Superconducting Magnetic Energy StorageConcepts and applications

Antonio MorandiDEI Guglielmo MarconiDep. of Electrical, Electronic andInformation Engineering

University of Bologna, Italy

Tuesday, November 27, 2018

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• Energy Storage

• SMES TechnologyPower conditioning system & operationSC CoilState of the art

• SMES ApplicationsCustomer / IndustryGrid

Outline

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The need for electric energy storage / chapter 1 - grid

• Generation / load imbalance is inherent inthe power grid due to random fluctuation of loads

induced by customers variation of generation from

renewables

• Sudden and large generation/loadimbalance can also occur due tocontingency

• Continuous and fast regulation of the generated power and/or loads isrequired for controlling the frequency and stability of the grid.

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Load diagram

Due to random nature of fluctuations regulating power is cyclic Regulation is a zero energy service

• Prediction is made by the TSO in order toplan the generation so as to satisfy theenergy need

actual

predicted

imbalance

12500

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Methods/technologies for grid energy management

• Curtailment of renewables• Improved control of convent. gen.• Demand control• Network upgrade ( … Supergrid )• Energy storage

Energy storage system allows to shift electric energy in time so as to decouple productionand consumption

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The need for electric energy storage / chapter 2 – customer

Energy storage

• Power quality and UPS

• Leveling of impulsive/fluctuating power

(industry, physics, … )

Sensitive customers (semiconductors, oil, data centers …) cannot tolerate power

interruptions or voltage sags

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Which storage technology?Parameters of the energy storage system

• Absorbed/supplied power, P• Duration delivery, t• Number of cycles, N• Response time, tr

No unique storage technology exists able to span the wide range of characteristicsrequired for applications

• Most suitable storage technology mustbe chosen from case to case

• Hybrid systems, obtained by combiningdifferent storage technologies,represents the best solution in manycases

In many applications the parametersof the operating cycle changescontinuously and randomly.

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• Energy Storage

• SMES TechnologyPower conditioning system & operationSC CoilState of the art

• SMES ApplicationsCustomer / IndustryGrid

Outline

PCS

Control andprotectionsystem

Coolingsystem

Superconductingcoil

gridCurrent leads

vacuumvessel

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SMES – Superconducting Magnetic Energy Storage

2

0

2

0

2

2

1

22ILd

Bd

BW

coil

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• For typical design assumptions for power electronics current of SMES operating in theMW range is in the order of kAs

• More conductors have to be put in parallel for reaching the required transport current

Continuously transposed (Roebel) cable

• Scraps are produced• Je cable = 0.8 – 0.9 Je tape

Magnet design – cable requirement

Conductor on Round Core (CORC) cable

• Je cable > 200 A/mm 2 @ 4.2 K and 20 T

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5 MJ coil - 4TTorus2G HTS

Magnet design – coil geometry – a study

5 MJ coil - 4TSolenoid2G HTS

• Simpler and more cost effective• Easier handling of the electromagnetic stress• Smaller foot-print

• Low stray field• Reduced perp. field on conductor

Mechanical design includes• Pretensioning due to winding of the coil• Thermal contraction during cool down• Lorentz force

Von Mises stress Strain

Mechanical analysis

204 MPa maxon G10

0,15% maxon cond.

Stress within allowable limitfor all materials

Strain within allowable limitfor all materials

Equivalent Young’s modulus of the tape of 157.3 MPaobtained from weighted average

Elastic’s moduli and thermal expansion coefficients ofall materials taken from• K Konstantopoulou et al., “Electro-mechanical characterization of MgB2

wires for the SC Link Project at CERN”, SUST 2016• J. W. Ekin, Experim. Techniques for Low Temp. Measurements, OUP, 2006• P. Bauer et al., EFDA Material Data Compilation for Supercond. Simulation• CRYOCOMP

Quench Detection&Protection

Temperature distrbution at 1 sT/n=0

T/n=0

T/n=0

=0L = 6.8 HR = 2.1 Ω = 3.3 sHeat

injection

0.2 s

SMES discharged on the dumpresitor by means of the QPS

The appearance of the resistance in onehalf of the coil is detected by means ofbalanced bridge

Discharge of the coil on a dump resistoris commanded if the quench is detected

• The dump resistor must be chosen so as that the voltageon the coil does not exceed the allowed limit

• Thermal analysis must be carried out to calculate the hotspot temperature reached

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Power conditioning system – black box

SMES

0

PCSAC

Grid

P I

2 20 0

1 1( )

2 2L I LI P t t

Energy balance

I0

SMES current

Delivered/absorbed powerI0, current of SMES at time t0

20 0

2( )I I P t t

L

“−” and “+” apply duringdischarge/charge respectively

Unidirectional current, changing as sqrt of time, is obtained in the SMES duringcharge and discharge

L

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• Flexible architecture - Control algorithm defined based on the service to be provided• Power modulation• Islanding operation• Active filtering

• Magnet protection system integrated in the PCS both at HD and the SW level

Power Conditioning System - detail

System level control P*, Q*, v*

DC/AC - inverter DC/DC - chopper

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Discharge (or charge)

L

C

Vdc

ISMES

• Controlled power transferred from the DC bus thegrid by means of the inverter

• The voltage of the DC bus is kept constant by theSMES by means of the two quadrant chopperDC

/ AC

Idc Idc

Vdc constant < I dc > = < Idc > P = P

< I dc >ISMES

time

TON

TOFF

Tcycle

Idc

L

C

Vdc

ISMESDC /

AC

Idc Idc

L

C

Vdc

ISMESDC /

AC

Idc Idc

Similar behavior during charge

Negative voltage on coil ( - Vdc )Current slightly decreasing

Zero voltage on coilCurrent constantTcycle typically 0.1 – 1 ms

(1 – 10 kHz)

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Ripple• Smooth average current profile during charge or

discharge of the SMES coil• Time change (functional) of the smooth current

profile is responsible for AC loss induced in thecoil (and metallic parts)Example:

1 MW 5 s dischargeLSMES = 1.250 Hfchopper = 500 Hz

A ripple at the same frequency of choppercommutation is superimposed to thesmooth profile

This ripple has negligible amplitude and hassmall effect in terms of AC loss

20 0

2( )I I P t t

L

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To know on SMES – 1 / Energy capacity

Typical rating of SMES in the order of MJs (MW × seconds)

• Energy: MJs kWs

32 cm

1.2 kWhCommercial Li-battery module

Energy capacity of large SMEScomparable with that of smallbattery systems

• Power: MWs

1 MW Li-battery system(groupnire.com)

Power capacity of SMES comparablewith that of large battery systems

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To know on SMES – 2 / Standby lossesCurrent of SMES free-wheels through PE switches when no power is delivered/absorbed.Losses are produced during the standby

Von IGBT = 0.5 1.5 VVon DIODE = 0.5 1 V

PIGBT = ISMES Von IGBT

PDIODE = ISMES Von DIODE

Pidling = 1 5 kW / kA

SMES currentdelivered power LC

Vdc

ISMESDC /

AC

SMES

• The whole energy of the SMESis lost in the power electronicswithin a few minutes

• SMES is only suitable forcontinuous operation

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The use of thermal actuated SC switch foravoiding idling losses is possible in principle butit is unfeasible in practice since switching timebelow 1 ms would be required

LC

Vdc

DC /

AC

Idc Idc

Strong synergy possible with cryo power electronics

Great R&D effort (not publically available) on CPE isin progress for application in spacecraft, ships,aircraft, and datacenters

MTECH Laboratories, LLC

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To know on SMES – 3 / Efficiency

cs

tPtP

P, deliverable powert , duration of delivery tcycle , duration of the cycle tidle, duration of idling phases , intrinsic efficiency of the storage devicec , efficiency of the convertersPaux , power required for auxiliary servicesPidle , power loss (if any) during idling

cycle

power

energy

idleidlecs

tPtP

tP

aux cycle idle idles c

P tP t

P t P t

High efficiency of SMES achieved in case• High exchanged power• No (or short) stand-by / continuous power

management(additional services can mitigate this)

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Japan

Germany

EM Laucher

JapanUSA

Japan

Italy

France

GermanyPower modulatorFlicker

Gridcompensation

The state of the art of SMES technology

The DRYSMES4GRID project:• 500 kJ / 200 kW SMES• MgB2 material• Cryogen free cooling

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The Kameyama SMES

10 MW – 1 s SMES system

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• TechnologyPower conditioning system & operationSC CoilState of the art

• ApplicationsCustomer / IndustryGrid

• SMES experience at the University of Bologna

Outline

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To summarize ….

• Energy capacity of SMES is much smaller compared to batteries

• Idling losses in power converters do not allow long term storage

• Cooling power continuously required

Is there room for SMES?

At customer level ?At grid level ?

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1. Leveling of impulsive/fluctuating loads by SMESPl

oad

• Continuous management of high power makes cooling and idling loss negligible• No battery can be considered due to the prohibitive number of cycles• Advantages brought by SMES can be significant also for moderate size systems

• AC loss may be a limiting factor

Pgrid Pload

Sizing of the supply system based on average ratherthan peak power

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2. Hybrid SMES - Battery systems

Complementary characteristics exploited

• Battery provides long term basepower – hence energy

• SMES provides peak power andfast cycling

Advantages:

• Reduced power rating of batteries• Reduced wear and tear of batteries

(no minor cycling)• Reduced energy rating of SMES

Qualitative (not a real case)

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3. Combined use with synergistic technologies

A 350kW/2.5MWh Liquid Air Energy Storage (LAES)pilot plant was completed and tied to grid during2011-2014 in England.

Fundraising for further development is in progress

• LAES is used as energy intensive storage• Large cooling power (not all) is available for SMES

due to the presence of Liquid air at 70 K• SMES is used as power intensive storage

Effective hybrid (Energy intensive +Power intensive) storage can beconceived based on combined useof SMES and LAES

A 1-2 MW – 5 min ratingmay be of interest

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• TechnologyPower conditioning system & operationSC CoilState of the art

• ApplicationsCustomer / IndustryGrid

• SMES experience at the University of Bologna

Outline

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1. A 200 kJ Nb-Ti µSMES ( 2000 – 2004 )

Cold test in 2004 (and 2013)

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2. Conduction cooled MgB2 SMES demonstrator (2014 – 2016)

• 3 kJ MgB2 Magnet• 40 KW Mosfet Based PCS

Cold test completedFull test at 1-10 kW to come shortly

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• Transmission and distribution• Dispersed generation, active networks and storage• Renewables (PV and Biomass )• Energy efficiency in the civil, industry and tertiary sectors• Exploitation of Solar and ambient heat for air conditioning

MISE - Italian Ministry of Economic DevelopmentCompetitive call: research project for electric power grid

The DRYSMES4GRID Project

Partners• University of Bologna• ICAS - The Italian Consortium for ASC, Frascati (Rome)• RSE S.p.A - Ricerca sul Sistema Energetico, Milan• CNR – SPIN, Genoa

Project DRYSMES4GRID funded

• Budget: 2.7 M€• Time: June 2017 – June 2020

Project Coordinator:• Columbus Superconductors SpA, Genova, Italy

• developm. of dry-cooled SMES based on MgB2• 300 kJ – 100 kW / full system

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Project Workplan

WP2. Layout and functionsWP3. Detailed design and manufact. of converters

Power conditioning system

WP1. Electromagnetic & thermal design

Design of the magnet

WP4. Optimization of in-field perform. of the wireWP5. Manufacturing of wire, cable and winding

Wire, cable and winding

WP6. Assembly of coil and cooling & prelim. testWP7. Assembly of PCS & Experiments in test facility

Assembling and test

WP8

. Diss

emin

atio

n

WP9

. Pro

ject

man

agem

ent

WP1

0.Te

ch.&

Econ

.ana

lys.

of S

MES+ PE industry

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Thank you for your attentionantonio.morandi@unibo.it