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Solar Radiation
The Sun • Solar Radiation •
Sun-Earth Relationships • Array
Orientation • Solar Radiation Data
Sets • Estimating Array Performance
The Sun • Solar Radiation •
Sun-Earth Relationships • Array
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A false color image
of the sun enhances the turbulent nature of the sun’s
photosphere,
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Even over the vast distance, an enormous
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Solar irradiance is
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The inverse square law states that irradiance is
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Solar irradiation
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The electromagnetic
spectrum is the
range of all types of electromagnetic
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The wavelength
distribution of extraterrestrial solar radiation forms a spectral
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Solar radiation
entering Earth’s
atmosphere consists of direct, diffuse,
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Air mass is a
representation of the amount of
atmosphere
radiation that must pass through to
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Peak sun hours is an
equivalent measure of total solar irradiation in a day.
For example, a day with an
average irradiance of 600 W/m2 over 8 hr may only
reach peak sun condition for an hour or less around noon. However, the total irradiation of 4800 Wh/m2
(600 W/m2 × 8 hr = 4800
Wh/m2) is equivalent to 4.8
peak sun hours (4800 Wh/ m2 ÷ 1000 W/m2 = 4.8
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Insolation (solar
irradiation received over a period of time, kWh/m2/day) maps
rate locations by their average daily peak
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The atmosphere
absorbs
extraterrestrial
radiation at certain wavelengths,
resulting in an altered spectral distribution for
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A pyranometer
measures total global solar
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Diffuse solar
irradiance can be measured by
adding a shadowing device to a
pyranometer, which blocks the direct
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Handheld
pyranometers use less precise sensors than precision
pyranometers but
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A pyrheliometer
measures the
direct component of solar irradiance, which is important when installing
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The ecliptic plane is formed by Earth’s elliptical orbit around the sun. In one year, Earth makes a slightly elliptical orbit around the sun.
Perihelion is the point in Earth’s orbit when it is closest to the sun.
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The equatorial plane is tipped 23.5° from the
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The summer solstice
occurs when the Northern
Hemisphere is tipped towards the sun. The winter solstice
occurs when the Northern
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The fall and spring
equinoxes occur when the sun is
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Two angles are used to define the sun’s
position, relative to an observer on Earth:
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Array orientation can be described using
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Energy production at certain times of the year
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The average
seasonal declinations define the optimal
