Supercapacitor Working, Applications, Advantages, Disadvantages, and Future

Supercapacitor/Ultracapacitor/Electrical Double Layer Capacitor(EDLC)

A Supercapacitor is a device that can store electrical energy quickly and discharge slowly. We know that the normal capacitors like Electrolytic Capacitors, Ceramic Capacitor, etc can store electrical energy very quickly and discharge also very quickly but the supercapacitor does not the same. The Supercapacitor is also called Ultracapacitor or Electrical Double Layer Capacitor(EDLC). In this post, we are going to know the applications, advantages, and disadvantages of Supercapacitor.

What is the difference between Supercapacitor and Normal Capacitor?

1.     A normal capacitor has dielectric material but the supercapacitor has no dielectric material.

2.     The supercapacitor has an electrolyte solution but the normal capacitor does not have the electrolyte solution.

3.     In a normal capacitor, the dielectric materials provide the insulation between the plates or electrodes but in Supercapacitor a separator is used to provide insulation between electrodes.

4.     The charging and discharging rates of a normal capacitor are very fast but in the case of a supercapacitor, the charging rate is very fast but the discharging rate is slow.

5.     The voltage capacity of the supercapacitor is very low usually 2.7V but the normal capacitors like electrolytic capacitors are available of very high voltage ratings.

6.     The capacitance of the supercapacitor is very high generally above 500F are used.

What inside a Supercapacitor?

click on the image to enlarge

As you see in the above figure, the supercapacitor has the following parts,

1.     Two Electrodes

2.     Two current collectors

3.     A Separator

4.     Electrolyte Solution

A brief description of each part of the Supercapacitor:

(1) Electrodes: The electrodes of the supercapacitor is made of Activated Carbon material. The electrodes have a Porous nature which helps to store more charge carriers. And we know that if the electrodes are able to store more charge carrier then the capacitance will be increased. There are two electrodes one is the positive electrode and another is the negative electrode.

(2) Current Collectors: The current collectors are used to connect the electrodes and the terminals of the capacitor. The current collectors are generally made up of foil metals. Mostly aluminum is used. There are two current collectors in the supercapacitor one for the positive electrode and another is the negative electrode.

(3) Separator: The separator is used to provide insulation or separate the electrodes to prevent the short circuit. The separator is mainly made up of Kapton material. The separator is very thin like paper. The separator provides insulation between the electrodes but it allows to the flowing of charge carriers through it.

(4) Electrolyte Solution: Mainly the Acetonitrile or propylene carbonate as solvents are used as electrolytic in the supercapacitor. The electrolyte solution consists the charge carriers like positive cations and negative anions. 

From the above explanation, you may think that the supercapacitor has the construction same as a lead-acid battery. I also agree with you. The concept of the supercapacitor nearly the same as a lead-acid battery, in fact, we can say the supercapacitor is the combination of battery and capacitor. The supercapacitor uses the charging property of a normal capacitor and the discharging property of the battery.

Working Principle of Supercapacitor:

First of all, I would like to say that if you see the below diagrams carefully then you can easily understand the charging and discharging concepts of the Supercapacitor.

Charging of Supercapacitor:

We already know that the positive and negative Ions are present in the electrolyte solution with mixed in.

So at first when we apply a voltage across the electrodes of the supercapacitor then it starts charging. The electrodes start to attract the Ions of opposite polarity. That means the positive electrode attracts the negative Ions or charges and the negative electrode attracts the positive Ions or charges. As a result, the positive ions or charges creates a layer near the negative electrode and the negative ions create a layer near the positive electrode.

As there two layers is formed by the electrical charge carriers that is why it is called Electrical Double Layer Capacitor(EDLC).

Discharging of Supercapacitor:

 When we connect a load across the supercapacitor, the electrodes cannot attract the ions and the ions start distributing through the electrolyte solutions and go to the mixed state. The discharging of the supercapacitor is shown in the below figure.

Supercapacitor VS Battery:

In the future, the batteries are may be fully replaced by the supercapacitors but at this time it is not possible because many improvements are needed in the supercapacitor.

1.     A single battery can store more electrical energy than a single supercapacitor. 

2.     We have very little voltage capacity supercapacitor (mostly 2.7V) yet. But we have 12V, 24V batteries.

3.     Although the supercapacitor has a slower discharge rate than a normal capacitor but it has a faster discharge rate than a battery, for this reason in many applications the batteries cannot be replaced by the supercapacitor.

4.     The supercapacitor has very high efficiency even more than the batteries.

5.     For the fast charging property of supercapacitors, in many applications batteries are replaced by the supercapacitors.

Advantages of Supercapacitor:

The supercapacitor has many advantages like,

1.     Very High efficiency.

2.     Fast charging property.

3.     Supercapacitor has a longer life than a battery 10 to 15 years.

4.     The supercapacitor can withstand any temperature between -30 to 65 degrees centigrade whereas a battery can withstand -10 to 40 degrees centigrade.

5.     The supercapacitor is very light in weight.

6.     Supercapacitors can be installed in a short area as it has very small in size.

7.     The supercapacitor has a very fast transient response.

Disadvantages of supercapacitor:

The supercapacitor has some disadvantages also,

1.     The supercapacitor has very low specific energy.

2.     It is very difficult to make high-voltage capacity supercapacitors at the present time which is why most 2.7V supercapacitors are available in the market.

3.     The linear discharge voltage property of the supercapacitor is a disadvantage for us. Linear discharge voltage property means that when the supercapacitor discharges 50% of total stored energy, the voltage also reduces half of the full voltage which means if the full voltage of the supercapacitor is 2.7V then the voltage will be reduced to 1.3V. But in the case of a battery, the voltage will be near to the full voltage even if the battery discharges 50% energy.

4.     Price of supercapacitors is more than  Li-ion batteries for the same capacity.

5.     The supercapacitor quickly discharges than a battery when it is not connected with the load or in other words the self-discharging property of the supercapacitor is a disadvantage for us.

Applications of Supercapacitor:

1.     The supercapacitor mainly used in where very fast charging and discharging needed.

2.     The supercapacitor is used in digital cameras for flashing of light.

3.     Supercapacitors are used in electric vehicles and the regenerative braking mechanism is used for charging the supercapacitor. The regenerative braking helps to charge in a very short time.

4.     They also used in defibrillators to shock the human heart.

5.     They are used to provide power backup to the low-power devices like PC Cards, automated meter reading equipment.

6.     Nowadays the supercapacitors are used in many electrical and electronic tools.

7.     They are also used in many portable gadgets and devices.

Read Also:

• Line Capacitance and Earth Capacitance Effect in Transmission Line
• Capacitive Load Examples, Properties, Power Consumption
• Can use of Capacitor or Power Saver device reduce our Electricity Bill?
• [Actual] Difference Between Capacitor and Condenser
• Meaning of Capacitor Voltage Rating and Value in Specification
• When Capacitor store more Energy Series or Parallel connection?

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