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. 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. Three key factors affect the amount of energy a turbine can harness from the wind: wind speed, air density, and swept area. Mechanical power can also be utilized directly for specific tasks such as pumping water. The U.S. Department of Energy developed a short wind power animation that provides an overview of how a wind turbine works and describes the wind resources in the United States.

Wind Energy Stakeholder Engagement & Outreach Portal

The U.S. Department of Energy offers the following resources:

• Small Wind Guidebook
• Wind for Schools Portal
• Distributed Wind Installers
• Community Wind Handbook
• Distributed Wind Resource Assessment Workshop materials

Also on OpenEI, you can find more information about the following topics:

• Siting wind projects
• Federal, state, & local policies
• Wind projects on Native American Lands

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. 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. Offshore wind projects, of course, capture the winds off the coasts and convert them to electricity. Learn more about the technology classes at the links below.

• Utility-Scale Wind Turbines
• Small Wind Turbines
• Distributed Wind Energy
• Built-Environment Wind Turbines
• Community Wind Energy
• Offshore Wind Energy

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.

DOE Wind Programs & Information

• DOE's Wind Energy Technologies Office works to improve the performance, lower the costs, and accelerate the deployment of innovative wind and water power technologies. Greater use of the nation's abundant wind and water resources for electric power generation will help stabilize energy costs, enhance energy security, and improve our environment.
• WINDExchange is a nationwide initiative designed to increase the use of wind energy across the United States by working with regional stakeholders. The WINDExchange program illustrates the Department of Energy's commitment to dramatically increase the use of wind energy in the United States. The WINDExchange website provides a wide range of wind-related information, including: State-by-state breakdowns of wind resource potential, success stories, installed wind capacity, news, events, and other resources, which are updated regularly.
• The National Wind Technology Center (NWTC) is the nation's premier wind energy technology research facility. The goal of the research conducted at NWTC is to help industry reduce the cost of energy so that wind can compete with traditional energy sources, providing a clean, renewable alternative for our nation's energy needs.
• The U.S. Wind Turbine Database allows users to discover and learn more about wind turbine sites throughout the United States. This database was jointly funded by the U.S. Department of Energy Wind Energy Technologies Office via the Lawrence Berkeley National Laboratory Electricity Markets and Policy Group, the U.S. Geological Survey Energy Resources Program, and the American Wind Energy Association.

Wind Farm Development

Siting a wind farm varies from one location to another, but there are some important matters for land owners to consider:

1. Understand your wind resource
2. Evaluate distance from existing transmission lines
3. Determine benefits of and barriers to allowing your land to be developed
4. Establish access to capital
5. Identify reliable power purchaser or market
6. Address siting and project feasibility considerations
7. Understand wind energy’s economics
8. Obtain zoning and permitting expertise
9. Establish dialogue with turbine manufacturers and project developers
10. Secure agreement to meet O&M needs

Land Requirements

The amount of land required for a wind farm varies considerably, and is particularly dependent on two key factors: the desired size of the wind farm (which can be defined either by installed capacity or the number of turbines) and the characteristics of the local terrain. Typically, wind turbine spacing is determined by the rotor diameter and local wind conditions. Some estimates suggest spacing turbines between 5 and 10 rotor diameters apart. If prevailing winds are generally from the same direction, turbines may be installed 3 or 4 rotor diameters apart (in the direction perpendicular to the prevailing winds); under multi-directional wind conditions, spacing of between 5 and 7 rotor diameters is recommended.

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.

• 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.

• 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.

Wind Decision Support Tools

• Wind Atlas Analysis and Application Program (WAsP) is a PC program for predicting wind resources and power productions from wind turbines and farms.

Map of Wind Farms

OpenEI has a Map of Wind Farms, which displays a comprehensive list of wind farms for the United States.

Global Renewable Resource Potential

OpenEI uploaded research and data on International Wind Resource Potential

Wind & Water Materials and Structures Database

The U.S. Department of Energy Wind Energy Technologies 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