Solar Panels and Shade | Bypass Diodes

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How does shade affect solar panels?
To understand how shade affects solar panels, we first need to understand how solar panels work. At the heart of every solar panel are dozens of solar cells. Each of these cells produces a little bit of electricity when light falls on it. To increase the power output, solar panel manufacturers daisy-chain a whole load of these cells, usually about 60.
The power output of solar cells will drop if they get shaded. The good news is that as long as the cells are equally shaded, they will continue to work in harmony. While they won’t produce as much power as they might in full sun, the cells will make the most of the light that’s available. This way, they can continue to produce a worthwhile, albeit reduced amount of power.
But what if only some of the cells get shaded? The problem here is that a few shaded cells can act as a bottleneck, reducing the power output all the others too. So does this mean that shade on one of your panels will spoil your solar production across the board? The answer is no and you can thank a little device called the bypass diode.
Just about every solar panel sold today comes with three bypass diodes. These diodes make sure that a few shaded cells won’t drag down the power output of all the others. If any of the cells in your solar panel array are causing a bottleneck, the bypass diodes will jump into action, and allow the rest of the cells to get back to work as they should. The common notion that one shaded panel will stop all the others working is a total misconception.
It’s a relief to know that a few shadows here and there won’t spoil all of your electricity generation. However, to get the most of your solar panel system, you’ll still want to minimise shading as much as possible. If you can’t totally avoid shading, then you might be considering power optimisers or microinverters. These devices are supposed to minimise the negative impact of shade on solar panels. But power optimisers and microinverters are not always what they’re hyped up to be. Follow the link in the description to learn why.

[@wulfriclee1983]

This is the best explaination I found currently.

[@ruwanwijekoon1122]

Thanks a lot for taking your time to produce such a simple and clear video.

[@Energyd]

Glad it was helpful!

[@SnarkySolarGuy]

Shading is a tricky thing and very hard to model. What these demonstrations lack is the connection to the inverter. Once that happens then the whole "Shading half of one module drags down the entire string to 50%" myth out the window. Thank you for addressing that! One little thing *solar module. Solar panels heat water :D I know its a moot point when the module manufacturers even gave up and started calling them panels. Great video!

[@Energyd]

Yep, great point about the issue of modelling shade. It's pretty easy to forecast energy generation from unshaded solar modules. But throw in some shading and most solar installers are quickly reduced to "rules of thumb"

[@singerkgreen]

You only used shade crossing 1/3 of the panels in series withe diode... What happens when you shade the bottom 1/3 of the panel instead of the right 1/3? What happens to the string when that is shaded out?

[@user-kx4ty5dl3i]

There's nothing in your description that links to the explanation about microinverters

[@davidsheerin6230]

Good graphics and explanation

[@guywhoknows]

The bypass diode only works in certain ways depending where the shade is and how the panel is set out. Micro inverters make mains power at the panel or panel group. This allows the array to be further away as there is not so much detriment to voltage loss. (Longer cables lower voltage). This issue occurs when running long DC cables to inverters. Optimisers are essentially buck converters. Set to the right specs, for example a 60 cell panels may be 30v 8a. They may make 35v and 4a on a typical day. But if you're off grid and charging 24v batteries, you may drop the Voltage to 26v Taking down 35v to 24v will raise the amps proportional to the change (see ohm's law). You can set them for a constant voltage and variable current. Which is the better way, or you could set them as a constant current, but the voltage could drop out of spec or fail to produce any power at all. Hence why voltage is important. Solar panels voltage has a curve which is fairly small. A cell is around 0.5v, but it's current can vary by 2.2amps. Hence why voltage works best and can add stability to inverters, or bring systems into spec.

[@APatchworkCanvas]

I have a 7kwh array that is shaded right up until noon. It doesn’t start producing until the last shaded panel has some light on it.

[@pfwag]

If shading is an issue and you can't cut down the trees, Sunpower panels have a bypass diode across each cell. They also are on the top of the $/W scale too so it may be cheaper to simply by more panels.

[@guywhoknows]

Wrong. There not at the cell level but string. Of the 60 cells, two rows are connected to a single diode. And the three rows make the panel. Take a close look at the wiring on the front to see this fact.

[@danielmcgowan9534]

The comment at 1:42 should be made with a qualification. Solar panels with partial shade don't suffer reduced output IF the panels have bypass diodes. The panels I worked with in 2007 didn't have diodes. They were terrible. I'm sure almost all new panels have bypass diodes because a single leaf or a bit of mud spatter was terrible on the panels I had to use 'back in the day'.

[@Energyd]

Yeah very fair point. I'll clarify that my comment applies to modern PV modules for rooftop and ground-mounted applications, which come with bypass diodes pretty universally.

[@milyasanjum6418]

Very nice profact

[@adarshmishra3224]

Thank you sir 🙏

[@tusharsomaiya5035]

Means if I have 10 module 1 partially shaded, remaining 9 will output normally?

[@Energyd]

Exactly!

[@bhagyeshtrivedi6799]

What if the shadow is not vertical as shown in this video? Assume the shaded portion is a small horizontal strip at the bottom, in this case will it triggers all bypass diodes? Will the panel be producing similar amount then?

[@Energyd]

That depends on what's happening with the other panels in the string. If other panels are receiving full sun then yes the bypass diodes will trigger. However, if all panels are getting the same shade then they will all work at reduced output, without triggering the bypass diodes

[@Jenuin]

Shady business here 😳

[@Energyd]

Just trying to shine some light on the subject