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NTREG Glossary of Renewable Energy & Related Terminology
Updated: April 12, 2024Terms Defined: 210
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
| A | ||
AAC | "AAC " is an abbreviation for "Autoclaved Aerated Concrete". AAC is a lightweight, precast, foam concrete building material suitable for producing blocks that resemble concrete masonry blocks. | |
AC | See "Alternating current." | |
AC-Coupled System | An AC-coupled system combines batteryless and battery-based inverters in the same system. In AC-coupled systems, one or more grid-tied inverters can work with certain battery based inverters to disconnect from the utility grid and continue to supply electricity for critical loads when the utility power fails. Special battery-based inverters are required in ac-coupled systems. AC-coupled systems are slightly less efficient than "DC-coupled" systems. See also "DC-coupled systems and grid-tied inverter". (Note: Do not attempt to create an ac-coupled system with a conventional battery-based inverter.) | |
AC Module | An inverter that's permanently attached to and an integral part of a photovoltaic module. All DC wiring is completely internal to an ac-module inverter. For that reason, unlike "micro-inverters", ac module inverters are not required to have DC-side ground-fault detection. Not to be confused with "micro-inverter" (also "microinverter"). See also "micro-inverter". | |
AI | Abbreviation for "Artificial Intelligence". The simulation of human intelligence in machines that are programmed to think like humans and mimic their actions. "AI" may also be applied to any machine that exhibits traits associated with a human mind such as learning and problem-solving. A few examples of "AI" include items such as "smart" smoke detectors, door locks, flood alert sensors and other automation such as "smart" lights, drapes, appliances, etc., among many others. | |
AIA | Abbreviation for "American Institute of Architects". Any individual displaying "AIA" after their name must be a licensed architect, and a member of the American Institute of Architects. See also "Assoc. AIA" | |
Albedo | The fraction of solar radiation reflected from the ground, ground cover, and bodies of water on the surface of the earth. | |
Alternating Current | Electric current that reverses direction 50 or 60 times per second (depending on the country). | |
Amorphous Photovoltaic | Amorphous photovoltaic modules are commonly made from a special form of silicon that's applied like other "thin-film" materials. Typically brownish in color. Often found used in calculators and similar applications. | |
Amp, Ampere | Electrical current. A measure of the quantity of electricity flowing in a circuit. (Think of "Amps" as if they were gallons of water, and "Amps" are the gallons flowing per minute through a pipe.) | |
Amp-hour | Often abbreviated "A-H" or "AH". A measure of the amount (quantity) of electrical current flowing for a given period of time. Typical time unit is "hours", thus "amp-hours". | |
Aperture Area | At the PV module level, the total area including the frame may be used to define the "module area efficiency". For prototype modules, where the frame design is less important than the encapsulation and cell interconnections, an "aperture-area" definition is often used. The aperture-area is the total PV area minus the frame area. Aperture-area calculations yield a higher efficiency value due to the smaller area compared to the entire PV module. However, in modules where the PV frame represents a notable percentage of the total area, it's the total area efficiency that often matters. | |
Array | Two or more photovoltaic modules connected together. | |
ASHRAE | Abbreviation for "American Society of Heating, Refrigerating and Air-Conditioning Engineers". ASHRAE is an American professional association seeking to advance heating, ventilation, air conditioning and refrigeration systems design and construction. | |
Assoc. AIA | Abbreviation for "Associate Member of the American Institute of Architects". An Associate member is an individual without architectural license from a US licensing authority who meets other architectural educational or employment requirements set out in the Institute's Bylaws. | |
Azimuth Angle | The angle between the horizontal direction (of the sun, for example) and a reference direction (usually north). A typical azimuth angle for photovoltaic modules in America would be 180 degrees (facing south at latitudes north of the equator), and 0 degrees (facing north at latitudes south of the equator, such as South America Australia, and others). | |
| B | ||
B2O | A fuel containing a mixture of 20 percent bio-diesel and 80 percent petroleum-based diesel. | |
B50 | A fuel containing a mixture of 50 percent bio-diesel and 80 percent petroleum-based diesel. | |
Balance-of-System | All parts of a solar electric system OTHER than the photovoltaic modules. Balance-of-system components include but are not limited to inverters, racking, wires, conduit, switches, fuses, and so forth. | |
Base Load | The average minimum amount of electricity a utility company must supply to meet consumer electricity demand. | |
Baseload Capacity | The generating equipment normally operated to serve loads on an around-the-clock basis. | |
BEV | Abbreviation for Battery Electric Vehicle. A vehicle that operates exclusively on battery power, without an internal combustion engine. | |
Bio-diesel | Bio-diesel is an alternative fuel produced from renewable resources such as plant oils, animal fats, used cooking oil, and new sources such as algae. Bio-diesel contains no petroleum, but can be combined in any quantity with petroleum diesel to create a bio-diesel blend. Bio-diesel blends can be used in most "compression-ignition" (diesel) engines with little or no modifications. Bio-diesel is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics (the "diesel" odor). (Bio-diesel is not raw vegetable oil.) | |
Biofuels | Liquid fuels and blending components produced from biomass (plant) feedstocks, used primarily for transportation. | |
Biomass | Biomass means "natural material", and refers to biological materials that were alive or created during our lifetimes. When burned, biomass materials release heat - just like wood logs in a campfire. Biomass energy uses natural materials like trees and plants. It can also mean waste products like trash. Examples of biomass include grass clippings, wood chips, animal manure, and non-toxic trash. Biomass exists in landfills, where bacteria break down the waste material, creating methane gas in the process, which can be captured and burned. Energy from biomass is most often captured to generate electricity. Biomass specifically excludes coal and petroleum. | |
BPI | Abbreviation for Building Performance Institute. BPI is a certification and standard-setting organization for home performance professionals. BPI offers certifications, standards, and programs such as BPI GoldStar Contractor, Rater, and product evaluations. | |
British Thermal Units | Often abbreviated "Btu" or "btu". The amount of heat energy needed to raise the temperature of one pound of water by one degree F (for example, from 39 degrees F to 40 degrees F). A water temperature of 39 degrees F is used as the reference starting point because water is the most dense at this temperature. Air conditioners are rated in three ways: by BTUs; tons of refrigeration, or by horsepower. One ton of refrigeration removes the amount of heat needed to melt one ton of ice in 24 hours. One ton of refrigeration can remove 12,000 BTUs of heat in one hour, and would use approximately 3,517 watt-hours of electrical energy. To convert a "one ton" air conditioning unit into kilowatts-per-hour consumed is dependent type of air conditioner, its Energy Efficiency Rating ("EER"), and the environment in which it's operated. For instance, a typical one-ton air conditioner operating 20 minutes out of each hour consumes approximately 1,335 watt-hours (1.335 kilowatt-hours) of electrical energy. | |
Building-Integrated Photovoltaics ("BIPV") | Photovoltaic products (see "PV") used in the construction of buildings that replace standard building materials, such as the roof, walkways, windows, and awnings. | |
| C | ||
California Energy Commission ("CEC") | The California Energy Commission ("CEC")is the State of California's primary energy policy and planning agency. Among their missions is supporting renewable energy by providing market support to existing, new, and emerging renewable technologies; providing incentives for small wind and fuel cell electricity systems; and providing incentives for solar electricity systems in new home construction. The CEC requires independent performance certification on renewable energy products sold within the state of California. Certification tests are conducted under more real-world conditions. Many other states now rely on the product specifications from the CEC published on the CEC "Go Solar California" website. | |
Capacity Factor | The ratio of the electrical energy produced by a generating unit for a given period of time to the electrical energy that could have been produced at continuous full power operation during the same period. | |
CdTe | Abbreviation for "cadmium telluride", a combination of two metals used in the manufacture of photovoltaic modules. See "Thin-Film". | |
CEM | Abbreviation for "Certified Energy Manager". A CEM is an individual who optimizes the energy performance of a facility, building or industrial plant. | |
CFM | Abbreviation for "Certified Floodplain Manager". CFMs help guide responsible land use decisions and protect citizens and property in a community. They meet the challenges of breaking the damage cycle and stopping the negative drain on our nation's human, financial, and natural resources. | |
CFM | Abbreviation for "Cubic Feet Per Minute. Context will determine whether the abbreviation applies to the flow of air or liquid (typically water). | |
CIGS | Abbreviation for "copper indium gallium selenide", a type of photovoltaic module manufacturing technology. See "Thin-Film". | |
Clipping | This term is commonly but incorrectly applied to inverters when the output power reaches the inverter's design limit. "Clipping" of the output power infers causing distortion, which is not the case. When an inverter's output is "limited", there is no distortion to the waveform. It's simply not capable of increasing beyond its design limit. See also "Limiting". | |
Compact Fluorescent Light ("CFL") | Fluorescent light manufactured to occupy a very small area and able to be installed in an ordinary light fixture. CFL bulbs use a fraction of the electricity used by incandescent light bulbs. | |
Concentrated Solar Power | A solar energy conversion system characterized by the optical concentration of solar rays through an arrangement of mirrors to heat working fluid to a high temperature. Concentrated solar power (but not solar thermal power) may also refer to a system that focuses solar rays on a photovoltaic cell to increase conversion efficiency. | |
Conservation | The reduction of energy usage through increased efficiency and/or reduced waste. | |
Conversion Efficiency | A measure that gauges the percentage of solar energy reaching a module that in turn is converted into electrical power. | |
Cooling Degree-Days | The amount of air-conditioning needed, created by adding up all temperature differences of the form ( daily temperature in degrees F - 65 degrees F ) for each day in which the temperature exceeds 65F. See also "heating degree days". | |
Crystalline Modules ("c-Si") | Photovoltaic cells made from thinly-sliced silicon. See also "Monocrystalline" and "Polycrystalline". | |
| D | ||
DC-Coupled System | "DC-coupled systems" are comprised of solar panels, batteries, and one or more inverters. The solar panels generate direct-current electricity that charges batteries. Electrical energy stored in the batteries then provides the source of power for one or more inverters that may be connected to the residence or business, and may be capable of operating in conjunction with the utility grid or as a "stand-alone" solar elecric system to continue providing power without utility power present. DC-coupled systems are more efficient than AC-coupled systems by approximately six percent, but also require more hardware compared to an AC-coupled system. | |
Deep-cycle Battery | A battery (typically lead-acid) designed and constructed in a manner to withstand many discharges to a very low state-of-charge without seriously affecting its life. An ordinary automotive battery discharged from fully charged to 10% state of charge, then recharged to 100% will typically be worn out after approximately 200 such cycles. A genuine deep-cycle battery can generally handle several thousand such discharge-recharge cycles. "Marine" (trolling motor) batteries are often labeled "deep cycle", but are typically an automotive battery with slightly thicker lead plates. Battery life expectancy in all cases depends on how rapidly the battery is discharged, how long it sits in a discharged state, and the temperature at which it's used. Heat (among other things) reduces battery life expectancy. | |
DER | Abbreviation for Distributed Energy Resource. DER produce and supply electricity on a small scale and are spread out over a wide area. Rooftop solar panels, backup batteries, and emergency diesel generators are examples of DER. While traditional generators are connected to the high-voltage transmission grid, DER are connected to the lower-voltage distribution grid, in the same manner residences and businesses are connected. | |
Direct Current Electricity ("DC") | Electricity that flows only in one direction. Direct Current is the type of electricity supplied by batteries. | |
Dispatchable Power | Electrical sources such as power plants that can be turned on or off as needed, and can have their power output adjusted up or down in response to utility grid power demand requirements. | |
Distributed Generation | Distributed generation is a term applied to utility-connected solar energy systems, particularly those systems that generate more energy than is needed at times, and feeds that excess back into the utility grid. Distributed generation reduces the amount of energy required to be consumed from the utility grid. If more power is generated at a given time than is needed, the excess flows backward through the utility meter for consumption by other nearby utility customers. Such systems are typically installed over a widespread area (such as rooftops on buildings throughout cities), hence *"distributed". Often abbreviated "DG". | |
DOE | Sometimes "US DOE". In this context, an abbreviation for the United States Department of Energy. | |
| E | ||
E85 | A fuel containing a mixture of 85 percent ethanol (alcohol) and 15 percent gasoline. | |
"EEM" | EEM is an abbreviation for Energy Efficient Mortgage. When you are buying, selling, refinancing, or remodeling your home, you can increase your comfort and actually save money by using the Energy Efficient Mortgage (EEM). It is easy to use, federally recognized, and can be applied to most home mortgages. EEMs provide the borrower with special benefits when purchasing a home that is energy efficient, or can be made efficient through the installation of energy-saving improvements. To learn more about Energy Efficient Mortgages, click here. | |
"EER" | "EER" is an abbreviation for "Energy Efficiency Ratio". (EER) is a measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific value (95° F). The higher the EER, the more efficient the system. In technical terms, EER is the steady-state rate of heat energy removal (i.e. cooling capacity) by the product measured in Btu per hour divided by the steady-state rate of energy input to the product measured in watts. This ratio is expressed in Btu per hour/watt. (See also "SEER".) | |
Elevation | In this context, "Elevation" refers to either the height of the sun in the sky relative to the horizon (measured in degrees), or the tilt angle of photovoltaic modules or other solar energy collectors. Sun elevation is zero degrees when the sun is directly on the horizon (as in the exact moment of sunrise or sunset), to 90 degrees when directly overhead. A sun angle of 90 degrees occurs only at latitudes between the Tropic of Cancer through the Tropic of Capricorn. Photovoltaic module elevation is zero degrees when perfectly horizontal relative to the earth's surface, and 90 degrees when perpendicular to the earth's surface. | |
EMP | Abbreviation for "ElectroMagnetic Pulse". An electromagnetic pulse can purportedly be generated by nuclear weapons that are exploded high in the atmosphere. Extremely strong solar flares and even very nearby lightning can generate such pulses. These pulses can in turn cause very high voltages in electronic equipment leading to damage and total destruction of the equipment. | |
Energy | When associated with "solar", energy is the amount of power generated or consumed in a given amount of time (typically hours). One kilowatt of power generated or consumed for one hour equals one kilowatt-hour of energy. A watt‑hour meter measures the total amount of electrical energy flowing through it. | |
Energy Efficient Appliances | Electrical devices or appliances that perform their task, and use less electricity than lower-efficient devices. Electrical inefficiency in many devices is directly related to the heat they produce. For example, energy efficient light bulbs use most of the incoming electrical energy to produce light, not heat. | |
Energy Information Administration | The U.S. Energy Information Administration ("EIA") collects, analyzes, and disseminates independent and impartial energy information to promote sound policymaking, efficient markets, and public understanding of energy and its interaction with the economy and the environment. | |
EPC | "EPC" is an abbreviation for "Engineering, Procurement, and Construction". A solar EPC is typically a firm that's responsible for all aspects of a project, from design and construction to final "commissioning" of the system. Firms that aren't an "EPC" typically handle some parts of a project, and sub-contract the remaining tasks to other companies. Each approach has benefits and drawbacks. Advantages with an EPC may include a "one-stop shop", where the EPC is responsible for everything. Conversely, an EPC that keeps all of the expertise "in house" can result in higher overhead (thus higher project costs). Outside sources such as specialized engineering and design firms may offer different and more-innovative perspectives on a project, particularly by not being limited to a specific technology or brand of hardware in the design. | |
EPRI | The Electric Power Research Institute, a research consortium of electric power companies in the United States. | |
ERCOT | The Electric Reliability Council of Texas ("ERCOT") manages the flow of electric power to 23 million Texas customers representing 85 percent of the state's electric load. As the independent system operator for the region, ERCOT schedules power on an electric grid that connects 40,500 miles of transmission lines and more than 550 generating stations. | |
Ethanol | A clear, colorless, flammable oxygenated hydrocarbon. Ethanol is typically produced chemically from ethylene, or biologically from fermentation of various sugars from carbohydrates found in agricultural crops and cellulosic residues from crops or wood. It is used in the United States as a gasoline octane enhancer and oxygenate (blended up to 10 percent concentration). Ethanol can also be used in high concentrations (E85) in vehicles designed for its use. | |
EUI | "EUI" is an abbreviation for "Energy Use Intensity", and is expressed as energy consumed per square foot per year. It's difficult to compare energy consumption between buildings or structures. Simply measuring the amount of energy used in a given amount of time doesn't consider building size, configuration, or how it's used. For example, a public building such as a school would tend to use more energy per square foot than a home. EUI is calculated by dividing the total gross energy consumed in a one-year period (expressed in kilowatt-hours ["kW-h"]or thousands of British Thermal Units ["BTU"]) by the total gross square footage of the building. A low "EUI" generally indicates good energy performance. | |
EV | Abbreviation for "Electric Vehicle", a vehicle that derives all of its ability to move from energy stored in batteries, and does not have an internal combustion engine of any type. | |
E-Waste | "E-waste" is anything electronic that's put into the garbage. E-waste includes (but isn't limited to) old computers, printers, modems, scanners, mobile phones, televisions, stereo equipment, and radios .. for openers. E-waste typically contains lead, cadmium, selenium, phosphors, precious metals, plastics, fiberglass, chromium, steel, aluminum, and various assorted plastics, among many other materials. | |
| F | ||
"FAIA" | "Fellow of the American Institute of Architects. Architects who have made significant contributions to the profession and society and who exemplify architectural excellence can become a member of the AIA College of Fellows. Only 3 percent of the AIA members have this distinction. See also "AIA". | |
Federal Energy Regulatory Commission | The federal agency with jurisdiction over interstate electricity sales, wholesale electric rates, hydroelectric licensing, some natural gas pricing, oil pipeline rates, and gas pipeline certification. FERC is an independent regulatory agency within the Department of Energy (DOE) and is the successor to the Federal Power Commission. | |
Feed-in-Tariff | Money paid to a customer by a power company for excess electricity generated by a renewable energy source. The renewable energy source is most often either solar or wind generated electricity. This excess is connected to the power lines at the customer's residence, and most commonly on the customer's side of the electric meter. For example, if you had a solar electric system installed on your home, and had signed a feed-in-tariff agreement ("FIT") with your power company, you could find the power company selling electricity to you at one price per kilowatt-hour, but BUYING the excess from you for more than they sell it to you at retail. Feed-in-tariffs are implemented to encourage end users to install renewable energy equipment and sell excess renewable energy back to the utility company. | |
Filament | The part of an incandescent lamp through which electricity passes and gets extremely hot, producing light. | |
Flat-Plate Collector | A solar power collector that absorbs the sun's energy on a flat surface without concentrating or refocusing it. | |
Flexible-Fuel Vehicles | Vehicles that can operate on (1) alternative fuels (such as E85); (2) 100 percent petroleum-based fuels; (3) any mixture of an alternative fuel (or fuels) and a petroleum-based fuel. Flexible-fuel vehicles have a single fuel system to handle alternative and petroleum-based fuels. | |
Fluorescent light | A lighting device that uses an electrified gas rather than a filament to produce light. | |
Fuel Cell | A device that produces electricity by converting the chemical energy of a fuel (e.g., hydrogen) directly into electrical energy. Fuel cells differ from conventional electrical cells in that the active materials such as fuel and oxygen are not contained within the cell but are supplied from outside. It does not contain an intermediate heat cycle, as do most other electrical generation techniques. In this context, "fuel cells" are most commonly a device that combines hydrogen gas with oxygen (usually derived from the air around us rather than a separate storage tank) to produce electricity. Hydrogen-oxygen fuel cells typically convert approximately 40 to 60% of the available "fuel" energy to electricity. (Compare this to the typical 20-25% efficiency of the common automobile engine.) The waste by-products of a hydrogen-oxygen fuel cell are heat, and water (or water vapor). | |
| G | ||
"GCEC" | Abbreviation for "Grayson County Electric Cooperative", an electric utility company in north Texas. This term is local to north Texas. | |
Generation | The total amount of electric energy produced by generating units and measured at the generating terminal in kilowatt-hours (kWh) or megawatt-hours (MWh). | |
Geothermal | Heat from the earth. Often thought of as energy from geysers and hot springs. More recently, this term is applied to any heat stored in earth and available as a renewable energy resource. | |
Geothermal Energy | The heat that is extracted from hot water or steam that is mined from geothermal reservoirs in the earth's crust. Water or steam can be used as a working fluid for geothermal heat pumps, water heating, or electricity generation, and then is injected back into the earth. | |
Geothermal Heat Pump | A heat pump in which the refrigerant exchanges heat (in a heat exchanger) with a fluid circulating through an earth connection medium (ground or ground water). The fluid is contained in a variety of loop (pipe) configurations depending on the temperature of the ground and the ground area available. Loops may be installed horizontally or vertically in the ground or submersed in a body of water. Sometimes called a "ground-source heat pump", or "GSHP" for short." | |
GHG | Abbreviation for "Greenhouse Gas". Examples of greenhouse gases are: Water vapor (H2O), carbon dioxide ( CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and chlorofluorocarbons .. among others. The term "greenhouse gas" is based on the action of these substances trapping heat in the atmosphere, the same as a greenhouse traps warmer air inside for growing plants in cool or cold weather. | |
Gigawatt | From "giga", meaning billion, and "watt", a unit of energy (see "watt"). A gigawatt is one billion watts of electrical energy. To give you an idea how large one gigawatt is, it's the energy consumed by 10 million 100 watt light bulbs illuminated at the same time. | |
Gigawatt-hour | One billion watt-hours. (This is the equivalent energy consumed by 1,900 sixty-watt incandescent lights operating 24 hours a day for one year.) | |
Global Warming | The Earth's gradual warming due to the "greenhouse effect". | |
Greenhouse Effect | The rise in temperature the Earth experiences because certain gases in the atmosphere (such as water vapor, carbon dioxide, nitrous oxide, and methane) trap energy from the sun. Without these gases, heat would escape back into space and Earth's average temperature would be about 60 degrees F colder. Because of how they warm our world, these gases are referred to as greenhouse gases. | |
Greenhouse Gases | Gases in the Earth's atmosphere that produce the greenhouse effect. Changes in the concentration of certain greenhouse gases, due to human activity such as fossil fuel burning, increase the risk of global climate change. Greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, ozone, and various forms of fluorocarbon gas (used in air conditioners and refrigerators). | |
Grid | The network of wires and cables that transport electricity from a power plant to homes and business. | |
Grid-tied Inverter | An inverter that converts direct current (DC) into alternating current (AC) and feeds the power into the utility grid of homes and businesses on the customer's side of the meter. This has the effect of reducing the amount of power purchased from the utility company. In certain cases, more power may be produced by the system, in which case the utility meter may run "backwards", which at the discretion of the power company, may provide credit to the customer for the back-fed power. The most common source for the DC energy are photovoltaic modules or small wind turbines. Also commonly called "grid-interactive" inverter(s). | |
Grid tied | A solar electric system that's connected to the utility power grid and uses the utility grid as a backup source of power. If more energy is needed than is being generated by the solar electric system, the difference is supplied to the customer by the utility company. If more energy is being produced than needed, the excess electrical power flows backwards through the electrical meter to the utility company, where it is then used by others. | |
Ground-Source Heat Pump | See "Geothermal Heat Pump". | |
| H | ||
Heating Degree-Days | The amount of building heating needed, created by adding up all temperature differences of the form ( 65F - daily temperature in degrees F ) for each day in which the temperature falls below 65F. See also "cooling degree days". | |
Heat Pump | Heat pumps, like a refrigerator, use electricity to transfer heat from a warm area. In the summer, heat is removed from your home or other building and dissipated outside. In the winter, warmth is extracted from the outside air and moved into your home or building. Heat pumps transfer heat using refrigerant. Because they handle both cooling and heating, homeowners may not need to install separate systems to heat their homes. In colder climates, an electric heating element can be installed or included for additional heating capability. Heat pumps do not burn fossil fuel like furnaces, making them more environmentally friendly. | |
"HERS" | "HERS", an abbreviation for "Home Energy Rating Systems", provides a standardized evaluation of a home's energy efficiency and expected energy costs. A home energy rating can qualify a home owner or home buyer for an energy efficient mortgage (EEM) or an energy improvement mortgage (EIM). A HERS Report is similar to getting a miles-per-gallon report on a car - but in this case, lower is better (lower energy usage means a more efficient home). To find a HERS Certified Home Energy Rater, click here. | |
"HVDC" | "HVDC", an abbreviation for "High Voltage Direct Current". High-voltage direct current is used to send electricity over very long distances. It has less loss than alternating current, but requires conversion from alternating current to direct current, then back again. HVDC is used in our national electrical grid when the losses in the transmission lines is less than the loss in converting from AC to DC, then back again. | |
Hybrid System | A heating system or energy generator that does not rely on one exclusive energy source. For example, many domestic photovoltaic systems use gasoline generators as backup systems during periods of extreme cloudiness. Utility-scale hybrid solar thermal power plants use sunlight to boil water, and an alternative energy source such as natural gas when there is insufficient sunlight. | |
| I | ||
ICC | An abbreviation for International Code Council. The International Code Council is the leading global source of model codes and standards and building safety solutions that include product evaluation, accreditation, technology, training, and certification. The Code Council's codes, standards, and solutions are used to ensure safe, affordable, and sustainable communities and buildings worldwide. | |
"ICE" | "ICE" is an abbreviation for Internal Combustion Engine. Internal combustion engines in this context use petroleum in some form (gasoline, diesel) as fuel, and are known for emitting noxious pollutants such as carbon monoxide and particulates, among others. Not to be confused with internal combustion engines that utilize hydrogen, where the byproducts are heat and water. | |
"IECC" | "IECC" is an abbreviation for International Energy Conservation Code, a model code designed to create and uphold minimum energy efficiency standards for the design and construction of new residential buildings and commercial buildings. | |
Illuminance | Solar radiation in the visible region of the solar spectrum to which the human eye responds. | |
Incandescent Bulb | A light source that produces light by heating a wire filament to a very high temperature. | |
Incremental Capacity | Electrical generating capacity added on an annual basis. | |
Insolation | A measure of the solar radiation energy reaching the earth in a given region over a specific period of time. Not to be confused with "insulation" - material that slows the movement of heat toward cold (such as in attics). Insolation is related to irradiance in a manner similar to how miles-per-hour are related to miles-per-day. Irradiance is the amount of solar energy falling on the earth's surface at any given moment. Insolation relates to the amount of energy over a longer period of time. | |
Insulation | Materials that keep energy from moving from one place to another: on electrical wire, it is the plastic or rubber that covers the conductor; in a building, insulation makes the walls, floor, and roof more resistant to the outside (ambient) temperature. | |
Inverter | An electrical device that changes direct current ("DC") into alternating current ("AC"). See also "Micro-inverter" and "String Inverter". | |
IoT | Abbreviation for "Internet of Things". An IoT is a system of interrelated, internet-connected objects that are able to collect and transfer data over a wireless network without human intervention. | |
IOU | Abbreviation for "Investor Owned Utility". A utility company owned by stockholders. | |
Irradiance | The rate at which solar radiant energy arrives on a specific area of surface during a given time interval. The typical unit is watts per square meter W/m2. | |
| J | ||
Joule | Joule is a derived unit of energy in the International System of Units equal to the energy expended (or work done) when an electric current of one ampere passes through a resistance of one ohm for one second. Named after the English physicist James Prescott Joule. Some mechanical definitions for Joule also apply, but are not included here. | |
Junction box | An electrical box designed to be a safe enclosure in which to make electrical connections. On photovoltaic modules, the junction box is on the back of the module, and is where the connections from the module and the wires are attached. Other electronics may also be present in the junction box. | |
| K | ||
Kilowatt ("kW") | One thousand watts of electricity. (See also "Watt".) | |
Kilowatt-hour ("kW-h") | Frequently written "KWH" or "kwh". One thousand watt-hours. Calculated by multiplying the number of watts being used times the length of time in hours that amount of electricity is used. A refrigerator that uses 250 watts will consume one kilowatt-hour of energy in four hours (250 watts x 4 hours = 1,000 watt-hours .. or one kilowatt-hour). Utility bills are based on the number of kilowatt-hours consumed each month. One kilowatt-hour is equivalent to 3412 btu of energy. (See "btu".) | |
| L | ||
Landfill Gas | Gas that is generated by decomposition of organic material at landfill disposal sites. The average composition of landfill gas is approximately 50% methane and 50% carbon dioxide and water vapor by volume. The methane in landfill gas may be vented, flared, or combusted to generate electricity or useful thermal energy on-site, or injected into a pipeline for combustion off-site. | |
LEED | Abbreviation for "Leadership in Energy and Environmental Design". | |
LEED AP | Abbreviation for "LEED Accredited Professional". Holders of a LEED AP Certification have passed an exam administered by the Green Building Certification Institute, a third-party organization that provides independent oversight of professional credentialing and project certification programs related to green building. Through tests and examinations monitored by the GBCI, LEED AP have proven their understanding and knowledge of the LEED Rating System, green design, construction, and operations. Specialty certifications also exist for new construction, schools, retail establishments, commercial interiors, existing building operation and maintenance, and neighborhood development. | |
LEED BD+C | Abbreviation for "LEED Building Design & Construction". LEED Building Design and Construction (LEED BD+C) provides a framework for building holistic green buildings, giving an opportunity to create a healthy, resource-efficient, cost-effective building. Architects qualify by study and taking an examination to prove their expertise in this specialization. | |
LEED Rating Systems | LEED Green Building Rating System is a third-party certification program and the nationally accepted benchmark for the design, construction and operation of high performance green buildings. LEED provides building owners and operators with the tools they need to have an immediate and measurable impact on their buildings' performance. LEED certification provides independent, third-party verification that a building project is environmentally responsible, profitable and a healthy place to live and work. The LEED Green Building Rating System encourages and accelerates global adoption of sustainable green building and development practices through the creation and implementation of universally understood and accepted tools and performance criteria. The LEED rating system offers four certification levels for new construction -- Certified, Silver, Gold and Platinum -- that correspond to the number of "credits" (think of them as "points") accrued in five green design categories: sustainable sites, water efficiency, energy and atmosphere, materials and resources, and indoor environmental quality. LEED standards cover new commercial construction and major renovation projects, interiors projects and existing building operations. | |
Light Emitting Diode | An extremely efficient source of light, "LED" lamps convert from 65% to 95% of the electric energy to light energy (depending on the color of the light). LEDs also typically last 50,000 to 100,000 hours. Light emitting diodes are made from the same material as transistors and give off light when electricity is passed through them. | |
Limiting | "Limiting" occurs when more direct current ("DC") power is available from the photovoltaic modules ("PV") connected to an inverter than an inverter can change into alternating current ("AC") power. Inverters are required by established safety standards (in this case, UL 1741 and UL 62109) not to exceed their rated output power, regardless of the amount of power available from the photovoltaic modules. When this occurs, the inverter limits its output power to the maximum in its design specifications. Often erroneously termed "clipping" due to the manner in which the output power stops increasing at a specific wattage and the flattened appearance that results in the graph of the output power. | |
| M | ||
MACRS | See "Modified Accelerated Cost Recovery System". | |
Maximum Power Point Tracker | An electronic circuit that automatically adjusts for and "harvests" the maximum power available from a photovoltaic system under any conditions such as very clear to very cloudy weather, seasonal differences, and time of day. | |
Megawatt | From "mega", meaning million, and "watt", a unit of energy (see "watt"). A megawatt is one million watts of electrical energy. To give you an idea how large one megawatt is, it's the energy consumed by 10 thousand 100 watt light bulbs illuminated at the same time. | |
Megawatt-hour | One thousand kilowatt-hours, or 1 million watt-hours. | |
Microgrid | A microgrid consists of an energy generation and energy storage system that can power multiple sites at one time, such as several homes or buildings. Energy storage (batteries) may be charged from photovoltaic sources, a generator, the utility grid, or any combination of the preceding. Microgrids can be grid-interactive or stand-alone depending on their design. | |
Microinverter | A complete small inverter (typically 200 to 300 watts) that's attached to the frame or rack-mount hardware of a photovoltaic module. Microinverters connect to the existing DC wiring of a photovoltaic module, and by requirement of the National Electric Code and Underwriters Laboratories Safety Standards, must contain ground-fault detection circuits that disable the microinverter in the event of a detected DC-side ground fault. Microinverters are so named due to their very small physical size. See also "AC Module". | |
Modified Accelerated Cost Recovery System | Also known by the abbreviation "MACRS" (pronounced "makers"). Officially, the Federal Modified Accelerated Cost Recovery System. Under this system, a businesses may recover investments in certain property through rapid depreciation deductions. The MACRS establishes a set of classes for various types of property, ranging from three to 50 years, over which the property may be depreciated. A number of renewable energy technologies are classified as five-year property (26 USC § 168(e)(3)(B)(vi)) under the MACRS, which refers to 26 USC § 48(a)(3)(A), often known as the "Energy Investment Tax Credit" (or "ITC") to define eligible property. Such property currently includes a variety of solar-electric and solar-thermal technologies, small wind turbines (100 kW or less), and a variety of other renewable and alternative power sources. For more information on the federal MACRS, see IRS Publication 946, IRS Form 4562: Depreciation and Amortization, and Instructions for Form 4562. | |
Monocrystalline Cells | Monocrystalline photovoltaic ("PV") cells are cut from cylindrical ingots that resemble a large round salami. They tend to convert more sunlight energy to electricity than other types of photovoltaic cells, but they are also the most expensive. Crystalline PV cells are made from silicon, the same material we use to make window glass, and typically have a very dark-to-black appearance over the entire surface of each cell. | |
Multicrystalline | See "Polycrystalline" | |
Municipal Solid Waste | Residential solid waste and some nonhazardous commercial, institutional, and industrial wastes. | |
| N | ||
NABCEP | Abbreviation for "North American Board of Certified Energy Practitioners". NABCEP is a volunteer board of renewable energy stakeholder representatives whose mission is to support, and work with the renewable energy and energy efficiency industries, professionals, and stakeholders to develop and implement quality credentialing and certification programs for practitioners (better known as solar energy installers). | |
Nameplate Capacity | The maximum rated output of a generator under specific conditions designated by the manufacturer. Nameplate capacity is usually indicated in units of kilovolt-amperes (kVA) and in kilowatts (kW) on a nameplate physically attached to the generator. | |
National Electrical Code | Guidelines for electrical installations in the USA. Often adopted by cities and other government entities as their official "Code". 1984 and later editions of the NEC contain Article 690, "Solar Photovoltaic Systems" that apply when installing a PV system. | |
NDA | Abbreviation for "Non-disclosure Agreement". An NDA is a contract involving two or more parties when information considered proprietary will be shared. The NDA restricts the information that may or may not be released to others not involved in the Agreement. | |
NERC | NERC is the Electric Reliability Organization ("ERO") for North America, subject to oversight by the Federal Energy Regulatory Commission ("FERC"). NERC's jurisdiction includes users, owners, and operators of the bulk power system, which serves nearly 400 million people. | |
Net Metering | A contractual arrangement that permits an electrical utility customer to turn their electric meter backwards and sell any excess power generated (over and above their usage requirement) back to the electrical grid to offset some, to all of their consumption. Depending on individual state or utility rules, the net excess generation may be credited to their account (in many cases at the retail price), carried over to a future billing period, or ignored. | |
Net Zero | A "net-zero" building is generally considered to be connected to commercial utility power, and produces as much energy as it consumes. Most commonly, the energy sources are sunlight and/or wind. Buildings achieve "net-zero" status through a combination of energy-efficiency measures and on-site generation of electricity. Net-Zero buildings produce energy during the day, feeding any excess power to the utility grid, and use energy from the grid at night. An extensive review of "net-zero" buildings is offered by the U.S. National Renewable Energy Laboratory ("NREL"). NREL defines "net-zero" structures in a report titled "Zero Energy Buildings: A Critical Look at the Definition.". In their definition, NREL looks at where the energy is produced, and then how the energy is measured. | |
Nominal Operating Cell Temperature ("NOCT") | Also called "Normal Operating Cell Temperature". When exposed to sunlight, photovoltaic equipment operates at temperatures higher than the surrounding air. NOCT is the estimated temperature of the cells within a PV module when operating under 800 watts per square irradiance, 20 degrees C ambient temperature, and a wind speed of 1 meter per second (2.2 miles per hour). NOCT is used to estimate the nominal operating temperature of a module in its working environment. | |
NREL | Abbreviation for the National Renewable Energy Laboratory in Golden, Colorado. NREL is a United States National Laboratory specializing in developing technologies and procedures for using renewable energy sources. | |
| O | ||
Ocean Energy | Energy conversion technologies that harness the energy in tides, waves, and thermal gradients in the oceans. | |
"OCPD" | An abbreviation for "over-current protection device". In plain language, this would be a circuit breaker, a fuse, or other device that opens an electrical circuit in the event too much current is flowing, such as too large of a load for the wiring .. or a short-circuit. | |
Off-grid ("Off-the-grid") | Not connected to the commercial power lines. | |
Oncor | (Texas-specific term.) Oncor is the largest public utility in Texas. They own the transmission lines that move the electricity from the companies that generate the electricity to homes, businesses, and other consumers that use the electricity. Oncor does NOT sell electricity. They're a "transmission and distribution company", simply move the electricity from generator to consumer. The charge for this service appears on utility bills under various terms, most commonly of which is the "T & D" fee, "UDC" charges (abbreviation for "Utility Distribution Company", or other terminology. In the end, they're all referring to the cost for moving the electricity from the generator to the consumer. Electrical co-ops may not show this as a separate cost. | |
Open Circuit | A break in an electrical wire or other path where electricity would normally flow. An open circuit prevents any electrical current from flowing. Examples of an "open circuit" would be a broken wire, or even something like a wall or other switch that's "open" such that no current flows. | |
| P | ||
Panelboard | The official National Electric Code term for "breaker panel", "breaker box", or similar terms. An electrical distribution board that houses electrical circuit breakers. A panelboard is the main point at which electricity is distributed throughout a building. In commercial installations, it's often termed "electrical cabinet". | |
Passive Solar | Technology for using sunlight to illuminate and heat buildings directly, with no circulating fluid or energy conversion system, and usually no moving parts. Sunlight admitted into your home in the winter that helps to heat the house is a considered a "passive" energy source. | |
Perovskite | Perovskite< is a mineral comprised of calcium and titanium oxide. When added to solar cells, the conversion efficiency of light into electrical energy increases up to 50%. | |
PHEV | Abbreviation for "Plug-in Hybrid Electric Vehicle". A "PHEV" battery is capable of being charged from utility power or the on-board internal combustion engine creating electricity from a generator. | |
Photovoltaic | "Light-generated voltage". ("Photo" means "light". "Voltaic" (vol-TAY-ick) means "voltage". It's difficult to pronounce .. which is why we say "PV". | |
Photovoltaic ("PV") Cell | An electronic device consisting of layers of special materials capable of converting light directly into electricity. | |
Photovoltaic ("PV") Module | An assembly of interconnected photovoltaic cells enclosed in a protective assembly (usually glass and plastic). | |
Photovoltaic ("PV") Temperature Coefficient | Photovoltaic modules are affected by temperature. Contrary to what many people would think, PV efficiency goes UP in cold weather, and DOWN in hot weather. The rate at which the PV is affected by changes in temperature is known as its "temperature coefficient". | |
Polycrystalline Cells | Also called "poly-silicon" or "multi-crystalline" cells. Polycrystalline cells are made from square silicon ingots. Poly-cells are less expensive to produce than cells formed from single crystals, but are lower in efficiency (convert less of the sun's energy to electricity). Polycrystalline cells are easily distinguished by their mosaic blue appearance. | |
Power | The amount of work or energy expended in a given amount of time. Typical units of power are "watts", joules, and calories". | |
Power Purchase Agreement | A contract between a power producer and a power consumer, which states that the customer will purchase a certain amount of power at a certain price from the producer. | |
Pumped-Storage Hydroelectric Plant | A plant that usually generates electric energy during peak load periods by using water previously pumped into an elevated storage reservoir during off-peak periods when excess generating capacity is available to do so. | |
PV | See "Photovoltaic". | |
Pyranometer | A device for measuring and reporting the amount of solar irradiance striking the earth's surface at any given moment. See also "irradiance". | |
| Q | ||
"Quad" | One quadrillion Btu (1,000,000,000,000,000 Btu). A British thermal unit ("Btu" is the amount of heat required to raise the temperature of one pound of water one degree Fahrenheit. In 2019 the United States produced 101.0 quads of energy and consumed 100.2 quads. (Source: US Energy Information Administration) | |
| R | ||
REC | See "Renewable Energy Credits". | |
REP | See "Retail Electric Provider". | |
R-value | "Resistance value". Used specifically for insulating materials to indicated its effectiveness against the movement of heat toward cold. The higher the number, the greater the slowing of the flow of energy. Three inches of fiberglass insulation has an R value of 7.5. | |
Rack | Mechanical structures that attache a photovoltaic or other solar energy array to the roof of a building, or to the ground. | |
Radiant Barrier | A layer of foil-type material typically attached to the underside of roof decking or attached to attic rafters. Radiant barrier consists of highly reflective material such as aluminum foil or other metal that reflects (or more specifically, re-emits) radiant heat rather than absorbing it. Radiant barriers don't, however, reduce heat conduction like thermal insulation. Radiant barriers have a products have a reflectivity of 95%-97%. Radiant barriers are more effective in hot climates than in cool climates, especially when cooling air ducts are located in the attic. Radiant barrier is not insulation, and will not prevent heat-loss in cold weather. Paint-on materials are not radiant barriers, in spite of frequent advertising claims to the contrary. | |
Renewable Electricity | Renewable electricity is electricity generated without use of fossil fuels. | |
Renewable Energy ("RE") | An energy source that renews itself without effort. Fossil fuels, once consumed, are gone forever, while solar energy is renewable in that the sun energy we harvest today has no effect on the sun energy we can harvest tomorrow. See also "biomass". | |
Renewable Energy Credits ("RECs") | Renewable energy credits, or RECs, are tradable commodities that represent the green attributes associated with energy generated from renewable energy resources. One "REC" is generated every time one megawatt-hour (MWh) of renewable electricity is produced. Solar renewable energy credits, or "SRECs" are RECs generated from solar power sources. SRECs are valuable because some states have passed legislation requiring energy suppliers to provide a certain percentage of their electricity from renewable energy sources. This type of legislation is called a "Renewable Portfolio Standard" ("RPS"). Under certain types of Renewable Portfolio Standard legislation, energy suppliers must either generate a certain amount of solar electricity, or purchase SRECs to avoid paying a fine. | |
Renewable Energy Resources | Energy resources that are naturally replenishing but flow-limited. They are virtually inexhaustible in duration but limited in the amount of energy that is available per unit of time. Renewable energy resources include: biomass, hydro (water), geothermal, solar, wind, and ocean energy. | |
Renewables | Shorthand term for "renewable energy" or easily renewable material sources. | |
Renewable Portfolio Standard ("RPS") | A renewable portfolio standard (RPS) requires that energy suppliers in a certain state produce a proportion of their energy from renewable energy. To meet these RPS requirements, energy suppliers can: 1) Develop their own renewable energy facilities such as solar energy power plants or wind farms to produce RECS, or; 2) Purchase RECs from others that own renewable energy facilities. | |
Residential Energy Services Network | A not-for-profit, membership corporation governed by a Board of Directors (who are elected by membership). In April 1995, the National Association of State Energy Officials and Energy Rated Homes of America founded the Residential Energy Services Network (RESNET) to develop a national market for home energy rating systems and energy-efficient mortgages. RESNET is a recognized national standards-making body for building energy efficiency rating and certification systems in the United States. | |
Retail Electric Provider | Abbreviation for "Retail Electric Provider". A Retail Electric Provider sells electricity, but is not responsible for generating electricity. In the "electrical world", the REP is the equivalent of the grocery store. The "T&D" utility is analogous to the trucking company that transports the food to the store, and the power generating companies are the "farmer" where it all originates. See also "T&D". | |
| S | ||
SEER | "SEER" is an abbreviation for "Seasonal Energy Efficiency Ratio". Seasonal Energy Efficiency Ratio (SEER), is most commonly used to measure the efficiency of a central air conditioner. The higher the SEER value, the more efficient the system. SEER measures how efficiently a cooling system will operate over an entire season. In technical terms, SEER is a measure of the total cooling of a central air conditioner or heat pump (in Btu) during the normal cooling season as compared to the total electric energy input (in watt-hours) consumed during the same period. This measure of efficiency is specific to the temperate climate in the middle of the U.S. (See also "EER"). | |
Short Circuit | A "short circuit" is an unwanted path for electrical current between two points in a circuit. In the case of electrical power, a short-circuit usually allows excessive current to flow (more than the wires are designed to handle), in which case a circuit breaker or fuse will open the circuit, stopping the current flow, and thus preventing damage and/or a fire. (See also "OCPD"). | |
Silicon | Semiconductor material made from silica (beach sand), which is then purified for photovoltaic applications. | |
Smart Grid | The "smart grid" is an electrical network that includes numerous upgrades in its operation and energy measures compared to the electrical grid we use today. The "smart grid" includes "smart" utility meters, "smart" appliances, renewable energy resources, and various energy efficient resources. | |
SOC | Abbreviation for "State of Charge" - a reference to the amount of energy stored in a battery. A 100% state of charge ("SOC") means the battery is fully charged and cannot accept more. A 50% SOC means the battery has delivered half of its available energy. 0% SOC means the battery is totally discharged. | |
Solar Cell | A device made of silicon and other materials. Solar cells generate electricity when exposed to sunlight. Multiple solar cells (typically from 36 to 96 cells) are used in the construction of one photovoltaic module. | |
Solar Collector | A solar collector is that part of the system which absorbs the sun's energy and converts it into heat, such as a solar collector for a solar hot water system. Solar collectors can convert typically up to 85% of the sun's energy to heat. Not to be confused with a photovoltaic module, sometimes called a "solar panel". The heat collected by the solar collector may be used immediately or stored for later use. Solar collectors are used for space heating; domestic hot water heating; and heating swimming pools, hot tubs, or spas. | |
Solar Energy | The radiant energy of the sun, which can be converted into other forms of energy such as heat or electricity. | |
Solar Modules | Also called "solar panels". These are the large collections of solar cells that can produce electricity in a worthwhile quantity. | |
Solar Noon | The time of day when the sun reaches its highest point in the sky. This time divides the daylight hours for that day exactly in half. Solar noon may be quite a bit different from 'clock' noon depending on the location relative to the time zone in which the measurement is taken. | |
Solar Renewable Energy Credits | SREC program provides a means for Solar Renewable Energy Certificates (SRECs) to be created for every megawatt-hour of solar electricity created. | |
Solar Thermal Electric Generation (STEG) | Conversion of solar energy to electricity using various technologies to heat a working fluid to power a turbine that drives a generator. Examples of these systems include central receiver systems, parabolic dish, and solar trough. | |
SREC | See "Solar Renewable Energy Credits". | |
Stand-alone | See "Off-grid". | |
Standard Test Conditions ("STC") | "Standard Test Conditions". An attempt by the renewable energy industry, and photovoltaic manufacturing in particular, to provide consistent test conditions for photovoltaic performance. STC is based on an irradiance of 1,000 watts per square meter of sunlight, a solar spectrum of air mass 1.5, and a module temperature of 25C. | |
STEM | Acronym for "Science, Technology, Engineering, and Mathematics". STEM Education, a term originated by the National Science Foundation, is an educational approach that focuses on the disciplines of science, technology, engineering, and math. | |
String | Photovoltaic modules connected electrically one after the other in a "string" to produce the operating voltage required by the load. The total voltage increases by the amount of voltage for each module in the string. | |
String Inverter | A "string inverter" is a device that changes direct current from solar panels into household alternating current suitable for connecting to your home electrical system. It's called a "string" inverter because power is provided by a "string" of solar panels connected to each other the way train cars are connected together - one after another in a long line (the same way we refer to a "string" of Christmas lights). | |
Sustainable | "Sustainability" relates to the quality of life in a community, and is frequently used as meaning not taking more from a resource than is replenished naturally. In a broader sense, sustainability pertains to the economic, social and environmental systems that make up a community as a whole, and whether all three are working in concert to provide a healthy, productive, meaningful life for all community residents, present and future. | |
| T | ||
Thermal Solar | The process of deriving or concentrating heat from sunlight. Examples of "derived heat" are: home heating, solar cooking, clothes drying, solar heated water, and so forth. Concentrated solar thermal heat is often used to create steam, from which electric power is generated. | |
Thin Film | Thin-film photovoltaic modules are manufactured using spray-on or print-on techniques, rather than forming cells from ingots or blocks of molten silicon. Thin-film photovoltaic modules are significantly lower in efficiency than crystalline PV, but are also lower in cost per watt of energy generated, and often less affected by heat. Thin-film technologies involve many types of metals including silicon, gallium, cadmium, tellurium, copper, and others. | |
Tilt Angle | The angle at which a photovoltaic array 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. | |
Time-of-Use Metering | A utility billing system in which the price of electricity depends upon the hour of day at which it is used. Rates are typically higher during the afternoon when electric demand is at its peak. Rates are lower during at night when electric demand is much less. | |
TMY | Abbreviation for "Typical Meteorological Year" -- a "typical" year of hourly solar and meteorological values which are designed to produce the expected climate of a location throughout a year. TMY data is provided by the United States Department of Energy National Renewable Energy Laboratory Solar Radiation Database. ("TMY 2") data (1961 to 1990) is available from the National Solar Radiation TMY2 Database (Note: Large file! 515 MB). Data for 1991 through 2005 ("TMY 3") is available from the National Solar Radiation TMY3 Database. (Note! EXTREMELY large file! 3.1 GB!) | |
Tracker | Mechanical device used in solar electric and solar thermal systems. Follows the movement of the sun (daily and sometimes seasonally) and keeps the energy collection device pointed directly at the sun. Allows for the harvest of the maximum available solar energy. | |
Tracking Collector/Tracker | Any mechanical structure that that changes its orientation throughout the day in order to follow the path of the sun in the sky. Two-axis trackers continually face the sun throughout the day, changing direction with the time of day and the season. Single-axis trackers rotate on one axis for time-of-day only, and must be manually adjusted for the season. See also "tracker". | |
Transmission & Distribution | An abbreviation for "Transmission and Distribution" of electricity. | |
| U | ||
U-Factor | U-factor is a metric used in the building industry to quantify the rate of heat transfer through a material. U-factor measures how well a window or door insulates, signifying the rate at which heat is lost through the window or door assembly. The lower the U-factor, the better. The United States uses the "I-P" (Inch-Pound) system. U-factor (I-P) is expressed in terms of BTU/(hr-ft²-°F) (British Thermal Units per hour per square foot per degree Fahrenheit). | |
Uninterruptible Power Supply ("UPS") | A device that provides power when utility or other power is unavailable, such as during a power failure. Small UPS units (such as for computers) typically have internal batteries. Larger UPS systems have batteries external to the unit. Some residential-sized systems now incorporate internal batteries. | |
| V | ||
Vehicle-to-Grid | "Vehicle-to-Grid" (sometimes abbreviated "V2G" or "V-2-G") is a reference to an electric vehicle connected to the utility grid (typically a house, but may also be other locations) where it can charge from the grid, and more importantly give energy BACK to the grid under control of the utility company. In this manner, electric vehicles can serve as a widely dispersed energy resource. (See also "Vehicle-to-House".) | |
Vehicle-to-House | "Vehicle-to-House" (sometimes abbreviated "V-2-H" or "V2H") is a reference to an electric vehicle connected to and supplying power to a house through an inverter. Special steps must be taken to ensure power from the vehicle flows only to the house, and not to the utility grid. (See also "Vehicle-to-Grid".) | |
Volatile Organic Compound ("VOC") | Volatile organic compounds are organic compounds that contain carbon. VOCs have a boiling point below that of water, and easily vaporize (or "volatilize"). VOCs are solvents that get released into the air, such as when paint dries. Other products that emit VOCs include adhesives, cleaning supplies, and even some home furnishings. A few examples of VOCs are formaldehyde, toluene, acetone, and benzene. Products may be described as "low-VOC" when they emit significantly less than other products, but they still emit potentially harmful substances, which can accumulate in enclosed or poorly ventilated areas. | |
Volt | Unit of electrical pressure. Think of "volts" as if it were water pressure. | |
VPP | Abbreviation for "Virtual Power Plant". A virtual power plant is a network of distributed energy resources ("DER") that are grouped together to generate electricity and respond to demand. DERs include solar panels, batteries, electric vehicles and other devices that can generate, store or consume electricity, and are often at many different locations. Some VPP systems can be controlled by a local electrical utility (by permission of the VPP owner), to adjust and reduce consumption of non-critical loads during periods of high electrical demand. Other options include the ability for the utility company to "command" the DER up to maximum output to the grid where they serve to provide additional power to the grid. See also "V2G" and "V2H" for examples of possible "utility-commandable" energy sources. | |
| W | ||
Watt | Unit of electrical power. "Watts" are calculated by multiplying the electrical pressure in a circuit ("volts") by the amount of electricity moving in the circuit ("amps"). For example, 120 volts times 2 amps equals 240 watts. | |
Watt-hour ("W-h") | The electrical energy unit of measure equal to one watt of power supplied to, or taken from, an electric circuit steadily for one hour. For instance, a 60 watt incandescent light will consume 600 watt-hours of energy when used for ten hours (60 watts x 10 hours = 600 watt-hours.). Our electric bills are based on the number of watt‑hours of energy consumed each month. | |
Watt-hour Meter("W-h Meter") | Often called a "utility meter" or "electric meter", a watt‑hour meter measures and mechanically or digitally records the amount of energy passing through it in a given amount of time. For utility billing purposes, this period is typically 30 days (more or less). | |
Wind Energy | Kinetic energy present in wind motion that can be converted to mechanical energy for driving pumps, mills, and electric power generators. | |
Wind Turbine | Also called "Wind Generator" or incorrectly "windmill". Devices consisting of blades that turn a shaft that turns a generator to harvest wind energy and produce electrical power. | |
| X | ||
Xeriscape | "Xeriscape" is a combination of the Greek word "xeros", meaning "dry", and "-scape," as in landscape. Xeriscape landscaping essentially refers to a creating a landscape design that's low-water use, and tailored to withstand drought conditions. Pronounced as if it begins with the letter 'z' (as in "xylophone"), use of the word "xeriscaping" originated with the Denver Colorado Water Department in 1981. Also known as "low-water-use" landscaping. | |
| Y | ||
| No entries (yet) for the 'Y' category. Do you have a suggested/requested 'Y' word or phrase for our Glossary? Contact Us! | |
| Z | ||
Zenith | At the "zenith" in the sky, the sun will be directly overhead in relation to the observer. | |
Zenith Angle | The angle between the direction of interest (of the sun, for example) and the zenith (directly overhead). See also "zenith". | |
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