Glossary of Energy Terminology

Abiogenic theory – the theory of the origin of fossil fuels from processes
deep inside the Earth
Absorption – the penetration of one substance into another substance
Active solar – systems that collect and convert solar energy into other
forms of energy such as heat and electrical energy
Adsorption – the accumulation of one substance on the surface of
another substance
Aerobic – in biology, an organism that consumes oxygen
Albedo – the fraction of incident solar radiation that is reflected back into
space by the Earth-atmosphere system
Alternating current – the movement of electric charge that periodically
reverses direction
Anaerobic – in biology, an organism that does not consume oxygen
Anode – a positively charged electrode that attracts negatively charged
Arable land – land that is suitable for farming

Biogenic gas – gases formed when buried organic matter decays in
lower temperature environments on or near the subsurface
Biogenic theory – the theory of the origin of fossil fuels that depends on
the death and decay of life from the surface of the Earth
Biomass – biological material obtained from living or recently living
Biomass conversion – conversion of biomass to synthetic fuels
Biopower – the use of biomass to generate power
Breeder reactor – a nuclear fission reactor that produces more fissile
material than it consumes

Capacity factor – ratio of average output power to peak power
Casing – a conduit, typically made of steel, used in drilling to isolate rock
formations from fluid in the wellbore
Cash flow – net cash generated as a function of time
Catalyst – a substance that increases the rate of a chemical reaction
without itself undergoing change
Cathode – a negatively charged electrode that attracts positively charged
Chernobyl – site in Ukraine of nuclear fission plant that suffered containment
failure in 1986
Chromosphere – the atmosphere of a star
Cleat – a fracture in the fracture network of a coal seam
Closed system – a system that has a negligible interaction with other
Coal gasification – conversion of large coal molecules into gaseous
Coalbed methane – methane found in the micropores of coal
Coalification – the process of heating and compressing organic materials
over time to form water and gas and coal
Cogeneration – the simultaneous production and application of two or
more forms of energy
Compressed air energy storage (CAES) – system of energy storage in
which off-peak energy from a power plant is used to inject gas into a highpressure
reservoir which can later be withdrawn to drive a gas turbine
Conduction – transfer of energy as the result of a temperature difference
between substances in contact
Containment building – building at nuclear fission facilities designed to
prevent radioactive pollution from escaping into the atmosphere and to
protect reactors from external threats
Convection – transfer of energy by the movement of a heated substance
Darcy – unit of measurement of fluid permeability in a rock
Decarbonization – progressive decrease in the amount of carbon used
to produce a given amount of energy
Deepwater Horizon – deepwater drilling rig that exploded in 2010 causing
an oil spill in the Gulf of Mexico
Delineation well – a well drilled to establish the boundaries of a reservoir
Desorption – the escape of one substance from the surface of another
Direct current – the movement of electric charge in a constant direction
Discovery well – the first well drilled into a prospect that finds hydrocarbons
Distributed generation – the generation of energy where it is needed
and on a scale that is suitable for the consumer
Dose equivalent – a measure of radiation that is used to monitor the biological
effects of radiation

– in economics, the sensitivity of the quantity supplied or demanded
to price changes
Electrolysis – the technique that uses electrical energy to split water into
its constituent elements
End use efficiency – the overall efficiency of converting primary energy
to a useful form of energy
Endothermic reaction – a reaction that consumes more energy than it
Energy density – the amount of energy available from a given volume or
mass of a substance; it is the heat of combustion of flammable materials
Energy intensity – defined on the national level as total national primary
energy consumption divided by gross domestic product
Energy mix – a selection of primary energy sources
Enzymes – a biological molecule that acts as a catalyst for reactions
Ethanol – an alcohol that is used as a gasoline additive
Exergy – a measure of the energy that is available for doing useful work
Exothermic reaction – a reaction that consumes less energy than it releases

– the flickering light effect on the area of land in a wind turbine’s
shadow caused by rotating turbine blades during daylight hours
Fossil fuel – carbon-based materials such as coal, oil and natural gas
that are formed by the death and decay of ancient life forms
Fukushima – nuclear fission plant in Japan that suffered a reactor meltdown
in 2010 following a major earthquake and tsunami

Gas-to-liquids (GTL) – process of producing synthetic diesel fuel from
natural gas
Gasification – conversion of a solid substance (such as biomass) into a
Gaussian curve – mathematically, a bell shaped curve
Geothermal energy – energy from the Earth, e.g. geysers
Greenhouse gases – gases in the atmosphere that can absorb infrared
light and trap heat
Gross Domestic Product (GDP) – the market value of the goods and
services produced by a country
Gross National Income (GNI) – GDP plus income received from other
countries less payments made to other countries

– the length of time it takes half of the original quantity of a radioactive
substance to decay
Heliostat – large sun-tracking mirror used to concentrate sunlight on a
Human Development Index – HDI is a quantitative measure of the quality
of life
Hydrate – a cage-like structure that is formed when mobile molecules of
a substance (such as a gas) are bound inside a lattice of water molecules
Hydraulic fracturing – the injection of liquid slurry at high pressure to
break low permeability rock to allow for fluid flow
Hydrocarbon – organic compound consisting of hydrogen and carbon
Hydroelectric power – the use of potential energy from flowing or falling
water to move turbines which then generate electricity
Hydrosphere – groundwater and water found in oceans, glaciers, surface
waters such as rivers and lakes, and atmospheric moisture

Inertial confinement – a method that uses pulsed energy sources such
as lasers to concentrate energy onto a small pellet of material that is suitable
for nuclear fusion
Intangible cost – the costs of a project or program that tend to be difficult
to quantify and can be financial or societal, e.g. pollution
Intermittence – the act of occurring occasionally or irregularly, e.g. sunlight
on the surface of the earth
Isotope – nuclei with the same atomic number but different numbers of

Kinetic energy – energy of motion
Kyoto Protocol – an international treaty that establishes limits on the
amount of greenhouse gases a country can emit into the atmosphere

Levelized cost of energy (LCOE) – total life cycle cost divided by total
lifetime energy production
Life cycle analysis – the analysis of all revenues and expenses associated
with the use of an energy system throughout the life of the system
Luminosity – total energy of light radiated per second by a light source

Magnetic confinement – in nuclear fusion, a method that uses magnetic
fields to confine an ionized gas called plasma
Manhattan Project – the project undertaken by the US during World War
II to develop a bomb based on nuclear fission
Methane digester – a biomass conversion system that converts biological
feed to methane
Multilateral well – well with more than one horizontal branch extending
from the main wellbore
Mutual Assured Destruction – Cold War policy for nuclear deterrence in
which both parties in a nuclear conflict would be obliterated

Nacelle – name given to the machine cabin of a wind turbine that houses
the electrical generator
Net present value – the difference between revenue (income) and expenses
Non-renewable energy – energy that is obtained from sources at a rate
that exceeds the rate at which the sources are replenished
Nuclear fission – large nucleus splits into smaller fragments
Nuclear fusion – small nuclei combine to form larger nuclide
Nuclear winter – a decline of air temperature resulting from an increase
of particulates in the atmosphere following the detonation of many nuclear
Nucleons – particles inside the nucleus of an atom
Nucleus – the small, central region of an atom that contains all of the
positive charge and most of the mass

Ocean thermal energy conversion (OTEC) – power plants that convert
temperature differences between warm surface water and cool deeper
water into useful energy
Opportunity cost – in economics, the concept that the selection of one
opportunity that requires the use of scarce resources means another opportunity
is not selected
Oxidation – in chemistry, the loss of electrons in a redox reaction
Oxidizing agent – see redox reaction

Paradigm – a model that is realistic enough to help us make predictions
and understand events, but not so realistic that it tends to confuse rather
than clarify issues
Passive solar – technology that integrates building design with environmental
factors that enable the capture or exclusion of solar energy
Peak oil – the point in time at which maximum oil production rate is
reached and less than half of the producible oil remains
Penstock – the pipeline that allows water to flow from a higher elevation
to a lower elevation and into a turbine adjacent to a dam
Per capita – per person
Permeability – a measure of the connectivity of pore spaces in porous
Photocell – a cell that converts light into electrical energy
Photoelectric effect – uses energy from a photon to eject an electron
from its position in a metal lattice to generate an electric current
Photon – particle of light
Photosphere – the surface of a star
Photosynthesis – a process that uses electromagnetic radiation (e.g.
sunlight) to synthesize biologically useful chemical compounds
Photovoltaics – the use of light to generate electrical current
Plasma – the state of matter containing bare nuclei and free electrons
Plate tectonics – theory that the crust of the earth is a collection of plates
floating and shifting on the mantle
Pore space – the void space in a porous material
Porosity – a measure of the void space in a porous material
Porous material – a material that has void space between grains of material,
such as a rock or sponge
Potential energy – the energy of an object due to its position relative to
other objects or due to its composition
Prime mover – the facility that supplies mechanical work using energy
that is provided by a non-mechanical source such as chemical or electrical

Quad – a unit of energy commonly used for discussing energy on a national
scale; a quadrillion BTU

Radiation (Light) – energy transfer by emission and absorption of electromagnetic
Radioactive waste – nuclei that emit biologically harmful radiation and
can be found in spent fuel rods
Real Options Analysis – an analytical technique that attempts to incorporate
flexibility in the management of investment decisions that are
subject to a significant amount of uncertainty
Redox reaction – also known as oxidation-reduction reaction; a process
in which electrons are transferred from one reactant (reducing agent) to
another reactant (oxidizing agent)
Reducing agent – see redox reaction
Reduction – in chemistry, the gain of electrons in a redox reaction
Relativity – the study of how relationships between physically significant
quantities may change when the relationships are described by observers
moving relative to one another
Renewable energy – energy that is obtained from sources at a rate that
is less than or equal to the rate at which the sources are replenished
Reservoir – geologic trap capable of holding fluids
Reservoir management – management of subsurface resources, especially
oil and gas reservoirs
Risk – in economic forecasting, the possibility than an unexpected event
will occur and adversely affect the value of an asset
Risk analysis – an analytical technique that attempts to quantify the risks
associated with investing under uncertainty

Seepage – gradual discharge of a fluid
Seismic survey – a measurement that uses the movement of disturbances
(or displacements from an undisturbed position) through a medium
such as the interior of the earth to study the structure of the medium
Semiconductor – in electronics, a material that conducts electrical current
more effectively than an electrical insulator (such as plastic), but not
as well as an electrical conductor (such as metal)
Sequestration – the storage of a material, such as greenhouse gases
Solar constant – the amount of radiation from the sun that reaches the
earth’s atmosphere
Solar irradiance – solar energy striking an area of surface each second
Solar spectral irradiance – solar irradiance per unit wavelength of light
Superconductivity – the flow of electrons through a material with no energy
Superconductor – a material that offers no resistance to electron flow
Sustainable development – a policy that is concerned with meeting the
needs of the current generation and the needs of future generations
Synfuels – synthetic fuels (synfuels) are fossil fuel substitutes created by
chemical reactions using basic resources, e.g. coal or biomass

Tangible cost – the costs of a project or program that are readily quantified,
e.g. equipment, personnel
Thermogenic gas – gases formed when organic matter is heated in high
temperature, subsurface environments
Three Mile Island – nuclear fission plant in Pennsylvania that suffered a
containment failure in 1979
Tight gas – gas found in low permeability reservoirs
Tokamak reactor – in nuclear fusion, a reactor that uses a magnetic field
to confine plasma
Transformer – a device that converts voltages from one circuit to another

Uncertainty – in economic forecasting, the idea that our limited
knowledge and understanding of the future does not allow us to predict
the consequences of our decisions with 100% accuracy

Volatile – in chemistry, a material that evaporates quickly

Work function – the smallest energy needed to extract an electron from
a metal