Shading Analysis in Photovoltaics

SHADING ANALYSIS

Shading analysis is one of the most essential steps in phase of solar energy system design or analysis. In photovoltaics it is important to analyse shading caused by surrounding objects and/or vegetation.

In special cases like analysis or design of BIPV systems, exact analysis of "shadow-voltaic" systems (overhangs, vertical shading fins, awnings etc.) is also very important. Similar analysis is also part of passive house or solar house design - overhangs must also be planned very carefully in such case.

Basic calculations can be done by some simple equations - formulas for some typical simple cases you may find below. Some graphical tools like solar path calculator (pilkington) are also available. For analysis of complex objects several computer tools are available. Some of them offer even 3D simulation.

Shading is especially important in photovoltaics. It should be eliminated as much as possible. Even small obstacles like chimneys, telephone poles etc. shouldn't be neglected. To minimise influence of photovoltaic array shading (if shading can not be avoided) different system optimisation techniques can be used.

SHADING CALCULATIONS

Shading devices, general

For different simple cases it is in general not difficult to calculate shadows for particular day and time. Below you will find some formula's end equations which may help you to calculate shadows for most common particular cases in engineering practice.

vertical shading device, vertical fin, top view (right)

h, D - geometry of horizontal shading device (overhang dimension, see picture above)
α - sun height, Φ - solar azimuth, Ψ - plane azimuth

w, D - geometry of vertical shading device (vertical fin, see picture above)
Φ - solar azimuth, Ψ - plane azimuth

γ = vertical shadow angle (VSA)
w, D - geometry of vertical shading device (see picture above)
Φ - solar azimuth, Ψ - plane azimuth