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Power transmission is the movement of energy from its place of generation to a location where it is applied to perform useful Mechanical work.
Power is defined formally as units of energy per unit time. In SI units:
Since the development of technology, transmission and storage systems have been of immense interest to technologists and technology users.
Power transmission is usually performed with overhead lines as this is the most economical way to do so. Underground transmission by high-voltage cables is chosen in crowded urban areas and in high-voltage direct-current (HVDC) submarine connections.
Power might also be transmitted by changing electromagnetic fields or by radio waves; microwave energy may be carried efficiently over short distances by a waveguide or in free space via wireless power transfer.
From the 16th century through the Industrial Revolution to the end of the 19th century, mechanical power transmission was the norm. The oldest long-distance power transmission technology involved systems of push-rods or Flatrod system ( stängenkunst or feldstängen) connecting waterwheels to distant mine-drainage and brine-well pumps.Dianne Newell, Technological Innovation and Persistence in the Ontario Oilfields: Some Evidence from Industrial Archaeology, World Archaeology 15, 2, Industrial Archaeology (Oct., 1983), pp. 184-195 A surviving example from 1780 exists at Bad Kösen that transmits power approximately 200 meters from a waterwheel to a salt well, and from there, an additional 150 meters to a brine evaporator.Michael Pfefferkorn, Der Solschacht von Bad Kösen und sein Feldgestänge, Grubenarchäologischen Gesellschaft, 2004. This technology survived into the 21st century in a handful of oilfields in the US, transmitting power from a central pumping engine to the numerous pump-jacks in the oil field.Keith Kinney, The last two oil leases in Illinois using a central power and rod lines -- Powered by 35 H.P. Superior Oil Field Engines, Flat Rock, Illinois, 2003
Mechanical power may be transmitted directly using a solid structure such as a driveshaft; transmission can adjust the amount of torque or force vs. speed in much the same way an electrical transformer adjusts voltage vs Electric current. Factories were fitted with overhead providing rotary power. Short line-shaft systems were described by Georg Agricola, connecting a waterwheel to numerous ore-processing machines.Georgius Agricola, De re metallica, 1556. See While the machines described by Agricola used geared connections from the shafts to the machinery, by the 19th century, drivebelts would become the norm for linking individual machines to the line shafts. One mid 19th century factory had 1,948 feet of line shafting with 541 pulleys. The United States Magazine of Science, Art, Manufactures, Agriculture, Commerce and Trade, Vol. 2, 1856, page 164.
Hydraulic systems use liquid under pressure to transmit power; and hydroelectric power generation facilities harness natural water power to lift or generate electricity. Pumping water or pushing mass uphill with (windmill pumps) is one possible means of energy storage. London had a hydraulic network powered by five operated by the London Hydraulic Power Company, with a total effect of 5 MW.
Pneumatic systems use gasses under pressure to transmit power; Pneumatics is commonly used to operate pneumatic in factories and repair garages. A pneumatic wrench (for instance) is used to remove and install automotive tires far more quickly than could be done with standard manual hand tools. A pneumatic system was proposed by proponents of Thomas Edison direct current as the basis of the power grid. Compressed air generated at Niagara Falls would drive far away generators of DC power. The war of the currents ended with alternating current (AC) as the only means of long distance power transmission.
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