Abstract
In the WESE project scope, Work Package 2 aims to collect, process, analyse and share environmental data collected in sites where Wave Energy Converters (WEC) are operating in real sea conditions in Spanish and Portuguese coastal waters, representing different types of technology, sites and, therefore, types of marine environment (onshore, nearshore and offshore) that can potentially be affected by wave energy projects: (i) Idom-Oceantec MARMOK-A-5, installed in the Biscay Marine Energy Platform (BiMEP) in Spain; (ii) Mutriku Wave Power Plant, in operation in the Mutriku (Spain); and (iii) WaveRoller (AW-Energy), installed in Peniche (Portugal).
This specific deliverable presents the results of the task 2.3, that is, the reports of the acoustic monitorization campaigns and, most significant, the characterization of the wave energy converters through analysis of the acquired data by the monitorization plans designed in deliverable D2.1. To this end, acoustic signal processing techniques were applied to the raw audio data gathered from the monitoring campaigns, and mean sound pressure levels were obtained for all third octave frequency bands between 10 and 1000 Hz, taking into account sea state conditions.
In general, the contribution of the devices operation to the ambient soundscape is not very significative. Starting with the MARMOK-A-5 device, the most significative contribution to its surrounding soundscape appears between 40 and 120 Hz, with increments of 14 dB re ?Pa (??<1 m), 13 dB re ?Pa (1 ?≤??<2 ?) and 6 dB re ?Pa (??>2 m), even though the variability is relevant. Another sources of noise, most relevant with high wave heights, are the mooring chains, which can be perceived at frequencies beyond 2500 Hz, with SPL values approximately ranging from 90 (for lower wave heights) to 105 (higher wave heights) dB re 1 μPa. It should be noted that this metrics have been calculated at a distance of 90 meters away from the converter.
Following with the Mutriku Power Plant, there is no clear indication of an increase in the sound pressure levels when the plant is operating, at least at a distance of 1000 meters away from the central. As it corresponds to a shallow water environment, the lower frequencies are shown to be filtered out, therefore being the higher frequencies those with more acoustic energy. In any case, the higher difference (between background noise and the sound with the plant working) of sound pressure levels is just about 5 dB re 1 μPa, at 80 Hz, below typical deviations.