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Dictionary of Energy

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of overburden that can be profitably removed to obtain a unit amount of coal.

stripper Oil & Gas. a term for an oil or gas well that produces at relatively low rates.

strobe (light) Lighting. 1. a lamp that is capable of producing an extremely brief and intense flash of light; used in high-speed photography of rapidly moving objects. 2. a similar bright, flashing light used for visual effects, as for a theatrical performance, concert, and so on.

stroke Transportation. the linear distance traveled in either direction by a piston or rod in an engine; the standard fuel cycle for a car or truck engine consists of four strokes: intake, compression, power, and exhaust.

strontium Chemistry. an alkaline-earth metal and element having the symbol Sr, the atomic number 38, an atomic weight of 87.62, a melting point of 770°C, and a boiling point of 1380°C; a silvery metal that rapidly turns yellowish in air, found naturally as a nonradioactive element with 16 known isotopes, 12 of which are radioactive.

strontium-90 Chemistry. a heavy radioactive isotope of strontium with a half-life of 29.1 years, formed as a fission product and present in the fallout from nuclear explosions; it poses a significant hazard in humans and animals because, like calcium, it can be assimilated and deposited in bones.

structural trap Oil & Gas. a sealed oil or gas reservoir that results from structural deformation, rather than from changes in the physical properties of the formation.

stückofen History. an important precursor to the blast furnace, in which malleable iron was produced directly from the ore; widely employed in Saxony, Austria, and the Rhineland in the medieval era. [Literally, “wolf oven”; the large mass of iron produced by this oven was known as a stücke, or wolf.]

stumpage Biomass. 1. timber in the form of standing uncut trees; i.e., still on the stump. 2. the value or rate paid to a property owner for a stand of trees before their harvest.

Sturgeon, William 1783–1850, English engineer who built the first practical electromagnet (1825), invented the commutator for electric motors (1832), and made the first moving-coil galvanometer (1836).

styrene Materials. C6H5CH=CH2, a colorless, toxic liquid with a strong aromatic aroma. Insoluble in water, soluble in alcohol and ether; it polymerizes rapidly and can become explosive. Used in making polymers and copolymers, polystyrene plastics, and rubbers.

subatomic Physics. below the atomic level; describing a particle of matter smaller than an atom, such as an electron.

subbituminous coal Coal. a black to dark brown coal that ranks above lignite and below bituminous coal, used mainly as fuel for steam-electric power generation. It has a higher carbon content and lower moisture content than lignite. The heat content of subbituminous coal generally ranges from 16 to 24 million Btu per ton on a moist, mineral- matter-free basis.

subcooler Refrigeration. a condenser device that improves the energy efficiency of a chiller by reducing the temperature of the condensed refrigerant liquid.

subcooling Refrigeration. 1. the process of creating a decrease in temperature by removing sensible heat from a refrigerant liquid. 2.


subcritical Nuclear. the condition of a nuclear reactor system when the rate of production of fission neutrons is lower than the rate of production in the previous generation, owing to increased neutron leakage and poisons. Thus, subcriticality.

subcritical mass Nuclear. an amount of fissile material that by its mass or geometry is incapable of sustaining a fission chain reaction.

subcritical reactor Nuclear. a nuclear reactor in which the number of fissions decreases over time.

subduction zone or boundary Earth Science. a region along which one lithospheric plate descends into the earth’s mantle relative to another plate.

sublimate Chemistry. 1. to carry out a process of sublimation. 2. a product obtained from sublimation.

sublimation Chemistry. 1. the phase change of a material directly from a solid to a gas without passing through an intermediate liquid phase. 2. the reverse of this same process.



suction pump

submergence Earth Science. 1. the fact of a site being submerged under water, especially the permanent flooding of land upstream from a dam. 2. a change in the level of water in relation to the land, so that formerly dry land becomes inundated due to sinking of the land or a rise in water level.

submersible Oil & Gas. describing oil drilling equipment that can be submerged; see


subsidence Earth Science. 1. a local mass movement in which a portion of the earth’s surface gradually settles downward or is displaced vertically, with little or no horizontal movement. 2. a descent of air in the atmosphere, usually over a wide area. 3. Mining. the sinking of strata, including the surface, as a result of underground excavations such as coal mining or crude oil extraction.

subsidy Economics. money paid, usually by a government, to either a producer or consumer of a certain product or service that alters its production cost or selling price to the benefit of the recipient; e.g., payments made to farmers to grow or not grow certain crops.

subsistence farming (agriculture) Ecology. the practice of farming in which the yield is only sufficient to feed the farmer and his family, with little or no surplus that could be sold or traded to others for a profit.

subsistence fishery (fishing) Ecology. the practice of catching fish (or harvesting other aquatic organisms) for the purpose of immediate household consumption, rather than for sale to others.

subsonic Physics. 1. below the speed of sound (about 331 meters per second at standard temperature and pressure). 2. describing an aircraft or other body moving at less than this speed.

substrate Materials. the physical support material on which an integrated circuit is constructed or to which it is attached; e.g., a photovoltaic cell.

subsurface mining see UNDERGROUND MIN-


sub-synchronous Physics. describing a device or system that operates at a lower rate relative to something else; e.g., a machine that operates at a speed below that of its power source.

suburbanization Social Issues. the fact of becoming suburban; a population shift from a large central city to smaller nearby communities. This has significant implications for energy use; e.g., increased dependence on private vehicles for transportation.

subway Transportation. an underground rail transport system, or a train that is part of such a system. In British English the term tube or underground is usually used for this, and subway refers to an underground passageway, as beneath an urban street.

subway Variously known as the MTA, MBTA, or simply the T, the Boston subway began service in 1897 and is generally considered North America's oldest subway system.

sucker rod Oil & Gas. one of a string of steel rods that connect a downhole oil-well pump to a pumping unit on the surface.

sucrose Materials. C12H22O11, table sugar, a substance in the form of combustible, hard, dry, white crystals; extensively used as a sweetener in foods and beverages.

suction Physics. 1. a force that produces a condition of reduced pressure in a given region, so that a fluid in this region will flow to an adjacent region of greater pressure, or a rigid body will be held in place on a surface. 2. the movement of a fluid, or adherence of a body to a surface, produced by this condition.

suction head Hydropower. additional energy in a hydropower system, obtained when the vacuum created by a closed outlet system exerts a pulling force on the turbine as the water leaves the system.

suction pump Conversion. a type of pump in which atmospheric pressure pushes the

Suess, Hans


sulfur cycle

fluid to be raised into a partial vacuum created under a retreating valved piston on the upstroke, while a valve in the pipe prevents return flow; often used for raising or moving water.

Suess, Hans 1909–1993, U.S. chemist who developed an improved method of carbon-14 dating and used it to document that the burning of fossil fuels had a profound influence on the earth’s stocks and flows of carbon. (Fossil fuels are so ancient that they contain no C-14.)

Suess effect Climate Change. a relative change in the ratio of C-14/C or C-13/C for a carbon pool or reservoir; this indicates the addition of fossil fuel CO2 to the atmosphere.

Suez Crisis History. a military conflict that pitted Egypt against an alliance between France, the United Kingdom, and Israel. The Suez Canal was the principal route for oil shipments from the Middle East to Europe. In 1956, Egypt blockaded the Gulf of Aqaba, closed the Suez canal to Israeli shipping, and announced the nationalization of the canal. This resulted in a sharp increase in the price of oil.

Suezmax Oil & Gas. Suez maximum; the largest size of fully loaded oil tanker that can navigate the Suez Canal.

sugar Chemistry. 1. a family of simple, often sweet, compounds consisting of carbon, hydrogen, and oxygen; obtained from the juice of many plants and particularly from sugarcane and sugar beets. 2. specifically, SUCROSE, a particular type of this compound.

sugarcane or sugar cane Biomass. a tall grassy plant, Saccharum officinarum, characterized by a stout, jointed stalk and cultivated for its sugar content; native to tropical and subtropical regions. Also widely used as a source for biomass fuel production.

sulfate aerosol Climate Change. particulate matter that consists of compounds of sulfur, formed by the interaction of sulfur dioxide and sulfur trioxide with other compounds in the atmosphere. These aerosols are injected into the atmosphere from the combustion of fossil fuels and the eruption of volcanoes such as MOUNT PINATUBO. Recent studies indicate that sulfate aerosols may lower the earth’s temperature by reflecting away solar radiation.

sugarcane Sugarcane is a food crop and also a widely used source of biomass for fuel.

sulfation Materials. 1. a process in which large crystals of lead sulfate form on a battery plate; a condition that affects unused and discharged batteries, making them difficult to recharge. 2. any process of formation of lead sulfate.

sulfur Chemistry. a nonmetallic element having the symbol S, the atomic number 16, and an atomic weight of 32.06; pure sulfur exists in two stable crystalline forms and in at least two liquid forms. The native form of this element is a yellow mineral occurring as thick crystals and as granular to powdery masses, found in volcanic or hot springs deposits, in sedimentary beds, and in salt domes. Sulfur is present at various levels of concentration in many fossil fuels.

sulfur content Oil & Gas. a categorization of commercial fuels based on the amount of sulfur they contain, with lower sulfur content fuels usually selling at a higher price; e.g., no. 2 distillate fuel is rated as having a 0.05% or lower sulfur content level for on-highway vehicle use, or greater than 0.05% for off-high- way use and home heating oil.

sulfur cycle Earth Science. the cyclic movement of sulfur in different chemical forms; a complex sequence of reactions brought about by bacteria in water and soil, in which sulfur is changed from organic sulfur compounds in plants and animals to elemental sulfur

sulfur dioxide


sun path diagram

and sulfates, and then eventually returned to organic sulfur.

sulfur dioxide Chemistry. SO2, a toxic, irritating, colorless gas that is soluble in water and alcohol; freezes at –72.7°C and boils at –10°C; an oxidizing and reducing agent formed naturally by volcanic activity and organic decay. Used as a chemical intermediate, in paper pulping and ore refining, and as a solvent.


sulfur dioxide pollution Environment. a process in which sulfur dioxide (SO2) dissolves in water vapor to form acid, and interacts with other gases and particles in the air to form products that can be harmful to humans and the environment. Over 65% of SO2 released to the air comes from electric utilities, especially those that burn coal. Other sources include petroleum refineries, cement manufacturing plants, or metal processing facilities. SO2 contributes to respiratory illness and aggravates existing heart and lung diseases.

sulfur hexafluoride Chemistry. SF6, a colorless gas that is slightly soluble in water and soluble in alcohol; it freezes at –50.5°C and sublimes at –63.8°C; used as a dielectric in electronics. One of the six greenhouse gases to be curbed under the Kyoto Protocol, it has the highest known GWP (Global Warming Potential of any gas (23,900 times that of carbon dioxide over a 100-year horizon).

sulfuric Chemistry. 1. describing various compounds of sulfur, especially those in which the element has a valence of 6. 2. relating to or derived from sulfuric acid.

sulfuric acid Chemistry. H2SO4, a highly corrosive, dense, oily liquid, colorless to dark brown depending on its purity; its addition to water generates heat and explosive spattering. Used in the manufacture of a wide range of chemicals and materials including fertilizers, paints, detergents, and explosives.

sulfurous Chemistry. describing various compounds of sulfur, especially those in which the element has a valence of 3.

sulfur oxides Environment. compounds made up of only sulfur and oxygen. Natural sources include volcanoes and hot springs, while energy use and metal refining are the principal human sources, particularly for sulfur dioxide, a major air pollutant (see above).

On a global basis, natural sources contribute about the same amount of sulfur oxides to the atmosphere as human industrial activities.

sulfur trioxide Chemistry. SO3, a compound occurring as silky, fibrous needles; it decomposes in water, melts at 16.8°C and boils at 44.8°C; a very toxic and a strong irritant that is used in detergents and solar energy collectors. See also SULFUR OXIDES.

sulphur another spelling of SULFUR.

Summerland History. an oil field off the coast of Santa Barbara, California, considered to be the first productive offshore oil facility in the world (1898). Similar offshore wells were reported in the Caspian Sea about five years later.

sump Mining. 1. a basin or pit in a mine where water is allowed to collect, as at the bottom of a shaft. 2. Environment. any pit, pool, or other depression in which water collects, especially waste water.

sun Solar. 1. also, Sun. the star that is the central celestial body in the solar system and the ultimate source of all energy for the earth. 2. any star that is the source of light and heat for a planetary system.

Sun Day Solar. a symposium, demonstration, or other event focusing on the use of solar energy as a replacement for fossil fuel sources.

sundial Solar. a timepiece employed since ancient times to indicate daylight hours by the shadow that the gnomon (a rod or fin) casts on a calibrated dial.

sunk cost Economics. a cost that has already been incurred, and therefore cannot be avoided by any strategy going forward.

sunlight Solar. the electromagnetic energy that is visible to the human eye at the earth’s surface.

sun motor History. an early solar energy system developed by Swedish-American engineer John Ericsson (about 1883); it consisted of a displacer type (Stirling) engine powered by a parabolic reflector. Ericsson’s system was not adopted commercially at the time, but his parabolic collector became the model for many modern solar systems.

sun path diagram Solar. a circular projection of the sky vault onto a flat diagram, used to determine solar positions and the shading


effects of landscape features for a solar energy system.

sunroom another term for a SOLARIUM.

sunshine duration Solar. the sum of time intervals within a given period, during which the irradiance from direct solar radiation on a plane normal to the sun direction is equal to or greater than 120 watts per square meter.

sunspace Solar. a type of passive solar heating in which radiant energy from the sun is collected and stored in a space separate from the living space, and is transferred either by natural convection or by fans.

sunspot Solar. a relatively cool and dark area that can be observed on the sun's photosphere, characterized by a strong magnetic field; sunspots are cyclically variable in number and magnetic polarities. It has been speculated that variations in sunspot activity may affect weather and climate on earth.

sun-tempered Solar. 1. describing a building that is specifically designed for high solar energy efficiency; e.g., its longer wall is oriented east to west and the majority of its windows are on the south side. 2. specifically, a house having south-facing glass making up 7–12% of the total floor area of the house. Thus, sun-tempering.

super cetane Biomass. a biomass-derived product used as a diesel fuel or a diesel additive to improve engine performance; so called because it has a cetane value as high as 100.

supercapacitor see ULTRACAPACITOR.


supercritical mass

superconducting magnetic energy storage (SMES) Storage. a technology in which the superconducting characteristics of low-tem- perature materials produce intense magnetic fields to store energy; proposed as a storage option in photovoltaics to smooth out fluctuations in power generation.

Superconducting Super Collider (SSC)

Nuclear. a massive ring particle accelerator that was planned to be built by the U.S. government near Waxahachie, Texas. Due to concern over the high cost of the project, it was eventually canceled by Congress in 1993 after 22.5 km (14 mi) of its tunnel had already been excavated and $2 billion spent.

superconductivity Electricity. a phenomenon shown by certain metals, alloys, and other compounds of having negligible resistance to the flow of electric current at temperatures approaching absolute zero. Each material has a critical temperature Tc, above which it is a normal conductor, operating as a superconductor only under extreme low-temperature conditions. In addition, certain materials are now known to exhibit superconductivity at temperatures well above absolute zero.

superconductor Electricity. any material that can exhibit superconductivity (see previous).

supercooling Thermodynamics. a condition in which a pure substance is cooled below its freezing, condensation, or sublimation point, without experiencing the corresponding change of state that this would normally bring about. Thus, supercooled.

supercharge Transportation. to force air into an internal-combustion engine at a pressure (significantly) above the atmospheric pressure at the start of the compression stroke; the degree of pressure retained determines the level of supercharging.

supercharger Transportation. a blower that increases the intake pressure of an engine, so as to make fuel burn more quickly and increase engine power.

supercomputer Communication. a term for any extremely powerful, large-capac- ity computer that is capable of processing huge amounts of data in an extremely short time.

superconducting Electricity. relating to or having the capacity for superconductivity (see below). Also, superconductive.

supercritical Chemistry. describing a mobile phase of a substance intermediate between a liquid and a vapor, maintained at a temperature greater than its critical point.

supercriticality Chemistry. 1. the fact of being supercritical; i.e., at a temperature above the critical point although no phase change is observed. 2. Nuclear. a condition for increasing the level of operation of a reactor, in which the rate of fission neutron production exceeds all neutron losses, and the overall neutron population increases. Thus, supercritical reactor.

supercritical mass Nuclear. a mass of fissionable material in excess of a critical mass, i.e., an amount of fissionable material greater than that needed to maintain a chain reaction with a constant rate of fission.

supercritical reactor



supercritical reactor Nuclear. a nuclear reactor in which the number of fissions increases from one generation to the next generation and the energy released by the chain reaction increases with time.

supercritical turbine Conversion. a steam turbine in which the feed steam is above the critical point.

supercritical water-cooled reactor (SCWR)

Nuclear. an advanced nuclear reactor design in the development stage that features a high-temperature, high-pressure water-cooled reactor that operates above the thermodynamic critical point of water. It enables a thermal efficiency about one-third higher than current light-water reactors, as well as simplification in the balance of the plant.

superfluid Physics. a collection of particles that exhibit zero viscosity and zero entropy (roughly speaking, a complete lack of friction); the particles are known to obey the



Superfund see CERCLA.

superheat Thermodynamics. 1. to bring a substance to a temperature above that at which a change of state would normally occur, without this change taking place; e.g., to heat a liquid above its normal boiling point without producing vaporization. 2. the temperature of a substance in this state. 3. see SUPERHEATED


superheated steam Geothermal. steam heated to a temperature significantly higher than the boiling point corresponding to its pressure, so that it does not recondense to water as readily as ordinary steam; it cannot exist in contact with water or contain water. A natural feature of certain geothermal areas and also created artificially to provide increased efficiency in steam engines.

superheated vapor Thermodynamics. a vapor that is heated to a temperature exceeding the boiling point of the liquid phase.

superheating Thermodynamics. 1. a condition in which a pure substance is heated above its boiling point, melting point, or sublimation point, without experiencing a phase change. 2. a process in which such a condition is induced as part of a refrigeration cycle.

superinsulated or super-insulated Consumption & Efficiency. describing a type of building that has massive amounts of insulation, airtight construction, controlled ventilation, and other features that maximize the efficiency of its inherent climate control. Thus superinsulation.

superphosphate Materials. a mixture of calcium sulfate and dihydrogen calcium phosphate made by treating bone ash or basic slag with sulfuric acid; used as an agricultural fertilizer. Its development as the first artificial fertilizer (1850s) freed farmers from their historic dependence on animal manure for fertilizer.

superposition Physics. a principle that may be applied to systems in which individual influences act linearly; the resultant effect on the system is equivalent to the sum of the effects of the individual influences that are acting on the system.

supersaturation Chemistry. 1. a condition in which a solution contains more solute than is normally necessary to achieve saturation under the same conditions. 2. Hydropower. such an overabundance of gases in turbulent water (e.g., nitrogen), as at the base of a dam spillway; this can cause a fatal condition in fish similar to the bends in humans. 3. Earth Science. a local atmospheric condition in which the relative humidity is greater than 100%, with more water vapor than is needed to produce saturation of a plane surface of pure water or ice.

supersonic Physics. 1. above the speed of sound (about 331 meters per second at standard temperature and pressure). 2. describing an aircraft or other body moving at greater than this speed. 3. another term for ULTRA-


superstrate Photovoltaic. a covering on the sun side of a photovoltaic module, providing protection for the materials from impact and environmental degradation while allowing maximum transmission of the appropriate wavelengths of the solar spectrum.

super-synchronous Physics. describing a device or system that operates at a higher rate relative to something else; e.g., a machine that operates at a speed above that of its power source.



surface tension

supertanker Oil & Gas. a very large oil tanker, typically defined as a vessel designed to transport more than 500,000 deadweight tons of oil. RSee below.

supplementarity Policy. in the context of the Kyoto Protocol, the use of flexibility mechanisms such as emissions trading to achieve greenhouse gas reduction goals, while also instituting adequate domestic energy and other policies for the same purpose.

supply bid Electricity. a bid to an electric power exchange indicating a price at which a seller is prepared to sell energy or ancillary services.

Rsupertanker A term originally applied to the class of tankers too large to transit

international canals while carrying cargo, and currently defined by two ship classes: Very Large Crude Carriers (VLCCs) between ~200,000 and ~300,000 deadweight tons (dwt) and Ultra Large Crude Carriers (ULCCs) greater than ~300,000 dwt. Supertankers are a remarkable technological response to market conditions that promoted economies of scale without apparent bound in the 1960s, 70s, and 80s. The first modern tanker (tanks integral with hull) was the ~3000 dwt Glukauf, built in 1886. Until the 1950s, most crude oil was refined at source and transported to market in products tankers, sized between 12,000 and 30,000 dwt. Larger vessels became economically feasible when oil companies began locating refineries near energy markets, although the Suez Canal restricted tanker size. Energy market shifts and the 1956 closure of the Suez Canal created new routes, removing geographic barriers to construction of the first VLCCs and ULCCs. Fully-loaded supertankers (especially efficient diesel-powered VLCCs built in 1990s) reduced unit shipping costs dramatically, but partial loads could not sustain economies of scale; many were scrapped in the 1980s and 1990s or used for storage. The largest supertanker ever built was the 555,843 dwt Seawise Giant, refitted in 2004 as a floating storage and offloading unit named the Knock Nevis. Current supertanker sizes are defined by market conditions providing an economic upper bound and geophysical limitations defining the number of routes and ports (or offshore terminals) that these very large vessels can safely serve.

James J. Corbett

University of Delaware

supply elasticity Economics. the response of supply to a change in the price of a commodity.

supply-side Economics. 1. having to do with the supply of energy resources to consumers. 2. relating to or based on the concept that the proper way for a government to stimulate economic growth is by encouraging increases in supply, as through tax cuts and incentives for producers. Compare DEMAND-SIDE.

suppressed demand Economics. a situation in which the demand for energy services is low due to constraints of income, access, and infrastructure, not because of an absence of consumer interest.

suppressor see SURGE SUPPRESSOR.

surface drift Earth Science. 1. loose surface material transported from one place and deposited elsewhere by the action of such agents as wind, waves, currents, glaciers, or running water from a glacier. 2. the flow of waters on the surface of the ocean. 3. Mining. a lateral tunnel (usually inclined) from the surface to a coal seam or ore body to be developed.

surface energy Materials. the work per unit area required to bring fluid molecules to the interface between two immiscible liquids, or between a liquid and a gas.

surface (boundary) layer Earth Science. a thin layer of air, extending from near the earth's surface up to the base of the EKMAN CON- VERGENCE (less than 300 feet), within which shearing stresses are nearly constant and wind distribution is determined largely by the vertical temperature gradient and the nature and contours of the underlying surface.

surface mining Mining. a method of mining that involves extraction by removing the layer of earth and/or rock (overburden) at the surface to gain access to a coal bed that is at a relatively shallow depth; the coal is then mined with surface excavation equipment. Thus, surface mine.

surface pipe Oil & Gas. the first casing set into a well, cemented into place as a foundation for subsequent operations and as a means of shutting off shallow water formations from being contaminated by deeper, saline waters.

surface tension Chemistry. the stretching force required to form a liquid film; it is equal

surface warming


Swan lamp

to the surface energy of the liquid per unit length of the film at equilibrium; the force tends to minimize the area of a surface.

surface warming Climate Change. a process of gradual warming of the earth's surface, caused at least in part by temperature increases resulting from the buildup of greenhouse gases in the atmosphere.

surge Electricity. a sudden unplanned change in an electrical system's voltage that is capable of damaging electrical equipment, especially an increase in voltage significantly above the designated level; e.g., above 120 volts for U.S. household and office wiring.

surge capacity Electricity. the maximum power, usually 3–5 times the rated power, that can be provided to an electrical system over a short time without damage to the system.

surge suppressor Electricity. a component that responds to the rate of change of a current or voltage in order to prevent damage from a sudden fluctuation in power, especially a large increase above a predetermined value; often used to protect computer systems and other electronic equipment. Also, surge protector.

survival of the fittest Ecology. 1. a popular term for NATURAL SELECTION, the concept that individuals best adapted to their environment will survive to pass on their genes. 2. Social Issues. the application of this principle to human societies; see SOCIAL DARWINISM.

suspension Chemistry. 1. a system in which very small particles of solid, semisolid, or liquid material are more or less evenly dispersed in a liquid or gas phase; e.g., fog is a suspension of liquid (water droplets) in a gas (air). 2. Transportation. a system of springs, shock absorbers, or similar devices connecting the axles to the chassis of an automobile, railroad car, or other such vehicle; designed to reduce unwanted motion transmitted from the riding surface.

sustainability Sustainable Development. the fact of being sustainable; preservation of the overall viability and normal functioning of natural systems.

sustainable Sustainable Development. 1. describing activities that make use of the earth's living and physical resources, including humans and their technologies, cultures, and

institutions, in a way that does not diminish their ability to support future generations. 2. specifically, the consumption of energy in a manner that emphasizes renewable sources and the judicious use of non-renewable sources.

sustainable agriculture see TRADITIONAL


sustainable capacity Oil & Gas. the daily amount of oil that an individual oilfield or a group of fields can produce at a rate that can be sustained for more than 90 days.

sustainable development a collective term for efforts to develop technological, economic, political, and social systems, so as to provide the goods, services, and amenities that people need or value, at an acceptable cost, while at the same time maintaining the natural environment so that a comparable quality of life will be available to future generations.

sustainable development indicator Sustainable Development. an indicator that measures or monitors progress toward sustainable development; e.g., CO2 emissions per capita, participation in international environmental treaties, or the equity of income distribution.

sustainable energy Sustainable Development. energy that is produced and used in ways that will support long-term human development in all its social, economic, and environmental dimensions.

sustainable tourism Sustainable Development. tourism that suits the needs of current tourists and host regions, while at the same time protecting and enhancing similar opportunities for the future.

sustaining chain reaction Nuclear. a chain reaction in which an average of exactly one fission is produced by the neutrons released by each previous fission.


Sv sievert.

Swan, Joseph 1828–1914, English inventor noted for his development of the light bulb. He received a British patent for his device in 1878, about a year before Edison's U.S. patent. He later teamed with Edison for the commercial development of electric lamps, under the brand name Ediswan.

Swan lamp History. a pioneering electric lamp developed by Joseph Swan, distinguished by


having too small an amount of residual oxygen in the vacuum tube to ignite the filament, thus allowing it to glow almost white-hot without catching fire.


sweet Oil & Gas. having a low level of the acidic gases that are typically associated with oil and gas drilling and production, such as hydrogen sulfide or carbon dioxide. Thus, sweet gas, sweet crude.

sweetening Oil & Gas. the process of removing unwanted gas components from oil and natural gas; e.g., hydrogen sulfide.

swept area Wind. the area through which the rotor blades spin on a wind energy device, as seen when directly facing the center of the rotor blades.

swidden (agriculture) another term for


switch Electricity. a device that is used to open or close an electric circuit.

switched-reluctance motor Conversion. a motor in which motion is produced as a result of the variable reluctance in the air gap between the rotor and the stator.

switchgrass Biomass. a warm-season perennial grass native to North America, Panicum virgatum, that has potential as a biomass energy crop.

symbiosis Ecology. a biological relationship between individuals of two different species in which one member benefits and the other may or may not benefit. Thus, symbiotic.

Symington, William 1763–1831, English engineer who developed the first steam-powered marine engine (1788). He then developed a successful steam-driven paddle wheel and used it to propel one of the first practical steamboats, the Charlotte Dundas.

synchro- short for SYNCHRONOUS.

synchrocyclotron Nuclear. a particle accelerator similar to the cyclotron, in which the frequency of the accelerating voltage is varied in order to track the change in relativistic energy of the particles.

synchronous Physics. 1. occurring at the same time or rate; e.g., an artificial satellite with a one-day orbital period that is the same as that of the earth. 2. Electricity. describing a machine operating at the same speed as the


synthetic natural gas (SNG)

existing power supply. Thus, synchronous motor, synchronous generator, synchronous speed, and so on. 3. Earth Science. describing geologic features or formations that exist or are deposited at the same time.

synchrotron Nuclear. a large ring particle accelerator in which the particles move in an evacuated tube at constant radius, accelerated by radio frequency applications with synchronous magnetic field increases to maintain the constant radius.

syncline Earth Science. a downward fold of stratified rocks in which the sides slope inward toward each other.

syncrude Oil & Gas. synthetic crude; oil processed from unconventional sources such as oil sands.

synfuel short for SYNTHETIC FUEL.

syngas Oil & Gas. synthesis gas; a mixture of hydrogen and carbon monoxide obtained by the reforming of methane, used as a fuel and as an intermediate in the production of various chemicals.

synoptic Measurement. 1. referring to or based on data obtained from a large-scale or overall view. 2. specifically, referring to weather data obtained simultaneously over a large area in order to provide a simultaneous overall view.

synthesis Chemistry. 1. the process of forming chemical compounds from more elementary substances by means of one or more chemical reactions, or by nuclear change. 2. any unified whole formed by combining constituent elements.

synthesis gas see SYNGAS.

synthetic Materials. 1. describing a material or item produced by synthesis, especially a compound formed artificially by chemical synthesis. 2. more generally, describing any product or item that is the result of human technology rather than something that exists in nature in that form.

synthetic crude see SYNCRUDE.

synthetic fuel Renewable/Alternative. a liquid or gaseous fuel derived from a source such as coal, shale oil, tar sands, or biomass, used as a substitute for oil or natural gas. RSee next page.

synthetic natural gas (SNG) Oil & Gas. a manufactured product, chemically similar

Système International


Szilard, Leo

Rsynthetic fuel A generic term applied to any manufactured fuel with the approximate

composition and comparable specific energy of a natural fuel. In the broadest definition, a liquid fuel that is not derived from natural occurring crude oil is a synthetic fuel. Modern transportation fuels demand uniform physical properties produced from varying feed stocks with the chemical compositions essentially “synthesized” from petroleum or other fossil fuels. The fraction of petroleum that has boiling points for use in spark-ignition engine is referred to as naphtha. The term “gasoline” implies that many of the components have been synthesized using cracking or reforming techniques, and the term “gasoline” is used rather than synthetic fuel. The term “reformulated gasoline” identifies gasoline containing a greater fraction of reformed petroleum molecules. Fuels from oil sands and heavy oil (naturally de-volatilized petroleum) are referred to using the same terminology as petro-

in most respects to natural gas, resulting from the conversion or reforming of petroleum hydrocarbons; may easily be substituted for or interchanged with pipelinequality gas.

Système International Measurement. French


official name for this system; abbreviated SI.

Szargut, Jan born 1923, Polish engineer noted for his advances in the theory of energy balances of chemical processes, and for impor-

leum-based fuels. Liquid fuels produced from coal, peat, natural gas, and oil shale are properly referred to as synthetic fuels. Renewable biomass produced by photosynthesis can be converted to a variety of synthetic fuels. Ethanol, methanol, and biodiesel are appropriately referred to as synthetic fuels independent of origin. Coal gasification and natural gas reforming are sources of “synthesis gas”, a mixture of hydrogen and carbon monoxide, the feed for synthetic fuel production. The SASOL complex in South Africa gasifies coal to feed a Fischer-Tropsch process to obtain high quality motor fuels. A range of oxygenated organic chemicals for fuels and commerce are produced with selected Fischer-Tropsch catalysts and adjusted operating conditions.

Truman Storvick

University of Missouri

tant studies of the exergy analysis of thermal, chemical, and metallurgical processes.

Szilard, Leo 1898–1964, Hungarian-born physicist who was one of the first to realize that nuclear chain reactions could be used in weapons. He worked with Fermi to develop the first self-sustained nuclear reactor based on uranium fission, and he helped convince Einstein to write to President Roosevelt about the need for an atomic bomb project. After World War II, he actively protested nuclear weaponry.