Power transmission
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Since the development of technology, power transmission and storage systems have been of immense interest to technologists and technology users.
Power is defined formally as units of energy per unit time. In SI units: 1 watt = 1 joule/s = 1 newton * metre/second (1W=1J/s=1N·m/s).
Transmission is relocating energy from its place of origin to a location where it is applied to performing useful work.
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Electrical power
Main article: electric power transmission
With widespread establishment of power grids, power transmission has come to be associated most often with electric power transmission. Alternating current is normally preferred as its voltage may be easily stepped up by a transformer in order to minimise resistive loss in the conductors used to transmit power over great distances; another set of transformers is required to step it back down to safer or more usable voltage levels at destination.
Power may also be transmitted by changing electromagnetic fields or by radio waves; microwave energy may be carried efficiently over short distances by a waveguide.
Mechanical power
Main article: transmission (mechanics)
Mechanical power may be transmitted directly using a solid stucture such as a driveshaft; transmission gears can adjust the amount of torque or force vs. speed in much the same way an electrical transformer adjusts voltage vs current.
Hydraulic systems use liquid under pressure to transmit power; canals and hydroelectric power generation facilities harness natural water power to lift ships or generate electricity. Pumping water or pushing mass uphill with (windmill pumps) is one possible means of energy storage.
Pneumatic systems use gasses under pressure to transmit power; compressed air is commonly used to operate pneumatic tools in factories and repair garages. A pneumatic wrench (for instance) is used to remove and install automotive tyres far more quickly than could be done with standard manual hand tools.
Chemicals and fuels
Power (and energy) may be transmitted by physically transporting chemical or nuclear fuels. Possible artificial fuels include radioactive isotopes, wood alcohol, grain alcohol, methane, synthetic gas, cryogenic gas, hydrogen gas (H2) and liquified natural gas (LNG).