By Kiran Mahurkar, Sidwell Friends School
What is Hydroelectric Energy?
Hydroelectric energy is any method that uses the movement of water to generate electricity for use. It can also be referred to as hydropower, hydroelectric power, and hydroelectricity.
How Does it Work?
The most common method of generating hydroelectricity is by placing turbines, devices that turn rotational energy into electricity through the use of magnets, in a place where water is flowing quickly, usually accompanied by rotors. There are three main methods that use this process to generate hydroelectricity. In the simplest method, known as “run-of-the-river,” turbines are placed in a river, usually on a dam that only partially confines water. As the water flows through the turbines, electricity is generated. However, there is little to no control over the flow of water and therefore, in times of drought when the water level is lower, less power is generated, while after heavy rains, more pressure leads to more power. This variability is solved through the use of dams. In a dam-limited system, a river is completely blocked. This leads to the creation of a large lake just upstream of the dam. Floodgates allow water to flow downstream and out of the lake. As it goes through the dam, the water usually falls down a steep drop and then passes through electrical turbines. By controlling the size of the floodgates, power plant engineers can control the flow of water and the amount of electricity generated. The final main method of hydroelectric energy generation, tidal turbines, uses turbines implanted into the water in a tidal region, such as at the mouth of a bay or near a shoreline, to generate power. While this method offers less control than the dammed-water plant method, it is extremely predictable in its output and does not have as large of an impact on the environment.
Environmental Impact
Because it generates force from the effect of gravity on water, hydropower is renewable. Additionally, unlike nuclear, coal or gas energy, hydropower does not consume any fuel, and the hydropower plant instead produces all the power it needs, meaning that the water is not “used up.” However, the generation of hydroelectric energy does affect local environments to varying degrees. Both dammed-water and run-of-the-river hydropower plants involve blocking off some or all of a river. This often harms the local environment. In the Pacific Northwest, as several rivers have been dammed to create power stations, salmon populations have drastically decreased in number. While unsure at first of what had caused this, scientists soon realized that because of the dams, the fish were unable to migrate upriver to breed and were therefore failing to lay eggs. This has led to the introduction of fish ladders, small waterways that allow fish to bypass a dam moving upstream. The creation of a large upstream lake in different methods of hydroelectric energy generation also causes many environmental issues. In addition to displacing anyone who lives in the area, these large upstream lakes also destroy ecosystems, permanently flooding some areas and changing the downstream topography drastically.
Usage
According to a World Bank report, hydropower currently accounts for approximately 16 percent of the world’s electric power supply, and provides power to 48 U.S. states. In addition, according to the International Energy Agency, the total amount of electricity generated by hydroelectric plants has been steadily increasing since 1990.
Fun Facts
- Hydroelectric dams are usually made of concrete, and because of the large volume of concrete being used, can take years to fully dry and harden.
- The first devices to harness the power of flowing water for human use were mills.
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