Monitoring the condition of Marine Renewable Energy Devices through underwater acoustic emissions: Case study of a wave energy converter in Falmouth Bay, UK
© 2016 Elsevier Ltd. All rights reserved.
Reason for embargo
Abstract Maintaining the engineering health of Marine Renewable Energy Devices (MREDs) is one of the main limits to their economic viability, because of the requirement for costly marine interventions in challenging conditions. Acoustic Emission (AE) condition monitoring is routinely and successfully used for land-based devices, and this paper shows how it can be used underwater. We review the acoustic signatures expected from operation and likely failure modes of MREDs, providing a basis for a generic classification system. This is illustrated with a Wave Energy Converter tested at Falmouth Bay (UK), monitored for 2 years. Underwater noise levels have been measured between 10 Hz and 32 kHz throughout this time, covering operational and inactive periods. Broadband MRED contributions to ambient noise are generally negligible. Time-frequency analyses are used to detect acoustic signatures (60 Hz–5 kHz) of specific operational activities, such as the active Power Take Off, and relate them to engineering and environmental conditions. These first results demonstrate the feasibility of using underwater Acoustic Emissions to monitor the health and performance of MREDs.
JW is funded by the Natural Environment Research Council (NERC grant NE/L002434/1) as part of the GW4+ Doctoral Training Partnership (http://www.nercgw4plus.ac.uk/). IB is funded through the SuperGen UK Centre for Marine Energy Research (EPSRC grant EP/M014738/1). The authors would also like to thank M.J. Witt (U. Exeter) for his invaluable assistance with acoustic data collection  and , funded by ESF, PRIMaRE, MERiFIC, TSB and Fred Olsen Renewables.
Vol. 102, Part A, pp. 205 - 213