Assessment of Strike of Adult Killer Whales by an OpenHydro Tidal Turbine Blade

Abstract

SummarySnohomish Public Utility District #1 (SnoPUD) proposes to deploy two OpenHydro tidal turbines in Admiralty Inlet, Puget Sound. The fisheries service of the National Oceanic and Atmospheric Administration (NOAA Fisheries) has expressed concerns that the turbines may cause a risk for the highly endangered Southern Resident Killer Whale (SRKW) population if a whale is struck by an operating turbine. NOAA Fisheries is responsible for protecting the (fewer than 90) SRKWs under the Endangered Species Act and the Marine Mammal Protection Act. Because the SRKW numbers are so small, significant injury of a single animal could place the population in jeopardy.The potential risk to a SRKW can be parsed into the probability that a whale would encounter a turbine, the probability that the encounter would injure the whale, and the severity of any injury. During a meeting with representatives of SnoPUD, OpenHydro, the Department of Energy, and NOAA Fisheries, participants agreed that the probability of a SRKW encountering a turbine by chance is negligibly small as the whales spent greater than 97 percent of their time in Admiralty Inlet in the top 30 meters of water, while the turbines are located at 55 meters of depth, and the SRKW have highly evolved acoustic sensory capabilities that would help them detect the presence of a turbine. NOAA Fisheries expressed concerns over the potential severity of a strike on a SRKW should it occur. A proposed solution was to conduct an estimate of the level of injury that might occur from an encounter between a turbine blade and a SRKW, which would allow NOAA Fisheries to determine the permitting requirements for the tidal project.Pacific Northwest National Laboratory (PNNL) and Sandia National Laboratories (SNL) were tasked by the Department of Energy to carry out an analysis of the mechanics and biological consequences of strike of a SRKW by an OpenHydro turbine blade. The approach taken by the two laboratories was to: 1) develop a scenario for the most severe strike of a SRKW; 2) determine the morphological and biomechanical properties of SRKW tissues that might be affected by a strike; 3) model the forces of a strike; and 4) estimate the potential effects on SRKW tissue and bone of a strike.PNNL and SNL developed a worst case exposure scenario for strike of a SRKW. SNL modeled a turbine blade (based on proprietary design data obtained from OpenHydro), and calculated the force of blade impact on the head of an adult male SRKW, weighing approximately 4000 kilograms. The adult SRKW was selected for the model because an adult has a large body mass where more of the energy in a blade strike will be absorbed by the whale's tissue rather than going into momentum transfer that would push the whale out of the path of the turbine blade. This scenario would maximize the risk of injury to the SRKW. Although a juvenile SRKW might intuitively be considered to be at greater risk of injury, because of much smaller mass (~500 kg) more of the energy in the blade strike would go into momentum trans...

Empirical determination of severe trauma in seals from collisions with tidal turbine blades

“…Theoretical models of interactions between larger marine mammals and tidal turbines have suggested that impacts may be benign across all scenarios. Carlson et al (2014) Covariates are denoted by Sp (speed of collision), L (location of strike), Sx (Sex), Sc (strike count) and B (Axial blubber depth). A colon (:) denotes an interaction term between covariates.…”

Finite Element Analysis of Tidal Turbine Blade Subjected to Impact Loads from Sea Animals

“…The killer whale was modelled using a simplified geometry considering a solid cylinder, as shown in Figure 2. The diameter of the model is D skin = 1.2 m, and it was based on the maximum diameter of the model presented by Carlson et al [17]. The length (L wh ) is equal to 3.557 m, which was determined in order to obtain the same volume with the model used by Carlson et al [17].…”

“…Furthermore, as the tidal blades are placed underwater, another problem associated with impact damage from large debris and sea animals arises with the increased number of turbine blades [17]. Payne et al [18] conducted preliminary small-scale impact tests, investigating the peak loading on a variety of materials with similar properties with the skin, bones and flesh of sea animals.…”

A Review of the Environmental Impacts for Marine and Hydrokinetic Projects to Inform Regulatory Permitting: Summary Findings from the 2015 Workshop on Marine and Hydrokinetic Technologies, Washington, D.C.

“…The modeling concluded that interaction was likely to result in bruising or minor laceration under a worst-case scenario; however, the study did not account for aspects of whale behavior nor provide detailed information about the strengths of specific whale tissues. This analysis may not be generally applicable to encounters between other species of animals and other turbine designs and is still ongoing (Carlson et al 2014).…”