Sun angle in winter

On a flat roof, it is desirable that the rows of solar panels are not placed in each other's shadow (during the whole year). So the sun angle in the winter is important if you want to calculate the distance between rows of solar panels (because then the sun is at its lowest point).

If there is sufficient space on a roof, it is recommended to place the rows in a way that they are not in each other's shadow during the whole year. However, the profit of an extra row of solar panels weights sometimes higher compared a few centimeters shadow. For lack of space, you can chose deliberately to place the rows closer to each other because of the minor output in the winter.

However, there are panels that will be turned off in case of a small portion of shadow (the entire panel, the entire row or the entire string). In that case (or in case for more than a few centimeters shadow) it is recommended to reduce the angle of inclination of the panels so that there are no portion of shadow on the panels at any time of the year.

Although the table shows the angle in half degrees, the App only uses up-rounded numbers.

Calculation
At the equator on 21 March and 21 September in the middle of the day the sun stands at 90 degrees.

For example, at 52 degrees of the North or South of the equator the sun stands 52 degrees lower. So from the horizon measured the sun stands at 90 - 52 = 38 degrees. The Earth's axis is tilted 23.5 degrees comparing the sun. So in the summer, this number has to be added and during the winter this number has to be subtracted.

In this example, at 52 degrees of the North or South of the equator, the sun stands in the summer at 38 + 23.5 = 61.5 degrees.

In the winter the same number should be subtracted: 38 - 23.5 = 14.5 degrees.