Active area

The area of a fuel cell electrode which is electrochemically active and able to produce electricity from the supplied fuel.

Alkaline fuel cell (AFC)

Alkaline fuel cells (AFC), also known as the Bacon fuel cell after its British inventor, were one of the first fuel cell technologies developed, and they were the first type widely used by NASA to produce electrical energy and water on-board spacecrafts. These fuel cells use a solution of potassium hydroxide in water as the electrolyte and can use a variety of non-precious metals as a catalyst at the anode and cathode. High-temperature AFCs operate at temperatures between 100°C and 250°C (212°F and 482°F). However, newer AFC designs operate at lower temperatures of roughly 23°C to 70°C (74°F to 158°F) AFCs’ high performance is due to the rate at which chemical reactions take place in the cell. They have also demonstrated efficiencies near 60% in space applications. The disadvantage of this fuel cell type is that it is easily poisoned by carbon dioxide (CO2). In fact, even the small amount of CO2 in the air can affect this cell’s operation, making it necessary to purify both the hydrogen and oxygen used in the cell. This purification process is costly. Susceptibility to poisoning also affects the cell’s lifetime (the amount of time before it must be replaced), further adding to cost. Cost is less of a factor for remote locations, such as space or under the sea. However, to effectively compete in most mainstream commercial markets, these fuel cells will have to become more cost-effective. AFC stacks have been shown to maintain sufficiently stable operation for more than 8,000 operating hours. To be economically viable in large-scale utility applications, these fuel cells need to reach operating times exceeding 40,000 hours, something that has not yet been achieved due to material durability issues. This obstacle is possibly the most significant in commercializing this fuel cell technology.


The fuel electrode in a fuel cell at which oxidation occurs.


An auxiliary power unit (for example a fuel cell) provides electricity and is supplemental to the main power source of a vehicle (such as an internal combustion engine).



The balance of plant in a fuel cell system is the auxiliary equipment required to ensure the fuel cell operates as a reliable power source. This may include fuel reformers and pumps, for example.

Bipolar plate

A fuel cell stack component which allows electricity to be conducted between adjacent fuel cell membrane electrode assemblies in a stack. They are often designed to channel the flow of gases and heat to and from the cell.


Fuel cell in German language



A catalyst increases the rate of a reaction without itself being consumed. In a fuel cell catalysts are used for the electrodes (to break down hydrogen into electrons and protons).

Catalyst loading

This refers to the mass of catalyst per unit area of a fuel cell electrode.


The oxygen/air electrode in a fuel cell where reduction occurs.


Combined cooling, heat and power utilises the waste heat from the fuel cell with absorption chillers to provide air conditioning and hot or cold water alongside electricity.


Combined heat and power is a way to make even more efficient use of fuel cells. The waste heat from the electricity production is used to heat water or for space heating.

Commercially available

Fuel Cell Today considers a fuel cell commercially available if it is: 1 Offered for sale to the public. 2 Offered with a written warranty, supported by service capability. 3 Meets approved industry standards or is certified by an established industry body.


Combined water and power is similar to CHP, but in this instance the waste heat is used to produce potable water.


Direct methanol fuel cell (DMFC)

A direct methanol fuel cell functions in a similar way to a PEMFC and uses the same electrolyte, but reforms methanol directly on its electrode to form hydrogen.

Distributed generation

The production of electrical power close to the end user.



The electrode is where reaction of a chemical species occurs and electrons are either released or accepted.


An electrochemical device which works like a fuel cell in reverse and can split water into its constituent molecules, hydrogen and oxygen, by passing an electric current through it.


A substance which carries charge via the migration of ions; together with the external connections of a fuel cell, an electrical circuit can be created.



Fuel cell electric vehicle.

Fuel cell

A fuel cell is an electrochemical device, which converts chemical energy to electrical energy without combustion. Unlike a battery, a fuel cell will continuously produce electricity as long as fuel is supplied and the catalyst remains active.



Gas diffusion layers, typically made out of carbon paper or cloth, play a number of important roles in a fuel cell, such as structural support, reactant transport, water removal, and heat conduction.



Hydrogen is the fuel most commonly used in fuel cells.

High temperature proton exhange membrane fuel cell (HT PEMFC)

A variant of the PEMFC which uses a mineral acid based electrolyte rather than an aqueous one and can operate at temperatures up to 200°C. These cells are more tolerant to impurities in the fuel as a result.

Hydrogen economy

The hydrogen economy is a scenario where the world uses hydrogen as the primary energy carrier in place of fossil fuels. Hydrogen would be used to provide electrical power, heat homes and power vehicles. Ideally this hydrogen would be generated from renewable energy, resulting in zero emissions.


Island, Islanding, Off Grid

Relates to distributed generation where local generators continue to power a location when power from the electricity grid is no longer present. When a fuel cell is grid-connected, islanding (isolation) of the fuel cell is required to allow safe work at that location.



The joule is a derived unit of energy in the International System of Units. It is equal to the energy transferred to an object when a force of one newton acts on that object in the direction of the force's motion through a distance of one metre.



Kilowatt, a unit of power equal to 1,000 watts.


Kilowatt electric, a measure of electric power output.

kWth / kWt

Kilowatt thermal, a unit of thermal (heat) power output.


Kilowatt-hour, a unit of energy. A device with a power output of one kilowatt running for one hour would generate one kilowatt-hour of energy.


Load following

A load-following fuel cell generates variable amounts of electrical power depending on the requirements of the devices it is powering.


Low emission vehicles are light duty passenger vehicles meeting strict emissions regulations in California. These can be divided into a number of sub-categories including ultra-low emissions vehicles (ULEV), super-ultra-low emissions vehicles (SULEV), partial zero emissions vehicles (PZEV) or zero emission vehicles (ZEV).



Membrane electrode assembly, a structured component in a PEM-FC and DM-FC, consisting of a membrane with an electrode on each side.

Membrane (at FuelCell)

This separates two electrodes of a fuel cell, acting as the electrolyte and allowing passage of ions between the electrodes.


Methanol is a fuel used in Methanol Fuel Cells

Micro CHP

Micro-combined heat and power fuel cells refer to stationary units designed to provide electricity, hot water and sometimes space heating. These can either be for residential use or for small offices and commercial buildings.

Molten carbonate fuel cell (MCFC)

Molten carbonate fuel cells (MCFC) are currently being developed for natural gas, biogas (produced as a result of anaerobic digestion or biomass gasification), and coal-based power plants for electrical utility, industrial, and military applications. MCFCs are high-temperature fuel cells, operating at temperatures of 600 °C and above, that use an electrolyte composed of a molten carbonate salt mixture suspended in a porous, chemically inert ceramic matrix of beta-alumina solid electrolyte (BASE). Because they operate at extremely high temperatures of 650°C (roughly 1,200°F) and above, non-precious metals can be used as catalysts at the anode and cathode, reducing costs.



Nationale Organisation Wasserstoff- und Brennstoffzellentechnologie. Based in Germany and founded in 2008, this state organisation coordinates and manages market preparation programmes for products and applications based on hydrogen, fuel cell and battery electric powertrain technology.


O2 , Oxygen, Ambien Air Oxigen

Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. At Fuel Cell O2 act as a reactant to H2.


Pd , Palladium

Palladium is one of the platinum group metals and can be used for the purification of reformed hydrogen for fuel cells.

Phosphoric acid fuel cell (PAFC)

Phosphoric Acid Fuel Cells (PAFC) use liquid phosphoric acid as an electrolyte—the acid is contained in a Teflon-bonded silicon carbide matrix—and porous carbon electrodes containing a platinum catalyst.

Pile a combustibile

Fuel cell in Italian language.

Pile à combustible

Fuel cell in French language.

Palivový článek

Fuel Cell in Czech language.

Planar Solid Oxide Fuel Cell

SOFCs can have multiple geometries. The planar geometry is the typical sandwich type geometry employed by most other fuel cells, where the electrolyte is sandwiched in between the electrodes.

Polarisation curve

A measure of cell performance that indicates the relationship between current density and voltage across a fuel cell.

Proton exchange membrane (PEM) (also Polymer Exchange Membrane)

Proton exchange membranes, also referred to as polymer electrolyte membranes due to their composition, separate the feed gases in a PEMFC or DMFC and act as the electrolyte by allowing the passage of protons.

Proton exchange membrane fuel cell (PEMFC)

Proton exchange or polymer electrolyte membrane fuel cells use a solid acid membrane as the electrolyte. PEMFC operate at low temperatures (40 - 90°C) and use platinum-containing electrodes. Alternatively graphene electrodes in latest applications.

Power density

The power density of a fuel cell is the power produced in relation to the active area or volume of the cell, expressed in W/m2 or W/m3 respectively.

Pt , Platinum

Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Platinum is a commonly used catalyst material for PEMFC and DMFC technologies.



Reformate is the output of a fuel reformer. Such a gas stream often contains hydrogen, carbon monoxide and carbon dioxide. This reformate gas can be fed to a fuel cell, generally after some degree of cleanup.

Reversible fuel cell

A reversible, or regenerative, fuel cell can operate as a fuel cell, or in reverse like an electrolyser.

Ru, Ruthenium

Ruthenium is a chemical element with the symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most other chemicals and is used in DMFC to assist with internal fuel reforming.


Separator plate

Separator plates are used to physically separate individual fuel cells in a stack.

Single cell

A single cell is the smallest and most basic form of fuel cell. It is useful for testing and development purposes to predict how stacks will perform.

Solid oxide fuel cell (SOFC)

Solid oxide fuel cells have a solid metal oxide as the electrolyte and can exist in multiple geometries including planar and tubular. They function at the highest temperature of the different types of fuel cell (about 900°C to 1,000°C) and can reform most fuels internally.


A fuel cell stack is an arrangement of individual fuel cells, usually in series to provide a useful output voltage.


Thermal efficiency

The thermal efficiency of a fuel cell system is the ratio between the output of the system (as heat and power) and the heat-content of the input fuel.

Tubular solid oxide fuel cell

SOFC can have multiple geometries. The tubular geometry is where either air or fuel is passed through the inside of a tube and the other gas is passed along the outside of the tube.



Uninterruptible power supply.


A unitised regenerative fuel cell is a reversible fuel cell which can operate either as a fuel cell, or in reverse like an electrolyser.



Hydrogen in Czech language


W, Watt

Watt, a unit of power. It is a measure of the rate of energy conversion or generation, equivalent to one joule per second.



A zero emission vehicle is one which has no tailpipe exhaust or evaporative emissions of fuel; hydrogen fuel cell cars count as zero emission vehicles. Their only output is water.

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