Siemens installs BorWin2 platform

Siemens has completed the long-delayed installation of the HVDC converter platform for the 800MW BorWin2 offshore grid link in the Germany North Sea.

On the platform built by Nordic Yards at its shipyard in Warnemünde, the alternating current (AC) generated by wind turbines is transformed into low-loss direct current (DC) for transmission to the mainland using Siemens technology.

The BorWin2 onshore converter station, likewise supplied to transmission system operator TenneT by Siemens, is located in Diele. There the electric power from the connected wind farms is converted back into the alternating current required to feed into the power grid.

“Once more we have mastered the challenging offshore installation part. We are now in the final stretch to achieve commissioning in the first half of 2015, as promised,” says Karlheinz Springer,chief executive of the Power Transmission Division within the Energy Sector of Siemens AG.

“When the two platforms yet installed by us go on line, they will be able to supply more than 1.3 million households.”

The completion of the BorWin2 link originally was planned for spring 2013. Its delay is forcing utilities Stadtwerke München (SWM) and HEAG to feed electricity from the 400MW Global Tech 1 wind park that is slated to be completed this summer via an alternative grid link that only has limited capacity to receive power from Global Tech 1.

Several German offshore links have encountered lengthy and painful delays in part as TenneT’s financing was unclear, and partly because companies such as Siemens and their suppliers to which TenneT awarded the contracts needed more time than expected to build the links, due to the technical novelty of the complicated structures.

German projects are being built further out to sea than, for example, their UK counterparts, causing the need for expensive, complex converter platforms and HVDC links to the coast.

While TenneT and suppliers had stipulated a period of 30 months to get the first grid links up and running, the industry now reckons construction times of 50 or even 60 months to be more realistic.

For the latest offshore grid links, such as the 900MW BorWin3 link that TenneT awarded to Siemens earlier this month, construction periods of four to five years are granted to guarantee their completion on time.

Siemens says the first four of its HVDC offshore links will commence operation one after the other between the second half of 2014 and the first half of 2015.

The BorWin2 platform has now been safely anchored at its final position northwest of the island of Borkum. Siemens had already installed the platform’s support substructure at this location in the 39-meters-deep North Sea in 2013.

Six steel pilings measuring up 2.5 meters in diameter and with a wall thickness of eight centimetres were anchored around 50 meters deep in the seabed.

To protect it against giant waves, the platform is installed 20 meters above sea level. BorWin2 is designed for decades of operation in the rugged North Sea, Siemens claims.