JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III NON-CONVENTIONAL ENERGY SOURCES Previous Question Paper (August/September - 2021 - R18)

Solar power is widely regarded as a clean energy source, yet it carries specific environmental implications across its lifecycle:

• Lifecycle Emissions: While solar panels produce zero emissions during operation, their manufacturing, transportation, and installation involve energy-intensive processes. The production of silicon wafers and thin-film materials requires significant electricity, often sourced from fossil fuels.
• Land Use and Habitat Loss: Large-scale utility solar farms require extensive land areas. This can lead to the fragmentation of ecosystems, loss of biodiversity, and displacement of local wildlife if not properly managed.
• Hazardous Materials: The manufacturing of photovoltaic (PV) cells involves toxic substances such as cadmium telluride, lead, and hydrofluoric acid. Improper disposal or recycling of end-of-life panels poses a risk of soil and groundwater contamination.
• Water Consumption: Concentrated Solar Power (CSP) plants, which use steam turbines, require significant water for cooling, potentially stressing local water resources in arid regions where solar potential is highest.
• Resource Extraction: The mining of rare earth metals and minerals like silver, indium, and tellurium for PV components can cause localized environmental degradation and pollution at extraction sites.

Overall, the net environmental impact is significantly lower than that of conventional fossil fuel-based energy, provided that sustainable manufacturing and recycling programs are implemented.

The primary difference between these two instruments lies in the type of solar radiation they measure:

• Pyrheliometer: Measures beam radiation (direct solar radiation) at normal incidence. It must be pointed directly at the sun using a tracking mechanism.
• Pyranometer: Measures global solar radiation, which is the sum of direct beam radiation and diffuse radiation from the entire hemisphere (180-degree field of view).

Angstrom Type Pyrheliometer:

The Angstrom pyrheliometer operates on the principle of electrical compensation. It consists of two identical thin manganin strips, blackened to act as near-perfect absorbers.

• One strip is exposed to direct solar radiation, causing its temperature to rise.
• The other strip is shielded from the sun and is heated electrically.
• A thermocouple connected between the two strips detects the temperature difference.
• The electrical current in the shielded strip is adjusted until the temperature difference between the two strips is zero.

At this balanced state, the solar energy absorbed by the first strip is equal to the electrical power supplied to the second strip. The intensity of the radiation is calculated using the formula:

Where I is the solar intensity, K is the instrument constant, V is the voltage, and I_e is the electrical current supplied.