İzmir Institute of Technology

Department of Mechanical Engineering

Introduction to Renewable Energy Resources

ME427

Group #6

Off-shore Wind Energy

Cem Güngör 250203021 Mert Emrem 250203015

Sıla As 250203056 Talha Burak Dağ 250204081

Fall 2021-2022

i
Contents

1 Introduction 1
1.1 The Climate Crisis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Advantages and Disadvantages of Wind Energy . . . . . . . . . . . . . . . . . . . 2
1.2.1 Implications of Offshore Wind Energy . . . . . . . . . . . . . . . . . . . . . 2
1.3 History and Development of Offshore Wind Energy . . . . . . . . . . . . . . . . . 3
1.3.1 History of Wind Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3.2 History of Offshore Wind Energy . . . . . . . . . . . . . . . . . . . . . . . . 5

2 Offshore Wind Energy - State of the Art: The Current Situation of Offshore Wind
Turbines in a Technical Standpoint 6
2.1 Various Types of Wind Turbines and Their Elements . . . . . . . . . . . . . . . . 6
2.1.1 Foundation and Transition Piece . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.2 Rotor-Nacelle Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3 Global Status of Offshore Wind Energy Capacity 14

4 Offshore wind turbine installation operation and maintenance: Cost analysis of

OWT 18

5 Environmental Impacts of Offshore Wind Energy 20

5.1 Impacts on Local Ecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.2 Impacts on Fishing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

6 Case Study: Hornsea One Wind Farm 21

7 Discussion - Conclusion 22

ii
List of Figures
1.1 Comparison of time-averaged velocity profiles of winds over surfaces of varying
roughness [4]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2 Artist’s rendition of Blyth’s windmill [7]. . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Various types of wind turbines used throughout history. . . . . . . . . . . . . . . 4
1.4 Main classifications of wind turbines [8]. . . . . . . . . . . . . . . . . . . . . . . . 4
1.5 Comparison of a generic WT blade used in contemporary WTs versus a blade
from the 1980s [9]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1 Components of a: (a) wind turbine (b) offshore wind turbine [13]. . . . . . . . . 6
2.2 Support structures: Grounded systems: (a) Gravity Based Foundation (b) Monopile,
(c) Suction Caisson, (d) Tripod, (e) Jacket. Floating systems: (f) Tension Leg
Platform, (g) Ballast stabilized spar buoy. . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 External loads acting on a monopile offshore wind turbine [15]. . . . . . . . . . 8
2.4 The prototype (a) and the equivalent dynamic model (b) of an offshore wind
turbine with bucket foundation [16]. . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.5 Schematic of an offshore wind turbine rotor-nacelle assembly components [13]. 9
2.6 Rotor swept area [13]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.7 Wind turbine model used for aerodynamic calculations; (a) tilt, (b) yaw and (c)
pitch [13]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.8 Wind turbine model used for aerodynamic calculations; (a) tilt, (b) yaw and (c)
pitch [13]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.1 New and total offshore wind installations according to country and region [18]. 14
3.2 The new installations in China [18]. . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3 Global offshore wind growth to 2030 for the predetermined regions [18]. . . . . 17

iii
List of Tables
2.1 Details of the various turbines showing the cut-in and rated frequencies. . . . . 12

iv
Abstract
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lum rhoncus molestie odio. Sed lobortis, justo et pretium lobortis, mauris turpis condimen-
tum augue, nec ultricies nibh arcu pretium enim. Nunc purus neque, placerat id, imperdiet
sed, pellentesque nec, nisl. Vestibulum imperdiet neque non sem accumsan laoreet. In hac
habitasse platea dictumst. Etiam condimentum facilisis libero. Suspendisse in elit quis nisl
aliquam dapibus. Pellentesque auctor sapien. Sed egestas sapien nec lectus. Pellentesque
vel dui vel neque bibendum viverra. Aliquam porttitor nisl nec pede. Proin mattis libero vel
turpis. Donec rutrum mauris et libero. Proin euismod porta felis. Nam lobortis, metus quis
elementum commodo, nunc lectus elementum mauris, eget vulputate ligula tellus eu neque.
Vivamus eu dolor.

v
Nomenclature
Abbreviations

OWT Offshore Wind Turbine

HEX Heat exchanger
STHX Shell-and-tube heat exchanger
PHX Plate heat exchanger
PFHX Plate-fin heat exchanger
TFHX Tube-fin heat exchanger

vi
Introduction
As a result of the earth being heated unevenly by the sun, areas of high pressure and low
pressure arise at different regions, which in turn causes convections in the atmosphere that
we perceive as winds. Long have we harnessed the power of the winds, initially by setting sail
out on the ocean, then by using it to grind grain, and since relatively recent times, to produce
electricity.

The advent of wind turbines dates back merely around two centuries, with pioneers
such as James Blyth and Charles F. Brush. Even the most primitive innovations in the field
of electricity generation with wind turbines turned out to be exceptionally promising, as it
required nothing more than a generator and a set of blades or sails, paired with a placement
that sees a decent amount of wind. The wind turbines have been incrementally improved
upon ever since, with the working principle remaining the same.

With the technology today being on the verge of the physical limits in terms of inland
wind turbines, more and more innovators have been looking into the potential of harvesting
energy from wind over the seas. Other reasons for this push include the energy crisis facing
humanity today, and the ever-decreasing land available of onshore wind turbines.

Offshore turbine technology is considered by many to be at its infancy, and many

innovations are being made at a rapid pace. One can appreciate the added complexity of
design compared to an onshore wind turbine, and this added complexity manifests in places
such as costs, environmental impacts and total energy yield. The purpose of this report is
to outline all engineering aspects of offshore energy industry, with a focus on offshore wind
turbines.

1.1 The Climate Crisis

The term “anthropogenic climate change” coined around the 70’s refers to the overall
upward trend of Earth climate average temperature caused by human activities, specifically
from the massive increase in the utilization of fossil fuels since the industrial revolution [1].
The cumulative increase of greenhouse gases –that continues at increased rates– threatens
all life on the planet. This major threat pushed nations all around the world to mobilize for
a long term-solution to this life threatening crisis. Currently, research and development of
renewable alternatives such as wind power are funded by government subsidies. The research
and development efforts paved the way for groundbreaking technologies and improvements
that would have been impossible by efficiency incentives alone. In order to keep renewables

1
profitable in energy sector, the maturation of the technology has been a big leap that has to
be dealt with back in the day. Conventional renewable energy production methods such as
wind power and photovoltaics are currently as profitable as their fossil fuel counterparts –in
a areas with suitable wind or sun resources–[2].

Offshore wind energy is set to play a huge role in fighting greenhouse gas emissions
by incrementally replacing the electricity that would have been sourced from fossil fuels. It
is estimated by U.S. Department of Energy that 1.8 million tons of carbon emissions and
consumption of 5.9 billion liters of water can be circumvented by each GW of wind power [3].

1.2 Advantages and Disadvantages of Wind Energy

1.2.1 Implications of Offshore Wind Energy
Advantages

MENTION TYPES OF WINDS SPECIFIC TO SHORES AND WHY THEYRE SO GOOD

Off the shore,

Figure 1.1: Comparison of time-averaged velocity profiles of winds over surfaces of varying
roughness [4].

Therefore, offshore wind energy has the substantial advantage of available locations
with relatively stable winds and relatively consistent wind directions.

Disadvantages and Risks

Offshore wind farms face not only harsher weather, but also hydrodynamic loads in
addition to aerodynamic ones, therefore not only do they require more structural support,
but also a more rigorous analysis. In addition to all design engineering concerns, moving the

2
plant offshore brings with it many troubles regarding logistics. One such examples of these
problems would be that the systems of the plant such as the rotor

1.3 History and Development of Offshore Wind Energy

1.3.1 History of Wind Energy
Harnessing the energy of winds dates back over thousands of years, as early civilizations
set sails to the sea. Not long after, in the form of windmills, with the earliest ones in use
by the 9th century [5]. The first wind turbine to generate electricity was built in 1887 by
James Blyth [6], shown in fig. 1.2, from which point on, the technology of wind turbines
improved incrementally, while the working principle remained the same. Most wind energy
technologies work by utilizing the kinetic energy of the wind to induce rotational energy to a
mass –usually blades or sails–, which in turn is connected to a generator to create electricity.
Many different methods have been devised to accomplish this, as can be seen in figure 1.3.

Figure 1.2: Artist’s rendition of Blyth’s windmill [7].

3
 Figure 1.3: Various types of wind turbines used throughout history.

Hundreds of types of wind turbines have been used since its origination, however, all
such turbines can be classified into either of the two categories: horizontal axis wind turbines
(HAWTs) and vertical axis wind turbines (VAWTs). Axis, in this context, denotes the direction
into which the turbine in question is facing. Alternatively, instead of by their rotation axis,
WTs can be categorized by their working principles: lift or drag, as shown in figure 1.4.

Figure 1.4: Main classifications of wind turbines [8].

4
 Figure 1.5 demonstrates the aforementioned incremental improvements, spurred by the
advent of groundbreaking optimization techniques improvements in computational power
[9]. Along with the blades, structural integrity, grid integration, rotors, control systems and all
other subsystems involved saw great improvements over time.

Figure 1.5: Comparison of a generic WT blade used in contemporary WTs versus a blade
from the 1980s [9].

1.3.2 History of Offshore Wind Energy

Offshore wind energy can be defined as the energy generated from the wind over bodies
of water. The working of offshore wind turbines principle is the same as inland wind energy.

With first offshore wind farms installed in Europe starting from 1991 [10], offshore
wind technology has been in use only since very recent times when compared to onshore
wind technology. As a result of this, offshore wind turbines (OWTs) and farms had the
distinct advantage of utilizing and building on top of the established industry practices of
onshore wind energy –with some change– as a result. Control systems, grid integration
technologies, blade geometries etc. for instance, had already matured by the time offshore
wind technologies came into existence.

The increasing prevalence of OWTs of the last few decades is largely owed to three main
factors: the constraints imposed by regulations, such as the Kyoto Protocol and Paris Climate
Accords [11], the increasing need for independence from fossil fuel, and the decrease in the
available locations of inland renewable energy.

5
Offshore Wind Energy - State of the Art:
the Current Situation of OWTs

2.1 Various Types of Wind Turbines and Their Elements

The majority of offshore wind turbines conform to the industry standard wind energy
converter design, similar to wind turbines that are employed onshore. In parallel to inland
wind turbines, of the total amount erected thus far, HAWTs far outnumber the VAWTs in
offshore applications [12]. The design is characterized by having a three-blade horizontally
mounted gearbox and generator hub that is placed on top of a tower. The general terminology
and the components of a generic wind turbine is shown in figure 2.1.

Figure 2.1: Components of a: (a) wind turbine (b) offshore wind turbine [13].

In the case of offshore wind turbines, the tower is either placed upon a foundation
situated within the seabed (grounded system) or floated on top of the sea by a buoy (floating
system). Some variations on said support structure types are shown in figure 2.2.

6
Figure 2.2: Support structures: Grounded systems: (a) Gravity Based Foundation (b)
Monopile, (c) Suction Caisson, (d) Tripod, (e) Jacket. Floating systems: (f) Tension Leg
Platform, (g) Ballast stabilized spar buoy.

2.1.1 Foundation and Transition Piece

The foundations of OWTs are subjected to large overturning moments due to the action
of wind on the turbine and the tower structure as well as the wave and sea current loads on
the support structure. The design considerations for the foundations include:

• Ultimate load bearing capacity of the foundation: Analyzing extreme cases e.g., under
storm loading conditions. The results are compared with the empirical formulas, limit
equilibrium solutions and the finite element solutions to verify the accuracy of the
analysis.

• Accumulated rotation of the foundation after a lifetime of load cycles (for structures (a)
to (e) in fig. 2): Estimation of permanent rotation of the foundation. Methods that are
used in ultimate load bearing capacity is employed.

• Fatigue of the support structure: Fatigue due to variations in loads and moments acting
upon the wind turbine. Modal analysis.

The total load acting on a monopile offshore wind turbine is composed of several types
of loads. Said loads can be modeled separately and the equivalent dynamic model can then
be constructed based upon the given loads shown in figure 2.3.

7
 Figure 2.3: External loads acting on a monopile offshore wind turbine [15].

The equivalent dynamic model shown in figure 2.4 is a simplified model in which a
general understanding of the design can be obtained. Variation in loads with respect to time
can be estimated based on the conditions of the environment which the wind turbine is
planned to be built as well as some geometric and material parameters with regards to the
design.

Figure 2.4: The prototype (a) and the equivalent dynamic model (b) of an offshore wind
turbine with bucket foundation [16].

8
2.1.2 Rotor-Nacelle Assembly
Rotor-nacelle assembly (RNA), as seen from the fig. 2.1, is located at the top part of the
wind tower works both as a structural piece connecting the rotor to the tower and the hub
that is responsible for electric production. The design and selection of the assemblies based
on location and tower strength is both a question of funding as well as engineering. Similar
to any other energy production plant, in order to operate an offshore wind turbine or a wind
farm, the production of electricity should be profitable, or at the very least sustainable. In
this section, the engineering and financial side of designing the assembly is discussed. The
components forming the RNA is shown in figure 2.5.

Figure 2.5: Schematic of an offshore wind turbine rotor-nacelle assembly components [13].

The RNA is the part of the turbine where the rotational kinetic energy of the wind turbine
is converted to electricity. The shaft driven by the wind is connected to a gearbox having
a speed ratio of 1:n, since rotation speeds of the turbine blades are too low to operate the
generator. The speed ratio requirement of the gearbox is decided considering the expected
power, rotation speed of the turbine blades (e.g., considering a typical case where the speed
of the turbine blade is 20 rpm, the gearbox has a speed ratio of around 1:100). The relevant
formula is as follows:

9
 1
P = C p ρ AU 3 (2.1)
2

P : expected power output of the wind turbine,

C p : power coefficient (overall machine aerodynamic-mechanical-electrical perfor-

mance measure),

ρ: density of the medium (air),

A: Area swept by the blades (rotor swept area, see fig ??),

U : Horizontal wind speed.

The power coefficient term represents the ratio of ro-

tational kinetic energy converted from the total kinetic
energy of the wind passing through the rotor swept area.
Betz’s law states that the power coefficient is theoretically
limited to 16/27 and below, which is around C p,max ≈ 0.59.
In current state, well designed wind turbines’ power coeffi-
cients fall within the range of 0.35-0.45. Calculating C p of a
wind turbine design is a major area of research on its own,
though some basic models for aerodynamic calculations Figure 2.6: Rotor swept area
are present in the literature that are still used to this day for [13].
preliminary design.

Figure 2.7: Wind turbine model used for aerodynamic calculations; (a) tilt, (b) yaw and (c)
pitch [13].

10
 Wind speeds are varied with time and thus there is a large amount of power fluctuation
as predicted from eq. 2.1. This poses one of the major challenges with wind turbines in
general in terms of supplying electricity to the power grid. The fluctuation phenomenon is
commonly referred as power take-off (PTO) issues. Another notable issue is the changing
direction of the wind which apart from affecting the wind speed fluctuation, poses a threat in
a structural standpoint (e.g., variation of loads in the hub due to blade aerodynamics). There
are control systems that are put in place with the purpose of ensuring that the rotor turns at a
constant rate as well as reducing the problems born from the changing direction of wind by
rotating the hub normal to the direction of wind.

Based on the given relations, possible ways to increase the power output of the offshore
wind turbines are:

• Increasing the power coefficient C p of the turbine by fine tuning the rotor blade design.
This is done via aerodynamic and aeroelastic analyses and various optimization meth-
ods based on the characteristics of the environment that the wind turbine is going to
be built.

• Extending the rotor swept area through means in the point above.

• Choosing a location in which the average wind speed is comparably high. Another way
to ensure the average wind speed is great enough for wind turbine to be profitable is to
extend the size of the tower so that the upper wind blows through the rotor. In offshore
wind turbines however, the size is also a more sensitive constraint.

The literature study with regards to the current offshore wind turbines shows that it
is in fact more convenient to increase the rotor diameter rather than to invest in a more
efficient blade design. The swept area is proportional to the second power of the rotor radius.
Downside of this approach is the requirement of taller and stronger wind towers with heavier
nacelle and components, which poses many challenges apart from its costs in offshore wind
turbine setup and maintenance.

The definition of the terms related with the rotor rotation speed –which is often required
for the design stage of wind turbines–are start-up speed, cut-in speed, rated speed, and
cut-out speed. These terms are assigned, since the behavior of the rotor is dependent on
various factors and a constant rotation speed cannot be maintained. Start-up speed refers to
the wind speed at which the rotor begins to rotate. Wind speeds below the start-up speed are
not able to deliver required torque to actuate the rotor and blade assembly, which depends
on the setup. Locations receiving relatively low wind speeds require designs with low start up
speeds for example. The rotation of rotor assembly is not sufficient to produce usable power
on its own, the rotation must be within a given power range. The cut-in speed describes
the minimum wind speed that the wind turbine starts to generate usable work (typically 2.8

11
to 4.1 m/s). Rated speed on the other hand refers to the magnitude of wind speed that is
required for the wind turbine to generate its rated power. Since during the power generation
phase, due to the inertia of the rotor and blade assembly, the wind turbine continues to
produce usable power even the wind speeds drop below the given values momentarily. The
cut-out speed refers to a higher wind speeds that the wind turbine is shut down due to safety
concerns. These definitions related to wind speeds are commonly given by the frequency
with which the rotor and blade assembly rotate under their respective wind speeds. Wind
turbines from various manufacturers, the power rating, cut-in and rated frequencies are
shown in table 2.1.

Turbine make and details Rating (MW) Cut-in (rpm) Rated (rpm)
Vestas V 164-8.0 MW 8 4.8 12.1
Siemens SWT-6.0-154 6 5.0 11.0
RE power 6 M 6.15 7.7 12.1
RE power 5 M 5.075 6.9 12.1
Vestas V120 4.5 9.9 14.9
Vestas V90 3 8.6 18.4
Sinovel SL3000/90 3 7.5 17.6

Table 2.1: Details of the various turbines showing the cut-in and rated frequencies.

In addition to the aforementioned terms, 1P range is the range spanning from cut-in
of the turbine to rated speed or frequency of the turbine. The term basically describes the
turbines operational range over its entire life cycle.

Figure 2.8: Wind turbine model used for aerodynamic calculations; (a) tilt, (b) yaw and (c)
pitch [13].

12
 Based on the typical wind speeds, the manufacturer can obtain a power curve for its
wind turbine. The power curve can be read as a function of the wind speed that outputs the
power produced by the wind turbine. Power density is the mean power available per square
meter of swept area of a turbine, as shown in figure 2.8.

The foundation of the wind turbine is designed by considering the 1P range of the wind
turbine to avoid resonance related phenomena that reduce the operational life of the plant.

13
Global Status of
Offshore Wind Energy Capacity
The total wind power capacity of OWTs has reached 35.3 GWs in the world, which
accounted for 5% of total global wind capacity at the end of 2020. There are huge amounts
of wind farms that form a great portion of the power generation of wind energy systems
in the continents Europe, USA and Asia. Europe still has the largest offshore market with
70% of total global offshore wind installations at the end of 2020. In addition, cumulative
installations in Asia, especially in China, showed a huge increase by passing 10 GWs by the
end of 2020, and the growth made it the second largest regional offshore market. Also, the UK
remains leader of cumulative offshore wind capacity as of the end of 2020 [18]. Offshore wind
installations according to country and region are shown by pie charts in Figure 3.1.

Figure 3.1: New and total offshore wind installations according to country and region [18].

14
 Current installation capacity, the rate of developments over the past years, and the total
number of OWTs are explained for almost each pioneering country in offshore wind power
generation in the following passages.

In Germany, the total electricity generated by OWTs was established as 27 TWhs. The
country did not have a significant performance in the year 2020, with only 219 MW additional
capacity. The Government in Germany planned to operate 15 GW of the new offshore capacity
adhering to their target of using 65% renewable energy sources by 2030 [17].

In Belgium, the offshore wind turbines which have 2262 MW installed power capacity
generate 8 TWhs of electricity until this time, and this generation corresponds to 10% of the
consumption of electricity in Belgium. The country aims to add new energy capacity of an
extra 2000 MWs, which is provided by new OWTs that will be installed by 2026 [17].

Denmark has become well-known in the world by their remarkable studies about off-
shore wind energy. Denmark is the first country to install the offshore wind energy turbine in
1991. At the end of 2020, the country has 1703 MWs of offshore wind energy capacity. The
government in Denmark has a significant goal that is getting rid of usage of coal, gas and oil
by 2050. Consequently, the country planned to contribute three new OWTs with an extra 2400
MW installed power capacity by the years between 2027 and 2030. In addition to this, the
Danish government has been studying a project called “Thor Offshore Wind Energy Systems”.
The project aims to install 80 to 100 offshore wind systems in two predetermined islands,
Hesselo and Bornholm. The power capacity of the Hesello project was determined as 2 GWs
and the second island project Bornholm was 3GWs through tangible researches [17].

Netherlands has access to an area 1.5 times larger in the North Sea than the land area of
the country. Thereby, there is a great opportunity to use the offshore wind energy systems in
the North Sea. Additionally, low sea depth, high wind intensity and availability of suitable
ports make the offshore wind energy systems more favorable. A plant comprised of five off-
shore wind turbines with a total of 1500 MW power capacity exists in Netherlands. According
to the Offshore Wind Energy Roadmap’s strategy document published in 2018, a target of 11.5
GWs has been set to be achieved by 2030 [17].

U.K. is the world leader with 12,000 MWs installed power capacity of OWTs. Many
reasons can be cited to explain the said leadership, the main reasons being that: ease of
seabed allocation, high-intensity wind and appropriate sea depth, most of which due to
U.K. being comprised of islands. In the U.K., the offshore wind power generation met the
electricity consumption of 5 billion of houses at the end of the year 2020. Also, 50% of
percentage of installed offshore wind power in the world belongs to the U.K. The English
government has provided the enormous investment of £40 million to expand the power
generation of the offshore farms, and aims to operate 30 GWs offshore wind power systems by
2030. The research regarding offshore wind systems are backed by the English government,

15
which determined a target of net zero fossil fuel emissions until 2050 with the help of 75 GWs
offshore wind power installed. Additionally, the biggest offshore wind farm in the world is
located at the coast of northeast England in the North Sea, with a total capacity of 3.6 GWs
[17].

In Asia, marked growth is seen for offshore wind power, and surpassing the new instal-
lations in Europe makes them new leader of regional offshore wind. China and Japan are
important two countries in Asia which have remarkable proportions in offshore wind power
generation and the other countries in Asia are still at early stage of development. China had
increased their offshore wind energy capacity to 11.8 GWs (63% of the world) at the end of the
2020. As a result of the growth, China ranked third behind the UK and Germany, according to
the Global Wind Energy Council [19]. The new installations in China is shown as percentages
in Figure 2 by comparing Europe and rest of the world. Additionally, In Japan, 65 MWs of
offshore wind capacity has installed to operate at the end of 2020 [20].

Figure 3.2: The new installations in China [18].

In US, especially in North America, there are effective wind farms along the coasts. The
overall offshore wind power 29,00 MW has installed in U.S. In addition, The Departments of
Energy, Interior and Commerce U.S. studies to rise offshore wind capacity to 30 GWs by 2030
[21].

Additionally, it is clearly seen that each country has plans to expand their offshore wind
capacity and their targets are generally determined until the year 2030 by related associations
in these countries. Global offshore wind growths as a new installation for some countries and
regions are shown in Figure 3.3.

16
 Figure 3.3: Global offshore wind growth to 2030 for the predetermined regions [18].

In Turkey, no OWTs have been installed thus far. There exists an association related to
offshore wind energy called “Deniz Üstü Rüzgar Enerjisi Derneği (DÜRED)”. The association
published a report to inform about the of absence of the installations for the following
reasons:

• A separate law regarding Offshore Wind Energy usage can be passed in Turkey, as do
the other countries that endorse the industry.

• For Turkey to be the leader country in offshore wind energy systems in its region, they
should announce their targets until 2030.

• OWTs should be endorsed not only as production facilities, but as a whole with the
offshore wind energy industry.

• Projects regarding offshore wind energy systems are a strategic technology.

17
Offshore wind turbine installation operation
and maintenance: Cost analysis of OWT
In order for any power production method to be profitable, total energy produced over
the plant’s life cycle compared to its installation, operation and maintenance expenditures
should be greater than other alternative energy production methods with similar energy
potential. This is often compared by the levelized cost of energy (LCOE), which is the measure
of the average net cost of electricity generation in current, normalized prices. To analyze fea-
sibility of renewables which may be argued to be relatively new compared to well researched
and optimized non-renewable options such as power generation by fossil fuels, the external
effects i.e., government incentives in the form of subsidies or laws and regulations such as
emission allowances must be accounted in. These forms of government intervention in
energy sector are agreed upon to be necessary by United Nations to aid maturation of re-
newable technologies which otherwise -in a profit centered viewpoint- would seem to suffer
from the lack of knowledge and consequently sub-optimal design and thus the investments
may not reach a suitable level to let renewables be a strong alternative. Other variables such
as scalability and energy demand are also considered in a proposal but for the sake of the
simplicity, installation operation and maintenance costs (IOMs) and LCOE compared to other
renewable options as well as conventional non-renewables are discussed in given report.

The levelized cost of energy is given as:

PN I t +M t +F t
sum of the costs over lifetime t =1 (1+r )t
LCOE = = P Et
(4.1)
sum of electrical energy produced over lifetime N
t
t =1 (1+r )

Where:

I t : Investment expenditures in the year t

M t : Operation and maintenance expenditures in the year t

F t : Fuel expenditures in year t

E t : Electrical energy generated in the year t

r : Discount rate

n: Expected lifetime of the power station

18
 The LCOE represents the cost of electricity from the producer’s standpoint. The dis-
count rate accounts for the factors such as public funding govt subsidies and social cost of
capital. According to the National Renewable Energy Laboratory technical report: Installation,
Operation, and Maintenance Strategies to Reduce the Cost of Offshore Wind Energy [0], the
LCOE of an offshore wind turbine is given as following:

ICC · F C R
µ ¶
LCOE = + OM (4.2)
AE P

Where financial parameters; ICC (Installed Capital Cost):

ICC · F C R
µ ¶
LCOE = + OM (4.3)
AE P

OCC (Overnight Capital Cost):

OCC = T CC + BOS + SC (4.4)

TCC (Turbine Capital Cost)

BOS (Balance of Station Cost)
SC (Soft Costs —insurance+contingency+decommissioning-—)

insurance ≈ (T CC + BOS) · 0.02, contingency ≈ (T CC + BOS) · 0.1 (4.5)

CF (Construction Financing) AEP (Annual Energy Production)

FCR (Fixed Charge Rate)
O&M (Operation and Maintenance)

For the purpose of a cost study of OWT, some values of parameters are often assumed
based on the region that the wind turbine is proposed to be built. The average LCOE of all
power plants that are built in a given year is used to represent the unit cost of the electricity
based on the method of production. Projecting based on the historical data that is obtained,
it is possible to crudely foresee the reduction of cost of energy assuming the rates of change
are going to be similar in the future.

19
Environmental Impacts of
Offshore Wind Energy

5.1 Impacts on Local Ecology

Stuff

Sea Birds and Migratory Birds

Marine Mammals

Underwater Noise
Noise Reduction

Usage of Bubble Curtains

5.2 Impacts on Fishing

20
Case Study: Hornsea One Wind Farm
Hornsea One earned the title of largest offshore wind farm by having a capacity of 1.2 GW
of clean electricity, almost double the second largest wind farm in the world. The wind farm is
located 120 kilometers off the Yorkshire coast in the UK and is installed over an enormous area
of nearly 407 square kilometers, which is three times the size of Manchester. The installation
was completed and the wind farm began supplying power to the National Grid in 2019 ??.

Choosing the perfect location has been a significant challenge that the engineers en-
countered due to the sheer magnitude of the Hornsea One Project. Before the selection of
the best location, wind farm developers took into consideration some important parameters
such as water depth, cable landfall options and environmental factors. As a result of the
evaluation, the ideal location for the installation of Hornsea One was selected just off the UK’s
east coast as seen in figure ??. Consistently high wind speed and shallow but stable seabed
affected the selection significantly ??.

21
Discussion - Conclusion
The challenge of making the switch to clean, sustainable and renewable energy has
been faced by humankind for generations. With the ever-growing threat of climate crisis, the
significance of such technologies are acknowledged at an increasing rate. Apart from the
necessities arisen from the crisis from a purely economical standpoint, renewable energy
technologies are clearing the path for the future of humanity. In the report written, the
offshore implementation of wind energy structures and its impact on the environment are
covered. The literature survey shows that the offshore wind energy technologies still have
potential for growth. In terms of cost and ease of implementation, it is on route to be the
leading renewable energy generation method. The impact on marine and avian life and
relatively high installation/maintenance costs of this technology are mentioned as the major
drawbacks.

22
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