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What Are Ultra Capacitors?

written by: Raunekk • edited by: KennethSleight • updated: 10/23/2009

Is there a probable substitute for batteries in the near future? Can ultra capacitors be termed as the next ultimate source for storing energy?

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    Ultra capacitors or super capacitors are the new alternate sources for storing energy. Possible future substitutes of batteries, ultra capacitors are gradually finding their way into almost every kind of house hold electronic devices, especially the portable ones.

    However, it is to note that ultra capacitors are not batteries. So what is the difference?

    Conventional batteries store energy in an enclosed arrangement using chemicals and electrodes whereas in ultra capacitors electricity is stored between two charged plates. One more difference is that conventional capacitors discharge electricity gradually as the chemical reaction takes place whereas the ultra capacitors can discharge all energy in one go. Now, let’s take a look as to how ultra capacitors work.

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    The main advantage of ultra capacitors is that they have high energy density as compared to conventional batteries. Moreover, ultra capacitors are bio degradable and can be used for both small portable electronic items and also huge aircrafts.

    Super capacitors, as they are also known, are double layer capacitors with electrolytic solution. The polarized solution stores energy inside the capacitor. It is to note that no chemical reaction takes place inside the solution as it does inside a conventional battery. Moreover, this mechanism is also reversible, which means that ultra capacitor can store and discharge electricity hundred times to that of conventional batteries.

    This high electricity storage capacity is possible because of two main reasons. Firstly, ultra capacitors use porous carbon electrodes, which increases the surface area and thus allow more energy storage. Secondly, it has a dielectric capacitor which creates a small charge separation, allowing maximum storage of power throughout the capacitor.

    Just check out the diagrams below which show the construction schematic of a single cell and a series arrangement of such cells

    Ultra Capacitor Cells 

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    Ultra capacitors are used almost in every mobile electronic device; however its main application is considered automobiles. With the trend of green energy on the rise, ultra capacitors can be used to drive green electric cars. The main advantage of using an ultra capacitor in cars is that they can be recharged millions of times and the recharging time is also less than 90 seconds. Moreover, there is no need for replacement and a single battery can go on for years together.

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    Though it is proved that ultra capacitors can store large quantity of power, no product in the market uses ultra capacitors for storing large amount of electrical power. Presently only small consumer items in the market are using ultra capacitors.

    One reason is that as ultra capacitors lose energy quickly they need continuous recharging. Also, while a conventional battery when stored drains only 10% of its energy, an ultra capacitor drains almost half of it. However, as they can be charged within few seconds, these problems are not considered road blocks. It is expected that within few years even the existing problems will be resolved.

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    Prasad, P.P.S. & Munshi, M.Z.A. (1995) Handbook of Solid State Batteries & Capacitors. New Jersey: World Scientific Pub Co Inc