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Tapping the Mighty Mississippi and Coastal Tides with Underwater Turbines

The turbines work by capturing the energy of flowing water, which they pick up from waves, tides and currents
Mississippi River



Courtesy Iowa Department of Transportation

Experts at the Federal Energy Regulatory Commission are taking a cautious look at 123 applicants who want to generate renewable energy underwater, using a relatively untested technology.

The technology in question is called hydrokinetic. Like the turbines in dams, hydrokinetic turbines generate power from the movement of water. But these turbines don't need dams and don't present some of the challenges and expenses that come with them, explained Ed Lovelace, executive vice president of engineering at Free Flow Power, based in Gloucester, Mass.

The turbines work by capturing the energy of flowing water, which they pick up from waves, tides and currents. Because water has greater density than air and flows are more constant than wind, underwater turbines can deliver much more energy than wind turbines.

In the past few years, more than 100 proposals for hydrokinetic projects have been filed with FERC. On average, the projects include clusters of 20 or more turbines. Free Flow Power is behind 88 of them, which are slated for the Mississippi River Basin between St. Louis and Gulf of Mexico. Proposed locations from other companies include ocean coasts, where turbines can capture tidal action.

This rush to development is prompted by hydrokinetic's potential to produce renewable energy on a large scale in places where it can easily connect to the nation's power grid, Lovelace said. The Mississippi River offers a massive resource, drawing water from a drainage area that covers about 40 percent the total area of the lower 48 states in the United States.

But placing a mechanism that is similar to a wind turbine in the water could have its consequences. Turbines can be insulated well so they do not leak electricity, but they still generate small electromagnetic fields around them. They also may be loud, and noise travels farther and faster underwater and could impair wildlife.

Drawn-out licensing procedure
FERC has kept most of these projects at a slow pace by requiring that companies go through multiple stages of scrutiny before getting a green light.

Before FERC can grant a license, companies have to apply for permits that give them priority over a site. Once granted, the permits give the company in question priority over a site for up to three years. This period lets the companies study the site for feasibility of the technology. They also have to prove the projects will minimize harm. If the company likes the site, it can next apply for a license through FERC that would allow power production on it.

For each permit proposal, FERC does an environmental review and takes in public opinion. The regulatory agency also grants shorter "pilot" licenses as an alternative to streamline the process. While FERC's conventional hydropower licenses can last 40 to 50 years, pilot licenses cut that down to five years. Part of this is because regulators want to be cautious with relatively untested technology.

"FERC has to be convinced these can generate electricity in safe matter," said Glenn Cada, a researcher at the Oak Ridge National Laboratory. "The licenses have a provision in them that if something unexpected happens, FERC can remove [the turbines]."

In the years since applications started hitting the agency, it has granted only one license to a project that would have generated power from waves on the coast of Washington state. That was back in December of 2007, and the company behind it, Finavera Wind Energy, has since surrendered its license, said FERC spokeswoman Celeste Miller.

In 2008, FERC also allowed Hydro Energy Green, a company based in Hastings, Minn., to put two 35-kilowatt turbines in the Mississippi River. At the time, the city of Hastings had already had a conventional hydroelectric FERC license. Hastings asked FERC to allow the hydrokinetic turbines to operate by adding them as an amendment to its conventional license. FERC allowed it, and the Hydro Energy initiative became the first in the country. To date, they're the only hydrokinetic turbines generating power to the grid.

Currently, three projects are pending license, including one by Verdant Power that will install up to 30 turbines in New York City's East River. There are 111 projects with issued FERC permits, with 12 others pending.

Because each hydrokinetic proposal with FERC was submitted at different times, many are in different stages with FERC. Free Flow Power expects its hydrokinetic projects to be commercial in the next two and a half years.

Testing the effects on freshwater fish
Cada is heading Department of Energy-sponsored research at Oak Ridge on how the turbines affect freshwater fish and life. His team is looking into how fish respond to the electromagnetic fields that the turbines generate and the noise they create.

His lab identified 50 species of freshwater fauna that could be affected by the turbines, including snails, clams, minnows and sturgeon, he said. Most of Oak Ridge's research has been on lake sturgeon and paddlefish, which both live in the Mississippi River Basin, where many of the projects are being proposed. Lake sturgeon travel long distances, hiking roughly 100 miles upstream in the spring and laying eggs along the way. The eggs then hatch while drifting downstream. In the fall, the sturgeon travel back downstream.

A concern with these migratory fish is that the turbines will stop or alter them in their paths, changing how they live and reproduce. So far, Cada has not found any evidence of that. One of the reasons is that the electromagnetic fields generated by the turbines are relatively small, reaching out about 3 feet on average.

In his lab, Cada has an electromagnetic switch in a tank that he can turn on and off. He has noticed that when he turns it on, some of the fish "stop in their track and kind of look around," he said. If all the electromagnetic field does is make the fish stop momentarily, it won't too difficult to fix, he said.

A possible solution could be burying the cables that connect the turbines and transfer the power to the grid. Burying them 2 or 3 feet in sediment would bury the magnetic fields. But that still leaves the generator inside the turbine. When the blades spin, the generator also produces an electromagnetic field.

Much work still needs to be done, Cada said. Other concerns include whether the noise of the turbine could attract or repel fish and whether turbine blades could strike and kill fish as they swim through them. Before it got the two turbines going in Hastings, Hydro Energy Green tested a turbine in the Mississippi River by floating it from a raft and releasing hundreds of fish in front of it. The good news, said Cada, is that none of them died. This could be because like wind turbines, the blades rotate at relatively slow speeds.

The U.S. Geological Survey's Conte Anadromous Fish Research Center and the Alden Research Laboratory, both in Massachusetts, are studying likelihoods of the "blade strike" reaction. Oak Ridge will start looking into it this summer.

Ocean studies pending
Studies on ocean life are less complete. At the Pacific Northwest National Laboratory in Washington state, Andrea Copping is leading research on how the turbines can affect ocean life like crab, halibut and salmon. Like Oak Ridge, the Pacific Northwest Lab is generating electromagnetic fields and measuring underwater acoustic noise.

Some areas of potential concern come with sharks, which use magnetic fields to hunt prey. Some mammals use noise for communication and navigation. When thinking about risks, Copping lists some hypotheticals: What if an endangered salmon species got attracted to the electromagnetic field, making it easier for predators to hunt and kill the fish? What if large migratory whales got put off by the turbines and traveled farther with less food?

While Copping says some data suggest risks like these, she has yet to be convinced the turbines will cause significant problems.

"We don't think this is going to be a showstopper, but there's not much evidence yet. We really don't know," she said.

So far, Pacific Northwest's electromagnetic studies "haven't been startling," Copping said. She is still trying to understand which species react to them and whether they have caused any to change their behavior. As for measuring how they react to acoustics, Copping said in many cases she expects no effect.

Both Oak Ridge and Pacific Northwest have been testing hydrokinetic effects for about two years. Congress directed DOE to study it when the project proposals started piling up.

Power companies are allowed their own tests with the technology without seeking FERC's approval as long as testing does not add power to the grid.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500

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