Monobuckets and the competitiveness versus monopiles and jacket structures.

Transcription

1 Monobuckets and the competitiveness versus monopiles and jacket structures. Lars Bo Ibsen, Aalborg University, Professor. Foundation concepts for offshore Wind Turbines The Universal Foundation Carbon Trust Foundation Competition Conclusion

2 Structural and foundation for Wind Turbines but also applicable to other offshore renewable Cost of energy

3 Foundation concepts for offshore Wind Turbines Shallow depth 5-10m Gravity based Fabrication/material costs are low (concrete) Limited water depths (5-10m) Possible to float out Vulnerable to soft soil erosion & scour Sea bed preparation necessary Ice-cone usually integrated in design 3

4 4 9th Deep Sea offshore Wind R&D seminar 2012

5 Mono piles Foundation concepts for offshore Wind Turbines Shallow depth 10-30m 75% of all wind parks today Simple fabrication with welded steel pile No preparations of the seabed are necessary. Requires heavy duty piling/drilling equipment Not suitable for locations with many large boulders in the seabed. 5

6 Noise The recommended requirements of maximum: 160 db SEL and 190 db Peak for underwater pile driving noise levels. So far, Germany is the only country having ratified the legislation, but the remaining EU countries are expected to follow Germany s example.

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8 Foundation concepts for offshore Wind Turbines Depth 30-60m Jackets and Tripod Suitable for larger water depths. Minimum of preparations are required at the site before installation Complex welded main structure Known technology from oil & gas industry 8

9 Foundation concepts for offshore Wind Turbines Depth 30-60m 9 Tripod

10 Offshore wind turbine foundations 10 The flexibility of the bucket foundation gives wider range of application. Platform Bucket Mono pile Tripod/ jacket Sites with complex geotechnical properties can be cover by a single foundation concept 10

11 11 The Bucket foundation

12 Universal foundation solutions 12 Variation in water depth 0-60 m Variation in seabed properties Hard clay, soft clay, sand, silt

13 Vision for Installation in th Deep Sea offshore Wind R&D seminar 2012

14 14 Universal Foundation A/S MBD Offshore Power A/S -> Universal Foundation A/S Universal Foundations - Concept IP Holder Universal Foundations Solution Provider Fred.Olsen Dong Energi Novasion Aalborg University

15 15 Transport / Installation Buoyant horizontal wet tow/ vertical a/o horizontal on jack-up or crane ship / purpose build vessel Snap-on pump unit interfacing the lid The structure is upended by ballast water or by crane Crane is hooked on to stabilize touch down After initial penetration, suction is applied Installation is finalized by void filling by injecting cement slurry under the lid if needed. OBMC 2011 November 7th 2011

16 Reference 1: Pos. 1-Frederikshavn in operation 9 years 16 The Ø12x6 m prototype bucket foundation was designed for a Vestas V90 3MW turbine placed on 4 m of water. The design is certified by DNV. The bucket was installed in late 2002 and is in normal operation. The structure/soil interaction has been investigated with sophisticated modal analyse equipment.

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18 18 The bucket foundation technology Installation advantages: Minimum noise impact. No pile driving hammers or drill drives are used No grouted connections Minimum disturbance to the existing seabed The use of excess material for scour protection is reduced or not necessary All steel materials can be recovered from the seabed and reused / recycled when the foundation is decommissioned 18

19 Monobuckets - competitiveness versus Monopiles 19 Reduced steel consumption Use of simple geometric welded steel structures suitable for mass production Few offshore operations, with utilizing smaller equipment/vessels during installation No seabed preparation and no or reduced need for scour protection No transition peace - Adjusting the upper part of the shaft to fit the standard wind turbine tower. Simple decommissioning Cost is reduktion 20%. 19

20 Reference 2: The Mobile Met Mast Horns Rev II 2009 "The Mobile Met Mast" is a prototype of a bucket foundation designed as support structure for a metmast. Purpose: To gain confidence that a monopod bucket foundation can be successfully installed offshore. To obtain a movable metmast, which can be used in several offshore wind farms. Specification Total height: 34 m Weight: 165 tones Skirt length: 6 m Skirt diameter: 12 m Fabricated in Aalborg in August Installed at Horns Rev 2 Offshore wind farm in March

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22 Site for installation Horns Rev 2 Denmark Wind turbines: 91 Siemens 2.3MW 200 MW Scheduled installation: : Foundations : Turbines The Mobile Met Mast 3 installation tests were planned at different locations. (depending on weather) Was only installed on the final location. No data from CPT or borings are available (yet) Horns Rev 1 Esbjerg 22

23 Float out to site Floated to site using 2 tug boats 40 m 3 water was pumped into the head of the Mobile Met Mast to ensure a horizontal orientation when floating. 23

24 Up-ending procedure Up-ended with M/S SeaPower by A2SEA. The lift was performed with a heave-compensator. Inflation/deflation of air to the bucket skirt was necessary during up-ending Water depth (15 m) was close to the lower limit only 1 meter water below skirt during up-ending. 24

25 The Mobile Met Mast Offshore installation Horns Rev II

26 Installation A penetration velocity of 2 m/hour. Tilt after 2.5 m penetration. At 4 m penetration, the process was reversed until 3 m penetration, and suction process reengaged The foundation was successfully installed with a 0.1 degree inclination out of vertical. 26

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28 Carbon Trust Foundation Competition 28

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31 31 The Challenges

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33 33 Stage I: Foundation Designs total 72 Fixed prices Two turbine: 3.6 and 5 MW Water depts: 35m, 45m and 55m Two see condition Aver. and Exp. 6 seabed profiles

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35 35 Buckets a wide-ranging foundation solution OBMC 2011 November 7th

36 3,6 MW 5 MW 9th Deep Sea offshore Wind R&D seminar 2012 Cases: Carbon Trust Wind Accelerator Project 36 Water depth 5 m 15 m 25 m 35 m 45 m 55 m Moment knm Bucket size m Ø14x11 Ø15x12 Ø16x13 Ø17x14 Ø17x15 Ø17x16 Weight tons Moment knm Bucket size m Ø18x15 Ø18x16 Ø18x17 Weight tons

37 Moent load, MNm Dogger Bank,Foundation loads at seabed Loads 3,6 MW turbine Loads 5 MW turbine Reference jacket 3,6 MW Reference jacket 5 MW Water depth Dogger Bank, data from Carbon Trust OWA study and met mast project. Loads Bucket foundation MNm *) Water Depths Loads 3,6 MW turbine Loads 5 MW turbine Reference jacket 3,6 MW Reference jacket 5 MW *) breaking waves

38 38 Comparison of Foundation Types Basis of Comparison - Tenders for Manufacture of 80 No. Foundations Foundation Type Steel Weight (Gross) each Cost % comparison Tripod Leg Jacket Leg Lightweight Jacket Universal Foundation Comments Note to balance the cost, Insurance, Bonds and Guarantees have been removed, where appropriate, as these were not applied equally to all tenders. Where service cranes were required to certain types, these have been removed Load out and transportation has been removed, where appropriate

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41 Wind turbine Cabling 41 The Supply Chain Project development Fabrication Transport Installation Operation Universal Foundation Solution Supplier Concept IP s / Configuration / Contract Management / R&D Buckets a wide-ranging foundation solution Document / Material Flow Client Design / Methodologies / Procedures / Feed-back Universal Foundation Document Supply Contract Fred. Olsen United AS Fred.Olsen & Co / Support by way of Legal Accounting HR Finance 41

42 Conclusion 42 Monobuckets - competitiveness versus Monopiles Reduced steel consumption compared. Few offshore operations, with utilizing smaller equipment/vessels during installation. No seabed preparation and no or reduced need for scour protection. No transition peace - Adjusting the upper part of the shaft to fit the standard wind turbine tower. Simple decommissioning. Reduces cost of energy by reducing foundation cost by 20%

43 Monobuckets - competitiveness versus Jackets 43 Reduced steel consumption compared to any other substructure solution. Use of simple geometric welded steel structures suitable for mass production. Few offshore operations, with utilizing smaller equipment/vessels during installation. No seabed preparation and no or reduced need for scour protection. No transition peace - Adjusting the upper part of the shaft to fit the standard wind turbine tower. Simple decommissioning. Cost reduktion 30-50%.

44 44 Thank you for listening Lars Bo Ibsen