 7:00, which is within my peak time of use.

21 kWh vs. 40 kWh for South facing, is that for same total panel wattage rating?
How does peak wattage (that inverter has to process) of West facing array compare to South facing?
Pretty much. South panels are 20 pc 310 watts so 6100w, West panels are 325 x 19 panels so 6175w .
West panels peak 4.4 kw at 5:15pm
South pole tops peak 12:00pm 4,900W
 
Could you cut the flat bar into little 1-2" "clamps" in the same profile you are picturing, instead of a long continuous bar?
Yes, that is a good idea. It does not have to be continuous. That would bring the costs down dramatically. Cut to about 3" long so that 1 "clamp" holds each panels at the corners. Or in the middle, no big difference, but way cheaper.

By the way, the way they are set up is that each panel is held in at the top an bottom of the aluminum on the panel. You can lift the panels up, tilt the bottom out and remove any panel. As it is now, the 1/2" thick wood in the middle does shade a small amount of the cells on the bottom panels. A small detail I did not think of initially. Just wanted to get the wall covered with as many panels a possible.

Will be interesting to see how much more production is with the new "clamps" that don't shade any of the cells.
 
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Nice. I just started up my 270 degree (due west) array as well. But mine is angled at 25 degrees.
View attachment 212627
In the winter, there's going to be more of a penalty. In the summer though, it's a good curve especially with our peak rates being 4-9pm.
It is interesting that your peak is like 3 hrs before mine (2pm vs 5pm). You can adjust things. If you want later peak, you go more vertical. If you want earlier peak you can angle the panels more. Me, I wanted more power later in the afternoon. As late as possible and practical.
 
It is interesting that your peak is like 3 hrs before mine (2pm vs 5pm). You can adjust things. If you want later peak, you go more vertical. If you want earlier peak you can angle the panels more. Me, I wanted more power later in the afternoon. As late as possible and practical.
Yes I had originally envisioned mine at more like 45 degrees. But after I set the foundations I did more production math and realized a shallower angle was gonna reduce the overall year round penalty.

Eventually I want to add some south facing arrays as well, and if I had some of those for "bulk" production I'd consider tipping my west array up.
 
Pretty much. South panels are 20 pc 310 watts so 6100w, West panels are 325 x 19 panels so 6175w .
West panels peak 4.4 kw at 5:15pm
South pole tops peak 12:00pm 4,900W

Suggesting longer path through atmosphere doesn't make much difference, and you can't over-panel without clipping.
Of course, over-paneling would reduce drop-off in production for other seasons.
Good to know when favoring hours of peak rates.
 
Really cool set-up! the solar cube :) It looks like you basically built an 'exoskeleton' of 2x4s around the structure?

We have a 40ft, high cube as well and I've been mulling over how to mount them on the roof. At our spot the recommendation is due south at 32 degrees. This is perfect because our container is east/west lengthwise. Any suggestions?

Related to this - how have you taken care to protect your roof from rust / sitting water? Our container is old so this feels like a battle I really need to be proactive on, getting rust off, repainting etc..
 
Thanks! It was an interesting build. Yes, exoskeleton. Here is a pic that shows it. There are no holes in the container wall or roof. Just to bottom rail. I put 4"x4" beams in the bottom channel and drilled and bolted them. They hold all of it up.The verticals are 10' 2x4's. The panels are held in by a rail at the top and bottom. The rail is large enough so that any panel can be put it or taken out easily, but still so secure that they can't fall out by themselves. The bottom panels are sitting on the 4x4.The top panes are side ways and are supported by the horizontal 2x4" Less panes in it so less weight to support. So far so good. You could do an exoskeleton also or weld brackets on. I've been thinking that an ideal situation would be 40' high cube situate N-S with panes on walls and roof. E and West walls produce power in the AM and PM, roof makes power during the day. A benefit of the panels is they they will probably keep the container cooler because they shade the metal walls. You could do 6kw + 6+ kw + say 10KW +/- if you also do a roof overhang. 16kw on a container!

Ours has some dents but leak free. Neighbor has a reefer container that he says leaks. I suggested puting a plastic sheet on the bottom and then putting his roof frame made of 2'6's over that. Anchor to side of container with hurricane ties. No penetrations in the roof that way. Plus the solar panes keep the UV off of the plastic and make it leek free. heavy duty pond liner 41' long 10' wide, attach things to top side ? No holes in the roof that way.

If you have room cover it all with panels . They are cheap enough to to that. We paid $100 for 325w panels. Could have gotten them for $50 when they were on sale.
E-W lengthswise - you mean the long side is facing e-w direction? Ok. Ours is vertical. Nothing to say you can't angel the panels at 32 deg. Seen people do that also. "Container Guy" on Youtube has angled brackets that you can pull away form the wall.

By the way, we also sealed behind the panels so mice could not get behind them and cause trouble.
Might be able to seal roof with car undercoating or roofing tar.

The top 2x8 is attached to a structure on the other side of the container. So it is secure. Making about 20-22kwh now (June) Peak solar is now 4pm. Used to be more like 1pm.
 

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Ours has some dents but leak free. Neighbor has a reefer container that he says leaks. I suggested puting a plastic sheet on the bottom and then putting his roof frame made of 2'6's over that. Anchor to side of container with hurricane ties. No penetrations in the roof that way. Plus the solar panes keep the UV off of the plastic and make it leek free. heavy duty pond liner 41' long 10' wide, attach things to top side ? No holes in the roof that way.

If you have room cover it all with panels . They are cheap enough to to that. We paid $100 for 325w panels. Could have gotten them for $50 when they were on sale.
E-W lengthswise - you mean the long side is facing e-w direction? Ok. Ours is vertical. Nothing to say you can't angel the panels at 32 deg. Seen people do that also. "Container Guy" on Youtube has angled brackets that you can pull away form the wall.
Thanks for the follow up.

What kind of rails are you using?

I am overwhelmed by the zillion results on Amazon etc when I look for mounting solutions.

That is a really interesting idea - use some sort of sheeting or underlayment then essentially deck it with 2x6s. Then secure with hurricane ties. Thanks for the idea.

Direction wise, what I meant is that door opens to the east, back faces the west. We have a long north side and a long south side.

I have attached a picture of my inverter set up that is waiting for use. Still need batteries and more panels. I assume you have all you stuff inside container? Then wired to building where you need power?

What climate zone are you in? Have you noticed how the batteries / panels affect temps inside?

Probably won’t do any serious mounting til next spring but I could prep with underpayment and 2x6s later this year.
 

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My neighbor did a similar system. He used 2 x 6 x 16 feet long and made a roof or frame on top of the container. Same as normal house framing. Used hurricane ties to attach the framing to the side of the container. So only holes in the side of the container. He also use the pond liner on the top of the container to keep water out. His frames were basically 2 x 6 lumber. He made it 16 feet wide so the container would have shading on the sides. You could do it that way or just put a vertical wall on yours. No, the containers just for storage. All the electrical equipment is somewhere else. If used for electrical equipment, I would certainly consider a refrigerated container since those are made to keep food frozen and they already come insulated. No need to mess with two by fours and fiberglass. Don’t have any batteries yet, but trying to figure out how to do this new non-export stuff. It’s a completely different world than net metering. The shipping container might be a good place to put batteries, though since they are flammable, we need to have something relatively fireproof. Of course, only the floor on a regular shipping container can burn. But again, if you get a refrigerated container that is completely non-flammable, including the floor. Only stainless steel and aluminum. And it’s insulated and will keep stuff cool. Most people never think about refrigerated containers, but if it’s a habitable place or you need to temperature control it I think it’s the only way to go. Normal shipping containers are great for storing items and keeping rodents and insects out but not for much else. Once you start having to insulate and do two by fours and sheet rock you might as well just buy the reefer to begin with. Cost will probably end up the same, but the reefer will be 10 times better.
 
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