Energy density is a term used for the amount of useful energy In physics, energy is a quantity that is often understood as the ability to perform work. This quantity can be assigned to any particle, object, or system of objects as a consequence of its physical state stored in a given system or region of space per unit volume Volume is how much three-dimensional space a substance or shape occupies or contains, often quantified numerically using the SI derived unit, the cubic metre. The volume of a container is generally understood to be the capacity of the container, i. e. the amount of fluid (gas or liquid) that the container could hold, rather than the amount of.[1][clarification needed]
For fuels, the energy per unit volume is sometimes a useful parameter. In a few applications, comparing, for example, the effectiveness of hydrogen Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of 1.00794 u (1.007825 u for Hydrogen-1), hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its fuel to gasoline Gasoline or petrol is a petroleum-derived liquid mixture which is primarily used as a fuel in internal combustion engines. It is also used as a solvent, mainly known for its ability to dilute paints it turns out that hydrogen has a higher specific energy than does gasoline, but, even in liquid form, a much lower energy density.
Energy per unit volume has the same physical units as pressure Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure, and in many circumstances is an exact synonym Synonyms are different words with identical or very similar meanings. Words that are synonyms are said to be synonymous, and the state of being a synonym is called synonymy. The word comes from Ancient Greek syn ("with") and onoma (ὄνομα) ("name"). The words car and automobile are synonyms. Similarly, if we talk about a: 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.
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Energy density in energy storage and in fuel
Selected Energy Densities PlotIn energy storage Energy storage media are matter that store some form of energy at a later time to perform some useful operation. A device that stores energy is sometimes called an accumulator applications the energy density relates the mass In physics, mass commonly refers to any of three properties of matter, which have been shown experimentally to be equivalent: Inertial mass, active gravitational mass and passive gravitational mass. In everyday usage, mass is often taken to mean weight, but in scientific use, they refer to different properties of an energy store to the volume of the storage equipment. The higher the energy density, the more energy may be stored or transported for the same amount of volume. In the context of fuel Fuel is any material that can be used to generate energy to produce mechanical work in a controlled manner. The processes used to convert fuel into energy include chemical reactions, such as combustion, and nuclear reactions, such as nuclear fission or nuclear fusion. Fuels are also used in the cells of organisms in a process known as metabolism selection, that energy density of a fuel per unit mass is the specific energy Specific energy is defined as the energy per unit mass. Common metric units are J/kg. It is an intensive property. Contrast this with energy, which is an extensive property. There are two main types of specific energy: potential energy and specific kinetic energy. Others are the gray and sievert, measures for the absorption of radiation. The of that fuel, though in general an engine Engines come in many types, a common type is a heat engine such as an internal combustion engine which typically burns a fuel with air and uses the hot gases for generating power. External combustion engines such as steam engines use heat to generate motion via a separate working fluid using that fuel will yield less energy due to inefficiencies and thermodynamic In science, thermodynamics is the study of energy conversion between heat and mechanical work, and subsequently the macroscopic variables such as temperature, volume and pressure considerations—hence the specific fuel consumption of an engine will be greater than the reciprocal In mathematics, a multiplicative inverse or reciprocal for a number x, denoted by 1⁄x or x −1, is a number which when multiplied by x yields the multiplicative identity, 1. The multiplicative inverse of a fraction a⁄b is b⁄a. For the multiplicative inverse of a real number, divide 1 by the number. For example, the reciprocal of 5 is one of the specific energy of the fuel.[clarification needed]
The highest density sources of energy are fusion In nuclear physics and nuclear chemistry, nuclear fusion is the process by which multiple atomic nuclei join together to form a single heavier nucleus. It is accompanied by the release or absorption of energy. Large scale fusion processes, involving many atoms fusing at once, must occur in matter which is at very high densities and fission. Fusion includes energy from the sun which will be available for billions of years (in the form of sunlight Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon) but humans have not learned to make our own sustained fusion power Fusion power is the power generated by nuclear fusion reactions. In this kind of reaction, two light atomic nuclei fuse together to form a heavier nucleus and in doing so, release a large amount of energy. In a more general sense, the term can also refer to the production of net usable power from a fusion source, similar to the usage of the term & sources. Fission of U-235 in nuclear power Nuclear power is produced by controlled nuclear reactions. Commercial and utility plants currently use nuclear fission reactions to heat water to produce steam, which is then used to generate electricity plants will be available for billions of years because of the vast supply of the element on earth.[2] Coal Coal is a readily combustible black or brownish-black sedimentary rock normally occurring in rock strata in layers or veins called coal beds. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon along with variable, gas Gas is one of four classical states of matter. Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons are so energized that they leave their parent atoms, and petroleum Petroleum or crude oil is a naturally occurring, toxic, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights, and other organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling. It is refined and separated, most easily by are the current primary energy sources in the U.S.[3] but have a much lower energy density. Burning local biomass Biomass, a renewable energy source, is biological material from living, or recently living organisms, such as wood, waste, gas, and alcohol fuels. Biomass is commonly plant matter grown to generate electricity or produce heat. In this sense, living biomass can also be included, as plants can also generate electricity while still alive. The most fuels supplies household energy needs (cooking fires, oil lamps Oil lamps have traditionally been used as a basic form of lighting, and were widely used as an alternative to candles prior to the era of electric lights. Starting in 1780 the Argand lamp quickly replaced earlier oil lamps still in their basic ancient form. These were, in turn, replaced by the kerosene lamp in about 1850. In small towns and rural, etc.) worldwide.
Energy density (how much energy you can carry) does not tell you about energy conversion efficiency Energy conversion efficiency is the ratio between the useful output of an energy conversion machine and the input, in energy terms. The useful output may be electric power, mechanical work, or heat. Energy conversion efficiency is not defined uniquely, but instead depends on the usefulness of the output. All or part of the heat produced from (net output per input) or embodied energy Embodied energy is defined as the available energy that was used in the work of making a product. Embodied energy is an accounting methodology which aims to find the sum total of the energy necessary for an entire product lifecycle. This lifecycle includes raw material extraction, transport, manufacture, assembly, installation, disassembly, (what the energy output costs to provide, as harvesting The energy industry is a generic term for all of the industries involved the production and sale of energy, including fuel extraction, manufacturing, refining and distribution. Modern society consumes large amounts of fuel, and the energy industry is a crucial part of the infrastructure and maintenance of society in almost all countries, refining A refinery is a production facility composed of a group of chemical engineering unit processes and unit operations refining certain materials or converting raw material into products of value, distributing, and dealing with pollution Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat, or light. Pollutants, the elements of pollution, can be foreign substances or energies, all use energy). Like any process occurring on a large scale, intensive energy use impacts the world. For example, global warming Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation. According to the 2007 Fourth Assessment Report by the Intergovernmental Panel on Climate Change , global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 20th, nuclear waste Radioactive waste is a waste product containing radioactive material. It is usually the product of a nuclear process such as nuclear fission, though industries not directly connected to the nuclear power industry may also produce radioactive waste storage, and deforestation Deforestation occurs for many reasons: trees or derived charcoal are used as, or sold, for fuel or as a commodity, while cleared land is used as pasture for livestock, plantations of commodities, and settlements. The removal of trees without sufficient reforestation has resulted in damage to habitat, biodiversity loss and aridity. It has adverse may be some of the consequences of supplying our growing energy demands from fossil fuels, nuclear fission, or biomass.
No single energy storage method boasts the best in specific power, specific energy Specific energy is defined as the energy per unit mass. Common metric units are J/kg. It is an intensive property. Contrast this with energy, which is an extensive property. There are two main types of specific energy: potential energy and specific kinetic energy. Others are the gray and sievert, measures for the absorption of radiation. The, and energy density. Peukert's Law Peukert's Law, presented by the German scientist W. Peukert in 1897, expresses the capacity of a lead-acid battery in terms of the rate at which it is discharged. As the rate increases, the battery's available capacity decreases describes how the amount of useful energy that can be obtained (for a lead-acid cell) depends on how quickly we pull it out.
Gravimetric and volumetric energy density of some fuels and storage technologies (modified from the Gasoline Gasoline or petrol is a petroleum-derived liquid mixture which is primarily used as a fuel in internal combustion engines. It is also used as a solvent, mainly known for its ability to dilute paints article):
- Note: Some values may not be precise because of isomers In chemistry, isomers are compounds with the same molecular formula but different structural formulas. The word is derived from the Greek ισομερης, isomerès; isos = "equal", méros = "part". There are many different classes of isomers, like stereoisomers, enantiomers, geometrical isomers, et cetera . Isomers do not or other irregularities. See Heating value The heat of combustion is the energy released as heat when a compound undergoes complete combustion with oxygen under standard conditions. The chemical reaction is typically a hydrocarbon reacting with oxygen to form carbon dioxide, water and heat. It may be expressed with the quantities: for a comprehensive table of specific energies of important fuels.
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