…engineers and entrepreneurs are pressing an alternative view of hydropower that doesn’t involve new dams. They argue that plenty of efficient, economical energy can be wrung from other water resources, including ocean waves, free-flowing rivers, irrigation ditches—even the effluent discharged from wastewater treatment facilities. There’s a surge of interest, too, in adding small power plants to dams built years ago for flood control or navigation—as well as in turning reservoirs into battery packs of sorts, releasing energy when the grid needs it most.
Globally, hydropower provides 16% of electricity, slightly more than nuclear power and closing in on natural gas, according to the London-based International Hydropower Association. In the U.S., by contrast, hydropower now provides about 7% of electricity generation. All other renewable sources combined account for about 3%. Even without building large dams, expanding efforts to draw power from water could add 40,000 megawatts to the grid by 2025, says the Electric Power Research Institute, a nonprofit research firm in Palo Alto, Calif. That’s the equivalent of putting at least two dozen new nuclear power plants online…
In the U.S., one strategy gaining popularity is to add power plants to some of the 80,000 existing dams that don’t have hydroelectric capacity. Technological advances like turbines that are gentler on fish and oxygen-injection systems that help balance aquatic ecosystems have won favor even among some environmental groups…
Several companies are experimenting with “low-head” turbines that can pull energy from relatively small volumes of water dropping as little as five feet over natural or man-made falls. One such project, launched by Natel Energy Inc. of Alameda, Calif., uses low-head technology to extract energy from an Arizona irrigation canal…
A less-experimental technology, dating back more than a century, is also gaining currency as a means to store energy and back up the grid: pumped storage, the system used by the Mount Elbert hydro plant outside Denver. The plant, sitting on the jewel-like Twin Lakes and managed by the Bureau of Reclamation, plays a key role in keeping lights on and air conditioners humming across the West. At night, when demand on the power grid is low, the Mount Elbert plant sucks water from the lakes, sometimes using wind power to pump that water up into a reservoir above the plant. The reservoir acts as a liquid battery—a huge pool of potential energy. As the day warms up and the grid shows signs of strain, workers begin to release the water down a 470-foot drop, through devices that turn the pent-up energy into usable electricity. The water eventually pours back into the lakes, where it can be recycled into power again the next evening.
