Plane orientations and radiation components

Last update: May 2019

     Conventions on SoDa - For beginners

 

Conventions on SoDa: plane modes and azimuth conventions

Plane mode               

         Plane mode Tilt (degrees) Azimuth (degrees) Albedo Animations
June 21st Dec. 21st
Horizontal Plane 0 NA NA See animated GIF See animated GIF
Fixed tilted plane <user setting> <user setting> <user setting> See animated GIF See animated GIF
2D Sun Tracking (DNI) Sun Tracking Sun Tracking <user setting> See animated GIF See animated GIF
1D Sun Tracking (North-South axis) Sun Tracking 90° or 270° <user setting> See animated GIF See animated GIF
1D Sun Tracking (East-West axis) Sun Tracking 0° or 180° <user setting> See animated GIF See animated GIF
1D Sun Tracking (Tilt tracking) Sun Tracking <user setting> <user setting> See animated GIF See animated GIF
1D Sun Tracking (Azimuth tracking) <user setting> Sun Tracking <user setting> See animated GIF See animated GIF

 

Azimuth convention adopted by SoDa

Firstly, the azimuth convention is:

   Azimuth (degrees) Orientation
North
90° East
180° South
270° West
    

So orientation checking is :

  • A tilted plane is north oriented if azimuth < 90° or azimuth > 270°
  • A tilted plane is south oriented if azimuth > 90° and azimuth < 270°

NB: A plane which is not facing the sun might either be a human error, or may also be due to infrastructure or environmental needs (e.g. part of the rooftop north oriented).

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For beginners

Radiation components over the horizontal plane     Radiation components over the tilted plane     Radiation components over the normal plane

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Note on the relationship between RTI (or RNI) and albedo:

The irradiation collected by a tilted surface is composed of a part of direct irradiation (as soon as the sun is visible by the panel), a part of diffuse irradiation coming for the portion of the sky vault visible by the panel, and a part of irradiation reflected by the ground. Indeed, when the plane is tilted, it "sees" a portion of the ground. Consequently the plane receives more solar radiation if the ground is highly reflected sun rays, i.e. for high albedo. The albedo caracterizes the reflective capacity of the ground. The default value on SoDa is 0.2. If the ground is not very reflective, like for instance dark ground, just set 0.1. Other examples of albedo values for oceans and seas is 0.05, 0.5 for sands, and 0.8 for snow.

Anyway, the reflected part is small compared to the other components, so the ground albedo is a second order input parameter.

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