Horns Rev 2_BB by MuhammadRusdan


									                                     PROJECT INFORMATION

                        Horns Rev 2 Offshore Windfarm
                                   Monopile Foundations

1. Project Information
In the summer 2002 the Danish Government
and a number of parties concerning wind power
and energy conservation agreed on political
support for the erection of two offshore wind
farms of 200 MW each. After screening the
Danish waters it was initially decided to
proceed with an offshore wind farm next to
existing Horns Rev 1 Offshore Wind Farm
BERGER – Joint Venture was awarded with
the contract for the manufacture and installation
of the Monopile foundations for the worlds
largest Offshore Wind Farm Horns Rev 2. The
design of the foundations have been executed
by the client DONG Energy A/S.
The Horns Rev 2 Offshore Wind Farm is
located on the west coast of Jutland, Denmark.
The Farm consists of 91 Monopile Foundations
for Wind Turbines and one Monopile
Foundation for an Accommodation Platform.
After final completion in 2009 Horns Rev 2 will
be the biggest operating Offshore Wind Farm
with an overall output of approx. 200 MW.
The water depth in the area is varying from                        Monopile Installation - Offshore
-7,00 m to –17,00 m compared to MSL with soil
conditions which allowed for driving method.
                                                                   The Monopiles have a Diameter of 3,90 m
Horns Rev 2 Offshore Wind Farm consists of                         and a length varying between 28 and 40 m.
91 Turbines located in 13 rows along 7 radial                      The Transition pieces equipped with all
circles. The complete size of the wind farm                        appurtenances such as boat landings,
area is approx. 35 km² with the nearest                            platforms and ladders have a diameter of
distance to shore of approx 27 km.                                 4,20 m and a unit length of 17 m.
2. Technical Solution                                              The sections are connected offshore by a
The Foundations are divided into the two main                      grout joint where the annular gap between
sections:                                                          the two sections is filled with high strength
- Monopile                                                         grout mortar. The Transition pieces have a
- Transition piece                                                 corrosion protection painting.
                                          PROJECT I NFORMATION

The cable      connections     between     the
                                                                    3.2 Concrete Platform
foundations and towards the transformer
                                                                    As part of the foundations contract
station are executed by inner J-Tubes
                                                                    AARSLEFF / BILFINGER BERGER – Joint
whereby the high voltage cable is protected.
                                                                    Venture has executed the top platform as a
                                                                    variation in concrete compared to the
3. Execution                                                        clients steel design. Due to harsh offshore
3.1 Steel Fabrication                                               conditions in abrasive sea water conditions
Monopile Production Aalborg                                         in the North Sea, concrete has various
The Foundation sections have               been                     advantages concerning corrosion and
manufactured at Bladt Industries A/S                                lifetime maintenance compared to a normal
production yard in Aalborg. Due to the design                       steel platform. The platforms have been
using internal J-tubes for guiding the high                         manufactured by ABJV at Bladt Industries
voltage cables through the foundations and                          facilities in Aalborg and have been grouted
due to the entire layout of the wind farm, each                     to the Transition piece before load out.
foundation is unique. The load out of the                           Various tests have been executed at a pre-
foundations had to follow strictly the                              fabricated mock-up to evaluate and
installation schedule offshore. Therefore high                      minimise possible risks offshore and to
demands on the production schedule have                             demonstrate the         feasibility of this
been made. The fabrication consisted of 92                          innovative solution.
Monopiles with a length of up to 40 m and 92
Transition pieces equipped with internal
platforms, Boatlandings, etc. incl. corrosion

Monopile Production Aalborg
                                          PROJECT I NFORMATION

3.3 Transportation
                                                                    The project specific build pile guidance
Loading operations - Aalborg
                                                                    system had been designed in such a way
The foundations have been loaded in Aalborg
                                                                    to cover the positioning misalignment of the
on transport barges, sea fastened and
                                                                    SEAJACK and to cover minimum allowable
transported by Tugs to the Offshore Base
                                                                    installation tolerances offshore.
Harbour located at Tauruskaj in Esbjerg. Due
                                                                    After up-ending of the monopile from
to the unique design of each foundation the
                                                                    horizontal to vertical
complete transportation had to be arranged in
                                                                    position and placing same in the guiding
such a way that the installation vessel waiting
                                                                    system the monopiles have been driven
in Esbjerg for loading the foundation sections
                                                                    into the seabed by means of a hydraulic
can follow straight forward the completion
                                                                    hammer IHC S1200 to predefined
schedule of the wind farm. Therefore the
                                                                    installation depth.
complete logistics of fabrication, transportation
                                                                    After installation of the Transition piece the
and installation had to be mutually agreed                          cable connection for the high voltage cable
between all parties involved and was one of
                                                                    has been prepared. Divers installed a
the major tasks in early project stage.                             flexible pipe outside the monopile and
                                                                    connected it to the inner J-Tubes.
                                                                    Installation of the cover layer of the scour
                                                                    protection completed the works and left the
                                                                    foundations prepared for the remaining
                                                                    turbine installation and grid connection
                                                                    The offshore operations have been
                                                                    executed 24 hours, 7 days a week from
                                                                    May through the whole summer period to
                                                                    cope with the ambitious time schedule to
                                                                    install all foundations within one season.
Loading operations - Aalborg

3.4 Offshore Installation
All offshore operations have been coordinated
from the base port in Esbjerg. The installation
started with placing of a filter layer to avoid
scour occurring around the Monopile
immediately after driving of the pile.
The foundation sections have been loaded in
sets of 4 on the installation jack-up barge “Sea
Jack”, which had been the main installation
vessel. Upon arrival in the offshore field area
the jack-up has positioned itself by use of 4
point mooring system within 1 m of the
designated installation spot of a foundation.                       Installation Jack-up Barge “SEAJACK”
                            PROJECT INFORMATION

                        Horns Rev 2 Offshore Windfarm

Project data

Total Steel amount: ~25.000 to
Total Concrete amount: ~2.000 m³
Total Reinforcement amount:~275 to

Length: 28 - 40 m
Diameter: 3900 mm
Wall thickness: 40 - 82 mm
Weight: 150 - 210 to

Transition pieces incl. secondary
steel and platform:
Length: 17 m
Diameter: 4200 mm
Wall thickness: 45 - 50 mm
Weight: ~170 to

Scour Protection:
Filter and Cover Stones: ~ 35.000 m³
Installation Time Offshore: 03/2008 – 11/2008

                                                  Bilfinger Berger
                                                  Ingenieurbau GmbH
  Per Aarsleff A / S
  Lokesvej 15                                     Marine Engineering and Construction
  DK-8230 Åbyhøj                                  Kanalstrasse 44
  Danmark                                         D-22085 Hamburg
  Tel.: +45 8744 2222                             Phone: +49 (0) 40 - 22 72 47 - 0
  Fax: +45 8744 2249                              Fax: +49 (0) 40 - 22 72 47 - 240
  www.aarsleff.com                                www.fz-bau.de

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