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.
Adsorption is a process that occurs when a gas or liquid
solute accumulates on the surface of a solid or a liquid (adsorbent), forming a film of molecules or atoms (the
adsorbate).
The
atom is the smallest unit of an
element that retains the chemical properties of that element. An atom has an
electron cloud consisting of negatively
chargedelectrons surrounding a dense
nucleus. The nucleus contains positively charged
protons and electrically neutral
neutrons.
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.
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 is a combination of two or more
electrochemical cells which store chemical energy and make it available as electrical energy.
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 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
MEA.
Black start
A
black start is the process of restoring a
power station to operation without relying on external energy sources.
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 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 (450 g) of
water from 32 to 212 °F (0 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 (5⁄9°C).
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
nameplate capacity the entire time.
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.
A
carbon dioxide sensor (CO2) is an instrument for the measurement of
carbon dioxide gas. The most common principles for CO2 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.
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.
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
reforming technique depends on the
sulfur content of the fuel being used. CPOX can be employed if the sulfur content is below 50
ppm. A higher sulfur content would poison the catalyst, so the TPOX procedure is used for such fuels.
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(a difference between two temperatures or an
uncertainty).
A
centrifugal governor is a specific type of
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
load or fuel supply conditions.
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
flames.
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.
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).
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 limit (generally 1%).
Diffusion is part of
transport phenomena. Diffusion is the movement of molecules from a region of higher concentration to one of lower concentration by random molecular motion.
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 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 gases produced or in the reformed gas when used as a fuel;[1] however, if steam is to be considered in the product composition data as well, then the calculation would be
wet basis.
An
electrical insulator is a material that resists the flow of
electric current. It is an object intended to support or separate electrical
conductors without passing current through itself.
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.
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.
In
physics and other
sciences, energy is a
scalarphysical quantity that is a property of objects and systems which is conserved by nature. Energy is often defined as the ability to do
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 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
The
enthalpy of vaporization, (symbol ), also known as the heat of vaporization or heat of evaporation, is the energy required to transform a given quantity of a substance into a gas.
Ethanol
Ethanol, also called ethyl alcohol, grain alcohol, or drinking alcohol, is a
volatile,
flammable, colorless liquid.
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.
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.
A mechanical
fan is an electrically powered device used to produce an airflow for the purpose of creature comfort (particularly in the heat),
ventilation, exhaust, or any other gaseous transport.
A
failure mode and effects analysis (FMEA) is a 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 it can charge from an external source as well as from its on-board
fuel cell.
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.
Fluid mechanics is the study of how
fluids move and the
forces on them. (Fluids include liquids and gases.) Fluid mechanics can be divided into
fluid statics, the study of fluids at rest, and
fluid dynamics, the study of fluids in motion.
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 gases (LPG) as used in this standard, shall mean and include any material which is composed predominantly of any of the following
hydrocarbons, or mixtures of them: propane, propylene, butanes (normal butane or isobutane) and butylenes.
LP gas–air mixture – Liquefied petroleum gases distributed at relatively low pressures and normal atmospheric temperatures which have been diluted with air to produce desired heating value and utilization characteristics.
Natural gas – Mixtures of hydrocarbon gases and vapors consisting principally of
methane (CH4) in gaseous form.
Gas 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 electrodes are electrodes with a conjunction of a solid, liquid and gaseous interface, and an electrical conducting catalyst supporting an electrochemical reaction between the liquid and the gaseous phase.
Gases in the Earth's atmosphere that contribute to the
greenhouse effect, effectively absorbing thermal
infrared radiation, emitted by the
Earth’s surface
Greenhouse gases
Warming of the Earth's atmosphere due to
greenhouse gases in the atmosphere that allow solar radiation (visible, ultraviolet) to reach the Earth's atmosphere but do not allow the emitted infrared radiation to pass back out of the Earth's atmosphere.
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 electrical grid.
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.
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 °C) once it is
combusted and the products have returned to a temperature of 25 °C.
Interlocking is a method of preventing undesired states in a
state machine, which in a general sense can include any electrical, electronic, or mechanical device or system.
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.
Kröger–Vink notation is set of conventions used to describe electrical charge and lattice position for point
defect species in
crystals.
Kilogram
The
kilogram or kilogramme (symbol: kg) is the
base unit of
mass in the
International System of Units (known also by its French-language initials “SI”). The kilogram is almost exactly equal to the mass of one
liter of water.
Kilowatt
The
kilowatt (symbol: kW), equal to one thousand watts, is typically used to state the power output of engines and the power consumption of tools and machines.
Kilowatt hour
The
kilowatt hour, also written kilowatt-hour (symbol kW·h, kW h or kWh) is a unit of energy.
A
life cycle assessment (LCA, also known as life cycle analysis, ecobalance, and cradle-to-grave analysis) is the investigation and valuation of the
environmental impacts of a given product or service caused or necessitated by its existence.
In
physics, to
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
contaminating substances. The following
list of chemical purification methods should not be considered exhaustive.
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.
Mean time between failures (MTBF) is the
mean (average) time between
failures of a system, and is often attributed to the "useful life" of the device i.e. not including 'infant mortality' or 'end of life' if the device is not repairable.
The
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.
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.
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
impedance. This is helpful in analysing the voltage drop which occurs as current is drawn.
When the
voltage in a
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
redoxchemical reaction. In both cases, the oxidizing agent becomes
reduced in the process.
Palladium is a rare and lustrous silvery-white metal with the symbol Pd, and its
atomic number is 46.
Parallel circuit
Parallel circuit, if two or more components are connected in parallel they have the same potential difference (
voltage) across their ends. The potential differences across the components are the same in magnitude, and they also have identical polarities. Hence, the same voltage is applicable to all circuit components connected in parallel.
In a mixture of
ideal gases, each gas has a
partial 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
particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas.
Parts per million
Parts per million (ppm) denotes the amount of a given substance in a total amount of 1,000,000 regardless of the units of measure used as long as they are the same. e.g. 1 milligram per kilogram. 1 part in 106.
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.
In
physics,
power (symbol: P) is the rate at which
work is performed or
energy is transmitted, or the amount of energy required or expended for a given unit of time.
The
power factor of an
AC electric power system is defined as the
ratio of the
real power to the
apparent power, and is a number between 0 and 1 (frequently expressed as a percentage, e.g. 0.5 pf = 50% pf).
Power-to-weight ratio (specific power) is a calculation commonly applied to
engines and other mobile power sources to enable the comparison of one unit or design to another.
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 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-
carbonalkane, normally a gas, but compressible to a liquid that is transportable. See also
LPG.
A hydrogen
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.
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.
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 circuits are sometimes called current-coupled or
daisy chain-coupled. The
current that flows in a series circuit has to flow through every component in the circuit. Therefore, all of the components in a series connection carry the same current. It has been noted that current flows in series.
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
current along a different path from the one intended.
Specific gravity is defined as the ratio of the
density of a given solid or liquid substance to the density of
H2O at a specific temperature and pressure, typically at 4 °C (39 °F) and 1
atm (29.92
inHg), making it a dimensionless quantity
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.
In
electrochemistry, the
standard electrode potential, abbreviated Eo, E0, or EO (with a superscript
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).
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).
Syngas (from synthesis 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.
The
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
When the
temperature of a substance changes, the energy that is stored in the
intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bonds. As a result, solids typically expand in response to heating and contract on cooling; this dimensional response to temperature change is expressed by its coefficient of
thermal expansion.
Thermoplastic elastomers (TPE), sometimes referred to as thermoplastic rubbers, are a class of
copolymers or a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both
thermoplastic and
elastomeric properties.
A
transfer switch allows
switching from a primary power source to a secondary or tertiary power source and are employed in some electrical power distribution systems.
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.
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.
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
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.
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 [m3 s−1] in
SI units, or
cubic feet per second [cu ft/s]). It is usually represented by the symbol Q.
Water (H2O) in typical usage, water refers only to its liquid form or
state, but the substance also has a solid state, ice, and a
gaseous state, water vapor or steam.
The
watt (symbol: W) is the
SIderived unit of
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 gases produced or in the reformed gas when used as a fuel;[1] however, if steam is to be considered in the product composition data as well, then the calculation would be
wet basis.
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,
regulators, etc.). For example, 6 wt.% on a system-basis means that 6% of the entire system by weight is hydrogen. On a material basis, the wt.% is the mass of hydrogen divided by the mass of material plus hydrogen.
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.
Adsorption is a process that occurs when a gas or liquid
solute accumulates on the surface of a solid or a liquid (adsorbent), forming a film of molecules or atoms (the
adsorbate).
The
atom is the smallest unit of an
element that retains the chemical properties of that element. An atom has an
electron cloud consisting of negatively
chargedelectrons surrounding a dense
nucleus. The nucleus contains positively charged
protons and electrically neutral
neutrons.
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.
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 is a combination of two or more
electrochemical cells which store chemical energy and make it available as electrical energy.
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 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
MEA.
Black start
A
black start is the process of restoring a
power station to operation without relying on external energy sources.
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 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 (450 g) of
water from 32 to 212 °F (0 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 (5⁄9°C).
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
nameplate capacity the entire time.
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.
A
carbon dioxide sensor (CO2) is an instrument for the measurement of
carbon dioxide gas. The most common principles for CO2 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.
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.
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
reforming technique depends on the
sulfur content of the fuel being used. CPOX can be employed if the sulfur content is below 50
ppm. A higher sulfur content would poison the catalyst, so the TPOX procedure is used for such fuels.
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(a difference between two temperatures or an
uncertainty).
A
centrifugal governor is a specific type of
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
load or fuel supply conditions.
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
flames.
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.
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).
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 limit (generally 1%).
Diffusion is part of
transport phenomena. Diffusion is the movement of molecules from a region of higher concentration to one of lower concentration by random molecular motion.
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 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 gases produced or in the reformed gas when used as a fuel;[1] however, if steam is to be considered in the product composition data as well, then the calculation would be
wet basis.
An
electrical insulator is a material that resists the flow of
electric current. It is an object intended to support or separate electrical
conductors without passing current through itself.
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.
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.
In
physics and other
sciences, energy is a
scalarphysical quantity that is a property of objects and systems which is conserved by nature. Energy is often defined as the ability to do
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 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
The
enthalpy of vaporization, (symbol ), also known as the heat of vaporization or heat of evaporation, is the energy required to transform a given quantity of a substance into a gas.
Ethanol
Ethanol, also called ethyl alcohol, grain alcohol, or drinking alcohol, is a
volatile,
flammable, colorless liquid.
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.
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.
A mechanical
fan is an electrically powered device used to produce an airflow for the purpose of creature comfort (particularly in the heat),
ventilation, exhaust, or any other gaseous transport.
A
failure mode and effects analysis (FMEA) is a 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 it can charge from an external source as well as from its on-board
fuel cell.
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.
Fluid mechanics is the study of how
fluids move and the
forces on them. (Fluids include liquids and gases.) Fluid mechanics can be divided into
fluid statics, the study of fluids at rest, and
fluid dynamics, the study of fluids in motion.
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 gases (LPG) as used in this standard, shall mean and include any material which is composed predominantly of any of the following
hydrocarbons, or mixtures of them: propane, propylene, butanes (normal butane or isobutane) and butylenes.
LP gas–air mixture – Liquefied petroleum gases distributed at relatively low pressures and normal atmospheric temperatures which have been diluted with air to produce desired heating value and utilization characteristics.
Natural gas – Mixtures of hydrocarbon gases and vapors consisting principally of
methane (CH4) in gaseous form.
Gas 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 electrodes are electrodes with a conjunction of a solid, liquid and gaseous interface, and an electrical conducting catalyst supporting an electrochemical reaction between the liquid and the gaseous phase.
Gases in the Earth's atmosphere that contribute to the
greenhouse effect, effectively absorbing thermal
infrared radiation, emitted by the
Earth’s surface
Greenhouse gases
Warming of the Earth's atmosphere due to
greenhouse gases in the atmosphere that allow solar radiation (visible, ultraviolet) to reach the Earth's atmosphere but do not allow the emitted infrared radiation to pass back out of the Earth's atmosphere.
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 electrical grid.
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.
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 °C) once it is
combusted and the products have returned to a temperature of 25 °C.
Interlocking is a method of preventing undesired states in a
state machine, which in a general sense can include any electrical, electronic, or mechanical device or system.
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.
Kröger–Vink notation is set of conventions used to describe electrical charge and lattice position for point
defect species in
crystals.
Kilogram
The
kilogram or kilogramme (symbol: kg) is the
base unit of
mass in the
International System of Units (known also by its French-language initials “SI”). The kilogram is almost exactly equal to the mass of one
liter of water.
Kilowatt
The
kilowatt (symbol: kW), equal to one thousand watts, is typically used to state the power output of engines and the power consumption of tools and machines.
Kilowatt hour
The
kilowatt hour, also written kilowatt-hour (symbol kW·h, kW h or kWh) is a unit of energy.
A
life cycle assessment (LCA, also known as life cycle analysis, ecobalance, and cradle-to-grave analysis) is the investigation and valuation of the
environmental impacts of a given product or service caused or necessitated by its existence.
In
physics, to
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
contaminating substances. The following
list of chemical purification methods should not be considered exhaustive.
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.
Mean time between failures (MTBF) is the
mean (average) time between
failures of a system, and is often attributed to the "useful life" of the device i.e. not including 'infant mortality' or 'end of life' if the device is not repairable.
The
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.
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.
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
impedance. This is helpful in analysing the voltage drop which occurs as current is drawn.
When the
voltage in a
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
redoxchemical reaction. In both cases, the oxidizing agent becomes
reduced in the process.
Palladium is a rare and lustrous silvery-white metal with the symbol Pd, and its
atomic number is 46.
Parallel circuit
Parallel circuit, if two or more components are connected in parallel they have the same potential difference (
voltage) across their ends. The potential differences across the components are the same in magnitude, and they also have identical polarities. Hence, the same voltage is applicable to all circuit components connected in parallel.
In a mixture of
ideal gases, each gas has a
partial 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
particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas.
Parts per million
Parts per million (ppm) denotes the amount of a given substance in a total amount of 1,000,000 regardless of the units of measure used as long as they are the same. e.g. 1 milligram per kilogram. 1 part in 106.
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.
In
physics,
power (symbol: P) is the rate at which
work is performed or
energy is transmitted, or the amount of energy required or expended for a given unit of time.
The
power factor of an
AC electric power system is defined as the
ratio of the
real power to the
apparent power, and is a number between 0 and 1 (frequently expressed as a percentage, e.g. 0.5 pf = 50% pf).
Power-to-weight ratio (specific power) is a calculation commonly applied to
engines and other mobile power sources to enable the comparison of one unit or design to another.
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 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-
carbonalkane, normally a gas, but compressible to a liquid that is transportable. See also
LPG.
A hydrogen
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.
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.
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 circuits are sometimes called current-coupled or
daisy chain-coupled. The
current that flows in a series circuit has to flow through every component in the circuit. Therefore, all of the components in a series connection carry the same current. It has been noted that current flows in series.
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
current along a different path from the one intended.
Specific gravity is defined as the ratio of the
density of a given solid or liquid substance to the density of
H2O at a specific temperature and pressure, typically at 4 °C (39 °F) and 1
atm (29.92
inHg), making it a dimensionless quantity
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.
In
electrochemistry, the
standard electrode potential, abbreviated Eo, E0, or EO (with a superscript
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).
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).
Syngas (from synthesis 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.
The
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
When the
temperature of a substance changes, the energy that is stored in the
intermolecular bonds between atoms changes. When the stored energy increases, so does the length of the molecular bonds. As a result, solids typically expand in response to heating and contract on cooling; this dimensional response to temperature change is expressed by its coefficient of
thermal expansion.
Thermoplastic elastomers (TPE), sometimes referred to as thermoplastic rubbers, are a class of
copolymers or a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both
thermoplastic and
elastomeric properties.
A
transfer switch allows
switching from a primary power source to a secondary or tertiary power source and are employed in some electrical power distribution systems.
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.
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.
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
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.
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 [m3 s−1] in
SI units, or
cubic feet per second [cu ft/s]). It is usually represented by the symbol Q.
Water (H2O) in typical usage, water refers only to its liquid form or
state, but the substance also has a solid state, ice, and a
gaseous state, water vapor or steam.
The
watt (symbol: W) is the
SIderived unit of
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 gases produced or in the reformed gas when used as a fuel;[1] however, if steam is to be considered in the product composition data as well, then the calculation would be
wet basis.
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,
regulators, etc.). For example, 6 wt.% on a system-basis means that 6% of the entire system by weight is hydrogen. On a material basis, the wt.% is the mass of hydrogen divided by the mass of material plus hydrogen.