Electrochemical double-layer capacitors, also known as supercapacitors or ultracapacitors,are electrical storage devices, which have a relatively high energy storage density simultaneously with a high power density.These capacitors are used in applications reserved for batteries. The supercapacitor is ideal for energy storage that undergoes frequent charge and discharge cycles at high current and short duration.
For instance, a typical electrolytic capacitor will have a capacitance in the range of tens of millifarads. The same size super capacitor would have a capacitance of several farads, an improvement of about two or three orders of magnitude in capacitance but usually at a lower working voltage.
The most significant advantage supercapacitors have over batteries is their ability to be charged and discharged continuously without degrading like batteries do. This is why batteries and supercapacitors are used in conjunction with each other.
CONSTRUCTION
A supercapacitor cell basically consists of two electrodes, a separator, and an electrolyte.The electrodes are made up of a metallic collector, which is the high conducting part, and of an active material, which is the high surface area part. The two electrodes are separated by a membrane, the separator,which allows the mobility of the charged ions but forbids the electronic conductance. This composite is rolled or folded into a cylindrical or rectangular shape and stacked in a container. Then the system is kept with an electrolyte. The electrolyte may be of solid state, organic or aqueous type, depending on the application power requirement.
The working voltage of supercapacitor is determined by the decomposition voltage of the electrolyte and depends mainly on the environmental temperature, the current intensity and the required lifetime.
SOME FACTS:
While the electrostatic capacitor can be made to withstand high volts, the supercapacitor is confined to 2.5–2.7V.The specific energy of the supercapacitor is low and ranges from 1 to 30Wh/kg.The charge time of a supercapacitor is about 10 seconds.
MEASURING THE CAPACITANCE OF A SUPERCAPACITOR:
There are a couple of ways used to measure the capacitance of supercapacitors.
1. Charge method
2. Charging and discharging method.
The modern supercapacitor is not a battery per but crosses the boundary into battery technology by using special electrodes and electrolyte. Rather than operating as a stand-alone energy storage device, supercapacitors work well as low-maintenance memory backup to bridge short power interruptions. They are also used as fuel cell applications. Supercapacitors are expensive in terms of cost per watt. Some design engineers argue that the money for the supercapacitor would better be spent on a larger battery.
APPLICATIONS
1) Computer systems
2) UPS systems
3) Power conditioners
4) Welders
5) Inverters
6)Automobile regenerative braking systems
7) Power supplies
Cameras9) Power generators
To know about the basic working of capacitors visit: http://freecircuits.org/2012/01/capacitors-basics-working/
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