Hydroelectricity, or hydroelectric power, is
electricity generated from
hydropower
Hydropower (from el, ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water to produce electricity or to power machines. This is achieved by converting the gravitational potential or kinetic energy of ...
(water power). Hydropower supplies one sixth of the world's
electricity, almost 4500
TWh in 2020, which is more than all other
renewable sources combined and also more than
nuclear power.
Hydropower can provide large amounts of
low-carbon electricity on demand, making it a key element for creating secure and clean electricity supply systems.
A hydroelectric power station that has a dam and
reservoir
A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation.
Reservoirs can be created in a number of ways, including control ...
is a flexible source, since the amount of electricity produced can be increased or decreased in seconds or minutes in response to varying electricity demand. Once a hydroelectric complex is constructed, it produces no direct waste, and almost always emits considerably less
greenhouse gas
A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
than
fossil fuel
A fossil fuel is a hydrocarbon-containing material formed naturally in the Earth's crust from the remains of dead plants and animals that is extracted and burned as a fuel. The main fossil fuels are coal, oil, and natural gas. Fossil fuels ...
-powered energy plants.
[Renewables 2011 Global Status Report, page 25, Hydropower](_blank)
'' REN21'', published 2011, accessed 2016-02-19. However, when constructed in lowland
rainforest
Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...
areas, where part of the forest is inundated, substantial amounts of greenhouse gases may be emitted.
Construction of a hydroelectric complex can have significant environmental impact, principally in loss of arable land and population displacement. They also disrupt the natural ecology of the river involved, affecting habitats and ecosystems, and siltation and erosion patterns. While dams can ameliorate the risks of flooding,
dam failure can be catastrophic.
Hydroelectricity plays a leading role in countries like Brazil, Norway and China.
but there are geographical limits and environmental issues.
Tidal power can be used in coastal regions.
History
Hydropower has been used since ancient times to grind flour and perform other tasks. In the late 18th century hydraulic power provided the energy source needed for the start of the
Industrial Revolution
The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
. In the mid-1770s, French engineer
Bernard Forest de Bélidor published ''Architecture Hydraulique'', which described vertical- and horizontal-axis hydraulic machines, and in 1771
Richard Arkwright
Sir Richard Arkwright (23 December 1732 – 3 August 1792) was an English inventor and a leading entrepreneur during the early Industrial Revolution. He is credited as the driving force behind the development of the spinning frame, known as t ...
’s combination of
water power, the
water frame, and
continuous production played a significant part in the development of the factory system, with modern employment practices. In the 1840s the
hydraulic power network
A hydraulic power network is a system of interconnected pipes carrying pressurized liquid used to transmit mechanical power from a power source, like a pump, to hydraulic equipment like lifts or motors. The system is analogous to an electrical gri ...
was developed to generate and transmit hydro power to end users.
By the late 19th century, the
electrical generator
In electricity generation, a generator is a device that converts motive power (mechanical energy) or fuel-based power (chemical energy) into electric power for use in an external electrical circuit, circuit. Sources of mechanical energy include s ...
was developed and could now be coupled with hydraulics.
The growing demand arising from the
Industrial Revolution
The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...
would drive development as well.
In 1878, the world's first hydroelectric power scheme was developed at
Cragside in
Northumberland, England, by
William Armstrong. It was used to power a single
arc lamp in his art gallery. The old
Schoelkopf Power Station No. 1, US, near
Niagara Falls, began to produce electricity in 1881. The first
Edison
Thomas Alva Edison (February 11, 1847October 18, 1931) was an American inventor and businessman. He developed many devices in fields such as electric power generation, mass communication, sound recording, and motion pictures. These invention ...
hydroelectric power station, the
Vulcan Street Plant, began operating September 30, 1882, in
Appleton, Wisconsin, with an output of about 12.5 kilowatts. By 1886 there were 45 hydroelectric power stations in the United States and Canada; and by 1889 there were 200 in the United States alone.
At the beginning of the 20th century, many small hydroelectric power stations were being constructed by commercial companies in mountains near metropolitan areas.
Grenoble
lat, Gratianopolis
, commune status = Prefecture and commune
, image = Panorama grenoble.png
, image size =
, caption = From upper left: Panorama of the city, Grenoble’s cable cars, place Saint- ...
, France held the
International Exhibition of Hydropower and Tourism, with over one million visitors. By 1920, when 40% of the power produced in the United States was hydroelectric, the
Federal Power Act was enacted into law. The Act created the
Federal Power Commission
The Federal Power Commission (FPC) was an independent commission of the United States government, originally organized on June 23, 1930, with five members nominated by the president and confirmed by the Senate. The FPC was originally created in 1 ...
to regulate hydroelectric power stations on federal land and water. As the power stations became larger, their associated dams developed additional purposes, including
flood control
Flood control methods are used to reduce or prevent the detrimental effects of flood waters."Flood Control", MSN Encarta, 2008 (see below: Further reading). Flood relief methods are used to reduce the effects of flood waters or high water level ...
,
irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been dev ...
and
navigation
Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation, ...
. Federal funding became necessary for large-scale development, and federally owned corporations, such as the
Tennessee Valley Authority (1933) and the
Bonneville Power Administration
The Bonneville Power Administration (BPA) is an American federal agency operating in the Pacific Northwest. BPA was created by an act of Congress in 1937 to market electric power from the Bonneville Dam located on the Columbia River and to con ...
(1937) were created.
Additionally, the
Bureau of Reclamation
The Bureau of Reclamation, and formerly the United States Reclamation Service, is a federal agency under the U.S. Department of the Interior, which oversees water resource management, specifically as it applies to the oversight and opera ...
which had begun a series of western US irrigation projects in the early 20th century, was now constructing large hydroelectric projects such as the 1928
Hoover Dam
Hoover Dam is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the U.S. states of Nevada and Arizona. It was constructed between 1931 and 1936 during the Great Depression and was dedicated on ...
.
The
United States Army Corps of Engineers was also involved in hydroelectric development, completing the
Bonneville Dam in 1937 and being recognized by the
Flood Control Act of 1936 as the premier federal flood control agency.
[The Evolution of the Flood Control Act of 1936, Joseph L. Arnold]
United States Army Corps of Engineers, 1988
Hydroelectric power stations continued to become larger throughout the 20th century. Hydropower was referred to as "white coal".
Hoover Dam
Hoover Dam is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the U.S. states of Nevada and Arizona. It was constructed between 1931 and 1936 during the Great Depression and was dedicated on ...
's initial power station was the world's largest hydroelectric power station in 1936; it was eclipsed by the
Grand Coulee Dam
Grand Coulee Dam is a concrete gravity dam on the Columbia River in the U.S. state of Washington, built to produce hydroelectric power and provide irrigation water. Constructed between 1933 and 1942, Grand Coulee originally had two powerho ...
in 1942. The
Itaipu Dam opened in 1984 in South America as the largest, producing , but was surpassed in 2008 by the
Three Gorges Dam in China at . Hydroelectricity would eventually supply some countries, including
Norway
Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...
,
Democratic Republic of the Congo
The Democratic Republic of the Congo (french: République démocratique du Congo (RDC), colloquially "La RDC" ), informally Congo-Kinshasa, DR Congo, the DRC, the DROC, or the Congo, and formerly and also colloquially Zaire, is a country in ...
,
Paraguay
Paraguay (; ), officially the Republic of Paraguay ( es, República del Paraguay, links=no; gn, Tavakuairetã Paraguái, links=si), is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to th ...
and
Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, with over 85% of their electricity.
Future potential
In 2021 the International Energy Agency (IEA) said that more efforts are needed to help
limit climate change. Some countries have highly developed their hydropower potential and have very little room for growth: Switzerland produces 88% of its potential and Mexico 80%.
Modernization of existing infrastructure
In 2021 the IEA said that major modernisation refurbishments are required.
Generating methods
Conventional (dams)
Most hydroelectric power comes from the
potential energy
In physics, potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.
Common types of potential energy include the gravitational potentia ...
of
dammed water driving a
water turbine and
generator. The power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the
head
A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste. Some very simple animals may ...
. A large pipe (the "
penstock") delivers water from the
reservoir
A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation.
Reservoirs can be created in a number of ways, including control ...
to the turbine.
Pumped-storage
This method produces electricity to supply high peak demands by moving water between
reservoir
A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation.
Reservoirs can be created in a number of ways, including control ...
s at different elevations. At times of low electrical demand, the excess generation capacity is used to pump water into the higher reservoir, thus providing
demand side response
In economics, demand is the quantity of a good that consumers are willing and able to purchase at various prices during a given time. The relationship between price and quantity demand is also called the demand curve. Demand for a specific item ...
.
When the demand becomes greater, water is released back into the lower reservoir through a turbine. In 2021 pumped-storage schemes provided almost 85% of the world's 190 GW of
grid energy storage
Grid energy storage (also called large-scale energy storage) is a collection of methods used for energy storage on a large scale within an electrical power grid. Electrical energy is stored during times when electricity is plentiful and inexp ...
and improve the daily
capacity factor of the generation system. Pumped storage is not an energy source, and appears as a negative number in listings.
Run-of-the-river
Run-of-the-river hydroelectric stations are those with small or no reservoir capacity, so that only the water coming from upstream is available for generation at that moment, and any oversupply must pass unused. A constant supply of water from a lake or existing reservoir upstream is a significant advantage in choosing sites for run-of-the-river.
Tide
A
tidal power station makes use of the daily rise and fall of ocean water due to tides; such sources are highly predictable, and if conditions permit construction of reservoirs, can also be
dispatchable to generate power during high demand periods. Less common types of hydro schemes use water's
kinetic energy or undammed sources such as undershot
water wheel
A water wheel is a machine for converting the energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a wheel (usually constructed from wood or metal), with a number of blades or buck ...
s. Tidal power is viable in a relatively small number of locations around the world.
Sizes, types and capacities of hydroelectric facilities
Large facilities
The largest power producers in the world are hydroelectric power stations, with some hydroelectric facilities capable of generating more than double the installed capacities of the current
largest nuclear power stations.
Although no official definition exists for the capacity range of large hydroelectric power stations, facilities from over a few hundred
megawatts are generally considered large hydroelectric facilities.
Currently, only seven facilities over () are in operation worldwide, see table below.
Small
Small hydro is
hydroelectric power on a scale serving a small community or industrial plant. The definition of a small hydro project varies but a generating capacity of up to 10
megawatts (MW) is generally accepted as the upper limit. This may be stretched to and in
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...
and the United States.
Small hydro stations may be connected to conventional electrical distribution networks as a source of low-cost renewable energy. Alternatively, small hydro projects may be built in isolated areas that would be uneconomic to serve from a grid, or in areas where there is no national electrical distribution network. Since small hydro projects usually have minimal reservoirs and civil construction work, they are seen as having a relatively low environmental impact compared to large hydro. This decreased environmental impact depends strongly on the balance between stream flow and power production.
Micro
Micro hydro means
hydroelectric power installations that typically produce up to of power. These installations can provide power to an isolated home or small community, or are sometimes connected to electric power networks. There are many of these installations around the world, particularly in developing nations as they can provide an economical source of energy without purchase of fuel. Micro hydro systems complement
photovoltaic
Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially us ...
solar energy systems because in many areas water flow, and thus available hydro power, is highest in the winter when solar energy is at a minimum.
Pico
Pico hydro is
hydroelectric power generation of under . It is useful in small, remote communities that require only a small amount of electricity. For example, the 1.1 kW
Intermediate Technology Development Group Pico Hydro Project in Kenya supplies 57 homes with very small electric loads (e.g., a couple of lights and a phone charger, or a small TV/radio). Even smaller turbines of 200-300 W may power a few homes in a developing country with a drop of only . A Pico-hydro setup is typically
run-of-the-river, meaning that dams are not used, but rather pipes divert some of the flow, drop this down a gradient, and through the turbine before returning it to the stream.
Underground
An
underground power station is generally used at large facilities and makes use of a large natural height difference between two waterways, such as a waterfall or mountain lake. A tunnel is constructed to take water from the high reservoir to the generating hall built in a cavern near the lowest point of the water tunnel and a horizontal tailrace taking water away to the lower outlet waterway.
Calculating available power
A simple formula for approximating electric power production at a hydroelectric station is:
where
*
is
power (in
watts)
*
(
eta) is the coefficient of efficiency (a unitless, scalar coefficient, ranging from 0 for completely inefficient to 1 for completely efficient).
*
(
rho
Rho (uppercase Ρ, lowercase ρ or ; el, ρο or el, ρω, label=none) is the 17th letter of the Greek alphabet. In the system of Greek numerals it has a value of 100. It is derived from Phoenician letter res . Its uppercase form uses the sa ...
) is the
density of water (~1000
kg/
m3)
*
is the
volumetric flow rate
In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol (sometimes ). I ...
(in m
3/s)
*
is the
mass flow rate (in kg/s)
*
(
Delta h) is the change in height (in
meters)
*
is
acceleration due to gravity (9.8 m/s
2)
Efficiency is often higher (that is, closer to 1) with larger and more modern turbines. Annual electric energy production depends on the available water supply. In some installations, the water flow rate can vary by a factor of 10:1 over the course of a year.
Properties
Advantages
Flexibility
Hydropower is a flexible source of electricity since stations can be ramped up and down very quickly to adapt to changing energy demands.
[ Hydro turbines have a start-up time of the order of a few minutes.] Although battery power is quicker its capacity is tiny compared to hydro. It takes less than 10 minutes to bring most hydro units from cold start-up to full load; this is quicker than nuclear and almost all fossil fuel power. Power generation can also be decreased quickly when there is a surplus power generation. Hence the limited capacity of hydropower units is not generally used to produce base power except for vacating the flood pool or meeting downstream needs. Instead, it can serve as backup for non-hydro generators.
High value power
The major advantage of conventional hydroelectric dams with reservoirs is their ability to store water at low cost for dispatch later as high value clean electricity. In 2021 the IEA estimated that the "reservoirs of all existing conventional hydropower plants combined can store a total of 1 500 terawatt-hours (TWh) of electrical energy in one full cycle" which was "about 170 times more energy than the global fleet of pumped storage hydropower plants". Battery storage capacity is not expected to overtake pumped storage during the 2020s. When used as peak power to meet demand, hydroelectricity has a higher value than baseload power and a much higher value compared to intermittent energy sources such as wind and solar.
Hydroelectric stations have long economic lives, with some plants still in service after 50–100 years. Operating labor cost is also usually low, as plants are automated and have few personnel on site during normal operation.
Where a dam serves multiple purposes, a hydroelectric station may be added with relatively low construction cost, providing a useful revenue stream to offset the costs of dam operation. It has been calculated that the sale of electricity from the Three Gorges Dam will cover the construction costs after 5 to 8 years of full generation. However, some data shows that in most countries large hydropower dams will be too costly and take too long to build to deliver a positive risk adjusted return, unless appropriate risk management measures are put in place.
Suitability for industrial applications
While many hydroelectric projects supply public electricity networks, some are created to serve specific industrial enterprises. Dedicated hydroelectric projects are often built to provide the substantial amounts of electricity needed for aluminium
Aluminium (aluminum in AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately o ...
electrolytic plants, for example. The Grand Coulee Dam
Grand Coulee Dam is a concrete gravity dam on the Columbia River in the U.S. state of Washington, built to produce hydroelectric power and provide irrigation water. Constructed between 1933 and 1942, Grand Coulee originally had two powerho ...
switched to support Alcoa aluminium in Bellingham, Washington, United States for American World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
airplanes before it was allowed to provide irrigation and power to citizens (in addition to aluminium power) after the war. In Suriname
Suriname (; srn, Sranankondre or ), officially the Republic of Suriname ( nl, Republiek Suriname , srn, Ripolik fu Sranan), is a country on the northeastern Atlantic coast of South America. It is bordered by the Atlantic Ocean to the north ...
, the Brokopondo Reservoir was constructed to provide electricity for the Alcoa aluminium industry. New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 List of islands of New Zealand, smaller islands. It is the ...
's Manapouri Power Station was constructed to supply electricity to the aluminium
Aluminium (aluminum in AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately o ...
smelter
Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including Silver mining#Ore processing, silver, iron-making, iron, copper extracti ...
at Tiwai Point.
Reduced CO2 emissions
Since hydroelectric dams do not use fuel, power generation does not produce carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
. While carbon dioxide is initially produced during construction of the project, and some methane is given off annually by reservoirs, hydro has one of the lowest lifecycle greenhouse gas emissions for electricity generation. The low greenhouse gas
A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
impact of hydroelectricity is found especially in temperate climates. Greater greenhouse gas emission impacts are found in the tropical regions because the reservoirs of power stations in tropical regions produce a larger amount of methane than those in temperate areas.
Like other non-fossil fuel sources, hydropower also has no emissions of sulfur dioxide, nitrogen oxides, or other particulates.
Other uses of the reservoir
Reservoirs created by hydroelectric schemes often provide facilities for water sports, and become tourist attractions themselves. In some countries, aquaculture in reservoirs is common. Multi-use dams installed for irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been dev ...
support agriculture with a relatively constant water supply. Large hydro dams can control floods, which would otherwise affect people living downstream of the project. Managing dams which are also used for other purposes, such as irrigation
Irrigation (also referred to as watering) is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been dev ...
, is complicated.
Disadvantages
In 2021 the IEA called for "robust sustainability standards for all hydropower development with streamlined rules and regulations".
Ecosystem damage and loss of land
Large reservoirs associated with traditional hydroelectric power stations result in submersion of extensive areas upstream of the dams, sometimes destroying biologically rich and productive lowland and riverine valley forests, marshland and grasslands. Damming interrupts the flow of rivers and can harm local ecosystems, and building large dams and reservoirs often involves displacing people and wildlife.[ The loss of land is often exacerbated by ]habitat fragmentation
Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological processes ...
of surrounding areas caused by the reservoir.
Hydroelectric projects can be disruptive to surrounding aquatic ecosystem
An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...
s both upstream and downstream of the plant site. Generation of hydroelectric power changes the downstream river environment. Water exiting a turbine usually contains very little suspended sediment, which can lead to scouring of river beds and loss of riverbanks. Since turbine gates are often opened intermittently, rapid or even daily fluctuations in river flow are observed.
Drought and water loss by evaporation
Drought and seasonal changes in rainfall can severely limit hydropower. Water may also be lost by evaporation.
Siltation and flow shortage
When water flows it has the ability to transport particles heavier than itself downstream. This has a negative effect on dams and subsequently their power stations, particularly those on rivers or within catchment areas with high siltation. Siltation can fill a reservoir and reduce its capacity to control floods along with causing additional horizontal pressure on the upstream portion of the dam. Eventually, some reservoirs can become full of sediment and useless or over-top during a flood and fail.
Changes in the amount of river flow will correlate with the amount of energy produced by a dam. Lower river flows will reduce the amount of live storage in a reservoir therefore reducing the amount of water that can be used for hydroelectricity. The result of diminished river flow can be power shortages in areas that depend heavily on hydroelectric power. The risk of flow shortage may increase as a result of climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
.[Frauke Urban and Tom Mitchell 2011]
Climate change, disasters and electricity generation
. London: Overseas Development Institute and Institute of Development Studies
The Institute of Development Studies (IDS) is a think tank affiliated with the University of Sussex in Brighton, England, and based on its campus in Falmer, East Sussex. It delivers research and teaching in the area of development studies, an ...
One study from the Colorado River in the United States suggest that modest climate changes, such as an increase in temperature in 2 degree Celsius resulting in a 10% decline in precipitation, might reduce river run-off by up to 40%.[ ]Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
in particular is vulnerable due to its heavy reliance on hydroelectricity, as increasing temperatures, lower water flow and alterations in the rainfall regime, could reduce total energy production by 7% annually by the end of the century.[
]
Methane emissions (from reservoirs)
Lower positive impacts are found in the tropical regions. In lowland rainforest
Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...
areas, where inundation of a part of the forest is necessary, it has been noted that the reservoirs of power plants produce substantial amounts of methane. This is due to plant material in flooded areas decaying in an anaerobic environment and forming methane, a greenhouse gas
A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
. According to the World Commission on Dams report, where the reservoir is large compared to the generating capacity (less than 100 watts per square metre of surface area) and no clearing of the forests in the area was undertaken prior to impoundment of the reservoir, greenhouse gas emissions from the reservoir may be higher than those of a conventional oil-fired thermal generation plant.
In boreal reservoirs of Canada and Northern Europe, however, greenhouse gas emissions are typically only 2% to 8% of any kind of conventional fossil-fuel thermal generation. A new class of underwater logging operation that targets drowned forests can mitigate the effect of forest decay.
Relocation
Another disadvantage of hydroelectric dams is the need to relocate the people living where the reservoirs are planned. In 2000, the World Commission on Dams estimated that dams had physically displaced 40-80 million people worldwide.
Failure risks
Because large conventional dammed-hydro facilities hold back large volumes of water, a failure due to poor construction, natural disasters or sabotage can be catastrophic to downriver settlements and infrastructure.
During Typhoon Nina in 1975 Banqiao Dam in Southern China failed when more than a year's worth of rain fell within 24 hours (see 1975 Banqiao Dam failure). The resulting flood resulted in the deaths of 26,000 people, and another 145,000 from epidemics. Millions were left homeless.
The creation of a dam in a geologically inappropriate location may cause disasters such as 1963 disaster at Vajont Dam in Italy, where almost 2,000 people died.[References may be found in the list of Dam failures.]
The Malpasset Dam failure in Fréjus
Fréjus (; ) is a commune in the Var department in the Provence-Alpes-Côte d'Azur region in Southeastern France. In 2019, it had a population of 54,458.
It neighbours Saint-Raphaël, effectively forming one urban agglomeration. The north of ...
on the French Riviera
The French Riviera (known in French as the ; oc, Còsta d'Azur ; literal translation " Azure Coast") is the Mediterranean coastline of the southeast corner of France. There is no official boundary, but it is usually considered to extend fro ...
(Côte d'Azur), southern France, collapsed on December 2, 1959, killing 423 people in the resulting flood.
Smaller dams and micro hydro facilities create less risk, but can form continuing hazards even after being decommissioned. For example, the small earthen embankment Kelly Barnes Dam failed in 1977, twenty years after its power station was decommissioned, causing 39 deaths.[Toccoa Flood](_blank)
USGS Historical Site, retrieved 02sep2009
Comparison and interactions with other methods of power generation
Hydroelectricity eliminates the flue gas emissions from fossil fuel combustion
Flue gas is the gas exiting to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. Quite often, the flue gas refers to the combustion exhaust gas produced a ...
, including pollutants such as sulfur dioxide
Sulfur dioxide (IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic activ ...
, nitric oxide
Nitric oxide (nitrogen oxide or nitrogen monoxide) is a colorless gas with the formula . It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its che ...
, carbon monoxide
Carbon monoxide ( chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...
, dust, and mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
in the coal
Coal is a combustible black or brownish-black sedimentary rock, formed as stratum, rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen ...
. Hydroelectricity also avoids the hazards of coal mining
Coal mining is the process of extracting coal from the ground. Coal is valued for its energy content and since the 1880s has been widely used to generate electricity. Steel and cement industries use coal as a fuel for extraction of iron from ...
and the indirect health effects of coal emissions. In 2021 the IEA said that government energy policy
Energy policy is the manner in which a given entity (often governmental) has decided to address issues of energy development including energy conversion, distribution and use as well as reduction of greenhouse gas emissions in order to contri ...
should "price in the value of the multiple public benefits provided by hydropower plants".
Nuclear power
Nuclear power is relatively inflexible; although it can reduce its output reasonably quickly. Since the cost of nuclear power is dominated by its high infrastructure costs, the cost per unit energy goes up significantly with low production. Because of this, nuclear power is mostly used for baseload. By way of contrast, hydroelectricity can supply peak power at much lower cost. Hydroelectricity is thus often used to complement nuclear or other sources for load following. Country examples where they are paired in a close to 50/50 share include the electric grid in Switzerland, the Electricity sector in Sweden and to a lesser extent, Ukraine and the Electricity sector in Finland.
Wind power
Wind power goes through predictable variation
Variation or Variations may refer to:
Science and mathematics
* Variation (astronomy), any perturbation of the mean motion or orbit of a planet or satellite, particularly of the moon
* Genetic variation, the difference in DNA among individual ...
by season, but is intermittent
Intermittency is a behavior of dynamical systems: regular alternation of phases of apparently periodic and chaotic dynamics.
Intermittent or intermittency may also refer to:
*Intermittent river or stream, the one that ceases to flow every year or ...
on a daily basis. Maximum wind generation has little relationship to peak daily electricity consumption, the wind may peak at night when power isn't needed or be still during the day when electrical demand is highest. Occasionally weather patterns can result in low wind for days or weeks at a time, a hydroelectric reservoir capable of storing weeks of output is useful to balance generation on the grid. Peak wind power can be offset by minimum hydropower and minimum wind can be offset with maximum hydropower. In this way the easily regulated character of hydroelectricity is used to compensate for the intermittent nature of wind power. Conversely, in some cases wind power can be used to spare water for later use in dry seasons.
An example of this is Norway's trading with Sweden, Denmark, the Netherlands, Germany and the UK. Norway is 98% hydropower, while its flatland neighbors have wind power. In areas that do not have hydropower, pumped storage serves a similar role, but at a much higher cost and 20% lower efficiency.
World hydroelectric capacity
The ranking of hydroelectric capacity is either by actual annual energy production or by installed capacity power rating. In 2015 hydropower generated 16.6% of the worlds total electricity and 70% of all renewable electricity.
Hydropower is produced in 150 countries, with the Asia-Pacific region generated 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. Brazil
Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...
, Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...
, New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 List of islands of New Zealand, smaller islands. It is the ...
, Norway
Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...
, Paraguay
Paraguay (; ), officially the Republic of Paraguay ( es, República del Paraguay, links=no; gn, Tavakuairetã Paraguái, links=si), is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to th ...
, Austria
Austria, , bar, Östareich officially the Republic of Austria, is a country in the southern part of Central Europe, lying in the Eastern Alps. It is a federation of nine states, one of which is the capital, Vienna, the most populous ...
, Switzerland
; rm, citad federala, links=no). Swiss law does not designate a ''capital'' as such, but the federal parliament and government are installed in Bern, while other federal institutions, such as the federal courts, are in other cities (Bellinzon ...
, Venezuela
Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in ...
and several other countries have a majority of the internal electric energy production from hydroelectric power. Paraguay
Paraguay (; ), officially the Republic of Paraguay ( es, República del Paraguay, links=no; gn, Tavakuairetã Paraguái, links=si), is a landlocked country in South America. It is bordered by Argentina to the south and southwest, Brazil to th ...
produces 100% of its electricity from hydroelectric dams and exports 90% of its production to Brazil and to Argentina. Norway
Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...
produces 96% of its electricity from hydroelectric sources. Large plants tend to be built by governments, so most capacity (70%) is publicly owned, even though most plants (nearly 70%) are owned and operated by the private sector, as of 2021.
A hydroelectric station rarely operates at its full power rating over a full year; the ratio between annual average power and installed capacity rating is the capacity factor. The installed capacity is the sum of all generator nameplate power ratings.
Economics
The weighted average cost of capital is a major factor.
See also
* Energy transition
The energy transition is the process of downshifting fossil fuels and re-developing whole systems to operate on low carbon energy sources. More generally, an energy transition is a significant structural change in an energy system regarding ...
* Hydraulic engineering
* International Hydropower Association
* International Rivers
* List of energy storage power plants
* List of hydroelectric power station failures
This is a list of major hydroelectric power station failures due to damage to a hydroelectric power station or its connections. Every generating station trips from time to time due to minor defects and can usually be restarted when the defect h ...
* List of largest power stations
* List of renewable energy topics by country and territory
* Lists of hydroelectric power stations
* Marine current power – electricity from sea currents
* National Hydropower Association (US)
References
External links
*
Hydropower Reform Coalition
Interactive demonstration on the effects of dams on rivers
European Small Hydropower Association
IEC TC 4: Hydraulic turbines
(International Electrotechnical Commission - Technical Committee 4) IEC TC 4 portal with access to scope, documents an
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