What is hydropower? Draw a suitable diagram and explain how hydropower is generated.
Hydropower uses the Earth's water cycle to generate electricity because movement of water as it flows downstream creates kinetic energy which can be then converted into electricity. Hydropower is the leading renewable source for electricity generation globally, supplying 71% of all renewable electricity. Reaching 1,064 GW of installed capacity in 2016, it generated 16.4% of the world’s electricity from all sources.
Hydropower uses the natural gradient force of water flowing down from a considerably
height under gravity which is capable to turn turbines to generate electricity.
There are three types of hydropower plants:
- ‘run of river’: where the electricity is generated through the flow of a river
- ‘reservoir’: where power is generated through the release of stored water
- ‘pumped storage’: where stored water is recycled by pumping it back up to a higher reservoir in order to be released again
Construction and Working:
The basic components of a conventional hydropower plant are:
- Dam: a large reservoir that holds back water
- Control gates: gates built on the inside of the dam, when opened the water flows due
to gravity through the penstock and towards the turbines
- Penstock: a pipe which is connected between dam and turbine blades, used to
increase the kinetic energy of water
- Turbine: as water falls on the blades of the turbine, the kinetic and potential energy
of water is converted into the rotational motion of the blades of the turbine
- Generators: generator produces electricity, as the turbine blades turn, so do a series
of magnets inside the generator producing a magnetic field which is converted into
electricity by electromagnetic field induction
- Transformer: the transformer inside the powerhouse takes the alternating current
and converts it to higher-voltage current.
- Transmission lines: out of every power plant come four wires: the three phases of
power being produced simultaneously plus a neutral or ground common to all three
- Outflow: used water is carried through pipelines, called tailraces, and re-enters the
- The water in the reservoir is considered stored energy. The height of water in the reservoir decides how much potential energy the water possesses. The higher the height of water, the more its potential energy. The overall potential energy of water, helps to produce more electricity in the power generation unit.
- When the control gates open, the water flows through the penstock becomes kinetic energy because it's in motion.
- The amount of electricity that is generated is determined by the flow and the head. The flow of water through the penstock is controlled by the control gates. The head refers to the distance between the water surface and the turbines, usually dependent upon the amount of water in the reservoir.
- Water flowing from the penstock is allowed to enter the power generation unit, which houses the turbine and the generator. When water falls on the blades of the turbine, the kinetic and potential energy of water is converted into the rotational motion of the blades of the turbine.
- The rotating blades causes the shaft of the turbine to also rotate. The turbine shaft is enclosed inside the generator. In most hydroelectric power plants there is more than one power generation unit.
- The shaft of the water turbine rotates in the generator, which produces alternating current in the coils of the generator. It is the rotation of the shaft inside the generator that produces magnetic field which is converted into electricity by electromagnetic field induction.
- Hence the rotation of the shaft of the turbine is crucial for the production of electricity and this is achieved by the kinetic and potential energy of water.
- The electricity produced is then stepped up in voltage through the hydroelectric power station transformers and sent across transmission lines.
- The used water having performed its intended purpose is channelled out of the power generation station as outflow to the mainstream of the river to continue the cycle of power generation.