Energy terms starting with D

205 terms

Daily (or Next-Day) Indexes Published (Platts, NGI, Dow Jones, SNL, ICE, NGW) price indices for commodities (gas or electricity) to be delivered the next day based on transactions…
Daily Deals Usually transactions done on a day for delivery or settlement or both, the next day.
Dam A structure for impeding and controlling the flow of water in a water course, and which increases the water elevation to create the hydraulic head.
Damper A movable plate used to control air flow; in a wood stove or fireplace, used to control the amount and direction of air going to the fire.
Darrius (Wind) Machine A type of vertical-axis wind machine that has long, thin blades in the shape of loops connected to the top and bottom of the axle; often called an…
Day-ahead markets Forward markets for electricity to be supplied the following day. This market closes with acceptance by the independent system operator, power exchange…
Day-night average noise level Twenty-four-hour average noise level, obtained after the addition of a 10-dB penalty for environmental noise occurring from 10 p.m. to 7 a.m.
Daylighting The use of direct, diffuse, or reflected sunlight to provide supplemental lighting for building interiors.
Daytime mean rural background level Daytime (7 a.m. to 10 p.m.) average sound level in the rural environment, from all sources other than a particular noise that is of interest.
DC See Direct current
De-energize(d) To disconnect a transmission and/or distribution line; a power line that is not carrying a current; to open a circuit.
Deaeration Removal of gases from a liquid.
Debris flow A mixture of water-saturated rock debris that flows downslope under the force of gravity (also called lahar or mudflow).
Debris flow fans Alluvial fans prone to debris flows; a mixture of water and debris, such as mudslides, mudflows, or debris avalanches.
Debt financing Providing capital by selling bonds, bills, or notes to individuals or institutions.
Decentralized (Energy) System Energy systems supply individual, or small-groups, of energy loads.
Decibel (dB) A standard unit for measuring the loudness or intensity of sound. In general, a sound doubles in loudness with every increase of 10 decibels.
Decibel, A-weighted (dBA) A measurement of sound approximating the sensitivity of the human ear and used to characterize the intensity or loudness of a sound.
Decibels (dBA) A scale to measure sound levels.
Deciduous Plants that shed their leaves annually. Not evergreen.
Decision notice The written record of a federal agency decision after an environmental assessment.
Declination The angular position of the sun at solar noon with respect to the plane of the equator.
Declining Block Rate An electricity supplier rate structure in which the per unit price of electricity decreases as the amount of energy increases.
Decommissioning The process of removing a power plant, apparatus, equipment, building, or facility from operation.
Decomposition The process of breaking down organic material; reduction of the net energy level and change in physical and chemical composition of organic material.
Decoupling A regulatory design that breaks the link between utility revenues and energy sales to encourage utility investment in conservation.
Deed Restriction A legally binding restriction on the use, activity, and/or limitation of property rights, recorded at the registry of deeds.
Deep Discharge Discharging a battery to 20 percent or less of its full charge capacity.
Deep-cycle battery A battery with large plates that can withstand many discharges to a low state of charge.
Degree Day A unit for measuring the extent that the outdoor daily average temperature (the mean of the maximum and minimum daily dry-bulb temperatures) falls below…
Degree Hour The product of 1 hour, and usually the number of degrees Fahrenheit the hourly mean temperature is above a base point (usually 65 degrees Fahrenheit)…
Dehumidifier A device that cools air by removing moisture from it.
dehydration A condition caused by the loss of too much water from the body. Severe diarrhea or vomiting can cause dehydration.
dehydrogenation A chemical reaction in which hydrogen is removed from a compound.
dekatherm or decatherm (DTH) Ten therms, same as one million British thermal units or one MMBtu.
Delivery Point(s) An industry-designated location at which delivery may be made in fulfillment of contract terms.
Delta The relationship between an option's price and the price of the underlying stock or futures contract is called its delta.
Demand Form PCT/IPEA/401, filed with an International Preliminary Examining Authority, demanding that an international application shall be the subject of an…
Demand (Tankless) Water Heater A type of water heater that has no storage tank thus eliminating storage tank stand-by losses.
Demand Charge A charge for the maximum rate at which energy is used during peak hours of a billing period.
Demand elasticity The degree to which demand changes relative to a change in price.
Demand Power see Peak Power
Demand responsiveness/demand response A change in demand for a good or service in response to a change in price for the good or service.
Demand(ed) Factor The ratio of the maximum demand on an electricity generating and distribution system to the total connected load on the system; usually expressed as a…
Demand-side management Specific actions taken by utility companies, their regulators, and other entities to induce, influence, or compel consumers to reduce their energy…
Demand-Side Management (DSM) The process of managing the consumption of energy, generally to optimize available and planned generation resources.
Demographic Related to the vital statistics of human populations (size, density, growth, distribution, etc.) and the effect of these on social and economic conditions.
denaturant A substance that makes ethanol unfit for consumption.
Denatured Ethanol that has had a substance added to make it unfit for human consumption.
Dendrite Extension of a nerve cell, typically branched and relatively short, that receives stimuli from other nerve cells.
Dendritic Web Technique A method for making sheets of polycrystalline silicon in which silicon dendrites are slowly withdrawn from a melt of silicon whereupon a web of silicon…
Densification A mechanical process to compress biomass (usually wood waste) into pellets, briquettes, cubes, or densified logs.
Density The average number of people, families, or housing units on one unit of land. Density is also expressed as dwelling units per acre.
Density bonus Allows developers to build in specified areas densities that are higher than normally allowed.
Department of Agriculture (USDA) A federal government agency involved in rural development, marketing and regulatory programs, food safety, research, education and economics, food…
Department of Energy (DOE) In 1989, the Department of Energy (DOE) created the Office of Environmental Management (EM) to mitigate the risks and hazards posed by the legacy of…
Dependable Capacity The load-carrying ability of an electric power plant during a specific time interval and period when related to the characteristics of the load to…
Depletion Net loss of water through consumption, export, and other uses to a given area, river system, or basin.
Deposit An amount of money paid to the court. Hennepin County Housing Court can only accept cash and certified checks; personal checks, third-party checks, and…
Derating The production of energy by a system or appliance at a level less than its design or nominal capacity.
Deregulation The process of changing regulatory policies and laws to increase competition among suppliers of commodities and services.
Desert Arid region receiving less than 10 inches of precipitation annually.
Desert bench A relatively flat terrace elevated above the surface of a desert alluvial feature, such as an ephemeral stream or wash.
Desert dune A wind-created ridge or mound of sand that is found in deserts or near oceans and lakes.
Desert floor The land surface in a desert valley.
Desert focal bird species Bird species whose requirements define spatial attributes, habitat characteristics, and management regimes representative of a healthy desert system.
Desert pavement A surface layer of closely packed, loosely cemented pebbles. See also Pediment
Desert riparian habitat Habitats characterized as dense groves of low shrublike trees, or tall shrubs to woodlands of small to medium-sized trees.
Desert scrub The desert scrub community is characterized by plants adapted to seasonally dry climate.
Desert varnish The thin red to black coating found on exposed rock surfaces in arid regions. Varnish is composed of clay minerals, oxides, and hydroxides of manganese…
Desert wash A usually dry desert streambed that flows only after periods of heavy rain.
Desiccant Any compound used to remove moisture or water.
Desiccant Cooling To condition/cool air by dessication.
Desiccation The process of removing moisture; involves evaporation.
Design basis The set of conditions, dimensions, needs, and requirements used to design a solar energy facility.
Design Cooling Load The amount of conditioned air to be supplied by a cooling system; usually the maximum amount to be delivered based on a specified number of cooling degree…
Design features Measures or procedures incorporated into the proposed action or alternatives which could avoid or reduce adverse impacts.
Design Heating Load The amount of heated air, or heating capacity, to be supplied by a heating system; usually the maximum amount to be delivered based on a specified number…
Design Life Period of time a system or appliance (or component of) is expected to function at its nominal or design capacity without major repair.
Design Standards Design standards or guidelines can serve as a community's desire to control its appearance, from within and without, through a series of standards that…
Design Temperature The temperature that a system is designed to maintain (inside) or operate against (outside) under the most extreme conditions.
Design Tip Speed Ratio For a wind turbine, the ratio of the speed of the tip of a turbine blade for which the power coefficient is at maximum.
Design Voltage The nominal voltage for which a conductor or electrical appliance is designed; the reference voltage for identification and not necessarily the precise…
Designated Roads and Trails Specific roads and trails identified by the agencies where some type of motorized vehicle use is appropriate and allowed, either seasonally or yearlong.
Desired future condition A vision of the desired future state of a specific area. A description of land and resource conditions expected to result if management goals and…
Desuperheater An energy saving device in a heat pump that, during the cooling cycle, recycles some of the waste heat from the house to heat domestic water.
Detention Ponds (Extended Detention Basins) An area surrounded by an embarkment, or an excavated pit, designed to temporarily hold stormwater long enough to allow…
Detritus Loose natural materials, such as rock fragments or organic particles, that result directly from disintegration of rocks or organisms.
Development Rights Development rights give property owners the right to develop land in ways that comply with local land use regulation.
Dewatering The separation of free water from the solids portion of spent mash, sludge, or whole stillage by screening, centrifuging, filter pressing, or other means.
Dewpoint The temperature to which air must be cooled, at constant pressure and water vapor content, in order for saturation or condensation to occur; the…
Diagnostic An item that is indicative of a particular time and/or cultural group.
Diameter at breast height (DBH) The diameter of a tree measured 4 feet 6 inches above the ground.
Diesel engine A compression-ignition piston engine in which fuel is ignited by injecting it into air that has been heated (unlike a spark-ignition engine).
Difference of Potential The difference in electrical pressure (voltage) between any two points in an electrical system or between any point in an electrical system and the earth.
Differential compaction May occur over a large area when the compaction of soil or deeper sediments occurs at different rates and degrees.
Differential Thermostat A type of automatic thermostat (used on solar heating systems) that responds to temperature differences (between collectors and the storage components) so…
Diffuse Solar Radiation Sunlight scattered by atmospheric particles and gases so that it arrives at the earth's surface from all directions and can not be focused.
diffusion The spontaneous movement of molecules from a region of higher concentration to a region of lower concentration.
Diffusion Length The mean distance a free electron or hole moves before recombining with another hole or electron.