Weapons delay 108MW Riffgat link

The Riffgat project in the German North Sea has been completed on time – but the 108MW wind farm cannot be connected yet as transmission system operator (TSO) TenneT is still finishing its grid connection, utility EWE said.

The grid-link delay is due to World War II debris, according to officials at EWE and TenneT.

The utility expects the connection work at Riffgat to be finished in the next few weeks, EWE added.

Riffgat project manager Wilfried Hube had previously told Recharge that TenneT’s grid connection is expected to be delayed due to difficulties in clearing unexploded weaponry from the seabed, before laying in part of the 50km cable route from the wind farm north of the island of Borkum to the northern German coast.

TenneT indeed found various different kinds of weapons there, among others World War II grenades and boxes full of ammunition, a TenneT press official told Recharge today. While it was known at the onset of the project that the area could be infested with weapons, TenneT found more there than expected, she said.

Strong currents and a low visibility due to algae made clearing works even more difficult, she added.

Other German offshore wind projects have also suffered from explosive challenges on the bottom of the sea. WindMW, the company developing the 288MW Meerwind offshore wind farm has spent up to €15m ($19.9m) clearing unexploded weapons from the seabed.

Some 1.6 million tonnes of weapons from both world wars are still lying on the bottom of the North and Baltic Seas, estimates Heinrich Hirdes, a company specialising in explosive ordnance disposal services.

Allied bombers often dropped unused bombs on the island of Helgoland or the open water when returning to UK bases, while some additional ammunition ended up in the sea for training purposes after the war. The weaponry near Borkum probably was dumped there by the German army at the end of the war.

Most delays to German offshore wind projects have arisen from difficulties faced by TenneT in providing grid connections in time, in part due to financial difficulties by TenneT and in part to project over-runs involving Siemens and other suppliers.

The grid connection at Riffgat should have been less complicated than that of other German offshore wind parks. With a distance of only 15km to the island of Borkum, Riffgat lies much closer to the coast than most German North Sea projects and will have a direct grid link to the shore.

Other wind farms are up to 100km from the coast and their output is first bundled in converter platforms to then be transmitted to land via high-voltage direct-current (HVDC) links. Both are complicated and expensive to build.

The Riffgat project site was the scene of a fatal accident last weekend, when a 26-year-old British diver died. The incident is still being investigated by local authorities.