JNTU
JNTU B.Tech III NONCONVENTIONAL POWER GENERATION Previous Question Paper (September - 2021 - R16)
Answer any five questions. All questions carry equal marks.
Main
What are solar collectors? Compare different types of solar collectors on the basis of construction and application.
Answer
Solar collectors are specialized heat exchangers that transform solar radiation into thermal energy by absorbing sunlight and transferring it to a working fluid, such as water or air. They are categorized primarily into non-concentrating and concentrating types.
| Type | Construction | Application |
|---|---|---|
| Flat Plate Collector | Consists of an absorber plate, insulation, and a transparent cover; simple, static design. | Domestic water heating, space heating (low temperature). |
| Evacuated Tube Collector | Uses glass tubes with a vacuum between layers to minimize heat loss. | High-efficiency water heating, industrial process heat. |
| Parabolic Trough | Uses curved mirrors to focus sunlight onto a central receiver pipe. | Power generation, large-scale industrial heating. |
| Central Receiver | Uses a field of heliostats to focus light on a tower-mounted receiver. | High-temperature power plants and solar thermal electricity. |
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 a surface, the material absorbs the photons, causing the atoms to vibrate and increase in kinetic energy, which manifests as a rise in temperature.
The process involves three main mechanisms:
- Absorption: The collector surface, typically coated with a selective material (high absorptivity for short-wave solar radiation and low emissivity for long-wave infrared radiation), captures the incident solar flux.
- Heat Transfer: The absorbed energy is conducted through the material of the absorber plate to a fluid flowing through attached pipes or channels.
- Energy Transport: The heated fluid is then circulated to a storage tank or directly to a point of use, effectively transporting the thermal energy for practical application.
The efficiency of this conversion depends on minimizing heat losses through convection, conduction, and radiation, often achieved through insulation and vacuum sealing.
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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