Question

In solar flat plate collectors, the absorber plate is painted with selective paints. The selectivity is the ratio of 
1. Solar radiation-absorption to thermal infrared radiation emission
2. Solar radiation emission to thermal infrared radiation absorption
3. Solar radiation reflection to thermal infrared radiation absorption
4. Solar radiation-absorption to thermal infrared radiation-reflection

Answer 1

Correct Answer - Option 1 : Solar radiation-absorption to thermal infrared radiation emission

Concept:

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 (α_sol) to thermal infrared radiation emission (ε_therm).