2. Wind Power
The first use of a large windmill
to generate electricity was a
system built in Cleveland,
Ohio, in 1888 by Charles F.
Brush. The Brush machine
was a postmill with a
multiple-bladed "picket-
fence" rotor 17 meters in
diameter, featuring a large
tail hinged to turn the rotor
out of the wind. It was the
first windmill to incorporate a
step-up gearbox (with a ratio
of 50:1) in order to turn a
direct current generator at its
required operational speed
(in this case, 500 RPM.)
3. Modern Wind Turbine
Commercial wind energy is one of the
most economical sources of new
electricity available today. Wind
turbines can be set up quickly and
cheaply compared with building new
coal-fired generating stations or
hydroelectric facilities. Modern wind
generating equipment is efficient,
highly reliable, and becoming cheaper
to purchase. The environmental impact
of large wind turbines is negligible
compared with an open pit coal mine
or a reservoir, and during their
operation produce no air pollution.
Because of these factors, wind energy
is recognized as the world's fastest-
growing new energy source.
4. How does a Wind Turbine Work?
• Wind turbines operate on a simple
principle. The energy in the wind turns
two or three propeller-like blades
around a rotor. The rotor is connected
to the main shaft, which spins a
generator to create electricity.
• Wind turbines are mounted on a tower
to capture the most energy. At 100 feet
(30 meters) or more above ground,
they can take advantage of faster and
less turbulent wind.
• Wind turbines can be used to produce
electricity for a single home or building,
or they can be connected to an
electricity grid (shown here) for more
widespread electricity distribution.
Office of Energy Efficiency and Renewable Energy.
5. How does a Wind Turbine Work?
Inside view of Wind Turbine
Office of Energy Efficiency and Renewable Energy.
6. How does a Wind Turbine Work?
•Anemometer: Measures the wind speed and transmits wind speed data to the controller.
•Blades: Most turbines have either two or three blades. Wind blowing over the blades causes the blades to
"lift" and rotate.
•Brake: A disc brake, which can be applied mechanically, electrically, or hydraulically to stop the rotor in
emergencies.
•Controller: The controller starts up the machine at wind speeds of about 8 to 16 miles per hour (mph) and
shuts off the machine at about 55 mph. Turbines do not operate at wind speeds above about 55 mph
because they might be damaged by the high winds.
•Gear box: Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds
from about 30 to 60 rotations per minute (rpm) to about 1000 to 1800 rpm, the rotational speed required by
most generators to produce electricity. The gear box is a costly (and heavy) part of the wind turbine and
engineers are exploring "direct-drive" generators that operate at lower rotational speeds and don't need gear
boxes.
•Generator: Usually an off-the-shelf induction generator that produces 60-cycle AC electricity. High-speed
shaft: Drives the generator. Low-speed shaft: The rotor turns the low-speed shaft at about 30 to 60 rotations
per minute.
•Nacelle: The nacelle sits atop the tower and contains the gear box, low- and high-speed shafts, generator,
controller, and brake. Some nacelles are large enough for a helicopter to land on.
•Pitch: Blades are turned, or pitched, out of the wind to control the rotor speed and keep the rotor from
turning in winds that are too high or too low to produce electricity.
•Rotor: The blades and the hub together are called the rotor.
•Tower: Towers are made from tubular steel (shown here), concrete, or steel lattice. Because wind speed
increases with height, taller towers enable turbines to capture more energy and generate more electricity.
•Wind direction: This is an "upwind" turbine, so-called because it operates facing into the wind. Other
turbines are designed to run "downwind," facing away from the wind.
•Wind vane: Measures wind direction and communicates with the yaw drive to orient the turbine properly with
respect to the wind.
•Yaw drive: Upwind turbines face into the wind; the yaw drive is used to keep the rotor facing into the wind as
the wind direction changes. Downwind turbines don't require a yaw drive, the wind blows the rotor downwind.
•Yaw motor: Powers the yaw drive.
8. How much Power does a Wind
Turbine Generate?
Kinetic Energy = Work = ½mV2
Where:
M= mass of moving object
V = velocity of moving object
What is the mass of moving air?
= density (ρ) x volume (Area x distance)
= ρ x A x d
= (kg/m3) (m2) (m)
= kg V
A
d
9. How much Power does a Wind
Turbine Generate?
Power = Work / t
=
Kinetic Energy / t
= ½mV2 / t
= ½(ρAd)V2/t
= ½ρAV2(d/t)
= ½ρAV3
Power in the Wind =½ρAV3
d/t = V
10. A couple things to remember…
Power in the Wind = ½ρAV3
Swept Area – A = πR2
(m2) Area of the circle
swept by the rotor.
ρ = air density – in
Colorado its about 1-
kg/m3
11. Example – Calculating Power in the Wind
Power in the Wind = ½ρAV3
V = 5 meters (m) per second (s)
m/s
ρ = 1.0 kg/m3
R = .2 m >>>> A = .125 m2
Power in the Wind = ½ρAV3
= (.5)(1.0)(.125)(5)3
= 7.85 Watts
Units = (kg/m3)x (m2)x (m3/s3)
= (kg-m)/s2 x m/s
= N-m/s = Watt
12. Is Wind Power 100% efficient?
Power from a Wind Turbine Rotor = Cp½ρAV3
Cp is called the power coefficient.
Cp is the percentage of power in the wind that is
converted into mechanical energy.
What is the maximum amount of energy that can be
extracted from the wind?
Betz Limit: 5926
.
27
16
max
,
p
C
What’s the most power the .2-m turbine in the
example can produce in a 5 m/s wind?
7.85 Watts x .5926 (Betz Limit) = 4.65 Watts
Or try this
online
Power
calculator
13. Building your own Wind Turbine
Instructions and Lessons:
•Kidwind Project - Wind Turbine Blade Design (pdf),
Building the Basic PVC Wind Turbine (pdf)
•Re-energy.ca - Build your own Wind Turbine
•Renewable energy The infinite power of Texas – Wind
Power Basics
•Danish Wind Industry Association - WIND TURBINES
ENERGY FROM THE WIND
•An Investigation of Wind Power as an Energy Resource
in Pennsylvania - As the Rotor Turns: Wind Power & You
•American Win Energy Association – Wind Energy
Teachers Guide, Student Guide
•Information and Activities To Increase the
Understanding of Wind – Wind as a Resource
14. Building your own Wind Turbine
Just Instructions:
•DanF's Science Fair Wind Turbine Article - Science Fair
Wind Generators
•Wind Power.org - Build a Lattice Tower, More wind Activities
•National Renewable Energy Laboratory - RESEARCH PROJECTS
IN RENEWABLE ENERGY FOR HIGH SCHOOLSTUDENTS page 18-27.
15. Review
Want to know more, Click here! WIND ENERGY SYSTEMS
By Gary L. Johnson
U.S. Dept of Energy
If movie doesn’t play click here for web page.
