The hydroelectric dam, or "impoundment facility," is the most widely used water-powered technology. Typically, water from a river is impounded behind a barricade, or dam, creating a reservoir. Water is released from the reservoir as needed to flow through a turbine, causing it to spin, thus activating a generator, which produces electricity.
The "diversion facility," the second means of harnessing major water power, uses a conduit to divert, parts of a river to the turbines which set the generator in motion. Not surprisingly, the power plants at Niagara Falls, New York, are diversion facilities.
Ocean Power Technologies
Using the ocean's waves, tides and currents to generate renewable, sustainable energy is leading to interesting experimental projects world-wide. There are many companies with promising technologies who are engaged in the years-long process of building, siting and deploying pilots for longterm testing in various parts of the world. So far, though, only a few companies have successfully installed their technologies and linked them to their respective grids.
Ireland's Galway Bay hosts two projects with very different approaches to ocean wave technology. Wavebob's WEC-1 is a floating buoy, an oscillating system capable of "tuning in" to and absorbing the variable wave periods and heights, then maximizing their useful power output. The other, Ocean Energy's OE Buoy works on the oscillating water column principle to spin a turbine which powers a generator. The deployed unit produces .015 MW of power.
Off the coast of Oahu, Hawaii Ocean Power Technologies (OPT) has anchored its PowerBuoy®, another bobbing device that uses its movements to drive a generator, which produces electricity that is sent to shore via underwater cable.
New Fresh Water Technologies
New Energy Corporation makes turbine devices similar to those used to generate wind power that can be used in tidal or fresh water condition. So far they've deployed one 5 kW project in the U.S. (Ruby, Alaska) and several more in Canada.
Hydro Green Energy's deployed project on the Mississippi River at Hastings, Minnesota, utilizes hydrokinetic turbine power, which is generated from the flow, current or velocity of water. The project currently produces .07 MW of electricity using two turbines, which can be maintained above water level. It is an adjunct to a lock-and-dam owned by the city, and it is the first commercial hydrokinetic power facility approved by the FERC.
Verdant Power is now commercially licensed to expand its "Free Flow" tidal system, the RITE Project, in New York's East River, as well as its and its "Free Flow" river system, the CORE Project, in the St. Lawrence River at Cornwall, Ontario. Free Flow's underwater 3-blade, horizontal-axis turbines rotate with the flow of the currents to drive a speed increase which powers a grid-linked generator.