Fatigue reliability assessment of co-located offshore wind and wave energy systems

Offshore renewable energy, generated from wind and waves is being increasingly considered in many parts of the world. The efficient and sustainable use of marine space and co-location of ocean infrastructure to meet several needs including energy generation, fishing, transportation, etc. is also being proposed. Co-location of multiple activities allows the use of a shared space and possible interaction among the different uses. In this dissertation, we focus on the co-location of offshore wind turbines (OWTs) and wave energy converters (WECs). If WEC arrays are deployed in the direction of dominant incoming waves at OWTs, the resulting reduction in wave loading can serve to protect the OWT, thus enhancing its structural reliability and extending its service life. To assess this benefit, fatigue damage on an OWT is studied, while considering uncertainties in the wave climate and structural dynamics of the OWT, with and without the benefit of a sheltering WEC. This dissertation represents a collection of three papers that address this problem. First, we assess the structural performance of a fixed-bottom offshore jacket platform in a fatigue reliability analysis. We explore the reuse and repurposing of an oil and gas (O&G) platform to serve as the support structure for an OWT. Fatigue damage assessment in the O&G and the OWT phases is studied. Critical sea states and structural members are identified. Understanding the differences in dynamic behavior in the two phases helps gain insight into the structural reliability of fixed-bottom OWTs. Next, this same framework is employed to assess possible life extension that could result from co-location of the OWT with a WEC. Wave energy extraction estimates are developed using a power matrix for the WEC device, and fatigue assessment of a floating offshore wind turbine is conducted for representative sea states, with and without the WEC-sheltering influence. Greater wave energy extraction leads to more effective sheltering and a longer OWT service life when both the preferred wave periods for the WEC and the metocean data are considered. Lastly, for a floating OWT, an efficient fatigue assessment approach is considered as an alternative to exhaustive consideration of all sea states in Monte Carlo simulations. Using uncertainty quantification, surrogate models are generated and serve as response surfaces for fatigue damage variation with sea state. We apply Gaussian process regression (GPR) for this purpose and propose an adaptive (learning) approach to improve the surrogate model’s accuracy. The three studies taken together all address fatigue damage assessment of offshore renewable energy systems.

Name thesis:degree_name

Doctor of Philosophy

Discipline thesis:degree_discipline

Civil Engineering

Grantor

The University of Texas at Austin

Year dc:date.issued

2024

Author dc:creator

• Liu, Ding Peng

Advisor dc:contributor.advisor

• Manuel, Lance

Committee members dc:contributor.committeemember

• Kinnas, Spyros A
• Lee, Jun-Whan
• Wilson, Preston S.

• Renewable energy
• Co-location
• Wave energy convertor
• Offshore structures
• Offshore wind energy
• Surrogate model
• Fatigue reliability

Identifier URI

https://doi.org/10.26153/tsw/55915

OAI identifier oai:identifier

oai:repositories.lib.utexas.edu:2152/129411