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ULTRACAPACITOR
TECHNICAL DETAILS & APPLICATIONS
Report by:
Vivek Nandan
Emtech Foundation
Table of contents
1.Introduction.
2.Attractive Features.
3.Advantages to conventional Energy
Storing Devices.
4.Inside a Supercapacitor/Ultracapacitor.
5.Working.
6.Applications.
7.Drawbacks.
Introduction
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What is a Ultracapacitor?
A charge storing device(Capacitor) .
Differ in constructional features with respect
to simple capacitors.
Has ability to store tremendous charge.
Capacitance ranges up to 5000F!
Also called Super capacitor or Doublelayered capacitor.
Invented by Engineers at Standard Oil,1966.
Attractive Features
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Capacitance ranges to 5000 F.
No chemical reaction involved.
Much more effective at rapid, regenerative energy
storage than chemical batteries .
Works even at low temperatures -40 degrees Celsius.
Ultracapacitors can store 5 percent as much energy as a
modern lithium-ion battery.
5000 farads measure about 5 centimeters by 5 cm by 15 cm,
which is an amazingly high capacitance relative to its volume.
Can effectively fulfill the requirement of High current pulses
that can kill a battery if used instead.
Advantages to conventional energy storing
devices.
 Batteries:
 Degrade within a few thousand charge-discharge cycles. Ulracapacitors can have more
than 300 000 charging cycles, which is far more than a battery can handle.
 Ultra capacitor charges within seconds whereas batteries takes hrs.
 Because no chemical reaction is involved, ultracapacitors--also known as supercapacitors
and double-layer capacitors--are much more effective at rapid, regenerative energy
storage than chemical batteries are.
 Batteries fail where high charging discharging takes place whereas ultracapacitor fares
extremely well.
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Ordinary Capacitors:
 Higher capacitance.
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Put two ordinary capacitors the size of a D-cell battery in your flashlight, each
charged to 1.5 volts, and the bulb will go out in less than a second, if it lights at all.
An ultracapacitor of the same size, however, has a capacitance of about 350 farads
and could light the bulb for about 2 minutes.
 Ultra Capacitors are Expensive.
Inside a Super Capacitor
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Two Electrodes coated with sponge like activated carbon.
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Electrolyte :Contains free mobile ions.
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Porous Seprator-:Prevents electrodes from shoritng out.
•The combination of
enormous surface area
and extremely small
charge separation gives
the ultracapacitor its
outstanding capacitance
relative to conventional
capacitors.
Constructional Features
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Originally electrodes were made of aluminum.
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Standard Oil engineers coated these aluminum with 100-micrometer-thick layer of
carbon.
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The carbon was first chemically etched to produce many holes that extended
through the material, as in a sponge, so that the interior surface area was about 100
000 times as large as the outside. (This process is said to ”activate” the carbon.)
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They filled the interior with an electrolyte and used a porous insulator, one similar
to paper, to keep the electrodes from shorting out.
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carbon is inert and does not react chemically with the ions attached to it. Nor do
the ions become oxidized or reduced, as they do at the higher voltages used in an
electrolytic cell.
Working
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When a voltage is applied, the ions are attracted to the electrode
with the opposite charge, where they cling electrostatically to the
pores in the carbon.
At the low voltages used in ultracapacitors, carbon is inert and
does not react chemically with the ions attached to it. Nor do the
ions become oxidized or reduced, as they do at the higher voltages
used in an electrolytic cell.
As the effective area where ions are stuck is much larger,
appreciably high value of capacitance is obtained.
Modern Ultracapacitors
Nanotechnology is being employed in the
design.
 The active carbon is replaced by a thin
layer of billions of Nanotubes .
 Each Nanotube is like a uniform hollow
cylinder with 5nm and 100 µm long.
 These Nanotubes are verically grown
over the conducting electrodes.
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NANOTUBES STRUCTURES
Benefits of Nanotubes
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Several Advantages over Activated carbon.
Limitations of Actiavated carbon are
The high porosity means there isn't much carbon material to carry
current.
The material must be ”glued” to the aluminum current collector
using a binder, which exhibits a somewhat high resistance.
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Carbon Nanotubes
 Depending on their geometry, can be excellent
conductors .Thus they can supply more power than
ultracapacitors outfitted with activated carbon.
 Their structure makes them less chemically reactive, so they can
operate at a higher voltage.
Applications
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Military projects — for example, starting the engines of battle tanks and
submarines or replacing batteries in missiles.
Common applications today include starting diesel trucks and railroad
locomotives, actuators, and in electric/hybrid-electric vehicles for transient
load leveling and regenerating the energy of braking.
A bank of ultracapacitors releases a burst of energy to help a crane heave
its load aloft; they then capture energy released during the descent to
recharge.
They're being explored as replacements for the batteries in hybrid cars.
In ordinary cars, they could help level the load on the battery by powering
acceleration and recovering energy during braking.
Delivering or accepting power during short-duration events is the
ultracapacitor's strongest suit.
ultracapacitors function well in temperatures as low as –40 C, they can
give electric cars a boost in cold weather, when batteries are at their
worst.
Drawbacks of Ultracapacitors
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Linear discharge voltage prevents use of the full
energy spectrum
Low energy density - typically holds one-fifth to
one-tenth the energy of an electrochemical battery
Cells have low voltages - serial connections are
needed to obtain higher voltages.Voltage balancing
is required if more than three capacitors are
connected in series
High self-discharge - the rate is considerably higher
than that of an electrochemical battery.
Requires sophisticated electronic control and
switching equipment