Energy density is the amount of energy stored in a given system or region of space per unit volume. Often only the useful or extractable energy is quantified, which is to say that chemically inaccessible energy such as rest mass energy is ignored. Quantified energy is energy that has some sort of, as the name suggests, quantified magnitude with related units.
For fuels, the energy per unit volume is sometimes a useful parameter. Comparing, for example, the effectiveness of hydrogen fuel to gasoline, hydrogen has a higher specific energy (energy per unit mass) than gasoline does, but, even in liquid form, a much lower volumetric energy density.
Energy per unit volume has the same physical units as pressure, and in many circumstances is an exact synonym: for example, the energy density of the magnetic field may be expressed as (and behaves as) a physical pressure, and the energy required to compress a compressed gas a little more may be determined by multiplying the difference between the gas pressure and the pressure outside by the change in volume. In short, pressure is a measure of the volumetric enthalpy of a system, that is, the enthalpy per unit volume. A pressure gradient has a potential to perform work on the surroundings by converting enthalpy until equilibrium is reached.
Read more about Energy Density: Introduction To Energy Density, Energy Density in Energy Storage and In Fuel, Energy Density of Electric and Magnetic Fields, Energy Density of Empty Space
Other articles related to "energy, energy density, density":
... other two being the matter-dominated era and the dark-energy-dominated era. 3600, at which point the expansion of the universe caused the mass–energy density to surpass the radiation energy density ... Even though the matter energy density surpassed the radiation density at this point, the universe remained optically thick to radiation until a cosmological redshift of approximately 1100, when ...
... higher average output voltage, lighter weights thus higher energy density, and longer cycling life than typical rechargeable batteries ... promising systems for satisfying the demand of high specific energy and high power ... is not ideal for designing a system that has high energy density ...
... This number density of "dead quasars" was attributed by Lynden-Bell to high mass-to-light ratio objects found at the center of galaxies ... number of observed quasars at various redshifts, he was able to derive an integrated energy density due to quasar output ... on Earth are flux limited, there are always more quasars that exist than are observed and thus the energy density he derived is a lower bound ...
... In physics, "vacuum energy" or "zero-point energy" is the volumetric energy density of empty space ... More recent developments have expounded on the concept of energy in empty space ... In general relativity, the cosmological constant is proportional to the energy density of empty space, and can be measured by the curvature of space ...
... The energy density (energy/volume) of a new LFP battery is some 14% lower than that of a new LiCoO2 battery ... a LiFePO4 cell typically has approximately the same energy density as a LiCoO2 Li-ion cell, because of LFP's slower decline of energy density ... Thereafter, LiFePO4 likely has a higher density ...
Famous quotes containing the word energy:
“I rather think the cinema will die. Look at the energy being exerted to revive it—yesterday it was color, today three dimensions. I don’t give it forty years more. Witness the decline of conversation. Only the Irish have remained incomparable conversationalists, maybe because technical progress has passed them by.”
—Orson Welles (1915–1984)