COWRIE is pleased to announce the publication of a new report into the potential effects of electromagnetic fields generated by the sub-sea power cables associated with offshore windfarms on electrically and magnetically sensitive marine organisms.
The report follows a first phase of research completed in July 2003 which identified the generation of magnetic and induced electric fields from sub-sea cables such as those associated with offshore windfarms. That first report concluded that even though these fields are within the range of detection by certain aquatic species no clear scientific guidance on the effects on receptor species could be provided without further work.
COWRIE then commissioned the Centre for Marine and Coastal Studies Ltd (CMACS) and the Institute of Water and Environment, Cranfield University, to review all currently available information to update the original Phase 1 investigation. CMACS was also tasked with identifying priorities for the next phase of research to improve understanding and assist the offshore wind industry and regulators in inappropriately managing EMF.
The study aimed to explore whether the interaction between the fish and the artificial fields will have any consequences for the fish. The study found that there are fish species present at development sites which may respond to anthropogenic sources of E field. Although the information available on magnetosensitive species is limited, it does suggest that potential interactions with a number of UK coastal organisms could occur from the cellular through to the behavioural level.
The study presents a prioritised list of species that are most likely to interact with offshore wind farm generated EMFs. It also offers practical guidance for developers in terms of suitable monitoring that may be undertaken and an overview of possible survey methods for electrically and magnetically sensitive species, their advantages and disadvantages.
The report concludes that greater understanding of the environmental impact of EMF emissions is urgently required owing to the lack of current knowledge and scale of the planned wind programme. The report makes recommendations for a final study and this is currently under consideration by the COWRIE Environmental Working Group.
Background
Offshore windfarms require a network of interconnecting cables and a cable link to land for connection to the national grid. These cables generate electromagnetic fields and may impact Elasmobranch species as these are known to have electro-receptive organs and to utilise electric fields for prey detection, orientation and navigation. These effects need to be quantified and reviewed
The 2001 report (Gill & Taylor) commissioned by the Countryside Council for Wales (CCW) into the potential effects of electromagnetic fields generated by cabling for offshore windfarms re-emphasised these potential impacts and recommended that further studies would be required.
Anthropogenic sources of electric and magnetic fields have been present in the marine environment for many years, eg offshore cables and pipelines. Although these sources are more limited in their spatial extent, they do have varying potential to produce electric and/or magnetic fields of comparable magnitude to those associated with the offshore wind farms. It is clear from the review of industry based material that the issue of the effects on electrically and magnetically sensitive species has not been addressed consistently and that there are a number of important misconceptions.
Phase 1.5 Report
The potential effects of electromagnetic fields generated by sub-sea power cables associated with offshore wind farm developments on electrically and magnetically sensitive marine organisms – a review
Contract awarded to Cranfield University Silsoe and Centre for Marine and Coastal Studies (CMACS)
Contract Completed: September 2005
Objectives
Following the Phase 1 recommendations, COWRIE prioritised the need to update the original study with the most recently available information and further consider the potential effects of EMF on electrically and magnetically sensitive marine organisms. This would help inform a final, and potential larger investigation (Phase 2).
This interim investigation (Phase 1.5) aimed to prioritise those fish species most likely to interact with the EMFs generated by offshore wind farm cables.
In light of the results of the review and analysis, a key objective was to produce practical guidance to developers where possible. For example, FEPA licensing conditions which determine the environmental monitoring requirements for consented offshore windfarms generally state broad principles but leave the details open for discussions between the developer (and their scientific consultants) and statutory bodies. To assist in this process, the study considered monitoring that would be appropriate in light of the review undertaken. An overview of possible survey methods for electrically and magnetically sensitive species has also been included, together with advantages and disadvantages.
This included suitable monitoring that could be undertaken and an overview of possible survey methods for electrically and magnetically sensitive species, their advantages and disadvantages.
Methodology
The study included a comprehensive review and analysis of information currently available on electrosensitive and magnetosensitive species. It also involved consultation with the offshore wind industry and the review of a range of industry information.
From the conclusions of this work, practical guidance was developed to help overcome problems that are currently faced.
Conclusions and Recommendations
- 1. From the review of industry-based material it is clear that the issue of electromagnetic effects on electrically and magnetically sensitive species has not been addressed consistently. Despite the other anthropogenic sources of electric and magnetic fields in the marine environment, the wind industry’s attempts to consider environmental interaction of EMFs is hampered by a lack of information and guidance.
- 2. The study considers that identification of species most likely to interact with the EMFs is an important first step, acknowledging that this will vary according to habitat, conservation status and that different life stages need to be considered. It must also be determined whether these species will be affected and the potential significance of any effects identified.
- 3. The study recommends that the significance of larger Round Two projects is specifically considered and that cumulative impacts of adjacent developments, not just windfarms, are addressed.
- 4. To advance the work, a two-stage programme is suggested. The first stage would definitively determine whether an electromagnetically sensitive species responds to the EMF associated with an industry-standard offshore wind farm electricity cable. Should this conclude that there are effects, a second stage would involve monitoring electrically and magnetically sensitive species.
This next phase of work is currently under consideration.
Phase 1 Report:
A Baseline Assessment of Electromagnetic Fields Generated by Offshore Windfarm Cables
Contract awarded to Centre for Marine and Coastal Studies (CMACS), University of Liverpool.
Contract Completed: July 2003
Aims and Objectives
Phase 1 was a desk based study to calculate the strength, frequencies and wavelengths of the electromagnetic fields produced by 33 kV (EPR) and 132 kV (XLPE) cables. The study also calculated the effects of burial and / or shielding (at various depths, strata, sediment type and thickness) on electromagnetic fields.
Key Outputs
A technical report which progresses the work undertaken by the Countryside Council for Wales and draws upon that being conducted in European offshore windfarms
‘Best practice’ guidance for developers on the mitigation measures required for offshore and intertidal cabling
Presentation to the BWEA offshore focus group and at BWEA conference or workshop as required by COWRIE
Methodology
The project specification required the following:
- Literature review of data on electromagnetic fields related to existing sub-sea and terrestrial power cables.
- Identification and assessment of work in progress in other European windfarm sites (e.g. Denmark) and contact with similar research programmes.
- Calculate the strength, frequency and wavelength of electromagnetic fields generated by 33 kV (EPR) and 132 kV(XLPE) cables in air, freshwater and seawater (average).
- Calculate the variation in electromagnetic fields generated by 33 kV and 132 kV cables after burial at different depths, in different sediment types (silt, sand) and above different rock strata.
- Calculate the variation in electromagnetic fields generated by 33 kV and 132 kV cables incorporating different thickness of shielding – a description of the type of shielding available is also required (average).
- Review and calculation of various combinations of burial and shielding (average).
- Review the possible causes of fluctuation in and calculation of a maximum and minimum (if appropriate) for electromagnetic fields generated by the above permutations, including combined effects of multiple adjacent cables.
- Limited field measurements at an existing offshore windfarm site for comparison / validation of calculations for a subset of the above mentioned permutations, including a full description of cable shielding, burial depth, overlying sediment type, underlying strata etc in use.
Objectives
Phase One was intended as a baseline assessment of electromagnetic fields and the study focused on mathematically modelling the likely EMF emitted from a subsea power cable.
The Objectives study were to investigate:
- The likely EMF emitted from a subsea cable
- A suggested method to measure EMF in the field which could be applied by windfarm developers
- guidance on mitigation measures to reduce EMF
- consideration of the results for the next stage of investigation into the effects of EMF on electrosensitive species
Results and Recommendations
The study found that the EMF emitted by industry-standard AC offshore cables had a magnetic (B) field component and an induced electric (iE) field component that are within the range of detection by EM-sensitive aquatic species.
Potential mitigation measures to reduce the induced E-field include changes to the permeability of power cable armour and conductivity of the cable sheath and armour. Cable burial was found to be ineffective in ‘dampening’ the B-field but burial to a depth of at least 1m is likely to provide some mitigation for the possible impacts of the strongest B-field and iE-fields on sensitive fish species due to the physical barrier of the substratum. Using substations to convert the voltage from 33kV to 132kV also reduces the current carried by the cable and therefore the induced E-fields.
The report identifies that further studies are needed to fully understand the interaction of the induced E-fields from subsea power cables with electrosensitive fish and the implications of the B-fields for organisms that rely on a magnetic sense.
