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Wave energy conversion can have a significant role in the transition to a net-zero energy system. However, cost reductions are still required for this technology to be commercially competitive. To achieve commercialisation at a reasonable expense, disruptive innovations at early stages of development need to be enabled. Thus, to explore more of the design space, design limits need to be defined. Although physical limits, such as the maximum capture width and the Budal upper bound, have been defined, more realistic limits considering the variability of the resource, device dimensions and the actual hydrodynamic behaviour of different shapes can help provide further insights. This is relevant to both technology developers and funding bodies wanting to identify potential areas for innovation. In this study, the use of multi-objective optimisation is proposed to explore these limits, by investigating the optimal relationship between average annual power production and device size. This relationship depends on resource level, mode of motion used for power extraction and hull shape. The obtained fundamental relationships fall within the existing physical limits, but provide further insights into the impact of different factors on these limits. This allows for a more direct comparison with the performance of state-of-the-art wave energy converters. • A flexible method to explore wave energy converter design limits is presented. • Design limits for power and volume are obtained with multi-objective optimisation. • The design limits are verified against the state of the art and physical limits. • The method can be used to obtain other types of fundamental relationships. • These relationships help identify areas with potential for disruptive innovation. [ABSTRACT FROM AUTHOR]

This work investigates potential cost reduction trajectories of three emerging offshore renewable energy technologies (floating offshore wind, tidal stream, and wave) with respect to meeting ambitious cost targets set out in the Strategic Energy Technology Implementation Plans (SET-Plans) for Offshore Wind and Ocean Energy. A methodology is presented which calculates target costs for current early-stage devices, starting from the 2030 SET-Plan levelised cost targets. Component-based experience curves have been applied as part of the methodology, characterised through the comparative maturity level of each technology-specific cost centre. The resultant early-stage target costs are then compared with actual costs for current devices to highlight where further cost reduction is still required. It has been found that innovation and development requirements to reach these targets vary greatly between different technologies, based on their current level of technological maturity. Future funding calls and programmes should be designed with these variables in mind to support innovative developments in offshore renewables. The method presented in this paper has been applied to publicly available cost data for emerging renewable technologies and is fully adaptable to calculate the innovation requirements for specific early-stage renewable energy devices. [ABSTRACT FROM AUTHOR]

Wave Energy Converters (WECs) with optimised geometries and control systems have been developed in recent years to advance marine energy technologies towards commercialisation. In particular, a number of WEC hull geometry optimisation studies have been performed, due to the high cost reduction potential associated with the device structure. However, no standard and consistent method has been established for this purpose. For example, different optimisation formulations (single-objective and multi-objective), have been used, applying different optimisation algorithms. Additionally, a range of objective functions have been employed, where power maximisation has been represented through a variety of metrics, and cost minimisation expressed with diverse cost proxies. The goal of this study is to address the challenge of finding a suitable optimisation problem formulation with single-objective or multi-objective implementations, and the respective objective functions, that support the exploration of shapes that reduce the levelised cost of energy. Results show that submerged surface area cost proxies are more suitable for this purpose than volume-based cost proxies. Results from a multi-objective optimisation formulation can provide a good understanding of the solution space, whereas results from single-objective studies can be used for seeding these multi-objective optimisation approaches. • Different objective functions are compared for wave energy converter optimisation. • Using volume based cost proxies results in more complex WEC shapes. • From a techno-economic perspective surface area based cost proxies are more suitable. • Multi-objective implementations are studied and compared to single-objective approaches. • Single-objective results should be used as inputs to multi-objective formulations. [ABSTRACT FROM AUTHOR]