Science for a Superconductor Power Grid A. P. Malozemoff American Superconductor Corp., Devens MA

1. Science for a Superconductor Power Grid A. P. Malozemoff American Superconductor Corp., Devens MA USDOE BESAC Meeting Bethesda MD, July 9-10, 2009 1

2. Revolutionizing the Way the World Uses Electricity™ Superconductors - Basic Facts • Superconductors discovered in 1911 • Require cryogenic cooling • High Temperature Superconductors (HTS) discovered in 1986 - cuprates • 6X higher temperature (135 K vs 23 K) • Less cooling drives commercial economics • Zero DC electrical resistance • Yields high electrical efficiency • >100X more power capacity than copper wire of same dimensions • High power density - reduced size and weight • Cooling with environmentally benign liquid nitrogen Copper, HTS @ equivalent 1000 A capacity: Power density drives system economics 2

3. lighting. heating refrigeration hydro wind solar coal gas transportation power grid electrical generators electricity motors heat industry nuclear fission information technology fuel cells Superconductors: Poised for a Major Role in Addressing Key Challenges in the Power Grid superconductivity 2G wires - foundation of grid applications: cables, generators, transformers, FCLs, motors, synchronous condensers, etc. 3

4. 6 Transmission Investment 5 US Energy Consumption (Trillion BTUs) US Transmission Investment (Billion $s) 4 Total energy consumption 3 2 Electric energy consumption 1 0 Source: Cambridge Energy Research Associates 1 9 4 0 1 9 5 0 1 9 6 0 1 9 7 0 1 9 8 0 1 9 9 0 2 0 0 0 Under-investment has spawned a host of technical problems US Electric Power System under Severe Stress The underlying problem: Under-investment in electric power grid while demand for electric power steadily increases Source: EIA

5. Grand Challenges in Electric Power • Demand growing relentlessly, doubling by 2050, tripling by 2100, plus need to reduce dependence on foreign oil 1. Need a major enhancement in overall energy efficiency • Increasing grid efficiency • Electrification of transportation • Reurbanization 2. Need major new sources of renewable energy • Power outages and disturbances cost >10B$ per year 3. Need a secure and ultra-reliable grid • Environmental issues growing 4. Assure an environmentally clean energy infrastructure

6. 1. Enhancing Efficiency in the Electric Power Grid • 7-10% of 1 Terawatt US electric power now lost in ac power grid • Superconductor equipment could cut this by half, save 50 Gigawatts! • Reducing delivery bottlenecks even more impactful • E. g. superconductor cables bringing 50%-efficient generation to cities, replacing 30%-efficient “reliability-must-run” generators • Dc Supergrid: a radical leap in grid efficiency • Westinghouse’s ac grid won out over Edison’s dc grid • Reduced I2R loss by efficient transformers, high voltage • Superconductors break this paradigm • I2R = 0 enables high dc current, low voltage • First step: delivering renewable energy to urban centers

7. Enhancing Efficiency through Electrification of Transportation • Electric vehicles ~2x more energy efficient than gas in original BTU content of oil • ‘A 5% penetration of plug-in vehicles in Manhattan will create a 50% increase’ in rate of demand growth - ConEd, 11/15/05 • Superconductors key in enabling urban grids to handle this demand • Maglev an efficient alternative to intracontinental aviation • Military ship propulsion with HTS motors - 15% efficiency gain at half speed over conventional motors Japanese Maglev flies with HTS coils, (courtesy CJR)

8. Enhancing Efficiency by Opening the Urban Power Bottleneck • Reurbanization driven by rising energy costs • Requires more power capacity in dense urban areas • But overhead lines near impossible to permit, underground infrastructure clogged New York then New York now: it only gets worse! Lower Manhattan underground infrastructure (Courtesy of Con Edison) 2003 1913

9. Getting Power into Our Cities 138 kV, 600 m, 574 MVA cable installed and operating since April 2008 in LIPA grid Need underground power cables which are • High capacity in same X-section • Compact, light – easy to install by retrofitting existing ducts or boring • Non-interfering (no EMF or heat) • Low voltage for easy permitting Superconductors - the ideal solution! Southwire TriaxTM power cable

10. Significant power blackouts becoming all too frequent Establishing a Secure and Reliable Grid: an Urgent Need China …’03, ’04, ’05… U.S. Northeast ‘03 London ‘03 Moscow ‘05 Athens ‘04 New York ‘99 Denmark ‘03 U.S. West Coast ‘96 Italy ‘03 Delaware ‘99 New Orleans ‘99 Chicago ‘99 Detroit ‘00 San Francisco ‘00 Atlanta ‘99 Northern California ‘01

11. j X I ~ V R Need a solution, or must drastically reconfigure and break up the grid Reliability: Controlling Fault Currents in Urban Grids Faults short out resistive loads, leave grid primarily reactive! • Every added power source adds parallel output impedance • increases fault current • In large urban grids, fault currents can exceed 60,000 A • approaching maximum breaker capability!

12. w/o FCL w/FCL Fault current limiters a major opportunity for grid stabilization Reliability: Superconductors Enable “Resistive” Fault Current Limiters • Superconductors -“smart” materials, switch to resistive state above critical current • Increased resistance limits current flow • Many FCLs demonstrated; commercialization beginning Siemens/AMSC 2 MVA FCL Need a solution, or must drastically reconfigure and break up the grid

13. Reliability: Current Limiting Essential for Rewiring Urban Grids ConEd’s System of Today Powered by Copper Cables ConEd’s System of the Future with MV Connections Copper power cables HTS power cables Project Hydra (AMSC/ Con Edison/Southwire/DHS) demonstrates current limiting cable 13

14. Renewable Energy: Opportunity for Off-shore Windpower via HTS Generators • Off-shore wind - strong and steady • But only 2% of total windpower now off-shore • Opportunity to double windpower production! • Cost the obstacle • Increased power rating key to economics • Systems up to 5 MW demonstrated • Above 5 MW, conventional generator simply too large and heavy • HTS generators offer the needed breakthrough in size and weight to 8-10 MW • Lowest cost of energy: lowest installed cost per MW, highest efficiency, longest maintenance interval HTS generators could enable major expansion of offshore windpower

15. Renewable Energy: Comparison of Wind-power Generators n small, high power AMSC/TWMC ATP program addressing design and technology for 8/10 MW generator 15

16. Rotating Machinery: Successful Full Power Test of AMSC’s 36.5 MW HTS Motor- Dec. ‘08 1.5MW Copper Motor AMSC’s 36.5 MW HTS Motor 50% more power, half the weight • Key Advantages: • Less than half the size and weight • Higher efficiency • Less noise Technology platform established for high power generator for wind-power 16

17. Renewable Energy : Need to Carry 100’s of Gigawatts of Green Power to Market New transmission options needed to bring wind and solar energy to main US markets 17

18. Renewable Energy: DC “Superconductor Electricity Pipeline” for Long-Length, High Power First DC HTS cable demonstration – Chubu U., Sumitomo Electric 1000-Mile, 5 gigawatt power equivalents: right-of-way advantage for HTS DC cables 18

19. Laminates – copper, stainless… Insert – substrate, buffer, YBCO “344 superconductors” cross-section The Foundation: Second Generation (2G) HTS Wires - YBCO Coated Conductors AMSC wire: 4.4 mm wide, single-coat Cu, HTS power equivalents • HTS wire in production – commercially available AMSC 4 cm Technology 19

20. What is Needed to Assure Major Impact and Benefit of Superconductors on Power Grid? • Existing technology works, but HTS wire and refrigeration costs still limit range of application • Wire figure of merit: $/kA-m • Now 200 $/kA-m ; need $25/kA-m to undercut copper • Even lower would be better! • So both cost per meter and current-carrying capacity are critical • New processes to reduce wire cost • Higher critical currents • At higher temperatures and fields • Higher Tc? - to decrease refrigeration load 20

21. Science Opportunities: New Superconductors • Discovery of new superconductors • Track record is exciting – major discoveries every few years! • New theoretical and calculational tools, more powerful measurement tools • Understanding HTS mechanism HTS cuprates - a supernova – what other supernovae await? 21

22. Flux creep Science Opportunity: What Kind of New Superconductors Should We Search For? • Higher Tc, of course • But need to understand flux creep - thermal activation of vortices from pinning centers • Reduces critical current in higher Tc materials a lot! • Lower anisotropy materials • Interlayer coupling dominates flux creep • Can one tune interlayer coupling of existing highly anisotropic materials? • May be a more practical route to higher critical currents at higher temperature Broaden scope of search beyond just higher Tc 22

23. Field Dependence of YBCO HTS Wires – Rapid Dropoff of Ic with Field, Temperature Wire Performance with Magnetic Field Perpendicular to Tape Surface Need to increase! Performance data courtesy Railway Technical Research Institute, Tokyo, Japan AMSC Confidential and Proprietary

24. Control of Grain Boundary Currents by Texturing - Key to Second Generation (2G) YBCO Wire Grain boundary critical current vs misorientation angle AMSC 2G wire architecture: RABiTSTM process Dimos, Chaudhari + Mannhart, PR 1990 Texturing within ~50 enables Jc(77 K) ~ 3x106 A/cm2 over 100’s of meters – An amazing success, though it has taken 18 years to get to this point! 24

25. Science Opportunity: Understanding Grain Boundaries Better • Grain boundaries are principal obstacle to current flow in HTS wires • Contributions of in-plane and out-of-plane components still not well understood • Amazing reversible behavior under compression • Ic can recover from 5% of its value! • Mechanism unknown D. Van der Laan, SUST 2009 25

26. Science Opportunity: Vortex Physics Vortex: nanoscale quantum of magnetic flux • Pinning vortices – basis for high critical current density • Much effort on existing materials (e. g. YBCO) during last 15 years • But much still to do to increase Ic • Understanding magnetic pinning • Interplay of columnar and planar pinning centers • Flux cutting • Minimizing flux creep Still significant fundamental issues in existing materials like YBCO 26

27. Science Opportunity: Vortex Dynamics • Vortex liquid (flux flow state) • Huge area of HTS B-T phase diagram • Properties in high drive flux flow state hardly investigated, yet very important, e. g. for fault current limiters YBCO

28. Resistance linear in voltage at short times! Example: Understanding Properties of High Current Flux Flow State • Discovery of resistance linear in voltage via quench experiment: • YBCO film on sapphire • In liquid nitrogen • 0.1 msec after applied voltage drives film into flux flow state Kraemer et al., IEEE Trans. On Appl. Superconductivity 13, 2044 (2003) 28

29. Understanding Flux Flow State • High speed photos of lN2 bubbling reveal novel domain state in flux flow • Length of quenched area increases with applied voltage - mechanism unknown • Topic being addressed in Superconductivity EFRC time 50 V 100 V 150 V YBCO on sapphire for three different voltages, in liquid N2 (Kraemer et al., 2003) 29

30. Processing Science for Superconductor Films • Increasing the limiting cracking thickness for metal-organic deposition (liquid phase) processes • Key to achieving highest critical current per width need high thickness t: Ic/w = Jc t • During removal of organics, subtle chemical interactions and kinetics determine limiting thickness • Achieving high texture in non-magnetic substrate • Texture in low stacking fault energy alloys • Establishing a single-layer buffer architecture • Maintaining uniform properties during film growth through precursor layer 30

31. Tilted YBCO grain Interface Multi-layer interface Top layer has reduced texture and lower Jc Lower layer has consistent texture and Jc Process Science Challenge – Achieving Uniform Growth through Thick Ex-Situ HTS Films Through-thickness of hybrid YBCO film - 2006 • AMSC MOD ex-situ films: decreased performance from poor texture across multilayer interfaces 31

32. Science in Related Technologies • Cost reduction of cryogenics (cryostat, refrigeration) also key • Now, refrigeration stations required at several kilometer intervals of ac HTS cable, ten kilometer for dc HTS cable • How can we achieve 10x distance between refrigeration stations? • Improved MLI? • Peltier effect – flush out phonons with electric current • Reduced ac and dielectric losses • >1 kW pulse tube refrigerators ? 32

33. Support needed for a broad range of superconductor science Conclusion • Superconductivity can play major role in addressing grand challenges of energy generation, delivery and use: • Engineering foundation in place • Cables, rotating machines, fault current limiters… • But important issues remain for broad impact • HTS wire $/kAm and cryogenic costs • Major science opportunities to address these issues • Discovery of new superconductors, HTS mechanism, increasing current density, processing breakthroughs… 33