ABSTRACT
Humanity first learnt to harvest the natural power of the wind in the early civilizations of ancient Iran. Four sails were attached to a vertical shaft inside a chamber, into which the wind could pass and escape, causing the sails to rotate and turn two flat stones that crushed the grain placed between them. Windmills have taken many forms in their evolution from these simple milling devices, through the complex mechanical windmills of industrial-age Europe, to the ultra high-tech wind turbines of today. Wind turbines generate electricity, as distinct from windmills, which were, like their water-powered counterparts, primarily used for milling grain. At their peak, the number of traditional ‘Dutch’ windmills in Europe reached 100,000 and constituted an essential part of industry, employment and rural industrial life. Traditional windmills were eventually superseded by newer technologies, such as coal and gas, but today, it is these polluting ‘conventional technologies’ which are in turn being superseded by wind power – in the form of the efficient, modern wind turbine. In 1939, a 1.25MW wind turbine was installed at Grandpa’s Knob in the US state of Vermont. The installation brought together some of the finest scientists and engineers of the time and constituted a landmark in the development of wind technology. Since then, many different designs have been trialled, using different materials and taking very different forms; turbines have been designed with two or three blades, running at various speeds and using varying control technologies. The most common type of wind turbine today is the three-bladed, vertical axis turbine, ranging in size from a few watts (for charging batteries), up to the largest 5MW turbines, generating electricity for thousands of homes.
