Hydroelectricity
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.
[3] However, when constructed in lowland rainforest areas, where part of the forest is inundated, substantial amounts of greenhouse gases may be emitted.
[4] Construction of a hydroelectric complex can have significant environmental impact, principally in loss of arable land and population displacement.
Meanwhile, globally, hydropower generation increased by 70 TWh (up 2%) in 2022 and remains the largest renewable energy source, surpassing all other technologies combined.
In the mid-1700s, French engineer Bernard Forest de Bélidor published Architecture Hydraulique, which described vertical- and horizontal-axis hydraulic machines, and in 1771 Richard Arkwright'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.
The first Edison hydroelectric power station, the Vulcan Street Plant, began operating September 30, 1882, in Appleton, Wisconsin, with an output of about 12.5 kilowatts.
[13] At the beginning of the 20th century, many small hydroelectric power stations were being constructed by commercial companies in mountains near metropolitan areas.
As the power stations became larger, their associated dams developed additional purposes, including flood control, irrigation and navigation.
Hydroelectricity would eventually supply some countries, including Norway, Democratic Republic of the Congo, Paraguay and Brazil, with over 85% of their electricity.
Because environmental permitting and construction times are long, they estimate hydropower potential will remain limited, with only an additional 40 GW deemed possible in the accelerated case.
[23] This method produces electricity to supply high peak demands by moving water between reservoirs at different elevations.
In 2021 pumped-storage schemes provided almost 85% of the world's 190 GW of grid energy storage[2] and improve the daily capacity factor of the generation system.
[24] 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.
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.
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.
[citation needed] Hydropower is a flexible source of electricity since stations can be ramped up and down very quickly to adapt to changing energy demands.
[2] 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.
[39] 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.
[39] 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.
Dedicated hydroelectric projects are often built to provide the substantial amounts of electricity needed for aluminium electrolytic plants, for example.
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.
[2] 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.
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.
[56] Brazil 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.
In lowland rainforest 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.
[59] 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.
[62] The Malpasset Dam failure in Fréjus on the French Riviera (Côte d'Azur), southern France, collapsed on December 2, 1959, killing 423 people in the resulting flood.
For example, the small earthen embankment Kelly Barnes Dam failed in 1977, twenty years after its power station was decommissioned, causing 39 deaths.
[64] Hydroelectricity eliminates the flue gas emissions from fossil fuel combustion, including pollutants such as sulfur dioxide, nitric oxide, carbon monoxide, dust, and mercury in the coal.
