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

Project Description:

This PhD scholarship is offered by the Aura Centre for Doctoral Training 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.

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The Project

The aim of this project 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. Specifically, bespoke frames containing infrastructure samples (including different materials relevant to the sector) will be deployed and periodically retrieved for sample collection based on a system developed by Want et al. [2021].

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. Opportunities to ‘piggy-back’ marine operations with other research projects to allow additional sampling points or to extend the period of data collection will be pursued. Community composition analysis will use PRIMER techniques. Opportunities to receive additional in situ data from ORE installation surveys will be pursued and may allow the inclusion of thermal and electromagnetic effects on biofouling generated by ‘live’ cables to be investigated. OrcaFlex and ANSYS/UFLEX software may be used in modelling the impact of marine growth on cable structural response and predicted fatigue life.

For more information visit www.auracdt.hull.ac.uk. If you have a direct question about the project, you may email auracdt@hull.ac.uk or the project supervisor.

Training and skills 

This programme provides training and networking opportunities, and these will be encouraged throughout this studentship. Postgraduate training provided by the University of Hull includes courses in project management, research grant writing, manuscript development, and developing statistical analysis skills. Specific training and development opportunities may include:

• Development of novel field experimentation to study cable responses to different levels of marine growth
• Training in community composition analysis using PRIMER techniques
• Development of research skills available through ‘in-house’ training at UHull
• OrcaFlex and ANSYS/UFLEX software (or similar) for modelling cable behaviour
• Applying GIS to map and study spatial and temporal data
• Engagement with a broad range of stakeholders beyond academia, e.g. regulators, industry, etc.
• Development of peer-reviewed publications
• Presentations at leading scientific/engineering conferences

Entry requirements

This PhD research project is suitable for applicants with a background in Engineering, Biosciences, Environmental Sciences or Physics. If you have received a First-class Honours degree OR a 2:1 Honours degree and a Masters OR a Distinction in a Masters Degree, with any Undergraduate Degree, in one of the above subjects, (or the international equivalents,) 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. This course requires academic IELTS 7.0 overall, with no less than 6.0 in each skill.

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). For full eligibility information, please refer to the EPSRC website. Please note, we have already allocated all our places for International Students to this cohort, so please do not apply unless you are a Home student.

How to apply

Recruitment is open until 16 April 2023 for Aura CDT PhD Scholarships beginning study in September 2023.

Applications are made via the University of Hull admissions system.

If you have not applied with the University of Hull before, you will need to set up an account to enable you to track the progress of your application and upload supporting documents.

With your application, you need to upload copies of the following supporting evidence:

• complete transcripts (and final degree certificate(s) where possible). If your qualification documents are not in English, you will need to supply copies of your original language documents as well as their official translation into English.
• A completed Supplementary Application Form (please upload when asked to add Personal Statement).

Guidance on completing your Supplementary Application Form: The Aura Centre for Doctoral Training is committed to generating a diverse and inclusive training programme. As part of our inclusive practices, the Centre adopts a process of assessing applications purely based on skills and attributes and does not consider any personal details. As such we ask applicants to remove any personal details from the Supplementary Form which is used by the Panel to assess and select applicants for interview. The form asks for details of your education, training and employment history as well as some specific questions about your motivations and research experience and interests. It is very important that you do not include any personally identifying information.

Applicants must:

Remove all personal references in their application. Specifically, do not include the following details: Names, age, country, sex, gender, religion, disability, race, sexual orientation

Complete all sections of the form in font and size Calibri 11pt

Indicate your interest in applying to a maximum of two Research Projects (you may apply for one or two, but no more than two)

Once fully completed, you should upload the form when asked for your Personal Statement, as part of your application through the University of Hull student application portal using the links below. (You will also be asked for your degree transcripts during the application process). Please do not send your form directly to the Aura CDT.

Application links:

Apply for a full-time PhD Scholarship with the Aura CDT.

Apply for a part-time PhD Scholarship with the Aura CDT.