Numerical design study of multipoint mooring systems for the floating wave energy converter in deep water with a sloping bottom

The use of a floating wave energy converter (WEC) in the deep water zones around islands is increasing, but conventional mooring configurations often do not provide suitable station keeping options. This paper focus on the assessment of a suitable mooring design for floating WECs in deep water locations, with a sloping seabed. The mooring study considers a 50-year return period to assess the survival rate for three mooring designs i) catenary mooring systems, ii) synthetic cable (polyester) taut mooring system, and iii) suspended anchoring point mooring system. Furthermore, the variations of bathymetry conditions around the oceanic islands are considered, as well as factors directly influencing these deep-water mooring installations (e.g. anchor uplift forces, weight of mooring system). The coupled motion dynamics of the WEC and the mooring system are studied using a potential theory in a time-domain model, and the power production is also considered. The Chinese 100 kW Sharp Eagle WEC [22] is used as the reference design. The deployment site has a water depth of 200-700 m and the angle of the slope ranges from 30 degrees to 90 degrees. The paper is investigating the effects of (i) the features of the seabed condition; (ii) the mooring line material, size and layout; and (iii) the installation and maintenance costs. The outcomes of the studies for the three different mooring designs are compared and an additional fatigue analysis has been implemented to obtain fatigue damage criteria for the mixed catenary mooring system. A cost analysis has been implemented, and recommendations provided discussing the most suitable mooring design configuration. (C) 2019 Elsevier Ltd. All rights reserved