The Bay of Fundy’s acclaimed “highest tides in the world” have long been a tourist attraction, but the powerful natural phenomenon is proving to be one of the most challenging places on Earth to produce electricity.
On June 15, the Cape Sharp Tidal demonstration project retrieved its five-storey high turbine from the ocean floor before barging it to Saint John, New Brunswick for repairs and upgrades. But no date has been set for the 1,000-tonne unit to return to the waters of the Minas Passage near Parrsboro, or for when a second turbine completed last year will be deployed.
“Cape Sharp Tidal does not have target dates for deployment of either unit at this time,” confirms Emera’s Stacey Pineau, Cape Sharp Tidal’s community relations manager. “This is the first time this exact turbine design has been deployed in the world and, since the recovery of the Cape Sharp Tidal turbine, we have been taking the time needed to perform a detailed evaluation of the unit in port. This work is ongoing.”
Last November, the first turbine — built by Aecon in Pictou — hit a key milestone when, for the first time, energy from waves in the Minas Passage were transformed into grid-grade electricity via a subsea cable to an onshore substation. At that point, Cape Sharp’s joint venture partners Emera and Open Hydro (owned by DCNS of France) had spent $33 million in Nova Scotia, a figure they said represented 70 per cent of their total spend. More than $15 million in public money has gone to various studies and the infrastructure associated with tidal power development.
But in April, Cape Sharp made a decision to haul the turbine out of the water because an electrical subsystem called the Turbine Control Centre, which converts raw power into commercial-grade electricity, wasn’t performing at what it called “optimum efficiency.”
In a report to the Utility and Review Board in December, Cape Sharp reported it had sold Nova Scotia Power 5.4 MWh (megawatt hours) of electricity during the first two months of commissioning. That translates into only a few hours of production at full capacity, even though figures supplied by Cape Sharp indicate the turbine operated for 1,500 hours and reached 90 per cent of capacity during testing.
Production figures for the period January-March won’t be made public until later this year.
Cape Sharp spokesperson Stacey Pineau says the 5.4 MWh figure represents “net” production — that is, the total power minus the amount produced by the turbine to energize the subsea transmission line which delivers it to the substation onshore. Pineau says that energizing amount represented about 20 per cent of the total production during the first seven weeks.
“The production of electricity from the turbine during this period was limited as we continued to ramp up production over time while we tested the system in different conditions and tidal cycles,” says Pineau. “It’s not representative of what will be normal operations over time.”
While a forensic examination of the turbine’s control centre, or “brain,” continues, Cape Sharp also plans to make changes to equipment tasked with monitoring how close marine mammals such as porpoises and whales are coming to the device. Some but not all of the sensors were working, although Cape Sharp says “built-in redundancies” mean that enough data were collected to fulfil the conditions laid out in its Environmental Effects Monitoring program. That program is designed to gather information that can be analyzed to figure out how fish and other marine wildlife are interacting with a turbine.
Cape Sharp’s monitoring report for the period (February-April) states that two of the four hydrophones that act as microphones for vocalizations from marine mammals were unable to communicate. A third hydrophone recorded intermittently because of interference from other devices attached to the turbine, but the fourth hydrophone operated consistently, picking up frequent sounds from porpoises and detecting the presence of a vessel.
The hydrophones are manufactured by Ocean Sonics of Great Village, an experienced company that exports worldwide. The same report notes the sonar imaging system takes in such a large viewing area — more than 100 meters wide in front of the turbine — that it detected “false positives” and generated a gusher of data difficult for computers to analyze efficiently.
“Based on our learnings to date, we may make some adjustments to the positioning of the Gemini sonar and the placement of some of the hydrophones for the next deployment,”, says Pineau.
The Bay of Fundy’s harsh environmental conditions also rendered a video camera attached to the subsea base useless.
Pineau says researchers believe the strength of the Bay’s currents were also responsible for removing 10 anti-corrosion anodes attached to the turbine’s rotor. The anodes are roughly three feet long pieces of 4 x 4, according to Pineau, and will be replaced. Dozens of anodes located elsewhere on the turbine are still in good shape.
Bay of Fundy Inshore Fishermen’s representative Colin Sproule recalled that during a court case over whether environmental monitoring was adequate for deployment to proceed, a Cape Sharp lawyer stated the company would bBut when it came time to actually get the turbine out of the water in June, it took two months to plan. Cape Sharpe said the planning was complicated by a mooring line that became entangled in the subsea base.
in terms of returning the turbine to the water, Stacey Pineau says there are no deadlines to meet and the only focus is to “carefully and thoroughly complete the work” before the next trial in the Bay of Fundy’s real-life laboratory to see if commercial development could be viable.