how a hydroelectric power station works

How A Hydroelectric Power Station Works

How A Hydroelectric Power Station Works


A hydroelectric power station is a power station that uses gravitational potential energy of dammed water to generate electricity.

In a hydroelectric power station, water is dammed in a large reservoir to raise its gravitational potential energy. The difference in height of the water between the source and the water’s outflow, called the head, is proportional to the potential energy of the stored water. When released, the potential energy of the water creates a high pressure water flow that drives a turbine connected to an electrical generator. The electrical generator then converts the kinetic energy of the rotating turbines into electricity by a process called electromagnetic induction.

hydroelectric power
How a hydroelectric power station works. Image source

Interesting facts about hydroelectricity

  • China is the largest hydroelectricity producer
  • hydropower contributes to about 20% of the world’s total electricity and 70% of all renewable electricity.
  • The hydroelectric power plant on the Three Gorges Dam in Central China is the world’s largest power–producing facility.

Advantages of hydroelectric power

  • Hydropower is a renewable source of energy because it relies on the water cycle, which is driven by the sun.
  • Hydropower is a clean energy source because it powered by water.
  • Water is a resource that is virtually everywhere, allowing each country to produce its own energy without being reliant on international fuel sources.
  • Hydropower reservoirs can offer recreational opportunities to the public such as fishing, swimming, and boating.
  • Hydropower facilities can provide other benefits beyond electricity generation, such as providing flood control, irrigation support, and clean drinking water.
  • Hydropower provides low-cost electricity and durability compared to other sources of energy.

Disadvantages of hydroelectric power

  • Hydropower facilities are not easy to situate, because when one is built with a dam a previously dry land area might be flooded with water to be used as a reservoir. This means whatever habitat was in that location will be ruined.
  • Affects the natural flow of rivers.
  • Expensive to build.
  • Easily affected by droughts because less rainfall means less water in the reservoirs.

Examples of Hydroelectric Power Stations

Kariba South Power Station in Zimbabwe

The decision to dam the Zambezi River was made in 1955. The idea was to dam the Zambezi River at the Kariba Gorge to supply power to both Zimbabwe and Zambia.

In 1959, the first generator was commissioned and all 6 generators were in operation by 1962, with a generation capacity of about 700MW.

In 2014, Zimbabwe Power Company (ZPC) started to extend the existing plant by adding two more units with a total generation capacity of 300MW. The project was completed and commissioned in March 2018, making Kariba South Power Station the biggest power generation plant in Zimbabwe with a total generation capacity of 1050MW.

At Kariba South Power Station, electricity is generated by drawing water from Lake Kariba to the turbine spiral casing where it rotates the turbine coupled to a generator. The generator produces electricity.

The low pressure spent water is then passed through a suction cone and draft tube to the tailrace and discharged downstream of the dam, back into the Zambezi River.

The Zambezi River Authority (ZRA), formed by the Zimbabwean and Zambian governments, is responsible for the allocation of water used by Zimbabwe’s Kariba South and Zambia’s Kariba North Power Stations.

Hydroelectric power station, Gravitational potential energy, Renewable source of energy, Kariba South Power Station, Zimbabwe

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