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Affect of Shading on a Photo Voltaic (PV) Panel

PV Shading Types defined:

The following comes from the Kyocera website.  Their website http://www.kyocerasolar.com is a good read and informative  and explains shading well
 

Shading:

PV modules are very sensitive to shading. Unlike a solar thermal panel which can tolerate some shading, many brands of PV modules cannot even be shaded by the branch of a leafless tree.
Solar Cell Shading
Shading obstructions can be defined as soft or hard sources. If a tree branch, roof vent, chimney or other item is shading from a distance, the shadow is diffuse or dispersed. These soft sources significantly reduce the amount of light reaching the cell(s) of a module. Hard sources are defined as those that stop light from reaching the cell(s), such as a blanket, tree branch, bird dropping, or the like, sitting directly on top of the glass. If even one full cell is hard shaded the voltage of that module will drop noticeably compared to its un-shaded value. If enough cells are hard shaded, the module will not convert any energy and will, in fact, become a small drain of energy on the entire system.

Partial-shading even one cell of a 36-cell module, such as the KC120, will reduce its power output. Because all cells are connected in a series string, the weakest cell will bring the  others down to its reduced power level. Therefore, whether of one cell is shaded, or a row of cells is shaded as shown above, the power decrease will be the same and proportional to the percentage of area shaded, in this case on a small 17V system loss can be up to 50%. Solar Cell shadingThe modern 36V solar panels tend to have cells grouped in behind three separate diodes.  Depending on the layout and configuration of the three sets only one or group might be affected.

When a full cell is shaded, it not only doesn't contribute but can act as a consumer of energy produced by the remainder of the cells, and trigger the module to protect itself.  The module will route the power around that series string.  If even one full cell in series string is shaded, as seen on the right, it will likely cause the module to reduce its power level to of its full available value. If a row of cells at the he bottom of a module is fully shaded the power output may drop to zero. The best way to avoid a drop in output power is to avoid shading whenever possible.

 

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We use a tool called a Solar Pathfinder to determine Solar Panel shading when establishing the site and capacity of a PV array, there is an APP available that

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Last modified: November 13, 2018