Foundations for Horns Rev

The first step is the hardest, so they say. After a sluggish start, the installation is now well under way of the eighty foundations for the wind turbines in the Horns Rev offshore wind farm. By April 24, fourteen foundations are ready for installation of turbine towers and Vestas has, in fact, already started!

The actual pile driving is done by the jack-up vessel Buzzard whereas the final fitting of transition pieces, platforms, J-tubes, etc. is done by the jack-up vessel Wind. The last thing to be done prior to the turbine installation is the placement of the reinforcement layer of boulders. This is done by the vessel Pompei.

The Buzzard ready to lower the first foundation pile

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.First foundation pile ready to be driven by the pile driver onboard the Buzzard

 Wind.First transition piece put in place by the vessel Wind

Foundation ready for turbine installation. In the background: installation of Eltra's substation

The vessel Pompei prepares for installation of reinforcement layer

The Elsam Horns Rev wind farm is well under way…

Eltra's substation in place

On April 15 the barge carrying Eltra's substation arrived at the Port of Esbjerg after an approximately 70-hour transport from Rotterdam. In the Port of Esbjerg the great crane Asian Hercules was ready to hook the 1,150-tonnes substation and transport it to the Horns Rev construction site. The maximum capacity of the Asian Hercules is 3,200 tonnes!

Early in the morning on April 16, at 5 am, the Asian Hercules set off for the Horns Rev. The weather was perfect: sunny, no wind and almost a totally calm sea. The conditions for the offshore installation couldn't have been better!

After having waited for the tides to shift so that the currents were minimal, the lifting operations were initiated, which should place the substation on its tripod foundation. At 2 pm, the substation was in place in the right position and the Asian Hercules was able to dismantle the hoisting devices and return to the Port of Esbjerg.

Now, some work has to be done prior to the commissioning of the substation. This work is also progressing well and the substation is now ready for helicopter landings and take-offs. Now, all that is needed is the final approval from the Danish Civil Aviation Administration.

Cable pulling is expected to be initiated in the very near future.

Asian Hercules at work

Eltra's substation in place

The installation of turbines has begun…

Vestas has now initiated the installation of wind turbines at Horns Rev. They are working on installing the turbines in the northernmost row where the foundations have been released for turbine installation. To make the most of the favourable weather window, Vestas has decided to install the first ten turbine towers and then fit the nacelles and rotors later.

As much as possible of the fitting work will be done at the pre-assembly facilities on Tværkaj in the Port of Esbjerg. The individual tower sections are fully assembled including ladders, electrical and control systems, wiring and lighting before being lifted onboard the crane vessel Ocean Hanne.

A2Sea's other crane vessel, Ocean Addy, has been rebuilt at Ørskov Christensens Staalskibsværft A/S and is sailing for Esbjerg. Vestas expects that both crane vessels are available within very short time for the installation of nacelles and rotors on the first ten turbines so that these ten turbines are complete by early May work is initiated of pulling the sub-sea cables.

Towers being lifted onboard the crane vessel Ocean Hanne

Picture from tower top

Installation works

By April 24 - 8 towers has been installed

Marine environment during construction

One of the aspects of the environmental monitoring programme is to monitor the marine environment in the construction phase. Elsam does the utmost to ensure that the impact is limited on the local marine environment during the installation of foundations and turbines.

At international level, great focus is put on the noise produced during pile driving. It is a fact that the undersea noise level is quite high and might damage the hearing abilities of porpoises and seals. As regards porpoises, it is of utmost importance that their hearing organs are not damaged since these are used in connection with their hunting and communication.

Elsam examines and makes sure that the porpoises and seals are not in the waters around the wind farm when pile driving is begun. To ensure this, we have invested in pingers and other devices to warn off the seals. The fishermen are familiar with the pingers and use them on their pound nets to keep porpoises from swimming into them. This electrical device emits special, high-frequency notes which scare off the animals. Our equipment is fitted to the pile driving vessel and is lowered into the water approx. 30 minutes before pile driving, thus giving the animals plenty of time to leave the area before the real noise begins.

 Work place: Horns Rev. Front: installation of foundation for Eltra's substation. Background: the jack-up vessel Buzzard