Glossary
I-J
Last Updated Monday, July 24, 2000
compiled by Nick Sundt


I, J

I

ice age - A glacial epoch or time of extensive glacial activity. Also, as Ice Age, which refers to the latest glacial epoch, the Pleistocene Epoch. (Source: Carbon Dioxide Information Analysis Center, 1990a).

ice and snow albedo - The reflectivity of ice and snow-covered surfaces. The albedo of freshly fallen snow may be as much as 90%, while older snow may have values of 75% or less. The larger the areal extent of snow and ice cover, the higher the albedo value. The surface albedo will also increase as a function of the depth of snow cover up to 13 cm and be unaffected by increased snow cover after reaching that depth. (Source: Carbon Dioxide Information Analysis Center, 1990a).

ice and snow-albedo-temperature feedback - Interactions that can be described as a theoretical concept of a feedback mechanism in which the interacting elements are the areal extent of polar ice and snow cover, the albedo of the polar region (dependent on areal extent of ice and snow), absorption of solar radiation (dependent on the albedo), temperature (dependent on the absorption of solar radiation) and the area of ice and snow cover (dependent on temperature). Less snowfall would mean more absorption of solar radiation, therefore a surface warming would occur. Climate modeling studies indicate an amplification effect (i.e., positive feedback) of the iceand snow-albedo feedback on increased surface air temperatures caused by increases in the atmospheric concentration of carbon dioxide. (Source: Carbon Dioxide Information Analysis Center, 1990a).

ice cover - During the present time, the extent, especially the thickness, of glacier ice on a land surface. Also the same as ice concentration, which is the ratio of an area of sea ice to the total area of sea surface within some large geographic area. (Source: Carbon Dioxide Information Analysis Center, 1990a).

ice flow - See glacier flow. (Source: Carbon Dioxide Information Analysis Center, 1990a).

ice front. The floating vertical cliff that forms the seaward face or edge of a glacier or an ice shelf that enters water. It can vary from 2 to 50 meters in height. (Source: Carbon Dioxide Information Analysis Center, 1990a).

ice sheet (continental glacier). A glacier of considerable thickness and more than 50,000 sq km in area. It forms a continuous cover of ice and snow over a land surface. An ice sheet is not confined by the underlying topography but spreads outward in all directions. During the Pleistocene Epoch, ice sheets covered large parts of North America and northern Europe but they are now confined to polar regions (e.g., Greenland and Antarctica). (Source: Carbon Dioxide Information Analysis Center, 1990a).

ice shelf. A sheet of very thick ice with a level or gently undulating surface. It is attached to the land on one side, but most of it is floating. On the seaward side, it is bounded by a steep cliff (ice front) 2 to 50 meters or more above sea level. Ice shelves have formed along polar coasts (e.g., Antarctica and Greenland); they are very wide with some extending several hundreds of kilometers toward the sea from the coastline. They increase in size from annual snow accumulation and seaward extension of land glaciers. They decrease in size from warming, melting, and calving. (Source: Carbon Dioxide Information Analysis Center, 1990a).

Ignite. To heat a gaseous mixture to the temperature at which combustion takes place. (Source: US Department of Energy, 1999a).

Ignition Point. The minimum temperature at which combustion of a solid or fluid can occur. (Source: US Department of Energy, 1999a).

ILEV (Inherently Low Emission Vehicle). Term used by federal government for any vehicle that is certified to meet the California Air Resources Board's Low Emission Vehicle (LEV) standards for non-methane organic gases and carbon monoxide, ULEV standards for nitrogen oxides and does not emit any evaporative emissions. (Source: California Energy Commission, 1999a.)

Illuminance. A measure of the amount of light incident on a surface; measured in foot-candles or Lux. (Source: US Department of Energy, 1999a).

Incandescent. These lights use an electrically heated filament to produce light in a vacuum or inert gas-filled bulb. (Source: US Department of Energy, 1999a).

Incident Solar Radiation. The amount of solar radiation striking a surface per unit of time and area. (Source: US Department of Energy, 1999a).

Independent Power Producer (IPP). A wholesale electricity producer (other than a qualifying facility under the Public Utility Regulatory Policies Act of 1978), that is unaffiliated with franchised utilities in the area in which the IPP is selling power and that lacks significant marketing power. Unlike traditional utilities, IPPs do not possess transmission facilities that are essential to their customers and do not sell power in any retail service territory where they have a franchise. (Source: US Energy Information Administration, 1997a.)

Indirect Solar Gain System. A passive solar heating system in which the sun warms a heat storage element, and the heat is distributed to the interior space by convection, conduction, and radiation. (Source: US Department of Energy, 1999a).

Indirect Water Heater. A type of water heater that circulates water through a heat exchanger in a boiler. The heated water then flows into an insulated storage tank. (Source: US Department of Energy, 1999a).

Induction. The production of an electric current in a conductor by the variation of a magnetic field in its vicinity. (Source: US Department of Energy, 1999a).

Induction Generator. A device that converts the mechanical energy of rotation into electricity based on electromagnetic induction. An electric voltage (electromotive force) is induced in a conducting loop (or coil) when there is a change in the number of magnetic field lines (or magnetic flux) passing through the loop. When the loop is closed by connecting the ends through an external load, the induced voltage will cause an electric current to flow through the loop and load. Thus rotational energy is converted into electrical energy. (Source: US Department of Energy, 1999a).

Induction Motor. A motor in which a three phase (or any multiphase) alternating current (i.e. the working current) is supplied to iron-cored coils (or windings) within the stator. As a result, a rotating magnetic field is set up, which induces a magnetizing current in the rotor coils (or windings). Interaction of the magnetic field produced in this manner with the rotating field causes rotational motion to occur. (Source: US Department of Energy, 1999a).

Industrial Process Heat. The thermal energy used in an industrial process. (Source: US Department of Energy, 1999a).

Industrial Sector. Manufacturing industries, which make up the largest part of the sector, along with mining, construction, agriculture, fisheries, and forestry. Establishments in this sector range from steel mills, to small farms, to companies assembling electronic components. (Source: US Energy Information Administration, 2000a) (Source: US Energy Information Administration, 2000a)

Inert Gas. A gas that does not react with other substances; e.g. argon or krypton; sealed between two sheets of glazing to decrease the U-value (increase the R-Value) of windows. (Source: US Department of Energy, 1999a).

infiltration. The uncontrolled inward leakage of air through cracks and gaps in the building envelope, especially around windows, doors and duct systems. (Source: California Energy Commission, 1999a.)

infiltration (soil). Movement of water from the ground surface into the soil. (Source: Carbon Dioxide Information Analysis Center, 1990a).

infiltration barrier. A material placed on the outside or the inside of exterior wall framing to restrict inward air leakage, while permitting the outward escape of water vapor from the wall cavity. (Source: California Energy Commission, 1999a.)

infrared radiation. Electromagnetic radiation lying in the wavelength interval from 0.7 micrometers to 1000 micrometers. Its lower limit is bounded by visible radiation, and its upper limit by microwave radiation. Most of the energy emitted by the Earth and its atmosphere is at infrared wavelength. Infrared radiation is generated almost entirely by large-scale intra-molecular processes. The tri-atomic gases, such as water vapor, carbon dioxide, and ozone, absorb infrared radiation and play important roles in the propagation of infrared radiation in the atmosphere. Abbreviated IR; also called longwave radiation. (Source: Carbon Dioxide Information Analysis Center, 1990a).

inorganic compound. Combination of two or more elements other than those used to form organic compounds. See organic compound.(Source: US Environmental Protection Agency, 1999a)

inorganic fertilizer. See synthetic fertilizer. (Source: US Environmental Protection Agency, 1999a)

insolation. The solar radiation incident on a unit horizontal surface at the top of the atmosphere. It is sometimes referred to as "solar irradiance". The latitudinal variation of insolation supplies the energy for the general circulation of the atmosphere. Insolation depends on the angle of incidence of the solar beam and on the solar constant. (Source: Carbon Dioxide Information Analysis Center, 1990a).

Installed Capacity. The total capacity of electrical generation devices in a power station or system. (Source: US Department of Energy, 1999a).

Instantaneous Efficiency (of a Solar Collector). The amount of energy absorbed (or converted) by a solar collector (or photovoltaic cell or module) over a 15 minute period. (Source: US Department of Energy, 1999a).

Insulation. Insulation is a substance that resists the transfer of heat, generally by incorporating small pockets of air. Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness.The R-value of thermal insulation depends on the type of material, its thickness and density. An excellent website covering insulation is the Department of Energy's Insulation Fact Sheet, produced by Oak Ridge National Laboratory (Source: Lawrence Berkeley Laboratory, 1999)

Insulation Blanket. A pre-cut layer of insulation applied around a water heater storage tank to reduce standby heat loss from the tank. (Source: US Department of Energy, 1999a).

Insulator. A device or material with a high resistance to electricity flow. (Source: US Department of Energy, 1999a).

Integrated Collector/Storage (ICS) Solar Systems. ICS solar systems are also called "batch" or "breadbox" water heaters. They combine the collector and storage tank in one unit. The sun shining into the collector strikes the storage tank directly, heating the water. The large thermal mass of the water, plus methods to reduce heat loss through the tank, prevent the stored water from freezing. (Source: US Department of Energy, 1999a).

Integrated Heating Systems. A type of heating appliance that performs more than one function, for example space and water heating. (Source: US Department of Energy, 1999a).

Integrated Resource Plan (IRP). A plan developed by an electric utility, sometimes as required by a public regulatory commission or agency, that defines the short and long term capacity additions (supply side) and demand side management programs that it will undertake to meet projected energy demands. (Source: US Department of Energy, 1999a).

Interconnection. A connection or link between power systems that enables them to draw on each other's reserve capacity in time of need. (Source: US Department of Energy, 1999a).

Intergovernmental Panel On Climate Change (IPCC). The IPCC was established jointly by the United Nations Environment Programme and the World Meteorological Organization in 1988. The purpose of the IPCC is to assess information in the scientific and technical literature relat-ed to all significant components of the issue of climate change. The IPCC draws upon hundreds of the world’s expert scientists as authors and thousands as expert reviewers. Leading experts on climate change and envi-ronmental, social, and economic sciences from some 60 nations have helped the IPCC to prepare periodic assess-ments of the scientific underpinnings for understanding global climate change and its consequences. With its capacity for reporting on climate change, its conse-quences, and the viability of adaptation and mitigation measures, the IPCC is also looked to as the official adviso-ry body to the world’s governments on the state of the science of the climate change issue. For example, the IPCC organized the development of internationally accepted methods for conducting national greenhouse gas emission inventories.(Source: US Environmental Protection Agency, 1999a)

Intermittent Generators. Power plants, whose output depends on a factor(s) that cannot be controlled by the power generator because they utilize intermittent resources such as solar energy or the wind. (Source: US Department of Energy, 1999a).

Internal Combustion Electric Power Plant. The generation of electric power by a heat engine which converts part of the heat generated by combustion of the fuel into mechanical motion to operate an electric generator. (Source: US Department of Energy, 1999a).

Internal Gain. The heat produced by sources of heat in a building (occupants, appliances, lighting, etc). (Source: US Department of Energy, 1999a).

Internal Mass. Materials with high thermal energy storage capacity contained in or part of a building's walls, floors, or freestanding elements. (Source: US Department of Energy, 1999a).

Internal Rate of Return. A widely used rate of return for performing economic analysis. This method solves for the interest rate that equates the equivalent worth of an alternative's cash receipts or savings to the equivalent worth of cash expenditures, including investments. The resultant interest rate is termed the internal rate of return (IRR). (Source: US Department of Energy, 1999a).

Interruptible Gas. Gas sold to customers with a provision that permits curtailment or cessation of service at the discretion of the distributing company under certain circumstances, as specified in the service contract. (Source: US Energy Information Administration, 1999b)

Interruptible Load. Energy loads that can be shut off or disconnected at the supplier's discretion or as determined by a contractual agreement between the supplier and the customer. (Source: US Department of Energy, 1999a).

intertie. A transmission line that links two or more regional electric power systems. (Source: California Energy Commission, 1999a.)

Intrinsic Layer. A layer of semiconductor material (as used in a solar photovoltaic device) whose properties are essentially those of the pure, undoped, material. (Source: US Department of Energy, 1999a).

inversion. An increase in temperature with height. The reverse of the normal cooling with height in the atmosphere. (Source: National Weather Service, 1999a.)

Inverter. A device that that converts direct current electricity (from for example a solar photovoltaic module or array) to alternating current for use directly to operate appliances or to supply power to a electricity grid. (Source: US Department of Energy, 1999a).

inversion. An anomaly in the normal positive lapse rate; usually refers to a thermal inversion, in which temperature increases rather than decreases with height. (Source: Carbon Dioxide Information Analysis Center, 1990a).

Investment Tax Credit. A tax credit granted for specific types of investments. (Source: US Department of Energy, 1999a).

Investor Owned Utility (IOU). A utility owned by stockholders or other investors; sometimes referred to as a private utility, in contrast to a public utility that is owned by a government agency or cooperative. (Source: US Department of Energy, 1999a).

Ion. An electrically charged atom or group of atoms that has lost or gained electrons; a loss makes the resulting particle positively charged; a gain makes the particle negatively charged. (Source: US Department of Energy, 1999a).

Ionizer. A device that removes airborne particles from breathable air. Negative ions are produced and give up their negative charge to the particles. These new negative particles are then attracted to the positive particles surrounding them. This accumulation process continues until the particles become heavy enough to fall to the ground. (Source: US Department of Energy, 1999a).

irradiance. The total radiant flux received on a unit area of a given real or imaginary surface. Also called the radiant flux density. (Source: Carbon Dioxide Information Analysis Center, 1990a).

irreversibilities. Changes that, once set in motion, cannot be reversed, at least on human time scales. (Source: US Environmental Protection Agency, 1999a)

ISO. Independent System Operator. A neutral operator responsible for maintaining instaneous balance of the grid system. The ISO performs its function by controlling the dispatch of flexible plants to ensure that loads match resources available to the system.

Isolated Solar Gain System. A type of passive solar heating system where heat is collected in one area for use in another. (Source: US Department of Energy, 1999a).

isopynic. A line on a chart that connects all points of equal or constant density. (Source: Carbon Dioxide Information Analysis Center, 1990a).

isotherm. A line on a chart that connects all points of equal or constant temperature. (Source: Carbon Dioxide Information Analysis Center, 1990a).

isotope. One of two or more atoms that have the same atomic number (i.e., the same number of protons in their nuclei) but have different mass numbers. (Source: Carbon Dioxide Information Analysis Center, 1990a).


J

Jacket. The enclosure on a water heater, furnace, or boiler. (Source: US Department of Energy, 1999a).

jet fuel. Includes both naphtha-type and kerosene-type fuels meeting standards for use in aircraft turbine engines. Although most jet fuel is used in aircraft, some is used for other purposes such as generating electricity.(Source: US Environmental Protection Agency, 1999a)

jet stream: Strong winds concentrated within a narrow band in the atmosphere. The jet stream often "steers" surface features such as front and low pressure systems. (Source: National Weather Service, 1999a.)

joint implementation (JI). The Kyoto Protocol of the UN Framework Convention on Climate Change establishes a mechanism whereby a developed country can receive "emissions reduction units" when it helps to finance projects that reduce net emissions in another developed country (including countries with economies in transition). (Source: UN Climate Change Secretariat, 1999a)

Joist. A structural, load-carrying building member with an open web system that supports floors and roofs utilizing wood or specific steels and is designed as a simple span member. (Source: US Department of Energy, 1999a).

Joule. A metric unit of energy or work; the energy produced by a force of one Newton operating through a distance of one meter; 1 Joule per second equals 1 Watt or 0.737 foot-pounds; 1 Btu equals 1,055 Joules. (Source: US Department of Energy, 1999a).

Joule's Law. The rate of heat production by a steady current in any part of an electrical circuit that is proportional to the resistance and to the square of the current, or, the internal energy of an ideal gas depends only on its temperature. (Source: US Department of Energy, 1999a).