C1 - Structural Integrity in the Marine Environment (corrosion, fatigue, coatings etc.)

C - Materials and Manufacturing

Status - published
Last updated on: 21/06/2022

Challenges/Opportunities

Corrosion and Fatigue degrade structural integrity and need to be better understood.

Solution

Experimental, Numerical and analytical damage models need to be developed, validated and verified for offshore structural integrity.

Context And Need

Offshore/marine renewables are subject to harsh deployment environments; corrosion fatigue is the primary progressive damage mechanism adversely affecting structural integrity and hence safety and LCoE; New markets, including USA and China, include extreme deployment conditions

Summary

Offshore wind components/assets need to withstand the harsh marine environment hence understanding of degradation mechanisms should warrant operability and safety of personnel.

Impact Potential

Expected potential impact is high in CAPEX/OPEX/survivability and safety.

Research Status

Joint Industry Projects over the past 4-5 years have mainly tackled such issues, informing fatigue assessment practices. However issues remain concerning corrosion fatigue, in particular:

  1. EPSRC CAMREG project
  2. Carbon Trust Projects
  3. Major Delft Corrosion projects
  4. Offshore wind structural lifecycle industry collaboration (SLIC): Joint industry project

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Active research projects:

  • Connectivity of Hard Substrate Assemblages in the North Sea (CHASANS) - Funded by NERC: NE/T010886/1: The aim of this project is to enhance our understanding of the connectivity of marine growth across artificial substrata in the North Sea. Team expertise in biofouling monitoring, oceanographic modelling, and population genetics will be used to generate a multidisciplinary dataset to validate biologically realistic models of larval connectivity. These models will be used to predict how networks of offshore renewable energy and oil & gas infrastructure in the North Sea function in biofouling dispersal and metapopulation structure.
  • Biodiversity characterisation and hydrodynamic consequences of marine fouling communities on marine renewable energy infrastructure in the Orkney Islands Archipelago, Scotland, UK: As part of ongoing commitments to produce electricity from renewable energy sources in Scotland, Orkney waters have been targeted for potential large-scale deployment of wave and tidal energy converting devices. Orkney has a well-developed infrastructure supporting the marine energy industry; recently enhanced by the construction of additional piers. A major concern to marine industries is biofouling on submerged structures, including energy converters and measurement instrumentation. In this study, the marine energy infrastructure and instrumentation were surveyed to characterise the biofouling. Fouling communities varied between deployment habitats; key species were identified allowing recommendations for scheduling device maintenance and preventing spread of invasive organisms. A method to measure the impact of biofouling on hydrodynamic response is described and applied to data from a wave-monitoring buoy deployed at a test site in Orkney. The results are discussed in relation to the accuracy of the measurement resources for power generation. Further applications are suggested for future testing in other scenarios, including tidal energy.
  • Self-Sensing and Energy-Harvesting (SSEH) composite materials for coastal infrastructure: The project is developing electrospun poly(vinylidene fluoride) sensors for integrity monitoring, and for energy-harvesting, on structures located in or adjacent to the marine environment.
  • Biostabilisation of sediments for erosion prevention: a cost-effective and sustainable solution: Biostabilisation artificially induces cohesion in sediments to produce highly resilient substrata to complement or replace traditional, hard-engineered scour prevention methods. It employs inert, natural biological polymers - 'biopolymers' - to inhibit particle movement, thereby increasing the sediment's resistance to erosion. A cost-effective and sustainable solution to a ubiquitous engineering problem.


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 Funding Research

Advanced, Modular Power Take-Off Design for Marine Energy Converters - Lead Institution: University of Edinburgh

Harvesting untapped wave energy represents both an attractive solution to support the move towards a carbon-free society and a major technical challenge to develop reliable Power Take-Off (PTO) systems that convert mechanical motion into electrical power. In recent years, all-electric PTO systems have been proposed with an aim to reduce system complexity in order to increase reliability and, ultimately, reduce the Levelized Cost of Energy (LCOE). This has led to the development of novel direct-drive generators that couple directly to the prime mover; the mechanical interface is therefore eliminated along with the wear and lubrication issues that have caused so many component failures in the wind energy industry. Despite the progress made in PTO design in recent years and the steps taken to reduce the LCOE of wave energy conversion, costs are still high compared to other renewable energy technologies where Operation and Maintenance (O&M) is still a key issue.

The project aims to reduce O&M costs by improving PTO reliability and simplifying maintenance through the use of integrated, power electronics – electrical machine, modular design. This aim addresses a very relevant and timely challenge in wave energy conversion by a need to reduce LCOE initially to be competitive alongside other renewable energy sources, with the longer-term goal to compete with established fossil-fuel generation.

COrrosion And fatigue protection of offshore wind Turbine structures using additive manufacturing technology (COATing): Lead Institution: Cranfield University

An efficient source of renewable energy, which is increasingly the preferred solution for realising Britain’s short- and long-term energy ambitions, is offshore wind. While Britain is presently the global leader in offshore wind energy, the national target set by the UK government to increase the installed capacity of offshore wind energy from approximately 10 GW in 2020 to 40 GW in 2030 demonstrates the strategic importance of this clean source of energy for the UK’s energy mix

Offshore wind turbines (OWTs) are typically designed for 20-25 years of operation. One of the main barriers for extending the operational lifespan of OWTs beyond 25 years is the evolution of corrosion-fatigue damage due to the constant exertion of wind, wave and current variable amplitude forces in the highly corrosive environments. The overall aim of this project is to develop permanent additively manufactured protective layers, as a novel coating technology, in the critical areas of offshore wind turbine (OWT) support structures. This will extend the lifespan, optimise and reduce the number of frequent inspections and deliver a direct beneficial impact on Operations and Maintenance (O&M) costs of OWTs.

LoadTide - Lead Institution: University of Edinburgh

This project will directly solve the challenge of measuring the fatigue performance of tidal turbine blades by generating, for the first time globally, statistically robust accelerated cyclic loading data for the lifetime of a fullscale tidal blade. This will be carried out at economic cost over a short timescale that will enable developer designs to be more quickly refined than is currently possible. Tidal turbines operate in a harsh marine environment, characterised by significant levels of flow unsteadiness, with tidal blades needing to withstand both deterministic (e.g. shear profile, tidal fluctuations) and stochastic (e.g. waves, turbulence) induced loads. The resulting fatigue loading is a significant cause of blade failure. Understanding these loads and their impact on blade structural performance is crucial in order to avoid premature failure and to increase confidence in tidal blade design, leading to reduced cost of energy. This project will model, define and apply these fatigue loads to develop a process for full-scale tidal blade testing.

Development of Thermoplastic Composite Tidal Blades for Enhanced End of Life Recycling and Lower Cost Manufacturing (ThermoTide): Lead Institution: University of Edinburgh

The ThermoTide project will investigate new sustainable tidal blade materials and manufacturing routes that are needed to meet mechanical fatigue and seawater erosion resistance requirements, facilitate low-cost manufacturing, installation and operation and enable maintenance, repair, recycling and reuse of tidal turbine blades. The proposed thermoplastic materials are processed rapidly at room temperature and can enable more effective assembly techniques such as automated thermal welding or novel, room-temperature cold infusion welding. Successful implementation of this novel thermoplastic composite technology in the tidal sector will reduce the manufacturing, maintenance and life cycle cost of blades and initiate a circular economy in this sector, leading to reductions in LCoE via reduced OPEX and CAPEX. This project will develop an understanding of the processing, mechanical performance, surface erosion, welding, effective repair and recycling of the new sustainable materials. Subsequent steps will be to design, manufacture and test a full-scale tidal blade from recyclable thermoplastic composites.

Physics-informed machine learning for rapid fatigue assessments in offshore wind farms
Lead Institution: University of Hull

Offshore wind energy is key in the UK’s plan to deliver the legally binding Net Zero 2050 targets, quadrupling the capacity by 2030. First-generation offshore wind monopiles are rapidly approaching their end of designed life. The next-generation of wind turbines are significantly larger, yet still monopile support
structures dominate. Accurate estimation of accumulated monopile fatigue is essential now, to inform decommissioning decisions, and optimise future design and maintenance. Due to unpredictable offshore environments, and the difficulty of taking structural measurements, fatigue predictions are subject to significant error.

This project proposes an industry-compatible step-change advance in accumulated fatigue assessment via novel integration of physical modelling and machine learning. The proposed model provides intuitive prediction of the level of fatigue for any turbine within the farm, at any point of its lifetime from distinct operational and environmental conditions, verifiable against physical models, yet with increased efficiency and fidelity of lifetime fatigue estimation

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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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