SOLAR RADIATIONS AND ITS GEOMETRY

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1. PRESENTATION ON SOLAR RADIATIONS AND ITS GEOMETRY PARVAIZ MAQBOOL B.Tech ME 4 th YEAR ERP ID: 15BTME1062

2. SOLAR ENERGY ● Sun is the basic source of energy for E arth. Solar energy is available in the form of Electromagnetic Radiations. Sun is the large sphere of very hot gases, heat being generated by various fusion reactions in it. D iameter of sun = 1.27 × 10 4 km. Sun subtends an angle of only 32° at the Earth’s surface (because of large distance between them).

3. SOLAR ENERGY The direct/ beam radiation received from the Sun on the Earth is almost parallel. Brightness of the Sun varies from its centre to its edge, however , for engineering calculations , it is assumed to be uniform over the entire solar disc. The Sun generates an economous amount of energy – approximately 1.1 × 10 20 killowatt - hours every second. ( A killowatt -hour is the amount of energy needed to power a100 watt light bulb for ten hours.)

4. SOLAR ENERGY ON EARTH The earth’s outer atmosphere intercepts about two-billion of the energy generated by the sun, or about 1500 quadrillion (1.5 x 10^18 ) kilowatt-hours per year . Due to Reflection, Scattering, and Absorption by gases and aerosols in the atmosphere, however, only 47% of this or approximately 700 quadrillion (7 x 10^17 ) kilowatt-hours per year , reaches the surface of the earth.

5. SOLAR ENERGY ON EARTH (contd.) In the earth’s atmosphere, solar radiations are received: - directly (Direct Radiation) and - by diffusion in air, dust, water, etc., contained in the atmosphere (Diffusion Radiation). ● Global radiation = Direct Radiation + Diffuse Radiation. ● The amount of incident energy per unit area and day depends on a number of factors, e.g. : - Solar Radiation Geometry, which includes Solar Angles, Location or Geographical factors and Season / Time of the year.

6. SOLAR ENERGY ON EARTH (contd.) - Locate climate. - Inclination of the collecting surface in the direction of the sun.

7. SOLAR RADIATION GEOMETRY Angles useful in solar Radiation Analysis: 1. Latitude of Location ( φ l ). 2. Declination .( δ ) 3. Hour Angle.( ω ) 4. Altitude Angle.( α ) 5. Zenith Angle.( θ z ) 6. Solar Azimuth Angle.( ϒ s ) 7. Slope (s)

8. LATTITUDE ANGLE ( φ l ) Latitude Of Location : Angle made by radial line joining the location to the centre of the Earth and the projection of that line on the Equatorial plane.

9. LATTITUDE ANGLE ( φ l ) contd. It is the angular distance on north or south of equator measured from centre of the earth. It varies from 0° at equator to 90° at poles .

10. LATTITUDE ANGLE( φ l ) contd.

11. DECLINATION ( δ ) Declination ( δ ) : Angular distance of the Sun’s rays north or s outh of the equator. It is the angle between a line extending from the centre of Sun to c entre of Earth and the projection of this line u pon Earth’s Equatorial Plane. It is due to tilt of Earth’s Axis and it varies between 23.5° ( Summer Solstice : June 22) to -23.5° (Winter Solstice : December 22).

12. DECLINATION ( δ ) (contd.)

13. HOUR ANGLE ( ω ) Hour Angle ( ω ) : The angle through which the earth must turn to bring t he Meridian of a point directly in line with the Sun’s rays. It is a measure of the time of the d ay with respect t o solar noon. At noon, ω = 0. ω = 15° per hour.

14. ALTITUDE ANGLE ( α ) Altitude Angle or Solar Altitude Angle ( α ) : Vertical angle between the projection of Sun’s rays on the horizontal plane on Earth’s surface and the direction of sun’s ray. The altitude angle ( α ) is maximum at solar noon.

15. ZENITH ANGLE ( θ z ) Zenith Angle ( θ z ) : Complimentary Angle of Solar Altitude Angle, i.e. Vertical Angle between Sun’s rays and a line perpendicular to the horizontal plane through the point, i.e. Angle between the beam from the sun and the vertical.

16. SOLAR AZIMUTH ANGLE ( ϒ s ) Solar Azimuth Angle ( ϒ s ) : Solar Angle in degrees along the horizon east or west of North. It is a horizontal angle measured from North to horizontal projection of sun’s rays. It is considered positive west-wise.

17. SLOPE (s) Slope (s) : Angle made by plane surface with the horizontal. It is : +ve : for surfaces slopping towards South. -ve : for surfaces slopping towards North.

18. THANKS !! For Any Query Visit : https://www.youtube.com/watch?v=q95MwkMNDac