Regenerative BrakingA feature of hybrid and plug-in electric vehicles that captures energy normally lost during braking by using the electric motor as a generator and storing…
Regenerative CoolingA type of cooling system that uses a charging and discharging cycle with a thermal or latent heat storage subsystem.
Regenerative HeatingThe process of using heat that is rejected in one part of a cycle for another function or in another part of the cycle.
Region of Influence (ROI)(ROI)Area occupied by affected resources and the distances at which impacts associated with license renewal may occur.
Regional Transmission Organization (RTO)(RTO)A voluntary organization of electric transmission owners, transmission users and other entities approved by the Commission to efficiently coordinate…
Regular-track proposalsProposals on public land with pending applications considered as potential future projects, but not necessarily foreseeable projects, since not all…
Reid vapor pressure (RVP)(RVP)A standard measurement of a liquid´s vapor pressure at 100 degrees Fahrenheit. An indication of the propensity of the liquid to evaporate.
ReinjectionThe feeding of unburned char and fly ash obtained from mechanical collectors into the furnace for further combustion.
RelampingThe replacement of a non-functional or ineffective lamp with a new, more efficient lamp.
Relative HumidityA measure of the percent of moisture actually in the air compared with what would be in it if it were fully saturated at that temperature.
ReliabilityThe consistency of a measure or question in obtaining very similar or identical results when used repeatedly; for example, if you repeated a blood test…
Reliability must run (RMR)(RMR)A unit that must run for operational or reliability reasons, regardless of economic considerations. Also called a reliability agreement.
RelictA land surface that was once a basin (valley) floor.
Renewable EnergyEnergy derived from resources that are regenerative or for all practical purposes can not be depleted.
Renewable Energy Certificate (REC)A tradable certificate representing the generation attributes of energy derived from a qualified renewable energy source. In the U.S.
renewable energy resourceAn energy resource that can be replaced as it is used. Renewable energy resources include solar, wind, geothermal, hydro, and biomass.
Renewable energy sourceAn energy source that is replenished continuously in nature or that is replaced after use through natural means. Sustainable energy source.
Renewable Fuels StandardA regulation created under the Energy Policy Act of 2005 and implemented by the U.S.
Repetition/replicationThere are four plots in a repetition/replication, the early, mid and late seral treatment plots and a control plot.
ReptileCold-blooded vertebrate of the class Reptilia whose skin is usually covered in scales or scutes.
Reserve marginThe percentage of installed capacity exceeding the expected peak demand during a specified period.
Reserved Water RightA special water right accompanying federal lands (military reservations, national parks, forests, or monuments) or Indian reservations.
ReservoirA reservoir of an infectious agent, such as a virus, is any animal, person, plant, soil, substance—or combination of any of these — in which the…
Resident fishFish species that complete their entire life cycle in freshwater. Non-anadromous fish. An example is rainbow trout.
Residual fuel oilHeavy fuel oil produced from the residue in the fractional distillation process rather than from the distilled fractions. No.
residues, biomassByproducts from processing all forms of biomass that have significant energy potential.
ResiduumUnconsolidated, weathered, or partly weathered mineral material that accumulates by disintegration of bedrock in place.
ResistanceThe ability of an organism to develop ways to be impervious to specific threats to their existence.
Resistance HeatingA type of heating system that provides heat from the resistance of an electrical current flowing through a conductor.
Resistive Voltage DropThe voltage developed across a cell by the current flow through the resistance of the cell.
ResistorAn electrical device that resists electric current flow.
Resource Conservation and Recovery Act (RCRA)(RCRA)The primary goals of the Resource Conservation and Recovery Act (RCRA) are to protect human health and the environment from the potential hazards of waste…
Resource Management Plan (RMP)(RMP)A land use plan that establishes land use allocations, multiple use guidelines, and management objectives for a given planning area.
Resource RecoveryThe process of converting municipal solid waste to energy and/or recovering materials for recycling.
Resource valuesA resource, natural or social, that is found in an area. Resource values may have varying levels of significance.
RestructuringThe process of changing the structure of the electric power industry from one of guaranteed monopoly over service territories, as established by the…
Retail unbundlingDisaggregating electric utility service into its basic components and offering each component separately for sale with separate rates for each component.
Retail WheelingA term for the process of transmitting electricity over transmission lines not owned by the supplier of the electricity to a retail customer of the…
Retinal damageDamage to photoreceptor cells of the retina. One mechanism for such damage is exposure to bright light that triggers chemical reactions in the tissues…
RetrofitThe process of modifying a building's structure.
RetrofittingThe application of conservation, efficiency, or renewable energy technologies to existing structures.
Return AirAir that is returned to a heating or cooling appliance from a heated or cooled space.
Return DuctThe central heating or cooling system contains a fan that gets its air supply through these ducts, which ideally should be installed in every room of the…
Return on investment (ROI)(ROI)The interest rate at which the net present value of a project is zero. Multiple values are possible.
ReuseThe reclamation of water diverted from a municipal or industrial wastewater conveyance system.
Reverse ThermosiphoningWhen heat seeks to flow from a warm area (e.g., heated space) to a cooler area, such as a solar air collector at night without a reverse flow damper.
Reversing ValveA component of a heat pump that reverses the refrigerant's direction of flow, allowing the heat pump to switch from cooling to heating or heating to…
RhyoliteVolcanic rock (or lava), characteristically light in color and containing 69% silica or more and generally rich in potassium and sodium (felsic…
Ribbon (Photovoltaic) CellsA type of solar photovoltaic device made in a continuous process of pulling material from a molten bath of photovoltaic material, such as silicon, to form…
Richter Magnitude ScaleDeveloped in 1935 by Charles Richter to measure and compare the size of earthquakes.
RiftAn area where the Earth's crust and lithosphere is being pulled apart by extensional tectonic forces.
Rift zoneA tectonic feature characterized by a central linear downfaulted segment (graben) with parallel normal faulting and flanking uplifts (horsts).
Right-of-way (ROW)(ROW)The legal right to cross the lands of another. Also used to indicate the strip of land for a road, railroad, or power line.
Rigid Insulation BoardAn insulation product made of a fibrous material or plastic foams, pressed or extruded into board-like forms.
RillA small and shallow incision into topsoil layers resulting from erosion by overland flow or surface runoff that is common on slopes of unvegetated ground…
Ring-fencingTechniques used to isolate the credit risk of a subsidiary within a corporation from the risk of its affiliated companies.
RinsateWater that is used to rinse or clean equipment or reaction vessels and that may, as a result, become contaminated and require special handling and…
RiparianRelating to, living in, or located on the bank of a river, lake, or tidewater.
Riparian AreaVegetated ecosystems along a waterbody through which energy, materials, and water pass.
Riparian bufferRiparian areas that are managed to protect the aquatic and riparian ecosystem. A riparian buffer protects water quality and temperature, habitat along the…
RiskThe possibility of loss; the uncertainty of future returns.
risk managementThe process, distinct from risk assessment, of weighing policy alternatives, in consultation with all interested parties, considering risk assessment and…
River BasinThe land area surrounding one river from its headwaters to its mouth. The area drained by a river and its tributaries.
Riverine wetlandWetlands within river and stream channels, generally characterized by flowing water. Ocean-derived salinity is less than 0.5 part per thousand.
Rock artImages on rock surfaces. There are two types of rock art: pictographs, which are drawn or painted onto the surface, and petroglyphs, which are pecked…
Rock BinA container that holds rock used as the thermal mass to store solar energy in a solar heating system.
Rock outcropThe part of a rock formation that appears above the surface of the surrounding land.
Rock WoolA type of insulation made from virgin basalt, an igneous rock, and spun into loose fill or a batt. It is fire resistant and helps with soundproofing.
Rolling blackoutsA controlled and temporary interruption of electrical service. They are necessary when a utility is unable to meet heavy peak demands because of an…
RoofA building element that provides protection against the sun, wind, and precipitation.
Roof PondA solar energy collection device consisting of containers of water located on a roof that absorb solar energy during the day so that the heat can be used…
Roof VentilatorA stationary or rotating vent used to ventilate attics or cathedral ceilings; usually made of galvanized steel, or polypropylene.
RoostAn area where birds or bats rest or sleep. Birds often use branches or tree cavities for roosts while bats use tree bark, tree hollows, caves, mines…
RotationThe number of years allotted to establish and grow a forest stand to maturity.
RotorAn electric generator consists of an armature and a field structure. The armature carries the wire loop, coil, or other windings in which the voltage is…
Rough treesLive trees of commercial species which do not contain a sawlog because of roughness, poor form, splits, or cracks.
RoundwoodLogs, bolts, or other round sections cut from trees.
Run-of-River HydropowerA type of hydroelectric facility that uses the river flow with very little alteration and little or no impoundment of the water.
RunoffThe water that flows off the surface of the land, ultimately into our streams and water bodies, without being absorbed into the soil.
saccharideA simple sugar or a more complex compound that can be hydrolyzed to simple sugar units.
saccharificationA conversion process using acids, bases, or enzymes in which long-chain carbohydrates are broken down into their component fermentable sugars.
Sacred landscapesNatural places recognized by a cultural group as having spiritual or religious significance.
Sacred siteAny specific, discrete, narrowly delineated location on federal land that is identified by an Indian tribe, or Indian individual determined to be an…
Sacrificial AnodeA metal rod placed in a water heater tank to protect the tank from corrosion. Anodes of aluminum, magnesium, or zinc are the more frequently metals.
Safe Drinking Water Act (SWDA)(SWDA)Act authorizing development of maximum contaminant levels for drinking water applicable to public water systems (i.e.
Safe harborThe ability of management to discuss in good faith a company's prospects and financial projections with analysts and investors without fearing litigation.
Safe yieldThe amount of groundwater that can be withdrawn from a groundwater basin over a period of time without exceeding the long-term recharge of the basin or…
Safety DisconnectAn electronic (automatic or manual) switch that disconnects one circuit from another circuit.
SalinityA measure of the amount of salt and other mineral substances dissolved in water.
Salt flatLow-lying ground where salts collect in the soil because of the evaporation of standing water.
Salt Gradient Solar PondsConsist of three main layers. The top layer is near ambient and has low salt content.
Salvage loggingThe harvest of dead, dying, damaged or weak trees after a forest fire to prevent the spread of disease or insects and to reduce the risk of high intensity…
SandA rock or mineral fragment of any composition that has a diameter ranging from 0.5 to 2.0 mm. Sand has a gritty feel.