VII. Radiation Capture at the Surface
Efficiency of solar radiation capture depends on a number of factors, two of which include diffuse radiation loss and the sun’s change in position throughout the day. The sun’s motion is covered more in detail in the following section.
Due to the scattering discussed in Atmospheric Effects on Solar Intensity, there is much diffuse radiation that is lost from the direct sunlight. This diffuse radiation is light that was scattered throughout the atmosphere at various angles, and makes up about 15% of the AM0 radiation1. This is a significant percentage that we can’t fully capture with solar cells. By using non-reflective coatings and rough solar cell surfaces, it is possible to capture more of this diffuse radiation by allowing less light to escape, even if the incident light is not perpendicular to the surface.
The sun’s changing position also interferes with the consistency of solar radiation capture, due to changes in air mass. There are tracking systems that can be utilized to continuously capture the direct component of sunlight by moving the cell throughout the day to face the sun, however the advantage is largely offset by the energy cost and the loss of some diffuse radiation capture because of this angular motion. However, by studying the amount of energy required to utilize tracking systems and improvements in the light capture of the solar cell itself are used to improve efficiency (see Solar Cell Efficiency).
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1. Nelson, Jenny. The Physics of Solar Cells. London: Imperial College Press, 2003.