Tidal Power

Castine
Castine Patriot, February 3, 2011
Tidal power: Cobscook Bay study bodes well for fish

by Colin Powell


The Maine coast provides some of the best spots for tidal power generation in the country, experts agree.


But while engineers test turbines to exploit that potential, those who work on the coast have major questions about their environmental impact.


That’s where the Maine Tidal Power Initiative comes in.


The goal of the initiative is to evaluate and develop Maine’s tidal energy resources responsibly, according to fish ecologist Gayle Zydlewski.


Zydlewski spoke on Monday, January 31, as the first lecturer in this year’s Ocean Studies Lecture series at Maine Maritime Academy.


She explained that MTPI comprises staff and faculty from the University of Maine and MMA, from fields as diverse as mechanical and civil engineering to marine science and sociology. Zydlewski herself is an assistant professor at the University of Maine.


Over the next seven to 10 years, Zydlewski said, Maine is expected to produce 250 to 400 megawatts of power from tidal sources.


While there are a number of individuals and companies working on turbines that produce consistent and high quality electricity, recent problems with wind farms, both off-shore and land-based, have exposed a need to do extensive environmental and social studies.


Zydlewski described how one of her MTPI colleagues, Teresa Johnson, conducted a survey of people in the Cobscook Bay area. That’s where the Ocean Renewable Power Company is close to deploying a production-ready turbine.


Johnson, an assistant professor of marine policy, is a social scientist who specializes in fishing communities.


In Johnson’s survey, the majority of respondents said environmental impacts are the most important area of research that’s needed before a tidal generator is installed.


Given the interest, Zydlewski and her colleagues at MTPI set about to create experiments to determine the type, quantity and behavior of marine life at the proposed site for the ORPC device.


While there was some past data for the marine life in the general area, Zydlewski said much of it was from research papers nearly 30 years old, and not even from Cobscook Bay, but nearby Passamaquoddy Bay.


With limited studies to draw on, Zydlewski and her partners had to create their own experiments.


They designed a dual-sonar system that was mounted to a moored boat over the proposed site. One sonar provided images to a depth of 10 meters, with the other providing images from the sea floor.


There was also a second rig set up to monitor a “control site,” picked for having similar characteristics to the proposed site, and that could be monitored after the device is installed to measure changes in marine life at the installation point.


What her group discovered was surprising, Zydlewski said.


Data gathered in the spring and fall, during both the day and night, showed the bulk of fish were located about 20 to 25 meters off the sea floor.


The ORPC device is designed to be installed only 10 meters off the sea floor, so this means the number of fish affected by the installation would be minimal.


Besides testing for the presence of fish in the water column, the group performed another experiment using a test turbine anchored below a barge.


The group mounted the device in front of and behind the turbine, which looks like a large reel lawnmower.


While all the data from that test has not yet been analyzed, Zydlewski said preliminary results are interesting.


After the schools pass through the device, she said, they seem to experience a moment of confusion, but then usually reorient themselves after a moment and move on. The scientists also watched a large species of fish approach the intake end of the device, stop, turn and move upstream.


While the MTPI data has so far been good news for the tidal power industry, Zydlewski was careful to point out that the data was only for two small locations in Cobscook Bay.


She said there is still a need to perform similar tests elsewhere on the Maine coast. There is also a need to make such studies easier to perform with fewer people, she said, as there is interest in private tidal generators operated by small groups or individuals.


While her group’s data on fish populations in the water column have been very well received, she said state and federal natural resource agencies still need data for summer and winter.


“We’ve been collecting data that is relative to the time of year when fish are known to be there,” Zydlewski said.


But without official data for the other times of the year, she said, the natural resource departments have to use the only data they have—namely for spring and fall— for other times of the year.


These are the agencies that are striving to define license requirements even as devices are being prepared for installation.


“So now we’ve been collecting some data this past January and will be collecting more this February,” Zydlewski said.

Fly a Kite for Energy

Deep Green underwater kite to generate electricity (w/ Video)
May 11, 2010 by Lin Edwards Enlarge
The Deep Green technology converts energy from tidal stream flows into electricity by way of a novel principle, somewhat similar to the posture of a wind kite. Image credit: Minesto

(PhysOrg.com) -- An underwater tidal turbine called an “underwater kite” has just secured finance from investors to ensure its 2011 tests can go ahead.

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The turbine, known as “Deep Green” was developed by a privately-owned Swedish/UK company, Minesto, and is intended to be tethered 100 meters above the sea bottom. It has a wingspan of 12 meters and a turbine one meter in diameter. The “kite” comprises a wing with a rudder to steer the turbine to face in the direction that will allow it to capture the maximum amount of tidal energy, and generate up to 500 kW of electricity. The kite flies in a figure eight and travels 10 times faster than the water it is tethered in.





Ted Rosendahl, chief technical officer with Minesto, said the design will enable Deep Green to operate efficiently at greater depths and with lower current velocities than other tidal energy generators, which opens up new areas of the sea for tidal power generation, increasing the market potential by 80 percent, according to Minesto. Deep Green’s unique ability to work in deep water where there is low velocity water movement means it can operate cost effectively in areas otherwise unavailable for power generation.

There are two major types of tidal energy generator installations at present: one is the tidal barrage, which works in a similar way to a hydroelectric power station, and the other uses the flow of the tide and works in a similar way to wind power installations. In comparison with other tidal systems Deep Green is lightweight and much smaller, which translates to lower manufacturing costs.

The company will receive two million Euros (around 2.5 m USD) in investment funding, which will enable it to test a 1:4 scale prototype off the coast of Northern Ireland in 2011. The test site, at Strangford Lough, County Down is the location of a tidal generator owned by the UK company SeaGen. If the Deep Green trials are successful, the next step will be to test a full-scale demonstration plant consisting of up to 10 kites. Financing needed for this stage is expected to be around 40 million Euros.

Rosendahl said the company hopes a full-scale Deep Green generator will be commercially available within the next four years, adding to the available options for renewable energy sources. Tidal energy generation is usually more expensive than wind or solar power, but the predictability of the tides compensates for the extra initial cost, because unlike solar and wind energy, the tides operate every day of the year. Minesto says its Deep Green project is expected to be “very competitive in comparison with traditional electricity production.”

Minesto was formed in 2007 for the purpose of developing tidal power generators. Deep Green began as a Saab Group project in 2003, and Minesto was formed as a spin-off company.