What is hydropower?

Hydropower, also known as hydroelectric energy or hydroelectricity, uses the power of flowing water to generate electricity. People have used water to generate electricity for thousands of years and records of water mills being used dates back as early as 3 B.C.

A dam, or other structure, is used to alter the natural flow of a body of water and create a change in elevation from one point to another. Water gains potential energy right before it flows downhill, this energy is converted to kinetic energy as the water flows downhill. The greater the flow of water and the larger the elevation difference is, the more power will be generated.

The flow of water is used to spin a turbine connected to a generator which then converts the energy to electricity. This electricity is then fed into the National Grid and into homes and buildings supplied by the power plant.

Hydropower is considered a renewable energy as water is an infinite resource and the water cycle on which it relies on is constant and continuous.

Types of Hydropower Plants

There are 3 different types of hydroelectric energy plants.

An impoundment facility is the most common type, where a dam is used to store water in a reservoir and control the flow of water. A dam, or other structure, is used to alter the natural flow of a body of water and create a change in elevation from one point to another. Water gains potential energy right before it flows downhill and this energy is converted to kinetic energy as the water flows downhill. The greater the flow of water and the larger the elevation difference is, the more power will be generated. These tend to be large hydropower systems

A diversion facility channels a portion of the river through a penstock to utilise the natural decline of the elevation to produce energy. A penstock is a closed channel that regulates the flow of water using valves, gates, and turbines. Diversion facilities typically do not require the use of a dam but have limited flexibility to follow peak variation in demand.

The third type of hydropower facility is called pumped storage hydropower (PSH). These store energy in the form of gravitational potential energy and work by pumping water from low elevation to high elevation. Additionally, they store electricity generated from other power sources such as wind and solar and aim to store excess power during low demand periods for release as demand rises. These reservoirs tend to be quite small compared to the impoundment facilities that use dams.

Advantages

• It is a renewable source of energy.
• No greenhouse gas emissions are created.
• It is a reliable energy source; water is constantly flowing.
• Hydro plants are flexible in terms of controlling the flow of water to meet demand.
• The lakes or reservoirs created by dams can be used for recreational purposes
• Hydro plants need little maintenance therefore are cheaper to manage than other types of power station.
• Hydropower stations are long lasting and can remain functional for up to 100 years after they are built.

Disadvantages

• Only certain locations and sites are suitable for the construction of hydroelectric power plants.
• The cost of building a power plant can be extremely high.
• Risk of flooding. Although dams are built to be incredibly strong and safe, there are risks to surrounding towns with the Banqiao Dam failure being a tragic example.
• Global warming and climate change impacts the water cycle, the weather and threatens large bodies of water which all affects the safety and stability of hydropower plants.
• Dams can cause environmental concern as riverside habitats and freshwater species are affected.
• Similarly, fish get blocked from swimming if a dam doesn’t have a fishway. This can affect their migration patterns as well as other animals that rely on fish for food.
• Siltation can occur when a dam blocks the flow of the river and silt builds up on the reservoir bed which reduces the effectiveness of the power plant. Some can only operate for 20-30 years.
• Sometimes, whole communities have to be relocated when dam construction begins which causes disruption and inconvenience to them.

Currently, around 74% of the world’s renewable energy comes from hydropower, making it the most common source of renewable energy. China is the world’s largest producer of hydropower and home to the world’s largest dam, the Three Gorges Dam on the Yangtze River. Brazil, the USA, and Canada are the other top producers of hydroelectricity around the world and although a much smaller country, nearly all electricity generated in Norway comes from hydropower.

Three Gorges Dam in China

The potential for hydropower to increase in the future is there however there are concerns for the environment that could affect the global reach and development of hydroelectric power plants. With climate change, large bodies of water are continuously under threat which poses a risk to the efficiency and future of hydropower plants and there are fewer acceptable places to build new plants. However, the development of technology could help make hydropower smarter and more efficient and the current capacity could be tripled if all available resources are harnessed.