Basic Questions for Wind System Design
Monitor speed, direction and temperature
Wind resource Evaluation
Components of WECS, their Functions
Operating characteristic speeds
Gear for turbine to generator speed
Energy Flow and Control in WECS
Basic questions for
Wind System Installation
• Is there enough wind ?
• Are tall wind towers allowed in your area?
• Do you have enough space?
• How much electricity do you need or want
• Do you want to connect to the utility grid
or be grid-independent?
• Can you afford a wind energy system?
Basic questions for
Wind System Installation
• What does it take to
install and maintain a
system? Is there enough
wind where you install it ?
• How much electricity do
you need or want to
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
Wind resources evaluation
• Apart from having a good wind turbine, the most
critical aspects for the success of investment in the
wind energy sector are (i) having a good site and
(ii) an accurate assessment of the wind resource at
the site over the season of active wind.
Wind Resource Monitoring consists of following
activities (i) Siting, (ii) Wind Monitoring
(iii) Wind Resource Mapping
On farm tower for Pumping Water
• 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.
Contains the key components of the wind turbine,
including the gearbox, yaw system, and electrical
Captures the wind and transfers its power to the rotor
Attaches the rotor to the low-speed shaft of the wind
Low speed shaft
Connects the rotor hub to the gearbox.
Connects to the low-speed shaft and turns the highspeed shaft at a ratio several times (approximately 50
for a 600 kW turbine) faster than the low-speed shaft.
Drives the electrical generator by rotating at
approximately 1,500 revolutions per minute (RPM).
The mechanical brake is used as backup to the
aerodynamic brake, or when the turbine is being
Usually an induction generator or asynchronous
generator with a maximum electric power of 500 to
1,500 kilowatts (kW) on a modern wind turbine.
Turns the nacelle with the rotor into the wind using
electrical or other motors.
Continuously monitors the condition of the wind
turbine. Controls pitch and yaw mechanisms. In
case of any malfunction (e.g., overheating of the
gearbox or the generator), it automatically stops
the wind turbine and may also be designed to
signal the turbine operator's computer via a modem
Resets the aerodynamic brakes of the wind turbine.
May also perform other functions.
Cools the electrical generator using an electric fan
or liquid cooling system. In addition, the system
may contain an oil cooling unit used to cool the oil
in the gearbox.
Carries the nacelle and the rotor. Generally, it is
advantageous to have a high tower, as wind
speeds increase farther away from the ground.
Anemometer and wind
Measures the speed and the direction of the wind
while sending signals to the controller to start or
stop the turbine.
• 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
• 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.
Wind Speed at 10 m height
Beaufort scale Wind
0.0-0.4 m/s (0.0-0.9 knots)
0.4-1.8 m/s (0.9-3.5 knots)
1.8-3.6 m/s (3.5-7.0 knots)
3.6-5.8 m/s (7-11 knots)
5.8-8.5 m/s (11-17 knots)
8.5-11 m/s (17-22 knots)
11-14 m/s (22-28 knots)
14-17 m/s (28-34 knots)
17-21 m/s (34-41 knots)
21-25 m/s (41-48 knots)
25-29 m/s (48-56 knots)
29-34 m/s (56-65 knots)
>34 m/s (>65 knots)
Requirements: wind to electric Conversion
• Force of wind needs turbine area, height
and direction control:
• turn turbine and generator shaft,
• wind resources at 50meter height
• Wind translational > rotational > electric
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
Turbines today are horizontal axis upwind
machines with two or three blades, made of
a composite material like fiberglass.
The amount of power a turbine will produce
depends on the diameter. 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.
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 rotors
All wind machines share certain operating
characteristics, such as cut-in, rated and cut-out
• 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.
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.
The generator is what converts the turning
motion of a wind turbine's blades into
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 electricity,
even when the wind speed is fluctuating.
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.
Towers: Tall structures
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 meters tall.