E2 - Extending limits to operation or performance by mitigating extreme actions

E - Survivability, Reliability and Design

Status - published
Last updated on: 25/03/2022

Challenges/Opportunities

High loads can occur due to dynamic response and interaction of response modes that limit system design.

Solution

Identification *and mitigation* of extreme loads and aggregated actions at system and component level.

Context And Need

A key cost reduction mechanism is the increase of the size of the power generating element of the ORE system, e.g. the turbine size or rated power of a wave device. As these parameters increase, stresses (actions) due to dynamic response can become prohibitive and so development of methods to mitigate and control system dynamics are required. To enable such increase of scale of key ORE design parameters improved understanding is required of the interaction of the environment with both the fundamental structural dynamics and control of the system.

Fundamental challenge is to enable modelling and prediction of peak (extreme) loads or actions accounting for environmental conditions interacting with the underlying system dynamics and control applied.

Designs in which load mitigation by continuous control of dynamic response becomes lower cost and / or larger scale than traditional design approaches.

Significant reduction of design safety factors.

Summary

Establish and extend operational limits or performance by better identifying and mitigating extreme loads and aggregated actions vs. operation behaviour at system and component level. Including interaction between environment and system control parameters and to extend operational limits of devices extending turbine size limits and fatigue life, understanding localised environment conditions to inform aggregated effects (e.g. on fatigue); modelling/prediction of extreme environmental loads.

Impact Potential

Increased reliability and reduced OPEX of existing designs

New designs with lower CAPEX per MW and / or increased performance

Research Status

Currently active research

  • Morphing-Blades: New-Concept Turbine Blades for Unsteady Load Mitigation
    Lead institution: University of Edinburgh
    Tidal turbines experience large load fluctuations due to the unsteady environment and the shear in the tidal flow. Mitigating these fluctuations without affecting the mean load would result in lower capital and operational costs. In this project we develop a morphing blade concept that achieves this goal by cancelling unsteady loads at the source.
  • Current EU and NREL projects on large wind turbines
  • FLOTANT - Innovative, low cost, low weight and safe floating wind technology optimized for deep water wind sites:The main objective of FLOTANT project is to develop the conceptual and basic engineering, including performance tests of the mooring and anchoring systems and the dynamic cable to improve cost-efficiency, increased flexibility and robustness to a hybrid concrete-plastic floating structure implemented for DWWF.
  • Autonomous Robotic Intervention System For Extreme Maritime Environments (ARISE) Stage 2: The Autonomous Robotic Intervention System For Extreme Maritime Environments will apply artificial intelligence to result in safer and more efficient operation, maintenance and inspection of offshore assets.
  • Extreme Loading on Floating Offshore Wind Turbines (FOWTs) under Complex Environmental Conditions: This project aims to fill an important gap in the design, manufacturing and testing of emerging FOWT techniques by specifically characterising extreme loading on FOWTs under complex and harsh marine environments. These are typically represented by storm conditions consisting of strong wind, extreme waves, significant current, rising sea level and complex interplay between these elements, through a coordinated campaign of both advanced CFD modelling and physical wave tank tests. This has direct relevance to the current and planned activities in the UK to develop this new technology in offshore wind.
  • SURFTEC - SUrvivability and Reliability of Floating Tidal Energy Converters: Identifying and understanding extreme and fatigue loads on tidal energy converters (TEC), understanding environmental extremes (other than main resource), and determining accessibility, serviceability criteria, fault intervals and associated device life cycles, are all important factors that can determine CAPEX and OPEX cost of devices and array deployments. This project will provide a holistic vision for design optimisation to ensure, reliability and survivability for floating TECs (FTECs). Computational modeling and real sea deployment measurements will provide a tool to inform the optimum operational strategy and maximise survivability and reliability for FTEC devices and arrays.

________________________________________________________________________________________

Supergen ORE Hub - Flexible Funding Research

  • 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.
  • iDRIVE: Intelligent Driveability Forecasting for Offshore Wind Turbine Monopile Foundations
    Lead Institution: Oxford University

    The UK government has set a new ambitious target of 40GW of offshore wind energy by 2030, aiming to produce sufficient wind capacity to power every UK home. The size of offshore wind turbines is increasing rapidly and continued optimisation in installation and design is key to the sustained expansion of the industry. Impact-driven monopiles remain the foundation of choice and accurate prediction of monopile driving behaviour is key to (i) choosing the optimal hammer size, (ii) ensuring that driving does not induce excessive fatigue stresses in the pile and (iii) avoiding an installation failure from refusal or free fall under self-weight. Industry currently relies on empirical methods to estimate soil resistance to driving (SRD) combined with soil rheological models built into wave equation software. Prediction of monopile installation behaviour has been shown to be uncertain using currently available empirical methods developed from a small database of long slender piles for the oil and gas industry. Given the large-scale nature of next-generation offshore wind farms (OWF), considerable savings (installation failures lead to multi-million pound remediation costs) can be realised if a more optimal, automated and adaptive approach to driveability prediction is adopted. The proposed framework uses Bayesian machine learning fused with conventional wave equation analysis to develop an up-to-date ‘uncertainty-quantified’ pile installation forecasting model. The tool will be rigorously validated using driving data from real-world OWF sites provided by industry partners. The research will develop new reliable tools for use by practitioners to predict the safe installation of monopile foundations.
  • Cost Effective Methods of Installing Offshore Wind Infrastructure
    Lead Institution: Aberdeen University
    This collaborative research proposal addresses a need for the development of novel, more efficient and cost effective methods for the installation of offshore windfarms. This is especially important in the context of the quest for obtaining Net Zero goals in the UK and is also of interest for temporary power supply during decommissioning of offshore Oil & Gas assets. The project builds on patented pumpable variable buoyancy technology (Deepbuoy), based on noncompressible liquids (deployable at depths up to 3000 m), incorporated into the Underwater Lifting System (ULS), developed and validated through the Knowledge Transfer Partnership project funded by Innovate UK to Technology Readiness Level 5. The proposed research programme will be underpinned by detailed modelling studies utilizing a state-of-the-art, real-time, real-physics Marine Simulator. This will be used to build models of the Deepbuoy technology to assess its applicability, benefits in terms of costs and reduced carbon footprint for installation of wind farms infrastructure. This project will also benefit from support Offshore Renewable Energy Catapult's Floating Offshore Wind Centre of Excellence (FoW CoE).
  • SharEd Anchor Multidirectional Load Envelopes with Strength Synthesis (SEAMLESS)
    Lead Institution: Southampton University
    This project addresses cost reduction in mooring/anchoring which is highlighted as an important research priority for floating wave and wind energy. Anchor sharing, by reducing the number of installed anchors, reduces capital expenditure of floating ORE farms that require hundreds of anchorages. The goal of this project is to identify a method for shared anchor geometry optimisation and develop new design guidance to unlock performance gains. This will be achieved by answering two fundamental questions: "What threshold level of upwards cyclic load can be sustained without significant ratcheting?" and "How does the stress history of vertical-lateral load interactions affect the capacity?" To address these questions, and create a framework for design solutions, this project will identify realistic shared-type loading and use a geotechnical centrifuge to apply these to caisson anchors in dense sand, representative of UK and European seabeds. Additional data from pressure sensors and X-ray tomography of the centrifuge samples alongside element level cyclic direct shear tests (CDSS) will be combined to study the fundamental mechanisms underlying the anchor-scale behaviour. A predictive framework for capacity variations and ratcheting quantification will be developed to create V-H failure envelopes combined with cyclic degradation/enhancement diagrams, extending current practice.

____________________________________________________________________________________________

Links to Industry Priorities:

____________________________________________________________________________________________

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

____________________________________________________________________________________________

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.

Return to homepage