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Bi Facial output

gray webber

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Feb 4, 2022
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Hi there!
I am doing my final tests before locking in my system for the camp to be built this summer off grind. At 47 degrees latitude and cold with lots of snow, I decided to try Bi Facial panels. Maybe the snow reflection could bring in more watts the standard panels but I was told not to expect near the outputs that are claimed. Understood but oh well, may as well try. Today at 1;30 solar time I got to my shop and it was sunny after a big storm last night. I thought I would try a panel for fun. Last week I got 1206 watts from a set of 445 panels and wanted to know if that was just a freak thing?
I hooked up just one panel by placing it outside my garage door on an angle of maybe 12 degrees and checked it out-------618 watts!!!!!!!!!!!!!!!!!!! Thats 39% over the panel rating. I am impressed! Thought I would share:)
 
Hi there!
I am doing my final tests before locking in my system for the camp to be built this summer off grind. At 47 degrees latitude and cold with lots of snow, I decided to try Bi Facial panels. Maybe the snow reflection could bring in more watts the standard panels but I was told not to expect near the outputs that are claimed. Understood but oh well, may as well try. Today at 1;30 solar time I got to my shop and it was sunny after a big storm last night. I thought I would try a panel for fun. Last week I got 1206 watts from a set of 445 panels and wanted to know if that was just a freak thing?
I hooked up just one panel by placing it outside my garage door on an angle of maybe 12 degrees and checked it out-------618 watts!!!!!!!!!!!!!!!!!!! Thats 39% over the panel rating. I am impressed! Thought I would share:)

How measured?

12° from vertical or 12° from horizontal?

Either way, it sounds like there wasn't any realistic exposure to the back side of the panel, thus you weren't getting any significant input from the back side.

If 12° from vertical, that's hard to believe unless it's incredibly cold, and the cells are incredibly cold as well. ~20% over rating is possible under optimal conditions, but 40% is hard to believe.

If 12° from horizontal, that's impossible.

I'm very inclined to think that you are not getting accurate readings. There's just not enough sun at 47°N latitude to get those kinds of numbers.
 
That is impressive ! My flat roof will be painted white and I'll go for bifacial panels.

Read a report lately that compared several installations all over China by insolation and type of background. I lost the link. It concluded that the gain of bifacial is between 5% and 20%, and that bifacials also perform pretty well in diffuse lighting conditions (cloudy), with a gain between 7% and 11% (numbers from memory).
 
How measured?

12° from vertical or 12° from horizontal?

Either way, it sounds like there wasn't any realistic exposure to the back side of the panel, thus you weren't getting any significant input from the back side.

If 12° from vertical, that's hard to believe unless it's incredibly cold, and the cells are incredibly cold as well. ~20% over rating is possible under optimal conditions, but 40% is hard to believe.

If 12° from horizontal, that's impossible.

I'm very inclined to think that you are not getting accurate readings. There's just not enough sun at 47°N latitude to get those kinds of numbers.
12 off of vertical and 16f outside
Just bottom on snow drive and top leaning against with garage door. The door could have benifits? It’s only a few inches away.
Measured with Midnight Solar Classic charge controller. Checked amps with zeroed out clamp on amp meter. Math from that and volts equaled the watts stated on charge controller.
I think it’s right-totally surprised.
 
16°F is pretty chilly. It could be right, but it won't be sustained. As solar hits the panels, the cells will warm (~80% of the energy hitting the panel is NOT converted to electricity and mostly converted to heat) and performance will taper accordingly.
 
You may be right on that. I called up a couple photos from last week and they were marked about an hour apart. The one just after Solar noon was 580 watts and the one an hour later was 503 watts.
I’ll have to get them out earlier in a bright day and monitor more closely to figure if anything is causing a flawed outcome?
 
I never posted pictures before but I’ll try now? I guess that kinda worked. Now I’ll try the one from last week? I think these work. One is a single panel with about 41volts and the other is a pair of them at about 84vilts. 5CDBF0F7-DDE2-4AEF-BDF1-FF467283D1A0.jpegAE07D2CD-1F5B-4A66-AE5A-978E0FF46277.jpeg
 
That is impressive ! My flat roof will be painted white and I'll go for bifacial panels.

Read a report lately that compared several installations all over China by insolation and type of background. I lost the link. It concluded that the gain of bifacial is between 5% and 20%, and that bifacials also perform pretty well in diffuse lighting conditions (cloudy), with a gain between 7% and 11% (numbers from memory).
I had heard 12% extra gain is all one could expect. The charts say up to 30%.
These outcomes surprised me. I looked up a couple pictures of the charge controller from last week. I had not set out to test for output, just to see if my components were working right. I put the battery box and components mounted on a 3/4” board onto a rolling mini scaffold and brought them to an overhead door. Then dragged(heavy) a panel or two out and tipped against the adjacent garage door-I hooked them up to the charge controller. Watched to see if the equipment was set up right and all was good. That’s when I first saw the output numbers. Surprised I took a couple photos. Not at the peak but close. Last week I had put two panels on a string and today I put one out. That’s why the voltage was about half today.
Either way—if I can not find a flaw in the readings or set up then they are right.
I did mention-my garage door is white. About 0-18” away on a tapper. I’ll see if I can find a picture of it and post with this note? Only one I found was from today. 53C5A035-3C7E-4DD5-9AC5-8BCE3A0B5AF1.jpeg
 
I found a picture of my set cart and thought I could share.
What you will see is
1. Insulated battery box with 2-12volt 300amp lithium batteries
2. Component board with inverter, charge controller and combiner box mounted with breakers at lower part

These are mounted on a roll around mini scaffold so I could move it where needed in my shop. D8CFABE8-7F36-4E80-A335-DFAE4F085DE0.jpeg
 
16°F is pretty chilly. It could be right, but it won't be sustained. As solar hits the panels, the cells will warm (~80% of the energy hitting the panel is NOT converted to electricity and mostly converted to heat) and performance will taper accordingly.
I found two pictures of output a bout 50 min apart. One was 1160watts was about two hours after first set up and 20 min after Solar noon. and one 1013 watts about 50 min later. As the second was almost an hour later and about 1:15 after Solar noon I’m guessing cold panel alone is not causing such readings?
 

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Using specs from a similarly sized Bi-facial panel, ~15°F would result in a 13% boost in power due to increased Vmp and increased Imp, but that would taper a bit due to cell heating.

Are you at high elevation? Thinner atmosphere means more sun. My non-bi-facial array regularly meets and exceeds rated due to 6500ft elevation and colder temps even with suboptimal tilt (year round, not winter). The most I've ever seen was +20%.

You might have several things working for you and/or you just have fricken magic panels...
 
I’m at 700ft.
They may be magic? I plan on a focused test next time good sun is seen. I never set out to do a focused test on output but when I saw those numbers on the Midnite I had to take notice. Then I did the quick meter test. Snow here now and tomorrow:(.
All I can do is try it again, double check measurements with my VOM , do the math again and report it out. Hell, I’ll even check the panel labels as maybe they sent me panels I had not ordered?
I hope they are magic?
Hope we get a real sun day soon now that these things are in question.
 
I’m at 700ft.
They may be magic? I plan on a focused test next time good sun is seen. I never set out to do a focused test on output but when I saw those numbers on the Midnite I had to take notice. Then I did the quick meter test. Snow here now and tomorrow:(.
All I can do is try it again, double check measurements with my VOM , do the math again and report it out. Hell, I’ll even check the panel labels as maybe they sent me panels I had not ordered?
I hope they are magic?
Hope we get a real sun day soon now that these things are in question.
I may have found the info that explains the high output.
Pulled up the data sheet on the Canadian 445
Bi-facial and it’s tested at 20c. If I read it right, the power increases .34% for every degree below that. I was at about -10c or 30 points below so adding 10% to the 30% optimal gain you can get up to 623watts. That’s just above my highest reading. While it may be freaky, it’s possible. I’m feeling better about my observations.
I will still run a check on it when sun allows.
 
Update on Bi-facials:
I set up a pair of panels to rest again about 10am today. Took a picture of what I saw at 12:38 pm.
1338 watts From 2-445 watt panels????
That’s 40%+ over rating. Saw 1420 watts before I got out my phone. Crazy!
It was 24f out. 24 degree tilt. About an hour before Solar noon.
Had to leave for a few hours so no idea of noon outputs.
Just impressed with the output!
Attached is one of the pictures of the Midnight solar charge controller——
 

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Tried any more tests? The results from your first tests were incredible. Granted it was cold, sunny, and snow on the ground, which are ideal conditions, but still impressive. I'm working on a system for our place and was considering bifacials. With readings like yours, it would be hard to design a system when the panels can overproduce like that. Based on Canadian Solar datasheets, the voltage gets to a certain point (40.9 Vmp, 48.9 Voc), but the current continues to rise. So, I guess I could design it based on these two voltages.
 
After at least 6 set up tests I am fully convinced that numbers I was getting are for real. I was getting 20-45% more power on any good sunny days. My issue then became the temp coefficient that on very cold days the voltage could go too high for three units in series so I’m sticking with two. Withe the extra power output I may never need any more panels then the 4 I have. The bump in power was a concern but after many checks it became clear my SCC could handle the accidental over paneling. I can’t wait to set them up permanently and see how they perform in real time.
I will be mounting them on a home made ground anchor mount. The lowest a panel will be is 30” over ground for snow clearance. They will be able to tilt from vert to about 65 degrees. I will set them near vertical for winter snow resistance when I am not there to clean as needed. Then -30 then 55 then 30 again for none snow times.
We still have 3’ of snow on the ground at the camp site so many weeks before any set up.
I will take pics and post as things move along.
 
I’m posting a few other pics I took during testing. Some are single panels putting out 600 + watts on different days. A picture of the two panel set up against my garage door.
Oh and one of ice fishers on the lake in front of the house 4 days ago. Still lots of snow!
Also a 390 watt version found that a friend may pick up for his camp. The 445 I got are sold out at 5 outlets I checked on?????
If the 390 work like the 445 then still lots of extra power. These 390 are available in as few as 5 on eBay. Decent shipping cost. He may get 6 as the cost would be about the same as the 4 -445s I got. A bit more power but that’s a good thing.
Hope your choices and project works good!
 

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Good day.
I set a single panel out at 10am. Set at 15degrees but should be 38 degrees this time of year. Very cloudy today. The panel after 5 hours had provided over .45 kWh. It was at about 150watts when I left about 1pm Solar time. Should provide about .8-.9 kWh for full day? One panel, cloudy.
I will not go back to shop today to check on evening final power?
 

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Good day.
I set a single panel out at 10am. Set at 15degrees but should be 38 degrees this time of year. Very cloudy today. The panel after 5 hours had provided over .45 kWh. It was at about 150watts when I left about 1pm Solar time. Should provide about .8-.9 kWh for full day? One panel, cloudy.
I will not go back to shop today to check on evening final power?
Thx!
I live in the far north (with lots of snow, lots of shade) and have been debating bifacials for a while. Decided to pull the trigger!
 
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