Hydropower: Time-tested Renewable Energy

Today, hydropower provides about 80,000 MW of capacity in the United States—enough to power more than 25 million average homes—and accounts for about 75 percent of all renewable electricity used by co-ops.
    
But how does it work? Simply, hydropower converts the natural energy of moving water to mechanical energy, using a water wheel or its modern-day equivalent, a turbine, attached to a generator.
    
With highly efficient turbine-generators doing the job formerly performed by water wheels, electricity flows in a number of ways:
Impoundment: When most people think of hydropower, dams come to mind. By plugging a river and amassing water in a reservoir, its flow (and the resulting electricity) can be better controlled and generated as needed.
Diversion: Water is channeled away from a river, typically near natural falls, down to generators at the falls’ base. This can be done without any visible impact to the natural course of a river. In fact, this kind of generation was used to bring electricity to Buffalo, New York, from Niagara Falls in the late 1800s.
Pumped storage: This method essentially uses off-peak electricity to make electricity for use during times of high consumption. Two reservoirs are filled, one typically uphill from the other, with an electric pump/generator in between. At night, when demand is low and electricity is less expensive, water from the lower reservoir gets pumped uphill. During the day, when demand for power increases, that water is released down through the generator to make electricity.
    
More than 600 electric co-ops across the country purchase power from 134 federally owned and operated dams, most of which were built between the late 1930s and early 1960s. Despite the incredible importance of these resources, maintenance has lagged in recent years and created room for improvement.
    
Electric co-ops are making efforts to address this problem, advocating that the government set aside funds to repair and maintain dams and the turbines inside them. Researchers are also looking to create more efficient and fish-friendly ways of generating hydropower. Careful studies of aquatic environments have given dam operators a better idea of how to simulate a natural river downstream.
    
A 2012 report from the U.S. Department of Energy (DOE) revealed many of the nation’s dams hold untapped power. Roughly 2,500 dams provide conventional and pumped-storage hydropower in the United States. But the vast majority of dams?some 80,000, ranging from 4-ft.to 770-ft. high?are non-powered. DOE analyzed 54,391 of them.
    
Locks and dams on the Ohio, Mississippi, Alabama, and Arkansas rivers?facilities owned and operated by the U.S. Army Corps of Engineers?offer the most untapped potential. The top 10 sites alone could provide approximately 3,000 MW.

Sources: U.S. Department of Energy, NRECA

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