Ultracapacitors and its applications in energy storage in vehicles and hybrid energy storage systems contents *Introduction *Capacitors and Ultracapacitors *Advantages of ultracapacitors *Conventional ESS *HESS(Hybrid Energy Storage Systems) *Design and Working *Operation of Proposed Systems *Conclusion

1. Ultracapacitor Based Energy
Storage System for Hybrid and
Electric Vehicles
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2. CONTENTS
 Introduction
 Capacitors and Ultracapacitors
 Advantages of ultracapacitors
 Conventional ESS
 HESS(Hybrid Energy Storage Systems)
 Design and Working
 Operation of Proposed Systems
 Conclusion
 Reference
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3. Introduction
 Using HESS system in place of conventional Energy systems
 Ultracapacitors are introduced in to the system, which act as a buffer that
gives higher performance to Energy systems
 Battery will only provide power directly whenever the Ultracapacitor voltage
drops below battery voltage. Therefore, a relatively constant load profile is
created for the battery also satisfying the real-time peak power demands
 Battery is not used to directly harvest energy from the regenerative braking;
thus, the battery is isolated from frequent charges, which will increase
battery life.
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4. Capacitors
&
Ultracapacitors
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5. Capacitors
 A capacitor is made up of two conductors separated by an insulator called dielectric
 𝐶 =
𝜀0 𝐴
𝐷
 The dielectric can be made of paper, plastic, mica, ceramic, glass, a vacuum or
nearly any other nonconductive material
 When a potential difference applied across the capacitor, electric
field develops across the dielectric causing positive charge +Q to
collect on one plate and negative charge −Q to collect on the
other plate
𝐶 =
𝑄
𝑉
𝜀0 = Dielectric constant or Permittivity of the medium
A = Area of the plates
D = Distance between the plates
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6. Ultracapacitors
 Also called Supercapacitors or Double layer capacitors , Invented by engineers at
Standard Oil of Ohio(SOHIO) in 1966
 High-capacity electro chemical capacitor with capacitance value much higher than
other capacitors that bridge the gap between electrolytic capacitors and
rechargeable batteries
 10 to 100 times more energy per unit volume than electrolytic capacitors
 Capacitance ranges up to 5000f!
 Principle:- Energy is stored in ultracapacitor
by polarizing the electrolytic solution. The
charges are separated via electrode–electrolyte
interface
 Types
EDLC(Electrochemical Double Layer),
Pseudocapacitors and Hybrid capacitors 6

7.  An ultracapacitor cell basically consists of two
electrodes, a separator, and an electrolyte
 As , 𝑪 =
𝜺 𝟎 𝑨
𝑫
,in order to increase the capacitance,
need to change
A, Materials with highest specific surface area
used for electrodes
eg: Highly porous carbon , Activated carbon,
Carbon nanotubes , graphite etc.
D, The distance between the plates is in the
order of angstroms(10-10 meters)
𝜺 𝟎, Electrolytic solution with high conductivity
and adequate electrochemical stability
 Separator is to prevent the charges moving across
the electrodes
 The amount of energy stored is very large as
compared to standard capacitor,the small charge
separation created by the dielectric separator.
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8. Advantages
 Long life: It works for large number of
cycles without wear and aging
 High power storage: It stores huge amount
of energy in a small volume
 Very high rates of charge and discharge:
Ultracapacitor charges within seconds whereas
batteries takes hours
 High cycle efficiency (95% or more)
 Ultra capacitors are able to attain greater energy densities while still maintaining the
characteristic high power density of conventional capacitors
 Conventional capacitors have relatively high power densities, but relatively low energy densities when
compared to batteries, while a battery have low power density and high energy density.
Ultracapacitors have moderate energy density and power density
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9. 9

10. 10

11. Activated carbon
Carbon nanotubes
Inside-ultracapacitor
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12. ESS(Energy Storage Systems)
 Batteries are most widely
used energy storage
devices
 The Toyota Prius, Honda
Insight, and Ford Escape
are examples of
commercially available
HEVs with efficiencies
around 40 mi/gal in the
market(old models).
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13. Drawbacks
 Power density is low, incompatible to meet peak power demands
 Batteries with higher power densities are of higher cost and large size
 Needs intensive thermal management systems, to cool it and also to
warm it up in cold temperatures
 It cannot be used for high rate charge discharge operations, which causes
unbalance of voltages between individual cells eventually the total
capacity decreases
 Vehicles in most driving conditions requires instantaneous power input
and output, a conventional battery(with cycle life up to 2000times) is
inappropriate for this application
in order to solve these problems
HESS(Hybrid Energy Storage Systems) have been proposed. 13

14. HESS(Hybrid Energy Storage Systems)
 The basic idea of HESS is to combine UCs and batteries to achieve a better overall
performance
 UCs having higher power density but a lower energy density act as a Buffer or an
assistant energy source between battery and the DC link.
 There are several conventional HESS configurations proposed , while Most of these
combinations share one common feature which is to efficiently combine fast response
devices with high power density and slow response components with high energy
density.
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15. Classifications and Topologies
 HESS can be classified in to PASSIVE and ACTIVE based on power electronic convertors used
in it
 PASSIVE: Battery pack is directly paralleled with the UC bank , battery voltage always same
as that of UC nominal voltage, battery must charge the UC and provide power to
the load side
Passive cascaded battery/UC system 15

16.  ACTIVE: * A DC-DC converter added between the battery pack and the UC bank
* The battery voltage is boosted to a higher level
* Small sized battery can be employed, reduces cost
* Battery can be more efficiently controlled and stress on battery gets
reduced
Active cascaded battery/UC system
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17. Advantages
 The Active type topologies are more used
 The battery supplies average power to the load, and the UC delivers instantaneous
power charge and recovers fast charging from regenerative braking
Drawbacks
 Battery can not directly charged by breaking energy or by UC due to unidirectional
boost converter
Therefore parallel and multi input topologies were used
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18. Parallel active battery/UC system Multiple-input battery/UC system
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19. Parallel active battery/UC system
 Battery and UC are at a Low voltage than DC link Voltage
 When the Drive train
Demands power, The voltage on the battery and UC will level up
Supplies power, The voltages are stepped down for recharge
Multiple-input battery/UC system
 BOOST mode: When input sources supply energy
 BUCK mode : When recovering braking energy
 Only one inductor is needed even if more inputs are added
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20. Design
&
Working
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21. DESIGN TOPOLOGIES
 Design focus on which topology is uses, the basic design considerations include
Voltage strategy
 Both battery and UC have different voltages of operation
 The demand of balancing the system increases with high voltage capacity of the
system
 A better matched system can be build with a bigger batch of cells ,which in turn
increases the cost
 Therefore a voltage tradeoff between storage elements by considering that UC are
more easier to balance( lower additional cost)
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22. Effective utilization of stored energy
 In battery system, the energy delivered is not a function of voltage , but in HESS
energy delivered is a function of voltage because UC obeys law of standard
capacitors
𝐸𝑐𝑎𝑝 =
1
2
𝐶𝑉2
 Voltage of UC needs to be discharged to half of original voltage in order to deliver
75% of energy stored
 If Vuc<Vbatt=Vdc, 100% energy will deliver theoretically but not practically because of
presence of unbalanced cells
 A 66% reduction in UC voltage considered to discharge 90% of stored energy, in
passive systems which is further limited to 20%
 But a margin need to be allowed for UC to operate in Regenerative Braking
Conditions ,therefore actual energy discharged limited to a nominal 36%
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23. Protection from overcurrent
 Design consideration is to fully utilize the higher power limit of UC to support accilaration
and fully recover energy through regenerative breaking
 But there is current surges due to unpredictable Regenerative breaking
 Solution is to give a charging and discharging limits to the controller
 Mechanical braking is used to absorb extra energy
 Trade off between energy and security
Cost control
 Uc adds extra costs 23

24. OPERATION OF
PROPOSED
SYSTEM
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25. Proposed system
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26. Operation
MODE 1-Vehicle low constant speed operation
 Pconst≥Pdemand
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27. MODE 2:Vehicle High Constant Speed Operation
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28. Mode III: Acceleration
Acceleration mode phase I energy flow.
Acceleration mode phase II energy
flow
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29. Mode IV: Deceleration (Regenerative Braking)
Regenerative braking phase I energy flow when VUC< VUC tgt Regenerative braking phase I energy flow when VUC ≥ VUC tgt .
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30. Regenerative braking phase II energy flow
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31. Conclusion
 In this seminar, a new HESS design has been proposed. Compared to the
conventional HESS, the new design is able to fully utilize the power capability
of the UCs
 Much smoother load profile is created for the battery pack
 Future work related to this design will focus on the analysis of the system
efficiency in the high-voltage conditions
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32. REFERENCES
 v M. R. Rade, Prof. S. S. Dhamal, “Battery-Ultracapacitor Combination used as
Energy Storage System in Electric Vehicle”, International Conference on Emerging
Research in Electronics, Computer Science and Technology – 2015.
 v Jian Cao, Member, IEEE, and Ali Emadi, Senior Member, IEEE, “A New
Battery/UltraCapacitor Hybrid Energy Storage System for Electric, Hybrid, and
Plug-In Hybrid Electric Vehicles”, IEEE TRANSACTIONS ON POWER ELECTRONICS,
VOL. 27, NO. 1, JANUARY 2012.
 v Khaligh, Z. Li, “Battery, Ultracapacitor, Fuel Cell, and Hybrid Energy Storage
Systems for Electric, Hybrid Electric, Fuel Cell, and Plug-In Hybrid Electric
Vehicles: State of the Art”, IEEE Transactions on Vehicular Technology vol. 59, no.
6, pp. 2806-2814, 2010.
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