Internship report_Georgios Katsouris

Cost Modeling of the Installation
of Offshore Wind Farms
Georgios Katsouris
InternshipReport

Cost Modeling of the Installation of
Oﬀshore Wind Farms
Internship Report
For the degree of Master of Science in Sustainable Energy Technology
at Delft University of Technology
Georgios Katsouris
October 30, 2015
Faculty of Applied Sciences Wind Energy Unit

IV
Georgios Katsouris Internship Report

Delft University of Technology
The following readers certify that they have read and recommend to the Faculty of
Applied Sciences for acceptance an internship report entitled
Cost Modeling of the Installation of Offshore Wind Farms
by
Georgios Katsouris
in partial fulﬁllment of the requirements for the degree of
Master of Science Sustainable Energy Technology
Dated: October 30, 2015
Supervisors: Dr. ir. Michiel Zaaijer
Ir. Ashish Dewan
Readers: Dr. ir. Michiel Zaaijer
Ir. Ashish Dewan

Table of Contents
1 Introduction 3
1-1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1-2 Objective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1-3 Report Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Installation of Oﬀshore Wind Farms 7
2-1 Installation Phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2-1-1 Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2-1-2 Wind Turbines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2-1-3 Electrical Infrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2-2 Cost factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2-2-1 Vessels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2-2-2 Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2-2-3 Ports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2-2-4 Technicians . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2-3 ECN Install . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2-3-1 Added value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2-3-2 User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2-3-3 The Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3 Cost module and additional features 19
3-1 Cost module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3-1-1 Cost inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3-1-2 Resources utilization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3-1-3 Cost calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3-2 Additional features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3-2-1 Gantt charts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
3-2-2 Excel summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3-2-3 Output graphs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Internship Report Georgios Katsouris

ii Table of Contents
4 Case study: Gemini oﬀshore wind farm 25
4-1 General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4-2 Climate data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
4-3 Installation planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4-4 Modeling the installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4-4-1 Sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4-4-2 Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4-4-3 Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4-5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4-6 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5 Conclusions and Recommendations 41
5-1 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5-2 Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
A Planning of Gemini installation model 43
A-1 Scour Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
A-2 Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
A-3 Export cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
A-4 Substations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
A-5 Inﬁeld cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
A-6 Wind turbines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
B Inputs of Gemini installation model 47
B-1 Wind turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
B-2 Vessels and Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
B-3 General Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Glossary 51
List of Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Bibliography 53

List of Figures
1-1 Capital cost breakdown for typical offshore wind farms. . . . . . . . . . . . . . . 4
2-1 Typical offshore wind fixed foundations. . . . . . . . . . . . . . . . . . . . . . . 8
2-2 Offshore wind turbine installation methods (1-4). . . . . . . . . . . . . . . . . . 9
2-3 Inter-array cables, export cables and substation installation. . . . . . . . . . . . . 10
2-4 Jack-up barge, jack-up vessel and heavy lift vessel. . . . . . . . . . . . . . . . . 11
2-5 Hydrohammer, drill and grout spreader. . . . . . . . . . . . . . . . . . . . . . . 13
2-6 Cable burying ROV and Plough. . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2-7 Offshore wind port and installation technicians. . . . . . . . . . . . . . . . . . . 14
2-8 ECN Install User Interface. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4-1 Gemini wind farm location. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4-2 Annual variation of wind speed and significant wave height at Gemini location. . 26
4-3 Monthly variation of wind speed and significant wave height at Gemini location. . 26
4-4 Gemini installation works. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4-5 Model development flow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4-6 Components cost breakdown. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
4-7 Gantt chart - Pre-Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4-8 Gantt chart - Post-Process. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4-9 Average delays breakdown per step and delay type. . . . . . . . . . . . . . . . . 34
4-10 Total delays per simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4-11 Resources cost per simulation. . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
4-12 Delays overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4-13 Resources variable costs overview. . . . . . . . . . . . . . . . . . . . . . . . . . 37
4-14 Average cost breakdown for resources. . . . . . . . . . . . . . . . . . . . . . . . 38
4-15 ECN Install results for Gemini. . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

iv List of Figures

List of Tables
3-1 ECN Install resources cost inputs. . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3-2 Vessel and Equipment utilization. . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3-3 Labour utilization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

vi List of Tables

Acknowledgements
First of all, I would like to thank my ECN supervisor Ashish Dewan for giving me the opportu-
nity to follow this internship and explore offshore wind installation modeling. His supervision
was vital for the realisation of the project and our discussions offered me constantly new
insights. I should not forget Rens Savenije for his guidance and overall role during the case
study. Last but not least, Vaidehi Parab, for our collaboration in this project and the time
spent discussing and programming.
Special thanks to my TU Delft supervisor, Michiel Zaayer, for his willingness to supervise my
internship and his discreet presence during this period. His feedback halfway through this
process was crucial for the further evolvement of this work.
On a personal level, I wish to thank first my partner Valentina, for bearing with me all
these months. Her valuable support helped me overcome the difficulties that I encountered
through this work. Moreover, I have to thank my family for believing in me and supporting
me throughout my studies. Last, I should not forget my friends, both in Delft and Greece,
for the relaxing moments we shared.
Georgios Katsouris
Petten, October 2015

2 List of Tables

Chapter 1
Introduction
The first chapter of the report presents the motivation for this internship. First, the impor-
tance of installation modeling of offshore wind farms is outlined with emphasis given to the
cost modeling. Next, the objectives are described in alignment with the work that has been
done in the field from Energy research Centre of the Netherlands (ECN). Finally, the last
section provides the outline of the following chapters.
1-1 Motivation
The continuously increasing energy demand which has led to the depletion of fossil fuels
alongside with the evident signs of climate change have escalated the efforts towards an
energy transition. Over the past years, Renewable Energy Sources (RES) such as solar,
biomass, geothermal, hydroelectric and wind energy have emerged as potential alternatives
to fossil fuels. The main driver behind this transition is the fact that the exploitation of RES
can reduce the global warming emissions and offer secure and inexhaustible energy supply.
The regulations which have been established in an international level, among which the most
significant are the Kyoto Protocol and European Commission 20-20-20 targets, contributed to
the implementation of RES. The penetration of RES reached 19% of the global final energy
consumption for 2011 where particularly, wind energy was 39% of the global renewable power
added in 2012 [1].
Furthermore, offshore wind farms are continuously gaining attention as power stations. The
European Wind Energy Association (EWEA) predicts installed capacity in Europe to rise
from currently about 7 GW to 150 GW by 2030 [2]. A highly dissuasive factor for the further
implementation of offshore wind energy still is its relatively high cost of energy compared
to other energy sources. Compared to onshore wind farms where costs are dominated by
the wind turbine, as far as offshore wind farms are concerned the wind turbines, support
structures, electrical infrastructure, installation and maintenance all contribute significantly
to the LCOE. Figure 1-1 presents the capital cost breakdown of offshore wind.

4 Introduction
Figure 1-1: Capital cost breakdown for typical offshore wind farms [3].
As Figure 1-1 illustrates, the installation activities account for 20% of the capital cost of
offshore wind. With larger and far-offshore wind farms planned in future, resulting in more
complex processes and harsher offshore weather conditions respectively, the installation be-
comes vital for the viability of an offshore wind project. Hence, robust installation planning
concepts are essential in order to reduce the project risk and subsequently lead to the opti-
mization of the resource management.
ECN, by using its in-depth knowledge in modeling operation and maintenance of offshore
wind farms, has developed "ECN Install" [4], a software tool that simulates the installation
planning, as given by the user. The first version of the tool includes only time information,
meaning that it provides the project’s time to completion and the relative delays that may
occur. However, the installation costs are also of great importance and particularly their
variation depending on weather.
1-2 Objective
Taking into account all the above, the objective of the internship is to provide a cost module
for the offshore wind farm installation tool, ECN Install. The approach that is used to achieve
the aforementioned objective is described in the following steps:
• Identify the main cost parameters of the offshore wind farm installation
• Analyse ECN Install tool
• Develop and implement the cost module
• Validate the tool in a case study.

1-3 Report Outline 5
1-3 Report Outline
The layout of the report is organized as follows:
Chapter 2 presents the main installation practices of oﬀshore wind farms, the relative cost
characteristics and an overview of ECN Install tool.
Chapter 3 includes the structure of the cost module and general additions that were made
in this work to ECN Install.
Chapter 4 provides the case study that was used during the validation.
Chapter 5 gives the conclusions of the internship and recommendations about future work.

6 Introduction

Chapter 2
Installation of Offshore Wind Farms
This chapter explains firstly the major phases of the installation of offshore wind farms. Then,
the main cost parameters are presented, followed by a brief overview of the ECN Install tool.
2-1 Installation Phases
The construction activities of an offshore wind farm constitute the realisation of the project
and include the procurement of goods, fabrication, assembly and installation. Installation
is the second largest cost component after procurement [5]. It constitutes of all activities
involving transportation and installation of wind farm components.
Installation activities can be split in three major phases depending on the component that
is installed: foundations, turbines and electrical infrastructure installation. For each of the
aforementioned phases, specific weather restrictions apply where the most strict among them
concern the turbines installation. Despite the differentiation resulting from the chosen in-
stallation concept, installation depends heavily on the weather conditions. Delays during
installation are the main reason for the delay in commissioning an offshore wind farm and
they can significantly affect the overall project profitability. The following sections present
the various installation concepts for each installation phase.
2-1-1 Foundations
The main considerations during the selection of the support structure include site-specific
conditions such as water depth, weather conditions and seabed properties, as well as turbine
characteristics, cost and and technical/commercial risk factors [2]. The type of the foundation
defines subsequently the installation method. Figure 2-1 presents typical offshore wind fixed
foundations that are used nowadays. Moreover, several floating offshore wind turbine concepts
have been proposed [6]. In the current work, fixed foundations are considered.

8 Installation of Offshore Wind Farms
Monopile Gravity-based Tripod Jacket Tri-pile
Figure 2-1: Typical offshore wind fixed foundations [2].
Monopiles
Monopiles are the most popular foundations for offshore wind turbines located in shallow
water depths (≤ 40 m) [7]. They consist of a large diameter (4−6 m) steel tubular pile whose
40 − 50% of its length penetrates the seabed [5]. The installation of a monopile is relatively
simple. After its arrival on site, vertical positioning on the seabed is performed. Then, the
monopile is driven in the seabed until the required penetration length is achieved. Several
driving/piling concepts have been proposed [8]. Next, a transition piece is lifted and grouted
onto the pile. Finally, rock dumping is performed as a scour protection method.
Gravity Based
The gravity type support structure has been used mainly in low depths (< 27 m) [5] and it
can replace monopiles at locations where piling is not possible and the seabed allows its use.
Gravity foundations are concrete structures that use their weight to resist wind and wave
loading. Their fabrication is cheap but the installation becomes more complex due to their
weight and the necessary seabed preparation and extensive scour protection [9].
Tripods
The tripod is a standard three legged structure that have a central steel shaft that is attached
to the turbine tower. Similar to the monopiles, each leg is inserted into the sea bed, but its
overall good stability makes it suitable for deeper waters [10]. Piles are used to secure the
structure to the seafloor. Their stiffness and stability advantages come with the disadvantage
of more complex transportation and installation.
Jackets
Jacket foundations are mainly considered for deeper waters. A jacket is an open lattice steel
truss template consisting of a welded frame of tubular members extending from the mud-
line to above the water surface. In general, the jacket structures are attached in the seabed
through piles. Piles are either driven through sleeves at each corner of the foundation or the

2-1 Installation Phases 9
foundation may be placed over pre-driven piles. Then, the sleeves are usually grouted to the
pile. Their fabrication as well as their transportation is relatively costly [8].
Tri-piles
The tri-piles consist of three foundation legs (piles), which are connected at the turbine tower
with a transition piece located above the water level. The piles are rammed into the seabed
with the help of a special guiding frame [11]. The advantage of this concept is that it can
easily be adjusted to accommodate water depth variations while maintaining the transition
piece dimensions.
2-1-2 Wind Turbines
Wind turbine installation follows the installation of support structures. The strong depen-
dence on the weather conditions gave rise to various installation concepts. Their distinction
concerns the degree of pre-assembly of turbine components which subsequently differentiates
the number of offshore lifts. Onshore assembly can decrease installation time but it affects
vessel selection and consequently cost. Generally, the turbine components that are installed
include the tower in one or more pieces, the nacelle, the hub and three blades. The methods
that are commonly used for offshore wind turbine installation are [5], [12]:
1. Nacelle and hub pre-assembly. In this concept, the nacelle and hub are pre-assembled
onshore and the tower can be one or more pieces. Each blade requires a single lift. In
total, the number of lifts required are 4 plus the number of tower pieces.
2. Bunny ear. For the bunny ear method, the nacelle, hub and 2 blades are assembled
onshore. The number of offshore lifts are equal to 2 plus the number of tower pieces.
3. Pre-assembed rotor. This method requires 1 lift for the nacelle, 1 lift for the rotor (3
blades and hub) and as many lifts as the tower pieces.
4. Entire turbine pre-assembly. For the case where the entire turbine is pre-assembled, a
heavy lift vessel is required to perform the turbine installation in a single lift.
Figure 2-2: Offshore wind turbine installation methods (1-4).

2-1-3 Electrical Infrastructure
The electrical system for an offshore wind farm usually consists of a medium-voltage electrical
collection grid within the wind farm and a high-voltage electrical transmission system to
deliver the power to an onshore transmission line [13]. Its installation is a long installation
sub-process and consists of three major parts: inter-array cables, export cables and substation
installation.
Inter-array cables
The inter-array cables, as part of the collection system, are medium-voltage cables that in-
terconnect the turbines and transmit the power to an offshore substation if present. They
are trenched (1 − 2 m) to the seabed. The installation of infield cables requires the pulling
of the cables through the J-tubes by using a winch, their laying and simultaneous burying by
a plough or Remotely Operated underwater Vehicle (ROV) or by following a post-lay burial
by a different vessel [5], [14].
Export cables
Export cables are high-voltage submarine cables that transmit the power to the point of con-
nection with the onshore grid. The two technologies that are used for the transmission system
are High Voltage Alternating Current (HVAC) or High Voltage Direct Current (HVDC). Ex-
port cables are usually installed by a simultaneous lay and bury method because of their
size and weight. The landing of the export cables can be performed either by horizontal
directional drilling or high tides may be used by the cable laying barge [5], [14].
Substation
The transmission system starts at the offshore substation, which steps up the voltage in order
to minimize transmission losses. The use or not of an offshore substation depends on the wind
farm power output and the distance to shore. In most cases, an onshore substation is also
needed to match the voltage of the transmission onshore grid. As far as the installation of the
offshore substation is concerned, it is usually positioned on a monopile or jacket foundation
by a heavy-lift vessel.
Figure 2-3: Inter-array cables, export cables and substation installation.

2-2 Cost factors 11
2-2 Cost factors
After the financial close of an offshore wind project, components are procured and the con-
struction organisation is set. Constructing an offshore wind farm involves a complex interac-
tion with many suppliers and installers of different components. Developers have chosen to
manage these interactions either through a single contractor, namely Engineering Procure-
ment Construction (EPC) contractor, separate contractors for each aspect (multi-contractor)
or through a mixed system (package management). Each option involves a different balance
of risks, and therefore different costs [15]. Irrespective of the way the installation costs are
allocated, the main cost parameters during the installation remain the same and specifically
include vessels, equipment, ports/staging and labour costs.
2-2-1 Vessels
During offshore wind installation, several vessels are involved for each activity. Characteris-
tically, 52 different vessels were involved during the installation of a relatively medium-sized
offshore wind farm such as Horns Rev 2 [16] while up to 30 different vessels could be found
on-site at a time [17]. As it is expected, vessels constitute the most important cost parameter.
The following vessel types are used during offshore wind installation [18], [19]:
Survey vessels
Survey Vessels are used for a wide range of activities, including scientific and environmen-
tal research at the pre-construction phase by the offshore wind developers. These include
environmental surveys, geophysical surveys and geotechnical surveys.
Jack-up barges and vessels
The installation of turbines is performed either by jack-up barges or jack-up vessels. The
jack-up barges are self-elevating mobile platforms that consist of a buoyant hull fitted with a
number of movable legs, capable of raising their hull over the surface of the sea. They are not
self-propelled which meabs that they must be on-site. The jack-up vessels are self-propelled
units that are specially designed in line with the industry demands. These purpose-built
self-propelled installation vessels have jack-up legs, cranes with big lifting capacities and they
are equipped with a Dynamic Positioning (DP) system.
Figure 2-4: Jack-up barge, jack-up vessel and heavy lift vessel.

Heavy lift vessels
Heavy-lift vessels are barge-shaped hulls with high capacity cranes that do not employ an
elevating system. They may or may not be self-propelled and may be dynamically positioned
or conventionally moored. They are rarely used to install turbines, but may be used for
foundation work, installing fully assembled turbines, or installing substations.
Cable laying vessels
Cable laying vessels are used to lay the inner-array cables and export cables to shore. Export
cable laying vessels are large barges or self-propelled vessels dedicated specifically for cable
laying operations. Inner-array cables may be laid by a variety of vessels because cable distance
and weight restrictions are smaller.
Support vessels
Support vessels are required for all installation stages and their involvement depends on the
capability of the main installation vessel and the scope of work. Briefly, diving support ves-
sels/boats are used to provide commercial diving services and construction support vessels
are used as suppliers of transportation services for components. Moreover, service crew ves-
sels or personnel transfer vessels are designed to transport personnel comfortably and safely
between the shore and offshore wind farms. Multi-purpose vessels, usually equipped with a
small crane and a large open deck, are primarily used for anchor handling and light transport
duties. Last, several tugboats may be used at each stage of the offshore wind supply chain.
2-2-2 Equipment
In addition to vessels, specialised offshore wind equipment is necessary for the realisation of
an offshore wind project. Equipment is usually leased to the EPC contractor from a third
party which results in additional costs. Offshore wind installation equipment is summarised
below in correspondence with the installation activity during which it may be involved:
Foundation installation equipment
Monopiles installation is usually carried out by hammering or drilling. Therefore, a hydro-
hammer or drill may be used respectively. Hammers are also used for installation of jackets,
tripods and tri-piles [8]. Moreover, the placement of the transition piece on top of a monopile
requires the filling of the gap between them with cement grout. As far as jackets or tripods
are concerned, the sleeves at each corner of the foundation through which piles are driven,
are grouted to the pile. The grouting process requires grouting spread equipment, as the one
depicted in Figure 2-5.

2-2 Cost factors 13
Figure 2-5: Hydrohammer, drill and grout spreader.
Cable installation equipment
Cable installation is a crucial installation activity of high complexity due to the need of
underwater operations. Cable laying is simpler in the sense that specialised vessels are used
which are equipped with all necessary equipment such as turntables/carousels, cable tensioners
and crawler cranes. On the other hand, cable burying is more complex and depending on the
seabed properties jetting, ploughing or mechanical trenching may be used [20]. ROVs and
ploughs constitute the necessary trenching equipment.
Figure 2-6: Cable burying ROV and Plough.
2-2-3 Ports
Ports constitute an important link of the offshore wind installation supply chain. They serve
as the central logistical point for delivery of components and construction of wind turbines
before they are loaded onto installation vessels. As it can be seen in Figure 1-1, they represent
1% of offshore wind Capital Expenditure (CAPEX) and they are considered hereby as part of
the installation costs. In order to consider a port as an offshore wind port, strict conditions
apply [21].
2-2-4 Technicians
Offshore wind installation requires highly-experienced personnel, able to handle sensitive
activities in often harsh weather conditions. Contributing 7% of the total installation costs
[22], labour costs are an important cost parameter.

Figure 2-7: Offshore wind port and installation technicians.
2-3 ECN Install
ECN Install is a MATLAB based offshore wind installation simulation tool. The main idea is
to give the opportunity to the user to model the installation planning and extract as outputs
time and cost information of the project. Its structure is highly user-defined which means
that the usefulness of the results depends heavily on the quality of inputs. The following
sections present the motivation behind the development of ECN Install, an overview of the
user interface and the logic of the modeling.
2-3-1 Added value
The importance of offshore wind installation modeling has already been outlined in Section 1-
1. A variety of users could benefit including wind farm developers, installation contractors and
port authorities. The added value of a robust installation planning model can be summarised
in the following key points:
• Provide accurate time and cost overview of the installation activities
• Initiate a dialogue process between the actors involved (developers-contractors)
• Identify barriers during the installation and eliminate project risks
• Lead to the optimization of resource management (e.g. vessels, equipment, ports and
personnel)
• Allow the testing of conceptual installation strategies (e.g. new methodologies and
vessels)
• Reduce possible delays and overall costs.
2-3-2 User Interface
In the first release of ECN Install, three main modules can be found in the user interface:
inputs, planning and outputs modules.

2-3 ECN Install 15
Inputs
The inputs module is organized in several sub-modules assisting the user to define relative
parameters of the installation. Starting from the wind turbine type, basic wind turbine
characteristics may be given such as power curve, hub height, number of turbines and power
output. Wind turbine inputs are used mainly to approximate the energy yield and allow the
calculation of the wind speed at the hub height. Moreover, climate data at various locations
(e.g. wind farm and ports) where installation activities take place should be included. Then,
the operation bases sub-module allows the connection of the climate data with all possible
locations. Especially for ports, information regarding their cost, distance to farm and possible
fixed delays due to harbour lock may be given. In addition, cost and weight parameters of
the components that need to be installed may be included.
Most importantly, relevant inputs of the vessels and equipment that are used during the
installation are required. These include cost parameters, speed of activities and weather
restrictions (wind speed and wave height) that may apply at each activity. Additionally for
vessels, travel speed is included to allow calculations concerning transportation activities.
Furthermore, shift related information including starting and ending times as well as labour
costs can be given in the working shifts module. Last, general fixed costs could be provided
alongside with the electricity price.
Planning
Following the inputs module, the proposed planning of the installation is given in the form
of installation steps. Three types of steps are considered:
• Loading step, which describes the set of activities to load the components from the
ports to the vessel
• Travelling step, which describes the travelling of the vessels
• Installation step, which is used to describe all installation activities being performed
with vessels and equipment.
The user can select the vessel and equipment that are used at each step, define the step
duration and the corresponding weather window as well as the number of technicians involved.
Depending on the step type, specific options are enabled or disabled. Additionally, for the
first step of a sequence of steps, the starting time should be given.
Outputs
The processing of the planning leads to the final outputs of the tool. These include the
starting and ending time of each step and possible delays that may occur due to weather
limits, shift availability and harbour lock. The summary of all steps provides subsequently
the overview of the installation time and its comparison with the idealised case where delays
are not present.

Figure 2-8: ECN Install User Interface.
2-3-3 The Model
A brief explanation of the way the installation modeling is performed by ECN Install is
necessary for the reader to get acquainted with the tool and acts as introduction to the cost
module which is presented in the following chapter.
As it was aforementioned, the installation is performed in the form of steps. In general, the
given weather data is used to provide accessibility vectors for performing each step, according
to the applied weather restrictions (wind speed Ws and significant wave height Hs). Starting
from the weather restrictions, one step may include vessel weather restrictions, equipment
weather restrictions and step weather restrictions. These weather restrictions are combined
in order to provide an aggregate weather restriction for each step as given in the following
expression:
{Ws, Hs} = {min(VWs , EWs , SWs ), min(VHs , EHs , SHs )} (2-1)
where V , E, and S represent vessel, equipment and step respectively.
By applying the aforementioned weather restriction at each step, all individual restrictions
are respected. It should be noted that only one vessel and one piece of equipment may be used
at one step. After the weather restrictions are defined, the accessibility vectors are formed for
each step by examining the climate data. Successively, the starting time of the step is used
as the starting point for which accessibility is considered.
Two main parameters that affect the completion of one step is the step duration, which shows
the time required to complete the step and the step weather duration which corresponds

2-3 ECN Install 17
to the necessary weather window. These two can be the same but usually a greater step
weather duration is assumed in order to account for uncertainty. All steps are considered as
weather non-splittable which means that the necessary weather window should be found in
order for a step to be performed. Besides weather limits, shift should be present but it is
possible that one working shift starts one step and another shift completes it (shift-splittable
step). Especially for travelling steps, they are considered as non-splittable. As long as the
necessary weather window is found and shift is present, the step is performed. After one step
is completed, the same procedure is carried out for the next step and so on.
As far as the climate data is concerned, the simulation of the installation is performed for
each year of weather data. In order to make clear the latter, the following example is used.
Assuming that the first step is scheduled to start on 1st of July 2015 and the available
climate date concern years 1990-1999. In this case, 10 simulations are performed by treating
deterministically each year of weather data. This means that for each simulation, the actual
starting date is adjusted in order to correspond to the time slot of each particular year of
the climate data. Specifically for the 1st simulation, as starting time for the first step, 1st of
July 1990 is used. For the case where the installation exceeds the current year, it proceeds
with year 1991 and so on. If the last of the climate data years is exceeded, climate data is
repeated starting from the 1st year which in this case concerns year 1990.

Chapter 3
Cost module and additional features
The following sections present the cost module that was developed for ECN Install including
other functionalities that were added to the software.
3-1 Cost module
Referring to a process as cost modeling basically means collecting cost data related to a certain
activity and deriving empirical relations that approximate the costs of this activity after inputs
are given by the user. Since, a model for the installation of offshore wind farms is already
present within the framework of the current work, the focus is on developing a cost module in
alignment with the existing model. Specifically, the objective of the cost module is to express
the time information given from the existing model into monetary terms. The development
of the cost module is split in two phases: resources utilization and cost calculations. The
following sections describe the aforementioned sub-modules after the relative cost inputs of
ECN Install are explained.
3-1-1 Cost inputs
An overview of the cost factors, which represent the resources used during offshore wind
installation was given in Section 2-2 including vessels, equipment, ports and technicians. The
way the cost inputs are broken down for each of the aforementioned resources is summarized
in the following Table.

20 Cost module and additional features
Table 3-1: ECN Install resources cost inputs.
Resource Cost Input Unit
Vessels
Fixed e /project
Day rate e /day
Day rate waiting e /day
Mob/Demob e /mob
Additional e /trip
Equipment
Fixed e /project
Day rate e /day
Day rate waiting e /day
Ports Cost per day e /day
Technicians Hourly rate e /hour
Starting from the vessel cost inputs, the term day rate is used which refers to the amount
the contractor is paid by the developer for one day of operating the vessel. It is possible that
a different day rate, namely day rate waiting, is defined for days when the use of the vessel
is not possible (e.g. bad weather). Additionally, the possibility is given to the user to select
a fixed cost which can replace the day rate costs and/or it may be used as insurance costs.
One vessel may be used for various installation activities (e.g. installation of foundations
and installation of turbines) which means that a de- and mobilization of the vessel should be
followed between two activities in order to adjust it according to the new requirements. This
results in extra costs expressed by the mob/demob costs. Finally, additional costs are defined
for each trip of the vessel which are mainly related to the fuel consumption.
As far as equipment is concerned, the same concept for fixed, day rate and day rate waiting
costs applies as for the vessels. Furthermore, the ports that are used during the installation of
one wind farm are compensated based on a cost per day. Last, an hourly rate for technicians
is defined to account for labour costs.
3-1-2 Resources utilization
The aforementioned cost inputs pinpoint the need for a daily overview of resources utilization.
For this reason, an intermediate module, namely resources module, was developed. The
resources module stores the hourly utilization of resources by keeping track of the installation
activities in the time domain. Specifically, for each simulation that is performed (see Section
2-3-3) the following information is stored for each vessel and equipment.
Table 3-2: Vessel and Equipment utilization.
Day



Working Time
Waiting Time
Harbour delay
Shift delay
Weather delay

3-1 Cost module 21
Additionally for each vessel, the number of trips as well as the number of mobilizations and
demobilizations are saved. As far as technicians are concerned, the same structure is used but
in order to account for the number of technicians, the labour cost per day is also calculated
at this level. Obviously, shift delay is not present in this case.
Table 3-3: Labour utilization.
Day



Paid Time
Waiting Time
Harbour delay
Weather delay
Labour Cost
In this case, it is assumed that technicians are paid according to their hourly rate even if there
is harbour and/or weather delay. Last, the days when each port was utilized are stored. Port
utilization is considered during loading steps where components are loaded at vessels or when
a vessel arrives at or leaves from a port. It should be noted that costs of storing components
in a port may apply but the current version of ECN Install does not treat logistics.
3-1-3 Cost calculations
The costs of resources that are used during the installation are calculated based on the
following expressions:
cvessels =
v∈V
cv
fixed + Nv
dr
∗ dv
r + Nv
drw
∗ dv
rw + Nv
mob/demob ∗ cv
mob/demob + Nv
trips ∗ cv
add (3-1)
where:
v and V denote a vessel and the set of vessels used respectively
cv
fixed is the ﬁxed cost of the vessel
Nv
dr
and Nv
drw
are the number of working and waiting days respectively
dv
r and dv
rw are the day rates while working and waiting respectively
Nv
mob/demob and cv
mob/demob give the number and cost of demobilizations
Nv
trips and cv
add represent the number of trips and the additional cost.
cequipment =
e∈E
ce
fixed + Ne
dr
∗ de
r + Ne
drw
∗ de
rw (3-2)
where:
e and E denote the equipment and the set of equipment used respectively

ce
fixed is the fixed cost of the equipment
Ne
dr
and Ne
drw
are the number of working and waiting days respectively
de
r and de
rw are the day rates while working and waiting respectively.
cports =
p∈P
cp ∗ Dp (3-3)
where:
p and P denote one port and the set of ports respectively
cp and Dp are the port cost per day and the number of days the port used.
clabour =
dl∈Dl
cdl
l (3-4)
where:
dl and Dl denote one day and the set of days for which labour is performed
cdl
l is the labour cost per day.
The summation of the resources cost (Equations (3-1)-(3-4)) yields the total installation cost:
Installation cost = cvessels + cequipment + cports + clabour
Besides installation cost related inputs, components cost and other fixed costs are given
as inputs to ECN Install. All these contribute to the CAPEX of the project. Specifically
regarding the cost of components, the cost input per component is given in terms of installed
power capacity (e /kW). The power capacity of the farm can be calculated by multiplying
the number of turbines with their power rating, as given in the wind turbines inputs tab.
Components cost =
comp∈Comp
NWT ∗ Pr ∗ ccomp (3-5)
where:
comp and Comp denote the component and the set of components installed
NWT and Pr represent the number of turbines and their power rating
ccomp is the cost of the component per kW.
Hence, the CAPEX of the project can now be calculated:

3-2 Additional features 23
CAPEX = Installation cost + Components cost + Fixed costs
Last, as it was mentioned in Section 2-3-2, the comparison of the installation cost with the
idealized case where delays are not present is also of value. For this reason, one simulation
is performed, namely pre-processor, which simulates the installation planning assuming that
weather restrictions do not apply, shift is always present and harbour delay is zero. The
resources and cost modules were designed in order to incorporate also this scenario. Moreover,
the delay in commissioning the project results not only in higher installation costs but also in
loss of revenue due to the failing to produce energy. Starting with the energy yield calculation,
if the wind turbine power curve is known the following expression is used:
Ey =
Ws,co
Ws,ci
Pel(Ws)f(Ws)dWs (3-6)
where:
Ws,ci and Ws,co denote the cut-in and cut-out wind speeds
Pel(Ws) represents the turbine power curve
f(Ws) is the weibull distribution of the wind speed at the wind farm.
It should be noted that the aforementioned energy yield concerns one turbine and one hour
period. For the weibull distribution, the wblfit.m built-in function of MATLAB is used. Since
the weather data in most cases concern 10m height, the logarithmic law for the wind speed
is used by using a roughness lenght of zo = 0.0002m. Finally, the loss revenue is calculated:
Loss revenue = Delay ∗ NWT ∗ Ey ∗ ep (3-7)
where:
Delay denotes the hours for which the project was delayed compared to the pre-processor
ep is the electricity price.
3-2 Additional features
Besides the resources/cost module, several additions were made to the existing software con-
cerning mainly its outputs.
3-2-1 Gantt charts
First, the possibility is given to the user to extract Gantt charts of the installation planning.
For this reason, a MATLAB script was developed which extracts the results in Microsoft
Project. The Gantt charts include information concerning the steps such as name, start
and end time and delays. Same information is displayed also for each sequence of steps (e.g.

installation of foundations). Hence, a quick time overview of the installation planning can be
performed and the most time-consuming steps/sequences can be identified. Since, multiple
simulations are performed according to the years of weather data, the Gantt chart of the
average of the simulations is displayed.
3-2-2 Excel summary
The key outputs of the modeling as well as the inputs are summarised in a Microsoft Excel
file which enhances also the transferability. As far as the inputs are concerned, they are split
in wind turbine related inputs, resources inputs and general inputs. The outputs include
time (e.g. project duration and delays) and cost (e.g. installation cost and cost breakdown
per resource) data of the project. In order to indicate the uncertainty the average, minimum
and maximum values of the aforementioned outputs are included. Moreover, detailed time
overview of each simulation is included.
3-2-3 Output graphs
Finally, output graphs strengthen the user-friendly character of the software while providing
useful feedback concerning the installation planning. They are divided in three categories:
time, cost and resources graphs. The idea is to present to the user graphically the key figures
of the simulations. The generated graphs offer insights for the project both on a high level
but also detailed analysis during its duration.

Chapter 4
Case study: Gemini offshore wind farm
For the validation of the cost module and in general ECN Install tool, a case study was
used which corresponds to the installation of Gemini offshore wind farm [23]. The following
sections provide general information about Gemini, how the planning of the installation was
formulated including the assumptions that were made and finally the results of the modeling.
4-1 General information
Gemini is a 600 MW under construction offshore wind farm located in the Dutch North Sea,
85 kilometres north of the Dutch coast. Construction started in 2015 with final commissioning
expected in 2017. It consists of two sites, ZeeEnergie and Buitengaats (blue and orange sites
in Figure 4-1 respectively), each containing 75 Siemens SWT-4.0-130 turbines [24].
Figure 4-1: Gemini wind farm location [25].

26 Case study: Gemini offshore wind farm
The wind farm is being developed by a consortium of four project partners Northland Power
(60% project interest), Siemens Wind Power (20%), Van Oord (10%) and HVC (10%). A
"two party" contracting strategy was chosen where Van Oord is the Engineering Procurement
Construction (EPC) contractor and Siemens is the turbine supplier. The total construction
cost of the Gemini project is estimated at around 2.8 billion e [23].
4-2 Climate data
The climate data for Gemini location was obtained by Energy research Centre of the Nether-
lands (ECN) from BMT ARGOSS using satellite data [4]. They correspond to 20 years
(1992-2011) of 3-hourly time-series of wind speed and significant wave height. Figures 4-2
and 4-3 show the annual and monthly variation of wind speed and wave height respectively.
Year
1992 1994 1996 1998 2000 2002 2004 2006 2008 2010
3-hourwindspeed[m/s]
6.8
7
7.2
7.4
7.6
7.8
8
8.2
8.4
Annual variation of wind speed
Year
1992 1994 1996 1998 2000 2002 2004 2006 2008 2010
3-hoursignificantwaveheight[m]
1.3
1.35
1.4
1.45
1.5
1.55
1.6
1.65
1.7
1.75
Annual variation of significant wave height
Figure 4-2: Annual variation of wind speed and significant wave height at Gemini location.
As it can be seen in Figure 4-2, weather conditions vary significantly over the 20-years period.
Consequently, same bahavior is expected for installation time and cost.
Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
3-hourwindspeed[m/s]
5.5
6
6.5
7
7.5
8
8.5
9
9.5
10
Monthly variation of wind speed
Month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
3-hoursignificantwaveheight[m]
1
1.2
1.4
1.6
1.8
2
2.2
Monthly variation of significant wave height
Figure 4-3: Monthly variation of wind speed and significant wave height at Gemini location.
The monthly variation of the weather parameters indicates the strong correlation between

4-3 Installation planning 27
wind speed and wave height. Moreover, the difference between winter and summer periods is
notable.
4-3 Installation planning
The installation planning of Gemini is split in the following phases [26], [27], [28]:
1. Scour protection. Rock dumping is performed for each of the 150 monopiles as scour
protection method by Van Oord’s vessel Nordnes [29]. It is assumed that rock loading
to the vessel takes place in the port of Eemshaven [30].
2. Foundations. The foundations of Gemini consist of a monopile and a transition piece.
Two vessels were employed for the installation of foundations, Van Oord’s Aeolus [31]
and Swire Blue Ocean’s Pacific Osprey [32]. Both vessels carry three complete founda-
tions at a time. The installation of 90 foundations is performed by Aeolus while 60 of
them by Pacific Osprey. Loading of foundations to the vessels is carried out in Orange
Blue Terminal [33] of Eemshaven port. Last, it is noted that piling is restricted in the
Netherlands from January 1st until July 1st [34].
3. Export cables. Two AC 220 kV export cables of over 100 km each, weighting 90 kg/m
are installed for Gemini. Their installation is a challenging and complex engineering
process because of several restricted areas [35]. Briefly, the installation of export cables
is split in shallow waters, near shore, deep waters and connector cable installation. For
shallow waters, Vetag 8 [36] and Nessie 5 lay 10 and 5 km of export cable respectively
which are buried by Nessie 2 until Rottumeroog. From this point, laying of cables is
carried out by Nexus [37] and subsequently Jan steen buries them by using a ROV. The
horizontal drilling operation in order for the two export cables to be laid under two
existing submarine cables is performed by WaveWalker 1 [38]. Last, cable jointing is
done by MPB Scheldeoord vessel.
4. Substations. Two 300 MW substations are installed on top of two jacket structures.
Rambiz 3000 heavy lift vessel of Scaldis [39] installs first the two jackets and subse-
quently positions the substations. The jackets are towed by tugboats from Bow Ter-
minal of Vlissingen port [40] whereas the substation are transported from Hoboken,
Antwerp.
5. Inter-array cables. Approximately 140 km of inter-array cables are required to in-
terconnect the wind turbines with an average weight of 30-40 kg/m. Inter-array cable
laying is carried out by HAM 602 cable laying vessel [41] whereas the post-burying is
performed by Jan Steen multi purpose vessel [42] and a ROV.
6. Wind turbines. Wind turbines installation is performed by Aeolus and Pacific Osprey
(75 turbines each) while components are loaded in the port of Esbjerg [43]. For both
vessels, one loading includes three complete wind turbines and for each turbine, the
tower comes at one piece while nacelle and hub are pre-assembled. Hence, five lifts are
required for the installation of one turbine.

The installation of first five components started in 2015 whereas installation of turbines is
scheduled for 2016. As an indication of the project status, it is mentioned that installation of
foundations was completed on the 17th of October [44].
Substations
Cables
Foundations
Figure 4-4: Gemini installation works.
4-4 Modeling the installation
Based on the installation planning of Gemini and for the purposes of the current work, a
model of the installation was developed. Hence, the installation phases (Section 4-3) were
translated in sequences of steps that can be handled from ECN Install. The idea to split the
installation in individual sequences comes from the fact that it allows their parallel process-
ing which subsequently offers significant time advantages regarding the project completion
date. The development of the model required a reverse flow compared to ECN Install layout
(inputs→planning) and specific assumptions. Particularly, since general information about
the planning was available, first the planning of the installation was formulated and the inputs

4-4 Modeling the installation 29
were subsequently aligned with the planning. The flow for the model development is depicted
in Figure 4-5.
Define
parallel
sequences
Break
down of
sequences
in steps
Approximate
load-outs
Step
duration
and
restrictions
Align
inputs
with the
planning
Figure 4-5: Model development flow.
The first step for the model development is to define the parallel sequences. Then for each
sequence, the installation steps are specified and vessel carrying capacities and weight of com-
ponents are compared to estimate the load-outs if data is not available. Then, step duration
and weather restrictions are defined and the model is completed by including the necessary
inputs. The following sections describe how the modeling of the installation planning for
Gemini was formulated including the necessary inputs for the model and the assumptions
that were made.
4-4-1 Sequences
The sequences that constitute the installation planning, correspond to the installation phases
of Section 4-3 but since both installation of foundations and wind turbines are performed by
two vessels, each of these phases is further split in two sequences (one for Aeolus and one
for Pacific Osprey). In total, 8 parallel sequences are defined. Moreover, a starting time for
each sequence is defined according to the available information. This means that for each
sequence, the first step starts at the specified starting time and the subsequent steps can only
be performed once the previous steps are completed.
Scour protection
Before the installation of foundations and in order to prevent erosion around the monopiles,
rock dumping is performed by Nordnes. According to the vessel carrying capacity (24,000
tons) and the rocks that are deposited for each monopile (2300 tons), 15 load-outs are required
at Eemshaven [28]. During each trip of Nordnes, rock dumping is performed for 10 monopiles.
The steps that are performed include rock loading at the port, travelling to the wind farm,
rock dumping for 10 locations and travelling back to the port. The details of the steps
including step durations and weather restrictions (wind speed and significant wave height)
can be found in Appendix A-1. Last, 1st of June 2015 is chosen as the starting time for scour
protection installation activities.
Foundations
As it was aforementioned, 90 foundations are installed by Aeolus and 60 by Pacific Osprey.
Both vessels carry 3 complete foundations at a time, hence 30 and 20 load-outs are required.

Installation from Aeolus starts at 30th of June whereas Pacific Osprey starts on 25th of July.
Technical specifications are available only for Pacific Osprey jack-up vessel [45]. It is assumed
that both vessels have same capabilities and hence, the same sequence of steps is used and
same steps duration and restrictions apply. Last, two IHC Hydrohammers S-2000 [46], one
for each vessel, are used for the piling. Appendix A-2 includes the sequence of foundations
installation.
Export cables
Export cables installation includes 6 sub-sequences: horizontal directional drilling, shallow
waters export cable installation, deep waters export cable laying and subsequent burying,
cable jointing and finally cable pull-in to the substations. These sequences can be performed
in parallel [35] but in order to simplify the modeling and avoid interactions between sequences,
it is assumed that they follow the order in which they were presented. Firstly, the drilling
operation starts on 1st of March by Wavewalker 1 jack-up barge. Then, for shallow waters
installation [47], 4 load-outs of export cable are required for Vetag 8 including two offshore
load-outs to Nessie 5. These two vessels perform the laying and Nessie 2 buries simultaneously
the cable. Subsequently, Nexus lays 30 km of export cable in deeper waters at each trip while
6 load-outs of export cable are required in total. After the export cable laying is completed,
Jan Steen and a Remotely Operated underwater Vehicle (ROV) bury the deep waters export
cables and it is assumed that after burying 30 km of cable, a trip for refuel is required. Next,
8 cable jointings are carried out by MPB Scheldeoord where each jointing takes 4 days [27].
The export cable installation is completed after the cables are pulled-in to each substation.
The detailed overview of the export cable installation is provided in Appendix A-3.
Substations
The installation of substations starts with the transportation of the jackets from Vlissingen to
the wind farm location and their installation by Rambiz 3000 heavy lift vessel. Next, after the
substations are transported from Antwerp, Rambiz 3000 positions them on top of the jacket
structures. Since, the installation vessel is not a jack-up vessel, strict weather restrictions
apply (see Appendix A-4). 1st of August 2015 is chosen as the starting date for this sequence.
Infield cables
For the infield cable installation between two turbines, a pre-lay grapnel run is carried out
firstly. Then, pull-in operation is performed at the first turbine, the cable is laid and finally
the second end is pulled-in at the second turbine. HAM 602 is the laying vessel with carrying
capacity of 1000 tonnes in its carousel. Since, 140 km of infield cable are laid with an average
weight of 30-40 kg/m, 5 load-outs are required. After cable laying, Jan steen vessel and a
ROV bury the infield cables. This sequence starts on 1st of July 2015. Details of the steps
overview are provided in Appendix A-5.

4-4 Modeling the installation 31
Wind turbines
After the completion of the aforementioned sequences, the installation of wind turbines can be
performed, which starts on February 2016. Jack-up vessels Aeolus and Pacific Osprey install
75 wind turbines each and also for this case, it is assumed that same conditions apply for both
vessels. Hence, 25 load-outs are required in Esbjerg for each vessel. For blade installation,
the wind speed is extrapolated at hub height of 88.5 m. The steps overview is included in the
Appendix A-6.
4-4-2 Inputs
In order for the model to be complete, the required inputs (Section 2-3-2) are given. They
are summarised in Appendix B, as they are displayed in the Excel file that is created.
Starting with the wind turbine specifications, 150 Siemens SWT-4.0-130 turbines are installed
[48]. The power curve was approximated as a 4.0 MW wind turbine with high wind ride
through system. Weights of components were collected from the aforementioned sources and
components costs were assigned according to Figure 1-1, in order to represent 60% of the
2.8 billion e Capital Expenditure (CAPEX). Wind turbine inputs are provided in Appendix
B-1.
11%
11%
Cost Breakdown per Component
32%
3%6%7%
9%
21%
Monopile
Transition Piece
Substations
Export Cables
Infield Cables
Rotor
Tower
Nacelle
Figure 4-6: Components cost breakdown.
Regarding vessel and equipment specifications, the weather restrictions and speed of opera-
tions were defined according to the step details, found in Appendix A. Particularly for vessels,
inputs as the travel speed, number of technicians and transport capacity were found in their
technical data sheets. Finally, typical cost inputs for both equipment and vessels were found
in literature [5], [49]. The vessel and equipment inputs of the model are included in Appendix
B-2.
As far as climate data is concerned, the time-series that was used for the simulation corre-
sponds to the location of the wind farm as it was presented in Section 4-2. However, it should

be noted that installation activities take place in various locations including harbours and off-
shore locations such as shallow waters, deep waters and wind farm location. Particularly for
harbours, four harbours are considered including Eemshaven which is the main harbour for
the installation, Vlissingen and Antwerp harbours from which substations and their support
structures are transported and finally, Esbjerg where wind turbines are loaded to the vessels.
Last, 24/7 working shift is considered for the entire installation. Details for these inputs are
provided in Appendix B-3.
4-4-3 Assumptions
The development of the model required several assumptions mainly due to the lack of informa-
tion and the fact that the project was realised while the model was formulated. The previous
sections provided already the points where assumptions were made. The model assumptions
are summarised as follows:
• The parallel sequences of the planning are processed individually which means that a
delay in one sequence cannot affect other sequences. In principle, this could be the case
especially for foundations and turbines installation or foundations and infield cables.
Moreover, a resource overlap (e.g. same vessel being used from two sequences at the
same time) could occur. In order to overcome these issues, the starting time of each
sequence was "wisely" chosen and for resources which are used in more than one sequence
sufficient time gap is present. The results confirm the latter.
• The duration of installation activities and weather restrictions were chosen according
to prior installation models that have been developed in ECN and after consultation
with ECN experts. In some cases, vessel and equipment capabilities (e.g. jack-up and
trenching speeds respectively) were available and thus used. Moreover, for all steps,
the step duration and weather restrictions match the vessel and equipment operation
duration and restrictions which are involved in this particular step.
• As it was mentioned, climate data of the wind farm location was only available. In
order to avoid excessive delays, especially for loading steps which mainly take place in
harbours, and assuming that the weather in harbours is better than offshore, milder
weather restrictions were chosen for steps that occur close to shore.
• In principle, the duration of travelling steps are automatically calculated from the tool
by using distances and travelling speeds. Since the maximum travelling speed of the
vessels is given as input, it was observed that the travelling time is under-estimated,
compared to the actual travelling time, found in vessel traffic services. For this reason,
the travelling times were hard-coded in order to be more realistic.
• The current version of the tool does not support weather splittable steps which practi-
cally means that the necessary weather window should be found in order for a step to
be completed. Hence, effort has been put to split each sequence in smaller steps as far
as time is concerned. Furthermore, all steps are considered shift splittable.
• It was not possible to retrieve cost information of the specific resources that were used
or will be used during the installation of Gemini wind farm. Hence, cost figures of

4-5 Results 33
comparable resources were used. In addition, for all steps the number of involved
technicians varies between 10 and 20.
• Logistics are not treated in this work. Thus, it is assumed that components are already
present in the harbours before each loading takes place. Moreover, the transportation
of components from the construction sites is not considered (except substations).
• Last, the installation of the onshore substation is not included in the planning, as well
as the commissioning phase of the project.
4-5 Results
Before the results of the simulation are presented, a brief explanation of the way the sim-
ulations are performed is required (Section 2-3-3). Firstly, the pre-processed simulation is
carried out which concerns the case where delays are not present. The pre-processing of the
planning is nothing more than fitting the installation steps in time meaning that after the
completion of one step, the next step is immediately performed irrespective of weather, shift
and harbour delays. For this idealised scenario, resources and cost calculations are made and
later compared with the actual simulations. As far as the latter are concerned, the number
of the simulations corresponds to the number of years of weather data which is available.
In this case, 20 simulations are performed (1992-2011) by adjusting the starting year of the
project to correspond to each year of the weather data. In order to make this clear, the first
simulation uses weather data of year 1992 for the first year of the project (2015) and year
1993 for the second year (2016) of the project. The last simulation uses year 2011 as the first
year of the project and year 1992 as the second year. Hence, each year of weather data is
used deterministically during the simulations.
To start with, the Gantt chart of the Pre-Processor (Figure 4-7) gives an overview of the
installation sequences. For the Pre-Processor, the duration of each sequence is the summation
of the steps duration.
ID Task Name Duration
1 Scour protectior 29.38 days
2 Foundations - Aeolus 83.75 days
3 Infield cables 105.08 days
4 Export cables 165.75 days
5 Foundations - P. Osprey 55.83 days
6 Substations 11 days
7 Turbines - Aeolus 106.4 days
8 Turbines - P. Osprey 106.4 days
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul
2015 2016
Figure 4-7: Gantt chart - Pre-Process.
In order to compare the pre-processed planning of the installation with the results of the
simulations, the Gantt chart of the Post-Process is created. It should be noted that since 20
simulations are performed according to the years of weather data, same number of installation
planning is generated. Figure 4-7 depicts the Gantt chart of the installation planning including
the average values of weather, shift and harbour delays for each sequence of steps.

ID Task Name Duration
1 Scour protectior 35.03 days
2 Foundations - Aeolus 106.52 days
3 Infield cables 140.65 days
4 Export cables 193.3 days
5 Foundations - P. Osprey 71.36 days
6 Substations 22.5 days
7 Turbines - Aeolus 131.23 days
8 Turbines - P. Osprey 127.68 days
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul
2015 2016
Weather Delay
Shift Delay
Harbour DelayProject: Gemini
Date: October 26, 2015 9:49 AM
Figure 4-8: Gantt chart - Post-Process.
As it can be seen, because of the fact that the project is divided over parallel installation
activities, the delays that occur do not affect significantly the project completion date (≈ +3
weeks on average). However, delays are translated mainly into cost due to the increased
resources utilization that is required.
In order to get an insight regarding the delays that were calculated, the following figure
categorizes them according to the step types during which they occurred and their type. In
addition to loading, travelling and installation steps, mob/demob step type is used.
Figure 4-9: Average delays breakdown per step and delay type.
As it was expected, most delays concern installation steps. Moreover, a significant number of
travelling steps were delayed due to the fact that they are considered as non-splittable. As
far as the breakdown per delay type is concerned, weather delays dominate. However, even
if a 24*7 shift pattern was selected, shift delays appeared due to the non-splittable travelling
steps and the default option to postpone a step when the previous step is completed within
two hours until the shift change (06:00 and 18:00 hrs).
Next, Figure 4-10 is used to illustrate the uncertainty of the delays that are calculated for
each simulation. In this case, simulations 1-20 correspond to years 1992-2011. Weather
characteristics for this period can be found in Figure 4-2.

4-5 Results 35
Simulation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Delays[h]
0
1000
2000
3000
4000
5000
6000
Total Delays per Simulation
Weather Delay Shift Delay Harbour Delay
Figure 4-10: Total delays per simulation.
As Figure 4-9 indicates, weather delays vary signiﬁcantly for each simulation whereas shift
delays are more or less constant. It is noted that harbour delays are considered ﬁxed and
hence, they are constant for all simulations. Corresponding the simulation results with the
wind and wave data of Figure 4-2, the peaks of delays match the peaks of weather data in
a great extend. It should be noted that since the project is scheduled in two-years period
(2015-2016), not only the starting year but also the next year is used for each simulation.
Furthermore, the resources cost which correspond to the installation costs for each simulation
performed are presented in Figure 4-11.
Simulation
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
Cost[MEuro]
0
50
100
150
200
250
Resources Cost per Simulation
Vessels Equipment Harbours Labour
Figure 4-11: Resources cost per simulation.

In general, the cost of resources follows the delays for each simulation. Specifically, based
on the model that was created for the installation of Gemini, the way that delays affect
installation costs can be explained according to the resources that they concern. As far as
vessels and equipment are concerned, delays affect their day-rate and day-rate waiting costs.
On the one hand, the hiring period is extended which directly means a greater number of
days for which day-rate costs apply and on the other hand, days for which day-rate waiting
costs apply may occur. For harbours, delays during mob/demob, loading and travelling steps
contribute to their overall costs. The reason is that day-rate costs apply for harbours only
for these types of steps. Last, labour costs are directly affected by weather and harbour
delays because of the assumption that technicians are paid according to their hourly-rate
even if these delays are present. Summarising, the type of delays as well as the resources
that were supposed to be used during these delays play an important role in the way the
overall installation costs are impacted. Therefore, it is not always the case that more delays
are translated in higher installation costs (e.g. simulation 2).
Besides the uncertainty of delays and installation costs for each simulation, their monthly
overview during the project duration is also of importance. First, Figure 4-12 presents the
delays overview for three scenarios (16, 17 and 11) which correspond to the scenarios which
yielded the most delays, the delays closest to the average delays and the least delays.
Project duration
Mar15 Apr15 May15 Jun15 Jul15 Aug15 Sep15 Oct15 Nov15 Dec15 Jan16 Feb16 Mar16 Apr16 May16 Jun16
Delays[h]
0
200
400
600
800
1000
1200
1400
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Best
Best
Best
Best
Best
Best
Best
Best
Best
Best
Best
Best
Best
Delays overview - Worst, Average & Best scenarios
Weather Delay
Shift Delay
Harbour Delay
Worst: 5417 hrs (sim. 16)
Average: 4085 hrs (sim. 17)
Best: 2319 hrs (sim. 11)
Figure 4-12: Delays overview.
As it can be seen, delays vary significantly depending on the weather of each month. Moreover,
the scenarios which were chosen show that is possible that the best scenario leads to more

4-5 Results 37
delays during one month compared to the worst scenario.
Next, the same scenarios were chosen in order to illustrate how the variable costs of resources
are distributed during the project duration. Resources variable costs include only day-rates,
hence fixed costs were omitted from this graph.
Project duration
Mar15 Apr15 May15 Jun15 Jul15 Aug15 Sep15 Oct15 Nov15 Dec15 Jan16 Feb16 Mar16 Apr16 May16 Jun16
Cost[MEuro]
0
5
10
15
20
25
30
35
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Worst
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
Best
Best
Best
Best
Best
Best
Best
Best
Best
Best
Best
Best
Best
Resources Variable Costs overview - Worst, Average & Best scenarios
Vessels
Equipment
Harbour
Technicians
Worst: 181.5 MEuro (sim. 16)
Average: 170 MEuro (sim. 17)
Best: 160.5 MEuro (sim. 11)
Figure 4-13: Resources variable costs overview.
In this case, the differences in terms of cost between these three scenarios in relatively smaller
compared to the corresponding delays. The monthly variation between the costs is also
worth-mentioning. It should be noted that for this graph and according to the cost inputs
that were chosen for this model, higher costs are not expected for the months that most
delays occurred. The reason is that lower day-rate waiting rates were chosen compared to
day-rate costs which means that delays postpone the expected costs for next months. Another
outcome of Figure 4-13 is that the months during which most cash flows are expected could
be identified. In this case, the period betweeen July and September 2015 is crucial for the
realisation of the project.
Next, Figure 4-14 presents how installation costs are allocated according to the resources
that were used. In addition, for vessels, equipment and harbours, the costs are further broken
down to each particular resource.

Average Cost Breakdown per Resource
1%4%
83%
12%
Vessels
Equipment
Harbours
Labour
4%
3%
1%
3%< 1%< 1%< 1%
Average Cost Breakdown per Vessel
2%
30%
5%
3%< 1%1%3%10%
35%
Aeolus
Pacific Osprey
Wavewalker 1
MPB Scheldeoord
Rambiz 3000
Nordnes
Tug-Jackets
Tug-Substations
Nessie 5
Vetag 8
Nexus
Jan Steen
Crew Transfer
Support vessel-export
Support vessel
Ham 602
5%7%
52%
S2000 IHC Hydrogammer 1
S2000 IHC Hydrogammer 2
Nessie 2
ROV
43%
Average Cost Breakdown per Harbour
< 1%1%
55%
Eemshaven
Esbjerg
Vlissingen
Antwerp
Average Cost Breakdown per Equipment
Figure 4-14: Average cost breakdown for resources.
As Figure 4-14 indicates, vessels constitute the most important cost factor of the installation.
Specifically, the two main installation vessels Aeolus and Pacific Osprey represent 65% of the
total vessel costs which corresponds to 54% of the total installation costs. As far as equipment
is concerned, only minor contribution to the overall costs is observed due to their limited use
for this model whereas harbours represent 4% of the installation costs. It should be noted
that harbour costs are considered only during travelling and loading steps, hence costs of
storing components are ignored. Last, cost of technicians is a significant cost component of
the installation and they were derived after assuming that 10-20 technicians participate at
each installation activity.
The previous figures presented the key aspects of the simulations including the Gantt chart
of the project, delays and costs break-downs, their uncertainty according to the the years of
weather data and the way they are distributed over the duration of the project. Moreover,
the main figures of the modeling can be easily assessed by using the overview sheet of the
Excel file that is created from the post-processor module of the software (Figure 4-15). First,
the summary of delays and costs provides information about the project and average figures
of the simulations. In the main table of the sheet, delays and costs are broken-down in their
components and simulation results are compared with the pre-processed outputs. For this
case, the average of simulations does not correspond to an actual average-estimate scenario
but it includes average values of the simulations. The minimum and maximum simulations
correspond to the best and the worst case simulation scenarios and they are used to indicate
the extreme values of delays and costs.

4-5 Results 39
Summary of delays & costs
Project Gemini Key simulation results (average)
Installed wind farm capacity 600.0 MW Project duration [months] 16.0
Number of wind turbines in farm 150 Delays [days] 164.69
Simulation Installation costs [M€] 195.53
Simulation period 20 yr Revenue losses [M€] 19.95
Unit Pre-Processor Average of simulations Minimum Maximum
Delays per delay type
Permits/Contract delays h 0.00 0.00 0.00
Resources delays h 0.00 0.00 0.00
Weather delays h 2,741.60 1,172.10 4,117.40
Shift delays h 1,097.90 1,033.60 1,186.80
Harbour_delays h 113.00 113.00 113.00
TOTAL h 3,953 2,319 5,417
Installation Costs
Vessels costs Fixed costs k€ 13,440 13,440 13,440 13,440
Mob/Demob costs k€ 5,300 5,300 5,300 5,300
Day rate costs k€ 113,430 131,249 126,560 136,630
Day rate waiting costs k€ 5,393 1,993 8,708
Additional costs k€ 6,156 6,156 6,156 6,156
TOTAL k€ 138,326 161,538 153,449 170,234
Equipment costs Fixed costs k€ 218 218 218 218
Day rate costs k€ 1,898 2,089 1,946 2,124
Day rate waiting costs k€ 18 18 46
TOTAL k€ 2,116 2,325 2,182 2,388
Harbours costs Day rate costs k€ 7,730 8,010 8,110 8,495
TOTAL k€ 7,730 8,010 8,110 8,495
Labour costs Hourly Wages k€ 19,978 23,659 21,595 25,449
TOTAL k€ 19,978 23,659 21,595 25,449
Total Installation Costs M€ 168 196 185 207
Other Costs
Components costs TOTAL k€ 1,686,000 1,686,000 1,686,000 1,686,000
Other Fixed costs TOTAL k€ 90,000 90,000 90,000 90,000
Total Other Costs M€ 1,776 1,776 1,776 1,776
Total Project Costs M€ 1,944 1,972 1,961 1,983
Simulations
Figure 4-15: ECN Install results for Gemini.
According to the results for the Gemini wind farm installation model, the project duration
is estimated at 16 months from which, over 5 months correspond to delays. The installation
costs are 196 Me whereas 20 Me is the loss to the cash ﬂows due to the delay of 3 weeks to
commission the project. In addition, installation costs can vary from 185-207 Me depending
on the weather whereas delays span is relatively wider. Components and other ﬁxed costs are
included in order to derive the total project costs.
Last, in order to avoid misinterpretation of the results, it should be noted that for the mini-
mum and maximum simulations, their total installation costs correspond to the minimum and
maximum installation costs, derived from the 20 simulations that were performed. Hence, it
is possible that individual costs of one resource may be higher for the minimum scenario com-
pared to the average of simulations or even compared to the maximum scenario. Especially,
this is the case for harbours, where the minimum scenario yielded higher costs compared to
the average of simulations. This means that for the minimum scenario, the delays led to
higher costs for harbours (e.g. they occurred during loading steps).

4-6 Discussion
The main scope of this chapter was the verification of the cost module that was added to
ECN Install. For this reason, a model for the installation of Gemini wind farm was developed.
In general, building a model requires several assumptions depending on the accuracy that is
desirable and the available information. As far as the current model is concerned, information
was limited and hence the validation of results is rather difficult. Ideally, by using accurate
cost inputs and a detailed installation planning, the model should approximate the actual
installation costs.
However, a rough installation planning was only available in this case. Hence, the first
step during the model development was to adjust the installation planning in a form which
ECN Install can handle (installation steps) while several modifications were needed to allow
the parallel sequences of steps. Next, cost inputs were assigned according to data found in
literature. In order to examine the contribution of the installation costs to the total project
costs as a validation of the results, the known project costs of 2.8 bn e should be used.
According to the results of the developed model, the installation costs account for 7% of the
CAPEX for Gemini wind farm. Compared to the rule of thumb for the installation costs of
an offshore wind farm (≈ 20%), the deviation is significant.
Assuming that the cost inputs used for the resources approximate in a great extend the actual
values, the reason for this deviation is that phases of the installation were ignored during the
development of the model mainly due to the limitations of the existing software which in its
current form allows the modeling of harbour and offshore activities. Particularly, these phases
include the transportation of foundations and cables to the port which in this case occurred
merely onshore and offshore, the construction of the onshore substation and the onshore
cable for the grid connection, the commissioning of the turbines and various surveys both
before and after the installation. Moreover, various parallel activities of the installations were
not modelled as crew transfers, diving activities and measuring and controlling processes.
These sub-activities alongside to the main installation activities require additional vessels,
equipment and technicians which all contribute to the installation costs. Last, project support
such as vessel consumables, site facilities, maritime services and personnel besides installation
technicians are also part of the installation costs which were not included in the modeling.

Chapter 5
Conclusions and Recommendations
The final chapter of the report provides the conclusions of the internship and recommendations
about future extensions to ECN Install tool.
5-1 Conclusions
The main objective of this internship was the cost modeling of the installation of offshore
wind farms. The project was realised within the framework of the offshore wind installation
modeling tool ECN Install. Hence, a firm starting point was provided but immediately
brought restrictions during the development since the alignment to the existing model was
necessary. Overall, the objective was met and a cost module is now included in the tool.
The theoretical cost model required thorough understanding of the tool and offered insights
about the offshore wind installation practices with an emphasis to the related cost parameters.
These include vessels, equipment, harbours and technicians. Moreover, the cost inputs to
the tool were verified and confirmed that the concept of day-rate costs dominates currently
offshore wind installation.
In addition to the cost module, the outputs of the tool were enriched to enhance the user-
experience of the tool. During this procedure, effort was put to identify which are the outputs
that may be of value to the various users of the tool. These include Gantt charts of the project,
graphs that provide time and cost overview during the project duration, break-downs of delays
and costs and a summary of the key figures, simulation outputs and inputs to the model.
As a validation of the cost module, a case study was used. The offshore wind farm that
was chosen was Gemini wind farm. The idea behind the development of the model for the
installation of Gemini wind farm came from the challenging character of the project, its
size and overall importance for the development of offshore wind energy in the Netherlands.
Since it is the first time such a comprehensive model is developed by using ECN Install, it is
considered as a milestone for the testing of the software and its further development.

42 Conclusions and Recommendations
Thorough testing of the model proved the robustness of the cost module. In general, the
dependence of the model outputs on the given inputs was evident. The results of the Gemini
model indicated that delays account for 1/3 of the project duration thereby increasing instal-
lation costs by 20%. Most of the delays concerned weather delays (69%) and 73% of the total
delays occurred during installation steps, for which the strictest weather restrictions apply.
As far as cost is concerned, vessels contribute over 80% of the total installation costs where
the main installation vessels (foundations and wind turbines) contribute over 60% of it.
5-2 Recommendations
The recommendations about the future extensions to ECN Install concern the cost module
but primarily the general logic of the modeling.
As far as the cost module is concerned, inputs could be modified to increase the accuracy.
First, for each trip of the vessel, fixed costs are assumed. However, fuel consumptions could
be given as inputs which will account for the cost of travelling steps according to the distance
covered. Moreover, the duration of travelling steps which is calculated based on the maximum
speed of the vessel is underestimated. Hence, an average travelling speed should be given as
input or the maximum speed should be treated in a different way from the software. Next,
components costs as a percentage of the installed capacity are rough estimates and therefore
could be replaced either by exact figures or weights and costs of materials, depending on the
user.
Addressing the core of the modeling, currently installation steps are treated as weather non-
splittable which leads to excessive delays for the cases where the duration of steps is increased.
This fact narrows down the applicability of the software to users who have detailed knowledge
of the installation activities including durations, weather windows and restrictions, hence
mainly contractors. On the other hand, developers would be interested in a more general
picture of the installation from which they can estimate project duration and installation
costs. In this case, a dynamic installation planning should be created according to the inputs
given by the user. This would require the development of default installation concepts which
will be adjusted according to the inputs (e.g. number of turbines). Overall, in its current
form, ECN Install is more valuable for contractors and significant changes would be required
to make it attractive also for developers.
Last, the case study that was used pinpointed the need for decisions regarding the number of
simulations performed. As it was mentioned in the previous chapter, every year of weather
data is used deterministically for the simulations. During the case study, the time-series of
20 years alongside with the large number of steps indicated issues about the memory usage
and overall speed of the software. Moreover, it was observed that an educated selection
of the years of simulation could provide similar results without compromising the level of
uncertainty. The options to avoid memory/speed issues of the software in the future besides
the obvious optimization that is required are either to select wisely the years of weather data
and perform the simulation deterministically or even better build a probabilistic weather
model and choose the confidence level for the simulation (e.g. P70, P90).

Appendix A
Planning of Gemini installation model
A-1 Scour Protection
Code Operation Duration [h] Ws [m/s] Hs [m] Location Vessel Equipment
1.1 Rock loading 12 17 10 Eemshaven Nordnes -
1.2 Travelling 5 20 3 Wind farm→Eemshaven Nordnes -
1.3 Rock dumping 2.5 17 2.5 Wind farm Nordnes -
repeat 1.3 9 times
1.4 Travelling 5 20 3 Eemshaven→Wind farm Nordnes -
repeat 1.1-1.4 14 times
A-2 Foundations
2.1 Loading 1 MP 3 20 10 Eemshaven Aeolus/P. Osprey -
2.2 Loading 1 TP 2 20 10 Eemshaven Aeolus/P. Osprey -
2.3 Travelling 7 23 4 Eemshaven→Wind farm Aeolus/P. Osprey -
2.4 Anchoring and positioning 1 20 3.5 Wind farm Aeolus/P. Osprey -
2.5 Jacking-up 0.7 14 2 Wind farm Aeolus/P. Osprey -
2.6 Upending and positioning MP 1.8 20 3.5 Wind farm Aeolus/P. Osprey -
2.7 Piling 4.5 20 3.5 Wind farm Aeolus/P. Osprey IHC S-2000
2.8 Lifting and stabilizing TP 1.3 20 3.5 Wind farm Aeolus/P. Osprey -
2.9 Grouting 2 20 3.5 Wind farm Aeolus/P. Osprey -
2.10 Jacking-down 0.7 14 2 Wind farm Aeolus/P. Osprey -
2.11 Travel to next turbine 1 23 4 Wind farm Aeolus/P. Osprey -
2.12 Travelling 7 23 4 Wind farm→Eemshaven Aeolus/P. Osprey -
repeat 2.1-2.12 29 times for Aeolus and 19 times for P. Osprey

44 Planning of Gemini installation model
A-3 Export cables
3.1 Travelling 7 20 4 Eemshaven→Wind farm Wavewalker 1 -
3.2 Positioning 2 20 2 Wind farm Wavewalker 1 -
3.3 Jacking-up 1 14 2 Wind farm Wavewalker 1 -
3.4 Drilling 24 20 2 Wind farm Wavewalker 1 -
repeat 3.4 9 times
3.5 Jacking-down 1 14 2 Wind farm Wavewalker 1 -
3.6 Travelling 7 20 4 Wind farm→Eemshaven Wavewalker 1 -
repeat 3.1-3,6
3.7 Loading 8 km of export cable 24 15 10 Eemshaven Vetag 8 -
3.8 Travelling 5 20 2.5 Eemshaven→ Shallow waters Vetag 8 -
3.9 Lay and bury 1 km of export cable 10 17 2 Shallow waters Vetag 8 Nessie 2
repeat 3.9 7 times
3.10 Travelling 5 20 2.5 Shallow waters→ Eemshaven Vetag 8 -
3.11 Loading 8 km of export cable 24 15 10 Eemshaven Vetag 8 -
3.12 Travelling 5 20 2.5 Eemshaven→ Shallow waters Vetag 8 -
3.13 Loading 4 km of export cable 16 15 2 Shallow waters Nessie 5 -
3.14 Lay and bury 1 km of cable 10 17 2 Shallow waters Nessie 5 Nessie 2
repeat 3.14 3 times
repeat 3.13-3.14
3.15 Travelling 5 20 2.5 Shallow waters→ Eemshaven Vetag 8 -
3.16 Loading 30 km of export cable 48 15 10 Eemshaven Nexus -
3.17 Travelling 6 20 3 Eemshaven→ Deep waters Support vessel-export -
3.18 Travelling 6 20 3 Eemshaven→ Deep waters Nexus -
3.19 Pre-lay grapnel run 1 17 2 Deep waters Support vessel-export -
3.20 Lay 1 km of export cable 2 17 2 Deep waters Nexus -
3.21 Travelling 6 20 3 Deep waters→Eemshaven Support vessel-export -
3.22 Travelling 6 20 3 Deep waters→Eemshaven Nexus -
3.23 Travelling 8 20 3 Eemshaven→ Deep waters Jan Steen -
3.24 Bury 15 km of export cable 30 17 2 Deep waters Jan Steen ROV
repeat 3.24
3.25 Travelling 8 20 3 Deep waters→Eemshaven Jan Steen -
3.26 Travelling 7 20 4 Eemshaven→Wind farm MPB Scheldeoord -
3.27 Positioning 2 20 2.5 Wind farm MPB Scheldeoord -
3.28 Jacking-up 1 14 2 Wind farm MPB Scheldeoord -
3.29 Jointing cables 96 20 2.5 Wind farm MPB Scheldeoord -
repeat 3.29
3.30 Jacking-down 1 14 2 Wind farm MPB Scheldeoord -
3.31 Travelling 7 20 4 Wind farm→Eemshaven MPB Scheldeoord -
3.32 Travelling 5 17 3 Eemshaven→Wind farm Crew Transfer -
3.33 Pull-in export cable to substation 12 15 2 Wind farm Crew Transfer -
repeat 3.33
3.34 Travelling 5 17 3 Wind farm→Eemshaven Crew Transfer -

A-4 Substations 45
A-4 Substations
4.1 Loading Jacket1 5 15 10 Vlissingen Tug-Barge -
4.2 Loading Jacket2 5 15 10 Vlissingen Tug-Barge -
4.3 Travelling 48 15 3 Vlissingen→Wind farm Tug-Barge -
4.4 Travelling 11.5 20 2.5 Eemshaven→Wind farm Rambiz 3000 -
4.5 Anchoring and positioning 1 14 1.5 Wind farm Rambiz 3000 -
4.6 Lifting and Positioning Jacket1 10 5 1 Wind farm Rambiz 3000 -
4.7 Driving the pin piles 10 14 1.5 Wind farm Rambiz 3000 -
4.8 Grouting 6 14 1.5 Wind farm Rambiz 3000 -
4.9 Travel to next location 6 20 2.5 Wind farm Rambiz 3000 -
repeat 3.5-3.8
4.10 Travelling 11.5 20 2.5 Wind farm→Eemshaven Rambiz 3000 -
4.11 Loading Substation1 5 15 10 Antwerp Tug-Barge 2 -
4.12 Loading Substation2 5 15 10 Antwerp Tug-Barge 2 -
4.13 Travelling 60 15 3 Antwerp→Wind farm Tug-Barge 2 -
4.14 Travelling 11.5 20 2.5 Eemshaven→Wind farm Rambiz 3000 -
4.15 Anchoring and positioning 1 14 1.5 Wind farm Rambiz 3000 -
4.16 Lifting and Positioning Substation1 10 5 1 Wind farm Rambiz 3000 -
4.17 Travel to next location 6 20 2.5 Wind farm Rambiz 3000 -
repeat 3.15-3.16
4.18 Travelling 11.5 20 2.5 Wind farm→Eemshaven Rambiz 3000 -
A-5 Inﬁeld cables
5.1 Loading 28 km of cable 36 15 10 Eemshaven HAM 602 -
5.2 Travelling 8 20 3 Eemshaven→Wind farm Support vessel -
5.3 Travelling 10 20 3 Eemshaven→Wind farm HAM 602 -
5.4 Travelling 5 17 3 Eemshaven→Wind farm Crew Transfer -
5.5 Pre-lay grapnel run 2 17 2 Wind farm Support vessel -
5.6 Pull-in ﬁrst end 4 15 2 Wind farm Crew Transfer -
5.7 Cable Laying 2 17 2 Wind farm HAM 602 -
5.8 Pull-in second end 4 15 2 Wind farm Crew Transfer -
5.9 Travelling 8 20 3 Wind farm→Eemshaven Support vessel -
5.10 Travelling 10 20 3 Wind farm→Eemshaven HAM 602 -
5.11 Travelling 5 17 3 Wind farm→Eemshaven Crew Transfer -
5.12 Travelling 8 20 3 Eemshaven→Wind farm Jan Steen -
5.13 Bury 1km of cable 2 17 2 Wind farm Jan Steen ROV
repeat 5.13 69 times
5.14 Travelling 8 20 3 Wind farm→Eemshaven Jan Steen -
repeat 5.12-5.14

46 Planning of Gemini installation model
A-6 Wind turbines
6.1 Loading 3 towers 6 20 10 Esbjerg Aeolus/P. Osprey -
6.2 Loading 3 nacelles-hubs 6 20 10 Esbjerg Aeolus/P. Osprey -
6.3 Loading 9 blades 9 20 10 Esbjerg Aeolus/P. Osprey -
6.4 Travelling 12 23 4 Esbjerg→Wind farm Aeolus/P. Osprey -
6.5 Anchoring and positioning 1 20 3.5 Wind farm Aeolus/P. Osprey -
6.6 Jacking-up 0.7 14 2 Wind farm Aeolus/P. Osprey -
6.7 Installing tower 3 17 3 Wind farm Aeolus/P. Osprey -
6.8 Installing nacelle 2.5 17 3 Wind farm Aeolus/P. Osprey -
6.9 Installing Blade1 2 17 3 Wind farm Aeolus/P. Osprey -
6.12 Jacking-down 0.7 14 2 Wind farm Aeolus/P. Osprey -
6.13 Travel to next turbine 1 23 4 Wind farm Aeolus/P. Osprey -
6.14 Travelling 7 23 4 Wind farm→Esbjerg Aeolus/P. Osprey -
repeat 6.1-6.14 24 times for Aeolus and P. Osprey

Appendix B
Inputs of Gemini installation model
B-1 Wind turbine
Project: Gemini
Wind Farm
Unit Input
Nr. Turbines - 150
Wind turbine
Type - SWT 4.0 130
Rated Power MW 4
Rotor diameter m 130
Hub height m 88.5
Components
Euro/kW 590
tonnes 850
Euro/kW 250
tonnes 200
Euro/kW 200
tonnes 5000
Euro/kW 180
tonnes 21000
Euro/kW 90
tonnes 5000
Euro/kW 300
tonnes 100
Euro/kW 300
tonnes 300
Euro/kW 900
tonnes 140
Tower
Nacelle
Monopile
Transition Piece
Substations
Export Cables
Infield Cables
Rotor
0 5 10 15 20 25 30 35
0
500
1000
1500
2000
2500
3000
3500
4000
Power Curve
Wind Speed [m/s]
Power[kW]

48 Inputs of Gemini installation model
B-2 Vessels and Equipment
Project: Gemini
Resources type no. Type Name
1 Vessel Aeolus
Capabilities Unit Input Weather limits Hs max Ws max Cost Unit Input
Travel speed knots 12 Activity m m/s Fixed Euro/project 5,000,000
Max. technicians - 74 Sailing 4 23 Day rate Euro/day 200,000
Transport Capacity tonnes 5000 Loading 10 20 Day rate waiting Euro/day 150,000
Loading 1 MP h 3 Jacking 2 14 Mob/Demob Euro/mob 2,000,000
Loading 1 TP h 2 Jacked-Working 3.5 20 Additional Euro/trip 20,000
Sailing h 7 Mobilisation 10 25
Anchoring and Positioningh 1 Installing turbines 3 17
Jacking-up h 0.7
Upending and positioning MPh 1.8
Piling MP h 4.5
Lifting and stabilizing TP h 1.3
Grouting h 2
Jacking-down h 0.7
Sailing within h 1
Mobilisation h 336
Installing tower h 3
Installing nacelle h 2.5
Installing blade h 2
2 Vessel Pacific Osprey
Transport Capacity tonnes 5000 Loading 10 20 Day rate waiting Euro/day 150,000
Loading 1 MP h 3 Jacking 2 14 Mob/Demob Euro/mob 2,000,000
Loading 1 TP h 2 Jacked-Working 3.5 20 Additional Euro/trip 20,000
Sailing h 7
Anchoring and Positioningh 1
Jacking-up h 0.7
Upending and positioning MPh 1.8
Piling MP h 4.5
Lifting and stabilizing TP h 1.3
Grouting h 2
Jacking-down h 0.7
Sailing within h 1
3 Vessel Wavewalker 1
Transport Capacity tonnes 2400 Jacking 2 14 Day rate waiting Euro/day 75,000
Sailing h 7 Jacked-Working 2 20 Mob/Demob Euro/mob 1,000,000
Jacking-up h 1 Mobilisation 10 25 Additional Euro/trip 20,000
Jacking-down h 1
Mobilisation h 336
Drilling h 24
Positioning h 2
4 Vessel MPB Scheldeoord
Travel speed knots 12 Activity m m/s Fixed Euro/project 150,000
Transport Capacity tonnes 2400 Jacking 2 14 Day rate waiting Euro/day 75,000
Sailing h 7 Jacked-Working 2.5 20 Mob/Demob Euro/mob 200,000
Jacking-up h 1 Additional Euro/trip 20,000
Jacking-down h 1
Jointing h 96
Positioning h 2
5 Vessel Rambiz 3000
Max. technicians - 75 Sailing 2.5 20 Day rate Euro/day 70,000
Transport Capacity tonnes 3300 Lifting 1 5 Day rate waiting Euro/day 50,000
Lifting h 10 Installing 1.5 14 Mob/Demob Euro/mob 1,000,000
Sailing h 11.5 Additional Euro/trip 10,000
Sailing within h 6
Driving the pin piles h 10
Grouting h 6
Anchoring and Positioningh 1
6 Vessel Nordnes
Travel speed knots 14 Activity m m/s Fixed Euro/project 200,000
Transport Capacity tonnes 24000 Dumping 2.5 17 Day rate waiting Euro/day 70,000
Sailing h 5 Loading 10 17 Mob/Demob Euro/mob 0
Dumping h 2.5 Additional Euro/trip 20,000
Loading h 12

Internship report_Georgios Katsouris

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