Shading Analysis for Building Integrated Photovoltaic (BIPV)


Shading analysis is one of the most necessary step in designing the solar energy system for buildings. While designing the BIPV system it is important to analyze shading caused by surrounding objects and/or vegetation. Similar analysis is also a part of passive house or solar house design – overhangs must also be planned very carefully in such cases. Shading should be eliminated as much as possible. Even small obstacles like chimneys, telephone poles etc. shouldn’t be neglected. In fact, shading caused by a neighbor’s trees or own chimneys, skylights building may be losing between 20% -40% of the potential output of their solar installations. Just 10% shading of a solar array can lead to a 50% decline in efficiency and even, on occasion, total system shutdown.

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To minimize influence of photovoltaic array shading (if shading cannot be avoided) different system optimization techniques can be used. Basic calculations can be done by using some simple equations – formulas for some typical simple cases.

 SHADING CALCULATIONS

For different simple cases it is in general not difficult to calculate shadows for particular day and time. Shadow effect can be calculated by using some formula’s for most common engineering practice.

Horizontal Shading Device (Overhang) Side view

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h,D– geometry of horizontal shading device

                  α-sun height

                  ɸ -solar azimut

Ψ-plane azimuth

Vertical Shading Device (Fins) Top view

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W,D- geometry of vertical shading device

                           ɸ -solar azimuth

                          Ψ-plane azimuth

Imageγ – Vertical shadow angle (VSA)

Image  The above table explains the percentage loss (%) due to the shading. Shading of the panels can reduce the power output up-to 50%.

–Er. Sheelam Khare..

Source-pvresources.com
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