What Is Wind Power?

Have you ever wondered what causes wind? The sun heats the Earth's atmosphere unevenly, because of the changing seasons, the day and night, and because some of the Earth's surface is water and some is land. This uneven heating causes different temperatures in the air in different places, which leads to pressure differences, and this leads to wind. Therefore, the wind we experience actually comes from solar energy.

Wind is an abundant and powerful source of energy that is available consistently. Wind resources vary with location, but in certain areas, wind power can be more economical than solar power – even in Israel.

Wind power is perhaps one of the simplest and most direct forms of energy production. The way we exploit wind power is with turbines. The wind blows a the blades of a turbine, which rotates to generate electricity with a generator. This generator is the same type of generator as found in all mechanical power stations, but unlike regular power stations, there are no intermediary steps. This means that the efficiency of wind turbines can be very high.

Turbines come in many different types and sizes. There are two main types of wind turbine, Horizontal Axis Wind Turbines (HAWT), and Vertical Axis Wind Turbines (VAWT). Horizontal axis turbines rotate around a horizontal axis, and vertical axis turbines rotate around a vertical axis. There are advantages and disadvantages in both types, and the type of system you choose will depend on your specific requirements.

Horizontal Axis Turbine	Vertical Axis Turbine

For most applications, horizontal axis turbines are the most appropriate choice. These work best in free flowing, high wind situations without any obstructions nearby. These turbines can give the highest efficiencies.

Vertical axis wind turbines will be most appropriate for certain situations in urban areas, because they perform better in more turbulent air, and in lower wind speeds.

Another important aspect of wind power is the wind itself. Choosing a site based on the wind resources requires a little more analysis than choosing a site based on its solar resources. In general, the higher you are the more wind there is, so if you can put a wind turbine higher up, it is better. It is also important to ensure that your wind turbine is clear of obstructions, because they can reduce the amount of wind arriving at your turbine, and cause turbulence around the turbine. Turbulence is bad for a turbine’s longevity, and ability to produce power optimally.

You can get a good idea of the amount of wind available around your location by looking at things such as trees and flags. Images like this one indicate that the wind is strong and if this is how the trees look regularly, you have a good candidate site for a wind turbine.

Unlike solar, it is not possible to just look at a site to assess quickly if it is suitable for a wind turbine. It is necessary to test the average wind speed. This test should be done at the exact site of the proposed turbine, because even by moving a few meters away from the proposed site, the wind resources can change considerably. This test is done with an anemometer. This device sits at one location for a few months and records the wind speed regularly, and calculates the average over a long period of time. Once the average speed is known, it is possible to predict the expected power generation of a wind turbine at that location with fairly good accuracy.

The longer the testing period, the more accurate the measure of your average wind speed will be. This will give you a better idea of whether or not to place a wind turbine at your site. The minimum recommended testing time is one month.