A bypass diode is a particular kind of diode that is installed for bypassing current around different parts within a solar module. Each module can perform at its best without interfering with the outputs of other modules.
The problem arises when part of the solar cell is shaded or has some other defect and hence, does not generate current as it’s supposed to. Such could lead to lowered power output for the entire module. Bypass diodes enable string connection of cells or panels and allow them to generate a lower voltage or power as compared to no electric output at all.
Currently, every single solar panel available in the market comes with at least a single bypass diode, and sometimes even more diodes than that. This is one of the common processes. When you pop open the junction box on the back of your solar panel, you will notice the black lines inside that indicate bypass diodes.
Purpose of Bypass Diode
The main function of a bypass diode is to divert the current passing through a string into another cell. In order to do that, there are circumstances under which the output voltage must be less than zero, like when there is heavy shade, rain, or snowy weather conditions.
Solar panels have cells that are strung together to create strings. This current flows within each string from cell to cell in one direction – from the positive terminal of one cell to the negative terminal of that one cell and then enters the negative terminal of the next succeeding cell.
In every string, there exists an incorporated bypass diode that facilitates the flow of current in the presence of a few shaded cells. The role of the bypass diodes is to permit the passage of high voltage for each current direction. This is done by allowing the electric current to follow a lower resistance way around the parts of the cell that are in shade or defective.
One small cell can produce little electricity when it is exposed to direct sunlight. Every cell should be lit or else it would not make power. Nevertheless, this is not the fundamental challenge hindering the efficiency of a solar array.
Bypass diodes prevent disruption such as a series of shaded cells (defective cells) in case the disruption can cause voltage drop on all line lengths leading to stoppage of a system itself.
Also See: What is Blocking Diode?
Bypass Diode Configuration
Suppose one solar panel has failed and produces zero output current. In this instance, the bypass diode forms alternative paths of current flowing through to complete circuits, thus ensuring that no current will flow back from other panels already producing power at higher voltages. Consequently, it becomes possible for the entire solar system with reduced voltage to continue running despite the faulty parts.
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