CEESAT NOTES 3
From wind to electricity.
10 to 50 m High above GL, Turn
turbine and generator,
Wind resources: assessment, monitoring,
Energy conversion: wind turbine, gear[?],
Tower : support at 50 m height with a
CEESAT NOTES 4
wind energy conversion systems
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:
wind turbine (aerodynamic),
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
CEESAT NOTES 7
India’s Installed Wind Power
Gen Capacity at end of 2001
State Installed capacity, MW
Tamil nadu 828
All Others 111
CEESAT NOTES 9
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 13
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
CEESAT NOTES 14
A counting anemometer has cups or a fan
whose rotation is transmitted to a counter
which integrates directly the air movement
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 16
Hurricane12>34 m/s (>65 knots)
1129-34 m/s (56-65 knots)
Strong Gale1025-29 m/s (48-56 knots)
Gale921-25 m/s (41-48 knots)
Gale817-21 m/s (34-41 knots)
Strong714-17 m/s (28-34 knots)
Strong611-14 m/s (22-28 knots)
Fresh58.5-11 m/s (17-22 knots)
Moderate45.8-8.5 m/s (11-17 knots)
Light33.6-5.8 m/s (7-11 knots)
Light21.8-3.6 m/s (3.5-7.0 knots)
Light10.4-1.8 m/s (0.9-3.5 knots)
Calm00.0-0.4 m/s (0.0-0.9 knots)
Wind Speed at 10 m height
CEESAT NOTES 17
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:
Anemometer height and exposure
Type of observation (instantaneous or
Duration of record.
CEESAT NOTES 19
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)
Proximity to transmission lines.
CEESAT NOTES 20
For verifying site conditions items of
Available land area
Location of obstructions
Trees deformed by persistent strong winds (flagged
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-
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
Centre for Wind Energy Technology (C-WET)
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-
•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 32
Choosing an exact location for the
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 33
Wind energy basics
Kinetic energy >
Mechanical [Rotational] >
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 34
Horizontal Axis upwind
Most turbines today are Horizontal Axis
upwind machines with two or three blades,
made of a composite material like
CEESAT NOTES 36
•The amount of power a
turbine will produce depends
primarily on the diameter of its
•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 39
Small WECS for Pumping Water
One- to 10-kW turbines can be used
in applications such as pumping
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 40
Small wind turbines
Usually machines under about 10 kW in
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 41
The formula for calculating the
power from a wind turbine is:
CEESAT NOTES 42
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 43
All wind machines share certain operating
characteristics, such as cut-in, rated and cut-
out wind speeds.
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.
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 44
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 45
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
CEESAT NOTES 46
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 47
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 48
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
CEESAT NOTES 49
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 50
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
CEESAT NOTES 51
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
CEESAT NOTES 52
generators for SMALL wind
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 53
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
CEESAT NOTES 55
Applications adapted to run on
• 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 56
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
CEESAT NOTES 57
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 58
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
CEESAT NOTES 59
drawback of the induction
Reactive power consumption and poor
voltage regulation under varying speed are
the major drawback of the induction
the development of static power converters
has facilitated the control of induction
generator, regarding output voltage and
CEESAT NOTES 60
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 61
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 62
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
Tower costs will vary widely as a function
of design and height.
CEESAT NOTES 63
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
CEESAT NOTES 64
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 65
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 66
Research and development
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
CEESAT NOTES 67
Research and development
Efforts are being made to reduce the cost of
wind power by:
better manufacturing technology,
finding new sites for wind systems,
development of better control strategies (for
output and power quality control),
development of policy and instruments,
human resource development, etc
CEESAT NOTES 68
About Enercon- E-30-230 kW-
Variable speed drive, Continuous pitch
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 69
About Enercon - E-30-230 kW-
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
CEESAT NOTES 70
Wind Turbine Design
Wind turbine design is dictated by a combination
prevailing wind regime, and
Wind turbine manufacturers optimize machines to deliver
electricity at the lowest possible cost per kilowatthour
(kWh) of energy.
CEESAT NOTES 71
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
Optimizing for the lowest overall cost
considers design factors such as relative
sizes of rotor, generator, and tower height.
CEESAT NOTES 72
Thanks to extensive R&D 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
The average availability of commercial wind
power plants is now around 98%.