U.S. Department of Energy - Energy Efficiency and Renewable
Wind and Water Power Program
How Wind Turbines Work
Wind is a form of solar energy. Winds are caused by the
uneven heating of the atmosphere by the sun, the irregularities
of the earth's surface, and rotation of the earth. Wind flow
patterns are modified by the earth's terrain, bodies of water,
and vegetation. Humans use this wind flow, or motion energy, for
many purposes: sailing, flying a kite, and even generating
The terms wind energy or wind power describe the process by
which the wind is used to generate mechanical power or
electricity. Wind turbines convert the kinetic energy in the
wind into mechanical power. This mechanical power can be used
for specific tasks (such as grinding grain or pumping water) or
a generator can convert this mechanical power into electricity.
So how do wind turbines make electricity? Simply stated, a
wind turbine works the opposite of a fan. Instead of using
electricity to make wind, like a fan, wind turbines use wind to
make electricity. The wind turns the blades, which spin a shaft,
which connects to a generator and makes electricity. Take a look
inside a wind turbine to see the various
parts. View the wind
turbine animation to see how a wind turbine works.
This aerial view of a wind power plant shows how a group of
wind turbines can make electricity for the utility grid. The
electricity is sent through transmission and distribution lines
to homes, businesses, schools, and so on.
Learn more about wind energy technology:
Many wind farms have sprung up in the
Midwest in recent years, generating power for utilities.
Farmers benefit by receiving land lease payments from wind
energy project developers.
GE Wind Energy's 3.6 megawatt wind turbine
is one of the largest prototypes ever erected. Larger wind
turbines are more efficient and cost effective.
Modern wind turbines fall into two basic groups: the
horizontal-axis variety, as shown in the photo, and the
vertical-axis design, like the eggbeater-style Darrieus model,
named after its French inventor.
Horizontal-axis wind turbines typically either have two or
three blades. These three-bladed wind turbines are operated
"upwind," with the blades facing into the wind.
Utility-scale turbines range in size from 100 kilowatts to as
large as several megawatts. Larger turbines are grouped together
into wind farms, which provide bulk power to the electrical
Single small turbines, below 100 kilowatts, are used for
homes, telecommunications dishes, or water pumping. Small
turbines are sometimes used in connection with diesel
generators, batteries, and photovoltaic systems. These systems
are called hybrid wind systems and are typically used in remote,
off-grid locations, where a connection to the utility grid is
Energy 101: Wind Turbines Video
This video explains the basics of how wind turbines operate
to produce clean power from an abundant, renewable
- Measures the wind speed and transmits wind speed data to
Most turbines have either two or three blades. Wind
blowing over the blades causes the blades to
"lift" and rotate.
A disc brake, which can be applied mechanically,
electrically, or hydraulically to stop the rotor in
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
- 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.
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.
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
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.
- The blades and the hub together are called the rotor.
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 vane:
Measures wind direction and communicates with the yaw
drive to orient the turbine properly with respect to the
- 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.