HelWin2 has just gone online. The offshore platform is located around 85 kilometers off the north west coast of the island of Helgoland from which it takes its name. It can transmit up to 690 MW of green electricity, allowing the connected wind farm to be successively expanded with Siemens 3.6 MW wind turbines and additional turbines to be linked into it virtually every day.
There are now four Siemens grid links in the North Sea, with a transmission capacity of over 2.9 GW. The grid links are capable of supplying around 4 million German households with HelWin2 alone being capable of providing enough power for nearly 900,000 German households.
“This year we’ve completed the first four offshore grid links of this performance class in the world using efficient direct current technology” said Tim Dawidowsky, CEO of the Transmission Solutions business unit within the Siemens Energy Management Division. “Thanks to Siemens technology, nearly four million German households can be supplied with wind power generated offshore.”
Lex Hartman, member of the managing board of TenneT, added that the completion of HelWin2 marks an important milestone for the company in its implementation of the offshore development goals set by the German government. This entails the installation of 6.5 GW of offshore wind power capacity by 2020 of which TenneT has already installed more than 50 percent.
TenneT awarded the project to a consortium consisting of Siemens and Italian cable specialist Prysmian. It entails the delivery of offshore grid links HelWin1 (576 MW) and HelWin2 (690 GW) along with BorWin2 (800 MW), located off the coast of Borkum, and SylWin1 (864 MW) off Sylt. All four North Sea grid links are now in normal operation and are transporting electricity generated at sea onto land with minimal losses.
Siemens received its latest order for a grid connection in the North Sea, BorWin 3, in the spring of 2014. The fifth grid link, to be developed by the company in a consortium with Petrofac, will go into commercial operation in 2019. After commissioning, the five grids will have a total transmission capacity of 3.8 GW and will theoretically be able to supply nearly five million households.
Thanks to the Siemens high-voltage direct-current (HVDC) technology, transmission losses for each grid connection, including cable losses, are less than four percent. The technology is installed on the offshore platforms and in the land-based converter stations. The electricity generated by the accompanying wind farms is transmitted as alternating current to the converter stations where it is transformed into direct current and fed to the mainland via a subsea cable. The land-based station converts the direct current back into alternating current and feeds the electricity into the extra-high voltage grid.
HVDC is the only efficient transmission solution for cable lengths of more than 80 kilometers. Siemens HVDC Plus technology is less complex and also extremely compact. This makes it ideal for use in sea-based applications.
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