What is a supercapacitor?
Issuing time:2021-11-04 22:04
supercapacitor, ultracapacitor also called the Electrical Doule - Layer Capacitor, gold capacitors, farad capacitors, energy storage by polarization electrolyte. It is an electrochemical device, but there is no chemical reaction during its storage, which is reversible, which is why supercapacitors can be charged and discharged hundreds of thousands of times.
Pieces of the super capacitor can be seen as two are suspended in the electrolyte without reactivity of the porous plate electrode, on the plate, electric, positive plate attract negative ions in the electrolyte, negative plate attract positive ions, actually formed two capacitive storage layer, near by separation of positive ions in the negative plate, negative ions near the positive plate. (See Figure 1)
Why are supercapacitors different from conventional capacitors?
◆ Supercapacitors store energy in the separated charge. The larger the area used to store the charge and the denser the separated charge, the greater the capacitance.
◆ The area of a conventional capacitor is the flat surface area of the conductor. In order to obtain a large capacity, the conductor material is rolled to a very long length, sometimes with special structure to increase its surface area. Traditional capacitors are separated from their two plates by insulating materials, usually plastic film, paper, etc., which are usually required to be as thin as possible.
◆ The area of the supercapacitor is based on the porous carbon material. The porous junction of the material allows the area to reach 2000m2/g. Through some measures, a larger surface area can be achieved. The distance a supercapacitor's charge separates is determined by the size of the electrolyte ions that are attracted to the charged electrode. The distance (< 10 A) and conventional capacitor film materials can achieve A smaller distance.
◆ This large surface area combined with a very small charge separation distance makes supercapacitors have an extremely large electrostatic capacity compared with traditional capacitors, which is also its "super".
What are the advantages and disadvantages of supercapacitors?
◆ In a small volume to achieve the capacitance of farad;
No special charging circuit and control discharge circuit
◆ Compared with the battery, overcharge and overdischarge do not have a negative impact on its life;
◆ From the perspective of environmental protection, it is a kind of green energy;
◆ Super capacitor can be welded, so there is no problem like battery contact is not firm;
Second, the disadvantages
◆ If improper use will cause electrolyte leakage and other phenomena;
◆ Compared with aluminum electrolytic capacitor, its internal resistance is larger, so it can not be used for AC circuit;
What are the applications of supercapacitors?
◆ The low impedance of ultracapacitors is essential for many high power applications today. For fast charging and discharging, a small ESR of a supercapacitor means a larger power output.
◆ Instantaneous power pulse application, important storage, memory system short time power support.
Application, for example,
1. Quick charging application, charging in seconds, discharging in minutes. Such as power tools, electric toys;
2. In UPS systems, supercapacitors provide instantaneous power output to supplement backup power for engines or other uninterrupted systems;
3. It is applied to energy with sufficient energy and insufficient power, such as solar energy;
4. Power support when the bus switches from one power source to another power source;
5, small current, long time continuous discharge, such as computer memory backup power supply;
How fast can I discharge the supercapacitor?
◆ Supercapacitors can be charged and discharged quickly, and peak current is limited only by their internal resistance. Even short circuit is not fatal.
◆ Actually depends on the size of capacitor monomer. For matching load, small monomer can be put 10A, large monomer can be put 1000A.
◆ Another limiting condition of discharge rate is heat. Repeated discharge at a violent rate will raise the temperature of the capacitor and eventually lead to circuit break.
How do I control the discharge of the supercapacitor?
◆ The resistance of the supercapacitor prevents its rapid discharge. The time constant of the supercapacitor is between 1 and 2s. It takes about 5τ to discharge a full resistive and capacitive circuit, that is, it takes about 5 to 10s to discharge a short circuit. (Because of the electrodes' configuration, they can actually take hours to remove any residual charge completely.)
Are supercapacitors better than batteries?
◆ Supercapacitors are different from batteries and may be superior to batteries in some applications. Sometimes a better approach is to combine the two, combining the power characteristics of a capacitor with the high energy storage of a battery.
◆ Supercapacitor can be charged to any potential within its rated voltage range, and can be fully released. Batteries, on the other hand, are chemically constrained to operate within a narrow voltage range, which can cause permanent damage if overextended.
◆ The state of charge (SOC) of supercapacitor and voltage form a simple function, while the state of charge of battery includes a variety of complex conversion.
◆ Supercapacitors can store more energy than conventional capacitors of the same size, and batteries can store more energy than supercapacitors of the same size. In some applications where power determines the size of energy storage devices, ultracapacitors are a better approach.
◆ Ultracapacitors can transmit energy pulses repeatedly without any adverse effects. On the contrary, if the battery transmits high power pulses repeatedly, its life will be greatly reduced.
◆ Supercapacitors can be charged quickly while batteries can be damaged by rapid charging.
◆ Supercapacitors can be repeated hundreds of thousands of times, while the battery life is only a few hundred cycles.
How do I choose the supercapacitor I need?
◆ First, power requirements, discharge time and system voltage changes play a decisive role.
◆ The output voltage drop of the supercapacitor is composed of two parts, one is the energy released by the supercapacitor; The other part is caused by the internal resistance of the supercapacitor. Which of the two parts is mainly depends on the time, in very fast pulse, the internal resistance part is the main, on the contrary, in the long discharge, the capacitive part is the main.
The following basic parameters determine the size of the capacitor you choose
1, the highest working voltage;
2, working cut-off voltage;