Near Shadings: Irradiance Loss

[Ben]

As an experiment, I set up the Orientation of a field with 11,111 Meter spacing between sheds, using the "Unlimited Sheds" option.

After running the simulation, there is still a 1.0% "Near Shadings: Irradiance Loss" listed in the Loss Diagram. With essentially an inifnite amount of space between rows of modules, I expected 0% near shading loss. Is the 1.0% loss inaccurate? I am asking because, based on this experiment, I am not sure if I can trust PVsyst's production estimates as I vary the inter-row spacing.

[LoicA]

Hi

Could it be the impact of the albédo loss due to the rows ?

If you shift the rows so that they are not in front of each other, do you have the same results ?

But interesting question...

[André Mermoud]

These are indeed the effects of the losses on the albedo and diffuse parts.

The albedo is only "seen" by the first row. It is shaded for all other ones behind.

[Ben]

LoicA, André, thank you for your help. I tried adjusting the field to only include 1 shed and the near shading loss dropped to 0.1%.

And I read these articles:

http://files.pvsyst.com/help/shading_treatment.htm

http://beyondpenguins.ehe.osu.edu/issue/energy-and-the-polar-environment/solar-energy-albedo-and-the-polar-regions

But I'm still having trouble understanding why only the first row "sees" the albedo reflections, even when rows are spaced far apart. Can you clarify this, or point me to an article that explains? I would expect that rows behind the first row will "see" albedo as the rows are spaced farther apart.

[LoicA]

If I remember well the albedo visible by the array for the rows behind the first one, is equal to (n_rows-1)/n_rows * (Albedo of the first one). But I am not sure at all about that.

[Ben]

If I remember well the albedo visible by the array for the rows behind the first one, is equal to (n_rows-1)/n_rows * (Albedo of the first one). But I am not sure at all about that.

 

LoicA,

Thanks for this information. Can you also explain for me why the distance between rows has no effect on the Albedo, and only the number of rows matters? I must be thinking of this too simplisticly, but if it is a reflection of light that strikes the entire surface of the array, then I would expect for light to be reflected onto every row, as long as the row in front doesn't cast too long of a shadow.