Underwater Noise Measurements around a Tidal Turbine in a Busy Port Setting

Abstract

Acoustic emissions from current energy converters remain an environmental concern for regulators because of their potential effects on marine life and uncertainties about their effects stemming from a lack of sufficient observational data. Several recent opportunities to characterize tidal turbine sound emissions have begun to fill knowledge gaps and provide a context for future device deployments. In July 2021, a commercial-off-the-shelf hydrophone was deployed in a free-drifting configuration to measure underwater acoustic emissions and characterize a 25 kW-rated tidal turbine at the University of New Hampshire’s Living Bridge Project in Portsmouth, New Hampshire. Sampling methods and analysis were performed in alignment with the recently published IEC 62600-40 Technical Specification for acoustic characterization of marine energy converters. Results from this study indicate acoustic emissions from the turbine were below ambient sound levels and therefore did not have a significant impact on the underwater noise levels of the project site. As a component of Pacific Northwest National Laboratory’s Triton Field Trials (TFiT) described in this Special Issue, this effort provides a valuable use case for the IEC 62600-40 Technical Specification framework and further recommendations for cost-effective technologies and methods for measuring underwater noise at future current energy converter project sites.

A Summary of Environmental Monitoring Recommendations for Marine Energy Development That Considers Life Cycle Sustainability

“…The International Electrotechnical Commission (IEC) 62600-40 Technical Specification (TS) provides a valuable framework and guidance for selecting equipment and conducting data collection, analysis, and presentation of results for underwater noise measurements and acoustic characterization of CECs [11]. The IEC 62600-40 TS should be followed to the greatest extent possible to collect the most transferable data and analysis for comparisons across sites and devices [11]. An underwater noise field effort deployed a drifting hydrophone at the Portsmouth Memorial Bridge in New Hampshire and performed calibration tests in Sequim Bay (Figure 1).…”

“…Still, given the logistical challenges and data limitations, some modifications to field and analysis efforts will be needed to acquire meaningful data. For instance, moving the measurement zones to accommodate flow characteristics and avoid site-specific obstacles (e.g., reefs, piers, pilings) might be required [11]. Additionally, for acoustic measurements of CECs, flow shield mitigation strategies are critical [24,25].…”

“…These birds may be exposed to collision risk or underwater noise stressors while diving near an operational WEC. Deployment of hydrophones and underwater acoustic cameras near the WEC using similar technologies to [10,11] for short-term deployments may provide information necessary for understanding seabird diving behavior around WECs and the exposure time to underwater noise and collision risk stressors. Data may be used in ecological models to understand population effects over time [16].…”

“…This represents a scenario where the inclusion of a temporal parameter would aid the regulatory community by providing an opportunity to observe endangered species around ME devices. In combination with the integration of TFiT-tested technologies [10][11][12][13], temporal data may provide insight into stressor-receptor interactions necessary for removing barriers to the implementation of marine energy.…”

“…In this Special Issue, recommendations for monitoring technologies and methodologies are evaluated for four common environmental concerns: collision risk [10], underwater noise [11], electromagnetic fields (EMFs) [12], and changes in habitat [13,14]. The research reviewed technologies and methods to measure the impacts of ME devices in the open ocean and riverine environments around current energy converter (CEC) devices and a wave energy converter (WEC).…”