Bristol firm’s turbines spinning underwater

NEW WAVE: Hall Spars & Rigging of Bristol, best known for its work with sailing components, created the turbine blades for the nation’s first underwater commercial generator. / PHOTO COURTESY HALL SPARS & RIGGING/MARY HUNT
NEW WAVE: Hall Spars & Rigging of Bristol, best known for its work with sailing components, created the turbine blades for the nation’s first underwater commercial generator. / PHOTO COURTESY HALL SPARS & RIGGING/MARY HUNT

A new power-producing technology, the first of its kind in North America, is up and running off the coast of Maine at the Canadian border. Operating since September, the nation’s first underwater generator has been delivering commercially produced tidal power to the Bangor Hydro Electric Co., the area’s electrical company. A Rhode Island company has played an important role in its fabrication and is under contract to make two more units.
Hall Spars & Rigging of Bristol is known for manufacturing world-class, seamless sailing components, including masts. In this case, however, the company fashioned the turbines – the spinning blades – for the generator.
The Ocean Renewable Power Co. of Portland, Maine, built and installed the unit in Cobscook Bay at a cost of $15 million. Company spokeswoman Susy Kist said the Bristol firm’s contribution was crucial to the generator’s success. “The attraction of Hall Spars is that they are well-versed in all composite-material manufacturing, and that is what is required for our underwater turbines,” she said.
The entire unit consists of a generator, the turbines, a chassis and a bottom support frame that mounts the unit to the ocean floor at a depth less than 100 feet. ORPC began transmission to the grid on Sept. 13 and a power-purchase agreement with the utility is being finalized. “It’s our very first unit and our first commercial project,” she said.
The rectangular turbine resembles a 100-foot-long and 20-foot-high paddle wheel and weighs 80,000 pounds. When submerged in a 6-knot tidal current like Cobscook Bay, the unit can generate 150 kilowatts, or enough to power a modest 25 to 30 homes. Two more generators, each with turbine blades fabricated by Hall Spars, are scheduled to be installed at Cobscook Bay in 2013. “It’s a great opportunity for ORPC and Hall Spars,” said Mary Hunt, sales and marketing director at Hall Spars & Rigging. “I think it’s a good relationship and we have the technology to help them engineer and manufacture the turbines.”
The company specializes in making one-piece spars – booms and masts – for the sailing industry, and has done so since 1980. They are well-versed in the rigors of marine environments when designing and manufacturing spars and rigging for some of the most prestigious yachts in the world. Drawing from that expertise, Hall Spars built ORPC’s turbines with carbon-fiber reinforced composites, an ideal material for the loads the turbines will encounter and the marine environment in which they will operate. Many factors, such as compression, shear and torsional forces, flexibility and hydrodynamics to name a few, were considered.
“The marine industry is wonderful but it is not always steady, so this has been a good way for us to fill in the gaps,” Hunt said.
The three-turbine contract could lead to additional work and has the potential to expand tremendously. On Oct. 26, ORPC revealed to the state of Maine their plan to begin placing 24 underwater turbines in the Western Passage of the Bay of Fundy bordering Canada in 2014.
So far, the proposal is for the deployment of the turbines in the fast-flowing waters in the bay at depths – from 150 feet to 400 feet – deeper than the present units. The turbines will be tied to the ocean floor and in the deepest locations the turbines will be stacked atop each other. Eventually, units will be placed off the coast of Lubec and Eastport and ORPC’s goal is to produce 4 MW, the energy-equivalent of powering 1,000 homes.
Kist also said that Ocean Renewable sees an international market for the system and has entered into negotiations with Nova Scotia-based Fundy Tidal Inc., in the hopes of installing units off the coast off Nova Scotia. The company has set a lofty goal of up to 50 MW of tidal-power potential off Lubec, Eastport and the surrounding area. But the technology isn’t for everyone and isn’t suitable for all coastal locations. For example, tidal-power turbines off the coast of Rhode Island, or for that matter the coast of southern New England, are impractical and highly unlikely.
“The Bay of Fundy is one of the best places in the world to install a tidal generator,” said professor Stephan Grilli, of the University of Rhode Island’s ocean-engineering department. He explained the tide rises and falls in the bay about 20 feet, and twice each day. “There, the current is amplified,” he said.“For a generator to be economically worthwhile there has to be a current of at least 4 to 5 knots. In Rhode Island we have seen only one or two knots in areas that are practical and available. We also looked at areas off Block Island and in Long Island Sound but there wasn’t enough current.”
Grilli said the closest practical application of installing a turbine in the area would be either in the Hudson or East rivers, both of which are in New York City. “There you have much stronger currents that would make putting a generator there practical,” he said.
Ocean Renewable’s Maine tidal project is one of two tidal programs to receive pilot-project licenses from the Federal Energy Regulatory Commission, the governmental authority responsible for regulating such projects. The other company, Verdant Power of New York City, is working on the installation of a tidal-energy system in the East River and is referred to as the Roosevelt Island Tidal Energy project. The company’s goal is to generate 1.05 MW, using several units. •

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