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Recent studies have focused on optimising wave energy converter (WEC) designs, maximising their power performance and techno‐economic feasibility. Reliability has yet to be fully considered in these formulations, despite its impact on cost and performance. In this study, this gap is addressed by developing a reliability‐based design optimisation framework for WEC hull geometries to explore the trade‐off between power performance and power take‐off (PTO) system damage equivalent loading (DEL). Optimised hull geometries for two sites are considered (from the centre of the North Sea and off the west coast of Norway), and two directions of motions (heave and surge). Results indicate that site characteristics affect the potential power production and DEL for an optimal WEC design. These are also affected by the direction of motion for power extraction, which also significantly changes optimal hull shape characteristics. Optimal surging WEC designs have edges facing oncoming wave directions, while heaving WECs have pointed bottoms, both to streamline movement. Larger, more convex WECs result in greater power production and DEL, while smaller, more concave WECs result in lesser power production and DEL. These findings underline the importance of considering WEC hull geometry in early design processes to optimise cost, power production, and reliability. [ABSTRACT FROM AUTHOR]

Abstract Offshore wind and wave energy are co-located resources, and both industries are driven to reduce cost of energy. Due to the maturity of offshore wind technology and continued growth of both offshore floating wind and wave energy converter (WEC) technology, there is new opportunity to combine wind and wave technologies in the same leased ocean space through co-located array development. Co-location is projected to have synergistic effects that reduce direct and indirect costs for developments, but few of these synergistic effects have been quantified, and many have not been related to cost. Moreover, there is currently no cost model that incorporates these effects. In this study, we address this need by developing a cost model that represents co-located array developments, particularly for floating offshore wind and WEC technologies. We exemplify the use of this cost model through a case study. Results suggest floating wind-wave co-located arrays are advantageous to WEC-only or floating wind-only. These results are contingent on our assumptions regarding cost categories and values included in the model and also the power production and reliability of the devices. We conclude by identifying research gaps and uncertainties to be minimized in future improvements of the model. Highlights • A lifecycle cost model for co-located offshore wind-wave arrays is developed. • Cost of co-located arrays is comparable or less than floating offshore wind turbine arrays. • Model can be used in computational optimization to further decrease costs of co-located systems. [ABSTRACT FROM AUTHOR]

Abstract Offshore wind farm operations and maintenance costs currently total 6 m€/year, or 25–28% of total costs. For wave and tidal energy converters, this cost is projected to be twice that of offshore wind, but has high levels of uncertainty. As the wave and tidal energy industries mature, decreasing O&M costs through reliability-based design optimization is critical to increasing feasibility and competitiveness with other energy technologies. In this paper, we will synthesize existing information on reliability-based optimization in systems analogous to offshore renewable energy systems. We will conclude by highlighting opportunities for future work in this field. Highlights • Explores state-of-the-art optimization for reliability in offshore renewable energy systems. • Operations and Maintenance costs for offshore renewable energy systems are very high. • Reliability-based design optimization increases the longevity of these systems, reducing costs. • Not accounting for reliability can lead to inviable designs or higher probabilities of failure. • RBDO methods accelerate convergence, improve reliability, and enhance market competitiveness. [ABSTRACT FROM AUTHOR]