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Dictionary of Energy

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drilling mud


dry cell

drilling mud Oil & Gas. a mixture of finely divided heavy material consisting of clay, water, and chemical additives that is pumped downhole through a drill pipe; used for such purposes as cooling, lubrication, the transport of cuttings to the surface, and the prevention of foreign fluids entering the wellbore. Also, drilling fluid.

drilling rig Oil & Gas. a structure housing the equipment used to drill for and extract oil and natural gas from underground reservoirs.

drillpipe Oil & Gas. a heavy steel pipe that is rotated to give motion to a drilling bit and that is used to circulate drilling fluid.

drill stem Oil & Gas. a term for the entire assembly of a drilling apparatus.

drill string Oil & Gas. the column (string) of drill pipe with attached tool joints that links the drill bit to a mechanism imparting rotary or reciprocating motion.

drive Physics. 1. a source of power or the application of power. 2. a mechanism that imparts or transfers power to or within a machine.

driveline retrofit Refrigeration. a conversion of refrigeration equipment to an alternative refrigerant that requires the replacement of the compressor motor.

drivepower Consumption & Efficiency. a term for energy consumed by motors and motordriven equipment.

driver fuel Nuclear. nuclear reactor fuel that contains the fissionable isotopes along with fertile isotopes that are bred into fissionable isotopes.

driveshaft Transportation. the shaft in a motor vehicle that transfers power from the engine or motor to the unit where this power is applied.

driving force Social Issues. a term used to describe any of the social forces that are identified as the sources of environmental problems, such as population expansion, economic growth, political and economic institutions, technological developments, and cultural values.

drought Global Issues. a period of less than average or normal precipitation over an extended period of time in a given area, severe enough to affect the water supply and cause biological damage and/or economic loss.

drum brake Transportation. a brake system in which a pair of brake shoes are pressed against the inner surface of a shallow metal drum rigidly attached to a wheel; a historic advance (about 1900) in stopping power for motor vehicles.

dry ash-free (daf) Coal. a theoretical measure of coal (or other organic material), based on a sample in which the moisture and ash are totally eliminated and the remaining constituents are recalculated to total 100 percent.

dry basis Coal. a theoretical description of coal quality, based on a sample with zero moisture.

dry-bulb temperature Measurement. air temperature that is not affected by atmospheric humidity; ordinary household thermometers measure ambient temperature in this manner. Thus, dry-bulb thermometer.

dry cask Nuclear. a large container used for storing spent nuclear fuel, using thick layers of materials such as steel, concrete, and lead (instead of water) as a radiation shield. A dry cask can hold multiple fuel assemblies. Thus, dry-cask storage.

dry cell (battery) Storage. a term for cells that use a solid or powdery electrolyte and that rely on ambient moisture in the air to complete the chemical process; the electrolyte

drought Abandoned Colorado farmhouse submerged by winds that have shifted topsoil from the neighboring arid fields; a depiction of the “Dust Bowl” landscape of the Depression era.



Dutch disease

is immobilized, making the battery portable; e.g., the Leclanche or carbon-zinc cell commonly used in flashlights, toys, and portable electronic devices.

dry-charged Storage. describing a storage battery in which the electrolyte is drained after the plates are formed; before being placed in service, the battery is filled with electrolyte and charged for a short time.

dry circuit Electricity. a term for a circuit with extremely low maximum voltages and very small maximum currents, so that there is no arcing to roughen the contacts, and an insulating film develops that prevents closing of the circuit.

dry deposition see DEPOSITION.

dry hole Oil & Gas. 1. a drill hole that has been abandoned due to a lack of production of marketable petroleum materials. 2. by extension, any speculative venture that has been unsuccessful.

dry natural gas Oil & Gas. natural gas that remains after the removal of the liquefiable hydrocarbon portion from the gas stream, or after the removal of any volumes of nonhydrocarbon gases that would render the gas unmarketable.

dry steam Geothermal. 1. a term for a geothermal fluid that is primarily very hot steam.

2. Consumption and Efficiency. a vapor with a very low water content, produced at high temperatures; used in various cleaning processes.

dry steam plant Geothermal. a geothermal power plant in which steam is conveyed directly to a turbine to generate electricity; e.g., Lardarello, Italy or The Geysers in northern California. This is the earliest form of geothermal power generation.

dry ton Measurement. one ton (2000 pounds) of material dried to a constant weight.

DTW dealer tank wagon.

dual condenser HVAC. a heat pump system that has the capability to switch, usually automatically, between an air and a water heat exchanger.

dual-fired Electricity. describing a generating unit that can produce electricity by means of two or more input fuels. In some of these units, only the primary fuel can be used

continuously; the alternate fuels can be used only for start-up or in emergencies.

dual flash cycle Geothermal. a second stage of a FLASH STEAM process in which any liquid that remains in the vaporizing tank is flashed again at a different pressure in a second tank, to extract more energy in addition to that provided by the initial stage.

dual fuel vehicle Transportation. see BI-FUEL


duality Thermodynamics. the concept that electrons (and all particles) behave both as classical particles and as waves depending on how they are observed (i.e., they cannot be both at the same time).

Dubai crude Oil & Gas. one of an array or “basket” of seven crude oil types used by OPEC as reference points for pricing.

ducted HVAC. describing a heating/cooling system that regulates temperatures throughout a building by means of a series of ducts in the floor or ceiling. The compressor unit is located outside the building.

dump energy Hydropower. a term for energy that is lost (i.e., dumped) by a hydroelectric system, usually because it is in excess of the capacity or requirements of the system; typically defined as the number of megawatt hours of energy produced in excess of aggregate load.

dung Biomass. solid animal waste matter; a traditional fuel source in dried form; e.g., cow dung.

Dunlop, John Boyd 1840–1921, Scottish inventor credited with the development of the first practical pneumatic tire (Dunlop tire), based on experiments with his son’s bicycle. The company bearing his name would grow to be a major international corporation.

Durnin, J. V. Scottish nutritionist noted for his seminal work in the field of human nutrition and the energetics of human metabolism.

Dutch disease Economics. 1. a phenomenon that occurs when a resource boom causes exchange rates to rise and labor and capital to migrate to the booming sector; the result is higher costs and reduced competitiveness for domestic goods and services, effectively crowding out previously productive sectors. 2. any situation in which an income windfall from an energy resource leads to adverse

Dutch oven



consequences for the nation’s economy. Also, Dutch curse. [Named after the negative effects of the recent North Sea oil boom on the Dutch nation (The Netherlands).]

Dutch oven Consumption & Efficiency. an early type of furnace, having a large, rectangular box lined with firebrick on the sides and top, commonly used for burning wood.

Dutch windmill Wind. a term for the familiar historic type of European windmill; so called because of its early and widespread use by the Dutch.

duty cycle Storage. 1. the amount of time it takes to start, operate, stop, and idle a machine when it is being used for intermittent duty. 2. a percentage that expresses the amount of “on” (working) time as compared to total time for an intermittently operating device or system.

duty rating Consumption & Efficiency. the amount of time that a unit or system can deliver peak output (e.g., electrical power).

dye-sensitized solar cell Photovoltaic. an advanced type of photovoltaic cell that uses a dye-impregnated layer of titanium dioxide to generate a voltage, rather than the semiconducting materials used in most solar cells. Also, dye solar cell.

dynamic head Hydropower. the vertical distance from the water level of a pump or reservoir to the point of free discharge of the water; measured during actual flow and taking into account the effects of friction, since resistance to friction is not the same at all flow rates. The total dynamic head (TDH) is the total resistance from both friction and gravity that a pump will experience when delivering a given rate of flow.

dynamic height Earth Science. a measure of the level of a system of ocean water, relative

to mean sea level; used to describe the height of a current, eddy, or column of water. The dynamic height can be negative in cases of extreme cold or salinity.

dynamic pressure Hydropower. an expression of the pressure of a flowing fluid, such as water flowing in a pipeline; equal to onehalf the fluid density, multiplied by the fluid velocity squared. It is equivalent to the static pressure minus any actual pressure loss from friction, turbulence, and so on.

dynamics Physics. 1. the field of mechanics that deals with the study of motion and of the forces that bring about motion. 2. see POPULA-


dynamite Materials. a powerful blasting explosive that was originally manufactured by the absorption of nitroglycerine into a porous base material such as charcoal or wood pulp; now generally manufactured with ammonium nitrate or cellulose nitrate.

dynamo Electricity. a device for converting mechanical energy into electrical energy, especially one that produces direct current.

dynamoelectric Electricity. relating to or involving the exchange of energy between mechanical and electrical processes.

dynamometer Transportation. any of various devices used in testing a motor or engine for such characteristics as efficiency and torque, especially a device used to simulate road conditions and loads in stationary settings and to gather data about vehicle performance under those conditions.

dyne Measurement. a unit equal to the amount of force that will cause a mass of 1 gram to accelerate at a rate of 1 cm per second per second; the basic unit of force in the centime- ter-gram-second system.


E- Oil & Gas. ethanol; a designation of the amount of ethanol contained in a fuel mixture with gasoline; e.g., E-10. 10% ethanol and 90% gasoline (gasohol); E-95. 95% ethanol and 5% gasoline.

earth Earth Science. 1. also, Earth. the planet inhabited by humans; the third planet from the sun, at a mean distance of about 92.9 million miles. 2. soil; the loose, fragmented material that composes part of the surface of this planet, especially soil that can be cultivated.

earth berm see BERM.

earth-cooling tube Renewable/Alternative. an underground metal or plastic pipe employed in home cooling; as air travels through the pipe it gives up some of its heat to the soil, and enters the house as cooler air (assuming the earth is significantly cooler than the incoming air). A potential alternative to air conditioning, but at present not sufficiently efficient or economical.

earth-coupled heat pump see GROUND-


earth dam Hydropower. a dam whose main section is composed primarily of tightly compacted earth (soil, gravel, sand, silt, clay, and so on), as opposed to concrete or another manufactured material; e.g., Fort Peck Dam on the Missouri River.

Earth Day History. an annual nationwide demonstration in the U.S. (founded 1970), advocating environmental protection and preservation; originally conceived by Gaylord Nelson, U.S. Senator from Wisconsin, and organized by Denis Hayes.

earthfill dam 1. see EARTH DAM. 2. see FILL


earthmover Mining. any of various large vehicles used to excavate and transport earth at a mine site.

Earth Summit Sustainable Development. another name for the United Nations Conference on Environment and Development (UNCED), a meeting of people and organizations from 178 nations held in Rio de Janeiro, Brazil in 1992. The meeting produced the Rio Declaration on Environment and Development, a statement of 27 principles upon which the nations agreed to base their actions in dealing with environment and development issues.

Easter Island History. a remote island in the Pacific Ocean about 2000 miles west of South America, historically settled by Polynesian peoples; the site of a once-flourishing society that began to decline about 1400 AD; now studied as a model of the collapse of a civilization due to overconsumption of resources.

ebb generation Renewable/Alternative. the simplest mode of operation for a tidal plant, in which the production of electricity occurs during the part of the cycle when water flows through the turbines from the basin to the sea (i.e., during ebb tide).

ebb tide Earth Science. a falling tide; the phase of the tide between a high water and the following low water.

ebb tide Tides on the north coast of France are among the most extreme in the world. The ebb tide at the historic Mont St. Michel abbey leaves behind an expanse of mud flats.

EBR-1 Nuclear. Experimental Breeder Reactor 1, the first nuclear reactor in the world to produce useable quantities of electric power, lighting four 100-Watt light bulbs at the National Reactor Testing Station in Arco, Idaho (1951).


ECCS emergency core-cooling system.

ECN Energy Research Centre of the Netherlands, the largest Dutch research center in the field of energy.

ecoefficiency Economics. a business strategy to produce goods with lower levels of use of materials and energy, in order to realize the economic benefits of environmental improvements.

eco-industrial park (EIP) Environment. a community of manufacturing and service businesses located on a common property and sharing resources to improve their environmental and economic performance; e.g., savings from waste recycling, the ability to avoid regulatory penalties, and increased efficiency in material and energy use. These parks employ ecological principles to achieve the least damaging interaction with the environment.

ecolabel Environment. an official symbol or logo displayed on, or in connection with a certain product to show that the product is “environmentally friendly”; i.e., that it has been designed to do as little harm to the environment as possible. Thus, ecolabeling or ecolabelling.

ecological Ecology. having to do with the relationship between organisms and their environment.


ecological footprint

ecological deficit Ecology. the amount by which the ecological footprint (see below) of a human population (e.g., a country or region) exceeds the biocapacity of the space available to that population.

ecological economics Economics. a transdisciplinary field that examines the relationship between ecological and economic systems from a number of integrated viewpoints, including principles from economics, the natural sciences, and other social sciences; practitioners are interested in the broad question of the use of resources by society and in understanding the nature, behavior, and dynamics of the economy-environment system.

ecological energetics Biological Energetics.

1. the branch of ecology that studies ecosystems or communities in terms of the energy flows within them. 2. specifically, the energy flows associated with a given species; e.g., the ecological energetics of the desert tortoise. RSee below.

ecological engineering Economics. the application of basic and applied principles from engineering, ecology, economics, and natural sciences, for the restoration and construction of aquatic and terrestrial ecosystems.

ecological footprint Ecology. a concept used to describe the impact that a given human entity (e.g., a nation such as Japan, or a large

Recological energetics Ecological energetics refers to a suite of approaches

in the environmental sciences that attempts to understand ecological structure and especially function from the perspective of energy costs and gains. It has been applied at scales from individual organisms to entire ecosystems. Generally there is an implicit evolutionary backdrop, in other words the question is often how does this or that morphology, physiology, or behavior contribute to selective advantage, that is survival and the leaving of progeny. A particularly good example of this is a study of European chickadees who examined explicitly their reproductive output in terms of the timing of their migration relative to the spring pulse of caterpillars, in turn attuned to the timing of leaf outbreak. Those birds that nested just prior to the outbreak had much food for their young which could be gathered with relatively little effort. Those that were too early or late left far

fewer offspring. Climate changes were impacting which behaviors were rewarded and not. Energy studies have also been undertaken at the level of populations and ecosystems, and still one of the best is that of Silver Springs by Howard Odum. Perennial questions of such studies are those of the efficiency of trophic (or food level) processes as energy goes from sunlight to sugars produced by photosynthesis to herbivores to carnivores, and also the role of power in fitness. Finally, some ecologists have used such concepts applied originally to natural ecosystems to look at national economies from an energetic perspective. Such studies are thought to be increasingly useful as humanity appears to be facing an increasingly energy-constrained future.

Charles A. S. Hall

College of Environmental Science and Forestry State University of New York, Syracuse

ecological integrity


economizer system

Recological footprint A resource accounting framework for measuring human

demand on the biosphere. The Footprint of a population is the biologically productive land and water area that the population requires to produce the resources it consumes and absorb the waste it generates, using prevailing technology. Because people consume resources and ecological services from all over the world, their Footprint is the sum of these areas, wherever they are on the planet. Results are expressed in global hectares, hectare of biologically productive space with world-average productivity. This measurement unit, or ‘ecological currency’ makes comparisons possible across the world. Governments and organizations to measure and manage sustainability efforts use the Footprint. In consuming nature’s products and services, peo-

city such as São Paulo) has on the biological resources of the earth; a measure of how much biocapacity a population or process requires to produce its resources and absorbs its waste. RSee above.

ecological integrity Ecology. the condition of an ecosystem that has its native components intact and is self-sustaining and selfregulating, including abiotic components (e.g., water), biodiversity, and ecosystem processes (e.g., fire, predation); such a system has a self-correcting ability to recover when subjected to a disturbance.

ecological overshoot Ecology. the overexploitation of resources or accumulation of waste; growth beyond an area’s carrying capacity. ecological pyramid Ecology. a description of the flow of energy in an ecosystem, expressed in a graphical format resembling a pyramid; the parameter being displayed can be the number of organisms at each level (number pyramid), energy present at each level (energy pyramid), or amount of biomass per level

(biomass pyramid).

ecological risk assessment (ERA) Ecology. a process evaluating the likelihood that adverse ecological effects may occur or are occurring as a result of the exposure of terrestrial, avian, and aquatic receptors to one or more stressors.

ecological terrorism see ECOTERRORISM.

ecology the scientific study of the relationship between organisms and their environ-

ple have an impact on the earth. But since nature has the ability to renew, it can cope with human demand as long as this demand stays within the regenerative capacity of the biosphere. The earth's biologically productive area is approximately 11.3 billion hectares or 1.8 global hectares per person in 2001. The global Ecological Footprint in 2001 is estimated at 13.5 global hectares or 2.2 global hectares per person. This finding implies and suggests that society must develop more sustainable technologies, institutions, and behaviors to avoid eroding the supply of natural resources and environmental services for future generations.

Mathis Wackernagel

Global Footprint Network

Oakland, California

ment, including their relationship with other organisms, ranging from the relationship of two individuals to the organismal interactions of the biosphere as a whole.

econometrics Economics. economic measurement; the application of statistical methods to the analysis of economic data and theories. Thus, econometric.

economic efficiency Economics. a condition in which the organization of production minimizes the ratio of inputs to outputs, and goods are thus produced at minimum cost in money and resources.

economic geography Economics. the principles and processes associated with the spatial allocation of human and natural resources, and the environmental, economic, and social consequences resulting from such allocations.

economic globalization see GLOBALIZATION.

economic rent see RENT.

economiser a British spelling of ECONOMIZER.

economizer Consumption & Efficiency. 1. an apparatus that uses warm flue gases exiting a steam boiler to preheat feedwater entering the system, thus improving boiler efficiency and economy. 2. a compartment in a continu- ous-flow oxygen system that collects exhaled oxygen for reuse. 3. see ECONOMIZER SYSTEM.

economizer system HVAC. a system that takes advantage of favorable weather conditions to reduce the amount of mechanical

economy in transition (EIT)


Edison effect

cooling required for a building, by introducing naturally cool outside air into the building.

economy in transition (EIT) Economics. a descriptive term for a nation that is in transition from a centrally-planned economy to a market-based economy; especially applied to nations that were part of the Soviet sphere of influence; i.e., Russia, various Central and East European countries such as Poland and Hungary, and former republics of the USSR.

ecosphere Ecology. the earth conceived of as a living system; the planet and all the living organisms that inhabit it, along with the environmental factors that affect them.

ecosystem Ecology. an identifiable entity in nature, consisting of a community of living organisms and their surrounding environment of air, soil, water, mineral cycles, and so on, which they interact with and affect; e.g., the savanna ecosystem of central and southern Africa, the boreal forest ecosystem of northern Canada.

ecosystem health Ecology. the functional integrity of an ecosystem, as characterized by a state of ongoing self-renewal in the system as a whole and in its particular components (soil, water, animals, plants, and so on).

ecoterrorism Global Issues. violence carried out to further the political or social objectives of environmental activists, who ostensibly are motivated by concern for the natural environment.

ecotourism Global Issues. tourist activity that is ecologically sustainable and that focuses on experiencing natural areas in a manner that will encourage environmental appreciation and conservation of resources.

ecotoxicology Health & Safety. a scientific discipline that studies the adverse effects of chemicals, both synthetic and natural, on biological and ecological systems, especially on a large scale. Thus, ecotoxicological, ecotoxicologist.

ectotherm Biological Energetics. a coldblooded animal; i.e., an organism that regulates its body temperature largely by exchanging heat with its surroundings, such as a reptile, amphibian, or fish. Thus, ectothermy. Contrasted with ENDOTHERM.

ectothermic Biological Energetics. deriving body heat from the sun and other external sources.

eddy conductivity Thermodynamics. a fluidflow quantity describing the heat transfer due to eddies (whirling or circular flow) in a fluid, caused by a temperature difference between the fluid near the boundary and the fluid in the center of the stream, so that hot fluid is carried to the cooler regions and cold fluid to the warmer regions.

eddy current Electricity. an electric current produced in a conductor as it moves through a magnetic field.

Edison,Thomas Alva 1847–1931, prolific U.S. inventor who held more than 1000 patents for his inventions, including innovations such as the incandescent electric lamp (1879) and the phonograph (1877). Edison did not invent the light bulb, but he produced an improved version using a small carbonized filament. In 1882, he opened the first commercial power station in New York City, thus beginning the electric era.

Thomas Edison

Edison battery another name for a NICKEL-


Edison effect Electricity. a phenomenon observed by Thomas Edison; the emission of electrons from a heated cathode. Though he did not recognize the importance of this

Edison Electric Institute


Einstein, Albert

discovery, subsequent scientists used the effect as the basis for the electron tube.

Edison Electric Institute (est. 1933), an influential U.S. trade association for shareholderowned electric companies that represents utility interests in the legislative and regulatory arenas.

EDP Economics. environmentally adjusted net domestic product; an environmental accounting aggregate obtained by deducting the cost of resource depletion and environmental degradation from net domestic product.

EEI Edison Electric Institute. EER energy efficiency ratio.

effective current Electricity. the amount of alternating current that produces the same power dissipation effect on a load resistor as the corresponding amount of direct current.

effective dose Nuclear. a measure of toxicity calculated by multiplying equivalent doses by a tissue-specific weighting factor that is intended to take into account differences in sensitivity of different organs and tissues to the effects of ionizing.

effective dose equivalent Nuclear. the sum of the dose equivalents to various organs or tissues and the weighting factors applicable to each of these that are irradiated.

effective half-life Nuclear. the time required for the concentration of a radionuclide in a biological system to be reduced to one-half of the original concentration.

effective internal resistance Storage. the apparent opposition to current within a battery that manifests itself as a drop in battery voltage proportional to the discharge current; depends on factors such as the battery design, state of charge, temperature, and age.

effective nocturnal energy Solar. the energy transfer required to maintain a horizontal upward-facing blackbody surface at the ambient air temperature, in the absence of solar irradiance.

effective temperature Measurement. the temperature at which motionless, saturated air would create the same sensation of comfort in a sedentary worker wearing ordinary indoor clothing as that created by actual conditions of temperature, humidity, and air movement.

efficacy Lighting. a measure used to compare light output to energy consumption, mea-

sured in lumens per watt. A 100-watt light source producing 1750 lumens of light has an efficacy (efficiency) of 17.5 lm/W.

efficiency Consumption & Efficiency. 1. in general, the relative effectiveness of a system or device, especially in terms of the total resources required to attain a desired output. See also various specific terms such as ECONOMIC EFFI-


and so on. 2. Thermodynamics. a dimensionless quantity that characterizes an energy conversion process based on the relationship of work output to energy input. See also FIRST LAW EFFI-


efficiency gap Consumption & Efficiency. the difference between the actual level of investment in energy efficiency and a higher level that would be cost-beneficial from the standpoint of consumers and society.

efficiency service company (ESCO)

Electricity. a company that offers to reduce a client’s electricity consumption with the cost savings being split with the client.

effluent Environment. 1. a liquid or gas that flows out or flows away; e.g., a stream that flows out of a larger stream, a lake, or another body of water. 2. liquid waste matter that results from sewage treatment or industrial processing, especially such waste liquid released into waterways.

E-fuel Oil & Gas. a fuel consisting of an ethanol/gasoline mixture.

egg coal see COAL SIZING.

eggbeater turbine Wind. a term for a wind turbine whose blades resemble the motion of the common kitchen eggbeater; i.e., it has thin blades that rotate about a vertical axis; e.g., the Darrieus turbine.

EGS enhanced geothermal system.

EIA 1. environmental impact assessment. 2. Energy Information Administration.

Einstein, Albert 1879–1955, German-born physicist who published three papers in 1905 that had a profound effect on the development of physics. In one paper, he proposed the theory of special relativity (see RELATIVITY). In a second paper, he explained the PHOTOELEC- TRIC EFFECT. In the third paper he provided evidence for the physical existence of atomsized molecules. With the rise of fascism in Germany, Einstein moved to the U.S., where



electrical energy

Albert Einstein

his correspondence with President Franklin D. Roosevelt concerning atomic energy contributed to the establishment of the MANHAT-


einsteinium Chemistry. a synthetic radioactive chemical element having the symbol Es, the atomic number 99, and an atomic weight (of the most stable isotope) 252.08; produced by bombarding berkelium and californium with helium ions and deuterons.

Einstein’s (relativity) theory see RELATIVITY.

Einstein shift Physics. the lengthening of the wavelengths of light that are emitted by bodies with strong gravitational fields, causing a displacement of spectral lines toward the redder part of the spectrum; predicted in Einstein’s general theory of relativity.

EIOLCA Economics. economic input–output life cycle assessment; a method of estimating the overall environmental impacts from producing a certain dollar amount of any of various products, materials, services, or industries, with respect to resource use and emissions.

EIS environmental impact statement; see


EKC environmental Kuznets curve.

Ekman convergence Earth Science. a zone of convergence between warm and cold water masses, caused by the Ekman transport of surface water (see below). Also, Ekman layer. [Described by Swedish oceanographer Vagn Wilfrid Ekman, 1874–1954.]

Ekman transport Earth Science. the net mass displacement of water from one place to another, caused by wind blowing steadily over the surface; the net mass transport is 90° to the right (in the Northern Hemisphere) of the wind’s direction.

el short for ELEVATED RAILWAY.

elastic Materials. 1. having the property of elasticity; able to return to its original shape after experiencing strain and removal of deforming stress. 2. Economics. having an economic elasticity that is greater than or equal to one.

elasticity Materials. 1. a property of materials in response to stress, indicating the degree to which strain disappears from a material when the stress is removed. 2. Economics. the relative responsiveness of an economic condition to change; generally measured as the percentage change that will occur in a given variable, in response to a 1% change in another variable. Thus, elasticity of demand, elasticity of supply. RSee next page.

elasticity of substitution (ESUB) Economics. the percentage change in the relative use of inputs (capital, labor, energy, materials) in response to changes in their relative costs. A high ESUB implies an easy ability to switch away from a given input as its relative price increases, and a low ESUB indicates the opposite.

elastomer Materials. a natural or synthetic material having elastic properties similar to rubber. Thus, elastomeric.

Electra History. an advance in aviation (1937), the first airplane with a fully pressurized cabin, developed by Lockheed Aircraft.

electric Electricity. 1. having to do with or involving electricity. 2. produced by or carrying electricity.

electrical Electricity. 1. having to do with electricity; electric. 2. having to do with the science or technology of electricity. Thus, electrical engineer(ing).

electrical conductance see CONDUCTANCE.

electrical energy Electricity. 1. the energy inherent in an array of charged particles because of their relative positions. 2. the energy inherent in a circuit because of its position in relation to a magnetic field.

electrical fault

Relasticity Introduced by Alfred Marshall in the early 1880s, the concept of elasticity

has assumed an important role in modern energy analysis. Intuitively, elasticity means responsiveness; in policy circles it is generally measured as the per cent change in one variable that is associated with a 1% change in another (presumably causal) variable. The most common elasticities used in energy analysis are price and income elasticities of demand as well as supply elasticities. Economists typically distinguish short-run elasticities (responses with a fixed capital stock) from long-run elasticities (where the response can include an adjustment of the capital stock) and have found, not surprisingly, that long-run elasticities are typically larger. Elasticities are commonly used in energy forecasting either as the basis for the forecast (in simpler models) or to summarize the demand or supply responsiveness implied by more complicated forecasting models. Elasticities also have behavioral implications for key participants in the energy market. For example, the low price elasticity of demand for oil allows OPEC to increase revenue by raising oil prices, while the higher income elasticity for oil demand subjects the cartel to potentially destabilizing demand volatility. For the energy market, the low short-run price elasticity of demand, combined with the low short-run supply elasticity, imply the potential for quite large swings in the oil prices in response to shocks, such as when production is curtailed by war. For governments, the low price elasticity of oil demand also implies that price-based conservation policies must raise prices by a large amount to have much effect.

Tom Tietenberg

Colby College

electrical fault see


electrical induction


electrical power see ELECTRICAL ENERGY.

electrical resistance see RESISTANCE.

electrical thermometer Measurement. a thermometer using a transducing element whose element properties are a function of its thermal state.

electrical ground see GROUND.

electrical transient Electricity. any voltage or current that deviates from the normal steadystate condition.

electric baseboard see BASEBOARD HEAT.


electric radiant heating

electric battery


electric car Transportation. a passenger vehicle that is powered exclusively by an electrochemical power source, or partially so powered (hybrid electric).

electric cell see CELL (def. 2).

electric charge


electric current


electric dipole


electric energy see ELECTRICAL ENERGY.

electric field Electricity. a region in space in which lines of force produced by an electric charge exert a force on other electric charges.

electric force Electricity. a force between two objects such that each have the physical property of charge.

electric generator see GENERATOR.

electric heat(ing) HVAC. a process in which electric energy becomes heat energy by resisting the free flow of electric current; e.g., radiant heating.

electricity 1. a fundamental form of energy, consisting of oppositely charged electrons and protons that produce light, heat, magnetic force, and chemical changes. 2. the flow of this energy; electric current. 3. the general phenomenon of charges at rest and in motion.

electric light(ing) Lighting. 1. an incandescent lamp, or the light produced by this. 2. any form of lighting powered by electricity.

electric–magnetic field see ELECTROMAGNETIC


electric motor Conversion. a device that converts electrical energy into mechanical energy using forces exerted by magnetic fields on current-carrying conductors.

electric polarization Electricity. the separation of charges in a material to form electric dipoles, or the alignment of existing electric dipoles in a material when an electric field is applied.

electric potential Electricity. the potential measured by the energy of a unit positive charge at a point, expressed relative to an equipotential surface that has zero potential, generally the surface of the earth.

electric power see ELECTRICAL ENERGY.

electric radiant heating see RADIANT HEATING.