JNTU
JNTU B.Tech III NON-CONVENTIONAL POWER GENERATION Previous Question Paper (September - 2021 - R16)
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What are solar collectors? Compare different types of solar collectors on the basis of construction and application.
Answer
Solar collectors are specialized devices designed to absorb solar radiation, convert it into thermal energy, and transfer this heat to a working fluid such as water, air, or oil. They act as the primary heat exchangers in solar thermal systems.
| Type | Construction | Application |
|---|---|---|
| Flat Plate Collector | Insulated metal box with a dark absorber plate and transparent cover. | Low-temperature heating (water heating, space heating). |
| Evacuated Tube Collector | Series of glass tubes with vacuum insulation to minimize heat loss. | Medium-temperature applications (industrial process heat). |
| Concentrating Collector | Uses mirrors or lenses (parabolic/trough) to focus sunlight onto a small receiver. | High-temperature applications (power generation, steam production). |
Explain the principle of conversion of solar energy into heat.
Answer
The conversion of solar energy into heat is based on the principle of photothermal conversion. When solar radiation (electromagnetic waves) strikes an object, the surface absorbs the energy, causing the atoms in the material to vibrate more rapidly, which increases the internal kinetic energy and thus the temperature of the material.
The process follows these key steps:
- Absorption: The collector surface, typically coated with a selective material having high absorptivity for short-wave solar radiation, captures the incoming photons.
- Thermalization: The absorbed energy is converted into heat within the absorber material.
- Heat Transfer: The generated heat is transferred to a circulating fluid via conduction through the absorber plate and then convection into the fluid.
- Retention: Insulation and glazing are used to minimize heat losses (conduction, convection, and radiation) to the surroundings, ensuring maximum thermal efficiency.
Discuss with sketch and equations how solar radiation measurement is calculated on a horizontal surface.
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Discuss about the main elements of a PV system and its Equivalent Circuit.
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Draw the V-I characteristics of PV system and explain.
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Define Maximum Power Point Tracking(MPPT) and explain its significance.
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Enumerate the design parameters to be considered to implement MPPT technique.
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What is the total power of a wind stream? What do you mean by coefficient of performance and tip speed ratio of a windmill? On what factors does the performance of windmills depend?
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How do vertical shaft windmills compare with windmills having horizontal shaft? Explain the use of windmills.
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List out the Biomass resources. What are biofuels?
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What do you understand by thermochemical and biochemical conversions?
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State the merits and demerits of OTEC plants. Explain the major problems that need to be solved.
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How does a fuel cell operate? How is it different from a battery? Explain the hydrogen-oxygen and carbon-oxygen fuel cells.
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