201110141-chandan kumar.doc

8/10/2019 201110141-chandan kumar.doc

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SUPER CAPACITOR

Seminar ID: 694

A Technical Seminar ReportSubmitted in partial fulfillment ofthe requirement for the B.Tech.

Under Biju Patnaik University of Technoloy! Rourkela.

Submitted By

CHANDAN KUMAR Roll No.#ECE201110141

AU"UST # $%&'

Under the uidance of

Mr. SANTSH KUMAR !ADHI

A!E" INSTITUTE TECHN$%& ' MANA%EMENT!a(ala) *(+,ane-ar) /i-(a 2101) In/ia


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A!E" INSTITUTE TECHN$%& ' MANA%EMENT!a(ala) *(+,ane-ar) /i-(a 2101) In/ia

CERTIFICATE

This is to certify that the seminar report entitled Super Capacitoris a

bonafide work done by Chandan Kumar bearing Registration No.

1101314071 of ECE branch.

This seminar report is submitted in partial fulfillment for the

requirement of the B.Tech degree under Biju atnaik !ni"ersity of

Technology# Rourkela# $disha.

(Mr. San3o-( K+mar !a/(i

Seminar %+i/e

5Mr-. T. Mi3a K+mari 5!ro. R. C.Da-

*.Te7( Seminar Coor/ina3or !RINCI!A$


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ABSTRACT

The super capacitor# also known as ultra capacitor or double%layer capacitor differs

from a regular capacitor in that it has a "ery high capacitance. & capacitor stores energy

by means of a static charge as opposed to an electrochemical reaction. &pplying a

"oltage differential on the positi"e and negati"e plates charges the capacitor. This is

similar to the buildup of electrical charge when walking on a carpet. Touching an object

releases the energy through the finger.

The modern super capacitor is not a battery but crosses the boundary into battery

technology by using special electrodes and electrolyte. 'e"eral types of electrodes ha"e

been tried and we focus on the double%layer capacitor ()*C+ concept. ,t is carbon%

based# has an organic electrolyte that is easy to manufacture and is the most common

system in use today.

&ll capacitors ha"e "oltage limits. -hile the electrostatic capacitor can be made to

withstand high "olts# the super capacitor is confined to ./0.12. 2oltages of .32 and

higher are possible but they would reduce the ser"ice life. To achie"e higher "oltages#

se"eral super capacitors are connected in series. The specific energy of the super

capacitor is low and ranges from 4 to 56-h7kg. &lthough high compared to a regular

capacitor# 56-h7kg is one%fifth that of a consumer *i%ion battery.

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ACKNOWLEDGEMENT

, would like to e8press my immense sense of gratitude to my guide# Mr. Santosh

Kumar Padhi# for his "aluable instructions# guidance and support throughout myseminar.

, again owe my special thanks to Mrs. T. Mita Kumari# Technical 'eminar

Coordinator for gi"ing me an opportunity to do this report.

&nd finally thanks to Pro. !. C. "as# rincipal# &,T9# Bhubaneswar for his

continued dri"e for better quality in e"erything that happens at &,T9. This report is a

dedicated contribution towards that greater goal.

C#$%"$% K&M$!

'C'(01110141

ii


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TABLE OF CONTENTS

$)ST!$CT...................................................................................................................i

$CK%*+,'"-'M'%T...........................................................................................ii

,ST */ /-&!'.......................................................................................................i

1. %T!*"&CT*%....................................................................................................1

(. #ST*!..................................................................................................................(

3. C*%ST!&CT*% 2 C*%C'PT..........................................................................3

4.P!%CP,' */ &,T!$C$P$CT*!..................................................................

. M$T'!$,S............................................................................................................7

. "'%ST *)T$%'" ) M$T'!$,S.............................................................5

7. C#$!$CT'!STCS...........................................................................................11

6. $"$%T$-'S.......................................................................................................1(

5. "S$"$%T$-'S................................................................................................13

10. $PP,C$T*%....................................................................................................14

10.1 M*T*! !$C%-.........................................................................................14

10.( C*%S&M'! ','CT!*%CS.....................................................................1

10.3 $,T'!%$T' '%'!-............................................................................1

10.4 P!C'..............................................................................................................1

10. M$!K'T........................................................................................................1

11. )$TT'!'S S &,T!$ C$P$CT*!............................................................1

11.1 )$TT'!'S....................................................................................................1

11.( &,T!$ C$P$CT*!....................................................................................1

1(. C*%C,&S*%.....................................................................................................17

!'/'!'%C'S...........................................................................................................16

iii


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LIST OF FIGURE

/ig. 3.1 Construction o Supercapacitor.......................................................................3

/ig. 3.( Cure o Po8er and 'nerg9 "ensit9 o Supercapacitor................................4

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1. INTRODUCTION

The electrochemical ultra capacitor is an emerging technology that promises to play

an important role in meeting the demands of electronic de"ices and systems both now

and in the future. This newly a"ailable technology of ultracapacitors is making it

easier for engineers to balance their use of both energy and power. Energy storage

de"ices like ultracapacitors are normally used along with batteries to compensate for

the limited battery power capability. E"idently# the proper control of the energy

storage systems presents both a challenge and opportunity for the power and energy

management system. This paper traces the history of the de"elopment of the

technology and e8plores the principles and theory of operation of the ultracapacitors.

The uses of ultracapacitors in "arious applications are discussed and their ad"antages

o"er alternati"e technologies are considered. To pro"ide e8amples with which to

outline practical implementation issues# systems incorporating ultracapacitors as "ital

components are also e8plored. This paper has aimed to pro"ide a brief o"er"iew of

ultracapacitor technology as it stands today. re"ious de"elopment efforts ha"e been

described to place the current state of the technology within an historical conte8t.

'cientific background has also been co"ered in order to better

understand performance characteristics. ossible applications of ultracapacitor

technology ha"e also been described to illustrate the wide range of possibilities that

e8ist. Because of the ad"antages of charging efficiency# long lifetime# fast response#

and wide operating temperature range# it is tempting to try and apply ultracapacitors

to any application that requires energy storage. The limitations of the current

technology must be fully appreciated# howe"er# and it is important to reali:e that

ultracapacitors are only useful within a finite range of energy and power requirements.

$utside of these boundaries other alternati"es are likely to be the better solution.

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2. HISTORY

;eneral Electricengineers e8perimenting with de"ices using porous carbon electrodes

first obser"ed the E)*C effect in 4

researchers at'tandard $il of $hiode"eloped the modern "ersion of the de"ices# after

they accidentally re%disco"ered the effect while working on e8perimental fuel

cell designs. Their cell design used two layers of acti"ated charcoalseparated by a

thin porous insulator# and this basic mechanical design remains the basis of mostelectric double%layer capacitors.

'tandard $il did not commerciali:e their in"ention# licensing the technology

toNEC# who finally marketed the results as ?supercapacitors@ in 4


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3. CONSTRUCTION & CONCEPT

i8. .1 Con-3r+73ion o S+er7aa7i3or

Comparison of construction diagrams of three capacitors. *eft =normal= capacitor#

middle electrolytic# right electric double%layer capacitor.,n a con"entional capacitor#

energy is stored by the remo"al of charge carriers# typically electrons# from one metal

plate and depositing them on another. This charge separation creates a potential

between the two plates# which can be harnessed in an e8ternal circuit. The total

energy stored in this fashion is proportional to both the amount of charge stored and

the potential between the plates. The amount of charge stored per unit "oltage is

essentially a function of the si:e# the distance# and the material properties of the plates

and the material in between the plates (the dielectric+# while the potential between the

plates is limited by breakdown of the dielectric. The dielectric controls the capacitorFs

"oltage.

$ptimi:ing the material leads to higher energy density for a gi"en si:e of

capacitor.E)*Cs do not ha"e a con"entional dielectric. Rather than two separate

plates separated by an inter"ening substance# these capacitors use =plates= that are in

fact two layers of the same substrate# and their electrical properties# the so%called

=electrical double layer=# result in the effecti"e separation of charge despite the

"anishingly thin (on the order of nanometers+ physical separation of the layers. The

lack of need for a bulky layer of dielectric permits the packing of plates with much

larger surface area into a gi"en si:e# resulting in high capacitances in practical%si:ed

packages.,n an electrical double layer# each layer by itself is quite conducti"e# but the2
http://upload.wikimedia.org/wikipedia/commons/8/83/Supercapacitor_diagram.svg


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SUPER CAPACITOR

physics at the interface where the layers are effecti"ely in contact means that no

significant current can flow between the layers. Aowe"er# the double layer can

withstand only a low "oltage# which means that electric double%layer capacitors rated

for higher "oltages must be made of matched series%connected indi"idual E)*Cs#much like series%connected cells in higher%"oltage batteries.E)*Cs ha"e much higher

power density than batteries. ower density combines the energy density with the

speed that the energy can be deli"ered to the load. Batteries# which are based on the

mo"ement of charge carriers in a liquid electrolyte# ha"e relati"ely slow charge and

discharge times. Capacitors# on the other hand# can be charged or discharged at a rate

that is typically limited by current heating of the electrodes. 'o while e8isting E)*Cs

ha"e energydensities that are perhaps 4746 that of a con"entional battery# theirpower

density is generally 46 to 466 times as great (see diagram# right+.

i8. .2 C+r;e o !oer an/ Ener8< Den-i3< o S+er7aa7i3or

The capacitor then e"ol"ed into an electrostatic capacitor where the electrodes

were made up of foils and separated by paper that ser"ed as the dielectric. These

capacitors are used in the electronic circuit boards of a number of consumer

applications. Aere the surface area of one electrode was increased by etching the

3


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electrode to roughen it# reducing the thickness of the dielectric and using a paste%like

electrolyte to form the second electrode.

&n ultra%capacitor howe"er has a significantly larger storage area. !ltra

capacitors are made with highly porous carbon materials. These materials ha"e the

capability of increased surface areas ranging greater than 4#/66 square feet per gram.

The separation distance between the charged plates is reduced significantly to

nanometers (46(%


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4.PRINCIPLE OF ULTRACAPACITOR

The charge%storage mechanism and the design of theultra%capacitor are described.

Based on a ceramic with an e8tremely high specific surface area and a metallic

substrate# the ultra capacitor pro"ides e8tremely high energy density and e8hibits low

E'R (equi"alent series resistance+. The combination of low E'R and e8tremely low

inductance pro"ides the ultra%capacitor with a "ery high power density and fast

risetime as well. &s a double%layer capacitor# the ultra%capacitor is not constrained by

the same limitations as dielectric capacitors. Thus# although its discharge

characteristics and equi"alent circuit are similar to those of dielectric capacitors# the

capacitance of the ultra%capacitor increases with the ceramic loading on the substrate

and its E'R is in"ersely proportional to the cross%sectional area of the de"ice.

Theultra%capacitor is composed of an inline stack of electrodes# which leads to an

e8tremely low inductance de"ice# and it e8hibits interesting frequency dependence.

The ultra%capacitor principlehas been e8tended to no aqueous electrolytes and to a

wide temperature range.


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. MATERIALS

,n general# E)*Cs impro"e storage density through the use of a nanoporousmaterial#

typically acti"ated charcoal#in place of the con"entional insulatingbarrier.&cti"ated

charcoalis a powder made up of e8tremely small and "ery =rough= particles# which#

in bulk# form a low%density heap with many holes that resembles a sponge.The

o"erall surface area of e"en a thin layer of such a material is many times greater than

a traditional material like aluminum# allowing many more charge carriers (ions or

radicals from the electrolyte+ to be stored in any gi"en "olume. The charcoal# which is

not a good insulator# replaces the e8cellent insulators used in con"entional de"ices# so

in general E)*Cs can only use low potentials on the order of to 5 2.

&cti"ated charcoal is not the =perfect= material for this application. The charge

carriers are actually (in effect+ quite largeIespecially when surrounded by sol"ent

moleculesIand are often larger than the holes left in the charcoal# which are too

small to accept them# limiting the storage.

&s of 646 "irtually all commercial super capacitors use powdered acti"ated

carbon made from coconutshells. Aigher performance de"ices are a"ailable# at a

significant cost increase# based on synthetic carbon precursors that are acti"ated with

potassium hydro8ide (J$A+.

Research in E)*Cs focuses on impro"ed materials that offer higher usable surface

areas.

;raphene has e8cellent surface area per unit of gra"imetric or "olumetric

densities# is highly conducti"e and can now be produced in "arious labs# but is nota"ailable in production quantities. 'pecific energy density of 3/.> -h7kg at room

temperature and 45> -h7kg at 36 KC (all based on the total electrode weight+#

measured at a current density of 4 &7g ha"e been obser"ed. These energy density

"alues are comparable to that of theNickel metal hydride battery.

The de"ice makes full utili:ation of the highest intrinsic surface capacitance and

specific surface area of single%layer graphene by preparing cur"ed graphene sheets

!
http://en.wikipedia.org/wiki/Nanoporehttp://en.wikipedia.org/wiki/Activated_carbonhttp://en.wikipedia.org/wiki/Insulator_(electrical)http://en.wikipedia.org/wiki/Activated_charcoalhttp://en.wikipedia.org/wiki/Activated_charcoalhttp://en.wikipedia.org/wiki/Spongehttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Radical_(chemistry)http://en.wikipedia.org/wiki/Electrolytehttp://en.wikipedia.org/wiki/Charcoalhttp://en.wikipedia.org/wiki/Solventhttp://en.wikipedia.org/wiki/Solventhttp://en.wikipedia.org/wiki/Activated_carbonhttp://en.wikipedia.org/wiki/Activated_carbonhttp://en.wikipedia.org/wiki/Coconuthttp://en.wikipedia.org/wiki/Potassium_hydroxidehttp://en.wikipedia.org/wiki/Graphenehttp://en.wikipedia.org/wiki/Nickel_metal_hydride_batteryhttp://en.wikipedia.org/wiki/Nanoporehttp://en.wikipedia.org/wiki/Activated_carbonhttp://en.wikipedia.org/wiki/Insulator_(electrical)http://en.wikipedia.org/wiki/Activated_charcoalhttp://en.wikipedia.org/wiki/Activated_charcoalhttp://en.wikipedia.org/wiki/Spongehttp://en.wikipedia.org/wiki/Ionhttp://en.wikipedia.org/wiki/Radical_(chemistry)http://en.wikipedia.org/wiki/Electrolytehttp://en.wikipedia.org/wiki/Charcoalhttp://en.wikipedia.org/wiki/Solventhttp://en.wikipedia.org/wiki/Solventhttp://en.wikipedia.org/wiki/Activated_carbonhttp://en.wikipedia.org/wiki/Activated_carbonhttp://en.wikipedia.org/wiki/Coconuthttp://en.wikipedia.org/wiki/Potassium_hydroxidehttp://en.wikipedia.org/wiki/Graphenehttp://en.wikipedia.org/wiki/Nickel_metal_hydride_battery


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that do not restack face%to%face. The cur"ed shape enables the formation of

mesopores accessible to and wettable by en"ironmentally benign ionic liquids

capable of operating at a "oltage LD 2.

Carbon nanotubes ha"e e8cellent nanoporosity properties# allowing tiny

spaces for the polymer to sit in the tube and act as a dielectric. Carbon nanotubes

can store about the same charge as charcoal (which is almost pure carbon+ per unit

surface area but nanotubes can be arranged in a more regular pattern that e8poses

greater suitable surface area.

"
http://en.wikipedia.org/wiki/Mesoporeshttp://en.wikipedia.org/wiki/Carbon_nanotubehttp://en.wikipedia.org/wiki/Mesoporeshttp://en.wikipedia.org/wiki/Carbon_nanotube


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!. DENSITY OBTAINED BY MATERIALS

The energy densityof e8isting commercial E)*Cs ranges from around 6./ to 56

-Mh7kg including lithium ion capacitors# known also as a =hybrid capacitor=.

E8perimental electric double%layer capacitors ha"e demonstrated densities of 56

-Mh7kg and ha"e been shown to be scalable to at least 45> -Mh7kg# D/while others

e8pect to offer energy densities of about D66 -Mh7kg. Oor comparison# a con"entional

lead%acid battery stores typically 56 to D6 -Mh7kg and modern lithium%ion batteries

about 4>6 -Mh7kg. ;asolinehas a net calorific "alue(NC2+ of around 4#666 -Mh7kgP

automobile applications operate at about 6Q tank%to%wheel efficiency# gi"ing an

effecti"e energy density of #D66 -Mh7kg.

&bo"e chartshowing energy densitypower densityfor "arious energy%storage de"ices

'ome polymers (e.g. polyacenes and conducting polymers+ ha"e a redo8

(reduction%o8idation+ storage mechanism along with a high surface area.

Carbon aerogelpro"ides e8tremely high surface area gra"imetric densities of

about D6604666 m7g.

The electrodes of aerogel supercapacitors are a composite material usually

made of non%wo"en paper made from carbon fibers and coated with organic

aerogel# which then undergoes pyrolysis. The carbon fibers pro"ide structural

integrity and the aerogel pro"ides the required large surface area. 'mall aerogel

supercapacitors are being used as backup electricity storage in microelectronics.

&erogel capacitors can only work at a few "oltsP higher "oltages ioni:e the

carbon and damage the capacitor. Carbon aerogel capacitors ha"e achie"ed


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9ineral%based carbon is a nonacti"ated carbon# synthesised from metal or

metalloid carbides# e.g. 'iC# TiC# &lDC5. The synthesised nanostructured porous

carbon# often called Carbide )eri"ed Carbon (C)C+# has a surface area of about

D66 m7g to 666 m7g with a specific capacitance of up to 466 O7m* (in organicelectrolyte+. ,t pro"ides 46 -h7kg energy density and /6 k-7kg power density.

&s of 66> this material was used in a supercapacitor with a "olume of 45/

m* and 66 g weight ha"ing 4.> kO capacitance. The energy density is more than

D1 kS7* at .3/ 2 and power density of o"er 6 -7g.

,n &ugust 661 researchers combined a biodegradable paperbattery with

aligned carbon nanotubes# designed to function as both a lithium%ion battery and a

supercapacitor (called bacitor+. The de"ice employed an ionic liquid# essentially a

liquid salt# as the electrolyte. The paper sheets can be rolled# twisted# folded# or cut

with no loss of integrity or efficiency# or stacked# like ordinary paper (or a "oltaic

pile+# to boost total output.

They can be made in a "ariety of si:es# from postage stamp to broadsheet.

Their light weight and low cost make them attracti"e for portable electronics#

aircraft# automobiles#and toys (such as model aircraft+# while their ability to use

electrolytes in blood make them potentially useful for medical de"ices such as

pacemakers.

$ther teams are e8perimenting with custom materials made of acti"ated

polypyrrole# and nanotube%impregnated papers.

$
http://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Biodegradablehttp://en.wikipedia.org/wiki/Battery_(electricity)http://en.wikipedia.org/wiki/Ionic_liquidhttp://en.wikipedia.org/wiki/Salt_(chemistry)http://en.wikipedia.org/wiki/Electrolytehttp://en.wikipedia.org/wiki/Voltaic_pilehttp://en.wikipedia.org/wiki/Voltaic_pilehttp://en.wikipedia.org/wiki/Postage_stamphttp://en.wikipedia.org/wiki/Broadsheethttp://en.wikipedia.org/wiki/Aircrafthttp://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Model_aircrafthttp://en.wikipedia.org/wiki/Pacemakershttp://en.wikipedia.org/wiki/Polypyrrolehttp://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Biodegradablehttp://en.wikipedia.org/wiki/Battery_(electricity)http://en.wikipedia.org/wiki/Ionic_liquidhttp://en.wikipedia.org/wiki/Salt_(chemistry)http://en.wikipedia.org/wiki/Electrolytehttp://en.wikipedia.org/wiki/Voltaic_pilehttp://en.wikipedia.org/wiki/Voltaic_pilehttp://en.wikipedia.org/wiki/Postage_stamphttp://en.wikipedia.org/wiki/Broadsheethttp://en.wikipedia.org/wiki/Aircrafthttp://en.wikipedia.org/wiki/Automobilehttp://en.wikipedia.org/wiki/Model_aircrafthttp://en.wikipedia.org/wiki/Pacemakershttp://en.wikipedia.org/wiki/Polypyrrole


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". CHARACTERISTICS

The 'ignificant Characteristics of !ltra capacitors are

Aigh power density due to high discharge currents.

*ow internal resistance in comparison with batteries.

&bility to operate at temperatures as low as %D6KC.

Effecti"e capacitance for specific pulse widths.

*ow equi"alent series resistance (E'R+.

Aigher cycle life# making them suitable for automoti"e applications.

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#. AD%ANTAGES *ong life# with little degradation o"er hundreds of thousands of charge cycles.

)ue to the capacitorFs high number of charge%discharge cycles (millions or more

compared to 66 to 4666 for most commercially a"ailable rechargeable batteries+

it will last for the entire lifetime of most de"ices# which makes the de"ice

en"ironmentally friendly. Rechargeable batteries wear out typically o"er a few

years# and their highly reacti"e chemical electrolytes present a disposal and safety

ha:ard. Battery lifetime can be optimised by charging only under fa"orable

conditions# at an ideal rate and# for some chemistries# as infrequently as possible.

E)*Cs can help in conjunction with batteries by acting as a charge conditioner#

storing energy from other sources for load balancing purposes and then using anye8cess energy to charge the batteries at a suitable time.

*ow cost per cycle

;ood re"ersibility

2ery high rates of chargeand discharge.

E8tremely low internal resistance (E'R+ and consequent high cycle efficiency

(k-7kg at


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$. DISAD%ANTAGES The amount of energy stored per unit weight is generally lower than that of an

electrochemical battery (50/ -Mh7kg for an standard ultracapacitor# although 3/

-.h7kg has been achie"ed in the lab as of 646 compared to 56%D6 -Mh7kg for a

lead acid battery+# and about 474#666th the "olumetric energy density of gasoline.

Typical of any capacitor# the "oltage "aries with the energy stored. Effecti"e

storage and reco"ery of energy requires comple8 electronic control and switching

equipment# with consequent energy loss.

Aas the highestdielectric absorptionof any type of capacitor.

Aigh self%discharge % the rate is considerably higher than that of anelectrochemical battery.

Cells hold low "oltages % serial connections are needed to obtain higher

"oltages. 2oltage balancing is required if more than three capacitors are connected

in series.

*inear discharge "oltage pre"ents use of the full energy spectrum.

)ue to rapid and large release of energy (albeit o"er short times+# E)*CFs ha"e

the potential to be deadly to humans.

12
http://en.wikipedia.org/wiki/Lead_acid_batteryhttp://en.wikipedia.org/wiki/Dielectric_absorptionhttp://en.wikipedia.org/wiki/Self-dischargehttp://en.wikipedia.org/wiki/Lead_acid_batteryhttp://en.wikipedia.org/wiki/Dielectric_absorptionhttp://en.wikipedia.org/wiki/Self-discharge


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10. APPLICATION

'ome of the earliest uses were motor startup capacitors for large engines in tanksand

submarines# and as the cost has fallen they ha"e started to appear on dieseltrucks and

railroad locomoti"es. ,n the 66Fs they attracted attention in the green energy world#

where their ability to charge much faster than batteries makes them particularly

suitable for regenerati"e braking applications. New technology in de"elopment could

potentially make E)*Cs with high enough energy density to be an attracti"e

replacement for batteries in all%electric cars and plug%in hybrids# as E)*Cs charge

quickly and are stable with respect to temperature.

China is e8perimenting with a new form of electric bus(capabus+ that runs

without powerlines using large onboard E)*Cs# which quickly recharge whene"er the

bus is at any bus stop(under so%called electric umbrellas+# and fully charge in the

terminus. & few prototypes were being tested in 'hanghaiin early 66/. ,n 66># two

commercial bus routes began to use electric double%layer capacitor busesP one of them

is route 44 in 'hanghai. &n hybrid busthat uses a diesel%electricbattery dri"e system

with electric double%layer capacitors. 'ince 665 9annheim 'tadtbahn in 9annheim#

;ermany has operated a light%rail "ehicle(*R2+ that uses E)*Cs to store braking

energy.$ther public transport manufacturers are de"eloping E)*C technology#

including mobile storage and a stationary trackside power supply. ,n 664 and 66

2&;# the public transport operator inNuremberg# ;ermany tested

$ trip:e h9brid or;:it truc; uses ue: ce::s and batteriesas primar9 energ9

storage

201110141-chandan kumar.doc

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