In solar thermal collectors, a selective surface is chosen based on the ratio of radiation-absorption (alpha) to radiation-emission (epsilon), with a higher ratio meaning better performance. Selective surfaces take advantage of the differing wavelengths of incident solar radiation and the emmissive radiation from the absorbing surface.

Normally, a combination of materials is used. One of the first selective surfaces investigated was simply copper with a layer of black cupric oxide. Black chromium ("black chrome") nickel-plated copper is another selective surface that is very durable, highly resistant to humidity or oxidizing atmospheres and extreme temperatures while being able to retain its selective properties - but expensive. Another combination consists of steel plated with gold, silicon, and silicon dioxide. Ordinary steel or aluminum can also be spray-painted black for a cheaper (but less effective) collector surface.

Typical values for a selective surface might be 0.90 absorption and 0.10 emissivity.

See also

• Insulated glazing
• Solar box cooker
• Solar collector
• Solar oven
• Solar power
• Solar thermal collector
• Trombe wall

External links

• Selective Surface for efficient Solar Thermal Conversion