Hydroelectric generators use moving water to produce electricity, often by damming a river and directing water through turbines. They are a primary source of clean, renewable energy, accounting for 20% of the world’s electricity. Run-of-river generators and tidal flow generators are alternative methods. Pumped storage systems can increase generator capacity. Dams can have environmental consequences but also provide flood control and irrigation. Hydroelectric generators do not produce greenhouse gases but may create some pollutants during construction.
Hydroelectric generators can transform the energy of moving water into usable electricity. This is most commonly accomplished by damming a river and then directing the water through one or more turbines. As the water turns the turbines, they in turn drive electric generators. While damming rivers can have environmental impacts, hydroelectric generators are generally considered a primary source of clean, renewable energy. About 20% of the world’s electricity comes from hydroelectric generators, which accounts for the majority of electricity generated from renewable sources.
Most hydroelectric generators are part of dam installations that use reservoirs, although there are many other ways to tap hydroelectric power. Run-of-river generators operate in much the same way as traditional dam and reservoir generators, although they typically have little or no dock capacity. Instead of creating an artificial blockage of flow and elevation change, river power generation utilizes the natural water flow and characteristics of the river. In order for a run-of-the-river plant to generate constant electricity, the river it is installed on typically must have a consistently high flow of water.
The movement of water in daily tidal flows can also be harnessed by hydroelectric generators. This is usually achieved by installing turbines in a tidal area which are driven by the daily fluctuation of the tide. Tanks can sometimes be built into these systems, allowing for additional generator capacity in high demand situations.
Another way that additional hydroelectric generator capacity can be added to a system is through pumped storage. This system can be used in conjunction with a traditional dam-type hydroelectric plant, or in a standalone capacity. During times when electricity demand in an area is low, water can be pumped up to high-altitude reservoirs. Then, when demand increases, the stored water can be used to increase generator capacity. These pumped-storage systems ultimately generate less energy than is used to fill reservoirs, but in some areas, pumped-storage storage for hydroelectric generation can be a key method of grid energy storage.
Some hydroelectric power generation can have environmental consequences, particularly when large dams are involved. A potentially undesirable consequence of some dams is the way they can effectively carve out a river’s ecosystem. While some dams include fish ladders to allow certain species to travel upriver to spawn, other fish may not be able to use them. This can interfere with the life cycle of some species or reduce the biodiversity of some populations.
Dams can also have positive effects, such as providing flood control and a reliable source for irrigation. The tanks can also be used for aquaculture and recreation. Unlike most ways to generate electricity, hydroelectric generators do not produce greenhouse gases such as carbon dioxide (CO2). Some CO2 and other pollutants can be created in the construction of the generators, although they are usually very clean once in operation.
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