Wind power
Wind energy - is transformed energy from solar radiation, and while the Sun shines, and the winds will blow. Thus, the wind - it is also a renewable source of energy.
People use wind energy since time immemorial - is enough to recall the sailing fleet, which was already ancient finikyan and living simultaneously with other peoples, and windmills. In principle, to convert wind energy into electric current, it would seem, it is not difficult - it is sufficient to replace the millstone generator. The winds are blowing everywhere, they can blow in summer and winter, day and night - in that they are a significant advantage over by solar radiation. It is therefore understandable numerous attempts to "harness the wind to harness and get him to produce electricity.
In many countries of Western Europe built quite a few plants of 100-200 kW. In France , Denmark and some other countries were put into operation the wind power plant with a nameplate capacity of over 1 MW.
One of the most well-known plants of this class Grovian was established in Germany , its rated capacity - 3 MW. But the most extensive development of wind energy was in the United States . Even in 1941 there was built the first wind power station with 1250 kW, and now the total capacity of wind power in this country reached 1,300 MW, and among them are giants with a capacity of up to 4 MB. The entire world currently has about 3 million wind turbines, of which about 3.5 thousand of us.
Windmills have reached this level of commercial maturity, and in locations with favorable wind speeds can compete with traditional sources of electricity. Of the various devices that convert wind energy into mechanical work, in most cases used rotary machine with a horizontal shaft mounted on the wind direction. Much less frequently used the device with a vertical shaft.
The kinetic energy transferred by the wind flow per unit time through an area of 1 m2 (specific power flow) is proportional to the cube of wind speed. Therefore, installation of wind power is viable only in areas where the average wind speeds are large enough.
The windmill, located in the free flow of air, at best, theoretically converted to power on its shaft 16/27 = 0.59 (Betz criterion), the power flow of air passing through the cross-sectional area, wind wheel. This factor can be called a theoretical efficiency of an ideal wind wheel. In reality, efficiency and lower reaches for the best wind wheel around 0,45. This means, for example, that the wind wheel with a blade length of 10 m at wind speed of 10 m / s may have a shaft horsepower at best, 85 kW.
The most common of plants, connected to a network, now have the wind plants with a unit capacity from 100 to 500 kW. Specific cost of wind power installed capacity of 500 kW is now about 1200 dollars / kW and has a tendency to decrease.
Along with this are windmills and with significantly greater unit capacity. In 1978, the U.S. established the first experimental wind plants megawatt class, with an estimated capacity of 2 MW. This was followed in 1979-1982 years in the United States were built and tested 5 wind plants with a unit capacity of 2.5 MW. The biggest to that time, wind power (Grovian) capacity of 3 MW was built in Germany in 1984, but, unfortunately, she worked only a few hundred hours. Constructed later in Sweden windmills WTS-3 and WTS-4 Power 5 and 4 MW have been installed in Sweden and the United States and worked for the first 20 and the second 10 tys.ch.
In Canada , work is underway on the creation of large wind turbine with vertical shaft. One such plant with capacity of 4 MW is being tested with the 1987 total for 1987-1993 years. The world was built around 25 megawatt wind power class.
Estimated wind speed for large wind plants is usually taken at the level of 11- 15 m / sec. Generally, as a rule, the more power the unit, the greater the wind speed it is calculated. However, the variability of wind speeds most of the time wind power generates less power. It is believed that if the average wind speed at a given location for at least 5- 7 m / s, and an equivalent number of hours per year, which produced a nominal capacity of not less than 2000, such a favorable place to install a large wind turbines and even wind farms.
Standalone installation of kilowatt-class, intended for relatively small energy consumers, can be used in areas with lower average annual wind speeds.
Today, in some industrialized countries, the installed capacity of wind turbines reaches significant values. Thus, in the United States has more than 1.5 million kilowatt wind turbines in Denmark windmills produce about 3 ° / of the country's energy consumption, high installed capacity of wind power in Sweden, the Netherlands, Britain and Germany.
With the improvement of equipment and wind plants and increase their production cost of wind power, and hence the value of their total energy decreases. If in 1981 the cost of electricity produced by wind power accounted for around 30 U.S. cents per kWh. / H, today it is 6.8 cents. Given the fact that only in 1995 in the United States were working on four large wind farms with a total capacity of 200 MW, it is clear that the planned U.S. Department of Energy reduce the cost of wind electricity to 2.5 cents / (kWh) is quite real.
In developing countries, interest in wind power is connected mainly with the autonomous units of small capacity, which can be used in villages remote from the centralized power systems. Such systems already competitive with diesel engines running on imported fuel. However, in some cases, the variability of wind speed causes a set in parallel with wind power from the battery or back up its on fossil fuel. Naturally, this increases the cost of installation and operation, so the spread of such plants were low.