Shadowing is a critical issue for BIPV. In general, designs in which the PV modules are shaded for much of the year should be avoided. For low-rise areas, the problem is easy to solve. The distance between individual houses can be calculated. For mixed-height neighborhoods, it will be more difficult. A high-rise apartment building in a low-rise neighborhood can cause a lot of unwanted shading.
The density of an area also has a lot of influence. In high-density areas (cities) the distances between buildings are often so small that there is significant shadowing throughout a large part of the year.
On a general note, it is worth mentioning that facade systems (vertical) are more sensitive to shading and need longer distances from other buildings than tilted systems (roofs). Horizontal systems have a lower irradiance, as previously mentioned, but will be the best solutions for avoiding shadow. Only neighborhoods with a mixture of low – and high-rise buildings might be unsuitable for horizontal systems.
Greening the area around buildings makes the area look very attractive and the microclimate more comfortable for the inhabitants.
The shadowing effect of trees is very important, as the trees will be very dense during the summer. Even during the winter, when trees lose their leaves, the branches give too much shade.
The aspect of growth is sometimes underestimated. Planning for the future growth of trees is very important and must be done carefully to avoid problems a few years after the building has been completed or the PV system has been installed.
Solutions can be to:
• only plant trees on the north side of buildings;
• plant only small trees up to two stories high;
• prune trees annually to keep them small.