ASTM E957-03(2019)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E957 − 03 (Reapproved 2019)
Standard Terminology Relating to
Geothermal Energy
This standard is issued under the fixed designation E957; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
aquifer, n—a water-bearing, permeable body of rock or granu- geothermal facility,n—thephysicalcomponentsnecessaryfor
lar material below the surface of the earth. the utilization of geothermal energy, including the reservoir,
production and injection wells, pipelines, and the power
binary cycle plant, n—a facility that generates electric power
plant or direct-use facility.
by transferring heat from produced geothermal fluids to a
non-aqueous working fluid that vaporizes and causes a geothermal fluid, n—water in a vapor or liquid phase or in a
turbine to rotate the shaft of a generator.
mixtureofthesephasesthatexistswithinorhasbeenemitted
from a geothermal reservoir, together with any entrained or
brine,n—ingeothermal,fluidsinaliquidphasethathavebeen
dissolved substances.
producedfromgeothermalwellsorfromhotspringsandthat
contain appreciable amounts of sodium chloride and other geothermal gradient, n—the change in temperature of the
salts.
earth with depth, expressed either in degrees of temperature
per unit depth, or units of depth per degree.
capacity, n—the power which a component of a geothermal
facility (for example, a well, a reservoir, a power plant, or a
geothermal power plant, n—a facility for the production of
direct-use facility) is capable of supplying at a point in time, electricity using geothermal energy, typically including a
assuming that other required components of the geothermal
turbine, a generator, and associated surface equipment.
facilityareavailable.Capacityisexpressedinunitsofpower
geothermal heat pump, n—a heat pump that transfers energy
(for example, megawatts, kilowatts).
to or from the earth.
direct-use facility, n—a facility which uses geothermal energy
geothermal reserves, n—the amount of energy anticipated to
for purposes other than the generation of electricity (for
beeconomicallyrecoverablefromageothermalfacilityover
example, space heating, greenhouses, bathing, and industrial
a specified time period (for example, the project life) using
processes).
existing technology. Geothermal reserves are expressed in
fumarole, n—a vent at the earth’s surface that emits steam or
units of energy (for example, terajoules in SI units), which
gaseous vapor.
aredimensionallyequivalenttounitsofpowermultipliedby
DISCUSSION—Such vents are usually found in volcanic areas.
units of time (for example, megawatt-years or kilowatt-
hours). Geothermal reserves may also be expressed as an
geochemistry, n—the study of the chemistry of the rocks and
equivalent amount of another energy source (for example,
fluids of the earth for the purpose of understanding their
barrels of oil equivalent).
composition, their temperature, and their origin.
DISCUSSION—Geothermal reserves can also be characterized as to the
geothermal, adj—relating to or derived from the natural heat degree of certainty of recovery. By analogy to usage in the mining and
petroleum industries, reserves may be qualified as proven, probable, or
of the earth.
possible.
geothermal anomaly, n—a conspicuous deviation of the
Example of usage:
earth’s temperature, geothermal gradient, or heat flow from
This facility has geothermal reserves of 4,000 megawatt-
average values; an area where such a deviation exists.
years, recoverable over a project life of 30 years.
geothermal energy, n—the thermal energy contained in the
geothermal reservoir, n—an aquifer of sufficient temperature
rocks and fluids of the earth.
and permeability to support the economic use of geothermal
energy.
DISCUSSION—The extent of a geothermal reservoir is determined by
This terminology is under the jurisdiction of ASTM Committee E44 on Solar,
the degree of hydrologic interconnection. When an aquifer contains
GeothermalandOtherAlternativeEnergySourcesandisthedirectresponsibilityof
bothhotportionsandportionsthataretoocoolforeconomicuse,those
Subcommittee E44.01 on Terminology and Editorial.
portions that are sufficiently interconnected to have a significant
Current edition approved April 1, 2019. Published April 2019. Originally
ɛ1
hydrologic or thermal impact on each other are considered part of the
approved in 1983. Last previous edition approved in 2011 as E957–03 (2011) .
DOI: 10.1520/E0957-03R19. same geothermal reservoir.
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E957 − 03 (2019)
geothermal steam, n—a geothermal fluid in the vapor phase. project life, n—the time period over which the economic
viability of a geothermal facility is evaluated.
geothermometer, n—a method of estimating the temperature
reinjection/injection, n—theprocessofconveyinggeothermal
of a geothermal reservoir based on the minerals in the
reservoir rock or the concentration of chemical species in fluids to sub-surface formations through wells.
DISCUSSION—After such fluids have been processed by a geothermal
geothermal fluids that have come from the reservoir.
power plant or its associated facilities, or both, this process is
geyser, n—a spring that intermittently blows forth hot water
sometimes referred to as “reinjection” when injected water circulates
back through the geothermal reservoir to the production wells.
and steam.
steam purity, n—the proportion by mass of pure vapor-and
heat flow, n—dissipation or transfer of heat coming from
liquid-phase water in a fluid mixture that consists primarily
within the earth by conduction, convection, or radiation at
of steam.
the surface; usually reported in units of energy per unit time
DISCUSSION—Geothermal steam may contain impurities, such as
per unit area, for example, joules per second per square
silica, sodium, chloride, iron, and solid particulates. Steam purity
metre or watts per square metre.
expresses the proportion by mass of pure water (in both liquid and
vapor phases) in this mixture. Typically, only steam impurity is
hot spring, n—a thermal spri
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