In general, hydropower plants obtain the energy of falling water and convert them to generate electricity. This conversion is done by the turbine in which it converts the kinetic energy of the falling water into the mechanical energy. The generator will convert the mechanical energy obtained from the turbine into electrical energy.
The size of the power plants varies and depends on the individuals who operate for their own energy needs or to sell the power to other utilities. The sizes can be categorized as large, small and micro hydropower.
Hydroelectric power Dam storage: It is a conventional hydroelectric power station which involves, building a dam across a river which traps water, creating lake or reservoir behind it. Water flows through the dam with high potential which turns the turbines and runs the generator system. This converts kinetic energy into electrical energy.
Pumped Hydro Energy Storage: There is another type of hydro energy storage called as pumped storage. The working of it is similar to the battery since it stores the electricity generated from various power sources like solar, wind and nuclear for future use. There are two reservoirs involved in this hydropower storage system. When the demand for electricity is high, the water from the upper reservoir is released to the lower reservoir which turns a turbine and produces electricity. When the electrical demand is low, pumped storage facility stores energy by pumping water from the lower reservoir to the upper reservoir. It is basically the recycling the water again and is done during the periods of peak consumption.
Run-of-the-River Hydroelectricity: In this system, the natural flow of the river is used to produce electricity without building a dam. These hydroelectric power stations use river flow through penstocks and turbines to produce electricity.
There are six major components involved in the working of the hydroelectric dam. They are
Reservoir: It is a place behind the dam where the water is stored. In general, it is located higher than the remaining dam structure since the height of the water in the reservoir decides the potential energy of the water. Potential energy will be more only if the height of the water is high. Also, the position of water in the reservoir helps to move down effortlessly.
Dam: Dam is a barrier that holds the water or underground streams. It is the most important component of hydroelectric power generation. Generally, the dam is built on a large river which has water abundantly throughout the year and also built at a location where the height of the river is sufficient to get maximum possible potential energy from water.
Spillways: The main purpose of the spillway is to provide a controlled release of water flow from the dam into downstream areas. A spillway helps in releasing floods to avoid the water overflow which in turn can damage or even destroy the dam.
Intake or control gates: They are built inside the dam to control and release water from the reservoir and are also called as inlet gates. Water will be taken to the power generation unit through these gates. When these gates are open, water flows due to gravity through the penstock and towards turbines. Both potential and kinetic energy will be possessed by water while flowing through these gates.
Penstock: It is a long pipe which carries water flowing from the reservoir to the power generation unit. The penstock contains water which possesses kinetic energy due to its motion and potential energy is due to its height. The height of the water reservoir and water flowing through penstock decides the amount of energy generated and water flow through penstock is controlled by control gates.
Turbines: Water from penstock enters power generation unit containing a turbine and generator. Water will fall on the blades of the turbine where the potential and kinetic energy of water is converted to rotational energy due to the motion of the blades in the turbine. The shaft of the turbine also rotates due to the rotating blade. The turbine shaft is placed inside the generated. In general, more than one power generation unit is present in a hydroelectric power plant.
Generators: Electricity is produced in the generator. When the shaft of the water turbine rotates in the generator, produces alternating current in the coils. Rotation of shaft inside the generator produces a magnetic field which in turn is converted into electricity by the electromagnetic field induction.
The typical hydroelectric dam is shown in the figure below. Here the potential energy of water is converted into electrical energy.