Mooring analysis and design for offshore WEC survivability and fatigue (MoorWEC)

海上 WEC 生存能力和疲劳的系泊分析和设计 (MoorWEC)

• 批准号: EP/V039946/1
• 负责人: Peter Stansby
• 金额: $ 129.12万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FV039946%2F1
• 关键词: Mooring; analysis; design; offshore; WEC

Wave energy globally has potential average power slightly less than wind but this has been unexploited to date. We are concerned here with wave energy converters (WECs) offshore, before the energy resource is reduced by shallow-water effects, which would be suitable for grid scale electricity generation. Individual WEC capacity has been considered to be much smaller than for wind turbines and cost of energy (COE) considerably larger. However, with multi-mode, multi-float systems, capacity may be similar to or greater than wind in some locations and COE has been estimated to be similar to offshore wind. Survivability in extreme waves needs to be established, along with reliability of components. The mooring is the most vulnerable structural component of an offshore wave energy converter. Snap loads are a particular problem in extreme waves, and also in intermediate waves affecting fatigue. There is a widespread consensus in the wave energy community that mooring system design and modelling is a major challenge that needs to be overcome. Although literature and design guidelines for conventional ocean engineering applications are abundant, in general they do not account for the requirements of wave energy conversion, where the mooring should not inhibit platform motion causing the energy generation. Design, optimization, and assessment of mooring systems require efficient hydrodynamic and dynamic mooring models, which should be fully coupled to represent all interactions. There are various mooring options: catenary slack moored, elastic taut moored, combinations with single point (buoy) moorings, and nylon/polyester ropes offer an economic option while reducing snap loads. While some progress has been made with nonlinear hydrodynamic WEC loading models for point absorbers, an efficient general nonlinear hydrodynamic loading model for multi-bodies, accounting for wave breaking, is presently not available. Computational fluid dynamics (CFD) simulations require days, even weeks, to run on multiple processors and is unreliable for complex dynamic problems. The intention here is generalise efficient linear hydrodynamic load models by including the fully nonlinear force component due to the pressure field in the waves, known as the Froude-Krylov force. This has improved predictions of response and mooring load, markedly in some cases. This will be advanced through comparison with experimental wave basin tests and formally generalised through system identification, for single and multi-bodies with a range of mooring configurations in representative, generally multi-directional wave fields and currents. The convenient simplification of linear wave input will also be assessed with a revised force formulation determined by system identification. These force formulations will be coupled with the general industry-standard mooring model Orcaflex accounting for dynamic and material properties enabling design optimization using multi-objective genetic algorithms. This will enable survivability, fatigue and reliability analyses.

全球波浪能的潜在平均功率略低于风能，但迄今为止尚未开发。我们在这里关注的是波浪能转换器（WEC）离岸，在能源资源减少浅水效应，这将是适合电网规模的发电。单个WEC容量被认为比风力涡轮机小得多，能源成本（COE）要大得多。然而，对于多模式、多浮子系统，在某些位置，容量可能类似于或大于风力，并且COE估计类似于海上风力。需要确定在极端波浪中的生存能力沿着组件的可靠性。系泊系统是海上波浪能转换装置中最脆弱的结构部件。突变载荷在极端波浪中是一个特别的问题，在影响疲劳的中间波浪中也是如此。在波浪能界有一个广泛的共识，即系泊系统的设计和建模是一个需要克服的重大挑战。虽然传统海洋工程应用的文献和设计指南是丰富的，但一般来说，它们不考虑波能转换的要求，其中系泊不应抑制引起能量产生的平台运动。系泊系统的设计、优化和评估需要高效的流体动力学和动力学系泊模型，这些模型应完全耦合以代表所有相互作用。有多种系泊选项：悬链松弛系泊、弹性拉紧系泊、与单点（浮标）系泊组合，以及尼龙/聚酯绳索提供了一种经济的选择，同时减少了突然载荷。虽然点吸收器的非线性水动力WEC加载模型已经取得了一些进展，但目前还没有一个有效的多体非线性水动力加载模型，考虑波浪破碎。计算流体动力学（CFD）模拟需要几天甚至几周的时间在多个处理器上运行，并且对于复杂的动态问题是不可靠的。这里的目的是通过包括由于波浪中的压力场而产生的完全非线性力分量（称为Froude-Krylov力）来概括有效的线性水动力载荷模型。在某些情况下，这显著改善了对响应和系泊载荷的预测。这将通过与实验性波浪水池试验的比较来推进，并通过系统识别正式推广，适用于具有代表性的一系列系泊配置的单体和多体，通常是多方向波场和海流。线性波输入的方便简化也将与系统识别确定的修订的力公式进行评估。这些力公式将与通用行业标准系泊模型Orcaflex相结合，考虑动态和材料特性，从而使用多目标遗传算法进行设计优化。这将使生存性，疲劳和可靠性分析。

项目成果

Trends in Renewable Energies Offshore

海上可再生能源趋势

• DOI: 10.1201/9781003360773-34
• 发表时间: 2022
• 作者: Zhao C

OrcaFlex predictions for a multi-float hinged WEC with nonlinear mooring systems: Elastic mooring force and dynamic motion

• DOI: 10.1016/j.oceaneng.2023.115504
• 发表时间: 2023-10
• 期刊: Ocean Engineering
• 影响因子: 5
• 作者: Chenyu Zhao;P. Stansby;L. Johanning

Experimental measurements of two elastic taut-slack mooring configurations for the multi-float M4 WEC

多浮体 M4 WEC 的两种弹性紧松弛系泊配置的实验测量

• DOI: 10.36688/ewtec-2023-485
• 发表时间: 2023
• 期刊: Proceedings of the European Wave and Tidal Energy Conference
• 作者: Draycott S

System Identification and Generalisation of Elastic Mooring Line Forces on a Multi-Float Wave Energy Converter Platform in Steep Irregular Waves

陡峭不规则波浪中多浮式波浪能转换器平台上弹性系泊线力的系统识别和推广

• DOI: 10.2139/ssrn.4592389
• 发表时间: 2023
• 作者: Zhang L

The numerical re-creation of experimentally generated nonlinear irregular wave fields using a time-reversal approach

• DOI: 10.1016/j.apor.2022.103397
• 发表时间: 2022-12
• 期刊: Applied Ocean Research
• 影响因子: 4.3
• 作者: S. Draycott;P. Stansby;M. L. McAllister;T. Davey;L. Jordan;T. Tosdevin;M. Hann