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Renewable and Sustainable Energy Reviews 139 (2021) 110576
Available online 27 January 2021 1364-0321/© 2020 The Author. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Installation of offshore wind turbines: A technical review
Zhiyu Jiang
Department of Engineering Sciences, University of Agder, N-4898, Grimstad, Norway
A R T I C L E I N F O
Keywords: Installation method Offshore wind turbine Bottom-fixed foundation Floating foundation Wind turbine component Modelling and analysis
A B S T R A C T
The installation phase is a critical stage during the lifecycle of an offshore wind turbine. This paper presents a state-of-the-art review of the technical aspects of offshore wind turbine installation. An overview is first pre- sented introducing the classification of offshore wind turbines, installation vessels, rules and regulations, and numerical modelling tools. Then, various installation methods and concepts for bottom-fixed and floating wind turbines are critically discussed, following the order of wind turbine foundations and components. Applications and challenges of the methods are identified. Finally, future developments in four technical areas are envisioned. This review aims to guide research and development activities on offshore wind turbine installation.
1. Introduction
The offshore wind energy community has undergone an evident expansion over the past three decades. In 1991, the world’s first ever offshore wind farm (OWF), Vindeby [1], was constructed in Denmark. That wind farm has already been decommissioned, and interest in floating wind farms in deep waters has since increased. For example, the 30-MW (MW) Hywind Scotland pilot park was commissioned in October
- This park consists of five spar floating wind turbines (FWTs) and demonstrates the feasibility of future commercial floating wind farms [2]. Today, many offshore wind turbine (OWT) technologies have reached a high technology readiness level, and a substantial decline of 20% in the levelised cost of energy (LCOE) of offshore wind projects has been observed between 2010 and 2018. Such a decline is due to factors including larger rotor diameter, OWF clustering effect, and improved wind turbine technology and installation technology. Still, compared with onshore wind energy and other renewable energy sources like solar photovoltaics, offshore wind energy has a significantly higher LCOE, with a global weighted average of $ 0.127/kWh [3]. To boost the competitiveness of offshore wind energy, it is important to identify the major cost drivers during the lifecycle of an OWF. Then, research-based innovations should be carried out to advance existing technologies. Because different phases of a lifecycle are interconnected, a holistic view is perferred when considering a technology. For example, a novel foundation may be used as fish habitat, replacing the need for decommissioning. The lifecycle of an OWF consists of a few stages. Although several
definitions exist for the stages [4–6], five representative stages can be considered for an OWF, as illustrated in Fig. 1. Here, Stage 1 involves site selection and preparation of a formal consent application. Wind speed, water depth and seabed conditions are considered during a site assess- ment. The application includes details of the wind turbines, environ- mental impact assessment along with other considerations. Stage 2 refers to the manufacturing and production of turbines, moorings, and cables. The turbine costs have been significant traditionally. Stage 3 involves installation of multiple components of OWTs including cables, foundations, tower, nacelle, and blades. At this stage, installation vessels and handling equipment are needed, depending on the installation methods chosen. To guarantee the efficient operation of an OWF after commissioning, inspection and maintenance activities are called for during its lifespan. In a broad sense, this stage includes various marine operation activities like transportation from port to site, lift-off of wind turbine components at the site and assembly of the components. Strictly speaking, transportation and installation are separate activities, but this paper discusses both. Stage 4 includes online condition monitoring, collection of SCADA data as well as routine inspections and repairs of wind turbine components like blades and gearboxes. Finally, after an OWF reaches the end of its lifespan, the developer will decide whether the OWF is to be decommssioned or repowered (Stage 5). While decommissioning indicates the complete removal of an OWF, repower- ing accomplishes the updating of wind turbines at an existing OWF by either replacing older turbines with new ones or swapping out the parts in the original turbines with new, more efficient technologies. Because of the complexities involved, offshore installations are nonstandard operations. Depending on factors like rotor size, foundation
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Renewable and Sustainable Energy Reviews
journal homepage: http://www.elsevier.com/locate/rser
https://doi.org/10.1016/j.rser.2020. Received 9 April 2020; Received in revised form 23 August 2020; Accepted 13 November 2020
type, technology development, and site conditions, each OWF has unique requirements for offshore installation. The associated costs can also be high. The capital expenditures (Capex) and the operational ex- penditures (Opex) are two ubiquitous contributors that influence the LCOE of many power generating systems including OWTs. Stehly et al. [7] estimated the LCOE for representative bottom-fixed and floating wind turbine projects. In Stehly’s work, the monopile foundation was considered for the bottom-fixed project and the semi-submersible foundation for the floating project, respectively. It was reported that the installation (Stage 3) accounts for 6.3% and 2.4% of the Capex for the bottom-fixed and floating projects, respectively, albeit the installa- tion methods assumed are not specified. Despite the relatively small contribution for the floating project, selecting a suitable installation method for an OWF strongly depends on the foundation types, site conditions, and equipment availability. Thus, it is an important and practical consideration for OWF development. Along with wind turbine technologies, installation technologies have witnessed development since the inception of the offshore wind in- dustry. For installed OWTs, there have been heated research activities spanning aerodynamics, hydrodynamics, structural loads, dynamics and control, operation and maintenance, drivetrain, and foundation and moorings. In contrast, the research field of OWT installation is relatively new and only receives late attention. A comprehensive overview of the installation methods is lacking so far. What are the installation methods for different types of OWTs? What are the challenges? What are the development trends? This review aims to address these questions by summarising the state of the art of the field. The article is structured into the following sections. Section 2 classifies the OWTs based on the foundation or substructure types. Section 3 lays a foundation for the following discussions and presents the installation vessels and equip- ment, classification rules, and numerical modelling tools. Section 4 re- views the installation methods for various bottom-fixed and floating foundations with a focus on most common foundation types. Section 5
discusses the research frontiers of wind turbine component installation. Section 6 discusses the future prospects of OWT installations. A final conclusion is drawn in Section 7.
2. Classification of offshore wind turbines
2.1. General
Wind turbines can be classified on the basis of different criteria. A wind turbine can either be vertical- or horizontal-axis if the criterion is the direction of the rotating axis. If the criterion becomes the power transmission method, then direct drive and gearbox transmissions are two main categories. For an OWT, the foundation type is also an important criterion that governs the installation method. Bottom-fixed and floating OWTs are two main categories; a brief overview is pro- vided here.
2.2. Bottom-fixed offshore wind turbines
The current offshore wind energy market is dominated by bottom- fixed OWTs [3]. Fig. 2 illustrates three common types. Among them, the monopile foundation has the simplest form as it consists of one single steel tube pile. Typical monopile OWTs have a diameter of 3–8 m and are considered economic for water depths of 20–40 m, and the development of monopiles of larger diameters and lengths is ongoing [8]. Gravity base foundations (GBFs) are usually made of concrete. They use their self weights to resist overturning moments and are appropriate for the clay, sandy soil and rock seadbed conditions [9]. GBFs used to be situated in water depths less than 10 m. Jacket foundations are space frame struc- tures welded from steel tubular members. Despite storage and logistics challenges [10], jacket-supported OWTs are competitive for intermedi- ate water depths (50–70 m) [11].
Fig. 1. Five stages typical of an offshore wind farm.
Mean water level
Blade
Mudline Monopile
Pile
Tower
Soil
Grouting
Shaft Gravity base Leg pile
Transition piece
Jacket
Hub and nacelle
Transition piece
Fig. 2. Schematic of monopile, gravity-based and jacket offshore wind turbines.
m. Jackup barges of old generations have mooring systems, and it is necessary to have forecasts of wind and wave directions prior to in- stallations in order to moor the vessel in a safe position relative to the OWT [16]. Another downside of these vessels is that the crane height and crane capacity are inadequate for MW-sized OWTs. To meet this end, purpose-built jackup vessels were constructed in the past decade; see Fig. 5 e ) for an example. Compared to the older counterparts, these vessels are often in excess of 100 m in hull length, less susceptible to weather conditions, and are equipped with dynamic positioning systems [17]. The large deck spaces make it possible for them to transport and install several OWTs in one trip. Although the day rate is higher, the offshore wind energy sector sees a huge demand for such specialised vessels. The semi-submersible crane vessels have the largest displacements in the list. Because the lifting capacity of such vessels can reach up to 20,000 tonnes, they are well-suited to lift heavy wind turbine assemblies in demanding installation scenarios. Nevertheless, due to the high day
rate, renting such vessels has economic restrictions. An offshore installation task cannot be fulfilled without involving specialised equipment. Such equipment can be installation vessel- or OWT-related and is under continuous development. Fig. 6 lists the two categories and several examples under each category. The vessel-related equipment, e.g., motion compensation devices [18], has been integrated into installation vessels and increases the operational efficiency and safety in offshore environments. The OWT-related equipment has been designed in tandem with the OWT technologies. Based on the func- tionality, the OWT-related equipment can be applied in transport or installation scenarios. In transport, excessive accelerations or vibrations of wind turbine components should be limited due to vessel motions, and sea fastening equipment like transport frames and racks are currently in use [19]. In installation scenarios, various solutions have been proposed to address complex lifting operations [20]. This paper will discuss the equipment for OWT components in Sec. 5.
Fig. 5. Common vessels used in OWT installation [153–156] (photo courtesy of Damen Shipyards Group, Spanopoulos Group and Fred Olsen ASA).
Table 1 OWT installation vessels and day rates (in US$), sources [21–23].
Type Specifications Day ratea Tugboat Diesel engines; large power-tonnage ratio (2.2–9.5) $ 1000– 5000 Crane barge Sheerleg or rotating crane; large crane capacity (1000–4000 tonnes) $ 80,000– 100000 Heavy lift cargo vessel Loading and discharging of heavy objects; spacious main deck area. $ 30,000– 50000 Jackup barge Non-self-propelled; medium to large crane capacity (200–1300 tonnes); dynamic positioning or mooring sytem; $ 100,000–180, Purpose-built jackup vessel Self-propelled; jacking system; dynamic positioning; large working deck; large crane capacity (800–1500 tonnes) $ 150,000–250, Semi-submersible crane vessel Self-propelled; large lifting height and crane capacity (3000–20000 tonnes). $ 280,000– 500000 a (^) Not necessarily representative of the
present market rates.
3.3. Standards and guidelines
The OWT installation activities, like any other offshore activites, must follow guidelines of regulatory authorities to ensure safety. The planning and execution of OWT installations should address various aspects including risk management, operation criteria, weather forecast, and structural integrity, as required by the offshore oil and gas industry [24]. Table 2 lists a few standards pertinent to OWT installations. Among them, DNVGL-ST-N001 [25] is a unified standard that replaces the legacy DNV–OS–H series standards [26,27]. In this standard, guidance is provided on marine operations of various types of offshore structures, and chapter 8 provides general requirements for installation of OWFs. ISO 29400:2015 [28] is another comprehensive standard with a similar scope. This standard is applicable to port and marine operations for offshore structures including subsea templates, foundations, and OWTs. DNVGL-RP-H103 [29] provides simplified formulas for establishing design loads useful for planning and execution of marine operations. This guideline covers towing operations, weather criteria as well as lifting operations but does not address OWTs in particular. The DNVGL-ST-0378 [30] standard provides requirements for offshore cranes and platform cranes. DNVGL-ST-0054 [31] is a recent standard that provide safety principles and guidance for transport and installation of onshore and OWTs. This standard is applicable to different wind turbine components, bottom-fixed support structures, substations, meteorological masts and power cables, but does not cover installation vessels or lifting equipment. DNVGL-ST-0437 [32] provides guidance for loads and site conditions of wind turbines. As the design situation of transport, installation, maintenance and repair is a design load case, this standard should be used with reference to design standards of OWTs [33, 34]. Although these standards and guidelines reflect the best practices of the day, improvements are always needed. Acero et al. [35] proposed a method for assessing the operational limits and operability of marine operations. As novel marine operation activities are not covered by standards and guidelines either, industry knowledge, experience, and technical know-how should be exercised for evaluating new installation
concepts.
3.4. Numerical modelling tools
Numerical modelling provides an economical means for design, testing, and verification of novel installation methods. Numerical tools are also important for identifying potential risks during the planning phase and hence for improving safety of marine operations during execution. Here, the focus is on physics-based simulation tools rather than the financial model-based tools [36,37]. To simulate an OWT installation typically involves modelling of mechanical systems under complex load effects, several disciplines are covered including aero- dynamics (Aero) [38], hydrodynamics (Hydro) [39], structural dy- namics (StrD) [40], and automatic control (AutoC) [41]. The numerical tools applied to OWT installation are collected from literature and summarised in Table 3. As shown, “Y” and “N” respec- tively denote yes and no, and not all tools can handle the described disciplines in abbreviations. ABAQUS [42] and ANSYS [43] are general-purpose finite element codes. Both can be used to address structural problems that occur during OWT intallations. AQWA and Fluent are ANSYS modules that extend the modelling capability to hy- drodynamics. Bladed [44] and HAWC2 [45] are aeroelastic programs for fully coupled calculations of OWTs and rotor aerodynamics. Both pro- grams allow for user-specified controllers limited to blade pitch or generator torque control. Because of the multibody fomulation and the bearing functionalities, HAWC2 can be applied to calculate the dynamic response of individual wind turbine components in lifting scenarios. EllipSys [46] is an incompressible Navier-Stokes flow solver that can be regarded as a high-fidelity numerical tool. It can be used to derive 2-dimensional airfoil data or to resolve the unsteady vortex shedding on wind turbine blades during installations. The MarIn toolbox [47] is an open-source modularised blade installation simulation toolbox devel- oped in MATLAB/Simulink. MarIn is suitable for design and testing of controller, e.g., tugger line force control, for installation-related prob- lems. Riflex [48] and SIMO [49] are two numerical codes widely used by the offshore industry. Riflex can be applied to simulate the dynamic behaviour of slender structures, while SIMO was originally developed to simulate marine operations of offshore structures. Through external Dynamic Link Libraries, Zhao et al. [50] enhanced the functionality of SIMO by including the aerodynamic load calculation for a nonrotating blade. There exist other numerical tools that can handle certain aspects of OWT installations. To make proper use of these numerical tools, the users should not only have modelling skills but also show un- derstandings of the underlying physical problems and relevant theories. The numerical modelling theories, e.g., the multibody dynamics [40] and the finite element method [67], are well-established and thus not covered in this paper.
4. Foundation installation
4.1. Bottom-fixed foundations
4.1.1. Monopile A monopile is typically used in hard to semi-hard seabed conditions.
Fig. 6. Category of specialised equipment involved in OWT installations.
Table 2 Standards and guidelines for offshore wind turbine installation. Standards Title DNVGL-ST-N001 [25] Marine operations and marine warranty ISO 29400:2015 [28] Ships and marine technology – Offshore wind energy – Port and marine operations DNV-RP-H103 [29] Modelling and analysis of marine operations DNVGL-ST-0378 [30] Standard for offshore and platform lifting appliances DNVGL-ST-0054 [31] Transportation and installaltion of wind power plants DNVGL-ST-0437 [32] Loads and site conditions for wind turbines
horizontal position (unlike the figure), it must be upended first. After- wards, the jackets are lowered and mated with the pre-installed piles. The locating cones help to expedite the mating process. To control a successful mating, the inclination, position, and heading of the piles are of importance, and underwater sensors are usually used to provide real- time decision support. Next, the annulus between the pile and the pile
sleeve in the jacket is filled with concrete and left to cure before erecting the wind turbine. There are relatively few research works in the public domain that address challenges of the jacket OWT installation. Thompson et al. [75] used acoustic monitoring to examine costal cetaceans response to the jacket pile-driving noise during the installation of two OWTs. They concluded that a short-term response by porpoises could occur within 1 – 2 km of the site. This noise issue is similar to those of monopile in- stallations. Zhang and Wang [76] considered the pile jacking method as a low-noise alternative to pile driving and conducted field study to compare the stress conditions caused by the installation processes. In comparison with the installation of monopiles, the jacket instal- lation involves more steps and is of a longer duration. So, the installation efficiency can be regarded as another challenge. To address this, Ruij- grok [77] designed alternative installation frames for pile installation based on an ultimate limit state check of the static internal loads. In this work, the frames were named “Pre-Piling Templates” and were used to
Fig. 8. Installation of monopile foundations. (a) Schematic of main components. (b) Procedure of the initial hammering process [158].
Table 4 Selected noise mitigation measures for pile driving, adapted from [71,74].
Category Mitigation measure Application Noise reduction Bubble curtains Big bubble curtain Trianel Wind park 11 – 21 dB Bubble curtains Little bubble curtain OWF Alpha Ventus 11–15 dB Isolation castings IHC Noise mitigation system OWF Riffat 5 – 17 dB Isolation castings BEKA shells ESRa project 6 – 8 dB Cofferdam Cofferdam Aarhus Bight 17 – 23 dB Cofferdam Pile-in-pipe piling Model testing 27 dB
speed up the installation process for three- and four-legged configura- tions of jackets. Actually, the design of installation frames should consider dynamic loads because such frame structures may experience large hydrodynamic loads when being lowered across the splash zone [78]. Apart from the pile-supported jackets, suction bucket jacket foun- dations have also been tested at the Borkum Riffgrund OWF [79]. The cup foundations can be installed in a single lifting and assembly process, reducing both the construction time as well as the associated costs. An additional advantage is that the installation noise is very low.
4.1.3. Gravity-based foundation GBFs stand on the seabed by their heavy weights, ranging from 1500 to 4500 tonnes [10]. GBFs have been put into use since the inception of the offshore wind industry in the 1990s. A review of European OWFs with GBFs and three generations of the foundation types can be found in Refs. [80]. Despite the differences in existing concepts, Esteban et al. [81] identified common phases in the installation procedure of GBFs: seabed preparation, support structure manufacturing, support structure installation, and ballasting and anti-scour protection. Seabed preparation is a unique step for GBFs that is not required for monopiles or jackets. This step appears because the weight of the GBFs will require huge ground-bearing capacity of the seabed, and soils with low bearing capacity must be removed. As mentioned by Ruiz De Termi˜no Alonso [82], during the seabed preparation, the removable layer thickness varies from 0.5 to 10 m and dredgers and offshore tools are invovled. As GBFs are cast in steel-reinforced concrete using molds, manufacturing of these foundations is time-consuming. There are three different types of facility for manufacturing GBFs: dry dock, floating pontoons and onshore [82]. Details of the manufacturing processes are
beyond the scope of this paper. The size and weight of the foundations make the load-out, transport, and installation cumbersome. As illustrated in Fig. 10(a), an offshore installation is traditionally carried out using a large barge, a floating crane vessel, and tugboats in the absence of self-propulsion systems for the vessels. The barge can possibly transport a number of foundations onboard and the crane vessel must be equipped with a large lifting ca- pacity in order to lift and place the foundation onto the seabed. The traditional method faces the challenges of offshore heavy lifts and utilising expensive heavy-lift crane vessels. To resolve these chal- lenges, the “float and submerge” installation method has been applied to the Blyth OWF recently. Fig. 10(b) demonstrates the procedures of this installation method. First, a GBF is produced on land, in a dry dock. Then, the self-floating GBF is wet-towed to its destination using tug- boats. Afterwards, the GBF is progressively submerged to the seabed by ballasting it with water and sand. During ballasting, sensor and control technologies are involved to ensure a proper weight distribution of the foundation. Similar to the installation process of the oil and gas gravity platforms [83], this method has good potential to be further adapted to achieve cost reduction and standardisation for large-scale deployment of GBF-supported OWTs.
4.1.4. Other foundation types There exist other alternative foundation types for bottom-fixed OWTs, including tripod [84] and suction bucket [84,85]. A tripod has a single steel tube above water and a three-legged foundation fitted with anchor piles, and the installation is difficult primarily due to the large footprint. In contrast, the suction bucket foundations could have easier installations. Zhang et al. [86] described an integrated transportation and installation technique that erects wind turbine assemblies like “tree planting”. Due to content limitations, these alternative foundation types
Fig. 9. Key steps of a jacket foundation installation.
location, the ballast tanks of the barge are filled with water until the barge and the attached wind turbine are flipped 90◦. The turbine is then released from the barge and towed to its final position for mooring connection. The resuable transport frame [89] can be used to attach multiple turbines and allows towing of the turbines at reduced draughts. Inspired by this concept, Lande-Sudall et al. [95] experimentally investigated the collision loads between a towing barge and an FWT and evaluated the feasibility of the installation method. The fork-on and float-off method [90] utilises a connective system that enables a connection of the wind turbine assembly from the spar at the offshore site. A transportation vessel with twin forks will be used to pick up the assembly, transport it to the site, and connect the assembly onto a pre-installed spar foundation. The vessel with a handling system [91], wind turbine shuttle [92] and catamaran installation [66,96] share the idea of using specialised vessels to transport and install wind turbine assemblies and do not address the intallation of spar foundations. As shown in Fig. 12, the catamaran vessel is equiped with sliding and lifting
grippers. During installation, the sliding grippers constrain the relative planar motions between the spar and the catamaran, whereas the lifting grippers play a key role by moving the wind turbine assemblies. An active heave compensator was developed in Ref. [97] to cancel the relative motion between the spar top and the assembly. Lately, a large floating dock [93] was proposed to faciliate mating of spar foundation and wind turbine components in open seas. As presented in Fig. 13, the initial design of the dock has a cylindrical shape and can shield one spar foundation from the external wave excitations. Despite the good in- tentions, the dock may be subjected to challenges like the piston-mode resonance and the sloshing effects [98].
4.2.2. Semi-submersible A semi-submersible foundation is principally composed of three or four columns that are at a distance from and connected to each other. Compared to a single-column spar, a semi-submersible has increased waterplane area which provides more hydrodynamic stability and more structural stiffness to resist wave loads. Liu et al. [99] provided a review of popular semi-submersible FWT designs and identified advantages and challenges of different concepts. One particular feature of semi-submersible FWTs is their superior tow- ability,^1 and hence simpler installation and decommissioning than other FWT concepts. Take WindFloat [100] for example. This 2-MW turbine was commissioned off the Portuguese coast in 2011 and operated for five years. The assembly of WindFloat composed of hull, tower and turbine took place onshore in a dry dock. The entire foundation was then towed to the site and tied to a pre-intalled mooring system. Fig. 14 illustrates the installation process. As shown, only three tugboats were used during the transport. When on site, the mooring hook-up was assisted by an
Fig. 11. Key steps of the Hywind Scotland spar FWT installation; adapted from Ref. [2,160].
Table 5 Selected installation methods for spar FWTs.
Method description Originator Year Country Barge with flipping capability [88] Windflip AS 2009 Norway Reusable transport frame [89] Atkins 2015 UK Fork-on and float-off [90] MODEC Inc 2015 Japan Vessel with a handling system [91] Ulstein Group ASA 2015 Norway Wind turbine shutttle [92] Huisman Equipment BV 2015 The Netherlands Catamaran installation vessel [66] SFI MOVE 2018 Norway Floating dock [93] Equinor ASA 2020 Norway
(^1) a factor that describes how easily a concept may be transported at sea [5].
anchor handling vessel. This convenient installation procedure makes it possible to carry out repair or maintenance of the FWT in a dry dock as well. To date, many alternative semi-submersible concepts have been developed, e.g., the Ideol platform with a damping pool [101] and the braceless V-shaped floating foundation [102]. Regardless of their indi- vidual differences, the installation superiority remains the same.
4.2.3. Tension leg platform A TLP is a vertically moored compliant platform with excess buoy- ancy. Many TLP FWT concepts have been proposed in the past; see Refs. [103–107]. Although these designs vary in platform displacement and stability, number of tendons, hull shapes, and number of columns, common features include taught tendons, compact mooring footprint, and limited platform motions. Compared to spar and semi-submersible FWTs, TLP FWTs are less commercialised primarily due to the com- plexities in anchoring systems and of installations. In spite of small-scale prototypes, e.g., the Blue H [108], installations of the utility-scale TLP FWTs have rarely been reported and experiences can be drawn from the offshore industry [109–111]. The tendons are usually installed before the platform. If a mechanical connector is used to join together the tendon sections, then the tendons can be dry-towed by a cargo barge to the site, where they are lifted and upended by a crane vessel. Alternatively, the individual tendon sections can be welded together and subsequently wet-towed to the site with buoyancy mod- ules. Once on site, the buoyancy modules are removed; winches or cranes of a crane vessel are used to upend the tendons. Depending on the design, the free-floating stability of TLPs during transit and installation can be an issue. A TLP FWT system may be fully
Fig. 12. Illustration of installation steps using a catamaran installaltion vessel, adapted from Ref. [66].
Fig. 13. Schematic of the floating dock concept, adapted from Ref. [93].
Fig. 15. Installations of TLP FWTs.(a) Installation method for the MIT/Enel TLP, adapted from Ref. [103]. (b) Installation concept for the GICON TLP [113].
although an increased number of pre-assembled pieces reduces the number of offshore lifts, an efficient use of the deck space of the trans- port vessel may be prevented, and large-capacity cranes may be required during the offshore construction consequently. Fig. 17 lists the six installation methods summarised by Ahn et al. [22] and Kaiser et al. [4]. These methods differ because of the number of pre-assembled compo- nents. All methods have been applied to installing OWFs in Europe and pertinent works can be found. Uraz [115] distinguished these methods considering site-specific factors and installation vessels. Wang and Bai [116] defined “overall installation” and “split installation” as the two main categories. This definition indiscriminately places most methods listed in Fig. 17 under the “split installation” category. The trend is that more OWTs are assembled in a “split” manner because of the growing wind turbine sizes.
6.2. Blade installation
Blades are airfoils made of composite or reinforced plastics. Table 7 lists the weight and length information of blades of representative commercial and academic OWTs, and the latest announced wind turbine models have power capacities above 10 MW. Even for the largest blades, the low weights ( < 100 tonnes) are well within the capacity of offshore cranes. However, given the large lengths ( > 100 m) and blades’ sensi- tivity to wind loads, lifting operations are not without challenges. In an early work, Wang et al. [57] considered the full rotor of a 1.5-MW wind turbine and calculated the hoisting forces for several rotor configurations and wind conditions using an aeroelastic tool. The analysis was simplified as only steady wind conditions were considered and the rotor was fixed during the simulations. Following the work, the Fig. 16. Installation of TetraSpar FWT (picture courtesy of Henrik Stiesdal). authors applied computational fluid dynamics (CFD) methods to
Table 6 Tradeoffs of mainstream installation methods for various foundation types.
Tradeoffs/types Monopile Jacket GBF Spar Semi-sub TLP Key installation steps
Pile driving and grouting
Pre-piling, lifting, and lowering
Seabed preparation, lowering, and scour protection
Upending, deballasting, and mooring hook-up
Mooring hook- up
Tendon upending and platform connection Installation simplicity
Relative advantage
Neutral Neutral Neutral Relative advantage
Relative disadvantage
Technical maturity
High High High Medium High Low
Main challenge Noise issue Noise issue and efficiency
Heavy lifts Foundation motions N/A Hull instability
Potential Noise mitigation Suction buckets Self-floating foundations Specialised vessels N/A Novel platform Water depth 0 – 40 m 30 – 70 m 0 – 30 m > 100 m > 50 m > 80 m
Fig. 17. Installation methods for component installation of OWTs (selected literature is included).
multibody model of the DTU 10-MW wind turbine blade with two tugger lines and a yoke and analysed the dynamic behaviour of the blade in different wind conditions. Ren et al. [47] conducted code-to-code comparison for a simplified blade lifting system composed of a blade, a hook and lifting wires. Zhao et al. [50] developed a numerical model and identified characteristics of a blade installation system. These works only address the installation systems. When a single blade is mated with a hub of an OWT, motions of the foundations can be very important. Fig. 18(a) illustrates the blade mating scenario for a monopile- supported OWT. This scenario bears a similarity to the floatover installation of offshore platforms [130]. As shown, the relative motions in the yz -plane should be a critical factor for the mating during which the long guide pin will enter a flange hole before other bolts (Fig. 18(b)). According to a numerical study [131] where both the monopile and blade motions are analysed, the monopile resonant motions can be dominant for sea states with low spectral wave periods. Such large relative motions may cause unwanted consequences. Verma et al. [53, 54] performed impact analysis of blade root and found that the blade-root impact can lead to damaged guide pins and delayed offshore operations in the worst case, which is confirmed by offshore experiences [132]. To address this issue, various means have been proposed. Jiang [61] suggested using passive tuned mass dampers to mitigate the resonant monopile motions during the blade mating phase. Following that, Sander et al. [133] reported the results of a monitoring campaigan during an offshore installation in the North Sea and confirmed the effectiveness of a tuned mass damper system. The downside of the passive mass dampers is due to their heavy mass and narrow effective frequency range. Ren et al. [62] focused on the blade installation system and designed an active control scheme to reduce the blade motions by controlling the tugger line forces. The scenario of using three tugger lines was also addressed in another work [134]. These approaches, if combined with motion tracking techniques [63,135], have potential to be applied in other OWT component installations. A variety of industrial equipment has been developed to facilitate blade installations. These are typically tailor-made mechatronic devices with remote control. Fig. 19(a)(b) show two representative products, the Blade Dragon technology [136] and the Boom Lock technolgy [137], respectively. The Blade Dragon is a lifting yoke that can grip a blade and install it at different inclined angles without the need to turn the rotor. The Boom Lock is an intelligence system that locks the lateral motion of the crane hook and significantly reduces the blade motion. Using these devices, it is possible to increase the wind speed threshold, to reduce human actions, and eventually to reduce risks during blade installations. More descriptions of industrial equipment can be found in Ref. [20]. Some novel concepts, e.g., Ref. [138], still have a low technology readiness level.
6.3. Installation of transition piece and tower
For many conventional bottom-fixed foundations, a transition piece is placed on top of the foundation to levelise the horizontal inaccuracies after the foundation is installed. Transition pieces pass through the majority of the water column but do not rest on the seabed. For monopile foundations, the gap between the pile and the transition piece is normally filled with cement grout. For jacket foundations and GBFs, transition pieces are installed in port and would not require a separate offshore lift. Following a lift-off operation very similar to that of a monopile foundation (see Fig. 7(a)), a transition piece will be lifted by an offhore crane and mated onto a pre-installed monopile foundation. Images of transition pieces during and after an installation for two European OWFs are presented in Fig. 20. In the left figure, a transition piece is being mated. This process can be deemed a docking operation. Acero et al. [55] carried out nonstationary and nonlinear time-domain simulations and identified the structural damage of the transition piece’s bracket
Fig. 19. Industrial equipment for blade installation (a) Horizontal blade mounting with a lifting yoke; source: Simens Wind Power GmbH. (b) Inclined blade mounting with a lifting yoke; source: Liftra ApS. (c) Blade mounting using the BoomLock technology; source: High Wind NV.
supports as a critical event and large horizontal motions of the transition piece bottom as a restricting event. Such mating operations are also analogous to the floatover operations [139] and active motion compensation systems can be used to improve the success rate [140]. For installation of a single OWT tower, the lifting and mating pro- cedures do not vary much from those of a transition piece. To the au- thor’s knowledge, there is little relevant literature. Nevertheless, a few concepts have been proposed to address the installation of a tower and rotor nacelle assembly. Sarkar and Gudmestad [64] presented the idea of a floatable subsea structure fitted with a hull on the top for installing tower assembly. Although the authors claimed that this concept is more environmentally robust than existing methods and can be performed at a significant wave height of 2.5 m, an uncommon telescopic wind turbine tower is assumed which hinders the application potential. In a separate work, Acero et al. [56] proposed a novel procedure for installing the tower assembly onto bottom-fixed foundations. The procedure is based on the inverted pendulum principle and requires a medium-sized heavy lift vessel together with a special upending frame. The feasibility of this concept has only been shown by numerical analysis so far. Beyond the numerical studies, model testing and prototypes are needed to elevate the technology readiness level.
6.4. Nacelle installation
The nacelle is a “box-shaped” structure composed of a main frame and a cover. A nacelle houses the generator, drivetrain (with or without), and monitoring, communications, control and environmental maintenance equipment [141]. Selected weights and dimensions of large OWTs are summarised in
Table 8. Most wind turbine models presented use gearboxes, but the latest IEA 15-MW reference turbine and the GE Haliade-X 12-MW tur- bine use direct drive generators. The nacelle dimensions of the 10-MW OWTs are quite close. During transportation and installation, it is common to have pre-assembled nacelle and rotor hub units, and a transport frame has been suggested to facilitate the transportation of the heavy units [143]. As the nacelles are much heavier than the blades, the nacelle lifting operations require offshore cranes with greater capacities. A typical installation involves lifting of the nacelle unit from the transportation vessel and mating with the tower. As shown in Fig. 21(b), the mating phase is similar to that of a blade, and a nacelle is connected to lift wires, a crane hook, and tugger lines. Before mating, the nacelle and the tower must be aligned first, often with the assistance of the installation crew. Among the few works that specifically addressed na- celle installation, Søvik et al. [144] investigated the final mating phase of a nacelle for a monopile-supported 10-MW OWT and found that the nacelle motions are small compared to the tower oscillations, and a tuned mass damper can be used to improve the mating process. Their analysis used constant drag coefficients to calculate the aerodynamic forces on the nacelle. As a nacelle has sharp edges and may experience vortex shedding in the wind, advanced computational methods [145] or experimental methods [146] are needed for accurate representations of the unsteady aerodynamics.
7. Future outlook
The prospects of the OWT installation market look promising as many novel solutions exist. Yet, no consensus has been reached on how a wind turbine should be assembled offshore. Based on the previous
Fig. 20. Installation of transition piece for monopiles left: Anholt OWF [161] right: Veja Mate OWF [162].
Table 8 List of nacelle specifications of offshore wind turbines. Wind turbine model Weight (tonnes) Dimension (m) Year Country IEA 15 MW [117] 821 N/A 2020 USA GE Haliade-X 12 MW [118] 600 20_._ 6 × 10_._ 4 × 8 N/A N/A MHI Vestas V164 10 MW [119] 390 20 × 8 × 8 2022 France DTU 10 MW [120] 446 21_._ 7 × 8_._ 7 × 8_._ 7 a^2013 Denmark LEANWIND 8 MW [121] 285 20 × 7_._ 5 × 7_._ 5 2016 Ireland Simens SWT-6-154 6 MW [142] 200 N/A 2013 Germany Sevion 5 MW [123] 290 N/A 2010 Germany NREL 5 MW [124] 240 N/A 2009 USA Simens SWT 3.6 MW [125] 125 N/A 2007 UK Bonus B76 2 MW [126] 82.5 N/A 2000 Denmark a (^) Values derived based on description.
solution because of their good towability. Tension leg platform floating wind turbines are the least commercialised, and many con- cepts face installation challenges because of the platform stability issue and the complex anchoring systems, and the installation method is expected to evolve with the foundation technology.
- For installation of offshore wind turbine components, significant interests have been shown in the single-blade installation method. To facilitate the installation in higher wind speeds and with less human intervention, a trend has been observed of utlising specialised lifting, mating and damping devices. Meanwhile, a few novel concepts have also been suggested for offshore installations of the tower assemblies, but most concepts still have low technology readiness levels.
- Numerical modelling and anlysis has proved to be a useful means for design and verification of novel installation concepts, and for determination of operational limits at the planning phase of a marine operation. To deal with practical installation tasks, numerical sim- ulations can complement, but not replace model testing, prototyping, or real-time measurements during actual operations.
The scope of this paper is limited. The author does not consider hydraulic wind turbines, vertical-axis wind turbines or airborne wind turbines because these are less mature wind turbine technologies with few installation examples. The paper does not establish any financial models [36] or carry out any economical analysis for the installation methods, either. It is believed that a comparison of the installation costs of the preliminary concepts can lead to biased conclusions [5].
Credit author statement
Zhiyu Jiang: Conceptualization, Methodology, Investigation, Writing, Reviewing and Editing, Resources.
Declaration of competing interest
The author declares that he has no known competing financial in- terests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgements
This work has been partly funded by the Peder Sather Grant awarded by the Peder Sather Center for Advanced Study at University of Cali- fornia, Berkeley. The author also extends gratitude to various research collaborators on the topic of offshore wind turbine installation.
References
[1] Olsen F, Dyre K. Vindeby off-shore wind farm-construction and operation. Wind Eng 1993;17:120–8. [2] Lien KH. Hywind Scotland – marine operations. 2017. 02-01, http://www.sintef. no/projectweb/deepwind_2016/presentations/. [3] IRENA. Renewable power generation costs in 2018, Technical Report. Abu Dhabi: International Renewable Energy Agency; 2019. [4] Kaiser MJ, Snyder B. Offshore wind energy installation and decommissioning cost estimation in the U.S. Outer continental shelf, technical report, US Dept. Of the interior, Bureau of ocean energy management, regulation and enforcement, Herndon. VA TA&R study 2011;648:340. [5] Myhr A, Bjerkseter C, Ågotnes A, Nygaard TA. Levelised cost of energy for offshore floating wind turbines in a life cycle perspective. Renew Energy 2014;66: 714 – 28. [6] Ulstein Group ASA. 5 Stages in the lifecycle of an offshore wind farm. 2019. 10- 23, https://ulstein.com/equipment/ulstein-windlifter. [7] Stehly TJ, Beiter PC, Heimiller DM, Scott GN. 2017 Cost of wind energy review. Technical Report, NREL/TP-6A20-72167. Denver, CO, USA: NREL; 2018. [8] Hermans K, Peeringa J. Future XL monopile foundation design for a 10 MW wind turbine in deep water, Technical Report, ECN-E–16-069. The Netherlands: ECN;
[9] Wu X, Hu Y, Li Y, Yang J, Duan L, Wang T, Adcock T, Jiang Z, Gao Z, Lin Z, et al. Foundations of offshore wind turbines: a review. Renew Sustain Energy Rev 2019;104:379–93. [10] Thomsen K. Offshore wind: a comprehensive guide to successful offshore wind farm installation. Academic Press; 2014. [11] Dong W, Moan T, Gao Z. Long-term fatigue analysis of multi-planar tubular joints for jacket-type offshore wind turbine in time domain. Eng Struct 2011;33: 2002 – 14. [12] Castro-Santos L, Diaz-Casas V. Floating offshore wind farms. Springer; 2016. [13] Guachamin-Acero W, Moan T, Gao Z. Steady state motion analysis of an offshore wind turbine transition piece during installation based on outcrossing of the motion limit state. In: ASME 2015 34th international conference on ocean, offshore and arctic engineering. American Society of Mechanical Engineers; 2015. V003T02A064–V003T02A064. [14] Richmond M, Balaam T, Causon P, Cevasco D, Leimeister M, Kolios A, Brennan F. Multi-criteria decision analysis for benchmarking human-free lifting solutions in the offshore wind energy environment. Energies 2018;11:1175. [15] SAL Heavy Lift GmbH. Veja Mate offshore wind farm. 2019. 04-01, https://sal-he avylift.com/solutions/shipping/reference-projects/veja-mate-offshore-wind- farm. [16] Jiang Z, Acero WG, Gao Z, Li L. A numerical study on a flopper stopper for leg positioning of a jack-up barge. In: ASME 2017 36th international conference on ocean, offshore and arctic engineering. American Society of Mechanical Engineers; 2017. V009T12A028–V009T12A028. [17] Skjetne R, Ren Z. A survey on modeling and control of thruster-assisted position mooring systems. Mar Struct 2020;74:102830. [18] Woodacre J, Bauer R, Irani R. A review of vertical motion heave compensation systems. Ocean Eng 2015;104:140–54. [19] Simens wind power A/S, sea transport design guideline - SWT 6.0-7.0 MW (confidential), technical report. 2016. Technical Report Document ID: D1072599. [20] Haselsteiner AF, Ohlendorf J-H, Oelker S, Str¨oer L, Thoben K-D, Wiedemann K, De Ridder E, Lehmann S. Lifting wind turbine components from a floating vessel: a review on current solutions and open problems. J Offshore Mech Arctic Eng 2019;141. [21] Nordic Heavy Lift ASA. General presentation – first mover in the heavy lift installation market. 2019. 10-05, http://otc.nfmf.no/public/news/7548.pdf. [22] Ahn D, Shin S-c, Kim S-y, Kharoufi H, Kim H-c. Comparative evaluation of different offshore wind turbine installation vessels for Korean west–south wind farm. Int. J. Naval Arch. and Ocean Eng 2017;9:45–54. [23] Fred. Olsen Windcarrier AS. Hohe See and Albatros. 2019. 10-05, https://wind carrier.com/gallery. [24] ISO, 19901-1: 2015. Petroleum and natural gas industries-specific requirements for offshore structures-Part 1: metocean design and operating conditions. 2015. [25] DNV GL. DNVGL-ST-N001 Planning and executation of marine operations. 2016. [26] DNV GL. DNV-OS-H101 Marine operations. General; 2014. [27] DNV GL. DNV-OS-H202 Sea transport operations. 2015. [28] ISO. Ships and marine technology—Offshore wind energy—Port and marine operations. ISO 29400; 2015. [29] DNV GL. Recommended practice DNV-RP-H103, Modelling and analysis of marine operations. 2014. [30] DNV GL. Offshore Standard DNVGL-ST-3078, Standard for offshore and platform lifting appliances. 2016. [31] DNV GL. DNVGL-ST-0054 Transportation and installation of wind power plants.
[32] DNV GL. DNVGL-ST-0437 Loads and site conditions for wind turbines. 2016. [33] IEC. Wind turbine generator systems part 3: design requirements for offshore wind turbines, IEC61400-3. 2009. [34] DNV GL. DNVGL-ST-0119 Floating wind turbine structures. 2018. [35] Acero WG, Li L, Gao Z, Moan T. Methodology for assessment of the operational limits and operability of marine operations. Ocean Eng 2016;125:308–27. [36] Judge F, McAuliffe FD, Sperstad IB, Chester R, Flannery B, Lynch K, Murphy J. A lifecycle financial analysis model for offshore wind farms. Renew Sustain Energy Rev 2019;103:370–83. [37] McAuliffe FD, Desmond C, Chester R, Flannery B, Judge F, Lynch K, Murphy J. A tool to simulate decommissioning offshore wind farms. In: Journal of physics: conference series, vol. 1356. IOP Publishing; 2019, 012021. [38] Hansen MO. Aerodynamics of wind turbines: rotors, loads and structure, vol. 17. Earthscan; 2000. [39] Newman JN. Marine hydrodynamics. The MIT press; 1977. [40] Craig Jr RR, Kurdila AJ. Fundamentals of structural dynamics. John Wiley & Sons; 2006. [41] Kuo BC. Automatic control systems. Prentice Hall PTR; 1987. [42] Hibbitt H, Karlsson B, Sorensen P. ABAQUS theory manual, version 6.3, Technical Report. Pawtucket: Rhode Island, USA; 2006. [43] Kohnke P. ANSYS theory manual, Technical Report. ANSYS Inc; 2001. [44] DNV GL. Wind turbine design software — Bladed. 2019. 11-3, https://www.dn vgl.com/services/wind-turbine-design-software-bladed-3775. [45] Larsen TJ, Hansen AM. How 2 HAWC2, the user’s manual, Technical Report. Denmark: Risø National Laboratory; 2007. [46] Sørensen NN. General purpose flow solver applied to flow over hills, Technical Report. Risø National Laboratory Roskilde; 1995. [47] Ren Z, Jiang Z, Skjetne R, Gao Z. Development and application of a simulator for offshore wind turbine blades installation. Ocean Eng 2018;166:380–95.
[48] Fylling I, Larsen C, Sødahl N, Ormberg H, Engseth A, Passano E, Holthe K. Riflex theory manual, technical report. SINTEF report no. STF70 F; 1995. [49] MARINTEK. SIMO Theory Manual 2016. Version 4.8.4. [50] Zhao Y, Cheng Z, Sandvik PC, Gao Z, Moan T. An integrated dynamic analysis method for simulating installation of single blades for wind turbines. Ocean Eng 2018;152:72–88. [51] Ringsberg JW, Daun V, Olsson F. Analysis of impact loads on a self-elevating unit during jacking operation. J Offshore Mech Arctic Eng 2017;139. [52] Xu R. Stress analysis of a monopile foundation under the hammering loads, Master’s thesis. Trondheim, Norway: Department of Marine Technology, Norwegian University of Science and Technology; 2017. [53] Verma AS, Jiang Z, Vedvik NP, Gao Z, Ren Z. Impact assessment of a wind turbine blade root during an offshore mating process. Eng Struct 2019;180:205–22. [54] Verma AS, Vedvik NP, Haselbach PU, Gao Z, Jiang Z. Comparison of numerical modelling techniques for impact investigation on a wind turbine blade. Compos Struct 2019;209:856–78. [55] Acero WG, Gao Z, Moan T. Methodology for assessment of the allowable sea states during installation of an offshore wind turbine transition piece structure onto a monopile foundation. J Offshore Mech Arctic Eng 2017;139:061901. [56] Acero WG, Gao Z, Moan T. Numerical study of a novel procedure for installing the tower and rotor nacelle assembly of offshore wind turbines based on the inverted pendulum principle. J Mar Sci Appl 2017;16:243–60. [57] Wang Y, He W, Tian D. Calculation of hoisting forces of the wind turbine rotor based on wind conditions. Renew Energy 2012;39:323–8. [58] Skrzypi´nski W, Gaunaa M, Heinz J. Modelling of vortex-induced loading on a single-blade installation setup. In: Journal of physics: conference series, vol. 753. IOP Publishing; 2016, 082037. [59] Gaunaa M, Heinz J, Skrzypi´nski W. Toward an engineering model for the aerodynamic forces acting on wind turbine blades in quasisteady standstill and blade installation situations. In: Journal of physics: conference series, vol. 753. IOP Publishing; 2016, 022007. [60] Kuijken L. Single blade installation for large wind turbines in extreme wind conditions: a quasi-steady aeroelastic study in high wind speeds under different inflow angles, Master’s thesis. Delft University of Technology & Technical University of Denmark; 2015. [61] Jiang Z. The impact of a passive tuned mass damper on offshore single-blade installation. J Wind Eng Ind Aerod 2018;176:65–77. [62] Ren Z, Jiang Z, Gao Z, Skjetne R. Active tugger line force control for single blade installation. Wind Energy 2018;21:1344–58. [63] Ren Z, Skjetne R, Jiang Z, Gao Z, Verma AS. Integrated gnss/imu hub motion estimator for offshore wind turbine blade installation. Mech Syst Signal Process 2019;123:222–43. [64] Sarkar A, Gudmestad OT. Study on a new method for installing a monopile and a fully integrated offshore wind turbine structure. Mar Struct 2013;33:160–87. [65] Li L, Gao Z, Moan T. Response analysis of a nonstationary lowering operation for an offshore wind turbine monopile substructure. J Offshore Mech Arctic Eng 2015;137:051902. [66] Jiang Z, Li L, Gao Z, Halse KH, Sandvik PC. Dynamic response analysis of a catamaran installation vessel during the positioning of a wind turbine assembly onto a spar foundation. Mar Struct 2018;61:1–24. [67] Zienkiewicz OC, Taylor RL, Zhu JZ. The finite element method: its basis and fundamentals. Elsevier; 2005. [68] Ramboll. Monopile installation at Lucherduinen with Aeolus installation vessel.
- 11-20, https://ramboll.com/media/rgr/luchterduinen-and-gemini -two-success-stories-in-offshore-wind. [69] Kikuchi R. Risk formulation for the sonic effects of offshore wind farms on fish in the eu region. Mar Pollut Bull 2010;60:172–7. [70] Dai K, Bergot A, Liang C, Xiang W-N, Huang Z. Environmental issues associated with wind energy–a review. Renew Energy 2015;75:911–21. [71] Koschinski S, Lüdemann K. Development of noise mitigation measures in offshore wind farm construction, Technical Report. Germany: Federal Agency for Nature Conservation, Nehmten and Hamburg; 2013. [72] Li L, Gao Z, Moan T. Operability analysis of monopile lowering operation using different numerical approaches. Int J Offshore Polar Eng 2016;26:88–99. [73] Tygesen UT, Jepsen MS, Vestermark J, Dollerup N, Pedersen A. The true digital twin concept for fatigue re-assessment of marine structures. In: International conference on offshore mechanics and arctic engineering, vol. 51203. American Society of Mechanical Engineers; 2018, V001T01A021. [74] Nehls G, Rose A, Diederichs A, Bellmann M, Pehlke H. Noise mitigation during pile driving efficiently reduces disturbance of marine mammals. In: The effects of noise on aquatic life II. Springer; 2016. p. 755–62. [75] Thompson PM, Lusseau D, Barton T, Simmons D, Rusin J, Bailey H. Assessing the responses of coastal cetaceans to the construction of offshore wind turbines. Mar Pollut Bull 2010;60:1200–8. [76] Zhang LM, Wang H. Field study of construction effects in jacked and driven steel H-piles. Geotechnique 2009;59:63–9. [77] Ruijgrok R. Design optimization of an adjustable Pre-Piling-Template: for wind- turbine installation, Master’s thesis. The Netherlands: Department of Mechanical, Maritime and Materials Engineering, TU Delft; 2019.
[78] Sandvik PC, Solaas F, Firoozkoohi R. Hydrodynamic forces on complex subsea structures. In: Marine operations special symposium (MOSS 2016), Singapore;
[79] DONG ENERGY. First suction bucket jacket is complete. 2018. 11-20, htt ps://www.offshorewindindustry.com/gallery/first-suction-bucket-jacket. [80] Esteban MD, Lopez-Guti´ ´errez J-S, Negro V. Gravity-based foundations in the offshore wind sector. J Mar Sci Eng 2019;7:64. [81] Esteban M, Cou˜nago B, L´opez-Guti´errez J, Negro V, Vellisco F. Gravity based support structures for offshore wind turbine generators: review of the installation process. Ocean Eng 2015;110:281–91. [82] Ruiz de Temi˜no Alonso I. Gravity base foundations for offshore wind farms: marine operations and installation processes, Technical Report, Master in European Construction Engineering. Spain: University of Cantabria; 2013. [83] Dean E. Offshore geotechnical engineering, principles and practice. first ed. ThomasTelford; 2009. [84] Kwag D, Choi Y-S, Oh M, Kwon O, Bang S. Design and installation of small-scale monopod suction pile and tripod suction buckets for offshore wind farms. In: The twenty-second international offshore and polar engineering conference. International Society of Offshore and Polar Engineers; 2012. [85] Ding H, Lian J, Li A, Zhang P. One-step-installation of offshore wind turbine on large-scale bucket-top-bearing bucket foundation. Trans Tianjin Univ 2013;19: 188 – 94. [86] Zhang P, Han Y, Ding H, Zhang S. Field experiments on wet tows of an integrated transportation and installation vessel with two bucket foundations for offshore wind turbines. Ocean Eng 2015;108:769–77. [87] Crome T. Hywind floating wind turbine project. In: Underwater technology conference. Norway: Bergen; 2010. [88] Windflip AS. Windflip - a specialized barge for transportation of floating wind turbines. 2019. 02-01, https://www.youtube.com/watch?v=G0I3HCmANVc. [89] Atkins. Hywind floating wind installation challenge. 2019. 02-01, https://www. atkinsglobal.com/en-GB/projects/hywind-installation-challenge. [90] MODEC, D-Spar & Fork-on. Float-off installation methods. 2019. 02-01, https:// www.modec.com/fps/offshorewind/d-spar/index.html. [91] Ulstein Group ASA. Windlifter. 2019. 02-01, https://ulstein.com/equipment/ulst ein-windlifter. [92] Huisman BV. Wind turbine shuttle. 2019. 02-01, https://www.huismanequipmen t.com/en/products/renewables/offshore_wind/wind_turbine_shuttle. [93] Jiang Z, Yttervik R, Gao Z, Sandvik PC. Design, modelling, and analysis of a large floating dock for spar floating wind turbine installation. Mar Struct 2020;72:
[94] Statoil AS. Hywind installation. 2016. 02-01, https://www.statoil.com/en/h ow-and-why/innovate/the-hywind-challenge.html. [95] Lande-Sudall D, Høyven T, Herfjord K, Thuestad T. Wave-induced collision loads and moments between a spar-buoy floating wind turbine and an installation vessel. In: Journal of physics: conference series, vol. 1669. IOP Publishing; 2020,
[96] Rangel Valdes JL. Dynamic response analysis of a catamaran wind turbine installation vessel with focus on the transportation stage. Trondheim, Norway: Master’s thesis, Department of Marine Technology, Norwegian University of Science and Technology; 2018. [97] Ren Z, Skjetne R, Verma AS, Jiang Z, Gao Z, Halse KH. Active heave compensation of floating wind turbine installation using a catamaran construction vessel. Mar Struct 2021;75:102868. [98] Faltinsen O, Timokha A. Sloshing. Cambridge University Press; 2009. [99] Liu Y, Li S, Yi Q, Chen D. Developments in semi-submersible floating foundations supporting wind turbines: a comprehensive review. Renew Sustain Energy Rev 2016;60:433–49. [100] Roddier D, Cermelli C, Aubault A, Weinstein A. WindFloat: A floating foundation for offshore wind turbines. J Renew Sustain Energy 2010;2:033104. [101] Alexandre A, Percher Y, Choisnet T, Buils Urbano R, Harries R. Coupled analysis and numerical model verification for the 2MW Floatgen demonstrator project with IDEOL platform. In: ASME 2018 1st international offshore wind technical conference. American Society of Mechanical Engineers Digital Collection; 2018. [102] Karimirad M, Michailides C. V-shaped semisubmersible offshore wind turbine: an alternative concept for offshore wind technology. Renew Energy 2015;83:126–43. [103] Sclavounos P, Lee S, DiPietro J, Potenza G, Caramuscio P, De Michele G. Floating offshore wind turbines: tension leg platform and taught leg buoy concepts supporting 3-5 MW wind turbines. In: European wind energy conference EWEC;
- p. 20–3. [104] Crozier A. Design and dynamic modeling of the support structure for a 10 MW offshore wind turbine, Master’s thesis. Trondheim, Norway: Department of Energy and Process Engineering, Norwegian University of Science and Technology; 2011. [105] Bachynski EE, Moan T. Design considerations for tension leg platform wind turbines. Mar Struct 2012;29:89–114. [106] Kausche M, Adam F, Dahlhaus F, Großmann J. Floating offshore wind-economic and ecological challenges of a tlp solution. Renew Energy 2018;126:270–80. [107] Uzunoglu E, Soares CG. Hydrodynamic design of a free-float capable tension leg platform for a 10 MW wind turbine. Ocean Eng 2020;197:106888. [108] Blue H. Engineering BV, historical development. 2020. 08-01, http://www.bluehe ngineering.com.
