ENERGY KIDS

Wind energy source and energy production


Wind is air in motion. It is produced by the uneven heating of the earth’s surface by the sun. Since the earth’s surface is made of various land and water formations, it absorbs the sun’s radiation unevenly. When the sun is shining during the day, the air over landmasses heats more quickly than the air over water. The warm air over the land expands and rises, and the heavier, cooler air over water moves in to take its place, creating local winds. At night, the winds are reversed because the air cools more rapidly over land than over water. The large atmospheric winds that circle the earth are created because the surface air near the equator is warmed more by the sun than the air over the North and South Poles.

Wind is a renewable energy source because wind will continually be produced as long as the sun shines on the earth. Wind energy is mainly used to generate electricity.

Like the weather is general, the wind can be unpredictable. It varies from place to place, and from moment to moment. The wind is practicaly invisible and bacause of that it's not easy to be measured without special equipment.

Wind speed is the rate at which air flows past a point above the earth surface. Wind spead is measured in meter per second (m/s). Tha standart meteorogical wind speed emasurement is at 10 meters above the ground surface.
 

Wind power is a measure of the energy available in the wind. It is measured as watt per square meter (w/m2). Wind power is a function of the cube of the wind speed. For example if the wind speed is 3 m/s so the wind power will be about 9 w/m2.

Wind and geographycal landscape
Each geographical varieties as hills, valleys, river bluffs, lakes and even trees and buildings created influence on the wind flow regime. For example hills and plateaus provide ground regions with higher wind speeds.

Surface roughness affect to the wind speed as well. For example Surface areas with trees or buildings create more friction and turbolence that affect on the wind speed near to the ground surface.

Indicators of the wind - usually trees growing in areas of high speed winds are often permanently deformed. But the absence of the deformation does not necessary indicate that the wind potential is weak at this area.

The most popular device for wind speed measurement is the anemometer. Most anemometers are designed with cups mounted on short arms connected to a rotating vertical shaft. Sometimes small propellers are used as well.

Wind turbines (windmills)

Main wind turbine concepts


Wind rose
Wind roseA wind rose is a graphic tool used by meteorologists to give a view of how wind speed and direction are typically distributed at a particular location. Presented in a circular format, the wind rose shows the frequency of winds blowing from particular directions. The length of each "spoke" around the circle is related to the frequency that the wind blows from a particular direction per unit time. Each concentric circle represents a different frequency, emanating from zero at the center to increasing frequencies at the outer circles. A wind rose plot may contain additional information, in that each spoke is broken down into color-coded bands that show wind speed ranges. Wind roses typically use 16 cardinal directions, such as north (N), NNE, NE, etc., although they may be subdivided into as many as 32 directions.

Wind electricity production
There are two terms to describe basic electricity production: efficiency and capacity factor.

Wind energy at houseEfficiency refers to how much useful energy (electricity, in this case) we can get from an energy source. There is no such thing as a 100 percent energy efficient machine. Some energy is always lost or wasted when one form of energy is converted to another. The lost energy is usually in the form of heat, which dissipates into the air and cannot be used again economically.

Capacity refers to the capability of a power plant to produce electricity. There is no way to have a power plant with a 100 percent capacity rating - because it means the machines to run all day, every day at full power without down time for repairs or refueling.

Wind turbines and the environment

Wind turbines characteristics