Analysis - Riffgat completion held up by cable issues

GERMANY: EWE has announced that all turbines have been installed at the 108MW Riffgat wind farm in the German North Sea. However, the 50-kilometre cable connection has been delayed by World War II munitions on the seabed and the death of a diver.

The project, located 15 kilometres north-west of the island of Borkum, consists of 30 Siemens 3.6MW turbines with 120-metre rotors. It was launched in 2008, when offshore wind developer Enova teamed up with regional energy company EWE to found a joint venture, named Offshore Windpark Riffgat. The aim at the time was to complete the project this year.

That aim is looks set to be achieved, albeit formally. The wind farm, which is the first commercial German offshore project to be completed, is to be officially opened by Lower Saxony prime minister Stephan Weil this month. However, due to some last minute hold-ups, it is not known when the project will come fully online.

Transmission system operator Tennet's push to install the cable has been accompanied by some recent setbacks.

"Despite statements from elsewhere", transmission system operator Tennet declined to comment to Windpower Monthly on when the sea cable link to the 108MW Riffgat offshore station will be completed. Energy company EWE, majority owner of the project, stated 17th July 2013 that "several weeks will still have to pass before the completed wind station can actually deliver electricity – Tennet is currently still working on the last section of the total 50 kilometre long sea cable to connect to the onshore grid."

Last month, a diver was killed after becoming trapped under a concrete block designed to hold down cables. According to reports, the diver was working on concrete bases designed to hold cables down to the seabed. The incident occurred in 20-metre-deep waters. As a result, work was put on hold pending an investigation.

A few weeks earlier, it was discovered there were substantial quantities of ammunition on the seabed. At the time, a Tennet spokeswoman declined to confirm press reports that work would now be completed by the end of the year, stressing it is not possible to definitely say how fast work will progress. "Work is ongoing around the clock by a 60-strong team clearing the material, including mines and boxes of munitions, but the situation is complicated by strong currents and turbulence, and problems with algae," she said.

Tennet was also unable to comment on whether the situation comprises force majeure, which in contractual terms would allow the company to pass it as an unavoidable problem. The spokeswoman said that any compensation due to energy company EWE Vertrieb, which owns 90% of Riffgat, and renewable energy company Enova Energiesysteme, which owns the other 10%, would be made in line with legal requirements.

This not the first time WW2 ammunition has impeded the development of offshore wind farms. In recent years, unexploded bombs were removed at UK North Sea projects Greater Gabbard and Sheringham Shoal.

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