Small hydro is the development of hydroelectric power on a scale suitable for local community and industry, or to contribute to distributed generation in a regional electricity grid. Exact definitions vary, but a "small hydro" project is less than 50 megawatts (MW), and can be further subdivide by scale into "mini" (<1MW), "micro" (<100 kW), "pico" (<10 kW). 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.
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. A PSH system 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.
Hydroelectricity, or hydroelectric power, is electricity generated from hydropower. Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, 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 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 than fossil fuel-powered energy plants. However, when constructed in lowland rainforest areas, where part of the forest is inundated, substantial amounts of greenhouse gases may be emitted.
Run-of-river hydroelectricity (ROR) or run-of-the-river hydroelectricity is a type of hydroelectric generation plant whereby little or no water storage is provided. Run-of-the-river power plants may have no water storage at all or a limited amount of storage, in which case the storage reservoir is referred to as pondage. A plant without pondage is subject to seasonal river flows, so the plant will operate as an intermittent energy source. Conventional hydro uses reservoirs, which regulate water for flood control, dispatchable electrical power, and the provision of fresh water for agriculture.
The Baihetan Dam is a large hydroelectric dam on the Jinsha River, an upper stretch of the Yangtze River in Sichuan and Yunnan provinces, in southwest China. The dam is a 289-meter-tall double-curvature arch dam with a crest elevation of 827 m, and a width of 72 m at the base and 13 m at the crest. It is considered to be the last large hydropower project in China after a series of projects starting with the Three Gorges Dam. It is also the second largest hydropower plant in the world. The hydropower station is equipped with 16 hydro-generating units each having a capacity of 1 billion Watts, the world's largest turbines. All hydro-generating units of the Baihetan hydropower station became fully operational on 20 December 2022.
According to the International Hydropower Association, Canada is the fourth largest producer of hydroelectricity in the world in 2021 after the United States, Brazil, and China. In 2019, Canada produced 632.2 TWh of electricity with 60% of energy coming from Hydroelectric and Tidal Energy Sources).
There are almost 200 large dams in Myanmar. Myanmar (Burma) has a large hydroelectric power potential of 39,000 megawatts (52,000,000 hp), although the economical exploitable potential is about 37,000 megawatts (50,000,000 hp). Between 1990 and 2002, the country tripled its installed capacity of hydro plants, increasing from 253 megawatts (339,000 hp) to 745 megawatts (999,000 hp). Total installed capacity in 2010 is at least 2,449 megawatts (3,284,000 hp) MW, 6% of potential. Several large dams are planned to increase future hydro utilization.
The Lai Châu Dam is a hydroelectric dam on the Black River inaugurated on 20 December 2016 in Nậm Nhùn District, Lai Châu Province, Vietnam. The owner of the power station is Vietnam Electricity.
Renewable energy in Russia mainly consists of hydroelectric energy. Russia is rich not only in oil, gas and coal, but also in wind, hydro, geothermal, biomass and solar energy – the resources of renewable energy. Practically all regions have at least one or two forms of renewable energy that are commercially exploitable, while some regions are rich in all forms of renewable energy resources. However, fossil fuels dominate Russia’s current energy mix, while its abundant and diverse renewable energy resources play little role.
Hydropower is the most used form of renewable energy in Russia, and there is large potential in Russia for more use of hydropower. According to the International Hydropower Association Russia is the seventh largest producer of hydroelectricity in 2020. It is also second in the world for hydro potential, yet only 20% of this potential is developed. Russia is home to 9% of the world's hydro resources, mostly in Siberia and the country's far east. At the end of 2005, the generating capacity from hydroelectric sources in Russia was 45,700 MW, and an additional 5,648 MW was under construction. The World Energy Council believes that Russia has much potential for using its hydro resources, with a theoretical potential of about 2,295 TWh/yr, with 852 TWh being economically feasible.
Hydroelectricity is currently China's largest renewable energy source and the second overall after coal. According to the International Hydropower Association, China is the worlds largest producer of hydroelectricity as of 2021. China's installed hydroelectric capacity in 2021 was 390.9 GW, including 36.4 GW of pumped storage hydroelectricity capacity, up from 233 GW in 2011. That year, hydropower generated 1,300 TWh of power, an increase of 68 TWh over 2018 when hydropower generated 1,232 TWh of power, accounting for roughly 18% of China's total electricity generation.
