Wind Energy   Winds kinetic energy can be converted to useful mechanical or electrical energy. The lifted sail on a boat drives it through the waters. Windmills turn grinding stones, or pump water from the wells. Nowadays, wind is also used to generate electricity. Just like a toy pinwheel, the blades of a wind mill can turn by blows of wind. Using the wind energy for electricity, speed of turning must be increased, which is done through gear transmission box. Using a brake mechanism will keep the blades from too fast turning during too high winds. A small wind turbine has enough power to provide electricity for a house or school. Wherever in the world with windy climate can use of this energy. The problem on wind energy is its availability all the times. To have an efficient turbine, wind speed must exceed 14 miles per hour. An average turbine produce about 50 to 300 kilowatt of electricity. Have a good sense of such a power, you can image of lighting up 3000 100 Walt lamps. By grouping wind turbines in an area known as wind farms, more power can be produced. This way enough power for an entire city is feasible.   To transfer the mind farms electricity to long distances, voltage must be increased through a transformer.