Lecture Notes on Solar Radiation

Vocabulary flashcards for key terms related to solar radiation, the sun-earth relationship, and solar energy systems.

The Sun

The star at the centre of our Solar System, with a diameter of about 1,392,000 km and a mass of about 330,000 times the mass of the Earth.

Nuclear Fusion

The process that creates energy in the Sun's core.

Average distance from the Sun to the Earth

Approximately 150 million km.

Time for light to reach Earth from the Sun

Approximately 8 minutes and 20 seconds.

Photosphere

The surface of the Sun.

Temperature of the Sun's photosphere

Approximately 6000 K.

Black Body

Describes a body that absorbs all radiation without emitting any back into the atmosphere.

Ultraviolet (UV) region

The range approximately from 100 to 400 nm that includes 7% of the Sun's emission.

Visible Light

The range between 400 to 750 nm that includes 43% of the Sun's radiation.

Infrared Region

The region where about 50% of the sun's radiation falls.

Extraterrestrial Irradiance

On average 1353 W/m2, varying by ±3% as the earth orbits the sun

Direct Beam Solar Radiation

Solar radiation that reaches the Earth's surface without being diffused.

Air Mass (AM)

How much atmosphere solar radiation has to pass through before reaching the earth.

AM0

Solar radiation outside the Earth’s atmosphere.

AM1

The air mass when the sun is directly overhead at sea level.

D in AM1.5 D

Represents direct radiation.

G in AM 1.5 G

Represents Global radiation (Direct + Diffused).

Declination Angle (δ)

The angle, denoted by δ, which varies seasonally due to the tilt of the Earth on its axis of rotation and the rotation of the Earth around the sun.

Hour Angle (ω)

The angular displacement of the sun east or west of the local meridian due to rotation of the earth on its axis at 15° per hour; morning negative, afternoon positive.

Azimuth Angle (ɣ)

The angular displacement from south of the projection of beam radiation on the horizontal plane.

Elevation Angle

The angular height of the sun in the sky measured from the horizontal.

Zenith Angle

Angle measured from vertical rather than horizontal. θ = 90° − α

Equation of Time (EoT)

Corrects for the eccentricity of the Earth's orbit and the Earth's axial tilt.

Tilt Angle

The angle formed between the horizontal plane and the pitch of our solar panels.

Sun Path Diagram

Provides the track of the sun over a year's time for your local latitude and time zone.

Solar Window

The area that should be clear and not be shaded by trees or any other obstacle between 9.00 a.m. and 3.00 p.m.

Solar Irradiance

Sunlight intensity measured in watts or kW on one square meter (kW/m2).

Solar Insolation

Measure of solar radiation energy received on a given surface area in a given time, expressed in kWh/m2.

Peak Sun Hours (PSH)

The equivalent number of hours of being under 1kWh/m2/day.