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Energy.gov - Energy industry terms Category: Earth and Environment > Energy industry terms Date & country: 26/02/2017, USA Words: 1299

Total Heat
The sum of the sensible and latent heat in a substance or fluid above a base point, usually 32 degrees Fahrenheit.

Tip Speed Ratio
In reference to a wind energy conversion device's blades, the difference between the rotational speed of the tip of the blade and the actual velocity of the wind.

Ton
(of Air Conditioning) A unit of air cooling capacity; 12,000 Btu per hour.

Topping-cycle
A means to increase the thermal efficiency of a steam electric generating system by increasing temperatures and interposing a device, such as a gas turbine, between the heat source and the conventional steam-turbine generator to convert some of the additional heat energy into electricity.

Torque
(Motor) The turning or twisting force generated by an electrical motor in order for it to operate.

Tilt Angle
(of a Solar Collector or Module) The angle at which a solar collector or module is set to face the sun relative to a horizontal position. The tilt angle can be set or adjusted to maximize seasonal or annual energy collection.

Timer
A device that can be set to automatically turn appliances (lights) off and on at set times.

Timer
(Water Heater) This device can automatically turn the heater off at night and on in the morning.

Three-phase Current
Alternating current in which three separate pulses are present, identical in frequency and voltage, but separated 120 degrees in phase.

Tidal Power
The power available from the rise and fall of ocean tides. A tidal power plant works on the principal of a dam or barrage that captures water in a basin at the peak of a tidal flow, then directs the water through a hydroelectric turbine as the tide ebbs.

Thermosiphon
The natural, convective movement of air or water due to differences in temperature. In solar passive design a thermosyphon collector can be constructed and attached to a house to deliver heat to the home by the continuous pattern of the convective loop (or thermosyphon).

Thermostat
A device used to control temperatures; used to control the operation of heating and cooling devices by turning the device on or off when a specified temperature is reached.

Thin-Film
A layer of semiconductor material, such as copper indium diselenide or gallium arsenide, a few microns or less in thickness, used to make solar photovoltaic cells.

Thermopile
A large number of thermocouples connected in series.

Thermoelectric Conversion
The conversion of heat into electricity by the use of thermocouples.

Thermography
A building energy auditing technique for locating areas of low insulation in a building envelope by means of a thermographic scanner.

Thermophotovoltaic Cell
A device where sunlight concentrated onto a absorber heats it to a high temperature, and the thermal radiation emitted by the absorber is used as the energy source for a photovoltaic cell that is designed to maximize conversion efficiency at the wavelength of the thermal radiation.

Thermocouple
A device consisting of two dissimilar conductors with their ends connected together. When the two junctions are at different temperatures, a small voltage is generated.

Thermodynamic Cycle
An idealized process in which a working fluid (water, air, ammonia, etc) successively changes its state (from a liquid to a gas and back to a liquid) for the purpose of producing useful work or energy, or transferring energy.

Thermodynamics
A study of the transformation of energy from one form to another, and its practical application. (see Law(s) of Thermodynamics above).

Thermal Storage Walls
(Masonry or Water) A thermal storage wall is a south-facing wall that is glazed on the outside. Solar heat strikes the glazing and is absorbed into the wall, which conducts the heat into the room over time. The walls are at least 8 in thick. Generally, the thicker the wall, the less the indoor temperature fluctuates.

Thermal Resistance
(R-Value) This designates the resistance of a material to heat conduction. The greater the R-value the larger the number.

Thermal Energy
The energy developed through the use of heat energy.

Thermal Energy Storage
The storage of heat energy during power provider off-peak times at night, for use during the next day without incurring daytime peak electric rates.

Thermal Mass
Materials that store heat.

Thermal Efficiency
A measure of the efficiency of converting a fuel to energy and useful work; useful work and energy output divided by higher heating value of input fuel times 100 (for percent).

Thermal Capacitance
The ability of a material to absorb and store heat for use later.

Tempering Valve
A valve used to mix heated water with cold in a heating system to provide a desired water temperature for end use.

Termite Shield
A construction element that inhibits termites from entering building foundations and walls.

Therm
A unit of heat containing 100,000 British thermal units (Btu).

Thermal Balance Point
The point or outdoor temperature where the heating capacity of a heat pump matches the heating requirements of a building.

Temperature/Pressure Relief Valve
A component of a water heating system that opens at a designated temperature or pressure to prevent a possible tank, radiator, or delivery pipe rupture.

Temperature Zones
Individual rooms or zones in a building where temperature is controlled separately from other rooms or zones.

Temperature Humidity Index
An index that combines sensible temperature and air humidity to arrive at a number that closely responds to the effective temperature; used to relate temperature and humidity to levels of comfort.

System Mix
The proportion of electricity distributed by a power provider that is generated from available sources such as coal, natural gas, petroleum, nuclear, hydropower, wind, or geothermal.

Tankless Water Heater
A water heater that heats water before it is directly distributed for end use as required; a demand water heater.

Task Lighting
Any light source designed specifically to direct light a task or work performed by a person or machine.

Temperature Coefficient
(of a solar photovoltaic cell) The amount that the voltage, current, and/or power output of a solar cell changes due to a change in the cell temperature.

Synchronous Motor
A type of motor designed to operate precisely at the synchronous speed with no slip in the full-load speeds (rpm).

Supply Side
Technologies that pertain to the generation of electricity.

Swamp Cooler
A popular term used for an evaporative cooling device.

Swept Area
In reference to a wind energy conversion device, the area through which the rotor blades spin, as seen when directly facing the center of the rotor blades.

Synchronous Generator
An electrical generator that runs at a constant speed and draws its excitation from a power source external or independent of the load or transmission network it is supplying.

Synchronous Inverter
An electrical inverter that inverts direct current electricity to alternating current electricity, and that uses another alternating current source, such as an electric power transmission and distribution network (grid), for voltage and frequency reference to provide power in phase and at the same frequency as the external power source.

Superconducting Magnetic Energy Storage
(SMES) SMES technology uses the superconducting characteristics of low-temperature materials to produce intense magnetic fields to store energy. SMES has been proposed as a storage option to support large-scale use of photovoltaics and wind as a means to smooth out fluctuations in power generation.

Superconductivity
The abrupt and large increase in electrical conductivity exhibited by some metals as the temperature approaches absolute zero.

Supplementary Heat
A heat source, such as a space heater, used to provide more heat than that provided by a primary heating source.

Sunspace
A room that faces south (in the northern hemisphere), or a small structure attached to the south side of a house.

Super Insulated Houses
A type of house that has massive amounts of insulation, airtight construction, and controlled ventilation without sacrificing comfort, health, or aesthetics.

Super Window
A popular term for highly insulating window with a heat loss so low it performs better than an insulated wall in winter, since the sunlight that it admits is greater than its heat loss over a 24 hour period.

Substrate
The physical material upon which a photovoltaic cell is applied.

Sun Path Diagram
A circular projection of the sky vault onto a flat diagram used to determine solar positions and shading effects of landscape features on a solar energy system.

Sun Tempered Building
A building that is elongated in the east-west direction, with the majority of the windows on the south side. The area of the windows is generally limited to about 7% of the total floor area. A sun-tempered design has no added thermal mass beyond what is already in the framing, wall board, and so on. Insulation levels are generally high.

Stud
A popular term used for a length of wood or steel used in or for wall framing.

Supply Duct
The duct(s) of a forced air heating/cooling system through which heated or cooled air is supplied to rooms by the action of the fan of the central heating or cooling unit.

Substation
An electrical installation containing power conversion (and sometimes generation) equipment, such as transformers, compensators, and circuit breakers.

Stranded Investment
(Costs and Benefits) An investment in a power plant or demand side management measures or programs, that become uneconomical due to increased competition in the electric power market. For example, an electric power plant may produce power that is more costly than what the market rate for electricity is, and the power plant owner may have to close the plant, even though the capital and financing costs of building the plant have not been recovered through prior sales of electricity from the plant. This is considered a Stranded Cost. Stranded Benefits are those power provider investments in measures or programs considered to benefit consumers by reducing energy consumption and/or providing environmental benefits that have to be curtailed due to increased competition and lower profit margins.

Storm Windows
Glass, plastic panels, or plastic sheets that reduce air infiltration and some heat loss when attached to either the interior or exterior of existing windows.

Storage Tank
The tank of a water heater.

Storage Water Heater
A water heater that releases hot water from the top of the tank when a hot water tap is opened. To replace that hot water, cold water enters the bottom of the tank to ensure a full tank.

Storm Door
An exterior door that protects the primary door.

Storage Hydropower
A hydropower facility that stores water in a reservoir during high-inflow periods to augment water during low-inflow periods. Storage projects allow the flow releases and power production to be more flexible and dependable. Many hydropower project operations use a combination of approaches.

Storage Capacity
The amount of energy an energy storage device or system can store.

Stoichiometric Ratio
The ratio of chemical substances necessary for a reaction to occur completely.

Stoichiometry
Chemical reactions, typically associated with combustion processes; the balancing of chemical reactions by providing the exact proportions of reactant compounds to ensure a complete reaction; all the reactants are used up to produce a single set of products.

Steam Boiler
A type of furnace in which fuel is burned and the heat is used to produce steam.

Stirling Engine
A heat engine of the reciprocating (piston) where the working gas and a heat source are independent. The working gas is compressed in one region of the engine and transferred to another region where it is expanded. The expanded gas is then returned to the first region for recompression. The working gas thus moves back and forth in a closed cycle.

Steam
Water in vapor form; used as the working fluid in steam turbines and heating systems.

Stand-by Heat Loses
A term used to describe heat energy lost from a water heater tank.

Starting Torque
The torque at the bottom of a speed (rpm) versus torque curve. The torque developed by the motor is a percentage of the full-load or rated torque. At this torque the speed, the rotational speed of the motor as a percentage of synchronous speed is zero. This torque is what is available to initially get the load moving and begin its acceleration.

Static Pressure
The force per unit area acting on the surface of a solid boundary parallel to the flow.

Standard Cubic Foot
A column of gas at standard conditions of temperature and pressure (32 degrees Fahrenheit and one atmosphere).

Standard Industrial Classification (SIC) Code
Standardized codes used to classify businesses by type of activity they engage in.

Standard Conditions
In refrigeration, an evaporating temperature of 5 degrees Fahrenheit (F), a condensing temperature of 86 degrees F., liquid temperature before expansion of 77 degrees F., and suction temperature of 12 degrees F.

Stand-Alone Generator
A power source/generator that operates independently of or is not connected to an electric transmission and distribution network; used to meet a load(s) physically close to the generator.

Stand-Alone Inverter
An inverter that operates independent of or is not connected to an electric transmission and distribution network.

Standard Air
Air with a weight of 0.075 pounds per cubic foot with an equivalent density of dry air at a temperature of 86 degrees Fahrenheit and standard barometric pressure of 29.92 inches of mercury.

Stall
In reference to a wind turbine, a condition when the rotor stops turning.

Stagnation Temperature
A condition that can occur in a solar collector if the working fluid does not circulate when sun is shining on the collector.

Stack
A smokestack or flue for exhausting the products of combustion from a combustion appliance.

Stack (Heat) Loss
Sensible and latent heat contained in combustion gases and vapor emitted to the atmosphere.

Staebler-Wronski effect
The tendency of the sunlight to electricity conversion efficiency of amorphous silicon photovoltaic devices to degrade (drop) upon initial exposure to light.

Squirrel Cage Motor
This is another name for an induction motor. The motors consist of a rotor inside a stator. The rotor has laminated, thin flat steel discs, stacked with channels along the length. If the casting composed of bars and attached end rings were viewed without the laminations the casting would appear similar to a squirrel cage.

Sputtering
A process used to apply photovoltaic semi-conductor material to a substrate by a physical vapor deposition process where high-energy ions are used to bombard elemental sources of semiconductor material, which eject vapors of atoms that are then deposited in thin layers on a substrate.

Square Wave Inverter
A type of inverter that produces square wave output.; consists of a DC source, four switches, and the load. The switches are power semiconductors that can carry a large current and withstand a high voltage rating. The switches are turned on and off at a correct sequence, at a certain frequency. The square wave inverter is the simplest and the least expensive to purchase, but it produces the lowest quality of power.

Spreader Stocker
A type of furnace in which fuel is spread, automatically or mechanically, across the furnace grate.

Spray Pyrolysis
A deposition process whereby heat is used to break molecules into elemental sources that are then spray deposited on a substrate.

Split System Air Conditioner
An air conditioning system that comes in two to five pieces: one piece contains the compressor, condenser, and a fan; the others have an evaporator and a fan. The condenser, installed outside the house, connects to several evaporators, one in each room to be cooled, mounted inside the house. Each evaporator is individually controlled, allowing different rooms or zones to be cooled to varying degrees.

Spectrum
see Solar Spectrum above.

Spillway
A passage for surplus water to flow over or around a dam.

Spinning Reserve
Electric power provider capacity on line and running at low power in excess of actual load.

Split Spectrum Photovoltaic Cell
A photovoltaic device where incident sunlight is split into different spectral regions, with an optical apparatus, that are directed to individual photovoltaic cells that are optimized for converting that spectrum to electricity.

Spectrally Selective Coatings
A type of window glazing films used to block the infrared (heat) portion of the solar spectrum but admit a higher portion of visible light.

Spectral Reflectance
The ratio of energy reflected from a surface in a given waveband to the energy incident in that waveband.

Spectral Irradiance
The monochromatic irradiance of a surface per unit bandwidth at a particular wavelength, usually expressed in Watts per square meter-nanometer bandwidth.

Specific Heat Capacity
The quantity of heat required to change the temperature of one unit weight of a material by one degree.

Specific Humidity
The weight of water vapor, per unit weight of dry air.

Specific Volume
The volume of a unit weight of a substance at a specific temperature and pressure.

Spectral Energy Distribution
A curve illustrating the variation or spectral irradiance with wavelength.

Specific Heat
The amount of heat required to raise a unit mass of a substance through one degree, expressed as a ratio of the amount of heat required to raise an equal mass of water through the same range.