This is a list of acronyms and terms used in the Hydrogen Analysis Resource Center. A full glossary of hydrogen terms is also available on the EERE Fuel Cell Technologies Office website.

• AEO - Annual Energy Outlook
• Alkaline Fuel Cell (AFC) - a type of hydrogen and/or oxygen fuel cell in which the electrolyte is concentrated potassium hydroxide (KOH), and hydroxide ions (OH^-) are transported from the cathode to the anode.
• ANL - Argonne National Laboratory
• APCI - Air Products and Chemicals
• ASME - American Society of Mechanical Engineers
• ASPEN - Advanced System for Process Engineering
• AQMD - Air Quality Management District
• Autonomie - Vehicle system simulation tool for vehicle energy consumption and performance analysis
• BAAQMD - Bay Area Air Quality Management District
• BP - British Petroleum
• British Thermal Unit (Btu) - 1/180 of the heat required to raise the temperature of one pound (1lb.) of water from 32 ºF to 212 ºF at a constant atmospheric pressure. It is about equal to the quantity of heat required to raise one pound (1 lb.) of water 1 ºF.
• Boiling Water Reactor (BWR) - a light water reactor design used in some nuclear power stations. It has many similarities to the pressurized water reactor (PWR), except that in a BWR the steam going to the turbine is produced in the reactor core rather than in a steam generator or heat exchanger.
• CARB - California Air Resources Board
• CA RFG - California Reformulated Gasoline (see also Reformulated Gasoline)
• CBSAs - Census Bureau Statistical Areas
• CGH₂ - Compressed Gaseous Hydrogen
• CH₂ - Compressed Hydrogen (also known as CGH₂)
• Combined Heat and Power (CHP) - also known as cogeneration, CHP is the use of a power station to simultaneously generate both heat and electricity.
• CNG - Compressed Natural Gas
• CSAs - Consolidated Statistical Areas
• Density - a measure of mass per unit of volume. The higher an object's density, the higher the mass per volume. The units of density for this data book are typically kilograms per cubic meter (kg/m³) or pounds per cubic foot (lb/ft³).
• DFMA - Design for Manufacture and Assembly
• DOE - U.S. Department of Energy
• EERE - Energy Efficiency and Renewable Energy
• EIA - Energy Information Administration
• Enthalpy - the sum of the internal energy of matter and the product of its volume and pressure. The units of specific entropy for this data book are typically Joules (J) or British thermal units (Btu).
• Entropy - a measure of the amount of energy in a physical system that cannot be used to do work. The units of entropy for this data book are typically Joules per Kelvin (J/K) or British thermal units per Rankine (Btu/ R). An important law of physics, the second law of thermodynamics, states that the total entropy of any isolated thermodynamic system tends to increase over time, approaching a maximum value.
• EPA - U.S. Environmental Protection Agency
• FCV - Fuel Cell Vehicle
• Fuel Cell (FC) - a device that produces electricity through an electrochemical process, usually from hydrogen and oxygen.
• GDP - Gross domestic product
• Gallon Gasoline Equivalent (GGE) - is the amount of alternative fuel it takes to equal the energy content of one liquid gallon of gasoline.
• GM - General Motors Corporation
• GREET - Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation
• H2 - Hydrogen
• H2VRC - Hybrid and Hydrogen Vehicle Research Center
• HCATT - Hawaii Center for Advanced Transportation Technologies
• HF 150 - APCI brand name for mobile hydrogen fueling station
• Higher Heating Value (HHV) - the amount of heat released by a specified quantity (initially at 25 ºC) once it is combusted and the products have returned to a temperature of 25 ºC. The units of HHV for this data book are typically mega-joules per kilogram (MJ/kg) or British thermal units per pound (Btu/lb).
• Hybrid Electric Vehicle (HEV) - a vehicle combining a battery-powered electric motor with a traditional internal combustion engine. The vehicle can run on either the battery or the engine or both simultaneously, depending on the performance objectives for the vehicle.
• Internal Combustion Engine (ICE) - an engine that converts the energy contained in a fuel inside the engine into motion by combusting the fuel. Combustion engines use the pressure created by the expansion of combustion product gases to do mechanical work.
• Internal Rate of Return (IRR) - the internal rate of return is defined as the discount rate that gives a net present value (NPV) of zero.
• kg - kilogram
• kg/d - kilograms per day
• kg/h- kilograms per hour
• LAWA - Los Angeles World Airports
• LAX - Los Angeles International Airport
• Liquefied Hydrogen (LH₂) - hydrogen in liquid form. Hydrogen can exist in a liquid state, but only at extremely cold temperatures. Liquid hydrogen typically has to be stored at -253 ºC (-423 ºF). The temperature requirements for liquid hydrogen storage necessitate expending energy to compress and chill the hydrogen into its liquid state.
• Liquefied Natural Gas (LNG) - natural gas in liquid form. Natural gas is a liquid at -162 ºC (-259 ºF) at ambient pressure.
• Liquefied Petroleum gas (LPG) - any material that consists predominantly of any of the following hydrocarbons or mixtures of hydrocarbons: propane, propylene, normal butane, isobutylene, and butylenes. LPG is usually stored under pressure to maintain the mixture in the liquid state.
• Lower Heating Value (LHV) - the amount of heat released by combusting a specified quantity (initially at 25 ºC) and returning the temperature of the combustion products to 150 ºC. The units of LHV for this data book are typically mega-joules per kilogram (MJ/kg) or British thermal units per pound (Btu/lb).
• lpm- liter per minute
• Modified Accelerated Cost Recovery System (MACRS) - the current method of accelerated asset depreciation required by the United States income tax code. Under MACRS, all assets are divided into classes which dictate the number of years over which an asset's cost will be recovered.
• Molten Carbonate Fuel Cell (MCFC) - a type of fuel cell that contains a molten carbonate electrolyte. Carbonate ions (CO₃^2-) are transported from the cathode to the anode. Operating temperatures are typically near 650 ºC.
• MEA - Membrane Electrode Assembly
• MMCFD - million cubic feet per day
• Mpa - Megapascal (35 Mpa =5000 psig =350 bar)
• NAICS - North American Industry Classification System
• NGV - Natural Gas Vehicle
• NIST - National Institute of Standards and Technology
• Nm³/h - Normal cubic meters per hour
• NMHC - Non-Methane Hydrocarbon Concentration
• Normal Temperature and Pressure (NTP)- It is necessary to define the standard reference conditions of temperature and pressure when expressing a gas volume or a volumetric flow rate because the volume of a gas varies with the temperature and pressure of the gas.
• PEMFC - Proton Exchange Membrane Fuel Cell
• PGM - Platinum Group Materials
• Phosphoric Acid Fuel Cell (PAFC) - a type of fuel cell in which the electrolyte consists of concentrated phosphoric acid (H₃PO₄). Protons (H⁺) are transported from the anode to the cathode. The operating temperature range is generally 160-220 ºC.
• PNNL - Pacific Northwest National Laboratory
• Polymer Electrolyte Membrane (PEM) - 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 ºC.
• Polymer Electrolyte Membrane Fuel Cell (PEMFC or PEFC) - a type of acid-based fuel cell in which the transport of protons (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 ºC).
• Pressure Swing Adsorption (PSA) - a special method for purifying gases.
• psi - pounds per square inch
• psig - pounds per square inch (gauge pressure)
• Pressurized Water Reactor (PWR) - a pressurized water reactor (PWR) is a type of nuclear power reactor that uses ordinary light water for both coolant and for neutron moderation.
• REIS - Regional Economic Information System
• Reformulated Gasoline - gasoline that is blended so that, on average, it significantly reduces volatile organic compounds and air toxics emissions relative to conventional gasolines.
• SCAQMD - South Coast Air Quality Management District
• SCF - Standard Cubic Feet
• SMUD - Sacramento Municipal Utility District
• Standard Industrial Classification (SIC) - a United States government system for classifying industries by a four-digit code. Established in the 1930s, it was supplanted by the six-digit North American Industry Classification System in 1997.
• SLPM - Standard Liters Per Minute
• Solid Oxide Fuel Cell (SOFC) - a type of fuel cell in which the electrolyte is a solid, nonporous metal oxide, typically zirconium oxide (ZrO₂) treated with Y₂O₃, and O^2- is transported from the cathode to the anode. Any CO in the reformate gas is oxidized to CO₂ at the anode. Temperatures of operation are typically 800-1,000 ºC.
• STH - Solar-to-hydrogen
• Thermal Conductivity - the intensive property of a material that indicates its ability to conduct heat. The units of thermal conductivity for this data book are typically Watts per meter-Kelvin (W/m-K) or British Thermal Units per foot-hour-Rankine (Btu/ft-h- R).
• UC - University of California
• UNLV - University of Nevada, Las Vegas
• Universal Transverse Mercator (UTM)- a grid-based method of specifying locations on the surface of the Earth. It is used to identify locations on the earth, but differs from the traditional method of latitude and longitude in several respects. The UTM system is not a map projection, but rather employs a series of zones based on specifically defined Transverse Mercator projections.
• VDP - Vehicle Development Program
• Viscosity - a measure of the resistance of a fluid to deformation under shear stress. It is commonly perceived as "thickness", or resistance to pouring. The units of viscosity for this data book are typically grams per centimeter-second (g/cm-s) or pounds per foot-second (lb/ft-s).

Sources: Some definitions and acronyms are adapted from:

1. EERE Fuel Cell Technologies Office
2. Wikipedia