Solar Radiation

Sun-Earth relationships

Array Orientation

Solar Radiation Data Sheets

US Energy Consumption

A false color image of the sun enhances the turbulent nature of the sun’s photosphere, including a roiling surface, sunspots, and giant flares.

Distance from Sun to Earth

Even over the vast distance, an enormous amount of energy reaches Earth from the sun.

Even over the vast distance, an enormous amount of energy reaches Earth from the sun.

Harnessing the Sun

Solar irradiance is solar radiation power per unit area.

Inverse Square Law

The inverse square law states that radiation energy is reduced in proportion to the inverse square of the distance from the source.

The inverse square law states that radiation energy is reduced in proportion to the inverse square of the distance from the source.

Solar Irradiation

Solar irradiation equals to solar irradiance over time.

Electromagnetic Spectrum

The electromagnetic spectrum is composed of electromagnetic radiation with varying with wavelengths.

The electromagnetic spectrum is composed of electromagnetic radiation with varying with wavelengths.

Solar Spectrum

The wavelength distribution of the sun from UV to infrared reaching earth.

Atmospheric Effects

Solar radiation entering Earth’s atmosphere becomes direct, diffuse, or albedo radiation.

Air Mass

Air mass is a representation of the amount of atmosphere radiation that must pass through to reach Earth’s surface.

Air mass is a representation of the amount of atmosphere radiation that must pass through to reach Earth’s surface.

Peak Sun Hours

Peak sun hours is an equivalent measure of total solar irradiation in a day.

Average Annual Isolation Map

Insolation maps rate locations by their average daily peak sun hours.Insolation maps rate locations by their average daily peak sun hours.

Terrestrial Solar Spectrum

The atmosphere absorbs extraterrestrial radiation at certain wavelengths, resulting in an altered spectral distribution for terrestrial radiation.

The atmosphere absorbs extraterrestrial radiation at certain wavelengths, resulting in an altered spectral distribution for terrestrial radiation.

Spectral PV Device Response

PV devices are designed to respond to the wavelengths corresponding to the greatest amount of solar energy.

PV devices are designed to respond to the wavelengths corresponding to the greatest amount of solar energy.

Pyranometers

A pyranometer measures total solar irradiance from the whole sky.

A pyranometer measures total solar irradiance from the whole sky.

Handheld Pyranometers

Handheld pyranometers use less precise sensors than precision pyranometers but are more suitable for field measurements. Some use separate sensors that are connected to a meter, while some have the sensor and meter integrated in one unit.

Handheld pyranometers use less precise sensors than precision pyranometers but are more suitable for field measurements. Some use separate sensors that are connected to a meter, while some have the sensor and meter integrated in one unit.

Pyrheliometers

A pyrheliometer measures the direct component of solar irradiance, which is important when installing concentrating collectors.

A pyrheliometer measures the direct component of solar irradiance, which is important when installing concentrating collectors.

Reference Cells

Reference cells output a certain electrical current for each unit of solar irradiance received.

Reference cells output a certain electrical current for each unit of solar irradiance received.

Earth’s Orbit Around the Sun

The ecliptic plane is formed by Earth’s elliptical orbit around the sun.The ecliptic plane is formed by Earth’s elliptical orbit around the sun.

Solar Declination

The equatorial plane is tipped 23.5° from the ecliptic plane. Over a year, this orientation produces a varying solar declination.

The equatorial plane is tipped 23.5° from the ecliptic plane. Over a year, this orientation produces a varying solar declination.

Solstices

The summer solstice occurs when the Northern Hemisphere is tipped towards the sun. The winter solstice occurs when the Northern Hemisphere is tipped away from the sun.

The summer solstice occurs when the Northern Hemisphere is tipped towards the sun. The winter solstice occurs when the Northern Hemisphere is tipped away from the sun.

Equinoxes

The fall and spring equinoxes occur when the sun is directly in line with the equator.

The fall and spring equinoxes occur when the sun is directly in line with the equator.

Solar Azimuth and Altitude Angles

Solar azimuth and altitude angles are used to describe the sun’s location in the sky.Solar azimuth and altitude angles are used to describe the sun’s location in the sky.

Sun Paths

The sun’s path across the sky at various times of the year can be illustrated on a diagram. The diagrams change for different latitudes.

The sun’s path across the sky at various times of the year can be illustrated on a diagram. The diagrams change for different latitudes.

Solar Window

The solar window is the area of sky containing all possible locations of the sun throughout the year for a particular location.

The solar window is the area of sky containing all possible locations of the sun throughout the year for a particular location.

Array Orientation

Array orientation can be described using azimuth and tilt angles.Array orientation can be described using azimuth and tilt angles.

Optimum Array Tilt Angles

Energy production at certain times of the year can be optimized by adjusting the array tilt angle.Energy production at certain times of the year can be optimized by adjusting the array tilt angle.

Seasonal Declination

The average seasonal declinations define the optimal tilt angles for those periods.

The average seasonal declinations define the optimal tilt angles for those periods.

NREL Solar Radiation Data

The National Renewable Energy Laboratory (NREL) provides solar radiation data for various locations, times of the year, and array orientations for use in planning PV installations.

The National Renewable Energy Laboratory (NREL) provides solar radiation data for various locations, times of the year, and array orientations for use in planning PV installations.