Glossary - Environmental Impacts of Renewable Energy - page 408

Economy of scale: The principle that larger production facilities have lower unit
costs than smaller facilities.
Ecoregion: A territory defined by a combination of biological, social, and geo-
graphic criteria rather than geopolitical considerations; generally, a system
of related, interconnected ecosystems.
Ecosystem: A natural community of organisms interacting with its physical envi-
ronment, regarded as a unit.
Ecosystem service: A benefit or service provided free by an ecosystem or by the
environment, such as clean water, flood mitigation, or groundwater recharge.
Efficiency: The ratio of the useful energy output of a machine or other energy-
converting plant to the energy input.
Electric energy: The ability of an electric current to produce work, heat, light, or
other forms of energy. It is measured in kilowatt-hours.
Electric power sector: An energy-consuming sector that consists of electricity only
and combined heat and power (CHP) plants whose primary business is to
sell electricity, or electricity and heat, to the public (i.e., North American
Industry Classification System code 22 for plants).
Electric utility: A corporation, person, agency, authority, or other legal entity or
instrumentality aligned with distribution facilities for delivery of electric
energy for use primarily by the public. Included are investor-owned elec-
tric utilities, municipal and state utilities, federal electric utilities, and rural
electric cooperatives. A few entities that are tariff based and corporately
aligned with companies that own distribution facilities are also included.
Elution: The process of using a solvent (eluent) to remove select ions (e.g., uranium)
from an adsorbent such as ion-exchange resins.
Embayment: A bay or baylike formation.
Emissions: Anthropogenic releases of gases to the atmosphere. In the context of
global climate change, they consist of radiatively important greenhouse
gases (e.g., the release of carbon dioxide during fuel combustion).
Emissions coefficient: A unique value for scaling emissions to activity data in terms
of a standard rate of emissions per unit of activity (e.g., pounds of carbon
dioxide emitted per Btu of fossil fuel consumed).
Emissions factor: A rate of carbon dioxide output resulting from the consumption
of electricity, natural gas, or any other fuel source.
End user: A firm or individual that purchases products for its own consumption and
not for resale (i.e., an ultimate consumer).
Endothermic: A chemical reaction that absorbs or requires energy (usually in the
form of heat).
Energy: The ability to do work—that is, the capacity for doing work as measured by
the capability of doing work (potential energy) or the conversion of this capa-
bility to motion (kinetic energy). Energy has several forms, some of which are
easily convertible and can be changed to another form useful for work. Most
of the world's convertible energy comes from fossil fuels that are burned to
produce heat, which is then used as a transfer medium to mechanical or other
means in order to accomplish tasks. Electrical energy is usually measured in
kilowatt-hours, and heat energy is usually measured in British thermal units.