In general I like your idea of putting the camera in the position of the 
solar panel, but I am afraid that this would only give a first approximation 
to the true value.

It would be OK if the sun's position (declination) moved in a linear 
fashion, but it doesn't. It is much more like a sine wave. It starts off 
moving slowly at the southernmost point (23.5 S) and accellerates northwards 
until it crosses the equator when it starts to slow down until it stops at 
its northernmost position (23.5 N)...  The band 0 to 1 deg will have the sun 
in it a lot less than the band +20 to +21 deg!

To correct for this you could either pigment the sky band, or position 
several thousand "suns" along it to simulate the differing light "density" 
coming from the different bands of the sky.

Another point, you'd need a camera with more than 180deg field to do this in 
one pass... Although it shouldn't be too difficult to do it in segments.

Rarius

"Grassblade" <nomail@nomail> wrote in message 
news:web.4639bbc01bad02ca6955f970@news.povray.org...
> "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.
>
>
>
>

Post a reply to this message