Everything about Fuel Value totally explained
Energy density is the amount of
energy stored in a given system or region of space per unit
volume, or per unit
mass, depending on the context. In some cases it's obvious from context which quantity is most useful: for example, in
rocketry, energy per unit mass is the most important parameter, but when studying pressurized gas or
magnetohydrodynamics the energy per unit volume is more appropriate. In a few applications (comparing, for example, the effectiveness of
hydrogen fuel to
gasoline) both figures are appropriate and should be called out explicitly. (Hydrogen has a higher energy density per unit mass than does gasoline, but a much lower energy density per unit volume in most applications.)
Energy density 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 gas may be determined by multiplying the pressure of the compressed gas times its change in volume.
Energy density in energy storage and in fuel
In
energy storage applications, the energy density relates the
mass of an energy store to its stored energy. The higher the energy density, the more energy may be stored or transported for the same amount of mass. In the context of
fuel selection, that energy density of a fuel is also called the
specific energy of that fuel, though in general an
engine using that fuel will yield less energy due to
inefficiencies and
thermodynamic considerations—hence the
specific fuel consumption of an engine will be greater than the
reciprocal of the specific energy of the fuel. And in general, specific energy and energy density are at odds due to
charge screening.
Gravimetric and volumetric energy density of some fuels and storage technologies (modified from the
Gasoline article):
» Note: Some values may not be precise because of
isomers or other irregularities. See
Heating value for a comprehensive table of specific energies of important fuels.
This table doesn't take into account the mass and volume of the oxygen required for many of the chemical reactions, as it's assumed to be freely available and present in the atmosphere. In cases where this isn't true (such as rocket fuel), oxygen is included as an oxidizer.
| Storage type |
Energy density by mass (MJ/kg) |
Energy density by volume (MJ/L) |
Peak recovery efficiency (%) |
Practical recovery efficiency (%) |
| Mass-energy equivalence |
89,876,000,000 |
|
|
|
| Binding energy of Helium-4 nucleus |
683,000,000 |
8.57x1024 |
|
|
| Nuclear fusion of hydrogen (energy from the sun) |
645,000,000 |
|
|
|
| Nuclear fission (of U-235) (Used in nuclear power plants) |
88,250,000 |
1,500,000,000 |
|
|
Natural uranium (99.3% U238, 0.7% U235) in fast breeder reactor(External Link ) |
24,000,000 |
|
|
50% |
| Enriched uranium (3.5% U235) in light water reactor |
3,456,000 |
|
|
30% |
| Hf-178m2 isomer |
1,326,000 |
17,649,060 |
|
|
| Natural uranium (0.7% U235) in light water reactor |
443,000 |
|
|
30% |
| Ta-180m isomer |
41,340 |
689,964 |
|
|
| Liquid hydrogen |
143 |
10.1 |
|
|
| Compressed gaseous hydrogen at 700 bar (External Link) |
143 |
5.6 |
|
|
| Gaseous hydrogen at room temperature |
143 |
0.01079 |
|
|
| Beryllium (toxic) (burned in air) |
67.6 |
125.1 |
|
|
| Lithium borohydride (burned in air) |
65.2 |
43.4 |
|
|
| Boron (External Link) (burned in air) |
58.9 |
137.8 |
|
|
| Compressed natural gas at 200 bar |
|
10 |
|
|
| LPG propane (External Link) |
49.6 |
25.3 |
|
|
| LPG butane |
49.1 |
27.7 |
|
|
| Gasoline(External Link) |
46.9 |
34.6 |
|
|
| Diesel fuel/residential heating oil(External Link) |
45.8 |
38.7 |
|
|
| Polyethylene plastic |
46.3 (External Link) |
42.6 |
|
|
| Polypropylene plastic |
46.3 (External Link) |
41.7 |
|
|
| gasohol (10% ethanol 90% gasoline) |
43.54 |
28.06 |
|
|
| Lithium (burned in air) |
43.1 |
23.0 |
|
|
| Jet A aviation fuel(External Link) |
42.8 |
33 |
|
|
| Biodiesel oil (vegetable oil) |
42.20 |
33 |
|
|
| DMF (2,5-dimethylfuran) |
42 (External Link) |
37.8 |
|
|
| Crude oil (according to the definition of ton of oil equivalent) |
41.87 |
37 (External Link) |
|
|
| Polystyrene plastic |
41.4 (External Link) |
43.5 |
|
|
| Body fat metabolism |
38 |
35 |
|
|
| Butanol |
36.6 |
29.2 |
|
|
| Specific orbital energy of Low Earth orbit |
33 (approx.) |
|
|
|
| Graphite (burned in air) |
32.7 |
72.9 |
|
|
| Anthracite coal |
32.5 |
72.4 |
|
|
| Silicon (burned in air)(External Link) |
32.2 |
75.1 |
|
|
| Aluminum (burned in air) |
31.0 |
83.8 |
|
|
| Ethanol |
30 |
24 |
|
|
| Polyester plastic |
26.0 (External Link) |
35.6 |
|
|
| Magnesium (burned in air) |
24.7 |
43.0 |
|
|
| Bituminous coal (External Link) |
24 |
20 |
|
|
| PET plastic |
23.5 (impure) (External Link) |
|
|
|
| Methanol |
19.7 |
15.6 |
|
|
| Hydrazine (toxic) combusted to N2+H2O |
19.5 |
19.3 |
|
|
| Liquid ammonia (combusted to N2+H2O) |
18.6 |
11.5 |
|
|
| PVC plastic (improper combustion toxic) |
18.0 (External Link) |
25.2 |
|
|
| Sugars, carbohydrates & protein metabolism |
17 |
26.2(dextrose) |
|
|
| Cl2O7 + CH4 - computed |
17.4 |
|
|
|
| Lignite coal |
1414-19 |
|
|
|
| Calcium (burned in air) |
15.9 |
24.6 |
|
|
| Dry cowdung and cameldung |
15.5 (External Link) |
|
|
|
| Wood |
6–17 (External Link) |
1.81.8–3.2 |
|
|
| Liquid hydrogen + oxygen (as oxidizer) (1:8 (w/w), 14.1:7.0 (v/v)) |
13.333 |
5.7 |
|
|
| Sodium (burned to wet sodium hydroxide) |
13.3 |
12.8 |
|
|
| Cl2O7 decomposition - computed |
12.2 |
|
|
|
| Nitromethane |
11.3 |
12.9 |
|
|
| Household waste |
|
|
|
|
| Sodium (burned to dry sodium oxide) |
9.1 |
8.8 |
|
|
| Octanitrocubane explosive - computed |
7.4 |
|
|
|
| Ammonal (Al+NH4NO3 oxidizer) |
6.9 |
12.7 |
|
|
| Tetranitromethane + hydrazine explosive - computed |
6.6 |
|
|
|
| Hexanitrobenzene explosive - computed |
6.5 |
|
|
|
| Zinc (burned in air) |
5.3 |
38.0 |
|
|
| Teflon plastic (combustion toxic, but flame retardant) |
5.1 |
11.2 |
|
|
| iron (burned to iron(III) oxide) |
5.2 |
40.68 |
|
|
| iron (burned to iron(II) oxide) |
4.9 |
38.2 |
|
|
| TNT |
4.184 |
6.92 |
|
|
| Copper Thermite (Al + CuO as oxidizer) |
4.13 |
20.9 |
|
|
| Thermite (powder Al + Fe2O3 as oxidizer) |
4.00 (External Link) |
18.4 |
|
|
| compressed air at 300 bar (at 12°C), without container |
0.512 |
0.16 |
|
|
| ANFO |
3.88 |
|
|
|
| Hydrogen peroxide decomposition (as monopropellant) |
2.7 |
3.8 |
|
|
| Lithium ion battery with nanowires |
25.42.54-2.72? |
29 |
|
95%(External Link) |
| Lithium thionyl chloride battery (External Link) |
2.5 |
|
|
|
| Fluoride ion battery (External Link) |
1.71.7-4.2 |
2.82.8-5.8 |
|
|
| Regenerative Fuel Cell (fuel cell with internal Hydrogen reservoir used much as a battery) |
1.62 (External Link) |
|
|
|
| Hydrazine(toxic) decomposition (as monopropellant) |
1.6 |
1.6 |
|
|
| Ammonium nitrate decomposition (as monopropellant) |
1.4 |
2.5 |
|
|
| Capacitor by EEStor (claimed capacity) |
1.0 (External Link) |
|
|
|
| Molecular spring |
1~1 |
|
|
|
| Sodium-sulfur battery |
|
1.23 (External Link) |
|
85%(External Link) |
| Liquid nitrogen |
0.77 |
0.62 |
|
|
| Lithium ion battery-predicted future capability |
|
|
|
95%(External Link) |
Lithium ion battery-present capability |
|
|
|
|
| Lithium sulphur battery |
|
|
|
|
| Kinetic energy penetrator |
|
|
|
|
| 5.56 × 45 mm NATO bullet |
|
|
|
|
| Zn-air batteries |
|
|
|
|
| Flywheel |
0.5 |
|
|
|
| Ice |
0.335 |
0.335 |
|
|
| Zinc-bromine flow battery |
|
|
|
|
| Compressed air at 20 bar (at 12°C), without container |
0.27 |
0.01 |
|
64%(External Link) |
| NiMH Battery |
0.22 (External Link) |
0.36 |
|
60% (External Link) |
| NiCd Battery |
0.140.14-0.22 |
|
|
80% (External Link) |
| Lead acid battery |
0.090.09–0.11 (External Link) |
|
|
|
| Compressed air in fiber-wound bottle at 200 bar (at 24°C) |
0.1 |
0.1 |
|
|
| Commercial lead acid battery pack |
0.0720.072-0.079 (External Link) |
|
|
|
| Vanadium redox battery |
0.09 (External Link) |
0.1188 |
|
|
| Vanadium bromide redox battery |
0.18 (External Link) |
0.252 |
|
81% |
| compressed air in steel bottle at 200 bar (at 24°C) |
0.04 |
0.1 |
|
|
| Ultracapacitor |
0.0206 (External Link) |
0.050 (External Link) |
|
|
| Supercapacitor |
0.01 |
|
98.5% |
90%(External Link) |
| Capacitor |
0.002 (External Link) |
|
|
|
| Water at 100 m dam height |
0.001 |
0.001 |
|
8585-90%(External Link) |
| Spring power (clock spring), torsion spring |
0.0003 (External Link) |
0.0006 |
|
|
The highest density sources of energy are
fusion and
fission. Fusion includes energy from the sun which will be available for billions of years (in the form of
sunlight) but humans have not learned to make our own sustained fusion power sources. Fission of U-235 in
nuclear power plants will be available for billions of years because of the vast supply of the element on earth
(External Link).
Coal and
petroleum are the current primary energy sources in the U.S. but have a much lower energy density. Burning local
biomass fuels supplies household energy needs (
cooking fires,
oil lamps, etc.) worldwide.
Energy density (how much energy you can carry) doesn't tell you about
energy conversion efficiency (net output per input) or
embodied energy (what the energy output costs to provide, as
harvesting,
refining, distributing, and dealing with
pollution all use energy). Like any process occurring on a large scale, intensive energy use creates environmental impacts: for example,
global warming,
nuclear waste storage, and
deforestation are a few of the consequences of supplying our growing energy demands from fossil fuels, nuclear fission, or biomass.
By dividing by 3.6 the figures for megajoules per kilogram can be converted to kilowatt-hours per kilogram. Unfortunately, the useful energy available by extraction from an energy store is always less than the energy put into the energy store, as explained by the
laws of thermodynamics. No single energy storage method boasts the best in
specific power,
specific energy, and energy density.
Peukert's Law describes how the amount of energy we get out depends how quickly we pull it out.
Energy density of electric and magnetic fields
Electric and
magnetic fields store energy. In a vacuum, the (volumetric) energy density (in SI units) is given by
» J/kg, where
v is the
speed in m/s. See also
kinetic energy per unit mass of projectiles.
Potential energy with respect to gravity, close to earth, per unit mass: ca. 9.8 h J/kg, with h the height in m.
Heat: energies per unit mass are specific heat capacity times temperature difference, and specific melting heat, and specific heat of vaporizationFurther Information
Get more info on 'Fuel Value'.
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