Iberdrola has banked a wealth of experience during construction of its 350MW Wikinger wind farm in the German Baltic Sea, where handover to the operations team is scheduled for spring.

The Spanish utility-developer said the lessons learned across the 18-month campaign will be put into practice at projects in the first instance off the UK and then elsewhere.

“Noise mitigation requirements during pile driving and heterogeneous soil conditions were among the main challenges,” said Wikinger operations director Alvaro Martinez Palacio.

In mid-2016 the OWF joint venture of Boskalis and Volker Stevin International started driving the project’s 286 piles into the seabed in water depths of around 40 metres. Boskalis vessel Giant 7 was deployed, using a pre-piling template.

The takeaway here was extensive preparations, said Palacio. Iberdrola also developed a range of noise mitigation systems to comply with German regulations, including ‘base case’ deployment of up to two traditional bubble curtains.

The company carried out an extensive soil investigation and pile testing campaign at the site some 30km north-east of the island of Rugen. The campaign included tension tests to find the right individual design for all 286 tubulars.

All the pin piles were installed “more or less” on time by Giant 7, said Iberdrola Germany head Jurgen Blume. “In the beginning there was a learning curve,” he added.

Installation of 70 jacket foundations by vessel Taklift 4 was completed in early 2017 followed by a Prysmian-led infield cable-lay campaign.

Adwen 5MW turbines started going up in January 2017 with the manufacturer making the jump to 135-metre rotors from its previous 116-metre units. Fred Olsen Windcarrier jack-up Brave Tern installed all 70 of the machines.

“They learned fast how to manage the installation of the bigger rotor fully assembled then ramped up installation and completed it on time last autumn,” said Palacio.

Iberdrola’s first outing in Germany has also given the company valuable cultural insights.

“We learned what the interests of the stakeholders are and what they expect from us,” said Palacio. “We managed to develop a good relationship with local and federal authorities.”

With Wikinger now nearly finished some team members have moved on to the 714MW East Anglia 1 wind farm off the coast of Suffolk, east England, where construction is due to begin shortly.

In the German market, Iberdrola is getting ready for the country’s second 1.61GW offshore wind auction in April.

The developer could potentially win up to 750MW of grid capacity in the Baltic Sea to bring its Wikinger Nord/Sud extension and Baltic Eagle projects online in 2021 and 2022.

This web exclusive article first appeared in subscriber-only newsletter reNEWS on 8 February.

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Image: Iberdrola