TIDAL TURBINE FOUNDATION OPTIMISATION RAMBOLL ENERGY MOJO MARITIME Alternative title slide

INTRODUCING RAMBOLL Content slide, two columns with image Ramboll is a leading engineering, design and consultancy company founded in Denmark in 1945 Today, we employ more than 10,000 ambitious experts. Ramboll has a significant presence in Northern Europe, India, Russia and the Middle East With close to 200 offices in 20 countries we emphasise local expertise combined with a global knowledge-base.

INTRODUCING MOJO MARITIME Mojo provide Marine Operations Management and Consultancy Services to the Offshore Renewable Energy Sector. WINDWAVETIDE Content slide, two columns with image

TIDAL FOUNDATIONS Tidal foundations have huge challenges: uneven rocky seabeds, high current speeds, water turbulence and limited access. At present foundations are trials and so are not suitable for mass production. The next stage is a repeatable structure. Ramboll and mojomaritime are drawing on considerable experence in marine engineering from both oil and gas and offshore wind sectors to derive a solution. Content slide, two columns with image

CONTEXT OF PRESENTATION - FOUNDATION DESIGN AND INSTALLATION STUDY Working on a 10MW array in NE Scotland. Concept phase leading to reduction to 4 concepts. Review of each concept leading to elimination two (Gravity base and Duopod) and development of two (Monopile and Tripod). Tripod selected for detail design. Modelled and analysed ULS, ALS, FLS, SLS. Content slide, two columns with image

FOUNDATION DESIGN AND INSTALLATION “INTER-TWINED”

Must be considered together, foundation design impacts installation – a major project cost driver. It goes beyond installation - the design of foundation also impacts the cost of other interventions: Decommissioning · Cable connection · Turbine O&M Content slide, two columns with image

FOUNDATION OPTIONS Gravity Bases Moored Seabed Engagement Content slide, two columns with image Note that all of these require gravity at some stage!

GRAVITY BASES

GRAVITY BASE– STRUCTURAL CONSIDERATIONS 1 of 2 Option 1 Floating Gravity Base Option 2a Streamlined Modular GBA Option 2b Tripod Modular GBA Modular Gravity Sensitive to seabed slope, limit <10° Less technical risk than floating GB Lower potential for cost reduction at array scale More expensive vessels required Floating Gravity Sensitive to seabed slope, limit <10° Novel Concept = High Risk Minimal Vessel Requirements High CapEx investment Investment recovered for large array deployment

GRAVITY BASE– STRUCTURAL CONSIDERATIONS 2 of 2 Content slide, two columns with image Conclusion Substantial mass required - expensive Highest risk option Minimal vessel requirements

GRAVITY BASES – INSTALLATION CONSIDERATIONS Content slide, two columns with image Monoblock GBA –Attractive solution, marine operations simple and quick –Ideal for smaller scale devices and prototype deployment –BUT… unlikely to be long term foundation solution: –Limited in scalability –Little opportunity for cost reduction –Not applicable at sites with significant seabed slopes –Carbon footprint large for big lumps of steel/concrete –Long term reliability concerns Modular GBA Floating GBA 12

MOORED

MOORED – INSTALLATION CONSIDERATIONS Still requires fixation by GBA or seabed engagement Potential application at some sites Obvious O&M benefits But introduces some additional considerations: Dynamic export cable Mooring spread vs. array layout Dynamic platform Failure modes Needs Naval Architecture Content slide, two columns with image Hydra tidal moored device

SEABED ENGAGEMENT

MONOPILE – STRUCTURAL CONSIDERATIONS Design Conclusions Pile Diameter at upper limit of drilling capability Simple design and proven construction Fatigue governs so ULS utilisation ratios are low Content slide, two columns with image Feasible and well researched concept Material thickness / diameters governed by fatigue Low ULS/fatigue life ratios Simple Fabrication, weld automation No fatigue sensitive joints

DUOPOD – STRUCTURAL CONSIDERATIONS The Duopod benefits from bi- directional flow, resulting in more axial load path rather than bending in a monopile. Reduction in pile diameter. Can have problems with alignment to flow. Content slide, two columns with image

TRIPOD–STRUCTURAL CONSIDERATIONS Content slide, two columns with image Similar to Duopod in the manner that axial load paths are set up. Smaller pile diameter than monopile. Additional leg reduces flow direction problem presented by the Duopod. Weight reductions compared to monopile. Angles dependant on turbine rotor exclusion zone.

JACKET–STRUCTURAL CONSIDERATIONS Content slide, two columns with image Additional weight savings over monopile. Use in larger water depths. Majority of forces in axial manner. Reduction in pile diameter however multiple piles leading to installation complexity. Angles dependant on turbine rotor exclusion zone.

JACKUPS AND TOPSIDE DRILLING 1 of 2 Content slide, two columns with image –Topside drilling requires stable platform such as a Jack up barge. –BUT... successful application of Jack ups in tidal races is limited.

JACKUPS AND TOPSIDE DRILLING 2 of 2 Content slide, two columns with image –Jack ups in tidal races Out of class operation Possible stability/VIV issues Susceptible to weather downtime Depth limited Expensive day rates Restricted availability Topside drilling from a DP vessel or moored barge? Not likely. Bottom line: If “no” to jackups  it’s “no” to topside drilling.

SUBSEA DRILLING 1 of 3 Content slide, two columns with image Post-install piles Drilling within foot sleeves of jacket held temporarily in place under gravity. Smaller diameter percussive drilling demonstrated by TGL Pre-install pile(s) Drilling through template placed temporarily on seabed Monopile, Duopod, Tripod, Quadrapod etc. (or anchor piles for moored solutions) 22

SUBSEA DRILLING 2 of 3 Content slide, two columns with image 23

SUBSEA DRILLING 3 of 3 Content slide, two columns with image CONCEPT t = 0 DESIGN t = 3 months BUILT & TESTED t = 6 months

CONCLUSIONS

CONCEPT ELIMINATION PROCESS More detailed study of risk, cost and schedule for 4 options

TIDAL FOUNDATIONS Every tidal foundation is unique due to site requirements and device needs. For an optimum foundation which is cost effective and efficient, every aspect has to be individually analyised. Content slide, two columns with image

CONCLUSIONS – INSTALLATION 1 of 4 No “one size fits all” solution when considering various sites and devices: Content slide, two columns with image SITE DEPTHmay preclude the use of jackups SEABED CONDITIONSoverburden, voids and other drilling challenges SLOPEon bottom stability by gravity, levelling for drilling CURRENT VELOCITIESdon’t forget forces~v 2, best DP OCVs max 6kn WAVE EXPOSUREimpacts design and marine ops ENVIRONMENTALnever under-estimate these factors LOGISTICS/VESSEL AVAILABILITYmuddle through with a barge?

CONCLUSIONS – INSTALLATION 2 of 4 The cost (and technical ability) of intervention is the tidal energy sticking point Content slide, two columns with image

CONCLUSIONS – INSTALLATION 3 of 4 Content slide, two columns with image

CONCLUSIONS – INSTALLATION 4 of 4 Fit-for-purpose vessels are required if the tidal energy industry is to be economically viable. Not just lower day rates on: Charter Fuel Required crew Also compound savings from increased capability and shortened ops time: Fuel Personnel ROV/equipment hire Reduced weather exposure Content slide, two columns with image FUTURE VESSEL EXISTING DP OCV

THANK YOU Endslide.