Solar absorptance is a measure of the ability of an object to absorb solar radiation. The ratio of the total absorbed solar radiation to the incident radiation is called solar absorptance or solar absorption factor.

When light or electromagnetic radiation sticks the surface of a matter, a portion of the energy of a photon is absorbed by electrons of an atom and the electromagnetic energy is transformed to other forms of energy such as, heat. Absorptance is the measure of the ability of an object to absorb radiation.

Units and Measures

Solar absorptance relies on colour of the material. Dark materials have a higher solar absorptance and will absorb more solar energy. It is measured as a unitless factor between 0 and 1.

Example Units

Following is the colour range with the relevant solar absorptance:

  • Light colour: < 0.475
  • Medium colour: 0.475 – 0.7
  • Dark colour: > 0.7

Useful References

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