TECHNICAL PAPER - 2H Offshore

TECHNICAL PAPER

Offshore Wind Energy for

Australia, A Case Study with a

Floating 15MW Turbine

Nitin Repalle, Yusuf Arikan and Mike Campbell

AOG March 2021

AOG Energy | Offshore Wind Energy for Australia - A Case Study with a Floating 15MW Turbine

2021

Nitin Repalle, Yusuf Arikan and Mike Campbell2H Offshore Engineering

Learn more at www.2hoffshore.com

• Introduction to NREL 15MW Wind Turbine

• Numerical Modelling and Validation

• Floating Foundation - Stinger Keel Concept

• Floater Mooring Configuration Optimisation

• Fully Coupled Analysis Results

• Pilot Site In Australia

• Wind Profile

• Energy output

• Levelized Cost of Energy (LCOE)

• Summary and Conclusions

Agenda


NREL 15MW Reference Wind Turbine Generator – Released March, 2020

240m15 000kW

Height 270m

NREL 15MW WTG

12MW GE Haliade-X220m Rotor DiameterPrototype - 2019Certification - 2020Serial Production - 2021

Wind Turbine Generator Capacity and Blade Sizes

Show Increasing Trend into the Future Learn more at www.2hoffshore.com

NREL 15MW Reference Wind Turbine Generator

342 km/h


-5.00

0.00

5.00

10.00

15.00

20.00

25.00

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

wind speed (m/s)

15MW Published (Monopile) vs OrcaFlex (Fixed)

Blade Pitch (deg) Rotor RPM Torque (MN.m) TSR

PITCH RPM TORQUE TSR

NREL-15MW Turbine – Model Validation

Reference

Model

0

0.5

1

1.5

2

2.5

3

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Pow

er M

W

Wind Speed (m/s)

NREL 15MW Reference WTG

POWER THRUST

Thru

st M

N

• Power is produced with wind speeds 3m/s to 25m/s

• After rated wind speed of 10.6m/s blades start to pitch to keep power production at rated 15MW. Turbine is parked for wind speeds over 25m/s

Numerical Model show excellent correlation (<2% difference) to the reference model Learn more at www.2hoffshore.com

Floating Foundation - Stinger Keel Concept

• Developed by Floating Energy Systems (FESL), UK (https://floatingenergysystems.com/)

• A hybrid system between spar and semi-submersible.

• Deployable ballast keel frame (stinger) stays in horizontal during transit, and deployed to vertical for operation.

• Stability is provided by ballast weight like spars, turbine tower and turbine are installed at quayside like semi-submersible (no need for heavy lift vessel)

• 1/50 scale model wave tank tested in September 2020


https://floatingenergysystems.com/

15MW Stinger Keel Foundation

15MW NREL Stinger Keel Foundation Data

Total height 132m

15m water level to turbine tower base

Minimum operating water depth 130m

COG 77.5m below MWL

~4400 Te Steel weight

~2500 concrete weight

~7500Te Ballast weight

Total ~14,500Te without turbine

Turbine tower base


CAD Model Panel Model

15MW Stinger Keel Hydrodynamics


0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

0 5 10 15 20 25 30 35 40 45 50

m/

m

Period s

Heave

0 deg 30 45 90

0.00

0.10

0.20

0.30

0.40

0.50

0 5 10 15 20 25 30 35 40 45 50

de

g/

m

Period s

Roll

0 deg 30 45 90

0.00

0.10

0.20

0.30

0.40

0.50

0 5 10 15 20 25 30 35 40 45 50

de

g/

m

Period s

Pitch

0 deg 30 45 90

Used in Coupled Analysis (Load RAOs)

Hull Only

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

0 5 10 15 20 25 30 35 40 45 50

m/

m

Period s

Heave

0 deg 30 45 90

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 5 10 15 20 25 30 35 40 45 50

de

g/m

Period s

Roll

0 deg 30 45 90

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 5 10 15 20 25 30 35 40 45 50

de

g/

m

Period s

Pitch

0 deg 30 45 90

Used in Free Decay Tests

Hull & Turbine/Tower

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

0 5 10 15 20 25 30 35 40 45 50

m/

m

Period s

Heave

0 deg 30 45 90

0.00

5.00

10.00

15.00

20.00

0 5 10 15 20 25 30 35 40 45 50

de

g/

m

Period s

Roll

0 deg 30 45 90

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

0 5 10 15 20 25 30 35 40 45 50

de

g/

m

Period s

Pitch

0 deg 30 45 90

Used in Wave Tank Tests

Hull & Turbine/Tower

& Mooring

15MW Stinger Keel Hydrodynamics

Calculated RAO’s show good match with the scaled prototype Learn more at www.2hoffshore.com

Mooring Configuration Optimisation

• 4 Mooring Configurations Considered

• Semi-Taut with Polyester

• Catenary with All Chain

• Taut with Polyester

• Taut with Nylon

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

Su

rge

(m

)

Foundation Offset

Semi-Taut All Chain Taut-Polyester Taut-Nylon

0

100

200

300

400

500

600

700

800

An

ch

or

Ra

diu

s (

m)

Mooring Footprint

Semi-Taut All Chain Taut-Polyester Taut-Nylon

Taut Mooring with Polyester and Chain provides a good balance for loads, motion and

footprint for the considered water depth of 130m Learn more at www.2hoffshore.com

Fully Coupled Analysis Results

▪ Coupled Model

▪ Turbine Model

▪ Foundation RAOs

▪ Mooring model

▪ Design Load Cases (IEC 61400-3-1)

DLC 1.6 Power Production

Wind speed= Vrated=10.6m/s

Wave=Severe Sea Sate

Hs=6m, Tp=11.2sAnimation Speed = 4X

0

5,000

10,000

15,000

20,000

25,000

0 1000 2000 3000 4000

Po

we

r k

W

Time (s)

Generated Power

0 degree 45 degree 90 degree 180 degree

Average Power = 13.3MW

Governing Operational Load case resulted in 13.3MW of Power over

one hour duration


Pilot site In Australia

Offshore Geraldton WA, 400km North of Perth


Pilot Site Wind Profile

• Wind Data obtained from Australian Government Bureau of Meteorology

http://www.bom.gov.au/climate/averages/tables/cw_008050_All.shtml

• Average monthly wind speed at 3m reference height

• Average monthly wind speed at 15MW WTG hub height (150m)

0.0

2.0

4.0

6.0

8.0

Win

d S

pe

ed

(m

/s)

Average Wind Speed

9am 3pm

0.0

5.0

10.0

15.0

Win

d S

pe

ed

(m

/s)

Average Wind Speed Hub Location (150m)

9am 3pm

α=0.14, IEC 61400-3-1 eq 6


http://www.bom.gov.au/climate/averages/tables/cw_008050_All.shtml

Wind Speed Distribution

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 4 8 12 16 20 24

Pro

ba

bil

ity D

en

sit

y

Wind Speed (m/s)

Wind Speed Distribution (Rayleigh)

January February March April May June

July August September October November December

• Wind Speed Distribution Based on Average Wind Speed

IEC 61400-1 eq 8


Power Production

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

Average Monthly Wind Speed and Power

Average Wind Speed (m/s) Average Power (MW)

Win

d S

pee

d (

m/s

) /

Po

wer

(M

W)

15MW Annual Power Production 58911 MW.hr

Gross Annual Production per MW 3927 MW.hr/MW

Uptime 85%

Net Annual Production per MW 3338 MW.hr/MW

Capacity Factor 38.1%Learn more at www.2hoffshore.com

LCOE for a Single 15MW Floating WTG

Component Unit Cost 15MW-Floating WTG PercentTurbine 1691$/kw $25.4M 16.7%Foundation 1873$/kw $28.1M 18.5%Assembly & Installation 567$/kw $8.5M 5.6%Electrical 1296$/kw $19.4M 12.8%PM, Development, Lease 507$/kw $7.6M 5.0%

Soft Cost (Finance, Insurance) 1023$/kw $15.3M 10.1%O/M (25 years) 178$/kw/yr $66.6M 31.3%Total $170.9 100.0%Based on NREL’s “2018 Cost of Wind Energy Review” Report for Floating WTG , ALL cost in AUD

Turbine Foundation Assembly &Installation

Electrical PM, Devp,Lease

Soft Cost(Finance,Insurance,Decom)

O/M (Annual)

15MW Floating Wind Cost Distribution

LCOE = AUD 170 / MW.hr

Design Life 25 years

FCR = 5.6%

USD to AUD = 1.30


$170

$230

$170

$160

$150

$170$165

$159

$120

$146

$100

$250

LCOE Sensitivity -1GW Floating Wind Farm


Source : RBA Bulletin March 2020

Floating Wind

Floating Wind - Future in Australia ?• Floating Wind is currently the most expensive option

However increasing WTG capacities and decreasing foundation costs is encouraging to keep the concept in the mix of considerations

• Potential Applications • Energy Storage : hydrogen storage technologies gaining

traction and being trialed• Offshore wind to power offshore field operations

• Inter- Continental Power transmission

Source : Equinor Website

Source : Suncable WebsiteLearn more at www.2hoffshore.com

Summary• Fully coupled global analysis of wind turbine, ‘Stinger Keel’ floating foundation,

and the mooring lines has been performed.

• Good accuracy of the model compared to NREL reference turbine and model testing. “Stinger Keel” offers a viable hybrid floating foundation solution for offshore wind

• Catenary, semi-taut and taut mooring configurations with various materials can be developed for floating foundations based local seabed and station keeping requirements

• It is estimated that LCOE will be approximately $170/MW.hr for a single 15MW WTG with floating foundation considering local wind conditions based on case study at the selected location with 25 years design life

• LCOE for a wind farm can be as low as $120/MW.hr considering 35 year design life and 20% savings on CapEx and OpEx costs

• Favourable trend of increasing WTG capacities and decreasing foundation costs is encouraging for uptake of floating wind concepts in Australia.

Authors gratefully acknowledge Gary Ross (FESL) for providing the details of the stinger keel foundation concept and prototype testing data for model validation Learn more at www.2hoffshore.com

Questions ?


Documents

TECHNICAL PAPER - 2H Offshore