This question can be answered very easily - because the earth rotates around the sun and the its position is therefore constantly changing. We perceive the sun as moving from east to west and, vertically, from the horizon to its highest elevation at midday and then back again. As we know, photovoltaic modules achieve their highest performance when the sun’s rays strike the modules at the right angle. As a result of this, a large share of the possible yield is lost in single-axis and fixed-installation systems!
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