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Wind energy

The History of Windmills and Wind Turbines


Technologically-savvy agrarian societies have been harnessing wind as a source of energy for centuries, with the first windmills originating in China and Persia over a thousand years ago. Long before the discovery of electricity, windmills were used to pump water, grind grain and saw lumber.

The original designs involved a series of sails attached to vertical axes. By the early middle ages, in the British Isles, northern Europe and the eastern Mediterranean, horizontal axis windmills emerged. Others were built in the early fortifications of New France (Quebec). Generally, they consisted of a squat tower supporting a set of windmill blades that could be moved to face the prevailing wind. Many survive to this day in the United Kingdom and the Netherlands.


Holland was best known for innovation in windmill design, which can be traced back to the 14th century. These windmills performed many functions, including timber milling, but the most significant involved pumping water to drain marshy, low-lying areas and reclaim large tracts of the Netherlands for farming.

According to wind historian Darrell Dodge, “The Dutch essentially affixed the standard post mill to the top of a multi-story tower, with separate floors devoted to grinding grain, removing chaff, storing grain, and (on the bottom) living quarters for the windsmith and his family.”

In the American mid-west in the late 19th century, farmers came to rely on a leaner design featuring a trestle tower topped by wooden or steel paddle-type blades. As Dodge notes, “Between 1850 and 1970, over six million mostly small (1 horsepower or less) mechanical output wind machines were installed in the U.S. alone. The primary use was water-pumping and the main applications were stock watering and farm home water needs.”

It was the Danish meteorologist, Poul La Cour (1846-1908) who pioneered the development of modern electricity generating wind turbines. In 1891, he designed an electrical output wind turbine replicating the aerodynamic design principles that were used in European tower mills. Unlike previous designs, the four-bladed airfoil-shaped rotor's higher speed and the structure's low solidity proved to be more efficient for generating electricity. By the end of the First World War, the total amount of power generated by Denmark's wind turbines, which produced about 20 to35kW each, reached 3MW according to the Danish Wind Industry Association. These turbines accounted for about 3 percent of the country's electricity consumption. (DWIA) However, fossil-fuel steam plants were still favored above wind turbines for their more efficient and inexpensive energy production.

In the 1920s, wind generator electrical systems began to follow the design of airplane propellers and monoplane wings. In the Midwestern Great Plains of the U.S., 1 to 3-kW wind generators were commonly used to provide lighting for farms and charging batteries for crystal radio sets. Their use was gradually extended to driving appliances that were powered by direct current, such as refrigerators and power tools. The world’s first alternating current wind turbines appeared in the 1950s, pioneered by La Cour’s former student Johannes Juul . The early 1980s witnessed a revival in wind energy production with California at the helm. Tax cuts and an energy crisis in the U.S. prompted developers to seek alternative energy options, and the 55kW generation of turbines offered just that. Although fossil fuels soon regained their prominence, increased technology and the pursuit of cleaner energy in recent years are bringing wind turbines back to the forefront of renewable energy development.

In Canada, Hydro-Québec Research and Natural Resources Canada installed experimental vertical-axis turbines in the 1970s and 80s; however most of these are no longer in operation. Horizontal-axis wind turbines proved to be more efficient, and in 1986 Hydro-Québec constructed the 65kW Kuujjuaq Wind Turbine as a demonstration project. The Cowley Ridge wind plant, Canada’s first commercial wind farm, was constructed in southern Alberta in 1994 . Since then, all of Canada’s provinces have adopted wind energy including BC, which began construction of its first wind farm near the town of Chetwynd in 2008 . Canada has great potential for more land-based wind farm sites, and has only recently turned to offshore projects. By 2012, BC and Ontario will be the first provinces with offshore wind farms under development.

The increased grid integration of wind energy has led to the manufacturing of larger, higher capacity wind turbines. Early wind turbine models, which generated about 20-60kWh, were not cost-effective in terms of producing grid quality electricity. Smaller turbines need to be taller in proportion to their diameter for optimum wind flow. They also require more investment in maintenance, control and electrical connection to grid systems than larger-scale wind utilities. Larger turbines also allow for better land utilization for onshore wind farms, and even bigger sizes are needed for offshore projects. In 2009, turbines reached capacities of up to 6MW, and designs are underway for both onshore and offshore turbines of up to 8MW.

Synopsis

This slideshow contains six images of technology used to harness the power of wind throughout history. The images include an Egyptian sailboat, windmills from Holland and rural North America, and three wind turbines used for generating power in 1888, 1941 and 2006.



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How Contemporary Wind Turbines Work


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Quiz :

Which country leads the world in proportion that wind energy contributes to its total energy supply?

Denmark
Canada
Germany