Cryogenic Efficiency & Losses in AC Power Machines

Dr. Philip Sargent MIM MBCS CDipAF CEng.

Diboride Conductors Ltd.

Power SuperconductorsRefigeration Energy Consumption

(normalised at 4K)Carnot Thermodynamics

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0.40

0.60

0.80

1.00

1.20

1.40

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Temp (K)

EC

Power Superconductors

How far to "Liquid Nitrogen" regime

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60.0%

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100.0%

0 10 20 30 40 50 60 70

Temperature

Ho

w f

ar

to L

q N

2 f

rom

Lq

He

?

Cost of Capital – when the superconductor is costly

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100.0%

0 10 20 30 40 50 60 70

Temperature

Ho

w f

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to L

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rom

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Lower running costs,Cheap capital,

Cheap superconductor

Lower capital costs,Expensive capital

Engineering Needs

• Generators, Transformers, Cables, FCLs, Motors, Grid conditioning, power storage

• Capital cost is most important for all of these in deregulated power markets

• Why superconductors?• Higher power density, 100x the current• Smaller• Lighter (MgB2 is 1/3 the density of Copper)• Cheaper to buy and install• Cheaper to operate• Entirely new capabilities (FCLs)

HyperTech CTFF for MgB2CONTINUOUS TUBE FORMING AND FILLING (CTFF)

Boron Chemistry

• Pyrometallurgy: Mg + B + heat• Powder in tube in situ• Powder in tube ex situ• Powder in tube ex situ + Mg• Powder in tube + HIP

• CVD Mg + diborane• Electrochemistry: Mg-borates in KCL• Other chemical routes… ??

Materials Requirements

• Magnetic Fields 2-5 T (except cables)• AC use requires T > 20 K (cryogenic cost)• Materials parameters:

• Low cost: ~ 10 $/kA.m

• Practical volumes: Je (Jc 105 A/cm2 )

• Low AC losses: W/kA.m at 50Hz.

• Flexible, low Je / strain sensitivity

Targets

• Copper: 6 – 22 $/kA.m (400 to 100 A/cm2)• Bi2223: 100 – 25 $/kA.m (2002 – 2005)

Device kA/cm2 T $/kA.m

Motor 105 4 10

Generator 105 4 10

Transformer 8.104 0.5 - 2 <10

FCL 8.104 0.2 10

Cable 7.104 <0.5 10-100Dick Blaugher, NREL

Market SegmentationMarket Segmentation

100

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10000

100000

1000000

0 2 4 6 8 10

Magnetic Field (T)

Cri

tica

l C

urr

ent

Den

sity

(A

.cm

-2)

Transformers and Fault-Current LimitersMotors, Generators, Energy-storagePower transmissionElectronics

Wire $/kA.m Cost Driver

NbTi (4.2 K, 2 T) 0.90 Materials (Nb)

Nb3Sn (4.2 K, 10 T) 10 Materials (Nb)

Bi-2223 (25 K, 1 T) 25 Materials (Ag)

Y-123 (25 K, 1 T) 4 Capital Plant

MgB2 (25 K, 1 T) 0.8 – 3.6 ? Capital Plant

Competitive Costs

Paul Grant EPRI

1000 100 10 1 0.11

10

100

1000

10000

Y-123 IBAD77K, 0T

Bi-222377K, 0TNKT Target

"Sokolowski Plot" of HTSC Wire Performance and Cost

NbTi4.2K, 2TBi-2212

4.2K, 0TIGC

Nb3Sn4.2K, 12-15 T

$1,000

$100$10 $1 /kAm

Op

era

tin

g C

urr

en

t, Ic

(A

)

Cost ($/m)

Bi-222377K,0T

ASC “50”

Comparative Performance

Paul Grant EPRI

Transformers: a big prizeCost of Ownership in $/kW

2000 ABB SPI Phase I Analysis

Cu (300 K)@ 300 A/cm2

HTS (68 K) MgB2 (25 K)

Losses 60

Cryo -

Wire 5

Total 65

5

25

50

80

5 5

34

8

48

Paul Grant EPRI

First Major Applications

• Current Leads? No.• FCLs ? New capabilities!• Transmission Cables ? • Distribution Cables ?

• Dielectric + thermal + AC lossses• Transformers ? 98% efficient.• Generators ?

• Power stations,Wind turbines?

• Non-Utility Power ApplicationsMotors 68% of industrial powerHalf of that over 750kW

• Power electronics & Cryogenics

Years

Ma

rke

t Sh

are

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100%

10 155

Materials ChangeoversMaterials Changeovers

Effort

Pe

rfo

rman

ce

Technology ‘S’ Curves

Effort

Pe

rfo

rman

ce

Copper-Iron

HTCs

MgB275y 16y

2002

Power Technologies

Conclusions

• Necessary Partner Technologies• Cryogenics, not 99.999% reliable• Power electronics, why use AC if DC can do it?

• Motors• Higher power density, 100x the current• Smaller, Lighter • Cheaper to buy and install• Transport: ships, trains• Environmentally friendly• Prefer wire not tape! 12 April 2002