Swedish utility Vattenfall has started installing the first of 80 Siemens 3.6MW turbines at its 288MW Dan Tysk wind park off the German North Sea coast, project co-director Holger Grubel said at an offshore wind conference in Hamburg.
The company plans to install the wind farm’s substation in the course of June or July this year, and hopes that transmission operator TenneT and its subcontractor Siemens will provide grid access by September or October this year, without further delays.
While Vattenfall and its partner Stadtwerke München (SWM) have stuck largely to their schedule in developing the project, “we can’t control the grid access,” Grubel complained.
“We have no transparency; we cannot see what has been delivered by our supplier. We were not sure whether the risk profile was reported correctly to us.”
After suddenly being informed by TenneT on February 28 2013 - in the middle of a main construction period - that grid access would be delayed by a year, Vattenfall and SWM have had to postpone the date for the planned turbine installation twice already.
“Installing turbines out there with no grid for over a year would pose some severe stress on the turbines. It would provide some great challenges for making sure that the turbines always are maintained in a right way.”
The utilities now hope that grid access this time around won’t be postponed again, Grubel stressed. Otherwise, there would be a “significant risk to the project, the turbines and the equipment out there,” he added.
Next to the grid access issue, Vattenfall also faced strict environmental requirements by German authorities that it hadn’t encountered in offshore projects in other countries, Grubel said. The company has opted for a double bubble curtain to reduce noise levels in order to protect marine mammals during the installation of foundations that was completed in mid-December.
The - for the company - unprecedented noise mitigation efforts cost some €20m ($27m), and kept 70 people working on three extra vessels.
“We were quite successful. On 60% of locations we were below the threshold of what was indicated by authorities,” Grubel said.
A further critical issue is that each of Vattenfall’s offshore projects so far has been more expensive than the previous one on a per megawatt basis, Grubel said.
In part, that has to do with ever bigger equipment, and the fact that Dan Tysk at a distance of 70km from the German island of Sylt is further out to sea than any previous offshore project carried out by the utility, he added.
To contain the cost spiral, Vattenfall is seeking synergies with future projects in the same offshore wind cluster as Dan Tysk, such as the Sandbank or Nordpassage projects, Grubel says, for which the company should be able to bundle maintenance efforts.