our new hope------ green energy: Post 3 : Wind power

Wind power

1. Windmill

I guess that we are all familiar with windmills. You might make yourself a toy windmill in your kindergarden art class, or watched it on a very famous cartoon, "Teletubbies(天線寶寶)" . However, windmills are essential tools for whole human race now. They now transfer wind power into electricity we need! In my opinion, windmills are such beautiful tools because of their simple design . What's more, every time I think of windmills rotating elegantly in the winds, I wish that I can be one of them.

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video 1

2. Wind power

According to a data, "in 2011/9 electricity generated by wind power plants aroud the world reached 200 million kW!!!! Besides, wind power are now growing at an incredible pace. If it keeps growing, there will be 12% of electrity provided by wind power in 2020."(#1) Let's take a look at some factors making wind power grow so fast recently.

(1) It's cheap

(2) It can not be used up, or say it's sustainable.

(3) It is accessible in many regions.

We now konw that wind power plants transfer the energy of wind into electricity, but a question may flash into our mind immediately, 'How dose it work?' Let me explain it briefly for you. There are two kinds of forces that make windmills rotate, drag force(阻力) and lift force(升力). In pic.3 the drag force acting on wing A is bigger than that of wing B, so the windmills will rotate clockwise. In pic.4 there are two winds flow through the wing, the speed of A is higher than the speed of B. By Bernoulli's principle(白努力定律) the pressure below the wing is bigger than the pressure beneath the wing. Thus, a lift force is generated by this difference of pressure, and its direction is up. Finally this lift force makes the windmill rotate clockwise.

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