In solar thermal collectors, a selective surface or selective absorber is a means of increasing its operation temperature and/or efficiency. The selectivity is defined as the ratio of solar radiation-absorption (alpha) - to thermal infrared radiation-emission (epsilon).
Selective surfaces take advantage of the differing wavelengths of incident solar radiation and the emissive radiation from the absorbing surface:
- Solar radiation covers approximately the wavelengths 350 nm...4.000 nm; UV-A, visible and near infrared (NIR - or IR-A plus IR-B)).
- Thermal infrared radiation, from materials with temperatures approximately in the interval -40..100°C, covers approximately the wavelengths 4.000 nm...40.000 nm = 4 um...40 um; The thermal infrared radiation interval being named or covered by: MIR, LWIR or IR-C.
Read more about Selective Surface: Selective Materials, Other Selective Surfaces
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