Noise emissions from two tidal turbines; an experimental field campaign

The first tidal turbine arrays have now been installed as the world strives to reach net zero carbon targets by 2050. Underwater noise emissions from single tidal turbine devices have caused some environmental concern in the past and therefore determining levels of noise emitted from these structures has become a crucial component of the consenting process. Ecological concerns include auditory masking for local fauna, presenting potential migration barriers and affecting predation. While some progress has been made in characterising noise emissions from individual tidal turbines in realistic field conditions, little is known about the noise field created by multiple turbines. This paper presents a first analysis of the variation of noise emissions of an array of two test turbines, deployed from a moored floating platform in the Strangford Narrows, Northern Ireland. Data was acquired using a drifting hydrophone for zero, one and two turbines operating under different control settings. Data analyses were complicated by the limited amount of data. Stopping the turbines completely does not necessarily result in minimum noise emissions, potentially due to flow separation from the stationary blades, turbulence and induced structural vibrations.