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Key Concepts of Solar Energy

Solar Reflectance Illustration
 

Components of solar energy

Energy from the sun has three components, most of which we cannot see. The energy that determines the color of an object, the visible spectrum, represents 46% of the sun’s energy. Ultraviolet light  (UV) is about 5% of the spectrum and is the most damaging, giving us sunburns as well as degrading paints and polymers. Infrared light, the invisible portion, represents about 49% of the spectrum.

Invisible spectrum

Infrared light contributes to heat build-up. Products containing infrared-absorbing pigments will heat up faster and to a greater degree than products colored with infrared-reflecting pigments. Heat accelerates the degradation of color, gloss, elasticity, and other physical properties of roofing materials.

Energy efficiency

Various scientific studies document that the energy efficiency of a building is dependent upon many factors, including among others the selection of construction materials. One study of more than 200 homes in central Florida, reports that air conditioning accounts for 33% of electrical consumption. The report notes that the lower attic temperatures produced by reflective roofs is one major factor in reducing air conditioning energy use and demand.

Important Definitions

Total Solar Reflectance (TSR) - Amount of infrared radiation reflected from a surface, expressed in terms of % or decimal  (i.e., 68% or 0.68).

Thermal Emittance (TE) - Percentage of radiation emitted from a heated body, compared to a perfect black body, expressed in terms of % or decimal  (i.e., 68% or 0.68)