WIND AND WATER ENERGY

Windmills were developed in Persia by the 9th century все. This technological innovation was spurred by the need to mill corn in areas lacking consistent water supplies. Early windmills used an upright shaft, rather than a horizontal one, to hold the blades. This system was housed in a vertical adobe tunnel with flues to catch the wind (similar to a revolving door). The concept of harnessing wind energy via windmills reached Britain and Europe by 1137, where it underwent significant changes, with horizontal (rather than vertical) shafts and horizontal rotation. A form of solar energy, climate-dependent wind power has been unreliable and difficult to accumulate and store.

Roman aqueducts provided a system of fast­flowing water to watermills. By the 1st century все, Romans used an efficient horizontal axis where the waterwheel converted rotary motion around a horizontal axis into motion around a vertical axis; water passed under the wheel, and kinetic water energy turned the wheel. Draft animals and water­power were harnessed to turn millstones. Rudimen­tary primitive watermills used vertical axes, with millstones mounted directly to waterwheel shafts. In mountainous regions, water was channeled through a chute into the wheel. Although power output was minimal (~300W), this type of watermill was used in Europe until the late medieval period.

During the late 18th and early 19th centuries, waterwheel efficiency was improved. English engi­neer John Smeaton, expanding on the systems of early Roman waterwheels, found that more energy was generated when water was delivered to the top of the wheel via a chute. An overshot waterwheel used both kinetic and potential water energy and was capable of harnessing 63% more potential energy than was the undershot. The growing demand for energy intensified use of the waterwheel. While toiling in the gold mines of California during the 1870s, a British mining engineer, Lester Pelton, discovered that a waterwheel could be made more powerful if high-pressure jets of water were directed into hemispherical cups placed around its circumfer­ence. This waterwheel design, generating 500 horse­power (hp), was used 20 years later in the sodden mines of Alaska.

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