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Jai Ganesh

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Hydroelectric power

Hydroelectric power

Gist

Hydroelectric power is electricity generated by harnessing the energy of flowing or falling water, which spins turbines connected to generators. It is a renewable energy source that converts the kinetic and potential energy of water into electricity, which is then transmitted to the grid. While it is efficient and reliable, its construction can be expensive and have significant environmental impacts.

Hydroelectricity is power generated by harnessing the energy of flowing or falling water, which spins turbines connected to generators to produce electricity. This process converts the potential energy of water stored at a height into kinetic energy as it flows downhill, which then turns turbines to create electricity. It is a form of renewable energy, as it uses the natural water cycle without depleting water resources, and is a reliable source with zero greenhouse gas emissions from power generation itself. 

Summary

Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). 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.

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.

In 2021, global installed hydropower electrical capacity reached almost 1,400 GW, the highest among all renewable energy technologies. 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.

China added 24 GW in 2022, accounting for nearly three-quarters of global hydropower capacity additions. Europe added 2 GW, the largest amount for the region since 1990. Meanwhile, globally, hydropower generation increased by 70 TWh (up 2%) in 2022 and remains the largest renewable energy source, surpassing all other technologies combined.

Details

Hydroelectric power is electricity produced from generators driven by turbines that convert the potential energy of falling or fast-flowing water into mechanical energy. In the early 21st century, hydroelectric power was the most widely utilized form of renewable energy; in 2019 it accounted for more than 18 percent of the world’s total power generation capacity.

In the generation of hydroelectric power, water is collected or stored at a higher elevation and led downward through large pipes or tunnels (penstocks) to a lower elevation; the difference in these two elevations is known as the head. At the end of its passage down the pipes, the falling water causes turbines to rotate. The turbines in turn drive generators, which convert the turbines’ mechanical energy into electricity. Transformers are then used to convert the alternating voltage suitable for the generators to a higher voltage suitable for long-distance transmission. The structure that houses the turbines and generators, and into which the pipes or penstocks feed, is called the powerhouse.

Hydroelectric power plants are usually located in dams that impound rivers, thereby raising the level of the water behind the dam and creating as high a head as is feasible. The potential power that can be derived from a volume of water is directly proportional to the working head, so that a high-head installation requires a smaller volume of water than a low-head installation to produce an equal amount of power. In some dams, the powerhouse is constructed on one flank of the dam, part of the dam being used as a spillway over which excess water is discharged in times of flood. Where the river flows in a narrow steep gorge, the powerhouse may be located within the dam itself.

In most communities the demand for electric power varies considerably at different times of the day. To even the load on the generators, pumped-storage hydroelectric stations are occasionally built. During off-peak periods, some of the extra power available is supplied to the generator operating as a motor, driving the turbine to pump water into an elevated reservoir. Then, during periods of peak demand, the water is allowed to flow down again through the turbine to generate electrical energy. Pumped-storage systems are efficient and provide an economical way to meet peak loads.

In certain coastal areas, such as the Rance River estuary in Brittany, France, hydroelectric power plants have been constructed to take advantage of the rise and fall of tides. When the tide comes in, water is impounded in one or more reservoirs. At low tide, the water in these reservoirs is released to drive hydraulic turbines and their coupled electric generators (see tidal power).

Falling water is one of the three principal sources of energy used to generate electric power, the other two being fossil fuels and nuclear fuels. Hydroelectric power has certain advantages over these other sources. It is continually renewable owing to the recurring nature of the hydrologic cycle. It does not produce thermal pollution. (However, some dams can produce methane from the decomposition of vegetation under water.) Hydroelectric power is a preferred energy source in areas with heavy rainfall and with hilly or mountainous regions that are in reasonably close proximity to the main load centers. Some large hydro sites that are remote from load centers may be sufficiently attractive to justify the long high-voltage transmission lines. Small local hydro sites may also be economical, particularly if they combine storage of water during light loads with electricity production during peaks. Many of the negative environmental impacts of hydroelectric power come from the associated dams, which can interrupt the migrations of spawning fish, such as salmon, and permanently submerge or displace ecological and human communities as the reservoirs fill. In addition, hydroelectric dams are vulnerable to water scarcity. In August 2021 Oroville Dam, one of the largest hydroelectric power plants in California, was forced to shut down due to historic drought conditions in the region.

Additional Information

Water can be a powerful force in nature. Its power can be seen in floods that uproot trees or heard in the roar of a waterfall. That power, called waterpower or hydropower, can be used as an alternative energy source. Unlike fossil fuels, it cannot be used up. When waterpower is harnessed, it can be used to create electricity, or hydroelectricity.

Hydroelectric power plants are usually located in dams that are built across rivers. In a dam water is collected at a higher elevation and is then led downward through large pipes to a lower elevation. The falling water causes wheels called water turbines to rotate. The rotating turbines run machines called generators, which produce electricity.

Oceans can also be used to create hydroelectricity. Those waterpower sources are known as tidal power and wave power. Tidal power is created during the tide, when the water level along the oceanic coast changes. Wave power is harnessed by the up-and-down motion of waves.

Waterpower has been in use for thousands of years. The waterwheel was probably invented in the 1st century bce. Ancient Romans used it to grind grain. It was widely used throughout the Middle Ages and into modern times. Water turbines were first introduced in 1827. They were used originally for irrigation. Today, water turbines are used almost exclusively to generate electric power.

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