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The role of biofouling on the performance and survivability of dynamic subsea cables in floating offshore renewables


   Energy and Environment Institute

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  Dr Andrew Want, Dr Stuart McLelland, Dr Krysia Mazik  No more applications being accepted  Funded PhD Project (Students Worldwide)

About the Project

This PhD scholarship is offered by the Aura CDT in Offshore Wind Energy and the Environment; a partnership between the Universities of Durham, Hull, Newcastle and Sheffield. The successful applicant will undertake a PG-Dip training year and will continue their PhD research at University of Hull.

For more information visit www.auracdt.hull.ac.uk. Or if you have a direct question about the project, please email [Email Address Removed] and we will forward the query to the relevant supervisor. Please do not contact the project supervisors directly.

The project aim is to better understand how marine growth or biofouling impacts the functionality and vulnerabilities of dynamic subsea power cables (dSPCs) used in floating wind and marine renewable energy technologies. These technologies are expected to play a major role in fulfilling societal and governmental objectives to decarbonise electricity generation. However, success in the sector is partly dependent on removing economic uncertainties associated with these new technologies. An important concern is the impact of marine growth on the survivability of dSPCs. While cabling for an offshore wind farm accounts for around 9% of overall cost, dSPC failures may account for 75-80% of the costs of insurance claims on these projects. Such failures are costly to repair and may result in a significant loss of revenue due to disruption in power supply.

Dynamic subsea power cables, necessary to transmit electricity from floating devices to the seabed, are vulnerable to fatigue due to exposure to cyclic wave and tidal loads in the water column. The resulting structural failure is caused by lift and drag forces from the dynamic environment which are exacerbated by marine growth. Compared with static cables, the design of dSPCs is still under development as implications of operation in an exposed, dynamic environment continue to be assessed. Replacement of cables and components is costly in terms of materials, vessel-use, and operational ‘down-time’ of the turbine/farm.

The settlement and growth of marine organisms on submerged infrastructure (biofouling) will increase loading on dSPCs and may affect hydrostatic properties. Coupled with exposure to extreme hydrodynamics forces in the inherently energetic, resource-rich environments targeted for ORE deployments, dSPCs are highly vulnerable to fatigue failure. Existing studies on marine growth on offshore infrastructure, including dynamic mooring systems, are mostly restricted to the Oil and Gas (O&G) sector and inferences from these mooring systems to dSPCs are limited. Biofouling of dSPCs, and the subsequent impacts, are likely to differ considerably from existing studies because: (i) different component materials are used, with substrate being a major factor in the settlement and growth of marine organisms; (ii) installations are expected in ‘data poor’ regions without detailed knowledge of growth rates and species of biofouling organisms; (iii) heat and electromagnetic fields generated during cable operation will affect marine growth; and (iv) dSPC functioning is more complex with greater vulnerabilities than mooring structures. Standards and guidelines used in the ORE sector provide broad generalisations on marine growth, typically informed by surveys of large O&G structures, but these will have limited application for smaller diameter structures such as cables.

The objectives of this studentship are: to identify and assess impacts unique to these technologies, explore risk and economic consequences, highlight mitigation strategies and knowledge gaps, and to develop novel approaches to in situ ground-truthing of models used to predict cable behaviour.

A multi-disciplinary approach will be adopted to gather and quantify information on targeted knowledge gaps of the impacts to dSPCs from biofouling. The following topics will be addressed in this project: identification of marine growth specific to dSPCs and associated components; assessment of potential mitigations, including the latest antifouling strategies; characterisation of the impact of marine growth on hydrodynamic and structural response of dSPCs, with focus on fatigue life prediction; and appraisal of economic impacts and risks to assess installation, operation and maintenance costs of ORE farms.

This will be achieved through assessment of literature and investigation of current data on biofouling from floating offshore platforms, fixed offshore wind farms, O&G installations, etc. Monitoring methodologies to gather in situ fouling data will adapted to novel opportunities to study smaller diameter infrastructure in hydrodynamically energetic conditions. Boat based work will be conducted by the Primary Supervisor with possible opportunities for the student to engage in training necessary to work at sea.

Entry requirements

If you have received a First-class Honours degree or a 2:1 Honours degree and a Masters (or the international equivalents) in Engineering, Biosciences, Chemistry, Environmental Sciences, or Physics, we would like to hear from you.

If your first language is not English, or you require Tier 4 student visa to study, you will be required to provide evidence of your English language proficiency level that meets the requirements of the Aura CDT’s academic partners

Funding

The Aura CDT is funded by the EPSRC and NERC, allowing us to provide scholarships that cover fees plus a stipend set at the UKRI nationally agreed rates, circa £17,668 per annum at 2022/23 rates (subject to progress).

Eligibility

Research Council funding for postgraduate research has residence requirements. Our Aura CDT scholarships are available to Home (UK) Students. To be considered a Home student, and therefore eligible for a full award, a student must have no restrictions on how long they can stay in the UK and have been ordinarily resident in the UK for at least 3 years prior to the start of the scholarship (with some further constraint regarding residence for education).

How to apply

Applications are via the University of Hull online portal; you must download a supplementary application from the Aura CDT website, complete and submit.

For more information about the Aura CDT including links and detailed instructions on how to apply, please visit the website: https://auracdt.hull.ac.uk/how-to-apply/

Webinar

For more information why not watch a recording of the webinar we held on 29 November. You will be able to hear the Project Leads from each partner institutions, as well as the question and answer session that followed the presentations.


References

-Det Norske Veritas (2016). Loads and site conditions for wind turbines. DNVGL-ST-0437
-Marty, A., Berhault, C., Damblans, G., Facq, J.V., Gaurier, B., Germain, G., Soulard, T. and Schoefs, F., 2021. Experimental study of hard marine growth effect on the hydrodynamical behaviour of a submarine cable. Applied Ocean Research, 114, p.102810.
-Strang-Moran, C. and Mountassir, O.E. (2018). Offshore wind subsea power cables: installation, operation, and market trends, ORE Catapult
-Taormina, B., Bald, J., Want, A., Thouzeau, G., Lejart, M., Desroy, N. and Carlier, A. (2018). A review of potential impacts of submarine power cables on the marine environment: knowledge gaps, recommendations and future directions. Renewable and Sustainable Energy Reviews 96: 380-391.
-Want, A., Crawford, R., Harris, R.E., Kakkonen, J., Kiddie, G., Miller, S. and Porter, J.S. (2017). Biodiversity characterisation and hydrodynamic consequences of marine fouling communities on marine renewable energy infrastructure in the Orkney Islands Archipelago, Scotland, UK. Biofouling, 33(7), 567-579.
-Want, A., Bell, M. C., Harris, R. E., Hull, M. Q., Long, C. R., & Porter, J. S. (2021). Sea-trial verification of a novel system for monitoring biofouling and testing anti-fouling coatings in highly energetic environments targeted by the marine renewable energy industry. Biofouling, 37(4), 433-451.
-Yang, S.H., Ringsberg, J.W., Johnson, E. and Hu, Z. (2017). Biofouling on mooring lines and power cables used in wave energy converter systems Analysis of fatigue life and energy performance. Applied Ocean Research, 65, pp.166- 177.
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