1. Estimation of the Optimum Wind Turbine Size for Two Different Offshore Sites and Wind Farm Rated Powers
MSc. Candidate: Shajid Kairuz Fonseca Supervisor: Dr. ir. Michiel B. Zaaijer Faculty of Aerospace Engineering Wind Energy Department August 30th 2017

2. Outline Introduction Approach Models Results Sensitivity analysis
Conclusions and recommendations

3. Outline Introduction Approach Models Results Sensitivity analysis
Conclusions and recommendations

4. Problem Overview: Large turbines more energy yield, but high costs
Which is the optimum turbine size?
Difficulties:
The industry has not reached to this optimum size
Lack of data regarding turbine components dimensions and costs
The optimum turbine size is not the same for all situations

5. Objectives: Main Objective
Gain insight into the optimum size of wind turbines for offshore applications.
Specific Activities
Determine scaling approach for main components of an offshore wind farm.
Determine how the cost of the components changes for different turbine scales and case characteristics
Establish a cost of energy function to identify the optimum turbine size in each case.
Determine components that have largest impact on optimum turbine scale with a sensitivity analysis. 

6. Outline Introduction Approach Models Results Sensitivity analysis
Conclusions and recommendations

7. How to define ‘size’ for a wind turbine?
The turbine size is defined in terms of the turbine power and the rotor diameter
Although a correlation may be expected between these two parameters they are independent from each other

8. What is optimum?
The Levelized Production Cost (LPC) is the objective function
Composed by:
Cinvestment  Capital investment costs
CO&M  Operation and Maintenance costs
Cdecommissioning  Decommissioning costs
r  project discount rate
T  project lifetime
A  Annuity factor
Ey  Energy yield

9. Which LPC components to model?
Costs:
Turbines
Support Structure
Electrical Infrastructure
O&M
Energy yield
Individual turbine energy yield
Wake efficiency
Electrical losses
Availability

10. How to approach upscaling?
Square cube law
Empirical Analysis

11. Case Studies
Since the optimum turbine size is not the same for all situations
Far North Sea
Baltic Sea
Farm rated power  500MW
Distance to grid  100km
Water Depth  40m
Farm rated power  100MW
Distance to grid  20km
Water Depth  15m

12. The MZ tool Outputs: Inputs: System Farms Support structure Sites
Layout
Electrical system
Maintenance
Cost Details
Inputs:
Farms
Sites
Turbines

13. Outline Introduction Approach Models Results Sensitivity analysis
Conclusions and recommendations

14. Turbines cost model
Blades costs ≈ 32% of turbine cost excluding tower and transformer
Other components as:
Direct drive generator
Power converter
Pitch system
Cost models taken from (L. Fingersh et al., 2006) NREL

15. Turbines cost model - Blades
Driver of blades cost  materials  carbon fiber  hybrid carbon-glass fiber blade

16. Support structure cost model
Monopile foundation  most used for offshore wind farms & suitable up to ≈ 40m
Main drivers for the cost:
Water Depth  Site location
Wave conditions  Site location
Thrust Force  Turbine characteristics (Pnew & Dnew)
Assuming that the new turbine achieves the same maximum CP & rated wind speed as the reference turbine (V80-2MW)
Scaling law:
Specify the concept: Monopile
Components: Monopile, transition piece, tower, scour protection etc

17. Support structure cost model
MZ inputs
Maximum operational thrust  scaling law
Rotor radius  empirical approach
Yaw diameter  square cube law
Front area nacelle  square cube law
Tower top mass  square cube law
MZ outputs
Technical data & costs of:
Monopile
Transition piece
Tower
Scour protection
Installation foundation

18. Support structure cost model
Power
Thrust
Diameter

19. Electrical Infrastructure cost model
HVAC system  cost effective up to km
Main components:
Cables
Transformers
Shunt reactor
Switch gear
Largest weight in the total cost of the system
Dependent on:
Distance to shore  Case characteristic
Farm rated power  Case characteristic
Turbine rated power  Turbine characteristic
Specify the concept: AC transmission, also the components that make the whole: cables, transformers, switch gear, shunt reactor

20. Electrical Infrastructure cost model
MZ tool inputs:
Distance to shore  (100km for Far North Sea & 20km for the Baltic Sea)
Voltage at grid coupling point  400kV for both cases
Voltage of the turbine generator  empirical approach for the upscaled turbines
A square layout is established

21. Electrical Infrastructure cost model

22. O&M cost model The MZ tool requires of the following inputs:
Preventive maintenance cost & frequency
Consumables repairs costs
The MZ tool gives the following outputs:
Their cost increase linearly with the ratio of the turbine powers
Operation costs
Administration
Grid charge
Bottom lease
Maintenance costs
Consumables repairs & service
Personnel
Access vessels
Lifting equipment
Subsea inspections

23. O&M cost model
After using the MZ tool the cost models developed for the O&M components:
Administration – fixed cost for both cases
Grid charge – proportional to farm energy yield
Consumables repairs
Consumables service
Bottom lease – proportional to the farm area:
Fixed cost per case  dependent on farm rated power

24. O&M cost model
After using the MZ tool the cost models developed for the O&M components:
Personnel
Access vessel
Lifting equipment
Subsea inspections
Good correlation with the number of turbines in the farm, and therefore to the turbines rated power

25. Energy yield model Energy yield of a wind turbine 
Thr  Number of hours in a year
Vin  cut-in wind speed
Vout  cut-out wind speed
P(U)  wind speed U  power curve
f(U) du  Weibull distribution
Difference of 0.5Wh/y between 1.95MW to 20MW
Specify the height for the weibull parameters: 100m, mention it in the final report

26. Outline Introduction Approach Models Results Sensitivity analysis
Conclusions and recommendations

27. Results
After introducing the components costs and the energy yield model in the LPC function:

28. Results
LPC as a function of the turbine power for the optimum turbine sizes in the range from 2 to 20MW in steps of 1MW
Optimum turbine size  11MW-176m
Optimum turbine size  6MW-147m

29. Results
Behavior in the contribution to the LPC for different components plus the energy yield trend for the optimum turbine sizes in the range from 2 to 20MW in steps of 1MW for the Far North Sea case

30. Outline Introduction Approach Models Results Sensitivity analysis
Conclusions and recommendations

31. Far North Sea case
Sensitivity of the model when varying some components costs
Also:
The lower the price ratio of carbon fiber to glass fiber, the larger the optimum size hypothetical case of just glass fiber  15MW )

32. Baltic Sea case
Sensitivity of the model when varying some components costs
Also:
The lower the price ratio of carbon fiber to glass fiber, the larger the optimum size hypothetical case of just glass fiber  10MW )

33. Outline Introduction Approach Models Results Sensitivity analysis
Conclusions and recommendations

34. Conclusions
The optimum turbine size is result of trade-off between components that their cost reduce and the components that their cost rise as turbine scale increases.
The optimum turbine rated power for a far offshore, large wind farm is in the range of 10 to 13MW while for a small, near shore wind farm is in the range of 5 to 7MW.
The blades cost are a limiting factor for the increment in rotor diameter for large turbines scales.
The main objective of the project was achieved which was getting insight into the upscaling of wind turbines for offshore applications.

35. Recommendations
Incorporate support structure cost models of other foundations types and an electrical infrastructure cost model for HVDC transmission, so the model is more versatile.
Obtain actual costs of the largest blades manufactured nowadays so that these real costs are compared to the ones given by the blade cost model.

36. Thank you for your attention! Questions?

37. Approach
Annuity factor
Real interest or discount rate

38. Approach Full list of OWF components: Capital Investment:
Support Structure
Electrical Infrastructure
Turbines
Boat landing structure
Offshore Platform
Measuring tower
Onshore premises
Harbor use
Warranty
Transportation of the RNA onshore
Installation of the RNA offshore
Dune crossing
Grid connection
Transmission cable installation
Infield cables installation
Engineering
Site assessment
Management
O&M:
Administration
Grid charge
Bottom lease
Insurance
Personnel
Access Vessels
Lifting Equipment
Subsea inspections
Consumables repair
Consumables service
Management
Decommissioning:
Removal of the RNA’s
Removal of the foundations and scour protection
Removal of the offshore platform and meteo tower
Removal of the transmission cable
Removal of the infield cables
Site clearance
Disposal of the RNA’s
Management

39. Cost models
Turbine - Blades
Spare

40. Cost models Turbine - Blades weight ratio material cost ratio
total cost ratio

41. Cost models
Turbine - Blades
Spare

42. Cost models
Support structure cost model 
(5)
(6) 
(7)
(8)

43. Cost models
Support structure cost model

44. Cost models
Electrical Infrastructure - Layouts

45. Cost models
Electrical Infrastructure – Generator Voltage

46. Cost models
Electrical Infrastructure

47. Cost models
O&M

48. Cost models
O&M

49. Cost models
O&M

50. Energy yield model
Wind speed scaling for different heights:

51. Energy yield for the Baltic Sea case computed with the MZ tool
Energy yield model
Energy yield for the Baltic Sea case computed with the MZ tool

52. Energy yield model
To determine the power curve for the upscaled turbines:
Assume that upscaled turbines achieve the same maximum CP at rated power as the reference turbine (V80-2MW)
Adjust the wind speed axis of the power curve for the upscaled turbines with Ec.6
Vnew is introduced in Ec. 5 and using the same power coefficient values that the reference turbine has  power of the upscaled certain wind speed
Repeating step 3 for the velocity range of Vin to Vout  power curve dependent on the rotor diameter and the turbine power 
(5)
(6)

53. Increment when going from 400 to 300W/m2
Results
After introducing the components costs and the energy yield model in the LPC function:
Increment when going from 400 to 300W/m2
LPC as a function of the power and the rotor diameter for the Baltic Sea case

54. Results
Far North Sea

55. Results
Far North Sea

56. Results
Far North Sea

57. Results
Baltic Sea

58. Results
Baltic Sea

59. Results
Baltic Sea
Behavior in the contribution to the LPC for different components plus the energy yield trend for the optimum turbine sizes in the range from 2 to 20MW in steps of 1MW for the Baltic Sea case

60. Results
Baltic Sea

61. Results
Gradients comparison of the dominant components in the model results for the Far North Sea case
Gradients comparison of the dominant components in the model results for the Baltic Sea case

62. Sensitivity study
Far North Sea
Baltic Sea

63. Sensitivity study
Far North Sea

64. Sensitivity study
Baltic Sea

65. Sensitivity study
When the costs of the consumables repairs scales with the ratio of the upscaled turbine rated power to the reference turbine rated power to a power larger than 1

66. Appendix
Characteristics of the case studies:

67. Appendix
V80-2MW technical data:

68. Retrieved from: https://www. technologyreview