Breakthroughs in WEC arrays Shared moorings and cablings in the WETFEET project

The wave energy industry has had difficulty maintaining the rate of progress seen during the mid-portion of the last decade. To rectify this deceleration of progress, the reasons must be understood. Major obstacles to the success of wave energy (might) include: • Reliability of components, especially power take-offs • Survivability of the systems • Complexities and costs in the development-to-market cycle • Uncertainties in industrial scalability These obstacles have combined to limit the progress made in wave energy: in particular, the conceptual shortcomings associated with cost- and time-sensitive development and an underestimation of the operational challenge of the ocean environment. The WETFEET (Wave Energy Transition to Future by Evolution of Engineering Technology, www.wetfeet.eu) project was conceived to provide answers to technology-related challenges so that the gap between promising results and the necessary engineering knowledge can be closed. This is to bine achieved with ‘breakthrough' items, which may be components, systems and processes or intellectual property. One of the principal breakthrough areas addressed by the WETFEET project is array interaction and mooring. This two-year study is a collaboration between partners representing higher education and research institutes and industry and it will offer interesting insights and results throughout its project life cycle. The move from prototype or demonstrator deployment of wave energy converters (WECs) to operational devices requires the use of farms of WECs to generate enough energy to be economically viable. The need to reduce costs further drives the design of arrays to share moorings and/or electrical connections. The choice of mooring and connection type does not just affect cost; array geometry will affect the amount of energy generated, O&M viability, hydrodynamic response and therefore survivability, network safety and reliability. The first outcome of the study will be the development of an assessment methodology that will allow the technical and economic performances of configuration geometries to be compared. This methodology will be applied to both rigid and non-rigid mooring strategies. A rigid mooring configuration would comprise several WECs attached to a rigid frame that is in turn moored to the sea bed, whereas in a non-rigid mooring configuration, the WECs would be slack-moored to each other and to the sea bed. The most promising configurations will be studied in the latter half of the project in both numerical simulations and physical model teststo determine the mooring loads and the natural responses of the different configurations. The results of these later tests will be available to coincide with ICOE 2018 thus giving a follow-up on one aspect of a major Horizon 2020 project.