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The '''Glossary of fuel cell terms''' lists the definitions of many terms used within the [[fuel cell]] industry. The terms in this fuel cell [[glossary]] may 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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{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
==A==
 
===Activation loss===
: See [[overpotential]]
 
===Adsorption===
: [[Adsorption]] is a process that occurs when a  gas or liquid [[Solution|solute]] accumulates on the surface of a solid or a liquid (adsorbent), forming a film of molecules or atoms (the [[adsorbate]]).
 
===Alkali===
: In [[chemistry]], an [[alkali]] is a [[Base (chemistry)|basic]], [[Ionic compound|ionic]] [[salt (chemistry)|salt]] of an [[alkali metal]] or [[alkaline earth metal]] [[Chemical element|element]].
 
===Alkali anion exchange membrane===
An [[alkali anion exchange membrane]] (AAEM) is a [[semipermeable membrane]] generally made from [[ionomer]]s and designed to conduct [[anions]] while being impermeable to gases such as [[oxygen]] or [[hydrogen]].
 
===Alkaline fuel cell===
: [[Alkaline fuel cell]] (AFC) also known as the [[Francis Thomas Bacon|Bacon]] fuel cell.
 
===Alloy===
: An [[alloy]] is a [[solid solution]] or [[homogeneous (chemistry)|homogeneous]] mixture of two or more [[chemical element|elements]], at least one of which is a [[metal]], which itself has [[metallic]] properties.
 
===Alternator===
: An [[alternator]] is an [[generator (device)|electromechanical device]] that converts mechanical energy to [[alternating current]] electrical energy.
 
===Alternating current===
: An [[alternating current]] ('''AC''') is an [[electric current]] whose direction reverses cyclically, as opposed to [[direct current]], whose direction remains constant.
 
===Ambient Air===
: The [[air]] surrounding a given object or system.
 
===Ambient temperature===
: [[Ambient temperature]] is the [[temperature]] within enclosed space.
 
===Ampere===
: The [[ampere]], in practice often shortened to '''amp''', (symbol: A) is a unit of [[electric current]], or amount of [[electric charge]] per second.
 
===Anion===
: A negatively charged [[ion]]; an ion that is attracted to the anode.
 
===Anode===
: An [[anode]] is an [[electrode]] through which ''[[electric current]]'' flows ''into'' a polarized electrical device.
 
===Aqueous phase reforming===
: APR is the production of hydrogen from biomass-derived oxygenated compounds (such as glycerol, sugars and sugar alcohols).
 
===Artificial membrane===
: An [[artificial membrane]], also called a '''synthetic membrane''', is a membrane prepared for separation tasks in [[laboratory]] and industry.
 
===Atmospheric pressure===
: [[Atmospheric pressure]] is the [[pressure]] at any given point in the [[Earth's atmosphere]].
 
===Atom===
: The [[atom]] is the smallest unit of an [[chemical element|element]] that retains the chemical properties of that element. An atom has an [[electron cloud]] consisting of negatively [[Electric charge|charged]] [[electrons]] surrounding a dense [[atomic nucleus|nucleus]].  The nucleus contains positively charged [[proton]]s and electrically neutral [[neutron]]s.
 
===Autothermal reforming===
: [[Autothermal_reforming#Autothermal_reforming|Autothermal reforming]] (ATR) uses oxygen and carbon dioxide or steam in a reaction with methane to form [[syngas]].
 
===Auxiliary power unit===
: An [[auxiliary power unit]] (APU) is a device on a vehicle whose purpose is to provide energy for functions other than propulsion.
 
===Availability factor===
: The [[availability factor]] of a [[power plant]] is the amount of time that it is able to produce electricity over a certain period, divided by the amount of the time in the period.
 
==B==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Back pressure===
: [[Back pressure]] is the [[pressure]] exerted on a moving [[fluid]] by obstructions or tight bends in the confinement vessel along which it is moving, such as piping or air vents, against its direction of flow.
 
===Baffle===
: A device or construction used to restrain or regulate, e.g. gas, or a fluid.
 
===Balance of plant===
: [[Balance of plant]] (BOP) is the infrastructure of a fuel cell, not including the fuel cells. (See also Mechanical Balance of Plant [[MBOP]] and Electrical Balance of Plant [[EBOP]]).
 
===Battery===
: In electronics, a [[Battery (electricity)|battery]] is a combination of two or more [[electrochemical cell]]s which store chemical energy and make it available as electrical energy.
 
===Biofuel===
: [[Biofuel]] is defined as solid, liquid or gas [[fuel]] derived from recently dead [[biomass|biological material]] and is distinguished from [[fossil fuel]]s, which are [[petroleum#Formation|derived from long dead biological material]].
 
===Biogas===
: [[Biogas]] is a gas produced by the biological breakdown of [[organic matter]] in the absence of [[oxygen]].  Biogas originates from biogenic material and is a type of [[biofuel]].
 
===Bioreactor===
: A [[Bioreactor#Bioreactor|bioreactor]] is any device or system that supports a biologically active environment
 
===Biosensor===
: A [[biosensor]] is a device for the detection of an [[analyte]] that combines a biological component with a physicochemical detector component.
 
===Bipolar plate===
: Bipolar plate, conductive plate in a [[fuel cell stack]] that acts as an [[anode]] for one cell and a [[cathode]] for 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 [[Membrane electrode assembly|MEA]].
 
===Black start===
: A [[black start]] is the process of restoring a [[power station]] to operation without relying on external energy sources.
 
===Beta-alumina solid electrolyte===
: [[Beta-alumina solid electrolyte]] ('''BASE''') is a [[fast ion conductor]] material used as a [[semipermeable membrane|membrane]] in several types of molten salt [[electrochemical cell]].
 
===Boiling point===
: The [[boiling point]] of a liquid is the water temperature at which the [[vapor pressure]] of the liquid equals the environmental pressure surrounding the liquid.
 
===Borax===
: [[Borax]], also known as '''sodium borate''', '''sodium tetraborate''', or '''disodium tetraborate''', is an important [[boron]] compound, a [[mineral]], and a [[salt (chemistry)|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 (454&nbsp;g) of [[water]] from 32°F to 212°F (0°C to 100°C) at a constant [[atmospheric pressure]]. It is about equal to the quantity of heat required to raise one pound of water 1°F  ({{frac|5|9}}°C).
 
===Busbar===
: In [[electrical power distribution]], a [[busbar]] is the strips of [[copper]] or [[aluminium]] that conduct electricity within a [[Electric switchboard|switchboard]], [[fuel cell]], [[distribution board]], substation, or other electrical apparatus.
 
==C==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Capacity===
: Capacity is the ability to hold, receive or absorb, or a measure thereof, similar to the concept of [[volume]].
 
===Capacity factor===
: The net [[capacity factor]] of a [[power plant]] is the ratio of the actual output of a power plant over a period of time and its output if it had operated at full [[Intermittent power source#Terminology|nameplate capacity]] the entire time.
 
===Capital cost===
: [[Capital cost]] are costs incurred on the purchase of [[fuel cell]]s, [[building]]s, [[construction]] and equipment to be used in the use of fuel cells or the rendering of it.
 
===Carbon===
: [[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 [[combustion]] of fuel.
 
===Carbon black===
: [[Carbon black]] is a material produced by the incomplete [[combustion]] of heavy [[petroleum]] products such as FCC tar, coal tar, ethylene cracking tar, and a small amount from vegetable oil.
 
===Carbon dioxide===
: [[Carbon dioxide]] ([[chemical formula]]: '''{{co2}}''') is a [[chemical compound]] composed of two [[oxygen]] [[atom]]s [[covalent bond|covalently bonded]] to a single [[carbon]] atom.
 
===Carbon dioxide sensor===
: A [[carbon dioxide sensor]] (CO<sub>2</sub>) is an instrument for the measurement of [[carbon dioxide]] gas. The most common principles for CO<sub>2</sub> sensors are infrared gas sensors ([[NDIR]]) and chemical gas sensors.
 
===Carbon monoxide===
: [[Carbon monoxide]], with the chemical formula CO, is a colorless, odorless, tasteless yet highly toxic gas.
 
===Carbon monoxide detector===
: A [[carbon monoxide detector]] is a device that detects the presence of the [[toxic]] gas [[carbon monoxide]] (CO), a colorless and odorless compound produced by incomplete combustion and lethal at high levels.
 
===Carbon paper===
: [[Carbon paper]] (originally '''carbonic paper''') is [[paper]] coated on one side with a layer of a loosely bound dry [[ink]] or pigmented coating, usually bound with [[wax]].
 
===Carnot cycle===
: The [[Carnot cycle]] is a particular [[thermodynamic cycle]], modeled on the hypothetical [[Carnot heat engine]].
 
===Catalysis===
: [[Catalysis]] is the process in which the [[reaction rate|rate]] of a [[chemical reaction]] is increased by means of a [[chemical substance]] known as a [[:Category:Catalysts|catalyst]].
 
===Catalyst===
: A [[catalyst]] is 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 poisoning===
: [[Catalyst poisoning]] is the effect that a [[catalyst]] can be 'poisoned' if it reacts with another [[chemical compound|compound]] that [[bond (chemical)|bonds chemically]] (similar to an [[Reaction inhibitor|inhibitor]]) but does not release, or chemically alters the catalyst.
 
===Catalytic partial oxidation===
: In [[catalytic partial oxidation]] (CPOX) the use of a [[catalyst]] for [[partial oxidation]] reduces the required temperature to around 800°C – 900°C.  The choice of [[catalytic reforming|reforming]] technique depends on the [[sulfur]] content of the fuel being used.  CPOX can be employed if the sulfur content is below 50 [[Parts per million|ppm]].  A higher sulfur content would poison the catalyst, so the TPOX procedure is used for such fuels.
 
===Cathode===
: A [[cathode]] is an [[electrode]] through which ''(positive)'' ''[[electric current]]'' flows ''out of'' a polarized electrical device.
 
===Cation===
: A [[cation]] is a positively charged ion.
 
===Celsius===
: The degree [[Celsius]] ('''°C''') is a designation for specific temperatures on the '''Celsius scale''' as well as units of increment to indicate a temperature ''[[Interval (mathematics)|interval]] ''(a difference between two temperatures or an [[uncertainty]]).
 
===Centimeter===
: A [[centimetre]] ([[American English|American spelling]]: '''centimeter''', symbol '''cm''') is a [[Units of measurement|unit]] of [[length]] in the [[metric system]], equal to one hundredth of a [[metre]], which is the current [[International System of Units|SI]] [[SI base unit|base unit]] of length.
 
===Centrifugal governor===
: A [[centrifugal governor]] is a specific type of [[governor (device)|governor]] that controls the [[speed]] by regulating the amount of [[fuel]] (or [[working fluid]]) admitted, so as to maintain a near constant speed whatever the [[Structural load|load]] or fuel supply conditions.
 
===Ceramic===
: [[Ceramic]]s are [[inorganic]] non-[[metallic]] materials formed by the action of heat.
 
===Cermet===
:  A [[cermet]] is a [[composite material]] composed of [[ceramic]] (cer) and [[metal]]lic (met) materials.
 
===Chemical thermodynamics===
: In [[thermodynamics]], [[chemical thermodynamics]] is the mathematical study of the interrelation of [[heat]] and [[thermodynamic work|work]] with [[chemical reactions]] or with a physical change of [[thermodynamic state|state]] within the confines of the [[laws of thermodynamics]].
 
===Circuit===
: A [[Electronic circuit|circuit]] is a closed path formed by the interconnection of [[electronic components]] through which an [[electric current]] can flow.
 
===Circuit diagram===
: A [[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]].
 
===Circulation===
: In [[fluid dynamics]], [[Circulation (fluid dynamics)|circulation]] is the [[line integral]] around a closed curve of the [[fluid]] [[velocity]].
 
===Climate change===
: [[Climate change]] is any long-term significant change in the “average weather” that a given region experiences.
 
===Cogeneration===
: [[Cogeneration]] (also '''combined heat and power''', '''CHP''') is the use of a [[heat engine]] or a [[power station]] to simultaneously generate both electricity and useful [[heat]].
 
===Combustion===
:  [[Combustion]] or '''burning''' is a complex sequence of [[exothermic]] chemical reactions between a [[fuel]] and an [[oxidant]] accompanied by the production of [[heat]] or both [[heat]] and [[light]] in the form of either a glow or [[flame]]s.
 
===Combustion chamber===
: A [[combustion chamber]] is the part of an [[engine]] in which [[fuel]] is burned.
 
===Composite material===
: [[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===
: [[Compressed hydrogen]] (CGH<sub>2</sub>, CH2 or CH<sub>2</sub>) is the [[gaseous state]] of the element [[hydrogen]] which is kept under [[pressure]].
 
===Compressed natural gas===
: [[Compressed Natural Gas]] (CNG) is a [[fossil fuel]] substitute for [[gasoline]] (petrol), [[Diesel fuel|diesel]], or [[propane]] [[fuel]].
 
===Concentration===
: In [[chemistry]], [[concentration]] is the measure of how much of a given [[chemical substance|substance]] there is mixed with other substances.
 
===Condensate===
: Condensate, the liquid phase produced by the [[condensation]] of [[steam]] or any other gas
 
===Condensation===
: [[Condensation]] is the change of the physical state of aggregation (or simply state) of matter from gaseous phase into liquid phase.
 
===Condenser===
: In systems involving [[heat transfer]], a [[Condenser (heat transfer)|condenser]] is a [[heat exchanger]] which [[Condensation|condenses]] a substance from its gaseous to its liquid state.
 
===Contamination===
: [[Contamination]] is the introduction of material that "does not belong there".
 
===Coulomb===
: The [[coulomb]] (symbol: C) is the [[SI]] unit of [[electric charge]].
 
===Countercurrent exchange===
: [[Countercurrent exchange]] is a mechanism used to transfer some property of a [[fluid]] from one flowing current of fluid to another across a [[semipermeable membrane]], conductive material, or free surface (e.g. a liquid–gas absorption or extraction).
 
===Cryogenic liquefaction===
:  [[Cryogenic]] [[liquification]] is the process through which gases such as nitrogen, hydrogen, helium, and natural gas are [[liquification|liquefied]] under pressure at very [[low temperature]]s.
 
===Current===
: see [[electric current]].
 
===Current collector===
: The [[current collector]] is the conductive material in a [[fuel cell]] that collects [[electrons]] (on the [[anode]] side) or disburses electrons (on the [[cathode]] side). Current collectors are microporous (to allow for fluid flow through them) and lie in between the [[catalyst]]/[[electrolyte]] surfaces and the [[bipolar plate]]s.
 
==D==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===DC to DC converter===
:  In [[electronic engineering]], a [[DC to DC converter]] is a circuit which converts a source of [[direct current]] (DC) from one [[voltage]] level to another. It is a class of [[Electric power conversion|power converter]].
 
===Density===
: The [[density]] of a material is defined as its [[mass]] per unit [[volume]]
 
===Desiccant===
:  A [[desiccant]] is a [[hygroscopic]] substance that induces or sustains a state of dryness ([[desiccation]]) in its local vicinity in a moderately-well sealed container.
 
===Detection limit===
: In [[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 interval|confidence limit]] (generally 1%).
 
===Dew point===
: The [[dew point]] (sometimes spelled '''dewpoint''') is the [[temperature]] to which a given parcel of [[air]] must be cooled, at constant [[barometric pressure]], for [[water vapor]] to [[Condensation|condense]] into water.
 
===Diffusion===
: [[Diffusion]] is part of [[transport phenomena (engineering & physics)|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 cell]]s
 
===Direct carbon fuel cell===
:  [[Direct carbon fuel cell]] (DCFC), a [[fuel cell]] that uses a carbonaceous material as a fuel.
 
===Direct current===
: [[Direct current]] ('''DC''') is the unidirectional flow of [[electric charge]].
 
===Direct-ethanol fuel cell===
: [[Direct-ethanol fuel cell]] (DEFC) a subcategory of [[Proton exchange membrane fuel cell|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 membrane fuel cell|proton-exchange fuel cells]] where the [[methanol]] (CH<sub>3</sub>OH) fuel is not reformed as in the [[indirect methanol fuel cell]], but fed directly to the [[fuel cell]]
 
===Dispersion===
: ''Dispersion'', in fluid dynamics is [[dispersive mass transfer]], which is the spreading of mass from areas of high to low concentration
 
===Distributed Generation===
: [[Distributed generation]], also  called '''on-site generation''', '''dispersed generation''', '''embedded generation''', '''decentralized generation''', '''decentralized energy''' or '''distributed energy''',  generates electricity from many small energy sources.
 
===Doping===
: In [[semiconductor]] production, [[doping (semiconductor)|doping]] is the process of intentionally introducing impurities into an extremely pure (also referred to as ''intrinsic'') semiconductor in order to change its electrical properties.
 
===Downtime===
: [[Downtime]] or '''outage''' is a period of time or a percentage of a timespan that a [[system]] is unavailable or [[offline]].
 
===Dry basis===
: It is customary to report the product composition data in steam reforming reactions on a steam free basis ([[dry basis]]) since the steam is not a constituent in any of the [[synthesis gas]]es produced or in the reformed gas when used as a fuel;<ref name="zulekha">{{cite book|url=http://pecongress.org.pk/images/upload/books/513.pdf |title=Mass Balance Calculation Method in Methane-Steam Reforming |publisher=Mrs. Zulekha Soomro |date= |accessdate=2011-02-11}}</ref> however, if steam is to be considered in the product composition data as well, then the calculation would be [[wet basis]].
 
==E==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Effluent===
: [[Effluent]] is an outflowing of water from a natural body of water, or from a man-made structure.
 
===Electrical Balance of Plant===
: Electrical [[Balance of Plant]] (EBOP) ,the [[user interface]] panel, [[control equipment]], and converting the fuel cell [[Direct current|DC]] power to [[Alternating current|AC]] power.
 
===Electricity===
: Electricity is any phenomenon resulting from the presence and flow of [[electric charge]].
 
===Electrical conductivity===
: [[Electrical conductivity]] or '''specific conductivity''' is a measure of a material's ability to [[electrical conduction|conduct]] an [[electric current]].
 
===Electrical efficiency===
: The [[electrical efficiency]] of an entity (a [[machine|device]], [[electronic component|component]], or [[system]]) in [[electronics]] and [[electrical engineering]] is defined as useful power output divided by the total electrical power consumed (a [[vulgar fraction|fractional]] [[Expression (mathematics)|expression]]), typically denoted by the Greek letter small Eta (η).
 
===Electrical insulation===
: An [[Insulator (electrical)|electrical insulator]] is a material that resists the flow of [[electric current]].  It is an object intended to support or separate electrical [[Electrical conductor|conductors]] without passing current through itself.
 
===Electrical resistance===
: [[Electrical resistance]] is a ratio of the degree to which an object opposes an [[electric current]] through it, measured in [[Ohm]]s.
 
===Electric circuit===
: An [[electrical circuit]] is 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 current===
: [[Electric current]] is the flow (movement) of [[electric charge]]. The [[SI]] unit of electric current is the [[ampere]].
 
===Electricity generation===
: [[Electricity generation]] is the process of converting non-electrical energy to electricity.
 
===Electric power conversion===
: In [[electrical engineering]], [[Electric power conversion|power conversion]] has a more specific meaning, namely converting [[electric power]] from one form to another.
 
===Electrochemistry===
: [[Electrochemistry]] is a branch of [[chemistry]] that studies [[chemical reactions]] which take place in a [[solution]] at the interface of an electron [[Electrical conductor|conductor]] (a [[metal]] or a [[semiconductor]]) and an ionic conductor (the [[electrolyte]]), and which involve electron transfer between the electrode and the electrolyte or species in solution.
 
===Electrochemical cell===
:An [[electrochemical cell]] is a device used for generating an [[electromotive force]] ([[voltage]]) and current from [[electrochemistry|chemical reactions]].
 
===Electrochemical gas sensor===
: [[Electrochemical gas sensor]]s are [[gas detectors]] that measure the volume of a target gas by [[Redox|oxidizing]] or reducing the target gas at an [[electrode]] and measuring the resulting current.
 
===Electrode===
: An [[electrode]] is an [[electrical conductor]] used to make contact with a nonmetallic part of a [[Electronic circuit|circuit]] (e.g. a [[semiconductor]], an [[electrolyte]] or a [[vacuum]]).
 
===Electro-galvanic fuel cell===
: [[Electro-galvanic fuel cell]] (EGFC)an electrical device used to measure the concentration of [[oxygen]] gas in [[scuba diving]] and [[medical]] equipment.
 
===Electroosmotic flow===
: [[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===
: An [[electroosmotic pump]] (EOP), or EO pump, is used for removing liquid flooding [[water]] from channels and gas [[diffusion]] layers and direct [[Mineral hydration|hydration]] of the [[proton exchange membrane]] in the [[membrane electrode assembly]] (MEA) of the [[proton exchange membrane fuel cell]]
 
===Electrolysis===
: In chemistry and manufacturing, [[electrolysis]] is a method of separating [[Chemical bond|chemically bonded]] [[chemical element|elements]] and [[chemical compound|compounds]] by passing an [[electric current]] through them.
 
===Electrolyte===
: An [[electrolyte]] is any substance containing free [[ion]]s that behaves as an [[electrical conductor|electrically conductive]] medium.
 
===Electron===
: The [[electron]] is a [[fundamental particle|fundamental]] [[subatomic particle]] that carries a negative [[electric charge]].
 
===Emission===
: [[Air pollution|Emission]] of air pollutants
 
===Emission standard===
: [[Emission standards]] are requirements that set specific limits to the amount of [[pollutants]] that can be released into the environment.
 
===Endothermic===
: In [[thermodynamics]], the [[endothermic]] processes or reactions are those that absorb energy in the form of [[heat]].
 
===Energy===
: In [[physics]] and other [[science]]s, energy is a [[scalar (physics)|scalar]] [[physical quantity]] that is a property of objects and systems which is conserved by nature. Energy is often defined as the ability to do [[work (thermodynamics)|work]].
 
===Energy carrier===
: An [[energy carrier]] is a substance or phenomenon that can be used to produce mechanical work or heat or to operate chemical or physical processes (ISO 13600).
 
===Energy content===
: Amount of energy for a given weight of fuel. see also [[energy density]]
 
===Energy security===
: [[Energy security]]
 
===Energy storage===
: [[Energy storage]] is the storing of some form of energy that can be drawn upon at a later time to perform some useful operation.
 
===Engine===
: An [[engine]] is a machine that converts heat energy into mechanical energy.
 
===Energy conversion efficiency===
: [[Energy conversion efficiency]] is the ratio between the useful output of an [[energy conversion machine]] and the input, in energy terms.
 
===Energy density===
: [[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, although the latter is more formally [[specific energy]]
 
===Energy transformation===
: In [[physics]] and [[engineering]], [[energy transformation]] or '''energy conversion''', is any process of transforming one form of energy to another.
 
===Enthalpy===
: In [[thermodynamics]] and [[chemistry|molecular chemistry]], the [[enthalpy]] or '''heat content''' (denoted as ''H'', ''h'', or rarely as ''χ'') is a quotient or description of [[thermodynamic potential]] of a system that can be used to calculate the "useful" work obtainable from a [[closed system|closed]] [[thermodynamic system]] under constant pressure and [[entropy]].
 
===Enthalpy of vaporization===
: The [[enthalpy of vaporization]], (symbol <math>\Delta{}_{v}H</math>), also known as the '''heat of vaporization''' or '''heat of evaporation''', is the energy required to transform a given quantity of a substance into an gas.
 
===Ethanol===
: [[Ethanol]], also called '''ethyl alcohol''', '''grain alcohol''', or '''drinking alcohol''', is a [[volatility (chemistry)|volatile]], [[flammable]], colorless liquid.
 
===Evaporation===
: [[Evaporation]] is the process by which [[molecule]]s in a liquid state (e.g. [[water]]) spontaneously become gaseous (e.g. [[water vapor]]).
 
===Exergy===
: In [[thermodynamics]], the [[exergy]] of a [[System (thermodynamics)|system]] is the maximum [[Mechanical work|work]] possible during a [[Thermodynamic process|process]] that brings the system into [[Thermodynamic equilibrium|equilibrium]] with a [[heat reservoir]].
 
===Exergy efficiency===
: [[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 gas===
: [[Exhaust gas]] is [[flue gas]] which occurs as a result of the [[combustion]] of fuels such as [[natural gas]], [[gasoline]]/petrol, [[Diesel fuel|diesel]], [[fuel oil]] or [[coal]]. It is discharged into the atmosphere through an [[exhaust pipe]] or [[flue gas stack]].
 
===Exothermic===
: In [[thermodynamics]], [[exothermic]] processes or reactions are those that release energy, usually in the form of [[heat]] but also in the form of light (e.g. explosions), sound, or electricity.
 
===Expansion ratio===
: [[Expansion ratio]] is used in the context of liquefied and [[cryogenic]] substances. 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.
 
==F==
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===Fan===
: A mechanical [[Fan (mechanical)|fan]] is an electrically powered device used to produce an airflow for the purpose of creature comfort (particularly in the heat), [[Ventilation (architecture)|ventilation]], exhaust, or any other gaseous transport.
 
===Fahrenheit===
: [[Fahrenheit]] is a [[temperature|temperature scale]]. In this scale, the freezing point of [[water]] is 32 degrees Fahrenheit (°F) and the [[boiling point]] 212 °F
 
===Failure mode and effects analysis===
: A [[failure mode and effects analysis]] (FMEA) is a [[Procedure (term)|procedure]] for analysis of potential failure modes within a system for classification by severity or determination of the effect of failures on the system.
 
===FCEV===
: A Fuel Cell Electric Vehicle is a [[Fuel cell vehicle]] that has a [[Battery (electricity)|battery]] it can charge from an external source as well as from its on-board [[fuel cell]].
 
===FCV===
: [[Fuel cell vehicle]]
 
===Feedstock purification===
: [[Feedstock purification]], The process of removing poisons like [[sulfur]] (S) and [[chloride]] (Cl) from the [[feedstock]].
 
===Flammability===
: [[Flammability]] is the ease with which a substance will ignite, causing [[fire]] or [[combustion]].
 
===Flammability limit===
: [[Flammability limits]], also called '''flammable limits,''' give the proportion of [[Fuel|combustible]] gases in a mixture, between which limits this mixture is [[Flammability|flammable]].
 
===Flash point===
: The [[flash point]] of a flammable liquid is the lowest [[temperature]] at which it can form an ignitable mixture in air.
 
===Float valve===
: A [[float valve]] is a mechanical [[feedback]] mechanism 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===
: [[Flow battery]] (FB) a form of [[rechargeable battery]] in which [[electrolyte]] containing one or more dissolved electroactive species flows through a [[Electrochemical cell|power cell / reactor]] that converts [[chemical energy]] to electricity.
 
===Flow measurement===
: [[Flow measurement]] is the quantification of bulk [[fluid]] movement.  It can be measured in a variety of ways.
 
===Flue gas===
: [[Flue gas]] is gas that exits to the atmosphere via a [[flue]].
 
===Flue-gas desulfurization===
: [[Flue-gas desulfurization]] (FGD)  is the technology used for removing [[sulfur dioxide]] (SO<sub>2</sub>) from the exhaust [[Flue gas emissions from fossil fuel combustion|flue gases]].
 
===Fluid dynamics===
: [[Fluid dynamics]] is the sub-discipline of [[fluid mechanics]] dealing with '''fluid flow''': [[fluid]]s (liquids and gases) in motion.
 
===Fluid mechanics===
: [[Fluid mechanics]] is the study of how [[fluid]]s move and the [[force]]s 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.
 
===Flux===
: In the study of [[transport phenomena (engineering & physics)|transport phenomena]] ([[heat transfer]], [[mass transfer]] and [[fluid dynamics]]), [[flux]] is defined as the amount that flows through a unit area ''per unit time''.
 
===Formic acid===
: [[Formic acid]] (systematically called '''methanoic acid''') is the simplest [[carboxylic acid]]. Its [[formula]] is [[hydrogen|H]][[carbon|C]][[oxygen|O]]OH or CH<sub>2</sub>O<sub>2</sub>.
 
===Formic acid fuel cell===
: [[Formic acid fuel cell]] (DFAFC), a subcategory of [[proton-exchange fuel cells]] where, the fuel, formic acid, is not reformed, but fed directly to the fuel cell.
 
===Fossil fuel===
: [[Fossil fuels]] or '''mineral fuels''' are fossil source [[fuel]]s, that is, [[hydrocarbons]] found within the top layer of the Earth’s [[Crust (geology)|crust]].
 
===Fouling===
: [[Fouling]] is the accumulation of unwanted material on solid surfaces,
 
===Frequency changer===
: A [[frequency changer]] or '''frequency converter''' is an [[Electronics|electronic]] device that converts [[alternating current]] ([[Alternating current|AC]]) of one [[frequency]] to [[alternating current]] of another frequency.
 
===Fuel===
: [[Fuel]] is any material that is burned or altered in order to obtain energy.
 
===Fuel cell===
: A [[fuel cell]] (FC) is an [[Electrochemistry|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 [[catalyst poisoning]].
 
===Fuel cell vehicle===
: A [[fuel cell vehicle]] is any [[vehicle]] that uses a [[fuel cell]] to produce its on-board motive power.
 
===Fuel efficiency===
: [[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 [[fuel]] into [[kinetic energy]] or [[Mechanical work|work]].
 
===Fuel efficiency in transportation===
: [[Fuel efficiency in transportation]]
 
===Fuel processor===
: Device used to generate hydrogen from fuels such as [[natural gas]], [[propane]], [[gasoline]], [[methanol]], and [[ethanol]], for use in [[fuel cell]]s.
 
===Fuel processing system===
: [[Fuel processing system]] (FPS)
 
===Fuel pump===
: [[Fuel pump]]
 
===Fusible plug===
: A [[fusible plug]] is a threaded metal plug, usually made out of [[bronze]], [[brass]], or [[gunmetal]].
 
==G==
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===Gadolinium doped ceria===
: [[Gadolinium]] [[Doping (semiconductor)|doped]] [[Cerium(IV) oxide|ceria]] (GDC) – (for [[SOFC]])
 
===Gas===
: Fuel gas, such as natural gas, undiluted liquefied [[petroleum]] gases (vapor phase only), liquefied petroleum gas–air mixtures, or mixtures of these gases.
:: [[Liquefied petroleum gas]]es (LPG) as used in this standard, shall mean and include any material which is composed predominantly of any of the following [[hydrocarbon]]s, or mixtures of them: propane, propylene, butanes (normal butane or isobutane) and butylenes.
:: LP gas–air miixture – 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 compressor===
: A [[gas compressor]] is a mechanical device that increases the pressure of a gas by reducing its [[volume]].
 
===Gas detector===
: A [[gas detector]] is 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.
 
===Gas diffusion===
: 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 electrode]]s 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.
 
===Gasification===
: [[Gasification]] is a process that converts carbonaceous materials, such as [[coal]], [[petroleum]], or [[biomass]], into [[carbon monoxide]] and [[hydrogen]] by reacting the raw material at high temperatures with a controlled amount of [[oxygen]] and/or [[steam]].
 
===Gasoline gallon equivalent===
: [[Gasoline gallon equivalent]] (GGE) or gasoline-equivalent gallon (GEG) is the amount of alternative [[fuel]] it takes to equal the energy content of one liquid [[gallon]] of [[gasoline]].
 
===Gibbs free energy===
: In [[thermodynamics]], the [[Gibbs free energy]] ([[IUPAC]] recommended name: '''Gibbs energy''' or '''Gibbs function''') is a [[thermodynamic potential]] which measures the "useful" or process-initiating work obtainable from an [[isothermal]], [[Isobaric process|isobaric]] [[thermodynamic system]].
 
===Graphite===
: The [[mineral]] [[graphite]], as with [[diamond]] and [[fullerene]], is one of the [[allotropes of carbon]].
 
===Greenhouse effect===
: Gases in the Earth's atmosphere that contribute to the [[greenhouse effect]], effectively absorbing thermal [[infrared]] radiation, emitted by the [[Earth| Earth’s]] surface
 
===Greenhouse gases===
: Warming of the Earth's atmosphere due to [[Greenhouse gas|greenhous gas]]es 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 connection===
: [[Grid connection]]
 
===Grid-tied electrical system===
: A [[grid-tied electrical system]], also called Tied to grid  or Grid tie system, is a semi-autonomous electrical generation or [[grid energy storage]] system which links to the mains to feed excess capacity back to the local [[mains electricity|mains]] electrical grid.
 
===Grid tie inverter===
: [[Grid tie inverter]]
 
===Guard bed===
: [[Guard bed]], see [[guard catalyst bed]] and [[liquid-phase guard bed]].
 
===Guard catalyst bed===
: A [[guard catalyst bed]] is a fixed bed of pellets of the same [[catalytic]] material, see [[fixed bed reactor]].
 
==H==
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===Half-reaction===
: A [[half reaction]] is either the oxidation or reduction reaction component of a [[redox reaction]].
 
===Heat exchanger===
: A [[heat exchanger]] is a device built for efficient [[heat transfer]] from 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 pipe===
: A [[heat pipe]] is a heat transfer mechanism that can transport large quantities of heat with a very small difference in [[temperature]] between the hotter and colder interfaces.
 
===Heat transfer===
: In [[thermal science|thermal physics]], [[heat transfer]] is the passage of [[thermal energy]] from a hot to a colder body.
 
===Heating value===
: The [[heating value]] (TOTAL) (ΔH<sub>c</sub><sup>0</sup>) is the energy released as [[heat]] when a compound undergoes complete [[combustion]] with [[oxygen]]. (see also [[Higher heating value]] (HHV) and [[Lower heating value]]) (LHV).
 
===Heat of combustion===
: The [[heat of combustion]] (ΔH<sub>c</sub><sup>0</sup>) is the energy released as [[heat]] when a compound undergoes complete [[combustion]] with [[oxygen]]. The chemical reaction is typically a [[hydrocarbon]] reacting with oxygen to form [[carbon dioxide]], [[water]] and heat.
 
===Higher heating value===
: The [[higher heating value]] (HHV) (also known as the gross calorific value or gross energy) of a [[fuel]] is defined as the amount of [[heat]] released by a specified quantity (initially at 25&nbsp;°C) once it is [[combustion|combusted]] and the products have returned to a temperature of 25&nbsp;°C.
 
===High-temperature shift===
: High-temperature shift (HTS), the [[water gas shift reaction]] at 350 °C (662 °F) in the presence of a metal-based [[catalyst]] ([[nickel]])
 
===Hybrid electric vehicle===
: A [[hybrid electric vehicle]] (HEV) is a [[hybrid vehicle]] which combines a conventional [[ground propulsion|propulsion]] system with a [[rechargeable energy storage system]] (RESS) to achieve better [[fuel economy in automobiles|fuel economy]] than a [[conventional vehicle]].
 
===Hydride===
: [[Hydride]] is the name given to the [[Electric charge|negative]] [[ion]] of [[hydrogen]], H<sup>−</sup>.
 
===Hydride ion===
: Aside from [[electride]], the [[Hydride#Hydride_ion|hydride ion]] is the simplest possible [[anion]], consisting of two [[electron]]s and a [[proton]]. See also [[hydrogen anion]]
 
===Hydrocarbon===
: In [[organic chemistry]], a [[hydrocarbon]] (HC) is an [[organic compound]] consisting entirely of [[hydrogen]] and [[carbon]].
 
===Hydrocarbon dew point===
: The [[hydrocarbon dew point]] (HDP) or (HCDP) is the [[temperature]] (at a given  [[pressure]]) at which the [[hydrocarbon]] components of any hydrocarbon-rich gas mixture, such as [[natural gas]], will start to [[Condensation|condense]] out of the gaseous phase.
 
===Hydrodesulfurization===
: [[Hydrodesulfurization]] (HDS) is a [[catalytic]] chemical process widely used to remove [[sulfur]] (S) from [[natural gas]] and from [[oil refinery|refined petroleum products]] such as [[gasoline|gasoline or petrol]], [[jet fuel]], [[kerosene]], [[diesel fuel]], and [[fuel oil]]s.
 
===Hydrogen===
: [[Hydrogen]] is the [[chemical element]] with [[atomic number]] 1. It is represented by the [[chemical symbol|symbol]] '''H'''. At [[standard temperature and pressure]], hydrogen is a colorless, [[odorless]], [[nonmetal]]lic, [[tasteless]], highly [[combustion|flammable]] [[Diatomic molecule|diatomic]] gas with the [[molecular formula]] H<sub>2</sub>.
 
===Hydrogen anion===
: The [[hydrogen anion]] is a [[Electric charge|negative]] [[hydrogen ion]], H<sup>−</sup>. See also [[Hydride#Hydride_ion|hydride ion]].
 
===Hydrogen purity===
[[Hydrogen purity]] or hydrogen quality is the lack of impurities in [[hydrogen]] as a fuel gas.
 
===Hydrogen-rich fuel===
: A fuel that contains a significant amount of [[hydrogen]], such as gasoline, diesel fuel, [[methanol]] (CH3OH), [[ethanol]] (CH3CH2OH), [[natural gas]], and coal.
 
===Hydrogen sulfide sensor===
A [[hydrogen sulfide sensor]] or '''H<sub>2</sub>S sensor''' is a [[gas sensor]] for the measurement of [[hydrogen sulfide]] in a gas stream.
 
==I==
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===Impurity===
: [[Impurities]] are substances inside a confined amount of liquid, gas, or solid, which differ from the [[chemical composition]] of the material or compound.
 
===Influent===
:  [[Influent]]
 
===Interlock===
: [[Interlock (engineering)|Interlocking]] is a method of preventing undesired states in a [[Finite state machine|state machine]], which in a general sense can include any electrical, electronic, or mechanical device or system.
 
===Internal combustion engine===
: An [[internal combustion engine]] (ICE) is an engine in which the [[combustion]] of [[fuel]] and an [[oxidizer]] (typically air) occurs in a confined space called a [[combustion chamber]].
 
===Inverter===
:  An [[Inverter (electrical)|inverter]] is an electrical or electro-mechanical device that converts [[direct current]] (DC) to [[alternating current]] (AC)
 
===Ion===
: An [[ion]] is an [[atom]] or [[molecule]] which has lost or gained one or more [[valence electron]]s, giving it a positive or negative electrical charge.
 
===Ion exchange===
: [[Ion exchange]] is an exchange of [[ion]]s between two [[electrolyte]]s or between an electrolyte [[solution]] and a [[complex (chemistry)|complex]].
 
===Ion exchange resin===
: An [[ion exchange resin]] is 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 [[polymer]] substrate.
 
===Ionomer===
: An [[ionomer]] is a [[polyelectrolyte]] that comprises [[copolymer]]s containing both [[electric charge|electrically]] neutral repeating units and a fraction of [[ion]]ized units
 
===Islanding===
: [[Islanding]] is the condition of a [[distributed generation|distributed Generation]] (DG) generator continuing to power a location even though power from the [[electric utility]] is no longer present.
 
==J==
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{{Empty section|date=July 2010}}
 
==K==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Kröger–Vink notation===
: [[Kröger–Vink notation]] is set of conventions used to describe electrical charge and lattice position for point [[Crystallographic defect|defect]] species in [[Crystal structure|crystals]].
 
===Kilogram===
: The [[kilogram]] or '''kilogramme''' (symbol: kg) is the [[SI base unit|base unit]] of [[mass]] in 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 [[litre|liter]] of water.
 
===Kilowatt===
: The [[Kilowatt#Kilowatt|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===
: The [[kilowatt hour]], also written ''kilowatt-hour'' (symbol '''kW·h''', '''kW&nbsp;h''' or '''kWh''') is a unit of energy.
 
==L==
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===Landfill gas===
: [[landfill gas]] (LFG), see [[biogas]].
 
===Lanthanum carbonate===
: [[Lanthanum carbonate]] is used as a lanthanum source for solid-state production of [[lanthanum strontium manganite]] (LSM), primarily for [[solid oxide fuel cell]] applications.
 
=== LH<sub>2</sub>===
: See [[liquid hydrogen]].
 
===Life cycle assessment===
: A [[life cycle assessment]] ('''LCA''', also known as '''life cycle analysis''', '''ecobalance''', and '''cradle-to-grave analysis''') is the investigation and valuation of the [[Sustainability|environmental impact]]s of a given product or service caused or necessitated by its existence.
 
===Linear regulator===
: In electronics, a [[linear regulator]] is a [[voltage regulator]] based on an active device (such as a [[bipolar junction transistor]], [[field effect transistor]] or [[vacuum tube]]) operating in its "linear region"
 
===Liquid===
: liquid is one of the principal [[states of matter]].
 
===Liquid hydrogen===
: [[Liquid hydrogen]] (LH2 or LH<sub>2</sub>) is the [[liquid state]] of the element [[hydrogen]].
 
===Liquid–liquid extraction===
: [[Liquid–liquid extraction]], also known as '''solvent extraction''' and '''partitioning''', is a method to separate compounds based on their relative [[solubility|solubilities]] in two different [[miscible|immiscible]] liquids, usually [[Water (molecule)|water]] and an [[solvent|organic solvent]].
 
===Liquefied natural gas===
: [[Liquefied natural gas]] (LNG) is [[natural gas]] (primarily [[methane]], CH<sub>4</sub>) 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 [[fuel]] in heating appliances and vehicles
 
===Liquefaction===
: In [[physics]], to [[Liquefaction|liquefy]] (sometimes spelled as "liquify") means to turn something into the liquid state.
 
===Liquefaction of gases===
: [[Liquefaction of gases]] includes a number of phases used to convert a gas into a liquid state.
 
===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 [[contamination|contaminating]] substances.  The following [[List of purification methods in chemistry|list of chemical purification methods]] should not be considered exhaustive.
 
===Load following power plant===
: A [[load following power plant]] is a [[power plant]] that adjusts its power output as demand for electricity fluctuates throughout the day.
 
===Load profile===
: In [[electrical engineering]], a [[load profile]] is a graph of the variation in the [[electrical load]] versus 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===
: The [[lower heating value]] (also known as ''net calorific value'', ''net CV'', or ''LHV'') of a [[fuel]] is defined as the amount of [[heat]] released by combusting a specified quantity (initially at 25 °C or another reference state) and returning the temperature of the [[combustion]] products to 150 °C.
 
===Low temperature shift===
: Low temperature shift (LTS), the [[water gas shift reaction]] at 190–210°C (374–410°F) in the presence of a metal-based [[catalyst]] ([[nickel]]).
 
==M==
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===Maintenance, repair and operations===
: [[Maintenance, Repair and Operations]] or '''Maintenance, Repair and Overhaul''' ('''MRO''') is fixing any sort of [[machine|mechanical]] or [[electrical]] [[machine|device]] 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===
: A [[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) is the wall strength of a pressurized [[pneumatic cylinder|cylinder]] such as a [[Pipeline transport|pipeline]] or [[storage tank]] and how much pressure the walls may safely hold before rupturing.
 
===Mean down time===
: In [[organization]]al [[management]], [[mean down time]] (MDT) is the [[average]] time that a system is non-operational.
 
===Mean time between failures===
: [[Mean time between failures]] (MTBF) is the [[mean]] (average) time between [[failure]]s 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 [[system]] the [[mean time between outages]] ('''MTBO''') is the mean [[time]] between equipment failures that result in loss of system continuity or unacceptable [[Degradation (telecommunications)|degradation]].
 
===Mechanical energy===
: In [[physics]], [[mechanical energy]] is the [[potential energy]] and [[kinetic energy]] present in the components of a ''mechanical system''.
 
===Mechanical Balance of Plant===
: Mechanical [[Balance of Plant]] (MBOP), the process equipment needed to provide steam, gas, and air to the fuel cell stack.
 
===Membrane===
: See [[semipermeable membrane]] and [[artificial membrane]]
 
===Membrane electrode assembly===
: [[Membrane electrode assembly]] (MEA) is an assembled stack of [[proton exchange membrane]]s.
 
===Megawatt===
: The [[Watt#Megawatt|megawatt]] (symbol: MW) is equal to one million (1000000) watts.
 
===Meter===
: [[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.
 
===Methanation===
: [[Methanation]] is a physical-chemical process to generate [[Methane]] from a mixture of various gases out of biomass [[fermentation (biochemistry)|fermentation]] or thermo-chemical [[gasification]].
 
===Methane===
: [[Methane]] is a [[chemical compound]] with the molecular formula {{chem|CH|4}}. It is the simplest [[alkane]], and the principal component of [[natural gas]].
 
===Methane reformer===
: A [[methane reformer]] is a device used in [[chemical engineering]], which can produce pure [[hydrogen]] gas from [[natural gas]] using a [[catalyst]]. (See [[Autothermal_reforming#Autothermal_reforming|ATR]] and [[Steam reforming|SMR]]).
 
===Methanol===
: [[Methanol]], also known as '''methyl alcohol''', '''carbinol''', '''wood alcohol''', '''wood naphtha''' or '''wood spirits''', is a [[chemical compound]] with [[chemical formula]] [[carbon|C]][[hydrogen|H]]<sub>3</sub>[[Hydroxide|OH]] (often abbreviated MeOH).
 
===Methanol reformer===
: A [[methanol reformer]] is a device used in [[chemical engineering]], especially in the area of [[fuel cell]] technology, which can produce pure [[hydrogen]] gas and [[carbon dioxide]] by reacting a [[methanol]] and [[water]] (steam) mixture.
 
===MicroCHP===
: [[MicroCHP|"Micro cogeneration"]] or micro combined heat and power (mCHP) is a so called [[Distributed Energy Resource|distributed energy resource]] (DER).
 
===Microbial fuel cell===
: [[Microbial fuel cell]] (MFC) or '''biological fuel cell''' is a bio-[[electrochemical]] system that drives a [[Electric current|current]] by mimicking [[bacteria]]l interactions found in [[nature]].
 
===Micropump===
: A [[micropump]] is a small [[pump]], particularly one with 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 gallon]] of gasoline).
 
===Millimeter===
: [[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===
: [[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 cell]]s
 
==N==
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===Nafion===
: [[Nafion]] is a sulfonated tetrafluorethylene [[copolymer]]
 
===Nano iron powder===
: [[Nano iron powder]] is an iron powder with granules' sizes ranging on the [[nanoscale]].
 
===Nanowire===
: A [[nanowire]] is a wire of diameter of the order of a nanometer (10<sup>−9</sup> meters).
 
===Natural gas===
: [[Natural gas]] is a gaseous [[fossil fuel]] consisting primarily of [[methane]] but 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]], [[helium]] and [[hydrogen sulfide]].
 
===Nernst equation===
: In [[electrochemistry]], the [[Nernst equation]] is an equation which can be used (in conjunction with other information) to determine the equilibrium [[reduction potential]] of a [[half-cell]] in an [[electrochemical cell]].
 
===Net energy gain===
: In [[energy economics]], [[net energy gain]] ('''NEG''') is a surplus condition in the difference between the energy required to harvest an energy source and the energy provided by that same source.
 
===Nickel===
: [[Nickel]] is a metallic [[chemical element]] with the symbol '''Ni''' and [[atomic number]] 28.
 
===Nitrogen===
: [[Nitrogen]] N<sub>2</sub> a [[chemical element]] that has the symbol '''N''' and [[atomic number]] 7 and [[atomic weight]] 14.0067. Molecular nitrogen (N<sub>2</sub>) is a colorless, odorless, tasteless and mostly [[inert]] [[diatomic]] gas at [[standard conditions]], constituting 78.08% by volume of [[Earth's atmosphere]].
 
===Nitrogen oxide===
: [[Nitrogen oxide]] (NO<sub>x</sub>) is any [[binary compound]] of [[oxygen]] and [[nitrogen]] or a mixture of such compounds
 
===Nitrogen oxide sensor===
: A [[nitrogen oxide sensor]] or '''NOx sensor''' is typically a high temperature device built to detect [[nitrogen oxide]]s in combustion environments such as an [[automobile]] or truck [[tailpipe]] or a [[smokestack]].
 
==O==
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===Off board reforming===
: [[Off board reforming]], stationary reforming, see [[steam reforming]], [[methane reformer]], [[methanol reformer]]
 
===Ohm===
: The [[ohm]] (symbol: [[Ω]]) is the [[SI]] unit of [[electrical impedance]] or, in the [[direct current]] case, [[electrical resistance]], named after [[Georg Ohm]].
 
===Onboard reforming===
: [[On-board reforming]], reforming on board a [[vehicle]], see [[steam reforming]], [[methane reformer]], [[methanol reformer]]
 
===Open-circuit voltage===
: [[Open-circuit voltage]] or '''OCV''' is the [[potential difference|difference of electrical potential]] between two terminals of a device when there is no [[External electric load|external load]] connected, i.e. the [[electrical network|circuit]] is broken or open.
 
===Original equipment manufacturer===
: An [[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===
: [[Output impedance]], Any linear electronic circuit or device which supplies a current may be modelled as an [[ideal voltage source]] in series with an [[Electrical impedance|impedance]]. This is helpful in analysing the voltage drop which occurs as current is drawn.
 
===Overpotential===
: In [[electrochemistry]], [[overpotential]] is the difference in the [[electric potential]] of an electrode with no [[Electric current|current]] through it, at [[Chemical equilibrium|equilibrium]], and with a current.
 
===Overpressure===
: [[Overpressure]]
 
===Overvoltage===
: When the [[voltage]] in a [[Electrical network|circuit]] or part of it is raised above its upper design limit, this is known as [[overvoltage]].
 
===Oxidant===
: An [[oxidizing agent]] (also called an '''oxidant''' or '''oxidizer''') can be defined as either: a [[chemical compound]] that readily transfers [[oxygen]] atoms, or a substance that gains electrons in a [[redox]] [[chemical reaction]]. In both cases, the oxidizing agent becomes [[Redox|reduce]]d in the process.
 
===Oxidation===
: See [[redox]]
 
===Oxygen===
: [[Oxygen]] is the [[chemical element|element]] with [[atomic number]] 8 and represented by the symbol '''O'''.
 
===Oxygen sensor===
: An [[oxygen sensor]], or lambda sensor, is an electronic device that measures the proportion of [[oxygen]] (O<sub>2</sub>) in the gas or liquid being analyzed.
 
==P==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Palladium===
: [[Palladium]] is a rare and lustrous silvery-white metal with the symbol '''Pd''', and its [[atomic number]] is 46.
 
===Parallel circuit===
: [[Parallel_circuits#Parallel_circuits|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.
 
===Partial oxidation===
: In [[chemistry]], a [[partial oxidation]] ('''POX''') reaction occurs when a [[stoichiometry|substoichiometric]] fuel-air mixture is partially [[combustion|combusted]] in a reformer.
 
===Partial pressure===
: In a mixture of [[ideal gas]]es, each gas has a [[partial pressure]] which is the pressure which the gas would have if it alone occupied the volume. The total [[pressure]] of a gas mixture is the sum of the partial pressures of each individual gas in the mixture.
 
===Particulate===
: Particulates, alternatively referred to as [[Atmospheric particulate matter|particulate matter]] (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas.
 
===Parts per million===
: [[Concentration|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===
: In [[atmospheric chemistry]] and in [[air pollution]] regulations, the parts per notation is commonly expressed with a v following, such as '''ppmv''', to indicate [[Concentration|parts per million by volume]].
 
===Pascal===
: The [[pascal (unit)|pascal]] (symbol: '''Pa''') is the [[SI derived unit]] of [[pressure]], [[stress (physics)|stress]], [[Young's modulus]] and [[tensile strength]]. It is a measure of perpendicular [[force]] per unit [[area]] i.e. equivalent to one [[Newton (unit)|newton]] per [[square meter]] or one [[joule]] per cubic metre.
 
===Peak load===
: [[Peak load]]
 
===PEDOT===
: [[Poly(3,4-ethylenedioxythiophene)]] or '''PEDOT''' (or sometimes '''PEDT''')  is a [[conducting polymer]] based on [[3,4-ethylenedioxylthiophene]] or EDOT [[monomer]].
 
===Permeation===
: [[Permeation]], in [[physics]] and [[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.
 
===Phase transition===
: In [[thermodynamics]], [[phase transition]] or '''phase change''' is the transformation of a thermodynamic system from one [[phase (matter)|phase]] to another.
 
===Phosphoric acid===
: [[Phosphoric acid]], also known as '''orthophosphoric acid''' or '''phosphoric(V) acid''', is a [[mineral acid|mineral (inorganic) acid]] having the [[chemical formula]] [[Hydrogen|H]]<sub>3</sub>[[Phosphorus|P]][[Oxygen|O]]<sub>4</sub>.
 
===Phosphoric acid fuel cell===
: [[Phosphoric acid fuel cell]] (PAFC), a type of [[fuel cell]] that uses liquid [[phosphoric acid]] as an [[electrolyte]].
 
===Photoelectrochemical cell===
:  [[Photoelectrochemical cell]] (PEC), a [[solar cell]] that extracts electrical energy from light, including [[visible light]].
 
===Platinum===
: [[Platinum]] is a [[chemical element]] with the [[atomic symbol]] '''Pt'''
 
===Polybenzimidazole fiber===
: [[Polybenzimidazole]] (PBI) [[fiber]] (1983) is a [[synthetic fiber]] with an extremely high [[melting point]] that also does not ignite.
 
===Polyethylene===
: [[Polyethylene]] or '''polythene''' ([[IUPAC]] name '''poly(ethene)''') is a [[thermoplastic]] commodity
 
===Polymer===
: A [[polymer]] is a large [[molecule]] ([[macromolecule]]) composed of repeating [[structural unit]]s connected by [[covalent]] [[chemical bond]]s. See also [[plastic]].
 
===Polymer electrolyte membrane===
: A [[polymer electrolyte membrane]] (PEM), is 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.
 
===Polytetrafluoroethylene===
: In [[chemistry]], [[Polytetrafluoroethylene|poly(tetrafluoroethene)]] or poly(tetrafluoroethylene) ('''PTFE''') is a synthetic [[fluoropolymer]] which finds numerous applications.
 
===Polymer electrolyte membrane fuel cell===
: [[Polymer electrolyte membrane fuel cell]] (PEMFC or PEFC), a type of acid-based [[fuel cell]] in which the transport of [[proton]]s (H+) from the [[anode]] to the [[cathode]] is through a solid, aqueous membrane impregnated with an appropriate acid. The [[electrolyte]] is a called a [[polymer electrolyte membrane]] (PEM). The fuel cells typically run at low temperatures (<100°C).
 
===Potential difference===
: In [[physics]], the [[potential difference]] or '''p.d.''' between two points is the difference of the points' [[scalar potential]],  equivalent to the  line integral of the [[field strength]] between the two points.
 
===Portable fuel cell applications===
: [[Portable fuel cell applications]] (or portable fuel cell power systems) are portable (Movable) [[fuel cell]] applications{{Disambiguation needed|date=June 2011}}
 
===Potassium hydroxide===
: [[Potassium hydroxide]] is the [[inorganic compound]] with the formula [[potassium|K]][[hydroxide|OH]].
 
===Power===
: In [[physics]], [[Power (physics)|power]] (symbol: ''P'') is the rate at which [[mechanical work|work]] is performed or [[energy (physics)|energy]] is transmitted, or the amount of energy required or expended for a given unit of time.
 
===Power density===
: [[Power density]] (Pv), see [[power density|specific power]]
 
===Power factor===
: The [[power factor]] of an [[alternating current|AC]] electric power system is defined as the [[ratio]] of the [[AC power|real power]] to the [[AC power|apparent power]], and is a number between 0 and 1 (frequently expressed as a percentage, e.g. 0.5 pf = 50% pf).
 
===Power supply===
: [[Power supply]] is a source of [[electrical power]].
 
===Power-to-weight ratio===
: [[Power-to-weight ratio]] ([[Power-to-weight ratio|specific power]]) is a calculation commonly applied to [[engine]]s and other mobile power sources to enable the comparison of one unit or design to another.
 
===Power per unit of mass===
:  [[Power density#Power per unit of mass|Power per unit of mass]] is the [[power-to-weight ratio]], measured in kilowatts per [[kilogram]] (generally, [[kW]]/[[kg]]).
 
===PReferential OXidation===
: [[Preferential oxidation]] (PROX) is the preferential [[oxidation]] of a gas on a [[catalyst]].
 
===Pressure regulator===
: A [[pressure regulator]] is a [[valve]] that automatically cuts off the flow of a liquid or gas at a certain pressure.
 
===Pressure relief valve===
: A [[pressure relief valve]] (PRV), also called a pressure safety valve (PSV), is a safety device that relieves in case of overpressure in vessel or piping.
 
===Pressure sensor===
: A [[pressure sensor]] measures 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 [[adsorbent]] material.
 
===Pressure vessel===
: A [[pressure vessel]] is a closed container designed to hold gases or liquids at a [[pressure]] different from the ambient [[pressure]].
 
===Propane===
: [[Propane]] is  a three-[[carbon]] [[alkane]], normally a gas, but compressible to a liquid that is transportable. See also [[Liquefied petroleum gas|LPG]].
 
===Proton===
: The [[proton]] is a [[subatomic particle]] with an [[electric charge]] of one positive [[elementary charge|fundamental unit]]
 
===Proton exchange membrane===
: [[Proton exchange membrane]] (PEM) is a [[semipermeable membrane]] generally made from [[ionomer]]s and designed to [[proton conductor|conduct protons]] while being impermeable to gases such as [[oxygen]] or [[hydrogen]].
 
===Proton exchange membrane fuel cell===
: [[Proton exchange membrane fuel cell]] (PEMFC) a type of [[fuel cell]] based on a [[polymer]] [[electrolyte]] [[artificial membrane|membrane]].
 
===Protonic ceramic fuel cell===
: [[Protonic ceramic fuel cell]] (PCFC) based on a ceramic electrolyte material that exhibits high protonic conductivity at elevated temperatures.
 
==Q==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
{{Empty section|date=July 2010}}
 
==R==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Reactor===
: Reactor, see: [[Bioreactor#Bioreactor|bioreactor]], [[membrane reactor]] and [[chemical reactor]].
 
===Reagent===
: A [[reagent]] or '''reactant''' is a substance or compound  consumed during a [[chemical reaction]].
 
===Rectifier===
:  A [[rectifier]] is an electrical device that converts [[alternating current]] (AC) to [[direct current]] (DC), a process known as '''rectification'''.
 
===Redox===
: [[Redox]] (shorthand for '''reduction-oxidation''' reaction) is any [[chemical reaction]] in which atoms have their [[oxidation number]] ([[oxidation state]]) changed.
 
===Reformate===
: Reformate, [[hydrocarbon]] fuel that has been processed into hydrogen and other products for use in [[fuel cell]]s.
 
===Reformed Methanol Fuel Cell===
: [[Reformed methanol fuel cell]] (RMFC) or '''Indirect Methanol Fuel Cell''' (IMFC)s are a subcategory of [[proton exchange membrane fuel cell|proton-exchange fuel cells]] where, the fuel, [[methanol]] (CH<sub>3</sub>OH), is reformed, before being fed into the [[fuel cell]].
 
===Reformer===
: A hydrogen [[Hydrogen reformer|reformer]] another name for [[steam reforming]] a device that extracts hydrogen from other fuels, typically methanol or gasoline, not to be confused with the process [[catalytic reforming]]
 
===Reforming===
: A chemical process in which hydrogen containing fuels react with steam, [[oxygen]], or both to produce a hydrogen-rich gas stream. ([[syngas]])
 
===Reformulated gasoline===
: 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 [[Regenerative fuel cell]].
 
===Relief valve===
: The [[relief valve]] is a type of [[valve]] used to control or limit the [[pressure]] in a system or vessel which can build up by a process upset, instrument or equipment failure, or fire.
 
===Renewable energy===
: [[Renewable energy]] is energy generated from [[natural resource]]s—such as [[sunlight]], Including [[solar energy|solar]] and [[radiant energy]], [[wind]], [[rain]], [[tidal energy|tides]] and [[geothermal energy|geothermal heat]]—which are [[Renewable resource|renewable]] (naturally replenished).
 
===Reservoir===
: A [[reservoir]] is, most broadly, a place or hollow vessel where something [[fluid]] is kept in [[wikt:reserve|reserve]], for later use.
 
===Response time===
: In [[technology]], [[Response time (technology)|response time]] is the [[time]] a [[system]] or [[functional unit]] takes to react to a given input.
 
===Reversible fuel cell===
: [[Regenerative 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.
 
===Reynolds number===
: In [[fluid mechanics]] and [[heat transfer]], the [[Reynolds number]] <math>\mathrm{Re}</math> is a [[dimensionless number]] that gives a measure of the [[ratio]] of [[inertia]]l [[force]]s (<math>{\bold \mathrm V} \rho</math>) to [[viscosity|viscous]] forces (<math>\mu / L</math>) and, consequently, it quantifies the relative importance of these two types of forces for given flow conditions.
 
===Rupture disc===
: A [[rupture disk]] or '''bursting disc''' is a [[relief valve|pressure relief]] device that protects a vessel or system from overpressurization.
 
===Ruthenium===
: [[Ruthenium]] is used in Platinum-Ruthenium [[electrode]]s for Methanol-fuel cells
 
==S==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Safety shutoff valve===
: [[Safety shut-off valves]] are [[safety valve]]s used to close a line and stop the flow of material.
 
===Safety valve===
: A [[safety valve]] is a [[valve]] mechanism for the automatic release of a gas from a [[boiler]], [[pressure vessel]], or other [[system]] when the pressure or temperature exceeds preset limits.
 
===Salt bridge===
: A [[salt bridge]], in [[chemistry]], is a laboratory device used to connect the [[oxidation]] and [[Redox|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]].
 
===Scrubber===
: [[Scrubber]] systems are a diverse group of [[air pollution]] control devices that can be used to remove some [[particulate]]s and/or gases from industrial exhaust streams.
 
===Sensor===
: A [[sensor]] is 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 circuit===
: [[Series and parallel circuits#Series_circuits|Series circuits]] are sometimes called ''current''-coupled or [[daisy chain (electrical engineering)|daisy chain]]-coupled. The [[current (electricity)|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.
 
===Service life===
: A product's [[service life]] is 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===
: A [[short circuit]] (sometimes abbreviated to '''short''' or '''s/c''') allows a [[Electric current|current]] along a different path from the one intended.
 
===Sodium borohydride===
: [[Sodium borohydride]], also known as '''sodium tetrahydroborate''', has the [[chemical formula]] [[sodium|Na]][[boron|B]][[hydrogen|H]]<sub>4</sub>.
 
===Solenoid valve===
: A [[solenoid valve]] is an [[electromechanical]] [[valve]] for use with liquid or gas controlled by running or stopping an [[current (electricity)|electrical current]] through a [[solenoid]], which is a coil of wire, thus changing the state of the valve.
 
===Solid oxide electrolyser cell===
A [[solid oxide electrolyser cell]] (SOEC) is a solid oxide fuel cell set in [[Regenerative fuel cell|regenerative mode]] for the [[electrolysis of water]] with a solid oxide, or [[ceramic]], [[electrolyte]] to produce oxygen and [[hydrogen gas]].
 
===Solid oxide fuel cell===
: A [[solid oxide fuel cell]] (SOFC) is an electrochemical conversion device that produces electricity directly from oxidizing a fuel.
 
===Solubility===
: [[Solubility]] is the ability of a given substance, the [[Solution|solute]], to dissolve in a [[solvent]].
 
===Sorbent===
: A [[sorbent]] is a material used to [[adsorb]] either liquids or gases.
 
===Sorption===
: [[Sorption]] is the action of both [[absorption (chemistry)|absorption]] and [[adsorption]] takes place simultaneously.
 
===Specific gravity===
: [[Specific gravity]] is defined as the ratio of the [[density]] of a given solid or liquid substance to the density of [[water (molecule)|H2O]] 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
 
===Specific heat capacity===
: [[Specific heat capacity]], also known simply as '''specific heat''', is the measure of the [[energy|heat energy]] required to increase the [[temperature]] of a [[Quantity|unit quantity]]
 
===Specific power===
: In [[engineering]], the specific power is [[power (physics)|power]] either per unit of [[mass]], [[volume]], or [[area]].
 
===Specific weight===
: The [[specific weight]] (also known as the '''unit weight''') is the [[weight]] per unit [[volume]] of a material
 
===Stack===
: 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.
 
===Standard cubic foot===
: A [[standard cubic foot]] (SFC) is a measure of quantity of gas, equal to a cubic foot of volume at 60 degrees [[Fahrenheit]] and either 14.696 [[Pound-force per square inch|pounds-force per square inch]] (1&nbsp;[[Atmosphere (unit)|atm]] or 101.325&nbsp;kPa) or 14.73&nbsp;psi (30&nbsp;[[inHg]] or 101.6&nbsp;kPa) of [[pressure]].
 
===Standard electrode potential===
: In [[electrochemistry]], the [[standard electrode potential]], abbreviated E<sup>o</sup>, E<sup>0</sup>, or E<sup><s>O</s></sup> (with a superscript [[Standard state|plimsoll]] character, 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).
 
===Stationary fuel cell applications===
: [[Stationary fuel cell applications]] (or stationary fuel cell power systems) are stationary (not moving) [[fuel cell]] applications
 
===Steady state===
: [[Steady state]] is a more general situation than [[dynamic equilibrium]]. If a [[system]] is in steady state, then the recently observed behavior of the system will continue into the future.
 
===SMR===
: Steam methane reforming (SMR) another name for [[steam reforming]]
 
===Steam reforming===
: [[Steam reforming]] (SR), '''hydrogen reforming''' or '''catalytic oxidation''', is a method of producing [[hydrogen]] from [[hydrocarbons]] at high temperatures (700 – 1100 °C) in the presence of a metal-based [[catalyst]] ([[nickel]]).
 
===Switched-mode power supply===
: A [[switched-mode power supply]], '''switching-mode power supply''' or '''SMPS''', is an electronic [[power supply]] unit (PSU) that incorporates a switching regulator.
 
===Syngas===
: [[Syngas]] (from '''''syn'''thesis '''gas''''') is the name given to a gas mixture that contains varying amounts of [[carbon monoxide]] and [[hydrogen]] generated by the [[gasification]] of a carbon-containing fuel to a gaseous product with a heating value.
 
==T==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Tafel equation===
: The [[Tafel equation]] relates the rate of an [[Electrochemistry|electrochemical]] reaction to the [[overpotential]].
 
===Tail gas combustor===
: [[Tail gas combustor]] (TGC)
 
===Tar===
: [[Tar]] is a [[viscosity|viscous]] black liquid derived from the [[destructive distillation]] of organic matter.
 
===Technology assessment===
: [[Technology assessment]] ('''TA''', German ''Technikfolgenabschätzung'') is the study and [[evaluation]] of new [[technology|technologies]].
 
===Technology life cycle===
: The [[Technology life cycle|technology maturity lifecycle]] is the commercial gain of a product from its research and development phase to its vital life phase before it becomes outdated and replaced.  More [[mature technology]] has been tested and tweaked so as to reduce faults and flaws
 
===Technology readiness level===
: [[Technology readiness level]] (TRL) is a measure used by some [[United States government]] agencies and many of the world's major companies (and agencies) to assess the [[Mature technology|maturity of evolving technologies]] (materials, components, devices, etc.) prior to incorporating that technology into a system or subsystem.
 
===Technology validation===
: Technology validation, confirming that technical targets for a given technology have been met.
 
===Temperature===
: [[Temperature]] is  a [[physics|physical]] property of a [[Physical system|system]] that underlies the common notions of hot and cold
 
===Terbium===
:  [[Terbium]] is used as a crystal stabilizer of [[fuel cell]]s which operate at elevated temperatures, together with [[zirconium(IV) oxide|ZrO<sub>2</sub>]].
 
===Thermal===
: [[Thermal]]
 
===Thermal conductivity===
: In [[physics]], [[thermal conductivity]], <math>k</math>, is the [[List of materials properties|property]] of a material that indicates its ability to conduct [[heat]].
 
===Thermal efficiency===
: In [[thermodynamics]], the [[thermal efficiency]] (<math>\eta_{th} \,</math>) is a [[Dimensionless quantity|dimensionless]] performance measure of a thermal device
 
===Thermal expansion===
: When the [[temperature]] of a substance changes, the energy that is stored in the [[intermolecular bond]]s 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===
: [[Partial_oxidation#TPOX|Thermal partial oxidation]] (TPOX) is a thermal [[partial oxidation]] reaction, which is dependent on the [[air-fuel ratio]], proceed at temperatures of 1200[[Celsius|°C]] and above.
 
===Thermoelectricity===
: [[Thermoelectricity]] is a class of phenomena in which a [[temperature]] difference creates an [[electric potential]] or an electric potential creates a temperature difference.
 
===Thermoplastic===
A [[thermoplastic]] is a [[plastic]] that  [[melting|melts]] to a liquid when heated and freezes to a [[brittle]], very [[glass]]y state when cooled sufficiently.
 
===Thermoplastic elastomer===
: [[Thermoplastic elastomers]] ('''TPE'''), sometimes referred to as '''thermoplastic rubbers''', are a class of [[copolymer]]s or a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both [[thermoplastic]] and [[elastomer]]ic properties.
 
===Transducer===
: A [[transducer]] is a device, usually [[electricity|electrical]], [[electronics|electronic]], [[electro-mechanical]],  [[Electromagnetism|electromagnetic]], [[photonic]], or [[photovoltaic]] that converts one type of energy or physical attribute to another for various purposes including measurement or information transfer (for example, [[pressure sensor]]s).
 
===Transfer switch===
A [[transfer switch]] allows [[switches|switching]] from a primary power source to a secondary or tertiary power source and are employed in some electrical power distribution systems.
 
===Transformer===
: A [[transformer]] is a device that transfers [[electrical energy]] from one [[Electrical network|circuit]] to another through [[inductive coupling|inductively coupled]] [[electrical conductor]]s.
 
===Triple phase boundary===
: [[Triple phase boundary]] (TPB)
 
===Triple point===
: In [[thermodynamics]], the [[triple point]] of a substance is the [[temperature]] and [[pressure]] at which three [[Phase (matter)|phases]] (for example, gas, liquid, and solid) of that substance coexist in [[thermodynamic equilibrium]].
 
===Turbine===
: A [[turbine]] is a rotary [[engine]] that extracts energy from a [[fluid]] flow.
 
===Turbocharger===
: [[Turbocharger]], a device used for increasing the pressure and [[density]] of a fluid entering a [[fuel cell]] power plant using a compressor driven by a turbine that extracts energy from the exhaust gas.
 
===Turbocompressor===
: [[Turbocompressor]], a machine for compressing air or other fluid ([[reactant]] if supplied to a [[fuel cell]] system) in order to increase the reactant pressure and concentration.
 
==U==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Ullage===
: [[Ullage]] is the unfilled space in a container of liquid.
 
===Uninterruptible power supply===
: An [[uninterruptible power supply]] ('''UPS'''), also known as a '''continuous power supply''' ('''CPS''') is a device which maintains a continuous supply of [[electric power]] to connected equipment by supplying power from a separate source when utility power is not available.
 
===Unitized regenerative fuel cell===
A [[unitized regenerative fuel cell]] (URFC) is a [[fuel cell]] based on the [[proton exchange membrane]] which can do the [[electrolysis of water]] in [[Regenerative fuel cell|regenerative mode]] and function in the other mode as a fuel cell recombining oxygen and [[hydrogen gas]] to produce electricity.
 
==V==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Vacuum pump===
: A [[vacuum pump]] is a device that removes gas molecules from a sealed volume in order to leave behind a partial [[vacuum]].
 
===Vapor–liquid equilibrium===
: [[Vapor–liquid equilibrium]], abbreviated as '''VLE''' by some, is a condition where a liquid and its [[vapor]] (gas phase) are in [[Chemical equilibrium|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 pressure===
: [[Vapor pressure]] (also known as ''equilibrium vapor pressure'' or ''saturation vapor pressure''), is the [[pressure]] of a [[vapor]] in [[Thermodynamic equilibrium|equilibrium]] with its non-vapor [[Phase (matter)|phase]]s.
 
===Vapor recovery===
: [[Vapor recovery]] (or '''vapour''') '''recovery''' is the [[wikt:process|process]] of [[wikt:recovery|recovering]] the [[vapor]]s of [[gasoline]] or other [[fuel]]s, so that they do not escape into the [[atmosphere]].
 
===Voltage===
: '''Electrical tension''' (or '''[[voltage]]''' after its [[SI unit]], the ''[[volt]]'') is the [[potential difference|difference of electrical potential]] between two points of an electrical or [[electronic circuit]], expressed in [[volt]]s.
 
===Voltage converter===
: A [[voltage converter]] changes the [[voltage]] of an electrical power source and is usually combined with other components to create a [[power supply]].
 
===Voltage drop===
: [[Voltage drop]] is the '''reduction''' in [[voltage]] in an [[electrical]] [[electrical network|circuit]] between the source and load.
 
===Voltage regulator===
: A [[voltage regulator]] is an [[electricity|electrical]] [[regulator (automatic control)|regulator]] designed to automatically maintain a constant [[voltage]] level.
 
===Volumetric energy density===
: Volumetric [[energy density]], potential energy in a given [[volume]] of [[fuel]].
 
===Volumetric flow rate===
: The [[volumetric flow rate]] in [[fluid dynamics]] and [[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]] [m<sup>3</sup> s<sup>−1</sup>] in [[SI]] units, or [[cubic foot|cubic feet]] per second [cu ft/s]). It is usually represented by the symbol ''Q''.
 
===Volumetric heat capacity===
: [[Volumetric heat capacity]] (VHC) is the ability of a given [[volume]] of a substance to store [[internal energy]] while undergoing a given [[temperature]] change, but without undergoing a [[phase transition]].
 
==W==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Water===
: [[Water]] (H<sub>2</sub>O) in typical usage, ''water'' refers only to its liquid form or [[States of matter|state]], but the substance also has a solid state, ''[[ice]]'', and a [[gaseous]] state, ''[[water vapor]]'' or ''[[steam]]''.
 
===Water gas shift reaction===
: The [[water gas shift reaction]] (WGS) is a [[chemical reaction]] in which [[carbon monoxide]] reacts with [[water]] to form [[carbon dioxide]] and [[hydrogen]]
 
===Water purification===
: [[Water purification]] is the process of removing contaminants and other harmful microorganisms from a raw water source.
 
===Water vapor===
: [[Water vapor]] or '''water vapour''' (see [[American and British English spelling differences|spelling differences]]), also ''aqueous vapor'', is the gas phase of [[water (molecule)|water]].
 
===Watt===
: The [[watt]] (symbol: '''W''') is the [[SI]] [[SI derived unit|derived unit]] of [[power (physics)|power]], equal to one [[joule]] of energy per [[second]]. It measures a rate of energy use or production.
 
===Wet basis===
: It is customary to report the product composition data in steam reforming reactions on a steam free basis ([[dry basis]]) since the steam is not a constituent in any of the [[synthesis gas]]es produced or in the reformed gas when used as a fuel;<ref name="zulekha"/> however, if steam is to be considered in the product composition data as well, then the calculation would be [[wet basis]].
 
===W/kg===
: Kilowatts per [[kilogram]] (generally, [[Watt|W]]/[[kg]]).The [[Power_density#Power_per_unit_of_mass|power per unit of mass]] in relation to the [[power-to-weight ratio]].
 
===Wt.%===
: In [[hydrogen storage]] research, [[weight percent]] (wt.%, also called ''mass percent'') is the amount of hydrogen stored on a weight basis. This can apply to 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, [[regulator (disambiguation)|regulator]]s, 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.
 
==X==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
{{Empty section|date=July 2010}}
 
==Y==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Yttria-stabilized zirconia===
: [[Yttria-stabilized zirconia]] (YSZ) is a [[zirconium dioxide|zirconium-oxide]] based ceramic
 
==Z==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
===Zinc-air battery===
: A [[Zinc-air battery]] (non-rechargeable), and zinc-air [[fuel cell]]s, (mechanically-rechargeable) are [[Battery (electricity)|electro-chemical batteries]] powered by the [[oxidation]] of [[zinc]] with [[oxygen]] from the air.
 
===Zinc oxide===
: [[Zinc oxide]] is a [[chemical compound]] with the [[Chemical formula|formula]] ZnO. ([[sulfur]] sorbent)
 
==Acronyms==
{{Compact ToC|short1|top=yes|custom1=Acronyms}}
 
{| class="wikitable"
![[Acronym]]!! –
|-
|'''AAEM'''  || [[alkali anion exchange membrane]]
|-
|'''AC'''  || [[alternating current]]
|-
|'''AFC''' || [[alkaline fuel cell]]
|-
|'''ATR'''||[[autothermal reforming]]
|-
|'''APU'''||[[auxiliary power unit]]
|-
|'''BASE'''||[[beta-alumina solid electrolyte]]
|-
|'''BOP'''||[[balance of plant]]
|-
|'''BTU'''||[[British thermal unit]]
|-
|'''°C'''||[[celsius]]
|-
|'''C'''||[[carbon]]
|-
|'''C'''||[[coulomb]]
|-
|'''ca. or c.'''||[[circa]]
|-
|'''CGH<sub>2</sub>'''||[[compressed hydrogen]]
|-
|'''CH<sub>4</sub>'''||[[methane]]
|-
|'''CH<sub>3</sub>CH<sub>2</sub>OH'''||[[ethanol]]
|-
|'''CH<sub>3</sub>OH'''||[[methanol]]
|-
|'''CHP''' ||[[combined heat and power]]
|-
|'''CI''' ||[[chloride ion]]
|-
|'''CNG'''||[[compressed natural gas]]
|-
|'''CNT'''||[[carbon nanotube]]
|-
|'''CO<sub>2</sub>'''||[[carbon dioxide]]
|-
|'''CO'''||[[carbon monoxide]]
|-
|'''CPOX'''||[[catalytic partial oxidation]]
|-
|'''CPS'''||[[continuous power supply]]
|-
|'''DBFC'''||[[direct borohydride fuel cell]]
|-
|'''DC''' ||[[direct current]]
|-
|'''DCFC'''||[[direct carbon fuel cell]]
|-
|'''DEFC'''||[[direct-ethanol fuel cell]]
|-
|'''DER''' ||[[distributed energy resource]]
|-
|'''DFAFC'''||[[formic acid fuel cell]]
|-
|'''DMFC'''||[[direct methanol fuel cell]]
|-
|'''E<sup>0</sup>'''||[[standard electrode potential]]
|-
|'''EBOP'''||[[electrical balance of plant]]
|-
|'''EGFC'''||[[electro-galvanic fuel cell]]
|-
|'''EOF'''||[[electroosmotic flow]]
|-
|'''EOP'''||[[electroosmotic pump]]
|-
|'''°F''' ||[[fahrenheit]]
|-
|'''FB''' || [[flow battery]]
|-
|'''FC''' ||[[fuel cell]]
|-
|'''FGD''' ||[[flue-gas desulfurization]]
|-
|'''FMEA''' || [[failure mode and effects analysis]]
|-
|'''FPS'''||[[fuel processing system]]
|-
|'''GDC''' ||[[gadolinium]] [[Doping (semiconductor)|doped]] [[ceria]]
|-
|'''GEG'''||[[gasoline-equivalent gallon]]
|-
|'''GGE'''||[[gasoline gallon equivalent]]
|-
|'''GHSV'''|| gas hourly space velocity (see [[Space velocity (chemistry)|space velocity]])
|-
|'''H<sub>2</sub>'''||[[hydrogen]]
|-
|'''H<sub>2</sub>O'''||[[water]]
|-
|'''HC''' ||[[hydrocarbon]]
|-
|'''HCDP'''||[[hydrocarbon dew point]]
|-
|'''HCOOH'''||[[formic acid]]
|-
|'''HDP'''||[[hydrocarbon dew point]]
|-
|'''HDS'''||[[hydrodesulfurization]]
|-
|'''HEV''' ||[[hybrid electric vehicle]]
|-
|'''HHV'''  ||[[higher heating value]]
|-
|'''HTS''' ||[[high temperature shift]]
|-
|'''ICE'''||[[internal combustion engine]]
|-
|'''IMFC''' ||[[indirect methanol fuel cell]]
|-
|'''KG''' ||[[kilogram]]
|-
|'''KOH''' ||[[potassium hydroxide]]
|-
|'''kW'''||[[kilowatt]]
|-
|'''kWh'''||[[kilowatt hour]]
|-
|'''kW/kg'''||[[Kilowatt]]s per [[kilogram]]
|-
|'''kW/m3'''||[[Kilowatt]]s per [[cubic meter]]
|-
|'''kW/sq.m'''||[[Kilowatt]]s per [[square meter]]
|-
|'''LCA'''||[[life cycle assessment]]
|-
|'''LDH'''||[[layered double hydroxide]]
|-
|'''LEL'''||[[lower explosive limit]]
|-
|'''LFG'''||[[landfill gas]]
|-
|'''LFL''' ||[[lower flammable limit]]
|-
|'''LH<sub>2</sub>''' ||[[liquid hydrogen]]
|-
|'''LHSV'''|| liquid hourly space velocity (see [[Space velocity (chemistry)|space velocity]])
|-
|'''LHV''' ||[[lower heating value]]
|-
|'''LNG''' ||[[liquefied natural gas]]
|-
|'''LOD''' ||[[limit of detection]]
|-
|'''LPG''' || [[liquefied petroleum gas]]
|-
|'''LSM''' ||[[lanthanum strontium manganite]]
|-
|'''LTS'''||[[low temperature shift]]
|-
|'''MAF'''||[[mass flow sensor]]
|-
|'''MAOP''' ||[[maximum allowable operating pressure]]
|-
|'''MBOP'''||[[mechanical balance of plant]]
|-
|'''MCFC'''||[[molten-carbonate fuel cell]]
|-
|'''mCHP'''||[[micro combined heat and power]]
|-
|'''MDT'''||[[mean down time]]
|-
|'''MEA'''||[[membrane electrode assembly]]
|-
|'''MeOH'''||[[methanol]]
|-
|'''MFC'''||[[microbial fuel cell]]
|-
|'''mm''' ||[[millimeter]]
|-
|'''MPGe''' ||[[miles per gallon of gasoline equivalent]]
|-
|'''MRO''' ||[[maintenance, repair and operations]]
|-
|'''MSR''' ||[[methanol steam reforming]]
|-
|'''MTBF'''||[[mean time between failures]]
|-
|'''MTBO'''||[[mean time between outages]]
|-
|'''MW''' ||[[megawatt]]
|-
|'''mW'''||[[milliwatt]]
|-
|'''N<sub>2</sub>'''||[[nitrogen]]
|-
|'''NEG''' || [[net energy gain]]
|-
|'''NO<sub>x</sub>'''||[[nitrogen oxide]]
|-
|'''O''' ||[[oxygen]]
|-
|'''OCV'''||[[open-circuit voltage]]
|-
|'''OEM'''||[[original equipment manufacturer]]
|-
|'''Pa'''||[[pascal (unit)|pascal]]
|-
|'''PAFC'''||[[phosphoric acid fuel cell]]
|-
|'''PBI'''||[[polybenzimidazole]] fiber
|-
|'''PCFC'''||[[protonic ceramic fuel cell]]
|-
|'''Pd'''||[[palladium]]
|-
|'''p.d.'''||[[potential difference]]
|-
|'''PEC''' ||[[photoelectrochemical cell]]
|-
|'''PEDOT'''||[[poly(3,4-ethylenedioxythiophene)]]
|-
|'''PEDT''' ||[[poly(3,4-ethylenedioxythiophene)]]
|-
|'''PEFC''' ||[[polymer electrolyte membrane fuel cell]]
|-
|'''PEM''' ||[[polymer electrolyte membrane]] or [[proton exchange membrane]]
|-
|'''PEMFC'''||[[polymer electrolyte membrane fuel cell]] or [[proton exchange membrane fuel cell]]
|-
|'''PM'''||[[Atmospheric particulate matter|particulate matter]]
|-
|'''POX''' ||[[partial oxidation]]
|-
|'''ppm''' ||[[parts per million]]
|-
|'''ppmv''' ||[[parts per million volume]]
|-
|'''PROX'''||[[preferential oxidation]]
|-
|'''PRV'''||[[pressure relief valve]]
|-
|'''PSA'''||[[pressure swing adsorption]]
|-
|'''PSU''' ||[[power supply]] unit
|-
|'''Pt''' ||[[platinum]]
|-
|'''PTFE''' ||[[polytetrafluoroethylene]]
|-
|'''Pv''' ||[[power density]]
|-
|'''Re''' ||[[reynolds number]]
|-
|'''RESS''' ||[[rechargeable energy storage system]]
|-
|'''RFC'''||[[reversible fuel cell]]
|-
|'''RMFC'''||[[reformed methanol fuel cell]]
|-
|'''RWGS'''|| reversed [[water-gas shift reaction]]
|-
|'''s/c'''||[[short circuit]] or [[steam to carbon ratio]] (carbon = hydrocarbon used for SR)
|-
|'''SFC''' || [[standard cubic foot]] or sometimes [[solid oxide fuel cell]]
|-
|'''SMPS'''||[[switched-mode power supply]]
|-
|'''SMR'''||[[steam methane reforming]]
|-
|'''SOEC'''||[[solid oxide electrolyser cell]]
|-
|'''SOFC'''||[[solid oxide fuel cell]]
|-
|'''SR'''||[[steam reforming]]
|-
|'''TA''' || [[technology assessment]]
|-
|'''TGC''' ||[[tail-gas combustor]]
|-
|'''TOF''' ||[[turnover frequency]]
|-
|'''TOS''' || [[time on stream]] (also T.O.S)
|-
|'''TPB''' ||[[triple-phase boundary]]
|-
|'''TPE''' ||[[thermoplastic elastomers]]
|-
|'''TPOX'''||[[Partial oxidation|thermal partial oxidation]]
|-
|'''TRL'''||[[technology readiness level]]
|-
|'''UEL'''||[[upper explosive limit]]
|-
|'''UPS''' ||[[uninterruptible power supply]]
|-
|'''URFC''' ||[[unitized regenerative fuel cell]]
|-
|'''VHC'''||[[volumetric heat capacity]]
|-
|'''VLE'''||[[vapor–liquid equilibrium]]
|-
|'''W'''||[[watt]]
|-
|'''WGS'''||[[water–gas shift reaction]]
|-
|'''WHSV'''|| weight hourly space velocity (see [[Space velocity (chemistry)|space velocity]])
|-
|'''Wt.%'''||[[weight percent]]
|-
|'''YSZ'''||[[yttria-stabilized zirconia]]
|-
|'''ZnO'''||[[zinc oxide]]
|}
 
==References==
{{Reflist}}
 
[[Category:Glossaries|Fuel cell terms]]
[[Category:Fuel cells| ]]

Revision as of 16:40, 26 February 2014

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