second-generation hts wire for wind energy applications...application operating field (tesla)...

Symposium on Superconducting Devices for Wind Energy – February 25, 2011 – Barcelona, Spain

Second-generation HTS Wirefor Wind Energy Applications

1

Venkat Selvamanickam, Ph.D.

Department of Mechanical EngineeringTexas Center for SuperconductivityUniversity of Houston, Houston, TX

SuperPower Inc.

Symposium on Superconducting Devices for Wind Energy February 25, 2011 – Barcelona, Spain


Superconductivity can have a wide range of impact on wind energy• Light-weight, higher-power, direct drive turbines

– Preferred for off-shore wind energy for economy & less maintenance– Less than 500 tons for 10 MW compared to ~ 900 tons for conventional direct drive– More efficient, especially at part load– High air-gap flux density

• Superconducting Magnetic Energy Storage to address intermittency– Very efficient, short-term storage, complementing other storage methods

• Low-loss, long-distance power transmission from remote areas– Much reduced right of way (25 ft for 5 GW, 200 kV compared to 400 feet for

5 GW, 765 kV for conventional overhead lines)• Fault Current Limiters and Fault Current Limiting Transformers

• Built-in fault current limiting capability while benefiting from high efficiency• Liquid nitrogen coolant is also dielectric medium (no oil) eliminates the possibility of

oil fires and related environmental hazards

2


2G HTS wire: Great potential for applications• Second-generation (2G) HTS- HTS is produced by thin film vacuum deposition

on a flexible nickel alloy substrate in a continuous reel-to-reel process very different from mechanical deformation & heat treatment techniques used for Nb-Ti, Nb3Sn and 1G HTS wires

– Only 1% of wire is the superconductor– ~ 97% is inexpensive Ni alloy and Cu – Automated, reel-to-reel continuous manufacturing process– Quality of every single thin film coating can be monitored on-line

in real time !

2 μm Ag

20μm Cu

50μm Ni alloy substrate

1 μm YBCO - HTS (epitaxial)100 – 200 nm Buffer

40 μm Cu total

20μm Cu

Symposium on Superconducting Devices for Wind Energy – February 25, 2011 – Barcelona, Spain4

2G HTS wires provide unique advantages

0

200

400

600

800

0 0.1 0.2 0.3 0.4 0.5

Strain (%)

Stre

ss (M

Pa)

SP 2G HTSHigh Je

High Strength 1G HTS Low Je

Nb3Sn Moderate JeLow Strength

1G HTSModerate Je

< 0.

1 m

m

20μm Cu

50μm Hastelloy

20μm Cu

• 2G HTS wires provide the advantages of high temperature operation at higher magnetic fields.

• Mechanical properties of 2G HTS wires are alsosuperior

100

1000

10000

100000

0 5 10 15 20 25 30 35

Applied Field ( Tesla )

non-

Cu

Jc (

A/m

m2

)

YBCO (H//c) YBCO (H//ab) NbTi

Nb3Sn (Internal Sn) Nb3Sn (Bronze)

Symposium on Superconducting Devices for Wind Energy – February 25, 2011 – Barcelona, Spain5

Advantages of IBAD MgO-MOCVD based 2G HTS wires

YBCO

LaMnO3

MgO (IBAD + Epi layer)

Al2O3

100 nm

Y2O3

Hastelloy C-276

YBCO

LaMnO3

MgO (IBAD + Epi layer)

Al2O3

100 nm100 nm100 nm

Y2O3

Hastelloy C-276

2 μm Ag

20μm Cu

20μm Cu50μm Hastelloy substrate

1 μm YBCO - HTS (epitaxial)~ 30 nm LMO (epitaxial)

~ 30 nm Homo-epi MgO (epitaxial)~ 10 nm IBAD MgO

< 0.1 mm

• Use of IBAD MgO as buffer template provides the choice of any substrate– High strength (yield strength > 700 MPa)– Non-magnetic, high resistive (both important for low ac losses) – Ultra-thin (enables high engineering current density)– Low cost, off-the-shelf

• High deposition rate and large deposition area by MOCVD– enable high throughput

• Precursors are maintained outside deposition chamber– Long process runs (already shown 50+ hours)


Successful scale-up of IBAD-MOCVD based 2G HTS wires

• 500 m 2G HTS wire first demonstrated in January 2007 (crossed 100,000 A-m)

• 1,000 m 2G HTS wire first demonstrated in July 2008 (crossed 200,000 A-m)

• Crossed 300,000 A-m in July 2009 with 1,000 m wire.

• 1,400 m lengths are now routinely produced.

• High throughput processing (>> 100 m/h* in IBAD & buffer processes, > 100 m/h* in other processes)

• Manufacturing capacity of few hundred km/year

6*4 mm wide equivalent

040,00080,000

120,000160,000200,000240,000280,000320,000

Nov-01

Jul-02

Mar-03

Nov-03

Aug-04

Apr-05

Dec-05

Aug-06

Apr-07

Jan-08

Sep-08

May-09

Critical Current * Length (A-m)

62 m18 m1 m 97 m

206 m

90 A-m to 300,330 A-m

in seven years

158 m

322 m 427 m595 m

790 m

1,065 m

935 m

1,030 m


7

Meeting application requirements for HTS wire: Superior performance in operating conditions

Application Operating Field (Tesla) OperatingTemp. (K)

Key requirements Wire needed per device (kA-m)

Cables0.01 to 0.1 (ac)

0.1 to 1 (DC)70 to 77

Low ac losses (ac)High currents (dc)

40,000 to 2,500,000

Generators 1 to 3 30 to 65 In-field Ic 2,000 to 10,000

Transformers 0.1 65 to 77 Low ac losses 2,000 to 3,000

Fault current limiters 0.1 65 to 77Thermal recovery

High volts/cm500 to 10,000

SMES 2 to 30 T 4 to 50 In-field Ic 2,000 to 3,000


Wire price-performance is the key factor for commercialization• Today’s 2G wire (4 mm wide, copper stabilized) : 100 A performance at 77 K,

zero applied magnetic field, Price $ 30-40/m = $ 300-400/kA-m.

• At this price, cost of wire for typical device project (other than cable) > $ 1 M (more expensive than the typical cost of the device itself !)Cost of wire for a 500 km cable project = $ 20 M (~ cost of cable project itself !)

Metric Today Customer requirementPrice $ 300 -

400/kA-m< $ 100/kA-m* For commercial market entry

(small market)< $ 50/kA-m* For medium commercial market< $ 25/kA-m* For large commercial market

*at operating field and temperature

Four to 10-fold improvement in wire price-performance needed !Four to 10-fold improvement in wire price-performance needed !


Need for wire performance improvements

• Ten-fold reduction in price essentially impossible with $/m cost reduction.

• Increasing amperage is key to reaching price ($/kA-m) targets

• Opportunity to substantially increase self-field critical current in 2G wire by increasing film thickness

– HTS is still only 1 to 3% of 2G wire compared with 40% in 1G wire and is the only process that needs to be changed in 2G wire for high critical current

• Opportunity to significantly modify in-field critical current performance of 2G wire

– Numerous possibilities of rare-earth, dopant, nanostructure modifications to tailor in-field critical current

9


• SuperPower’s technology operations consolidated in Houston which enabled total focus on manufacturing in Schenectady.

SuperPower-UH 2G wire development strategy

National LabsNational LabsCustomersCustomers

CRADAs

SP staff @ Houston

UH research staff

SuperPowerManufacturing at Schenectady, NY

Manufacturing Operations in NY

Technology in Houston

Manufacturing objectives• High yield, high volume operation• On-time delivery of high-quality wire• Incorporate new technology advancementsTechnology objectives• High performance wires • Highly efficient, lower cost processes• Advanced wire architectures• Successful transition to manufacturing

Best of both worlds : strong and concentrated emphasis on technology development & manufacturingBest of both worlds : strong and concentrated emphasis on technology development & manufacturing


Outline

• Higher performance in operating conditions of interest• Low ac loss wires• Improving yield and reducing cost

11


0

1

2

3

4

5

6

7

8

0 0.5 1 1.5 2 2.5 3 3.5

Jc (M

A/c

m2 )

HTS film thickness

Research MOCVDPilot MOCVD

0

200

400

600

800

1000

0 1 2 3

Crit

ical

cur

rent

(A/c

m-

wid

th)

Thickness (µm)

Goal

12

Need for higher amperage production wires

• Address problems with decreasing current density with thickness

• High currents without significantly increasing film thickness by increasing current density (Jc)

– Microstructural improvement (texture, secondary phases, a-axis, porosity)

– Pinning improvement (interfacial & bulk defects)

• Opportunity to reduce factor of two difference between pilot and research MOCVD systems

2012 – 500 A/cm2014 – 750 A/cm

2016 – 1000 A

Increasing Ic

SP M3-714

Now Ic up to 375 A/cm (150 A/4 mm) in long lengths


Improvement in critical currents of thick film coated conductors with higher rare earth content

13

77K

0

1

2

3

4

5

6

0.9 1.1 1.3 1.5 1.7 1.9

Gd+Y

Jc

(MA

/cm

2 ) 0T1T, //ab1T, //c1T, min


Improved pinning by Zr doping of MOCVD HTS wires

Process for improved in-field performance successfully transferred to manufacturing at SuperPowerProcess for improved in-field performance successfully transferred to manufacturing at SuperPower

• Systematic study of improved pinning by Zr addition in MOCVD films at UH.• Two-fold improvement in in-field performance achieved !


Large improvements in in-field Ic of Zr-doped wires

100 A/4 mm

100 A/4 mm achieved at 65 K, 3 T in Zr-doped wire compared to 40 K, 3 T in undoped wire





Large improvements in in-field Ic of Zr-doped wires

Retention of 77 K, zero field Ic

65 K3 T

40 K3 T

18 K3 T

Undoped wire 0.27 1.02 2.13

Doped wire 0.73 1.99 3.50

Retention factor of doped wire is higher by 2.7 1.9 1.6

77 K zero-field Ic of 2009 undoped wire = 250 A/cm

77 K zero-field Ic of new doped wire = 340 A/cm

Retention factor of doped wire including higher zero field Ic is

higher by3.71 2.64 2.23


Superior performance at 4.2 K in recent Zr-doped MOCVD production wires

In-field performance of Zr-doped production wires improved by more than 50% in high fields at 4.2 KIn-field performance of Zr-doped production wires improved by more than 50% in high fields at 4.2 K

Measurements by V. Braccini, J. Jaroszynski, A. Xu,& D. Larbalestier, NHMFL, FSU

T, K

0 20 40 60 80

Jc, M

A/cm

2

0

10

20

30

40

50

60

Production wire1.1 µm thick HTS filmIc (77 K, 0 T) = 310 A/cm

1 10

100

1000

T=4.2K

I c - 4m

m w

idth

(A)

B (T)

undoped, B perp. wire undoped, B || wire FY'09 Zr-doped, B perp. wire FY'09 Zr-doped, B || wire FY'10 Zr-doped, B perp. wire FY'10 Zr-doped, B || wireJc @ 4.2 K (A/4 mm) 2009 2010

10 T, B ⊥ wire 201 310

20 T, B ⊥ wire 118 183

5 T, B || wire 1,219 1,893

10 T, B || wire 1,073 1,769


Benefit of Zr-doped wires realized in coil performance

Coil properties With Zr-doped wire With undoped wire

Coil ID 21 mm (clear) 12.7 mm (clear)

Winding ID 28.6 mm 19. 1 mm

# turns 2688 3696

2G wire used ~ 480 m ~ 600 m

Wire Ic 90 to 101 A 120 to 180 A

Field generated at 65 K 2.5 T 2.49 T

Same level of high-field coil performance can be achieved with Zr-doped wire with less zero-field 77 K Ic, less wire and larger bore

Same level of high-field coil performance can be achieved with Zr-doped wire with less zero-field 77 K Ic, less wire and larger bore


Goals for further performance improvements• Two-fold improvement in in-field performance achieved with Zr-doped wires• Further improvement in Ic at B || c : Now 30% retention of 77 K, zero field value at

77 K, 1 T ; Goal is 50%.• Improvement in minimum Ic controlling factor for most coil performance : Now 15 to

20% retention of 77 K, zero field value at 77 K, 1 T ; Goal is first 30% and then 50%• Together with a zero-field Ic of 400 A/4 mm at 77 K, self field 200 A/4 mm at

77 K, 1 T in all field orientations.• Achieve improved performance levels at lower temperatures too (< 65 K)

10

100

0 30 60 90 120 150 180 210 240

Critical cu

rren

t (A/4 mm)

Angle between field and c‐axis (°)

Standard MOCVD‐based HTS tape

MOCVD HTS w/ self‐assembled nanostructures

Goal

c‐axis

200

10x 77 K, 1 T


Ongoing research in pinning improvements• Raise minimum Ic in angular dependence

– Most defects in Zr-doped MOCVD wires are directional, BZO nanocolumns along the c-axis (with splay) and RE2O3 precipitate arrays along the a-b plane.

– Create new defect structure that is not directional or modify existing defect structure to be isotropic

– Create a splay in defects along a-b plane to broaden the peak in Ic at B || a-b just like the peak at B || c

• Determine contribution of different defect structures at lower temperatures and higher fields

10

100

0 30 60 90 120 150 180 210 240

Critical cu

rren

t (A/4 mm)

Angle between field and c‐axis (°)

Standard MOCVD‐based HTS tape

MOCVD HTS w/ self‐assembled nanostructures

Goal

c‐axis

200

10x


Multiple strategies to enhance in-field performance : higher Ic, more isotropic• Superconductor process modification

– Chemical modifications in MOCVD to modify defect density, orientation and size.

• Influence of film thickness on in-fieldIc of Zr-doped films

• Influence of rare earth type and content• Influence of Zr content at fixed

rare-earth type and content• Influence of other dopants• Influence of deposition rate

• Buffer surface modification buffer prior to superconductor growth• Post superconductor processing modification such as post annealing

etc.

2


Improvement with Zr in thicker films

Improvement in in-field critical current of Zr-doped wires increases with film thickness

Improvement in in-field critical current of Zr-doped wires increases with film thickness

All samples were of composition Y0.6Gd0.6BCO


In-field performance of Zr-doped films is drastically modified by rare earth content

Zr content maintained at 7.5% in all three samples

c‐axis

Fewer defects along a‐b plane in Y1.2 ; defects prominent along a‐b plane in (Y,Gd)1.5Fewer defects along a‐b plane in Y1.2 ; defects prominent along a‐b plane in (Y,Gd)1.5

Y1.2Y1.2

20 nm

(Y,Gd)1.5(Y,Gd)1.5


Thick film multilayers of Zr doped (Y,Gd)1.5 and (Y,Gd)1.2 compositions

• 7.5% Zr doping. 0.7 µm HTS film deposited in each pass.• Zero-field and in-field performance measured after each pass.


Multfilamentary 2G HTS tapes for low ac loss applications• Filamentization of 2G HTS tapes is desired

for low ac loss applications.• So far, there is no proven technique to

repeatedly create high quality mulfilamentary2G tapes. Also, adds substantial cost.

4 mm

32-filament tape, 4 mm wide (difficult to make even 1 m lengths)

5-filament tape, 4 mm wide (produced up to 15 m)

0.00 0.01 0.02 0.03 0.04 0.05 0.060

1

2

ac lo

ss (

W/m

)

Bac rms (T)

5.1 x

100 Hz unstriated

multifilamentary


Goals in multifilamentary 2G HTS wire fabrication• Maintaining filament integrity uniform over long lengths (no Ic reduction)• Striated silver and copper stabilizer (minimize coupling losses)• Minimum reduction in non superconducting volume (narrow gap) and

fine filaments

Ag

Substrate

Cu

HTS

A fully filamentized 2G HTS wire would need to have 20 – 50 µm of copper stabilizer striated !A fully filamentized 2G HTS wire would need to have 20 – 50 µm of copper stabilizer striated !


4. Remove remaining photoresist5. Wet etch silver and HTS

Cu

2. Transfer pattern from mask to photoresist

3. Electroplate copper

Photoresist

Ag

Substrate

YBCO1. Coat photoresist

on silver

Approach to make fully-filamentized 2G HTS wire

X. Zhang and V. Selvamanickam, US 7,627,356


Approach to make fully-filamentized 2G HTS wire

2

1 mm

100 μm

Cu Ag HTS

substrate

Cu

Fully-filamentized 2G HTS wire demonstrated, but still involves etchingFully-filamentized 2G HTS wire demonstrated, but still involves etching


Striate buffer layer, then deposit REBCO.

SubstrateBuffer Stack

Substrate Substrate

REBCO

Prerequisites:1.) ‘striation ‘phase’ needs favorable properties for minimal coupling

2.) no widening of ‘striation phase’ into REBCO

3.) No poisoning of REBCO (no diffusion barrier)

4.) No porosity or features that may initiate cracks

5.) Fully-filamentized silver and copper stabilizer

Alternate bottom-up approach being developed


500 µm

Mechanical striation with a diamond tip:

1 mm separationMilling reveals ~1.8 micron depth

Width ~ 25 µm.Repeated experiments with load control : width decreased to 12 µm

Striation of buffer layers


• REBCO texture typical of non-striated tape

• Striated texture polycrystalline, rough

• No apparent widening of striation!

Striated buffer after MOCVD


Cross section of striated region after MOCVD


Factor of five lower ac loss in multifilamentarywire made by bottom-up approach

SCR 5,6 – multifilamentary ; SCR 7ref – reference, no filaments


Improving yield through on-line vision QC in MOCVD

• Vision inspection algorithms assign quality values to images taken every ~15 mm of the wire as it emerges from the MOCVD deposition chamber

• Comparisons of ‘quality map’ with reference tape to discern process drift in real time

Real-time prediction of Ic during MOCVD process enabled by improved on-line Vision systemReal-time prediction of Ic during MOCVD process enabled by improved on-line Vision system

850 900 950 1,000 1,050 1,100 1,150 1,200 1,250 1,300100

80

60

40

20

0

0

100

200

300

400

500

Training from Reference ImagesNo Partial Training

Def

ect C

ode

Val

ue (%

)

Absolute Position (m)

COVG Ic1T

Ic-1

T (A

mps

)


Early detection of a-axis growth during MOCVD is valuable for high current wires

y = 1.0007x - 0.0235R² = 0.8411

0

100

200

300

400

0 100 200 300 400Pr

edic

ted

criti

cal c

urre

nt (A

)

Measured critical current (A)

Ic=4.95*counts (006)-125

Critical current predicted based on (006) XRD peak intensity

Good correlation between measured Ic and (006) XRD peak intensityGood correlation between measured Ic and (006) XRD peak intensity

0

50

100

150

200

250

300

0 0.5 1 1.5

YBCO (200)/(006) ratio

Crit

ical

Cur

rent

(A/c

m)


On-line XRD in new pilot-MOCVD system for real-time quality control

36


Significant improvement in quality of production wires in 2010

% wires > 2009 2010

250 A/cm 25% 60%

300 A/cm 8% 22%


Rapidly decreasing price of 2G HTS wire through technology advancements

10 m demo

100 m demo

First year of pilot production

2 to 4x higher throughput

Creation of separateManufacturing andR&D facilities

500 m demo 1,000 m

demo

AP wire (Zr-doped) product introduction


Projected improvements in in-field performance of production wires through technology

• 10-fold improvement by combination of higher self-field critical current and improved retention of in-field performance through technical innovations.

• Even at 4.2 K, 15 T, 2G HTS wire is comparable now with Nb3Sn wire. Opportunity to improve to be 10X better than Nb3Sn !


Significant price improvements projected through technological advancements

• Price reduction due to improvements in zero-field critical current, retention of in-field critical current and cost reduction ($/m)

• Applications that involve magnetic field benefit from the additional improvement factor in in-field Ic retention

• Increasing market opportunities with decreasing price at operating condition.

c

Small commercial market

Medium commercial market

Large commercial market

Prototype device market


0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70 80 90

Mag

netic

Fie

ld (

T)

Temperature (K)

A

D

C

B

Niobium‐Tin LTSNiobium‐Titanium LTS

2G HTS ‐ Small market2G HTS ‐Medium market2G HTS ‐ Large market

A. Cables, Transformers, Fault Current Limiters

B. Motors, Generators, Transportation, Aerospace

C. High‐field Magnets, MR, High Energy Physics, Fusion Reactors

D. High‐field Inserts, MR, High Energy Physics, Fusion Reactors

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70 80 90

Mag

netic

Fie

ld (

T)

Temperature (K)

A

C

B

D


2G HTS ‐ demo market

A. Cables, Transformers, Fault Current Limiters


C. High‐field Magnets

D. High‐field Inserts

Now to 2 yearsNow to 2 years

5+ years5+ years

Roadmap to realize large market potential

• Large market potential outside the capability of LTS wire.

• Wide range of applications with broad operating conditions & unique requirements – need highly sophisticated & engineered wire.

• Abundant opportunity to lead market capture through technology to improve wire performance and cost-profile

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60 70 80 90

Mag

netic

Fie

ld (

T)

Temperature (K)

A

C

B

D A. Cables, Transformers, Fault Current Limiters


C. High‐field Magnets,

D. High‐field Inserts


2G HTS ‐ Small market2G HTS ‐Medium market2G HTS ‐ Large market

2 to 5 years2 to 5 years


Applied Research Hub to accelerate technology transfer and commercialization• Formed in 2010 with $3.5 M funding from the state of Texas through the

Emerging Technology Fund. Additional $3.8 M provided by UH.• The initial focus of the Applied Research Hub is on power applications of

high temperature superconducting wire. SuperPower is the first industry partner

• Labs now in UH campus expanding to 70-acre UH Energy Research Park• New pilot-scale MOCVD

system procured and will be set up this summer.

• SuperPower to establishSpecialty Products Facilityin UH Energy Research Park this summer

Rapid transfer of technology advances to manufacturing to accelerate commercialization of HTS for wind energy and other applicationsRapid transfer of technology advances to manufacturing to accelerate commercialization of HTS for wind energy and other applications


Abundant potential for 2G HTS wires for several applications• 2G HTS wires have come a long way by combining complex materials

with novel processes and equipment innovations.• Among all superconducting materials, 2G HTS wires are the most

tunable plenty of opportunities to meet goals through R&D. • Potential for large improvements in performance (critical current in

operating condition) with modest price reduction ($/m)• Opportunities to tailor wire to meet complete specifications (ac losses,

stabilization, mechanical properties)• Focused R&D effort underway along with maturing manufacturing

operation for broad insertion of 2G HTS wire in several applications

second-generation hts wire for wind energy applications...application operating field (tesla)...

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