Mooring Options and Total Installed Cost
for a Commercial Scale Wind Farm
Tom Fulton, Head of Renewables and Mooring Development
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A MARINE ENERGY AND INFRASTRUCTURE SERVICES
PARTNER FOR THE ENERGY TRANSITION
Our aim is simple: to be the preferred
engineering, services and technology
partner for all our customers
Through a focus on technical improvement and
customer service, we are enabling the energy
transition across marine infrastructure
Delivering strong commercial and
environmental benefits in a complex
and rapidly changing market.
Presentation Contents
Project Highlights and Drivers
Mooring Types
Design Criteria
Mooring Analysis Results
Total Installed Cost
Conclusions
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Hannibal Wind Farm
Location: Offshore Sicily
Project
Highlights
Developers: 7 Seas Wind Power, NiceTechnology and
Copenhagen Infrastructure Partners
Floating Foundation: TetraSub - Stiesdal Offshore
Technologies
Turbine Size: 12MW
Number of Turbines: 21
Study water depth: 200m
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Project Drivers
Minimize
Environmental
Impact
High Bankability
Economics
• Minimize mooring footprint
• Minimize seabed impact
• Use mature mooring technology
• Low risk installation
• Keep costs low while
considering points above
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Mooring Selection Process
Metocean
Geotechnical
Local Requirements
Global Analysis
•
•
•
•
Turbine
Hull
Moorings
Cables
Total Installed Cost
•
•
•
•
Engineering
Procurement
Mooring Prelay
Tow and Hookup
Mooring Component
Selection
• Chain/Ropes
• Connectors
• Anchors
Installation Methods
• Vessels
• Supply Bases
• Depended on Mooring Components
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50-year storm conditions
• Hs = 6m
• Wind = 42.5m/s at hub height
• Current = 0.5m/s
Main Design
Criteria
Use DNV-ST-0119
Strength utilization <0.95
(consequence class 1)
Offset <50m (25% WD)
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7
Mooring Types
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Option 1: Polyester Taut Leg
Selected
Systems
Option 2: Chain Catenary
Option 3: Polyester Semi-Taut
Option 4: Nylon Taut Leg
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Polyester Taut Leg
▪
Components (Total Length: 478m):
▪ Top Chain (30m):
▪ 145mm R5 studless chain
▪ 2,024 Te MBL when considering 8mm corrosion
▪ Polyester Rope (428m unstretched):
▪ 2000 Te MBL
▪ Bottom Chain (20m):
▪ 145mm R5 studless chain
▪ 2,024 Te MBL when considering 8mm corrosion
30m chain
63°
428m polyester
(Preload: 6.9%, 138 Te)
20m chain
436m
10
Chain Catenary
▪
Components (Total:
771m):
▪ Chain (771m):
▪ 103mm R3 studless
chain
▪ 747 Te MBL when
considering 8mm
corrosion
38°
771m chain
(Preload: 13%, 97 Te)
342m (TDP)
702m
(Anchor)
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Polyester Semi-Taut
Components (Total Length: 620m):
▪ Top Chain (30m):
▪ 111mm R4 studless chain
▪ 1,060 Te MBL when considering 8mm
corrosion
▪ Polyester Rope (190m unstretched):
▪ 1000 Te MBL
▪ Bottom Chain (400m):
▪ 124mm R3 studless chain
▪ 1,062 Te MBL when considering 8mm
corrosion
30m chain
50°
190m polyester
(Preload: 10%, 95 Te)
400m chain (to anchor)
368m (TDP)
561m
(Anchor)
702m
(Anchor)
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Nylon Taut Leg
▪
Components (Total Length: 283m):
▪ Top Chain (30m):
▪ 175mm R4 studless chain
▪ 2,567 Te MBL when considering 8mm corrosion
▪ Nylon Rope (233m unstretched):
▪ 1500 Te MBL
▪ High stiffness for in-line (30xMBL)
▪ Low stiffness for between-line (10xMBL)
▪ Bottom Chain (20m):
▪ 175mm R4 studless chain
▪ 2,567 Te MBL when considering 8mm corrosion
30m chain
46°
233m nylon
(Preload: 15%, 225 Te)
20m chain
219m
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Mooring Analysis Results
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Min. Breaking Load and Offset
2500
30%
25%
2000
20%
1500
15%
1000
10%
500
5%
0
0%
Poly Taut
Nylon Taut
Min. Breaking Load (tons)
Poly Semi-Taut
Chain Catenary
Offset (%WD)
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Mooring Footprint and Chain on Bottom
700
600
Distance (m)
500
400
300
200
100
0
Horizontal Distance to
Anchor
Nylon Taut
Nominal Chain on
Seabed
Poly Taut
Min Chain on Seabed
Poly Semi-taut
Max Chain on Seabed
Catenary
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Anchor sizes for costed options
Options
Driven pile
Drag anchor
Polyester Taut
2.1m dia x 60m long,
137mt weight
Not applicable
Chain Catenary
1.5m dia x 42m long,
65mt weight
Bruce FFTS GP – 15mt
Polyester Semi-taut
1.5m dia x 39m long,
72mt weight
Bruce FFTS GP – 18mt
Nylon Taut
2.1m dia x 40m long,
105mt weight
Not applicable
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Total Installed Costs
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Mooring Procurement Breakdown
100%
9%
90%
80%
70%
13%
9%
26%
11%
60%
50%
28%
40%
30%
60%
74%
52%
6%
20%
16%
11%
10%
52%
18%
15%
0%
Poly Taut - Pile
Chain Catenary - Drag
Anchor
Connectors
Poly Semi-Taut - Drag
Fiber
Nylon Taut - Pile
Chain
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Total Installed Costs
100%
90%
80%
70%
Includes:
15%
18%
19%
60%
50%
40%
30%
22%
24%
14%
13%
64%
62%
•
All mooring components (including
shipping allowance)
•
Vessels w/fuel
•
Project equipment
o
Pile hammer
o
Survey
o
ROV
o
Handling Equip
•
Project crews
o
Marine supervisors
o
Engineers
o
Technicians for equipment
listed
21%
67%
20%
60%
Does not include
10%
0%
Option 1 - Poly Taut Pile
Mooring Components
Option 2 - Chain
Catenary - Drag
Option 3 Poly Semi- Option 4 - Nylon Taut Taut - Drag
Pile
Preset Operations
•
Base port services
•
Weather downtime
•
Mechanical downtime
•
Unforeseen complications
Tow and Hookup Operations
For reference, a 40 unit floating wind farm, total installed
mooring costs can range from $85-150m
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Conclusions
Multiple designs were determined technically feasible
Taut legs designs were preferable from an environmental standpoint
Polyester was preferred over nylon due to vast experience with polyester in long
term oil and gas moorings
Total installed cost ranged from $85m to $150m for 40 turbine farm
Project requirements, local conditions and technical feasibility can all impact
total installed costs
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THANK YOU!
Contact info:
Tom Fulton
tom.fulton@acteon.com
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