The super capacitor is a totally new concept and in near future, it might replace the conventional batteries, thus overcoming the limitations of the batteries.
The principle is identical to that of the electrochemical capacitors, and is based on the double layer concept. Working :
At first we shall quickly review the principle of normal capacitor. The charge carriers (electrons), from one metal plate are removed and are deposited on the other plate. As the charges are separated, a potential is developed between the two plates and is controlled by a dielectric medium.
Starter of a Motor Bike Using Super Capacitors
But, in super capacitors, instead of using two separate plates (as in conventional), it uses two layers of the same material (same electrical properties) which has a very thin physical separation (order of nanometers). This ensures effective charge separation. The first layer is the charge accumulated at the interface and the second layer is of the diffused ions. This double layer is capable of storing more energy than conventional capacitors. For instance, a capacitor of a specified size has a capacitance of the order of micro-farads. But the same sized super capacitor has a capacitance of the order of a few tens farads. This is due to the absence of bulky layers of dielectric.
The material with a very high surface area is used. For example activated carbon. A few grams of activated carbon may have a surface are as large as a football ground.
1. Long life and environment friendly.
2. Can be used with the batteries by storing the charge and then supplying when required.
3. It charges and discharges very fast.
4. Low internal resistance and low heating rate.
5. No corrosive or harmful electrolyte.
6. High energy and power density.
7. No danger of overcharging.
1. Used for starters in large tanks, vehicles etc
2. In Digi-cams, portable media players etc. where high charging rates are needed.
3. Can be used in conjunction with batteries as charge conditioners.
In near future with the further development in this field, super capacitors are expected to replace the conventional batteries.
Since the previous poster covered the basic principles - here is some insight to todays super-caps.
Current super capacitors are generally used to supplement batteries of various technologies.
Most frequently used to provide a load with a lower impedance than the battery can alone, allowing higher pulse currents, without voltage droop.
Used to absorb tranients, during charging of a battery; ie re-generative braking in vehicles, then used to help re-start the vehicle after stopping.
With super low, or very low current draw devices - used to replace batteries totally, ie solar charging of super-cap during daylight, and using the
stored energy during the evening or all night. Has issues with long periods of overcast clouds or storage in dark locations, however.
The major limitation with current super-caps is low voltage per cell, means stacked cells must be used - balancing those stacked cells during charge &
discharge, and storage or periods of non-use present challenges for cost vs benefit trade-offs in the design of solutions.