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Modern Definition Of Hydropower

Hoover Dam

Hydropower is another form of renewable energy that can become a main source of power in the future, when fossil fuels will become history, being replaced by free and clean sources of energy with zero emissions.

What is Hydropower?

Hydropower is the energy obtained by converting the kinetic energy of the flowing water into mechanical energy and then into clean electricity using underwater turbines and powerful generators.

The energy of the falling or fast moving water is considered renewable because is produced by gravity (the falling water) and by the water cycle on the planet (moving water).

The water cycle is renewable because water evaporates into clouds and recycles back to Earth as precipitation.

The water cycle is constantly recharging and can be used to generate free, affordable and clean electricity along the way.

Both gravity and the water cycle on the planet are considered renewable because they are continuous, so they become this way permanent sources of renewable energy for mankind.

How is Hydropower Produced Today?

People have been using the energy of the moving water for thousands of years on our planet (to pump water, grind grain, etc.), but today, we are mostly using this energy to produce clean electricity in hydroelectric power plants.

Hydropower or hydroelectric power is produced using the energy of the falling or fast-moving water.

A hydroelectric power plant that uses a dam, will release water located at a higher elevation to fall at a lower elevation where the facility uses turbines and generators to turn the kinetic energy of the falling water into clean electricity without releasing harmful emissions.

A hydroelectric power plant that uses flowing water in rivers and streams, will not require the presence of a dam to store water, because it channels a portion of the river thorough a channel or pipe to reach the power plant where it spins the turbines and produces electricity with the help of generators.

Types of Hydroelectric Power Plants – Advantages and Disadvantages

There are several ways hydropower technology can generate clean electricity today:

1. Impoundment – Hydroelectric Power Plants Using a Dam

To generate electricity using a hydro dam, we require a large volume of water (a water reservoir) and an elevation difference between the outlet and inlet sides of the dam.

The largest dam on the planet

The largest dam on the planet – Three Gorges Dam, China,

The difference in elevation is called ‘the head’, and the headwater is located upstream of the dam, while the tailwater is located downstream (the dam separates the headwater and tailwater).

How is electricity generated by a hydro dam?

Water from the reservoir enters the penstock (a sluice, gate or intake structure used to control the water flow) through the main inlets of the dam.

The water will travel down through penstocks until it reaches the hydroelectric turbines located within the powerhouse.

The water passing over each turbine will make the turbine spin (mechanical energy) and this energy will be transferred to the generators to be converted into electrical energy.

The electricity produced by the hydro dam will be distributed through a large transformer into the national grid.

The entire process is ended when water used to generate electricity flows from the powerhouse through draft tubes until reaches the tailwater.

This process is continuous, which means that the hydro dam is a constant and reliable source of clean electricity for the national grid.

Advantages of Hydroelectric Power Plants Using a Dam

1. Hydroelectric dams represent a constant and reliable source of clean electricity for our civilization.

2. Hydroelectric power plants using large reservoirs of water, generate renewable energy without releasing harmful emissions in the atmosphere and without producing any waste products.

3. This type of power plant is also very efficient (in terms of energy production), is cheap to operate, and can work for decades.
Some hydro power plants have been in operation for over 100 years.

Disadvantages of Hydroelectric Power Plants Using a Dam

1. The construction of the dam can disrupt local habitats, due to large changes required for the creation of the dam (these adverse effects are felt both by people, animals and plants).

2. The dam itself represents a huge financial investment (very high initial costs compared to other types of power plants).

3. The risk of failure associated with hydro dams is not always small, and the consequences can be catastrophic for both people and habitats located downstream the dam.

2. Diversion – Hydroelectric Power Plants Using a Small Canal to Channel the River Water

These hydroeletric power plants are also called run-of-river power plants, and they represent a smaller form of hydroelectric development.

They can use the entire river or a small volume of water diverted from the river.

A pipe (penstock) transports the diverted water downhill using the force of gravity and generating the pressure required to spin the turbine and produce electricity using a generator.

The generators are connected to a substation where the energy produced by the power plant is transmitted to the main grid.

The water is then returned to the river, so no water will be stored (these hydro power plants do not require the construction of a dam).

Advantages of Run-of-river Power Plants

1. Run-of-river power plants do not require the construction of a large water reservoir and a dam, which massively reduces the initial investment with the power plant.

2. The diverted water is used to generate electricity and after that is returned to the river, which preserves the natural downstream flow patterns.

3. Run-of-river power plants have a significantly smaller environmental footprint compared to traditional hydro power plants using a large reservoir to store water.

Disadvantages of Run-of-river Power Plants

1. Run-of-river power plants are smaller forms of hydroelectric development (compared to hydro dams), and not any river is suited for this type of power plants.

2. During drought periods, when the volume of water in the river is reduced, the power plant will no longer be able to produce power.

3. Pumped Storage Hydropower – Reversible Hydroelectric Power Plants

This type of hydroelectric power plant works like a very large and powerful battery.

To charge the battery, water is pumped back up to a reservoir located at a higher elevation during the night, when the energy consumption in the grid is reduced.

During the day, when the energy demand in the grid is growing, the water stored in the reservoir is released to produce electricity.

Pumped storage hydro power plants use reversible generators that spin in both directions to be able to pump water in the reservoir located at a higher elevation, and also to generate energy when water is released back into the reservoir located below.

Advantages of Pumped Storage Hydropower

1. Water in the upper reservoir (potential energy) can be stored for weeks or even months without losing its capacity to generate energy.

2. Pumped storage plants can come online very quickly and they are mainly used for peak power demands in the grid.

Disadvantages of Pumped Storage Hydropower

1. There are environmental factors to consider when building an upper reservoir for a pumped storage power plant.

2. Is more and more difficult to build pumped storage power plants today, because these power plants require certain geological features that could be found only in remote areas where protected wildlife would be affected by the presence of the water reservoirs.

4. Small Hydro – Micro-hydroelectric Power Systems for Homes, Farms, Ranches

Small hydro refers to a hydroelectric power plant that has a generation capacity between 100 KW and 30 MW.

These hydro power plants consist of installations with a pretty wide variety of designs and layouts, using different materials and equipment to maximize the amount of energy produced on a small scale.

Upgrading the Hydro Technology

About 8% of all the electricity in the United States is generated from hydropower, which means that hydroelectricity is the most developed renewable energy source in the country.

Older hydro facilities in the U.S. require an upgrade to increase the efficiency of the turbines and generators used in the clean energy production process.

Operators of neighboring hydro facilities work together to optimize the energy production across whole river systems instead of only concentrating on only one facility like before.

There are more than 80,000 dams in the U.S. today, but only about 3% of them are used for clean power generation.

This means that the country has a big opportunity to increase its generation capacity from hydropower by using the already built dams.


New technologies are also aiming to make hydropower a renewable energy source that is more environmentally friendly, by reducing the adverse impacts on fish (fish ladders will let the fish swim around dams) and their natural habitats.

Article written by:

I write about the renewable energy sector, electric cars and climate change issues. I love nature and good food, so I travel all over the world to see new places and meet new people. Magda Savin

1 Comment

  1. Md. Moniruzzaman

    I would like to see the world using 100% renewable energy.
    Unlimited source of energy ocean tides can take a big role.

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