Wave energy developers have additional concerns to the survivability issue which is predominant in the mooring of conventional offshore structures in exposed areas. These include the role moorings will play in the deployment of farms of devices or the manner in which moorings might influence the motion of individual devices and their corresponding effect on power capture. These issues are discussed in the context of assessing 5 mooring cable types, each sized for the same extreme load requirements. This extreme load was chosen to be the load associated with a 40m/s wind and 1.03m/s current load applied collinearly on a cylindrical floater of diameter 15m. In addition, a wave induced orbital motion of radius 6m is applied to the cable’s attachment point in order to represent the extreme wave induced load. A shallow water depth of 50m is assumed. The 5 cable types are then compared in terms of: • Overall weight and cost required to react the baseline extreme loads.
• Mechanical impedance of the mooring cable at the attachment point and its likely influence on the motion of the floater.
• The seabed footprint and horizontal movement at the surface due to steady or slowly varying loads and its likely influence on array efficiency
• Deployment considerations, required bollard pull for anchor embedding, etc.
The results highlight the potential of introducing elasticity and buoyancy in the cable. The introduction of modern efficient vertically loaded anchors in combination with flexible synthetic cables may mean that tension legs have the potential to provide very efficient mooring solutions in the future.