EEE 483[Wind Energy ,use of wind energy].pdf

About wind energy

1. EEE 483
RENEWABLE ENERGY




Wind Energy

Avijit Saha
Co-ordinator,
Power & Energy Training Academy
Lecturer, Dept. of EEE, UIU
M Rezwan Khan, PhD
Executive Director,
Institute of Advanced Research
Professor, Dept. of EEE, UIU

3. Introduction
Before industrial revolution, wind was a major
source of power for pumping water, grinding grains
and long distance transportation (sailing ships)

Advantages: Non-depleting, does not require water

Disadvantages: Variable, low density source, high
initial investment, long distance transportation of
power, visual, noise, mortality of birds and bats

4. Introduction
Applications: Electricity generation, water pumping

The overall capacity of all wind turbines installed
worldwide by the end of 2018 reached 597 GW

China – 221 GW
USA – 96.4 GW
Germany – 59.3 GW
India – 35 GW
Spain – 23 GW

5. How Winds are Created
The earth’s winds are caused by pressure differences
across the earth’s surface due to uneven heating

Local Winds: During the day the air over the land is
heated more than the air over the sea. Opposite during
the night
Day pattern: Wind blows from sea to land
Night pattern: Wind blows from land to sea

6. How Winds are Created
Global Winds: Occur due to greater heating of the air
near the equator than the poles. Thus wind blows in the
direction from the poles to the equator

Large ocean and land masses also affect the wind pattern

It is important to understand these wind patterns for the
evaluation of potential wind sites

7. Wind Power Density
Wind Power Density:

??????
??????
=0.5×�×??????
3

Here,
�= Air density
??????= Wind speed

Air density depends on temperature and barometric
pressure
Wind power decreases with elevation, around 10% per
1000 ft

8. Wind Shear
Wind Shear:
Wind shear is the change in wind speed with height

??????
??????
0
=
??????
??????
0
??????

Here,
??????
0 and ??????
0 are known velocity and known speed
respectively
?????? is the shear exponent varies with time and day.
Usual value is 0.4

10. Wind Turbine
Wind Turbines convert the kinetic energy in the wind to
mechanical power

A generator can convert the mechanical power into
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

11. Types of Wind Turbines
There are two basic types of wind turbines:

 Horizontal-axis turbines
 Vertical-axis turbines

The size of wind turbines varies widely. The length of the
blades is the biggest factor in determining the amount of
electricity a wind turbine can generate

12. Horizontal Axis Wind Turbine
Have blades like airplane
propellers, usually three blades

The largest horizontal-axis turbines
are as tall as 20-story buildings and
have blades more than 100 feet
long

Taller turbines with longer blades
generate more electricity. Nearly all
of the wind turbines currently in
use are horizontal-axis turbines

13. Vertical Axis Wind Turbines
Vertical-axis turbines have blades
that are attached to the top and
the bottom of a vertical rotor

Very few vertical-axis wind
turbines are in use today because
they do not perform as well as
horizontal-axis turbines

14. Construction of a Wind Turbine

15. Components of a Wind Turbine
Anemometer: Measures the wind speed and transmits
wind speed data to the controller
Blades: Lifts and rotates when wind is blown over them,
causing the rotor to spin. Most turbines have either two
or three blades
Brake: Stops the rotor mechanically, electrically, or
hydraulically, in emergencies
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 may be
damaged by the high winds

16. Components of a Wind Turbine
Gear box: Connects the low-speed shaft to the high-
speed shaft and increases the rotational speeds from
about 30-60 rotations per minute (rpm), to about 1,000-
1,800 rpm; this is 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: Produces 50or 60 cycle AC electricity; it is
usually an off-the-shelf induction generator
High-speed shaft: Drives the generator
Low-speed shaft: Turns the low-speed shaft at about
30-60 rpm

17. Components of a Wind Turbine
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: Turns (or pitches) blades out of the wind to control
the rotor speed, and to keep the rotor from turning in
winds that are too high or too low to produce electricity
Rotor: Blades and hub together form the rotor
Tower: Made from tubular steel (shown here), concrete,
or steel lattice. Supports the structure of the turbine.
Because wind speed increases with height, taller towers
enable turbines to capture more energy and generate more
electricity

18. Components of a Wind Turbine
Wind direction: Determines the design of the turbine.
Upwind turbines—like the one shown here—face into the
wind while downwind turbines face away
Wind vane: Measures wind direction and
communicates with the yaw drive to orient the turbine
properly with respect to the wind
Yaw drive: Orients upwind turbines to keep them
facing the wind when the direction changes. Downwind
turbines don't require a yaw drive because the wind
manually blows the rotor away from it
Yaw motor: Powers the yaw drive

19. Power Extracted by Wind Turbine
Power extracted by wind turbine:


Here,
Cp = Coefficient of performance (0.59 {Betz limit} is the
maximum theoretically possible, 0.35 for a good design)

??????
??????= 0.5×�×??????
3
×??????×??????
??????

20. Power Curve
Cut in speed : Speed
ay which WT starts to
produce electrical
power
Rated speed: Speed
at which WT produces
rated power
Cut off speed: Speed
at which power
production will be
stopped

21. Annual Energy Production
Annual Energy Production:

??????�??????=??????�×??????
??????×??????
??????×8.76 ????????????ℎ/????????????????????????

Here,
??????�= Capacity Factor, Depends on rated power vs rotor area
??????
??????= Rotor area = �??????
2

??????
??????= Rated power/unit area for that location from wind
map (W/m2)

22. Wildlife & Wind Power
When siting a wind farm, developers must consider any
possible wildlife impacts
Though this was not the case in early wind farm development
(1980’s), today all proposed wind farms must undergo a strict
environmental impact assessment

23. Wildlife and Wind Power
Wind Turbines kill very few birds compared to other human
activities
Estimates are ~1-2 bird deaths per turbine per year
Many bats die not from colliding with the turbines, but from a
sudden drop in air pressure. Their lungs cannot accommodate
for the change in pressure
Bats can detect most human-made structures through
echolocation.
An atmospheric-pressure drop at wind turbine blades is
undetectable through echolocation
Many migratory bats and bats that live in forest trees have
been affected: the bats come in at night to eat insects, and the
effects of the bat deaths can be far-reaching

24. Thank you