Bypass diodes, also known as free-wheeling diodes, are wired within the PV module and provide an alternate current when a cell or panel becomes shaded or faulty. Diodes themselves are simply devices which enable current to flow in a single direction.

The bypass diodes’ function is to eliminate the hot-spot phenomena which can damage PV cells and even cause fire if the light hitting the surface of the PV cells in a module is not uniform. The bypass diodes are usually placed on sub-strings of the PV module, one diode per up to 20 PV cells

Bypass diodes are connected in reverse bias between a solar cell (or panel) positive and negative output terminals and has no effect on its output. Ideally there would be one bypass diode for each solar cell, but this can be rather expensive so generally one diode is used per small group of series cells.

The failure of a bypass diode in a module usually results in the switching-off of one of three cell strings. The result is a sudden drop in output by one third. A decline in yield of this magnitude and in several modules can be detected in the yield curve of a string with good solar radiation conditions

Did you know that….

The Bypass diodes are incorporated to maximize the output of module sections.

More info on Bypass Diode here

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