Wind Power Fundamentals

With all the talk about oil dependence, global warming and go green campaigns, most of us have an idea of wind power, wind turbines, what they represent and what they do. The curious fact about this is that public perception varies so much around this subject. Some people think about wind energy as being efficient and clean, and even see wind turbines as elegant and beautiful structures, while other people see them as clumsy expensive and landscape destroying devices.

So let's now discuss how wind turbines actually work. Depending on the design of the wind turbine they transfer the kinetic energy in the wind by either lift or drag to a rotation mechanism that drives something. In the early days this force was used to grind grains and pump water, and some windmills are still used for these purposes as well by the way, but the main use they have now is to create electricity.

To create electricity the rotor drives a shaft that passes through a gearing mechanism to increase the rotational speed. Once the rotational speed is increased in a second shaft, it rotates a generator which is basically an electric motor run backwards; instead of spending electricity to drive the motor, you drive the motor and produce electricity.

Several factors determine the performance of the wind turbines. The faster the generator turns, the more energy is produced, so the goal is to build wind turbine that are able to create this with few losses. One thing to note is that the kinetic energy in the wind is proportional to the speed of the wind cubed. This means that small increases in wind speed give in turn greater increases in power.

This is the main reason why wind turbines are usually placed in high towers. The speed of the wind at ground level is always zero, and it increases with height, so the taller the wind turbine the faster the wind and the more energy it produces. This is also the main reason why some wind turbines are being built offshore.

Building wind turbines offshore is more challenging and expensive but there are reasons why it is done. The main reason is that wind blows more freely over the sea since there are no buildings, or hills to get in its way. This produces a higher power output that overtime offsets the costs faster. Building offshore also saves space that can be used for other applications in the land such as farming or housing.