JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III NON-CONVENTIONAL POWER GENERATION Previous Question Paper (November/December - 2020 - R16)

• Beam Radiation, also known as direct radiation, is the solar radiation received from the sun without having been scattered by the atmosphere. It casts a distinct shadow and can be focused by concentrating collectors.
• Diffuse Radiation is the solar radiation received from the sun after its direction has been changed by scattering by the atmospheric components such as clouds, dust, and gas molecules. It comes from all parts of the sky and cannot be focused by concentrating collectors.

The Solar Constant is defined as the intensity of solar radiation incident on a unit area perpendicular to the sun's rays at the mean earth-sun distance outside the earth's atmosphere. Its standard value is approximately:

The variation in solar radiation reaching the earth's surface compared to that outside the atmosphere is due to the following factors:

• Atmospheric Absorption: Gases like ozone, water vapor, and carbon dioxide absorb specific wavelengths of solar radiation, reducing the total energy reaching the surface.
• Scattering: Dust particles, aerosols, and air molecules scatter solar radiation in different directions, converting beam radiation into diffuse radiation.
• Reflection: Clouds and the earth's surface reflect a significant portion of incoming solar radiation back into space, a phenomenon measured by the earth's albedo.
• Air Mass: The path length of the solar radiation through the atmosphere changes with the sun's zenith angle. A longer path length results in greater attenuation of solar energy.
• Earth-Sun Distance: The earth's orbit is elliptical, causing the intensity of radiation to vary throughout the year as the distance between the earth and the sun changes.