Appendix 3: Sæby Offshore Wind Farm Technical Description, Offshore

Transcription

1 Appendix 3: Sæby Offshore Wind Farm Technical Description, Offshore

2 Appendix 3: Sæby Offshore Wind Farm Technical Description, Offshore Appendix 3: Sæby Offshore Wind Farm Technical Description, Offshore Published by Energinet.dk Published as Internet version only: Report no. 13/ Rapporten kan fås ved henvendelse til: Energinet.dk Tonne Kjærsvej Fredericia Tlf The report may be downloaded the Danish Energy Agency s (Energistyrelsens) website: Dok. 13/ /15

3 Table of contents 1. Location Wind farm layout Foundation and installation Foundation Construction features vs. water depths Installation scenario Pre-investigations Investigations Summary of seabed survey List of enclosures Dok. 13/ /15

4 Appendix 3: Sæby Offshore Wind Farm Technical Description, Offshore 1. Location Sæby Offshore Wind Farm (OWF) is located in Kattegat 4 km off the coast east of Sæby. The area appointed for the wind farm is approximately 53 km 2 (Figure 1) reduced however to approx. 47 km 2 by a cable and navigation corridor across the area in a W-E direction, where turbines cannot be installed. The navigation corridor splits the area for installation of windmills in a northern area of approximately 24 km 2 and a southern area of approximately 23 km 2. The water depth in the area varies between 6 and 19 m. A northern and a southern cable corridor, each 500 m wide, are identified for routing cables to the coast. The wind farm area with cable corridors is shown in Figure 1with bordering coordinates listed in Table 1. Figure 1 Sæby offshore pre-investigation area and cable corridors. Black numbers represents coordinates for OWF area, red numbers represents coordinates for export cable corridors. Dok. 13/ /15

5 Table 1 List of coordinates for pre-investigation area and export cable corridors for Sæby Offshore Wind Farm SITENAME ID AREA EASTING NORTHING UTMSYSTEM Sæby 1 Cable WGS84_UTM32N Sæby 2 Cable WGS84_UTM32N Sæby 3 Cable WGS84_UTM32N Sæby 4 Cable WGS84_UTM32N Sæby 1 Investigation area WGS84_UTM32N Sæby 2 Investigation area WGS84_UTM32N Sæby 3 Investigation area WGS84_UTM32N Sæby 4 Investigation area WGS84_UTM32N Sæby 5 Investigation area WGS84_UTM32N Sæby 6 Investigation area WGS84_UTM32N Sæby 7 Investigation area WGS84_UTM32N Sæby 8 Investigation area WGS84_UTM32N Sæby 9 Investigation area WGS84_UTM32N Sæby 10 Investigation area WGS84_UTM32N Sæby 11 Investigation area WGS84_UTM32N Sæby 12 Investigation area WGS84_UTM32N Sæby 13 Investigation area WGS84_UTM32N 2. Wind farm layout A maximum of 200 MW wind power may be installed at Sæby Offshore Wind Farm. Preliminary layouts for the wind farm have been developed by DTU Wind Energy for the purpose of serving as worst case scenarios for the Environmental Impact Assessment (refer to Enclosure 1). Layouts for 3.0 MW and 10.0 MW WTGs, respectively, are presented in Figure 2. The final layout will eventually be decided by the developer, based on an optimization of a number of parameters, within the frame of the consent to be issued by the authorities. Dok. 13/ /15

6 Figure 2 Sæby Offshore Wind Farm study area and preliminary wind farm layout for 3.0 MW and 10.0 MW WTGs, respectively 3. Foundation and installation 3.1 Foundation Foundation dimensions are given in tables below, based on the general indicative dimensions given in the generic technical project description. Table 2 Estimated monopile foundation dimensions Monopile Turbine capacity, MW Diameter at seabed level, m Pile Length, m Weight, t Penetration depth, m Transition piece Weight, t Dok. 13/ /15

7 Grout volume, m Scour protection Volume, m 3 2,200 2,200 2,600 3,100 3,600 Footprint, m 2 1,600 1,600 1,700 1,750 2,100 Table 3 Estimated GBS foundation dimensions Gravity Base Turbine capacity Shaft diameter, m 4, Base area, m Weight, t 1,200-1,700 1,500-1,800 1,500-2,000 2,500-3,000 Ballast, m ,500-2,500 2,500-4,000 2,000-3,000 Excavation Excavation area, m , ,950 Material excavation, m 3 1,000-1,300 1,000-1,300 1,200-1,500 1,400-2,000 1,600-2,500 Gravel bed, m , , , ,700 Scour protection Footprint, m 2 1,300-3,900 1,600-4,000 1,600-4,000 2,600-6,900 4,700-10,000 Volume, m 3 2,000-4,500 2,500-4,500 2,500-4,500 3,500-8,000 5,500-11,000 Table 4 Estimated jacket foundation dimensions Jacket Turbine capacity Footprint at top, m 8x8 10x10 12x12 15x15 18x18 Footprint at sea bed, m 15x15 17x17 20x20 25x25 32x32 Weight, jacket, t ,000 1,100 Weight, 4 piles, t Suction bucket foundations are at a prototype/testing stage and dimensions are uncertain, but they will be smaller than a GBS. For the purpose of environmental impact assessment they are assumed of smaller dimensions than a GBS. 3.2 Construction features vs. water depths The 3 MW layout consists of 66 positions, placed in 5 rows north to south more or less parallel to the shore. Dok. 13/ /15

8 The 13 positions in the western row are placed between the -6m and -10 depth contour line, nearer the -6m line towards the south, Figure 3. It has been possible to install 3MW WTGs at depths at approx. 6m at previous projects, however it must be expected that the shallow water will limit the options available with regards to foundation type and installation vessels. The eastern row of turbines placed between the -18 m and m, a depth where there are a wide range of options available, both with regards to foundation type and installation equipment. The 10 MW layout consists of 20 positions placed in 3 rows, north to south. The 7 positions in the western row, nearest the shore, are placed between the - 6m and -8m line, Figure 3. Based on the currently available equipment it must be expected to be quite challenging or impossible to install 10 MW WTGs at such shallow waters. Figure 3 Sæby Offshore Wind Farm bathymetry and shallow water limitations The next row towards the east is placed at -12m to -13m. This depth does open op the options, but does not necessarily leave much room to maneuver for the large installation vessels required. If the soil conditions (affecting jacking operations) or weather/wind/wave conditions (affecting the maneuvering of the Dok. 13/ /15

9 vessels) also prove challenging, it may also be difficult to bring in and out vessels with sufficient capacity to do the installation work. 3.3 Installation scenario An indicative construction schedule as shown in section 6.5 of the generic technical project description is assumed, and installation equipment and duration of operations are as indicated in section 3 of the generic technical project description: Seabed preparations/excavation and installation of gravel bed 5 days Installation of foundations, 1 day Installation of turbines 1 day Seaward transport of materials, mainly turbines, foundations and stone material, are assumed from appropriate port within 50 NM distance. 4. Pre-investigations 4.1 Investigations The Sæby offshore wind farm area and adjacent export cable corridors have been investigated using geophysical and geotechnical techniques and a Metocean modeling study have been performed for the site. The geophysical survey includes bathymetric mapping, side scan sonar mapping, single and multichannel sub-bottom profiling, magnetic profiling and ground truth sampling to facilitate seabed interpretation. Results and interpretation of the geophysical survey at Sæby can be found in Enclosure 2. The geotechnical campaign included 1 investigation to depth af 70 m below seabed using combined borehole drilling and Cone Penetration Test (CPT) testing. Furthermore 10 single CPT tests were completed using either a push CPT or a seabed unit CPT system reaching depths m below seabed. The results are presented in Enclosure 3. A Metocean study including provision of information and data on wind, waves, water levels, currents, ice etc. was conducted for Sæby offshore wind farm area. Furthermore provision of wind data and information on wind resource estimation was performed. Results and reports can be found in Enclosure Summary of seabed survey The objective of the site surveys is to provide an input to the Environmental Impact Assessments and an initial evaluation of the foundation of the wind turbines, as well as lower the risk for companies with interest in acquiring the license in 2015 to build and operate the wind farms providing a general assessment of the areas. Dok. 13/ /15

10 To meet the project objectives, a full geophysical and bathymetric survey was conducted with activities including: Bathymetric mapping with full seafloor search (>100% coverage) within the survey area. Side-scan sonar mapping (overlap >100% to cover nadir regions of adjacent survey lines). Sub-bottom profiling with two systems; one high resolution pinger (chirp) single channel system plus one deep penetration sparker multi-channel system. Magnetic profiling along all survey lines. Ground-truth sampling (grabs) to support seabed interpretation. The survey was conducted using two survey vessels; EGS Pioneer (24hr offshore) and the Føniks Miljø (12hr inshore), both operating out of the port of Frederikshavn. The main equipment spread for the offshore vessel consisted of a Kongsberg 2040 MBES, a Klein 3000 dual frequency SSS, a Knudsen 3260 Chirp, a Geo- Source Sparker and a Geometrics G882 marine magnetometer. An Applanix POSMV 320 was used for all (horizontal, vertical and motion reference) positioning (primary), in combination with a Sonardyne Scout Plus USBL system for the subsurface towed equipment (interfaced into the QPS QINSy navigation package). The main equipment spread for the inshore vessel consisted of a Kongsberg 3002D MBES, a Klein 3000 dual frequency SSS, a C-Products C-Boom SBP and a Geometrics G882 marine magnetometera Kongsberg SeaPath 330+ used for all (horizontal and vertical reference) positioning (primary), in combination with a Kongsberg MRU-5 (motion reference). All positions in this report and associated data are referenced to geographic (WGS84 Lat/Long) or projected (UTM32N) coordinates. All reported elevations and depths are referenced to the DVR90 vertical elevation system represented by the DKGEOID02 geoid model from the Danish Geodata Agency. The DVR90 system is considered as a valid approximation to MSL. The survey specifications required lines to be run with 65m and 50m line spacings, dependent upon water depth, over an approximate area of 57km 2. This equated to a total planned line length of km (897.0km EGS Pioneer, 483.1km Føniks Miljø), including cross lines spaced at 1km intervals. In total 2506km (1684km EGS Pioneer, 822km Føniks Miljø) line kilometers of SSS acoustic imagery, SBP (boomer, chirp and MCS) records, MAG data profiles and MBES bathymetric data were acquired (extra kilometers due to reruns and infill), processed and interpreted resulting in the interpretation of bathymetry, seabed features and shallow geological profiles. Full data coverage was achieved during survey operations. During the survey the client approved a reduction in the scope of the MCS work following an assessment of the widespread distribution of acoustic blanking, possibly related to shallow gas. Due to the reduced penetration of the seismic energy several lines were converted from MCS survey Dok. 13/ /15

11 lines to standard survey lines. It was also agreed that four short infill lines within the area of acoustic blanking would not be run. A total of 26 (20 EGS Pioneer, 6 Føniks Miljø) grab samples were taken as a ground-truth, primarily to the sonar data. The survey results have been presented as a series of 39 charts generated in ESRI ArcMap. These have been delivered both as PDFs and as ESRI projects to allow for full digital interaction with the supplied charted data. Of the 39 charts, an overview chart showing the coastline and the survey area, a vessel track chart plotting the common reference point (CRP) of the vessel, a bathymetric chart displaying shaded relief and contours, an SSS mosaic chart, and 6 charts displaying elements of the seabed features, morphology and sediments were charted at a 1:25,000 scale. An overview SBF chart has also been created at a scale of 1:25,000. Seven significant sub-seabed geological components were also charted at a 1:25,000 scale. Further to this, the geological interpretation for 8 mainlines and 4 cross lines were charted in profile at a scale of 1:7,500 and have been supplied as ESRI ArcScene 3D mapping projects. Digital datasets supporting the interpretation, reporting and charting have been delivered in CSV and shapefile formats. Processed seismic data, both single and multichannel, has also been supplied to facilitate additional future interpretation and quality control of this dataset. Figure 4. Overview of the Sæby site Bathymetri (Figure 20 in original report) The limits of the bathymetric data within the survey area at Sæby range from a minimum of approximately 6.2m below DVR90 at the southwestern extent, to a Dok. 13/ /15

12 maximum of approximately 18.7m below DVR90 at the southeastern extent. Figure 4 presents an overview of the bathymetry throughout the entire site. Figure 5. Overview of the Sæby seabed features (Figure 26 in original report) Greater than 100% SSS coverage was obtained of the seabed and has enabled seabed sediment type and distribution to be interpreted. The surficial material over the survey area shows a generally low to moderate acoustic reflectivity and is interpreted to be dominated by clay. Small amounts of gravel content account for the variation in acoustic reflectivity of the clay and silt is also present as a lesser constituent. No areas of glacial sediment are present at the seabed and it is generally featureless in nature, although scars and areas of disturbed seabed have been identified towards the east of the survey area. Figure 5 presents an overview of the seabed features throughout the entire site. A total of 257 sonar contacts were identified, including 16 contacts interpreted as items of debris (of possible man-made origin. The remaining 241 contacts have interpreted as boulders, including those marked representatively. No wrecks have been observed in the survey data. A total of 257 sonar contacts were identified, including 16 contacts interpreted as items of debris (of possible man-made origin. The remaining 241 contacts have interpreted as boulders, including those marked representatively. No wrecks have been observed in the survey data. The sub-surface sediments have been mapped on the basis of seismic evidences. The distribution of the most significant geological units has been Dok. 13/ /15

13 mapped as a background for the geotechnical evaluations of the turbines. The interpretations are primarily done on the basis of the seismic reflection pattern. The basement of the Quaternary sediments has been not been able to be located and as such no pre-quaternary strata has been identified within the sesimic datasets. The boundary between the recent holocene sediments and the underlying glacial deposits, thought to be of Weichselian age, has been interpreted where visible. The survey area suffers greatly from acoustic blanking, interpreted to be caused by shallow gas, both in the form of blanket and plume deposits, and this has limited both the depth of seismic penetration and also the planar distribution of interpretable seismic data. Using a target detection threshold of 2nT, 540 magnetic contacts were identified. In general the distribution of magnetic contacts appears well spread throughout the site with no particular pattern or significance. Geotechnical INTRODUCTION A preliminary geotechnical investigation was carried out by Fugro Seacore Limited (FSCL) on behalf of Energinet.dk (the Employer) and under the supervision of Ramboll. The investigation area was located in the Kattegat, approximately 4km off the coast of Jylland, Denmark, south east of Frederikshavn. OBJECTIVES OF THE GROUND INVESTIGATION The purpose of the ground investigation was to provide preliminary geotechnical data to allow for the evaluation of the site for further investigation and development into a nearshore wind farm. SCOPE OF THE GROUND INVESTIGATION The nearshore ground investigation was undertaken from Fugro s jack-up platform Excalibur and vessel Fugro Commander. The site work conducted from Excalibur was undertaken from 30th May to 5th June 2014; the site work conducted from Fugro Commander was undertaken between 24th May and 30th May The scope of works of the ground investigation comprised: One sampling borehole constructed using rotary open hole and rotary coring techniques, carried out from Excalibur. Four cone penetration tests, using the top-push system and/or the WISON XP system, carried out from Excalibur. Seven cone penetration tests, using the Fugro Seacalf Block-Drive seabed system, carried out from Fugro Commander. Four Ménard Pressuremeter tests carried out within the sampling borehole at appropriate depths. Dok. 13/ /15

14 Seabed gas was encountered at two locations, Safety concerns led to the cancellation of two exploratory positions (SBY-BH001 and SBY-CPT009). REPORTING The ground report is presented in three parts: Operations Report; including information on the field operations, health and safety and environmental information, procedures for the field testing and sampling techniques used, and data sheets and calibration certificates. Factual Report; including site setting, the exploratory hole and field testing records, laboratory test results, an overview of the ground conditions encountered and geotechnical evaluation of the field and laboratory test results. Cyclic Laboratory Test Report; including the cyclic triaxial and cyclic shear test results. FINDINGS OF THE GROUND INVESTIGATION The ground investigation encountered the following general succession of strata: Recent Marine Cohesive and Granular Deposits Yoldia Clay and Saxicava Sands Late Weichselian Granular Outwash Deposits Mid Danish Till Tebbestrup Formation Kattegat Till 5. List of enclosures Enclosure 1 Wind Farm layout: Wind farm layouts for Sæby. DTU Wind Energy, Report-I-0198(EN) to Energinet.dk, February 28, Enclosure 2 Geophysical surveys: Danish Wind Farm Site Surveys. Volume 2: Interpretive Report Site 3 Sæby. EGS Earth Sciences & Surveying report to Energinet.dk, April 2014 Enclosure 3 Geotechnical surveys: Preliminary geotechnical investigations Sæby Nearshore Wind Farm. Factual report on ground investigation. Fugro Seacore Limited report to Energinet.dk. October Dok. 13/ /15

15 Enclosure 4 Metocean investigations: Sæby offshore windfarm met-ocean report. COWI A/S report to Energinet.dk, January 2015 Six Nearshore Wind Farms Study Related to Wind Resource Wind Resource Report. COWI A/S report to Energinet.dk, November Six Nearshore Wind Farms Study Related to Wind Resource Validation Report. COWI A/S report to Energinet.dk, November Dok. 13/ /15