Aishwarya Kumar (2010102002)Bhargavi Ganesh (2010102014)Deepika Ramesh (2010102018)
•Offshore Wind Technology
•Objectives of Project
•Methodology
•Design of Structure
•Results
•Conclusion
• Introduction
• Global Scenario
• Potential and Application in India
To conduct the structural analysis of
possible supporting structures for an
offshore wind turbine
To design a suitable supporting structure in
accordance with the specific site conditions
•Introduction
•Software Used
•Schematic Diagram of Methodology
•*Load Estimation & Load Cases
•*Input parameters
•Power Production at Site
Capacity of selected turbine: 1.5 MW
Location of Site: Off the coast of Rameshwaram
Steps involved:
STAGE I: Load Estimation
STAGE II: Soil Structure Interaction
STAGE III: Structural Analysis & Design
STAGE IV: Power Production at Site
Software Used:
1) FAST (developed by NREL)
2) USFOS (developed by SINTEF marintek & NTNU)
Stage Code/ Theory based onSoftware
Used
I. Load Estimation
Aerodynamic Loads on turbine IEC 61400 – Part 1 (2005) FAST
Hydrodynamic Loads on tower Airy’s Theory, Morrison Equation
USFOS
Wind Loads on tower IS 875 – Part 3 (1987) USFOS
II. Soil Structure Interaction API RP 2A-WSD (2007) USFOS
III. Structural Analysis & Design IEC 61400 – Part 3 (2009),API RP 2A-WSD (2007)
USFOS
STAGE I: Load Estimation
•Aerodynamic•Hydrodynamic•Wind
STAGE II: Soil Structure Interaction•Foundation: Monopile•Modeled as springs in axial and lateral direction at every 5 m
STAGE III: Structural Analysis & Design
•Safety criteria: Displacement & Interaction Ratio•Designed such that criteria were met
Data obtained: Wind speeds at
10 m & 20 m above MSL from
September 1991 to August 1993
Collected at site in Rameshwaram
(09°13’40”N, 79°20’35”E)
Power Law used to extrapolate
speeds at different elevations
Power curve generated for site
0
200
400
600
800
1000
1200
1400
1600
0 5 10 15 20 25 30
Pow
er (k
W)
Wind Speed (m/s)
Power Curve
Turbine Parameters
Capacity of Turbine 1.5MW
Wind Turbine Class Class 2
Turbulence Category B
Cut-in Speed 5.0 m/s
Rated Speed 11.5 m/s
Cut-out Speed 25.0 m/s
Rotor Diameter 70.0 m
Hub Height84.3 m (from MSL to hub
of turbine)
Tower Parameters
Tower Height 80.0 m
Diameter of Tower 4.0 m
Thickness of Tower 0.05 m
Material of Tower Steel
Pile Parameters
Type of Foundation Monopile
Diameter of Pile 3.5 m
Thickness of Pile 0.085 m
Length of Monopile 30.0 m (below mudline)
Length of Monopole 15.0 m (above mudline)
Material of Pile Steel
Young’s Modulus of Steel 200,000 MPa
Yield Strength of Steel 250 MPa
Turbine parameters are defined by the manufacturer – This study uses the properties defined by NREL (inbuilt in FAST)
Design of Structure
Tower Height = 80 m
Hub Height = 85 m
Monopile Length= 30 m
Monopole Length = 15
m
Depth of Water = 10 m
Total Height of
structure above mudline
= 95 m
Turbine
Tower
Monopole
Monopile
30 m
15 m
80
m
10 m
85
mMSL
Mudline
•Displacement & Interaction Ratio
•Capacity of Tower
•Bending Moment & Shear Force Diagrams
•Simulation on USFOS
•Power Production
DISPLACEMENT
According to Nicholson (2011):
Limiting value: 1.25% of height of structure above mudline
(i.e. 95 m) (=1.1875)
INTERACTION RATIO
According to API RP 2A-WSD (2007):
Limiting value: 1
Maximum Value Corresponding Case
Displacement 1.16789 m ECD-R+2
Interaction Ratio 0.5979 EWM50
ECD-R+2: Extreme Coherent Gust with Direction Change when wind velocity at hub = Rated speed + 2 m/sEWM50 : Extreme Wind Speed Model with recurrence period of 50 years
Displacement & Interaction Ratio
•The highest value of
displacement obtained
was for Case No. 6. (ECD-
R+2). It occurred at a time
instant of 53.1 s.
•For Extreme Wind speed
Models (EWM), the rotor
stops rotating because the
cut-out speed is reached in
such extreme conditions.
Thus, displacements in
these cases are not
considered for analysis.
0
100
200
300
400
500
600
700
800
374 376 378 380 382 384 386
Ba
se S
he
ar
(KN
)
Time (sec)
TIME-HISTORY RESPONSE OF BASE SHEAR
Maximum Base Shear
0
10000
20000
30000
40000
50000
60000
68 70 72 74 76 78 80 82
Ove
rtu
rn M
om
en
t (K
Nm
)
Time (sec)
TIME-HISTORY RESPONSE OF OVERTURN MOMENT
Maximum Overturn Moment
Parameter Value
Maximum Base Shear 726.735 kN (at 380.1 s)
Maximum Overturn Moment 5.01 x 104 kNm (at 75.1 s)
Maximum Total Axial Load 5.11 x 103 kN
Factored Pile Axial Capacity 1.19 x 104 kN
Factor of Safety 2.5
All the aforementioned maximum values were found to be for the loading case ECD-R+2. Pile capacity was calculated as per API RP 2A-WSD.
B
B) Shear Force Diagram for the
Tower under ECD-R+2 loading
condition at the 53.1 s
A) Bending Moment Diagram for the
Tower under ECD-R+2 loading
condition at the 53.1 s
A
*Maximum Displacement occurred for this case at 53.1 s
*Maximum Displacement occurred for this case at 53.1 s
0.00
5.00
10.00
15.00
20.00
25.00
09/91 12/91 04/92 07/92 10/92 01/93 05/93 08/93
Win
d S
pp
ed
(m
/s)
Time (MM/YY)
Wind Speed (Hub Level)
0.00
500.00
1000.00
1500.00
09/91 12/91 04/92 07/92 10/92 01/93 05/93 08/93
Po
we
r P
rod
uct
ion
(k
W)
Time (MM/YY)
Power Production - 1.5 MW
726
1345
2306
2734
30032836
2389
1411
605
14839 2 00
200
400
600
800
1000
1200
1400
1600
1800
2000
2200
2400
2600
2800
3000
3200
0-2 2-4 4-6 6-8 8-10 10-12 12-14 14-16 16-18 18-20 20-22 22-24 24-26
FREQUENCY DISTRIBUTION
OF WIND SPEEDS AT
HUB
Fre
qu
en
cy
Wind Speed at Hub Height (m/s)
For the Rameshwaram site (using
Power Curve generated):
•Average wind speed = 9.14 m/s
•Standard deviation of wind speed
= 4.12
•Avg. power generated = 0.781 MW
• Plant Load Factor = 0.52
India has potential to support Offshore Wind
Technology
A 1.5 MW capacity turbine gives a PLF of 0.52 at
the Rameshwaram site
Based on analysis, the proposed design is
structurally feasible – further studies are
needed for cost analysis