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A capacitor vehicle or capa vehicle is a vehicle that uses supercapacitors (also called ultracapacitors) to store electricity. [1]
As of 2010 [update] , the best ultracapacitors can only store about 5% of the energy that lithium-ion rechargeable batteries can, limiting them to a couple of miles per charge. This makes them ineffective as a general energy storage medium for passenger vehicles. But ultracapacitors can charge much faster than batteries, so in vehicles such as buses that have to stop frequently at known points where charging facilities can be provided, energy storage based exclusively on ultracapacitors becomes viable [2]
China is experimenting with a new form of electric bus, known as Capabus, which runs without continuous overhead lines (is an autonomous vehicle) by using power stored in large onboard electric double-layer capacitors (EDLCs), which are quickly recharged whenever the vehicle 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 electric double-layer capacitor buses; one of them is route 11 in Shanghai. [3] In 2009 Sinautec Automobile Technologies, [4] based in Arlington, Virginia, and its Chinese partner Shanghai Aowei Technology Development Company [5] are testing, with 17 forty-one seat Ultracap Buses serving the Greater Shanghai area since 2006 without any major technical problems. [6] During the Shanghai Expo in 2010, however, 40 super-capacitor buses were being used on a special Expo bus service and owing to the super-capacitors becoming overheated some of the buses broke down. [7] Buses in the Shanghai pilot are made by Germantown, Tennessee-based Foton America Bus Company [8] Another 60 buses will be delivered early next year with ultracapacitors that supply 10 watt-hours per kilogram.
The buses have very predictable routes and need to stop regularly every 3 miles (4.8 km) or less, allowing quick recharging at charging stations at bus stops. A collector on the top of the bus rises a few feet and touches an overhead charging line at the stop; within a couple of minutes the ultracapacitor banks stored under the bus seats are fully charged. The buses can also capture energy from braking, and the company says that recharging stations can be equipped with solar panels. A third generation of the product, which will give 20 miles (32 km) of range per charge or better is planned. [2]
Sinautec estimates that one of its buses has one-tenth the energy cost of a diesel bus and can achieve lifetime fuel savings of $200,000. The buses use 40% less electricity even when compared to an electric trolley bus, mainly because they are lighter[ citation needed ]. The ultracapacitors are made of activated carbon and have an energy density of six watt-hours per kilogram (for comparison a high-performance lithium-ion battery can achieve 200 watt-hours per kilogram, but the ultracapacitor bus is about 40% cheaper than a lithium-ion battery bus and far more reliable). [2] [6]
There is also a plug-in hybrid version, which also uses ultracaps.
RATP, the public-owned company that manages most of Paris' public transport system, is currently performing tests using a hybrid bus outfitted with ultracapacitors. The model, called Lion's City Hybrid, is supplied by German manufacturer MAN. [9]
Foton America Bus is in talks with New York City, Chicago, and some towns in Florida about trialing the buses.[ citation needed ]
GSP Belgrade, Serbia has launched the first bus line operated solo by super-capacitor buses from Chinese manufacturer Higer. [10] Since 2014 the public transport authority of the city of Sofia, Bulgaria is also performing tests on a capabus made by Higer. Following the successful trials in 2019 Sofia purchased 15 of these buses.
In Graz, Austria, lines 50 and 34E are running with short intermediate recharging, using 24–32 kWh Supercaps/EDLC. [11]
Pantographs and underbody collectors are integrated in bus stops to recharge electric buses quickly, making it possible to use a smaller battery on the bus, which reduces the capital and running costs. [12] [13] [14] [15]
In a subway car or tram, an insulator at a track switch may cut off power from the car for a few feet along the line and use a large capacitor to store energy to drive the subway car through the insulator in the power feed. [16]
The new Nanjing tram uses supercapacitor technology, with charging hardware at each stop instead of continuous catenary. The first line started operating in 2014. The rail vehicles were produced by CSR Zhuzhou; according to the manufacturers, they are the world's first low-floor tram completely powered by supercapacitors. [17] Several similar rail vehicles have been ordered for the Guangzhou Tram line as well. [17]
In 2001 and 2002 VAG, the public transport operator in Nuremberg, Germany, tested a hybrid bus which uses a diesel-electric drive system with electric double-layer capacitors. [18]
Since 2003 Mannheim Stadtbahn in Mannheim, Germany, has operated a capa vehicle, an LRV (light-rail vehicle), which uses electric double-layer capacitors to store braking energy. [19] [20]
Other companies from the public transport manufacturing sector are developing electric double-layer capacitor technology: The Transportation Systems division of Siemens AG is developing a mobile energy storage based on ELDCs called Sibac Energy Storage [21] and also Sitras SES, a stationary version integrated into the trackside power supply. [22] Adetel Group has developed its own energy saver named ″NeoGreen″ for LRV, LRT and metros. [23] The company Cegelec is also developing an ELDC-based energy storage system. [24]
Proton Power Systems has created the world's first triple hybrid forklift truck, which uses fuel cells and batteries as primary energy storage with ELDCs to supplement them. [25]
University of Southampton spin-out Nanotecture [26] has received a Government grant to develop supercapacitors for hybrid vehicles. The company is set to receive £376,000 from the DTI in the UK for a project entitled "next generation supercapacitors for hybrid vehicle applications". The project also involves Johnson Matthey and HILTech Developments. The project will use supercapacitor technology to improve hybrid electric vehicles and increase overall energy efficiency.
Sinautec is in discussions with MIT's Schindall about developing ultracapacitors of higher energy density using vertically aligned carbon nanotube structures that give the devices more surface area for holding a charge. So far they are able to get twice the energy density of an existing ultracapacitor, but they are trying to get about five times. This would create an ultracapacitor with one-quarter of the energy density of a lithium-ion battery. [27]
Future developments includes the use of inductive charging under the street, to avoid overhead wiring. A pad under each bus stop and at each stop light along the way would be used.
The FIA, the governing body for many motor racing events, proposed in the Power-Train Regulation Framework for Formula 1 version 1.3 of 23 May 2007 that a new set of power train regulations be issued that includes a hybrid drive of up to 200 kW input and output power using "superbatteries" made with both batteries and supercapacitors. [28]
Ultracapacitors are used in some electric vehicles, such as AFS Trinity's concept prototype, to store rapidly available energy with their high power density, in order to keep batteries within safe resistive heating limits and extend battery life. [29] [30] The Ultrabattery combines a supercapacitor and a battery in a single unit, creating an electric vehicle battery that lasts longer, costs less and is more powerful than current technologies used in plug-in hybrid electric vehicles (PHEVs). [31]
Energy storage is the capture of energy produced at one time for use at a later time to reduce imbalances between energy demand and energy production. A device that stores energy is generally called an accumulator or battery. Energy comes in multiple forms including radiation, chemical, gravitational potential, electrical potential, electricity, elevated temperature, latent heat and kinetic. Energy storage involves converting energy from forms that are difficult to store to more conveniently or economically storable forms.
A hybrid vehicle is one that uses two or more distinct types of power, such as submarines that use diesel when surfaced and batteries when submerged. Other means to store energy include pressurized fluid in hydraulic hybrids.
A rechargeable battery, storage battery, or secondary cell, is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or primary battery, which is supplied fully charged and discarded after use. It is composed of one or more electrochemical cells. The term "accumulator" is used as it accumulates and stores energy through a reversible electrochemical reaction. Rechargeable batteries are produced in many different shapes and sizes, ranging from button cells to megawatt systems connected to stabilize an electrical distribution network. Several different combinations of electrode materials and electrolytes are used, including lead–acid, zinc–air, nickel–cadmium (NiCd), nickel–metal hydride (NiMH), lithium-ion (Li-ion), lithium iron phosphate (LiFePO4), and lithium-ion polymer.
An electric vehicle (EV) is a vehicle that uses one or more electric motors or traction motors for propulsion. An electric vehicle may be powered through a collector system by electricity from off-vehicle sources, or may be self-contained with a battery, solar panels, fuel cells or an electric generator to convert fuel to electricity. EVs include, but are not limited to, road and rail vehicles, surface and underwater vessels, electric aircraft and electric spacecraft.
A zero-emissions vehicle, or ZEV, is a vehicle that never emits exhaust gas from the onboard source of power.
Zinc–air batteries (non-rechargeable), and zinc–air fuel cells are metal–air batteries powered by oxidizing zinc with oxygen from the air. These batteries have high energy densities and are relatively inexpensive to produce. Sizes range from very small button cells for hearing aids, larger batteries used in film cameras that previously used mercury batteries, to very large batteries used for electric vehicle propulsion and grid-scale energy storage.
A mechanically powered flashlight is a flashlight that is powered by electricity generated by the muscle power of the user, so it does not need replacement of batteries, or recharging from an electrical source. There are several types which use different operating mechanisms. They use different motions to generate the required power; such as squeezing a handle, winding a crank, or shaking the flashlight itself. These flashlights can also be distinguished by the technique used to store the energy: a spring, a flywheel, a battery or a capacitor.
An electric bus is a bus that is powered by electricity.
Hybrid vehicle drive trains transmit power to the driving wheels for hybrid vehicles. A hybrid vehicle has multiple forms of motive power.
A battery electric bus is an electric bus that is driven by an electric motor and obtains energy from on-board batteries. Many trolleybuses use batteries as an auxiliary or emergency power source.
AFS Trinity Power Corporation is an American corporation headquartered in Medina, WA with an engineering center in Livermore, CA that develops technology for plug-in hybrids. The company has developed PHEV technology that actively combines batteries with ultracapacitors. The company asserts that the combination of high-power ultracapacitors, which prefer to discharge and recharge quickly, and high-energy lithium-ion batteries, which prefer to discharge and recharge slowly, makes for a system with both long-life and high energy-density storage.
A battery electric vehicle (BEV), pure electric vehicle, only-electric vehicle or all-electric vehicle is a type of electric vehicle (EV) that exclusively uses chemical energy stored in rechargeable battery packs, with no secondary source of propulsion. BEVs use electric motors and motor controllers instead of internal combustion engines (ICEs) for propulsion. They derive all power from battery packs and thus have no internal combustion engine, fuel cell, or fuel tank. BEVs include – but are not limited to – motorcycles, bicycles, scooters, skateboards, railcars, watercraft, forklifts, buses, trucks, and cars.
A lithium-ion capacitor (LIC) is a hybrid type of capacitor classified as a type of supercapacitor. It is called a hybrid because the anode is the same as those used in lithium-ion batteries and the cathode is the same as those used in supercapacitors. Activated carbon is typically used as the cathode. The anode of the LIC consists of carbon material which is often pre-doped with lithium ions. This pre-doping process lowers the potential of the anode and allows a relatively high output voltage compared to other supercapacitors.
The lithium-titanate-oxide (LTO) battery is a type of rechargeable battery which has the advantage of being faster to charge than other lithium-ion batteries, but the disadvantage of having a much lower energy density.
A kinetic energy recovery system (KERS) is an automotive system for recovering a moving vehicle's kinetic energy under braking. The recovered energy is stored in a reservoir for later use under acceleration. Examples include complex high end systems such as the Zytek, Flybrid, Torotrak and Xtrac used in Formula One racing and simple, easily manufactured and integrated differential based systems such as the Cambridge Passenger/Commercial Vehicle Kinetic Energy Recovery System (CPC-KERS).
A battery electric multiple unit (BEMU), battery electric railcar or accumulator railcar is an electrically driven multiple unit or railcar whose energy is derived from rechargeable batteries driving the traction motors.
Pseudocapacitors store electrical energy faradaically by electron charge transfer between electrode and electrolyte. This is accomplished through electrosorption, reduction-oxidation reactions, and intercalation processes, termed pseudocapacitance.
A supercapacitor (SC), also called an ultracapacitor, is a high-capacity capacitor with a capacitance value much higher than other capacitors, but with lower voltage limits, that bridges the gap between electrolytic capacitors and rechargeable batteries. It typically stores 10 to 100 times more energy per unit volume or mass than electrolytic capacitors, can accept and deliver charge much faster than batteries, and tolerates many more charge and discharge cycles than rechargeable batteries.
A solar bus or solar-charged bus is a bus which is powered exclusively or mainly by solar energy. A solar-powered bus service is referred to as a solar bus service. The use of the term "solar bus" normally implies that solar energy is used not only for powering electric equipment on the bus, but also for the propulsion of the vehicle.
Pseudocapacitance is the electrochemical storage of electricity in an electrochemical capacitor (Pseudocapacitor). This faradaic charge transfer originates by a very fast sequence of reversible faradaic redox, electrosorption or intercalation processes on the surface of suitable electrodes. Pseudocapacitance is accompanied by an electron charge-transfer between electrolyte and electrode coming from a de-solvated and adsorbed ion. One electron per charge unit is involved. The adsorbed ion has no chemical reaction with the atoms of the electrode since only a charge-transfer takes place.