By

Praveen Shirandasu

What is Capacitor?

A capacitor (originally known as condenser) isa passive two-terminal electrical component used tostore energy in an electric field.

What is Supercapacitor?

A supercapacitor or ultracapacitor is anelectrochemical capacitor that has anunusually high energy density when comparedto common capacitors. They are of particularinterest in automotive applications for hybridvehicles and as supplementary storage forbattery electric vehicles

History

The first supercapacitor based on a double layermechanism was developed in 1957 by General Electricusing a porous carbon electrode [Becker, H.I., “Lowvoltage electrolytic capacitor”, U.S. Patent 2800616, 23July 1957].

It was believed that the energy was stored in the carbonpores and it exhibited "exceptionally high capacitance",although the mechanism was unknown at that time. Itwas the Standard Oil Company, Cleveland (SOHIO) in1966 that patented a device that stored energy in thedouble layer interface [Rightmire, R.A., “Electrical energystorage apparatus”, U.S. Patent 3288641, 29 Nov 1966.].

Basic Design

• Electrochemical capacitors (supercapacitors) consist of two electrodes separated by an ion permeable membrane (separator), and an electrolyte electrically connecting both electrodes. When the voltage is applied, ions in the electrolyte form electric double layers of opposite polarity to the electrode's polarity.

• For example, positive electrodes will have a layer of negative ions and negative electrodes will have a layer of positive ions.

CONSTRUCTION

Features

Such energy storage has several advantagesrelative to batteries.

Very high rates of charge and discharge.

Little degradation over hundreds of thousandsof cycles.

Low toxicity of materials used.

High cycle efficiency (95% or more).

• High energy storage.

• Wide working temperature(-400c to 600c).

• Eco-friendly.

• Quick charging time.

• Maximum life cycle.

• High cycle efficiency (95%).

• High specific power up to 17 kW/kg.

• Extremely low internal resistance.

• Safe.

ADVANTAGES

Disadvantage

The amount of energy stored per unit weight isconsiderably lower than that of an electrochemicalbattery (3-5 W.h/kg for an ultracapacitor compared to30-40 W.h/kg for a battery). It is also only about1/10,000th the volumetric energy density of gasoline.

The voltage varies with the energy stored. To effectivelystore and recover energy requires sophisticatedelectronic control and switching equipment.

Has the highest dielectric absorption of all types ofcapacitors.

Applications:

Maintenance free applications

Public transportation, HEVs, Start-Stop System

Back-up and UPS systems

Systems of Energy Recuperation

Consumer electronics

• Supercapacitors may be used where high power or energy storage is required.

• Supercapacitors can be used widely because of their long life & short charging time.

• On the other hand it has limitations due to its high cost, self discharge, packaging problems etc.

CONCLUSION