Hydropower or water power (from Greek: ὕδωρ, "water") is power derived from the energy of falling water or fast running water, which may be harnessed for useful purposes. Since ancient times, hydropower from many kinds of watermills has been used as a renewable energy source for irrigation and the operation of various mechanical devices, such as gristmills, sawmills, textile mills, trip hammers, dock cranes, domestic lifts, and ore mills. A trompe, which produces compressed air from falling water, is sometimes used to power other machinery at a distance.
In the late 19th century, hydropower became a source for generating electricity. Cragside in Northumberland was the first house powered by hydroelectricity in 1878 and the first commercial hydroelectric power plant was built at Niagara Falls in 1879. In 1881, street lamps in the city of Niagara Falls were powered by hydropower.
Since the early 20th century, the term has been used almost exclusively in conjunction with the modern development of hydroelectric power. International institutions such as the World Bank view hydropower as a means for economic development without adding substantial amounts of carbon to the atmosphere, but dams can have significant negative social and environmental impacts.
In the Roman Empire, water-powered mills produced flour from grain, and were also used for sawing timber and stone; in China, watermills were widely used since the Han dynasty. In China and the rest of the Far East, hydraulically operated "pot wheel" pumps raised water into crop or irrigation canals.
The power of a wave of water released from a tank was used for extraction of metal ores in a method known as hushing. The method was first used at the Dolaucothi Gold Mines in Wales from 75 AD onwards, but had been developed in Spain at such mines as Las Médulas. Hushing was also widely used in Britain in the Medieval and later periods to extract lead and tin ores. It later evolved into hydraulic mining when used during the California Gold Rush.
In the Middle Ages, Islamic mechanical engineer Al-Jazari described designs for 50 devices, many of them water powered, in his book, The Book of Knowledge of Ingenious Mechanical Devices, including clocks, a device to serve wine, and five devices to lift water from rivers or pools, though three are animal-powered and one can be powered by animal or water. These include an endless belt with jugs attached, a cow-powered shadoof, and a reciprocating device with hinged valves.
In 1753, French engineer Bernard Forest de Bélidor published Architecture Hydraulique which described vertical- and horizontal-axis hydraulic machines. The growing demand for the Industrial Revolution would drive development as well.
Hydraulic power networks used pipes to carry pressurized water and transmit mechanical power from the source to end users. The power source was normally a head of water, which could also be assisted by a pump. These were extensive in Victorian cities in the United Kingdom. A hydraulic power network was also developed in Geneva, Switzerland. The world-famous Jet d'Eau was originally designed as the over-pressure relief valve for the network.
At the beginning of the Industrial Revolution in Britain, water was the main source of power for new inventions such as Richard Arkwright's water frame. Although the use of water power gave way to steam power in many of the larger mills and factories, it was still used during the 18th and 19th centuries for many smaller operations, such as driving the bellows in small blast furnaces (e.g. the Dyfi Furnace) and gristmills, such as those built at Saint Anthony Falls, which uses the 50-foot (15 m) drop in the Mississippi River.
In the 1830s, at the early peak in the US canal-building, hydropower provided the energy to transport barge traffic up and down steep hills using inclined plane railroads. As railroads overtook canals for transportation, canal systems were modified and developed into hydropower systems; the history of Lowell, Massachusetts is a classic example of commercial development and industrialization, built upon the availability of water power.
Technological advances had moved the open water wheel into an enclosed turbine or water motor. In 1848 James B. Francis, while working as head engineer of Lowell's Locks and Canals company, improved on these designs to create a turbine with 90% efficiency. He applied scientific principles and testing methods to the problem of turbine design. His mathematical and graphical calculation methods allowed the confident design of high-efficiency turbines to exactly match a site's specific flow conditions. The Francis reaction turbine is still in wide use today. In the 1870s, deriving from uses in the California mining industry, Lester Allan Pelton developed the high efficiency Pelton wheel impulse turbine, which utilized hydropower from the high head streams characteristic of the mountainous California interior.
A hydropower resource can be evaluated by its available power. Power is a function of the hydraulic head and volumetric flow rate. The head is the energy per unit weight (or unit mass) of water. The static head is proportional to the difference in height through which the water falls. Dynamic head is related to the velocity of moving water. Each unit of water can do an amount of work equal to its weight times the head.
The power available from falling water can be calculated from the flow rate and density of water, the height of fall, and the local acceleration due to gravity:
To illustrate, the power output of a turbine that is 85% efficient, with a flow rate of 80 cubic metres per second (2800 cubic feet per second) and a head of 145 metres (480 feet), is 97 Megawatts:[note 1]
Operators of hydroelectric stations will compare the total electrical energy produced with the theoretical potential energy of the water passing through the turbine to calculate efficiency. Procedures and definitions for calculation of efficiency are given in test codes such as ASME PTC 18 and IEC 60041. Field testing of turbines is used to validate the manufacturer's guaranteed efficiency. Detailed calculation of the efficiency of a hydropower turbine will account for the head lost due to flow friction in the power canal or penstock, rise in tail water level due to flow, the location of the station and effect of varying gravity, the temperature and barometric pressure of the air, the density of the water at ambient temperature, and the altitudes above sea level of the forebay and tailbay. For precise calculations, errors due to rounding and the number of significant digits of constants must be considered.
Some hydropower systems such as water wheels can draw power from the flow of a body of water without necessarily changing its height. In this case, the available power is the kinetic energy of the flowing water. Over-shot water wheels can efficiently capture both types of energy. The water flow in a stream can vary widely from season to season. Development of a hydropower site requires analysis of flow records, sometimes spanning decades, to assess the reliable annual energy supply. Dams and reservoirs provide a more dependable source of power by smoothing seasonal changes in water flow. However reservoirs have significant environmental impact, as does alteration of naturally occurring stream flow. The design of dams must also account for the worst-case, "probable maximum flood" that can be expected at the site; a spillway is often included to bypass flood flows around the dam. A computer model of the hydraulic basin and rainfall and snowfall records are used to predict the maximum flood.
Where there is a plentiful head of water it can be made to generate compressed air directly without moving parts. In these designs, a falling column of water is purposely mixed with air bubbles generated through turbulence or a venturi pressure reducer at the high-level intake. This is allowed to fall down a shaft into a subterranean, high-roofed chamber where the now-compressed air separates from the water and becomes trapped. The height of the falling water column maintains compression of the air in the top of the chamber, while an outlet, submerged below the water level in the chamber allows water to flow back to the surface at a lower level than the intake. A separate outlet in the roof of the chamber supplies the compressed air. A facility on this principle was built on the Montreal River at Ragged Shutes near Cobalt, Ontario in 1910 and supplied 5,000 horsepower to nearby mines.
Hydroelectricity is the application of hydropower to generate electricity. It is the primary use of hydropower today. Hydroelectric power plants can include a reservoir (generally created by a dam) to exploit the energy of falling water, or can use the kinetic energy of water as in run-of-the-river hydroelectricity. Hydroelectric plants can vary in size from small community sized plants (micro hydro) to very large plants supplying power to a whole country. As of 2019, the five largest power stations in the world are conventional hydroelectric power stations with dams.
Hydroelectricity can also be used to store energy in the form of potential energy between two reservoirs at different heights with pumped-storage hydroelectricity. Water is pumped uphill into reservoirs during periods of low demand to be released for generation when demand is high or system generation is low.
Other forms of electricity generation with hydropower include tidal stream generators using energy from tidal power generated from oceans, rivers, and human-made canal systems to generating electricity.
Electricity in Pakistan (Urdu: بجلی) is generated, transmitted, distributed, and retail supplied by two vertically integrated public sector utilities: Water and Power Development Authority (WAPDA) for all of Pakistan (except Karachi), and the Karachi Electric (K-Electric) for the city of Karachi and its surrounding areas. There are around 42 independent power producers (IPPs) that contribute significantly in electricity generation in Pakistan.Energy in Brazil
Brazil is the 10th largest energy consumer in the world and the largest in South America. It is an important oil and gas producer in the region and the world's second largest ethanol fuel producer. The government agencies responsible for energy policy are the Ministry of Mines and Energy (MME), the National Council for Energy Policy (CNPE), the National Agency of Petroleum, Natural Gas and Biofuels (ANP) and the National Agency of Electricity (ANEEL). State-owned companies Petrobras and Eletrobrás are the major players in Brazil's energy sector, as well as Latin America's.Energy in Egypt
This article describes the energy and electricity production, consumption and import in Egypt.Hydroelectricity
Hydroelectricity is electricity produced from hydropower. In 2015, hydropower generated 16.6% of the world's total electricity and 70% of all renewable electricity, and was expected to increase by about 3.1% each year for the next 25 years.
Hydropower is produced in 150 countries, with the Asia-Pacific region generating 33 percent of global hydropower in 2013. China is the largest hydroelectricity producer, with 920 TWh of production in 2013, representing 16.9% of domestic electricity use.
The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The hydro station consumes no water, unlike coal or gas plants. The typical cost of electricity from a hydro station larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt hour. With a dam and reservoir it is also a flexible source of electricity, since the amount produced by the station can be varied up or down very rapidly (as little as a few seconds) to adapt to changing energy demands. Once a hydroelectric complex is constructed, the project produces no direct waste, and in many cases it has a considerably lower output level of greenhouse gases than fossil fuel powered energy plants.Hydroelectricity in the United Kingdom
As of 2012, hydroelectric power stations in the United Kingdom accounted for 1.65 GW of installed electrical generating capacity, being 1.8% of the UK's total generating capacity and 18% of UK's renewable energy generating capacity. This includes four conventional hydroelectric power stations and run-of-river schemes for which annual electricity production is approximately 5,000 GWh, being about 1.3% of the UK's total electricity production. There are also pumped-storage hydroelectric power stations providing a further 2.8 GW of installed electrical generating capacity, and contributing up to 4,075 GWh of peak demand electricity annually.The potential for further practical and viable hydroelectricity power stations in the UK is estimated to be in the region of 146 to 248 MW for England and Wales, and up to 2,593 MW for Scotland.
However, by the nature of the remote and rugged geographic locations of some of these potential sites, in national parks or other areas of outstanding natural beauty, it is likely that environmental concerns would mean that many of them would be deemed unsuitable, or could not be developed to their full theoretical potential.
Interest in hydropower in the UK has been renewed in recent years due to new UK and EU targets for reductions in carbon emissions and the promotion of renewable energy power generation through commercial incentives such as the Renewable Obligation Certificate scheme (ROCs) and feed-in tariffs (FITs). Before such schemes, studies to assess the available hydro resources in the UK had discounted a large number of sites for reasons of poor economic or technological viability, but more recent studies in 2008 and 2010 by the British Hydro Association (BHA) identified a larger number of viable sites, due to improvements in the available technology and the economics of ROCs and FITSsSchemes up to 50 kW are eligible for FITs, and schemes over 5 MW are eligible for ROCs. Schemes between 50 kW and 5 MW can choose between either. The UK Government's National Renewable Energy Action Plan of July 2010 envisaged between 40 and 50 MW of new hydropower schemes being installed annually up to 2020. The most recent feedback for new hydro schemes is for 2009, and only about 15 MW of new hydropower was installed during that year.Jinping-I Dam
The Jinping-I Dam (simplified Chinese: 锦屏一级水电站; traditional Chinese: 錦屏一級水電站) also known as the Jinping-I Hydropower Station or Jinping 1st Cascade, is a tall arch dam on the Jinping Bend of the Yalong River (Yalong Jiang) in Liangshan, Sichuan, China. Construction on the project began in 2005 and was completed in 2014. Its power station has a 3,600 MW capacity to produce between 16 and 18 TW·h (billion kW·h) annually. Supplying the power station is a reservoir created by the 305-meter-tall arch dam, the tallest in the world. The project's objective is to supply energy for expanding industrialization and urbanization, improve flood protection, and prevent erosion.List of power stations in Africa
The following pages list the power stations in the Africa by country.List of power stations in Pakistan
This is a list of Power Stations in Pakistan. Pakistan had a total installed power generation capacity of over 34 GW by December 2018. However, de-rated capacity is approximately 31 GW during the year. Under China Pakistan Economic Corridor (CPEC) project, with an investment of $25 Billion, the power plants of 12,334 MW capacity would be completed on a priority basis. Pakistan has witnessed a sharp increase in electricity production of almost 11 GW in last five years bridging much needed gap between supply and demand. Pakistan has an installed electricity generation capacity of 33,836 MW in 2018. Furnace oil (16 percent), hydel (27 percent), Natural gas (12 percent), LNG (26 percent), Coal (9 percent), Renewable (Solar & Wind 5 percent) and nuclear (5 per cent) are the principal sources. In the next 10 years, peak electricity demand is expected to rise by four to five per cent, which is roughly 1,500 MW. Pakistan has a lopsided energy mix, diminishing indigenous fuel reserves, increasing circular debt and transmission hold-ups. Pakistan has almost exhausted its gas reserves. Imported oil's price hikes affect the budget and its constant supply cannot be guaranteed. Pakistan has the potential to meet these energy challenges through hydroelectric power, but there are political and environmental issues in building dams. Rationality demands reducing reliance on oil and going for alternatives. The development of alternatives does not happen overnight. Pakistan will have to rely on imported fuels for the interim period at a huge cost. LNG is difficult to import, using coal has environmental issues, using shale gas also has environmental issues attached with it, and wind power has transmission network challenges. With total estimated coal reserves of over 186bn tonnes, Pakistan ranks sixth among coal-rich countries. Yet, coal's potential has not been exploited adequately except only recently when over half dozen of coal power projects of 5GW have been completed and as many under constructionPumped-storage hydroelectricity
Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential energy of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost surplus off-peak electric power is typically used to run the pumps. During periods of high electrical demand, the stored water is released through turbines to produce electric power. Although the losses of the pumping process makes the plant a net consumer of energy overall, the system increases revenue by selling more electricity during periods of peak demand, when electricity prices are highest.
Pumped-storage hydroelectricity allows energy from intermittent sources (such as solar, wind) and other renewables, or excess electricity from continuous base-load sources (such as coal or nuclear) to be saved for periods of higher demand. The reservoirs used with pumped storage are quite small when compared to conventional hydroelectric dams of similar power capacity, and generating periods are often less than half a day.
Pumped storage is the largest-capacity form of grid energy storage available, and, as of 2017, the United States Department of Energy Global Energy Storage Database reports that PSH accounts for over 95% of all active tracked storage installations worldwide, with a total installed nameplate capacity of over 184 GW, of which about 25 GW are in the United States. The round-trip energy efficiency of PSH varies between 70%–80%, with some sources claiming up to 87%. The main disadvantage of PSH is the specialist nature of the site required, needing both geographical height and water availability. Suitable sites are therefore likely to be in hilly or mountainous regions, and potentially in areas of outstanding natural beauty, and therefore there are also social and ecological issues to overcome. Many recently proposed projects, at least in the U.S., avoid highly sensitive or scenic areas, and some propose to take advantage of "brownfield" locations such as disused mines.Renewable energy in Afghanistan
Renewable energy in Afghanistan includes biomass, hydropower, solar, and wind power. Afghanistan is a landlocked country surrounded by five other countries. With a population of less than 35 million people, it is one of the lowest energy consuming countries in relation to a global standing. It holds a spot as one of the countries with a smaller ecological footprint. Hydropower is currently the main source of renewable energy due to Afghanistan's geographical location. Its large mountainous environment facilitates the siting of hydroelectric dams (see also list of dams and reservoirs in Afghanistan) and other facets of hydro energy.The renewable energy resource potential of Afghanistan is estimated at over 300,000 MW according to the state's Ministry of Energy and Water.
The country has progressed in the last decade in becoming self sustainable with its use of energy. But it still imports significant amount of electricity from neighboring Uzbekistan, Tajikistan, Iran and Turkmenistan.Another form of renewable energy in Afghanistan is biogas. With the start of biogas, communities have begun to feel the benefits beyond that of the environment through capacity building as well.Renewable energy in Albania
Renewable energy in Albania includes biomass, geothermal, hydropower, solar, and wind energy. Albania relies mostly on hydroelectric resources, therefore, it has difficulties when water levels are low. The climate in Albania is Mediterranean, so it possesses considerable potential for solar energy production. Mountain elevations provide good areas for wind projects. There is also potentially usable geothermal energy because Albania has natural wells.Renewable energy in Bhutan
Renewable energy in Bhutan is the use of renewable energy for electricity generation in Bhutan. The renewable energy sources include hydropower.While Bhutan has seen great successes with developing its large hydropower projects through technical and financial assistance from India, little or no private sector participation with other forms of renewable energy has been evident. In part because of the Sustainable development goals, Bhutan has established a minimum goal of 20 megawatts (MW) of renewable energy product by 2025, through a mix of renewable energy technologies. Bhutan's Department of Renewable Energy helped formulate and launch its Alternative Renewable Energy Policy in order to promote in Bhutan a mix of clean Renewable Energy (RE) technologies—solar, wind, biomass, geothermal, pico/micro/mini/small hydropower plants up to 25 MW in size and waste-to-energy technologies.Renewable energy in Colombia
Colombia has 28.1 Megawatt installed capacity of renewable energy (excluding large hydropower), consisting mainly of wind power. The country has significant wind and solar resources that remain largely unexploited. According to a study by the World Bank’s Energy Sector Management Assistance Program (ESMAP), exploitation of the country’s significant wind potential alone could cover more than the country’s current total energy needs.Renewable energy in Honduras
In Honduras, there is an important potential of untapped indigenous renewable energy resources. Due to the variability of high oil prices and declining renewable infrastructure costs, such resources could be developed at competitive prices.
Currently hydropower, solar and biomass are used on a large scale for electricity generation. While the potential of large generation from hydropower and geothermal energy has been studied in detail, the potential for the development of other renewable energy resources is yet to be explored in depth.Renewable energy in Iceland
About 85% of the total primary energy supply in Iceland is derived from domestically produced renewable energy sources. This is the highest share of renewable energy in any national total energy budget.In 2016 geothermal energy provided about 65% of primary energy, the share of hydropower was 20%, and the share of fossil fuels (mainly oil products for the transport sector) was 15%. In 2013 Iceland also became a producer of wind energy.
The main use of geothermal energy is for space heating, with the heat being distributed to buildings through extensive district-heating systems. About 85% of all houses in Iceland are heated with geothermal energy.In 2015, the total electricity consumption in Iceland was 18,798 GWh. Renewable energy provided almost 100% of electricity production, with about 73% coming from hydropower and 27% from geothermal power. Most of the hydropower plants are owned by Landsvirkjun (the National Power Company) which is the main supplier of electricity in Iceland.
Iceland is the world's largest green energy producer per capita and largest electricity producer per capita, with approximately 55,000 kWh per person per year. In comparison, the EU average is less than 6,000 kWh.Renewable energy in Kazakhstan
There is enormous potential for renewable energy in Kazakhstan, particularly from wind and small hydropower plants. The Republic of Kazakhstan has the potential to generate 10 times as much power as it currently needs from wind energy alone. But renewable energy accounts for just 0.6 percent of all power installations. Of that, 95 percent comes from small hydropower projects. The main barriers to investment in renewable energy are relatively high financing costs and an absence of uniform feed-in tariffs for electricity from renewable sources. The amount and duration of renewable energy feed-in tariffs are separately evaluated for each project, based on feasibility studies and project-specific generation costs. Power from wind, solar, biomass and water up to 35 MW, plus geothermal sources, are eligible for the tariff and transmission companies are required to purchase the energy of renewable energy producers. An amendment that introduces and clarifies technology-specific tariffs is now being prepared. It is expected to be adopted by Parliament by the end of 2014. In addition, the World Bank's Ease of Doing Business indicator shows the country to be relatively investor-friendly, ranking it in 10th position for investor protection.Kazakhstan is a party to the UN Framework Convention on Climate Change (1995) and ratified the Kyoto Protocol in 2009. Kazakhstan has committed to reduce greenhouse gas emissions. Having more renewable energy in the energy balance of Kazakhstan is one of the most effective mechanisms to reduce harmful effects of the energy sector and to diversify the national power generation capacity.
To help Kazakhstan meet its goals for renewable energy generation, the European Bank for Reconstruction and Development (EBRD) is launching the Kazakhstan Renewable Energy Financing Facility (KazREFF). The KazREFF aims to provide development support and debt finance to renewable energy projects which meet required commercial, technical and environmental criteria. Renewable energy technologies supported will include solar, wind, small hydropower, geothermal, biomass, and biogas. The Facility comprises an amount of up to €50 million for financing projects together with up to €20 million of concessional finance from Clean Technology Fund (CTF), and the technical assistance funded by the Japanese government through the Japan-EBRD Cooperation Fund (JECF).Renewable energy in Nepal
Renewable energy in Nepal is a sector that is rapidly developing in Nepal.
While Nepal mainly relies on hydro electricity for its energy needs, solar and wind power is being seen as an important supplement to solve its energy crisis.
Nepal is one of three countries with the greatest increases in electricity access from 2006 to 2016, owing to grid-connected and off-grid renewables.Renewable energy in Russia
Renewable energy in Russia mainly consists of hydroelectric energy. The country is the sixth largest producer of renewable energy in the world, although it is 56th when hydroelectric energy is not taken into account. Some 179 TWh of Russia's energy production comes from renewable energy sources, out of a total economically feasible potential of 1823 TWh. 16% of Russia's electricity is generated from hydropower, and less than 1% is generated from all other renewable energy sources combined. Roughly 68% of Russia's electricity is generated from thermal power and 16% from nuclear power.While most of the large hydropower plants in Russia date from the Soviet era, the abundance of fossil fuels in the Soviet Union and the Russian Federation has resulted in little need for the development of other renewable energy sources. There are currently plans to develop all types of renewable energy, which is strongly encouraged by the Russian government. Russian Prime Minister Dmitry Medvedev has called for renewable energy to have a larger share of Russia's energy output, and has taken steps to promote the development of renewable energy in Russia since 2008.Small hydro
Small hydro is the development of hydroelectric generation facilities on a scale corresponding to river discharge and potential, and which is suitable for local community and industry, or to contribute to distributed generation in a regional electricity grid. The definition of a "small hydro" project varies based on different consideration of what should constitute bottom and top limits from country to country, but most common range, although not binding, in capacity of "small hydro" extend between 1 to 15 megawatts (MW), and can be further subdivide by scale into "mini" (<1MW), "micro" (<100kW), "pico" (<10kW). In contrast many hydroelectric projects are of enormous size, such as the generating plant at the Three Gorges Dam at 22,500 megawatts or the vast multiple projects of the Tennessee Valley Authority. In India, hydro projects up to 25 MW station capacities have been categorized as Small Hydro Power (SHP) projects.Small hydro projects may be built in isolated areas that would be uneconomic to serve from a national electricity grid, or in areas where a national grid does not exist.