Glossary of Terms
| Term | Definition |
| Ampere (amp) | An International System unit of electrical current flow. |
| Ballast factor | The ratio of the light output of a fluorescent lamp or lamps operated on a ballast to the light output of the lamp(s) operated on a standard (reference) ballast. Ballast factor depends on both the ballast and the lamp type; a single ballast can have several ballast factors depending on lamp type. |
| Color Rendering Index | A measure of the degree of color shift that objects undergo when illuminated by a lamp, compared with those same objects when illuminated by a reference source of comparable correlated color temperature (CCT). A CRI of 100 represents the maximum value. A lower CRI value indicates that some colors may appear unnatural when illuminated by the lamp. Incandescent lamps have a CRI above 95. The cool white fluorescent lamp has a CRI of 62; fluorescent lamps containing rare-earth phosphors are available with CRI values of 80 and above. |
| Color Temperature | Color temperature is measured in degrees Kelvin, which indicates hue of a specific type of light source. Higher temperatures indicate whiter, “cooler” colors, while lower temperatures indicate yellower, “warmer” colors. |
| Conductive heat transfer | Transfer of heat by physical contact between molecules without movement (flow) of the molecules. |
| Conductor | A material that allows electricity to flow through it easily. Water and most metals are good conductors. Conductors can allow electricity to flow through them because the electrons in their atoms move freely. |
| Convective heat transfer | Convection involves the transfer of heat by the motion and mixing (flow) of fluids such as air or water. |
| Current | The movement or flow of electricity. |
| Delta | A method of wiring a three phase transformer or load such that all three phases are connected to together. When drawn in a line diagram, it forms a triangle or delta shape. |
| Direct Emissions | Greenhouse gas emissions from sources that are owned or controlled by the report company. |
| Efficacy | In lighting design, “efficacy” refers to the amount of light (luminous flux) produced by a lamp usually measured in lumens, as a ratio of the amount of energy consumed to produce it, usually measured in watts. |
| Energy Intensity | The ratio of energy consumption to a measure of the demand for services. |
| Foot-Candle | The unit is defined as the amount of illumination the inside surface an imaginary 1-foot radius sphere would be receiving if there were a uniform point source of one candela in the exact center of the sphere. Alternatively, it can be defined as the illuminance on a 1-square foot surface of which there is a uniformly distributed flux of one lumen. This can be thought of as the amount of light that actually falls on a given surface. The foot-candle is equal to one lumen per square foot. The SI derived unit of illuminance is the lux. One footcandle is equal to 10.76 lux, although in the lighting industry, typically this is approximated as 1 footcandle being equal to 10 lux. |
| Generator | A machine that converts mechanical energy into electrical energy. |
| Gigawatt | 1,000,000,000 watts of power |
| Greenhouse Gas (GHG) | Naturally occurring and manmade gases that trap infrared radiation as it is reflected from the earth’s surface, trapping heat and keeping the earth warm. |
| Heat sink | A heat sink is device attached to an electronic component designed to keep the component cool. Heat sinks are made of materials with high heat transfer coefficients, such as aluminum, and are made with large surface areas. |
| Heat transfer coefficient | A numerical rating of the heat transfer properties (thermal conductivity) of some materials. The higher the heat transfer coefficient, the better the material transfers heat. |
| Hertz | Frequency of AC voltage oscillations in cycles per second. |
| High pressure sodium | A high-intensity discharge lamp type that uses sodium under high pressure as the primary light-producing element. HPS lamps produce light with a correlated color temperature (CCT) of approximately 2000 °K, although CCTs for lamps having higher CRI values range from 2200 to 2700 °K. Standard lamps have a CRI value of 22; others have CRI values from 60 to 80. HPS lamps are among the most efficacious light sources, with efficacies as high as 150 lumens per watt, although those with higher CRI values have efficacies as low as 25 lumens per watt. |
| IEC | The International Electrotechnical Commission, which governs electrical equipment standards in Europe and all other international countries. |
| Indirect Emissions | Greenhouse gas emissions from sources that are a consequence of the reporting company’s operation, but occur at sources owned or controlled by another company. |
| Instant start | A method of starting fluorescent lamps in which the voltage that is applied across the electrodes to strike the electric arc is up to twice as high as it is with other starting methods. The higher voltage is necessary because the electrodes are not heated prior to starting. This method starts the lamps without flashing. It is more energy efficient than rapid or preheat starting, but results in greater wear on the electrodes during starting. The life of instant-start lamps that are switched on and off frequently may be reduced by as much as 25 percent relative to rapid-start operation. However, for longer burning cycles (such as 12 hours per start), there may be no difference in lamp life for different starting methods. |
| Insulator | A material that does not allow electricity to flow through it easily because the electrons do not move easily from atom to atom. Glass and special rubber are good insulators. |
| Kilowatt | 1,000 watts of electricity. |
| Kilowatt-hour | One kilowatt of electricity consumed in one hour. |
| Lumen | The lumen (symbol: lm) is the SI unit of luminous flux, a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light. |
| Lumen depreciation | The decrease in lumen output that occurs as a lamp is operated, until failure. Also referred to as lamp lumen depreciation (LLD). |
| Lumen Maintenance | The lumens produced by a light source at any given time during its operating life as a percentage of its lumens at the beginning of life. Manufacturers measure and publish the lumen maintenance ratings for their lamps at 40% of rated lamp lifetime. |
| Luminaire | A complete lighting unit consisting of a lamp or lamps and the parts designed to distribute the light, to position and protect the lamp(s), and to connect the lamp(s) to the power supply. (Also referred to as a fixture.) |
| Lux | A measure of illuminance in lumens per square meter. One lux equals 0.093 foot-candle. |
| Megawatt | 1,000,000 watts of power or 1,000 kilowatts. |
| Mercury vapor lamp | A high-intensity discharge lamp type that uses mercury as the primary light-producing element. Mercury vapor lamps produce light with a CCT from 3000 to 7000 K. Mercury vapor lamps with clear outer bulbs have CRI values from 15 to 25, whereas phosphor-coated lamps have CRI values from 40 to 55. Mercury vapor lamps are less efficacious than other HID lamp types, typically producing only 30 to 65 LPW, but they have longer lamp lives and lower initial costs than other HID lamp types. |
| Metal halide lamp | A high-intensity discharge (HID) lamp that uses mercury and several halide additives as light-producing elements. |
| NEMA | The National Electrical Manufacturers Association, which sets standards for equipment used in the United States. |
| NIMBY | Acronym for not in my backyard, a term used to describe a person or group of people who strongly oppose new development in their communities. |
| Photopic | The vision of the eye under well-lit conditions. In humans and many animals, photopic vision allows color perception, mediated by cone cells. |
| Polarity | A measure of whether an electrical terminal contains a positive voltage or negative voltage. |
| Radiant heat transfer | Radiant heat transfer involves the transfer of heat by electromagnetic radiation that arises due to the temperature of a body. |
| Rapid Start | A method of starting fluorescent lamps in which the electrodes are heated prior to starting, using a starter that is an integral part of the ballast. Heating the electrodes before starting the lamps reduces the voltage required to strike the electric arc between the electrodes. A rapid-start system starts smoothly, without flashing. |
| Rated Lamp Lifetime | The number of hours at which half of a group of product samples fail. The rated life is a median value of life expectancy; any lamp or group of lamps may vary from the published rated life. Rated life is based on standard test conditions. |
| Renewable electricity standard(RES) | A government mandate requiring that electric utilities derive a certain percentage of their capacity or generation from renewable sources, such as wind, solar, or biomass, by a certain date. |
| Restrike Time | The time required for a lamp to restrike, or start, and to return to 90% of its initial light output after the lamp is extinguished. Normally, HID lamps need to cool before they can be restarted. |
| Scotopic | The monochromatic vision of the eye in dim light. Since cone cells are nonfunctional in low light, scotopic vision is produced exclusively through rod cells so therefore there is no colour perception. The human eye uses scotopic vision under low-light conditions. |
| Step down transformer | A transformer that produces an output voltage that is lower than the input voltage. |
| Step up transformer | A transformer that produces an output voltage that is higher than the input voltage. |
| Substation | A facility where transformers lower electricity’s voltage from the transmission system voltage. |
| Transformer | A device used to increase or decrease electricity’s voltage and current. |
| Volt, Voltage | A measure of the pressure under which electricity flows. |
| Watt, Wattage | A measure of the amount of work done by a certain amount or amperage of electric current at a certain pressure or voltage. |
| Wye | A method of wiring a three phase transformer or load such that all three phases are connected to a common point, usually an electrical ground. When drawn in a line diagram, the shape resembles a “Y.” |
