DECOMMISSIONING AND INSTALLATION PROJECT AT LILLGRUND
OFFSHORE WIND FARM
“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
DECOMMISSIONING AND INSTALLATION PROJECT AT LILLGRUND
OFFSHORE WIND FARM
“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"
ABSTRACT
The Lillgrund Offshore Wind Farm, located in a shallow area of Öresund between Sweden and
Denmark, suffered from a series of accidents, sea collisions and extreme winds. Fourteen out of
forty eight turbines have become dysfunctional along with substation and foundations. So the
objective of this project is to decommission the foundations, old turbines and substation and
install the new foundations, turbines and substation. The same turbine and substation technology
is used for reinstallation. In the first part of this report, decommissioning process and costs are
presented. In the second part, installation process and related costs are presented while in the last
part, total cost estimation is done by calculating net present value. Since there is a change in the
configuration, the substation which was located offshore in the original project is placed onshore
now. The comparison between both configurations is done by calculating net present value for
both. There is no difference in the estimated productions of wind turbines because these are
placed at their original spots. However, electrical losses are calculated because there is a change
of cable lengths. Microsoft Excel and WindPRO are used for calculations in this project while
Microsoft Project is used to make a project plan.
NOMENCLATURE
MW Megawatt
EAR Erection All Risk
CPM Copenhagen Malmö Port
VDR Vessel Day Rate
SDR Spread Day Rate
TDC Total Daily Cost
OSV Offshore Support Vessel
EIA Environmental Impact Assessment
EHA Environmental Hazard Assessment
MVA Mega Volt Ampere
GBP Great Britain Pound
USD United States Dollar
MWh Megawatt hours
NPV Net Present Value
Contents
LIST OF FIGURES …………………………………………………………………………....…i
LIST OF TABLES ……………………………………………………………………………….ii
Chapter 1 Introduction ........................................................................................................ 1
Chapter 2 Decommissioning Process .............................................................................. 2
Turbine Removal ........................................................................................................................ 3
Foundation and Transition Piece Removal ................................................................................. 4
Substation Removal .................................................................................................................... 5
Cable Removal ........................................................................................................................... 6
Scour Removal ........................................................................................................................... 6
Chapter 3 Installat ion Process .......................................................................................... 7
Foundation Installation ............................................................................................................... 7
Turbine Installation .................................................................................................................... 8
Cable Installation ........................................................................................................................ 9
Substation Installation ................................................................................................................ 9
Scour Protection ....................................................................................................................... 10
Chapter 4 Cost Estimations ............................................................................................. 10
Capital Cost Estimation ............................................................................................................ 10
Total Cost Estimation ............................................................................................................... 11
Gantt chart for Project .............................................................................................................. 12
Chapter 5 Comparison between Configurations ....................................................... 13
VITA ........................................................................................................................................ 15
Bibliography ................................................................................................................................. 16
i
LIST OF TABLES
Table 1. Decommission of Turbines ............................................................................................... 5
Table 2. Decommissioning of Foundations .................................................................................... 5
Table 3. Decommissioning of Substation ....................................................................................... 6
Table 4. Decommissioning of Cables ............................................................................................. 6
Table 5. Installation of Foundations ............................................................................................... 8
Table 6. Installation of Turbines..................................................................................................... 9
Table 7. Installation of Cable ......................................................................................................... 9
Table 8. Installation of Substation ................................................................................................ 13
Table 9. Comparison between Configurations ............................................................................. 14
ii
LIST OF FIGURES
Figure 1. Shaded Area and Substation needs to be reinstalled ....................................................... 2
Figure 2. Gantt chart for the Project ............................................................................................. 12
Figure 3. New Configuration ........................................................................................................ 14
1
Chapter 1 Introduction
The Lillgrund offshore wind power plant 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. The offshore wind power
plant is comprised of 48 wind turbines, each rated at 2.3 MW, resulting in a total wind power
plant capacity of 110 MW. The wind power plant system also includes an offshore substation,
an onshore substation and a 130 kV sea and land cable for connection to shore. (Joakim
Jeppsson, Poul Erik Larsen, Åke Larrson, 2009) The offshore wind farm started its operation in
the beginning of 2008. The construction of Lillgrund took about 2 years and there is a warranty
period for the turbines of 5 years. (Olsson, February 2009)
For managing the construction risk, Vattenfall purchased an owner-controlled „All risk‟
insurance policy from Codan that covered both of the two main suppliers as well as all minor
sub-contractors. For the construction phase of Lillgrund, Vattenfall signed an EAR insurance
with additional third party liability insurance and marine insurance. The policy covered all
construction work at Lillgrund, e.g. total construction costs for wind turbines, including
foundations, cables and offshore substations. However, temporary buildings and off-site
construction areas were not included, e.g. vessels. (Olsson, February 2009) Vettenfall did not
sign any insurance policy which covers decommissioning costs. Generally decommissioning
funds are used to provide security against environmental and decommissioning liabilities. In
Netherlands requires that offshore owners/operators must pay monies into a segregated
decommissioning fund for a minimum of 10 years, starting from the first year of operation of the
project. The US Environmental Protection Agency Brownfield Superfund requires operators to
2
set aside monies through annual payments into a fund in order to accrue clean-up costs.
(Offshore Renewable Energy Installation Decommissioning Study, Final Report)
Figure 1. Shaded Area and Substation needs to be reinstalled
3
Chapter 2 Decommissioning Process
The decommissioning process of an offshore wind farm takes place in well defined stages.
Several important factors such as environmental protection, safety, cost, and strategic
opportunity are kept in mind to conduct the decommissioning process. The developers work
according to the available options depending upon regulatory approval and technical feasibility.
(Department of Trade and Industry, 2006)
The decommissioning process starts with the engineering planning and project management. The
engineering personnel assess the work requirements and the project management team will
report on the options available, including the scope of work that needs to be performed and how
best to prepare the bid. The plan is developed for every stage in the project. Initially the process
of market surveying and vessel selection is started. There are 14 wind turbines at Lillgrund
offshore wind farm which have to be decommissioned along with one offshore substation.
Following are different steps to be performed for the decommissioning of the wind farm.
The port selected for decommissioning process is the Port of Malmö. Malmö is located on the
south western coast of Sweden and is the largest Swedish port in the area. The port is operated
by Copenhagen Malmö Port (CMP). The water depth is up to 13 meters alongside at normal
waters. The port is accessible all year round and 24 hrs per day with no tidal or light restrictions.
(The Port of Malmö). The weather factor is taken as 0.8, discount factor is 0.85 of installation
time and inflation factor for cable is 2.
Turbine Removal
The decommissioning process started with turbines removal. There are different methodologies
that can be implemented to decommission the turbine. Number of lifts for each case vary
4
however the decommissioning process is not as delicate as commissioning so an option is
selected keeping in view the disposal of wind turbines component. In the first step hub is
removed, in the second step, nacelle is removed and finally tower is removed. There are three
lifts required for this process. This option is selected because blades, nacelle and tower have to
be disposed off to landfill and scrape separately but more importantly this option will reduce the
cost due to optimum number of lifts.
The jackup barge vessel is used along with two tugs one cargo barge and one crew boat. The
operation started with the mobilization of vessel and cargo barge to the location. The cargo barge
can lift seven turbines, so removal vessel (jackup barge) removed 7 turbines and cargo barge sent
those turbines to onshore. The removal took place in two turns. The complete cost and operation
calculation of the turbine removal is done using Microsoft Excel. However main results are
shown in table1.
Foundation and Transition Piece Removal
After turbines removal, foundations and transition pieces are removed. The normal method to
decommission the foundations is first to cut them and then lift. But in this case cutting is not
required because monopiles are 5 meter long, these are only pulled outside. The operation started
with getting inside the pile and setting up the jetting and pumping equipment. The mud present
inside the monopiles is pumped out. The turbine cables at mud line are cut by the help of divers.
The jackup barge is used as a removal vessel to lift the transition piece and foundation. Spread
containing one barge, two tugs and crew boat is used. Cargo barge performed two rounds to put
the foundations to the port while removal vessel remained on site throughout the operation. The
complete cost and operation calculation of the foundation removal is done using Microsoft
Excel. However main results are shown in table2.
5
Table 1. Decommission of Turbines
Method Selected Single Vessel Method
Vessel Jack up Barge
Spread 1 cargo barge, 2 tugs, 1 crew boat
Time to Remove a Foundation (hours) 11
Time to Remove all Foundation (hours) 154
Vessel Day Rate (VDR, $/day) 64200
Spread Day Rate (SDR, $/day) 21750
Total Daily Cost (TDC, $/day) 85950
Total Cost to Remove Foundations (million $) 0.5515125
Table 2. Decommissioning of Foundations
Substation Removal
The topside of substation removed first transformer requires no cut so it is lifted as a whole. The
next step is to remove the monopile foundation for substation. It is done in the same way as
turbine foundations and transported to the port. An OSV is used to support divers and cutting
operations and OSV along with heavy-lift vessel remained on site throughout the operation. The
Model Selected Barge model
Vessels Jackup Barge
Spread 1 cargo barge, 2 tugs, 1 crew boat
Total removal time (hours) 1365
Vessel Day Rate (VDR, $/day) 64200
Spread Day Rate (SDR, $/day) 25250
Total Daily Cost (TDC, $/day)
89450
Total Project Cost (Cost, million $)
5.087469
6
complete cost and operation calculation of the substation removal is done using Microsoft Excel.
However main results are shown in table3.
Total Time to Remove Substation (hours) 80
Vessels OSV, Heavy lift vessel, barge spread
Total day rate ($/day) 131000
Cost (million $) 0.436667
Table 3. Decommissioning of Substation
Cable Removal
Mostly power cables do not constitute a hazard but removal option is selected because these
might interfere with commercial trawling or other activities. Only inner array cables for 14
turbines are removed with the help of OSV and spread barge. Inner array cables come in short
segments so recovered in one piece. The complete cost and operation calculation of the cable
removal is done using Microsoft Excel. However main results are shown in table4.
Total Length of Cable (km) 5.335
Vessels OSV, barge spread
Removal rate (Km/day) 1.115385
Removal time (day) 4.783103
Total day rate ($/day) 32000
Cost (million $) 0.153059
Table 4. Decommissioning of Cables
Scour Removal
Mechanical dredge is employed to conduct the scour removal operation. The cost to remove
scour is 12000$/foundation. So the total cost for the whole operation is 0.18 million $.
Site clearance is not required while material disposal has been contracted to a company which
will do this work without charge.
7
Chapter 3 Installation Process
The wind turbines and an offshore substation is planned to be reinstalled at Lillgrund wind farm.
The land is still under lease, so there is no such hurdle regarding lease. Generally, for setting up
new offshore wind turbines requires two main permits in Sweden. First is environmental impact
assessment (EIA) or Environmental Hazard Activity (EHA) and second is permit for hydraulic
operations. (Patrik Soderholm, MariaPettersson, 2011) The permit for hydraulic operations may
only be approved if the private and social benefits of the project exceed the corresponding costs
and damages. (Kenneth Hansen, Brian Vad Mathiesen, David Connolly , 2011) In addition to the
above, one final permit may be required (both on and outside Swedish territory), and this
concerns the installation of cables on the continental shelf. This permit is also granted by the
Government. (Patrik Soderholm, MariaPettersson, 2011)
In this case all the requisites were fulfilled before building the Lillgrund wind farm. The new
turbines are put exactly on the position of damaged ones. So no permission and legal issue arises
for reinstalling the wind turbines. Also it is planned to use the same turbine technology to reduce
any complications and increased expenses for operation and maintenance. The wind farm was
needed to be operational as soon as possible so the only change is the placement of offshore
substation. It is placed onshore however the comparison between new and old design will be
made later in the report.
Foundation Installation
The installation phase is started with the foundations. The jack up barge as an installation vessel
with spread containing cargo barge, two tugs and a crew boat is reached at the wind farm from
Malmö port. In the first trip, cargo barge contained seven foundations. The installation started
with the placement of pile into the seabed. After the monopile is secured in the seabed, a
8
transition piece is lifted and grouted onto the pile. The same vessel is used for transition piece
placement and scour protection. Seven more foundations are brought to the site in second trip
and installed in the same manner. The complete cost and operation calculation of the foundation
installation is done using Microsoft Excel. However main results are shown in table5.
Method Selected Self Transport Model
Vessel Jack up Barge
Spread 1 cargo barge, 2 tugs, 1 crew boat
Time to Install a Foundation (hours) 50
Time to Install all Foundation (hours) 750
Vessel Day Rate (VDR, $/day) 64200
Spread Day Rate (SDR, $/day) 25250
Total Daily Cost (TDC, $/day) 89450
Total Cost to Install Foundations (million $) 2.795313
Table 5. Installation of Foundations
Turbine Installation
After installing the foundations, turbines are installed. The vessel used for installation is Jack up
barge along with spread. The port used for turbines is Nyborg, Denmark due to production
facility of Siemens in Denmark. The installation method of turbines comprised of four lifts. The
tower is transported in two pieces and lifted in two lifts. The nacelle is lifted separately. The
rotor and blades are assembled onshore transported to the offshore site and lifted in one lift. The
advantage of using this method is to reduce the number of lifts and onshore off course onshore
assembling of rotor provide better and accurate fitting. The complete cost and operation
calculation of the turbines installation is done using Microsoft Excel. However main results are
shown in table6.
9
Method Selected Barge Model
Vessel Jack up Barge
Spread 1 cargo barge, 2 tugs, 1 crew boat
Time to Install a Turbine(hours) 82.5
Time to Install all Turbines (hours) 1155
Vessel Day Rate (VDR, $/day) 64200
Spread Day Rate (SDR, $/day) 25250
Total Daily Cost (TDC, $/day) 89450
Total Cost to Install Turbines (million $) 4.304781
Table 6. Installation of Turbines
Cable Installation
Inner array cables are installed between the turbines. Since the old layout is used so the time for
pre-excavating a trench is reduced. The cable is laid with the help of cable laying vessel and
trenches are filled with the help of dredge. The cables are then connected to wind turbines
through J tubes. The complete cost and operation calculation of the cable installation is done
using Microsoft Excel. However main results are shown in table7.
Total Length of Cable (km) 5.335
Vessels OSV, barge spread
Installation rate (Km/day) 0.55
Installation time (day) 9.7
Total day rate ($/day) 25000
Cost (million $) 0.2425
Table 7. Installation of Cable
Substation Installation
The substation mainly comprise of 120 MVA step up transformer, switch gears and other
equipment. The typical cost for 500 MW wind farm onshore substation is approximately 35
million GBP. (RWE npower renewables, August, 2011) So for 110 MW wind farm, the typical
10
cost of onshore substation would be approximately 1.3 million USD. Following is the
breakdown for substation cost. (RWE npower renewables, August, 2011)
High Voltage and Medium Voltage Equipment = 55%
Installation = 15%
Civil Engineering = 10%
Others = 20 %
The installation cost would be around 0.2 million USD. For capital cost estimation 4 million
USD will be subtracted from total capital cost
Scour Protection
The total time for the scour protection of fourteen foundations is approximately 10 days and 0.08
million dollars are spent on this.
Chapter 4 Cost Estimations
Capital Cost Estimation
A regression model, derived from previous projects, is used to calculate capital costs. The capital
cost does not include cost for decommissioning and installation costs. It includes cost for
turbines, foundations, substation and cables.
C = 0.73 + 0.0011CAP + 0.036 WD – 0.0036 DIS + 0.013 STEEL
C = Reported millions of dollar per MW
CAP = Install Capacity MW
WD = Water Depth
DIS = Distance to shore
STEEL = European Steel Index
11
Putting values
C = 0.73 + 0.0011*32 + 0.036*5 -0.0036*7 + 0.013*200
Reported millions of Dollars per MW (C) = 3.5704
Total Cost Estimation
Net positive value (NPV) calculation is performed to see if the project is profitable or not.
E = gross generated energy = 320000 MWh
CD = reported millions of dollars for decommissioning = 6.466
CT = reported millions of dollars for total capital costs CT = C*total capacity = 114.2528 - 4.0
CI = reported millions of dollars for installation = 7.622
Loss = Losses from WindPRO calculations = 3.06%
Price = price of electricity 90.00 $ / MWh
OM (operation and maintenance) = 10.00 $ / MWh
r = real interest rate 30 years fixed 4.50 %
NPV after 1year = -100.622 million $
NPV after 6 years = 3.219 million $
NPV after 30 years = 278.363 million $
12
Gantt chart for Project
The Microsoft Project is employed as a planning tool for different activities within this project.
The project is divided into 11 main tasks. The main tasks have subtasks as well. The complete
process is shown below using Gantt chart.
Figure 2. Gantt chart for the Project
13
Chapter 5 Comparison between Configurations
In the original design, the substation is located offshore. If the same configuration is selected, the
offshore substation has to be placed on monopile. The transformer would be assembled onshore,
lifted off the dock by a heavy-lift vessel, and would be transported to site. After the transformer
is placed on the foundation and secured, finishing work would be performed. The complete cost
and operation calculation of the substation installation is done using Microsoft Excel. However
main results are shown in table8.
Total Time to Install Substation (day) 4.8
Vessels Heavy lift vessel, barge spread
Total day rate ($/day) 119200
Cost (million $) 0.57216
Table 8. Installation of Substation
Now for the sake of comparison between new and old configurations, NPV is calculated to see if
the project is profitable or not. Following is the NPV using old configuration (offshore
substation)
E = gross generated energy = 320000 MWh
CD = reported millions of dollars for decommissioning = 6.466
CT = reported millions of dollars for total capital costs CT = C*total capacity = 114.2528
CI = reported millions of dollars for installation = 7.9947
Loss = Losses from WindPRO calculations = 1.84%
Price = price of electricity 90.00 $ / MWh
OM (operation and maintenance) = 10.00 $ / MWh
r = real interest rate 30 years fixed 4.50 %
14
NPV after 1year = -104.658 million $
NPV after 6 years = 0.660 million $
NPV after 30 years = 279.715 million $
Old Configuration New Configuration
Total Capital Cost (million $) 114.2528 110.253
Total Installation Cost
(million $)
7.9947 7.622
Losses (%) 1.84 3.06
NPV after 1year (million $) -104.658 -100.622
NPV after 6 years (million $) 0.660 3.219
NPV after 30 years (million $) 279.715 278.363
Table 9. Comparison between Configurations
Figure 3. New Configuration
15
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
16
Bibliography Department of Trade and Industry. (2006). Decommissioning of offshore renewable energy
installations under the Energy Act of 2004. London: Department of Trade and Industry.
Joakim Jeppsson, Poul Erik Larsen, Åke Larrson. (2009). Technical Description Lillgrund Wind
Power Plant. Sweden: The Swedish Energy Agency.
Kenneth Hansen, Brian Vad Mathiesen, David Connolly . (2011). Framework conditions and
public regulation for wind turbines in the Øresund Region. Sweden: EnergiØresund.
(Final Report). Offshore Renewable Energy Installation Decommissioning Study. UK: Department
of Energy and Climate Change UK.
Olsson, A. (February 2009). Analysis of ‘All risk’ insurance from an offshore wind farm
perspective. Sweden: The Swedish Energy Agency.
Patrik Soderholm, MariaPettersson. (2011). Offshore windpowerpolicyandplanninginSweden.
Energy Policy 39 , 518-525.
RWE npower renewables. (August, 2011). Onshore Substation Opportunities. An RWE Innology
Company.
The Port of Malmö. (n.d.). Retrieved March 20, 2012, from Maersk Broker Agency:
http://www.maerskbrokeragency.com/OFFICES/SWEDEN/MALM%C3%96.aspx
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