PM Generators and the Magnet price development. Drivetrain concepts for wind turbines Bremen, 22.Oct Christian Contini, Dipl.-Ing.

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1 PM Generators and the Magnet price development Drivetrain concepts for wind turbines Bremen, 22.Oct.2012 Christian Contini, Dipl.-Ing. (FH)

2 PM Generator Overview Magnet Price Development Alternatives to Rare Earth Magnets Current Excitation Ferrite Magnets Generators with less magnets

3 PM Generator: General

4 Generator Design Basics Generator dimensioned by torque, not by power Torque ~ Generator Length Torque ~ (Generator Diameter)² Torque ~ Current Cooling limits the current!

5 Generator size depends on Torque, Cooling and Converter System

6 Cross-Section of the Generator Magnets

7 Rare Earth Magnets Contains Nd, Fe, B and Dy Rare means: Not really rare worldwide, but dispersed and not found concentrated

8 Rare Earth Magnets World production 2009: 132 kt NdFeB magnet: 30% weight is Nd

9 Main producer: China Export quota Increasing demand woldwide Opening of mines in US and Australia

10 Rare Earth Magnet Use Used everywhere: Small Motors, Servos, Hard Disks, Capacitors, Electric Vehicle... Wind Turbine: 3000 PMSG-Turbines of 2.5MW each will need 1% of annual Nd production

11 Alternatives to Rare Earth Magnets Current Excitation Ferrite Magnets Comparison with existing design

12 Current Excitation

13 Current Excitation: Replacing PM by iron and copper ~80% more copper More laminated steel Excitation losses Higher weight

14 Cost and weight comparison Rare earth magnet prices based on Okt 2012

15 Generator cost depending on Magnet price and Copper price Ferrite Generator

16 Excitation Loss at Pmax: 126kW

17 Bad efficiency in partial load Cooling system: 73% more heat Slip ring for approx. 200A Excitation current generation Loss can be reduced by squareshaped poles short generator with big diameter Too big for transport as one piece

18 Ferrite Magnets

19 Ferrite Magnets: Raw Materials Iron(III) oxide: Rust Barium or strontium carbonate Mixing and heating of powder Milling, forming and re-sintering Magnetization

20 Ferrite Magnets: Material Properties Prices based on Oct 2012 NeFeB Ferrite Relative [%] Remanence Induction [mt] ,3 Intrinsic Coercivity [ka/m] ,4 Energy Product [kj/m³] ,9 Density [g/cm³] 7,5 4,85 64,7 Energy Product [kj/ton] 40,4 6,2 15,3 Price [ /kg] ,0 Energy Price [ /kj] 1237,62 808,33 65,3

22 Less specific energy: More magnet material Low and stable price: No Rare Earths Woldwide available Stable against demagnetization at high temperatures Corrosion resistant High electrical resistance no losses in magnets

23 Bigger Magnets different Generator Geometry Same outer dimensions, but FLUX CONCENTRATION!

24 Cost and weight comparison Rare earth magnet prices based on Oct 2012

25 Generator cost depending on Magnet price and Copper price Ferrite Generator

27 Same Efficiency Cheaper at NeFeB prices >60 /kg 42% more weight of the active part

28 Other ways to save magnets... Smaller (shorter) generators Can be used with every type of magnets or excitation

29 Half Generator Length Half Torque + Double Current Same Torque Double Current Density 4x specific losses Better Insulation (Class H) Double Losses Bigger Cooling system (2..4x size and losses) Efficiency in full load goes down

30 Cooling system cheap compared to generator Higher class insulation possible and not much more expensive Not linear: Saturation, Coil Heads... Efficiency under real conditions interesting

31 Ferrite generator efficiency including cooling system: Full length vs. 60% length

34 Conclusion NdFeB El. Ex. Ferrite Ferrite, Short Independence on Rare Earth / Copper prices Generator Cost Generator Weight Efficiency Additional Effort o o ++ + o -- + o

35 Thank you for your attention!

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