The Energy Glossary

Alternative Fuels – Alternative fuels are being used today in place of gasoline and diesel fuel made from petroleum. The U.S. Department of Energy classifies the following fuels as “alternative fuels”: Biodiesel, electricity, ethanol, hydrogen, methanol, natural gas, propane, p-series, and solar energy. Using these alternative fuels can help our nation reduce its dependence on imported petroleum and improve air quality.

Audit (Energy) – The process of determining energy consumption, by various techniques, of a building or facility.

Biodiesel- Derived from agricultural resources like vegetable oil or animal fats, biodiesel can be used in any diesel engine without modification and is widely available in the United States.

Bioenergy - Useful, renewable energy produced from organic matter. The conversion of the complex carbohydrates in organic matter into energy. Organic matter may either be used directly as a fuel or processed into liquids and gases.

Biogas – A combustible gas created by anaerobic decomposition of organic material, composed primarily of methane, carbon dioxide, and hydrogen sulfide.

Biomass – Agricultural crops and agricultural wastes and residues, wood and wood wastes and residues, animal wastes, municipal wastes, aquatic plants and any other organic matter available on a renewable basis. Defined by the Energy Security Act (PL 96-294) of 1980.

Biomass Energy – Energy produced by the conversion of biomass directly to heat or to a liquid or gas that can be converted to energy.

Biomass Fuel – Biomass converted directly to energy or converted to liquid or gaseous fuels such as ethanol, methanol, methane, and hydrogen.

Carbon Dioxide (CO2) – A greenhouse gas that traps heat in the atmosphere and contributes to global warming. This colorless, odorless noncombustible gas is formed by the combustion of carbon and carbon compounds (such as fossil fuels and biomass), by respiration, which is a slow combustion in animals and plants, and by the gradual oxidation of organic matter in the soil. Plants absorb carbon dioxide during photosynthesis.

Carbon Monoxide (CO) – A colorless, odorless poisonous combustible gas produced by the incomplete combustion of carbon and carbon compounds such as fossil fuels (i.e. coal, petroleum) and their products (e.g. liquefied petroleum gas, gasoline), and biomass.

Cogeneration – Cogeneration, also known as “combined heat and power” or CHP, is the simultaneous production of power and thermal energy from one fuel input.

Combined Heat and Power (CHP) – Also known as cogeneration, a combined heat and power generator creates both electricity and thermal energy. The heat that is wasted in conventional power generation is recovered for heating buildings and other uses such as transferring the heat to water.

Compact Fluorescent Lamps (CPL) - A smaller version of standard fluorescent lamps that can directly replace standard incandescent bulbs and reduce the amount of electricity used for lighting by 75% to 80%. These lights consist of a gas filled tube, and a magnetic or electronic ballast.

Composting – The process of degrading organic material (biomass) by microorganisms in aerobic conditions.

Compressed Natural Gas (CNG) – Natural gas (methane) that has been compressed to a higher-pressure gaseous state by a compressor; used in CNG vehicles.

Compression Chiller - A cooling device that uses mechanical energy to produce chilled water.

Cooling Degree Day - A value used to estimate interior air-cooling requirements (load) calculated as the number of degrees per day (over a specified period) that the daily average temperature is above 65 degrees Fahrenheit (or some other, specified base temperature). The daily average temperature is the mean of the maximum and minimum temperatures recorded for a specific location for a 24-hour period.

Controlled Lighting system- An energy saving technique that uses high efficiency fixtures and lamps to minimize energy use for lighting homes, offices and public spaces.

Cooling Pond – A body of water used to cool the water that is circulated in an electric power plant.

Demand Side Management (DSM) – The planning, implementation, and monitoring of utility activities designed to encourage consumers to modify patterns of electricity usage, including the timing and level of electricity demand. It refers to only energy and load-shape modifying activities that are undertaken in response to utility-administered programs. It does not refer to energy and load-shaped changes arising from the normal operation of the marketplace or from government-mandated energy-efficiency standards. Demand-Side Management covers the complete range of load-shape objectives, including strategic conservation and load management, as well as strategic load growth.

Department of Energy (DOE) – A federal government agency created in 1977, that is entrusted to contribute to the welfare of the United States by providing technical information, and a scientific and educational foundation for technology, policy and institutional leadership to achieve efficiency in energy use, diversity in energy sources, a more productive and competitive economy, improved environmental quality, and a secure national defense.

Dimmer – A light switch that allows light levels to be manually or automatically adjusted. A dimmer saves energy by reducing the amount of power delivered to the light.

Distribution Lines – Distribution lines bring power from a substation to the individual home or business. The distribution system covers a widespread area, carries lower voltage power than the transmission system and traverses narrow rights-of-way.

Distribution System Reliability – Distribution system outages can occur because of weather (lightning, winds, ice, etc.), equipment failure (poles, transformers, breakers, etc.), and when trees and animals contact the power lines or equipment.

Distributed Generation (DG) – Localized or on-site power generation providing an alternative to central station power plants. DG minimizes the need for transmission and distribution lines and subsequent line losses. The most common users of DG are businesses that choose to meet their own electricity needs. Fossil fuel burning DG contributes to emissions levels in urban areas. Renewable energy DG technologies produce no emissions.

Electric Reliability Council of Texas (ERCOT)- The Council oversees transactions associated with the newly restructured electric market and protects the overall reliability of the power grid. ERCOT oversees the transactions that result from the restructuring, while maintaining the overall reliability of the electrical grid.

Emission Factor – A measure of the average amount of a specified pollutant or material emitted for a specific type of fuel or process.

Energy - The capability of doing work; different forms of energy can be converted to other forms, but the total amount of energy remains the same.

Energy Efficiency – Reducing energy use without changing lifestyle or business practices. Reducing or eliminating unnecessary energy waste in buildings and appliances by using designs, building materials, insulation, high efficiency windows, space conditioning equipment and appliances developed to decrease energy use while providing the same or higher levels of service.

Energy Service Company (ESCO) – A company that specializes in performing services and providing energy efficiency measures under a contractual arrangement whereby the ESCO shares the value of energy savings with the customer.

Energy Star - The U.S. Environmental Protection Agency and the U.S. Department of Energy developed the Energy Star label to help purchasers identify the most energy efficient products in the marketplace. The label means that these products reduce energy use, thereby lessening the amount of fossil fuel being burned by power plants and the amount of carbon dioxide and other greenhouse gases emitted into the atmosphere. At the same time, these products help save taxpayer or stakeholder dollars and free up resources for vital programs and services.

Ethanol (E85)
Ethanol is an alcohol-based alternative fuel produced by fermenting and distilling starch crops that have been converted into simple sugars. Feedstocks for this fuel include corn, barley and wheat. Ethanol can also be produced from “cellulosic biomass” such as trees and grasses and is called bioethanol. Ethanol is most commonly used to increase octane and improve the emissions quality of gasoline. In some areas of the United States, ethanol is blended with gasoline to form an E10 blend (10% ethanol and 90% gasoline), but it can be used in higher concentrations such as E85 or E95. Original equipment manufacturers produce flexible-fuel vehicles that can run on E85 or any other combination of ethanol and gasoline.

Evaporative Cooling - A cooling system that uses evaporation instead of refrigerant to cool the air using very little electricity. A mechanical device uses heat from the outside air to evaporate water that is held by pads inside the cooler. The heat is drawn out of the air through this process and the cooled air is blown into the home by the cooler’s fan. Evaporative cooling systems are common in West Texas where the humidity is low.

Fluorescent Light – The conversion of electric power to visible light by using an electric charge to excite gaseous atoms in a glass tube. These atoms emit ultraviolet radiation that is absorbed by a phosphor coating on the walls of the lamp tube. The phosphor coating produces visible light. Fluorescent light uses substantially less electricity than incandescent light.

Fly Ash – The fine particulate matter entrained in the flue gases of a combustion power plant. Historically, fly ash had been considered a waste material. Due to the high metals content, disposal in landfills could cause contamination of groundwater sources. Recently, fly ash has been used as a material in concrete. Due to the properties of fly ash, and due to the capability for fly ash to substitute for a particular percentage of Portland cement, fly ash concrete reduces the amount of energy needed to produce concrete. Fly ash concrete also reduces the amount of carbon dioxide added to the atmosphere when Portland cement is processed.

Fuel Cell – A fuel cell consists of two electrodes—a negative electrode (or anode) and a positive electrode (or cathode)—sandwiched around an electrolyte. Hydrogen is fed to the anode, and oxygen is fed to the cathode. Activated by a catalyst, hydrogen atoms separate into protons and electrons, which take different paths to the cathode. The electrons go through an external circuit, creating a flow of electricity. The protons migrate through the electrolyte to the cathode, where they reunite with oxygen and the electrons to produce water and heat.

Geothermal Energy – Energy produced by the internal heat of the earth; geothermal heat sources include: hydrothermal convective systems, pressurized water reservoirs; hot dry rocks; manual gradients; and magma. Geothermal energy can be used directly for heating or to produce electric power.

Geothermal Heat Pump – A type of heat pump that uses the ground, ground water, or ponds as a heat source and heat sink, rather than outside air. Ground or water temperatures are more constant and are warmer in winter and cooler in summer than air temperatures. Geothermal heat pumps operate more efficiently than “conventional” or “air source” heat pumps.

Heating Degree Day(s) (HDD) – The number of degrees per day that the daily average temperature (the mean of the maximum and minimum recorded temperatures) is below a base temperature, usually 65 degrees Fahrenheit, unless otherwise specified; used to determine indoor space heating requirements and heating system sizing. Total HDD is the cumulative total for the year/heating season. The higher the HDD for a location, the colder the daily average temperature(s).

Heat Pump – a refrigerant-based system that provides both heating and cooling and is more energy efficient that electric resistance heating. Both air sources units and geothermal units have back up energy (usually electric resistance heating) to provide space heating when temperatures drop below freezing.

Heat Recovery Ventilation (HRV) – A device that captures the heat from the exhaust air from a building and transfers it to the supply/fresh fresh air entering the building to preheat the air and increase overall heating efficiency.

Home Energy Rating System (HERS) – A nationally recognized energy rating program that gives builders, mortgage lenders, secondary lending markets, homeowners, sellers, and buyers an evaluation of how the energy efficiency of one home compares with others. The home receives a rating from 1 to 100, depending on its relative efficiency. The score is than equated to a Star rating system. One star (Extremely Poor) five Stars (Extremely Efficient).

Hybrid Renewable Energy System – A renewable energy system that includes two different types of renewable energy technologies that produce the same type of energy, for e.g., a wind turbine and a solar photovoltaic array combined to meet a power demand.

Hybrid Electric Vehicles (HEVs): Combine the internal combustion engine of a conventional vehicle with the battery and electric motor of an electric vehicle, resulting in twice the fuel economy of conventional vehicles. This combination offers the extended range and rapid refueling that consumers expect from a conventional vehicle, with a significant portion of the energy and environmental benefits of an electric vehicle. The practical benefits of HEVs include improved fuel economy and lower emissions compared to conventional vehicles. The inherent flexibility of HEVs will allow them to be used in a wide range of applications, from personal transportation to commercial hauling.

Hydrothermal- Pertains to hot water or the action of heated water, often considered heated by magma or in association with magma.

Incandescent Bulbs – A standard light bulb that uses an electrically heated filament to produce light in a vacuum or inert gas-filled bulb. The amount of light produced per unit of energy, also known as “lumens per watt,” is not as great as compact fluorescent bulbs and many other lamp sources. In many instances, the amount of heat generated per lumen is also high. If not utilized, this heat is often an unwanted heat load and requires more cooling energy to neutralize the heat load.Indirect Solar Gain System – A passive solar heating system in which the sun warms a heat storage element, or surface, and the heat is distributed to the interior space by convection, conduction, and radiation.

 

Interruptible Power – A rate structure or other agreement to pay customers that will interrupt electric service when needed to maintain power to customers with firm power agreements.

Kilowatt- A watt is a unit of power in the International System of Units (SI) that is required to do work at the rate of 1 joule per second. Kilo is from the metric system and means 1,000. Therefore, a kilowatt is power required to do work at the rate of 1,000 joules per second.

Leader in Energy and Environmental Design (LEED) – is a voluntary, consensus based national standard for developing high performance, sustainable buildings. Developed by U.S. Green Building Council. There are LEED ratings for new construction and renovations (LEED 2.0/2.1), existing building operations (LEED-EB) and commercial interior projects (LEED-IC).

Life Cycle Cost – The sum of all the costs both recurring and nonrecurring, related to a product, structure, system, or service during its life span or specified time period. The cost also includes costs generated by demolition, re-use, recycling, or waste, depending on the product, structure, system or service.

Liquefied Natural Gas (LNG)- Natural gas converted to liquid form by cooling to a very low temperature.

Load Management – Using less energy during peak hours. Usually this term implies a change in lifestyle or business practice.

Low Emission Vehicle (LEV) – A vehicle meeting the low-emission vehicle standards.

Megawatt: one million watts. A standard unit of power usually used to describe larger-scale electricity generating facilities.

Methanol (M85)
Methanol is a liquid that can be made from a wide variety of raw materials like garbage, trees and seaweed. Today, most methanol is made from natural gas.

Microturbines – Microturbines are small combustion turbines that produce between 25 kW and 500 kW of power. Microturbines were derived from turbocharger technologies found in large trucks or the turbines in aircraft auxiliary power units (APUs).

Net Metering – is a utility resource usage and payment scheme in which a customer who generates their own power is compensated monetarily. Net metering originated with electric companies as a way to encourage consumers to invest in renewable energy sources such as solar or wind power. In a net metering program, the electric company allows a customer’s meter to actually run backwards if the electricity the customer generates is more than they are consuming. At the end of the billing period, the customer only pays for their net consumption: the amount of resources consumed, minus the amount of resources generated.

Nitrogen Dioxide (NO2) – This compound of nitrogen and oxygen is formed by the oxidation of nitric oxide (NO) that is produced by the combustion of solid fuels.

Nitrogen Oxide (NOx) - Gases consisting of one molecule of nitrogen and varying numbers of oxygen molecules. Nitrogen oxides are produced, for example, by the combustion of fossil fuels in vehicles and electric power plants. In the atmosphere, nitrogen oxides can contribute to formation of photochemical ozone (smog), impair visibility, and have health consequences; they are considered pollutants.

Nitrous Oxide (N2O) – A powerful greenhouse gas with a global warming potential most recently evaluated at 310. Major sources of nitrous oxide include soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning.

Occupancy Sensors - A device that switches lights on and off or dims and brightens them based on the presence or absence of people. Occupancy sensors are often based on motion detectors and/or infrared sensors.

Passive Solar (Building) Design – A building design that uses structural elements of a building and area landscape to heat and cool a building without the use of mechanical equipment. The principal elements include proper building orientation and location, proper window sizing and placement and design of window overhangs to reduce summer heat gain and ensure winter heat gain, and proper sizing of thermal energy storage mass. The heat is distributed primarily by natural convection and radiation, though fans can also be used to circulate room air or ensure proper ventilation.

Passive Solar Heater – A solar water or space-heating system in which solar energy is collected, and/or moved by natural convection or existing water line pressures without using pumps or fans. Passive systems are typically integral collector/storage (ICS or batch collectors) or thermosyphon systems. The major advantage of these systems is that they do not use controls, pumps, sensors, or other mechanical parts, so little or no maintenance is required over the lifetime of the system.

Peak Demand/Load - The maximum energy demand or load in a specified time period. Regional energy requirements are limited by the total energy demanded on the system during the hours of maximum use. Some power utilities offer discounts for energy usage during off-peak hours. Depending on the energy need and the amount of discount, some facilities include systems that use power in off-peak hours to cool or heat thermal storage systems for use later in a passive mode during peak hours.

Photovoltaic (Solar) Module or Panel – Groups of photovoltaic (PV) cells electrically connected to produce a specified power output under standard test conditions. The PV cells are mounted on a substrate, sealed with an encapsulant, and covered with a protective glazing, and sometimes further mounted on an aluminum frame. A junction box, on the back or underside of the module is used to allow for connecting the module circuit conductors to external conductors.

Propane - A hydrocarbon gas, C3H8, occurs in crude oil, natural gas, and refinery cracking gas. It is used as a fuel, a solvent, and a refrigerant. Propane liquefies under pressure and is the major component of liquefied petroleum gas (LPG). Propane typically produces less NOx than gasoline.

Renewable Energy – Energy derived from resources that are regenerative or for all practical purposes cannot be depleted. Types of renewable energy resources include moving water (hydro, tidal and wave power), thermal gradients in ocean water, biomass, geothermal energy, solar energy, and wind energy. Municipal solid waste (MSW) is also considered to a renewable energy source because of the methane that it creates.

Renewable Portfolio Standard (RPS)- is a requirement for electric retail suppliers to source a minimum percentage of their electricity needs from eligible renewable resources.

R-Value - A measure of the capacity of a material to resist heat transfer. Building materials, ceiling wall and floor insulation are rated with R-values. The higher the R-Value of a material, the greater its insulating properties. R-value tables to determine the equivalent R-value of high mass wall construction materials are found in the 2000 International Energy Conservation Code. Thermal resistance calculations are based on changes in temperature over a given surface in time. No factors are in the calculation for humidity. Because of this, some materials or assemblies may exhibit different R-values in high humidity situations.

Seasonal Energy Efficiency Ratio (SEER) – A measure of seasonal or annual efficiency of a central air conditioner or air conditioning heat pump. It takes into account the variations in temperature that can occur within a season and is the average number of BTU of cooling delivered for every watt-hour of electricity used by the heat pump over a cooling season. The higher the SEER the better for keeping utility bills low.

Solar Access or Rights - The legal issues related to protecting or ensuring access to sunlight to operate a solar energy system, or use solar energy for heating and cooling.

Solar Air Heater - A type of solar thermal system where air is heated in a collector and either transferred directly to the interior space or to a storage medium, such as a rock bin.

Solar Collector – Devices for capturing the sun’s energy over a large area and focusing it on a small area, thereby concentrating it. In this way, it can produce extremely high temperatures used to either generate steam that will expand, heat a working fluid for heat transfer, or to carry out a chemical reaction to create a portable fuel such as hydrogen. Solar collectors may be curved dishes – like satellite receiving dishes – coated with reflective material, or can consist of an array of reflectors, arranged like flower petals, focusing onto a central point or arranged lineally. Usually the dish or the individual reflectors can be steered to follow the sun across the sky.

Solar Cooling - The use of solar thermal energy or solar electricity to power a cooling appliance. There are five basic types of solar cooling technologies: 1) absorption cooling, which can use solar thermal energy to vaporize the refrigerant; 2) desiccant cooling, which can use solar thermal energy to regenerate (dry) the desiccant; 3) vapor compression cooling, which can use solar thermal energy to operate a Rankine-cycle heat engine; 4) evaporative coolers (“swamp” coolers); and 5) heat-pumps and air conditioners that can be powered by solar photovoltaic systems.

Solar Energy - Electromagnetic energy transmitted from the sun (solar radiation). The amount that reaches the earth is equal to one billionth of total solar energy generated, or the equivalent of about 420 trillion kilowatt-hours.

Solar Film - A window glazing coating, usually tinted bronze or gray, used to reduce building cooling loads, glare, and fabric fading.

Solar Gain - The amount of energy that a building absorbs due to solar energy striking its exterior and conducting to the interior or passing through windows and being absorbed by materials in the building.Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat caused by sunlight. The SHGC is the fraction of incident solar radiation admitted through a window, both directly transmitted and absorbed, then subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window’s SHGC, the less solar heat it transmits.

 

Solar Photovoltaic Cell - The smallest semiconductor element within a PV module that performs immediate conversion of light into electrical energy (dc voltage and current).

Solar Pond - A body of water that contains highly saline water that forms layers of differing salinity that absorb and traps solar energy. Solar ponds can be used to provide heat for industrial or agricultural processes, building heating and cooling, and to generate electricity.

Solar Thermal – Method of producing electricity from solar energy by using focused sunlight to heat a working fluid, which in turn drives a turbogenerator.

Solar Thermal Electric Systems – Solar energy conversion technologies that convert solar energy to electricity, by heating a working fluid to power a turbine that drives a generator. Examples of these systems include central receiver systems, parabolic dish, and solar trough.

Standard Offer Programs – A program operated by utility that pays private contractors for making improvements in homes, apartments and businesses that save energy to the advantage of the utility and customers. The utility defines the results it would like from the program and pays the contractor a standard amount for all energy saved. A contractor can recommend you buy anything that saves energy under a standard offer program. Regulated utility companies in Texas and Austin Energy operate a number of standard offer programs

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.

Sulfur Dioxide (SO2) - Gases emitted by power plants that cause acid rain and haze problems. Sulphur dioxide (SO2) is a colorless gas, belonging to the family of gases called sulphur oxides (SOx). It reacts on the surface of a variety of airborne solid particles, is soluble in water and can be oxidized within airborne water droplets.

System Benefit Fund – Historically, regulated electric utility companies have provided a number of energy-related public services beyond simply supplying electricity. Such services have included: bill payment assistance and energy conservation measures for low-income households; energy efficiency programs for residential and business customers; pilot programs and other efforts to promote renewable energy resources; and research and development efforts to foster the development of new energy supply and delivery technologies. The term “system benefits” has been coined to describe these corollary benefits of a regulated utility system.

Thermal Resistance (R-Value) – The resistance of a material to heat conduction. The higher the R-value, the greater the energy efficiency and the higher resistance to heat transfer.

Transmission – The movement or transfer of electric energy over an interconnected group of lines and associated equipment between points of supply and points at which it is transformed for delivery to consumers, or is delivered to other electric systems. Transmission is a factor in energy efficiency due to the loss of electricity transmitted over longer distances. Energy loss results in heat waste from the transmission lines and transformer points.

Transmission and Distribution Rates – In the deregulated Texas electric market, transmission and distribution services are provided by a separate wires company at a regulated rate. On an annual basis the transmission and distribution service provider may adjust it rates using a Transmission Cost Recovery Factor (TCRF) without having a formal PUC review.

Transmission System – The transmission system brings electricity at high voltages from the power plant to a local substation where it is transformed into lower voltages for delivery through the distribution system to homes and businesses.

Transmission Reliability – Like traffic on a highway, the transmission system must be built to a size with adequate capacity for the volume of electricity it must deliver. Transmission lines are built for heavy-duty service, carry high voltages, and utilize large structures on wide rights- of-way. Transmission system failures are caused by overload, and severe weather such as tornados, hurricanes, and ice storms.

Urban Heat Island Effect – Urban heat islands form as vegetation is replaced by asphalt and concrete for roads, buildings, and other structures necessary to accommodate growing populations. These surfaces absorb – rather than reflect – the sun’s heat, causing surface temperatures and overall ambient temperatures to rise. The displacement of trees and shrubs eliminates the natural cooling effects of shading and evapotranspiration (a natural cooling process in which water transpires from a leaf’s surface and evaporates into the atmosphere, reducing ambient temperature), increasing the need for artificial cooling and increasing energy use.

Watt - The rate of energy transfer equivalent to one ampere under an electrical pressure of one volt. One watt equals 1/746 horsepower, or one joule per second. It is the product of Voltage and Current (amperage).

Weatherization - A term commonly applied to improvements made in a building shell to reduce the exchange of indoor and outdoor heat. Common weatherization measures include ceiling, wall and floor insulation, caulking and weather-stripping to reduce air infiltration and exfiltration, storm windows, and solar screens.

Wind Energy – Energy available from the movement of the wind across a landscape caused by the heating of the atmosphere, earth, and oceans by the sun. It is one of the oldest renewable technologies. The most wide spread use of wind power is for pumping water.

Wind Power Plant – A group of wind turbines interconnected to a common utility system through a system of transformers, distribution lines, and (usually) one substation. Operation, control, and maintenance functions are often centralized through a network of computerized monitoring systems, supplemented by visual inspection. This is a term commonly used in the United States. In Europe, it is called a generating station.

Wind Turbine - A term used for a wind energy conversion device that produces electricity; typically having two or three blades.

Wires Company – A regulated utility responsible for providing transmission and distribution services in a deregulated electricity market.