The nature of diode in solar panels

[BjarneK]

I am in the process of making same simulations for solar panels. It includes things like shade and parallel or series connection. To get the best results, I would like to know as much as possible about the bypass diodes and blocking diodes for a typical large high output panel.

Does anybody know what type of diodes are normally used for the bypass diodes? Schottky diodes would have a low voltage drop, so be more efficient when shade is involved. But I guess that is probably not such a high priority for the panel producers since they assume that people will put the panels in an unshaded place.

And what about blocking diodes? I guess they are not generally built into the panels, right?

I am not on my boat right now, so can't go and check for myself.

[GordMay]

Bypass diodes are installed in parallel with modules, and they perform a bypass function, allowing current to pass around a shaded area of a module.
Blocking diodes are installed in series with a string of modules, and they perform a blocking function, preventing backflow [from battery to panel], thereby discharging the battery overnight.
The same type of diode is generally used for both, a Schottky barrier diode.

[noelex 77]

Bypass diodes are generally Schottky diodes. Blocking diodes are never fitted to panels that would be considered for marine use.

[John Gambill]

Bypass diodes are almost always included inside the solar panel. Like others have said, they allow the panel to continue making energy when partially shaded. Blocking diodes (or the same function) are nearly always included in the charge controller, and so additional diodes are not needed. Also, the energy lost at night with mono crystal panels is so small that you would loose more energy during the day than you would save at night.

[BjarneK]

Thanks a lot for the insightful replies. I will use Schottky diodes in my simulations.

[Statistical]

Keep in mind most panels today have standardized around three diodes. Older panels used two but three is pretty much universal today. You may also want to look into half cut cells if max output under partial shading is something you are interested in.

[s/v Jedi]

I also read that modern panels don’t really need blocking diodes anymore.

Big installations often have large series strings that are connected in parallel at the combiner breaker box. If two strings try to dump their output into one defective string, the breaker for that defective string will trip.