A B C D E F G H I J K L M N O P Q R S T U V W X Y Z A
Acid Rain: Common name for any precipitation (rain, snow, sleet, hail, fog) having a high amount of sulfuric acid and/or nitric acid or having a pH lower than 5.6. Normal rain has a pH of 5.6 - 5.7. Accumulation of acids in lakes and rivers damages or kills plant and animal life. Acid rain also dissolves building materials and leaches nutrients out of soil resulting in crop damage. Fossil fuel power plants are a major source of acid rain. Active power: The mean power in an alternating current circuit. With sinusoidal currents it is equal to the product of the voltage or e.m.f. and the active current.
Note 1: Active current is the component of the alternating current which is in phase with the voltage or e.m.f.
Note 2: It is used for exciting magnetic fields (in motors and transformers) or electric fields (in condensers). Agriculture: The growing (farming) of plants, flowers, trees, grains, and other crops. Greenhouses can be heated with hot water from geothermal reservoirs. In some places pipes of hot water are buried under the soil. Geothermal heat is also used to dry crops. Air pollution: Unwanted particles, mist or gases put into the atmosphere as a result of motor vehicle, exhaust, the operation of industrial facilities or other human activity. Ambient: Natural condition of the environment at any given time. Anthropogenic: Caused by human action, such as changes in vegetation, an ecosystem, or an entire landscape. Apparent power: The product of the root mean square (effective) current and the root mean square (effective) electromotive force or voltage, irrespective of the phase relationship between the voltage and current.
Note: It is a significant factor in the design of electrical equipment. Aquaculture: The farming of fish and other water-dwelling organisms in freshwater or seawater. Geothermal water is used to help speed the growth of fish, prawns and alligators. China probably has more aquaculture operations than any country. Aquifer: Formation of permeable water-bearing rock. Auxiliary or secondary power: Refers to an alternative, or reserve, power source. For instance, the generator in a recreational vehicle or boat would represent an auxiliary power source. Portable generators are another example. Available capacity (available power): At any given moment, the maximum power at which the station or unit can be operated for a given period under the prevailing conditions assuming unlimited transmission facilities. Availability factor: Means the ratio of the time a piece of equipment or a unit is ready for or in service to the total time interval under consideration, expressed as a percentage. Availability time: The sum of the operating time and the stand-by availability time. Availability time ratio: When referred to a plant or part of a plant, the ratio of the availability time to the reference period. Average generation: Means the total power produced over a period of time divided by the number of hours in the period time, which measurement can be expressed in kWh/day, MWh/month or average MW. This metric represents the generating capacity of a plant adjusted for its availability.
Avoided costs: Means "avoided costs" as that term is defined by FERC's regulations promulgated under PURPA, if context so requires, or otherwise means short-run avoided costs. Back to Top B
Backup power: Refers to a device that is only used when the primary source is unavailable, generally regarded as an infrequent occasion. For instance, batteries used in telecom sites when the grid power fails are an example of backup power. Balneology: Using hot spring mineral water for therapy. This is perhaps the oldest use of natural geothermal waters. Baseload: The lowest level of power production needs during a season or year Baseload facility: Means a power plant generally operated at a relatively constant level of generation to meet the minimum load demand. Baseload power station: A power station serving mainly to meet the peak load. Binary cycle: Is a thermodynamic cycle composed of two Rankine cycles in series using two fluids. Example: Top cycle Therminol, bottoming cycle pentane. Binary geothermal power plant: A geothermal electricity generating plant employing a closed-loop heat exchange system in which the heat of the geothermal fluid (the "primary fluid") is transferred to a lower-boiling-point fluid (the "secondary" or "working" fluid), which is thereby vaporized and used to drive a turbine/generator set. Binary system: Means the geothermal power plant technology by which geothermal fluid is used to heat a secondary working fluid with a low boiling point to generate the vapors that drive the turbine and produce electricity. Outdated not in use anymore. Biomass: Energy resources derived from organic matter. These include wood, agricultural waste and other living-cell material that can be burned to produce heat energy. They also include algae, sewage and other organic substances that may be used to make energy through chemical processes. Bituminous coal: A dense coal, ususally black, sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substancial quantities also used for heat and power applications in manufacturing and to make coke. Bituminous coal is the most abundant coal in active U.S. mining regions. Its moisture content usually is less then 20 percent. The heat content of bituminous coal ranges from 21 to 30 million Btu per ton on a moist, mineral-matter-free basis. The heat content of bituminous coal consumed in the Unted States averages 24 million Btu per ton, on the as-received basis (i.e., containing both inherent moisture and mineral matter). BLM: Means the Bureau of Land Management of the U.S. Department of the Interior. Boiling point: Temperature at which a single substance, such as water, changes from a liquid to a gas (steam) under normal atmospheric pressure. The boiling point at which water transitions to steam is 212°F (100°C). Some liquids boil at a lower temperature than water. Boiling temperature of a given substance is affected by pressure. The greater the pressure, the higher the boiling temperature. This principle is put to work in geothermal (flash) power plants when superheated (hotter than boiling) geothermal water is brought up wells. The hot water flashes to steam when the pressure is released as it reaches the surface. This phenomenon also occurs naturally, resulting in such features as geysers. Brine: Means geothermal water. Fluids in a liquid phase that have been produced from geothermal wells or from hot springs and that contain appreciable amounts of sodium chloride and other salts. Butane: A hydrocarbon gas found in the Earth along with natural gas and oil. Butane turns into a liquid when put under pressure. It is sold as bottled gas. It is used to run heaters, stoves and motors, and to help make petrochemicals. Btu (British Thermal Unit): A standard unit for measuring the quantity of heat energy equal to que quantity of heat required to raise the temperature of 1 pound of water by 1 degree Fahrenheit. Back to Top C
Caldera: A bowl-shaped landform, created either by a huge volcanic explosion (which destroys the top of a volcano) or by the collapse of a volcano's tip. Carbon dioxide (CO2): A gas produced by the combustion of fossil fuels and other substances. CO2 also occurs naturally in large amounts in molten magma, which is involved in the explosive eruption of volcanoes. See Greenhouse Effect. Capacity: Means the maximum load that a generator, piece of equipment, substation, transmission line, or system can carry under existing conditions. Capacity factor: Means the ratio of the average load on a generating resource to its capacity rating during a specified period of time, which ratio is expressed as a percent. Capacity, installed (or nameplate): The total manufacturer-rated capacities of equipment such as turbines, generators, condenser, transformers, and other system components. Carbon dioxide: A colorless, odorless, non-poisonous gas that is a normal part of the air. Carbon dioxide, also called CO2, is exhaled by humans and animals and is absorbed by green growing things and by the sea. Carcinogens: Potential cancer-causing agents in the environemt. They include among others: industrial chemical compounds found in food additives, pesticides and fertilizers, drugs, toy, household cleaners, toiletries and paints. Naturally occurring ultraviolet solar radiation is also c carcinogen. CCVT: See Closed Cycle Vapor Turobogenerator. Changeable demand: The demand taken into account for calculating the charges to be billed. Chemical energy: Energy inherent in the chemical bonds which hold molecules together.
Examples are coal and oil, which have energy potential that is released upon combustion. Circuit length: The average of the actual lengths of the lines of a circuit (taking account of variations in elevation and catenary dip). Closed Cycle Vapor Turbogenerator generic name: For hermetically sealed power unit operating according to the ORC such as OEC of the type used for remote unattended power supply. Coal: A readily combustible black or brownish-black rock whose composition, including inherent moisture, consists of more than 50 percent by weight and more than 70 percent by volume of carbonaceous material. It is formed from plant remains that have been compacted, hardened, chemically altered, and metamorphosed by heat and pressure over geologic time. Combined Cycle: An electric generating technology in which electricity is produced from otherwise lost waste heat exiting from one or more gas (combustion) turbines. The exiting heat is routed to a conventional boiler or to a heat recovery steam generator for utilization by a steam turbine in the production of electricity. This proces increases the efficiency of the electric generating unit. Combustion: The burning of gas, liquid, or solid, in which the fuel is oxidized, producing heat and often light. Commercial operations: Means, in connection with a plant, the achievement by that plant of certain operational and capability criteria specified in the power purchase agreement associated with that plant. Condensate: Water formed by condensation of steam. Condense: To change from a gas to drops of liquid. Water-cooled geothermal power plants use cooling towers to cool the used steam and condense it back to water for injection back to the edge of the reservoir. In binary power plants, an organic liquid is first vaporized (with heat from geothermal water) to drive a turbine, then cooled and condensed back to a liquid and recycled again and again in a closed loop. Conduction: The transfer of heat as a result of the direct contact of rapidly moving molecules through a medium or from one medium to another, without movement of the media. The heat from geothermal water, for instance can be conducted through metal plates or pipes to heat other water for district heating systems or a second organic liquid for use in binary power plants. Consumption (Fuel): The amount of fuel used for gross genertion, providing standby service, start-up and/or flame stabilization. Continental drift: The theory that the continents have drifted apart when a supercontinent, Pangaea, broke apart. See Plate Tectonics. Control room: A room in which control boards are installed. Converter station: An installation for converting current of one form into another or for converting one frequency into another. Convection currents: The currents caused by hot air or fluid rising and falling. Hot air or fluid expands and is therefore less dense than its cooler surroundings, thus it rises; as it cools it contracts, becomes more dense and sinks down creating something of a rolling motion. These motions are thought to be part of the dynamic geologic processes that drive the movement of crustal plates. See Plate Tectonics. Cooling tower: Means a heat rejection device, which extracts waste heat to the atmosphere through the cooling of a water stream to a lower temperature. Common applications for cooling towers include providing cooled-water for air-conditioning, manufacturing and electric power generation. The generic term "cooling tower" is used to describe both direct (open circuit) and indirect (closed circuit) heat rejection equipment. Cooling with dry cooling towers: A cooling system in which heat from the condensers of a power station is dissipated to the atmosphere in a cooling tower solely by convection. Cooling with wet cooling towers: A cooling system in which water passing through the power station condensers takes up heat, releases this heat subsequently to the atmosphere in a wet cooling tower mainly by evaporation and is then recycled. Core (outer and inner): The extremely hot center of the Earth.
The outer core is probably molten rock and is located about 3,200 miles (5,100 kilometers) down from the earth's surface; the inner core may be solid iron and is found at the very center of the Earth - about 4,000 miles (6,400 kilometers) down. Cost: The amount paid to acquire resources, such as plant and equipment, fuel, or labor services. Crust: The solid outermost layer of the Earth, mostly consisting of rock, and ranging from 3 0 35 miles (4.8 - 56 kilometers) thick, comprises the topmost portion of the lithosphere (see lithospheric plates). Earth's crust insulates us from the hot interior. Cultivate: To grow and tend (plants or crops), farm. Cycle: A system of phases through which the working substance passes in an engine compressor, pump, turbine or power plant. Back to Top D
Dehydrate: To free from moisture in order to preserve; to dry fruits, vegetables or lumber, for instance. A factory in Nevada, for example uses geothermal heat to dehydrate onions and garlic for restaurants. Demand (Utility): The level at which electricity or natural gas is delivered to users at a given point in time. Electric demand is expressed in kilowatts. Demand curve (load curve): A curve representing the changing values of output or load as a function of time. Density: The amount of mass in a given volume of something. Two objects can be the same size, but have different densities because one of the objects has more mass "packed" into the same amount of space.
Objects are smaller when they are cold, larger when hot. Department of Energy (U.S. DOE): The federal department established by the Department of Energy Organization Act to consolidate the major federal energy functions into one cabinet-level department that would formulate a comprehensive, balanced national energy policy. DOE's main headquarters are in Washington, D.C. Destillate fuel: A general classification for the petroleum fractions produced in conventional distillation operations. Included are products kown as No.1, No.2, and No.4 fuel oils and No.1, No.2, and No.4 diesel fuels. Used primarily for space heating, on-and off-highway diesel engine fuel (including railroad fuel and fuel for agricultural machinery), and electric power generation. Direct use: Use of geothermal heat without first converting it to electricity, such as for space heating and cooling, food preparation, industrial processes, etc. Distribution network/system: A system of distribution lines serving for the regional and local distribution of electrical energy. Distribution substation (HV/LV transforming station): A transforming station between high and low voltage systems/networks. District heating system: A heating system that provides heat to a large number of buildings all from a central facility. In geothermal district heating systems, one or more wells can serve entire districts. Dispatch: The operating control of an integrated electric system to: Assign geneation to specific generating plants and other sources of supply to effect the most reliable and economical supply as the total of the significant area loads rises or falls. Control operations and maintenance of high-voltage lines, substations and equipment, including administration of safety procedures. Operate the interconnection. Schedule energy transactions with other interconnected electric utilities. Drift: Drift droplets are any water droplets and dissolved and suspended solids that are entrained in the air and emited from the cooling tower stack. Drift eliminator: Drift eliminators reduce the amount of drift in the exiting air flow. Drift droplets can be reduced to less than 0.1% by effective use of an eliminator. Drilling: Boring into the Earth to access geothermal resources, usually with oil and gas drilling equipment that has been modified to meet geothermal requirement. Dry steam: Very hot steam that doesn not occur with liquid. Dual flash design: Means the geothermal power plant technology that uses a pressure reduction process to convert liquid geothermal fluids into steam, which, together with steam contained in the mixture of geothermal fluids extracted from a geothermal reservoir, is used by a turbine generator to produce electricity. Dual (multi) bore-hole technology: Process for exploiting the potential of geothermal energy with the use of two (or more) bore holes, in which the cooled heat-transfer medium (water) is returned to the geothermal rock formation through at least one of the bore holes.
Note: The number and arrangement of the bore holes employed is dependent on the temperature and pressure conditions and on the chemical composition of the geothermal fluid serving as heat-transfer medium. Back to Top E
Earthquake: The vibration or movement of the ground caused by a sudden shift along faults (cracks) in the earth's crust; most earthquakes occur at the places where tectonic plates edges meet. Efficiency: The ratio of the useful energy delivered by a dynamic system (such as a mchine, engine, or motor) to the energy supplied to it over the same period or cycle of operation. The ratio is usually determined under specific test conditions. Effluent: Treated wastewater. Electric current: The continuous flow of electrons; often referred to as electricity. Electrical circuit: An arrangement of bodies or media through which a current may flow. Electrical energy: Energy of electric charges or electric currents. Electricity generated: The electricity produced at the generator terminals. Electrical installation: Civil engineering works, buildings, machines, apparatus, lines and associated equipment together forming an integrated unit for the generation, conversion, transformation, transmission, distribution, storage or utilization of electrical energy. Electric line: A generic term for a set of conductors, with insulation and accessories, used for the transmission or distribution of electrical energy. Electricity supplied: The useful electricity supplied to the network. Electric utility company: Means" electric utility company" as that terms is defined in PUHCA. Electron: The smallest part of an atom (atoms are the tiny particles of which all substances are made). Electrons may be freed from atoms to produce an electric current. Emissions standard: The maximum amount of a pollutant legally permitted to be discharged from a single source. Energy: The capacity for doing work as measured by the capacity of doing work (potential energy) or the conversion of this capability 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 that is then used as a transfer medium to mechanical or other means in order to accomplish taks. Electrical energy is usually measured in kilowatt-hours, while heat energy is ususally measured in British thermal units. Energy conversion: The changing of energy from one form to another.
One of the many examples are heat energy being converted into mechanical energy, and then mechanical energy into electrical energy, as is done in steam-driven electric power plants. Energy efficiency: The measure of the amount of energy which any technology can convert to useful work; technology with the higher energy efficiency will require less energy to do the same amount of work. Energy resource: The primary source that provides the power that is converted to electricity through chemical, mechanical, or other means. Energy sources include coal, petroleum and petroleum products, gas, water, uranium, wind, sunlight, geothermal and other sources. Energy resources are often classified as renewable or non-renewable. Enhanced permeability: Process aimed at improving flow conditions for the heat-transfer medium. Environmental Protection Agency (EPA): A federal agency created in 1970 to permit coordinated governmental action for protection of the environment by systematic abatement and control of pollution through integration or research, monitoring, standards setting and enforcement activities. EP Act: Means the Energy Policy Act of 1992. The legislation creates a new class of power generators, exempt wholesale generators, that are exempt from the provisions of the Public Holding Company Act of 1935 and grants the authority to the Federal Energy Regulatory Commission to order and condition access by eligible parties to the interconnected transmission grid. Equipment rating: means the full-load electrical quantities assigned by the designer to a generator and its prime mover, under standardized conditions, expressed in kilowatts, which rating is unusually indicated on a nameplate attached to the individual machine or device. Eruption: The explosive discharge of material such as molten rock and gases, or hot water (as from volcanoes or geysers). Evaporite: A sedimentary rock that originates by evaporation of seawater in an enclosed basin. EWG or Exempt Wholesale Generator: Means an "exempt wholesale generator" as that terms is defined in 15 U.S.C. § 79z-5a(a-1) or any successor provision. Back to Top F
Facility: An existing or planned location or site at which prime movers, electric genertors, and/or equipment for converting mechanical, chemical, and/or nuclear energy into electric energy are situated, or will be situated. A facility may contain more than one generator of either the same or different prime mover type. For a cogenerator, the facility includes the industrial or commercial process. Fault: A crack or break in the Earth's crust along with movement has occurred, often resulting in earthquakes. FERC: Means the United States Federal Energy Regulatory Commission. Firm capacity: The capacity which can be made available, whose reliability for the supply system is specified and determined in advance. Flash steam: Steam produced when the pressure on a geothermal liquid is reduced. Also ccalled flashing. Flashing: Means the pressure reduction process by which, in a dual flash design geothermal power plant, liquid is converted into steam. Also called flash steam. Flue gas desulphurization unit (Scrubber): Equipment used to remove sulfur oxides from the combustion gases of a boiler plant before discharge to the atmosphere. Chemicals, such as lime, are used as the scrubbing media. Fly ash: Particulate matter from coal ash in which the particle diameter is less than 1 x 10(-4) meter. This is removed from the flue gas using flue gas particulate collectors such as fabric filters and electrostatic precipitators. Fossil fuel: Any naturally occurring organic fuel, such as petroleum, coal and natural gas. Fossil-fueled power station: A power station in which the chemical energy contained in solid, liquid and gaseous fuels of fossil origin is converted into electrical energy. A power station using coal, petroleu, or gas as its source of energy. FPA or Federal Power Act: Means the Federal Power Act of 1920, as amended. Fracture: A crack in the Earth's crust along which no movement has occurred. Fuel: Any substance that cn be burned to produce heat; also, materials that can be fissioned in a chain reaction to produce heat. Fuel cell: A device that enables chemical energy to be converted directly into electrical energy without the intervention of the heat engine cycle, in which electrical power is produced in a controlled reaction involving a fuel, generally hydrogen, methanol or a hydrocarbon.
Note: Fuel cells can have applications as small power sources in remote locations and possibly as sources of power for electric vehicles. Fumarole: A vent or hole in the Earth's surface, usually in a volcanic region, from which steam, gaseous vapors, or hot gases issue. Back to Top G
Gas: A fuel burned under voilers and by internal combustion engines for electric generation. These include natural, manufactured and waste gas. Generator: A machine that converts mechanical energy into electrical energy. Generation (Electricity): The process of producing electric energy by transforming other forms of energy; also, the amount of electric energy produced, expresses in watt-hours (Wh). Geochemistry: The study of the chemistry of the rocks and fluids of the Earth for the purpose of understanding their composition, their temperature and their origin. Geology: Study of the planet Earth, its composition, structure, natural processes, and history. Geothermal: Relating to or derived from the natural heat of the Earth. Geothermal anomaly: Conspicuous deviation of geothermal temperature gradient or heat flow from average values. Geothermal depth gradient: The reciprocal of geothermal temperature gradient. The mean value for geothermal depth gradient near the surface is approximately:33 m/K
Geothermal energy: The thermal energy contained in the rocks and fluids of the Earth. Geothermal fluid: The dry steam, wet steam or hot water, together with dissolved and entrained substances, conveyed or flowing out of the earth's crust. Geothermal gradient: The change in temperature of the earth with depth, expressed either in degrees of temperature per unit depth, or units of depth per degree. Geothermal gradient (geothermal temperature gradient): The increase in temperature per unit depth through the crust and upper layers of the earth's mantle in the direction of the center of the earth.
The average temperature gradient near the surface is approximately:0.03 K/m or 30 K/km Geothermal heat pump: A heat pump that transfers energy to or from the Earth. Geothermal (ground source) heat pump: A space heating/cooling system which moves heat from and to the earth, as opposed to making heat using a fuel source.
Geothermal heat pumps take advantage of the almost constant temperature just a few feet underground - usually warmer than the air in winter and cooler than the air in summer. Geothermal hot water field (geothermal hot water reservoir): The occurrence of water in an aquifer that is heated by the surroundings and that is maintained under a hydrostatic pressure greater than the saturation pressure so that no steam phase forms. Geothermal phenomena: An observable event at the surface, whose occurrence is the result of the Earth's internal heat; includes volcanoes, geysers, hot springs, mud pots and fumaroles. Geothermal potential: The quantity of heat that can be released by cooling a given volume component of the earth's crust at a known location down to a specific temperature (e.g. 100÷C).
Note: This term is not to be confused with geothermal energy potential. Geothermal power plant: A facility which uses geothermal steam or heat to drive turbine-generators to produce electricity. Three different types make use of the various temperature ranges of geothermal resources: dry steam, flash and binary. Geothermal power station/plant (geothermal heat station/plant): A geothermal power station or plant converts geothermal energy into electrical energy. A geothermal heat station or plant makes geothermal energy available as heat only, e.g. for space heating and process heating.
Note: The temperature of the geothermal fluid determines its potential application, namely:
up to 80÷C - space heating
up to 150÷C - process heating and/or electricity generation
over 150÷C - electricity generation Geothermal reservoir: A large volume of underground hot water and steam in porous and fractured hot rock.
The hot water in geothermal reservoirs occupies only 2 to 5% of the volume of rock, but if the reservoir is large enough and hot enough, it can be a powerful source of energy.
Geothermal reservoirs are sometimes overlain by a layer of impermeable rock.
While geothermal reservoirs usually have surface manifestations such as hot springs or fumaroles, some do not. Geothermal resource: The natural heat, hot water, and steam within the Earth. Geothermal steam: A geothermal fluid in the vapor phase. Geothermal steam field (geothermal steam reservoir): The occurrence of steam in underground structures that has been generated as a result of geothermal anomalies but which, due to enclosing strata, cannot escape or can only escape in negligible quantities. Geothermal water: Water heated by the natural heat inside the Earth. Geothermometer: Method of estimating the temperature of a geothermal reservoir based on the minerals in the reservoir rock or the concentration of chemical species in geothermal fluids that have come from the reservoir. Geyser: Hot spring that ejects steam and hot water; many geysers erupt at regular intervals of time. Geysers, The (note: "The" of "The Geysers" is always capitalized): A large geothermal steam field located north of San Francisco. Gigawatt (GW): One billion watts. Gigawatt-hour (GWh): One billion watt-hours. Global warming/greenhouse effect: The trapping of heat in the atmosphere. Incoming solar radiation goes through the atmosphere to the Earth's surface, but outgoing radiation (heat) is absorbed by water vapor, carbon dioxide, and ozone in the atmosphere. At certain levels this is beneficial because it keeps the planet warm enough for life as we know it. However, an increase in the normal amount of carbon dioxide and other gases may contribute to a human-caused warming trend that could have serious effects on global climate, the global ecosystem, and food supplies. Greenhouse effect: The increasing mean global surface temperature of the Earth caused by gases in the atmoshpere (including carbon dioxide, methane, nitrous oxide, ozone, and chlorofluorocarbon). The greenhouse effect allows solar radiation to penetrate but absorbs the infrared radiation to space. Grid: The layout of an electrical distribution system. Gross generating capacity: Means the total power output of a plant or project before deducting the amount of power that is used for the operation of all necessary auxiliary equipment (such as pumps and cooling towers). Back to Top H
Health spa: An establishment (often commercial) which is visited by guests seeking therapy and relaxation; many center around hot mineral springs or use hot water from geothermal wells. Heat exchanger: A device in which heat is transferred by conduction through a metal barrier from a hotter liquid or gas, to warm a cooler liquid or gas on the other side of the metal barrier. Types of heat exchangers include "shell and tube," and "plate". Heat flow: Dissipation or transfer of heat coming from within the earth by conduction, convection or radiation at the surface; usually reported in units of energy per unit per time per unit area, for example, joules per second per square meter or watts per square meter. Heat pumps: See Geothermal heat pumps. Heat rate: The ratio of the energy content of the fuel used to the electrical energy produced over a given period: it can be referred to the electricity generated (gross) or the electricity supplied (net).
The reciprocal of the heat rate expressed as a percentage is the thermal efficiency of the power station. In case of the "heat rate" the units should be stated; in the case of the "thermal efficiency" the energy content of the fuel and the electrical energy produced must be expressed in the same unit. Heat transfer: The transmission of heat.
There are three forms of heat transfer: "conduction," "convection," and "radiation." See these terms. High temperature area (hyper-thermal area): Area of geothermal potential with temperature gradients greater than 100 K/km.
Note: The classification of areas as above defined is not recognized in some countries, while in others the dividing line is taken as 80 K/km. High voltage: A voltage equal to or higher than a specified voltage that may vary legally from one country to another (e.g. in most European countries it now applies to voltage above 1000 V between conductors). Hot dry rock: A geothermal resource created when impermeable, subsurface rock structures, typically granite rock 15,000 feet or more below the Earth's surface, are heated by geothermal energy. The resource is being investigated as a source of energy production. Hot dry rock technology: A process of extracting useful geothermal energy by the injection of a heat-exchange medium (water) into hot dry rock. Hot lava: Geologically recent lava-fields with high rock temperatures, i.e. up to approximately 1200÷C. Hot spot: Areas of volcanic activity found n the middle of lithospheric plates, caused from an upwelling of concentrated heat in the mantle.
Hot spots remain stationary while the plates move over them, often leaving a chain of extinct volcanoes as the plate moves away from the hot spot; examples include the Hawaiian Islands and Yellowstone National Park. Hot spring: A thermal spring whose temperature is above that of the human body. Hydraulic fracturing: The fracturing of rock formations by hydraulic pressure, sometimes accompanied by the injection of propping material (e.g. sand) to hold open the hydraulically induced fracture. Hydroelectrical power station: A plant designed to convert the gravitational energy of waters into electrical energy. Hydrogeological flow: The movement of underground waters. Geothermal flows arise as a result of pressure and/or temperature differences and they produce convective heat transfer. Hydrothermal: Hydro means water and thermal means heat. Literally hydrothermal means hot water.
Steam and hot water reservoirs are hydrothermal reservoirs.
Hot dry rock resources and magma resources are not considered to be hydrothermal resources. Hydrothermal resource: Underground systems of hot water and/or steam. Back to Top I
Impermeable: Does not allow liquids to pass through easily - certain rock types and clay soil are impermeable. Impurities content of geothermal fluid: Substances in chemically combined, dissolved or undissolved state that are contained in the geothermal fluid.
Note: The impurity content of the geothermal fluid is a factor that may seriously affect the economics of exploiting a particular geothermal field.
Fluids with a high mineral content can involve special effluent risks and have corrosive effects on commercial plant. Injection: The process of returning spent geothermal fluids to the subsurface. Sometimes referred to as reinjection. Injection well: A well through which geothermal water is returned to an underground reservoir after use. Geothermal production and injection wells are constructed of pipes layered inside one another and cemented into the earth and to each other.
This protects any shallow drinking water aquifers from mixing with deeper geothermal water. Input to network: The sum of the electricity supplied by the electricity generators of the network and supplies from other sources. Installed capacity (gross installed capacity): The capacity measured at the output terminals of all sets in the station - it includes power taken for the station's internal load. Integrated Plant: The integrated power plant is a combination of a Combined Cycle Plant (OCCU, OCCM) heated by steam, and Ormat® Energy Converters (OEC) heated by brine.
Both the brine and the steam come from a geothermal fluid separator or from different wells.
Integrated plant may include a reinjection system.
For example:
i. The 27 MW ORMAT® Integrated Geothermal Power Plant at Rotokawa, New Zealand, comprises on 22 MW ORMAT® Combined Cycle Module (OCCM) operating on geothermal steam and one 5 MW ORMAT® Energy Converter (OEC) operating on geothermal brine.
ii. The Upper Mahiao Integrated Geothermal Plant is comprised of 4 ORMAT® Combined Cycle Modules (OCCU) and one OEC. Integrated Two Level Unit: An OEC comprised of two turbines on two end shafts of the same generator - each turbine driven by a vapor at a different pressure from a different vaporizer. Interconnected or interconnecting network/system: A network that can be regulated in its overall performance, both nationally and/or internationally in such a way that it enables electricity demand to be met with electricity generation optimally both as regards economics and reliability. Interconnecting or interconnected network: The interconnecting network makes it possible to connect two or more systems or networks in particular for interregional or international exchanges of large amounts of energy in order to improve the profitability and the reliability of supply. Interconnection: The connection, by one or more lines, between two or more systems or parts of systems, and the equipment for such connection. Inverter station: An installation for converting direct current into single or multi-phase alternating current. ITLU: See integrated two level unit. Back to Top K
Kilowatt (kW): Means one thousand Watt. Kilowatt-hour (kWh): A unit of electrical energy equal to the energy produced in one hour by a power supply of 1 kW of power output. One thousand Watt-hours kW month: A unit of electrical energy equal to the energy produced in one month by a power supply of 1 kW of power output. kW year: A unit of electrical energy equal to the energy produced in one year by a power supply of 1 kW of power output. Known geothermal resource area: A regionidentified by the U.S. Geological Survey as containing gothermal resources. Back to Top L
Lava: Magma that has flowed to the surface of the earth, at first in the molten state but becoming solidified after eruption from a vent (effusive rock, eruptive rock).
The rock ranges from basic to acid; when solidified it is generally vesicular due to the escape of gases during solidification and sometimes has a glassy appearance due to rapid cooling. Leaching: The removal of readily soluble components, such as clorides, sulfates, organic matter, and carbonates, from soil by percolating water. The remaining upper layer of leached soil becomes increasingly acidic and deficient in plant nutrients. Lead time: The period of time that elapses between the date of ordering of an installation or plant and the date on which the installation or plant or the first unit of the installation or plant is contractually deemed to be delivered or commissioned. Lignite: The lowest rank of coal, often referred to as brown coal, used almost exclusively as fuel for steam-electric power generation. It is brownish-black and has a high inherent moisture content, sometimes as high as 45 percent. The heat content of lignite ranges from 9 to 17 million Btu per ton on a moist, mineral-matter-free basis. The heat content of lignite consumed in the United States averages 13 million Btu per ton, on the as-received basis (i.e., containing both intherent moisture and minteral watter). Load (Electric): The amount of electric power delivered or required at any specific point of points on a system. The requirement originates at the energy-consuming equipment of the consumers. Load-controlled consumer: An electricity consumer whose demand may be regulated in such a way that it contributes to producing a smoother load curve of the electricity supply network/ system; an interruptible consumer is a particular case of a load-controller consumer. Load dispatching center: The appropriate center for switching or directing the switching of power stations on-line and for load changing. In general the load dispatching center and the system control center are one and the same in the case of centrally controlled systems/networks. Load factor: The ratio of consumption within a specified period of consumption that would result from continuous use reflecting maximum or other specified demand occurring within the same period. Low temperature area (semi-thermal area): Area of geothermal potential with temperature gradients less than 100 K/km. Low voltage: A voltage equal to or lower than a specified voltage that may vary legally from one country to another (e.g. in most countries it applies to voltage of 1000 V or below between conductors). Back to Top M
Magma: Mass of molten rock within the Earth's crust. Magma-chamber: An inclusion of magma in the Earth's crust. Mantle: The semi-molten interior of the Earth that lies between the core and the crust making up nearly 80% of the Earth's total volume; extends down to a depth of about 1800 miles (2,900 kilometers) from the surface. Maximum capacity (maximum electric capacity): In the case of a thermal unit or station, the maximum power that could be produced under continuous operation with the entire plant running and with adequate fuel stocks of normal quality.
In the case of a hydro-electric installation, the maximum power that could be produced throughout a given period of operation with the entire plant running and with flow and head at their optimum values. Maximum power produced: The maximum value of output or load which can be maintained for a specified period. Maximum output capacity (net output capacity; output capacity): The capacity measured at the point of outlet of the network. Mechanical energy: the energy an object has because of its motion or position and the forces acting on it. Megawatt (MW): A unit of power, equal to a thousand kilowatts (kW) or one million watts (W).
The watt is a unit of power (energy/time), the rate energy is consumed or converted to electricity.
One MW is enough energy to power 1,000 average homes. Megawatt-hour (MWh): One million watt-hours. Meshed network/system: A network or part of a network which is wholly or mainly composed of ring circuits all or most of which emanate from and terminate at different sources of supply, or any more complex system of multiple ring circuits with multiple supply sources. Methane: A light hydrocarbon that is the main component of natural gas and marsh gas. It is the product of the anaerobic decomposition of organic matter, enteric fermentation in animals and is one of the greenhouse gases. Chemical formula is CH4. Micron: A unit of length equal to one-millionth of a meter. Mineralized: Containing minerals; for example, mineralized geothermal water contains dissolved minerals from inside the Earth. Minimum capacity: The lowest capacity in a given period. Minimum stable generating/capacity: The lowest capacity at which a station can be operated without technical difficulty. Modular Plant: Power plant built from identical or similar units (OEC, ITLU, OCCU or OCCM)
For example:
i. The Puna Geothermal Power Plant comprises 10 combined cycle units.
The plant is modular because it contains OCCUs. ii The Ormesa IH Geothermal Power Plant comprises 12 ORMAT® Energy Converters.
The plant is modular because it contains OECs. iii The Upper Mahiao Geothermal Power Plant comprises 4 modules each composed of 1 Steam Turbine and 3 OECs.
The plant is modular because it contains OCCM. Mud pot (paint pot): thermal surface feature which occurs where there is not enough water to support a geyser or hot spring even though there may be some hot water below.
Steam and gas vapors bubble up through mud formed by the interaction of gases with rock. Multiple circuit line: A line comprising several electrical circuits. MW or MegaWatt: Means one million watts. A MegaWatt is equal to one thousand kilowatts. MWh or MegaWatt hour: Means one thousand kWh. Back to Top N
Natural gas: A gas mixture (mostly methane) trapped underground in many places near the surface of the Earth; a fossil fuel. Net electrical generating capacity: Means the power output that can be continuously sold to the purchasing utilities. Net generation: Means the amount of electrical energy available for sale to the purchasing utility. Network: All the pipework, stations and other installations which are interconnected.
A network may be named according to its function, its opening method, its voltage, its pressure, its quality and its legal status. Network system: A grouping of lines and of other electrical equipment connected for the purpose of conveying electricity from generating stations to the ultimate consumer. Network/system internal consumption: Such consumption of electrical energy by ancillary equipment as is required for the operation of the network/system. Network/system losses (transmission and distribution): The energy losses occurring in transmission and distribution in a specific network/system. Nitrogen oxides (NOx): Formed in combustion; appear as yellowish-brown clouds; can irritate lungs, cause lung diseases, lead to formation of ozone (which is harmful n the lower atmosphere, but necessary as protection from UV rays in the upper atmosphere). Nominal capacity (rated capacity, rated power, rating): The maximum continuous capacity/ power/rating for which the plant has been ordered and designed, as indicated on the makers' nameplate or in the manufacturers' specification. Nominal generation (nominal production): The product of the nominal capacity and the reference period.
The term "nominal output" is sometimes employed; the word "output" however, is imprecise and may mean either production or capacity. Noncondensible gases: In geothermal, chemical species (such as carbon dioxide or hydrogen sulfide) that are constituents of geothermal fluids, that partition primarily into the vapor phase when geothermal fluids boil, and that do not condense along with geothermal steam when put through a condenser in a geothermal power plant. Nonrenewable resource: Resources that are not replaced or regenerated naturally within a period of time that is useful; this includes fossil fuels, uranium and other minerals. NOx: Oxides of nitrogen that are a chief component of air pollution that can be produced by the burnng of fossil fuels. Also called nitrogen oxides. Nuclear energy: Power obtained by splitting heavy atoms (fission) or joining light atoms (fusion). A nuclear energy plant uses a controlled atomic chain reaction to produce heat. The heat is used to make steam run conventional turbine generators. Nuclear power station: A power station in which the energy released by nuclear fuels is converted into electrical energy. Back to Top O
OCCM: See Ormat Geothermal Combined Cycle Module. OCCU: See Ormat Geothermal Combined Cycle Unit. OEC: The ORMAT® Energy Converter is a power generation unit which converts low and medium temperature heat energy into electrical energy through an Organic Rankine Cycle. Once-through water-cooling: A cooling system in which water is drawn from an available source, e.g. river, sea, lake, canal, passed once through the power station condensers and returned in its heated condition directly to the source. Operating Time: The period of time during which a plant or part of a plant supplies useable energy. Operation time ratio: The ratio of the operating time to the reference period. Operating voltage: The voltage at any moment across two line wires of machines or apparatus in operation. Optimum capacity: The capacity at which a system or a station has its highest efficiency. ORC: See Organic Rankine Cycle Organic Rankine Cycle: The Organic Rankine Cycle (ORC) is a Rankine Cycle (where the working fluid is organic). Ormat Geothermal Combined Cycle Module (OCCM): The OCCM is based on a large back pressure steam turbogenerator and one or more OEC heated by the low pressure steam exiting from the steam turbine Ormat Geothermal Combined Cycle Unit (OCCU): The OCCU is based on a combined cycle consisting of a back pressure steam turbine and an OEC heated by the low pressure steam exiting from the steam turbine.
The two turbines are on the two end shafts of the same generator.
For example: Puna Unit. ORMAT® ENERGY CONVERTER (OEC): See OEC. OTU: Ormat® Topping Unit - see topping unit. Outage: The period during which a generating unit, transmissionline, or other facility is out of service. Overhead line/cable: an electric line situated above ground usually with the conductors supported on insulators and appropriate supports. The term would include works and fittings associated with the line. Oxides of Nitrogen: See NOx Back to Top P
Pangaea: The huge supercontinent which scientists think may have existed 250 million years ago. All of the continents may have at one time been joined together to make this huge land mass. Particulates (particulate matter): Dust, soot, smoke and other suspended matter; can be respiratory irritants.
Particulate matter smaller than 10 microns (pm 10) has been found to be particularly harmful to health. Permeable: Able to transmit water or other liquids; for example rock with tiny passageways between holes, fractured rock, and gravel are permeable. Petroleum: A mixture of hydrocarbons existing in the liquid state found in natural underground reservoirs, often associated with gas. Petroleum includes fuel oil No.2, No.4, No.5, No.6; topped crude, Kerosene, and jet fuel. Phreatic eruption: An explosion of the surface of the earth that results from a sudden increase in the volume of groundwater when it flashes to steam due to contact with hot rocks. Planned unavailability time: The period of time during which a plant or part of a plant is not in running order due to planned maintenance. Plant: A facility at which are located prime movers, electric generators, and auxiliary equipment for converting mechanical, chemical, and/or nuclear energy into electric energy. A plant may contain more than one type of prime mover. Electric utility plants exclude facilities that satisfy the definition of a qualifying facility under the Public Utility Regulatory Policies Act of 1978. Plant connection agreement: Means an agreement that governs the interconnection of and the transmission lines that interconnect a power plant and another electric facility. Plant maintenance: Means maintaining plant equipment in accordance with manufacturer specifications, operations and maintenance manuals and procedures. Plate tectonics: The study of the movement of the large crustal plates (lithospheric plates) of the Earth's shell.
The earth's shell is broken in several pieces (12 large ones and several smaller ones).
These plates move toward and away from one another at about the rate our fingernails grow.
The process that creates the dynamic movement of the plates includes the convection of magma in the mantle and lithosphere. Plate tectonics helps to explain continental drift, seafloor spreading, volcanic eruptions and other geothermal phenomena, earthquakes, mountain formation and the distribution of some plants and animal species. Pluton: Hot rock at varying depths. In cases of geological anomaly this rock may be relatively near the surface. Point source: A stationary location or fixed facility from which pollutants are discharged. Porosity: The ratio of the aggregate volume of interstices in a rock or soil to its total volume, usually stated as a percent. Porous: Full of small holes (pores); able to be filled (permeated) by water, air, or other materials. Power: Electricity for use as energy. Power factor: In the metered consumption of alternating current electrical equipment, the ratio of watts to volt-amperes or of active power to apparent power. Expressed as a decimal fraction, it provides a measure of the extent to which reactive power is being taken in addition to the power.
Note: Power factor indicates the efficiency with which electrical capacity is utilized and tariff/rate contracts can incorporate terms relating charges to power factor levels. Systems and devices may be applied to correct the power factor. Also called cosinus phi. Power plant: A central station generating facility that produces energy. Power produced, utilized capacity (operating capacity): The actual capacity operated. In principle it is measured as an instantaneous value and must refer to a given time, however, by convention it may be derived from the energy produced during a certain period which it is necessary to define for statistical purposes (the ratio of the electricity produced to the operating period). The power produced may be gross or net. Power purchase agreement nameplate: Means the maximum rate of energy production that the purchasing utility is obligated to purchase under the applicable power purchase agreement. Power station internal consumption (station service consumption): The electricity consumed by a power station or power station set in its auxiliary plant, including electricity consumed when out of service, together with the losses in its generator transformers. Power station internal load (station service load; auxiliaries load): The electrical capacity of a power station or power station set, that is required for its auxiliary plant, together with the capacity represented by the losses in its generator transformers. Pressure: The force exerted over a certain area. Our atmosphere exerts pressure on the surface of the earth, and layers of rock exert pressure on those below them. Price: The amount of money or consieration-in-kind for which a service is bought, sold or offered for sale. Primary power: Refers to the normal source of power a device uses to function.
For a home or business, the primary power would typically be the utility power grid (if attached to it), for most of today's vehicles, it would be the internal combustion engine. Zinc/air fuel cells powering cars would represent a primary power use - with drivers exchanging spent fuel for fresh fuel as regenerative fuel stations (equivalent to today's gas stations). PUHCA: Means the Public Utility Holding Company Act of 1935, as amended. PURPA: Means the Public Utility Regulatory Policies Act of 1978, as amended, and the regulations promulgated thereunder.
This statute requires States to implement utility conservation programs and create special markets for co-generators and small producers who meet certain standards, including the requirement that States set the prices and quantities of power the utilities must buy from such facilities. Pyroclastic: Formed by or involving fragmentation as a result of volcanic or igneous action. Back to Top Q
Qualifying Cogeneration Facility: Means a "Qualifying Cogeneration Facility" as that term is defined in PURPA, which is one of two types of Qualifying Facilities. Qualifying Facility (QF): A cogeneration or small power production facility that meets certain ownership, operating, and efficiency criteria established by the Federal Energy Regulatory Commission (FERC) pursuant to the Public Utility Regulatory Policies Act (PURPA). Qualifying Small Power Facility: Means a "Qualifying Small Power Facility" as that term is defined in PURPA, which is one of two types of Qualifying Facilities. Back to Top R
Radial system: A system or part of a system which is wholly or mainly composed of radial circuits and hence points to be supplied do not have a supply available to them in more than one direction Radiant energy: Energy (heat) that is transferred by rays or waves, especially electromagnetic waves, through space or another medium. Radiation. Rankine cycle: The Rankine Cycle is an ideal thermodynamic cycle consisting of heat addition at constant pressure, isentropic expansion, heat rejection at constant pressure, and isentropic compression: it is used as an ideal standard for the performance of heat-engine and heat-pump installations operating with a condensable vapor as the working fluid, such as a steam (steam Rankine cycle) or organic fluid (organic Rankine cycle). Rated voltage: The voltage used in the specification of a machine, plant, network or apparatus and from which the test conditions and the voltage limits for the use of the machine etc. are calculated. Rectifier station: An installation for converting single or multi-phase alternating current into direct current. Reference period: The period of time to which data relate; in the context of this section it is the sum of the availability time and the unavailability time. Regulation: The governmental function of controlling or directing economic entities through the process of rulemaking and adjudication. Reinjection: The return of water to an aquifer after the extraction of its thermal energy, for prevention of environmental pollution due to the mineral content of the water and/or for maintaining stable underground conditions of pressure and supply.
Water from another source may also be injected for the latter purpose. Reinjection/injection: The process of conveying geothermal fluids to sub-surface formations through wells. Reliability: Electric system reliability has two components: adequacy and security. Adequacy is the ability of the electric system to supply to aggregate electrical demand and energy requirements of the customers at all times, taking into account scheduled and unschedled outages of system facilities. Security is the ability of the electric system to withstand sudden disturbances, such as electric short circuits or unanticipated loss of system facilities. The degree of reliability may be measured by the frequency, duration,a nd magnitude of adverse effects on consumer services. Renewable energy: Resources that constantly renew themselves or that are regaarded as practically inexhaustible. These include solar, wind, geothrmall, hydro and wood. Although particular geothermal formations can be depleted, the natural heat in the Earth is a virtually inexhaustible reserve of potential energy. Renewable resources also include some experimental or less-developed sources such as tidal power, sea currents and ocean thermal gradients. Renewable energy credit: Means one megawatt hour of renewable energy that meets the renewable energy requirements.
The power from a renewable energy facility is not physically delivered to the customer, but the environmental benefits created by the facility are attributed to that customer, directly offsetting the environmental impact of the customer's conventional energy use. Renewable resource: A resource that can be used continuously without being used up (because it regenerates itself within a useful amount of time). Examples include water (small hydro) and wind power, solar energy, and geothermal energy. Reserve capacity: Cold stand-by, hot stand-by and spinning reserve capacities that serve to meet any difference between the anticipated capacity demand and the capacity demand actually occurring. Reservoir: A natural underground container of liquids, such as water or steam (or, in the petroleum context, oil or gas). Resource Conservation and Recovery Act (RCRA): A federal law enacted in 1976 to address the treatment, storage, and disposal of hazardous waste. Revenue: The total amount of money received by a firm from sales of its products and/or services, gains from the sales or exchange of assets, interest and dividends earned on investments, and other increases in the owner's equity except those arising from capital adjustments. Rift zone: Long narrow fractures in the crust found along ocean floor or on land, from which lava flows out; often associated with spreading centers from which tectonic plates are diverging, such as the mid-Atlantic Ridge. Ring of Fire: A belt of intense volcanic, geothermal and earthquake activity found all around the Pacific Rim caused by plate tectonic activity. Ringed network/system: A network or part of a network which is wholly or mainly composed of ring circuits, all or most of which individually emanate from and terminate at the same source of supply. Ripple control: A method of load management control which involves connecting and disconnecting consumer groups, the necessary remote control being effected via the distribution network/system. Back to Top S
Salinity: Dissolved salt content of a fluid, often a characteristic of geothermal fluids. Scrubber: See Flue gas desulphurization unit. Selective catalytic reduction: A post combustion control to reduce nitrogen oxide gas emissions. Short-run avoided costs: Means the incremental costs that a power purchaser avoids by not having to generate electrical energy. Short ton: A unit of weight equal to 2,000 pounds. Single bore-hole (concentric pipe) technology (down-hole heat-exchanger technology): process for exploiting the potential of geothermal energy with the use of a single bore hole in which the bore hole is fitted with twin pipes, generally concentrically arranged, the heat-transfer medium (water) being fed to the geothermal rock formation through the inner pipe and returned to the surface through the outer pipe; in the case of the down-hole heat-exchanger technology, the system is a closed one. Single bore-hole technology: The simplest system for the exploitation of geothermal energy, in which naturally occurring geothermal fluids are produced from a single bore hole and, after extraction of the available energy, the fluids are discarded at the surface. Single circuit line: A line having only one electrical circuit. Sinter: A chemical sedimentary rock deposited by precipitation from mineral waters, expecially siliceous sinter and calcareous sinter. Solfatara: Hot spring or pool venting sulphur-rich gases. SRAC: Means short-run avoided costs. Stability: The property of a system or element by virtue of which its output will ultimately attain a steady state. The amount of power that can be transferred from one machine to another following a disturbance. To stability of a power system is its ability to develop restoring forces equal to or greater than the distrurbing forces so as to maintain a state of equilibrium. Stand-by availability time: The period of time during which a plant or part of a plant could supply useable energy after the normal period of start-up. Steam: The vapor form of water that develops when water boils. Steam is made of very tiny heated water particles (molecules) which are bouncing around and bumping into each other at very high speeds.
These heated water molecules are also spreading out and expanding in every direction they can.
If we confine or trap water in a container, with a pipe as an opening, and heat the water to steam, it will create great pressure in the container and will rush out the pipe with a great deal of force. This force (the "power" of steam) can be put to work turning a turbine connected to an electricity generator. Steam Turbine Generator Unit: The Steam Turbine Generator Unit is a turbogenerator operated with steam. Subduction boundary: One of two types of converging plate boundaries which occurs when one plate plunges under another overriding plate. Subsidence: A sinking of an area of the Earth's crust due to fluid withdrawal and pressure decline. Sulfur oxides (Sox): Pungent, colorless gases (including sulfur dioxide SO2); formed primarily by the combustion of fossil fuels; may damage the respiratory tract, as well as plants and trees. Superconductor: An electrical conductor offering negligible resistance.
Note: With present technology superconductivity can be achieved as the extreme case of the phenomenon by which metals cooled from room temperature sees their resistivity decreased and they attain low value at low temperatures; some conductors have a critical temperature below which their electrical resistance approaches zero, i.e. they become superconducting. Supply terminals (delivery/terminal point): The point in a system/network at which a purchaser/consumer contractually receives electrical energy. Sustainable: Material or energy sources which, if managed carefully, will provide the needs of a community or society indefinitely, without disproving future generations of their needs. Switching station: An electrical installation of the selective connection and disconnection of the lines of a system/network and of consumer installations by means of switchgear. System: A combination of equipment and/or controls, accessories, interconnecting means and terminal elements by which energy is tansformed to perform a specific function, such as climate control, service water heating, or lighting. System control center: The appropriate center for switching or directing the switching of the lines of a network/system. System (Electric): Physically connected generation, transmission, and distribution facilities operated as an integrated unit under one central management, or operating supervision. System load factor (annual): The ratio of the average load throughout the year on an energy system to the maximum load on the system during that year, expressed as a percentage and employed as a measure of the fluctuating pattern of consumer demand. In order to allow for weather variations when comparing one year with another, the true system load factor may be adjusted to average climatic conditions. Back to Top T
Technique: Method of performance or manipulation.
The word can be used in reference to organized methods based on relevant scientific knowledge. Technology: The application of knowledge to achieve practical results. "Technology" may be embodied in a piece of equipment, or a technique of performing a particular manufacturing activity. Thermal pollution: A reduction in water quality caused by increasing its temperature, often due to disposal of waste heat from industrial, power generation processes, or urban impervious surfaces (such as parking lots). Thermally polluted water can harm the environment because plants and animals may have difficulty adapting to it. Terrestrial heat flow: The flow of heat traveling from the interior of the earth, in consequence of the higher temperatures prevailing in the interior arising from the natural decay of radioactive elements in the earth's crust and residual heat in the earth's formation.
The mean terrestrial heat flow at the earth's surface amounts to approximately: 0.06 J(m2.s)
Note: 1 HFU (Heat Flow Unit) = 4.18 x 10-6 J/(cm2.s), giving a mean terrestrial heat flow of approximately 1.5 HFU. Therapeutic: The treatment of disease or other disorder; something that may benefit health. (Geothermal) hot springs are often thought of as therapeutic. Thermal waters (geothermal warm water reservoir): The occurrence in geological structures of warm and hot water at a temperature below that of saturated steam at the prevailing pressure. Topping Unit (OTU): The Topping Unit is a back pressure steam turbine that produces power while reducing the high available steam pressure to a required condition upstream from an existing steam or combined cycle plant. Toxic/corrosive gases: Naturally occurring gases that may be associated with the geothermal fluid and that have corrosive or toxic characteristics, e.g. CO2, H2S, HCl, HF, NH3, etc. Transforming station: A substation which includes transformers for transferring electricity between systems operating at different voltage levels. Transmission: The movement or transfer of electric energy over an interconnected group of lines and associated equipment between points of supply and points at which it is transformed for delivery to consumers, or is delivered to other electric systems. Transmission is considered to end when the energy is transformed for distributrion to the consumer. Transmission capacity/capability: The highest permissible continuous loading of the transmission equipment with respect to heating, stability and voltage drop. Transmission lines: Wires that transport electricity over long distances. Transmission network/system: A system of transmission lines serving for the super-regional transport of electricity and feeding to subsidiary systems. Transmission or distribution route/right of way: the area required for running an overhead line or underground line, horizontally projected and measured along the route axis. Transmission service agreement: Means an agreement that governs the transmission and delivery of energy over a transmission system. Transmission serving utility: Means a utility that manages the transport of electricity from generation centers over significant distances to interchanges with distribution networks of utilities. Travertine: A mineral consisting of a massive usually layered calcium carbonate (as aragonite or calcite) formed by deposition from spring waters or especially from hot springs. Turbine: A machine with blades that are rotated by the forceful movement of liquid or gas, such as air, steam or water or a combination. Turbine generator: See Turbogenerator unit. Turbogenerator Unit: The Turbogenerator Unit is a basic generating unit consisting of a turbine operated by high pressure vapor or gas driving an electrical generator.
A device that uses steam, heated gases, water flow or wind to cause spinning motion that activates electromagnetic forces and generates electricity. Back to Top U
Unavailability time: The total of the planned and unplanned unavailability time. Underground/submarine line/cable: An electric line situated in the ground/under water. The terms would include works and fittings associated with the line. Unplanned unavailability time: The period of time during which a plant or part of a plant is not in running order due to unforeseen breakdowns. USFWS: Means the United States Fish & Wildlife Service. Utility: A regulated entity which exhibits the characteristics of a natural monopoly. For the purposes of electric industry restructuring, "utility" refers to the regulated, vertically-integrated electric company. "Transmission utility" refers to the regulated owner/operator of the transmission system only/ "Distribution utility" refers to the regulated owner/operator of the distribution system which serves retail customers. Utilization period: The quotient of the energy obtained, produced, distributed or consumed within a specific period and the maximum capacity of the plant occurring within the same period. Back to Top V
Vaporize: To change into gas form anything which is normally a liquid or a solid; the term is most commonly used in reference to water (which vaporizes to steam). Vapor dominated: A geothermal reservoir system in which subsurface pressures are controlled by vapor thatehr than by liquid. Sometimes referred to as a dry-steam reservoir. Volcano: An opening in the Earth's crust from which lava, steam, and/or ashes erupt (or flow), either continuously or at intervals. Voltage: The measure of the amount of force that "pushes" an electric current. Back to Top W
Warm spring: Thermal spring whose temperature is appreciably above the local mean annual temperature but below that of the human body. Water inclusions (depressurized system): Water locked in between layers of rock and maintained under lithostatic pressure. Water phases: The change of water from one state to another.
The change from ice to liquid is melting; the reverse process is freezing.
The change from liquid to gas is evaporation and the product is water vapor; the change from water vapor to liquid is called condensation. Evaporation and condensation are both important functions in geothermal phenomena and in geothermal technology. Watt (W): The electrical unit of power. The rate of energy transfer equivalent to 1 ampere flowing under a pressure of 1 volt at unity power factor. Watt-hour (Wh): An electrical energy unit ofmeasure equal to 1 Watt of power supplied to, or taken from, an electric circuit steadily for 1 hour. Wet cooling system: Means the cooling tower and associated systems (such as cooling water pumps, piping, valves, etc.) Back to Top | 
