| Energy density | |
|---|---|
| SI unit | J/m3 |
Other units | J/L, W⋅h/L,Pa |
| InSI base units | kg⋅m−1⋅s−2 |
Derivations from other quantities | U =E/V |
| Dimension | |
Inphysics,energy density is the quotient between the amount ofenergy stored in a given system or contained in a given region of space and thevolume of the system or region considered. Often only theuseful or extractable energy is measured. It is sometimes confused with stored energy per unitmass, which is calledspecific energy orgravimetric energy density.
There are different types of energy stored, corresponding to a particular type of reaction. In order of the typical magnitude of the energy stored, examples of reactions are:nuclear,chemical (includingelectrochemical),electrical,pressure,material deformation or inelectromagnetic fields.Nuclear reactions take place in stars and nuclear power plants, both of which derive energy from the binding energy of nuclei.Chemical reactions are used by organisms to derive energy from food and by automobiles from thecombustion of gasoline. Liquid hydrocarbons (fuels such as gasoline, diesel and kerosene) are today the densest way known to economically store and transport chemical energy at a large scale (1 kg of diesel fuel burns with the oxygen contained in ≈ 15 kg of air). Burning localbiomass fuels supplies household energy needs (cooking fires,oil lamps, etc.) worldwide.Electrochemical reactions are used by devices such as laptop computers and mobile phones to release energy from batteries.
Energy per unit volume has the same physical units as pressure, and in many situations issynonymous. For example, the energy density of a magnetic field may be expressed as and behaves like a physical pressure. The energy required to compress a gas to a certain volume may be determined by multiplying the difference between the gas pressure and the external pressure by the change in volume. Apressure gradient describes thepotential to performwork on the surroundings by convertinginternal energy to work until equilibrium is reached.
Incosmological and other contexts ingeneral relativity, the energy densities considered relate to the elements of thestress–energy tensor and therefore do include therest mass energy as well as energy densities associated withpressure.
When discussing the chemical energy contained, there are different types which can be quantified depending on the intended purpose. One is the theoretical total amount ofthermodynamic work that can be derived from a system, at a given temperature and pressure imposed by the surroundings, calledexergy. Another is the theoretical amount of electrical energy that can be derived fromreactants that are at room temperature and atmospheric pressure. This is given by the change in standardGibbs free energy. But as a source ofheat or for use in aheat engine, the relevant quantity is the change in standardenthalpy or theheat of combustion.
There are two kinds of heat of combustion:
A convenient table of HHV and LHV of some fuels can be found in the references.[1]
Forenergy storage, the energy density relates the storedenergy to the volume of the storage equipment, e.g. thefuel tank. The higher the energy density of the fuel, the more energy may be stored or transported for the same amount of volume. The energy of a fuel per unit mass is called itsspecific energy.
The adjacent figure shows thegravimetric andvolumetric energy density of some fuels and storage technologies (modified from theGasoline article). Some values may not be precise because ofisomers or other irregularities. Theheating values of the fuel describe their specific energies more comprehensively.
The density values for chemical fuels do not include the weight of the oxygen required for combustion. Theatomic weights of carbon and oxygen are similar, while hydrogen is much lighter. Figures are presented in this way for those fuels where in practice air would only be drawn in locally to the burner. This explains the apparently lower energy density of materials that contain their own oxidizer (such as gunpowder and TNT), where the mass of the oxidizer in effect adds weight, and absorbs some of the energy of combustion to dissociate and liberate oxygen to continue the reaction. This also explains some apparent anomalies, such as the energy density of a sandwich appearing to be higher than that of a stick of dynamite.
Given the high energy density of gasoline, the exploration of alternative media to store the energy of powering a car, such as hydrogen or battery, is strongly limited by the energy density of the alternative medium. The same mass of lithium-ion storage, for example, would result in a car with only 2% the range of its gasoline counterpart. If sacrificing the range is undesirable, much more storage volume is necessary. Alternative options are discussed for energy storage to increase energy density and decrease charging time, such assupercapacitors.[9][10][11][12]
No single energy storage method boasts the best inspecific power,specific energy, and energy density.Peukert's law describes how the amount of useful energy that can be obtained (for a lead-acid cell) depends on how quickly it is pulled out.
In general anengine will generate lesskinetic energy due toinefficiencies andthermodynamic considerations—hence thespecific fuel consumption of an engine will always be greater than its rate of production of the kinetic energy of motion.
Energy density differs fromenergy conversion efficiency (net output per input) orembodied energy (the energy output costs to provide, asharvesting,refining, distributing, and dealing withpollution all use energy). Large scale, intensive energy use impacts and is impacted byclimate,waste storage, andenvironmental consequences.
The greatest energy source by far is matter itself, according to themass–energy equivalence. This energy is described byE =mc2, wherec is the speed of light. In terms of density,m =ρV, whereρ is the volumetric mass density,V is the volume occupied by the mass. This energy can be released by the processes ofnuclear fission (~ 0.1%),nuclear fusion (~ 1%), or theannihilation of some or all of the matter in the volumeV by matter–antimatter collisions (100%).[citation needed]
The most effective ways of accessing this energy, aside from antimatter, arefusion andfission. Fusion is the process by which the sun produces energy which will be available for billions of years (in the form of sunlight and heat). However as of 2024, sustainedfusion power production continues to be elusive. Power from fission innuclear power plants (using uranium and thorium) will be available for at least many decades or even centuries because of the plentiful supply of the elements on earth,[13] though the full potential of this source can only be realized throughbreeder reactors, which are, apart from theBN-600 reactor, not yet used commercially.[14]
Nuclear fuels typically have volumetric energy densities at least tens of thousands of times higher than chemical fuels. A 1 inch tall uranium fuel pellet is equivalent to about 1 ton of coal, 120 gallons of crude oil, or 17,000 cubic feet of natural gas.[15] Inlight-water reactors, 1 kg of natural uranium – following a corresponding enrichment and used for power generation– is equivalent to the energy content of nearly 10,000 kg of mineral oil or 14,000 kg of coal.[16] Comparatively,coal,gas, andpetroleum are the current primary energy sources in the U.S.[17] but have a much lower energy density.
The density of thermal energy contained in the core of alight-water reactor (pressurized water reactor (PWR) orboiling water reactor (BWR)) of typically1 GW (1000 MW electrical corresponding to ≈ 3000 MW thermal) is in the range of 10 to 100 MW of thermal energy per cubic meter of cooling water depending on the location considered in the system (the core itself (≈ 30 m3), the reactor pressure vessel (≈ 50 m3), or the whole primary circuit (≈ 300 m3)). This represents a considerable density of energy that requires a continuous water flow at high velocity at all times in order to removeheat from the core, even after an emergency shutdown of the reactor.
The incapacity to cool the cores of three BWRs atFukushima after the 2011tsunami and the resulting loss of external electrical power and cold source caused the meltdown of the three cores in only a few hours, even though the three reactors were correctly shut down just after theTōhoku earthquake. This extremely high power density distinguishes nuclear power plants (NPP's) from any thermal power plants (burning coal, fuel or gas) or any chemical plants and explains the large redundancy required to permanently control theneutron reactivity and to remove the residual heat from the core of NPP's.
Because antimatter–matter interactions result in complete conversion of the rest mass to radiant energy, the energy density of this reaction depends on the density of the matter and antimatter used. Aneutron star would approximate the most dense system capable of matter-antimatter annihilation. Ablack hole, although denser than a neutron star, does not have an equivalent anti-particle form, but would offer the same 100% conversion rate of mass to energy in the form ofHawking radiation. Even in the case of relatively small black holes (smaller than astronomical objects) the power output would be tremendous.
Electric andmagnetic fields can store energy and its density relates to the strength of the fields within a given volume. This (volumetric) energy density is given bywhereE is theelectric field,B is themagnetic field, andε andµ are the permittivity and permeability of the surroundings respectively. The SI unit is the joule per cubic metre.
In ideal (linear and nondispersive) substances, the energy density iswhereD is theelectric displacement field andH is themagnetizing field. In the case of absence of magnetic fields, by exploitingFröhlich's relationships it is also possible to extend these equations toanisotropic andnonlinear dielectrics, as well as to calculate the correlatedHelmholtz free energy andentropy densities.[18]
In the context ofmagnetohydrodynamics, the physics of conductive fluids, the magnetic energy density behaves like an additionalpressure that adds to thegas pressure of aplasma.
When a pulsedlaser impacts a surface, theradiant exposure, i.e. the energy deposited per unit of surface, may also be calledenergy density or fluence.[19]
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The following unit conversions may be helpful when considering the data in the tables: 3.6 MJ = 1 kW⋅h ≈ 1.34 hp⋅h. Since 1 J = 10−6 MJ and 1 m3 = 103 L, dividejoule/m3 by 109 to getMJ/L = GJ/m3. Divide MJ/L by 3.6 to getkW⋅h/L.
Unless otherwise stated, the values in the following table arelower heating values forperfect combustion, not counting oxidizer mass or volume. When used to produce electricity in afuel cell or to dowork, it is theGibbs free energy of reaction (ΔG) that sets the theoretical upper limit. If the producedH2O is vapor, this is generally greater than the lower heat of combustion, whereas if the producedH
2O is liquid, it is generally less than the higher heat of combustion. But in the most relevant case of hydrogen, ΔG is 113 MJ/kg if water vapor is produced, and 118 MJ/kg if liquid water is produced, both being less than the lower heat of combustion (120 MJ/kg).[20]
| Material | Specific energy (MJ/kg) | Energy density (MJ/L) | Specific energy (W⋅h/kg) | Energy density (W⋅h/L) | Comment | |
|---|---|---|---|---|---|---|
| Hydrogen, liquid | 141.86 (HHV) 119.93 (LHV) | 10.044 (HHV) 8.491 (LHV) | 39405.6 (HHV) 33,313.9 (LHV) | 2790.0 (HHV) 2,358.6 (LHV) | Energy figures applyafter reheating to 25 °C.[21] See note above about use in fuel cells. | |
| Hydrogen, gas (681 atm, 69 MPa, 25 °C) | 141.86 (HHV) 119.93 (LHV) | 5.323 (HHV) 4.500 (LHV) | 39405.6 (HHV) 33313.9 (LHV) | 1478.6 (HHV) 1250.0 (LHV) | Data from same reference as for liquid hydrogen.[21] High-pressure tanks weigh much more than the hydrogen they can hold. The hydrogen may be around 5.7% of the total mass,[22] giving just 6.8 MJ per kg total mass for the LHV. See note above about use in fuel cells. | |
| Hydrogen, gas (1 atm or 101.3 kPa, 25 °C) | 141.86 (HHV) 119.93 (LHV) | 0.01188 (HHV) 0.01005 (LHV) | 39405.6 (HHV) 33313.9 (LHV) | 3.3 (HHV) 2.8 (LHV) | [21] | |
| Diborane | 78.2 | 88.4 | 21722.2 | 24600.0 | [23] | |
| Beryllium | 67.6 | 125.1 | 18777.8 | 34750.0 | ||
| Lithium borohydride | 65.2 | 43.4 | 18111.1 | 12055.6 | ||
| Boron | 58.9 | 137.8 | 16361.1 | 38277.8 | [24][better source needed] | |
| Methane (101.3 kPa, 15 °C) | 55.6 | 0.0378 | 15444.5 | 10.5 | ||
| LNG (NG at −160 °C) | 53.6[25] | 22.2 | 14888.9 | 6166.7 | ||
| CNG (NG compressed to 247 atm, 25 MPa ≈3,600 psi) | 53.6[25] | 9 | 14888.9 | 2500.0 | ||
| Natural gas | 53.6[25] | 0.0364 | 14888.9 | 10.1 | ||
| LPGpropane | 49.6 | 25.3 | 13777.8 | 7027.8 | [26] | |
| LPGbutane | 49.1 | 27.7 | 13638.9 | 7694.5 | [26] | |
| Petrol (Gasoline) | 46.4 | 34.2 | 12888.9 | 9500.0 | [26] | |
| Polypropylene plastic | 46.4[27] | 41.7 | 12888.9 | 11583.3 | ||
| Polyethylene plastic | 46.3[27] | 42.6 | 12861.1 | 11833.3 | ||
| Residentialheating oil | 46.2 | 37.3 | 12833.3 | 10361.1 | [26] | |
| Diesel fuel | 45.6 | 38.6 | 12666.7 | 10722.2 | [26] | |
| 100LLAvgas | 44.0[28] | 31.59 | 12222.2 | 8775.0 | ||
| Jet fuel (e.g.kerosene) | 43[29][30][31] | 35 | 11944.4 | 9722.2 | aircraft engine | |
| Gasohol E10 (10% ethanol 90% gasoline by volume) | 43.54 | 33.18 | 12094.5 | 9216.7 | ||
| Lithium | 43.1 | 23.0 | 11972.2 | 6388.9 | ||
| Biodiesel oil (vegetable oil) | 42.20 | 33 | 11,722.2 | 9,166.7 | ||
| DMF (2,5-dimethylfuran) | 42[32] | 37.8 | 11,666.7 | 10,500.0 | [clarification needed] | |
| Paraffin wax | 42[33] | 37.8 | 11700 | 10500 | ||
| Crude oil (tonne of oil equivalent) | 41.868 | 37[25] | 11630 | 10278 | ||
| Polystyrene plastic | 41.4[27] | 43.5 | 11500.0 | 12083.3 | ||
| Body fat | 38 | 35 | 10555.6 | 9722.2 | metabolism in human body (22% efficiency[34]) | |
| Butanol | 36.6 | 29.2 | 10166.7 | 8111.1 | ||
| GasoholE85 (85% ethanol 15% gasoline by volume) | 33.1 | 25.65[citation needed] | 9194.5 | 7125.0 | ||
| Graphite | 32.7 | 72.9 | 9083.3 | 20250.0 | ||
| Coal,anthracite | 26–33 | 34–43 | 7222.2–9166.7 | 9444.5–11944.5 | Figures represent perfect combustion not counting oxidizer, but efficiency of conversion to electricity is ≈36%[5] | |
| Silicon | 32.6 | 75.9 | 9,056 | 21,080 | See Table 1[35] | |
| Aluminium | 31.0 | 83.8 | 8611.1 | 23277.8 | ||
| Ethanol | 30 | 24 | 8333.3 | 6666.7 | ||
| DME | 31.7 (HHV) 28.4 (LHV) | 21.24 (HHV) 19.03 (LHV) | 8805.6 (HHV) 7888.9 (LHV) | 5900.0 (HHV) 5286.1 (LHV) | [36][37] | |
| Polyester plastic | 26.0[27] | 35.6 | 7222.2 | 9888.9 | ||
| Magnesium | 24.7 | 43.0 | 6861.1 | 11,944.5 | ||
| Phosphorus (white) | 24.30 | 44.30 | 6750 | 12310 | [38] | |
| Coal,bituminous | 24–35 | 26–49 | 6666.7–9722.2 | 7222.2–13611.1 | [5] | |
| PET plastic (impure) | 23.5[39] | < ~32.4 | 6527.8 | < ~9000 | ||
| Methanol | 19.7 | 15.6 | 5472.2 | 4333.3 | ||
| Titanium | 19.74 | 88.93 | 5480 | 24700 | burned totitanium dioxide | |
| Hydrazine | 19.5 | 19.3 | 5416.7 | 5361.1 | burned tonitrogen andwater | |
| Liquidammonia | 18.6 | 11.5 | 5166.7 | 3194.5 | burned to nitrogen and water | |
| Potassium | 18.6 | 16.5 | 5160 | 4600 | burned to drypotassium oxide | |
| PVC plastic (improper combustion toxic) | 18.0[27] | 25.2 | 5000.0 | 7000.0 | [clarification needed] | |
| Wood | 18.0 | 5000.0 | [40] | |||
| Peatbriquette | 17.7 | 4916.7 | [41] | |||
| Sugars, carbohydrates, and protein | 17 | 26.2 (dextrose) | 4722.2 | 7277.8 | metabolism in human body (22% efficiency[42])[citation needed] | |
| Calcium | 15.9 | 24.6 | 4416.7 | 6833.3 | [citation needed] | |
| Glucose | 15.55 | 23.9 | 4319.5 | 6638.9 | ||
| Drycow dung andcamel dung | 15.5[43] | 4305.6 | ||||
| Coal,lignite | 10–20 | 2777.8–5555.6 | [citation needed] | |||
| Sodium | 13.3 | 12.8 | 3694.5 | 3555.6 | burned to wetsodium hydroxide | |
| Peat | 12.8 | 3,555.6 | ||||
| Nitromethane | 11.3 | 12.85 | 3138.9 | 3570 | ||
| Manganese | 9.46 | 68.2 | 2630 | 18900 | burned tomanganese dioxide | |
| Sulfur | 9.23 | 19.11 | 2563.9 | 5308.3 | burned tosulfur dioxide[44] | |
| Sodium | 9.1 | 8.8 | 2527.8 | 2444.5 | burned to drysodium oxide | |
| Household waste | 8.0[45] | 2222.2 | ||||
| Iron | 7.4 | 57.7 | 2052.9 | 16004.1 | burned toiron(III) oxide[46] | |
| Iron | 6.7 | 52.2 | 1858.3 | 14487.2 | burned toIron(II,III) oxide[46] | |
| Zinc | 5.3 | 38.0 | 1472.2 | 10555.6 | ||
| Teflon plastic | 5.1 | 11.2 | 1416.7 | 3111.1 | combustion toxic, but flame retardant | |
| Iron | 4.9 | 38.2 | 1361.1 | 10611.1 | burned toiron(II) oxide[46] | |
| Gunpowder | 4.7–11.3[47] | 5.9–12.9 | 1600–3580 | |||
| TNT | 4.184 | 6.92 | 1162 | 1920 | ||
| Barium | 3.99 | 14.0 | 1110 | 3890 | burned tobarium dioxide | |
| ANFO | 3.7 | 1027.8 |
| Material | Specific energy (MJ/kg) | Energy density (MJ/L) | Specific energy (W⋅h/kg) | Energy density (W⋅h/L) | Comment |
|---|---|---|---|---|---|
| Zinc-air battery | 1.59[48] | 6.02 | 441.7 | 1672.2 | controlled electric discharge |
| Lithium air battery (rechargeable) | 9.0[49] | 2,500.0 | controlled electric discharge | ||
| Sodium sulfur battery | 0.54–0.86 | 150–240 | |||
| Lithium metal battery | 1.8 | 4.32 | 500 | 1200 | controlled electric discharge |
| Lithium-ion battery | 0.36–0.875[52] | 0.9–2.63 | 100.00–243.06 | 250.00–730.56 | controlled electric discharge |
| Lithium-ion battery withsilicon nanowireanodes | 1.566 | 4.32 | 435[53] | 1,200[53] | controlled electric discharge |
| Alkaline battery | 0.48[54] | 1.3[55] | controlled electric discharge | ||
| Nickel-metal hydride battery | 0.41[56] | 0.504–1.46[56] | controlled electric discharge | ||
| Lead-acid battery | 0.17 | 0.56 | 47.2 | 156 | controlled electric discharge |
| Supercapacitor (EDLC) | 0.01–0.030[57][58][59][60][61][62][63] | 0.006–0.06[57][58][59][60][61][62] | up to 8.57[63] | controlled electric discharge | |
| Electrolytic capacitor | 0.00001–0.0002[64] | 0.00001–0.001[64][65][66] | controlled electric discharge |
| Storage device | Energy content (J) | Energy content (W⋅h) | Typical mass (g) | Typical dimensions (diameter × height in mm) | Typical volume (mL) | Specific energy (MJ/kg) | Energy density (MJ/L) |
|---|---|---|---|---|---|---|---|
| AlkalineAA battery[67] | 9360 | 2.6 | 24 | 14.2 × 50 | 7.92 | 0.39 | 1.18 |
| AlkalineC battery[67] | 34416 | 9.5 | 65 | 26 × 46 | 24.42 | 0.53 | 1.41 |
| NiMH AA battery | 9072 | 2.5 | 26 | 14.2 × 50 | 7.92 | 0.35 | 1.15 |
| NiMH C battery | 19440 | 5.4 | 82 | 26 × 46 | 24.42 | 0.24 | 0.80 |
| Lithium-ion18650 battery | 28800–46800 | 8–13 | 44–49[68] | 18 × 65 | 16.54 | 0.59–1.06 | 1.74–2.83 |
| Material | Specific energy (MJ/kg) | Energy density (MJ/L) | Specific energy (W⋅h/kg) | Energy density (W⋅h/L) | Comment |
|---|---|---|---|---|---|
| Antimatter | 89875517874 ≈90 PJ/kg | Depends on the density of the antimatter's form | 24965421631578 ≈ 25 TW⋅h/kg | Depends on the density of the antimatter's form | Annihilation, counting both the consumed antimatter mass and ordinary matter mass |
| Hydrogen (fusion) | 639780320[69] but at least 2% of this is lost toneutrinos. | Depends on conditions | 177716755600 | Depends on conditions | Reaction 4H→4He |
| Deuterium (fusion) | 571,182,758[70] | Depends on conditions | 158661876600 | Depends on conditions | Proposedfusion scheme for D+D→4He, by combining D+D→T+H, T+D→4He+n, n+H→D and D+D→3He+n,3He+D→4He+H, n+H→D |
| Deuterium+tritium (fusion) | 337387388[69] | Depends on conditions | 93718718800 | Depends on conditions | D + T →4He + n Being developed. |
| Lithium-6 deuteride (fusion) | 268848415[69] | Depends on conditions | 74680115100 | Depends on conditions | 6LiD → 24He Used in weapons. |
| Plutonium-239 | 83610000 | 1300000000–1,700,000,000 (depends oncrystallographic phase) | 23222915000 | 370000000000–460000000000 (depends oncrystallographic phase) | Heat produced inFission reactor |
| Plutonium-239 | 31,000,000 | 490000000–620000000 (Depends oncrystallographic phase) | 8700000000 | 140000000000–170000000000 (depends oncrystallographic phase) | Electricity produced inFission reactor |
| Uranium | 80620000[71] | 1539842000 | 22394000000 | Heat produced inbreeder reactor | |
| Thorium | 79420000[71] | 929214000 | 22061000000 | Heat produced inbreeder reactor (experimental) | |
| Plutonium-238 | 2239000 | 43277631 | 621900000 | Radioisotope thermoelectric generator. The heat is only produced at a rate of 0.57 W/g. |
The mechanical energy storage capacity, orresilience, of aHookean material when it is deformed to the point of failure can be computed by calculating tensile strength times the maximum elongation dividing by two. The maximum elongation of a Hookean material can be computed by dividing stiffness of that material by its ultimate tensile strength. The following table lists these values computed using the Young's modulus as measure of stiffness:
| Material | Energy density by mass (J/kg) | Resilience: Energy density by volume (J/L) | Density (kg/L) | Young's modulus (GPa) | Tensile yieldstrength (MPa) |
|---|---|---|---|---|---|
| Rubber band | 1651–6605[72] | 2200–8900[72] | 1.35[72] | ||
| Steel,ASTM A228 (yield, 1 mm diameter) | 1440–1770 | 11200–13800 | 7.80[73] | 210[73] | 2170–2410[73] |
| Acetals | 908 | 754 | 0.831[74] | 2.8[75] | 65 (ultimate)[75] |
| Nylon-6 | 233–1,870 | 253–2,030 | 1.084 | 2–4[75] | 45–90 (ultimate)[75] |
| Copper Beryllium 25-1/2 HT (yield) | 684 | 5720[76] | 8.36[77] | 131[76] | 1224[76] |
| Polycarbonates | 433–615 | 520–740 | 1.2[78] | 2.6[75] | 52–62 (ultimate)[75] |
| ABS plastics | 241–534 | 258–571 | 1.07 | 1.4–3.1[75] | 40 (ultimate)[75] |
| Acrylic | 1530 | 3.2[75] | 70 (ultimate)[75] | ||
| Aluminium 7077-T8 (yield) | 399 | 1120[76] | 2.81[79] | 71.0[76] | 400[76] |
| Steel,stainless, 301-H (yield) | 301 | 2410[76] | 8.0[80] | 193[76] | 965[76] |
| Aluminium 6061-T6 (yield @ 24 °C) | 205 | 553 | 2.70[81] | 68.9[81] | 276[81] |
| Epoxy resins | 113–1810 | 2–3[75] | 26–85 (ultimate)[75] | ||
| Douglas fir Wood | 158–200 | 96 | 0.481–0.609[82] | 13[75] | 50 (compression)[75] |
| Steel, MildAISI 1018 | 42.4 | 334 | 7.87[83] | 205[83] | 370 (440 Ultimate)[83] |
| Aluminium (not alloyed) | 32.5 | 87.7 | 2.70[84] | 69[75] | 110 (ultimate)[75] |
| Pine (American Eastern White,flexural) | 31.8–32.8 | 11.1–11.5 | 0.350[85] | 8.30–8.56 (flexural)[85] | 41.4 (flexural)[85] |
| Brass | 28.6–36.5 | 250–306 | 8.4–8.73[86] | 102–125[75] | 250 (ultimate)[75] |
| Copper | 23.1 | 207 | 8.93[86] | 117[75] | 220 (ultimate)[75] |
| Glass | 5.56–10.0 | 13.9–25.0 | 2.5[87] | 50–90[75] | 50 (compression)[75] |
| Material | Specific energy (MJ/kg) | Energy density (MJ/L) | Specific energy (W⋅h/kg) | Energy density (W⋅h/L) | Comment |
|---|---|---|---|---|---|
| Silicon (phase change) | 1.790 | 4.5 | 500 | 1,285 | Energy stored through solid to liquid phase change of silicon[88] |
| Strontium bromide hydrate | 0.814[89] | 1.93 | 628 | Thermal energy of phase change at 88.6 °C (361.8 K) | |
| Liquid nitrogen | 0.77[90] | 0.62 | 213.9 | 172.2 | Maximum reversible work at 77.4 K with 300 K reservoir |
| Compressed air at 30 MPa (4,400 psi) | 0.5 | 0.2 | 138.9 | 55.6 | Potential energy |
| Latent heat of fusion of ice (thermal) | 0.334 | 0.334 | 93.1 | 93.1 | |
| Flywheel | 0.36–0.5 | 5.3 | Kinetic energy | ||
| Water at 100 m dam height | 0.000981 | 0.000978 | 0.272 | 0.272 | Figures represent potential energy, but efficiency of conversion to electricity is 85–90%[91][92] |
properly trained athlete will have efficiencies of 22 to 26%
The Higher Heating Values are 22.7, 29.7 or 31.7 MJ/kg for methanol, ethanol and DME, respectively, while gasoline contains about 45 MJ per kg.
Let ε = 0.85, signifying an 85% efficiency rating, typical of an older powerplant.
Authority control databases: National |
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