Gateway to a New Thinking in Energy Management - Ultracapacitors · 2005-01-24 · Gateway to a New...

Ultracapacitors Microelectronics High-Voltage Capacitors

Gateway to a New Thinking in Energy Management - Ultracapacitors

By:

Maxwell Technologies - San DiegoJanuary 18th, 2005


About Maxwell

Capacitor Manufacturer since 1965

www.maxwell.com

Manufacturing facilities:US, Europe, Asia

Maxwell is a leading developer and manufacturer of innovative,

cost-effective energy storageand power delivery solutions.

Certifications:ISO 9001:2000ISO/TS 16949

ISO 9002

http://www.maxwell.com/



Table of Content

1. When can I use an Ultracapacitor?2. What is an Ultracapacitor?3. Ultracapacitor Market4. Ultracapacitor Applications5. Sizing your System6. Sizing Examples7. Guidelines to Designing an Ultracapacitor System8. Summary


When can I use an Ultracapacitor?

• Applications that require high reliability back-up power solutions

• Short term bridge power 1 - 60 seconds for transfer to secondary source or orderly shut down

• Power quality ride-through to compensate for momentary severe voltage sags

• Power buffer for large momentary in-rush or power surges


Power vs Energy

What is the difference between Power and Energy?


Application Model


Peak Power Shaving

Peak Power Shaving• Ultracapacitors provide peak power ...

AvailablePower

Required PowerUltracapacitor Peak Power


Back-up PowerBack-Up Power Support

• Ultracapacitors provide peak power…...and back-up power.

Required Power

Available Power Ultracapacitor Backup Power


What is an Ultracapacitor?


Ultracapacitor Performance Characteristics

• Ultracapacitors perform mid-way between conventional capacitors and electrochemical cells (batteries).

• Fast Charge and Fast Discharge Capability• Highly reversible process, 100,000’s of cycles• Lower energy than a battery

~10% of battery energy• Greater energy than electrolytic capacitors• Excellent low temperature performance


What is an Ultracapacitor?

Ultracapacitors are:A 100-year-old technology, enhanced by modern materialsBased on polarization of an electrolyte, high surface area electrodes and

extremely small charge separationKnown as Electrochemical Double Layer Capacitors and Supercapacitors

C = εr A/dMinimize (d)Maximize (A)

E = 1/2 CV2

Dielectric

Film foil Electrode

Electrolyte

ECDL

Separator


Technology Comparison

AvailablePerformance

Lead AcidBattery

Ultracapacitor ConventionalCapacitor

Charge Time 1 to 5 hrs 0.3 to 30 s 10-3 to 10-6 sDischarge Time 0.3 to 3 hrs 0.3 to 30 s 10-3 to 10-6 sEnergy (Wh/kg) 10 to 100 1 to 10 < 0.1Cycle Life 1,000 >500,000 >500,000Specific Power (W/kg) <1000 <10,000 <100,000Charge/discharge efficiency

0.7 to 0.85 0.85 to 0.98 >0.95


Technology Comparison (page 2)

0,01

0,1

1

10

100

1000

10 100 1000 10000

Power Density/[W/kg]

Ener

gy D

ensi

ty/[W

h/kg

]

Double-Layer Capacitors

10h 1h0,1h

36sec

3,6sec

0,36sec

36msec

Lead Acid Battery

Ni/Cd

Li-Battery

Al-Elco

U/C

Fuel Cells


0

1

2

3

4Efficiency

Self Discharge

Availability

Cycle Stability

Energy Density

Power Density

Energy Cost

Power Cost

System Cost

Safety

Recycling

Environment

Temperature Range

Charge AcceptanceUltracapsPb-AGMNiMHLi Ion

Ultracap vs Battery Technologies


Ultracapacitor Market


Ultracapacitor Market

Ultracapacitor World Market

Consumer Products

Digital CameraPDA

Toys

Memory back-up

UPSWindmill

Industrial

Stationary Fuel Cell

Automation/Robotics

Transportation

Hybrid Bus/TruckEngine starting

Light Hybrid

Local Power

Rail


Available Products

• Aqueous Electrolyte: ESMA, Elit, Evan, Skeleton Technologies and Tavrima

• Advantages:• High electrolytic conductivity• No need for tight closure to isolate • Low environmental impact

• Disadvantages:• Low decomposition voltage (1.23V)• Narrow operational range (freezing point of water)

• Organic Electrolyte: Maxwell Technologies, Panasonic, EPCOS, Ness Capacitors, ASAHI GLASS• Advantages:

• High decomposition voltage• Wide operating voltage

• Disadvantages:• Low electrolytic conductivity• Need for tight closure to isolate from atmospheric moisture


Ultracapacitor Applications


Applications

Automotive14/42 V systemsHEVElectrical Subsystems

TractionRegen brakingVoltage stabilizationDiesel engine starting

IndustryPower quality Pitch systemsActuators

Consumer ElectronicsAMRPDAsDigital cameras2-Way pagersScannersToys

Large Cells

Small Cells


Today’s Markets

Wind power plant pitch systemsBurst power

Small cell applicationsDigital cameras, AMR, Actuators, Memory boards

Electric Rail PackBraking Energy Recapture Diesel engine starting

TRACTION INDUSTRY CONSUMER


SITRAS® SES - Solution

Energy storage system: Stationnary or on the vehicle

Time t1Vehicle 1 is braking

Energy storage system stores thebraking energy

Time t2Vehicle 2 is acccelerating

Energy storage system delivers the energy

Application: Time shifted delivery of the stored braking energy for vehicle re-accelerationSolutions: Possible with either stationary or on-vehicle energy storage system

Advantage: Cost savings through reduced primary energy consumption


SITRAS® SES - Benefits

Saved energy

⇒ Reduction of the power need by 50 kW

⇒ Energy saving of 340.000 kWh per year and per installation

⇒ thermal limit68 kWh/h

04.08.01 07.08.01 10.08.01 13.08.01

50

40

30

20

10

0

kWh/h Saved energy

⇒ Reduction of the power need by 50 kW

⇒ Energy saving of 340.000 kWh per year and per installation

⇒ thermal limit68 kWh/h

04.08.01 07.08.01 10.08.01 13.08.01

50

40

30

20

10

0

kWh/h

04.08.01 07.08.01 10.08.01 13.08.01

50

40

30

20

10

0

kWh/h


MITRAC of Bombardier Transport

MITRAC energy saver


Diesel Engine Cranking by Stadler

Ultracap module for diesel engine vehiclesRobust construction with voltage balancingEasy to scale up for additional cranking powerEasy to integrate in existing housingEasy to use, maintenance free


Wind Turbine Pitch Systems

Modern wind turbinesconsist of three-bladed variable speed turbines

Independent electro-mechanical propulsion units control and adjust the rotor-blades

Latest technology uses the wind not only to produce wind energy but also for its own safety


Pitch System Storage Systems

Each pitch systems is equipped with an ultracapacitor emergency power supply

Ultracapacitors represent an optimum emergency power supply system due to their• Enhanced level of

safety• High reliability• Efficiency• Scalability

Switch box including 2600F ultracapacitors

75 V, 81 F ultracapacitor module

4 modules are put in series to power 300 V

pitch systems of 3-5 MW wind power plants


Fuel Cell Powered Fork Lift

• BOOSTCAP module:48 BCAP0010112 V, 55 F40 kW peak power

• Fork lift equipped with a fuel cell

• Cell system and an ultracapacitor module


Vehicle Applications of Ultra-capacitors

• Distributed energy modules are located at the actuator level in the vehicle control hierarchy in close proximity to the actuator power driver (should be within 18”).

Vehicle SystemController

ISG SubsystemBelt or Crankshaft

Engine Transmission

High VoltageBattery Primary Storage

Other 42VLoads

Brake actuators

ETC, Fan, Water Pump

ISGTorque

Gear Sel, L/U ClutchOil Pump

SOC, SOH,Vsys

Continuous,Scheduled,Selectable

BrakesRegen Brake Sys

Steeringelectric assist

Steering actuator

UC UCUC

ECU

MtrRac

k ECU

HCU

ECU

Mtr ThrottleBody

SteeringWheel

BrakePedal

AccelPedal

Power & Communications (PDA)

DistributedEnergy StorageModules

Energy StorageSystem Mgm't

UC UC

ECU

HVAC

Electric aircond. comp.


Fuel Cells with Ultracapacitors

Ultracapacitors are accepted as the normal energy storage option for fuel cells

• Every major automotive company in the world is testing fuel cells as an alternative drive train power system.

• All significant fuel cell companies are either using or experimenting with ultracapacitors as an integral part of the system.

• Several major automotive companies have declared fuel cells with ultracapacitors as their baseline system architecture. Honda and Hyundai have gone public, others we are working with have not.

“Utilizing ultracapacitors we have gained an edge in energy efficiency and throttle responsiveness over competitors that are pursuing the hybrid battery–fuel cell model”Honda Motor Company


Sizing Your System


Data sheet


How to measure Ultracapacitors

• To measure UC you need:• bi-directional power supply (supply/load) OR• separate power supply and programmable load (constant current capable)• voltage vs. time measurement and recording device (digital scope or other data

acquisition)

• Capacitance and Resistance:Capacitance = (Id * td)/(Vw - Vf) = (Id * td)/Vd

ESR = (Vf - Vmin)/Id

Vw = initial working voltage Vmin = minimum voltage under loadId = discharge current Vf = voltage 5 seconds after removal of load.td = time to discharge from initial voltage to minimum voltage


Basic Equations

Definition of Capacitance: C = Q/V (1)

Charge = current * time: Q = I*t C = I*t/V (1a)

Solving for voltage: V = I*t/C (2)

Dynamic Voltage: dV/dt = I/C (3)

Stored Energy E = ½ C*V2(4)

At initial voltage Vo, Eo = ½ C*Vo2

At final voltage Vf, Ef = ½ C*Vf2

Delivered energy = Eo – Ef ∆E =½ C*(Vo2 – Vf

2) (5)


Voltage & Current vs. TimeC = 15 farad; Resr = 100 milliohm

Vo = 48V; I = 30A

-5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15Time (sec)

20

25

30

35

40

45

50

Vol

tage

(V)

0

5

10

15

20

25

30

35

40

45

50

Cur

rent

(A)

-

Resr

+

+C-

i

Voltage

Current

Vo

Vmin

Vf

V = Q/CdVesr = I*ResrdV/dt = I/C ; dV = I*dt/CdVtotal = I*dt/C + I*Resr∆E =½ C*(Vo2 – Vf

2)


Basic Model

• Series/Parallel configurations• Changes capacitor size; profiles are the same• Series configurations

• Capacitance decreases, Series Resistance increases• Cs=Ccell/(#of cells in series) Rs=Rcell*(# of cells in series)

• Parallel configurations• Capacitance increases, Series Resistance decreases• CP=Ccell*(# of cells in parallel) RP=Rcell/(# cells in parallel)

• Current controlled• Use output current profile to determine dV/dt

dV = I * (dt/C + ESR)• Power controlled

• Several ways to look at this:Pterm = I*Vcap –I2*ESR (solve quadratic for I)I = [Vcap - sqrt(Vcap

2-4*ESR*Pterm)]/(2*ESR)• Solve for dV/dt as in current-controlled• J=W*s=1/2CV2 Solve for C.


Applications with a singleenergy storage component

• Applications in which little total energy is required (i.e. memory backup)

• Possibly used with other energy sources• Short duration, high power (i.e. pulse transmit)• Long duration, low power (i.e UPS backup)• Opportunities for high charge rates (i.e toys)


Applications with twoenergy storage components

• Power vs. Energy design tradewhen using two components• Single component vs. two components

• Engines/Fuel cells/Batteries/Solar Arrays are energy rich/power poor (or poor response)

• Size these components for enough energy, system may be limited in power

• Size these components for power, system may have surplus of energy• Ultracapacitors are power rich/energy poor

• Size an ultracapacitor for enough energy, system may have a surplus of power

• Size an ultracapacitor for power, system may be limited in energy

• Two components• A primary source for energy; Ultracapacitor for power• Requires appropriate definition of peak power vs. continuous power


Ultracapacitor Aging

• Unlike batteries, Ultracapacitors do not have a hard end of life criteria.

• Ultracapacitors degradation is apparent by a gradual loss of capacitance and a gradual increase in resistance.

• End of life is when the capacitance and resistance is out of the application range and will differ depending on the application.

• Therefore life prediction is easily done.


Capacitance and ESR vs Frequency

ESR vs . Frequency

0,00E+00

1,00E-04

2,00E-04

3,00E-04

4,00E-04

5,00E-04

6,00E-04

7,00E-04

1,00E-02 1,00E-01 1,00E+00 1,00E+01 1,00E+02 1,00E+03Frequency [Hz]

ESR

[mO

hm]

Capacitance vs. Frequency

0,00E+00

5,00E+02

1,00E+03

1,50E+03

2,00E+03

2,50E+03

3,00E+03

3,50E+03

1,00E-02 1,00E-01 1,00E+00 1,00E+01 1,00E+02 1,00E+03

Frequency [Hz]

Cap

acita

nce

[F]


C and ESR Temperature Dependency

0,4

0,5

0,6

0,7

0,8

0,9

1

1,1

1,2

-60 -40 -20 0 20 40 60 80 100Temperature [°C]

ESR

[mO

hm]

1000

1200

1400

1600

1800

2000

Cap

acita

nce

[F]

ESR BCAP00 0 8 (DC)Cap acitance BCAP0 0 0 8


BCAP Self Discharge

Self Discharge vs Temperature

30,0

40,0

50,0

60,0

70,0

80,0

90,0

100,0

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30

Time [days]

% U

(t =

0)

- 35 °C

+ 5 °C

+ 25 °C

+ 65 °C


BCAP Cycling Capacity

90 A CC, 1.15-2.3 V, 25 s, RT

50.0

60.0

70.0

80.0

90.0

100.0

110.0

0 20000 40000 60000 80000 100000

Cycle Number

Cha

nge

in C

apac

itanc

e [%

]

0.0E+002.0E-044.0E-046.0E-048.0E-041.0E-031.2E-031.4E-031.6E-031.8E-032.0E-03

ESR

[Ohm

]

ESR

Capacitance


BCAP Cycling

500’000 cycles between 1.8 and 2.7 V, 100 AESR (1 Hz) increase 140 % (0.49 to 0.79 mOhm Capacitance decrease 38 % (2760 to 1780 F), 30% compared to rated capacitance


BCAP DC Life

Capacitance and ESR variation at U, T = 40 °C

50,0

55,0

60,0

65,0

70,0

75,0

80,0

85,0

90,0

95,0

100,0

105,0

0,0 100,0 200,0 300,0 400,0

duration [days]

% C

(t =

0)

2.5V 40°C

2.1V 40°C

2.3V 40°C

-40,0

-20,0

0,0

20,0

40,0

60,0

80,0

100,0

120,0

140,0

160,0

180,0

200,0

0,0 100,0 200,0 300,0 400,0duration [days]

% E

SR (t

= 0)

2.5V 40°C2.1V 40°C2.3V 40°C


BCAP DC Life

0,0

20,0

40,0

60,0

80,0

100,0

120,0

0 100 200 300 400

duration [days]

% C

(t =

0)

2.1V 65°C2.3V 65°C2.5V 65°C

-40,0

-20,0

0,0

20,0

40,0

60,0

80,0

100,0

120,0

0 100 200 300 400duration [days]

% E

SR (t

= 0)

2.5V 65°C2.1V 65°C2.3V 65°C

Capacitance and ESR variation at U, T = 65 °C


Sizing Examples


Example sizing

1) Define System Requirements15 W delivered for 10 seconds10V max; 5V min

2) Determine total energy needed: J=WS=10W*10sec=150Ja) Determine Capacitance based on: J=1/2CV2

b) Substitute the energy from above: 150J=1/2C(Vmax2-Vmin

2)c) Solve for C: C=300/(102-52)=4F

3) Add 20-40% safety margin to cover I2R losses Csystem = 4.8F4) Calculate number of cells in series (since maximum cell voltage = 2.5V)

10V/2.5V = 4 cells in series5) Calculate cell-level capacitance

C = Csys * # of series cells = 4.8F* 4 = 19.2F per 2.5V “cell”6) Calculate number of cells in parallel (we will assume a 10F cell)

# in parallel = 19.2/10F = 2 x 10F cells in parallel


Guidelines to Designing an Ultracapacitor System


Ultracapacitor Cell Balancing

Why Cell Balancing?

• Achieve cell to cell voltage balance

• Accounts for variations in capacitance and leakage current, initial charge and voltage dependent on capacitance, sustained voltage dependent on leakage current

• Reduces voltage stress on an individual cell

• Increase overall reliability of the individual cells



How to Cell Balance?

• Resistor method, resistor placed in parallel, resistor value calculated at 10x leakage current for slow balance, 100x for faster balance, good for low cycle when efficiency or stand by loss not an issue

Surface Mount Resistor for low

duty cycle application



• Active method, use semiconductors to limit or balance voltage between cells, best for high duty cycle or when efficiency and stand by loss from leakage current are important, highest cell reliability option

Active cell to cell balance circuit


Cell Balancing2600F cells; 4 in Series• Low Cost

• Scalable balance current• 10mA, 300mA circuits

• Very low quiescent current (<20µA)• No on/off required

• Modular installation• N cells requires N-1 circuits

• Voltage independent

Low capacitance,high leakage cell

Note high and low points;

low capacitance cell

1.5 hours of Vehicle cycling (~ 200A)

300mA balancer for 50 & 60mm Ø cells

10mA balancer for 5F & 10F cells


Cell Balancing

+

-

R3

R4

C2

C11M 1%

1M 1%

R1

R2

VPP

VNN

U1

499k 1%

475 1%Ultracapacitors

C1 Positive

C1-C2 Midpoint

C2 Negativ e

POS

NEG

+

-U1

VNN

VPP

R1100K 1%

R2100K 1%

R6

5.6 1% 1.5W

R549.9k 1%

C2

C1

Ultracapacitors

C1 Positive

C1-C2 Midpoint

C2 Negative

POS

NEG

Q1

Q2

TLV2211CDBV

R3

100

R4

100

MMBT2222AWT1

MMBT2907AWT1

10mA Balancer

300mA Balancer


Cell Balancing

Three cells with one cell balancing resistor removed:OCTA Cycles Max. Voltage Profiles

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

0 1 2 3 4 5 6 7 8 9 10

Day #

Cel

l vol

tage

(V)

C1-V

C2-V

C3-V


Ultracapacitor Packaging

Why Packaging?

• Ensure proper mechanical stress• Ensure robust low resistance interconnect• Ensure proper electrical isolation• Ensure proper thermal considerations• Ensure agency compliance• Increase overall cell reliability• Reduce or eliminate maintenance requirements



How to Package Cells?

• Care should be taken for the electrical interconnect, a few key guidelines to follow:

• Do not over torque. Over torque at the terminals may cause internal failure of contact points. For example, the Maxwell BCAP specification is 100 in.-lbs

• Use similar conductor metal interconnect bus bars to eliminate galvanic corrosion.

• Good surface to surface contact will reduce inter-cell resistance, reducing voltage drop and temperature stress



How to Package Cells?

• Cell to cell spacing should take into consideration two key points and can be accomplished by the design of the interconnect or the cell balancer:

• Depending on the cell some part of the outer case may be electrically the same as one of the terminals, ensure electricalisolation and watch for rubbing components that may wear through ultracapacitor insulation, do not remove the factory installed insulator sleeve

• Some air space between the cells allows convection cooling via air flow improving reliability, depends on cycle time, short duration high cycle applications may require forced air or othercooling method



Proper Torqueand Hardware

ElectricalIsolation

Aluminum Interconnect


Summary


Benefits Summary

Calendar Life• Function of average voltage and temperature

Cycle Life• Function of average voltage and temperature

Charge acceptance• Charge as fast as discharge, limited only by heating

Temperature• High temp; no thermal runaway• Low temp; -40°C


Benefits Summary

No fixed Voc• Control Flexibility; context-dependent voltage is permitted• Power Source voltage compatibility

• Examples; Fuel cells, Photovoltaics

No Vmin• Cell can be discharge to 0V.• Control Safety; No over-discharge• Service Safety

Cell voltage management• Only required to prevent individual cell over-voltage

State of Charge & State of Health• State of Charge equals Voc

• Dynamic measurements for C and ESR = State of Health• No historical data required


Useful Links

• Useful links on Maxwell Technologies Web-site:• White Papers• Technology Overview• Sizing worksheet• Application Notes• Data Sheets

www.maxwell.com


Gateway to a New Thinking in Energy Management - Ultracapacitors · 2005-01-24 · Gateway to a New...

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Transcript of Gateway to a New Thinking in Energy Management - Ultracapacitors · 2005-01-24 · Gateway to a New...