JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III NON-CONVENTIONAL ENERGY SOURCES Previous Question Paper (February - 2023 - R18)

A sunshine recorder is a meteorological instrument specifically designed to measure the duration of bright sunshine at a particular location over a given period, typically a day. Its primary function is to record the total number of hours during which the solar irradiance exceeds a certain threshold, usually defined as 120 W/m², which is sufficient to produce a distinct burn or trace on the recording medium.

The device operates by focusing direct solar radiation onto a sensitive strip of card or paper. As the sun moves, the focal point tracks across the card, leaving a charred line. By measuring the length of these charred segments, meteorologists and solar energy engineers can determine the daily sunshine duration, which is a critical parameter for:

• Assessing the solar energy potential of a geographical site for photovoltaic or solar thermal installations.
• Validating satellite-based solar radiation models.
• Studying climate patterns and long-term solar availability trends.

Solar radiation data provides essential quantitative information required for the design, performance analysis, and feasibility assessment of solar energy systems. The data typically includes the following components:

• Global Horizontal Irradiance (GHI): The total amount of shortwave radiation received from above by a surface horizontal to the ground. It is the sum of direct and diffuse radiation.
• Direct Normal Irradiance (DNI): The amount of solar radiation received per unit area by a surface that is always held perpendicular to the rays that come in a straight line from the sun.
• Diffuse Horizontal Irradiance (DHI): The amount of radiation received per unit area by a surface that does not arrive on a direct path from the sun but has been scattered by molecules and particles in the atmosphere.
• Sunshine Duration: The total time during a day when the direct solar irradiance exceeds a specific threshold (typically 120 W/m²).
• Ambient Temperature and Meteorological Conditions: Often bundled with radiation data, this includes wind speed, humidity, and cloud cover, which influence the efficiency of photovoltaic modules and thermal collectors.

The relationship between these components is expressed as:

where θ is the solar zenith angle. This data is usually presented as hourly, daily, or monthly averages to assist in calculating the expected energy yield of solar installations.