EME 810
Solar Resource Assessment and Economics

3.7. Introduction to Spectral Reflectance, or Albedo


Probing Question: Real Material Spectral Reflectance

I would like you to review Figures 5.8 and 5.9 in SECS Chapter 5 relating to the spectral reflectances of the following substances across a broad range of wavelengths:

  1. water
  2. roofing tiles
  3. trees
  4. sand

Material properties that interact with light from the Sun (terrestrial shortwave band is around 250-2500 nm) extend over a far greater spectrum than what our eyes can perceive (visible sub-band 380-780 nm). Consider the shortwave range of light 250-2500 nm. Anything with an albedo (reflectance) >0.2 could be a good contributor to a diffuse ground reflectance that increases light incident on a tilted collector. Even if the reflectance only cover a portion of the full spectrum from the Sun. Natural surfaces and built surfaces can be used to promote or inhibit solar reflectance, coupled to the performance of a Solar Energy Conversion System. Keep that in mind in the future!

Question: Which of these objects would be effective reflecting surfaces for shortwave irradiance? Which surface surprises you in its behavior?