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Lecture 10

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Environmental Science
Tanzina Mohsin

EESA09H WIND Lecture 10 Notes Wind Power Part 1: Harnessing the Wind 1.1 Flying 1.2 Sailing Part 2: Power Generation 2.1 Windmills 2.2 Wind Turbines Part 3: Special Topic: Permafrost in SW Hudson Bay Part 1: Harnessing the Wind 1.1 Flying Humans have long yearned to fly as represented in the Greek myth of Icarus. In the 15 century Leonardo da Vinci designed various flying machines (including designs for helicopters) but did not have the engineering skills to complete the designs. In the 19 century, Otto Lilienthal performed more than 2000 glider flights using his own designs. He perished in 1886 after a glider mishap. Manned flight was achieved first by the Wright Brothers on Dec.17, 1903. Bernoulli’s principle explains how flight is possible. A fluid that is moving faster has a relatively lower pressure. The shape of a wing causes air to flow faster over the top of the wing than it does beneath. This produces a lower pressure above the wind and a higher pressure below the wing; creating a pressure gradient force pushing upward. The wing experiences a lift and thus flight is enabled. The invention of flight has revolutionized travel. In 2000, 8,000 commercial flights were taking place at any given moment, carrying 1,000,000 passengers. There are some risks involved in flight but these have become smaller and smaller in recent years as revealed by data compiled by Boeing. 1.2 Sailing Sailing has a long history, particularly in the Middle East and China. Sailing was used as an efficient means of transportation, carrying people and goods from port to port and bringing prosperity to coastal regions. As ships became more seaworthy, sailing became an effective tool for exploration. Norse sailors used ships of type known as knarrs or cogs to cross the Atlantic to North America for the first time around 1000 AD. The “square rigged” sails on these ships were very sensitive to wind direction; the Norse travelled to Greenland and Newfoundland by following the Polar Easterly winds across the North Atlantic, returning to Europe slightly further south via the midlatitude Westerlies. In contrast, the junk rig used by Chinese ships had the capability of sailing into the wind as early as 220 BC. A major advance in European sailing occurred when square rigged sails were augmented by or replaced by lateen (triangular) sails in a moveable boom. This allowed greater boat maneuverability – and the ability to sail into the wind. By the 13 century sailing around the world had sufficiently advanced to allow the exploration of the entire planet. The age of sail continued until the 1860’s when it was outstripped by steam technology. It is now largely recreational. Sailing is based on the same principle as flying. In this case the “lift” or pull is horizontal rather than vertical. Moveable sails are oriented so that the wind flows faster over the front of the sail than the back, creating a pressure gradient force that pulls the sail forward. The use of a keel board (a piece of wood that penetrates into the water beneath) provides better control of the sailboat path. The sail pulls the boat in the direction of the front of the sail; the resistance between the water and the keel produces a force that keeps the motion of the boat in the direction chosen by the sailors. Part 2: Power Generation 2.1 Windmills Like sailing, windmills have a long history of providing energy for human needs. Early uses in Persia and China included grain grinding and water pumping. Two styles emerged, vertical axis and horizontal axis. The horizontal axis has been found to be more efficient and dominates current and historical design. th In 12 century Europe windmills were developed that could be turned in order to match the direction of the wind. In its heyday there were 90,000 windmills in England (“one for every field”), producing a wind-based economy with uses expanded to threshing grain, sawmills, and land drainage. It was gradually taken over by coal based energy after the Industrial Revolution which began in the 1820s. 2.2 Wind Turbines Wind turbines are a natural extension of windmills. Wind turbines are used to generate electricity rather provide direct energy for end use as wind mills commonly did and do, such as water pumping and grain grinding. The first wind turbine has been credited to Charles Brush in Cleveland in 1888. Brush later joined forces with Edison to form General Electric Company. His wind turbine had 144 blades and produced 12 kW. Poul la Cour, a Dane, modified the design in 1999 after years of wind tunnel experiments. Determining that the best design had fewer blades and a rapid rotation speed, la Cour’s windmill had only four blades and achieved a far more efficient wind turbine. In 1891 la Cour had also introduced the idea of using some type of battery to produce a constant power supply from the inconstant wind; his first designs used hydrogen power, although he later moved on to other chemicals. Wind turbine use received a boost from the OPEC crisis of the early 1970s, when high oil prices drove a search for alternative energy sources. Concerns about global warming and the Kyoto Protocol in the 1990s re-ignited interest in wind power. At present 1% of Canadian electricity is produced by wind power. This is rapidly increase and could supply up to 5%, 3 TWh. These efforts have been plagued by NIMBY (Not In My Back Yard) problems, with local residents complaining about the noise and unattractiveness of the turbines. Melancthan, near Shelburne, is an example of this. Worldwide wind power is growing rapidly. 2.3 Wind Energy Basics Basic information on wind energy and wind power technology, resources, and issues of concern. Wind Energy and Wind Power Wind is a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth's surface, and rotation of the earth. Wind flow patterns are modified by the earth's terrain, bodies of water, and vegetative cover. This wind flow, or motion energy, when "harvested" by modern wind turbines, can be used to generate electricity. How Wind Power Is Generated The terms "wind energy" or "wind power" describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power. This mechanical power can be used for specific tasks (such as grinding grain or pumping water) or a gen
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