What Is Solar Angle ? Why Is It Require

What is solar Angles?

In the areas of solar PV and solar thermal energy it is very important to find the position of the sun. When an imaginary line is drawn from sun center to earth center then it make various types of angles in between sunrise and sunset. Various type angles like Zenith Angle, Solar Azimuth angle, Angle of incidence etc. So it is very difficult to find where is the sun in the sky,From our perspective on Earth, the sun is always changing its position in the sky.

    It is pretty obvious that every day the sun moves from the east to the west between sunrise and sunset, but did you know that it also moves from north to south throughout the course of the year? If you were to measure the position of the sun every day at solar noon it would be at a different angle every day. 

Why Is It Require:

The exact location of the sun in the sky depends on where you live, the day of the year, and, of course, the time of day. This effects the design decisions engineers make when they are installing photovoltaic (PV) panels and other solar related application like solar collector etc. Finally we can say that it is required for the fixing multiple type arrangement of solar based applications.

Zenith Angle, Θ_z: This is the angle between the line that points to the sun and the vertical — basically, this is just where the sun is in the sky. At sunrise and sunset this angle is 90º.

Solar Altitude Angle, α_s: This is the angle between the line that points to the sun and the horizontal. It is the complement of the zenith angle. At sunrise and sunset this angle is 0º.

Solar Azimuth Angle, γ_s: This is the angle between the line that points to the sun and south. Angles to the east are negative. Angles to the west are positive. This angle is 0º at solar noon. It is probably close to -90º at sunrise and 90º at sunset, depending on the season. This angle is only measured in the horizontal plane; in other words, it neglects the height of the sun.

Angle of Incidence, θ: This is the angle between the line that points to the sun and the angle that points straight out of a PV panel (this is also called the line that is normal to the surface of the panel). This is the most important angle. Solar panels are the most efficient when pointing at the sun, so engineers want to minimize this angle at all times. To know this angle, you must know all of the angles listed and described next.

Hour Angle, ω: This is based on the sun's angular displacement, east or west, of the local meridian (the line the local time zone is based on). The earth rotates 15º per hour so at 11am, the hour angle is -15º and at 1pm it is 15º.

Surface Azimuth Angle, γ: This is the angle between the line that points straight out of a PV panel and south. It is only measured in the horizontal plane. Again, east is negative and west is positive. If a panel pointed directly south, this angle would be 0º.

Collector Slope, β: This is the angle between the plane of the solar collector and the horizontal. If a panel is lying flat, then it is 0º. As you tip it up, this angle increases. It does not matter which direction the panel faces.

Declination, δ: This is the angle between the line that points to the sun from the equator and the line that points straight out from the equator. North is positive and south is negative. This angle varies from 23.45 to -23.45 throughout the year, which is related to why we have seasons.

Latitude, φ: This is the angle between a line that points from the center of the Earth to a location on the Earth's surface and a line that points from the center of the Earth to the equator.

Tilt Angle:It is the angle between vertical earth surface and slope of PV panels.

Solar Noon: The time of day when the sun is the highest in the sky.