Siemens will supply the entire technology for efficient high-voltage direct-current transmission (HVDC) and will use DC CS (direct-current compact switchgear) for the first time. Nexans will provide the cable technology.
The new 320 kilovolts (kV) gas-insulated switchgear requires as much as 95 percent less space compared to current air-insulated solutions. If they are used on an offshore platform, the size of the platform can thus be reduced by approximately 10 percent. According to TenneT, DolWin6 is significantly helping to lower the cost of grid connections for offshore wind farms and thus to the cost parity of offshore wind energy in general.
Two parallel 320 kV DC cables with a total length of 90 km (45 km subsea and 45 km land cable) will be built for the transmission of 900 MW offshore wind capacity. The commissioning is scheduled for 2023.
Lex Hartman, member of the TenneT executive board said: “We are seeing continuous cost reductions in our offshore grid connections, from the DolWin3 to the BorWind3 project, which are currently under construction, and now DolWin6, which has resulted in an average reduction of the tender prices of around 15%”.
In spring 2018, a number of offshore wind farms will be competing for the connection to DolWin6 in an auction held by the German Federal Network Agency (BNetzA).
According to TenneT, the contract volume awarded for DolWin6 is worth less than a billion Euros – comparable predecessor projects cost well over one billion Euros. DolWin6 is the 10th offshore DC grid connection system implemented by TenneT in the German North Sea.