Super
capacitor
Super capacitor is an advance version of the conventional electrolytic
capacitor. It is also known as the ultra capacitor, electric double layer capacitor
or electrochemical double layer capacitor. It is a special type capacitor
that has high energy density and this energy density is usually hundreds of
times greater than conventional electrolytic capacitors. It also has a much
higher power density than batteries or fuel cells. Super capacitor is used for
energy storage rather than as general-purpose circuit components. It has a
variety of commercial applications, notably in "energy smoothing" and
momentary-load devices. Ultra capacitor also has applications as energy-storage
because it can quickly charge. Due to same reason, it is extremely essential
for domestic solar energy system.
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| Series connected super capacitor |
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| Voltage increased by series connection of Ultra capacitor |
Basic idea:
Conventional capacitor has two
metallic plates which are separated by insulation. When a voltage source
connects with capacitor, then charges flow through capacitor and capacitor is
charged. In this way a potential difference creates within two plates of
capacitor. There is used a dielectric material between the plates. Voltage of
capacitor can be controlled by dielectric, but ultra capacitor can not be
controlled by conventional dielectric.
Electric double layer capacitor
also has two metal plates which are coated with activated carbon and separated
by an intervening insulator. It uses virtual plates which are in fact two
layers of the identical substrate. Due to its electrochemical properties, it is
called electrical double layer. It has two electrodes positive and negative.
Capacitor capacitance can be increased by increasing surface area of each
electrode or decreasing distance between electrodes. As a result, stored energy
of the capacitor, which directly proportional to capacitance, also increases.
Super capacitor has two electrodes with much higher areas and much thinner
dielectrics. These dielectrics decrease the distance between two electrodes. These
implementations help to increase capacitance and stored energy in super
capacitor.
Super capacitor has low voltage,
but it can be increased by series combination of matched super capacitors.
Ultra capacitor has much higher power density than batteries. If power density
is high, energy will quickly deliver to the load (electronic
equipments).Movement of charge is slow in Batteries means power density is low
than super capacitors. So, batteries delivery speed of charge is slow and
charge discharge time also relatively slow.
Applications:
Some electric vehicle manufacturers are using
ultra capacitors for acceleration. Super capacitor also appears in hundreds of
other applications, from cell phone base stations to alarm clocks (as backup
power) to audio systems. Ultra capacitor is also used in electric power grid.
When transmission lines operate below full capacity, Ultra capacitors banks
could be set up to absorb power surges and enable transmission lines to
activate near to 100% capacity.
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| Super capacitor is used in vehicle for acceleration |
Advantages:
Super capacitor has low cost per cycle, good
reversibility, very high rates of charging and discharging ability. It also has
high output power. It can be used in simple charging method. It is free from
overcharging and need not any full-charge detection.
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| Electrochemical double layer capacitor |
