Name: Frank Thomsen
The construction and operation of marine renewable energy developments (MREDs) will lead to, among other things, the emission of electromagnetic fields (EMF), underwater sound, and vibrations into the marine environment. Knowledge on these pressures and associated effects has been increasing over the past decade. Yet, many open questions with regard to the potential for MRED to impact on marine life remain. These information gaps pose challenges to the planning and deployment of MREDs. To address this, the European Union (EU) Commission, Directorate-General for Research and Innovation commissioned a study of the environmental effects of noise, vibrations and electromagnetic emissions from MREDs (Marine Renewable Energy, Vibration, Electromagnetic fields and Noise - MaRVEN). MaRVEN provides a review of the available literature related to environmental impacts of marine renewable energy devices and an in-depth analysis of studies on the environmental effects of noise, vibrations and electromagnetic emissions during installation and operation of wind, wave and tidal energy devices. The current norms and standards related to noise, vibrations and EMF were reviewed. On-site measurements and field experiments to fill priority knowledge gaps and to validate and build on the results obtained in reviews were undertaken. Finally, we outline a programme for further research and development with justified priorities.
In a project for the European Union (EU) Commission, Directorate-General for Research and Innovation, we undertook a study of the environmental impacts of noise, vibrations and electromagnetic emissions from MREDs (Marine Renewable Energy, Vibration, Electromagnetic fields and Noise - MaRVEN). The aims of MaRVEN were to critically review the available scientific evidence and significance of those impacts and then make recommendations on solutions to mitigate or cancel any identified negative impacts. The investigation comprised several tasks including:
- Provision of an historical review of the publications related to environmental impacts of marine renewable energy developments
- An in-depth analysis of studies on the environmental impacts of noise and vibrations during installation and operation of marine renewable energy devices
- An in-depth analysis of studies on the environmental impacts of electromagnetic emissions during the operation of marine renewable energy devices
- An in-depth analysis of the current norms and standards related to noise, vibrations and EMF for marine renewable energy systems
- Performance of relevant on-site measurements and field experiments to validate and build on the results obtained in above studied
Electric and magnetic fields from industry standard inter-array and export electricity cables were clearly measurable during power generation by offshore wind turbines. The EM field emitted by a wind turbine was considerably weaker than the field from the cables.
The emitted EMFs were higher for the export cables to shore compared to the inter-turbine cables, which were predicted, based on the amount of power being transmitted and the lower electrical capacity rating of the cables.
Of the two components making up the EMF (E fields and B fields) of the AC cables studied, the electric fields measured were within the range of known detection by sensitive receptor species (principally the sharks, skates and rays). The magnetic field component was however at the lower end and potentially outside of the known detectable range of sensitive species.
Two different methods to measure EMF were trialed, drifting and sledge towing. The drifting method has the advantage that it can assess the EMF relatively quickly and it avoids the potential risk of damaging the sensors on the seabed. The seabed sledging demonstrated that the EMF at the seabed, where cables are buried, can be measured as well as the propagation distance if the sledge is pulled perpendicular to the axis of the cable.
The measurement technology was proven and demonstrates that components of the EM fields at biologically relevant levels can be observed both by suspending the sensors from the side of a boat as well as by sledging. The results are restricted to AC-transmission systems and are transferable between device types using cables of similar characteristics. The same methodologies should be employed on a DC-transmission system.
Thomsen, F.; Gill, A.; Kosecka, M.; Andersson, M.; André, M.; Degraer, S.; Folegot, T.; Gabriel, J.; Judd, A.; Neumann, T.; Norro, A.; Risch, D.; Sigray, P.; Wood, D.; Wilson, B. (2015). MaRVEN - Environmental Impacts of Noise, Vibrations and Electromagnetic Emissions from Marine Renewable Energy. Report by Danish Hydraulic Institute (DHI). pp 80.