Header Image SPF Testing Solarglas

SPF Testing – Solar Glass

The performance of thermal collectors and PV modules depends significantly on the glass used. The measurement and certification procedure developed at SPF is internationally recognized as a reference and evaluates the specific properties required for good solar glass

As a rule, special solar glass is used that is characterized by high purity. This achieves a significantly higher light transmission (= usable energy) compared to normal glass. Visually, however, good solar glass can hardly be distinguished from normal window glass.

The correct measurement of light transmission is very complex and requires special spectrometers and sensors. The measurement of structured glass is particularly demanding, since the angle-dependent transmission has a significant influence on the annual yield of solar systems.
The necessary infrastructure is available at SPF.

Testing and Certification

The SPF certificate for solar glass is available for PV and for thermal collectors (ST). The specific requirements for the optical properties are defined by the glass efficiency. This is determined on the basis of the following measured values:

  • Optical transmission
  • Angle factor (Incident Angle Modifier)
  • UV degradation

Glass efficiency and classification into performance classes Solar thermal (ST)

AR treated glasse
    Both sides
AR treated glasses
class U1ηGL ≥ 0.900 class Y1ηGL ≥ 0.925 class X1ηGL ≥ 0.950
class U2ηGL ≥ 0.885 class Y2ηGL ≥ 0.910 class X2ηGL ≥ 0.935
class U3ηGL ≥ 0.870 class Y3ηGL ≥ 0.895 class X3ηGL ≥ 0.920
class U4ηGL ≥ 0.850 class Y4ηGL ≥ 0.870 class X4ηGL ≥ 0.890
No solar glassηGL < 0.850 no solar glassηGL < 0.870 no solar glassηGL < 0.890

Glass efficiency and classification into power classes Photovoltaics (PV)

AR treated glasses
class P1ηGL ≥ 0.940 class R1ηGL ≥ 0.980 class P CηGL > 0.0
class P2ηGL ≥ 0.925 class R2ηGL ≥ 0.965   
class P3ηGL ≥ 0.910 class R3ηGL ≥ 0.950   
class P4ηGL ≥ 0.890 class R4ηGL ≥ 0.925   
no solar glassηGL < 0.890 no solar glassηGL < 0.925