1. The capacity for work or vigorous activity; vigor; power.
2. Exertion of vigor or power: "I have this project which is requiring a great deal of time and energy."
3. Vitality and intensity of expression; forcefulness of expression; such as, a speech delivered with energy and emotion.
4. Usable heat or power.
5. A source of usable power; such as, petroleum or coal.
6. In physics, the capacity to do work; the property of a system that diminishes when the system does work on any other system, by an amount equal to the work so done; potential energy.

Forms of energy include heat, light, sound, electricity, and chemical energy. Energy and work are measured in the same units—foot-pounds, joules, ergs, or some other, depending on the system of measurement being used. When a force acts on a body, the work performed (and the energy expended) is the product of the force and the distance over which it is exerted.

First recorded in 1599, from Middle French energie, from Late Latin energia, which was from Greek energeia, "efficiency, activity, operation" came from energos, "active, working" from en-, "at" + ergon, "work". Used by Aristotle with a sense of "force of expression"; the broader meaning of "power" was first recorded in English in 1665. To energize; that is, "rouse to activity" is from 1753; energetic of people, institutions, etc., is from 1796. The term energy crisis was first recorded in 1970.

A general term for renewable energy produced from plants, etc ; such as, wood and wood wastes, agricultural crops and wastes, or municipal and industrial wastes: "Biomass energy is the chemical energy content of non-fossil, energy-containing forms of carbon; such as, land-based and water-based vegetation, and waste materials; such as, municipal solid wastes, biosolids, forestry, and agricultural residues, and some industrial wastes."

That part of the binding energy of a solid associated with the electrostatic interaction of the ions and electrons.

A term for energy; such as, steam, hot water, or chilled water; which is produced at a central location and then transmitted to various specific sites in a given area (district) for uses; such as, space heating and cooling, or domestic hot water heating.

Such a system can substitute for furnaces, air conditioners, etc. within the district's individual buildings.

1. The energy inherent in an array or ordered arrangement of charged particles because of their relative positions.
2. The energy constituent in a circuit because of its position in relation to a magnetic field.
3. The energy of electric charges or currents because of their positions in an electric field.
4. The integral with respect to time of the instantaneous power input or power output of a circuit or appliance.

The basic unit is the watthour.

The measurement of the integral (entire, complete), with respect to time, of the power in an electric circuit.

A tool that measures the integral (an essential part or whole), with respect to time, of the power in an electric circuit.

For many years, the term power, in association with electricity, has tended to lose its true meaning; so, power is often found used in nontechnical literature where actually the correct term energy should be used.

By definition, power is the rate at which energy is transformed or is made available and is measured in watthours.

From an economic viewpoint, the most important of all electrical measurements is the measurement of energy. The watthour meter in various forms can be found in nearly every home, factory, highway billboard, and other locations where electrical energy is being purchased.

Metering, installation and wiring have been governed by national, industrial, and local codes for so many years that, at least in the United States, a particular type of installation is nearly identical everywhere in the country.

Measurement of energy is almost always with a "fixed-installation metering". This provides safety because of the grounding of the meter enclosure and ease of reading as a result of a proper location and mounting.

Tamper-proof housing, which are also weatherproof where necessary, are typical structures that normally insure the integrity of the electric meter readings.

1. The energy inherent in an array of charged particles because of their relative positions.
2. The energy inherent in a circuit because of its position in relation to a magnetic field.

1. The ability to move an electrical charge from one point to another.
2. Energy which is possessed by electric charges because of their positions in an electrostatic field.

Forms of radiant energy associated with radio waves, heat waves, light waves, gamma rays, cosmic rays, X-rays, and other types of electromagnetic radiation.

Energy which is present in an induction coil or solenoid.

1. The minimum amount of energy required to extract an electron from an atom or molecule.
2. The energy required to release an electron from its atomic or molecular orbital.

1. The quantum-mechanical representation of the energy level of an electron in an atom, which determines the orbit of the electron around the nucleus.
2. A quantum-mechanical concept for energy levels of electrons around the nucleus.

Electron energies are functions of each particular atomic species.

1. Photoelectron spectroscopy or the use of electron beams to induce transitions between electronic energy levels.

The study of the distribution of energy that is lost by scattered electrons when a substance is bombarded with monochromatic electrons.

2. A technique for studying atoms, solids, or molecules in which a substance is bombarded with monochromatic electrons, and the energies of scattered electrons are measured to determine the distribution of energy loss.

1. A graph that shows the range of energy levels in a diatomic (double atomic) molecule, based on the distance between the nuclei of its two atoms.
2. A graph of the energy of a diatomic (two atoms) molecule in a given electronic state as a function of the distance between the nuclei of the atoms.

1. The energy contained in electricity or in an electric charge at rest; such as, in the charge of a capacitor.
2. The potential energy that a collection of electric charges have as indicated by their positions as they relate to each other.

1. A process in which electrical energy is directly converted into heat energy.
2. The direct conversion of electric energy into heat energy, as in an electric heater.

A quantity measuring the rate of energy flow; the energy per unit time per unit area traveling across a surface element that is perpendicular to the energy flow.

A system of devices for the conversion of fossil energy to mechanical work or electric energy.

The main systems are the Steam (Rankine) Cycle and the Gas Turbine (Brayton Cycle).

1. Steam (Rankine) Cycle is an ideal thermodynamic cycle that consists of four processes:
   • Heat transfer to the system at constant pressure.
   • An expansion at constant entropy.
   • A constant-pressure heat transfer from the system.
   • A compression at constant entropy; used as a standard of efficiency.
2. Gas Turbine (Brayton) Cycle, an ideal gas cycle used as a standard for the actual performance of a simple gas turbine, consisting of four processes:
   • A reversible adiabatic (no heat transfer) compression at constant entropy.
   • A heat transfer at constant pressure up to the maximum temperature.
   • An adiabatic expansion at constant entropy back to the original pressure.
   • A heat transfer at constant pressure back to the original volume and entropy.
3. Entropy in thermodynamics is a measure of the disorder or randomness of a closed system; more entropy means less energy is available for doing work.

The total entropy of an isolated system cannot decrease when the system undergoes a change; it can remain constant for reversible processes, and will increase for irreversible ones.

The study of energy development, transportation, markets: The students were asked to name the different kinds of energy and find out the use of energy patterns from a geographical perspective for their report on the geography of energy.

1. Energy in the form of natural heat flowing outward from within the plant Earth and contained in rocks, water, brines, or steam: Geothermal heat is produced mainly by the decay of naturally occurring radioactive isotopes of thorium, potassium, and uranium in the Earth's core.

Geothermal energy is produced by tapping the Earth's internal heat. At present, the only available technologies to do this are those that extract heat from hydrothermal convection systems, where water or steam transfer the heat from the deeper part of the Earth to the areas where the energy can be tapped.

The amount of pollutants found in geothermal vary from area to area but may contain arsenic, boron, selenium, lead, cadmium, and fluorides. They also may contain hydrogen sulphide, mercury, ammonia, radon, carbon dioxide, and methane.

Getting the Earth's Heat

Geothermal power plants, which tap hot subterranean water or steam, are high on the lists of at least thirty states in the U.S. which are requiring utility companies to generate some portion of their electricity from such renewable sources.

Most utilities have not pursued geothermal energy primarily because up-front costs, including exploratory drilling, can be expensive since geothermal taps deep reservoirs, not groundwater, which collects much closer to the surface.

An extensive study recently released by the Massachusetts Institute of Technology has shown that the heat available under ground is surprisingly plentiful nationwide.

More information about special Geothermal Energy sources.

The amount of external energy which must be applied in order to ignite a combustible fuel mixture.

1. In spectroscopy, a spectroscopic technique for analyzing the energy of ionic products produced when a beam of ions having high kinetic energy is passed through a field-free reaction chamber.
2. A spectrometric technique that uses a beam of ions of high kinetic energy passing through a field-free reaction chamber from which ionic products are collected and energy analyzed.

It is a generalization of metastable ion studies in which both uni-molecular and bi-molecular reactions are investigated.

1. The amount of energy required to remove an electron from a specific atom or ion to an infinite point, generally expressed in electron volts and numerically equal to the ionization potential.
2. The energy required o remove completely the weakest bound electron from its ground state in an atom or molecule so that the resulting ion is also in its ground state.
3. Amount of energy required to remove an electron from an isolated atom or molecule.

There is an ionization potential for each successive electron removed, though that associated with removing the first (most loosely held) electron is most commonly used.

The ionization potential of an element is a measure of its ability to enter into chemical reactions requiring ion formation or donation of electrons and is related to the nature of the chemical bonding in the compounds formed by elements.

The average energy lost by ionizing radiation in producing an ion pair in a gas.

In air the value is approximately 33.73 electron volts.

The sum of the kinetic (motion) energy and the potential energy of an object.

A collective term for any form of energy that is extracted from the ocean; marine energy; ocean power; hydrokinetic energy: Ocean energy includes thermal energy from the difference between warmer surface waters and cooler deep waters, or mechanical energy from tides, waves, and currents.

One of the various techniques for extracting energy from the vertical temperature difference in the oceans: In principle, ocean thermal energy conversion can be used to generate electricity, desalinate water, support deep-water mariculture, and provide refrigeration and air-conditioning.

Energy emanating from the sun as electromagnetic radiation that is converted into electricity by means of solar (photovoltaic) cells or concentrating (focusing) collectors.

The energy stored in a body or system as a consequence of its position, composition, shape or state: Four types of potential energies are, for example, gravitational energy, electrical energy, nuclear energy, or chemical energy.

A statement of the amount of energy received from the sun in terms of some conventional energy unit; such as, kilowatt-hours, barrels of oil, tons of coal, etc.; used to describe the relative ability of solar energy to fulfill contemporary energy requirements as compared to fossil fuel sources.

1. Useful energy that is immediately derived from the sun; for example, a system that collects and uses the heat of the sun to warm a building or to generate electricity.
2. In the larger sense, any energy source that can be ultimately traced to the action of the sun.

The conversion of the radiant energy from the sun into heat, which can then be used for such purposes as space and hot water heating, industrial process heat, or power generation.

Solar thermal energy can be used for such applications as, space heating, air conditioning, hot water, industrial process heat, drying, distillation and desalination, and electrical power.

A technology in which the superconducting characteristics of low-temperature materials produce intense magnetic fields to store energy; proposed as a storage option in photovoltaics to smooth out fluctuations in power generation.

Energy that is produced and used in ways that will support long-term human development in all its social, economic, and environmental dimensions.

Radiant energy emitted by the Earth: Terrestrial energy includes not only the forces and power from the ground, but also from the atmosphere of the globe.

The kinetic energy associated with the motion of atoms or molecules in a substance; such as, heat.

The storage of heat energy by means of sensible or latent heat technologies, in order to provide heating or cooling services at a later date.

The total energy requirements of a person over the course of an entire day, including rest and sleep as well as actual physical activity.

A process that generates energy from useless, discarded materials; especially, by the incineration of municipal solid wastes or (MSW): The waste-to-energy process utilizes "waste" to generate useful energy; such as, electricity, heat, or both.

This waste-to-energy is possible, and convenient, when the heat generated by burning the "waste" is high enough to warrant satisfactory combustion conditions and to make enough energy available to overcome losses and auxiliary consumption.

Characteristics of waste-to-energy production

• Waste-to-energy is the offspring of the incineration of materials, which were originally introduced to sterilize and to reduce the volume of useless substances by burning it in a furnace.
• Modern waste-to-energy plants allow the export of energy, with very low environmental impact.
• The waste-to-energy plant consists of four basic sections: waste combustor, recovery boiler, flue gas treatment, and steam cycle.

Waste-to-energy is the process in which municipal waste is used to generate useful energy for electricity, heat, or both.

• The design of the combustor varies widely with the waste characteristics: physical state (solid versus liquid), size distribution, heating value, ash and moisture content, etc.
• Municipal solid waste is typically burned on a moving grate, where it is kept 20-30 minutes until it is completely burned.
• The hot gases generated in the combustor go through the recovery boiler to generate steam, which is used directly as a heat carrier or it is sent to a steam turbine to produce power.
• Flue gases are treated by adding reactants called sorbents and by filtering the particulate matter.
• A modern, large plant, treating a half-million tons of municipal solid waste per year, can generate more than 400 million kWh per year, meeting the electricity needs of more than 150,000 families.