SiPLABoratory

Wave Energy Acoustic Monitoring (WEAM)

WEAM aims at developing, testing and validating a monitoring system for determining underwater acoustic noise generated by wave energy-based generators and its impact in the sea fauna of. This study will be able to extend noise predictions to farms of wave generators with pre-determinined configurations. This project is financed by PTDC programme of FCT, with 182.4 kEuro for 3 years. Starting date: November 1st, 2007. Contract: PTDC/ENR/70452/2006

Whilst noise generation by single Wave Energy Devices (WED) is expected to be small, the presence of a large number of converters in the same area (wave energy farm) working in an almost continuous way may have some environmental impact due to the noise that propagates into the ocean. To present there are no acoustic environment impact studies based on real data and no experience on how such acoustic monitoring must be done. The development of a validated monitoring system, the characterization of up to three wave energy prototypes or farms of different technologies and the set-up of an acoustic monitoring plan are the expected results of the project. The results are expected to guide the development of a more environmental friendly technology and to clarify limits for the number and density of wave energy devices in a wave farm. The monitoring of the farms will be made using different acoustic receiver systems deployed in the vicinity of the wave farm: (a) a fixed stand alone system; (b) a mobile system; and an autonomous hydrophone with recording capabilities to be place a few meters away from the farm.

The resulting data will be analysed to characterize the generated noise (power spectral density content and spatial distribution of the generated noise) in the vicinity of the power plant/farm. This will clarify if the noise generated by the wave energy farm contributes significantly to the background noise of the area and, if so, if this is in a frequency range capable of affecting marine animals, in particular mammals. In such an event it is expected that the data will allow to identify the wave energy device components responsible for the generated noise, in order to improve the technology environmental friendliness and, as well, to identify the proper number and density of wave energy devices in a farm.

The objectives of the WEAM project are the following:

• To characterize noise generation by wave energy prototypes and farms in order to understand their contribution to the background noise at the site and, if this is significant, to identify the parts to the wave energy converters that contribute more to the generated noise, in particular in the frequency range with impact on marine animals, namely marine mammals.
• To develop a plan or guideline to perform acoustic monitoring of wave energy farms, including the type of monitoring equipment to be used, its location and monitoring duration and conditions and data analysis and output.
• To develop a fixed hydrophone calibrated system for long time series noise measurements including the spatial and time distribution of the underwater generated acoustic noise.