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Falling or flowing water can be used to power machinary or make electricity. Key benefits to hydropower are that it is a renewable energy source and does not diminish air quality, unlike many other energy sources. Hydropower can also help utilities meet peak electricity demand when water stored behind a resevoir is suddenly released. This "on-demand" process can make up for variances in wind or solar power performance and increase the electricity grid's reliability.
There are three types of hydropower systems:
1. Impoundment: An impoundment facility uses a dam to store river water in a reservoir. The most common type of hydroelectric power plant is an impoundment facility. An impoundment facility, typically a large hydropower system, uses a dam to store river water in a reservoir. Water released from the reservoir flows through a turbine to activate a generator and produce electricity. Large hydropower systems are usually impoundment systems
2. Diversion (sometimes called run-of-river): This facility channels a portion of a river through a canal or penstock. It may not require the use of a dam; instead, the force of the water's current turns turbines to create electricity.
3. Pumped storage: When the demand for electricity is low, a pumped storage facility stores energy by pumping water from a lower reservoir to an upper reservoir. Low-cost off-peak electric power is used to run the pumps. During periods of high electrical demand, the water is released back to the lower reservoir and passes through turbines to generate electricity. This process allows utilities to balance their loads and meet peak demand energy demand.
The US Department of Energy defines the size of hydropower facilities as follows:
1. Large hydropower: facilities that have a capacity of more than 30 megawatts. As a point of comparison, the smallest large-scale windfarm in Indiana has a capacity of 131 MW.
2. Small hydropower: facilities that have a capacity of 100 kilowatts to 30 megawatts
3. Microhydropower: facailities that have a capacity of up to 100 kilowatts. This could power a home or farm.
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