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Hydroelectric Power Definition

The Dalles Dam in Oregon

Hydro energy is called in many ways today, we have hydropower, hydroelectricity, water power or simply hydroelectric energy, but all these different names actually refer to the same renewable energy resource represented by the power of the water.

Water is considered a renewable resource because it can be used over and over again, and even if it evaporates in the clouds, it returns back to the earth through rain.

This is the water cycle that occurs every day on our planet and is renewed by the Sun.

Hydroelectric Power Definition

Hydro energy represents the kinetic energy of the falling water or of the fast moving water specific to streams, which is turned into mechanical energy (the spinning turbines) and then into clean electricity using a generator.

Water sustains all the life forms on the planet today, but is also a great free and clean source of power, which can be used over and over again to produce clean electricity for our energy needs.

Mankind uses the kinetic power of the falling or fast moving water in many ways today to generate electricity.

The known history of Hydroelectric Power

The first use of the hydro energy started in ancient times when water mills were first used for grain grinding.

The power of the water was also used to drive different mechanical processes such as: milling (grinding), hammering or rolling, etc., and also to pump water.

Hydro energy is used today to produce clean electricity in hydroelectric power plants.

Types of Hydroelectric Power Plants

Hydro energy or hydroelectricity is produced today using two main types of hydroelectric power plants such as: dams and run of river.

1. Dams

Hydro dams rely on the potential energy present in the stored water to generate electricity.

A dam is a barrier in front of the water, which is made of a very thick wall of concrete built to raise the level of the water and control its flow.

The dam creates elevation and when the water is released starts flowing from the dam down to the turbine due to the presence of gravity.

hydroelectric power plant

Hydroelectric power plant built on a fast river,

The kinetic energy of the falling water spins the turbine to generate electricity.

Some dams use an additional reservoir located at the base where water is stored to be pumped to the reservoir located higher.

These dams are called ‘pumped storage hydro’ and they release the water stored in the higher reservoir to generate electricity when the demand is high in the grid.

2. Run of river hydro

Run of river hydro also uses turbines and generators to produce electricity.

However, these hydroelectric power plants rely on the natural flow rates of the rivers, and they use only a small volume of water that is diverted from the water stream and used to spin the turbines and generate electricity.

Run of river hydroelectric power plants are subject to natural water variability, which makes them to be more intermittent in terms of energy generation compared to the dams.

All the hydroelectric power plants listed above are using the same technology to generate electricity.

They use the kinetic energy of the falling water (dams) or the fast moving water (run of river), which is turned into mechanical energy (the spinning turbine), and then into clean electricity due to the fact that a powerful electromagnetic generator is connected to the rotating turbine.

Hydroelectric Power Plants Classified After the Energy Output

There are various sizes of hydroelectric power plants producing hydro energy today.

1. Large Hydro

Refers to hydroelectric power plants with an energy output higher than 30 MW (megawatt).

Are included here the largest dams on the planet today, some of them having an output of thousands of MV and providing clean electricity for millions of people.

Hoover Dam located in the Black Canyon of the Colorado River has an energy output of 2,080 MW (2,08 GW) and provides clean electricity for 1,3 million people in Nevada and Arizona.

2. Small Hydro

Refers to hydroelectric power plants with an energy output between 100 KW and 30 MW.

3. Micro Hydro

Refers to the smaller hydroelectric power plants with an output of under 100 KW.

Hydro energy is the most developed renewable energy source on the planet today because it has the highest share among all renewables in the energy mix of the planet.

In the energy mix of the U.S., hydro energy has a share of 7%, which is the highest among all renewables.

Advantages of Hydroelectric Energy

Hydro energy has several benefits today.

1. Is a cost-competitive form of clean electricity

Hydro energy is considered a cost-competitive form of clean electricity today because compared with the other forms of electricity is cheaper (the electricity produced by a hydroelectric power plant is cheaper than the electricity produced by other energy sources).

The price of the electricity produced by the hydroelectric power plant is cheaper because the power station has low maintenance costs and the technology is designed to work properly for several decades.

2. Hydro energy is more reliable than other forms of renewable energy

A hydroelectric power plant using a dam generates electricity day and night because it controls the water flow that makes the turbines to spin.

The pumped storage hydroelectric power plants are using two different reservoirs of water (one being located at a higher altitude), which means that they produce electricity when needed.

Being a pretty constant source of clean electricity, hydro energy is more reliable compared to the other forms of renewable energy such as solar and wind power.

3. Can be paired with other sources of energy

Being a pretty reliable source of electricity, hydro energy can be used as base-load of power that makes a good pair with intermittent sources of energy such as solar and wind power.

4. Can become a reliable supply of water for communities

The huge volume of water stored by a dam can become a good sources of water for the local community if needed.

5. Can help with flood control

The same volume of water stored by the dam can help with flood control in the area of the hydroelectric power plant.

Disadvantages of Hydroelectric Energy

Hydro energy has many benefits, but also some drawbacks, mostly related to the environmental impact in the areas where the hydroelectric power plants are located.

1. Creating a dam on a river has a major impact on the local environment

Building a dam for a hydroelectric power plant will have a major impact on the local environment because will change the wildlife habitats, will block the passages used by fishes and often the people in riverside communities need to move out of their homes.

2. Dam failures can lead to catastrophic floods

People living downstream the dam can face catastrophic floods if the dam suffers a failure.

In many cases when the dam suffered a failure, people have lost their lives due to the catastrophic floods that invaded the downstream area.

3. Pretty high initial building costs

Building the dam and the hydroelectric power plant involves a huge volume of work, resources and workforce.

The construction of the dam and the hydroelectric power plant can take years and can involve huge financial resources because the land where the dam will be built needs to be cleared from all the trees, and people have to move and make room for the future dam.

4. Greenhouse gases can be released

When the concrete dam is built, the large number of vehicles involved in the project and the large volume of cement used will increase the level of harmful emissions in the area.

If the team that prepares the land for the future dam fails to completely clean all the trees and plants from the area, due to the decaying process that occurs after flooding the area with water, a large quantity of greenhouse gas emissions will be released into the atmosphere (methane being one of them).

Final conclusion

Hydro energy is one of the future sources of clean energy for mankind (at least if we don’t manage to master a massive source of clean, free and renewable energy such as the nuclear fusion).

For the current period and the next decades, hydro energy represents a reliable and affordable source of clean electricity, which is very needed in order to phase out the dirty fossil fuels used as energy sources.

Article written by:

I am a writer and reporter for the clean energy sector, I cover climate change issues, new clean technologies, sustainability and green cars. Danny Ovy

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