A Funding Grant was awarded from the European Union’s Horizon 2020 research and innovation programme to develop and validate an innovative tidal turbine control system, using the tidal turbine itself as a sensor, to deliver a step change improvement in the performance. This will demonstrate Effective Lifetime Extension in the Marine Environment for Tidal Energy (ELEMENT), driving the EU tidal energy sector to commercial reality. This report focuses on the characterization of the hydrokinetic resource and turbulence at the future tidal turbine testing sites, in Etel River as well as Bluemull Sound. This report summarizes the analysis of existing hydrokinetic data from both sites. In addition, the monitoring options that can enhance the design work under the ACAS (Automated Collision Avoidance System) are discussed.
At Etel Site, a 12.5 day-period, containing a full spring tide tidal cycle, was analyzed. Results on cumulative occurrence of the velocity magnitude suggest that a tidal turbine with a cut-in-speed of 0.5 m/s might generate electricity, 80% of the time. Moreover, the flow at Etel site is ebb-dominated. A substantial asymmetry in velocity magnitude recorded during flood and ebb tide was found. This asymmetry generates considerable gap in kinetic power density during both tidal phases with kinetic power density more than 3 times higher during ebb tide than flood tide. The turbulence intensity and the integral lengthscale were quantified along the three spatial directions. For both metrics, the streamwise direction is associated with the highest values. The depth-averaged streamwise turbulence intensity and the integral lengthscale was found to be 5% and 7.5 m.
At Bluemull site (Shetland), three 5-beam ADCPs were deployed in three locations North of the three operational M100 turbines at depths of approximately 30-35m. Cumulated occurrences of flow velocity magnitude indicate that 0.5 m/s and 1 m/s are exceeded 90% and 70% of the time respectively. The flow magnitude between flood and ebb tide was found to be globally symmetric. For flow velocity higher than 1 m/s, the turbulence intensity was found to be ranging from 12 to 20%.
The monitoring options that can enhance the design work under the Automated Collision Avoidance System (ACAS) have been the subject of discussions between FEM and Nova. The aim of discussions was to review the benefits of different methods of monitoring near-field interactions between marine life (more particularly mammals, birds and fish) and turbines. Exchanges between FEM and Nova have strengthened the general idea of developing a monitoring strategy combining sonar and digital cameras in order to gain in situ data that will enhance predictions of encounter and collision risk.