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Angle of inclination
As a rule, modules should be mounted with an optimium inclination (tilt) between 10° and 60° (with annual energy production loss no greater than 10%). The optimum tilt depends mainly on the latitude of the place but also on the context in which the module is inserted.
If the module is oriented to the east, the angle will take a negative value, if oriented to the west, the angle will be positive. To maximize the energy produced during the year, the plant orientation (azimuth) should be as south as possible. An orientation between 60° west and 60° east guarantees a result that is interesting with losses not greater than 10% (depending on the inclination).
Generally speaking at our latitudes you can say that:
- for BIPV systems integrated on sloping roofs tilted towards south, efficiency is optimal
- for BIPV systems vertically mounted on facades, efficiency is around 70% if orientated south, whereas it will fall to
50% if facing either east or west
- for horizontally mounted BIPV systems (flat roof), efficiency is still 90%
- orientating panels towards north should be avoided if not for aesthetic or architectural reasons.
If the average insolation of the project site is known, it is necessary to assess the rate of annual solar radiation on the horizontal plane considering the inclination of the modules and their orientation. To do so, transposition factors (this is the ratio of the incident solar energy annually on a horizontal plane and that incident on a plane differently oriented and tilted) are used. The following table shows the values for the city of Lugano.
Conversion factors for the region of Lugano