IS THERE ANY EFFECT OF SHADING ON SOLAR PANEL OUTPUT?

Solar panels are very sensitive to shading and can affect their output even through shading from the branch of a leafless tree.

Shading obstructions can be from “soft” or “hard” sources. If a tree branch, roof vent, chimney or other item is shading from a distance, the shadow is diffused or dispersed. These soft sources significantly reduce the amount of light reaching a solar panel’s cells. Hard sources are defined as those that stop light from reaching solar cells, such as a blanket, thick tree branch or bird dropping sitting directly on top of the glass. If even one full cell is hard shaded, the voltage of that module will drop to half of its un-shaded value in order to protect itself. If many cells are hard shaded, the solar panel will not convert any energy and will, in fact, become a tiny drain of energy on the entire system.

Examples of Partial Cell Shading that can reduce the solar panel power output by up to half.

Partial shading (as shown above) of even one cell on a 36-cell solar panel, 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 1/2 of one cell is shaded, or 1/2 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 50%.

Examples of Full Cell Shading that can reduce the solar panel power output by up zero.

When a full cell is shaded, it can consume energy produced by the remainder of the cells, and trigger the solar panel to protect itself. The solar panel will route the power around that series string. If even one full cell in a series string is shaded, as seen on the right, it will likely cause the solar panel to reduce its power level to 1/2 of its full available value. If a row of cells at the bottom or side of a solar panel is fully shaded, as seen in the figures below, the power output may drop to zero. The best way to avoid a drop in output power is to avoid shading whenever possible.