Large (size and power) solar panels

[Bluedog225]

I’d like to shop around for large size solar panels for a shipping container installation. This is my “tier 2” power house. Not so worried about UL listed products and willing to take some chances with cheaper components.

Ideally, the panels would be able to cover the entire roof surface (8 feet) because solar gain is significant. The closest I have found is something like the Canadian Solar HiKu7.

The more side to side coverage, the better shading I get, even if not the full 8 feet. Esp after putting them in at an angle. But big panels will make the job overall easier and better.

Three questions:
1. Are there any good sources for used (or new) commercial panels that I can realistically buy from?

2. What is the backstory on importing big panels from Ali Express or Alibaba? I’ve heard mention that there may be large import tariffs. But I have not followed.

3. Any downsides to this plan?

Many thanks.

 

[sunshine_eggo]

1. https://santansolar.com/

2. MANY panels listed on alibaba are complete hooey. Ratings are often over-stated. IMHO, the amount saved over a source with stock in the U.S. is not remotely worth the risk.

3. Beware Bifacial panels. Their ratings may include power collected from the backside, and you may find that disappointing.

I found that the most effective use of the container roof was to stack them horizontally:




They are actually about 10' in that direction, so larger than the container roof (poor quality screen grab from side):



These are 330W Talesun 72 cell panels - typical size. 2m x 1m

When the sun is furthest south, there is a tendency to get shading on the bottom row of the bottom panel. In this orientation, I only use about 1/9th of the string's performance. Had they been mounted vertically, it would kill most of the array's production.

 

[Bluedog225]

Thanks. Good info.

That actually looks about right. I’ve been reluctant to build the racking but I can see the benefit.

 

[sunshine_eggo]

I didn't plan for the bumps in the top of the container, so the gap wasn't intended. I'm going to drill new mouting holes in the panel frames and shift them so they don't have gaps in between them. They won't be centered on the racks, but I don't care. Once I shift them over, I'll be able to get the full 6kW array on the container.

 

[magic8192]

Check out fred480v on ebay. He has been selling solar panels for a long time. I have used him and got exactly what I expected.

 

[upnorthandpersonal]

What is the backstory on importing big panels from Ali Express or Alibaba? I’ve heard mention that there may be large import tariffs. But I have not followed.

Things might be looking better today then they were a year ago:

U.S. judge rejects Trump tariffs on imported solar panels

A U.S. judge overseeing trade issues on Tuesday overturned a decision by then-President Donald Trump to allow a reimposition of tariffs on some imported solar panels.

www.reuters.com

Still, I believe there are other additional costs besides these tariffs when importing to the States, so you might want to start checking the details. I know a year or so ago one member here got hit with a lot of costs on top which made him not accept the imported panels at all.

Things in Europe are a lot easier, which is why I got 20x 500W panels directly from China almost two years ago without issues.

 

[HRTKD]

These big Q Cells panels are available from CEDGreenTech. I bought my 320 watt panels from them and it was a good transaction for me.

Q.PEAK DUO XL-G10 : Utility & Large Commercial : U.S. & CANADA : SOLAR PANELS : PRODUCTS : Q CELLS

www.q-cells.us

 

[Bluedog225]

Sunshine-how did you attach the strut to the container? Weld or drill or something else? It will be tough for me to drill holes (emotionally-chuckle).

And thanks all! Good info and I will review.

 

[Prefersdirt]

Beware Bifacial panels. Their ratings may include power collected from the backside, and you may find that disappointing.

Wouldn't bifacial be a potential Positive if mounting above the container like you did? Paint the surface of the container white and capture what bounces off?

 

[schmism]

Wouldn't bifacial be a potential Positive if mounting above the container like you did? Paint the surface of the container white and capture what bounces off?

Its my understanding that bifacial is something like 450w = 225w/face. and with poor install you wind up with like 300w per panel instead of the sticker rating leaving you upset that you paid extra for watts you'll never be able to use, system shortages because its only making 60% of what you thought it would etc.

I thought typicall install for bifacial was vertical north south orientation.

 

[sunshine_eggo]

Sunshine-how did you attach the strut to the container? Weld or drill or something else? It will be tough for me to drill holes (emotionally-chuckle).

And thanks all! Good info and I will review.

Funny you should ask... I'll just say that I discovered that welding is a skill that requires far more time and effort than I'm willing to expend to get good at it. The first rack was welded. It is now bolted and welded.

For the subsequent racks, drilled and tapped the top rail of the container. Secured with red loctite.

Wouldn't bifacial be a potential Positive if mounting above the container like you did? Paint the surface of the container white and capture what bounces off?

My container roof is in shade. Nothing significant to reflect. Definitely diminishing returns for me. Also, why would I replace the 6kW of solar I've already bought?

Bifacial work best at steeper angles and when there's potential for a lot of reflected light like snow. At 29° tilt at 35° latitude, I'm still getting 70-80% of my array's rating this time of year. The racking is actually adjustable, but I can't be bothered.

 

[MichaelK]

I would recommend NOT buying panels online at all! I've found the best deals locally on Craigslist with local pickup. Pretty much everything is cash and carry. The BEST panels I've bought now are used grid-tie panels that got pulled back off of someone's roof that defaulted on payments.

Just to check, I went to Craigslist in my local area and checked to see what I could find in the size range you are looking for. On the first page I found 290W REC panels (new) for 200$ each. That's ~1.5W/$.
https://inlandempire.craigslist.org/hsh/d/phelan-290-watt-rec-solar-panel-new/7414204501.html
For the 250W panels I usually buy, I'm seeing prices in the 75-85$ range. Sadly, I was getting 245-250W panels last year for 55$ each. Should have bought as much as I could carry.

For the top of my workshop I built a angled fixed array that looks very much like SE's in pic #2. Those were made of unistruts. To anchor them on the roof, I first bolted down unitstruts perpendicular to the array frame with 3" bolts protruding upwards. I then bolted the array frame down onto those perpendicular roof unistruts.

I used rubber-gasketed roofing screws for all the roof penetrations. And yes, welding was an extended learning experience. At my 8th array frame, I'm starting to get good at it.

 

[sunshine_eggo]

Its my understanding that bifacial is something like 450w = 225w/face. and with poor install you wind up with like 300w per pannel instead of the sticker rateing leaving you upset that you paid extra for watts you'll never be able to use, system shortages because its only makeing 60% of what you thought it would etc.

I don't know if it's 50/50. The panels the OP linked are massive. Simply looking at their L * W * 20% * 1000W/m^2, they calculate out to very nearly 670W, so that particular rating doesn't appear to factor in anything from the backside.

 

[Bluedog225]

I’ll keep an eye on craigslit.

I had good luck mounting a single panel to my container. I sanded down to good paint and glued a strut down with PL premium. 10 years later, I can’t get if off by hand. Have not tried a prybar yet. It’s only a 3 foot section but the holding power is pretty impressive. Not sure I’d trust it for a full array.

With the right long metal (2x20’ per side), I may be able to run some discrete tie down straps around the container. Or go more Mad Max and use chain.

 

[sunshine_eggo]

Bifacial work best at steeper angles and when there's potential for a lot of reflected light like snow. At 29° tilt at 35° latitude, I'm still getting 70-80% of my array's rating this time of year. The racking is actually adjustable, but I can't be bothered.

Had to double check my claim...



Not bad at 9:50am (my peak is around 11:30am).

 

[HRTKD]

Sunshine-how did you attach the strut to the container? Weld or drill or something else? It will be tough for me to drill holes (emotionally-chuckle).

And thanks all! Good info and I will review.

The only benefit to welding that I can see is that there won't be any way for water to get into the container. That's assuming your welding is good and you don't weld through the container's roof.

 

[Bluedog225]

I forget who it was but someone on the forum drilled into the box tube on his conex and a steady stream of water came out.

I’ll go to great lengths not to put holes in those.

I could always mount an L bracket on the side through the sheet metal wall.

 

[Bluedog225]

This has good potential. I saw it on a ebay listing as part of a kit but not in real life. May be something I need to fabricate.

 

[sunshine_eggo]

That top member is completely sealed. I seriously doubt anything is getting past the loctite. Rain isn't much of a concern.

 

[tomy2]

I would recommend NOT buying panels online at all! I've found the best deals locally on Craigslist with local pickup. Pretty much everything is cash and carry. The BEST panels I've bought now are used grid-tie panels that got pulled back off of someone's roof that defaulted on payments.

Just to check, I went to Craigslist in my local area and checked to see what I could find in the size range you are looking for. On the first page I found 290W REC panels (new) for 200$ each. That's ~1.5W/$.
https://inlandempire.craigslist.org/hsh/d/phelan-290-watt-rec-solar-panel-new/7414204501.html
For the 250W panels I usually buy, I'm seeing prices in the 75-85$ range. Sadly, I was getting 245-250W panels last year for 55$ each. Should have bought as much as I could carry.

For the top of my workshop I built a angled fixed array that looks very much like SE's in pic #2. Those were made of unistruts. To anchor them on the roof, I first bolted down unitstruts perpendicular to the array frame with 3" bolts protruding upwards. I then bolted the array frame down onto those perpendicular roof unistruts.

I used rubber-gasketed roofing screws for all the roof penetrations. And yes, welding was an extended learning experience. At my 8th array frame, I'm starting to get good at it.

I see those REC panels on craigslist, they were not mono, you van get 365W mono panels at Signature solar for .53 a watt new plus shipping.