- Glossary of fuel cell terms
The Glossary of fuel cell terms lists the definitions of many terms used within the
fuel cellindustry. The terms in this glossarymay be used by fuel cell industry associations, in education material and fuel cell codes and standards to name but a few.
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Adsorptionis a process that occurs when a gas or liquid soluteaccumulates on the surface of a solid or a liquid (adsorbent), forming a film of molecules or atoms (the adsorbate).
Alkaline fuel cell
Alkaline fuel cell(AFC) also known as the Bacon fuel cell.
alloyis a solid solutionor homogeneousmixture of two or more elements, at least one of which is a metal, which itself has metallicproperties.
alternatoris an electromechanical device that converts mechanical energy to alternating currentelectrical energy.
alternating current(AC) is an electric currentwhose direction reverses cyclically, as opposed to direct current, whose direction remains constant.
airsurrounding a given object or system.
Ambient temperature(also referred to as room temperature) is a common term to denote a certain temperaturewithin enclosed space.
ampere, in practice often shortened to amp, (symbol: A) is a unit of electric current, or amount of electric chargeper second.
: A negatively charged
ion; an ion that is attracted to the anode.
anodeis an electrodethrough which " electric current" flows "into" a polarized electrical device.
artificial membrane, also called a synthetic membrane, is a membrane prepared for separation tasks in laboratoryand industry.
Atmospheric pressureis the pressureat any given point in the Earth's atmosphere.
atomis the smallest unit of an element that retains the chemical properties of that element. An atom has an electron cloudconsisting of negatively charged electronssurrounding a dense nucleus. The nucleus contains positively charged protons and electrically neutral neutrons.
: Autothermal reforming (ATR) uses oxygen and carbon dioxide or steam in a reaction with methane to form
Auxiliary power unit
auxiliary power unit(APU) is a device on a vehicle whose purpose is to provide energy for functions other than propulsion.
availability factorof a power plantis the amount of time that it is able to produce electricityover a certain period, divided by the amount of the time in the period.
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Back pressureusually refers to the pressureexerted on a moving fluidby obstructions or tight bends in the confinement vessel along which it is moving, such as piping or air vents, against its direction of flow.
: A device or construction used to restrain or regulate, e.g. gas, or a fluid.
Balance of plant
Balance of plant(BOP) (See also MBOPand EBOP).
: In electronics, a battery is a combination of two or more
electrochemical cells which store chemical energyand make it available as electrical energy.
Biofuelis defined as solid, liquid or gas fuelderived from recently dead biological materialand is distinguished from fossil fuels, which are derived from long dead biological material.
Biogastypically refers to a gasproduced by the biological breakdown of organic matterin the absence of oxygen. Biogas originates from biogenic material and is a type of biofuel.
: A bioreactor may refer to any device or system that supports a biologically active environment
biosensoris a device for the detection of an analytethat combines a biological component with a physicochemical detector component.
Bipolar plate, conductive plate in a fuel cell stackthat acts as an anodefor one cell and a cathodefor the adjacent cell. The plate may be made of metal or a conductive polymer(which may be a carbon-filled composite). The plate usually incorporates flow channels for the fluid feeds and may also contain conduits for heat transfer. See also MEA.
black startis the process of restoring a power stationto operation without relying on external energy sources.
Beta-alumina solid electrolyte
Beta-alumina solid electrolyte(BASE) is a fast ion conductormaterial used as a membrane in several types of molten salt electrochemical cell.
boiling pointof a liquid is the water temperature at which the vapor pressureof the liquid equals the environmental pressure surrounding the liquid.
Borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boroncompound, a mineral, and a salt of boric acid.
British thermal unit
: The mean
British thermal unit(BTU) is 1/180 of the heat required to raise the temperature of one pound (1lb) of waterfrom 32°F to 212°F at a constant atmospheric pressure. It is about equal to the quantity of heat required to raise one pound (1 lb.) of water 1°F.
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Capacityis the ability to hold, receive or absorb, or a measure thereof, similar to the concept of volume.
: The net
capacity factorof a power plantis the ratio of the actual output of a power plant over a period of time and its output if it had operated at full nameplate capacity the entire time.
Capital costare costs incurred on the purchase of fuel cells, buildings, constructionand equipment to be used in the use of fuel cells or the rendering of it.
Carbon(C), an atom and primary constituent of hydrocarbon fuels. Carbon is routinely left as a black deposit on engine parts, such as pistons, rings, and valves, by the combustionof fuel.
Carbon blackis a material produced by the incomplete combustionof heavy petroleumproducts such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil.
Carbon dioxide( chemical formula: co2) is a chemical compoundcomposed of two oxygen atoms covalently bonded to a single carbonatom.
Carbon dioxide sensor
carbon dioxide sensor(CO2) is an instrument for the measurement of carbon dioxidegas. The most common principles for CO2 sensors are infrared gas sensors ( NDIR) and chemical gas sensors.
Carbon monoxide, with the chemical formula CO, is a colorless, odorless, tasteless yet highly toxic gas.
Carbon monoxide detector
carbon monoxide detectoris a device that detects the presence of the toxicgas carbon monoxide(CO), a colorless and odorless compound produced by incomplete combustion and lethal at high levels.
Carbon paper(originally carbonic paper) is papercoated on one side with a layer of a loosely bound dry inkor pigmented coating, usually bound with wax.
Carnot cycleis a particular thermodynamic cycle, modeled on the hypothetical Carnot heat engine.
Catalysisis the process in which the rate of a chemical reactionis increased by means of a chemical substanceknown as a .
catalystis a chemical substance that increases the rate of a reaction without being consumed; after the reaction it can potentially be recovered from the reaction mixture chemically unchanged.
Catalyst poisoningrefers to the effect that a catalystcan be 'poisoned' if it reacts with another compound that bonds chemically (similar to an inhibitor) but does not release, or chemically alters the catalyst.
Catalytic partial oxidation
catalytic partial oxidation(CPOX) the use of a catalystfor partial oxidationreduces the required temperature to around 800°C - 900°C. The choice of reforming technique depends on the sulfurcontent of the fuel being used. CPOX can be employed if the sulfur content is below 50 ppm. A higher sulfur content would poison the catalyst, so the TPOX procedure is used for such fuels.
cathodeis an electrodethrough which "(positive)" " electric current" flows "out of" a polarized electrical device.
cationis a positively charged ion.
: The degree
Celsius(°C) can refer to a specific temperature on the Celsius scale as well as serve as a unit increment to indicate a temperature "interval "(a difference between two temperatures or an uncertainty).
centrifugal governoris a specific type of governor that controls the speedby regulating the amount of fuel(or working fluid) admitted, so as to maintain a near constant speed whatever the loador fuel supply conditions.
: The word
ceramicis derived from the Greek word κεραμικός ("keramikos"). The term covers inorganicnon- metallicmaterials which are formed by the action of heat.
cermetis a composite materialcomposed of ceramic(cer) and metallic (met) materials.
thermodynamics, chemical thermodynamicsis the mathematical study of the interrelation of heatand work with chemical reactionsor with a physical change of state within the confines of the laws of thermodynamics.
: An circuit is a closed path formed by the interconnection of
electronic componentsthrough which an electric currentcan flow.
circuit diagram(also known as an electrical diagram, wiring diagram, elementary diagram, or electronic schematic) is a simplified conventional pictorial representation of an electrical circuit.
fluid dynamics, circulation is the line integralaround a closed curve of the fluid velocity.
Climate changeis any long-term significant change in the “average weather” that a given region experiences.
Cogeneration(also combined heat and power, CHP) is the use of a heat engineor a power stationto simultaneously generate both electricityand useful heat.
Combustionor burning is a complex sequence of exothermicchemical reactions between a fueland an oxidantaccompanied by the production of heator both heatand lightin the form of either a glow or flames.
combustion chamberis the part of an enginein which fuelis burned.
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.
Compressed hydrogen(CGH2, CH2 or CH2) is the gaseous stateof the element hydrogenwhich is kept under pressure.
Compressed natural gas
Compressed Natural Gas(CNG) is a fossil fuelsubstitute for gasoline(petrol), diesel, or propane fuel.
chemistry, concentrationis the measure of how much of a given substance there is mixed with another substance.
Condensate, the liquid phase produced by the condensationof steamor any other gas
Condensationis the change of the physical state of aggregation (or simply state) of matter from gaseous phase into liquid phase.
Contaminationis the introduction of material that "does not belong there".
coulomb(symbol: C) is the SIunit of electric charge.
Countercurrent exchangeis a mechanism used to transfer some property of a fluidfrom one flowing current of fluid to another across a semipermeable membraneor thermally-conductive material between them.
Cryogenic liquefactionis the process through which gases such as nitrogen, hydrogen, helium, and natural gas are liquefied under pressure at very low temperatures.
current collectoris a term used to describe the conductive material in a fuel cellthat collects electrons(on the anodeside) or disburses electrons (on the cathodeside). Current collectors are microporous (to allow for fluid flow through them) and lie in between the catalyst/ electrolytesurfaces and the bipolar plates.
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DC to DC converter
electronic engineering, a DC to DC converteris a circuit which converts a source of direct current(DC) from one voltagelevel to another. It is a class of power converter.
densityof a material is defined as its massper unit volume
desiccantis a hygroscopicsubstance that induces or sustains a state of dryness ( desiccation) in its local vicinity in a moderately-well sealed container.
analytical chemistry, the detection limit, lower limit of detection, or LOD (limit of detection), is the lowest quantity of a substance that can be distinguished from the absence of that substance (a "blank value") within a stated confidence limit (generally 1%).
dew point(sometimes spelled dewpoint) is the temperatureto which a given parcel of airmust be cooled, at constant barometric pressure, for water vaporto condense into water.
Diffusionis part of transport phenomena. Diffusion is the movement of molecules from a region of higher concentration to one of lower concentration by random molecular motion.
Direct borohydride fuel cell
Direct borohydride fuel cell(DBFC) a subcategory of alkaline fuel cells
Direct carbon fuel cell
Direct carbon fuel cell(DCFC), a fuel cellthat uses a carbonaceous material as a fuel.
Direct current(DC) is the unidirectional flow of electric charge.
Direct-ethanol fuel cell
Direct-ethanol fuel cell(DEFC) a subcategory of Proton-exchange fuel cells where, the fuel, ethanol, is not reformed, but fed directly to the fuel cell.
Direct methanol fuel cell
Direct methanol fuel cell(DMFC) subcategory of proton-exchange fuel cells where the methanol(CH3OH) fuel is not reformed as in the indirect methanol fuel cell, but fed directly to the fuel cell
Dispersion, in fluid dynamics dispersive mass transfer, the spreading of mass from areas of high to low concentration
Distributed generation, also called on-site generation, dispersed generation, embedded generation, decentralized generation, decentralized energy or distributed energy, generates electricityfrom many small energy sources.
semiconductorproduction, dopingis the process of intentionally introducing impurities into an extremely pure (also referred to as "intrinsic") semiconductor in order to change its electrical properties.
Downtimeor outage refers to a period of time or a percentage of a timespan that a systemis unavailable or offline.
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Effluentis an outflowing of water from a natural body of water, or from a man-made structure.
Electrical Balance of Plant
Electricityis a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge.
Electrical conductivityor specific conductivity is a measure of a material's ability to conduct an electric current.
electrical efficiencyof an entity (a device, component, or system) in electronicsand electrical engineeringis defined as useful power output divided by the total electrical power consumed (a fractional expression), typically denoted by the Greek letter small Eta (η).
Electrical resistanceis a ratio of the degree to which an object opposes an electric currentthrough it, measured in Ohms.
electrical circuitis a network that has a closed loop, giving a return path for the current. A network is a connection of two or more components, and may not necessarily be a circuit.
Electric currentis the flow (movement) of electric charge. The SIunit of electric current is the ampere.
Electricity generationis the process of converting non-electrical energyto electricity.
Electric power conversion
electrical engineering, power conversion has a more specific meaning, namely converting electric powerfrom one form to another.
Electrochemistryis a branch of chemistrythat studies chemical reactionswhich take place in a solutionat the interface of an electron conductor (a metalor a semiconductor) and an ionic conductor (the electrolyte), and which involve electron transfer between the electrode and the electrolyte or species in solution.
electrochemical cellis a device used for generating an electromotive force( voltage) and current from chemical reactions.
Electrochemical gas sensor
Electrochemical gas sensors are gas detectorsthat measure the volume of a target gasby oxidizing or reducing the target gas at an electrodeand measuring the resulting current.
electrodeis an electrical conductorused to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyteor a vacuum).
Electro-galvanic fuel cell
Electro-galvanic fuel cell(EGFC)an electrical device used to measure the concentration of oxygengas in scuba divingand medicalequipment.
Electroosmotic flow(or Electro-osmotic flow, often abbreviated EOF) is the motion of liquid induced by an applied potential across a capillary tube or microchannel. Electroosmotic flow is an essential component in chemical separation techniques, notably capillary electrophoresis.
electroosmotic pump(EOP), or EO pump, is used for removing liquid flooding waterfrom channels and gas diffusionlayers and direct hydrationof the proton exchange membranein the membrane electrode assembly(MEA) of the proton exchange membrane fuel cell
electrolyteis any substance containing free ions that behaves as an electrically conductive medium.
electronis a fundamental subatomic particlethat carries a negative electric charge.
Emissionof air pollutants
Emission standardsare requirements that set specific limits to the amount of pollutantsthat can be released into the environment.
thermodynamics, the word endothermic"within-heating" describes a process or reaction that absorbs energyin the form of heat.
energy carrieris a substance or phenomenon that can be used to produce mechanical work or heat or to operate chemical or physical processes (ISO 13600).
: Amount of
energyfor a given weight of fuel. see also energy density
Energy storageis the storing of some form of energythat can be drawn upon at a later time to perform some useful operation.
engineis a machine that converts heat energy into mechanical energy.
Energy conversion efficiency
Energy conversion efficiencyis the ratiobetween the useful output of an energy conversion machineand the input, in energyterms.
Energy densityis the amount of energystored in a given system or region of space per unit volume, or per unit mass, depending on the context, although the latter is more formally specific energy
physicsand engineering, energy transformationor energy conversion, is any process of transforming one form of energyto another.
thermodynamicsand molecular chemistry, the enthalpyor heat content (denoted as "H", "h", or rarely as "χ") is a quotient or description of thermodynamic potentialof a system, which can be used to calculate the "useful" work obtainable from a closed thermodynamic systemunder constant pressure and entropy.
Enthalpy of vaporization
enthalpy of vaporization, (symbol ), also known as the heat of vaporization or heat of evaporation, is the energyrequired to transform a given quantity of a substance into an gas.
Ethanol, also called ethyl alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid.
Evaporationis the process by which molecules in a liquidstate (e.g. water) spontaneously become gaseous (e.g. water vapor).
Exergy efficiency(also known as the second-law efficiency or rational efficiency) computes the efficiency of a process taking the second law of thermodynamics into account.
Exhaust gasis flue gaswhich occurs as a result of the combustionof fuels such as natural gas, gasoline/petrol, diesel, fuel oilor coal. It is discharged into the atmosphere through an exhaust pipeor flue gas stack.
thermodynamics, the word exothermic"outside heating" describes a process or reaction that releases energyusually in the form of heat, but it can also release energy in form of light (e.g. explosions), sound, or electricity (e.g. a battery).
Expansion ratiois used in the context of liquefied and cryogenicsubstances. The expansion ratio of a substance is the volume of a given amount of that substance in liquid form compared to the volume of the same amount of substance in gaseous form, at a given temperature.
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Fahrenheitis a temperature scale.In this scale, the freezing point of wateris 32 degrees Fahrenheit (°F) and the boiling point212 °F
Failure mode and effects analysis
failure mode and effects analysis(FMEA) is a procedurefor analysis of potential failure modes within a system for classification by severity or determination of the effect of failures on the system.
Fuel cell vehicle
Feedstock purification, The process of removing poisons like sulfur(S) and chloride(Cl) from the feedstock.
Flammabilityis the ease with which a substance will ignite, causing fireor combustion.
flash pointof a flammable liquid is the lowest temperatureat which it can form an ignitable mixture in air.
float valveis a mechanical feedbackmechanism that regulates fluid level by using a float to drive an inlet valve so that a higher fluid level will force the valve closed while a lower fluid level will force the valve open.
Flow battery(FB) a form of rechargeable batteryin which electrolytecontaining one or more dissolved electroactive species flows through a power cell / reactor that converts chemical energyto electricity.
Flow measurementis the quantification of bulk fluidmovement. It can be measured in a variety of ways.
Flue gasis gasthat exits to the atmosphere via a flue.
Flue gas desulfurization
Flue gas desulfurization(FGD) is the technology used for removing sulfur dioxide(SO2) from the exhaust flue gases.
Fluid dynamicsis the sub-discipline of fluid mechanicsdealing with fluid flow: fluids ( liquids and gases) in motion.
Fluid mechanicsis the study of how fluids move and the forces on them. (Fluids include liquids and gases.) Fluid mechanics can be divided into fluid statics, the study of fluids at rest, and fluid dynamics, the study of fluids in motion.
: In the study of
transport phenomena( heat transfer, mass transferand fluid dynamics), fluxis defined as the amount that flows through a unit area "per unit time".
Formic acid fuel cell
Formic acid fuel cell(DFAFC), a subcategory of proton-exchange fuel cellswhere, the fuel, formic acid, is not reformed, but fed directly to the fuel cell.
Fossil fuelsor mineral fuels are fossil source fuels, that is, hydrocarbonsfound within the top layer of the Earth’s crust.
Foulingrefers to the accumulation of unwanted material on solid surfaces,
Fuelis any material that is burned or altered in order to obtain energy.
fuel cell(FC) is an electrochemical conversion device.
Fuel cell poisoning
: The lowering of a fuel cell's efficiency due to impurities in the fuel binding to the catalyst. See
Fuel cell vehicle
fuel cell vehicleis any vehiclethat uses a fuel cellto produce its on-board motive power.
Fuel efficiency, in its basic sense, is the same as thermal efficiency, meaning the efficiency of a process that converts chemical potential energy contained in a carrier fuelinto kinetic energyor work.
Fuel efficiency in transportation
Fuel efficiency in transportation
: Device used to generate hydrogen from fuels such as
natural gas, propane, gasoline, methanol, and ethanol, for use in fuel cells.
Fuel processing system
Fuel processing system(FPS)
fusible plugis a threaded metal plug, usually made out of bronze, brass, or gunmetal.
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Gadolinium doped ceria
Fuel gas, such as natural gas, undiluted liquefied petroleumgases (vapor phase only), liquefied petroleum gas-air mixtures, or mixtures of these gases.:: Liquefied petroleum gases (LPG) as used in this standard, shall mean and include any material which is composed predominantly of any of the following hydrocarbons, or mixtures of them: propane, propylene, butanes (normal butane or isobutane) and butylenes.:: LP Gas-Air Mixture - Liquefied petroleum gases distributed at relatively low pressures and normal atmospheric temperatures which have been diluted with air to produce desired heating value and utilization characteristics.:: Natural Gas- Mixtures of hydrocarbon gases and vapors consisting principally of methane(CH4) in gaseous form.
gas compressoris a mechanical device that increases the pressureof a gasby reducing its volume.
gas detectoris a device which detects the presence of various gases within an area, usually as part of a system to warn about gases which might be harmful to humans or animals.
: Mixing of two gases caused by random molecular motions. Gases diffuse very quickly; liquids diffuse much more slowly, and solids diffuse at very slow (but often measurable) rates. Molecular collisions make diffusion slower in liquids and solids.
Gas diffusion electrode
Gas diffusion electrodes are electrodes with a conjunction of a solid, liquid and gaseous interface, and an electrical conducting catalyst supporting an electrochemical reaction between the liquid and the gaseous phase.
Gasificationis a process that converts carbonaceous materials, such as coal, petroleum, or biomass, into carbon monoxideand hydrogenby reacting the raw material at high temperatures with a controlled amount of oxygenand/or steam.
Gasoline gallon equivalent
Gasoline gallon equivalent(GGE) or gasoline-equivalent gallon (GEG) is the amount of alternative fuelit takes to equal the energy content of one liquid gallonof gasoline.
Gibbs free energy
thermodynamics, the Gibbs free energy( IUPACrecommended name: Gibbs energy or Gibbs function) is a thermodynamic potentialwhich measures the "useful" or process-initiating work obtainable from an isothermal, isobaric thermodynamic system.
mineral graphite, as with diamondand fullerene, is one of the allotropes of carbon.
: Gases in the Earth's atmosphere that contribute to the
greenhouse effect, effectively absorbing thermal infraredradiation, emitted by the Earth’s surface
: Warming of the Earth's atmosphere due to greenhous gases in the atmosphere that allow solar radiation (visible, ultraviolet) to reach the Earth's atmosphere but do not allow the emitted infrared radiation to pass back out of the Earth's atmosphere.
Grid-tied electrical system
grid-tied electrical system, also called Tied to grid or Grid tie system, is a semi-autonomous electrical generation or grid energy storagesystem which links to the mains to feed excess capacity back to the local mainselectrical grid.
Grid tie inverter
Grid tie inverter
Guard bed, see guard catalyst bedand liquid-phase guard bed.
Guard catalyst bed
guard catalyst bedis a fixed bed of pellets of the same catalyticmaterial, see fixed bed reactor.
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half reactionis either the oxidation or reduction reaction component of a redox reaction.
heat exchangeris a device built for efficient heat transferfrom one medium to another, whether the media are separated by a solid wall so that they never mix, or the media are in direct contact.
heat pipeis a heat transfer mechanism that can transport large quantities of heat with a very small difference in temperaturebetween the hotter and colder interfaces.
: In thermal physics,
heat transferis the passage of thermal energyfrom a hot to a colder body.
Heating value(TOTAL) (ΔHc0) is the energyreleased as heatwhen a compound undergoes complete combustionwith oxygen. (see also Higher heating value(HVV) and Lower heating value) (LVV).
Heat of combustion
heat of combustion(ΔHc0) is the energyreleased as heatwhen a compound undergoes complete combustionwith oxygen. The chemical reaction is typically a hydrocarbonreacting with oxygen to form carbon dioxide, waterand heat.
Higher heating value
Higher heating value(HHV) (also known as the gross calorific value or gross energy) of a fuelis defined as the amount of heatreleased by a specified quantity (initially at 25 °C) once it is combusted and the products have returned to a temperature of 25 °C.
High temperature shift
: High temperature shift (HTS), the
water gas shift reactionat 350 ºC (662 ºF) in the presence of a metal-based catalyst( nickel)
Hybrid electric vehicle
hybrid electric vehicle(HEV) is a hybrid vehiclewhich combines a conventional propulsion system with a rechargeable energy storage system(RESS) to achieve better fuel economy than a conventional vehicle.
Hydrideis the name given to the negative ionof hydrogen, H−.
: Aside from
electride, the hydride ion is the simplest possible anion, consisting of two electrons and a proton. See also hydrogen anion
organic chemistry, a hydrocarbon(HC) is an organic compoundconsisting entirely of hydrogenand carbon.
Hydrocarbon dew point
hydrocarbon dew point(HDP) or (HCDP) is the temperature(at a given pressure) at which the hydrocarboncomponents of any hydrocarbon-rich gas mixture, such as natural gas, will start to condense out of the gaseous phase.
Hydrogenis the chemical elementwith atomic number1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gaswith the molecular formulaH2.
hydrogen anionis a negative hydrogen ion, H−. See also hydride ion.
: A fuel that contains a significant amount of
hydrogen, such as gasoline, diesel fuel, methanol(CH3OH), ethanol(CH3CH2OH), natural gas, and coal.
Hydrodesulfurization(HDS) is a catalyticchemical process widely used to remove sulfur(S) from natural gasand from refined petroleum products such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils.
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Impuritiesare substancesinside a confined amount of liquid, gas, or solid, which differ from the chemical compositionof the material or compound.
Internal combustion engine
internal combustion engine(ICE) is an engine in which the combustionof fueland an oxidizer(typically air) occurs in a confined space called a combustion chamber.
: An inverter is an electrical or electro-mechanical device that converts
direct current(DC) to alternating current(AC)
ionis an atomor moleculewhich has lost or gained one or more valence electrons, giving it a positive or negative electrical charge.
Ion exchangeis an exchange of ions between two electrolytes or between an electrolyte solutionand a complex.
Ion exchange resin
ion exchange resinis an insoluble matrix (or support structure) normally in the form of small (1-2 mm diameter) beads, usually white or yellowish, fabricated from an organic polymersubstrate.
ionomeris a polyelectrolytethat comprises copolymers containing both electrically neutral repeating units and a fraction of ionized units
Islandingrefers to the condition of a distributed Generation (DG) generator continuing to power a location even though power from the electric utilityis no longer present.
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kilogramor kilogramme (symbol: kg) is the base unit of massin the International System of Units(known also by its French-language initials “SI”). The kilogram is defined as being equal to the mass of the "International Prototype Kilogram" which is almost exactly equal to the mass of one liter of water.
: The kilowatt (symbol: kW), equal to one thousand watts, is typically used to state the power output of engines and the power consumption of tools and machines.
kilowatt hour, also written "kilowatt-hour" (symbol kW·h, kW h or kWh) is a unit of energy.
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landfill gas(LFG), see biogas.
Lanthanum carbonateis used as a lanthanum source for solid-state production of lanthanum strontium manganite(LSM), primarily for solid oxide fuel cellapplications.
Life cycle assessment
life cycle assessment(LCA, also known as life cycle analysis, ecobalance, and cradle-to-grave analysis) is the investigation and valuation of the environmental impacts of a given product or service caused or necessitated by its existence.
: In electronics, a
linear regulatoris a voltage regulatorbased on an active device (such as a bipolar junction transistor, field effect transistoror vacuum tube) operating in its "linear region"
Liquidis one of the principal states of matter.
Liquid hydrogen(LH2 or LH2) is the liquid stateof the element hydrogen.
Liquid-liquid extraction, also known as solvent extraction and partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible liquids, usually water and an organic solvent.
Liquefied natural gas
Liquefied natural gas(LNG) is natural gas(primarily methane, CH4) that has been converted to liquid form for ease of storage or transport.
Liquefied petroleum gas
Liquefied petroleum gas(also called LPG, GPL, LP Gas, or autogas) is a mixture of hydrocarbon gases used as a fuelin heating appliances and vehicles
physics, to liquefy (sometimes misspelt liquify) means to turn something into the liquidstate.
Liquefaction of gases
Liquefaction of gasesincludes a number of phases used to convert a gasinto a liquidstate.
List of chemical purification methods in chemistry
: Purification in a chemical context is the physical separation of a chemical substance of interest from foreign or contaminating substances. The following list of chemical purification methods should not be considered exhaustive.
Load following power plant
load following power plantis a power plantthat adjusts its power output as demand for electricityfluctuates throughout the day.
electrical engineering, a load profileis a graph of the variation in the electrical loadversus time.
Lower flammability limit
Lower flammability limit(LFL), usually expressed in volume per cent, is the lower end of the concentration range of a flammable solvent at a given temperature and pressure for which air/vapor mixtures can ignite.
Lower heating value
lower heating value(also known as "net calorific value", "net CV", or "LHV") of a fuelis defined as the amount of heatreleased by combusting a specified quantity (initially at 25 °C or another reference state) and returning the temperature of the combustionproducts to 150 °C.
Low temperature shift
: Low temperature shift (LTS), the
water gas shift reactionat 190-210ºC (374-410ºF) in the presence of a metal-based catalyst( nickel).
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Maintenance, repair and operations
Maintenance, Repair and Operationsor Maintenance, Repair and Overhaul (MRO) is fixing any sort of mechanical or electricaldevice should it become out of order or broken (repair) as well as performing the routine actions which keep the device in working order (maintenance) or prevent trouble from arising ( preventive maintenance).
Mass flow sensor
mass flow sensor(MAF) responds to the amount of a fluid (usually a gas) flowing through a chamber containing the sensor.
Maximum allowable operating pressure
Maximum allowable operating pressure(MAOP) refers to the wall strength of a pressurized cylindersuch as a pipelineor storage tankand how much pressure the walls may safely hold before rupturing.
Mean down time
organizational management, mean down time(MDT) is the averagetime that a system is non-operational.
Mean time between failures
Mean time between failures(MTBF) is the mean(average) time between failures of a system, and is often attributed to the "useful life" of the device i.e. not including 'infant mortality' or 'end of life' if the device is not repairable.
Mean time between outages
: In a
systemthe mean time between outages(MTBO) is the mean timebetween equipment failures that result in loss of system continuity or unacceptable degradation.
physics, mechanical energydescribes the potential energyand kinetic energypresent in the components of a "mechanical system".
Mechanical Balance of Plant
Balance of Plant(MBOP), the process equipment needed to provide steam, gas, and air to the fuel cell stack.
semipermeable membraneand artificial membrane
Membrane electrode assembly
Membrane electrode assembly(MEA) is an assembled stack of proton exchange membranes.
: The megawatt (symbol: MW) is equal to one million (106) watts.
Meter(m), Basic metric unit of length equal to 3.28 feet, 1.09 yards or 39.37 inches. Related units are the decimeter (dm) at 10 per meter, the centimeter (cm) at 100 per meter, the millimeter (mm) at 1000 per meter and the kilometer (km) at 1000 meters.
Methanationis a physical-chemical process to generate Methanefrom a mixture of various gases out of biomass fermentationor thermo-chemical gasification.
Methaneis a chemical compoundwith the molecular formula chem|CH|4. It is the simplest alkane, and the principal component of natural gas.
methane reformeris a device used in chemical engineering, which can produce pure hydrogengas from natural gasusing a catalyst. (See ATR and SMR).
methanol reformeris a device used in chemical engineering, especially in the area of fuel celltechnology, which can produce pure hydrogengas and carbon dioxideby reacting a methanoland water(steam) mixture.
: "Micro cogeneration" or micro combined heat and power (mCHP) is a so called distributed energy resource (DER).
Microbial fuel cell
Microbial fuel cell(MFC) or biological fuel cell is a bio- electrochemicalsystem that drives a current by mimicking bacterial interactions found in nature.
: A small pump is often referred to as
micropump, a more accurate and up-to-date definition restricts this term to pumpswith functional dimensions in the micrometre range.
Miles per gallon equivalent
Miles per gallon of gasoline equivalent(MPGe) is a unit of measurement that relates efficiencies of different systems to the traditional unit of measurement for fuel efficiency( miles per gallonof gasoline).
Millimeter(mm), Metric unit of length, equal to 0.04 inch (there are 25 mm in an inch). There are 1000 millimeters in a meter.
Milliwatt(mW), A unit of power equal to one-thousandth of a watt.
Molten-carbonate fuel cells
Molten-carbonate fuel cells(MCFCs) are high-temperature fuel cells
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Nafionis a sulfonated tetrafluorethylene copolymer
Nano iron powder
Nano iron powderis an iron powder with granules' sizes ranging on the nanoscale.
nanowireis a wire of diameter of the order of a nanometer (10−9 meters).
Natural gasis a gaseous fossil fuelconsisting primarily of methanebut including significant quantities of ethane, propane, butane, and pentane—heavier hydrocarbons removed prior to use as a consumer fuel —as well as carbon dioxide, nitrogen, heliumand hydrogen sulfide.
electrochemistry, the Nernst equationis an equation which can be used (in conjunction with other information) to determine the equilibrium reduction potentialof a half-cellin an electrochemical cell.
Net energy gain
Net energy gain(NEG) is a concept important in energy economics, referring to a surplus condition in the difference between the energy required to harvest an energy source and the energy provided by that same source.
Nickelis a metallic chemical elementwith the symbol Ni and atomic number28.
NitrogenN2 a chemical elementthat has the symbol N and atomic number7 and atomic weight14.0067. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomicgas at standard conditions, constituting 78.08% by volume of Earth's atmosphere.
: The term
nitrogen oxide(NOx) typically refers to any binary compoundof oxygenand nitrogen, or to a mixture of such compounds
Nitrogen oxide sensor
nitrogen oxide sensoror NOx sensor is typically a high temperature device built to detect nitrogen oxides in combustion environments such as an automobileor truck tailpipeor a smokestack.
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Off board reforming
Off board reforming, stationary reforming, see steam reforming, methane reformer, methanol reformer
ohm(symbol: Ω) is the SIunit of electrical impedanceor, in the direct currentcase, electrical resistance, named after Georg Ohm.
On-board reforming, reforming on board a vehicle, see steam reforming, methane reformer, methanol reformer
Original equipment manufacturer
original equipment manufacturer, or OEM is typically a company that uses a component made by a second company in its own product, or sells the product of the second company under its own brand.
Output impedance, Any linear electronic circuit or device which supplies a current may be modelled as an ideal voltage sourcein series with an impedance. This is helpful in analysing the voltage drop which occurs as current is drawn.
: When the
voltagein a circuit or part of it is raised above its upper design limit, this is known as overvoltage.
oxidizing agent(also called an oxidant or oxidizer) can be defined as either: a chemical compoundthat readily transfers oxygenatoms, or a substance that gains electrons in a redox chemical reaction. In both cases, the oxidizing agent becomes reduced in the process.
Oxygenis the element with atomic number8 and represented by the symbol O.
oxygen sensor, or lambda sensor, is an electronic device that measures the proportion of oxygen(O2) in the gas or liquid being analyzed.
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Palladiumis a rare and lustrous silvery-white metal with the symbol Pd, and its atomic numberis 46.
: Parallel circuit, if two or more components are connected in parallel they have the same potential difference (
voltage) across their ends. The potential differences across the components are the same in magnitude, and they also have identical polarities. Hence, the same voltage is applicable to all circuit components connected in parallel.
: In a mixture of
ideal gases, each gas has a partial pressurewhich is the pressure which the gas would have if it alone occupied the volume. The total pressureof a gas mixture is the sum of the partial pressures of each individual gas in the mixture.
: Particulates, alternatively referred to as
particulate matter(PM) or fine particles, are tiny particles of solid or liquid suspended in a gas.
Parts per million
: Parts per million (ppm) denotes the amount of a given substance in a total amount of 1,000,000 regardless of the units of measure used as long as they are the same. e.g. 1 milligram per kilogram. 1 part in 106.
Parts per million by volume
atmospheric chemistryand in air pollutionregulations, the parts per notation is commonly expressed with a v following, such as ppmv, to indicate parts per million by volume.
: The pascal (symbol: Pa) is the
SI derived unitof pressure, stress, Young's modulusand tensile strength. It is a measure of perpendicular forceper unit areai.e. equivalent to one newtonper square meteror one jouleper cubic metre.
Poly(3,4-ethylenedioxythiophene)or PEDOT (or sometimes PEDT) is a conducting polymerbased on 3,4-ethylenedioxylthiopheneor EDOT monomer.
Permeation, in physicsand engineering, is the penetration of a permeate (such as a liquid, gas, or vapor) through a solid, and is related to a material's intrinsic permeability. Permeability is tested by permeation measurement.
thermodynamics, phase transitionor phase change is the transformation of a thermodynamic system from one phase to another.
Phosphoric acid fuel cell
Phosphoric acid fuel cell(PAFC), a type of fuel cellthat uses liquid phosphoric acidas an electrolyte.
Photoelectrochemical cell(PEC), a solar cellthat extracts electrical energy from light, including visible light.
Platinumis a chemical elementwith the atomic symbolPt
Polybenzimidazole(PBI) fiber(1983) is a synthetic fiberwith an extremely high melting pointthat also does not ignite.
Polyethyleneor polythene ( IUPACname poly(ethene)) is a thermoplasticcommodity
polymeris a large molecule( macromolecule) composed of repeating structural units connected by covalent chemical bonds. See also plastic.
Polymer electrolyte membrane
polymer electrolyte membrane(PEM), in a fuel cell incorporating a solid polymer membrane used as its electrolyte. Protons (H+) are transported from the anode to the cathode. The operating temperature range is generally 60-100°C.
chemistry, poly(tetrafluoroethene) or poly(tetrafluoroethylene) (PTFE) is a synthetic fluoropolymerwhich finds numerous applications.
Polymer electrolyte membrane fuel cell
Polymer electrolyte membrane fuel cell(PEMFC or PEFC), a type of acid-based fuel cellin which the transport of protons (H+) from the anodeto the cathodeis through a solid, aqueous membrane impregnated with an appropriate acid. The electrolyteis a called a polymer electrolyte membrane(PEM). The fuel cells typically run at low temperatures (<100°C).
physics, the potential differenceor p.d. between two points is the difference of the points' scalar potential, equivalent to the line integral of the field strengthbetween the two points.
Portable fuel cell applications
Portable fuel cell applications(or portable fuel cell power systems) are portable(Movable) fuel cell applications
physics, power(symbol: "P") is the rate at which work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time.
Power density(Pv), see specific power
power factorof an AC electric power system is defined as the ratioof the real power to the apparent power, and is a number between 0 and 1 (frequently expressed as a percentage, e.g. 0.5 pf = 50% pf).
Power supplyis a reference to a source of electrical power.
Power-to-weight ratio( specific power) is a calculation commonly applied to engines and other mobile power sources to enable the comparison of one unit or design to another.
Power per unit of mass
: Power per unit of mass usually refers to the
power-to-weight ratio, measured in kilowatts per kilogram(generally, kW/ kg).
Preferential oxidation(PROX) refers to the preferential oxidationof a gas on a catalyst.
pressure regulatoris a valvethat automatically cuts off the flow of a liquid or gas at a certain pressure.
Pressure relief valve
pressure relief valveis a safety device that relieve in case of overpressure in vessel or piping. The generic term is or pressure relief Valve (PRV) or pressure safety valve (PSV).
pressure sensormeasures the pressure, typically of gases or liquids.
Pressure swing adsorption
Pressure Swing Adsorption(PSA) is a technology used to separate some gas species from a mixture of gases under pressure according to the species' molecular characteristics and affinity for an adsorbentmaterial.
pressure vesselis a closed container designed to hold gases or liquids at a pressuredifferent from the ambient pressure.
Propaneis a three- carbon alkane, normally a gas, but compressible to a liquid that is transportable. See also LPG.
protonis a subatomic particlewith an electric chargeof one positive fundamental unit
Proton exchange membrane
Proton exchange membrane(PEM) is a semipermeable membranegenerally made from ionomers and designed to conduct protons while being impermeable to gases such as oxygenor hydrogen.
Proton exchange membrane fuel cell
Proton exchange membrane fuel cell(PEMFC) a type of fuel cellbased on a polymer electrolytemembrane.
Protonic ceramic fuel cell
Protonic ceramic fuel cell(PCFC) based on a ceramic electrolyte material that exhibits high protonic conductivity at elevated temperatures.
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Reactor, see: bioreactor, membrane reactorand chemical reactor.
reagentor reactant is a substance or compound consumed during a chemical reaction.
rectifieris an electrical device that converts alternating current(AC) to direct current(DC), a process known as rectification.
Redox(shorthand for reduction-oxidation reaction) describes all chemical reactionsin which atoms have their oxidation number( oxidation state) changed.
hydrocarbonfuel that has been processed into hydrogen and other products for use in fuel cells.
Reformed Methanol Fuel Cell
Reformed methanol fuel cell(RMFC) or Indirect Methanol Fuel Cell (IMFC)s are a subcategory of proton-exchange fuel cells where, the fuel, methanol(CH3OH), is reformed, before being fed into the fuel cell.
: A hydrogen
reformeranother name for steam reforminga device that extracts hydrogen from other fuels, typically methanol or gasoline, not to be confused with the process catalytic reforming
: A chemical process in which hydrogen containing fuels react with steam,
oxygen, or both to produce a hydrogen-rich gas stream. ( syngas)
: Reformulated gsoline, a gasoline that is blended so that, on average, it significantly reduces volatile organic compounds and air toxics emissions relative to conventional gasolines. Gasoline that is blended so that, on average, it significantly reduces volatile organic compounds and air toxics emissions relative to conventional gasolines.
Regenerative fuel cell
: A fuel cell that produces electricity from hydrogen and oxygen and can use electricity from solar power or some other source to divide the excess water into oxygen and hydrogen fuel to be re-used by the fuel cell. See
reversible fuel cell.
relief valveis a type of valveused to control or limit the pressurein a system or vessel which can build up by a process upset, instrument or equipment failure, or fire.
Renewable energyis energygenerated from natural resources—such as sunlight, Including solar and radiant energy, wind, rain, tides and geothermal heat—which are renewable (naturally replenished).
reservoiris, most broadly, a place or hollow vessel where something fluidis kept in reserve, for later use.
technology, response time is the timea systemor functional unittakes to react to a given input.
Reversible fuel cell
Reversible fuel cell(RFC), a fuel cell that can consume chemical A to produce electricity and chemical B and be reversed to consume electricity and chemical B to produce chemical A.
fluid mechanicsand heat transfer, the Reynolds numberis a dimensionless numberthat gives a measure of the ratioof inertial forces () to viscous forces () and, consequently, it quantifies the relative importance of these two types of forces for given flow conditions.
rupture diskor bursting disc is a pressure relief device that protects a vessel or system from overpressurization.
Rutheniumis used in Platinum-Ruthenium electrodes for Methanol-fuel cells
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afety shutoff valve
Safety shut-off valvesare safety valves used to close a line and stop the flow of material.
safety valveis a valvemechanism for the automatic release of a gas from a boiler, pressure vessel, or other systemwhen the pressure or temperature exceeds preset limits.
salt bridge, in chemistry, is a laboratory device used to connect the oxidationand reduction half-cells of a galvanic cell(voltaic cell), a type of electrochemical cell. Salt bridge usually comes in two types: glass tube and filter paper.
Scrubbersystems are a diverse group of air pollutioncontrol devices that can be used to remove some particulates and/or gases from industrial exhaust streams.
sensoris a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument.
: Series circuits are sometimes called "current"-coupled or
daisy chain-coupled. The current that flows in a series circuit has to flow through every component in the circuit. Therefore, all of the components in a series connection carry the same current. It has been noted that current flows in series.
: A product's
service lifeis its expected lifetime, or the acceptable period of use in service. It is the time that any manufactured item can be expected to be 'serviceable' or supported by its originating manufacturer.
short circuit(sometimes abbreviated to short or s/c) allows a current along a different path from the one intended.
solenoid valveis an electromechanical valvefor use with liquidor gascontrolled by running or stopping an electrical current through a solenoid, which is a coil of wire, thus changing the state of the valve.
olid oxide fuel cell
solid oxide fuel cell(SOFC) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel.
Solubilityis a characteristic physical propertyreferring to the ability of a given substance, the solute, to dissolve in a solvent.
sorbentis a material used to adsorbeither liquids or gases.
Sorptionrefers to the action of both absorption and adsorptiontakes place simultaneously.
Specific gravityis defined as the ratio of the densityof a given solid or liquid substance to the density of water at a specific temperature and pressure, typically at 4°C (39°F) and convert|1|atm|inHg|2|abbr=on|lk=on , making it a dimensionless quantity
pecific heat capacity
engineering, the term Specific powercan refer to power either per unit of mass, volumeor area.
specific weight(also known as the unit weight) is the weightper unit volumeof a material
: Stack, to deliver the desired amount of energy, the fuel cells can be combined in
series and parallel circuits, where series yield higher voltage, and parallel allows a stronger current to be drawn. Such a design is called a fuel cell stack.
tandard cubic foot
standard cubic foot(SFC) is a measure of quantity of gas, equal to a cubic foot of volume at 60 degrees Fahrenheitand either 14.696 pounds per square inch (1 atm) or 14.73 PSI (30 inHg) of pressure.
tandard electrode potential
electrochemistry, the standard electrode potential, abbreviated Eo, E0, or E O(with a superscript plimsollcharacter, pronounced nought), is the measure of individual potential of a reversible electrode (at equilibrium) at standard state, which is with solutes at an effective concentration of 1 mol/kg, and gases at a pressure of 1 atmosphere / 100 kPa (Kilopascals)).
tationary fuel cell applications
Stationary fuel cell applications(or stationary fuel cell power systems) are stationary(Not moving) fuel cell applications
Steady stateis a more general situation than dynamic equilibrium. If a systemis in steady state, then the recently observed behavior of the system will continue into the future.
: Steam methane reforming (SMR) another name for
Steam reforming(SR), hydrogen reforming or catalytic oxidation, is a method of producing hydrogenfrom hydrocarbonsat high temperatures (700 – 1100 °C) in the presence of a metal-based catalyst( nickel).
witched-mode power supply
switched-mode power supply, switching-mode power supply or SMPS, is an electronic power supplyunit (PSU) that incorporates a switching regulator.
Syngas(from "synthesis gas") is the name given to a gas mixture that contains varying amounts of carbon monoxideand hydrogengenerated by the gasificationof a carbon-containing fuel to a gaseous product with a heating value.
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Tafel equationrelates the rate of an electrochemical reaction to the overpotential.
Tail gas combustor
Tail gas combustor(TGC)
Taris a viscous black liquidderived from the destructive distillationof organic matter.
Technology assessment(TA, German "Technikfolgenabschätzung") is the study and evaluationof new technologies.
: Most new technologies follow a similar technology maturity lifecycle describing the
technological maturityof a product.
Technology readiness level
Technology readiness level(TRL) is a measure used by some United States governmentagencies and many of the world's major companies (and agencies) to assess the maturity of evolving technologies (materials, components, devices, etc.) prior to incorporating that technology into a system or subsystem.
: Technology validation, confirming that technical targets for a given technology have been met.
Terbiumis used as a crystal stabilizer of fuel cells which operate at elevated temperatures, together with ZrO2.
physics, thermal conductivity, , is the property of a material that indicates its ability to conduct heat.
thermodynamics, the thermal efficiency() is a dimensionless performance measure of a thermal device
: When the
temperatureof a substance changes, the energy that is stored in the intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bonds. As a result, solids typically expand in response to heating and contract on cooling; this dimensional response to temperature change is expressed by its coefficient of thermal expansion.
Thermal partial oxidation
: Thermal partial oxidation (TPOX) is a thermal
partial oxidationreaction, which is dependent on the air-fuel ratio, proceed at temperatures of 1200°C and above.
Thermoelectricity( thermo- electricity) refers to a class of phenomena in which a temperaturedifference creates an electric potentialor an electric potential creates a temperature difference.
thermoplasticis a plasticthat melts to a liquid when heated and freezes to a brittle, very glassy state when cooled sufficiently.
Thermoplastic elastomers(TPE), sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both thermoplasticand elastomeric properties.
transduceris a device, usually electrical, electronic, electro-mechanical, electromagnetic, photonic, or photovoltaicthat converts one type of energyor physical attribute to another for various purposes including measurement or information transfer (for example, pressure sensors).
transfer switchallows switching from a primary power source to a secondary or tertiary power source and are employed in some electrical power distribution systems.
Triple phase boundary
Triple phase boundary(TPB)
: In thermodynamics, the
triple pointof a substance is the temperatureand pressureat which three phases (for example, gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.
turbineis a rotary enginethat extracts energyfrom a fluidflow.
Turbocharger, a device used for increasing the pressure and densityof a fluid entering a fuel cellpower plant using a compressor driven by a turbine that extracts energy from the exhaust gas.
Turbocompressor, a machine for compressing air or other fluid ( reactantif supplied to a fuel cellsystem) in order to increase the reactant pressure and concentration.
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Ullagerefers to the unfilled space in a container of liquid.
Uninterruptible power supply
uninterruptible power supply(UPS), also known as a continuous power supply (CPS) is a device which maintains a continuous supply of electric powerto connected equipment by supplying power from a separate source when utility power is not available.
vacuum pumpis a device that removes gas molecules from a sealed volume in order to leave behind a partial vacuum.
Vapor-liquid equilibrium, abbreviated as VLE by some, is a condition where a liquidand its vapor(gas phase) are in equilibrium with each other, a condition or state where the rate of evaporation(liquid changing to vapor) equals the rate of condensation(vapor changing to liquid) on a molecular level such that there is no net (overall) vapor-liquid interconversion.
Vapor recovery(or vapour) recovery is the processof recovering the vapors of gasolineor other fuels, so that they do not escape into the atmosphere.
: Electrical tension (or
voltageafter its SI unit, the " volt") is the difference of electrical potential between two points of an electrical or electronic circuit, expressed in volts.
voltage converterchanges the voltageof an electrical power source and is usually combined with other components to create a power supply.
Voltage dropis the reduction in voltagein an electricalcircuit between the source and load.
Volumetric energy density
energy density, potential energy in a given volumeof fuel.
Volumetric flow rate
volumetric flow ratein fluid dynamicsand hydrometry, (also known as volume flow rate or rate of fluid flow) is the volume of fluid which passes through a given surface per unit time (for example cubic meters per second[m3 s-1] in SIunits, or cubic feet per second [cu ft/s] ). It is usually represented by the symbol "Q".
Volumetric heat capacity
Volumetric heat capacity(VHC) describes the ability of a given volumeof a substance to store internal energywhile undergoing a given temperaturechange, but without undergoing a phase change.
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Water(H2O) in typical usage, "water" refers only to its liquidform or state, but the substance also has a solidstate, " ice", and a gaseousstate, " water vapor" or " steam".
Water gas shift reaction
water gas shift reaction(WGS) is a chemical reactionin which carbon monoxidereacts with waterto form carbon dioxideand hydrogen
Water purificationis the process of removing contaminants and other harmful microorganisms from a raw water source.
: Kilowatts per
kilogram(generally, W/ kg).The power per unit of mass in relation to the power-to-weight ratio.
: The term wt.% (abbreviation for
weight percent) is widely used in hydrogen storageresearch to denote the amount of hydrogen stored on a weight basis (the term mass % is also occasionally used). The term can be used for materials that store hydrogen or for the entire storage system (e.g., material or compressed/liquid hydrogen as well as the tank and other equipment required to contain the hydrogen such as insulation, valves, regulators, etc.). For example, 6 wt.% on a system-basis means that 6% of the entire system by weight is hydrogen. On a material basis, the wt.% is the mass of hydrogen divided by the mass of material plus hydrogen.
Yttria-stabilized zirconia(YSZ) is a zirconium-oxide based ceramic
Zinc-air battery(non-rechargeable), and zinc-air fuel cells, (mechanically-rechargeable) are electro-chemical batteries powered by the oxidationof zincwith oxygenfrom the air.
Zinc oxideis a chemical compoundwith the formula ZnO. ( sulfursorbent)
Glossary of terms for fuel cell power systems
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