Man has been using wind energy for thousands of years. The Egyptians were the first to experiment sailing on the Nile 5,000 years ago, while the first wind mills were made by the Babylonians and date back to the seventeenth century B.C. In the centuries that followed, wind mills spread all over the Middle East. Between 1200 and 1300 they were used in Europe too, especially in the northern countries. Even Leonardo da Vinci worked at perfecting these machines. In 1887, the French Duc de La Peltrie built the first aero generator to produce electrical energy. Today aero generators are utilised to obtain energy from the wind. These modern wind mills exploit the wind to make the blades of a big propeller rotate: the latter is connected to a generator that transforms mechanical energy (deriving from the movement of the blades) into electrical energy.
Aero generators vary in size and shape. In fact, they can have one, two or three blades of varying lengths: those with 50-centimetre-long blades are used as battery chargers; those with 30-metre-long blades are capable of producing energy to satisfy the daily electricity requirements of about 1000 households. When many aero generators are connected they form a wind-farm, which are real power stations. There are both on shore and off-shore wind farms.