Modeling Probability of Encounter of Freshwater and Marine Organisms with Hydrokinetic Devices in Riverine and Ocean Currents

Hydrokinetic (HK) technologies for placement in free-flowing river and ocean currents offer promise for contributing renewable electricity to future energy needs. These novel technologies include horizontal- and vertical-axis underwater turbines that differ in size and number of turbine blades.  Generators with rotating propeller-type blades or helical blades convert kinetic energy into electricity and, despite differences in general design, a common feature of these novel technologies is that they expose aquatic fauna to potential risk of blade strike. Because many of these emerging HK technologies are still under development, only limited empirical data on biotic interactions with HK turbines are available at present. However, research from conventional hydro and tidal energy production suggested that passage through the rotor-swept area of turbines can cause collision, with potentially fatal results.  In view of the scarcity of empirical data describing biotic interactions with HK technologies, as well as data on behavior and success in avoiding or evading blade strike from HK devices, a conceptual model for assessment of probability of blade encounter or strike to fish and other marine or freshwater aquatic biota is presented. Using type-specific habitat templates for distribution of local biota, the model allows for identification of species with greatest probability for blade encounter from HK devices deployed singly or in arrays, and estimates probabilities for blade strike over a range of flow velocities.  The conceptual model accommodates substrate-mounted or surface-deployed technologies, variations in turbine design, device dimensions, spatial arrangement in single deployment or arrays, and avoidance behavior of affected biota.  Although behavioral responses are included as a parameter in the model, this factor remains the greatest source of uncertainty in assessment of probability of blade strike. We present the conceptual modeling approach as a baseline for future comparisons and as a template for further model refinement, and expect further model improvement as observations and behavioral data from laboratory and field studies with potentially affected biota become available.