Acoustic life cycle assessment of offshore renewables—Implications from a wave-energy converter deployment in Falmouth Bay, UK

Marine Renewable Energy is developing fast, with hundreds of prototypes and operational devices worldwide. Two main challenges are assessing their environmental impacts (especially in near-shore, shallow environments) and ensuring efficient and effective maintenance (requiring specialised ships and fair weather windows), compounded by the lack of long-term measurements of full-scale devices. We present here broadband measurements (10 Hz to 32/48 kHz) acquired at the Falmouth Bay Test site (FaBTest, UK) from 2010 onwards, for a 16-m ring-shaped Wave Energy Converter, in waters up to 45 m deep. This period covers baseline measurements, including shipping from the neighbouring English Channel, one of the busiest shipping lanes in the world (ca. 45,000 ship transits annually) and the full period of installation and energy production, including maintenance episodes. Acoustic signatures are measured as Sound Pressure Levels (e.g. for impacts) and time/frequency variations (for condition-based monitoring via Acoustic Emissions). They change through time, depending on weather and modes of operation. Long-term measurements are compared with modelling of potential variations in this complex environment and with laboratory experiments. These are used to outline the varying acoustic contributions through the life cycle of a typical wave energy converter, yielding insights for other wave devices in other environments.