Hydro-Electric Power Plants – Explained

Another Summer 2016 topic worked upon by me was Hydro Electric Power Plants..

BASIC HISTORY of Some Popular Plants

  • Nearly 2000 years ago the Greeks used water wheels to grind wheat into flour
  • In the 1700’s, hydro-power was broadly used for milling of lumber and grain and for pumping irrigation water
    • Appleton, Wisconsin became the first operational hydroelectric generating station in the United States, in
      1882, producing 12.5 kilowatts (kW) of power
    • The total electrical capacity generated was equivalent to 250 lights
  • The largest and last masonry dam built by the U.S. Bureau of Reclamation was the Roosevelt Dam in Arizona
    between 1905-1911; its power output has increased from 4,500 kW to 36,000 Kw
  • Hoover Dam at the border of Nevada and Arizona is the largest sitting electricity producing dam in the world with it being able to supply up to 4.3 TW/h (tera watts/hour) over a year of use.
    • Still in use today, Niagara Falls was the first hydro-power site developed for a vast quantity of electricity.
    • Robert Moses Niagara hydro-electric power station in Lewiston, NY is home to 13 generators and helps generate electricity for the town of Lewiston and many other smaller towns in western NY state.
      • The station has a capacity of up to 20 MW (megawatts) and cost a total of $800 million to build
      • The plant houses its own artificial reservoir (Lewiston Reservoir) to pump water downstream.









A power plant by definition is a structure that has the capability to store electricity and distribute it by means of transformers and generators. The electricity will be produced by some sort of conversion of energy i.e Wind, Solar, Hydro, Potential and possibly organic fossil energy (coal power plants). The world today is starting to look more into renewable sources, meaning sources that can be used for longer periods of time and can be “renewed” at discretion. And by far Hydro power plants have taken the lead for majority of electricity generation across many nations, particularly the US. All hydro electric power plants combined (only 7 major ones) make about 6% of all electricity in the US and 34% of renewable electricity. The US is in the Top 5 for the nation that produces the most amount of hydro- electricity per year (numbers fluctuate)…

The basic principle of such a plant is that water gains more potential energy as it goes higher up in elevation (exponentially!). More potential energy results in more kinetic energy when flown back down to ground and hence gaining more speed. At the top a dam you will find a special intake system that will be specially designed to filter out any large debris (branches, rocks..) and also aquatic wildlife to enter the tunnels and potentially (pun intended) get hurt by the turbines. The fish are allowed to flow downstream by means of another smaller canal alongside the plant.


A gate after the filters controls the amount of water being allowed into the tunnel and hence control amount of electricity that will be produced. As the water flows down, it gains speed and KE and eventually spins a handful of turbines that will rotate the generator (alternator) axle to produce electricity. A generator works on the basic principle of electromagnetic induction, where a conductor (wire) is moved back and forth in a magnetic field. Using the right hand rule, magnetic field in one direction–a mechanical force up (perpendicular) and hence an AC electric voltage is produced. After flowing through the turbine, the water is allowed to freely flood a water body.

At night however, due to low electricity demand, water is flown back up the tunnels (using pumps) to the reservoir for further day use..

After the generator, the AC current is fed through a step-up transformer, a device that increases the voltage of the current (the force) for further travel and distribution through power lines. A transformer uses two ideas: a coiled wire with current can make a temporary magnetic field and the fact that a moving magnetic field can induce voltage (like an alternator). It combine these principles to increase or decrease the voltage (I will not go into to much detail here though).

A step up transformer increases the voltage.

From here the power is fed to power lines and to your homes, as simple as that!




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