WIND ENERGY ENGINEERING

Wind Energy Engineering
Wind energy Assessment by Measurement and instrumentation –
Beau fort number -Gust parameters – Wind type – power law index
-Betz constant -Terrain value.
Energy in wind– study of wind data and applicable Indian standards
– Steel Tables, Structural Engineering for tower design- Wind
farms–– fatigue stress.
Wind Energy Conversion Systems: Variables – wind power density
– power in a wind stream – Wind turbine efficiency – Forces on the
blades of a propeller –Solidity and selection curves.
Horizontal Axis –WT and Vertical Axis -WT– Tower design -Power
duration curves- wind rose diagrams -study of characteristics -
actuator theory- Controls and instrumentations.
Grid-Connected WECS and Independent WECS- Combination of
WECS and diesel generator, Battery storage – Wind Turbine
Circuits.

CEESAT NOTES 3
From wind to electricity.
At 10 to 50 m High above GL, wind
turns turbine and generator,
produces electricity. For this we need:
Wind resources: assessment, monitoring,
site selection
Energy conversion: wind turbine, gear[?],
generator, control
Tower : support at 50 m height with a
strong structure.

CEESAT NOTES 4
wind energy conversion systems
(WECs)
Design and successful operation of wind
energy conversion systems (WECs) is a very
complex task and requires many
interdisciplinary skills, e.g., civil, mechanical,
electrical and electronics, geography,
aerospace, environmental etc.
Yet success has been achieved...

CEESAT NOTES 5
Performance of WECS
The availability of wind resources are
governed by the climatic conditions of the
region concerned for which wind survey is
extremely important to exploit wind energy.
Performance of W E C S depends upon:
Subsystems like
wind turbine (aerodynamic),
gears (mechanical),
generator (electrical) and Control (electronic)

CEESAT NOTES 6
Potential in India :
Gross Potential :- 45,000 MW
Technical Potential :- 13,000 MW
Sites with Annual Average Wind Power
Density 200 watts/m2 generally viable, 208
such sites in 13 states identified
States with high potential :
Gujarat, Andhra Pradesh, Tamil Nadu,
Karnataka, Kerala, Madhya Pradesh, and
Maharashtra.

CEESAT NOTES 7
India’s Installed Wind Power
Gen Capacity at end of 2001
State Installed capacity, MW
Tamil nadu 828
Maharastra 236
Gujarat 167
Andhra 92
Karnataka 50
M.P. 23
All Others 111

CEESAT NOTES 8
Wind resources
Apart from having a good wind turbine, the
most critical aspects for the success of
investment in the wind energy sector are
having a good site and
an accurate assessment of the wind
resource at the site.

CEESAT NOTES 9
Wind Resource Monitoring
Site selection
Wind Monitoring
Wind Resource Mapping

CEESAT NOTES 12
anemometer
An instrument for measuring the force or
velocity of wind. There are various types:
A cup anemometer, is used to measure
the wind speed from the speed of rotation
of a windmill which consist of 3 or 4
hemispherical or conical cups, each fixed
to the ends of horizontal arms attached to
a vertical axis.
A Byram anemometer is a variety of cup
anemometer.

CEESAT NOTES 13
A counting anemometer has cups or a fan
whose rotation is transmitted to a counter
which integrates directly the air movement
speed.
A hand anemometer is small portable
anemometer held at arm's length by an
observer making a wind speed measurement.
A pressure tube anemometer (Dines
anemometer) is an instrument that derives
wind speed from measurements of the
dynamic wind pressures. Wind blowing into a
tube develops a pressure greater than the
static pressure, while wind blowing across a
tube develops a pressure less than the static.
This pressure difference is proportional to the
square of the wind speed.

CEESAT NOTES 15
Hurricane
12
34 m/s (65 knots)
11
29-34 m/s (56-65 knots)
Strong Gale
10
25-29 m/s (48-56 knots)
Gale
9
21-25 m/s (41-48 knots)
Gale
8
17-21 m/s (34-41 knots)
Strong
7
14-17 m/s (28-34 knots)
Strong
6
11-14 m/s (22-28 knots)
Fresh
5
8.5-11 m/s (17-22 knots)
Moderate
4
5.8-8.5 m/s (11-17 knots)
Light
3
3.6-5.8 m/s (7-11 knots)
Light
2
1.8-3.6 m/s (3.5-7.0 knots)
Light
1
0.4-1.8 m/s (0.9-3.5 knots)
Calm
0
0.0-0.4 m/s (0.0-0.9 knots)
SCALE
Wind
SPEED
Beaufort scale
WIND
Wind Speed at 10 m height

CEESAT NOTES 17
Some definitions….
1 m/s = 3.6 km/h = 2.237 mph = 1.944 knots
1 knot = 1 nautical mile per hour = 0.5144 m/s =
1.852 km/h = 1.125 mph
average wind speed: The mean wind speed over a
specified period of time.
PITCH CONROL: A method of controlling the
speed of a wind turbine by varying the orientation,
or pitch, of the blades, and thereby altering its
aerodynamics and efficiency.

CEESAT NOTES 18
For wind data from selected stations,
essential attributes are:
Station location
Local topography
Anemometer height and exposure
Type of observation (instantaneous or
average)
Duration of record.

CEESAT NOTES 19
Topographic maps
provide the analyst with a preliminary look
at other site attributes, including:
Available land area
Positions of existing roads and dwellings
Land cover (e.g., forests)
Political boundaries
Parks
Proximity to transmission lines.

CEESAT NOTES 20
For verifying site conditions items of
importance include:
Available land area
Land use
Location of obstructions
Trees deformed by persistent strong winds (flagged
trees)
Accessibility into the site
Potential impact on local aesthetics
Cellular phone service reliability for data transfers
Possible wind monitoring locations.

CEESAT NOTES 21
WIND RESOURCE ASSESSMENT-
in India- Implemented through :
(i) State Nodal Agencies
(ii) Centre for Wind Energy Technology (C-
WET)
Financial Assistance :
(i) Full establishment costs of Wind Resource
Assessment Project (WRAP) of C-WET by
the Central Government.

CEESAT NOTES 22
WIND RESOURCE ASSESSMENT
Implemented through…. :
(ii) The cost of setting up the wind monitoring
stations would be shared between MNES and
State Nodal agencies in 80:20 ratio, except
for North-eastern and hilly States, where it
would be in 90:10 ratio.

CEESAT NOTES 23
Resource Survey in India
Published databases
Centre for Wind Energy Technology (C-WET)
Chennai.
6 Volumes of “Wind Energy –Resource Survey in
India” , containing wind data have been published
Master Plans for 87 sites prepared and available
from C-WET at nominal cost.
Wind data available from C-WET on CD ROM.

CEESAT NOTES 24
Government of India
Ministry of New and Renewable Energy
(Wind Power Division)
Block No.14, CGO Complex,
Lodhi Road, New Delhi – 110003
•C-WET would evaluate the eligibility of manufacturer,
who approaches for Type. Certification, as per the
evaluation criteria in vogue, which is being followed by C-
WET.
•Validity of Self-Certification facility for models specified in
the List of Models and Manufacturers thereof issued by C-
WET is extended up to 30th September, 2007.
•Self-Certification facility would be available for a
maximum period of 18 months from the date of signing of
the agreement with C-WET for the models hereinafter
including in the category Model under Testing and
Certification at C-WET in the List to be issued by C-WET.

CEESAT NOTES 31
Choosing an exact location for the
monitoring tower:
Place the tower as far away as possible
from local obstructions to the wind
Select a location that is representative of
the majority of the site.

CEESAT NOTES 32
Wind energy basics
Kinetic energy
Mechanical [Rotational]
Electrical energy
Wind is created by the unequal
heating of the Earth’s surface by
the sun. Wind turbines convert
the kinetic energy in wind into
mechanical power that runs a
generator to produce electricity.

CEESAT NOTES 33
Horizontal Axis upwind
Wind Turbine
Most turbines today are Horizontal Axis
upwind machines with two or three blades,
made of a composite material like
fiberglass.

CEESAT NOTES 35
•The amount of power a
turbine will produce depends
primarily on the diameter of its
rotor.
•The diameter of the rotor
defines its “swept area,” or
the quantity of wind
intercepted by the turbine.
•The turbine’s frame is the
structure onto which the rotor,
generator, and tail are
attached. The tail keeps the
turbine facing into the wind.

CEESAT NOTES 38
Small WECS for Pumping Water
‘off grid’
One- to 10-kW turbines can be used
in applications such as pumping
water.
Wind-electric pumping systems can
be placed where the wind resource is
the best and connected to the pump
motor with an electric cable.

CEESAT NOTES 39
Small wind turbines
Usually machines under about 10 kW in
output.
In developing countries small wind turbines
are used for rural energy applications, and
there are many off-grid applications in the
developed world as well - such as providing
power for navigation beacons.
Since most are not connected to a grid, many
use DC generators and run at variable speed.
A typical 100 W battery-charging machine
has a shipping weight of only 15 kg

CEESAT NOTES 40
The formula for calculating the
power from a wind turbine is:

CEESAT NOTES 41
As the wind turbine extracts energy from
the air flow, the air is slowed down, which
causes it to spread out and diverts it
around the wind turbine to some extent.
Albert Betz, a German physicist,
determined in 1919 (see Betz' law) that a
wind turbine can extract at most 59% of
the energy that would otherwise flow
through the turbine's cross section. The
Betz limit applies regardless of the design
of the turbine.

CEESAT NOTES 42
Operating Characteristics
All wind machines share certain operating
characteristics, such as cut-in, rated and cut-
out wind speeds.
Cut-in Speed
Cut-in speed is the minimum wind speed at which the
wind turbine will generate usable power. This wind speed
is typically between 7 and 10 mph.
Rated Speed
The rated speed is the minimum wind speed at which the
wind turbine will generate its designated rated power. For
example, a 10 kilowatt wind turbine may not generate 10
kilowatts until wind speeds reach 25 mph. Rated speed
for most machines is in the range of 25 to 35 mph.

CEESAT NOTES 43
Rated Speed…
At wind speeds between cut-in and rated, the
power output from a wind turbine increases
as the wind increases. The output of most
machines levels off above the rated speed.
Most manufacturers provide graphs, called
power curves, showing how their wind
turbine output varies with wind speed.

CEESAT NOTES 44
Cut-out Speed
At very high wind speeds, typically between
45 and 80 mph, most wind turbines cease
power generation and shut down. The wind
speed at which shut down occurs is called
the cut-out speed. Having a cut-out speed is
a safety feature which protects the wind
turbine from damage. Shut down may occur
in one of several ways. In some machines an
automatic brake is activated by a wind speed
sensor.

CEESAT NOTES 45
Cut out speed yaw
Some machines twist or pitch the blades to
spill the wind. Still others use spoilers, drag
flaps mounted on the blades or the hub which
are automatically activated by high rotor
rpm's, or mechanically activated by a spring
loaded device which turns the machine
sideways to the wind stream. Normal wind
turbine operation usually resumes when the
wind drops back to a safe level.

CEESAT NOTES 46
Tip Speed Ratio
The tip-speed is the ratio of the rotational
speed of the blade to the wind speed. The
larger this ratio, the faster the rotation of the
wind turbine rotor at a given wind speed.
Electricity generation requires high rotational
speeds. Lift-type wind turbines have
maximum tip-speed ratios of around 10

CEESAT NOTES 47
number of blades
The number of rotor blades and the total area they
cover affect wind turbine performance. For a lift-
type rotor to function effectively, the wind must flow
smoothly over the blades.
To avoid turbulence, spacing between blades
should be great enough so that one blade will not
encounter the disturbed, weaker air flow caused by
the blade which passed before it.
It is because of this requirement that most wind
turbines have only two or three blades on their
rotors

CEESAT NOTES 48
Transmission
The number of revolutions per minute (rpm)
of a wind turbine rotor can range between
40 rpm and 400 rpm, depending on the
model and the wind speed.
Generators typically require rpm's of 1,200
to 1,800. As a result, most wind turbines
require a gear-box transmission to increase
the rotation of the generator to the speeds
necessary for efficient electricity production.

CEESAT NOTES 49
Electrical Generators
It converts the turning motion of a wind
turbine's blades into electricity. Inside
this component, coils of wire are rotated
in a magnetic field to produce electricity.
Different generator designs produce
either alternating current (AC) or direct
current (DC),

CEESAT NOTES 50
generators for wind turbines
At the present time and for the near
future, generators for wind turbines will
be synchronous generators, permanent
magnet synchronous generators, and
induction generators, including the
squirrel-cage type and wound rotor
type.

CEESAT NOTES 51
Squirrel cage induction
generator

CEESAT NOTES 52
Doubly Fed Wounded Rotor
Asynchronous Generator.

CEESAT NOTES 53
Grid Connected Permanent Magnets
Synchronous Generator in full
converter topology

CEESAT NOTES 54
generators for SMALL wind
turbines
For small to medium power wind turbines,
permanent magnet generators and squirrel-
cage induction generators are often used
because of their reliability and cost
advantages. Induction generators, permanent
magnet synchronous generators, and wound
field synchronous generators are currently
used in various high power wind turbines.

CEESAT NOTES 55
range of output power ratings.
Generators are available in a large range of
output power ratings.
The generator's rating, or size, is dependent
on the length of the wind turbine's blades
because more energy is captured by longer
blades.

CEESAT NOTES 56
Range of power
100 kW
101 kW - 250 kW
251 kW - 500 kW
501 kW - 750 kW
750 kW - 1000 kW
1001 kW - 2000 kW
2000 kW

CEESAT NOTES 57
Applications adapted to run on
DC.
• Storage systems using batteries store DC
and usually are configured at voltages of
between 12 volts and 120 volts in USA.
A typical 100 W battery-charging machine
has a shipping weight of only 15 kg.

CEESAT NOTES 58
A .C. Generators…..
• Generators that produce AC are generally
equipped with features to produce the correct
voltage (120 or 240 V) and
• constant frequency (60 / 50 cycles) of
electricity, even when the wind speed is
fluctuating.

CEESAT NOTES 59
Advantages of Induction
generator over synchronous
Induction generator offers many advantages over a
conventional synchronous generator as a source of
isolated [A .C] power supply.
Reduced unit cost, ruggedness, brush less (in
squirrel cage construction), reduced size, absence
of separate DC source and ease of maintenance,
self-protection against severe overloads and short
circuits, are the main advantages

CEESAT NOTES 60
induction generator…
Further induction generators are loosely
coupled devices, i.e. they are heavily damped
and therefore have the ability to absorb slight
change in rotor speed and drive train
transient to some extent can therefore be
absorbed.

CEESAT NOTES 61
drawback of the induction
generator
Reactive power consumption and poor
voltage regulation under varying speed are
the major drawback of the induction
generators, but
the development of static power converters
has facilitated the control of induction
generator, regarding output voltage and
frequency.

CEESAT NOTES 62
Synchronous generator
Synchronous generators are closely coupled
devices and when they are used in wind
turbines which is subjected to turbulence and
requires additional damping devices such as
flexible couplings in the drive train or to mount
gearbox assembly on springs and dampers.

CEESAT NOTES 64
Towers
Tower on which a wind turbine is mounted is
not just a support structure. It also raises the
wind turbine so that its blades safely clear
the ground and so it can reach the stronger
winds at higher elevations.
Maximum tower height is optional in most
cases, except where zoning restrictions
apply. The decision of what height tower to
use will be based on the cost of taller towers
versus the value of the increase in energy
production resulting from their use.

CEESAT NOTES 65
The tower must be strong enough to
support the wind turbine and to sustain
vibration, wind loading and the overall
weather elements for the lifetime of the
wind turbine.
Tower costs will vary widely as a function
of design and height.

CEESAT NOTES 66
Towers….
Studies have shown that the added
cost of increasing tower height is often
justified by the added power generated
from the stronger winds.
Larger wind turbines are usually
mounted on towers ranging from 40 to 70
meters tall.

CEESAT NOTES 67
Environmental Aspects of
Power Generation Using WECs
Wind turbines are most environment friendly method
of producing electricity.
They do not pose any adverse effect on the global
environment, unlike the conventional coal or oil-fired
power plants. The pollution that can be saved per
year from a typical 200 kW wind turbine, involving of
substitution of 120 - 200 tonnes of coal which
contain pollution contents as, Sulphur dioxide
(SO2): 2 –3 tonnes, Nitrogen oxide (NOX): 1.2 to
2.4 tonnes, and other particulates of 150-300 kg. .

CEESAT NOTES 68
Audible noise
The wind turbine is generally quiet. The wind turbine
manufacturers generally supply the noise level data
in dB versus the distance from the tower.
A typical 600 kW wind turbine may produce 55 dB
noise at 50 meter distance from the turbine and 40
dB at a 250 meter distance [4, 22] comparable with
the noise level in motor car which may be
approximately 75 dB.
This noise is, however, is a steady state noise. The
wind turbine makes loud noise while yawing under
the changing wind direction. Local noise ordinance
must be compiled with.

CEESAT NOTES 69
Research and development
is going on to make wind
power competitive with fossil
fuel and nuclear power in
strict sense, without taking
into account of wind power’s
social factors such as
environment benefits.

CEESAT NOTES 70
Efforts are being made to reduce the cost of
wind power by:
design improvement,
better manufacturing technology,
finding new sites for wind systems, including
off shore,
development of better control strategies (for
output and power quality control),
development of policy and instruments,
human resource development, etc

CEESAT NOTES 71
About Enercon - E-30-230 kW-
Gearless type--1
Variable speed drive, Continuous pitch
regulation,
Starts gen. at low speed of 2.5 m/s,
Gearless construction, no transmission loss,
Synchronous gen., draws one % reactive
power from grid,
By using AC_DC_AC conversion, pumps the
power at ‘grid frequency’,

CEESAT NOTES 72
About Enercon - E-30-230 kW-
Gearless type--2
Produces power at all loads at near unity
power factor without using capacitors
Supply reactive power to the grid to improve
grid power factor
Slow speed generator of maximum 50 rpm
Three independent air brakes, no
mechanical brakes
Lightning protection

CEESAT NOTES 73
Wind Turbine Design
Wind turbine design is dictated by a combination
of
technology,
prevailing wind regime, and
economics.
Wind turbine manufacturers optimize machines to deliver
electricity at the lowest possible cost per kilowatt-hour
(kWh) of energy.

CEESAT NOTES 74
Wind Turbine Design
Design efforts benefit from
knowledge of the wind speed distribution and
wind energy content corresponding to the
different speeds and
the comparative costs of different systems to
arrive at the optimal rotor/generator
combination.
Optimizing for the lowest overall cost
considers design factors such as relative
sizes of rotor, generator, and tower height.

CEESAT NOTES 75
Thanks to extensive RD efforts during the
past 30 years, wind energy conversion
has become a reliable and competitive
means for electric power generation.
The life span of modern wind turbines is
now 20-25 years, which is comparable to
many other conventional power generation
technologies.
The average availability of commercial wind
power plants is now around 98%.
Thank You

WIND ENERGY ENGINEERING

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