IN DEPTH: Meeting the Baltic challenge

Although offshore wind projects in the Baltic Sea have escaped some of the problems seen in the German North Sea, developers still face challenges with the potential for significant delay, says Udo Christiansen, project manager at the 288MW Baltic 2 plant for utility EnBW.

“Allow for (sufficient) time if you plan to build a wind park in that region,” Christiansen told a conference on offshore wind energy in Hamburg.

Water depths of between 23- and 44-metres as well as a tricky geology are particularly challenging, Christiansen said.

Next to sand and sedimentary till formed in the melting process of the ice-age glaciers, foundations have to fight their way through extensive layers of chalk below the Baltic's seabed.

Guidelines from Germany’s maritime and hydrographic agency on how to deal with chalk deposits are very complicated, Christiansen said.

EnBW is using both monopile and jacket foundations at Baltic 2, but Christiansen admitted that“monopiles are terrible in that region".

To create a stable anchor, the foundations penetrate up to 36-metres deep into the ground, the German utility reckons.

EnBW had to first run a test-pile programme to ensure that foundations can resist wind, weather and waves for at least 25 years. That programme lasted nine months and cost €12m, Christiansen said.

Judging the impact of ice covering parts of the Baltic Sea during the winter adds to the headaches.

Christiansen said there are only four specialists in the world who can carry out precise calculations on how ice affects offshore wind parks. EnBW has contracted one of them, a Finnish expert.

Laying energy cables also is more difficult than foreseen as they have to circumvent riffs and rocks that cannot be crushed, partly for environmental reasons, he said.

Despite the challenges, EnBW hopes to bring Baltic 2 into full operation by the end of 2014 as planned, Christiansen said.

He added that on the upside, weather conditions in the Baltic are better than in the North Sea, helping installation. Also, the grid connection in the Baltic is less complicated as parks tend to be closer to the coast, he said.

Transmission system operator (TSO) 50Hertz has told EnBW that a grid connection for the park is guaranteed in time, Christiansen said.

EnBW recently secured a €500m ($668m) loan from the European Investment Bank for Baltic 2. The wind farm will feature 80 Siemens SWT 3.6-120 turbines and be located 32km north of the island of Rügen.

EnBW already operates the 48MW Baltic 1 wind farm and holds licenses for two offshore wind projects in the German North Sea.