Don't bypass diodes reduce the effects of shading? Why are optimizers better?

Bypass diodes allow current to flow around shaded cells to reduce power loss and avoid creating hot spots in the module (since power loss is dissipated by the cells as heat.)

Shaded cells have reduced output current, which affects all cells in series unless optimized. Tigo optimizers allow string current to partially bypass shaded modules, which mitigates the effect of shaded modules on system production.

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    Gavin Rowley

    How much bypass is "partially bypassed"? At what point is the module bypassed and at what point does it contribute again to production as a function is solar exposure? Don't the optimizer's keep reducing current until at some point they are too shaded to contribute anything. Then, as it becomes more shaded, it is a load on the system to power the optimizer? Are there more losses? Is this what Is meant by partially bypassing? It bypassed but some is lost to factors I don't know and some is lost to power the optimizer itself? 

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    Scott Muir

    Hi Gavin,

    An optimized module will contribute its maximum output based on site conditions. Since a shaded module will pull down the production of other modules in the same string, optimizers allow some of the string current to bypass that module. That way, the output current from the optimizer matches the rest of the string. If a module was completely covered, it would be fully bypassed and would not contribute to the string until uncovered. We have an article that describes this in greater detail here.


    A basic summary of the bypass in action looks like this: 

    Edited by Scott Muir
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