Wind energy ultimately comes from the Sun as uneven heating and cooling of the land and water of Earth produces the wind. While it is sunny on one side of the Earth it is dark on the other. Similarly it is hotter on one side and colder on the other. Differences in thermal properties between land and water also create localized wind in addition to this effect from oceans and land. This imbalance of heating causes the winds as the atmosphere attempts to equalize temperatures. Wind energy is also responsible for a form of hydroelectricity, wave power, since it causes the waves.
Uses of Wind Energy
Wind energy has been used for hundreds of years in the form of wind mills and sail boats. It’s only recently that modern use has couple the concept of wind mills with electrical generators to produce wind power farms. Many recreational activities also make use wind energy such as kites, hang gliding, and surfing. Other renewable energy sources also make use of wind energy indirectly to generate electricity such as wave power.
Wind Energy TechnologyThere are two primary types of wind turbine used for generating electricity. HAWT (Horizontal Axis Wind Turbine) and VAWT (Vertical Axis Wind Turbine). Since HAWTs house their generator up the tower the rotor can be much higher than in VAWT systems where the generator remains on the ground. This higher rotor placement ensures more efficient operation as wind speeds get higher with altitude as well. Wind farms try to maximize efficiency and so primarily use HAWT systems.
Both HAWT and VAWT technology have essentially the same components they are just arranged differently. Wind turbines have blades which attach to a hub creating the rotor. This rotor is attached to a low speed shaft which connects to a gearbox that speeds up the rotation outputting it to a high speed shaft. This increase in rotational speed is done due to the demands of the electrical grid. Slow rotation couldn’t power a generator enough to add electricity to the grid. High speed shaft enters the generator which is connected to the electricity grid, battery bank, etc.
Additionally wind turbines have braking systems to stop the turbine in low wind speeds (otherwise the system would draw power from the grid to turn the blades), control systems to monitor safety and optimise performance, a tower and housing (nacelle) for the components, and wind monitoring equipment like anemometers and wind vanes that connect to the control system.
Environmental Impact of Wind EnergyMost of the environmental impact from wind energy is localized to the community where wind farms are placed. Carbon dioxide and other pollutants are only released as byproducts during manufacturing of wind turbine components. Carbon “payback” period is around 9 months meaning operation for 9 months is needed to offset more carbon than is consumed during production. With an average lifespan of over 20 years this is easily obtainable. Poor siting of wind farms in peat bogs, wet lands, and other ecologically and carbon dense biospheres can cause more damage than a project may offset.
Wind Energy in the News