Glossary

Energy glossary

747 definitions · page 4 of 13.

DEEP MINING: Extraction of coal or minerals at depths greater than 1,000 feet. Coal usually is deep-mined at not more than 1,500 feet.
DEGREE DAY: A unit, based upon temperature difference and time, used in estimating fuel consumption and specifying nominal annual heating load of a building. When the mean temperature is less than 65 degrees Fahrenheit the heating degree days are equal to the total…
DEINTEGRATION: (See disaggregation)
DELTA: A difference in temperature. Often used in the context of the difference between the design indoor temperature and the outdoor temperature.
DEMAND: The rate at which energy is delivered to loads and scheduling points by generation, transmission or distribution facilities.
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 BID: Demand Bid A bid into the PX indicating a quantity of energy or an ancillary service that an eligible customer is willing to purchase and, if relevant, the maximum price that the customer is willing to pay.
DEMAND BILLING: The electric capacity requirement for which a large user pays. It may be based on the customer's peak demand during the contract year, on a previous maximum or on an agreed minimum. Measured in kilowatts.
DEMAND CHARGE: The sum to be paid by a large electricity consumer for its peak usage level.
DEMAND SIDE MANAGEMENT (DSM): The methods used to manage energy demand including energy efficiency, load management, fuel substitution and load building. See LOAD MANAGEMENT.
DEMAND SITE MANAGEMENT: Planning, implementation, and evaluation of utility-sponsored programs to influence the amount or timing of customers' energy use.
DEMONSTRATION: The application and integration of a new product or service into an existing or new system. Most commonly, demonstration involves the construction and operation of a new electric technology interconnected with the electric utility system to demonstrate how…
DENSITY: The mass of a unit volume of a substance.
Dependable Capacity: The systems's ability to carry the electric power for the time inrval and period specific, when related to the characteristics of the load to be supplied. Dependable capacity is determined by such factors as capability, operating power factor, weather, and…
DEPLETABLE ENERGY SOURCES -- 1): electricity purchased from a public utility 2) energy obtained from burning coal, oil, natural gas or liquefied petroleum gases. [See California Code of Regulations, Title 24, Section 2-5302]
DEREGULATION: The elimination of regulation from a previously regulated industry or sector of an industry.
DERIVATIVES: A specialized security or contract that has no intrinsic overall value, but whose value is based on an underlying security or factor as an index. A generic term that, in the energy field, may include options, futures, forwards, etc.
DIESEL OIL: Fuel for diesel engines obtained from the distillation of petroleum. It is composed chiefly of aliphatic hydrocarbons. Its volatility is similar to that of gas oil. Its efficiency is measured by cetane number.
DIFFUSE RADIATION: Solar radiation, scattered by water vapor, dust and other particles as it passes through the atmosphere, so that it appears to come from the entire sky. Diffuse radiation is higher on hazy or overcast days than on clear days.
DIRECT ACCESS: The ability of a retail customer to purchase commodity electricity directly from the wholesale market rather than through a local distribution utility. (See also Retail Competition)
DIRECT CURRENT (DC): Electricity that flows continuously in the same direction.
DIRECT ENERGY CONVERSION: Production of electricity from an energy source without transferring the energy to a working fluid or steam. For example, photovoltaic cells transform light directly into electricity. Direct conversion systems have no moving parts and usually produce direct…
DIRECT EXPANSION: (refrigeration) - Any system that, in operation between an environment where heat is absorbed (heat source), and an environment into which unwanted heat is directed (heat sink) at two different temperatures, is able to absorb heat from the heat source at the…
DIRECT RADIATION: Radiation that has traveled a straight path from the sun, as opposed to diffuse radiation.
DIRECT SOLAR GAIN: Solar energy collected from the sun (as heat) in a building through windows, walls, skylights, etc.
DIRECTLY CONDITIONED SPACE: See conditioned space, directly.
DISAGGREGATION: The functional separation of the vertically integrated utility into smaller, individually owned business units (i.e., generation, dispatch/control, transmission, distribution). The terms "deintegration," "disintegration" and "delamination" are sometimes used…
DISPATCH: The operating control of an integrated electric system to: Assign generation 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…
DISSOLVED GAS: Natural gas that can be developed for commercial use, and which is found mixed with oil in naturally occurring underground formations.
DISTRIBUTED GENERATION: A distributed generation system involves small amounts of generation located on a utility's distribution system for the purpose of meeting local (substation level) peak loads and/or displacing the need to build additional (or upgrade) local distribution lines.
DISTRIBUTION: The delivery of electricity to the retail customer's home or business through low voltage distribution lines.
DISTRIBUTION SYSTEM (Electric utility): The substations, transformers and lines that convey electricity from high-power transmission lines to ultimate consumers. See GRID.
DISTRIBUTION UTILITY (Disco): The regulated electric utility entity that constructs and maintains the distribution wires connecting the transmission grid to the final customer. The Disco can also perform other services such as aggregating customers, purchasing power supply and…
DIVESTITURE: The stripping off of one utility function from the others by selling (spinning-off) or in some other way changing the ownership of the assets related to that function. Most commonly associated with spinning-off generation assets so they are no longer owned…
DOSE: The amount of ionizing radiation energy absorbed per unit mass of irradiated material at a specific location, such as a part of a human body.
DOUBLE GLAZING: Windows having two sheets of glass with an airspace between.
DOWNSTREAM: A term used in the petroleum industry referring to the refining, transportation and marketing side of the business.
DRY BULB TEMPERATURE: A measure of the sensible temperature of air.
DRY HOLE: A drilled well that does not yield gas and/or oil quantities or condition to support commercial production; also applied to gas that has been produced and from which liquid components have been removed.
DRY STEAM: The conventional type of geothermal energy used for electricity production in California. Dry steam captured at the earth's surface is used to run electric turbines. The principal dry steam resource area is the Geysers in Northern California; one of only two…
DUAL-DUCT SYSTEM: A central plant heating , ventilation and air conditioning (HVAC ) system that produces conditioned air at two temperatures and humidity levels. The air is then supplied through two independent duct systems to the points of usage where mixing occurs.
DUAL-FUEL or BI-FUEL VEHICLE: refers to a vehicle capable of operating on two different fuels, in distinct fueling systems, such as compressed natural gas and gasoline.
DUAL-PANED (double-glazed): Two panes of glass or other transparent material, separated by a space.
DUCT: A passageway made of sheet metal or other suitable material used for conveying air or other gas at relatively low pressures.
DUMP: Excess hydropower that cannot be stored or conserved. Also know as SPILL ENERGY.
ECOLOGY: The study of interrelationships of animals and plants to one another and to their environment.
ECONOMIC EFFICIENCY: A term that refers to the optimal production and consumption of goods and services. This generally occurs when prices of products and services reflect their marginal costs. Economic efficiency gains can be achieved through cost reduction, but it is better to…
ECONOMIES OF SALE: Economies of scale exist where the industry exhibits decreasing average long-run costs with size.
ECONOMIZER AIR: A ducting arrangement and automatic control system that allows a heating, ventilation and air conditioning (HVAC) system to supply up to 100 percent outside air to satisfy cooling demands, even if additional mechanical cooling is required.
ECONOMIZER WATER: A system which uses either direct evaporative cooling, or a secondary evaporatively cooled water loop and cooling coil to satisfy cooling loads, even if additional mechanical cooling is required.
ECONOMY ENERGY (Electricity utility): Electricity purchased by one utility from another to take the place of electricity that would have cost more to produce on the utility's own system.
ECOSYSTEM: The interacting system of biological community and its nonliving environment.
EDISON THOMAS ALVA: The "father" of the American energy industry, Thomas Edison was an American inventor who was born in 1847 and died in 1931. He patented a total of 1,093 inventions - more than any other person in American history. Among the most important were the…
EDISON, THOMAS ALVA: The "father" of the American energy industry, Thomas Edison was an American inventor who was born in 1847 and died in 1931. He patented a total of 1,093 inventions - more than any other person in American history. Among the most important were the…
EEI: Edison Electric Institute. An association of electric companies formed in 1933 "to exchange information on industry developments and to act as an advocate for utilities on subjects of national interest."
EER (Energy Efficiency Ratio): The ratio of cooling capacity of an air conditioning unit in Btus per hour to the total electrical input in watts under specified test conditions. [See California Code of Regulations, Title 20, Section 1602(c)(6)]
EER - (Energy Efficiency Ratio): the ratio of cooling capacity of an air conditioning unit in Btus per hour to the total electrical input in watts under specified test conditions. California Code of Regulations, Section 1602(c)(6).
EFFICACY LIGHTING: The ratio of light from a lamp to the electrical power consumed, including ballast losses, expressed as lumens per watt. [See California Code of Regulations, Title 24, Section 2-5302]
EFFICACY, LIGHTING: The ratio of light from a lamp to the electrical power consumed, including ballast losses, expressed as lumens per watt. [See California Code of Regulations, Title 24, Section 2-5302]
EFFICIENCY: The ratio of the useful energy delivered by a dynamic system (such as a machine, 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.