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)
| Untreated Glasses | One-sided AR treated glasses | Both sides AR treated glasses | |||||
| class U1 | ηGL ≥ 0.900 | class Y1 | ηGL ≥ 0.925 | class X1 | ηGL ≥ 0.950 | ||
| class U2 | ηGL ≥ 0.885 | class Y2 | ηGL ≥ 0.910 | class X2 | ηGL ≥ 0.935 | ||
| class U3 | ηGL ≥ 0.870 | class Y3 | ηGL ≥ 0.895 | class X3 | ηGL ≥ 0.920 | ||
| class U4 | ηGL ≥ 0.850 | class Y4 | ηGL ≥ 0.870 | class X4 | ηGL ≥ 0.890 | ||
| No solar glass | ηGL < 0.850 | no solar glass | ηGL < 0.870 | no solar glass | ηGL < 0.890 | ||
Glass efficiency and classification into power classes Photovoltaics (PV)
| Untreated Glasses | One-sided AR treated glasses | Colored Glasses | |||||
| class P1 | ηGL ≥ 0.940 | class R1 | ηGL ≥ 0.980 | class P C | ηGL > 0.0 | ||
| class P2 | ηGL ≥ 0.925 | class R2 | ηGL ≥ 0.965 | ||||
| class P3 | ηGL ≥ 0.910 | class R3 | ηGL ≥ 0.950 | ||||
| class P4 | ηGL ≥ 0.890 | class R4 | ηGL ≥ 0.925 | ||||
| no solar glass | ηGL < 0.890 | no solar glass | ηGL < 0.925 | ||||
