Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech III RENEWABLE ENERGY SOURCES Previous Question Paper (August/September - 2021 - R18)
Answer any five questions. All questions carry equal marks.
Main
What is distributed generation? What are the effects of DG on a transmission system?
Answer
Distributed Generation (DG) refers to the integration of small-scale power generation technologies, typically ranging from a few kilowatts to several megawatts, located close to the point of load consumption. Unlike traditional centralized power plants, DG units are connected directly to the distribution network or at the customer site. Common examples include solar photovoltaic systems, small wind turbines, fuel cells, micro-turbines, and reciprocating engines.
The integration of DG into the power system significantly alters the operational characteristics of the transmission and distribution network. The effects of DG on a transmission system include:
- Voltage Profile Improvement: DG units can act as local voltage support, reducing voltage drops along feeders and improving the voltage profile of the system, provided they are strategically placed and sized.
- Reduction in Transmission Losses: By generating power closer to the load, the need to transport electricity over long distances from centralized plants is reduced, which decreases the current flow in transmission lines and lowers I2R losses.
- Impact on Fault Levels: The addition of DG sources increases the short-circuit current levels in the network. This may necessitate the upgrading of existing circuit breakers and protection equipment to handle higher fault currents.
- Power Flow Reversal: In distribution systems with high DG penetration, power may flow from the distribution level back into the transmission system during periods of low local demand. This reverse power flow can interfere with traditional protection schemes and voltage regulation equipment like On-Load Tap Changers (OLTC).
- System Stability and Reliability: While DG can enhance reliability by providing backup power or islanding capabilities, intermittent sources like solar and wind can introduce power quality issues such as harmonics and frequency fluctuations, potentially impacting the stability of the interconnected transmission grid.
- Transmission Capacity Deferral: Effective deployment of DG can reduce the peak load demand on transmission infrastructure, potentially deferring the need for costly upgrades or the construction of new transmission lines.
What are renewable sources of energy? Enumerate the differences between renewable and nonrenewable sources of energy.
Answer
Renewable energy sources are energy resources that are replenished naturally on a human timescale, such as sunlight, wind, rain, tides, waves, and geothermal heat. Unlike finite resources, they are virtually inexhaustible.
| Feature | Renewable Energy | Non-Renewable Energy |
|---|---|---|
| Availability | Inexhaustible; naturally replenished. | Finite; depletes with use. |
| Environmental Impact | Low carbon footprint; sustainable. | High emissions; causes pollution. |
| Cost | High initial capital; low operating cost. | Low initial cost; high fuel/maintenance cost. |
| Examples | Solar, Wind, Hydro, Biomass. | Coal, Petroleum, Natural Gas, Nuclear. |
| Reliability | Intermittent (e.g., solar/wind). | Consistent and dispatchable. |
What are the specifications that the designer needs to follow before purchasing a wind turbine?
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How is PV cell Characteristic influenced by temperature?
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Explain the aspects of hydrogen as a fuel cell.
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What are the applications of Photovoltaic Solar Energy?
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What is meant by fuel cell equivalent circuit? Explain.
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What are the power and losses generated in an induction generator?
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What are the economic aspects of an induction generator?
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Explain the principle of operation of an induction generator.
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Write a short note on interconnected and stand-alone operation of an induction generator.
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Explain the economic aspects of energy storage systems.
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Explain pumped hydroelectric storage system with the help of a neat diagram.
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Briefly explain conversion technologies for injection of alternative energy power to the grid.
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Write a short note on Synchronous Generator Interconnection System.
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