Combination with Photovoltaic elements
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.
RENOLIT ALKORBRIGHT roofing membrane has been included by the CRRC in its list of solar reflecting materials. The CRRC (Cool Roof Rating Council) is an independent US organization which maintains an objective list of all materials which reflect sunlight.
At 91%, RENOLIT ALKORBRIGHT's reflectance is the highest of any roofing membrane. For more information, visit www.coolroofs.org.