Abstract
The following document was prepared for the Offshore Energy Research Association of Nova Scotia (OERANS). It summarizes the flow measurements that were made using acoustic Doppler current profilers (ADCPs) at three locations in Cape Breton: two in the Great Bras d’Or Channel (Carey Point and Seal Island Bridge), and one in the Barra Strait (near Iona). The measurements at Seal Island Bridge and Barra Strait were recorded over the duration of a month using a bottom mounted 600 kHz ADCP beginning in November 2011 and April 2012, respectively. These two deployments were conducted by Dalhousie University. The measurements at Carey Point were recorded for over 7 months beginning in October 2002 using a 300 kHz ADCP that was situated approximately 4 m above the seafloor and held in place by a taut wire mooring. The deployment at Carey Point was conducted by the Bedford Institute of Oceanography.
Of the three sites, Carey Point has the most energetic flow with horizontal currents reaching 2.8 m/s. The maximum currents at Seal Island Bridge and Barra Strait were 1.9 m/s and 1.1 m/s, respectively. Furthermore, the vertical velocities at all three sites exceeded 4 cm/s during some tidal cycles. The vertical profile of the horizontal currents at Seal Island Bridge and Barra Strait were used to determine the bottom friction coef-ficients during both the flood and ebb phases of the tide. The Barra Strait values were in agreement with the canonical value of 0.003, whereas the Seal Island Bridge values were an order of magnitude larger which suggests the possibility of turbulent flow in the boundary layer.
This document also presents the predicted output of four typical Tidal Energy Con-version (TEC) devices at each site. The TEC devices were assumed to be passive yaw devices with a water-to-wire efficiency of 0.4. Recognizing that these assumptions result in estimates greater than a realisable value, we compare the average daily energy produc-tion, maximum power output and operating time for the devices. The predictions indicate that an optimal 10 m diameter turbine could produce over 1000 kWh per day at the Carey Point ADCP deployment site. Given a Feed-In Tariff (FIT) rate of 60 cents/kWh, the resulting gross revenue would be $600/day. At the same FIT rate, the 10 m device at Seal Island Bridge and Barra Strait would produce $110/day and $20/day, respectively, due to lower flow speeds and power density. It is important to note that the water depth at all three sites is less than 22 m; therefore, a 10 m device may prove to be unfeasible due to navigational restrictions.