Mooring systems for marine energy converters
Institute of Electrical and Electronics Engineers (IEEE)
This paper discusses several new technologies for mooring floating marine energy converter (MEC) devices, such as wave energy generators, tidal current turbines and floating wind turbines. The principal mooring component is a special nylon fiber rope which provides cyclic tension fatigue endurance much superior to that of conventional nylon ropes. The nylon fiber is treated with a new proprietary coating which has excellent wet yarn abrasion properties. The parallel-subrope type rope construction further reduces internal abrasion. Extensive laboratory testing was carried out on this new nylon rope design. Cyclic tension fatigue tests were conducted at mean loads and load amplitudes typical of actual service conditions and at higher mean loads and amplitudes. These tests demonstrate that the special nylon rope has essentially the same, desirable stretch characteristics as conventional nylon rope and has much better endurance performance. The mooring connection to the floating MEC device consists of a high-modulus fiber rope pendant which passes through a low-friction bell-mouth nylon fairlead on the MEC device. This eliminates the use of heavy, unreliable chain in this critical connection. A unique bag anchor system would be used on sand, clay, rock and other sea beds in which conventional drag embedment anchors and driven piles are impractical. The bag anchor consists of a large abrasion resistant carcass with lifting straps and top closure. The bag is transported to site in a collapsed form and is filled with local sand or aggregate to provide ballast weight. Several or many such bags are enclosed within a fiber rope net for deployment and are grouped together for connection to the mooring line. The paper will be of particular interest to designers of moorings for MEC systems in shallow water and severe wave environments. It will also be of interest for other mooring applications.
This work would not have been possible without the funding and support of the Scottish Government, the Carbon Trust and Innovate UK. The project was funded under the Marine Renewables Commercialization Fund (MRCF) and Marine Energy Supporting Array Technologies (MESAT). Other partners who contributed to this project include Lloyd’s Register, DNV‐GL, TenCate, Orion Energy Centre, Nylacast, and offshore wind developer IDEOL. Input and encouragement was provided by tidal power developer partner Bluewater, and wave energy developers AWS Ocean Energy and Pelamis.
This is the author accepted manuscript. The final version is available from IEEE via the DOI in this record.
OCEANS 2016 MTS/IEEE Monterey conference, 19-23 September 2016, Monterey, USA