Wind energy is a form of solar energy. Wind energy (or wind power) describes the process by which wind is used to generate electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. A generator can convert mechanical power into electricity. Mechanical power can also be utilized directly for specific tasks such as pumping water. The US DOE 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 Basics
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 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.
Equation for Wind Power
- 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 (). Small changes in wind speed have a large impact on the amount of power available in the wind .
- Density of the air
- 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 , where r = radius of the rotor, a small increase in blade length results in a larger increase in the power available to the turbine.
DOE Wind Programs and Information
- DOE's Wind and Water Program 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.
- Wind Powering America is a nationwide initiative designed to increase the use of wind energy across the United States by working with regional stakeholders. The Wind Powering America program illustrates the Department of Energy's commitment to dramatically increase the use of wind energy in the United States. The Wind Powering America 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. Wind Powering America covers many program areas. A select few are included here:
- Wind Energy for Schools shows the location of installed and planned school wind energy projects in the United States.
- Anemometer Loan Program supports state and Native American anemometer loan programs. Anemometer data is available from many locations. The corresponding datasets can be accessed via OpenEI, such as: Anemometer Data (Wind Speed, Direction) for Laurel, Nebraska (2001 - 2002)
- State Wind Working Groups Wind Powering America educates, equips, and supports state wind working groups that form strategic alliances to communicate wind's benefits and challenges to state stakeholders.
- 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.
Worldwide Installed Capacity
|Country||Total Capacity, June 2010 (MW)||Total Capacity, end of 2009 (MW)||Total Capacity, end of 2008 (MW)|
United States Installed Capacity
In the U.S., installed wind energy capacity increased almost 10 times between 2000 and 2008. Between 2004 and 2008, U.S. wind power capacity grew by an average of 32% each year, making wind one of the fastest growing energy sources. Wind experienced record growth in 2009 and nearly 10 GW of new capacity was added. Texas led the United States in wind installations in 2009, installing more than 2,292 MW of wind capacity.
Wind Farm Development
Siting a wind farm varies from one location to another, but there are some important matters for land owners to consider:
- Understand your wind resource
- Evaluate distance from existing transmission lines
- Determine benefits of and barriers to allowing your land to be developed
- Establish access to capital
- Identify reliable power purchaser or market
- Address siting and project feasibility considerations
- Understand wind energy’s economics
- Obtain zoning and permitting expertise
- Establish dialogue with turbine manufacturers and project developers
- Secure agreement to meet O&M needs
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, including NREL's Wind Farm Calculator, 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 multidirectional wind conditions, spacing of between 5 and 7 rotor diameters is recommended.
- "AWEA Website Wind Energy Basics"
- "US DOE EERE: Wind Program: How Wind Turbines Work"
- "Danish Wind Industry Association Where does Wind Energy come From"
- "Danish Wind Industry Association The Energy in the Wind"
- Gipe, Paul. (2009).Wind Energy Basics. Chelsea Green Publishing Company. ISBN 978-1-60358-030-4
- "EERE Wind Program"
- "Wind Powering America"
- "16 Gigawatt of Wind Power added in First Half of 2010"
- (Published: Aug 2010) "2009 Renewable Energy Data Book"
- (Published: July 2009) "US DOE 2008 Renewable Energy Data Book"
- "AWEA 2009: Wind Energy Basics Fact Sheet"
- "AWEA: Ten Steps to Developing a Wind Farm (Updated 3-2010)"
- "Wind Power Project Site Identification and Land Requirements Prepared by: Global Energy Concepts and AWS Truewind, LLC"
- "Wind Farm Calculator"