Superconductor based fusion energyorbit.dtu.dk/files/2369422/Superconductor_based_fusi… · · 2012-02-29Superconductor based fusion energy Asger Bech Abrahamsen, Ph.d., Senior

Superconductor based fusion energyAsger Bech Abrahamsen, Ph.d., Senior Scientist

Materials Research Division, Risø-DTU, RoskildeFusionsklassen, ScienceTalenterMærsk Mc-Kinney Møller VidencenterSorø, November 15 (2010)

Risø DTU, Technical University of DenmarkRisø DTU, Technical University of Denmark

Outline• Can fusion prevent global warming?

• The Energy challenge

• Fusion and magnetic confinement

• Geometries and realizations

• ITER and superconductivity

• Superconductors for the fusion reactor beyond ITER

• Superconducting wind turbines?

• Conclusion

15-11-2010Fusions Klassen, Science Talenter


Motivation : Sex

[ ]( )tNtN βα −= exp)( 0

Birth rate : α(N, food, pollution, techno, energy,. )

NNdtdN βα −=

Birth rate : α Death rate : β15-11-2010Fusions Klassen, Science Talenter


The energy Challenge

• Coal, oil and natural gas → CO2 emission → Global warming• UN recommendation : 60-80 % fossil fuel reduction by 2050 • Fusion is a long term alternative for stable & clean energy.



Fusion time line

15-11-2010D. Clery, Science 314, 238 (2006)

Fusions Klassen, Science Talenter


Fusion

Star based• H + H → He + energy• Confinement by gravity

Earth based• D + T → 4He + n + 17.6 MeV• 6Li + n → T + 4He + 4.78 MeV• 7Li + n(E>2.5 MeV) → T + 4He + n

Fuels• Water contains 30 g/m3 of D• Li can be found in earth crust

Conditions• T > 100 million oC

15-11-2010

SOHO,NASA



Magnetic confinement of a plasma

• Plasma = gas of nucleus D+, T+ & 4He2+ and electrons e-

• Charge neutral• Plasma pressure:

• Magnetic energy density:

• Plasma and magnetic pressure ratio:

• Energy production:

Tnkp B=n: particle density

kB: Boltzman

T: Temperature

[ ] PamN

mNm

mJB

====⇒= 2330

20

2ε

µε B0: Magnetic field

μ0: Vac. permeability

εβ eion pp +

=

+

= 32

40

2

13.4

mMW

TeTiBPDT

β



Particle movement

• Equation of motion of a charged particle:

• m: Mass• v(t): Velocity• q: Charge• E(r,t): Electric field• B(r,t): Magnetic Field

• Circle movement in homogenous field • Gyro radius

[ ]),()(),()( trBtvtrEqdt

tvdm ×+=

qBmvR ⊥=

e-D+

VeVD

fefD

BR



Coil

Field lines

Torus geometryHomogenous magnetic field inside torus

Non-homogenous magnetic field• Magnetic gradient drift: Vd,grad ~ Φ x R Φ: magnetic flux• Centrifugal drift: Vd,cen ~ R x Φ R: Radial vector

• Positive charges drift down and negative up → Instability



TokamakSolving ideal magnetohydrodynamic equations suggest helical B field

• Induce plasma current by central coil to generate poloidal field component → Pulsed operation.

D. Clery, Science 314, 238 (2006)



Stellarator• Helical magnetic field inside torus created by DC coils

• Upcoming technology decades behind tokamak machines• NbTi superconductor: B = 6.7 tesla @wire & T = 4.2 K

WENDELSTEIN 7-X, Garching(D)



Superconductors and high magnetic field

• Electrons pair due to lattice distortion• Quantum fluid of Cooper pairs (+k↑, -k↓)• R = 0 !

• Magnetic field causes rotational flow• B = 0 Meissner state H < Hc1

• Vortex state Hc1 < H < Hc2

• Quantization of flux Φ0 = h/2e



Vortex movement and pinning

• Lorentz like force is acting on vortex lines when a supercurrent is flowing• Energy dissipation → Flux flow resistance• Pining by defects & impurities• Same size as vortex core • R = 0 only when J < JC

H

H = 0.002 Tesla

J

zJf 0Φ×=

f

∫= fdxw

Pinning centers



Critical surface of practical superconductors

15-11-2010

• Temperature • Magnetic field (angular)• Stress• Thermal cycling• Magnetic field cycling

• Neutron dose

Engineering current density

Je,Cu ~ 2-7 A/mm2

= 2mm

AA

IJconductor

Ce



Creating magnetic fields: Soleniod

15-11-2010

tJHBtJHtlJHl

dSJHdl

dSJdSH

JH

e

e

e

00 µµ ===

⇒=

⇒=

⇒=×∇

⇒=×∇

∫ ∫∫∫

l

t

a0



Superconducting materials

• Most simple metals• Metallic alloys• Semiconducting ceramics !

Gurevich at. al., SuST17,278 (2004)



International Thermonuclear Experimental Reactor(ITER)

• Plasma• Rmajor: 6.2 m• Rminor: 2.0 m• Volume: 840 m3

• Current: 15.0 MA• Temperature: 108 oC

• Toroidal B: 5.3 tesla• Power: 500 MW• Burn: > 400 sec• Amplification: > 10

• Price: 5 Billion €• 25 % to superconductors• Site: Cadarache (F)



Toroidal field coils• 18 coils : 9 x 14 meter

• Nb3Sn superconductor (760 km x 18)

• B = 11.8 Tesla @ conductor

• Forced flow liquid Helium

• I = 68 kA

• Transverse force : 800 kN / m80 tons / m

• Stored energy : 2300 MJ / coil

• Je = 67 A/mm2



Wire → cable → coil

• Wire: Nb + Sn in metal matrix → Nb3Sn• Nb3Sn is brittle !• Wind coil & react at T = 650 oC & 240 hours• Cable: Center flow tube for Liquid He

Wires wrapped in CuStainless steel conduit

• Insulation applied after heat treatment



Central field coil

• Nb3Sn superconductor (1489 km x 6)• Stabalizer : Cu• Conduit: Nickel superalloy

• B = 13.5 tesla @ conductor• I = 46 kA, Je = 45 A/mm2

• Ramp rate : 1 tesla / sec



Outer poloidal and correction coils

• 6 coils : R = 4.5 m, 8.5 m & 12.0 m• NbTi superconductor• Stabalizer : Cu• Conduit: Stainless steel

• B = 5 & 6 tesla @ conductor

• 18 correction coils:• NbTi superconductor• B < 5 tesla @ conductor



The fusion reactor in 2050Beyond ITER (Power Plant Conceptual Study PPCS report, EFDA 2005 )

Model A B C DP(GW) 5.0 3.60 3.41 2.53

TFaxis(T) 7.0 6.9 6.0 5.6

TFcond(T) 13.1 13.2 13.6 13.4

Efficiency 31 % 36 % 44 % 60 %

ITER : TF on axis = 5.3 Tesla

TF on Nb3Sn = 11.8 Tesla

PPCS : 20 % improvement &

½ price !15-11-2010Fusions Klassen, Science Talenter


Choice of superconductor?

• Can we get the high temperature superconductors ready? SuST19,S27(06)

40 60 80 100 120200

0

60

80

100

T [K]

Hc2 [T]

YBa2Cu3O6+x Bi2Sr2Ca2Cu3O10+x

20

40



Choice of superconductor?

American Superconductor(AMSC) 2G HTc

Grivel, Risø

SuST19,S27(06)

SuST19,S4(06)

Sumitomo



Superconducting wind turbines?


500 km

120 GW10 MW

12000 units120 x 100 km

v0

A = πR2

20 0

0

12

RP v Av Cpvωρ

=


Generator principle

2Power BI D l ω∝

1G : Copper + Iron2G : Permanent magnets + Iron3G : HTc Superconductors

I

B

l

r

• Lorentz force on wiref = I × B l

• Torque on wiresτ = 2 r × f

= BI Dl

• PowerP = τ ω

f

Direct drive: 1500 rpm → 15 rpm !Increase size or increase BI



5 MW Multi-pole synchronous generator


Warm rotor and stator Fetcryostat ~ 4 cm

Bairgap ~ 2.3 TeslaBFe < 2.5 TeslaAstator ~ 90 kA/mCu loss ~ 5 %

• 24 poles • R = 4.2 m• Lactive = 1.2 m• mactive = 34 tons

• Compete with Nd2Fe14B PM• Using only kg of Rare Earths elements instead of tons


Conclusion• Fusion is a long term strategic technology

• Energy security and backup for renewable sources

• Superconductor are likely to play a central role using magnetic confinement.

• Low temperature superconductor will do the job… But

• Depend on Liquid Helium• Operate at low temperature -> Expensive• Will become activated by the neutron radiation

• Are the High temperature superconductor ready? In principle but more research and development are needed.

• Superconducting wind turbines as a first step?



ContactAsger Bech Abrahamsen

Superconductivity and magnetism groupMaterials Research DivisionRisø National Laboratory for sustainable energyTechnical University of DenmarkBuilding 229, Room S47Frederiksborgvej 399DK-4000 RoskildeDenmark

Tel.: +45 4677 4741Fax.: +45 4677 5758Mobile: +45 2617 8757E-mail: [email protected]


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Superconductor based fusion energyorbit.dtu.dk/files/2369422/Superconductor_based_fusi… · · 2012-02-29Superconductor based fusion energy Asger Bech Abrahamsen, Ph.d., Senior