Profile angle

As the angle of incidence depends both on the solar height and the solar azimuth we operate with the so-called profile angle Q defined as the angle of incidence projected on a vertical normal plane for the actual face. The profile angle can be calculated from the solar height and the difference between solar and wall azimuth as:

\[ \theta = \tan^{-1} \left( \frac{\tan h}{\cos \gamma} \right) \tag{1} \]

hvor

• \(\theta\) is the profile angle,

• \(h\) is the solar height,

• \(\gamma\) is the solar azimuth minus the wall azimuth

In the figures below, the profile angle is shown as a function of the time of the day for different orientations of the WinDoor and for different months (the 21. in each month). It is seen that e.g. for the orientation South is the profile angle constant through the day at spring and autumn equinox, March 21. and September 21.

Examples of variation in calculated profile angle over the day and year for different orientations (South; South + 30 ° West, and West). The graphs are drawn for the 21. in each month (June, March/September, and December). Time is given in true solar time.