Energy Equation
The energy equation is a fundamental principle in physics and engineering that describes the conservation of energy within a system. It states that the total energy of a system remains constant, with energy being transferred or transformed but never created or destroyed. The equation is often used to analyze and solve problems related to energy transfer and conversion in various engineering applications.
6 Key excerpts on "Energy Equation"
eBook - ePubSustainable Energy Transitions
Socio-Ecological Dimensions of Decarbonization
- Dustin Mulvaney(Author)
- 2020(Publication Date)
- Palgrave Macmillan(Publisher)
...Throughout this chapter, there are example problems that review energy-to-power relations, unit conversions, and stoichiometry, in addition to a handful of empirical problem sets and assignment. The chapter ends with a discussion about how concepts like entropy can provide a scientific basis for understanding how natural resource use has implications for intergenerational equality—the idea that resources must be managed for future generations (Costanza et al. 2014). 2.1 Power and Energy Energy is fundamental stuff. It is what allows life to occur, through metabolism and eventually decay. It shapes where non-living things are and where they are going. As the property of a star, the amount of energy determines whether humans could eventually inhabit those places. Energy also enables humans to develop the societies that exist today, and the linkages between peoples, economies, and nature in different parts of the world. Vaclav Smil describes energy use by human civilization as its metabolism—borrowing a metaphor for how living organisms process energy to fuel their needs and wants. What is energy? From your biology, physics, or chemistry classes in school you may recall that energy is the ability to do work or the ability to transform a system. Energy is encountered in different forms, but most often its presence is suggested by motion, activity, light, heat, or change. As a fundamental law of the universe, energy is always conserved. The energy that was present at the start of the universe is all still in the universe. This means energy cannot be created, only converted and transformed. Energy is a discrete quantity. This makes it different than power, which is a flow rate quantity of energy. Energy is the amount of power over time measured in joules (J)...
eBook - ePub- Kornelis Blok, Evert Nieuwlaar(Authors)
- 2016(Publication Date)
- Routledge(Publisher)
...2 What is energy? Energy exists in many forms, including: • kinetic energy • potential energy • chemical energy • nuclear energy • electromagnetic radiation • electricity • heat. Many conversions exist between these various forms of energy. The first law of thermodynamics, also called the law of conservation of energy, states that energy can neither be created nor destroyed, but can only be converted from one form to another (or from several forms combined to one or more other forms). This well-known law is one of the most fundamental laws in the natural sciences. It also forms the basis for energy analysis, and is implicitly used in many types of analysis, for example in energy statistics. 2.1 Energy in energy systems Energy production, conversion and use can never be considered in isolation. All these operations take place in the context of an energy system (see Figure 2.1). The first stage in the energy supply system is the extraction of energy carriers. This can be the mining of coal or uranium, the extraction of oil or natural gas, or the cultivation of biomass for energy purposes. The resulting primary energy is energy as found in its original or natural form, so coal, natural gas, and crude oil, as they are extracted from the Earth’s crust are primary energy carriers. Crude biomass, like harvested wood, is also a primary energy carrier. Figure 2.1 Schematic diagram of the energy system with some illustrative examples of the energy sector, energy end-use and energy services. The list is not exhaustive and the links shown between stages are not ‘fixed’; for example, natural gas can also be used to generate electricity and coal is not used exclusively for electricity generation (source: adapted from Grübler et al. 2012, in turn adapted from the original figure in Rogner 1994) The primary energy carriers produced in such a way are often not suitable for a specific application, so conversion is needed...
eBook - ePubSustainable Development Indicators
An Exergy-Based Approach
- Søren Nors Nielsen(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...All we need is to organize this knowledge in a more systematic way for it to be useful. While a diagram such as Figure 2.1 shows that the conversions are possible it does not tell the full story. How does the conversion happen? How is it made possible, and how easily is it achieved? What are the costs— in terms of both energy and economics? Do we have the necessary technologies available to us?—and so on. 2.3 The Relevant Law(s) The First and the Second Laws of Thermodynamics are both essential to the analysis of the energy supply systems of today. However, analyses based on the first law are still far more common at the macroscopic level (demonstrated, for instance, by national energy accounting systems and energy budgets in many countries), whereas analyses based on the second law have mainly been implemented at lower levels for instance when optimizing factory equipment, production processes or assembly lines. There is no doubt that first law analysis provides us with a brilliant tool when serving purely as an accounting system to keep track of energy flows. But as mentioned earlier (Section 2.2), the first law does not distinguish between the various types of energy. To the first law, all amounts of energy that are equal are the same—1 kJ of energy in the form of solar radiation is the same as the energy contained in 1 kJ of sugar or 1 kJ of heat at 20 °C. The first law simply ignores the form or type of energy and its inherent capacity for doing work (quality). Energy is energy is energy, to paraphrase Gertrude Stein. This understanding gives a misleading picture, because the three types of energy mentioned earlier differ from each other in one important aspect—namely their ability to do work—which, in the three instances mentioned previously, is quite different...
eBook - ePubEnergy Storage
A New Approach
- Ralph Zito, Haleh Ardebili(Authors)
- 2019(Publication Date)
- Wiley-Scrivener(Publisher)
...Chapter 2 Fundamentals of Energy The concept of energy is elusive and mysterious. It is constantly being reexamined for greater understanding. It’s an idea or concept about which nearly everyone thinks they have some understanding. It is interesting to note how we refer to the idea by such phrases as “burning excess energy,” “using a lot of energy,” or someone “has a lot of energy,” as if it were a fuel of some sort. The repetition of the word, as with most concepts, conveys a vague feeling of comfort with the notion, that we indeed have a grasp of it. In this chapter, we discuss the concept of energy. We review the fundamentals of various types of energy including mechanical, electrical and chemical, and interject some historical perspectives of energy and its usage. 2.1 Classical Mechanics and Mechanical Energy Frequently, in ordinary conversation or in more popular literature, the term energy is confused with or substituted for force. This confusion dates back many centuries beginning with human attempts to comprehend physical phenomena and the world around them. Even after the beginning of what is known as the scientific method, attributed to Galileo, much about the subject has confounded our comprehension. In the next pages we will address the issue of what energy is. 2.1.1 The Concept of Energy We may never be actually able to observe the quantity named “energy,” but its effects are certainly and easily observable. Perhaps this also adds to the mystery of energy. Lindsay and Margenau presented a timeless review of the history of physical concepts in their book, Foundations of Physics (1936). Though dated, this text presents a very comprehensive treatment of basic concepts both in classical and quantum mechanics. Since we have seen little to compare with this and we don’t wish to compete with their treatment of mechanics, we quote their pointed and well-said statements: All the problems of classical mechanics can be solved without reference to it (energy)...
eBook - ePubThe Myth of Progress
Toward a Sustainable Future
- Tom Wessels(Author)
- 2013(Publication Date)
- University Press of New England(Publisher)
...Carnot’s observation certainly wasn’t new. But he took his observation a step further by showing that Newtonian mechanics couldn’t explain such a unidirectional movement. The result of his work launched a new branch of physics known as thermodynamics. By 1865 the German physicist Rudolf Clausius had drafted the first and second laws of this young science. The first law of thermodynamics, also known as the law of conservation of energy, simply states that energy can neither be created nor destroyed. This means that the amount of energy in the universe today is exactly what it was thirteen billion years ago, just after the Big Bang. This is a powerful concept, but from a practical standpoint it’s the second law of thermodynamics that is the most important to us. The second law, also known as the law of entropy, states that although energy can’t be created or destroyed, it can be transformed from one form to another. As I type, some of the electrical energy that runs my computer originally came from the decay of uranium atoms within the Vermont Yankee nuclear power plant. As a uranium atom breaks apart, a minute amount of the mass of its nucleus is transformed into heat energy. The heat energy is used to produce steam. The steam then turns electric turbines, this transformation producing kinetic energy, the energy of motion. The kinetic energy of the rotating turbines is then transformed into electrical energy. The electrical energy enters my computer and is transformed into light and the words that appear on my screen, finally being transformed into heat that dissipates into my room. Throughout all these transformations no new energy has been created and none has been destroyed. But the transformation of energy from one state to another is not the critical aspect of the second law. The critical point is that although energy can be transformed, no transformation is 100 percent efficient...
eBook - ePubFrom Vehicles to Grid to Electric Vehicles to Green Grid
Many a Little Makes a Miracle
- Fuhuo Li, Shigeru Kanemitsu;Jianjie Zhang(Authors)
- 2019(Publication Date)
- WSPC(Publisher)
...the extensive variable and intensive variable, where the former depends on the change of the object while the latter does not change, e.g. the pressure remains the same during changes and it is often denoted by p rather than P. But we shall not adopt this distinction in most cases. The first law of thermodynamics or the law of conservation of energy is one of the most universal laws that governs our space. In addition to the symbols P, V, T introduced in § 2.1, we need a few more to describe the basics of thermodynamics. We consider an isolated thermodynamical system, where isolated means that the system does not give or receive heat from outside sources. Although we are to use p to denote the state quantity, we follow the notation commonly used. • U means the inner energy • Q means the heat • W means the work • means the entropy The last is a temporary definition of entropy and a more proper definition is given by where d Q rev is the infinitesimal change of the heat under a reversible process and d S i rr is that of the entropy under an irreversible process. Also, to be most precise, we need to place a conversion factor = mechanical equivalent to heat, to convert the heat in work: where Q 2 and Q 1 are the heat exerted on and emitted from the system and W is the work done on the system. However, we may discard this factor if we measure the heat in Joules. Or if we take the ratio, such as heat efficiency, this disappears. As we have the equation of state (2.2), we always have a relation between these variables and the situation is such that there are only two variables can be independent. The first law of thermodynamics then reads i.e. the sum of the energy exerted on an object, to change its state, in the form of work W and of heat Q is independent of the way they are exerted. This implies the negation of the existence of a perpetual engine of the first kind, i.e. “Realizing a system which repeats a cyclic movement (e.g...
