Wind Energy conversion systems for India are discussed here.

1. WIND ENERGY ENGINEERING
Wind Electric Conversion Systems
* Wind Energy Availability
• Energy in wind, speed
• Wind Turbine, Design
• Variables – wind power density
• Generator and power output
• PV-Wind, Diesel-set-Wind Hybrid System
• Tower design
• Wind Electric Conversion System
economics

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Wind Energy Engineering Syllabus-1
 Wind energy Assessment by
Measurement and instrumentation –
Beaufort 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 – Tower design.

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Wind Energy Engineering Syllabus-2
 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-
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.

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CL 716 WIND ENERGY
ENGINEERING: Text & Reference Books
 1. S. Rao & B. B. Parulekar, “Energy Technology”,
3rd Edition, Khanna publishers, 1995.
 2. Wind and Solar Power Systems, Mukund. R.
Patel, 2nd Edition, Taylor & Francis, 2001
 3. Wind Energy Handbook, Edited by T. Burton, D.
Sharpe N. Jenkins and E . Bossanyi, John Wiley
& Sons, N.Y. 2001
 4. . L .L. Freris, Wind Energy Conversion Systems,
Prentice Hall, 1990.
 5. D. A. Spera, Wind Turbine Technology:
Fundamental concepts of Wind Turbine
Engineering, ASME Press

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From wind to electricity.
The first wind powered electricity was produced in
1888. It had a rated power of 12 kW (direct current - dc).
In the 1930's the first large scale AC turbine was constructed
in the USA.
In the 1970's the fuel crises sparked a revival in R & D
work in America (USA and Canada) and Europe (Denmark,
Germany, the Netherlands,Sweden and the UK) and
modern wind turbine-generators were developed. This was
achieved due to improvements in aerodynamic and
structural design, materials technology and mechanical,
electrical and control engineering and led to capablilty to
produce several megawatts of electricity.

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Wind power is
economically viable.
 Over the last two decades, there has been a
tremendous amount of technical
improvement in wind turbines. Their costs
have increased by about a factor of 9, due to
more advanced controls, materials, and
engineering, but at the same time their
energy production has increased by a factor
of 56, leading to a net decline in the cost per
watt of a factor of more than six. Wind power
is thus rapidly becoming economically viable.

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Kinetic energy >
Mechanical
[Rotational] >
Electrical energy
Wind turbines convert the
kinetic energy in wind into
mechanical power that runs a
generator to produce
electricity.

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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)
machines.
 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.

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Wind power for developing countries
 Large-scale grid connected wind turbines
are common with wind farm; This can be
the main national network, in which case
electricity can be sold to the electricity
utility.
 Micro-grids distribute electricity to smaller
areas, typically a village or town. When
wind is used for supplying electricity to
such a grid, a diesel generator set is often
used as a backup for the periods when
windspeeds are low.

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Figure: The Practical Action small
wind turbine ©Practical Action

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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)

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Wind Electric 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.

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

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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.

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Wind Resource Monitoring
 Site selection
 Wind Monitoring
 Wind Resource Mapping

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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.

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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.

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 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.

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WIND
Wind Speed at 10 m height
SPEED
Beaufort scale
SCALE
Wind
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

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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.

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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.

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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.

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Cost – economics-1
 The cost of producing electricity form the wind is
heavily dependent on the local wind regime.
 The power output from the wind machine is
proportional to cube of the windspeed and so a
slight increase in windspeed will mean a
significant increase in power and a subsequent
reduction in unit costs.
 Capital costs for windpower are high, but running
costs are low and so access to initial funds,
subsidies or low interest loans are an obvious
advantage when considering a wind-electric
system.

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Cost – economics-2
 If a hybrid system is used a careful cost-
benefit analysis needs to be carried out.
 A careful matching of the load and
energy supply options should be made to
maximise the use of the power from the
wind - a load which accepts a variable
input is ideally matched to the intermittent
nature of windpower.

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WIND RESOURCE ASSESSMENT-
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.

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

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Resource Survey in India
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.

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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.

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Wind Turbine, tail, support tower
 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.

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Wind Turbine, tail, support tower

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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.

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Some definitions:
 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
wind speed.
 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.

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46. CEESAT NITT NOTES 46
The formula for calculating the
power from a wind turbine is:

47. CEESAT NITT NOTES 47

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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.

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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. Generation requires
high rotational speeds. Lift-type wind turbines
have maximum tip-speed ratios of around 10.The
tip speed ratio (λ = ΩR/v), R Wind turbine blade
radius (m), Ω Wind turbine rotor angular speed
(rpm), v Wind speed [m/s].

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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.

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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.

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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.

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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.

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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

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Transmission- Gear box
 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.

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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),

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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.

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Squirrel cage induction generator

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Doubly Fed Wounded Rotor
Asynchronous Generator.

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Grid Connected Permanent Magnets
Synchronous Generator in full converter
topology

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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.

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Induction generator
 Induction generator offers many advantages over a
conventional synchronous generator as a source of
isolated 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

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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.

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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.

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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.

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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.

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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

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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.

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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.

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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

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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. .

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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.

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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.

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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.

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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.

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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 environment
benefits.
Efforts are being made to reduce the cost of wind
power by: design improvement, 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

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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‟,


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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 breaks, no
mechanical breaks
 Lightning protection

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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.

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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
technologies.
The average availability of commercial wind
power plants is now around 98%.
Thank You