Super Capacitors

A supercapacitor (or ultracapacitor) differs from an ordinary capacitor in two important ways: its plates effectively have a much bigger area and the distance between them is much smaller, because the separator between them works in a different way to a conventional dielectric. Although the words “supercapacitor” and “ultracapacitor” are often used interchangeably, there is a difference: they are usually built from different materials and structured in slightly different ways, so they store different amounts of energy. For the purposes of this simple introduction, we’ll assume they’re the same thing.

Like an ordinary capacitor, a supercapacitor has two plates that are separated. The plates are made from metal coated with a porous substance such as powdery, activated charcoal, which effectively gives them a bigger area for storing much more charge. Imagine electricity is water for a moment: where an ordinary capacitor is like a cloth that can mop up only a tiny little spill, a supercapacitor’s porous plates make it more like a chunky sponge that can soak up many times more. Porous supercapacitor plates are electricity sponges.

How To made Super Capacitors ?

In a supercapacitor, there is no dielectric as such. Instead, both plates are soaked in an electrolyte and separated by a very thin insulator (which might be made of carbon, paper, or plastic). When the plates are charged up, an opposite charge forms on either side of the separator, creating what’s called an electric double-layer, maybe just one molecule thick (compared to a dielectric that might range in thickness from a few microns to a millimeter or more in a conventional capacitor). This is why supercapacitors are often referred to as double-layer capacitors, also called electric double-layer capacitors or EDLCs). If you look at the lower diagram in the artwork, you’ll see how a supercapacitor resembles two ordinary capacitors side by side.

The capacitance of a capacitor increases as the area of the plates increases and as the distance between the plates decreases. In a nutshell, supercapacitors get their much bigger capacitance from a combination of plates with a bigger, effective surface area (because of their activated charcoal construction) and less distance between them (because of the very effective double layer).

The first supercapacitors were made in the late 1950s using activated charcoal as the plates. Since then, advances in material science have led to the development of much more effective plates made from such things as carbon nanotubes (tiny carbon rods built using nanotechnology), graphene, aerogel, and barium titanate.

Difference with capacitors

A supercapacitor is also known as an ultracapacitor or a double-layer capacitor. A supercapacitor differs from the ordinary capacitor in that it has much higher capacity and energy density, while at the same time having a higher power density. These characteristics make it a convenient power source for devices that require high power and durability of the power unit.

The capacitor is a passive electrical element, which accumulates energy in the electric field between the two conducting electrodes. A capacitor stores electrical charge and is capable of discharging it whenever required. It blocks DC and allows AC to pass through it. Due to its characteristics, a capacitor is widely used in the electronic circuits. Capacitor stores electrical energy directly, as an electrostatic field is created between two metal “plates”.

The supercapacitor can be charged and discharged continuously. Due to carbon technology, supercapacitors are able to create a very large surface area, which exists even with an extremely small separation distance.

Uses

Energy harvesting

Supercapacitors are suitable temporary energy storage devices for energy harvesting systems. In energy harvesting systems, the energy is collected from the ambient or renewable sources, e.g., mechanical movement, light or electromagnetic , and converted to electrical energy in an energy stored device. For example, it was demonstrated that energy collected from RF  fields (using an RF antenna as an appropriate rectifier circuit) can be stored to a printed supercapacitor. The harvested energy was then used to power an application-specific integrated circuit  circuit for over 10 hours.

Incorporation into batteries

The Ultra battery is a hybrid rechargeable and a supercapacitor. Its cell construction contains a standard lead-acid battery positive electrode, standard sulphuric acid electrolyte and a specially prepared negative carbon-based electrode that store electrical energy with . The presence of the supercapacitor electrode alters the chemistry of the battery and affords it significant protection from sulfation in high rate partial state of charge use, which is the typical failure mode of valve used this way. The resulting cell performs with characteristics beyond either a lead-acid cell or a supercapacitor, with charge and discharge rates, cycle life, efficiency and performance all enhanced.

Street lights

Street light combining a solar cell power source with led lamps and super capacitors for energy storage

Sado City, in Japan’s Niigata Prefecture, has street lights that combine a stand-alone power source with solar cells and LEDs. Supercapacitors store the solar energy and supply 2 LED lamps, providing 15 W power consumption overnight. The supercapacitors can last more than 10 years and offer stable performance under various weather conditions, including temperatures from +40 to below -20 °C.

Medical

Supercapacitors are used in  where they can deliver 500 joules to shock the heart back into sinus theme.

Transport

Aviation

In 2005, aerospace systems and controls company  GmbH chose super capacitors to power emergency actuators for doors and evacuation slides used in airliners, including the Airbus 

Military

Supercapacitors’ low internal resistance supports applications that require short-term high currents. Among the earliest uses were motor startup (cold engine starts, particularly with diesels) for large engines in tanks and submarines. Supercapacitors buffer the battery, handling short current peaks, reducing cycling and extending battery life.

Further military applications that require high specific power are phased array radar antennae, laser power supplies, military radio communications, avionics displays and instrumentation, backup power for airbag deployment and GPS-guided missiles and projectiles.

Automotive

Toyota’s Yaris Hybrid-R concept car uses a supercapacitor to provide bursts of power. PSA Peugeot Citroën has started using supercapacitors as part of its stop-start fuel-saving system, which permits faster initial acceleration. Mazda’s i-ELOOP system stores energy in a supercapacitor during deceleration and uses it to power on-board electrical systems while the engine is stopped by the stop-start system

Future developments

Recent developments include lithium-ion capacitors. These hybrid capacitors were pioneered by FDK in 2007.They combine an electrostatic carbon electrode with a pre-doped lithium-ion electrochemical electrode. This combination increases the capacitance value. Additionally, the pre-doping process lowers the anode potential and results in a high cell output voltage, further increasing specific energy.

Research departments active in many companies and universities are working to improve characteristics such as specific energy, specific power, and cycle stability and to reduce production costs.

Reference:

https://en.wikipedia.org/wiki/Supercapacitor

https://www.explainthatstuff.com/how-supercapacitors-work.html

https://batteryuniversity.com/learn/article/whats_the_role_of_the_supercapacitor