B5 - Design of reliable cabling systems

B - Fluid-structure Seabed Interaction

Status - published
Last updated on: 22/03/2022

Challenges/Opportunities

Degradation and failure of cables due to processes such as cable-seabed interactions affects ORE reliability and will be increasingly important for floating wind.

Solution

Better understanding of cable failure mechanisms including cable-seabed interaction is needed to support ORE expansion.

Context And Need

Cabling system can contribute to the total cost of the ORE system and can be a single point of failure. Therefore, a more cost effective cabling design will improve confidence in project financial projections. Existing cabling designs are generally inherited from the onshore/offshore wind farms or the offshore oil and gas sectors, which may not be effective for the floating ORE farms. More reliable cabling designs are needed for ORE systems by considering the cable damage hazards such as the exposure or suspensions caused by seabed variations, failures under extreme environmental loads. Detecting sensors are needed to monitor the electrical performance and physical condition of the cabling in a marine environment to reduce the O&M cost. Better cabling designs are needed to reduce the potential environmental impacts associated with thermal radiation and electromagnetic fields, etc.

Summary

Better understanding is needed of the cable mechanics, hydrodynamics, fluid-structure interaction and interaction with a moveable sea bed, thermal and electrical effects; revisit fundamentals of exposure and support to unlock more cost-effective designs.

Impact Potential

Impact on CAPEX as more reliable cabling will be designed and therefore the design can be less conservative. Impact on OPEX as the cabling damage hazards will be fixed and detecting system will be applied, leading to reduction of the O&M cost.

Research Status

Existing projects:

Previous research projects:

  • A review of potential impacts of submarine power cables on the marine environment: Knowledge gaps, recommendations and future directions: Submarine power cables (SPC) have been in use since the mid-19th century, but environmental concerns about them are much more recent. With the development of marine renewable energy technologies, it is vital to understand their potential impacts. The commissioning of SPC may temporarily or permanently impact the marine environment through habitat damage or loss, noise, chemical pollution, heat and electromagnetic field emissions, risk of entanglement, the introduction of artificial substrates, and the creation of reserve effects. While growing numbers of scientific publications focus on impacts of the marine energy harnessing devices, data on impacts of associated power connections such as SPC are scarce and knowledge gaps persist. The present study (1) examines the different categories of potential ecological effects of SPC during installation, operation and decommissioning phases and hierarchizes these types of interactions according to their ecological relevance and existing scientific knowledge, (2) identifies the main knowledge gaps and needs for research, and (3) sets recommendations for better monitoring and mitigation of the most significant impacts. Overall, ecological impacts associated with SPC can be considered weak or moderate, although many uncertainties remain, particularly concerning electromagnetic effects.

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Supergen ORE Hub - Flexible Fund Research

  • Impact of in-service oscillatory movement on insulation reliability of AC and DC cables serving offshore platforms
    Lead Institution: University of Manchester
    Offshore wind energy is central to UK’s ambition of reducing carbon emissions. Traditional fixed foundation wind farms have limitations due to their surrounding environment and congestion, whereas floating platforms provide utilisation of deeper waters and increased capacity, for example in the North Sea. The Floating Wind Joint Industry Project Report 2018 identified cables to be at the heart of priority innovation needs. Typically, cable assets contribute to 5-10% of the total investment costs for an offshore wind farm. However, cable failures cause the majority of the offshore power outages and account for approximately 80% of insurance claims in this industry.

    The hypothesis explored in this proposal is that repeated flexing of a cable significantly reduces the cable’s life expectancy through repeated extension and compression of the polymeric dielectric. In particular, the impact of dynamic strain on a failure mechanism known as electrical tree growth will be explored. Electrical trees are microscopic tree-like voids which grow inside the insulation that eventually lead to catastrophic asset failure. The project will work closely with ORE Catapult’s dynamic cable bend fatigue rig team in Blyth, to conduct the test trial combining the mechanical flexing and electrical treeing concurrently.
  • Cable scour from fluid-seabed interactions in regions of mobile sedimentary bedforms
    Lead Institution: Bangor University
    Growing demand for renewable forms of energy extraction highlights the essential role of subsea power cables. In 2018, UK’s operational offshore wind farms were using 1,499 km of export and >1,806 km of inter-array cables to transport 6,385 MW of electrical power. 43 array and export cable failures have been reported between 2007 and 2018, resulting from a number of reasons including sediment and sedimentary bedform mobility and accidents from e.g. dredging and benthic fishing.

    This proposal is the first to make detailed field measurements of scour development over a section of real subsea cable. Existing assessments of cable scour from state-of-the-art labs and numerical models have provided valuable insight but are inherently limited. This project aims to provide a validated benchmark scenario linking turbulent flow and scour development relevant to ORE subsea cables at local to centimetric scales. To allow industry to apply new knowledge in the development of upscaled lab experiments and numerical models to provide optimised methods for cable protection, particularly where array-scale effects may feedback to and modify seabed mobility over larger areas than expected.

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Links to Industry Priorities:

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We would also like to invite UK researchers and industry stakeholders within ORE to submit links to research projects, both past and present, for inclusion within the landscape.

Therefore, if you have a UK-based research project within an area of ORE that you feel is relevant to a specific research theme or challenge within the Research Landscape, click HERE to submit your research project to the research landscape

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PhD projects in Offshore Renewable Energy

In order to better understand the breadth of ORE research currently being conducted in the UK, the Supergen ORE Hub has collated from its academic network, UK Centres for Doctoral Training and Industrial partners, a list of PhDs currently being undertaken in ORE.

Access a PDF of the list and find out more about including your PhD.

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