Offshore Wind Access 2019
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OFFSHORE WIND ACCESS REPORT Westerduinweg 3 1755 LE Petten P.O. Box 15 1755 ZG Petten The Netherlands TNO report www.tno.nl TNO 2019 R10633 | Third edition T +31 88 866 50 65 Offshore Wind Access 2019 Date 12 May 2019 Author(s) B. Hu P. Stumpf W. van der Deijl Copy no 1 No. of copies 1 Number of pages 40 Number of 0 appendices Sponsor Project name Annual Offshore Wind Access Report Project number 060.34302 All rights reserved. No part of this publication may be reproduced and/or published by print, photoprint, microfilm or any other means without the previous written consent of TNO. In case this report was drafted on instructions, the rights and obligations of contracting parties are subject to either the General Terms and Conditions for commissions to TNO, or the relevant agreement concluded between the contracting parties. Submitting the report for inspection to parties who have a direct interest is permitted. © 2019 TNO OFFSHORE WIND ACCESS REPORT Since April 1st ECN and TNO have joined forces. Acknowledgement This report is the 3rd edition of TNO1’s Offshore Wind Access report. The previous edition [1] was published in 2018 (click here to download), and TNO intends to update this report on an annual basis. TNO would like to thank the following companies for providing essential inputs and contribution to this report (in alphabetical order): • Van Aalst Group B.V. • Ampelmann Operations B.V. • Barge Master B.V. • Eagle Access B.V. • Fassmer GmbH • Houlder Ltd • IHC Holland B.V. • Kenz Figee Group B.V. • Knud E Hansen AS • Lift2Work B.V. • MacGregor Norway AS • Osbit Ltd • Otso Ltd • Reflex Marine Ltd • Safeway B.V. • SMST Designers & Constructors B.V. • TTS Offshore Solutions AS • Uptime International A.S. • W3G Marine Ltd • Zbridge B.V. • Ztechnologies B.V. In case you wish to contact ECN part of TNO regarding the content of this report, please send an email to: [email protected]. 1 ECN, the organisation which published the previous two editions has become a part of TNO since April of 2018. Summary Offshore wind farms in Europe are moving further from shore in order to capture more favourable wind conditions. However, this creates additional challenges regarding their Operations & Maintenance (O&M). O&M costs contribute significantly (20-30%) to the Levelised Cost of Energy (LCOE) over the lifetime of an offshore wind farm. One of the main reasons is the relatively low accessibility to the wind farm, which increases the downtime and therefore lost energy production, especially for far-offshore wind farms. This has driven the research into innovative access systems which promise average annual accessibility of 90%. In this third edition, an updated overview is presented of commercially available and demonstrated access systems for offshore wind farms. Three categories of access system are identified, based on the point of access: i) access to the boat landing, ii) access to the platform of the transition piece, and iii) access to the helicopter hoisting platform on top of the nacelle. Besides the conventional method of access to the boat landing through Crew Transfer Vessels (CTVs), motion compensated gangways mounted on the deck of Walk-to-Work (W2W) Vessels or dedicated Service Operation Vessels (SOVs) have entered the market during the last decade, which moves the maintenance base offshore. The analysis in this report shows that the growth of this market is in alignment with the needs for more efficient and safer transfer of technicians and cargo. In addition, while the relatively close-to-shore locations of current offshore wind farms has driven the extensive use of CTVs, more SOVs are being deployed as wind farms move further from shore, and new designs for motion compensated gangways and cranes (for SOVs) are being introduced. Furthermore, the following trends are discovered: • The motion compensated gangway for CTVs are not well adopted by the industry. • Within the category of CTVs, the market share of SWATH vessels (a type of CTV with improved seakeeping performance) is increasing. • In addition to the wind farm installation and (short-term) maintenance campaign, a rising number of dedicated SOVs are entering the offshore wind industry for (long-term contract) daily operation and maintenance (O&M). It is important to model offshore wind farm Installation / O&M activities to fully assess the impacts of a particular access solution. By doing so, design drivers can be identified, business cases of new systems can be established and optimal decisions can be made both for defining the Installation / O&M strategy and choosing between different access solutions. ECN (now part of TNO) has been constantly developing software tools (e.g. ECN Install, ECN O&M Calculator) to make such analysis, and will constantly upgrade these tools to improve the fidelity and user-friendliness. TNO report | TNO 2019 R10633 | Third edition 5 / 40 Contents ..................................................................................................................................... Acknowledgement ................................................................................................... 2 Summary .................................................................................................................. 3 1 Introduction .............................................................................................................. 6 1.1 Offshore wind O&M background ............................................................................... 6 1.2 Access systems overview .......................................................................................... 9 1.3 Objective and report outline ..................................................................................... 10 1.4 Changes with respect to the 2018 Offshore Wind Access Report .......................... 11 2 Access to the boat landing ................................................................................... 12 2.1 Crew Transfer Vessels (CTVs) ................................................................................ 12 2.2 Systems that enhance access to the boat landing .................................................. 14 3 Access to the Transition Piece (TP) platform ..................................................... 18 3.1 Service Operation Vessel / Walk-to-Work Vessel ................................................... 18 3.2 Motion compensated systems for transfer of personnel.......................................... 21 3.3 Motion compensated cranes for components between 1 and 20 metric tons ......... 30 4 Access to the hoisting platform ........................................................................... 34 5 Conclusions & future work ................................................................................... 35 5.1 Conclusions ............................................................................................................. 35 5.2 Future work .............................................................................................................. 36 6 References ............................................................................................................. 37 TNO report | TNO 2019 R10633 | Third edition 6 / 40 1 Introduction Chapter 1 pinpoints the importance of offshore wind access, explains the motivation behind this work and provides the structure of this report. 1.1 Offshore wind O&M background Offshore wind energy has grown rapidly over the past decade and it is constantly moving further offshore into deeper waters. Figure 1 presents the capacity of all seabed-fixed offshore wind farms in Europe by the end of 2018, based on those wind farms which are commissioned (online), under construction, consented and application-submitted. Figure 1 Average water depth and distance to shore of seabed--fixed offshore wind farms, organised by development status. The size of the bubble indicates the overall capacity of the site [2]. As Figure 1 indicates, most of the existing wind farms (those that are already online) in Europe are located near-shore (<70 km), while a large capacity of new offshore wind farms (those being constructed and planned) will be located far- offshore (>70 km). Despite the favourable wind conditions, increasing distance from port leads to higher O&M costs. In an attempt to reduce these costs, new strategies for logistics are being developed using offshore-based accommodation and TNO report | TNO 2019 R10633 | Third edition 7 / 40 innovative access gangways. The distance to port has a large influence on the most suitable strategy, as can be seen in Figure 2. For near-shore wind farms, work-boats (medium sized CTVs) are most commonly used for daily mobilisation from the port base. The further offshore the wind farm is, the more the travelling time increases, which can significantly reduce the working time available on a turbine. Besides, long trips with CTVs in less favourable weather conditions can cause sea-sickness to the technicians onboard, especially when CTVs travel at high speed. In general, it is preferred to limit the transit time between the port and wind farm to less than one and a half hours, if work-boats are used to transfer technicians. Far-offshore wind farms therefore require an offshore base for accommodating the technicians and potentially spare parts. Helicopters can also support O&M activities when the use of work-boats leads to too short a working period, or when conditions are too rough for access onto the turbine. The most commonly used