The operation involved the use of more than 400 buoys to float a 1,800m stretch of cable weighing around 90 tonnes. The end of the cable was pulled to the top of the beach at around 0500 on Monday where it will be joined to onshore cables linked to a new electricity sub-station.
The operation had been delayed by technical issues when the cable lost buoyancy on two previous attempts. Cable laying contractor CTC Marine devised a different method, using a combination of pillow floats and buoys.
The operation restarted on Sunday following modifications to the cable laying ship Nordica at the A&P Falmouth shipyard on the south coast of Cornwall.
Guy Lavender, the South West Regional Development Agency’s (RDA’s) Wave Hub general manager, said: ’The next steps involve burying the cable on the beach and connecting it to the onshore cabling already in place, while the Nordica starts heading for the Wave Hub site offshore, laying the rest of the cable as she goes.’
The 20MW Wave Hub is planned to be the world’s largest test site for wave energy technology. It will comprise a grid-connected socket on the seabed, 16km off the coast of Cornwall in South West England, to which wave power devices can be connected and their performance evaluated.
Wave Hub is connected to the shore via a 25km, 1,300 tonne subsea cable. It has been manufactured in one continuous length and is made up of six copper cores, 48 fibre-optic cables, two layers of steel wire armouring and an outer polymer sheath.
The cable is being buried on the beach to a depth of around 2m using a machine that blasts a trench in the sand using high pressure water jets. The machine will continue offshore for a distance of 2km. Thereafter, a bigger trenching machine will take over for a further 5km and from there the cable will be held in place by rocks as the seabed it too hard to trench.
Once the cable has been laid offshore and the Nordica has reached the Wave Hub site, the 12 tonne hub will be lowered to the seabed in about 50m of water.
In the autumn, Wave Hub will undergo a series of tests in preparation for welcoming its first wave energy devices next year.
Wave Hub is being funded with £12.5m from the South West RDA, £20m from the European Regional Development Fund Convergence Programme and £9.5m from the UK government.