Bypass diode

[BruceT]

The only panels I can find that have a bypass diode for ever cell ( 1 for 1 )

Solid panel. AE-Solar.com
Flexible panel. Sinoltech.com

I plan on living on a sailboat. So shading is a big deal.
Has anyone used one or both? And can you give any heads up. Good Bad or Ugly.
Thank You , cheers
BruceT

 

[Dzl]

It may be worth taking a look at the Sunpower X-series, (I might be mistaken about it being the x-series that is designed to be shade tolerant) I don't believe they use per-cell diodes, but they are designed for partial shade tolerance. Here is an explanation from an article I found on the subject:

• Shade intolerance
  If you don’t need to know why -skip to the next point and just believe me that: SunPower panels perform better in partial shade. But if you are remotely interested, let me do my best to briefly explain why:
  A standard silicone cell has the positive on one side of the cell and the negative on the other. Because of the large electrical separation between the positive and negative, when the cell is shaded, it needs to produce a comparatively higher reverse bias voltage to overcome the resistance. A typical conventional cell has a ‘reverse bias voltage’ of 15V to 20V. This high voltage on a standard panel causes detrimental hot spots and reduces the panel’s efficiency. When the reverse bias voltage gets high enough, it will activate the protective bypass diode. While bypass diodes are installed in each third of a panel to protect it from hotspots, as each bypass diode activates, the panel reduces its production by one-third. To make things worse, bypass diodes have a limited lifetime. The more often they are activated, the sooner they will fail.
  Sunpower has designed the Maxeon cell to have positive and negative on the back of the cell – just a fraction of a millimetre apart. When shade occurs, instead of a huge 15 to 20 volts, the “reverse bias voltage” is 2.5 volts (X series) or 5.5 volts (E series). In summary, the advantage of the Maxeon back-contact in shaded conditions are:
• The reverse voltage is lower, therefore
• the heat created is less, therefore
• the more current and power flows, and
• bypass diodes operate less frequently giving more power and increasing their lifetime.Contrary to a popular myth, SunPower panels do have bypass diodes. One SunPower YouTube clip claims bypass diodes are in individual cells. They are not. Bypass diodes are installed at the string level, at each third of the panel. So if we get SunPower panels, there is no need for optimisers on a shaded roof right?
  Wrong. In heavily shaded situations, there will still be a current mismatch in a string of SunPower panels – albeit with significant less severity than a traditional panel. So optimisation (preferably in the form of a Tigo TS4 or SolarEdge) can still be advantageous. Optimisation can also have advantages of individual panel monitoring and a higher degree of safety in case of fire etc. Read my explanation of the purpose of optimisers at the beginning of this post.

The article is pretty uniformely positive towards sunpower, so I dunno how much is marketing speak/promotion, and how much data based and factual, but Sunpower is a top of the line manufacturer.

Here is an intro to bypass diodes for anyone else reading this post who isn't familiar with how they operate.