Thesis
Development and implementation of a multi-disciplinary optimisation framework to aid cost reduction for floating offshore wind support structures
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2026
- Thesis identifier
- T17580
- Person Identifier (Local)
- 202072867
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- In order to tackle climate change, a huge shift is required from several industries, namely the energy sector. The decarbonisation of the grid has become essential to adhere to government targets and legally binding treaties. One of the most prominent solutions is harnessing wind energy, having proven itself viable onshore and offshore prior to the new millennium. The development into the offshore environment allowed developers to benefiting from a stronger, more consistent resource. Since the first developments, the UK has grown its offshore capacity to just under 15 GW, with a strong pipeline and government support aiming for 43 to 50 GW by 2030 to meet the clean power plan. However, as build out has progressed, nearshore sites have become utilised, pushing developers into deeper waters where current fixed bottom solutions are no longer either technically or economically feasible. Floating wind is expected to be a solution for deeper water sites, overcoming the limitations linked with fixed offshore wind. However, with new technology and a harsher operating environment comes risks, lack of supply chain and an associated cost, which is expected to be around double the cost of its fixed counterpart in shallower waters. This research is centred on the exploration of potential cost reductions for floating offshore wind support structures to aid the needed CapEx minimisation, which is in alignment with the Industrial Growth Plan (IGP) published in 2024. The current study plays a crucial role in cost reduction of floating offshore wind to try and determine a more standardised but optimised set of geometries to bring down the cost. By standardising designs, it will allow supply chains to develop and mature, which also leads to a cost benefit and potential economic growth within the UK. The opportunity to manufacture and build locally is exceptionally strong for floating offshore wind platforms and the UK, given their large size, which not only makes them increasingly difficult to transport but also creates a larger carbon footprint, which is not desirable. Ultimately, cost reductions will allow floating to become more competitive with other energy sources to deliver green, secure, affordable energy. Few studies have carried out optimisations for current geometries in literature to seek cost-benefits, exploring non-traditional geometries, with an expected mass reduction and therefore cost. However, cost models utilised within these works often use a mass based pricing approach where only the materials consumed are considered or assumptions are made to increase density to reflect secondary steel cost. These presented approaches neglect all manufacturing costs or attempt to capture them through vague assumptions. This work presents a multi-disciplinary optimisation framework, which finds the optimal geometry for a range of different platform typologies, with appropriately sized mooring lines and anchors within a defined design space. This design space is controlled by bounds for each design variable to ensure sensible combinations are considered. The optimal solutions meet a number of constraints on the geometry, manufacturability, intact stability, floatability, and structural integrity. The overall objective seeks to minimise cost, to do so a structural model combined with detailed cost estimates of both material and manufacturing costs such as forming, welding, and painting are considered. This allowed the author to find the defining qualities of optimal solutions and whether there were any true benefits in exploring non-traditional geometries, other than the expected reduction in material mass. The optimisation technique used in this work was a pattern search combined with a multi-start approach to ensure the global minimum had been found. The framework quickly found optimal solutions which minimised cost while being constrained by the previously mentioned parameters, ensuring performance was not impacted and a realistic design was found. The solutions were then considered in frequency domain analysis, further assessing their stability capabilities. One of the difficulties of optimisation is the length of time required to carry out the task. An approach which was considered within this work is the Technique for Order of Preference by Similarity to Ideal Solutions (TOPSIS). This technique was used as a concept selection tool to rank different platform typologies at specific sites. This allowed a number of different criteria regarding site parameters such as soil condition, tidal range, water depth, and wave height compatibility to be considered. The remaining criteria were linked to the different substructure typologies, capital, operational and decommissioning costs, size and Technology Readiness Level. This step allowed the author to rule out platforms which were not suitable and, therefore, reduce the number of platforms which had to be optimised for specific sites. Implementing the presented techniques, this study demonstrated that firstly, the semi-submersible platform is highly flexible for a number of different sites, reinforcing its prominence within industry. The case studies for the optimisation found the TLP to be the cheapest, best-performing platform for Scotwind site NE8, noted as Site 8 in this work. Whereas site 14, otherwise known as N2 Scotwind, finds the Semi-submersible to be cheaper than the Spar, both have a dynamic response within the allowable limits. In terms of exploring non-traditional geometries, there was no benefit for Spar, however, there was a cost benefit for the TLP, but more so Semi-submersible, since they have a greater number of ’parts’ which can benefit from having reduced size, allowing both material and manufacturing cost to be reduced while keeping the desired stability. Overall, this work highlighted that the manufacturing cost should be considered when assessing different platform geometries, given that the material cost alone is expected to represent 40% of the total platform cost. Finally, setting a constraint on the static pitch angle of the platform resulted in the optimal platforms having good dynamic performance, and the exclusion of dynamics from the optimisation itself was justified. Looking ahead, the key insight from future work indicates that building upon the detailed model is essential. Including installation and Operations and Maintenance (O&M) specifically to capture the nuanced behaviours of each platform, allowing all of the benefits and drawbacks to be captured for each platform.
- Advisor / supervisor
- Collu, Maurizio
- Coraddu, Andrea
- Resource Type
- DOI
Relations
Items
| Thumbnail | Title | Date Uploaded | Visibility | Actions |
|---|---|---|---|---|
|
|
PDF of thesis T17580 | 2026-01-28 | Public | Download |