This presentation is a general overview of a floating offshore wind farm. The main goal is to design a semisubmersible platform for 5MW wind turbine. Most relevant marine topics were studied: sizing,stability,seakeeping,mooring,structure,ancillary systems,costs and viability.
8. 5. Hydrostatic and stability.
• Nowadays, there is not specific rules • General stability criteria for oil and gas
for floating offshore wind turbine platforms is applied.
platforms. • The basics rules that we have to evaluate
• Tanks comparments are the easiest – Area under heeling and righting arms:
A+B>1,3(B+C)
division as posible.
See figure: – Static angle of heel θ1 (first intersection point) shall not
be greater than 15º -17º, (depending of rule).
– Metacentric height GM shall be greater than 1m in
transit, operation and survival condition .
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9. 5. Watertight stability criteria
• Static angle of heel is 11º < 15º
• Ratio area Righting/Heeling is more than 1,3
• WATERTIGHT STABILITY CRITERIA IS PASSED.
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11. 6. Seakeeping
DESIGN REQUIREMENTS.
• Platform eigenperiods shall not be the same as wave periods in the
wind farm location.
• Nacelle accelerations should be < 3 m/s2.
ANALYSIS
• Frecuency domain analysis.
(M total A)η Bhyd η Chyd η Fwaves
Restoring forces of mooring are disregarded in catenary moored floating
structures, in first approximation.
Aerodynamics effects are not included in the numerical model.
Time domain analysis is not necessary in the first steeps of the design.
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12. 6. SEAKEEPING. PHASE I
• Frecuency domain analysis.
• Wave direction. Fore sea (0º)
• Until 11 s period waves, heave motion is very small
• Heave resonance period is 11 s antiheave plates are
neccesary
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13. 6. SEAKEEPING. PHASE II
• Frecuency domain analysis.
• Wave direction. Fore sea (0º)
• Heave, surge and ptich are the
most important responses.
• Heave resonance period 17,5 s.
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14. 6. SEAKEEPING: NACELLE ACCELERATIONS
FASE I FASE II
Periodo propio en largada (s) 13,18 17,5
Periodo propio en deriva (s) 0 0
Periodo propio en arfada (s) 0 0
Periodo propio en balance (s) 20,9 34
Periodo propio en cabeceo (s) 20,9 34
Periodo propio en guiñada (s) 0 0
Seastate 1 Seastate 2 Seastate 3
Velocidades en largada (m/s) 0,26 3,6 4,061
Velocidades en deriva (m/s) 0,34 2,55 1,42
Velocidades en arfada (m/s) 0,039 3,19 0,398
Velocidades en balance (rad/s) 0,0007 0,022 0,012
Velocidades en cabeceo (rad/s) 0,0019 0,028 0,017
Velocidades en guiñada (rad/s) 0,0009 0,0025 0,0024
Aceleraciones en largada (m/s2) 0,148 1,52 1,17
Aceleraciones en deriva (m/s2) 0,037 1,035 0,399
Aceleraciones en arfada (m/s2) 0,197 1,42 0,16
Aceleraciones en balance (rad/s2) 0,00042 0,0089 0,0033
Aceleraciones en cabeceo (rad/s2) 0,0012 0,012 0,0048
Aceleraciones en guiñada (rad/s2) 0,00043 0,0013 0,00063 14
15. 7. MOORING SYSTEM.
P Platform position at sea
Definition of mooring
system
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16. 7. MOORING.
Static analysis.
• Depth: 250 m
• Initial chain length : 680 m
• Chain type: Studless; Diameter 75 mm.
• Breaking loads:
• Grado 2: 2928,3 kN (298,6 ton)
• Grado 3: 4189,5 kN (427,2 ton)
• Grado 4: 5856,7 kN (597,2 ton)
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17. 8. MOORING.
Static analysis
Horizontal offset 143 m and ptich angle 6,4 º
Fairlead tension in fore lines: 83 ton
Reduction change length 620 m.
Horizontal design force effect (90 ton)
Horizontal offset 61 m y pitch angle 6,1 º
Fairlead tension in fore lines: : 106 ton
Dynamic analysis in different seastates
Same effect with 620 m lines(90 ton)
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18. 8. MOORING.
Dynamic analysis
SEASTATE 1. NORMAL OPERATION
• Low excurssions and rotations.
• Tension (95 ton) far from breaking loads.
• Mooring system is suitable.
SEASTATE 2. EXTREME OPERATION SEASTATE 3. 50 YEARS STORM
Bigger tensions (140 ton) although far from breaking loads. Tension 250 ton Chain grade R3.
High motions. ¿is it possible wind turbine running?
Developer has to decide
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19. 8. MOORING. FINAL ARRENGEMENT
Características generales
Profundidad d m 250
Tipo de fondeo catenaria
Longitud de líneas L m 620
Tipo de eslabón sin contrete
Dimensiones eslabón 75 mm
Grado R3
Carga de rotura KN 4189,5
Relación L/d 2,48
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24. 9. Ancillary systems : active ballast
Submerged pumps: 500 m³/h
Automatic ballast system Anti- rotations
Piping of GRE high performance with sea water
Simplification: no remote operated valves
Maintenance from upper zone of columns
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25. 9. Ancillary systems
Lighting, signaling and buoying
Access and docking
Comunications: SCADA system
Paint and cathodic protection.
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26. 10. Electric engineering.
Uninterrupted power system (UPS)
120 Ah / 60 kVA / max current 115 A
Situated in pump rooms
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27. 10. Electric engineering.
Cable in wind farm 33kV.
Cable to shore 132 kV
Platform with subestation
4 trafo 25kVA
One platform with different design
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31. 12. Viability
Rendimiento del
dinero prestado: 8%
Rate 190 €/MWh
TIR 1%
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32. Thanks.
• Ramón Barturen, MSc. Marine Engineer (UPM) and Master in
Marine Bussines and Laws (IME)
• Bernardino Couñago, MSc. Marine Engineer (UPM)
Project supervision
• D. Manuel Moreu Munaiz
• D. Miguel Ángel Herreros Sierra
For any question, please, contact us:
ramonbarturen@gmail.com
bernardinocounago@gmail.com
Rights reserved to autors and Politechnic University of Madrid (UPM)
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