FLOATING OFFSHORE WIND FARM

ILLAS SISARGAS

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ramonbarturen@gmail.com

bernardinocounago@gmail.com

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Project aims

Semisubmersible floating platform desing for 5MW wind turbine.

100 MW floating offshore wind farm.

Platform integration in the wind farm: Electric solution.

Mooring and seakeeping grid mooring array synergies .

Wind farm O&M: Full maintenance strategy.

Expenditures analysis and financial viability study .

1. Emplazamiento del parque• Depth: [250m-400m]

• Average distance to shore : 30 km.

• Annual average wind speed : 10,05 m/s Predominant direction: NE-SW

• Typical wave height: 2,5 m Predominant direction: NW-SE

• Significant wave height (50 years) :13,09 m

• Maximun wave height (50 years): 24 m

• Seabed type : Sandy-rocky

• Area: 17,25 km2

2. Sizing process

Final decisions.

Initial dimensions are fixed

Design Constraints

Parameter

model

Weight estimationInertia and CoG

estimation

GM > 0

w

zgA

AMT

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GM

dFarctg

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3. Loads in floating structures.

Dinámicas

Pesos

Viento

Corriente

Presión hidrostática

Olas

Cargas en estructuras offshore

Constantes

Dinámicas

Sustentación

Arrastre

Ecuación de Morison

Radiación

Excitación

Masa añadida

Amortiguamiento

Froude-Krylov

Difracción

Fuerzas

1er

orden

Fuerzas

2ºorden

Deriva

estacionaria

Potencial

ViscosaSlow drift motion

Efecto

Slamming

Olas

Rompientes

Efecto Run-up y

sloshing

Otras

Estáticas

5[NREL picture].

4. Lines optimization.• External hull

Lines optimization of the initial model:

Improve hydrodynamic behavior. Reduction of waves and currents loads.

Remove corners to avoid tensions ocurred during welding process.

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4. General Arrengement

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5. Hydrostatic and stability.

• Nowadays, there is not specific rules for floating offshore wind turbine platforms.

• Tanks comparments are the easiestdivision as posible.

See figure:

• General stability criteria for oil and gas platforms is applied.

• The basics rules that we have to evaluate

– Area under heeling and righting arms: A+B>1,3(B+C)

– Static angle of heel θ1 (first intersection point) shall notbe 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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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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5. Damage stability criteria

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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.

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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waveshydhydtotal FηCηBηA)(M

6. SEAKEEPING. PHASE I

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• 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

6. SEAKEEPING. PHASE II

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• Frecuency domain analysis.

• Wave direction. Fore sea (0º)

• Heave, surge and ptich are themost important responses.

• Heave resonance period 17,5 s.

6. SEAKEEPING: NACELLE ACCELERATIONS

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FASE I

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

FASE II

7. MOORING SYSTEM.

P Platform position at sea

Definition of mooring

system

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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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8. MOORING.

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Static analysis

Horizontal design force effect (90 ton)

Same effect with 620 m lines(90 ton)

Horizontal offset 143 m and ptich angle 6,4 º

Fairlead tension in fore lines: 83 ton

Reduction change length 620 m.

Horizontal offset 61 m y pitch angle 6,1 º

Fairlead tension in fore lines: : 106 ton

Dynamic analysis in different seastates

8. MOORING.

Dynamic analysisSEASTATE 1. NORMAL OPERATION

• Low excurssions and rotations.

• Tension (95 ton) far from breaking loads.

• Mooring system is suitable.

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SEASTATE 2. EXTREME OPERATION

Bigger tensions (140 ton) although far from breaking loads.

High motions. ¿is it possible wind turbine running?

Developer has to decide

SEASTATE 3. 50 YEARS STORM

Tension 250 ton Chain grade R3.

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8. MOORING. FINAL ARRENGEMENT

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

Características generales

8. STRUCTURAL DEFINITION.

• Local Design DNV OS-C101 Rules

– Hydrostatic pressures

– Dynamic affects

• Global Design Buckling, fatigue

Column-Pontoon nodes definition

Deck-columns definition.

FEM methods

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8. MAIN SECTIONS

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PONTOONS COLUMNS

8. STRUCTURE. GENERAL VIEW.

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8. NODE STRUCTURAL DETAIL

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COLUMN WITH DECKS

TOWER WITH DECK

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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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Lighting, signaling and buoying

Access and docking

Comunications: SCADA system

Paint and cathodic protection.

9. Ancillary systems

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10. Electric engineering.

Uninterrupted power system (UPS)

120 Ah / 60 kVA / max current 115 A

Situated in pump rooms

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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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11. Construction and installation: 3,5 years

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11. Operation and maintenance

20 years lifecycle operation

Dismantling vs increasing lifecycle

Operating a vessel in property

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12. Costs

Shipowner of

Vessel

Decrease other

expenditures

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12. Viability

Rendimiento del

dinero prestado: 8%

Rate 190 €/MWh

TIR 1%

Thanks.

ramonbarturen@gmail.com

bernardinocounago@gmail.com

Rights reserved to autors and Politechnic University of Madrid (UPM)

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• 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: