installation method 2.75 mw owec wp1 task 12 … method 2.75 mw owec wp1 task 12 installation of...

Installation method 2.75 MW OWEC WP1 task 12 Installation of structure

Dutch Offshore Wind Energy Converter project

Dowec-049/03-P

Dowec 49 rev. 4

Ballast Nedam 49 rev. A

Name: Signature: Date: Written by: MVE Ballast Nedam X 09-04-2002 version Date No of

pages

0 24-01-2002 First issue (PRELIMINARY) A 09-04-2002 28+1 Final B 15-12-2003 28+1 For publication

Ballast NedamA__________________________Engineering __________________________

DOWEC

Installation method 2.75 MW OWEC WP1 task 12 Installation of structure

Document nr. : 10013000\00C0003.Vos

Revision : A

Client : DOWEC

Internal Customer :

Ballast Nedam Engineering B.V. Ringwade 1 Postbus 1238 3430 BE Nieuwegein, The Netherlands tel.: +31 (30) 285 39 00 fax: +31 (30) 285 48 53 E-mail: [email protected]

A 9th April 2002

0 24th January 2002

Rev. Date Description Handled by Checked Approved

blad 1 van 28

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Table of contents (Rev. A) 1. General .....................................................................................................................................................3

1.1 Problem definition.................................................................................................................................3 1.2 Aim of this report ..................................................................................................................................3 1.3 Conditions and assumptions ................................................................................................................3 1.4 Topographical map...............................................................................................................................4

2. Offshore Wind Energy Converter (OWEC)...............................................................................................5 2.1 Concept choice.....................................................................................................................................6 2.2 Decomposition OWEC .........................................................................................................................6

2.2.1 Monopile...........................................................................................................................................7 2.2.2 Transition piece................................................................................................................................7 2.2.3 Turbine tower ...................................................................................................................................7 2.2.4 Nacelle / Generator..........................................................................................................................7 2.2.5 Rotor ................................................................................................................................................8

3. Preparation phase ....................................................................................................................................9 4. The production process ..........................................................................................................................10

4.1 Fabrication and transport of the elements..........................................................................................10 4.1.1 Monopile and transition piece ........................................................................................................10 4.1.2 Turbine tower, generator, nacelle and rotor blades.......................................................................11

4.2 Land installation .................................................................................................................................11 4.3 Site layout...........................................................................................................................................12 4.4 Equipment ..........................................................................................................................................14 4.5 Installation procedure A......................................................................................................................16

4.5.1 Schematic presentation .................................................................................................................16 4.5.2 Graphic presentation......................................................................................................................17

4.6 Installation procedure B......................................................................................................................21 4.6.1 Schematic presentation .................................................................................................................21 4.6.2 Graphic presentation......................................................................................................................22

4.7 Workability..........................................................................................................................................24 4.7.1 Weather conditions ........................................................................................................................24 4.7.2 Motion analyses Svanen................................................................................................................27

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1. General The Dutch government gave the initiative to carry out research for the installation method of an offshore wind farm with a total capacity of 300 - 500 MW near the Dutch shore. This wind farm is believed to be the first necessary step to take to get experience concerning the development, realization and exploitation of offshore wind energy. With this experience larger and more sophisticated offshore wind farms can be developed and exploited in the near future.

1.1 Problem definition The operational reliability for installing Offshore Wind Energy Converter Systems (OWECS) is highly influenced by the sensitivity of the used installation procedure for the weather conditions.

1.2 Aim of this report The aim of this report is to present an installation method, which makes is possible to install the predefined amount of OWECS in a operational reliable and safe manner within the given time span.

1.3 Conditions and assumptions • Installation of approx. 40 OWECS of 2,75 MW;1 • Total capacity of wind farm is 300 – 500 MW; • Installation in one season (April – September) 6 months; • Site wind farm near shore of Callandsoog (52º 50’ N; 4º 25’ E); • Installation yard in harbour of IJmuiden.

1 In the terms of reference is not clearly stated what the total size of the wind farm of the 2.75 MW OWECS should be. Therefore for WP1is decided to design a wind farm consisting of 40 OWECS of 2.75 MW. For WP2 this report will be rewritten for the design of a wind farm of 300-500 MW built up out of 6 MW OWECS.


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1.4 Topographical map

Figure 1.4-1: Location wind farm (incl. route from installation location onshore).

For the location of an offshore wind farm the Dutch government has given the following two locations:

- Site III center: Near shore of Callandsoog (52º 50’ N; 4º 25’ E); - Site VII center: Approx. 50 km offshore of Scheveningen (52º 15’ N; 3º 30’ E).

For the design of the installation procedure it is assumed that the wind farm will be located at site SIIIC. The onshore installation procedures will take place in the harbour of IJmuiden. In WP2 the installation procedure of 80 OWEC’s of 6 MW at the site SVIIC will be described.


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2. Offshore Wind Energy Converter (OWEC) Because of different types of superstructure, foundation and installation methods a range of configurations for an OWEC are possible. In the table below some possible configuration for an OWEC are presented. With the restrictions caused by the environment, like water depth, the form of the underground and the acting forces, there will be chosen an optimal configuration for this study that will be presented throughout this report. Table 2-1: Possible configurations for an OWEC.2

1 2 3 4 5 6 7 8 9 10 11 12Mono towerBraced / Lattice towerPiled / tripodGravity baseAfloatLiftingFloating

(A) Configuration superstructure(B) Configuration foundation(C) Installation method

(A)

(B)

(C)

OWEC Support Structures

Ad. A: Mono tower:

The simplest shape for the support of the superstructure is a mono tower made of steel or concrete. These types of structures are easy to fabricate and install on site. Braced / lattice tower: This is a more complex shape for the support structure. The stiff behavior makes it hard to tune the structure dynamic characteristics.

Ad. B: Piled:Most offshore foundations consist of hollow tubular steel piles. These are driven into the ground by a piling hammer. If the ground consists of rock or the diameter of the pile is to large, then it is possible to drill the piles. For this method it is not necessary to prepare the seafloor. Tripod: A tripod can be made of tubular steel pipes and will then be combined with a turbine tower of a monopile. For a braced/lattice structure, the turbine tower and the foundation will be built as one structure. Gravity base: A concrete caisson is the most well known shape for a gravity base foundation. A dry dock is used to build the caissons. After finishing they will be transported floating. At the building site they will be ballasted and lowered to the previously prepared seabed.

2 OPTI-OWECS; Final report volume 4; A typical design solution for an offshore Wind Energy Conversion System


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2.1 Concept choice 2.1 Concept choice The shape of an OWEC is determined by the dynamic behavior that is preferred and the simplicity of the installation procedure. The shape of an OWEC is determined by the dynamic behavior that is preferred and the simplicity of the installation procedure. In this study concept 1 from Table 2-1 will be used to illustrate how an offshore wind farm can be realized. This concept will be the reference design for future alternatives. In this study concept 1 from Table 2-1 will be used to illustrate how an offshore wind farm can be realized. This concept will be the reference design for future alternatives. The foundation is formed by a hollow tubular steel pipe (monopile), which is driven into the seabed. The turbine tower also consists of a tubular steel monopile. The foundation is formed by a hollow tubular steel pipe (monopile), which is driven into the seabed. The turbine tower also consists of a tubular steel monopile. For the installation methods see chapter 4. For the installation methods see chapter 4.

2.2 Decomposition OWEC 2.2 Decomposition OWEC If we consider different functions, the system “OWEC” can be divided into components. In the construction industry it is common to use terms as foundation and superstructure. The function of the foundation is to support the superstructure. The superstructure has an operational function. Further decomposition of the components results in the elements. The monopile supports the superstructure and discharges the acting forces on the superstructure to the ground. The transition piece connects the superstructure to the monopile. The turbine tower creates the needed height to let the rotor blades spin freely. The diameter of the rotor blades forms the wind catching area. The larger this area the more energy can be obtained from the wind. The generator transforms wind energy into electrical energy.

If we consider different functions, the system “OWEC” can be divided into components. In the construction industry it is common to use terms as foundation and superstructure. The function of the foundation is to support the superstructure. The superstructure has an operational function. Further decomposition of the components results in the elements. The monopile supports the superstructure and discharges the acting forces on the superstructure to the ground. The transition piece connects the superstructure to the monopile. The turbine tower creates the needed height to let the rotor blades spin freely. The diameter of the rotor blades forms the wind catching area. The larger this area the more energy can be obtained from the wind. The generator transforms wind energy into electrical energy. Table 2-2: Decomposition OWEC in different levels. Table 2-2: Decomposition OWEC in different levels.

System System Component Component Element Element

Foundation Monopile Transition piece

OWEC

Superstructure Turbine tower Generator / nacelle Rotor

Component ElementSystem

Figure 2.2-1: Graphic presentation decomposition OWEC.


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2.2.1 Monopile Calculations have been made with the available wave-, wind- and soil data. Following these calculations it is concluded that the foundation can be made of a monopile with a diameter of 4300 mm and a length of about 57 to 60 meters. In Table 2-3 the data for the maximum needed monopile are presented. The critical situation occurs with a scour hole of –27 m. Table 2-3: Data monopile.

Diameter Steel quality

Wall thickness Mass

Seafloor level (Variable)

Scour hole Pile foot level

4300 mm S355

45-56 mm 270-360 tons

-22 to –27 m to –27 m -47 to -50 m

With MSL is 0.00. Top of monopile at +10 m.

2.2.2 Transition piece At the top of the monopile a transition piece is mounted. The function of such a transition piece is to correct out of alignment of the monopile. The transition piece has to be placed over the monopile in such a way that the connecting flange is exactly horizontal. On top of this flange the superstructure is mounted. The transition piece also provides access to the turbine tower. Therefore it is equipped with mooring support and a platform. The platform is situated at a height, which provides safe working conditions for all occurring wave heights. The maximum extreme wave height is assumed to be 11.4 m high with a probability of occurrence of 1*10 –2

year. The platform is situated above this extreme wave height. In this stage the platform is designed at a height of 15 m above MSL. The length of the transition piece will be approx. 10 m. From about +5 m to +15 m above MSL. Its mass will be approx. 60 tons.

Figure 2.2-2: Transition piece.

2.2.3 Turbine tower Hub height: 70 m + MSL. Total length: 70-15 m = 55 m. The mass of the tower will be approx. 140 tons. Its diameter varies from about 4.7 at the foot to about 2.5 m at the top.

2.2.4 Nacelle / Generator The nacelle consists of the following parts:

- Main shaft; - Main gear; - Mechanical brake; - Hydraulic system; - Generator.

The total mass of the above-mentioned parts is 74 tons.


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2.2.5 Rotor The rotor consists of the rotor blades and the hub. Diameter rotor blades 92 m; Total mass rotor 75 tons (hub incl. rotor blades);


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3. Preparation phase In the preparation phase of the project the following tasks will be carried out:

• Setting up engineering plan; • Setting up engineering time schedule; • Soil measurements location wind farm; • Soil measurements installation yard IJmuiden; • Development installation yard IJmuiden; • Wind measurements; • Engineering preliminary design; • Engineering final design; • Engineering adjustments Svanen; • Contract forming with suppliers.

As soon as the soil data are known the final engineering can be started. Finishing the final design is important for ordering and fabricating the monopiles and the turbine towers. The final layout of the installation yard in IJmuiden is also determined in the preparation phase.


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4. The production process

4.1 Fabrication and transport of the elements

4.1.1 Monopile and transition piece The fabrication process of the monopiles is carried out according to the below mentioned process. The steel plant supplies flat steel plates that will be transported by road or rail to the steel-rolling factory. Here the plates will get cold rolled till they have the exactly desired diameter. These curled steel plates are welded together to ring sections and later on to a monopile. To insure the quality of the welds, a certified welding company in a special equipped hangar will carry out welding. The welds are finished and thoroughly tested. The production process can varies according to the location where the curled steel plates are welded together to rings and finally to a monopile. The way of transportation is dependent of the geometry of the pieces to be transported. The different processes are shown in Figure 4.1-1.

IJmuiden

Curledsteel plate

RoadRail

Steel plant Welding factoryRolling factory

Flatsteel plate MonopileRoad

Rail Inland navigation

Flatsteel plate

Curledsteel plate MonopileRing

sectionsRoadRail Inland navigationRoad

Rail

Flatsteel plate

Curledsteel plate MonopileRoad

Rail

RoadRail

Inland navigation

I

II

III

Figure 4.1-1: Different processes for fabrication of the monopiles.

Ad. I: This production process is highly preferred. The monopile is completely produced in a factory

and transported to IJmuiden. Because of the length and mass of the monopiles, transportation will take place by inland navigation. It is assumed that a part of the monopiles is fabricated before the actual installation takes place. The time needed for fabrication of all of the monopiles is about two months longer than the time needed to install the OWEC’s offshore. Therefore a storage facility is needed at the installation site in IJmuiden. To store all the monopiles an area of approx. 12000 m2 is required. At this stage a storage capacity of 30% is taken into account. Regarding pontoons of 11 by 54 meters, one monopile can be transported on each pontoon. The capacity of the pontoon is about 900 tons. Transport, including transshipment, will take maximum 3 days, depending on the location of the welding factory. A pontoon is also used to transport the transition pieces. Transportation by means of inland navigation is limited to a maximum length and height in order to safely pass bridges and locks. Most main inland waterways can handle pushed convoys of class Va with a maximum length of 120 meters. The workability of this production process is dependent on the location and transshipment capacity of the welding factory.

Ad.II: If the geometry of the monopile exceeds the limitations of inland navigation, parts of the monopile can be fabricated and transported to IJmuiden. These parts will then be welded together to a monopile in a temporary welding hangar on the installation site in IJmuiden.


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Ad. III: For this method all the welding will take place in a temporary welding hangar on the installation site in IJmuiden. The extra costs for building such a factory on site need to be on proportion to the normal transport costs.

As mentioned before, the transition pieces will be equipped with a connecting flange, which is exactly the same as the flange on the bottom plate of the turbine tower. The production of the transition piece, the connecting flange as well as the bottom plate, will be carried out by one and the same factory. This is done to be sure that the patterns of the boltholes are exactly the same.

4.1.2 Turbine tower, generator, nacelle and rotor blades All the other parts of the OWEC, like nacelle, rotor blades and generator, will be shipped by road or inland navigation. These parts will be transshipped by a mobile crane and placed in the lane of the gantry crane for temporary storage on the installation site. The production process of these parts will not be discussed in this report. Installation location IJmuiden

4.2 Land installation For the same kind of projects in other countries, the superstructure was built up at sea. Most of the times this meant that delays occurred and the base planning could not be met. Generally speaking installation activities at sea take twice as much time as the same operations onshore would take. Therefore an installation procedure is developed in which most of the installation activities take place on land. This has resulted in an installation method that builds up the whole superstructure on land. The superstructure will be lifted up and transported in total to its offshore location. This also provides a safer way of working for the installers. In the near past Ballast Nedam has successfully used similar work methods for the building of bridge. For the land installation a concrete foundation is required to install the superstructure. Design of this foundation is part of the preliminary design. It needs to be investigated if the existing quay is capable of transferring the forces acting during the installation process. If the quay is not capable of doing so, a pile foundation needs to be made. For an indication of such a foundation calculations show that probably 16 piles of 45 cm square will do. On this foundation a bottom flange with cast in anchors is mounted for fixation of the turbine tower.


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All the elements of the superstructure will be installed on the installation location. For lifting these elements a crawler crane will be needed (see Figure 4.2-1). This crawler crane should be capable of lifting 75 tons at a height of approx. 60 meters (the nacelle). A gantry crane will transport the elements from the storage to the installation location. The installation of the superstructures will take place at two out of three installation locations. Every superstructure takes 4 days to be built, so every 2 days a superstructure is ready for transport and installation offshore. The installation of all of the elements will be according to the manual provided by the supplier of that specific element. The third foundation is made in order to be able to continue building under weather conditions, which exceed the workability of the Svanen (see chapter 4.7). The superstructure built on the third installation location is also a backup in case the installation offshore is quicker than expected. After finishing the superstructure a test program will be run. After finishing this program the superstructure is ready to be shipped offshore. Figure 4.2-1: Rotor installation with

crawler crane.

4.3 Site layout Following the preparation phase the installation location in IJmuiden can be prepared. Site-offices are placed and the three foundations for the installation flanges can be built. The gantry crane will be installed. Construction roads, mechanical and electrical installation will be installed. Because there will be transshipment activities on a daily bases, a permanent availability of a mobile crane is desirable. The global area requirements for the different functions on the installation site are stated in the table below. Table 4-1: Global area requirements on installation yard.

Total Site offices and visitor center 4500 m2

Parking area 800 m2

Storage approx. 30% of elements 6000 m2

Installation locations 7200 m2

Storage at installation location 4800 m2

Transshipment water-quay 2400 m2

Hangars 7200 m2

Construction roads 6000 m2

Storage cables 1000 m2

39900 m2


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Figure 4.3-1: Global layout installation yard IJmuiden. Figure 4.3-1: Global layout installation yard IJmuiden.

3 Installation locations

Svanen

Storage

Site office


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4.4 Equipment The main equipment used for the different installation procedures is described below.

Crawler crane The crawler crane will be used for different tasks, meaning:

1. Transshipment of monopiles; 2. Land installation of superstructure.

Ad. 1: Needed reach approx. 15m with a load of 350 tons. Ad. 2: Maximum load of 75 tons at a height of approx. 60 meters. In order to be flexible in the installation process a mobile crane is required. Regarding the above-mentioned loads and reaches, only heavy crawler cranes will be able to do the job. An example for such a crawler crane is shown in Figure 4.4-1.

Figure 4.4-1: Crawler crane Liebherr LR1600.

General equipment Hydraulic hammer IHC S-500 (depends on soil data) Compressor / airlift installation Gantry crane Tilting pontoon (see installation procedure B)


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Svanen

Figure 4.4-2: Svanen during operation on Øresund bridge.

Technical data Main particulars Length o.a.: 102.75 m Length b.p.p.: 89.50 m Breadth moulded: 71.80 m Breadth floaters: 24.40 m Depth: 6.00 m Draught moulded: 4.50 m Lifting cap. (incl. rigging) : 8,200 T Lifting cap. (excl. rigging): 8,700 T Hoisting height (above deck) : 76 m Hoisting speed at max. load : 0.35 m/min Power plant Main power generating plant: 3 x 1,325 kW 3 x 660 V Auxiliary power generating plant: 2 x 1,000 kVA 380 V Emergency power generating plant: 200 kW 3 x 380 V Electric main power system: 660/380 V - 50 Hz Propulsion and Maneuvering Azimuthing thrusters aft: 2 x 1,250 kW Tunnel thrusters for: 2 x 630 kW Azimuthing thrusters fore: 2 x 1,850 kW (nom.) (diesel driven): 2 x 2,400 kW (interm.) Sailing speed Without wind: 7.0 knots

Alteration of the Svanen: - For this job the Svanen will be equipped with a new boom at the side (400 tons). - The Svanen will also be equipped with surge-compensators.

Buzzard

Figure 4.4-3: Buzzard.

Technical data Main particulars Length: 43.00 m Breadth: 30.00 m Depth: 4.20 m Draught max.: 2.97 m Displacement: 3,800 tons Deck load: 10 tonnes/m2 Pay load: 2,000 tons Power plant Main diesel generators: 3 x 250 kVA Harbour diesel generator: 1 x 110 kVA Jacking system Type: MSC Electr./ Hydr. Number: 4 Length: 55 m Cross section: 2.20 x 2.30 m Footing: Pointed for rock, spudcans available Jacking speed: 12 m/hr max Capacity leg: 1,300 tons preload Accommodation 2 Single bedrooms 1 Galley 1 Mess room (30 pers.) 2 Stores Offices/radioroom/deckhouse/sanitary


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4.5 Installation procedure A

4.5.1 Schematic presentation

System

Factory

IJmuiden

Storage

Installationlocation

Superstructure

Road, water, rail

Transhipment crawler cranegantry crane

Transhipment gantry crane andcrawler crane to Svanen

Inst

alla

tion

with

craw

ler c

rane

Wind farm

Transhipment to Svanen

Rotor, nacelle,generator, turbine

tower

Monopile,transitionpiece

Factory

IJmuiden

Storage

Road, water, rail

Transhipment crawler cranegantry crane

Transhipment gantry crane andcrawler crane to Svanen

Inst

alla

tion

with

Svan

en

OWECWind farm

Element Component

Inst

alla

tion

with

Svan

en

Installation procedure A:All offshore activities executed bythe Svanen .

Foundation

Figure 4.5-1: Schematic presentation installation procedure A.


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4.5.2 Graphic presentation The activities of the Svanen will be carried out in the following order.

Start of work The Svanen will load the monopile, transition piece and piling hammer on board in the harbour of IJmuiden.( See Figure 4.5-1/ Figure 4.5-13). The Svanen is self-propelled. It will sail to its destination and install the first monopile foundation. After the pile has been hammered into the seabed a transition piece will be placed on top of it. The first foundation is then completed and the Svanen can sail back to the harbour of IJmuiden.

Figure 4.5-2: Transshipment monopile and transition piece to Svanen.

Figure 4.5-3: Lifting and placing the monopile.

Figure 4.5-4: Pile driving by Svanen. Figure 4.5-5: Foundation complete for installation superstructure. Return IJmuiden.

Repetitive steps of the installation procedure The Svanen will load the next monopile and transition piece aboard in the harbour of IJmuiden. With the new boom the Svanen will hoist up a complete superstructure from its erection position on the quay. The total weight of the superstructure is almost 300 ton, which is less than the weight of the monopile.


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Figure 4.5-6: Transshipment monopile and transition piece to Svanen.

Figure 4.5-7: Transshipment superstructure to Svanen.

During the sailing of the Svanen to the installation position off shore the complete wind turbine will remain suspended from the additional boom. The turbine will be lashed and secured for the trip. The total weight on the Svanen during the trip is approximately 800 ton while the capacity of the Svanen is more than 8000 ton. However, the load is eccentric which will lead to a maximum rotation of the Svanen of 1 degree. During the trip of the self propelled Svanen an anchor vessel will position the anchors for the Svanen in a predefined anchor pattern. As soon as the Svanen is in position the anchor cables will be connected to the anchors and the Svanen can manoeuvre itself in the proper position for placing the wind turbine. During the whole operation from loading the elements from the shore till placing offshore there will be close coordination with a meteorological institute. After the positioning has been completed the Svanen will lower the wind turbine on to the previously placed transition piece. An essential aspect of the placing operation is the proper orientation of the door in the mast. For this the mast has to be rotated relative to the nacelle and rotor. The reason for this is the fact that the influence of waves on the motion of the Svanen can be minimised by positioning the Svanen in a certain angle relative to the wave direction (see 4.7 Workability). The hoisting system of the Svanen will be fitted with a surge compensation system or constant tensioning system. Both systems facilitate the controlled installation of the wind turbine on the transition piece.

Figure 4.5-8: Transport to waiting foundation. Figure 4.5-9: Installation superstructure on foundation.


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Figure 4.5-10: Completed OWEC.

After placing the wind turbine on the flange of the transition piece, bolts will be placed in the flange holes. A final inspection will be carried out and the Svanen can move to its next position in order to place a new monopile. For this the GPS positioning system of the Svanen will be used.

Figure 4.5-11: Lifting and placing the monopile. Figure 4.5-12: Pile driving by Svanen.

The monopile that lies on the deck of the Svanen is positioned in a sliding tilting frame on one end. The other end is hoisted up and the tilting frame will slide to the center of hoisting while the pile is tilted into a vertical position. When the pile is vertical it will be lifted of the tilting frame and placed along side the Svanen in a template. Subsequently the pile will be lowered until it reaches the sea floor. As a result of sinking into the sea bottom the lower end of the pile is fixated into its position while the template is holding the top of the pile. After checking the verticality and position of the pile the piling hammer can be lifted of the deck and placed on the pile and hammering can commence. In the first phase of the hammering the capacity of the hammer will not be used. During this phase small adjustments to the pile can be made. Once the pile is being hammered into the seabed to such depth that its position is stable the hammering can continue using maximum power. When the pile reaches its required depth the hammer will be taken of and an as-built position will be established. Following this the transition piece can be placed over the monopile. The transition piece must be positioned within the required tolerances of verticality. In order to do so, three adjustable brackets are welded inside of the transition piece. A rubber seal will seal off the opening between the monopile and the bottom of the transition piece. After checking the seal the opening will be filled with grout.


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By means of welded guides on the monopile the remaining J-tube can be lowered down the side of the monopile and transition piece. The J-tubes are going to be used for feeding the cables from the seabed into the turbine tower. When al the above activities are finished, the transition piece is ready to receive a wind turbine.

Figure 4.5-13: Foundation complete for installation superstructure. Return IJmuiden.

For the total cycle of above-mentioned activities a cycle time of 69 hours is determined. This is based on a workability of 60 % of the time in the period from April 1st till September 30th.


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4.6 Installation procedure B

4.6.1 Schematic presentation

Systeem

Factory

IJmuiden

Storage

Installationlocation

Superstructure

Road, water, rail

Transhipment crawler craneand gantry crane

Transhipment gantry craneand crawler crane

Inst

alla

tion

with

craw

ler c

rane

Wind farm

Transhipment to Svanenwith own boom

Rotor, nacelle,generator, turbine

tower

Monopile,transitionpiece

Factory

IJmuiden

Storage

Road, water, rail

Transhipment crawler craneand gantry crane

Transhipment gantry crane andcrawler crane to tilting pontoon

OWECWind farm

Element

Inst

alla

tion

with

Sva

nen

Installation procedure B:Offshore activities executed bySvanen, Buzzard and tilting pontoon.

SystemElement Component

FoundationIn

stal

latio

n w

ith B

uzza

rdan

d til

ting

pont

oon

Figure 4.6-1: Schematic presentation installation procedure B.


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4.6.2 Graphic presentation The installation method in which the Svanen is used to install the monopile and the wind turbine can be complemented by using a self elevating Platform (SEP) like the Buzzard together with a tilting pontoon. Using this auxiliary equipment diminishes the dependency of fair weather windows because work can be carried out at more than one location at the same time resulting in a higher production output in a given period of time. Below installation procedure B will be described.

Tilting pontoon

Figure 4.6-2: Transshipment monopile and transition piece to tilting pontoon.

Figure 4.6-3: Towing of the tilting pontoon.

In the harbour the monopile and transition piece will be lifted onto the tilting pontoon. A tugboat will tug the tilting pontoon to the installation position offshore. At the piling location a SEP is positioned with the help of a tugboat. The SEP is equipped with a 200-ton crane on deck. The lifting capacity is enough for lifting the transition piece but it is not enough to lift the monopile. To overcome this problem the monopile is capped on one end. With winches the monopile is being tilted into a vertical position whilst in the tilting pontoon. The trapped air in the monopile delivers extra buoyancy that can be controlled by opening or closing a valve in the lit. Hydraulic jacks are being used to lift the tilting point of the monopile thus ensuring that the bottom of the pile will not touch the seabed during the tilting operation.


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Figure 4.6-4: Tilting and positioning of monopile. Figure 4.6-5: Fixation of monopile to Buzzard.

After the monopile has reached the vertical position the tilting pontoon is positioned between the legs of the SEP in order to place the top of the pile in the template along the side of the SEP. When this is done the jacks will be let off and the monopile will sink into the seabed. The bottom of the pile is then fixed while the template is holding the top of the pile. After a final check of the pile position and its verticality the sealing cap can be removed and the crane of the SEP can place the hammer on top of the monopile and the hammering can commence.

Figure 4.6-6: Pile driving with crawler crane on Buzzard.

Figure 4.6-7: Foundation complete for installation superstructure.

Svanen For this installation procedure the activities of the Svanen are restricted to placing the superstructure only.


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Figure 4.6-8: Transshipment superstructure to Svanen.

Figure 4.6-9: Transport superstructure to foundation.

Figure 4.6-10: Installation superstructure on foundation.

Figure 4.6-11: Completed OWEC.

4.7 Workability

4.7.1 Weather conditions The workability for the NL 3 and NL 7 sites is based on the DOWEC-F1W1-WB-01-047/00C report from November 2001 WP1 Task 5 (Wind and Wave conditions). From this report the following graphs are used to determine the workability for the Svanen; Figure 5.6 Monthly variation of the mean wind speed, Figure 6.1 Average weather windows for the NL 3 site for periods up to 24 hrs, Figure 6.2 Weather windows for the NL 3 site over a period of 9 years, Figure 6.3 Distribution of wave heights per month. The conclusion is that although there is a fair variation in the weather over the years a workability of 60 % in the period starting at the beginning of April till the end op September is feasible. (see figure 5.6, 6.1 and 6.3)


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Based on the same report the assumption can be made that the fair weather windows last for an uninterruptible period of 15 hours. Since this is less then the cycle time of one installation additional calculations have been made.

Based on the same report the assumption can be made that the fair weather windows last for an uninterruptible period of 15 hours. Since this is less then the cycle time of one installation additional calculations have been made. These calculations showed that uninterruptible periods up to 60 hours, with wave heights till 1,5 meter occurred during 60 % of the time. These calculations showed that uninterruptible periods up to 60 hours, with wave heights till 1,5 meter occurred during 60 % of the time. Based on these data the cycle times for the installation activities were based on unworkable weather during 40 % of the available time. Based on these data the cycle times for the installation activities were based on unworkable weather during 40 % of the available time. From figure 6.2 the conclusion can be drawn that when worst comes to worst the minimal workability can drop to 50 % of the time. From figure 6.2 the conclusion can be drawn that when worst comes to worst the minimal workability can drop to 50 % of the time.

Figure 4.7-1: The monthly variation of the mean wind speed for the NL3 site.

Wind climate: from the middle of January till the end of October mean wind speeds are less than 9,0 m/s.


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0 2 4 6 8 10 1240

45

50

55

60

65

70

75

80

85weather window NL3 (6, 12 and 24 hours) - averaged over 9 years

month

% o

f tim

e

Figure 4.7-2: Percentage of time the significant wave height Hs is below 1.25 m values during uninterrupted time intervals of at least 6 hours (top line), 12 hours (middle) and 24 hours (bottom) for the NL3 site.

0 2 4 6 8 10 1210

20

30

40

50

60

70

80

90

100weather window NL3 (6 hours) - all 9 years

month

% o

f tim

e

Figure 4.7-3: Percentage of time the significant wave height Hs is below 1.25 m values during uninterrupted time intervals of 6 hours for the NL3 site; for each of the 9 years separately.


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0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

Occ

urre

nce

(%)

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR

Wave climate NL3

< 0.50< 0.75< 1.00< 1.25< 1.50< 2.00< 2.50<10.00

< 0.50 7.6% 12.1% 9.2% 12.2% 19.5% 22.4% 20.3% 21.6% 11.7% 14.7% 7.1% 10.1% 14.1%< 0.75 21.0% 31.7% 27.5% 35.6% 47.6% 51.8% 49.2% 47.1% 33.0% 33.1% 24.1% 24.1% 35.5%< 1.00 36.5% 50.8% 45.0% 57.7% 71.6% 70.0% 70.7% 67.9% 51.6% 48.3% 37.6% 37.9% 53.8%< 1.25 49.3% 63.6% 57.4% 75.1% 84.2% 83.1% 84.3% 79.8% 66.9% 61.0% 50.6% 49.1% 67.0%< 1.50 59.5% 71.9% 67.7% 83.9% 91.5% 92.2% 92.1% 85.6% 78.7% 72.9% 60.4% 59.1% 76.3%< 2.00 75.0% 85.4% 82.8% 93.3% 97.4% 98.8% 97.8% 94.1% 91.3% 87.3% 76.5% 75.0% 87.9%< 2.50 85.4% 92.1% 92.2% 97.6% 99.8% 99.5% 99.6% 97.8% 96.2% 94.4% 88.6% 85.5% 94.1%<10.00 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0%

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC YEAR

Figure 4.7-4: The distribution of the significant wave height of the NL3 site. Figure 4.7-4: The distribution of the significant wave height of the NL3 site.

4.7.2 Motion analyses Svanen 4.7.2 Motion analyses Svanen The installation procedures described above are influenced by the weather conditions. Waves, surge and wind have a great impact on the workability as well as on the efficiency of the work. IHC GUSTO engineering B.V. has carried out motion-analyses for the Svanen.

The installation procedures described above are influenced by the weather conditions. Waves, surge and wind have a great impact on the workability as well as on the efficiency of the work. IHC GUSTO engineering B.V. has carried out motion-analyses for the Svanen. For the workability the below stated criteria are analyzed: For the workability the below stated criteria are analyzed: - Vertical deflection at the top of the boom; - Vertical deflection at the top of the boom; - Horizontal deflection at the top of the boom; - Horizontal deflection at the top of the boom; - Horizontal deflection at the bottom of the wind turbine. - Horizontal deflection at the bottom of the wind turbine.


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Vertical motions at cranetip for Hs = 1.5m

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 30 60 90 120 150 180 210 240 270 300 330 360

Wave direction wrt. stern [deg.]

Max

imum

sin

gle

ampl

itude

[m]

Figure 4.7-5: Vertical motions at crane tip for Hs=1.5 m.

From this report it may be concluded that the workability of the Svanen is guaranteed up to a wave height of 1.25 meter. De Svanen has to be positioned in a way that the incoming wind makes an angle of 150 tot 210 degrees with the stern. The statistics show, see DOWEC work package 1 task 5, that between April and September the workability is 60%. Critical is a significant wave height of 1.25 meter. Surge with a long wavelength is not taken into account. The surge compensation system or constant tensioning system, with which the Svanen will be equipped, is primary designed for compensating the accelerations of short waves. The accelerations of long waves are less than those of short waves. Therefore at this stage it is assumed that the accelerations of long waves can be compensated without any problem It is assumed that the total cycle-time for transportation and installation offshore, for good weather conditions, will take 42 hours. For the time schedule is calculated with 40% longer cycle times. The probability that the wave heights are more than tolerated is statistical 40%. (See also research of Gusto d.d. 31-05-2001).


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