2009-11-15

         Wind is a kind of new energy with great potential. You may remember the violent gust swept across Britian and France at the beginning of 18^th century,it damaged four hundred wind mills ,egith hundred houses,one hundred churches,more than four hundred sailings,thousands of people got hurted,two hundred and fifty thousand trees were uprooted. So far as the tree uprooting was concerned,10 million horsepower(that is 7.5 kilowatts,1 horsepower is equal to 0.75 kilowatts) was produced in seconds. It is estimated that there are 10 billion kilowatts of wind resources can be used to generate electricity globally,ten times more than the global hydroelectric capacity. Now the energy we get from coal burning is only one third of that the wind will provide in one year. Thus,people at home and abrod are devoted much attention to use wind to generate electricity and develop new energy resources.

　

            The attempt to use wind energy can be traced to the beginning of this century. Denmark、Sweden、Soviet Union and the United State utilized the aviation rotor technology,sucessfully developed a number of small-scale wind power installation in Thirties. Such small-scale wind turbines are widely used in windy islands and remote villages,its cost is much lower than that of the internal combustion engines. However,the generating capacity is relatively low at that time,almost below 5 kilowatts.

　　

         At present,it is known that 15kw,40kw,45kw,100kw and 225kw wind turbines have been manufactured in abroad. 200kw wind turbine had been installed in Clayton Town,New Mexico,United State in January 1978,its blade diameter is 38 meters and the output power is enough for 60 residents. The early summer of 1978,the wind power installations went into operation in the west coast of Jutland in Denmark,its generating capacity goes up to 2000 kilowatts. The wind turbine is 57 meters high,75% of the electricity goes ino the grid,the rest is supplied to a school nearby.
 

        In the first half of 1979,the world’s biggest wind turbine had been installed in Blue Ridge Mountain in North Carolina,United State. This wind turbine is 10 stories high,and its steel blade diameter is 60 meter; the blade were mounted on a tower-shape building so that the wind turbine can rotate freely and get the power from any direction.
 

      How to make use of wind to generate electricity?

      Wind power generation is a process that kinetic energy of the wind was transformed to mechanical energy,which then was transformed to electricity. The device for wind power generation is called wind turbine generator system,which includes wind rotor(including the tail vane),generator and tower.( There are always no tail vane in large-scale wind power station,only small-scale wind power station (including household type) will have the tail vane).
 

         Wind rotor is an important compent which transfroms the kinetic energy of the wind to mechanical energy. It consists of two (or more) propeller-shaped impellers. When the wind blows to the blade,power was produced by the blade to make the rotor rotate. The material of the blade requires to be high strength,light weight. Now it is mainly used of glass fiber reinforced plastic and other composite material (such as carbon fiber). ( There are many vertical wind turbine,s-type

rotating blade,etc.,which has the same function as the normal propeller-shaped blade).

 

          The rotation speed is relatively low,moreover,the variability of the degree and direction of the wind make it unstable. Thus,before starting the generator,a gear box should be added to  increase the rotation speed to rated speed,coupled with a speed regulator to maintain stable,then they are connected to the generator. In order to gain the maximum power,a tail vane is needed at the back of the rotor.
 

           Tower is a structure for supporting the rotor,tail vane and the generator. It is usually buit high to gain larger and even wind with sufficient strength. The height of the tower depends on theinfluence that ground obstacles on the wind speed and the diameter of the rotor,normally it is between 6 to 20 meters.
 

           The generator plays a role to transfer the constant rotation from the rotor to the power generating sector for evenly operation by L-speed transmission,so the kinetic energy is transformed to electricity.

 

How strong does the wind can generate electricity? 

               Generally speaking,wind at third level can be utilized. But from the aspect of economic rationality,the wind speed greater than 4 m/s would be appropriate in electricity generation. It is tested that the output power will be 55 kilowatts for a 55 kilowatts wind turbine system when the wind speed is 9.5 m/s; the output power is 38 kilowatts when the wind speed is 6m/s; output power falls to 9.5 kilowatts when the wind speed goes to 5m/s.

 

In China,there are numbers of medium and small scale wind turbine devices in operation successfully.

             China’s wind resources are extremely abudant,the average wind speed in most areas is above 3 m/s,especially northeast、northwest、southwest plateu and costal islands,where have greater average wind speed. In some areas,more than one third of a year is windy day. Wind power generation is quite promising in those areas.