RE-Ba 2 Cu 3 O 7-d coated conductor helical cables for electric power transmission and SMES D.C. van der Laan and X.F. Lu University of Colorado & National Institute of Standards and Technology, Boulder, Colorado, USA J.F. Douglas C.C. Clickner, T.C. Stauffer and L.F. Goodrich National Institute of Standards and Technology, Boulder, CO 80305, USA T.J. Haugan Air Force Research Laboratory, Wright-Patterson AFB, OH 45433, USA D. Abraimov, A.A. Polyanskii and D.C. Larbalestier Applied Superconductivity Group, NHMFL, Tallahassee, FL 32310, USA G.E. Miller, P.D. Noyes and H.W. Weijers National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA Supported in part by NSF, agreement DMR-0654118, the State of Florida, and the U.S. Department of Energy. EPRI Superconductivity Conference Oct. 12 th 2011, Tallahassee, FL
Outline 1. Introduction of the REBCO coated conductor helical cabling concept for power transmission and high-field magnet applications. 2. Overview of initial helical cable prototypes. 3. DC transmission cable for Air Force applications. 4. Effect of strain on J c and pinning in REBCO CC 5. Mechanical testing on REBCO CC helical cables 6. Cable test at 4.2 K and 20 T 7. Summary.
High-current density REBCO CC helical cables Requirements for HTS cables: 1. Dc power transmission (Navy/Air Force): Low weight, high current (density). 2. High-field magnets for SMES (plus transformers, HEP/Fusion/Science): - High-current and high-current density windings. - Low conductor anisotropy. - Low magnetization loss. - Round conductor. REBCO CC helical cabling design: Helically-winding CCs with YBCO under => compression around a small former. D.C. van der Laan, SUST 22, 065013 (2009). Benefits: - Compact/low weight. - No tape scrap. - Round cable. - Isotropic field-dependence. - Optional cooling channel within former. - Full conductor transposition/easy striation. - High mechanical strength (no sharp edges). - Standard cabling technique applicable. - Current sharing/distribution adjustable.
Reversible strain effect in YBCO CC There is a large reversible effect of strain on I c : Reversible! e irr = 0.66% I c (e)/i c (e m ) = 1-a e - e m 2.2 e m = 0.15 % strain sensitivity strain at peak 76 K
I c [A] Helical cable design proof of principle Question 1: How much compressive strain is possible in CCs? SuperPower conductor: - I c = 133 A @ 76 K - 20 mm surround copper plating. - 1 mm YBCO. - 50 mm Hastelloy substrate. 76 K Loading Measurement procedure: - CC soldered to CuBe/brass bending beams, - strain gage mounted on top of sample. - beam is bent past its elastic limit. - reversibility of I c is confirmed by unloading the strain. Unloading D.C. van der Laan, SUST 22, 065013 (2009). -2.0-1.5-1.0-0.5 0.0 e [%] I c of the MOCVD-IBAD tape decreased reversibly by 95 % at -2 % compressive strain! The irreversible strain limit hasn t been reached! 140 120 100 80 60 40 20 0
Helical cable design proof of principle (Cont.) Question 2: Does the YBCO survive the mechanical deformation in the cable? D.C. van der Laan, SUST. 22, 065013 (2009). 1. 2. 3. 3.19 mm e winding econd. axis Helically cabling of YBCO coated conductors is possible! I c is determined by the strain along the tape axis!
J c -e of GdBa 2 Cu 3 O 7-d vs. YBa 2 Cu 3 O 7-d Benefit of GBCO CC over YBCO: Less strain sensitive! GBCO is the material of choice for cabling.
DC transmission cable 1: construction Cable 1: 5.5 mm former, 4 layers, 12 YBCO tapes @ 100 A each, no insulation. 5.5 mm OD 1 st layer 2 layers 4 layers 6.5 mm OD
E [V/m] DC transmission cable 1: testing 1.0E-03 1.0E-04 1232 A I c (s.f., 76 K) = 1232 A 1.0E-05 1.0E-06 76 K 0 500 1000 1500 I [A] Bending radius 12 cm: I c (s.f., 76 K) = 1239 A! High-current cables are possible! And you can bend them! D.C. van der Laan, X.F. Lu, and L.F. Goodrich, SUST 24, 042001 (2011).
Electric field [V/m] Cable 2: - 5.5 mm former - 8 layers,24 GBCO CC @ 130 A - no insulation. - Cable O.D. = 7.5 mm. DC transmission cable 2 Final diameter 7.5 mm. 1.0E-02 1.0E-03 1.0E-04 2796 A 1.0E-05 1.0E-06 1.0E-07 76 K 0 500 1000 1500 2000 2500 3000 Current [A] D.C. van der Laan, X.F. Lu, and L.F. Goodrich, SUST 24, 042001 (2011).
DC power transmission for Air Force applications Air Force power transmission is interested in: - 5 MW DC power transmission at 270 V => 18,500 A. Superconducting power transmission cable of 18,500 A at 50-55 K => 6200 A at 77 K => 6800 A at 76 K (Boulder LN 2 boiling). Our approach (due to limited current of 5000 A): => 2 phase coaxial cable: Our goal: Phase 1 I c (Phase 1) + I c (Phase 2) = 6800 A Phase 2
Air Force 5 MW cable Phase 1 1.2 meter - 5.5 mm former. - 5.8 cm OD copper endpieces. - 10 layers, 39 tapes
E [V/m] Air Force 5 MW cable Phase 1 test 76 K 1.0E-03 Ends Near ends Middle 1.0E-04 1.0E-05 Taps near center of cable: 1.0E-06 0 1000 2000 3000 4000 I [A] I c (Phase 1)= 3720 A B self = 181 mt Taps near cable ends: I c (Phase 1)> 3720 A Limited due to thermal runaway.
Air Force 5 MW cable Phase 2-10 mm cable outer diameter. - 7 layers, 40 tapes 11 4/0 cables per side for testing:
E [V/m] Air Force 5 MW cable Phase 2 test 76 K 1.0E-03 1.0E-04 Ends Cable 1.0E-05 1.0E-06 0 1000 2000 3000 4000 5000 I [A] I c (Phase 2)= 4595 A B self = 186 mt
Air Force 5 MW cable Phase 1&2 in series Current runs in opposite direction from Phase 1 to Phase 2 => self-fields cancel.
E [V/m] Air Force 5 MW cable Phase 1&2 in series 76 K 1.0E-03 1.0E-04 1.0E-05 1.0E-06 Ph. 1 series 1.0E-07 Ph. 2 series Ph. 1 alone Ph. 2 alone 1.0E-08 2000 2500 3000 3500 4000 4500 5000 I [A] I c (Phase 1)= 3946 A (6 % more than stand-alone). B self = 192 mt
Air Force 5 MW cable Phase 1&2 parallel Current runs in the same direction from Phase 1 to Phase 2 => self-fields add. D.C. van der Laan, L.F. Goodrich, and T.J. Haugan, accepted for publication SUST (2011).
Air Force 5 MW cable Phase 1&2 parallel 76 K I c (Phase 1)=3745 A; I c (Phase 2)=3816 A I c (total)= 7561 A (10 % less than stand-alone). The cable exceeds the goal of 6800 A at 76 K! B self = 302 mt
REBCO CC cables for SMES and other high-field apps. Benefits of high-current cables for SMES: - Stored energy could be raised by increasing the winding current. - High-power SMES possible at relatively low voltage. - Enables operation at higher temperatures. - Reduced ac-losses. - Avoiding single-tape related issues (defects, etc.). Possible issues for HTS in high-field magnets: - High-strength needed to withstand Lorenz forces. - Existence of a large effect of axial strain on flux pinning strength.
Measuring of strain effect on pinning in REBCO CC -1% Compression 1% Tension Strain spring - tensile and compressive strain - variable field angle a = 0 to 360-4.2 K and 65-90 K
Ic [A] Ic [A] I c -a for different e at 76 K (Bruker) HRPLD-ABAD: copper plated, 2.5 mm YBCO. 35 2 T -0.5% -0.3% 30 0% 0.4% 25 20 Sample 1 22 20 18 16 HRPLD-ABAD: copper plated, 2.8 mm YBCO. -0.2% 0% 0.4% 2 T Sample 2 15 10 B//c B//ab -10 0 10 20 30 40 50 60 70 80 90 100 Angle [degrees] - Strain influences pinning in YBCO! - Strain sensitivity larger at low angle. 14 12 B//c -10 0 10 20 30 40 50 60 70 80 90 100 Angle [degrees] - Sample 2 shows comparable pinning strength B//c and B//ab. B//ab a B
Ic/Ic(0) [-] Ic(B)/Ic(0) Ic(B)/Ic(0) I c -e-b for B //ab in MOD-RABiTS (AMSC) B I c (e) normalized to its peak at e m = 0%: 0 T 0.25 T 0.5 T 1 T 2 T 3 T 4 T 6 T 8 T e m 1 0.97 0.94 0.91 0.88 0.85 0.82 T= 75.9 K -0.6-0.4-0.2 0 0.2 0.4 e [%] 0 T 8 T 0.1 0.01 Location of peak in I c (e) shifts with field! Strain affects pinning through B irr (e). 1 Pinning is affected => B irr (e): 0.07 0.05 0.03 B B [T] - 0.5 % 0.4 % 4 6 8 10-0.5 % 0.4 % 0 2 4 6 8 10 B [T]
norm Ic Ic/Ic(0.05%) [-] norm Ic I c -e-b for B //c in MOCVD-IBAD (SuperPower) I c (e) normalized to its peak at e m = 0.05%. 0.25 T T= 75.9 K 1.05 0 T 0.1 T 0.25 T 1 0.95 0 T 0 T 5 T B 0.95 0.85 0.75 0.65 0.55 0 T 0.05T 0.1T 0.25T 0.5T 1T 2T 3T 4T 5T -0.70-0.50-0.30-0.10 0.10 0.30 0.50 e [%] I c (e) with double maximum at low field. Low-B behavior can be interpreted as a dip: role of grain boundary pinning? D.C. van der Laan, et al., SUST 23, 072001 (2010) 0.9 0.85 0.8 0.25 T -0.8-0.6-0.4-0.2 0 0.2 0.4 0.6 Intrinsic strain [%] 0.25 T 2 T 5 T 1 0.95 0.9 0.85 0.8 5 T 0.25 T -0.8-0.6-0.4-0.2 0 0.2 0.4 0.6 Intrinsic strain [%]
B irr [T] I c -e-b for B //c in MOCVD-IBAD and HRPLD-ABAD 8.8 7.1 8.4 Ic(B)/Ic(0) Ic(B)/Ic(0) 1 1 0.1 0.1 0.01 0.001 B 0.1 % -0.5 % 0.5 % 0.01 0.001 0.0001 B 0.2 % -0.5 % 0.5 % 0 2 4 6 8 B [T] 0 2 4 6 8 10 B [T] 8.0 Birr [T] 6.6 6.1 7.6-0.6-0.4-0.2 0 0.2 0.4 0.6 e [%] 5.6-0.6-0.4-0.2 0 0.2 0.4 0.6 e [%] Strain affects pinning through B irr (e). Likely caused by the pressure dependence of T c.
Relation between T c (e), J c (e) and pinning in REBCO YBa 2 Cu 3 O 7-d : Anisotropic effect of pressure on T c e In case T c (e) defines J c (e): T c, J c T c, J c I From: U. Welp, et al., Phys. Rev. Lett. 69, 2130-2133, 1992 Local competing changes in T c (e) result in a J c (e) dependence seen in REBCO.
Does the strain effect depend on the in-plane orientation? MOCVD-IBAD: a- and b -axes aligned with conductor axis! Bridges at various angles with the conductor axis: a b And apply strain along the bridge: a = 0 a = 45 a = 90
Strain effect at various in-plane angles a = 0, 90 a = 22.5, 67.5 - Effect of strain decrease when strain is no longer aligned with a- and b-axes! a = 45 - Strain effect almost absent at a = 45! D.C. van der Laan, et al., accepted for publication SUST (2011).
Anisotropic in-plane strain effect in REBCO I c (e)/i c (e m ) = 1-a(a) e - e m 2.2 a-dependent strain sensitivity a a a 0 cos a sin a Strain sensitivity is highly dependent on a. D.C. van der Laan, et al., accepted for publication SUST (2011).
Impact of strain effect for high-field applications Pressure dependence of T c causes a large reduction in pinning strength in high-b applications that are wound from single conductors. The change in T c with strain is expected to be highly-reduced in applications that are wound from helical cables: e winding tape axis e opp.
Mechanical testing of REBCO helical cables s 250 200 Solid copper former 5.2 mm diameter: Nylas extensometer LVDT s [MPa] 150 100 50 0 0 0.2 0.4 0.6 0.8 e [%] Important to measure displacement with extensometers!
Mechanical testing of REBCO helical cables cont. Cable installed with flexible current leads: Current leads handle >1000 A at 76 K.
I c [A] Mechanical testing of REBCO helical cables cont. 250 200 Cable: 2 layers, 4 tapes plus 2 dummy tapes on solid Cu former: Cable Former 2 700 600 500 s [MPa] 150 100 50 0 1 0 0.2 0.4 0.6 0.8 1 400 300 200 100 0 Tap 1 Tap 2 1 2 Tap 3 0 50 100 150 200 250 s [MPa] e [%] Initial damage at 144 MPa near current contacts due to stress concentrations. s irr expected to be >144 MPa.
I c /I c (0) [-] Strain effect on I c in helical cables vs. tapes 1.05 1 0.95 Tape: I c (s irr ) = 0.90 I c (0) Cable: I c (s irr ) = 0.97 I c (0) 0.9 0.85 Tape Cable 0 0.2 0.4 0.6 0.8 1 s/s irr [-] tape axis The strain effect in helical cables is highly reduced! e opp.
REBCO helical cable tests at 4.2 K, 20 T Cable 1: 2 layers, 6 GBCO CC, preformed Al former: I c = 600 A @ 76 K, s.f. Cable 2: 4 layers, 12 GBCO CC, flexible Cu former: I c = 1100 A @ 76 K, s.f. Cable 2 ready for testing:
Ic [A] Ic [A] REBCO helical cable tests at 4.2 K, 20 T 2000 1600 1200 Cable 1 Cable 2 4.2 K a. 3500 3000 4.2 K 2500 2000 b. 800 1500 400 76 K, self-field 1000 500 76 K, self-field 0 0 5 10 15 20 B [T] 0 0 5 10 15 20 B [T] I c = 534 A @ 4.2 K, 20 T I c = 875 A @ 4.2 K, 20 T Cable results at 20 T look promising for high-field magnets => next: higher currents!
Summary We ve demonstrated: - Possibility of helically winding YBCO coated conductors around very small formers. - High current DC transmission cables are possible: 2800 A in 7.5 mm diameter 7561 A in 10 mm diameter => exceeded the performance for Air Force 5 MW power transmission at 50-55 K - Large reduction in pinning expected in single-tape high-field applications. - The effect is highly-reduced when the application is wound from helical cables. - The first successful cable test at 4.2 K in fields up to 20 T
Commercialization of REBCO helical cables Danko van der Laan 720-933-5674