All of the elements for the turbines were shipped out from the Port of Esbjerg, Europe’s leading port in terms of handling and shipping wind power. The port played a key role in the rise of Denmark’s offshore wind industry, which took off more than a decade ago with the installation of the world’s first large-scale offshore wind park, Horns Rev I. Today, the Port of Esbjerg now has specialised facilities and flexible areas for transporting, pre-assembling, shipping and servicing offshore wind turbines. The companies established in the Port of Esbjerg represent the entire supply chain for the wind industry, including several of the world’s leading companies that specialise in handling and servicing wind installations. Eighty percent of the offshore wind capacity installed in Europe was shipped out from the Port of Esbjerg. Besides Horns Rev I and Horns Rev II, the Port of Esbjerg has been the primary base for a number of foreign wind parks. These include Butendiek, Northwind, Sandbank, Dantysk, Humber Gateway, Westermost Rough and, of course, Gemini.

Shipping out

Overseeing the shipping out from Esbjerg for Gemini was Mick Hoyle. His daily routine in Denmark mainly consisted of four activities: the preassembly of the components, the quality checks, loading out onto the vessels and shipping them out to sea, and finally the assembly offshore. The main challenge he confronted: the weather.



Bringing it out to sea

The offshore installation vessel Aeolus, which was purpose-built to construct wind parks, was put into service in 2014. With a top-range crane, the Aeolus can lift more than 900 tons. This makes the vessel suitable for transporting and installing foundations and wind turbines. It also has an advanced jacking system: four giant legs, each measuring 85 metres and weighing 920 tons, allow Aeolus to be jacked up and work in waters up to 45 metres deep.


The Pacific Osprey is a self-elevating, self-propelled wind turbine installation/offshore support vessel. It was designed for Swire Blue Ocean, Denmark, constructed at Samsung Geoje Shipyard and delivered in 2012. The vessel is equipped with 6 truss-type legs and a highspeed rack-and-pinion jacking system.
It can jack to a safe height of 22 metres above the sea surface based on a depth of 75 metres, where it can withstand even the most severe storm conditions. The 1,200 ton leg-mounted main crane is capable of installing 500-ton nacelles on top of turbine towers 120 metres above the sea, and the 4,300-square metre heavy-duty cargo deck has space for up to twelve 3.6-megawatt turbines.



It was a long-awaited moment: the installation of the first turbines in the Gemini Wind Park: 85 kilometres off the coast of the Netherlands, out in the North Sea, where the wind is almost always blowing. On 12 February 2016, the big day finally came: the departure! Six turbines, manufactured by Siemens, were loaded onto the Aeolus offshore installation vessel and dispatched from the Danish seaport of Esbjerg. The town of Esbjerg has grown significantly in recent decades as a result of all the offshore wind activities – offshore wind has now become even more important for the town than the fishing industry.

First power

First power: a day to remember

After the turbines were installed on the foundations in late February, they were connected to the electricity grid and tested as soon as possible. They started supplying power immediately after the test phase. The moment of ‘first power’ was truly a milestone, according to Matthias Haag, Gemini’s CEO: ‘It goes without saying that the generation of the first power was a very special moment. It was so satisfying to see that the dynamic way in which the construction process progressed was rewarded with the actual supply of sustainable electricity.’



The rotor blades were manufactured using Siemens’ proven IntegralBlade process, cast as a single piece without the use of adhesive bonding. At the time of the development and installation, the B63 rotor blade, measuring 63 metres in length, was the longest and technologically most advanced blade in the 4-megawatt class. The B63 sweeps an area equivalent almost to the size of two football fields. Thanks to optimised coupling of blade bending and twisting, these aero-elastic blades react more flexibly to high wind loads, absorbing forces in a similar way to the cushioning effect of shock absorbers on cars. This technology enables longer rotor blades to be used, which boosts wind power capture and therefore increases unit performance.

The blades