The sun heats the earth's atmosphere more, closer to the equator than at other latitudes. This creates rising air masses that the rotation of the earth moves wawy from the equator at high altitude. They cool off and drop back to the earth's surface at a higher latitude. By this circulation pressure differences occur near the earth's surface. Wind is the result. The prevailing winds on earth are determined by this circulation.
Wind energy is one of the oldest renewable energy sources to be exploited by mankind. In ancient Egypt, wind was the driving force for freight transport on the Nile, and in Persia, in about 200 BC, the first vertical-axis windmills were used for grinding grain. In Europe, the mills were introduced from the current French Flanders. The first records date from the mid 12th century, they therefore probably already existed in the 11th century.
Modern, bright and clean
The technology of modern wind turbines has become mature and continues to evolve to even better applications. Windturbines provide clean energy in the cheapest way.They are also very honest in their energy production. Windmills hide nothing. Everything that can go wrong, is visible to everyone. In windmills, there are no underground pipes where leaks can occur that can contaminate the underground or the drinking water, or create risk of explosions if not timely noticed.
Wind turbines cause no invisible emissions. They do not emit CO2, which could affect the climate, nor sulfur which causes acid rain.Wind turbines require no fuel supply. Thus they reduce the risk of maritime accidents involving oil or gas tankers - think of the massive bird mortality for the French coast when the Erika sank in the winter of '99-'00, and the sea and beach pollution that accompanied it, or the massive ecological disaster after the explosion of the oil rig Deepwater Horizon in the Gulf of Mexico in the middle of 2010.
Massive security measures such as for gas terminals are unnecessary. There is no need any more for transportation of nuclear fuel by rail or road. Wind turbines cause virtually no waste. No furnace slag after burning, no heavy metals. The material released after demolition can be recycled nearly without any problems. Finally, there is no risk of radiation or toxic nuclear waste, that should be stored and monitored for thousands of years.
Sunlight can be converted directly into electrical energy by photovoltaic cells (PV cells). They can be combined in modules, which in turn provide power to a battery or to the grid via inverters. The set of modules and peripherals is a photovoltaic system or PV system. In a photovoltaic cell, light is directly converted to electricity by absorption in a semiconductor material. This way, electrons are released and collected at the exposed front by a dense metal finger structure. At the rear a full metal backplate ensures that the electrons are led into the postively charged bottom layer of the solar cell. The incidence of light creates an electric tension between the front and back of the solar cell, which can be used to power of a battery charger, a radio, a lamp,...
The basic raw material for solar cells is usually silicon dioxide (available in abundance on Earth in the form of quartz stone and quartz sand - white sand). Pure silicon is extracted and further purified to monocrystalline, polycrystalline and amorphous silicon for the PV industry. Other materials for thin film solar cells are certainly promising, but still in development.