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A positive relationship exists between the output of photovoltaic cells and the reflection of sunlight from the roofing membrane upon which they are installed.
The effect upon the output is two-fold:
A small part of the solar energy converted by the photovoltaic cells originates from the solar radiation reflected by the roof.
This component is generally assumed to be approximately 1% for surfaces with an albedo* of 0.2.
For roof surfaces with an albedo of over 0.8, such as our RENOLIT ALKORBRIGHT roofing membrane, this energy component may rise to 4% or 5%. In practice, this equates to an increase in electrical output of 3% to 4% over that of roofs with low solar reflectance.
Higher roof surface temperatures also have a negative influence upon the output from crystalline silicon cells.
An increase of 2 °C is coupled with a drop in output of approximately 1%. A white reflecting roofing membrane such as our RENOLIT ALKORBRIGHT results in a lower air temperature around the photovoltaic modules. This in turn increases the output from the photovoltaic cells.
*The albedo or reflection coefficient of a surface is the relationship between the reflected radiation and the incident radiation.