Cost-effective mooring to boost wave power

Harnessing the vast energy found in Europe's waves could significantly contribute to the EU's commitment to meet 20 % of its energy demands through renewable energy resources by 2020. The region is an excellent test bed for new offshore mooring and anchoring systems, the lack of which are currently impeding widespread technology uptake. Exploitation would also put the EU at the forefront of a growing global renewable energy market.

The GEOWAVE (Geotechnical design solutions for the offshore renewable wave energy industry) project conducted industry-specific research on a new generation of offshore anchors and mooring components deemed to have the highest economical and technical merit for mooring wave energy devices.

Consortium members unveiled a new mooring configuration consisting of taut mooring lines, coupled with elasto-dynamic tendons and a novel drop-installed anchor that demonstrated reliable performance under extreme loading conditions. The reduced mooring line lengths in taut line configurations lead to significant installation cost savings; however, limited elasticity can impede WEC motion, which is necessary to create electricity. For this reason, partners incorporated an elastic tendon that minimises loading in the mooring lines (reducing the required anchor sizes) and tunes WEC hydrodynamic performance.

Dynamic cyclic loading imparted to the anchor from a WEC can degrade the anchor capacity below its design value, causing the anchor to fail and the WEC to break loose. However, GEOWAVE's efficient anchor shows good resistance to cyclic loading and can be easily installed into cohesionless seabeds, increasing reliability and acceptance of wave energy.

Three research partners applied their engineering expertise in the anchor geotechnics and the mooring hydraulics. A unique wave basin facility allowed characterisation of the performance of the new mooring line. Load test data was subsequently used to assess anchor performance in a geotechnical centrifuge facility.

GEOWAVE technology will provide an important boost to small and medium-sized partners with new products opening the door to new markets. It will also support the deployment of a wave energy industry with the important benefits of job creation and reduced global climate change.