Wave energy and underwater noise: State of art and uncertainties

After several years of maturation of wave energy concepts and technologies some developers have finally reached a pre-mature phase. Over the course of this progress some concern has arisen regarding possible environmental impacts, however due to the limited number of devices tested in real sea conditions the few environmental studies available seldom resort to field data. Preliminary studies of wave energy converters (WECs) indicate that few and low environmental impacts are expected. However, with the forthcoming large scale deployment of WECs it will become possible to monitor the positive and negative environmental effects in more detail. Developers and promoters have demonstrated particular concern regarding the possible effects of underwater noise emitted by WECs. There are several references throughout the environmental studies on the potential impacts; however they tend to rely on literature reviews or comparisons to similar other offshore structures. Consequently there are several uncertainties related with this topic. The acoustic signature of each device will be a product of the combination of the different sources of noise within each WEC. Noise generation has a potential impact on marine fauna, for that reason it is necessary to identify the species present within the vicinity of the deployment area. In special cases sound can travel thousands of kilometres in water hence potentially affecting species which are far from the noise source. The paper includes a brief review of existing environmental studies/documents of individual devices and projections of future wave farms regarding underwater noise as an environmental descriptor. It also addresses present uncertainties and knowledge gaps associated with this subject.