Near shadings procedure

Near shading calculations require the reconstitution of the exact geometry of the PV field and its environment, in the 3D-space.

First, build the global scene of the PV system by assembling parametrized elements (PV fields, shading obstacles, buildings, trees) that can be adapted from template shapes.

Assembly is done in a global perspective or plane view. Once the scene is well established, you can visualize shadows produced for any sun position or time of year. You can also run an animation of shadow evolution over a given day.

During simulation, calculating the shading factor for each hour would require excessive computing time. Therefore, the program establishes a table of shading factors in terms of solar height and azimuth. During simulation, hourly shading factors can be calculated very quickly through interpolation.

The iso-shading curves are a powerful information tool that superimpose an estimation of the shading factor on a sun path height/azimuth diagram, allowing quick assessment of shading effects according to season and time of day.

The shading factor is applied to the beam component. The program also has to calculate the shading factor for the diffuse component (as well as the albedo), that is independent of the sun position and therefore constant over the year.

Simulation results include shading loss calculations for Beam, Diffuse and Global irradiation components.

Note that the actual effect of partial shading on the electrical production of the PV field is non-linear and depends on interconnections between modules. The program provides the option to partition the field into rectangles, each intended to represent a string of series-connected modules, and calculate another shading factor according to module cabling. Although not perfect, this second approach provides an upper limit for realistic shading loss evaluation.