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Name: Dave Didonato
Status: Student
Age: 16
Location: N/A
Country: N/A
Date: N/A


Question:
How does the angle of descending light affect how much energy a solar panel absorbs?



Replies:
In at least three ways:

1) The angle that light from the sun makes with the Earth's atmosphere determines the distance the light must travel through the atmosphere. The greater this distance the more energy is absorbed by the air before the light even reaches the solar panel.

2) A large solar panel generally intercepts more light than a small panel, right? So the cross-sectional area matters. If you were to turn the panel edge-on to the sun, it would intercept almost no light. If the area of the panel is A, the cross-sectional area that the panel presents to the sun is A cos(theta), where the angle theta is defined to be zero when the panel is pointing directly at the sun.

3) The greater the angle theta, the more light is reflected from the surface of the panel. This doesn't matter much unless theta is greater than around 45 degrees or so.

Tim Mooney



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