Glossary of Energy Terms
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Note: No entries for Y or Z.
TAX CREDITS -- Credits established by the federal and state government to assist the development of the alternative energy industry. Beginning in 1976, California had a solar tax credit. From 1978 to 1985, both California and the federal government offered tax credits for alternative energy equipment. The state provided a 55 percent tax credit on solar, wind, geothermal and biomass for residential applications. However, the residential tax credits were reduced by applicable federal credits. State commercial tax credits for alternative energy systems in commercial and industrial sectors ranged from 10-15 percent. During this same time, the federal government offered a 40 percent tax credit on residential applications and a 10-15 percent credit on commercial and industrial applications. California in 1990 instituted a new 10 percent tax credit for commercial solar systems in excess of 30 watts of electricity per device. This credit expired December 31, 1993.
TASK LIGHTING (task-oriented lighting) -- Lighting designed specifically to illuminate one or more task locations, and generally confined to those locations. [See California Code of Regulations, Title 24, Section 2- 5302]
THERMAL BREAK (thermal barrier) -- An element of low heat conductivity placed in such a way as to reduce or prevent the flow of heat. Some metal framed windows are designed with thermal breaks to improve their overall thermal performance.
THERMAL (ENERGY) STORAGE -- A technology that lowers the amount of electricity needed for comfort conditioning during utility peak load periods. A buildings thermal energy storage system might, for example, use off-peak power to make ice or to chill water at night, later using the ice or chilled water in a power saving process for cooling during the day. See THERMAL MASS.
THERMAL MASS -- A material used to store heat, thereby slowing the temperature variation within a space. Typical thermal mass materials include concrete, brick, masonry, tile and mortar, water, and rock or other materials with high heat capacity.
THERMAL POWER PLANT -- any stationary or floating electrical generating facility using any source of thermal energy, with a generating capacity of 50 megawatts or more, and any facilities appurtenant thereto. Exploratory, development, and production wells, resource transmission lines, and other related facilities used in connection with a geothermal exploratory project or a geothermal field development project are not appurtenant facilities for the purposes of this division. Thermal powerplant does not include any wind, hydroelectric, or solar photovoltaic electrical generating facility.
- Law of Conservation of Energy -- energy may be transformed in an isolated system, but its total is constant
- Heat cannot be changed directly into work at constant temperature by a cyclic process
- Heat capacity and entropy of every crystalline solid becomes zero at absolute zero (0 degrees Kelvin)
THERMOSTAT, SETBACK -- A device, containing a clock mechanism, which can automatically change the inside temperature maintained by the HVAC system according to a preset schedule. The heating or cooling requirements can be reduced when a building is unoccupied or when occupants are asleep. [See California Code of Regulations, Title 24, Section 2- 5352(h)]
TLEV (TRANSITIONAL LOW EMISSION VEHICLE) - a vehicle certified by the California Air Resources Board to have emissions from zero to 50,000 miles no higher than 0.125 grams/mile (g/mi) of non-methane organic gases, 3.4 g/mi of carbon monoxide, and 0.4 g/mi of nitrogen oxides. Emissions from 50,000 to 100,000 miles may be slightly higher (See chart in Chapter 2.)
TRANSMITTANCE -- The time rate of heat flow per unit area under steady conditions from the air (or other fluid) on the warm side of a barrier to the air (or fluid) on the cool side, per unit temperature difference between the two sides.
TIME-OF-USE (TOU) RATES -- The pricing of electricity based on the estimated cost of electricity during a particular time block. Time-of-use rates are usually divided into three or four time blocks per twenty-four hour period (on-peak, mid-peak, off-peak and sometimes super off-peak) and by seasons of the year (summer and winter). Real-time pricing differs from TOU rates in that it is based on actual (as opposed to forecasted) prices which may fluctuate many times a day and are weather-sensitive, rather than varying with a fixed schedule.
TIME-OF-USE RATES -- Electricity prices that vary depending on the time periods in which the energy is consumed. In a time-of- use rate structure, higher prices are charged during utility peak-load times. Such rates can provide an incentive for consumers to curb power use during peak times.
TRANSFORMER -- A device, which through electromagnetic induction but without the use of moving parts, transforms alternating or intermittent electric energy in one circuit into energy of similar type in another circuit, commonly with altered values of voltage and current.
TRANSMISSION-DEPENDENT UTILITY -- A utility that relies on its neighboring utilities to transmit to it the power it buys from its suppliers. A utility without its own generation sources, dependent on another utility's transmission system to get its purchased power supplies.
TRANSMITTING UTILITY (TRANSCO) -- This is a regulated entity which owns, and may construct and maintain, wires used to transmit wholesale power. It may or may not handle the power dispatch and coordination functions. It is regulated to provide non-discriminatory connections,comparable service and cost recovery. According to EPAct, any electric utility, qualifying cogeneration facility, qualifying small power production facility, or Federal power marketing agency which owns or operates electric power transmission facilities which are used for the sale of electric energy at wholesale. (See also "Generation Dispatch & Control" and "PowerPool.")