# Wind Power

## Wind Power

Wind is caused by the uneven heating of the atmosphere by the sun, variations in the earth's surface, and rotation of the earth. Mountains, bodies of water, and vegetation all influence wind flow patterns[1]. Wind energy (or wind power) describes the process by which wind is used to generate electricity. Wind turbines convert the energy in wind to electricity by rotating propeller-like blades around a rotor. The rotor turns the drive shaft, which turns an electric generator.[1] Three key factors affect the amount of energy a turbine can harness from the wind: wind speed, air density, and swept area.[2] Mechanical power can also be utilized directly for specific tasks such as pumping water.

## Wind Energy Stakeholder Engagement & Outreach Portal

The U.S. Department of Energy hosts the following resources on OpenEI:

## Wind Energy Technologies

The U.S. Department of Energy defines the scale of wind turbine technologies as follows: utility-scale is greater than 1 megawatt (MW) in size, mid-size turbines are 101 kilowatts (kW) to 1 MW in size, and small turbines are up to 100 kW in size.[3] Distributed wind systems are defined as systems connected on the customer side of the meter (to meet the onsite load) or directly to the local grid (to support grid operations or offset large loads nearby). Community wind is characterized by local ownership and control and includes many distributed wind projects.[4] Offshore wind projects, of course, capture the winds off the coasts and convert them to electricity.[5] Learn more about the technology classes at the links below.

The Energy Department provides publications, data, analysis, and more regarding wind energy research at R&D labs and facilities. Learn more at the Wind Technology Resource Center.

CSV

## Equation for Wind Power

$P = {1\over2} \rho A V^3$
• Wind speed
The amount of energy in the wind varies with the cube of the wind speed; in other words, if the wind speed doubles, there is eight times more energy in the wind ($2^3 = 2 x 2 x 2 = 8$). Small changes in wind speed have a large impact on the amount of power available in the wind.[6]
• Air density
The more dense the air, the more energy received by the turbine. Air density varies with elevation and temperature. Air is less dense at higher elevations than at sea level, and warm air is less dense than cold air. All else being equal, turbines will produce more power at lower elevations and in locations with cooler average temperatures.[6]
• Swept area of the turbine
The larger the swept area (the size of the area through which the rotor spins), the more power the turbine can capture from the wind. Since swept area is $A = pi r^2$, where r = radius of the rotor, a small increase in blade length results in a larger increase in the power available to the turbine.[7]

## Map of Wind Farms

OpenEI has a Map of Wind Farms, which displays a comprehensive list of wind farms, seeded with United States data with plans to expand internationally.

## Wind & Water Materials and Structures Database

The U.S. Department of Energy Wind and Water Power Technology Office has funded Sandia National Laboratories and its partner, Montana State University, to conduct extensive testing and analysis on wind turbine blades and materials in support of the industry and research communities. The Structures & Materials Database can be accessed here