Hydro Electric Power 

 How do Hydroelectric Dams Work

    How do dams work? Hydroelectric dams work by converting the movement or falling of water into useful forms of energy such as electricity. Many forms of hydro power exist and have been used by humans throughout history. Some examples of this are watermills which powered machinery such as sawmills, irrigation which used gravity, and dams which use falling water to power turbines. This page will focus on hydroelectric dams as it’s the most commonly used hydro power today. 

     Hydroelectric dams use a reservoir to create potential energy from the dammed water. This water flows through an intake and into a large pipe called a penstock. The penstock feeds water into a turbine which powers a generator.

The dam generator consists of a turbine powered by water flowing through the wicket gate. This gate can be opened more or less to determine the rate of flow through the turbine and thus the amount of power generated. The turbine is attached by a shaft to an electric generator.

According to Faraday’s law of induction, “The induced electromotive force (EMF) in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit.” Essentially this means if you have a closed circuit (such as a coil of copper wire connected at both ends) and you move magnets through it (changing the magnetic flux) you can produce electromotive force (electricity).

Looking at the image above you’ll notice two parts at the top of a hydroelectric turbine, the stator and rotor. The stator provides the closed circuit by looping wire which leaves the generator (this loop is still connected but we place a load on the circuit, the electrical grid) and the rotor has magnets attached or evenly distributed metal with magnets outside the system (as shown in the image). When the rotor spins due to the water turning the blades of the turbine it begins to produce magnetic flux as the magnets move or system moves relative to the magnets. This creates electromotive force in the closed circuit of wire which is connected to the electrical grid and thus electricity has been generated from flowing water.

definition, explanations and diagrams provided by Renewable energy index

Maximum amount of Usable Energy from a Hydro Electric Dam

Advantages:

Most efficiency energy at around 90% efficiency 

Low operating costs once construction is complete

Proven economically viable energy source.

Zero greenhouse gas emissions during operation.

Sustainable renewable energy source (condensation/evaporation cycle).

Disadvantages:

 Dramatically alters local hydrology and habitat for plants, fishes, and microbial life.

Reduces amount of arable land available.

High up-front construction costs compared to conventional energy (fossil fuels).

Poses danger to downriver settlements if dam fails.

Most dams use concrete which produces a lot of greenhouse gas emissions during production.