Renewable Energy

(EE7601)
Unit-3: Wind Energy

By Dr. Trilochan Penthia

EE Dept., NIT Patna
 Contents of Unit-3

• Introduction of Wind energy

• Wind energy conversion
• Classification of wind turbines/WECS
• Basic components of WECS
• Electric generation schemes using synchronous
generator and induction generator
• Wind energy storage
• Application of Wind energy (onshore/offshore)
 Wind Power Generation

• Wind power generation means getting the electrical energy by

converting wind energy into rotating energy of the blades and
converting that rotating energy into electrical energy by the
generator.
• The terms "wind energy" and "wind power" both describe the
process by which the wind is used to generate mechanical power
or electricity. This mechanical power can be used for specific
tasks (such as grinding grain or pumping water) or a generator
can convert this mechanical power into electricity.
• Wind turns the propeller-like blades of a turbine around a rotor,
which spins a generator, which creates electricity.
Wind Power Generation

• Wind energy increases with

the cube of the wind speed,
therefore WTGs should be
installed in the higher wind
speed area.
• Grain grinding and water
pumping
• The first use of a large windmill
to generate electricity was a
system built in Cleveland, Ohio,
in 1888 by Charles F. Brush.
Modern Wind Turbine

• Commercial wind energy is

one of the most economical
sources of new electricity
available today.
• Wind turbines can be set up
quickly and cheaply
compared with building new
coal-fired generating stations
or hydroelectric facilities.
 Modern Wind Turbine
• Commercial wind energy is one of the most economical sources
of new electricity available today.
• Wind turbines can be set up quickly and cheaply compared with
building new coal-fired generating stations or hydroelectric
facilities.
• Modern wind generating equipment is efficient, highly reliable,
and becoming cheaper to purchase.
• The environmental impact of large wind turbines is negligible
compared with an open pit coal mine or a reservoir, and during
their operation produce no air pollution.
• Because of these factors, wind energy is recognized as the
world's fastest-growing new energy source.
 How does a Wind Turbine Work?

• Wind turbines operate on a simple principle. The energy in

the wind turns two or three propeller-like blades around a
rotor. The rotor is connected to the main shaft, which spins
a generator to create electricity.
• Wind turbines are mounted on a tower to capture the most
energy. At 100 feet (30 meters) or more above ground, they
can take advantage of faster and less turbulent wind.
• Wind turbines can be used to produce electricity for a
single home or building, or they can be connected to an
electricity grid (shown here) for more widespread
electricity distribution.
How does a Wind Turbine Work?
Block diagram of a wind-electric
conversion system (WECS)
 Components of a Wind Turbine
• Anemometer: Measures the wind speed and transmits wind speed data to the
controller.
• Blades: Most turbines have either two or three blades. Wind blowing over the
blades causes the blades to "lift" and rotate.
• Brake: A disc brake, which can be applied mechanically, electrically, or
hydraulically to stop the rotor in emergencies.
• Controller: The controller starts up the machine at wind speeds of about 8 to 16
miles per hour (mph) and shuts off the machine at about 55 mph. Turbines do
not operate at wind speeds above about 55 mph because they might be
damaged by the high winds.
• Gear box: 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 1000 to 1800 rpm, the rotational speed required by most generators to
produce electricity. The gear box is a costly (and heavy) part of the wind turbine
and engineers are exploring "direct-drive" generators that operate at lower
rotational speeds and don't need gear boxes.
• Generator: Usually an off-the-shelf induction generator that produces 60-cycle
AC electricity. High-speed shaft: Drives the generator. Low-speed shaft: The rotor
turns the low-speed shaft at about 30 to 60 rotations per minute.
Components of a Wind Turbine
• Nacelle: The nacelle sits atop the tower and contains the gear box, low- and
high-speed shafts, generator, controller, and brake. Some nacelles are large
enough for a helicopter to land on.
• Pitch: Blades are turned, or pitched, out of the wind to control the rotor speed
and keep the rotor from turning in winds that are too high or too low to
produce electricity.
• Rotor: The blades and the hub together are called the rotor.
• Tower: Towers are made from tubular steel (shown here), concrete, or steel
lattice. Because wind speed increases with height, taller towers enable
turbines to capture more energy and generate more electricity.
• Wind direction: This is an "upwind" turbine, so-called because it operates
facing into the wind. Other turbines are designed to run "downwind," facing
away from the wind.
• Wind vane: Measures wind direction and communicates with the yaw drive to
orient the turbine properly with respect to the wind.
• 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.
• Yaw motor: Powers the yaw drive.
 Orientation of wind turbines
• Turbines can be categorized into two overarching classes based
on the orientation of the rotor:
 Types of Wind Turbine Generators (WTG)
1. Horizontal Axis wind turbines (HA-WTs)
 Types of Wind Turbine Generators (WTG)
2. Vertical Axis wind turbines (VA-WTs)
Comparison of Wind Turbines
Items HA-WTs VA-WTs
Output power Wide range Narrow range
Starting Self starting Need starting means
Efficiency Higher Lower
Cost Lower Higher
Rotor shaft Runs horizontally Runs vertically
Wind direction Need redirected when Does not needs
the Wind change its redirected into the wind
direction direction
Wind speed Operate fine in moderate Can operate even in low
to high wind speed wind speed
Generator and gear At the top of the tower At the ground level
box
Maintenance Difficult Easy
 Synchronous and Induction
Generators in WECS
• The AC generators used in WECS are categorized into two:
a) Synchronous generators (commonly referred as
alternators) and
b) Induction generators (or asynchronous generators)
 Synchronous and Induction
Generators in WECS

• The AC generators used in WECS are categorized into two:

a) Synchronous generators (commonly referred as
alternators) and
b) Induction generators (or asynchronous generators)
• Generally, there are two types of induction generators
widely used in wind power systems – Squirrel-Cage
Induction Generator (SCIG) and Doubly-Fed Induction
Generator (DFIG).
• SCIG is widely accepted in fixed-speed applications
whereas, DFIG preferred in variable-speed applications.
Synchronous vs. Induction generators
Synchronous generators Induction generators
1. The AC generator which runs at 1. It runs at speed higher than
synchronous speed is known as the synchronous speed is
synchronous generator. known as Induction generator.
2. It is one type of machine whose 2. It is an electrical machine
rotor speed and stator whose rotor spins higher than
magnetic field speed are the the synchronous speed.
same.
3. There is a slip in an induction
3. In case of synchronous motor, generator whose value ranges
there is no slip. from 0 to 1.
4. DC supply is given to the rotor 4. AC supply (in wound type
of the synchronous generator. rotor) is fed to the rotor circuit.
5. Synchronous generators are 5. It has comparably less
more efficient efficiency.
Site selection criteria for wind turbines

• When selecting a site for wind turbines, several factors should be

considered to ensure the turbines operate efficiently and reliably. Here
are some common site selection criteria for wind turbines:
• Wind resource: The primary criterion for selecting a site for wind
turbines is the availability of wind. The wind speed and direction
should be measured and analyzed to determine the site's potential
wind energy production.
• Land use: Wind turbines require large areas of open land, typically
farmland or open plains. The site should be free from obstructions
such as trees, buildings, and other structures that could interfere with
wind flow. The land should also be suitable for construction and
provide access to roads for transporting equipment and materials.
• Environmental considerations: Wind turbines can have significant
impacts on the environment, including noise, visual impact, and
potential harm to wildlife. Thus, these studies should be conducted to
ensure compliance with local regulations and minimize potential
impacts on nearby residents.
Site selection criteria for wind turbines
• Grid connection: Wind turbines require a connection to the power
grid to transport electricity to consumers. The site should be located
near existing transmission lines or have the potential for a cost-
effective connection to the grid.
• Social considerations: Wind turbines can have significant impacts on
local communities. The site should be located away from sensitive
areas such as schools and hospitals.
• Economic considerations: The site's economic viability is also an
important consideration. The cost of building, operating, and
maintaining the wind turbines should be evaluated to ensure that the
project is financially feasible.
• Accessibility: The site should be easily accessible to accommodate
construction equipment, personnel, and maintenance vehicles.
Overall, site selection for wind turbines requires a comprehensive
evaluation of multiple criteria.
 Wind energy storage

• Wind energy storage refers to the ability to store excess energy

generated by wind turbines for later use when the wind is not
blowing.
• Energy storage is essential for integrating wind energy into the
electrical grid.
• There are several ways to store wind energy, including:
• Battery storage: This involves storing excess energy in batteries
for later use. Batteries can be charged when wind output is high
and discharged when needed, providing a reliable and flexible
source of electricity.
• Pumped hydro storage: This involves pumping water uphill into
a reservoir when wind output is high and using it to generate
electricity later by releasing the water through turbines.
 Wind energy storage
• Compressed air energy storage: This involves compressing air
and storing it in underground reservoirs or tanks. The
compressed air can then be released to power turbines and
generate electricity when needed.
• Flywheel storage: This involves storing energy by spinning a
large wheel at high speeds. The energy can then be released by
slowing down the wheel and using the kinetic energy to
generate electricity.
• Thermal storage: This involves using excess energy to heat or
cool materials, such as water or rocks, which can then be used
to generate electricity later.
Wind energy storage is still a developing technology, and the most
common methods of storage are currently battery storage and
pumped hydro storage.
 Application of Wind energy
• Wind energy has a wide range of applications and can be used in many
different ways. Some of the most common applications of wind energy
include:
• Electricity generation: Wind turbines can be used to generate
electricity for homes, businesses, and communities. Large-scale wind
farms are often connected to the electrical grid, while smaller turbines
can be used to power individual homes or buildings.
• Water pumping: Wind turbines can be used to pump water from wells
or other sources for irrigation, livestock, and other agricultural
applications.
• Transportation: Wind energy can be used to power vehicles, such as
sailboats, and can also be used to charge electric vehicles.
• Off-grid power: Wind turbines can be used to provide electricity to
remote or off-grid locations, such as islands or rural communities,
where traditional power sources may be unavailable or expensive.
 Application of Wind energy
• Mechanical power: Wind energy can be used to power
mechanical devices, such as water pumps, gristmills, and
sawmills. This application of wind energy was common in the
past, and there are still many historic windmills in operation
around the world.
• Disaster relief: Wind turbines can be used as part of disaster
relief efforts to provide power in areas that have been affected
by natural disasters or other emergencies.
• Industrial applications: Wind energy can be used in industrial
applications, such as powering factories, manufacturing plants,
and other industrial facilities.
As wind energy technology continues to improve, new applications
for wind energy are likely to emerge, making it an even more
important part of our energy mix.
End of Unit-3