Definitions for "Bypass diode"
A diode connected across one or more solar cells in a photovoltaic module such that the diode will conduct if the cell(s) become reverse biased. [UL 1703] Alternatively, diode connected anti-parallel across a part of the solar cells of a PV module. It protects these solar cells from thermal destruction in case of total or partial shading, broken cells, or cell string failures of individual solar cells while other cells are exposed to full light.[to top
A diode that is placed across a portion (or all) of the cells in a PV module. Since the current of a cell is proportional to its illumination, a shaded cell in series-connected module or string will "choke" the current through the other cells. To prevent this from happening, a bypass diode a placed across a fraction of cells in a module, say eah 1/3 of the cells in a module. In this way if a portion of the module is shaded, the bypass diode can "bypass" the current around those cells, preventing the "current choking" from happening. Unfortunately, the voltage drops to a fraction of a volt, greatly reducing the power availble from the bypassed cells. Nonetheless, the total current through the module is not compromised and the output power of a partially shaded module might frop to 2/3 or 1/3 of its potential output, which is better than something close to zero
(also called a shunt diode) - A diode placed in parallel with a photovoltaic module or group of modules allowing a route for the current under conditions of shading or cell failure.