ROV Simplifies Subsea Cable Installation at Gunfleet Sands Demonstration Project

The first phase of offshore construction at DONG Energy’s Gunfleet Sands Demonstration Project is now complete following installation of the two monopiles and transition pieces. Work on connecting the offshore and onshore elements of the project has now also reached the halfway point.

Marking an important milestone in the development of this ground breaking test site – which will see the first offshore installation of Siemens 6MW turbines anywhere in the world – the Gunfleet Sands demonstration project will enable DONG Energy to test a number of installation and construction methods, as well as collect valuable test data from the new turbines, as the company works to lower the cost of offshore wind.

This project is the first big step in reducing the cost of energy in offshore wind. Important developments including higher electricity production from fewer turbines, installation of fewer turbines and therefore using fewer inter-array cables all contribute to driving down cost and increasing efficiency.

Benj Sykes, DONG Energy Wind Power’s UK Country Manager said:

“We’ve reached a significant point in the construction of the Gunfleet Sands demonstration project. Completing the installation of the foundations and transition pieces means that we are now ready for the arrival of the two new, next generation direct drive Siemens 6 MW turbines.”

“These will be the first two turbines of their kind to be installed offshore in the world and we are very excited about the potential of this new technology. Crucial tests that we will conduct during the next three years will support the wider roll out of these direct drive turbines to our pipeline of projects in the UK.”

“We are committed to reducing the cost of energy through the deployment of new technologies, and this project is a tangible example of how we are doing just that.”

At the Gunfleet Sands Demonstration Project site near Clacton-on-Sea, Essex, a number of new methods have been tested during construction and installation.

Surveys are being conducted offshore to discover if one layer of scour protection around the monopiles – instead of the standard two layers – is sufficient. The results of these surveys could influence the construction methods on other DONG Energy projects.

Testing of a mini remote operated vehicle has also been carried out underwater. The vehicle will be used to simplify the cable installation, which as a result would not require divers to assist in installing the subsea cable.

Finally, a new cable protection system will be tested which could lead to potential reductions in cost by reducing the cable installation time and simplifying the installation process itself.

Onshore, complicated work was carried out as an 800-metre long flexible pipe duct, welded together from over 60 pieces of 12m long plastic pipe, was installed in Clacton-on-Sea. Using a specialist drilling technique, known as Horizontal Directional Drilling (HDD), a 560mm diameter hole was drilled under the sea wall out to sea. The duct was then floated out to sea from the beach, connected to the drill head by divers and “pulled-back” into position through the hole.

Later this year the offshore export cable will be pulled through the duct, connecting to the onshore section of the cable and in turn providing connection to the two demonstration turbines. Once completed, all sections of the cable will have been buried underground and protected offshore, onshore and within the duct in the critical ‘surf zone’ under the sea defences.

Now a major part of the offshore and onshore works are completed, attention turns to the laying of the subsea cables in November when the cable laying barge Discoverer will arrive on site, and to the installation of the two turbines which will arrive from Denmark in January 2013 with first power expected to be generated by spring 2013.

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Press Release, October 31, 2012