Underwater ‘windmills’ may feed power grid

While the so-called hydrokinetic turbines are still under development, and regulatory hurdles to placing turbine farms in ecologically sensitive waterways are still being addressed, company executives and analysts said the potential to help the United States produce more renewable energy is enormous.

The Mississippi is ideally suited to accommodating the devices, they said.

“It’s a very efficient and proven technology,’’ said Jon Guidroz, Free Flow Power’s director of project development. “It was economical before anyone cared about greenhouse gases.’’

Central to Free Flow Power’s plans, Guidroz said, is capturing the hydroelectric capacity now sitting idle. The United States’ use of hydropower accounts for about 2.5 percent of total energy consumption, and just a third of the renewable energy used in the country, according to the federal Energy Information Administration.

By harnessing rivers like the Mississippi and updating existing hydroelectric dams and other facilities, the association estimates the country could generate an additional 60 gigawatts of power by 2025. (A gigawatt powers around 1 million homes.)

Because grand projects like the Hoover Dam have already been erected on the country’s biggest rivers, and environmental barriers have kept companies from erecting hydroelectric dams elsewhere, said Guidroz, Free Flow Power wants to exploit that untapped power by installing clusters of turbines underwater in rivers with strong currents.

The trick is building enough turbines in the right spots to take advantage of economies of scale, said Sarah Ladislaw, a senior fellow and energy specialist at the Center for Strategic and International Studies in Washington, D.C.

“They’ve got to find places where the resources match the potential,’’ she said. “The Mississippi is a huge river and absolutely a great source of hydropower, especially with these new technologies coming online.’’