Experimental investigation on the influence of hybrid mooring system configuration and mooring material on the hydrodynamic performance of a point absorber

The performance of the three hybrid mooring systems was studied by conducting 1:40 model tests of a moored point absorber subjected to regular and irregular waves. The compact hybrid mooring adopts two segments design, i.e., a top synthetic fibre rope (polyester or nylon) and a bottom chain. A submerged buoy is installed on the joint between these two segments. Another design that installs two clumped weights at the end part of the chain in the nylon mooring system is also investigated. Seventeen regular and three irregular wave tests were conducted. Heave and pitch resonance wave conditions were tested to study the system dynamics in resonance modes. Results show that the nylon rope is a favourable material for mooring ropes of wave energy converters in terms of energy conversion efficiency. Compared with nylon rope, polyester restricts WEC heave motion responses effectively and reduces the energy conversion efficiency of the floater studied in this work. The compact compliant mooring system design that consists of nylon rope, buoy, chain and clumped weights is the best mooring concept for the specified floater in this work. It demonstrates that when pretension is not large enough during the tests, the mooring will experience slack configuration during the random waves.

Automated summary

This study investigated the performance of three hybrid mooring systems for a point absorber under regular and irregular waves by conducting model tests. Nylon rope was found to be the most suitable material for mooring ropes in terms of energy conversion efficiency. The compact compliant mooring system design with nylon rope, buoy, chain, and clumped weights was identified as the best mooring concept for the specified floater, showing improved performance under various wave conditions.