MC and BC series supercapacitors (up to 3000 farad capacitance) produced by Maxwell Technologies

Supercapacitors, also known as ultracapacitors or electrochemical double layer capacitors (EDLC), are electrochemical capacitors that have an unusually high energy density when compared to common capacitors, typically on the order of thousands of times greater than a high-capacity electrolytic capacitor. For instance, a typical D-cell sized electrolytic capacitor will have a storage capacity measured in microfarads, while the same size supercapacitor would store several farads, an improvement of about 10,000 times. Larger commercial supercapacitors have capacities as high as 5,000 farads.^[1] Examples of various types of capacitors. ... Maxwell Technologies - headquarters, San Diego, USA Supercapacitors MC2600 series (with capacitance 2600 farads) produced by Maxwell Technologies Maxwell Technologies - developer and manufacturer of energy storage and power delivery solutions. ... The electrical double layer describes the variation of electric potential near a surface, and has a large bearing on the behaviour of colloids and other surfaces in contact with solutions. ... See Capacitor (component) for a discussion of specific types. ... Energy density is the amount of energy stored in a given system or region of space per unit volume, or per unit mass, depending on the context. ... Electrolytic capacitors An electrolytic capacitor is a type of capacitor typically with a larger capacitance per unit volume than other types, making them valuable in relatively high-current and low-frequency electrical circuits. ... Four double-A batteries In science and technology, a battery is a device that stores energy and makes it available in an electrical form. ... Examples of various types of capacitors. ...

Supercapacitors have a variety of commercial applications, notably in "energy smoothing" and momentary-load devices. Some of the earliest uses were motor startup capacitors for large engines in tanks and submarines, and as the cost has fallen they have started to appear on diesel trucks and railroad locomotives.^[2] More recently they have become a topic of some interest in the green energy world, where their ability to quickly soak up energy makes them particularly suitable for regenerative braking applications, whereas batteries have difficulty in this application due to slow charging times. If the LEES or EEStor devices can be commercialized, they will make an excellent replacement for batteries in all-electric cars and plug-in hybrids, as they combine quick charging, temperature stability and excellent safety properties. For other uses, see Submarine (disambiguation). ... A solar trough array is an example of green energy Green energy is a term describing what is thought to be environmentally friendly sources of power and energy. ... Regenerative braking is any technology which allows a vehicle to recapture and store part of the kinetic energy that would otherwise be lost to heat when braking. ... Lees is the detritous of fermentation, consisting of dead yeast, fruit debris and schmutz. ... EEstor cell EEStor is a company based in Cedar Park, Texas, United States that claims to have developed a superior type of capacitor for electricity storage, which EEStor calls Electrical Energy Storage Units (EESU). ... For electric vehicles other than battery powered passenger automobiles, see electric vehicle. ... Hybrids Plus plug-in hybrid Toyota Prius conversion with PHEV-30 (30 mile or 48 km all-electric range) battery packs A plug-in hybrid electric vehicle (PHEV) is a hybrid vehicle with batteries that can be recharged by connecting a plug to an electric power source. ...

Concept

Comparison of construction diagrams of three capacitors. Left: "normal" capacitor, middle: electrolytic, right: supercapacitor

In a conventional capacitor, energy is stored by the removal of charge carriers, typically electrons, from one metal plate and depositing them on another. This charge separation creates a potential between the two plates, which can be harnessed in an external circuit. The total energy stored in this fashion is a combination of the number of charges stored and the potential between the plates. The former is essentially a function of size and the material properties of the plates, while the latter is limited by the dielectric breakdown between the plates. Various materials can be inserted between the plates to allow higher voltages to be stored, leading to higher energy densities for any given size. See Capacitor (component) for a discussion of specific types. ... Electrolytic capacitors An electrolytic capacitor is a type of capacitor typically with a larger capacitance per unit volume than other types, making them valuable in relatively high-current and low-frequency electrical circuits. ... For other uses, see Electron (disambiguation). ...

In contrast with traditional capacitors, supercapacitors do not have a conventional dielectric, as such. They are based on a structure that contains an electrical double layer. In a double layer, the effective thickness of the "dielectric" is exceedingly thin—on the order of nanometers—and that, combined with the very large surface area, is responsible for their extraordinarily high capacitances in practical sizes.

In an electrical double layer, each layer by itself is quite conductive, but the physics at the interface where the layers are effectively in contact means that no significant current can flow between the layers. However, the double layer can withstand only a low voltage, which means that supercapacitors rated for higher voltages must be made of matched series-connected individual supercapacitors, much like series-connected cells in higher-voltage batteries.

In general, supercapacitors improve storage density through the use of a nanoporous material, typically activated charcoal, in place of the conventional insulating barrier. Activated charcoal is a powder made up of extremely small and very "rough" particles, in bulk they form a low-density volume of particles with holes between them that resembles a sponge. The overall surface area of even a thin layer of such a material is many times greater than a traditional material like aluminum, allowing many more electrons to be stored in any given volume. The downside is that the charcoal is taking the place of the improved insulators used in conventional devices, so in general supercapacitors use low potentials on the order of 2 to 3 V. Activated carbon (also called activated charcoal) is the more general term which includes material mostly derived from charcoal. ... For other uses, see Sponge (disambiguation). ...

Activated charcoal is not the "perfect" material for this application. Free electrons are actually (in effect) quite large, often larger than the holes left in the charcoal, which are too small to accept them, limiting the storage. Recent research in supercapacitors has generally focused on improved materials that offer even higher usable surface areas. Experimental devices developed at MIT replace the charcoal with carbon nanotubes, which have similar charge storage capability as charcoal (which is almost pure carbon) but are mechanically arranged in a much more regular pattern that exposes a much greater suitable surface area.^[3] Other teams are experimenting with custom materials made of activated polypyrrole, and even nanotube-impregnated papers. An electronic device known as a diode can be formed by joining two nanoscale carbon tubes with different electronic properties. ... A Polypyrrole (PPy) is a chemical compound formed from a number of connected pyrrole ring structures. ...

A completely different approach is being pioneered by EEStor, who claim to have developed a dramatically improved insulator based on barium titanate that improves the permissivity of the insulator by several orders of magnitude, improving energy density not through electron capacity but via much higher potentials. EEStor claims that their capacitors can operate at extremely high voltages, on the order of several thousand volts.^[4] EEstor cell EEStor is a company based in Cedar Park, Texas, United States that claims to have developed a superior type of capacitor for electricity storage, which EEStor calls Electrical Energy Storage Units (EESU). ... Barium titanate is an oxide of barium and titanium with the chemical formula BaTiO3. ...

Ragone plot showing energy density vs. power density for various energy-storage devices

In terms of energy density, existing commercial supercapacitors range around 0.5 to 10 W·h/kg, with the standardized cells available from Maxwell Technologies rated at 6 W·h/kg. Experimental supercapacitors from the MIT LEES project have demonstrated densities of 30 W·h/kg and appear to be scalable to 60 W·h/kg in the short term,^[5] while EEStor claims their examples will offer capacities on the order of 200 to 300 W·h/kg. For comparison, a conventional lead-acid battery is typically 30 to 40 W·h/kg, modern lithium-ion batteries are about 120 W·h/kg, and in an automobile applications gasoline has a net calorific value (NCV) of around 12,000 W·h/kg operating at a 20% tank-to-wheel efficiency. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Ragone plot showing energy density vs. ... Energy density is the amount of energy stored in a given system or region of space per unit volume, or per unit mass, depending on the context. ... In engineering, specific power (sometimes also power per unit mass or power density) refers to the amount of power delivered by an energy source, divided by some measure of the sources size or mass. ... Maxwell Technologies - headquarters, San Diego, USA Supercapacitors MC2600 series (with capacitance 2600 farads) produced by Maxwell Technologies Maxwell Technologies - developer and manufacturer of energy storage and power delivery solutions. ... EEstor cell EEStor is a company based in Cedar Park, Texas, United States that claims to have developed a superior type of capacitor for electricity storage, which EEStor calls Electrical Energy Storage Units (EESU). ... A valve-regulated, sometimes called sealed, lead acid battery Lead-acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable battery. ... Lithium-ion batteries (sometimes abbreviated Li-ion batteries) are a type of rechargeable battery commonly used in consumer electronics. ...

Additionally, supercapacitors offer much higher power density than batteries. Power density combines the energy density with the speed that the energy can be drawn out of the device. Batteries, which are based on the movement of charge carriers in a liquid electrolyte, have relatively slow charge and discharge times. Capacitors, on the other hand, can be charged or discharged at a rate that is typically limited by current heating the electrodes. So while existing supercapacitors have energy densities that are perhaps 1/10 th that of a conventional battery, their power density is generally ten to one-hundred times as great (see diagram, right). In engineering, specific power (sometimes also power per unit mass or power density) refers to the amount of power delivered by an energy source, divided by some measure of the sources size or mass. ...

History

The supercapacitor effect was first noticed in 1957 by General Electric engineers experimenting with devices using porous carbon electrode.^[6] It was believed that the energy was stored in the carbon pores and it exhibited "exceptionally high capacitance", although the mechanism was unknown at that time. “GE” redirects here. ... Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ...

General Electric did not immediately follow up on this work, and it was Standard Oil of Ohio that eventually developed the modern version of the devices in 1966 after accidentally re-discovering the effect while working on experimental fuel cell designs.^[4] Their cell design used two layers of activated charcoal separated by a thin porous insulator, and this basic mechanical design remains the basis of most supercapacitors to this day. Standard Oil of Ohio or Sohio was an American oil company that was acquired by British Petroleum, now part of BP. It was one of the successor companies to Standard Oil after the antitrust breakup in 1911. ... A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ... Activated carbon (also called activated charcoal) is the more general term which includes material mostly derived from charcoal. ...

Standard Oil also failed to commercialize their invention, licensing the technology to NEC, who finally marketed the results as “supercapacitors” in 1978, to provide backup power for maintaining computer memory.^[4] The market expanded slowly for a time, but starting around the mid-1990s various advances in materials science and simple development of the existing systems led to rapidly improving performance and an equally rapid reduction in cost. In 2005, the ultracapacitor market was between US $272 million and $400 million, depending on the source. It is rapidly growing, especially in the automotive sector.^[4] For other uses, see NEC (disambiguation). ... The Materials Science Tetrahedron, which often also includes Characterization at the center Materials science or Materials Engineering is an interdisciplinary field involving the properties of matter and its applications to various areas of science and engineering. ... Car redirects here. ...

Recently ^[7], all solid state micrometer-scale supercapacitors based on advanced superionic conductors had been recognized as critical electron component of future sub-voltage and deep-sub-voltage nanoelectronics and related technologies (22 nm technological node of CMOS and beyond).

Technology advantages

Due to the capacitor's high number of charge-discharge cycles (millions or more compared to 200–1000 for most commercially available rechargeable batteries) there were no disposable parts during the whole operating life of the device, which makes the device environmentally friendly. Batteries wear out on the order of a few years, and their highly reactive chemical electrolytes represent a serious disposal and safety hazard. This can be improved by only charging under favorable conditions, charging at an ideal rate and as rarely as possible. Supercapacitors can help in this regard, acting as a charge conditioner, storing energy from other sources for load balancing purposes and then using any excess energy to charge the batteries only at opportune times.

Other advantages of supercapacitors compared with rechargeable batteries are extremely low internal resistance or ESR, high efficiency (up to 97-98%), high output power, extremely low heating levels, and improved safety. According to ITS (Institute of Transportation Studies, Davis, CA) test results, the specific power of supercapacitors can exceed 6 kW/kg at 95% efficiency ^[8] see Equivalent series inductance for a related discussion Equivalent series resistance (ESR) is an effective resistance that is used to describe the resistive parts of the impedance of certain electrical components. ... In engineering, specific power (sometimes also power per unit mass or power density) refers to the amount of power delivered by an energy source, divided by some measure of the sources size or mass. ... Kwai Lo is Chinese slang for foreigner or ghost person. ... KG, kg or Kg can refer to several things: Kilogram, the SI base unit of mass. ...

The idea of replacing batteries with capacitors in conjunction with novel alternative energy sources became a conceptual umbrella of the Green Electricity (GEL) Initiative [2], [3], introduced by Dr. Alexander Bell. One particular successful implementation of the GEL Initiative concept was a muscle-driven autonomous solution which employs a multi-farad supercapacitor (hecto- and kilofarad range capacitors are now available) as an intermediate energy storage to power a variety of portable electrical and electronic devices such as MP3 players, AM/FM radios, flashlights, cell phones, and emergency kits.^[9] As the energy density of supercapacitors is bridging the gap with batteries, it is hoped that in the near future the automotive industry will start to deploy ultracapacitors as a replacement for chemical batteries.

Transportation applications

China is experimenting with a new form of electric bus (capabus) that runs without powerlines using power stored in large onboard supercapacitors, which are quickly recharged whenever the electric bus stops at any bus stop (under so-called electric umbrellas), and fully charged in the terminus. A few prototypes were being tested in Shanghai in early 2005. In 2006, two commercial bus routes began to use supercapacitor buses; one of them is route 11 in Shanghai. ^[10] An articulated trolleybus in Arnhem, Netherlands A trolleybus (also known as electric bus, trolley bus, trolley coach, trackless trolley, trackless tram or simply trolley) is a bus powered by two overhead electric wires, from which it draws electricity using two trolley poles. ... Terminus can refer to: Terminal station, a bus or rail station acting as an end destination Terminus (mythology), a Roman god Jupiter (god) (also known by this name) Atlanta, Georgia, which was originally called Terminus Terminus (planet), the home planet of the Foundation in Isaac Asimovs Foundation series Terminus... For other uses, see Shanghai (disambiguation). ...

In 2001 and 2002, VAG, the public transport operator in Nuremberg, Germany tested a bus which used a diesel-electric drive system with supercapacitors.^[11] Nürnberg redirects here. ... A number of vehicles use a diesel-electric powerplant for providing locomotion. ...

Since 2003 Mannheim Stadtbahn in Mannheim, Germany has operated an LRV (light-rail vehicle) which uses supercapacitors.^[12][13]

Other companies from the public transport manufacturing sector are developing supercapacitor technology: The Transportation Systems division of Siemens AG is developing a mobile energy storage based on double-layer capacitors called Sibac Energy Storage ^[14] and also Sitras SES, a stationary version integrated into the trackside power supply ^[15]. The company Cegelec is also developing a supercapacitor-based energy storage system^{[citation needed]}. Siemens redirects here. ...

Proton Power Systems has created the world's first triple hybrid Forklift Truck, which uses fuel cells and battery as primary energy storage and supercapacitors to supplement this overall energy efficient storage solution.^[16] A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ... For other uses, see Battery. ...

Formula 1 Racing Application

The FIA proposed on May 23, 2007, in the Power-Train Regulation Framework for Formula 1, version 1.3, that a new set of power train regulations be issued that includes a hybrid drive of up to 200 kW input and output power, involving both batteries and supercapacitors. The Fédération Internationale de lAutomobile, commonly referred to as the FIA, is a non-profit association established in 1904 to represent the interest of motoring organisations and motor car users. ... is the 143rd day of the year (144th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era in the 21st century. ...

Technology

Carbon nanotubes and certain conductive polymers, or carbon aerogels, are practical for supercapacitors: 3D model of three types of single-walled carbon nanotubes. ... A conductive polymer is an organic polymer semiconductor, or an organic semiconductor. ... A 2. ...

• Carbon nanotubes have excellent nanoporosity properties, allowing tiny spaces for the polymer to sit in the tube and act as a dielectric. MIT's Laboratory of Electromagnetic and Electronic Systems (LEES) is researching using carbon nanotubes^[17].

• Some polymers (eg. polyacenes) have a redox (reduction-oxidation) storage mechanism along with a high surface area.

• Supercapacitors are also being made of carbon aerogel. This is a unique material providing extremely high surface area of about 400-1000 m²/g. The electrodes of aerogel supercapacitors are usually made of non-woven paper made from carbon fibers and coated with organic aerogel, which then undergoes pyrolysis. The paper is a composite material where the carbon fibers provide structural integrity and the aerogel provides the required large surface. Small aerogel supercapacitors are being used as backup electricity storage in microelectronics, but applications for electric vehicles are expected^[18]. The voltage of an aerogel capacitor is limited to a few volts. Higher voltages will lead to ionization of the carbon, which will damage the capacitor.

• The company Reticle Carbon claims to be able to make supercapacitors from activated carbon in solid form. This substance is called Reticle Carbon. It has a larger surface area than aerogel and should be cheaper to produce. This would result in a capacitor with an energy density of 7.5 kW·h/kg.

• The company Tartu Technologies Ltd. developed the supercapacitors from mineral based carbon. These nonactivated carbon are synthesised from the metal- or metalloid carbides, e.g SiC, TiC, Al4C3, etc. The synthesised nanostructured porus carbon, often called Carbide Derived Carbon (CDC), have surface area about 400 m²/g to 2000 m²/g with specific capacitance up to 100 F/cm³ (in organic electrolyte). The supercapacitor with the volume of 135 mL and 200 g weight have capacitance 1600 F. The energy density is more than 13 W·h/L at 2.85 V and outstanding power characteristics, over 20 kW/kg.

[4] An electronic device known as a diode can be formed by joining two nanoscale carbon tubes with different electronic properties. ... ed|other uses|reduction}} Illustration of a redox reaction Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... A 2. ... A woven is a cloth formed by weaving. ... Carbon fiber composite is a strong, light and very expensive material. ... Simple sketch of pyrolysis chemistry Pyrolysis usually means the chemical decomposition of organic materials by heating in the absence of oxygen or any other reagents, except possibly steam. ... A cloth of woven carbon fiber filaments, a common element in composite materials Composite materials (or composites for short) are engineered materials made from two or more constituent materials with significantly different physical or chemical properties and which remain separate and distinct on a macroscopic level within the finished structure. ... For battery powered passenger automobiles, see battery electric vehicle. ... Activated carbon Activated carbon, also called activated charcoal or activated coal, is a general term which covers carbon material mostly derived from charcoal. ... A 2. ...

In August 2007, a research team at RPI developed a paper battery with aligned carbon nanotubes, designed to function as both a lithium-ion battery and a supercapacitor (called bacitor), using an ionic liquid, essentially a liquid salt, as the electrolyte. The sheets can be rolled, twisted, folded, or cut into numerous shapes with no loss of integrity or efficiency, or stacked, like printer paper (or a Voltaic pile), to boost total output. As well, they can be made in a variety of sizes, from postage stamp to broadsheet. Their light weight and low cost make them attractive for portable electronics, aircraft, automobiles, and toys (such as model aircraft), while their ability to use electrolytes in blood make them potentially useful for medical devices such as pacemakers. In addition, they are biodegradable.^[19] Rensselaer Polytechnic Institute, or RPI, is a nonsectarian, coeducational private research university in Troy, New York, a city lying just outside the state capital of Albany. ... For other uses, see Battery. ... Ionic liquid An ionic liquid is a liquid that contains essentially only ions. ... This article is about common table salt. ... An electrolyte is any substance containing free ions that behaves as an electrically conductive medium. ... A copper-zinc Voltaic pile A Voltaic pile on display in the Tempio Voltiano The Voltaic pile is the first modern electric battery, invented by Alessandro Volta in 1800. ... A selection of Hong Kong postage stamps A postage stamp is evidence of pre-paying a fee for postal services. ... Newspaper sizes in August 2005. ... Flying machine redirects here. ... Car redirects here. ... A Die Cast Boeing 747-800 static model. ... A pacemaker (sometimes called a pacer) is a competitor who enters an athletics race with little or no intention of winning, but purely to set a fast pace for other competitors to follow. ... Biodegradation is the decomposition of material by microorganisms. ...

See also

• Capacitor
• Capacitor (component)
• EEStor
• Rechargeable energy storage system

See Capacitor (component) for a discussion of specific types. ... Practical capacitors are often classified according to the material used as the dielectric with the dielectrics divided into two broad categories: bulk insulators and metal-oxide films (so-called electrolytic capacitors). ... EEstor cell EEStor is a company based in Cedar Park, Texas, United States that claims to have developed a superior type of capacitor for electricity storage, which EEStor calls Electrical Energy Storage Units (EESU). ... A rechargeable energy storage system or RESS is a system that stores energy for delivery of electric energy and which is rechargeable. ...

References

Year 1957 (MCMLVII) was a common year starting on Tuesday (link displays the 1957 Gregorian calendar). ... is the 204th day of the year (205th in leap years) in the Gregorian calendar. ... Railway Gazette International is a monthly business journal covering the railway, metro, light rail and tram industries worldwide. ...

External links

• Article on ultracapacitors at electronicdesign.com
• Article on ultracapacitors at batteryuniversity.com
• A new version of an old idea is threatening the battery industry (The Economist).
• Site dedicated to information on Ultracapacitors and Supercapacitors