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REASSESSMENT OF LILLGRUND OFFSHORE WIND FARM USING
WINDPRO
“A Project”
by
HASEEB AHMAD
Submitted to the Office of Graduate Studies of
Gotland University
in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE IN WIND POWER PROJECT MANAGEMTENT
June, 2012
Major Subject: "Energy Technology"
“Master of science in Wind Power Project Management”
2012
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REASSESSMENT OF LILLGRUND OFFSHORE WIND FARM USING
WINDPRO
“A Project”
by
HASEEB AHMAD
Submitted to the Office of Graduate Studies of
Gotland University
in partial fulfillment of the requirements for the degree of
MASTER OF SCIENCE IN WIND POWER PROJECT MANAGEMENT
Examiner: Dr. Bahri Uzunoglu
June, 2012
Major Subject: "Energy Technology"
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ABSTRACT
The objective of this project is to reassess the Lillgrund Offshore Wind Farm using WindPRO as
a design tool. In this project, current layout of Lillgrund Wind Farm is used along with available
wind resources. The project consists of brief description of the project in terms of location,
components of the wind farm, their specifications and different calculation modules using
WindPRO. The project is reassessed in terms of Environmental Impact (noise, shadow and
visual impact) Annual Energy Production and Electrical Losses. The results obtained from the
calculations are compared with actual results and the difference between calculated and actual
results is discussed.
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NOMENCLATURE
GWh Giga Watt hour
Km Kilometer
MW Mega Watt
MWh Mega Watt hour
GPS Global Positioning System
kV Kilo Volt
mm2
Sq. Millimeter
MVA Mega Volt Ampere
kVA Kilo Volt Ampere
WAsP Wind Atlas Analysis and Application Program
NCAR National Center for Atmospheric Research
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Contents
LIST OF FIGURES …………………………………………………………………………….…i
LIST OF TABLES ……………………………………………………………………………….ii
Chapter 1 Introduction ................................................................................................................ 1
Project Description ..................................................................................................................... 1
History ........................................................................................................................................ 2
Chapter 2 Wind Farm Components ............................................................................................. 2
Foundations ................................................................................................................................ 2
Turbines ...................................................................................................................................... 4
Substations .................................................................................................................................. 9
Chapter 3 Calculations .............................................................................................................. 10
Noise ..................................................................................................................................... 10
Shadow ................................................................................................................................. 11
Visual Impact ........................................................................................................................ 11
Annual Energy Production ................................................................................................... 13
Electrical Losses ................................................................................................................... 14
Conclusion .................................................................................................................................... 15
VITA ............................................................................................................................................ 16
Bibliography ................................................................................................................................. 17
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LIST OF FIGURES
Figure 1. Lillgrund Offshore Wind Farm Location ........................................................................ 1
Figure 2. A tug takes the barge with four foundations from Poland to Lillgrund .......................... 3
Figure 3. Eide Barge 5 .................................................................................................................... 6
Figure 4. The Sea Power Vessel ..................................................................................................... 6
Figure 5. Lillgrund Wind Farm Cable Layout ................................................................................ 7
Figure 6. View from Klagshamn harbour 5.3 km ......................................................................... 12
Figure 7. View from Klagshamn harbour 5.3 km using WindPRO ............................................. 12
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LIST OF TABLES
Table 1. Specifications of Wind Turbines ...................................................................................... 5
Table 2. Characteristics of vessel used for foundation and turbine installation (Eide Barge 5) ..... 5
Table 3.Characteristics of vessels used for cable installation (CS Pleijel) (Nautilus Maxi) .......... 8
Table 4. Noise Calculations of Lillgrund Wind Farm .................................................................. 10
Table 5. Shadow Calculations of Lillgrund Wind Farm ............................................................... 11
Table 6. Annual energy production results comparing different wake models and wind
distributions .................................................................................................................................. 13
Table 7. Actual production of Lillgrund wind farm ..................................................................... 14
Table 8. Electrical losses of Lillgrund wind farm ........................................................................ 14
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Chapter 1 Introduction
Project Description
The Lillgrund wind farm is the largest offshore wind farm of Sweden designed to meet the
electricity demand of more than 60,000 homes. The wind farm consists of 48 Siemens 2.3 Mk II
wind turbines. The total wind power plant capacity is 110 MW and an approximate annual
generation is 330 GWh. The wind power plant includes an offshore substation, an onshore
substation and 130 kV sea and land cable for connection to the shore. The Lillgrund offshore
wind farm is located in a shallow area of Öresund, 7 km off the coast of Sweden and 9 km off
the coast of Denmark. The wind power plant is situated 7 km south of the Öresund Bridge,
which connects Copenhagen and Malmö. (Joakim Jeppsson, Poul Erik Larsen, Åke Larrson,
September 2008 )
Figure 1. Lillgrund Offshore Wind Farm Location
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History
The conditions were quite favorable to establish an offshore wind farm at Lillgrund. The
southern shallow part of Öresund is blessed with good wind speeds which results high energy
production. The closeness to the shore made the access for construction, operation and
maintenance really easy. Water depth is only 4 to 12 meters so cost of foundation was controlled.
(Flodérus, Experiences from the Construction and Installation of Lillgrund Wind Farm, May
2008)The transportation of materials including turbines was easily facilitated and shipped
directly to the site. Weather plays a vital role for developing an offshore wind farm. Proper
monitoring and daily log weather log was kept to make it possible to identify the weather
conditions at any given time.
Chapter 2 Wind Farm Components
Foundations
There are 49 foundations at Lillgrund wind farm. The foundations of 48 turbines and one
offshore substation are made up of gravity reinforced concrete. The Pihl-Hochtief consortium
rented a part of the harbor in Swinoujscie, Poland, to manufacture the foundations. A ready- mix
concrete plant was installed very close to the quay to facilitate concrete production, pouring and
transport. (Flodérus, Experiences from the Construction and Installation of Lillgrund Wind
Farm, May 2008)
The dredging work at seabed was done to achieve the sufficient bearing capacity of seabed. The
excavated area was filled with a 50 cm thick cushion layer of crushed stones, to form a
horizontal base for the foundation. (Flodérus, Experiences from the Construction and Installation
of Lillgrund Wind Farm, May 2008) The diver inspection continued during foundation
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placement to ensure high quality of work. Four foundations were cast on each individual barge.
As the bolt tolerances were very tight, the bolts were placed in fixing plates before the concrete
was poured into the shutter boarding. The total weight of a foundation is 2000 MT including 500
MT of ballast material on the base plate. (Flodérus, Experiences from the Construction and
Installation of Lillgrund Wind Farm, May 2008) After completion of required work on barge, a
tug pulled the barge from Poland to Lillgrund.
Figure 2. A tug takes the barge with four foundations from Poland to Lillgrund
A crane barge was used to lift the foundations from barge and place them on the specific
location. The exact position of each foundation was mapped precisely with the aid of a four-
anchor system and a global positioning system (GPS) and the crane barge was pulled to each
new location with the aid of a tug and anchors. The whole area of the seabed around the
foundation was covered with a rock-fill scour protection to prevent the ocean currents from
moving seabed material and thus undermining the stability of the foundation.
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Turbines
The Siemens 2.3 MW Mk II variable speed wind turbines are used. The turbines were
manufactured by Siemens. The rotor and nacelle were made in Jutland, Denmark. The
subcontractors located in Jutland, Denmark made the towers. All the equipment was transported
by lorries to the harbor of Nyborg, Denmark.
The towers (upper and lower sections), the nacelles and the rotors were loaded onto a special
ship by a large crane. The total average time for installing the load of three wind turbines took
five days: One day for the journey from Nyborg to Lillgrund, two days to erect three wind
turbines, one day for the return journey to Nyborg and finally one day to load three more wind
turbines. As long as weather permitted, these activities were carried out 24 hours a day, seven
days a week. (Flodérus, Experiences from the Construction and Installation of Lillgrund Wind
Farm, May 2008)
Rotor type 3-bladed, horizontal axis
Rotor position Upwind
Rotor diameter 93 m
Swept area 6800 m2
Rotor speed 6 to 16 rpm
Aerodynamic regulation Pitch regulation
Yaw system Active
Controller type Microprocessor
SCADA system WPS
Tower Cylindrical
Rotor weight 60 ton
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Nacelle weight 82 ton
Tower weight (70 m) 134 ton
Table 1. Specifications of Wind Turbines
Wind turbines were installed by the Sea Power with the help of large a crane. The operation took
place 15 meters away from the foundations; the vessel raised itself by two meters by means of
four jack-up legs to stabilize the hull for waves. The elevated deck provided stable platform for
work The Sea Power is capable of operating in marine conditions with wave heights of up to one
meter. Installation of towers and nacelles can be carried out in a wind speed of up to 10 m/s
whilst installation of rotors is limited to a wind speed of maximum 7 m/s. (Flodérus, Experiences
from the Construction and Installation of Lillgrund Wind Farm, May 2008)
Name Eide Barge 5
Owner and Operator Eide Marine Services A/S
Vessel type Heavy Lift Barge
Construction Company Germany
Overall Length 76 m
Breath 37 m
Maximum Draft 3.615 m
Maximum Lifting Capacity 1850 MT
Table 2. Characteristics of vessel used for foundation and turbine installation (Eide Barge 5)
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Figure 3. Eide Barge 5
Figure 4. The Sea Power Vessel
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Cables
The Lillgrund offshore wind farm electrical network consists of a series of inter-array cables and
an export cable. Voltage levels are 36 kV for inter-array cables and 145 kV for the export cable.
The inter-array cables connect the wind power generators with the transformer platform
(offshore substation). The inter-array cables are supplied in three different cross sectional sizes
95 mm2, 185 mm
2 and 240 mm
2. (Unosson, January 2009) The thickness of cable increases with
as it goes close to substation. There are 48 inter array cables in total. The length of the cables
varies, with 15 of the cables each approximately 350 meters, 28 of the cables approximately 450
meters and 5 cables up to 1500 meters. (Unosson, January 2009) The export cable connects the
transformer platform with the substation in Bunkeflo. The export cable is divided into a 7 km
submarine cable with a size of 400 mm2 and a 1.7 km land cable with a size of 630 mm
2. The
submarine cables include an integrated optic cable. The onshore cable includes a total of 4
separate cables, three AXLJ 1x 630 mm2 as well as an optic cable. (Unosson, January 2009)
Figure 5. Lillgrund Wind Farm Cable Layout
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The inter array cable installation was performed with the help of two vessels, C/S Pleijel and
M/S Peter Madsen, and their workboats. C/S Pleijel was responsible for laying down the inter-
array cable between the foundations and M/S Peter Madsen was used as the base for the divers
during the cable pull-in and the post-lay inspection. M/S Peter Madsen also transported ABB
team, tools and material between the foundations. (Unosson, January 2009)
The offshore part of the export cable installation consisted of trenching, laying, pull-in and
burying. The last 300 meters of the export cable, which was to connect to the transformer
platform, was installed on the seabed temporarily until the transformer platform had been
positioned.
The offshore export cable installation was carried out using the barge Nautilus Maxi. First, the
cable was pulled to shore from the barge. Then, all but the last 300 meters of the cable was laid
into the trench. The remaining was to be connected to the transformer platform. (Unosson,
January 2009)
Name C/S Pleijel Nautilus Maxi
Owner and Operator Baltic offshore Seløy under water services AS
Vessel type Cable laying ship Multipurpose/ cable lay barge
Construction Company Denmark Norway
Overall Length 72.4 m 47 m
Breath 13 m 20 m
Accommodation 20 Persons
1st and 2
nd crane capacity 7 tons and 3 tons 400 tons and 150 tons
Carousel and Turntable Capacity 900 tons
Table 3.Characteristics of vessels used for cable installation (CS Pleijel) (Nautilus Maxi)
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Substations
The offshore substation at Lillgrund is designed to visually harmonize with the marine
environment. The cylindrical substation has a diameter of 22 meters and reaches approximately
25 meters above sea level. The steel framework of the transformer platform was made in Poland.
It was transported to Århus, Denmark, where all electrical equipment was installed, along with
the internal and external walls. The completed transformer station was transported on a barge to
the Copenhagen harbor, where a marine crane lifted it directly to its planned location at
Lillgrund. (Flodérus, Experiences from the Construction and Installation of Lillgrund Wind
Farm, May 2008) The substation consists of the following electrical systems (Joakim Jeppsson,
Poul Erik Larsen, Åke Larrson, September 2008 )
138/33 kV main transformer, 120 MVA, with tap changer
33 kV switchgear for each feeder and the local power supply
33 kV/0.4 kV transformer for local power supply, 150 kVA
0.4 kV switchgear system for local power supply
Emergency diesel for back-up, 110 kVA
Control/monitoring system
Mechanical vibration protective device (which trips all electrical equipment in case of a
ship collision)
Lillgrund offshore wind power plant is connected to E.ON’s 130 kV onshore station Bunkeflo,
near Malmö. The main circuit breaker is located here.
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Chapter 3 Calculations
WindPRO is employed to make calculations about environment and visual effects, electrical
losses and annual energy production of the Lillgrund wind farm.
Environmental Report
Environmental monitoring measures performed for the Lillgrund offshore wind farm will be
described in the section and the results will be summarized.
Noise
According to environmental court, the equivalent noise level in the areas closest to the beach
shall not exceed 35 db. (Davy, 2009) However, the equivalent noise level measured varied
between 31-46 dB at wind speeds between 2-8 m/s when the initial noise measurement were
performed. The project was still approved by the authorities. (Davy, 2009) Following are the
measurements performed by WindPRO, different noise levels of Siemens 2.3 MW Mk II were
investigated. Eight noise sensitive areas are designated all along the beach.
No.
Noise Sensitive
Areas
Noise
Limit WindPRO Results
Level
0
Level
1
Level
2
Level
3
Level
4
Level
5
1 A 35 44.8 44 42.8 41.8 40.9 40.1
2 B 35 43.6 42.9 41.6 40.6 39.8 39
3 C 35 42.1 41.5 40.2 39.3 38.5 37.7
4 D 35 40 39.5 38.1 37.3 36.6 35.9
5 E 35 39.1 38.6 37.2 36.4 35.7 35
6 F 35 40.7 40.1 38.8 38 37.2 36.5
7 G 35 37.6 37.1 35.7 35 34.3 33.7
8 H 35 41.2 40.6 39.3 38.4 37.7 36.9 Table 4. Noise Calculations of Lillgrund Wind Farm
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Shadow
Shadow is not generally the point of concern for offshore wind farm developers because these
are situated quite away from the beaches or residential areas. However, shadow calculations are
made by using WindPRO. Nine different shadow receptors are placed along the beach to
measure the effect of wind turbines. Following are the results:
No. Receptors Shadow
hr/year days/year hr/day
1 A 0 0 0
2 B 0 0 0
3 C 0 0 0
4 D 0 0 0
5 E 0 0 0
6 F 0 0 0
7 G 0 0 0
8 H 0 0 0
9 I 0 0 0 Table 5. Shadow Calculations of Lillgrund Wind Farm
Visual Impact
The visualization of the impact of a wind farm on surrounding landscape is an important task
during permitting process. WindPRO is employed to fulfill this task. A view point “Klagshamn
harbour, 5.3 km” is selected and results are calculated using Photomontage module of
WindPRO.
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Figure 6. View from Klagshamn harbour 5.3 km
Figure 7. View from Klagshamn harbour 5.3 km using WindPRO
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Annual Energy Production
Wake Model Wind Distribution
Result
Park
MWh/y
Result
-10%
Park
Efficiency
%
Capacity
%
Mean
Wind
Speed
m/s
N.O.Jensen
(Riso/EMD)
Weibull_NCAR_BASIC
_N55.0_E12.5_42 m 229511 206560 69 21.3 6.8
N.O.Jensen
(Riso/EMD)
Measure_NCAR_BASIC
_N55.0_E12.5_42 m 235691.7 212123 70.4 21.9 6.8
N.O.Jensen
(Riso/EMD) WAsP Interface 429089.6 386181 78.1 39.9 9.2
N.O.Jensen
(Riso/EMD) ATLAS 416931.5 375238 78.2 38.3 9.1
Eddy Viscosity
Model
Weibull_NCAR_BASIC
_N55.0_E12.5_42 m 284751.1 256276 85.6 26.5 6.8
Eddy Viscosity
Model
Measure_NCAR_BASIC
_N55.0_E12.5_42 m 288689.7 259821 86.2 26.8 6.8
Eddy Viscosity
Model WAsP Interface 495307.5 445777 90.3 46.1 9.1
Eddy Viscosity
Model ATLAS 482424.6 434182 90.4 44.9 9.1
EWTS
II(G.C.Larsen)
Weibull_NCAR_BASIC
_N55.0_E12.5_42 m 270537 243483 81.3 25.2 6.8
EWTS
II(G.C.Larsen) WAsP Interface 480753.6 432678 87.5 44.7 9.3
Table 6. Annual energy production results comparing different wake models and wind distributions
Initially the measurements taken on a tower located at Lillgrund in Öresund, about 10 km west
of the Swedish coastline, have been analyzed from 1st September 2003 to 28
th February 2006.
The observed mean wind speed was found to be 8.4 m/s at 65 m height. (Bergström, March
2009) The actual production figures from 2008 to 2011 are taken from http://www.vindstat.nu
data base and compared with WindPRO results. Different wind distributions were used in
WindPRO including met mast data (Falsterborev) and NCAR data as shown above. The actual
production results are shown below.
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Year Av. Production GWh
2008 326.78312
2009 319.97166
2010 303.90538
2011 347.88777
Table 7. Actual production of Lillgrund wind farm
As it can be seen that the results obtained from NCAR data are much closer to the actual
production figures in Table.7. The eddy viscosity wake model gives better solution than other
models. The height of NCAR data is 42 m, and wind speed obtained from NCAR data at 42 m is
6.5 m/s. As described above, the observed wind speed near the site is 8.4 m/s. If we extrapolate
the production, obtained from WindPRO, at 6.8 m/s to 8.4 m/s, the figure come close to the
actual production. So it can be concluded that eddy viscosity model using NCAR data gives
reliable results in this case.
Electrical Losses
Reassessment of electrical losses is done using egrid module of WindPRO.
Table 8. Electrical losses of Lillgrund wind farm
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These results are calculated using annual energy production of 259821 MWh/year. The losses
are calculated using ambient temperature 20oC. The climate under sea is taken as moderate.
Conclusion
The reassessment of lillgrund wind farm is done using software WindPRO. The results are
obtained using different modules of WindPRO. The results are quite similar to the ones
calculated at the start of the project. While calculating annual energy production, the met mast
located at Falsterborev gave abnormal results possibly due to errors in the data base and also it is
short term data. The NCAR data is more reliable because it is long term. Rest of the modules
calculated accurate results.
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VITA
Name: Haseeb Ahmad
Address: Gotland University
Cramérgatan 3, 621 67 Visby, Sweden
Email Address: [email protected]
Education: Bachelor’s in Chemical Engineering. The University of Engineering and
Technology Lahore, Pakistan, 2003
Certified Professional Manager in Health, Safety and Environment, Pakistan
Institute of Modern Studies, 2011
Masters in Wind Power Project Management, Gotland University Sweden,
2012
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Bibliography
Bergström, H. (March 2009). Meteorological Conditions at Lillgrund. Sweden: The Swedish
Energy Agency.
CS Pleijel. (n.d.). Retrieved March 14, 2012, from
http://www.4coffshore.com/windfarms/vessel-cs-pleijel-vid5.html
Davy, T. (2009). Environmental Monitoring- Lillgrund Offshore Wind Farm. Sweden: The
Swedish Energy Agency.
Eide Barge 5. (n.d.). Retrieved March 13, 2012, from 4coffhore:
http://www.4coffshore.com/windfarms/vessel-eide-barge-5-vid55.html
Flodérus, A. (May 2008). Experiences from the Construction and Installation of Lillgrund Wind
Farm. Sweden: The Swedish Energy Agency.
Flodérus, A. (May 2008). Experiences from the Construction and Installation of Lillgrund Wind
Farm. Sweden: The Swedish Energy Agency.
Joakim Jeppsson, Poul Erik Larsen, Åke Larrson. (September 2008 ). Technical Description
Lillgrund Wind Power Plant. Sweden: The Swedish Energy Agency .
Nautilus Maxi. (n.d.). Retrieved March 14, 2012, from
http://www.4coffshore.com/windfarms/vessel-nautilus-maxi-vid28.html
Unosson, O. (January 2009). Offshore Cable Installation - Lillgrund. Sweden: The Swedish Energy
Agency.