Supercapacitor: A View Towards EV Technology
Understanding the subject of energy storage requires a basic understanding of supercapacitors. A supercapacitor is a high-capacitance capacitor designed for a specific application.
When an external voltage is applied, the surface of the electrode material becomes positively and negatively charged, and the presence of oppositely charged ions in the electrolyte begins accumulating on the electrode surface and forming double layers, which leads to the concept of a Supercapacitor. EDLC is the name given to this charge storage mechanism (Electrical Double Layer Capacitance).
The EDLC-type supercapacitor has a high power density but a low energy density. One of the drawbacks of its applicability to a wide range of devices is this. Scientists are working hard to increase the energy density of supercapacitors using various techniques. To address the issues, the concept of pseudo-capacitance is introduced. Faradic (battery-like) and non-faradic charge storage mechanisms are used in pseudo-capacitors (EDLC-like). As a result, when compared to EDLC-based supercapacitors, the device’s performance increases energy density by 10- 20 times.
The distinction between a supercapacitor and a battery
There are several differences between supercapacitors and batteries. The most important is the electrostatic surficial charge storage mechanism, which stores and supplies vast amounts of energy quickly. That is a high power density when compared to electrochemical charge storage in batteries, such as intercalation and deintercalation of ions, such as Na in a sodium-ion battery and Li in a lithium-ion battery
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Slow charging and discharging are caused by the charge storage mechanism of batteries, namely the redox reaction and phase change process. Because of a different method of charge storage, the amount of energy stored in a supercapacitor is 5-10 times less than in a battery.
As a result, supercapacitors have a low energy density. Another advantage of supercapacitors over batteries is that they can withstand more charge-discharge cycles before significant degradation of performance, making supercapacitors more durable. The supercapacitor field is still in its early stages, so it is more expensive than a battery, but the device’s durability makes it the most cost-effective in certain applications. On the Ragone plot shown below, the two types of devices are distinguished by their energy and power densities.
Use of Supercapacitor Devices in EV Regenerative Braking
One prominent example is the massive increase in efforts to conserve nonrenewable energy and develop alternative methods of producing renewable energy by harnessing waste heat to do useful work. In this regard, researchers are developing one of the technologies for extracting energy from kinetic energy when a vehicle applies the brakes.
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They are able to extract and convert it into electrical energy. Still, this energy conversion process is fast, and we need some energy storage devices. A battery came to mind as a possible solution. Still, due to the battery’s low power density, it cannot function in this situation; however, one device that can function is a supercapacitor, due to its high power density and long life cycle.
Maxwell Technologies has installed several regenerative braking devices on American light rail trains. The diagram below depicts additional applications of supercapacitors.
What is the definition of a Hybrid Energy Storage System (HESS)?
Researchers are developing hybrid energy storage devices that combine the high energy density of batteries with the high power density of supercapacitors due to the various energy delivery methods; in this case, we will refer to this device as BAT-CAP. As a result of this system, electric vehicles can address the issue of long-distance driving on a single charge as well as the issue of high vehicle speed, which was not possible with previous battery technology due to its limitations of low power density.
When will supercapacitor devices be available for purchase?
Because supercapacitor technology is newer than battery technology, a significant amount of research is being conducted in this field to improve its materials chemistry and other critical features. Several organizations now manufacture supercapacitor devices, including the well-known Maxwell technology, a company based in the United States that Tesla has already acquired in order to enter this field.
Other international companies in the market include Nippon Chemi-Con and Skeleton Technologies, among others. Nonetheless, India has begun to enter this market, and SPEL, based in Pune, is the country’s first Supercapacitor manufacturer. Taking all of these developments into account, it is estimated that supercapacitors will be commercially available on a large scale within one to two decades.
Conclusion
When needed, both supercapacitors and batteries can store and provide renewable energy. Their energy requirements for electric vehicles, however, are distinct. The supercapacitor provides power for the vehicle’s start and acceleration, whereas a battery is required for long-term operation. Both technologies have their uses and can help to improve future outcomes, but they cannot completely replace one another.
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