Turning River Current into Electricity

An inspector examines a large turbine designed for generating electricity from the flow of a river.   Photograph courtesy Free Flow Power Corporation

Willie Drye

National Geographic News

Published March 21, 2010

The steady roll of the Mississippi River, inspiration for so many great American songs and stories, also could light homes and power businesses, say developers who aim to turn that idea into reality.

The proposed project to convert the torrent beneath North America’s largest river into electricity is one of dozens of efforts across the United States to harness the energy produced by the constant surge of tides and rivers. These new proposals differ from traditional hydroelectric projects, which rely on dams to control the water’s flow.

Free Flow Power (FFP) of Gloucester, Massachusetts, has especially high hopes for its Mississippi project in part because of the river’s fresh—if not exactly clean—water. Efforts to harness energy offshore in salt water face greater difficulty, because of the changing direction of the tides and the higher risk of equipment corrosion and fouling.

The current of the Mississippi River flows past New Orleans at around 4 mph (6 kmh) at times, according to data from the U.S. Army Corps of Engineers. Since moving water can produce 800 times more energy than wind, the river could turn the blades of submerged turbines to produce electricity for thousands of homes—at least, that’s the theory.

But developers are still trying to determine whether the technology is commercially feasible.

FFP spokesman Jon Guidroz said his company was pleased with the results of a recently concluded six-month test of a turbine tethered to a dock near Baton Rouge. The tests were part of the company’s plan to start producing electricity in 2013. But Guidroz would not discuss details of the test, citing concerns about confidentiality. He also indicated it was too early to discuss how much power the company could produce.

Turbines Invisible from Shore

Eventually, however, FFP hopes to attach turbines to concrete pilings anchored deep in the Mississippi. The turbines would be invisible from the shore, and the only evidence of their presence would be cables emerging from the water.

Each turbine would have seven blades with a diameter of about 10 feet (3 meters). The blades would turn very slowly to minimize the danger to fish.

Designers sacrificed some efficiency to make the turbines more environmentally friendly, Guidroz said. “We increased the distance between the blades and removed all the lubricants,” he said. “The turbines are lubricated by water. If a bearing breaks, it’s not leaking anything into the river.

“The turbines are much smaller than a windmill, and spin much slower.”

The projects to generate hydrokinetic electricity must be approved by the Federal Energy Regulatory Commission (FERC) in Washington, D.C. FERC spokeswoman Celeste Miller said the agency first saw “a trickle” of applications for federal permission to develop the technology in 2004.

That trickle has increased since then, and FERC has 134 applications on file. The applications include projects on the Mississippi and Ohio rivers, as well as offshore projects along the U.S. Atlantic and Pacific coasts and Alaska and Hawaii.

Henry Dormitzer, FFP’s chief financial officer, said the development of hydrokinetic electricity would be helped by changes in federal tax laws. Current law allows extended tax credits to developers of wind and solar power. Hydrokinetic developers need similar laws, he said.

“The licensing period is so long that developers need a stable, predictable tax structure,” Dormitzer said.

Environmental Impacts

Questions also have been raised about possible environmental impacts. A 2008 report submitted to Congress by the U.S. Department of Energy noted that hydrokinetic technology “has the potential to impact fish and marine mammals.” Besides the danger of large turning blades, noise from the turbines could “disrupt” the behavior of marine animals far away, the report said.

Rupak Thapaliya, coordinator for the Hydropower Reform Coalition, a conservation group in Washington, D.C., said more research is needed. “I imagine that if you put something like that into the water, it could have an impact and change the behavior” of marine animals, he said.

Peter Asmus, a senior analyst with the market research firm Pike Research, said experiments on hydrokinetic technology are only being done in North America. He said that’s probably because the Mississippi River is one of the few places the technology could be cost-effective, due to the large size of the resource and plenty of nearby industrial development that needs power.

Asmus said the technology’s potential could be “huge,” but it’s too early to tell if it is economically feasible.

“The next five years is the key to determining whether this is big or whether it’s only a flash in the pan,” he said.

http://news.nationalgeographic.com/news/2010/03/100322/river-current-electricity/

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