RENEWABLE ENERGY RESOURCES

CIE-II
SAQ’s
Unit-III
1. List the advantages and disadvantages of Wind energy.
Ans: Advantages Disadvantages
Renewable and sustainable Intermittent energy source
Low operating costs High initial setup cost
Reduces greenhouse gas emissions Noise and visual pollution
Land beneath turbines can be used Impacts on wildlife (e.g., birds)
2. What are the various components of a wind turbine?
Ans: 1. Rotor Blades: Capture wind energy.
2. Hub: Connects blades to the rotor.
3. Nacelle: Houses the gearbox, generator, and control system.
4. Tower: Supports the turbine at an optimal height.
5. Foundation: Provides stability.
6. Yaw Mechanism: Aligns the rotor to the wind direction.
3. Explain the limitations and possible environmental impacts of wind energy
Ans: Limitations:
• Requires consistent wind speeds.
• Limited energy storage solutions.
• High installation costs.
Environmental Impacts:
• Noise and visual disruption.
• Bird and bat collisions.
• Land use and habitat disruption.
Unit-IV
1. Draw the diagram of a Double Basin Tidal Power Plant and name the parts.
Ans:

2. What are the different sources of Geothermal energy.

Ans: 1. Hydrothermal Reservoirs (hot water and steam below Earth's surface).
2. Geopressured Reservoirs (hot brine containing dissolved methane).
3. Hot Dry Rocks (heat from solid rock formations).
4. Magma (molten rock beneath Earth's crust).
3. What is the difference between open cycle and closed cycle OTEC system?
Ans: Open Cycle OTEC Closed Cycle OTEC
Uses warm seawater directly to generate Uses a working fluid (e.g., ammonia) in a
steam. heat exchanger.
Steam drives the turbine directly. Working fluid evaporates and condenses
in a cycle.
Unit-V
1. Write a short note on bio-gasifier.
Ans: A bio-gasifier is a device that converts biomass into a combustible gas mixture called
producer gas. It involves partial combustion of biomass at high temperatures in limited
oxygen. Producer gas can be used for heating, electricity generation, and as a fuel for
engines.
2. List the different Biomass resources.
Ans: 1. Wood and Forestry Residues
2. Agricultural Waste (e.g., crop residues, husks)
3. Animal Waste (e.g., manure)
4. Industrial Waste (e.g., sawdust, paper)
5. Energy Crops (e.g., switchgrass, sugarcane)
3. What are biomass conversion technologies?
Ans: 1. Thermochemical Conversion: Includes combustion, gasification, and
pyrolysis.
2. Biochemical Conversion: Involves anaerobic digestion and fermentation.
3. Chemical Conversion: Includes processes like transesterification for biofuel
production.
LAQ’s
Unit-III
1. Explain how the wind energy systems (WECS) are classified? Discuss in brief.
Ans: Classification of Wind Energy Systems (WECS):
1.Horizontal-Axis Wind Turbines (HAWT):
- Most common type.
- Features two or three blades mounted on a horizontal rotor.
- Efficient at capturing wind from any direction when equipped with a yaw
mechanism.

2. Vertical-Axis Wind Turbines (VAWT):

- Blades are oriented vertically, allowing wind to hit from any direction.
- Types include Savonius (drag-type) and Darrieus (lift-type).
- Generally easier to maintain and suitable for urban environments.

3. Small Wind Turbines:

- Designed for individual homes or small businesses.
- Typically have a power output of less than 100 kW.
- Can be either HAWT or VAWT configurations.
 4. Large Wind Turbines:
- Designed for wind farms, with power outputs ranging from 100 kW to several
megawatts.
- Primarily HAWT designs to maximize efficiency and power generation.

5. Offshore Wind Turbines:

- Installed in bodies of water to harness stronger and more consistent winds.
- Usually larger and designed to withstand harsh marine conditions.

6. Onshore Wind Turbines:

- Located on land and commonly used in wind farms.
- Easier and less expensive to install and maintain compared to offshore turbines.

7. Specialized Turbines:
- Include designs like floating turbines for deep water or hybrid systems that combine
wind and solar energy.
- Tailored to specific environmental conditions and energy needs.
2. Sketch and explain the different operational characteristics of Wind turbine.
Ans: Operational Characteristics of Wind Turbines:
Wind turbines function by converting wind energy into electrical power through the
rotation of blades. The performance of a wind turbine is governed by several critical
operational characteristics:

1. Cut-in Speed (3-4 m/s):

• This is the minimum wind speed at which the turbine blades start to rotate and
generate electricity. Below this speed, the turbine remains idle.
2. Rated Speed (12-15 m/s):
• At this wind speed, the turbine reaches its maximum power output, known as
rated power. The turbine is designed to operate most efficiently at this speed.
3. Cut-out Speed (20-25 m/s):
• When wind speeds exceed this limit, the turbine automatically shuts down to
prevent damage from excessive forces. The blades are feathered or turned to
minimize wind resistance.
4. Capacity Factor:
• This measures the actual output over a period of time compared to the turbine’s
maximum potential output. A higher capacity factor indicates better performance.
5. Power Curve:

• The power curve graphically represents the relationship between wind speed and
turbine power output. It illustrates how power increases with wind speed until
the rated power is achieved, after which it plateaus until the cut-out speed.
6. Betz Limit (59.3%):

• This is the maximum efficiency a wind turbine can achieve, indicating that no
turbine can convert more than 59.3% of wind energy into usable mechanical
energy.
 7. Yaw Control:
• A system that aligns the turbine with the wind direction to maximize energy
capture. Wind direction sensors guide the yaw motor to adjust the nacelle’s
position.
3. Explain in detail about the configuration of Horizontal and vertical axis wind
turbine.
Ans:

Configuration of Horizontal and Vertical Axis Wind Turbines:

1. Horizontal Axis Wind Turbine (HAWT):
• Configuration:
o Rotor shaft is horizontal and parallel to the ground.
o Blades face the wind directly (upwind or downwind).
o The nacelle (housing the gearbox and generator) is mounted at the top of
a tower.
o A yaw mechanism rotates the nacelle to align with wind direction.
• Components (as shown in diagram):
o Rotor Blades – Capture wind energy.
o Gearbox – Increases the rotational speed for efficient power generation.
o Generator – Converts mechanical energy into electricity.
o Nacelle – Contains the generator and gearbox.
o Tower – Provides height for stronger wind capture.
• Advantages:
o High efficiency and greater energy output.
o Can capture stronger and less turbulent winds at higher altitudes.
• Limitations:
o High maintenance due to nacelle height.
o More complex and expensive design.
 2. Vertical Axis Wind Turbine (VAWT):
• Configuration:
o Rotor shaft is vertical and perpendicular to the ground.
o Blades rotate around the vertical axis and capture wind from any direction.
o The generator and gearbox are located at the base of the tower.
• Components (as shown in diagram):
o Fixed Pitch Rotor Blades – Rotate around the central shaft.
o Gearbox – Transfers rotational energy to the generator.
o Generator – Converts mechanical energy into electrical power.
• Advantages:
o Simpler, more accessible design for maintenance.
o No yaw control required – captures wind from all directions.
• Limitations:
o Lower efficiency compared to HAWTs.
o Less effective in high wind speeds.

Key Differences:
• Wind Capture: HAWT requires wind from a specific direction, while VAWT
works with wind from any direction.
• Maintenance: Easier for VAWT as key components are at the base.
• Efficiency: HAWT is generally more efficient for large-scale power generation.
Unit-IV
1. State the basic principle of tidal energy production and write major components
of tidal power plant.
Ans: Basic Principle of Tidal Energy Production:
Tidal energy is harnessed by utilizing the movement of water caused by the
gravitational pull of the moon and the sun, which results in periodic high and low tides.
The potential energy of water during high tides and the kinetic energy of flowing water
during low tides are captured to drive turbines. These turbines generate mechanical
energy, which is subsequently converted into electrical energy using generators. This
renewable energy source is both predictable and sustainable, making it a valuable
method of power generation.

Tidal Power Plant Diagram

 Major Components of a Tidal Power Plant:
1. Barrage Dam: A large barrier built across an estuary or tidal basin to regulate
water flow and create a controlled environment for tidal energy generation.
2. Sluice Gates: Installed in the barrage, these gates control the entry and exit of
tidal water, allowing for efficient operation during high and low tides.
3. Turbines: Rotational devices placed in the barrage; they convert the kinetic
energy of flowing water into mechanical energy.
4. Generator: Attached to the turbines, it transforms mechanical energy from the
turbines into electrical energy.
5. Tidal Basin: Acts as a reservoir to store water during high tides, ensuring a
consistent water flow to the turbines during low tides.
6. Transmission Lines: Responsible for transferring the generated electricity from
the power plant to the main grid or distribution centers.
7. Control Systems: Include sensors and monitoring tools to optimize operations,
control the gates, and ensure safety and efficiency.
2. Explain the principle of operation of wave power generation with a neat sketch.
Ans: Principle of Operation of Wave Power Generation (7 Marks)
Wave power generation utilizes the kinetic and potential energy of ocean waves to
produce electricity. The process involves converting the mechanical energy from the
up-and-down motion of the waves into electrical energy through specialized devices
placed in the water. These devices are designed to harness the energy from the wave
movement, primarily focusing on the rise and fall of water levels caused by waves.

Working Principle:
1. Wave Motion:
o Waves are generated by the wind blowing across the surface of the ocean.
The energy from the wind causes water particles to move in an oscillating
pattern, creating waves. This movement of water, both vertically and
horizontally, contains a significant amount of energy.
2. Energy Conversion:
o The mechanical energy from the wave motion is captured by devices
designed to interact with the waves. The most commonly used device for
wave energy generation is the Oscillating Water Column (OWC). In this
 system, as waves cause the water level to rise and fall in a chamber, the air
inside the chamber is compressed and decompressed. This movement of
air is used to drive a turbine, which is connected to a generator to produce
electricity.
3. Types of Devices:
o Oscillating Water Column (OWC): As shown in the diagram, the rising
and falling waves force air to move in and out of the chamber, driving a
turbine connected to a generator. This process efficiently converts wave
energy into electrical energy.
o Other devices may include point absorbers or overtopping systems, but
OWC is one of the most widely used methods.
4. Power Output:
o The amount of electricity generated depends on the wave height,
frequency, and the efficiency of the conversion system. Larger, more
consistent waves generate more power. The OWC system, in particular,
works efficiently in regions where waves are frequent and have substantial
energy.
3. Discuss about various applications of geothermal energy systems, and its usage.
Ans: Applications and Usage of Geothermal Energy Systems:
Geothermal energy utilizes heat from the Earth's core to generate power or provide
direct heating. It is renewable, sustainable, and environmentally friendly.
1. Electricity Generation:
• High-temperature geothermal reservoirs (above 150°C) power steam turbines to
produce electricity.
• Used in geothermal power plants such as dry steam, flash steam, and binary
cycle plants.
• Example: Iceland and California utilize geothermal for large-scale electricity
production.
2. Direct Heating:
• Geothermal heat is directly supplied to homes, offices, and industrial buildings.
• Used in district heating systems that transfer hot water through pipelines.
• Example: Greenhouses, fish farming, and spas benefit from direct geothermal
heating.
3. Industrial Applications:
• Geothermal energy provides heat for food processing, pasteurization, drying
wood, and desalination of water.
• Efficient for industries requiring large amounts of continuous heat.
4. Agricultural Uses:
• Greenhouses and soil heating extend growing seasons in cold climates.
• Heated water from geothermal plants aids in aquaculture (fish farms).
5. Cooling and Heating (Geothermal Heat Pumps):
• Geothermal heat pumps (GHPs) use the stable underground temperature to heat
in winter and cool in summer.
• Applied in residential and commercial buildings for space heating/cooling.
6. Tourism and Recreation:
• Hot springs, geysers, and geothermal spas attract tourists.
• Examples: Blue Lagoon in Iceland and Onsens in Japan.
Advantages of Geothermal Energy Usage:
• Eco-Friendly: Low emissions compared to fossil fuels.
• Renewable: Continuous supply of heat from the Earth.
• Cost-Effective: After initial investment, operational costs are low.
By tapping into geothermal resources, industries and homes benefit from reliable and
clean energy, reducing reliance on fossil fuels.