Abstract
A variety of hydrokinetic turbines are currently under development for power generation in rivers, tidal straits and ocean currents. Because some of these turbines are large, with rapidly moving rotor blades, the risk of collision with aquatic animals has been brought to attention. The behavior and fate of animals that approach such large hydrokinetic turbines have not yet been monitored at any detail. In this paper, we conduct a synthesis of the current knowledge and understanding of hydrokinetic turbine collision risks. The outcome is a generic fault tree based probabilistic model suitable for estimating population-level ecological risks. New video-based data on fish behavior in strong currents are provided and models describing fish avoidance behaviors are presented. The findings indicate low risk for small-sized fish. However, at large turbines (≥5 m), bigger fish seem to have high probability of collision, mostly because rotor detection and avoidance is difficult in low visibility. Risks can therefore be substantial for vulnerable populations of large-sized fish, which thrive in strong currents. The suggested collision risk model can be applied to different turbine designs and at a variety of locations as basis for case-specific risk assessments. The structure of the model facilitates successive model validation, refinement and application to other organism groups such as marine mammals.
Highlights
Recent years have seen a growing development of tidal power, including the deployment of several pre-commercial units in different parts of the world [1,2,3]
We focus on two of the behavior-related model components, where very little information has been reported [21,22], providing novel data from a video-based study of fish movements in strong tidal currents and developing a model for simulating fish avoidance behavior
The recorded sergeants, most probably A. vaigiensis, typically occurred in loosely congregated shoals feeding on by-drifting plankton in the mid-water
Summary
Recent years have seen a growing development of tidal power, including the deployment of several pre-commercial units in different parts of the world [1,2,3]. Modern tidal power mostly concerns hydrokinetic turbines which generate electricity from the kinetic energy of fast-flowing water. Some of the operating turbines have large rotors sweeping through the water with blade-tip velocities exceeding 10 ms−1. Because most marine animals move at considerably lower velocities, concerns have been raised regarding potential collisions between hydrokinetic turbines and fish, marine mammals and diving birds [4,5,6,7]. PLOS ONE | DOI:10.1371/journal.pone.0117756 March 2, 2015
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