This article looks at the history of water-driven machinery and its modern application in the generation of electrical power. It also looks at some of the potential benefits and controversies surrounding water wheel electric generators, also known as hydroelectric generators.
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Capturing the immense energy created by moving water, water wheels were used by the Romans to turn mills to process grains into flour. The ancient Chinese took the process one step further and connected the drive axle of the water wheel to a cam which opened and closed bellows to stoke fires in the furnaces of Chinese ironworks. Medieval Europeans used watermills to pump water from mines, and process the resulting ore, from mines that stretched ever deeper. In the modern era, the most famous use of water wheels to generate electricity is, arguably, the Hoover Dam. Despite the advancement of time and technology, the basic premise has remained unchanged for thousands of years.
Electricity can be generated through three different configurations of a water wheel; horizontal, overshot, and undershot. An "overshot" water wheel is one in which the water flows over a wheel, the weight of the water pushing on a series of paddles set into a "wheel." As the wheel turns, it turns the axle or shaft of the waterwheel which in turn powers machinery or electrical generators. "Undershot" wheels apply the same principle, but the water source passes under the water wheel. Horizontal waterwheels are wheels with angled paddles sunk into a directed stream of water to capture the energy of the water. It is this last design which is most popular to use in hydroelectric plants.
Hydroelectric plants rely on a series of generators to produce electricity. As the shaft turns, it rotates a rotor within the generator. The rotor had large magnets wrapped in copper wire at the edges and rotates within a cylinder lined with more magnets called a "stator." The magnets, passing by each other, generate electricity, which is captured by the copper wire and transferred to wiring, which carries the current away to be used elsewhere.
Several factors determine the amount of electricity generated, including the kinetic energy of water and the size of the generator. Scale models can be constructed for school science fairs using simple objects found at a hobby shop, including using an electrical motor from a remote-controlled car as a stand-in for the generator. When operating as a motor, the electrical current generates motion, but in reverse, motion from the turning of the axle can create an electrical current.
Water is considered an excellent source of non-polluting energy. As long as there are sources of running water and a place to store that water to build up potential energy, then it is possible to generate electricity with water. There are no carbon emissions associated with hydroelectric power, which has led some to consider it a good source of "clean" energy production. Unlike some other technologies, the ability to generate electricity via water already exists and represents a tried-and-true technology with low initial output to construct plants.
Some environmentalists believe that hydroelectric power holds potential environmental dangers that have been largely ignored. Some argue that the storing of water to create sufficient kinetic energy requires the formation of reservoirs which may flood culturally, economically, or environmentally sensitive areas. For example, Philae Temple in Egypt was moved from its original location to prevent it from being submerged and lost in the waters of Lake Nasser following the construction of the Aswan Dam. Others argue that the diversion of waterways may harm fish, such as salmon, by denying them access to their spawning grounds. In response, some power companies have provided safe "channels" which mimic the original river up which the salmon may swim to reach their spawning grounds. Still others point out that the carbon emissions created by the construction of large hydroelectric dams offset their non-polluting reputation.
Other means of generating electricity using a waterwheel, such as so-called "tidal generators," are being explored as a way to generate electricity with water. Despite its potential drawbacks, hydroelectric power has been and continues to be a popular source of non-polluting electricity. Generating electricity via waterwheel has been used in the Tennessee Valley Authority, Hoover Dam, and the Three Gorges Dam in China. Not all water wheel electrical generators need to be so large, however, and some activists believe that small-scale hydroelectric plants can generate much needed, clean energy for small villages in developing nations.
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