JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III NON-CONVENTIONAL ENERGY SOURCES Previous Question Paper (August - 2022 - R18)

Solar radiation is the electromagnetic energy emitted by the sun, primarily consisting of ultraviolet, visible, and infrared light. As this radiation passes through the Earth's atmosphere, it undergoes several physical phenomena:

• Absorption: Atmospheric gases like ozone, water vapor, and carbon dioxide absorb specific wavelengths of solar radiation, converting them into thermal energy. Ozone effectively absorbs high-energy ultraviolet rays.
• Scattering: When radiation interacts with air molecules, dust particles, and aerosols, it is deflected in various directions. Rayleigh scattering occurs with small particles (wavelength-dependent), while Mie scattering occurs with larger particles like water droplets and dust.
• Reflection: Clouds and the Earth's surface reflect a portion of the incoming radiation back into space. The fraction of reflected radiation is known as the albedo.
• Transmission: The portion of radiation that reaches the Earth's surface without being absorbed or scattered is termed direct or beam radiation.

Total solar radiation received on a horizontal surface is the sum of beam (direct) and diffuse (scattered) components. The intensity of solar radiation reaching the surface depends on the angle of incidence.

For Beam Radiation (I_b), the intensity on a tilted surface is given by:

Where I_b,n is the beam radiation intensity on a surface normal to the sun's rays and θ is the angle of incidence between the sun's rays and the surface normal. For a horizontal surface, θ becomes the zenith angle (θ_z), thus I_b,h = I_b,n cos(θ_z).

For Diffuse Radiation (I_d), the radiation is assumed to be isotropic (uniform from all parts of the sky). The diffuse radiation on a tilted surface (I_d,t) is derived by integrating the sky view factor:

Where I_d,h is the diffuse radiation on a horizontal surface and β is the tilt angle of the surface from the horizontal. This expression accounts for the portion of the sky hemisphere visible to the tilted surface.