Assessing Degradation Mechanisms in Tidal Turbine Support Structures Under Marine Loading Conditions

Tidal energy is a promising renewable source that can reliably contribute to net-zero targets in the UK and globally. The predictable nature of tidal energy provides a significant advantage for energy security and decarbonization over other renewables, such as wind and solar, which are subject to weather variability. This predictability makes tidal energy particularly valuable as a stable and reliable source in the energy mix. One of the most critical components of tidal turbines facing severe degradation in marine conditions is the support structure. Limited access to these structures, especially in deep waters, restricts inspection and maintenance, requiring enhanced design and integrity assessments with minimal human intervention. This study evaluates the primary degradation mechanisms impacting both floating and fixed tidal turbine support structures under marine loading condition. One of the key environmental factors that contributes to the degradation of metallic tidal turbine support structures is corrosion. Since corrosion rates depend heavily on water depth and oxygen levels, it is crucial to minimise pitting and galvanic corrosion in the presence of higher oxygen levels in the design process. Conversely, the support structures in deeper waters may experience slower corrosion rates due to lower oxygen levels, though fluctuating oxygen can still challenge material selection and protection. Thus, effective corrosion protection mechanisms such as coatings are essential to ensure longevity for these marine structures. Erosion and abrasion also significantly impact the integrity of support structures, especially in high-sediment areas where tidal currents persistently wear down surfaces and damage protective coatings. This process can lead to severe corrosion once protective layers are compromised. Therefore, both seabed sediment abrasion and erosive wear from turbulent waters are critical design and integrity considerations for tidal turbine support structures. Similar to other offshore structures, tidal turbines are subject to cyclic loads that lead to progressive fatigue damage. Since fatigue damage depends heavily on stress levels, it is essential to consider fatigue at the core of design and life assessment procedures for tidal turbines. Fatigue damage is particularly concerning in corrosive environments due to corrosionfatigue interactions, especially in areas of high local stresses such as joints and welds. Considering the challenges of maintenance on deployed tidal turbines, this study investigates key degradation mechanisms in tidal turbine support structures to propose a framework for selecting resilient design concepts, damage-tolerant materials and effective coatings to ensure long-term durability and reduce operation and maintenance costs for tidal energy infrastructure.