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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.
 

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