Solar Energy - The Basics
The Sun --> Always there; lots of Energy
What
Makes the Sun Shine?
How many photons (energy) reach the surface of the
Earth on Average?
- Note that most of the energy is in visible (yellow-green)
photons
What is Photon Scattering
How much energy from the sun reaches the surface of the
Earth on Average?
Note that we measure energy in units of Watt-hours. A watt
is not a unit of energy, it is a measure of power. Energy equals
1 Kilowatt Hour = 1KWH = 1000 watts used in one hour =
10 100 watt light bulbs left on for an hour
Incident Solar Energy on the ground:
Average over the entire earth =
164 Watts per square meter over a 24 hour day
8 hour summer day, 40 degree latitude --> 600 Watts per sq. meter
So over this 8 hour day one receives:
8 hours x 600 watts per sq. m = 4800 watt-hours per sq. m which
equals 4.8 kilowatt hours per sq. m
This is equivalent to 0.13 gallons of gasoline
For 1000 square feet of horizontal area (typical roof area) this
is equivalent to 12 gallons of gas or about 450 KWH
But to go from energy received to energy generated requires
conversion of solar energy into other forms (heat, electricity)
at some reduced level of efficiency.
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The Electronic Universe Project
e-mail: nuts@moo.uoregon.edu