The following outline is provided as an overview of and topical guide to energy:
Energy – in physics, this is an indirectly observed quantity often understood as the ability of a physical system to do work on other physical systems.[1][2] Since work is defined as a force acting through a distance (a length of space), energy is always equivalent to the ability to exert force (a pull or a push) against an object that is moving along a definite path of certain length.
Potential energy – energy possessed by a body by virtue of its position relative to others, stresses within itself, electric charge, and other factors.[3][4]
Elastic energy – energy of deformation of a material (or its container) exhibiting a restorative force
List of common units for energy. Official or common symbol in brackets after name and exact or approximate value of unit in joule in brackets after description.
SI unit
Joule (J) – the SI-unit for energy. Also called newton meter, watt second, or coulomb volt.
Other metric units
Kilowatt-hour (kW·h) – corresponds to one kilowatt of power being used over a period of one hour (3.6 MJ).
Calorie (cal) – equal to the energy need to raise the temperature of one gram of water by one degree Celsius (~4.184 J).
Erg (erg) – unit of energy and mechanical work in the centimetre-gram-second (CGS) system of units (10−7 J).
Therm (thm) – unit of heat energy. In the US gas industry it is defined as exactly 100,000 BTU59 °F. It is approximately the heat equivalent of burning 100 cubic feet (2.8 m3) of natural gas (~105.5 MJ).
Quad – unit of energy equal to 1015 (a short-scale quadrillion) BTU.
Foot-pound (ft·lbf or ft·lbf) – unit of mechanical work, or energy, although in scientific fields one commonly uses joule (~1.356 J).
Other units
Electronvolt (eV) – the amount of energy gained by a single unbound electron when it falls through an electrostatic potential difference of one volt (~1.60 × 10−19 J).
Fill factor – defined as the ratio of the maximum power (Vmp x Jmp) divided by the short-circuit current (Isc) and open-circuit voltage (Voc) in light current density – voltage (J-V) characteristics of solar cells.
Gigaton – Metric Unit of mass, equal to 1,000,000,000 (1 billion) metric tons, 1,000,000,000,000 (1 trillion) kilograms
Any of various units of energy, such as gigatons of TNT equivalent, gigatons of coal equivalent, gigatons petroleum equivalent.
Gray (unit) – (symbol: Gy), is the SI unit of energy for the absorbed dose of radiation. One gray is the absorption of one joule of radiation energy by one kilogram of matter. One gray equals 100 rad, an older unit.
Energy crisis, the need to conserve energy resources
Energy development, development of energy resources — ongoing effort to provide abundant and accessible energy, through knowledge, skills and construction
Embodied energy, the sum total of energy expended to deliver a good or service as it travels through the economy
Hubbert peak theory, also known as peak oil – the theory that world oil production will peak (or has peaked), and will then rapidly decline, with a corresponding rapid increase in prices.
Potential energy, the form of energy that is due to position of an object
Kinetic energy, the form of energy as a consequence of the motion of an object or its constituents
Mechanical energy, the potential energy and kinetic energy present in the components of a mechanical system
Binding energy, a concept explaining how the constituents of atoms or molecules are bound together
Bond energy, a measure of the strength of a chemical bond
Nuclear energy, energy that is the consequence of decomposition or combination of atomic nuclei
Osmotic power, also salinity gradient power or blue energy, the energy available from the difference in the salt concentration between seawater and river water
Gibbs free energy, a related concept in chemical thermodynamics that incorporates entropy considerations
Helmholtz free energy, a thermodynamic potential that measures the "useful" work obtainable from a closed thermodynamic system at a constant temperature, useful for studying explosive chemical reactions
Elastic energy, which causes or is released by the elastic distortion of a solid or a fluid
Ionization energy (IE), the energy required to strip an atom of an electron
Interaction energy, the contribution to the total energy that is a result of interaction between the objects being considered
Internal energy (abbreviated E or U), the total kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the total potential energy associated with the vibrational and electric energy of atoms within molecules.
Wind energy is the kinetic energy of air in motion; Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships
Allegorical and esoteric
Energeticism, theory that there is no matter and everything is composed of energy
Energy (esotericism), invoked by spiritualists for alternative modes of healing the human body as well as a spirit that permeates all of reality.
Orgone, Wilhelm Reich discovered this energy and tried to use it to cure various physical ailments and control the weather.
