Investigation on the influence of IMPER*SAN Cool Roof Coating
reflection coefficient on the performance of PV modules.

The efficiency of solar cells decreases with increasing temperatures. A general rule of thumb is that the efficiency of a solar cell decreases with 0,5% for every 1°C above 25°C. This means that on a hot summer day, the efficiency of a solar cell could drop as much as 25%….!

The tests carried out confirmed that IMPER*SAN Cool Roof Coating will increase the performance of a typical roof-mounted PV system.

“Increased performance – from 5% to 20%”

How much these effects contribute to the power depends on factors such as mounting angle, distance between modules (packing density), wind speed, cell temperature coefficients etc.

The following tests have been carried out to show the
ENERGY SAVING potential of IMPER*SAN Cool Roof Coating.

ASTM E1980-01 Solar Reflectance Index (S.R.I). The calculation is based on a mathematical formula that includes values for thermal emittance, total solar reflectance, solar absorptance, three convective coefficients and various other coefficients. With this norm it is possible to calculate the roof surface temperature before and after the use of IMPER*SAN Cool Roof Coating.

EXAMPLE:
Even thought many metal roofs have
high solar reflectance, they will not
reject heat effectively if emittance is low.
The best performing materials for cooling
load reduction have both high reflectivity
(albedo) and high emittance.