After a windy site is evaluated and availability
of wind is assured, a set of wind turbines are
installed in the wind farm, and the power
extracted over the years will pay back.
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.
Wind Resource Monitoring consists of
Wind Resource Mapping
WIND RESOURCE ASSESSMENT-
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.
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.
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.
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.
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
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.
Wind Speed at 10 m height
0.0-0.4 m/s (0.0-0.9 knots) 0 Calm
0.4-1.8 m/s (0.9-3.5 knots) 1 Light
1.8-3.6 m/s (3.5-7.0 knots) 2 Light
3.6-5.8 m/s (7-11 knots) 3 Light
5.8-8.5 m/s (11-17 knots) 4 Moderate
8.5-11 m/s (17-22 knots) 5 Fresh
11-14 m/s (22-28 knots) 6 Strong
14-17 m/s (28-34 knots) 7 Strong
17-21 m/s (34-41 knots) 8 Gale
21-25 m/s (41-48 knots) 9 Gale
25-29 m/s (48-56 knots) 10 Strong Gale
29-34 m/s (56-65 knots) 11
>34 m/s (>65 knots) 12 Hurricane
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.
Wind energy basics
Kinetic > Mechanical > Electric
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 clean
How Do Wind Turbines Work?
Today’s turbines are versatile
modular sources of electricity.
Their blades are aerodynamically
designed to capture the maximum
energy from the wind. The wind
turns the blades, which spin a shaft
connected to a generator
horizontal-axis vs vertical-axis
There are two basic designs of wind electric
turbines: vertical-axis, or "egg-beater" style,
and horizontal-axis (propeller-style)
Horizontal-axis wind turbines are most
common today, constituting nearly all of the
"utility-scale" (100 kilowatts, kW, capacity and
larger) turbines in the global market.
What are wind turbines made of?
How big is a wind turbine?
The towers are mostly tubular and made
The blades are made of fiberglass-
reinforced polyester or wood-epoxy.
Utility-scale wind turbines for land-based
wind farms come in various sizes, with
rotor diameters ranging from about 50
meters to about 90 meters and with
towers of roughly the same size
A 90-meter machine, definitely at the large
end of the scale at this writing (2005), with
a 90-meter tower would have a total height
from the tower base to the tip of the rotor
of approximately 135 meters (442 feet).
Most turbines today are horizontal
axis upwind machines with two or three
blades, made of a composite material
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
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.
The formula for calculating the
power from a wind turbine is:
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.
Solidity: In reference to a wind energy
conversion device, the ratio of rotor blade
surface area to the frontal, swept area that
the rotor passes through.
wind rose: A diagram that indicates the
average percentage of time that the wind
blows from different directions, on a monthly
or annual basis.
power curve: A plot of a wind energy
conversion device's power output versus
power coefficient: The ratio of power
produced by a wind energy conversion
device to the power in a reference area of
the free wind stream.
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.
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
Cut out speed…
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.
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
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
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.
The generator is what 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), and they 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.
It is important to select the right type of
generator to match your intended use.
• Most home and office appliances operate
on 120 volt (or 240 volt), 60 / 50 cycle AC.
• Some appliances can operate on either
AC or DC, such as light bulbs and
resistance heaters, and
many others can be adapted to run on DC.
• Storage systems using batteries store DC
and usually are configured at voltages of
between 12 volts and 120 volts.
• 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
even when the wind speed is fluctuating.
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.
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
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