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Underwater ‘windmills’ may feed power grid

A Mass. company aims to tap the mighty Mississippi’s ceaseless currents

By John Dyer
Globe Correspondent / August 8, 2011

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In centuries past, water wheels drove New England mills and powered the Industrial Revolution in America. Now, a Boston company is hoping to harness river flows to profit from the green energy movement.

Since late June, Free Flow Power has been testing an underwater turbine in the Mississippi River near Baton Rouge, La. The equipment looks like a jet engine, but uses technology similar to what’s in windmill-powered electric generators, such as those proposed for Cape Wind, the energy project planned for Nantucket Sound.

Free Flow has also applied for more than 150 permits from the Federal Energy Regulatory Commission to sink “turbine farms’’ throughout the Mississippi and other US rivers, with hopes of receiving approval for many of those projects in the next few years.

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.’’

The 6,000-pound hydrokinetic turbines, about 10 feet tall and 13 feet long, function on the same principle as wind turbines. They use fluid dynamics to derive power from a renewable external source, either the wind or the current in a river.

“It’s effectively an underwater windmill,’’ Guidroz said.

But because water is 800 times denser than air, it is a better resource for generating energy than wind, said Ed Lovelace, Free Flow Power’s chief technology officer.

The average flow of the Mississippi is 5 miles an hour, a force equivalent to the wind blowing at 130 miles an hour, he said.

“Picture a massive wind tunnel at 130 miles per hour with some ships floating on top of it,’’ Lovelace said. “We believe it’s the world’s most impressive hydrokinetic opportunity.’’

As for Cape Wind, its website says its 440-foot windmills could produce 3.2 megawatts apiece - or 3.2 million watts, enough to power 32,000 100-watt light bulbs - to generate a total of 420 megawatts.

A hydrokinetic turbine produces less electricity - around 40 kilowatts, or 40,000 watts, Guidroz said.

But Free Flow Power would install about 120 turbines at each of the locations where it is applying for permission to build along the Mississippi, enabling it to generate about 4.8 million watts per turbine farm.

Guidroz and Lovelace would not disclose the price tag of their hydrokinetic turbines. But they said they planned to be competitive with commercial-grade windmills, which on average cost $3.8 million apiece, according to the Department of Energy.

Mike Rodgers, Cape Wind communications director, declined to discuss the cost of individual wind turbines proposed for Nantucket Sound, saying the company was involved in contract negotiations to supply power to utilities.

The added benefit of placing turbines underwater is that they are less obtrusive than windmills, and water flows are more predictable and constant than wind, Guidroz said.

“You can have a small device and generate power as long as the river is flowing, and rivers flow constantly during seasonal levels,’’ he said.

“It’s not going to fall off three hours from now. It’s going to fall off three weeks from now. Whereas this is a problem wind is facing.’’

Six turbines would hang on a piling standing in the center of a river, deep enough for ships to pass over them, and in the fast-moving central avenue of waterways where fish rarely dwell. “Fish don’t live where we put turbines,’’ Lovelace said.

Still, Ladislaw said, concerns about shipping and fish would probably dog the hydrokinetic industry for years, especially on the Mississippi, where federal, state, and local agencies have jurisdiction over the river.

She said hydrokinetic power is an important way to achieve President Obama’s goal of generating 80 percent of the nation’s electricity from renewable sources by 2035, but she does not see it displacing coal-fired power plants anytime soon.

“Just because there is this big resource out there, you can’t promise everyone there is going to be a sea change,’’ she said.

“It’s very much an incremental process. It takes a long time to get a lot of these projects together so that they actually scale and make a difference.’’

The Energy Department has boosted its funding for hydropower research in recent years, appropriating $130 million for subsidies for the industry and other institutions since 2008, up from an average of $3.2 million per year from 1999 through 2007. Obama is requesting $39 million for next year’s federal budget, department figures show.

Since it was founded in 2007, Free Flow has received $1.4 million in Department of Energy grants, said Lovelace, in addition to about $5.7 million from other investors.

With 30 employees, the company also earns money by consulting on hydropower projects.

The grants have been crucial in keeping the industry competitive internationally, Guidroz said. European rivers don’t rival the mighty Mississippi, but European companies are threatening to excel in hydrokinetics in the global drive for carbon-free energy, he said.

“There is absolutely a gold rush, and everyone is trying to build the shovels,’’ Guidroz said.

“There are around 40 companies worldwide [building hydrokinetic turbines]. Most are not in the US.

“The US didn’t create wind power. The US didn’t create solar. This is a chance for the US to make a new industry.’’