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What is hydropower? And how are they produced?


Hydroelectricity is renewable electrical energy that results from converting hydropower into electricity. The kinetic energy of the water current, natural or resulting from the difference in level, is converted into mechanical energy by a hydraulic turbine, and then into electrical energy by a synchronous electric generator.

In 2019AD, the installed capacity of hydropower plants was 1,308 gigawatts, producing about 4306 terawatt hours per year, or 70% of the world’s renewable energy production and 15.6% of the world’s electricity production.

Advantages and disadvantages of hydropower

Among its advantages:

  • Its renewable character.
  • Low operating cost.
  • Reduced greenhouse gas emissions.
  • The storage capacity of its tanks contributes to offset the changes in demand.

Among its shortcomings:

It has social and environmental impacts, especially in the case of dams in non-mountainous areas. Population displacement, possibly flooding arable lands, fragmentation and modification of water and terrestrial ecosystems, silt blockage, etc.

Major producers of hydropower:

In 2019 AD, the main producers were China (30.2%), Canada (9.2%), Brazil (9.0%) and the United States (6.4%).

What technology is hydropower produced?

Electrical energy is produced by converting the kinetic energy of water into electrical energy, by means of hydraulic turbines coupled with an electric generator. As for dams by accumulation, the amount of available energy depends on the water reserve of the dam, its size, natural inputs and losses during the fall and its height. As for river runoff dams, the amount of energy produced is directly related to the flow (m3 / s, m3 / h, m3 / d, m3 / year).

There are four main types of turbines:

The most suitable type of turbine is chosen by calculating the specific speed referred to as ns Pelton turbine, which is suitable for high drop with a bucket wheel, invented by Lester Allan Pelton in the year 1879 AD. It was designed for heights exceeding 200 meters, and in 1868AD Francis installed a turbine for medium or even high heads, with single or double thrusts.

The Kaplan turbine was invented in 1912 and is well suited for both low and high flow rates, with a propeller-type wheel, such as a boat. Victor Kaplan has developed a pusher whose blades can be steered according to usable flow rates, and a well turbine, uses the movement of air caused by the movement of waves through a vertical tube. It is the principle set forth by Alan Wells.

The history of hydropower

  • Humans have used paddle wheeled water mills to grind wheat for more than two thousand years. The Alpine watch and paper industry benefited greatly from the abundance of torrents that descended into the valleys.
  • In the nineteenth century, paddle wheels were used to generate electricity and were then replaced by turbines.
  • In 1869 AD, engineer Aristide Bergis used it on a two hundred meter fall in Lancey to turn shredders and wood graters to make paper pulp.
  • Since the twentieth century, technological advances in Swiss hydropower have led to intense stock market speculation on hydroelectric companies.
  • In the 1920s, he witnessed a rapid expansion of electricity in France, with electricity production from hydroelectricity increasing eightfold thanks to the first dams.

Hydroelectric power stations

There are three main forms of hydroelectric power generation:

Gravitational power plants:

It is so named because the water flows into its reservoirs or its water intake comes mainly from gravitational currents, such as running river power plants or hydroelectric power plants in the lake.

Standby hydraulic power stations:

They are pumped power transmission stations or pumped storage power stations, where a reversing turbine pumps water from a lower basin to an upper basin. It often also includes the gravitational fraction. Transmission is a temporary transfer (pumping during the basin in demand from the electricity produced by the basic equipment and the production of electricity by turbines during the peak.

Tidal power stations:  

It is a hydroelectric power station that uses tidal energy to generate electricity. An example is the Rance Tidal Power Plant, which was commissioned in 1966, to compensate for the reduced electricity production in Brittany. It is a station that uses the energy of the movement of the seas, whether that is the alternating tidal flow, or the permanent marine currents or the movement of waves.

Electrical power transmission stations

Production of electrical energy


The power transmission stations have two basins, an upper basin and a basin, between which a reverse hydroelectric machine is placed: the hydraulic part can work in addition to a pump, such as a turbine and an electrical part, as well as a motor or alternator (synchronous machine). In accumulation mode, the machine uses the energy available on the grid to raise water from the lower basin to the upper basin and in the production mode, the machine converts the potential gravitational energy of the water into electricity.

The efficiency (the ratio between the electricity consumed and the electricity produced) is about 82%. This type of factory has economic importance when the marginal production costs vary widely during a certain period of time (day, week, season, year..etc). They make it possible to store gravitational energy in periods when these costs are low, in order to save it in periods when they are high.

Water is the source of storable hydropower:

That is, the production of electricity can be stored during peak hours for use in times of need, that is, when the demand is greater on the public electricity distribution network, it can also be stored during weekends to be covered with turbines during the week, or even stored in the spring during the thaw to be used in the winter.

Hydropower production is limited by the flow and available water reserves. These reserves depend on the climate, on the pumping carried out at the source of reservoirs (for example for irrigation) and on the size of the water reservoirs (dams).

Installed hydroelectric power in the world

The installed hydropower capacity in the world reached 1,308 GW in 2019, an increase of 1.2%, and the production of hydropower was estimated at 4,306 TWh, an increase of 2.5%. The new additions reached 15.6 gigawatts in 2019, compared to 21.8 gigawatts in 2018. And the countries that have installed the largest capacities are:

  • Brazil: 4.92 GW of new installations.
  • China: 4.17 GW and Laos: 1.89 GWh, China largely dominates the ranking of countries with installed capacity of 356.4 GW, or 27.2% of the world’s total.

Total Pumped Storage Power Plants:

  • In China there are 158 gigawatts.
  • In Japan, 27.6 gigawatts.
  • In the United States is 22.9 gigawatts.

Hydropower and its contribution to electricity production

The share of hydropower in production is less than its share in installed capacity, as it increased 15.9% of the world’s electricity production in 2017, compared to 20.9% in 1973AD, but it plays a particularly important role in ensuring an immediate balance between production and consumption of electricity. Because of the flexibility of the hydroelectric power it can be mobilized in a few minutes, because electrical energy is difficult to store in large quantities.

Installed capacity of stored power plants:

Pumped installed capacity was 157.994 MW, of which 30,290 MW in China (19.2%), 27,637 MW in Japan (17.5%) and 22,855 MW in the United States (14.5%). These three countries account for 51.2% of the world total.

Largest hydroelectric producers:

The largest hydropower producers in 2017 were China (28.3%), Canada (9.4%), Brazil (8.8%) and the United States (7.7%). But the place of this renewable energy in national electricity production is very variable, with five countries emerging with a share of 95.7% in Norway, 62.9% in Brazil, 59.6% in Canada, 44.8% in Vietnam and 39.7% in Sweden.

Hydropower is a renewable energy

Hydropower is a renewable energy, unlike oil or natural gas. Some research raises doubts about the greenhouse gas balance of hydroelectric systems.

And the bacteriological activity in dam waters, especially in tropical regions, and the release of large quantities of methane , and in dam projects, the production of hydropower is often complementary, and it has other purposes such as:

  • Flood control and its consequences.
  • Improve the ability to navigation in the waterway.
  • Providing canal water.
  • Composition of stocks of water for irrigation and tourism.

Since the construction of the Three Gorges Dam on the Yangzi River in China in 2014 AD, this country has been a pioneer in hydropower production and in Asia, but also in Africa and South America. The economic stakes for such construction, as well as the fight against global warming, find themselves outweighing other environmental risks.

The effects of using hydropower on the environment and humanity

Environmental impacts vary according to the type and size of the structure that has been put in place: they are low when it comes to exploiting natural waterfalls, ocean currents and waves, but they become very dangerous when it comes to building dams and artificial water reservoirs. As it is possible for the agricultural lands and villages to disappear (which leads to the displacement of the population) as well as disrupt the movement of animals, and in general the entire surrounding ecosystem.

Some notable examples of the significant environmental impact of hydropower production include:

  • In 1982, the Seven Falls on the border between Brazil and Paraguay were destroyed by the Itaipu Dam, which was the largest dam in the world when it came into operation. Whereas, within two weeks of storing the artificial water of the dam, it inundated the waterfalls. Then the federal government of Brazil blew up the mountains that remained above the water, destroying one of the world’s greatest natural wonders.
  • And also the displacement of people to build the largest dam in China at the Three Gorges, which is a case of large-scale forced migration.
  • The Belo Monte Dam project has come under heavy criticism from American Indians including Leader Raoni and environmentalists because the dam will cause deforestation of 500 square kilometers of Amazonian forest.
  • In the twentieth century, according to the International Commission on Large Dams, 40 to 80 million people were displaced through the construction of reservoirs. This number continues to grow because since 2000 AD, hydropower has witnessed the largest expansion in its history (while 300 million refugees could also be displaced due to rising sea levels in the coming decades, according to updated projections in 2019).

Projections of the Intergovernmental Hydropower Authority

Most of the projections of the Intergovernmental Panel on Climate Change indicate that hydropower will reach from 1,700 to 2,400 gigawatts by the year 2050 AD, that is, double in 30 years, which implies manufacturing an additional 190,000 kilometers of waterways (dams are planned in all Major tropical rivers that are still free.



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