Conventional hydroelectric plants, the turbines that generate electricity are turned by falling water. Some conventional plants store water in reservoirs behind dams, controlling its release to generate predictable electric power (and often providing drinking water, irrigation, flood control or navigation as well). Other plants (called “run-of-river” facilities) simply take advantage of an elevation drop in free-flowing water, incorporating little or no water storage.

Hydrokinetic Systems

• Unlike conventional hydropower facilities, which require either a dam or a stream elevation drop to produce energy, newer in-stream or hydrokinetic systems place turbines below the surface of moving water — in tidal flows, rivers, canals and even wastewater treatment plants.

• Tidal in-stream hydrokinetic systems use pivoting turbines that capture energy for the majority of the day regardless of which way the tide flows. These systems are most productive in strong, fast currents, such as are found at the entrances to bays or in “narrows” between land masses. Inland hydrokinetic projects, on the other hand, use fixed turbines to provide round-the-clock electricity whenever streams are flowing.
• While hydrokinetic energy is not yet operating at commercial scale, research, development, and demonstration are well along. In New York, new tidal kinetic hydropower technology installed in New York City’s East River was recently connected to the electric grid, and a proposal now under development would test the feasibility of hydrokinetic generation in the Niagara River.

Pumped Storage Systems

• Pumped storage hydroelectricity is the largest-capacity form of grid energy storage currently available. Pumped-storage units located at Blenheim-Gilboa and Niagara Falls-Lewiston use inexpensive off-peak electricity to pump water to a high elevation, from which it is released to generate power during times of peak demand. Pumped storage facilities use more power for pumping than they generate during operation, but the electricity they produce helps to balance power grid loads and reduce the total cost of electric power