2. CONTENTS
Introduction.
Attractive Features.
Advantages to conventional Energy Storing Devices.
Inside a Super capacitor/Ultra capacitor.
Working.
Applications.
Drawbacks.
3. INTRODUCTION
What is a Ultra capacitor?
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 Double-layered
capacitor.
4.
5. ATTRACTIVE FEATURES
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.
Ultra capacitors can store 5 percent as much energy as
a modern lithium-ion battery.
Can effectively fulfil the requirement of High current
pulses that can kill a battery if used instead.
6. 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, ultra capacitors--
also known as super capacitors 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 ultra capacitor fares extremely well.
7. Ordinary Capacitors:
Higher capacitance.
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
ultra capacitor 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.
8. INSIDE A SUPER CAPACITOR
Two Electrodes coated with sponge like activated carbon.
Electrolyte :Contains free mobile ions .
Porous Separator-:Prevents electrodes from shorting out.
9. THE COMBINATION OF ENORMOUS SURFACE
AREAAND EXTREMELY SMALL
charge separation gives the ultra capacitor its outstanding capacitance
relative to conventional capacitors.
10. CONSTRUCTIONAL FEATURES
Originally electrodes were made of aluminium.
Standard Oil engineers coated these aluminium with 100-micrometer-
thick layer of carbon.
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.)
They filled the interior with an electrolyte and used a porous insulator,
one similar to paper, to keep the electrodes from shorting out.
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.
11. WORKING
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 ultra capacitors, 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.
12. Applications in Public Transport
China is experimenting with a new form of electric bus that
runs without powerlines using power stored in large
onboard supercapacitors, which are quickly recharged
whenever the electric bus stops at any bus stop, and get
fully charged in the terminus. A few prototypes were being
tested in Shanghai in early 2005. In 2006, two commercial
bus routes began to use supercapacitor buses, one of them
is route 11 in Shanghai.
In 2001 and 2002, VAG, the public transport operator in
Nuremburg, Germany tested a bus which used a diesel-
electric drive system with supercapacitors
13. Since 2003 Mannheim Stadtbahn in Mannheim, Germany
has operated an LRV (light-rail vehicle) which uses
supercapacitors. In this presentation, there is additional
information about that project by the builder of the
Mannheim vehicle, Bombardier Transportation, and the
possible application of the technology for DMUs (Diesel
Multiple Unit) trains.
Other companies from the public transport manufacturing
sector are developing supercapacitor technology: The
Transportation Systems division of Siemens AG is
developing a mobile energy storage based on double-layer
capacitors called Sibac Energy Storage. The company
Cegelec is also developing a supercapacitor-based energy
storage system.
14. Features
Such energy storage has several advantages relative to
batteries:
Very high rates of charge and discharge.
Little degradation over hundreds of thousands of
cycles.
Good reversibility
Low toxicity of materials used.
High cycle efficiency (95% or more)
15. Disadvantages:
The amount of energy stored per unit weight is
considerably lower than that of an electrochemical battery
(3-5 W.h/kg for an ultracapacitor compared to 30-40
W.h/kg for a battery). It is also only about 1/10,000th the
volumetric energy density of gasoline.
The voltage varies with the energy stored. To effectively
store and recover energy requires sophisticated electronic
control and switching equipment.
Has the highest dielectric absorption of all types of
capacitors.
16. Technology
Carbon nanotubes and certain conductive
polymers, or carbon aerogels, are practical for
supercapacitors. Carbon nanotubes have excellent
nanoporosity properties, allowing tiny spaces for
the polymer to sit in the tube and act as a
dielectric. Some polymers (eg. polyacenes) have a
redox (reduction-oxidation) storage mechanism
along with a high surface area. MIT's Laboratory of
Electromagnetic and Electronic Systems (LEES) is
researching using carbon nanotubes [1].
17.
18. Supercapacitors are also being made of carbon aerogel.
Carbon aerogel is a unique material providing
extremely high surface area of about 400-1000 m2/g.
Small aerogel supercapacitors are being used as
backup batteries in microelectronics, but applications
for electric vehicles are expected.
19.
20. The electrodes of aerogel supercapacitors are
usually made of non-woven paper made from
carbon fibers and coated with organic aerogel,
which then undergoes pyrolysis. The paper is a
composite material where the carbon fibers
provide structural integrity and the aerogel
provides the required large surface.
The capacitance of a single cell of an ultracapacitor
can be as high as 2.6 kF (see photo at the
beginning).
