Super-capacitors

Uncategorized — By on December 17, 2017 at 9:56 am

Article by Omar Khan

The popularity of electric power is on the rise. Fossil-fueled cars and home-heating are all going to, soon enough, change to electric power, in hopes to combat climate change. Now the problem with electric power is that it’s part of a one-or-the-other dilemma. You can either have a battery, which stores a ton of power but takes ages to charge up, or you can have a capacitor, which charges relatively quickly but – traditionally – can only store a very small amount of power. In an electric-powered future, we will need to store and release large amounts of electric power relatively quickly.

Unlike batteries, which utilize chemistry to generate electrical energy, capacitors use static electricity in order to store energy. Inside a capacitor, there are two conducting metal plates with an insulating material called a dielectric in between them. A dielectric is simply an electrical insulator. Positive and negative charges build up on the plates as it is connected to a sort of power source, and the insulator between them prevents the flow of charges. This allows the capacitor to store energy.

Capacitor

Capacitor

Retrieved from https://www.build-electronic-circuits.com

Now, the main advantage that capacitors have over batteries is that they are a lot faster when building up stored energy. However, they are also at a disadvantage because their technical design doesn’t let them get anywhere near the amount of energy that batteries can store. As mentioned earlier, in an electric-powered future, we will need to store and release large amounts of electric power relatively quickly. But how, you ask? Reader, meet the supercapacitor.

Retrieved from https://eu.mouser.com/applications/supercapacitors-hero-automotive/

Maxwell K2 Series                 Ultracapacitor

Retrieved from https://eu.mouser.com/applications/supercapacitors-hero-automotive/

A supercapacitor differs from ordinary capacitors in two ways:

  1. Its plates are substantially larger than those of the average capacitor, allowing it to carry a lot more electric charge.
  2. The separation between its plates is a lot smaller, which means that the molecules between the two plates have a much smaller level of interference with the charges stored in the two plates.

In a supercapacitor, there is no real conventional dielectric. Instead, both the plates are dipped in electrolytes, and then separated by a dielectric that is extremely thin, even as thin as simply one molecule thick.

The capacitance of a capacitor increases as the area of the plates increases and as the distance between the plates decreases. Since both factors here are being manipulated to increase capacitance, the electric output of energy increases by substantial amounts.

Retrieved from http://www.mpoweruk.com/supercaps.htm

Typical capacitors only rate their capacitance in units of microfarads (millionths of the unit Farad, from British physicist Michael Faraday). Supercapacitors have can have units in kilofarads, millifarads and even Farads. This means that their electrical energy output is comparatively huge; huge enough for some to even speculate their potential as a replacement for batteries. While batteries have a higher energy density (i.e: they carry more energy per unit mass), capacitors have a higher power density (i.e: they release more energy more quickly).

At this point you might be thinking that supercapacitors are this super advanced piece of technology that are very rare and hard to use, but that is actually not the case! There are several uses for supercapacitors, some of which you may see every day. One common application is in wind turbines, where very large supercapacitors help to smooth out the intermittent power supplied by the wind. In electric and hybrid vehicles, supercapacitors are increasingly being used as temporary energy stores for regenerative braking (where the energy a vehicle would normally waste when it comes to a stop is briefly stored and then reused when it starts moving again). The motors that drive electric vehicles run off power supplies rated in the hundreds of volts, which means hundreds of supercapacitors connected in series are needed to store the right amount of energy in a typical regenerative brake. With these applications of supercapacitors becoming more and more common, and as our understanding of them becomes more and more detailed, we can bet that they might come to be an important element in creating an electric-powered world.

Retrieved from http://articles.sae.org/11845/

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