Scientists in Minneapolis test turbines that get power from river and tidal flows

Minnesota researchers are helping a New York company try to advance new technology to generate electricity from rivers and tides.

The generating units look like small-scale wind turbines, with a major difference: they're placed on the bottom of rivers or tidal basins, where water flow spins the blades.

Verdant Power Inc., developer of the technology, has been testing it in New York City's East River since 2006, and has been granted regulatory approval to install 30 turbines on the riverbed — enough to generate 1 megawatt of power — the equivalent of a small utility-scale wind turbine.

University of Minnesota researchers, led by Prof. Fotis Sotiropoulos, director of the St. Anthony Falls Laboratory, are using supercomputers and the lab's water channels, known as flumes, to analyze the blades and help position units to capture the most energy from the East River's tidal flows.

"It is a small-scale project, but it is the first grid-connected hydrokinetic energy project in the nation," said Sotiropoulos, a professor in the Civil Engineering Department. "It has become the poster child for the success of this entire industry. If this project is successful, this whole industry will potentially take off."

The university research is being done under a two-year, $600,000 grant from the National Science Foundation. The grant is part of a program to link universities with companies developing new technologies, in this case Verdant Power and Energetx Composites, a Holland, Mich., company that produces the blades.

"We are going to re-create the East River environment in supercomputers," Sotiropoulos said of the St. Anthony Falls Laboratory's work. "We are going to virtually install turbines in the East River in order to identify what is the best way to place them. … The spacing between the turbines makes a big difference in terms of how they perform."

The Minneapolis laboratory, built in the 1930s under the federal Works Progress Administration, sits on Hennepin Island, next to the St. Anthony Falls dam, on a site that once was occupied by a water-driven lumber mill. It's a block away from the historic Pillsbury A Mill, an abandoned water-­powered flour mill that once was the world's largest.

Using water channeled from the dam, the lab has long been a center for hydraulic and river engineering research. Its focus has expanded to other areas of fluid dynamics, and the lab operates a ­utility-scale wind turbine in Rosemount.

In the main lab on the Mississippi River, graduate student Craig Hill is building a physical model of the East River. Scaled-down models of turbines are being placed in a test flume that will re-create the river flow to help verify the virtual model.

Sotiropoulos said the computational tools could be used by the industry for other projects on rivers or tidal areas.

Verdant Power, founded in 2000, is led by scientists focused on capturing the energy of flowing water but without building dams.

"What we are trying to do is use water that is already flowing, either a river flow, or tidal flow or ocean flow, and capture the energy in that, just as a windmill captures the energy in wind," said Dean Corren, Verdant's director of technology.

Corren, who began working on the technology in the early 1980s at New York University, said it is "more environmentally acceptable than damming every last river."

Verdant, a privately held company, has yet to make a profit, and is trying to raise $6 million from private investors to finance the installation of the 30 East River units in 2015, said company co-founder Trey Taylor. Last year, the company obtained the first Federal Energy Regulatory Commission license to operate submerged turbines for 10 years in the East River.

The company calls its technology, now in its fifth generation, the Free Flow System Turbine. Taylor said all the parts, including some custom elements, are manufactured under contract and assembled in a Bayonne, N.J., plant.

On the East River, the turbine blade lengths are being reduced from the optimum size to give clearance for ships to pass. The blades will sweep a circle 16 ½ feet across, enough to generate 35 kilowatts of each unit's rated 56 kilowatts of power. The turbines swivel as tides ebb and flow, and ­produce some power 77 percent of the time, officials said.

Taylor said generating units can be larger in tidal areas where greater depths allow larger blades. He sees a global market, including places where river flows can be harnessed to supply constant power, called base load.

"The world is moving toward decentralized power and distributed generation," Taylor said.

In Minnesota, Sotiropoulos sees the St. Anthony Falls Laboratory as a continuing partner in research on this energy source.

"This is a significant area where the lab can provide national leadership," he said.

David Shaffer • 612-673-7090 • @ShafferStrib