Wind power is the use of wind energy to generate useful work, transforming the invisible movement of air into electricity that powers modern civilization. This process relies on the fundamental physics of kinetic energy, where the power available from the wind is proportional to the third power of the wind speed. If the wind speed doubles, the available power increases eightfold, and a change in speed by a factor of 2.1544 increases the power by one order of magnitude. The atmosphere acts as a massive thermal engine, absorbing heat at higher temperatures and releasing it at lower temperatures, sustaining the circulation of air against friction at a rate of 2.46 W/m2. Global wind kinetic energy averaged approximately 1.50 MJ/m2 between 1979 and 2010, with the Southern Hemisphere holding 1.70 MJ/m2 compared to 1.31 MJ/m2 in the Northern Hemisphere. This vast resource is far more than present human power use from all sources combined, yet harnessing it requires sophisticated engineering to capture the variable nature of the air currents.
From Sails To Giants
The history of wind power stretches back over a millennium, with wind-powered machines used to grind grain and pump water developing in what is now Iran, Afghanistan, and Pakistan by the 9th century. The first wind turbine used for the production of electric power was built in Scotland in July 1887 by Professor James Blyth of Anderson's College, Glasgow. Blyth's 10-foot cloth-sailed wind turbine was installed in the garden of his holiday cottage at Marykirk in Kincardineshire and was used to charge accumulators developed by the Frenchman Camille Alphonse Faure to power the lighting in the cottage, making it the first house in the world to have its electric power supplied by wind power. Blyth offered the surplus electric power to the people of Marykirk for lighting the main street, however, they turned down the offer as they thought electric power was the work of the devil. Across the Atlantic, in Cleveland, Ohio, a larger and heavily engineered machine was designed and constructed in the winter of 1887 to 1888 by Charles F. Brush. The Brush wind turbine had a rotor 5 feet in diameter and was mounted on an 18-metre tall tower. Although large by today's standards, the machine was only rated at 12 kW, yet it operated from 1886 until 1900, charging a bank of batteries to operate up to 100 incandescent light bulbs and various motors in Brush's laboratory.The Physics Of Power
Wind turbines are devices that convert the wind's kinetic energy into electrical power, a process governed by the laws of conservation of mass and energy. In 1919, the German physicist Albert Betz showed that for a hypothetical ideal wind-energy extraction machine, no more than 16/27, or 59%, of the kinetic energy of the wind can be captured. This Betz limit can be approached in modern turbine designs, which may reach 70 to 80% of the theoretical Betz limit. The aerodynamics of a wind turbine are not straightforward, as the airflow at the blades is not the same as the airflow far away from the turbine. The very nature of how energy is extracted from the air causes air to be deflected by the turbine, affecting objects or other turbines downstream in a phenomenon known as the wake effect. Modern turbines generally use variable speed generators combined with either a partial or full-scale power converter, which have more desirable properties for grid interconnection and low-voltage ride-through capabilities. Most modern turbines use either doubly fed electric machines with partial-scale converters or squirrel-cage induction generators or synchronous generators with full-scale converters.