Strange as it may seem, wind energy comes from that ultimate power source, the sun. (In fact, almost all sources of energy originate with the sun!) As the sun shines on the surface of the earth, it heats the land faster than the oceans. The warm air above the land rises, and when it does so cooler air from over the water rushes in to take its place—this is wind! Meanwhile, the rising hot air cools and descends back down over the water. This air circulation is called convection. You may wonder how you have wind in your area if you don't live by the ocean. Convection is happening on a huge scale throughout Earth's atmosphere, so it doesn't just affect the coasts.
Wind is a form of kinetic energy, meaning that it is in motion. For centuries people have used windmills to harness that moving energy into a mechanical form to perform tasks such as grinding grain or pumping water. In our society we mostly use energy in the form of electricity, so modern wind turbines are designed to produce electricity that can be fed into the local power grid.
Wind turbines have three main parts:
While a single wind turbine can produce quite a bit of power, turbines are often built in groups, called wind farms. These are built in windy areas, usually open flat plains or exposed ridges.
Since wind energy is a renewable resource and does not produce any pollution, it is a good alternative to fossil fuels. A wind turbine can produce enough electricity in about 6 months to recover the amount of energy used in building it, although it takes much longer than that to pay for itself. In the US, the production of electricity by wind is increasing by up to 50% per year, as more wind farms are built. Countries like Denmark are producing close to 20% of their electricity needs from wind power. While wind energy is a great supplemental energy, it is unlikely to become a primary energy source due to limitations on where turbines can be built and the unpredictability of wind.