Techno-Economic Assessment of the Crestwing WEC Device

This is the final report from a Teamer-funded effort to perform a techno-economic assessment of the Crestwing WEC device.

Background: Crestwing (www.crestwing.dk) is a wave energy converter (WEC) of the attenuator type consisting of two large rectangular barges hinged together and lying perpendicular to the waves. The construction enables harvesting energy from a large area of water surface, which can be placed at all water depths, either in wave energy parks or in synergy with offshore wind parks. The Crestwing device's unique advantage lies in its per-device scale, enabling potentially attractive economics.

Work Carried Out: Re Vision started with a detailed review of the R&D to enable detailed implementation planning efforts. Subsequently, Re Vision engaged in a structured assessment process including:
- Developed a WEC-Sim time-domain model for WEC topology to enable performing trade-off studies.
- Validated the numerical model against wave tank testing data supplied by Crestwing and a high-fidelity CFD model (StarCCM+) developed at the Technical University of Denmark (DTU).
- We evaluated the performance of a set of different device configurations that captured the parametric space of interest. In the process, we identified an analytical performance function, which enabled a simplified implementation of the techno-economic model and allowed for the efficient completion of trade-off studies.
- Developed a structural cost model based on a review of barge manufacturing cost data in the US and China working with two different shipyards.
- Developed a set of cost-scaling functions that allowed the model to capture the effects of scaling the technology in the relevant dimensions.
- Implemented the techno-economic model in Excel and automated various trade-off functions using Visual Basic macros. The effect of design uncertainties on LCoE was evaluated using Monte Carlo simulations.
- Initial trade-off studies suggested that LCoE is sensitive to the absorber bodies' structural material. Standard barge design/construction resulted in a structurally inefficient overall system design. As a result, a concept structural design was developed for a shallow-draft barge system reinforced by load-bearing trusses.