Teamwork and a no-rush culture: Building Germany’s largest offshore wind project

Madrid / 21 September 2021

For nearly a decade, German utility EnBW has been transitioning to make renewables a mainstay in its energy mix. Its first offshore project - Baltic 1 - was also the country’s first offshore commercial wind power plant. In 2015, EnBW Baltic 2 started operations and by January 2020, both EnBW Hohe See and EnBW Albatros, built as one 610-MW offshore project, were connected to the grid. While Siemens Gamesa has been a trusted partner for all these projects, for Hohe See and Albatros, the company went beyond its usual scope of wind turbine delivery. Here’s an account of what it took to build this mega project on the high seas.
Head of Offshore Corporate Affairs
EnBW, Germany’s third-largest utility by customers served, has been realigning its corporate strategy towards sustainability. As early as 2008, EnBW secured four offshore wind projects – the first of these being the 48.3-MW Baltic 1 wind power plant. Siemens Gamesa was selected to supply 21 Siemens SWT-2.3-93 wind turbines. Operational since 2011, EnBW Baltic 1 generates 185 million kilowatt hours of clean electricity annually, enough to serve around 50,000 households. EnBW Baltic 2, a 288-MW wind power plant in the Baltic Sea, much bigger than its predecessor, operational since 2015, marked the second offshore collaboration between the two companies. 80 Siemens SWT-3.6-120 wind turbines generate 1.2 billion kilowatt hours, powering around 340,000 households. Together, these wind power plants avoid over 1 million tons of harmful CO2 emissions compared to fossil-fuel power generation.
Two wind power parks, one massive build
In August 2016, EnBW signed on Canadian energy infrastructure company Enbridge Inc. as a partner for its 497-MW Hohe See project, and later for the adjacent 112-MW Albatros project, both in the German North Sea. In a first for Siemens Gamesa, it came on board as a complete solution provider. Hohe See is around 95 kilometers north of Germany’s Borkum island while Albatros is 105 kilometers away – we’re talking about building right in the middle of the sea, in water depths of around 40 meters.
“Constructing an offshore wind power plant is no small feat. The decision to combine Hohe See and Albatros was a special case. It placed extraordinary demands on people and resources – no less than 200 Siemens Gamesa colleagues alone worked just in the back office during the project’s lifetime, and more than 10 ocean vessels were involved, excluding cargo runs and daily crew transfer vessels,” notes Sebastian Zaitz, Senior Project Manager for Hohe See & Albatros at Siemens Gamesa. “This joint effort also allowed us to leverage economies of scale and utilize resources more efficiently.”

Siemens Gamesa and its partners started from scratch. The company would supply and commission 87 SWT-7.0-154 turbines,then the latest products in its portfolioSCADA systems i.e. the ‘nerve center’ connecting the turbines, the offshore substation for Albatros, and other systems for monitoring and controlwhile also managing integration of interfaces. Construction of the foundations on which the turbines would be placed, offshore substations to collect and transmit the power generated, project certification, and servicing were part of the extended scope. 

With 30+ years in offshore wind, and more than 16GW installed globally offshorewe have proven experience along the entire value chain. With its EPCI scope - EngineeringProcurementInstallation, and Commissioning – Hohe See/Albatros is among the largest projects we’ve executed, taking on commercial and interface risksMitigating these risks for the mutual benefit of EnBW, Enbridge, ourselves, and society-at-large, has been central to our work,” explains Zaitz. 

A no-rush culture emphasizing safety

Safety is my choice. We value Siemens Gamesa's commitment to safety as a partner on this project.
Hardy Steinacker, Managing Director, EnBW Hohe See GmBH & Co. KG and EnBW Albatros GmbH & Co. KG.

He went on to say “During the construction of Hohe See and Albatros, more than 600 people worked and lived on the construction site. More than 80 vessels were deployed. Throughout this time, the team followed strict safety practices resulting in no significant safety incidents”.


DEME Offshore was responsible for the design, fabrication, installation, and commissioning of all 88 large monopile foundations. Some weighed over 1,000 tons and are more than 70 meters long. Additionally, DEME Offshore was responsible for the corresponding transition pieces including scour protection, along with the Offshore Transformer Module topside installation. 


“From the first day, the various teams of Siemens Gamesa and DEME Offshore engaged in a solution-oriented joint collaboration, which resulted in the successful development of a smart foundation design. In this process, turbine loads, site specific soil and sea conditions, fabrication constraints as well and transport and installation constraints were carefully considered whilst a strict time-schedule for design, review and certification was successfully maintained. Towards the end of the installation phase, DEME Offshore deployed its state-of-the-art installation vessels INNOVATION and SEA INSTALLER to ensure the originally planned start-date for both projects could be met. We are very proud of this joint achievement, which can be added to the many other successful joint achievements our companies have made,” notes Bas Nekeman, Business Unit Director, DEME Offshore.


The work on the offshore substation (OSS) ran in parallel. A vital part of offshore wind power plants, substationstransform voltage and transmit the energy as collected from the turbines to the grid. The OSS for Hohe See was constructed in Hoboken, Belgium, and installed by June 2018. Work on the Offshore Transformer Module (OTM) for Albatros started at Zwijndrecht, the Netherlands, in early 2018The OTM Albatros contributes to the success of Germany’s energy transition. Contamination of the marine ecosystem with mineral oil is impossible thanks to the use of ester as insulation material for the transformer and a battery system for emergency power instead of a diesel generator,” Simon IsenseeSenior Project Manager Offshore Platform, Siemens Energy Management. 


InOctober 2018, the first nacelle was ready to be shipped from Siemens Gamesa’s Cuxhaven factory. Nacelles weigh as much as 400 tonsand the factory’s proximity to the German North Sea reducetransportation costs and time. “This project was special – the first nacelles from our factory built for Germany’s largest offshore wind power plant. We were honored to contribute. Our young but experienced team did our utmost to deliver the nacelles at the high quality level our customers expect, on time in accordance with the project schedule,” states Anton Bak, Plant Manager – Cuxhaven, Siemens Gamesa. 

InMarch 2019, the Albatros substation was installed and by August, the installation of the turbines at Hohe See was completed. In September, the last of the 16 wind turbines were installed at AlbatrosSince January 2020, all 87 turbines from both plants feed electricity into the grid. Siemens Gamesa continues to service and maintain the turbines. specially commissioned ship acts as a floating service station. After two weeks at sea, the technicians are flown back to land by helicopter.

Powering Germany’s clean future
Hohe See and Albatros yield 2.5 billion kilowatt hours, while saving 1.9 million tons of carbon emissions annually, enough to power an equivalent 710,000 households. As Germany’s largest offshore wind power plant, they play a pivotal role in the country’s target to source 50% its energy from wind power, and become carbon neutral by 2050.


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