In case of installation of photovoltaic panels on a ground inclined to the horizontal, the installation distance between the rows that make up the photovoltaic field can be reduced compared to ‘installation plan, exploiting the effect of the slope, but can not drop below a minimum value which marks the beginning of the so-called phenomenon of shading.

An error in the definition of the minimum distance may bring some rows of panels in the shade, due to the previous row, with a consequent strong reduction of the production of electricity. To avoid this phenomenon and related economic losses, the rows of panels must be arranged at a distance to each other such that the shadow aggettata from each panel in no case reaches the next row, as shown in Figure 1, but is contained in ‘area that separates the rows of panels.

The minimum distance for the placement of parallel lines with β ≠ 0 ° can be derived from the triangle shadows.

With δm = 23.45 ° indicates the declination at the winter solstice (December 21), that is the time when the sun is at the lowest elevation and L is the latitude of the site. In order to optimize the area occupied by the photovoltaic field and mitigate losses due to shading, you have to find the minimum distance between the parallel rows from the consideration that the shading is zero to 12 noon on the day of the winter solstice. In principle is used to position the modules at a distance equal to 4 times the height H. It is advisable to check the values, which are variable depending on the latitude of the site, using the formula described above.