The prioritized position of turbines within a general deployment site is referred to as “micrositing”. This involves evaluating trade-offs between different performance metrics. Here, we discuss the implications of such metrics on siting a pair of small cross-flow turbines (1 m2 projected area) adjacent to PNNL’s Marine Sciences Laboratory (MSL) at the inlet of Sequim Bay, WA, USA. The deployment and operation of this scale of turbine will be executed by the University of Washington’s Applied Physics Laboratory in FY 2019.
Sequim Bay is at the eastern end of the Strait of Juan de Fuca. The narrow inlet leading into the bay is roughly 200 m wide, a constriction that produces tidal currents of up to 2 m/s in depths between 6-10 m. Moderate speed, diver-accessible depth, and proximity to MSL make the site favorable for demonstrating feasibility of harnessing marine resources to power maritime applications (e.g. persistent sensing).
Selection of a specific deployment location within Sequim Bay is complicated by relatively large variability in resource intensity, bathymetry, and depth over small spatial distances. This is analogous to the challenges of micro-siting in larger-scale projects where flow conditions have been shown to vary substantially over distances on the order of 100 m.
Here we primarily present three metrics that can be used for micro-siting: power output, foundation weight and overhead clearance limits. The output of a finite volume coastal ocean model (FVCOM) and multibeam sonar bathymetric survey are used to complete our analysis. While the outcomes are specific to this location and turbine, we believe that the metrics and underlying trends are useful to inform deployments at other sites and scenarios of interest.