HAVMØLLER PÅ MIDDELGRUNDEN - Offshore Center Danmark

1.1 Summary
Sammenfatning
This report describes the feasibility study done on the wind farm at Middelgrunden and the
cooperative Middelgrundens Vindmøllelaug I/S the largest wind farm cooperative in the
world with more than 8000 members. It is the final report on the investigations financed by
the DKK 4.05 million grant from the Danish Energy Agency. The report deals in particular
with the activities carried out in relation to the Middelgrundens Vindmøllelaug (the
cooperative). Activities during the construction phase of the farm are only dealt with to some
extend.
Chapter 2 describes the background as an Agenda 21 activity and presents the partners behind
the project.
Chapter 3 summarizes the development in chronological order from the very beginning in the
autumn 1996 to the final permission from the Danish Energy Agency was given in December
1999. The first feasibility study from 1997 reported earlier is mentioned. The establishment of
the cooperative and the grant from the Danish Energy Agency enabling the cooperative to
make the feasibility studies is mentioned. The planning procedure and the regulations dealing
with cooperatives involved in offshore wind farms are described. Finally the physical layout
of the farm is presented.
In Chapter 4 the joint working group with the power utilities is described. Advantages and
disadvantages for a cooperative engaging in such a working group are analyzed. The
disadvantage being that the cooperative had to follow the EU directives for public tender
procedure. On the other hand working together with the utilities has given the possibility of
utilizing their knowledge regarding public tender. Furthermore it has been an advantage that
the utilities guaranteed the project if not all shares were sold.
Chapter 5 gives the wind condition at the Middelgrunden, based on meteorological data
obtained by Risø National Laboratory from a measurement mast situated a few hundred
meters west of the site. The data shows a mean wind velocity at 7.2 m/sec in 50 meters height.
Based on a typical power curve from one of the turbine manufactures a power production of
3.99 to 4.25 GWh is expected depending on the rotor diameter (60 to 75 m).
Chapter 6 describes the choice of wind manufacturer in brief. The rules regarding the tender
procedure does not allow for details.
Chapter 7 describes the considerations behind the choice of foundation principle. Several
types of support structure have been investigated: gravity foundation in concrete or steel,
mono-pile, suspended foundation, and building an artificial island. Finally a call for tender
allowing a gravity foundation in steel or concrete, or a mono-pile solution was made. The
result was that in almost every tender the concrete gravity solution was about 20% cheaper
than the steel solution. A mono-pile solution seems to be too expensive, partly because of the
Copenhagen Limestone, and partly because of the actual combination with few units and a
short distance from shore to the offshore site. The design parameters for the seabed are
described and pollution data of the former waste deposits are given. Finally the increased
safety for ships in relation to collision with the reef or the wind turbines is discussed.
Chapter 8 deals with the grid connection and the power system within the wind farm. The
turbines are producing electricity at the 690V level, which in each turbine is transformed by a
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