Some PV installations are subject to increasing shading with the passing years as the result of trees (sometimes in neighbouring gardens) that are small and innocuous at first, but grow into large trees that can increasingly shade the installation during the winter. We know that partial solar generator shading reduces energy yield disproportionately (see Section 4.4.1). When the PV system shown in Figure 4.99 was realized, the shadow cast by the fir tree to the right in the picture did not cast a shadow on the installation’s modules. Trees planted near a PV system should (a) be located at a sufficient distance from the installation; (b) be a slow-growing species; and (c) lend themselves to cropping without disfigurement if they induce PV installation shading.
PV installations on landscaped flat roofs may also experience shading if the modules are mounted too low and the vegetation grows too high in summer.
Figures 10.2-10.4 display the progressive power loss in another installation resulting from gradually growing trees.