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Combined Elastomeric & Thermoplastic Mooring Tethers

Date: November 05, 2013 at 12:04 GMT

Marine energy device moorings need to protect against extreme weather events while allowing dynamic movement of the device during normal operation. They must also deliver a footprint suitable for multi-device deployments. Higher elasticity mooring tethers can reduce the loads on a mooring device, the reduced load being achieved because the tether can elongate through the entire orbital motion of the waves. Elastomeric tethers have the elasticity needed to achieve this, but they cannot deliver the protection in extreme weather without becoming so stiff that they no longer respond under normal loads.
To overcome this problem, a novel mooring tether was developed which combines elastomeric and thermoplastic elements within the one tether. This combined tether delivers low stiffness response in normal load scenarios and high stiffness response in extreme weather scenarios. This paper presents simulation results comparing this combined mooring tether with existing mooring configurations on a wave energy device. It was found that the combined tether significantly lowers the load on the system, by up to 90% compared to existing mooring architectures, while also delivering a smaller seabed footprint. These benefits reduce the mooring costs while allowing a higher density 

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