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ACCESSIBLE:
Readily. Having direct access without the need of moving or removing any panel, door or
similar covering of the item described.
Reasonably. Having access to, but which first may require the removal of a panel, door or
similar covering of the item described.
ACTIVATION:
Chemical. Treatment of a substance by heat, radiation, or other activating reagent to produce
a more complete or rapid chemical or physical change.
Electrical. The process of treating a cathode to increase its rate of reduction.
ACTIVATION POLARIZATION:
Activation Polarization is present when the rate of electrochemical reaction at an electrode
surface is controlled by sluggish electrode kinetics. This is similar to chemical reactions
where the reacting species must overcome an activation barrier. For fuel cells, this region is
characterized by a drop from the theoretical EMF or ideal voltage prior to electron or ion
flow.
AIR:
The mixture of oxygen, nitrogen and other gases which, with varying amounts of water vapor,
forms the atmosphere of the earth. Also referring to any or all air for combustion, heating,
cooling, ventilation and other uses as follows:
Ambient. Air that surrounds the equipment.
Atmospheric. Air under the prevailing atmospheric conditions.
Combustion. Air required for safe and proper combustion of fuel gas.
Dilution. Air which enters a draft regulator or similar device and mixes with the flue gases.
Excess. Air which passes through the combustion chamber and any flues in excess of that
which is theoretically required for complete combustion.
Exhaust. Air removed from a space and not reused.
Outdoor. Air taken from the outdoors and, therefore, not previously circulated through the
system.
Primary. Air introduced into a burner at the mixer head, which mixes with the gas before
reaching the port(s).
Recirculated. Air removed from a space and intended for reuse as supply air.
Return. Air removed from a space and recirculated or exhausted.
Secondary. Air externally supplied to the flame at the point of combustion.
Standard. Air at standard temperature and pressure, namely 70°F (21°C) and 29.92 inches
(760 mm mercury column, having a specific weight of 0.075 pounds per cubic foot (1.20
Fuel Cell Glossary
US Fuel Cell Council 3
kg/cu m). [Indicates a temperature of 70°F (21°C). The ISO standard (59°F) might be more
appropriate to allow direct comparisons with turbines].
Supply. That air delivered to each or any space in the system or the total delivered to all
spaces in the system.
Ventilation. That portion of supply air which comes from the outside (outdoors) plus any
recirculated air that has been treated to maintain the desired quality of air within a designated
space. BASE: The lowest frame or structure of the appliance, exclusive of legs that provides the primary
means of support. CAPACITY FACTOR: The ratio of the average power load of an electric power source to its rated capacity over a
selected period of time. (Also known as “plant factor”). DESULFURIZER: A component for removing sulfur from a fuel mixture. EFFICIENCY: A measure (usually a ratio) of the useful energy provided by a dynamic system versus the
total energy supplied to it during a specific period of operation. FAILURE MODES AND EFFECTS ANALYSIS (FMEA): A structured process of analysis to identify and classify concerns, features and reasoning, and
to recommend corrective actions for as many potential failures as is reasonably possible. 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 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.
Normal Butane (n-Butane), technical Grade. A liquefied
petroleum gas composed of a minimum of 95 percent n-butane
(C4H10) which may contain other impurities such as isobutane,
butylenes and propane not in excess of 5 percent.
Propane MD-5. A special grade of liquefied petroleum gas
composed of a minimum of 90 percent liquid volume of propane
(C3H8) and a maximum of 5 percent liquid volume of propylene
(C3H6). HEAT EXCHANGER: A vessel in which heat is transferred from one medium to another. IDLE POWER: The system rate of doing work when only the minimum work rate is employed by the system. JOINTS: Points of connection: between heat transfer surfaces; between positive and negative pressure
zones within components of the power plant; and between power plant components. LIQUID: A substance that, unlike a solid, flows readily but, unlike a gas, does not tend to expand
indefinitely. MAIN BURNER: A device or group of devices essentially forming an integral unit for the final conveyance of
fuel or a mixture of fuel and air to the combustion zone, and on which combustion takes place
to accomplish the function for which the equipment is designed. NAPHTHA: An artificially produced petroleum or coal tar fraction with a volatility between gasoline and
kerosene. OPEN CIRCUIT VOLTAGE: The voltage at device terminals when no appreciable current is flowing. Also known as NO LOAD
VOLTAGE. PARTIAL OXIDATION: Fuel reforming reaction where the fuel is partially oxidized to carbon monoxide and hydrogen
rather than fully oxidized to carbon dioxide and water. This is accomplished by injecting air
with the fuel stream prior to the reformer. The advantage of partial oxidation over steam
reforming of the fuel is that it is an exothermic reaction rather than an endothermic reaction
and therefore generates its own heat. RATED POWER: The value stated on the generator nameplate. It is the power available at the output terminals
of a component or piece of equipment that is operated in compliance with the manufacturer’s
performance specifications. SCHEDULED OUTAGE: An outage that results when a power plant is deliberately taken out of service at a selected
time, usually for the purposes of construction, maintenance or repair. TEMPERATURE: A measure of heat intensity.
Absolute: The temperature above absolute zero, or temperature
plus 273°C or 459°F.
Ambient: The temperature of the surrounding medium, usually
used to refer to the temperature of the air in which a structure is
situated or a device operates. VALVE: A device used in piping to control the fuel supply to any section of a system of piping or to
fuel utilization equipment.
Automatic. A device consisting essentially of a valve and operator that controls the fuel
supply to the burner during normal operation of the equipment. The operator may be actuated
by application of fuel pressure on a flexible diaphragm, by electrical means, by mechanical
means or by other means.
Diaphragm Type. A device consisting essentially of an automatic valve actuated by means of
the application of fuel pressure upon a flexible diaphragm.
Electric Type. A device actuated by electrical energy for controlling the fuel supply. These
consist of the following:
Modulating. A valve designed so the valve opening is controlled
within narrow limits throughout the entire range from the "full"
open to the "closed" position.
Motor. An electric control valve that is automatically closed by a
spring or other mechanical means in the event the electric circuit is
broken.
Solenoid. A valve that is opened or closed by the action of an
electrically excited coiled wire magnet upon a bar of steel attached
to the valve disc.
Step (Manual). A valve having a rotating plug with, generally,
three positions and different rates of fuel flow for each, the plug
being actuated by a solenoid or motor-driven rack and pinion and a
cam arrangement which, together with a combination push-button
switch, determines the position assumed by the plug. WORKING PRESSURE, ALLOWABLE: The maximum gauge pressure at which a part or system may be operated in accordance with
the provisions of this standard. It is the pressure used in determining the setting of pressurelimiting/
relieving devices installed to protect the part or system from accidental overpressuring.
ZERO ELECTRIC VEHICLE (ZEV):
Zero Emission Vehicle, a vehicle that produces no air emissions from its fueling or operation.
California regulations require in 2003, 10% of the vehicles sold in California by major auto
makers be ZEV or ZEV equivalent. California has established a comprehensive program for
determining this equivalency. See also LEV.
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