GC: n

CT: Hydraulic energy.
Itaipu produces electricity based on hydraulic energy, in other words, using potential gravitational energy from the water, contained in an elevated reservoir. This energy is present in nature and it can be used in sharp descents or waterfalls.
Before it turns into electric energy, this energy must be converted to kinetic energy. The device that does that conversion is a turbine. The turbine is composed basically in a wheel with paddles, which rotates when it is hit by the water mass. The last element of this chain of conversions is the generator,that converts the circular movement from the turbine into electrical energy.
The building of a hydroelectric plant in a river anticipates the building of a dam to contain it, forming an artificial lake that has two functions: accumulate water for when the flow rate lowers, and to provide a gap for the water to fall (raising potential energy).

S: https://www.itaipu.gov.br/en/energy/hydraulic-energy (last access: 11 February 2015)

N: 1. – hydraulic (adj): c.1600, from Greek hydraulikos organon “water organ,” from hydr-, stem of hydor “water” (see water) + aulos “musical instrument, hollow tube” (see alveolus). Extended by the Romans to other kinds of water engines.
– energy (n): 1590s, “force of expression,” from Middle French énergie (16c.), from Late Latin energia, from Greek energeia “activity, action, operation,” from energos “active, working,” from en “at” + ergon “work, that which is wrought; business; action”.
Used by Aristotle with a sense of “actuality, reality, existence” (opposed to “potential”) but this was misunderstood in Late Latin and afterward as “force of expression,” as the power which calls up realistic mental pictures. Broader meaning of “power” in English is first recorded 1660s. Scientific use is from 1807. Energy crisis first attested 1970.
2. Hydroelectric power: As to how the electric generator works, the Corps of Engineers explains it this way:
“A hydraulic turbine converts the energy of flowing water into mechanical energy. A hydroelectric generator converts this mechanical energy into electricity. The operation of a generator is based on the principles discovered by Faraday. He found that when a magnet is moved past a conductor, it causes electricity to flow. In a large generator, electromagnets are made by circulating direct current through loops of wire wound around stacks of magnetic steel laminations. These are called field poles, and are mounted on the perimeter of the rotor. The rotor is attached to the turbine shaft, and rotates at a fixed speed. When the rotor turns, it causes the field poles (the electromagnets) to move past the conductors mounted in the stator. This, in turn, causes electricity to flow and a voltage to develop at the generator output terminals.”
3. Old-fashioned term: white coal.

S: 1. OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=hydraulic&searchmode=none; http://www.etymonline.com/index.php?allowed_in_frame=0&search=energy&searchmode=none (last access: 11 February 2015). 2. http://water.usgs.gov/edu/hyhowworks.html (last access: 11 February 2015). 3. OG – https://bit.ly/2LrA1Pb (last access: 19 December 2018).

SYN:
S:

CR: energy, electrical energy, hydroelectric power, kinetic energy, mechanical energy, potential energy, water hammer.