Near shadings procedure

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

You have to 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 this scene has been well established you can visualise shadows produced for any sun position or time-of-the-year. You can also run an animation of the shadow evolution over a given day.

During simulation, the calculation of the shading factor for each hour would spend too much computing time. Therefore, the program establishes a table of shading factors in terms of the sun's height and azimuth. During simulation, the hourly shading factor can be calculated very fast by interpolation.

The iso-shading curves are a powerful information tool, that superimpose an estimatation of the shading factor on a sun's path height/azimuth diagram, allowing to estimate at a glance the shading effects according to the 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.

It is to be noted that the real effect of partial shading on the electrical production of the PV field is non-linear and depends on the interconnections between the modules. The program gives the possibility to partition the field into rectangles, each of which is suppose to represent a string of modules in series, and calculate another shading factor according to module cabling. Although not perfect, this second approach should give an upper limit for the real shading loss evaluation.