1. Superconducting Generators for Wind Turbines Abrahem Al-afandi Hamad Almutawa Majed Ataishi Advisor & Client Dr. James McCalley 1

2. Overview Project Background. - What is it? -Why? Objectives. Approach Taken. Suggested Designs. Design Evaluation Methods. 2

3. Project Background  What is it? Inland Direct-Drive Wind Turbines. 1. 5-MW PMSG. 2.10-MW HTS.  Why Direct-Drive? Integrated in nature. Avoiding the need for large, maintenance-intensive gearbox. Reduced size and weight. Efficient & Reliable. RPM 3

4. Objectives Suggested 5MW turbine using permanent magnet generator. Suggested 10 MW turbine using high temperature Superconductor generator.  Each suggested design has: 1.To be Cost-effective. 2.High Energy yield. 3.Low weight and volume. 4.Suitable cooling system. 4

5. Our Approach Top to bottom view of steps taken : components & operation of Generator Direct-Drive vs. Conventional PMSG HTS Different Topologies Suggested Design 1 Materials Different Topologies Materials Suggested Design 2 Designs Evaluation Feasible for 5-MW Feasible for 10-MW Cost Analysis 5 Performance Attributes

6. The Difference PMSG HTS 6 Schematic layouts HTS is lighter for higher MW Cooling Systems

7. Before Choosing Promising Designs There needs to be a balance among electrical, magnetic, thermal, mechanical, and economic factors for a well designed generator. These factors are always conflicting with each other. No matter what kind of methods designers use to optimize, the keys are: 1.Low cost. 2.High reliability and availability. 3.High cost always prevents generators from commercialization. In General, the better topology of DD generators has the maximum output, minimum expenses and highest reliability.

8. 1. PMSG Topologies Air Gap Orientation. 1.Radial has relatively small diameter. 2.Axial ha a compact design. Stator Core Orientation. 3. Longitudinal is used in conventional designs. 4. Transversal has less copper losses, diffi. To con. PM Orientation with respect to air-gap. 5. Surface-Mounted PM is easer to construct. 6. Flux- concentrating PM has higher remnant flux. 8 1. 2. VS. 3. 4. VS. 5. 6.

9. 1. PMSG Topologies Cont. Copper Housing. 7. Slotted has a better retention of the armature windings, but has cogging torque. 8. Slot-less has low cogging torque. Iron Core VS. Coreless 9. Iron-Core has lamination losses and more weight. 10. Coreless eliminates cogging torque and reduce weight. 9 VS. 7. 8. 9. VS. 10.

10. Two Possible PMSG Designs Design 1 Design 2 10 Radial-Longitudinal-Surface Mounted-Iron core-Slotted Inner-rotorOuter-rotor Simple ConstructionAccommodates multi- pole structure due to larger rotor periphery. Good Utilization of active materials With stands demagnetization Relatively Smaller diameter Avoids the increase in mass, Better torque density Outer-rotorDouble-rotor Reduced weight due to high no. of poles Simple Stator construction. Reduced Yoke thickness and armature overhang. Compact. No Cogging torqueNo vibrations Less iron losses and has a greater efficiency Axial-Longitudinal-Surface Mounted- Coreless- Slot-less Axial machines are not suited for MW power ratings, since the outer radius becomes larger, and the mechanical dynamic balance must be taken into consideration.

11. PMSG Materials 11 Three PM materials were investigated. Good Material to be used

12. 2. HTS Topologies Partially VS. fully superconductor. Axial VS. Radial flux. Air-core VS. Iron-core 12

13. Fully VS. Partially Fully Partially StrengthsWeaknesses Highest power density High AC losses Almost ½ the mass of partially SC Complicated cooling system (needs high power) Smaller air-gapIncrease the use of HTS> high cost. StrengthsWeaknesses Expected low AC loss (Damper shell) Air-gap is relatively large(using thermal Isolation Low cost ( SC only in field winding) Increased weight Rotating sealing(only with rotating field) Partially is dominant until a breakthrough in AC losses is made

14. Axial VS. Radial Axial Radial 14 StrengthsWeaknesses High power per unit volume Lower torque to mass ratio Shorter than radialStructurally unstable when diameter is large CompactHeavier than radial machines. StrengthsWeaknesses Suitable for MW DD due to large diameter. Lower torque to volume ratio Widely used in wind project. Simple Mech. Structure easier to be made stable enough. Suitable for MW class

15. Air-core VS. Iron-core Air-core Iron core 15 StrengthsWeaknesses Popular for 10 MW SCDDReluctance in magnetic circuit increases > more HTS wires needed > high cost Reduce WeightFor 10KW>7.5km Better transient stability (sy. Reac. Smaller) Higher peak torque and current when short circuit faults occur. For stator: better cooling scheme, no cogging torque, small air gap flux harmonics, reduce vibration, better insulation but causes cooling difficulty EMF acts directly on HTS coils > limits performance. StrengthsWeakness Less HTS wires>less costPresence of iron increases rotor mass. Better SC coil performances & higher sync. Reactance. Subject to eddy current losses. For 100KW> 2.6 kmFor stator: iron teeth brings unwanted teeth harmonics. For stator: possible to use iron teeth with less losses due to low freq. 10hz. Can reduce cost of HTS For Stator: Highly saturated. Offers robust mechanical support for armature windings. Less comp For Stator: Highly saturated. Offers robust mechanical support for armature windings. Less complicated. Less expensive. For Stator: cogging torque. Promising if HTS price goes down Better performance

16. HTS Material 16

17. Recommended Design 1 5-MW PMSG wind Generator: 17 Radial Inner-rotor Outer-rotor

18. Recommended Design 2 10 MW SCDD Wind Generator: Partially SC with HTS field winding on the rotor. Stationary armature windings. Radial flux machine. Iron-cored rotor with iron teeth stator winding. 18 From AMSC

19. Performance Attributes 19 A good design should not only have high torque density, but it has to have a low cost/torque ratio. This picture shows that RFPM has a relatively low Torque density. This picture shows that RFPM has the lowest cost/torque ratio. (good) Comparison table

20. Cost Analysis Model Existing model From the National renewable energy lab. The purpose of the model is to calculate ICC, AOE. The Model is valid for: 1-Power range from 0.75MW - 5MW. 2-Rotor diameter: 80m-120m. It is valid for extrapolation for power output up to 10MW and rotor diameter of 200m.

21. Variables For cost evaluation we need to get: AEP(Annual Energy production). ICC(initial capital cost). AOE(Annual operating expenses). FCR(Fixed charge rate). COE(Cost of Energy).

22. AEP AEP = CF(capacity factor) * rated power * 8760 hours The capacity factor varies depending on the wind farm. -AEP for 5MW generator is = 13.14GWh. -AEP for 10MW generator is = 26.28GWh. -The uncertainty percentage is: -+/- 0.02 for 5MW generator. -+/- 0.05 for 10MW generator.

23. Generator5 MW10 MW AEP13140 MWh26280 MWh ICC (total)5583.62k $25510.96k $ AOE145.4k $290.6k $ COE0.061 $/KWh +/- 0.05 0.13 $/KWh +/- 0.09 Calculated Results

24. Design evaluation Methods We were given 4 ways to evaluate our designs: 1- Evaluation using proper software. ✖ 2- Hardware evaluation. ✖ 3- Literature review. ✔ - Technical papers. - IEEE articles and researches. 4- Industry experts. ✔ - AMSC(HTS). - ABB & Gamesa(PMSG). 24

25. Cost Analysis Evaluation Validating AEP:

26. COE in $/KWh for different power ratings and diameters:

27. Cost Estimation Cost Estimation

28. Remarks Wind turbines are growing in power capacity with each new generation. Wind farm economics is demanding increased reliability to minimize cost and maximize productivity. More power per tower. 28

29. Question? 29