Ultra Capacitor

Wednesday, 28 February, 2018

Capacitor is an electronic component that stores electric charge. The capacitor is made of 2 close conductors (usually plates) that are separated by a dielectric material. The plates accumulate electric charge when connected to power source. One plate accumulates positive charge and the other plate accumulates negative charge.

A supercapacitor or ultracapacitor is an electrochemical capacitor that has an unusually high energy density when compared to common capacitors. They are of particular interest in automotive applications for hybrid vehicles and as supplementary storage for battery electric vehicles. The super capacitor, also known as ultra capacitor or double-layer capacitor, differs from a regular capacitor in that it has very high capacitance. A capacitor stores energy by means of a static charge as opposed to an electrochemical reaction. Applying a voltage differential on the positive and negative plates charges the capacitor. 




Temperature: Ultra capacitors operate in a wide range of temperature conditions — from +70 ° Celsius to –40° Celsius. Even in cold temperatures, ultra capacitors provide high charge acceptance, high-efficiency, cycle stability and excellent performance.

Size:  Batteries are large and heavy and offer only a limited charging rate. A hybrid energy storage system pairs ultra capacitors with a considerably smaller battery, thereby achieving the necessary power and performance in a smaller package with reduced weight.

Cycle life:  Ultra capacitors can handle millions of charge and discharge cycles. Little to no maintenance is required, which is another advantage over batteries. In hybrid vehicle start/stop applications, ultra capacitors can provide the required cycle life.

Power and efficiency:  Ultra capacitors are more efficient than batteries up to 95 percent as compared to an average of approximately 70 percent for batteries in automotive applications. since ultra capacitors are working along with small batteries, the system can power starting and ignition systems at a lower voltage regulation, which results in more fuel savings.


Types of Ultra capacitors

Electrochemical double layer capacitor:-EDLC are constructed from two carbon based electrodes an electrolyte and a seperator.EDLC utilize an electrochemical double layer of charge to store energy. As voltage is applied charge accumlates on the electrode surface.thus the double layer of charge produced at each electrode.it is coupled with an increase in surface area and decrease in distance between electrodes and aloows EDLC Achieve high energy densities than conventional capacitors.

Psudocapacitors:-ELDC which stores charge electrostatically,psudocapacitors store charge faradiacally through transfer of charge between electrode and eletrolyte.These Faradaic processes may allow psudocapacitors to achieve gretaer capacitance and energy densities than EDLC. There are two eletrode material are used to store charge in pseudocapacitors,conducting polymers and metal oxides.

Hybrid capacitors:-Hybrid capacitors attempts to exploit advatages and relative disadvantages of ELDC and pseudocapacitors to realize better performance characteristics.utilizing both faradaic and non faradiac processes to store charge.In Hybrid capacitors have achieved energy and power densities greater than EDLC without the sacrifices in cycling stability.

Advantages
1.High energy storage Compared to conventional capacitor technologies, EDLCs possesses orders of magnitude higher energy density.
2.Low Equivalent Series Resistance (ESR). Compared to batteries, EDLCs have a low internal resistance, hence providing high power density capability.
3.Low Temperature performance capable of delivering energy down to -40°C with minimal effect on efficiency.
4.Fast charge/discharge. Since EDLCs achieve charging and discharging through the absorption and release of ions and coupled with its low ESR, high current charging and discharging is achievable without any damage to the parts.

Disadvantages
1.Low per cell voltage. EDLC cells have a typical voltage of 2.7V. Since, for most applications a higher voltage is needed, the cells have to be connected in series.
2.The amount of energy stored per unit weight is considerably lower than that of an electrochemical battery (3-5 W.h/kg for an ultracapacitor compared to 30-40 W.h/kg for a battery). It is also only about 1/10,000th the volumetric energy density of gasoline.
3.The voltage varies with the energy stored. To effectively store and recover energy requires sophisticated electronic control and switching equipment.
4.Has the highest dielectric absorption of all types of capacitors.

Applications
1.Maintenance free applications
2.Used mobile phones,
3.Back-up and UPS systems
4.Systems of Energy Recuperation
5.Consumer electronics
6.Used in aircrafts.

Ultra capacitor Functions
1.Secure power
2.Provides reliable interim power, even if the primary source fails or fluctuates
3.Energy storage
4.Stores energy from low power sources, enabling support for high power loads
5.Pulse power
6.Supplies peak power to the load while drawing average power from the source

Features
1.Such energy storage has several advantages relative to batteries.
2.Very high rates of charge and discharge.
3.Low toxicity of materials used.
4.High cycle efficiency (95% or more).

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Category: Semiconductor

Tags: capacitor