"MustardMan" <nomail@nomail> wrote:
> Hi,
>
> I am using POVray to simulate the energy produced by solar panels at
> different orientations on a roof. My simulation includes the horizon, so
> the shadowing difference between summer & winter is realistic (as well as
> throughout the day).
>
> I can calculate the power generated by the panels by simply using some maths
> and the Az & Al variables generated by SUNPOS. However, this does not
> include shadowing caused by objects (horizon, trees, etc) - the value is
> what the panels would produce if they were always illuminated.
>
> Am I able to specify a point in the scene and get POVray to report the
> amount of light reaching that point?
>
> Cheers,
> MM.
In six months the sun appears to move at dawn from south to north. The area
covered by the sun in those six months is more or less an inclined band
that you can simulate by intersecting a sphere with an equivalently
inclined cylinder. You can get the cylinder thickness in Sunpos.inc, by
determining the hour of dawn on winter's solstice, and then sun's position
at the same hour on summer's solstice. The only shadows that can possibly
fall on the panel (apart from clouds, that is) are the objects that lay on
the band's path. So I would reverse the perspective: put the camera on the
panel and point at the horizon; remove all textures from the potentially
shading objects, make the band white, and make background transparent with
+ua. Render and check in the Gimp (histogram) how much white you have
compared to the sum of black and white. Repeat for other horizon, if
necessary. Don't forget to add the rest of the sunpath not covered by
shadows. ;) And then double the value, since this is valid for six months.

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