Abstract
The paper presents the results of an experimental study identifying the response of a 1.5 MW Wave Dragon to extreme conditions typical of the DanWEC test center. The best strategies allowing for a reduction in the extreme mooring tension have also been investigated, showing that this is possible by increasing the surge natural period of the system. The most efficient strategy in doing this is to provide the mooring system with a large horizontal compliance (typically in the order of 100 s), which shall be therefore assumed as design configuration. If this is not possible, it can also be partly achieved by lowering the floating level to a minimum (survivability mode) and by adopting a negative trim position. The adoption of the design configuration would determine in a 100-year storm extreme mooring tensions in the order of 0.9 MN, 65% lower than the worst case experienced in the worst case configuration. At the same time it would lead to a reduction in the extreme motion response, resulting in heave and pitch oscillation heights of 7 m and 19° and surge excursion of 12 m. Future work will numerically identify mooring configurations that could provide the desired compliance.
Highlights
The Wave Dragon is a floating, offshore Wave Energy Converter (WEC) of the overtopping type.Incoming waves are focused by two wing reflectors towards a doubly-curved ramp, by which they surge up into a reservoir placed above the mean water level
Assessment of the Survivability Mode In November 2010, the 1:51.8 scale model of a North Sea Wave Dragon was tested at the Hydraulic and Coastal Laboratories of Aalborg University (AAU), in order to assess the effectiveness a control strategy to be used in extreme storm conditions, aimed at reducing design loads on the structure and mooring system rather than power production optimization
This paper presents the results of tank tests carried out in spring 2012 on a new 1:50 model of the WD-DanWEC at AAU
Summary
The Wave Dragon is a floating, offshore Wave Energy Converter (WEC) of the overtopping type.Incoming waves are focused by two wing reflectors towards a doubly-curved ramp, by which they surge up into a reservoir placed above the mean water level. In November 2010, the 1:51.8 scale model of a North Sea Wave Dragon was tested at the Hydraulic and Coastal Laboratories of Aalborg University (AAU), in order to assess the effectiveness a control strategy to be used in extreme storm conditions, aimed at reducing design loads on the structure and mooring system rather than power production optimization. This strategy is referred to as the survivability mode, consisting in lowering the floating level of the device to its minimum so that a large part of the wave energy overtops and passes over the device to the lee side. As wave pressure decrease with the water depth, by floating in a lower position the device is exposed to lower wave-induced forces in the first place
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
