A solar panel that works with partial shade

[Guigsy]

Many people don't realise, that when a solar panel has even a small shadow across it, such as from an overhead wire or even a resting fallen leaf, the output plumets. Even if just a tiny corner is shadowed, putting 5% in the shade, the output might drop 80%. So installing a panel that uses up every bit of your roof space might perform worse than a smaller panel if it gets shaded by your TV aerial.

So this product is interesting:


I'm guessing there's just additional diodes in there? Or maybe active switching. But regardless, to maintain such a high output when it's partially shadowed would be very useful for motorhomes.

Are there other similar products about?

 

[Raul]

Many people don't realise, that when a solar panel has even a small shadow across it, such as from an overhead wire or even a resting fallen leaf, the output plumets. Even if just a tiny corner is shadowed, putting 5% in the shade, the output might drop 80%. So installing a panel that uses up every bit of your roof space might perform worse than a smaller panel if it gets shaded by your TV aerial.

So this product is interesting:


I'm guessing there's just additional diodes in there? Or maybe active switching. But regardless, to maintain such a high output when it's partially shadowed would be very useful for motorhomes.

Are there other similar products about?

He is flogging a old panel. Comercial/ domestic panels all work that way, keep trying to tell you guys for ages. If falls on deaf ears. Some even have bypass at cell level. Nothing new.

 

[Guigsy]

He is flogging a old panel. Comercial/ domestic panels all work that way, keep trying to tell you guys for ages. If falls on deaf ears. Some even have bypass at cell level. Nothing new.

So why aren't any that we see built that way? Even the premium brands?

 

[funflair]

So why aren't any that we see built that way? Even the premium brands?

Are you sure that some aren't ?

 

[lorger]

We manufacture the film for solar panels, a new product a year or so ago was double sided panels. I’ve no idea how that works I just make them

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[lorger]

Quick google

This is not the case with bifacial solar panels- instead, these types of panels have solar cells on both sides. This enables the panels to absorb light from the back and the front. Practically speaking, this means that a bifacial solar panel can absorb light that is reflected off the ground or another material.6 Nov 2023

 

[Guigsy]

Are you sure that some aren't ?

I know my Victron panel is terrible with even a finger of shade on it.

 

[funflair]

I know my Victron panel is terrible with even a finger of shade on it.

We have Buttner 72 cell panels and they claim good performance in partial shade, the CDS Power Line are even better I think but of course more money, sorry should say "even more money", never noticed a problem with our Buttner Black Line to be honest.

 

[Speve]

We have a pair of Buttñer black line panels and they are very efficient

 

[Guigsy]

We have a pair of Buttñer black line panels and they are very efficient

It sounds like Buttner panels are just slightly more parallel in the wiring. It would mitigate a bit of the 'all or nothing' effect I see on my Victron panel, but you'd still get a drop in current. Whereas that video suggests those panels are barely affected. I'd like to see some testing!

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[funflair]

It sounds like Buttner panels are just slightly more parallel in the wiring. It would mitigate a bit of the 'all or nothing' effect I see on my Victron panel, but you'd still get a drop in current. Whereas that video suggests those panels are barely affected. I'd like to see some testing!

I'd like to see some sun

 

[Raul]

So why aren't any that we see built that way? Even the premium brands?

What are you saying? There are loads with bypass diodes that shunts a row or two rows of cells if one row is shaded. The shotky diodes are at the back in the connection box.
Leisure panels, not all have them, but victron panels do.
There is nothing on that panel that old panels don't have. The old Trina 230w, very very old, has 3 diodes splitting the panel in 3 separate workable sections.
The new half cut cell panels are splitting the panel in 6 workable sections. And finaly SunPower and LG neon are shunting any shade at cell level, yes any cell shaded can be bypassed, way more advanced than that poxy bit in the video.

 

[Guigsy]

What are you saying? There are loads with bypass diedes that shunts a row or two rows of cells if one row is shaded. The shotky diodes are at the back in the connection box.
Leisure panels, not all have them, but victron panels do.
There is nothing on that panel that old panels don't have. The old Trina 230w, very very old, has 3 diodes splitting the panel in 3 separate workable sections.
The new half cut cell panels are splitting the panel in 6 workable sections. And finaly SunPower and LG neon are shunting any shade at cell level, yes any cell shaded can be bypassed, way more advanced than that poxy bit in the video.

If a shade a palm sized shadow on the corner of my 2 year old Victron 175w, I lose about 80% of the output. I have photos.

 

[Raul]

It sounds like Buttner panels are just slightly more parallel in the wiring. It would mitigate a bit of the 'all or nothing' effect I see on my Victron panel, but you'd still get a drop in current. Whereas that video suggests those panels are barely affected. I'd like to see some testing!

He is lying to you, that panel has 4 rows 2 workng sections, you shade any cells in the two rows you get cut half, its been working like that for the past 15-20 years. He compared it to a leisure panels without bypass, and shaded cells in all rows in portrait, crafty to make his test more obvious.

 

[Raul]

If a shade a palm sized shadow on the corner of my 2 year old Victron 175w, I lose about 80% of the output. I have photos.

Then you have bad diodes

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[Guigsy]

He is lying to you, that panel has 4 rows 2 workng sections, you shade any cells in the two rows you get cut half, its been working like that for the past 15-20 years. He compared it to a leisure panels without bypass, and shaded cells in all rows in portrait, crafty to make his test more obvious.

If it's so common, why are there YouTube channels that test this feature? And they're surprised that this panel is so good?

I'd like to be wrong. But I've played with several PV panels, including a brand new 400w domestic one this summer. I've never seen one that didn't stumble with shading.

 

[Raul]

If it's so common, why are there YouTube channels that test this feature? And they're surprised that this panel is so good?

I'd like to be wrong. But I've played with several PV panels, including a brand new 400w domestic one this summer. I've never seen one that didn't stumble with shading.

You will get there, that panel has nothing special and nothing extra than the traditional 60 cell panel. In fact the cell arrangement on a 60 cell panel, is superior compared to a 36 cell arrangement, as it gets a extra row and a extra diode.

Keep on testing, what was the 400w panel you tested?

 

[Guigsy]

Keep on testing, what was the 400w panel you tested?

It was big, rectangular and black. It was a spare from some new builds my brother was working on. He took it tent camping (his camping setup is nuts). Don't know the brand. I do know that it exceeded 400w in July sunshine. And it was just as sensitive to shadows as every other panel I've seen.

 

[Raul]

Another think to consider is, your mppt traking input range. If a given mppt gives input parameters, often are confused and belived that's the tracking range to. It isn't, the tracking range is much narower that the input parameters. If a shade brings the voltage down, enough to take it outside of mpp tracking range, it simply won't track for max power point at that moment. Wide mpp tracking range are on mppt's with a VOC limit of 150VDC and up. The smaller mppt's will stall at first shade. But will recover a little , after it sweeps the array for another sample, then it will pick best compromise. Also the tracking algorithm its important to how fast should react to sweep for another sample. Its like you have a torch in your hand, and if something moved and blocked your light beam, you react and move the torch. A good algorithm sweeps every few seconds looking for any change in light, and looking for best possible power point on I V curve, in any given moment.

 

[Otter Spotter]

I know my Victron panel is terrible with even a finger of shade on it.

Take your finger off it then

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[AlanandMayya]

It sounds like gee-whiz advertising to me. If you look at the back of a panel you can see the diodes. Can count them. Tells you how many separate sections you have. Also from the front you can see by the silver conductors how many sections the cells are wired as. In a way its true though - this panel will have superior shading performance to a panel with less diodes than it has - like maybe an ancient one, or a toy one. But solar panels get better by the week, they are sold by the million and competition is intense. All the big global manufacturers are duking it out publicly over a fraction of a % point in performance per $. There are no mysteries, no secrets - they all publish data sheets and are tested and certified by independent certifying agencies. No need for Amazing, Incredible exposes on You Tube.

 

[AlanandMayya]

He is flogging a old panel. Comercial/ domestic panels all work that way, keep trying to tell you guys for ages. If falls on deaf ears. Some even have bypass at cell level. Nothing new.

Ha ha ha you are such a skeptic Raul! I bet you dont even believe in Father Christmas, do you?? No, me neither. I believe in data sheets with a certifying body stamp.

 

[Guigsy]

It sounds like gee-whiz advertising to me. If you look at the back of a panel you can see the diodes. Can count them. Tells you how many separate sections you have. Also from the front you can see by the silver conductors how many sections the cells are wired as. In a way its true though - this panel will have superior shading performance to a panel with less diodes than it has - like maybe an ancient one, or a toy one. But solar panels get better by the week, they are sold by the million and competition is intense. All the big global manufacturers are duking it out publicly over a fraction of a % point in performance per $. There are no mysteries, no secrets - they all publish data sheets and are tested and certified by independent certifying agencies. No need for Amazing, Incredible exposes on You Tube.

Ok. But then why does it out perform the other brand name one he has. And he references others. And several panels I've seen also behave badly with shadowing.

My understanding is that diodes will cause about a volt of drop. So every set of diodes you add to isolate an array will decrease the output of your panel. Hence they are used pretty sparingly.

 

[AlanandMayya]

Ok. But then why does it out perform the other brand name one he has. And he references others. And several panels I've seen also behave badly with shadowing.

My understanding is that diodes will cause about a volt of drop. So every set of diodes you add to isolate an array will decrease the output of your panel. Hence they are used pretty sparingly.

Yes, they do drop about 700mV. But thats a concern with the blocking diodes that are in series with the cells, to avoid reverse current flow - you do indeed lose that 700mV under all conditions, which is a pity, especially in a low voltage (say 18V) panel. Less on a big 50V panel. The bypass diodes are different - they are in parallel with the cells, and conduct if the cells are dark. So although you lose the voltage from those dark (shaded) cells, and the 700mV, the other cells in the circuit can continue to flow their full current through the bypass diode - they are not limited to the tiny current that the dark cell is providing. Hence they improve partially shaded performance. When cells are generating, these bypass diodes have no effect, you dont lose anything from them being there. The guy in the video does a nice demonstration and I dont suspect him of falsifying anything, but he doesnt explain what he is demonstrating. Why can't he show us the data sheets for both panels, showing Voc, Wp, number of bypass diodes? Maybe even the price?? When he shaded that bottom row, was it part of one section, or was it one block from each section?? Then we would understand what the results mean. As it is, we just know that one new panel performed better than some other panel, whatever it is, in this test. Ive found that nearly all people selling technical stuff on You Tube to the general public 1) dont understand what they are talking about and 2) are being paid to say what they say so are not being totally honest. Any reputable manufacturer of technical goods will publish a data sheet and will say which independent certifying bodies have endorsed it. I would never buy a product without this. OK, a bottle of beer maybe but not a solar panel. And having read the data sheet I would then ignore anyone on You Tube who gave a hand-waving explanation to the contrary. Sorry if this sounds grumpy and miserable, I worked 45 years as an engineer and have spent my life designing stuff, procuring materials by competitive tender, constructing and commissioning stuff, operating stuff. Maybe I'm just an old guy in a rut and things are different these days, but I always relied on published, certified performance data and never consulted a you Tube influencer. I've found this approach worked well, stuff did perform as predicted.

 

[Guigsy]

Yes, they do drop about 700mV. But thats a concern with the blocking diodes that are in series with the cells, to avoid reverse current flow - you do indeed lose that 700mV under all conditions, which is a pity, especially in a low voltage (say 18V) panel. Less on a big 50V panel. The bypass diodes are different - they are in parallel with the cells, and conduct if the cells are dark. So although you lose the voltage from those dark (shaded) cells, and the 700mV, the other cells in the circuit can continue to flow their full current through the bypass diode - they are not limited to the tiny current that the dark cell is providing. Hence they improve partially shaded performance. When cells are generating, these bypass diodes have no effect, you dont lose anything from them being there. The guy in the video does a nice demonstration and I dont suspect him of falsifying anything, but he doesnt explain what he is demonstrating. Why can't he show us the data sheets for both panels, showing Voc, Wp, number of bypass diodes? Maybe even the price?? When he shaded that bottom row, was it part of one section, or was it one block from each section?? Then we would understand what the results mean. As it is, we just know that one new panel performed better than some other panel, whatever it is, in this test. Ive found that nearly all people selling technical stuff on You Tube to the general public 1) dont understand what they are talking about and 2) are being paid to say what they say so are not being totally honest. Any reputable manufacturer of technical goods will publish a data sheet and will say which independent certifying bodies have endorsed it. I would never buy a product without this. OK, a bottle of beer maybe but not a solar panel. And having read the data sheet I would then ignore anyone on You Tube who gave a hand-waving explanation to the contrary. Sorry if this sounds grumpy and miserable, I worked 45 years as an engineer and have spent my life designing stuff, procuring materials by competitive tender, constructing and commissioning stuff, operating stuff. Maybe I'm just an old guy in a rut and things are different these days, but I always relied on published, certified performance data and never consulted a you Tube influencer. I've found this approach worked well, stuff did perform as predicted.

That still doesn't explain why my panel behaves the same way. And several other panels I've played with. Or why the other YouTuber he references tests panels on the same way and hasn't seen any perform like the subject of the video. The other guy wouldn't have a financial incentive.

If there's a metric or feature that's easily identifiable in specs that means you know a panel will not fall on its face when a leaf sits on a corner, then tell me. I want a better panel.

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[Gromett]

My understanding is that diodes will cause about a volt of drop.

Yes, they do drop about 700mV. But thats a concern with the blocking diodes that are in series with the cells, to avoid reverse current flow - you do indeed lose that 700mV under all conditions

I am not getting involved with this debate. But although you are technically correct that normal silicon diodes have a forward drop of .7V you can get low voltage drop diodes like schottky diode which can have a forward drop of as little as 0.1V

 

[AlanandMayya]

That still doesn't explain why my panel behaves the same way. And several other panels I've played with. Or why the other YouTuber he references tests panels on the same way and hasn't seen any perform like the subject of the video. The other guy wouldn't have a financial incentive.

If there's a metric or feature that's easily identifiable in specs that means you know a panel will not fall on its face when a leaf sits on a corner, then tell me. I want a better panel.

There is a metric, its the number of sections the panel is divided into using bypass diodes - so, equal to the number of bypass diodes. That will be stated on the data sheet. So, if you want better partial shade performance, pay more for a panel with more bypass diodes. Note it also depends on how you install them. Say you have a panel with 3 diodes - so, in 3 sections. Say these are arranged as 3 strips parallel to the panel's long side. If you build an array with these panels in Landscape orientation the strips will lie horizontally. Then as the sun sets, the row of panels in front will shade first the bottom strip, then two, then eventually the whole panel. So you've gained performance from those diodes. NOW suppose you mount them in Portrait orientation. The strips are now vertical. The first bit of shade from the row in front shades the lowest bit of all 3 strips. Output immediately plummets! You have gained nothing from your diodes. (You would however be better protected from a vertical shade edge, from a house wall or lamp post, as the sun moves Westwards, so it may be a good decision). You could do a demo on YouTube and make a good panel look bad by doing a shading test this way. So, as for your panel and others you've played with : how many bypass diodes did each have? How were the sections arranged? When you did your shading tests, did you shade one section at a time, or a little bit of all of them together? I believe if you answer those questions you can explain the readings you are getting, and the results generated by the other You Tuber. If not, then someone has indeed found a new way to improve shaded performance. Im surprised this hasn't hit the headlines in the technical press and on the websites of the big wholesalers, because it revolutionises a multi-billion dollar industry. I look at a lot of panel data sheets and have not yet seen this mentioned. I assume it is patented, so all manufacturers will now be forced to buy a license from the patent holder in order to use this technique and remain competitive. But I doubt it. I think there is no new technique, it just influencers puffing products on You Tube for commission by doing graphic demos that cannot be properly evaluated. Yes,my children say that too "Dad, youre such a cynic".

 

[AlanandMayya]

I am not getting involved with this debate. But although you are technically correct that normal silicon diodes have a forward drop of .7V you can get low voltage drop diodes like schottky diode which can have a forward drop of as little as 0.1V

Yes, thanks, I forgot that. But even so, at low temp (20C) and near Imax I think Schottkies still drop 500mV or so. I looked at some data sheets when I was considering designing a B to B charger to charge a 50V battery from 12V. (Too hard for me; gave up and did it a different way). I remember in my youth Germanium was the semiconductor of choice and only dropped about 300mV. I suppose there are lots of good reasons it was replaced by Silicon.

 

[Guigsy]

There is a metric, its the number of sections the panel is divided into using bypass diodes - so, equal to the number of bypass diodes. That will be stated on the data sheet. So, if you want better partial shade performance, pay more for a panel with more bypass diodes. Note it also depends on how you install them. Say you have a panel with 3 diodes - so, in 3 sections. Say these are arranged as 3 strips parallel to the panel's long side. If you build an array with these panels in Landscape orientation the strips will lie horizontally. Then as the sun sets, the row of panels in front will shade first the bottom strip, then two, then eventually the whole panel. So you've gained performance from those diodes. NOW suppose you mount them in Portrait orientation. The strips are now vertical. The first bit of shade from the row in front shades the lowest bit of all 3 strips. Output immediately plummets! You have gained nothing from your diodes. (You would however be better protected from a vertical shade edge, from a house wall or lamp post, as the sun moves Westwards, so it may be a good decision). You could do a demo on YouTube and make a good panel look bad by doing a shading test this way. So, as for your panel and others you've played with : how many bypass diodes did each have? How were the sections arranged? When you did your shading tests, did you shade one section at a time, or a little bit of all of them together? I believe if you answer those questions you can explain the readings you are getting, and the results generated by the other You Tuber. If not, then someone has indeed found a new way to improve shaded performance. Im surprised this hasn't hit the headlines in the technical press and on the websites of the big wholesalers, because it revolutionises a multi-billion dollar industry. I look at a lot of panel data sheets and have not yet seen this mentioned. I assume it is patented, so all manufacturers will now be forced to buy a license from the patent holder in order to use this technique and remain competitive. But I doubt it. I think there is no new technique, it just influencers puffing products on You Tube for commission by doing graphic demos that cannot be properly evaluated. Yes,my children say that too "Dad, youre such a cynic".

Then why does shading just the corner of one strip destroy the output?

Also, my panel:

 

[AlanandMayya]

Do you have a data sheet for this panel? I assume its not made by Victron, they have re-branded someone's panel. From this we can see how many diodes; also the operating voltage, and compare that to the inverter (or solar charge controller) requirements. In the absence of this, lets assume 3 diodes. If you shade one little corner (really little, so no danger of shading more than one section) then the shaded cells will stop conducting and all the cells in that circuit (one third of your panel) will not work. The bypass diode will conduct. Lets guess the panel has Voc of 28V under Standard conditions (1000w /m2). So in UK in winter lets say about 27V (this is where we need the data sheet, to show this curve). So with one bypass diode conducting this falls to 18V (2/3 of 27) minus the Vdrop in the diode - lets say 0.5V, so 17.5V. So your inverter, which presumably is sized to work at about 50V and was working fairly happily at 27v is now seeing 17.5V. It will presumably keep the current the same as the MPPT point has not changed for the illuminated cells. So your output will drop in proportion to the voltage to 17.5/27 or 65% of what it was, LESS any losses due to your inverter / controller now working further from its ideal MPPT voltage - again, the data sheet will show this. This effect may be negligible, or it may significantly reduce your output. For example, my array works quite close to the Vmin of my inverter, so if I get more than about 1/2 of my array shaded, the whole thing shuts down to 0%, even though all those diodes are doing their jobs! Maybe your panel has only 2 diodes. In that case your voltage will fall to 13V, so 48% of unshaded, again LESS the effect of moving away from your inverter's Vmin. If its designed for 50V and happy at 27, it will probably shut down completely at 13V. If you can get the data sheets we could test this reasoning.

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