Environmental Impact from Wave Energy Converters : Underwater Noise

Abstract: Wave energy conversion is a potentially clean and sustainable form ofenergy conversion with no emissions of gases or liquids during operation.There are other environmental issues that need to be taken in consideration.The deployment of a wave power farm will contribute with new surface formarine organisms to colonize. Submerged structures attract marineorganisms, both sessile and mobile. This has been observed on thegenerators in Lysekil project, this is called reef effect. Several marineorganisms have sensory systems that allows them detect electromagnetism.If the electromagnetism in the generators and sea cables will have an impacton these organisms is yet to be studied. Underwater noise is another topicthat needs to be concerned. This thesis presents a study on underwater noisefrom a full scale Wave Energy Converter (WEC) in the Lysekil Project.A hydrophone measured the underwater noise emitted from operatingdirect driven linear Wave Energy Converters in the spring of 2011. The mainpurpose was to study the emitted noise from an operating WEC, to determinecharacteristics such as spectrum levels, Sound Pressure Level (SPL), pulseduration and repetition rate.The results showed that the main noise is a transient noise with most of itsenergy in frequencies below 1 kHz. These results indicate that severalmarine organisms (fish and mammals) will be able to hear the operatingWECs. Although no behavioural reactions or injuries due to high soundpressure levels (SPLs) are expected.