Hydroelectric dams are a very common form of hydroelectric generation used today and usually consists of large turbines that require a high volume of water flow.
Hydroelectric dams use a reservoir of water to capture and flow water through a hydro turbine generator to create electricity.
How a Hydroelectric Dam works:
A hydroelectric dam, like the one seen in the picture above, is usually built in a river or a lake. The main idea of a hydroelectric dam system is to create a water flow with a large vertical drop that creates enough force to turn a hydro turbine generator. Here is a simple step-by-step guide to how a standard hydroelectric dam creates electricity:
(1) A river or lake provides a source of water from a man-made dam reservoir. The water in the reservoir is kept at a higher elevation than the water that exits the dam downstream.
(2) The flow of water from the reservoir is then channeled down the intake valve into the penstock. In the penstock the water is stored where there is usually some sort of gate that separates the reservoir with the intake valve and penstock which controls the amount of water that is allowed to flow through the dam.
(3) The intake valve is what leads the water towards the blades of the hydro turbine blades. With the force of gravity, the water gains momentum as it flows down the intake valve and creates enough force to rotate the turbine blades as the water hits the blades of the turbine and flows through.
(4) The rotational force from the spinning turbine blades are attached to a rotating turbine shaft which is attached to an electric turbine generator. The electric generator creates electricity with the rotational force provided by the mechanical force of water that turns the turbine blades.
(5) The generator is attached to a transformer which can then transport the electricity outside the dam to be used as usable electricity.
(6) After the water flows through the turbine causing it to spin, the force of gravity continues to pull the water through, down another channel and eventually through the entire system and back into the downstream river.
(7) The electricity produced in the generator inside the hydroelectric dam can then be allocated outside the dam.
Most large scale hydroelectric power plants in the United States use the dam and reservoir system to generate electricity. The Hoover Dam is a great example of a large scale dam in the US.