The Sun above the horizon changes its position depending on the time of day. The horizon of the observer at the center and the position of the Sun relative to it as a function of time of day is shown in Fig. 1.

The sun changes its position in the sky from east to west, as well as rising above the horizon, throughout the day. It reaches its highest point at solar noon and then decreases until sunset. The horizontal position of the Sun is called the solar azimuth ( Fig. 1 ), which for the Northern Hemisphere is measured in degrees east and west of geographic south (not magnetic south). The Sun's azimuth angle is \( 180^{o}\textrm{} \) for geographic south. The vertical position of the Sun, or the angular height of the Sun (altitude), is measured in degrees above the horizon. At sunrise, it is \( 0^{o}\textrm{} \). As the Sun rises, the angle increases to a maximum value at noon and reaches up to \( 90^{o}\textrm{} \) (depending on latitude). The position of the Sun according to season and day is shown in Fig. 2 (based on data from Sunrise and Sunset in Kraków - see Wschód i zachód Słońca w Krakowie [1]). The observer's horizon is in the center, and the position of the Sun relative to it depends on the time of day and year. In the northern hemisphere, the highest angular height of the Sun is reached in the summer season and the lowest in the winter. The dashed line shows the impression of the projected motion of the Sun on the plane of the horizon as seen by the observer.

In order to make effective use of solar insolation, photovoltaic panels should be positioned in such a way that the energy of solar radiation falling on the panel is maximized. If the orientation of the panel is stationary, that is, it does not follow the sun, then the panel should be oriented toward the south. The angle of the photovoltaic panel is set according to its location on the Earth's surface (that is, according to the latitude of the PV panel's mounting) so that it can receive maximum sunlight. On Fig. 3 (data taken from [2]) an example of insolation differences for southern and northern Poland is shown. The optimal tilt angle of the photovoltaic panel for northern Poland is larger than for southern Poland.

From the above graph, it can be concluded, that setting the photovoltaic panel at an angle within \( 20^{o}\textrm{} \)- \( 50^{o}\textrm{} \) changes solar energy consumption from \( 1175\frac{kWh}{m^{2}} \) to \( 1204\frac{kWh}{m^{2}} \), that is in a range of less than \( 3\% \).
Photovoltaic panels are usually placed on the roof of a building, and this roof does not always face exactly south. Therefore, you should also analyze the situation where the photovoltaic panels have a different orientation with respect to the south.

Based on the experimental data presented ( Fig. 4 ) (data taken from [2]) it can be concluded that the more the photovoltaic panel is tilted away from the southern direction, the less solar energy it reaches. If the tilt away from the south direction does not exceed \( 30^{o}\textrm{} \), the solar insolation reduction of the panel will not exceed \( 5\% \). To summarize, deviation of the panel alignment from the south direction to \( 30^{o}\textrm{} \) and a possible change in the tilt angle within \( 20^{o}\textrm{} \) to \( 50^{o}\textrm{} \) do not result in larger losses than \( 8\% \). However, larger values of the aforementioned angles will result in a greater reduction in solar insolation for a given panel.
If there is a need for a so-called special photovoltaic installation, e.g., on a summer house, you need to take advantage of the largest insolation during the period when the house is used, i.e., in summer. Then the angle of deviation from the southern direction should not exceed \( 30^{o}\textrm{} \), while the angle of inclination of the panel should be adjusted to the summer season when the cottage will be used.