Hydroelectric Energy


Hydroelectric or hydroelectric energy is that which originates from the use of water that falls from a certain height. The falling water is driven by turbines that create a rotational movement that transforms it into mechanical energy, and all this energy passes through generators that transform it into electrical energy.

History of hydropower

This type of energy has been exploding for years. This energy has been exploited for centuries. Farmers in ancient Greece used watermills to grind wheat into flour. Located in rivers, water mills collect moving water in buckets located around the mill. The kinetic energy of moving water makes the mill turn and is converted into the mechanical energy that moves it.

At the end of the 19th century, hydroelectric power became a source of electricity generation. The first hydroelectric power station was built at Niagara Falls in 1879. In 1881, the city lights of Niagara Falls were powered by hydroelectric power. In 1882, the world’s first hydroelectric plant began operating in the United States in Appleton, Wisconsin.

A classic hydroelectric plant is a system that consists of three parts: a plant in which electricity is produced, a dam that can be opened and closed to control the passage of water, and a tank in which water can be stored. The water behind the dam flows through an inlet and presses against the turbine blades, causing them to move. The turbine turns a generator to produce electricity. The amount of electricity that can be generated depends on the distance the water reaches and the amount of water that passes through the system. Electricity can be carried over long electrical cables to homes, factories, and businesses.

Hydropower supplies almost a fifth of the world’s electricity. China, Canada, Brazil, the United States and Russia were the five largest producers of this type of energy in 2004. One of the largest hydroelectric plants in the world is located in the Three Canyons, on the Yangtze River, in China. The reservoir for these facilities began to fill in 2003, but the plant is not expected to be fully operational until 2009. The dam is 2.3 kilometers wide and 185 meters high.

The largest hydroelectric plant in the United States is adjacent to the Grand Coulee Dam on the Columbia River in northern Washington state. More than 70 percent of the electricity produced in this state comes from hydroelectric plants.

Hydropower is the cheapest source of electricity today. This is because once the dam has been built and the technical equipment installed, the energy source (moving water) is free. This source of energy is cleaned and renewed each year through de-icing and precipitation.

In addition, this type of energy is easily accessible, since engineers can control the amount of water that passes through the turbines to produce electricity as needed. Additionally, reservoirs can offer recreational opportunities, such as bathing and boating areas.

However, damming rivers can destroy or affect flora and fauna and other natural resources. Some fish, such as salmon, may find it impossible to swim upstream to spawn. The latest technologies, such as fish ladders, help salmon pass through dams and enter spawning grounds upstream, but the presence of hydroelectric dams changes their migration patterns and harms fish populations. Hydropower plants can also reduce the level of dissolved oxygen in water, which is detrimental to river habitats.

Hydropower generation methods

Conventional dams:

Most of the hydroelectric energy comes from the potential energy of the captured water that drives a turbine and an electric generator. The power extracted from the water depends on the volume and the difference in height between the source and the water outlet. This difference in height is called the hydraulic head. A large tube or gate carries the water from the tank to the turbine.

Pumped storage:

This method produces electricity to meet peak demand, moving water between reservoirs at different heights. In times of low electricity demand, excess generation capacity is used to pump water to the upper reservoir. When demand increases, the water is returned to the lower tank through a turbine. Pumped storage systems are currently the most commercially important means of large-scale energy storage in the grid and improve the daily capacity factor of the generation system. Pumped storage is not a source of energy and appears as a negative number in listings.

Arroyo del Río:

Cable hydroelectric plants are those with little or no reservoir capacity, so that only upstream water is available for generation at that time, and any excess supply is lost unused. A constant supply of water from an upstream lake or reservoir is a significant advantage in choosing river flow sites. In the United States, river hydropower could provide 60,000 megawatts (80,000,000 hp), about 13.7% of total use in 2011, if continuously available.16


A tidal power plant, also called tidal power, takes advantage of the daily rise and fall of tidal water; These sources are highly predictable and, if conditions allow the construction of reservoirs, they can also be used to generate power during periods of high demand. These types of hydroelectric schemes, which are less common, use kinetic energy from water or from undamaged sources, such as water wheels below the surface. Tidal power is feasible in a relatively small number of places around the world, since it is necessary that the difference in heights reached by high and low tides is important. In Britain, there are eight sites that can be developed, with the potential to generate 20% of the electricity used in 2012.

Disadvantages of hydropower

Damage to ecosystems and loss of land:

The large reservoirs associated with traditional hydromassage immersion are the result of extensive areas upstream from the dam, sometimes destroying biologically rich and productive forests and low coastal valleys, swamps, and grasslands. The dam stops the flow of rivers and can damage local ecosystems, and the construction of large dams and reservoirs often involves the displacement of people and wildlife.2 Land loss is often exacerbated by the fragmentation of the habitat of the surrounding areas caused by the reservoir.

Hydropower projects can be detrimental to the surrounding aquatic ecosystems, both upstream and downstream of the plant site. Hydroelectric power generation disrupts the downstream environment. The water coming out of a turbine generally contains very little suspended sediment, which can cause erosion in river beds and loss of river banks. As turbine gates are often open intermittently, rapid or even daily fluctuations are observed in river flow.

Loss of water through evaporation:

A study conducted in 2011 by the United States National Renewable Energy Laboratory concluded that hydroelectric plants in the United States consumed between 1,425 and 18,000 gallons of water per megawatt hour (gallons / MWh) of electricity generated, through losses by evaporation in the reservoir. The average loss was 4,491 gal / MWh, which is greater than the loss of generation technologies using cooling towers, including the concentration of solar energy (865 gal / MWh for the CSP channel 786 gal / MWh CSP Tower), coal ( 687 gal / MWh), nuclear (672 gal / MWh) and natural gas (198 gal / MWh). When there are multiple uses of reservoirs, such as water supply, recreation, and flood control, all evaporation from the reservoir is attributed to energy production.

Sedimentation and low flow:

When water flows, it has the ability to carry heavier particles than those found downstream. This has a negative effect on dams and subsequently their dams, especially those on rivers or in catchments with high levels of sedimentation. Sedimentation can fill a reservoir and reduce its ability to control flooding, and cause additional horizontal pressure in the upstream part of the dam. Eventually some reservoirs can be filled with sediment and become useless or excessive during a flood.

Changes in the amount of river flow are correlated with the amount of energy produced by a dam. Decreasing river flows will reduce the amount of water stored in a reservoir, thus reducing the amount of water that can be used for hydroelectricity. The result of decreasing river flow may be the cause of energy shortages in areas that are highly dependent on hydroelectric power. The risk of flow shortages may increase as a result of climate change. A study of the Colorado River in the United States suggests that moderate climate change, such as a 2 degree Celsius increase in temperature, resulting in a 10% decrease in precipitation, could reduce river runoff by as much as 40% . 42 Brazil is vulnerable due to its heavy dependence on hydroelectricity, as rising temperatures, decreasing water flow, and changes in precipitation patterns can reduce total energy production by 7% per year by the end of anus. Century

Container Methane Emissions:

The least positive impacts are found in tropical regions, as mill reservoirs in tropical regions have been observed to produce substantial amounts of methane. This is because plant material in flooded areas decomposes in an anaerobic environment and forms methane, a greenhouse gas. According to the World Commission on Dams report, when the reservoir is large compared to generating capacity (less than 100 watts per square meter of flooded area) and there has been no clearing of forests in the area before it started the construction of the reservoir, the greenhouse gas emissions of the reservoir may be higher than those of a conventional oil-based thermal power plant.

However, in the boreal fields of Canada and northern Europe, greenhouse gas emissions are generally only 2% to 8% of any conventional fossil fuel thermal generation. A new type of underwater exploration operation targeting flooded forests can mitigate the effect of forest decay.


Another disadvantage of hydroelectric plants is the need to relocate the people who live in the places where the reservoirs are planned. In 2000, the World Commission on Dams estimated that dams had physically displaced between 40 and 80 million people worldwide.

Risks of failure:

Because large hydroelectric plants with conventional dams retain large volumes of water, failures due to poor construction, natural disasters, or sabotage can be catastrophic for downstream settlements and infrastructure. During Typhoon Nina in 1975, the Banqiao Dam failed in southern China, when more than a year of rain fell in 24 hours. The resulting floods killed 26,000 people and another 145,000 due to the epidemic. Millions of people were left homeless. Creating a dam in a geologically unsuitable location can cause disasters like the one in 1963 at the Vajont Dam in Italy, where nearly 2,000 people were killed.

The failure of the Malpasset Dam at Fréjus, on the French Riviera in southern France, caused it to collapse on December 2, 1959, where 423 people died in the resulting flood. Smaller dams and microhydroelectrics create fewer risks, but can present ongoing risks even after they have been taken out of service. For example, the small Kelly Barnes Dam failed in 1977, twenty years after its plant entered service, causing 39 deaths.

Advantages of hydroelectric power


Hydropower is a flexible source of electricity, as stations can be increased and decreased very quickly to adapt to changing energy demands. Hydraulic turbines have a start-up time of the order of a few minutes. It takes 60-90 seconds to transport a fully loaded cold start unit. This is much shorter than for gas turbines or steam plants. Power generation can also be reduced rapidly when there is a surplus of power generation. Therefore, the limited capacity of hydroelectric units is not generally used to produce basic energy, except to dislodge the well from the flood or to meet subsequent needs. Instead, it serves as a backup for non-hydro generators.

Low cost / high power:

The main advantage of conventional hydroelectric dams with reservoirs is their ability to store water at low cost for later shipment as high value clean electricity. The average cost of electricity for a hydroelectric plant of more than 10 megawatts is 3 to 5 cents per kilowatt hour. When used as the maximum energy to meet demand, hydropower has a higher value than basic energy and a much higher value compared to intermittent energy sources.

Hydroelectric plants have a long economic life and some of them continue to operate after 50 to 100 years. Labor costs are also generally low, as the plants are automated and are understaffed on site during normal operation.

When a reservoir is multi-purpose, a hydroelectric plant can be added at a relatively low construction cost, providing a useful revenue stream to offset the reservoir’s operating costs. It has been calculated that the sale of electricity from the Three Gorges Dam will cover construction costs after 5 to 8 years of total generation. Furthermore, some data shows that in most countries, large hydropower plants will be very expensive and take a long time to build to provide a positive risk-adjusted return unless appropriate risk management measures are implemented.

Suitability for industrial applications:

Although many hydroelectric projects provide public power grids, some are designed to serve specific industrial companies. Dedicated hydroelectric projects are often built to provide the substantial amounts of electricity needed for electrolytic aluminum plants, for example: the Grand Coulee Dam was moved to support Alcoa’s aluminum in Bellingham, Washington, United States, for American aircraft from WWII, before it was allowed to provide irrigation and power to citizens after the war. In Suriname, the Brokopondo reservoir was built to supply electricity to Alcoa’s aluminum industry.

Reduction of CO2 emissions:

Because hydroelectric plants do not use fuel, power generation does not produce carbon dioxide. While carbon dioxide is initially produced during project construction and methane is emitted annually by dams, hydropower in specific cases in the Nordic countries has the lowest greenhouse gas emissions in the life cycle of the energy generated. Compared to fossil fuels that generate an equivalent amount of electricity, hydropower displaced three billion tons of CO2 emissions in 2011. Compared to fossil fuels that generate an equivalent amount of electricity, hydropower has saved three billion tons of CO2 emissions.

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