Renewable Energy Sources 2BETCK205E

Module-3

Wind Energy, Biomass Energy

Syllabus: WIND ENERGY- Properties of wind, availability of wind energy in India, wind velocity
and power from wind; major problems associated with wind power, Basic components of wind energy
conversion system (WECS); Classification of WECS Horizontal axis- single, double and multi blade
system. Vertical axis- Savonius and Darrieus types.

BIOMASS ENERGY-Introduction; Photosynthesis Process; Biofuels; Biomass Resources; Biomass

conversion technologies -fixed dome; Urban waste to energy conversion; Biomass gasification
(Downdraft).

Properties of wind: The definition of wind is the movement of gas molecules in the atmosphere
commonly known as air. The differences in air pressure in a specific location causes air to move from
areas of high pressure to areas of low pressure. The Earth is spherical, which means that the widest
part of the Earth, near the equator, is slightly closer to the sun and the sunlight hits the equator more
directly. Therefore, there is hotter air over regions near the equator, and cooler air at the poles. Just
like with the sea breeze, hot air at the equator rises, causing an area of low pressure in which cold polar
air moves from the north and south poles to the equator to fill that space. This motion, however, is
complicated by something called the Coriolis effect.

Winds are caused because of two factors:

(1) The absorption of solar energy on the earth’s surface and in the atmosphere.

(2) The rotation of the earth about its axis and its motion around the sun. Because of these factors,
alternate heating and cooling cycles occur, differences in pressure are obtained, and the air is caused
to move.

Wind energy or wind power describes the process by which wind is used to generate electricity. Wind
turbines convert the kinetic energy in the wind into mechanical power.

Wind has two important characteristics—direction and speed. The direction of wind can be gauged
using an instrument called the wind vane. The speed of wind is usually measured with an instrument
called the anemometer.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

1
Renewable Energy Sources 2BETCK205E

Availability of Wind Energy In India:

 The Indian wind energy sector has an installed capacity of 14,158.00 MW (as on March 31,
2011).

 In terms of wind power installed capacity, India is ranked fifth in the world.
 Today, India is a major player in the global wind energy market.
 Indian Wind Energy Association has estimated that with the current level of technology, the
‘on-shore’ potential for utilization of wind energy for electricity generation is of the order of
65,000 MW.

 Wind in India are influenced by the strong south-west summer monsoon, which starts in May-
June, when cool, humid air moves towards the land; further, the weak north-east winter
monsoon, which starts in October, when cool, dry air moves towards the ocean.

 During March-August, the winds are uniformly strong over the whole Indian Peninsula, except
the eastern peninsular coast.

 Wind speeds during November-March are relatively weak, although high winds are available
during a part of the period on the Tamil Nadu coastline.

 A notable feature of the Indian programme has been the interest among private investors or
developers in setting up of commercial wind power projects.

 The gross potential is 48,561 MW (source C-wet) and a total of about 14,158.00 MW of
commercial projects have been established until March 31, 2011.

 Tamil Nadu's wind production capacity was around 24% of India's total in 2021.
 Gujarat has around 22% of the total capacity of the country.
 The largest capacity wind turbine of 4.2 MW is installed in Tamil Nadu state as of October
2022. Muppandal wind farm, the total capacity is 1500 MW with nearly 3000 wind turbines,
the largest wind power plant in India.

 Karnataka Gadag by Shah Gajendragarph power plant produces 10.8MW.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

2
Renewable Energy Sources 2BETCK205E

Wind Velocity: The circulation of air in the atmosphere is caused by the non uniform heating of
earth’s surface by the sun.

 During the day air above the land heats up rapidly than air over water.

 During night it reverses.

 Wind speeds increases with height .

 Wind possesses energy by virtue of its motion.

 The device capable of slowing down the mass of moving air like a sail or propeller can
extract the part of energy and convert it into useful work.

 Three factors determine the output from wind energy converter.

1. Wind speed

2. Cross section of wind swept by rotor

3. Overall conversion efficiency of rotor

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

3
Renewable Energy Sources 2BETCK205E

 The cut-in speed (typically between 6 and 9 mph) is when the blades start rotating and
generating power.
 As wind speeds increase, more electricity is generated until it reaches a limit, known as the rated
speed.
 This is the point that the turbine produces its maximum, or rated power.
 As the wind speed continues to increase, the power generated by the turbine remains constant
until it eventually hits a cut-out speed (varies by turbine) and shuts down to prevent unnecessary
strain on the rotor.
 0-10 mph: Wind speed is too low for generating power. Turbine is not operational. Rotor is
locked.
 10-25 mph: 10 mph is the minimum operational speed. It is called "Cut- in speed".
 In 10-25 mph wind, generated power increases with the wind speed.
 25-50 mph: Typical wind turbines reach the rated power (maximum operating power) at wind
speed of 25mph (called Rated wind speed).
 Further increase in wind speed will not result in substantially higher generated power by design.
This is accomplished by, for example, pitching the blade angle to reduce the turbine efficiency.
 50 mph: Turbine is shut down when wind speed is higher than 50mph (called "Cut-out" speed)
to prevent structure failure.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

4
Renewable Energy Sources 2BETCK205E

MAJOR PROBLEMS ASSOCIATED WITH WIND ENERGY IN INDIA:

Site Selection Considerations:
1. High Annual Wind Speed: The fundamental requirement for the use of WECS system is
adequate supply of wind.
2. Availability of anemometer data: The anemometer data should be available over some
period of time.
3. Land availability: Wind turbines require a large area of land to be installed, and acquiring
land is a major challenge in India due to land-use regulations, competing land uses, and
complex land ownership patterns.
4. Transmission and grid integration: Wind farms are often located far from the load centers,
and the power generated needs to be transmitted over long distances. The transmission and
grid infrastructure in India is inadequate, and the integration of wind power into the grid is a
major challenge.
5. High capital costs: The installation and maintenance costs of wind turbines are high, making
wind energy less competitive than other sources of electricity.
6. Environmental impacts: Wind turbines can have environmental impacts such as bird and bat
collisions, noise pollution, and visual impacts.
7. Maintenance and reliability: Wind turbines require regular maintenance to ensure reliable
and efficient operation, and the availability of skilled technicians and spare parts can be a
challenge in remote locations.
8. Distance to roads or railways: For the movement of heavy machinery, structures, materials,
blades and other apparatus, WECS must be accessible.
9. Nature of Ground: Ground condition should be good enough to give secured foundation.
Erosion problem should not be there. Surface should be stable.
10. Other conditions such as icing problem, salt spray or blowing dust should not be present at
site. They may affect aero turbine blades.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

5
Renewable Energy Sources 2BETCK205E

BASIC COMPONENTS OF WIND ENERGY CONVERSION SYSTEM

(WECS)
The basic principle of every windmill is to convert kinetic energy of wind into mechanical energy which
is used to rotate the turbine of an electrical generator to produce electricity.
Basic components of a Wind Electric Systems are,
1. Tower
2. Nacelle
3. Rotor
4. Gearbox
5. Generator
6. Braking System
7. Yaw System
8. Controllers
9. Sensors

Block diagram wind energy conversion system

1. Blades-Most turbines have either 2 or 3 blades. Wind blowing over the blades causes the blades to
“lift” and rotate. Blades are made of Fibers with a polymer matrix, such as epoxy resin since it is
known for its good mechanical properties, such as high tensile strength, low weight, and resistance
to corrosion. Carbon fiber reinforced plastic (CFRP) can also be used as blade material. CFRP) is a
composite material made by combining carbon fibers with a polymer matrix, such as epoxy resin.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

6
Renewable Energy Sources 2BETCK205E

2. Nacelle-Nacelle sits at top of the tower and contains the gear box, low and high speed shafts,
generator, controller and brakes. A cover protects the components inside the nacelle. Some nacelles
are large enough for a technician to stand inside while working.
3. Rotor-Blades and hub together are called rotor.
4. Tower- Towers are made from tubular steel or steel lattice. Because wind speed increases with
height, taller towers enable turbines to capture more energy and generate more electricity
Four types of supporting towers deserve consideration; these are:
1. the reinforced concrete tower
2. the pole tower
3. the built up shell-tube tower, and
4. the truss tower
Among these, the truss tower is favoured because it is proved and widely adaptable, cost is low,
parts are readily available, it is readily transported, cost is low, parts are readily available, it is
readily transported, and it is potentially stiff.
Horizontal axis wind turbines are mounted on towers so as to be above the level of turbulence and
other ground related effects. The minimum tower height for a small WECS is about 10m, and the
maximum practical height is estimated to be roughly 60 m.
5. Pitch: Blades are turned, or pitched, out of the wind to keep the rotor from turning in winds that
are too high or too low to produce electricity.
6. Yaw drive: Upwind turbines face into the wind; the yaw drive is used to keep the rotor facing into
the wind as the wind direction changes. Downwind turbines don’t require a yaw drive, the wind
blows the rotor downwind.
7. Yaw motor: Powers the yaw drive.
8. Wind vane: Measures wind direction and communicates with the yaw drive to orient the turbine
properly with respect to the wind.
9. Anemometer-Measures the wind speed and transmit wind speed data to the controller
10.Controller-Controller starts up the machine at wind speeds of about 8 to 16 miles per hour(mph)
& shuts off machine at about 55 mph to avoid damage at high winds. The modern large wind turbine
generator requires a versatile and reliable control system to perform the following functions:
a. the orientation of the rotor into the wind (azimuth of yaw);s
b. tart up and cut-in of the equipment;
c. power control of the rotor by varying the pitch of the blades;
d. generator output monitoring - status, data computation, and storage;

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

7
Renewable Energy Sources 2BETCK205E

e. shutdown and cut out owing to malfunction of very high winds'protection for the generator
f. the utility accepting the power and the prime mover;auxiliary and /or emergency power;
g. and maintenance modeMany combinations are possible in terms of the control system and
may involve the following components:
h. Sensor - mechanical, electrical, or pneumatic:
i. Decision elements - relays, logic modules, analog circuits, a microprocessor, a fluidics, units, or
a mechanical unit;
j. Actuators - hydraulic, electric, or pneumatic. A recommended combination of electronic
transducers feeding into a micro-processor which, in turn, signals electrical actuators and
provides protection through electronic circuits, although a pneumatic slip clutch may be required.
11. Gearbox- Gears connect the low-speed shaft to the high-speed shaft and increase the rotational
speeds from about 30 to 60 rotations per minute (rpm) to about 1200 to 1500 rpm, the rotational
speed required by most generators to produce electricity
12. Low-speed shaft- The rotor turns the low-speed shaft at about 30 to 60 rotations per minute.
13. High-speed shaft- Drives the generator.
14. Generator- Usually an off-the-shelf induction generator that produces 60-cycle AC electricity.
It should have a cooling system to make sure there is no overheating. Either constant or variable
speed generators are a possibility, but variable speed units are expensive and/or unproved. Among
the constant speed generator candidates for use are synchronous induction and permanent magnet
types. The generator of choice is the synchronous unit for large aero generator systems because it
is very versatile and has an extensive database.

WORKING OF WIND MILL

● Wind blows toward the turbine's rotor blades.

● The rotors spin around, capturing some of the kinetic energy from the wind, and turning the central
drive shaft that supports them.
● Inside the nacelle, the gearbox converts the low-speed rotation of the drive shaft into high-speed
rotation fast enough to drive the generator efficiently.
● The entire top part of the turbine (the rotors and nacelle) can be rotated by a yaw motor, mounted
between the nacelle and the tower, so it faces directly into the oncoming wind and captures the
maximum amount of energy.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

8
Renewable Energy Sources 2BETCK205E

● If it's too windy or turbulent, brakes are applied to stop the rotors from turning (for safety reasons).
● The electric current produced by the generator flows through a cable running down through the
inside of the turbine tower.
● A step-up transformer converts the electricity to about 50 times higher voltage so it can be
transmitted efficiently to the power grid (or to nearby buildings or communities).
● Wind turbines are mounted on a tower to capture the most energy. At 30 meters or more above
ground, they can take advantage of faster wind.
CLASSIFICATION OF WECS (WIND ENERGY CONVERSION SYSTEM):
1.According to axis of rotation
(i) Horizontal Axis Machines.
(ii) Vertical Axis Machines.
2. According to size as determined by the useful electrical power output.
i) Small Scale (upto 2 kW).
(ii) Medium Size Machines (2-100 kW).
(iii) Large Scale or Large Size Machines (100 kW and up).
3. As per the type of output power, wind aero generators are
(i) DC output
(ii) AC output
4.As per the rotational speed of the aero turbines
(i) Constant Speed with variable pitch blades.
(ii) Nearly Constant Speed with fixed pitch blades.
(ii) Variable Speed with fixed pitch blades.
5. Wind turbines are also classified as per how the utilization of output is made
(i) Battery storage,
(ii) Direct connection to an electromagnetic energy
(iii) Other forms (thermal potential etc.) of storage, converter.
(iv) Interconnection with conventional electric utility grids.
6. Based on wind orientation
(i) Upwind turbine
(ii) Downwind turbine
HORIZONTALAXIS TYPE WIND TURBINE:
 The axis of rotation (Horizontal axis) of blades is parallel to the wind flow direction.
 Generally, these require massive tower construction to support heavy nacelle.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

9
Renewable Energy Sources 2BETCK205E

 An additional yaw control is required to turn the rotor towards the wind direction.
 Electric generator & gearbox are installed at the top of the tower.
 When it comes to the performance of the system, these are having high efficiency & most
used turbines.
 It is widely used for generation of electricity for commercial purposes.
TYPES OF HORIZONTAL AXIS
 Single Blade
 double Blade
 Multi-blade system
Single blade wind turbines
A single blade wind turbine has only one blade that rotates around a central hub.
 This design is simple and easy to maintain, but it is also less efficient compared to other
designs.
 It is subject to more vibration and noise.
 In this a long single blade is mounted on the rigid hub.
 If long blade (>60M) is used, it may causes root bending movements may occur due to
gravitational and sudden shifts in the wind direction.
 To reduce cost, a small counter weight has to be attached to the blade which balances the long
blade centrifugally.
Advantage of single blade rotor:
1) Simple blade control
2) Counter weight cost less than the second blade
3) Counter weight can be inclined to reduce blade coning
4) Pitch bearings do not carry centrifugal force.
Disadvantages:
1) Vibrations are produced due to aerodynamic torque
2) Unconventional appearance
3) Starting torque is low due to ground boundary condition.
Two blade wind turbine
 It has two blades that rotate around a central hub.
 It has less vibration and noise compared to single blade turbines.
 The blades are usually mounted on the same central hub, which provides a balanced torque
and increases efficiency.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

10
Renewable Energy Sources 2BETCK205E

 If the blades were made up of metal, reduces fatigue life and tower will also be subjected to
same forces.
 If this vibration matches to the natural vibration of the tower, Tower may be collapsed
 Because of the high cost of the blades, more than two blades are not recommended.

Multi blade wind turbine

 It has three or more blades that rotate around a central hub.
 This design provides even more stability and efficiency compared to single or double blade
wind turbines, as the multiple blades spread the wind energy across the entire rotor, reducing
stress on any one blade.
 This design uses no of blades made up of sheet metal and aluminum.
 This rotor have high strength to weight ratio and can sustain to work even under 60
km/h wind speeds
 This are tend to have good power coefficient, high starting torque, and simplicity and
low cost.
 Additionally, this design is more aerodynamic and less affected by wind turbulence, resulting
in higher energy production.
 Cost of manufacturing, transporting the blade is huge as the number of blades increases.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

11
Renewable Energy Sources 2BETCK205E

VERTICAL AXIS WIND TURBINE

 Here the axis of rotation (Vertical axis) of blades is perpendicular to the wind flow direction.
 Additional equipment mechanism is required to start it from a stationary position.
 he vertical axis wind turbine does not require a yaw mechanism because it receives wind from all
directions.
 Gearbox is installed at the bottom of the turbine.
 There is no need for nacelle in case of vertical axis wind turbines.
Types of vertical axis wind turbines
◆ Savonius -two half-cylindrical blades arranged in an 'S' shape.
◆ Darrieus types- curved aerofoil blades mounted on a rotating shaft or framework.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

12
Renewable Energy Sources 2BETCK205E

Savonius rotor:

 The main advantage of this rotor is that it can rotate even under low velocity winds.
 It consists of two half semi-circular cylinder blades facing opposite direction. They are almost
in s-shaped cross-section.
 These two blades are mounted on a vertical axis perpendicular to the wind direction with a gap
between the blades.
 This rotor rotates such that it faces convex side surface to wind .
 If wind speed is greater than in the convex side than the round surface, the blades tends to
rotate.
 Air whips around inside surface and forward moving cup face making the rotor to rotate in one
direction.
 The ratio of height to the diameter can be varied. Generally it is in the ratio of 3:1
 The power coeffiecnt of the rotor is low. But It can be increased by increasing more no of
vanes.

Characteristics of Savonius rotor:

i) Self starting torque
ii) Low speeds
iii) Low efficiency.
Advantages:
i) Eliminates the extensive slower transmission equipment from rotor to the ground.
ii) Has low cut in speed. Can run even under 8km/h wind speeds

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

13
Renewable Energy Sources 2BETCK205E

iii) Weight of the electric generator may be carried on the ground, without use of level gears.
iv) Cost is low as compared to other wind systems.
v) Requires small structure and reduced tower costs.
vi) No yaw and pitch controls
vii) Ground level monitoring is easy, as generator and gear can be monitored and maintained easily
on ground level.
Disadvantages:
i) This type of rotor is too solid and may be impossible to control during cyclones times as there is no
pitch control.
ii) May be difficult in tall installation as the shaft required to drive the generator will be lengthier.
Where as in horizontal axis machines, the generator lies beside the rotor requiring small shat lengths.
Applications od Savonius rotor:
1) Used for pumping, wind blowers, grinding, and bird scrarers.
2) Can be used with Darrieus rotors for starting purpose.
Darrieus rotor:

 This type of rotors comes under air lift principle.

 This consists of a rapid rotating propeller having thin air foils which can effectively intercept
large area of wind with thin blades.
 It consists of two or three thin curved shaped with air foil cross section and constant Chord
 Both the ends of the blades are attached to the central vertical shaft.
 Force in the blades due to rotation is pure tension. This provides stiffness to winds it
encounters.
 At the base of the central shaft, we have a generator for power generation.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

14
Renewable Energy Sources 2BETCK205E

 This type of rotors is less solidity, and low starting torque and high tip to wind speeds. Hence
produces large output power for the given rotor weight and cost.
 Various types of Darrieus rotors are
o ᴓ-Darrieus
o Δ-Darrieus
o Y-Darrieus
o -Darrieus.
 This rotor consists of 1,2,3 or more blades.
Advantages of VAWT:
● The generator and gearbox can be placed on the ground.
● The structure is usually simpler.
● You do not need a yaw (pointing) mechanism to turn the rotor against the wind.
● VAWTs typically generate less noise than horizontal axis wind turbines (HAWT).
Disadvantages of VAWT:
● Some VAWT designs can be more complex than HAWTs, making them more difficult to
manufacture and maintain.
● These structures are low to the ground, where wind speeds are lowest.
● The overall efficiency is much lower than horizontal axis machines.
● Maintenance is usually more difficult. For example, replacement of the generator typically
requires disassembly of the entire machine.
● Some VAWT designs have a higher start-up wind speed, meaning they may not generate
electricity in light wind conditions.

Department of Electrical and Electronics Engineering ,SGBIT,Belagavi

15