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.