Superconducting Magnetic Energy Storage Concepts and applications

Transcription

1 Superconducting Magnetic Energy Storage Concepts and applications Antonio Morandi DEI Guglielmo Marconi Dep. of Electrical, Electronic and Information Engineering University of Bologna, Italy ESAS Summer School on High Temperature Superconductors Technology for Sustainable Energy and Transport Systems

2 Outline SMES technology SC material and Conductor Coil Power conditioning system A case study - 1 MW / 5 s SMES Applications Energy storage SMES applications Grid Customer / Industry SMES actvities at the University of Bologna

3 SMES Superconducting Magnetic Energy Storage Current leads PCS grid vacuum vessel Control and protection system Cooling system Superconducting coil E B = dτ µ τ 0 τ coil B µ 0 d τ = 1 L I 3

4 Advantages High deliverable power Infinite number of charge discharge cycles High efficiency of the charge and discharge phase (round trip) Fast response time from stand-by to full power No safety hazard Critical aspects Low storage capacity Need for high auxiliary power (cooling) Idling losses 4

5 Conductor and cable YBCO 16 K 0 K 4 K 16 K 0 K 4 K MgB YBCO, B perpendicular MgB MaincharacteristicsofatypicalMgB Conductor Manufacturer Columbus Nominal radius 1.13 mm Number of filaments 36 Filling factor 0.14 Matrix Ni 70%, Copper 0% Critical tensile strength 300 MPa Critical current, K, self field 550 A Main charact. of a typical YBCO Coated Conductor Manufacturer Superpower Nominal Width 1 mm Nominal thickness 0.1 mm YBCO 1 µm Stabilizer, copper 0 µm Substrate, Hastelloy 100 µm Critical tensile strength 550 MPa Critical current, 77 K, self field 330 A 5

6 Typical current for the SMES operating in the MW range is in the order of several ka Several conductors have to be put in parallel for reaching the required transport current High current conductor made of G HTS tapes Continuously transposed (Roebel) cable Slotted cable made of Roebels Scraps are produced Je cable = Je tape Je cable << Je tape 6

7 Twisted stacked-tapes Cable made of twisted stacks Je cable << Je tape Conductor on Round Core (CORC) cable Institute of Electrical Engineering Slovak Academy of Science 7

8 CCRP Cable Centre de Recherches en Physique des Plasmas ENEA Cable 10 ka class cable: 150 G-wires (5 stacks x 30 wires) 8

9 Flat Rutherford cable High current conductor made of MgB wires example 6 wires Stranded MgB /Cu rope Copper MgB Example of Base Cable Unit: 1 MgB strands + 7 copper strands

10 Layout of the winding Arrangement of multiple pancake 5 MJ coil -4T Solenoid Torus Simpler and more cost effective Easier handling of the electromagnetic stress Smaller foot-print Low stray field Reduced component of magnetic field perpendicular to the conductor 10

11 Length of conductor versus the perpendicular field at the maximum current 5 MJ coil -4T A large portion of conductor experiences a large perpendicular field in the toroid as well 11

12 Coil design electromagnetic R 1 R 1 R 1 = p R 1 L = p L R 1 = R 1 R L R L H = J e R 1 H = J e R 1 E' = V SC H µ ' = π 0 π R' 1 L' = p 3 E ( R' 1+ R') R' 1 ) L' p VSC The volume of the superconductor scales less than linearly with the energy of the coil 3 V SC = k E 1

13 Coil design mechanic V k 1 σ E Virial s theorem limit V, volume of structural material [m 3 ] E, total energy of the coil [J] σ, allowable stress [N/m ] k, numerical coefficient ( 1 ) For solenoid k ranges from 1 if D/L tends to zero to 3 if D/L tends to infinite. At high energy the structural constraint is stricter than the electromagnetic one volume E Additional structural (and stabilizing ) material is required E /3 energy 13

14 Field dependence of the total conductor s length The required stored energy E is assigned The operating field B of a the SC coil is a design choice By increasing the field A reduced overall size of the coil is obtained which requires less conductor More ampere-turns at reduced Jcare needed which require more conductor Which of the two effects is dominant? 14

15 E Stored Energy B Nominal Field p aspect ratio( L/ D ) of the solenoid S tape cross section of the tape J e Eng. current dens. of the tape at field B k I / Icratio solenoid 0 solenoid 8 ) ( 1 8 ) ( 1 ) ( / B E p B J k S S S N B E p B J k S H L S B J k B E p p D L B E p D L D V B E V e tape tape SC tape e SC SC e = = = = = = = = µ π µ π π µ π µ π µ Volume of the solenoid Diameter of the solenoid Height of the solenoid Superconducting cross section Number of turns Total length of tape 15 slim solenoid given aspect ratio Isotropic conductor ) ( B J B E p k S D N L e tape tape SC = = µ π π π

16 L SC B' ( B) LSC ( B') Je( B) J e( B') B YBCO, 16 K, B perpendicular 1 3 ( 4 ) 1 3 J e ( 4)* B MgB, 16 K ( ) 1 3 J e ( )* B For practical superconductors (YBCO and MgB ) the required length of conductor needed for a solenoid with given Energy E increases with the operating field 16

17 Outline SMES technology SC material and Conductor Coil Power conditioning system Applications Energy storage SMES applications Grid Customer / Industry 17

18 PCS the magic box AC Grid P 0 PCS I SMES I 0, current of SMES at time t 0 I 1, current of SMES at time t 1 1 L I 1 LI 0 = P ( t t 0 ) I = I0 P ( t t L 0 ) During discharge 1 L I 1 L I 1 = P ( t t 1 ) I = I1 + P ( t t L 1 ) During charge I 0 I 1 t 0 t 1 18

19 PCS - Power Conditioning System Voltage source converter (VSC) V dc L C I SMES A controlled power is transferred from the DC bus to the grid by means of the inverter The voltage of the DC bus is kept constant by the SMES by means of the two quadrant chopper 19

20 I dc P = V I cosϕ V dc C The inverter regulates the power transfer between the grid and the capacitor An average positive current is established on the DC bus during power transfer to grid P V dc < I dc > The voltage of DC bus decreases if the capacitor is not recharged V dc time 0

21 The chopper controls the voltage of the DC bus Discharge I dc I dc P = V I cosϕ C V dc I SMES L < I dc > = < I dc > V dc constant i dc I SMES T ON T OFF T cycle < I dc > time The current of the SMES decreases during the ON phase If the power P is delivered to the grid during the interval t final current of the SMES is 1 L I 1 L I 1 = P t I, current of he SMES at the end of the delivery I 1, current of he SMES at the start of the delivery 1

22 Charge I dc I dc P = V I cosϕ C V dc I SMES L < I dc > = < I dc > V dc constant i dc T OFF time The current of the SMES increase during the ON phase I SMES T ON T cycle < I dc > If the power P is absorbed from the grid during the interval t final current of the SMES is 1 L I 1 L I 1 = P t I, current of he SMES at the end of the delivery I 1, current of he SMES at the start of the delivery

23 Implementation -control algorithm Grid SW v g i s L s i L Load inverter PWM * v s * i s R v g i s * V dc V dc + * i c R 3 PWM chopper * i + g R 1 i L v g * Q g ( = 0) * P g The inverter is controlled in order to provide the required service to the grid The SMES is controlled independently in order to stabilize the voltage of the DC bus 3

24 Idling Loss If no power is delivered/absorbed the SMES current of the free-wheels P = 0 C V dc I SMES L V on IGBT = V V on DIODE = V Losses are produced during the idling phase P IGBT = I SMES V on IGBT P DIODE = I SMES V on DIODE P idling = 1 10 kw / ka Time constants of RL circuit of typical SMES (1-5 MJ) during the standby phases are in the order of hundreds of seconds at most 4

25 SMES The whole energy of the SMES is lost in the power electronics within a few minutes Continuous recharge/compensation is needed

26 The use of a thermal actuated SC switch for avoiding the losses during the standby is possible in principle but it is unfeasible in practice since it lowers the response time of the SMES P = 0 V dc C I SMES L 6

27 Outline SMES technology SC material and Conductor Coil Power conditioning system A case study - 1 MW / 5 s SMES Applications Energy storage SMES applications Grid Customer / Industry SMES actvities at the University of Bologna 7

28 Main characteristics of the 1 MW - 5s SMES Systems 8

29 Grid performance of the 1 MW -5s SMES System 9

30 Estimated AC losses of the 1 MW -5s SMES System during one discharge/charge cycle. Round trip efficiency of the 1 MW -5 s SMES System during one discharge/charge cycle. 30

31 Outline SMES technology SC material and Conductor Coil Power conditioning system Applications Energy storage SMES applications Grid Customer / Industry 31

32 National electric balance - Italy Production (grid immission) 310 TWh, 014 Thermal 47.5% Rinnovabili 37.9% Importazioni 14.0% Loss 19.5 TWh(6 %) Average power demand 39.1 GW Night average (011).0 GW Day average(011) 5.0 GW Absolute minimum (009) 1.5 GW Absolute maximum ( 015) 53.3 GW, 1 July Installed power (01) 14.0 GW Installed power (010) GW Average available power (01) 69.3 GW Usage rate 57.3 % 3

33 Electric power system ICT storage storage Active load Non progr. power Non progr. power Non progr. power. Active load 33

34 Grid energy management Generation / load imbalance is inherent in the power grid due to random fluctuation of loads induced by customers variation of generation from renewables Sudden and Large generation / load imbalance can also occur due to contingency Continuous and fast regulation of the generated power and/or loads is required for controlling the frequency and stability of the grid. Technology for grid energy management Improved controllability of conventional generation Responsive load Supergrid(multi-terminal DC links ) Energy storage 34

35 Energy storage T&D system only allows to move energy in space Total power produced must instantaneouslybalance the total load (including the losses). Energy storage system allows to shift electric energy in time so as to decouple production and consumption 35

36 Performance of Storage Technologies Energy intensive storage Power intensive storage

37 1 MWh = 3600 MJ

38 1 MW 6h NAS module 1 MW 10 s SMES 38

39 6 MWh NAS system 6 MWh SMES system

40 Efficiency of an Energy Storage System P, deliverable power t, duration of delivery t cycle, duration of the cycle t idle, duration of idling phase η s, intrinsic efficiency of the storage device η c, efficiency of the converters P aux, power required for auxiliary services P idle, power loss (if any) during idling η = P t η = t P t η = t + P + PP t idle tidle + idle P t ηs ηc ηs ηc η η s c aux idle t energy idle power cycle cycle 40

41 By summarizing Energy capacity of SMES is ridiculous compared to batteries Idling losses in power converters do not allow long term storage Cooling losses further complicate losses Is the SMES useless and hopeless? 41

42 Parameters of the energy storage Power that can be absorbed or supplied, P Duration of the power delivery, t Number of cycles, N Response time, t r 4

43 Grid and Customer Applications of Energy Storage Bulk energy management market / less need for inefficient (low load) operation of power plants MW 1 h, 1 cycle per day Transient Stability Increased transmission limit MW 1-10 s, occasional grid Frequency regulation less need inefficient (low load) operation of power plant 1-50 MW 1-15 min, cycles per day Other applications with more limited cost/benefit trade-off damping of sub-synchronous resonance black start deferral of new transmission and distribution 43

44 Customer Power quality and UPS compensation of voltage sag + Power Quality services to the customer 1-10 MW s, occasional deep cycle + continuous minor cycles Leveling of impulsive power constant power absorption from grid 1-10 MW s, continuous cycles 44

45 Parmeters of Storage for Grid and CustomerApplications lev. imp. power Voltage quality UPS Trans. stability Freq. regulation Bulk en. man. lev. imp. power Voltage quality UPS Trans. stability Freq. regulation Bulk en. man. lev. imp. power Freq. regulation Voltage quality Bulk en. man. UPS Trans. stability

46 1. Power intensive systems Cost of battery scales with power and is roughly independent on the energy Example: battery system made of 1 MW 1 h module, 1M cost each Case 1 Rated power 30 MW Duration of delivery 1 h Rated energy 30 MWh Num. of modules 30 Total Cost 30 M Specific cost 1 M / MWh Case Rated power 30 MW Duration of delivery 6 min Rated energy 3 MWh Total Cost 30 M Specific cost 10 M / MWh 46

47 Cost of SMES scales with energy and is roughly independent on the power For example SMES is competitive in case if the cost of 3 MWh storage is lower than 10 M Case 1 Rated power 30 MW Duration of delivery 1 h Rated energy 30 MWh Num. of modules 30 Total Cost 30 M Specific cost 1 M / MWh Case Rated power 30 MW Duration of delivery 6 min Rated energy 3 MWh Total Cost 30 M Specific cost 10 M / MWh If a large power is required for a more limited time SMES can represent a cost effective storage technology 47

48 . Hybrid SMES - Battery systems load battery Lowpass control PCS High pass control SMES SMES can be conveniently used in combination with battery due to the complementary characteristics Battery provides long term base power hence energy SMES provides peak power and fast cycling 48

49 Power vs time total Advantages: Reduced power rating of batteries Reduced wear and tear of batteries (no minor cycling) Reduced energy rating of SMES battery SMES 49

50 3. Increasy peak power of industry scale batteries 1 MW 6h NaSbattery system with double peak power capacity The power rating of the system is to be doubled for short times ( < 10 s ) due to power quality requirement No impact is obtained on the total storage requirement due to the increased peak power capacity Solution 1 the battery pack is doubled Cost is doubled Energy capacity is also doubled but the system is greatly underexploited 50

51 Solution SMES is added to the battery to provide short term peak power To scale (roughly) 1 MW 6 h + 1 MW 10 s Size and cost of the system can be greatly reduced!! 51

52 4. Protection of sensitive equipment Sensitive customer Voltage sags may occur in power grid due to faults Sensitive customers can only tolerate a voltage reduction f 30 &% for 00 ms

53 1 MW 5 s SMES system

54 The KameyamaSMES 10 MW 1 s SMES system 54

55 5. Leveling of impulsive loads by SMES Pgrid Pload Ismes Pload Pgrid Pload Iload Igrid No battery can be used for this application due to the prohibitive number of cycles Advantages brought by SMES can be significant also for moderate size systems 55

56 Auxiliary network services by SMES I load I grid Ifilter ISMES Harmonic compensation Power factor correction 56

57 6. Hybrid SMES - Liquid Hydrogen system Liquid Hydrogen is used as energy intensive storage Free cooling power is available for SMES due to the presence of LH at 0 K SMES is used as power intensive storage 57

58 Shintomi et al. 58

59 Outline SMES technology SC material and Conductor Coil Power conditioning system A case study - 1 MW / 5 s SMES Applications Energy storage SMES applications Grid Customer / Industry SMES actvities at the University of Bologna 59

60 1. A 00 kj Nb-TiµSMES ( ) Cold test in 014 (and 013) 60

61 . Conduction cooled MgB SMES demonstrator ( ) 3 kj MgB Magnet 40 KW Mosfet Based PCS Cold test in porgress Full test at 1-10 kw to come shortly 61

62 3. Conduction cooled MgB SMES Prototype ( ) MISE - Italian Ministry of Economic Development Competitive call: research project for electric power grid Project funded Budget:.7 M Duration: kj 100 kw prototype full system

63 To resume on SMES.. SMES is feasible, but AC loss need to be investigated SMES is an option if Continuous deep charge/discharge cycling is required (leveling of impulsive loads) Short term increase of peak power of energy intensive systems is required Fast delivery of large power is required for short time 63

64 Thank you for your kind attention