Physics
Geothermal Energy
Geothermal energy is heat derived from the Earth's core, which can be harnessed for power generation and heating. This renewable energy source is obtained by tapping into hot water and steam reservoirs beneath the Earth's surface. Geothermal power plants use this heat to produce electricity, making it a sustainable and environmentally friendly energy option.
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11 Key excerpts on "Geothermal Energy"
- Radian Belu(Author)
- 2019(Publication Date)
- CRC Press(Publisher)
7 Geothermal Energy 7.1 Introduction, Earth Internal Structure Almost all countries are increasingly focused on the energy supply diversification, evaluating all energy alternatives, particularly those that are significant and well-distributed nationally. One such option, often ignored, is the Geothermal Energy. Geothermal Energy comes from Greek words: thermal meaning heat and geo meaning Earth, being the energy contained as heat into the Earth’s interior. The Earth gives us the impression that it is dependably constant, because over the human time scale, little seems to change. However, every Earth cubic centimeter is in motion, and has been since its formation. Earth is a dynamic entity, with time scales spanning from seconds for the earthquakes, years that volcanoes appear and grow, over millennia that landscapes slowly are evolving, to over millions of years the continents rearrange on the planet’s surface. The energy source to drive these processes is heat, with a constant flux from every square meter of the Earth’s surface. Earth average heat flux is 87 mW/m 2, or for the total global surface area of 5.1 × 10 8 km 2, this heat flux is equivalent to about 4.5 × 10 13 W. For comparison, it is estimated that the total power used by all human activity in one year is approximately 1.6 × 10 13 W. Clearly, the Earth heat has the potential to significantly contribute to satisfying world energy needs. This heat, the source of Geothermal Energy, is contained into the rock and fluid inside the Earth’s layers. Its origin is linked with the Earth’s internal structure and composition, and the associated physical processes. Despite the fact it is present in huge, inexhaustible quantities into the Earth’s crust or deeper layers, it is unevenly distributed, seldom concentrated, and most often at depths too great to be exploited industrially. There are almost 6300 km from the Earth’ surface to its center and the deeper it is the hotter it gets
eBook - ePubFlow and Heat Transfer in Geothermal Systems
Basic Equations for Describing and Modeling Geothermal Phenomena and Technologies
- Aniko Toth, Elemer Bobok(Authors)
- 2016(Publication Date)
- Elsevier(Publisher)
Chapter 1What Is Geothermal Energy?
Abstract
The knowledge and use of Geothermal Energy have a long history. The primary source of Geothermal Energy is the decay of radioactive elements. This energy is stored in the high temperature region of the Earth's crust, mantle, and core. From an engineering point of view, only the upper region of the crust has practical importance. Terrestrial heat-flow and geothermal gradient are the main parameters used to characterize a region's geothermal properties. These parameters correspond to the tectonic motion of the lithosphere plates. That geothermal phenomenon occurs most intensely at the boundaries of the lithosphere plates. Where subcrustal erosion and tension stresses have thinned the continental crust terrestrial heat-flow is also above average. A geothermal reservoir is that part of the Earth's crust from which internal energy content can be recovered with the help of some reservoir fluid: steam, hot water, or a mixture of both. When studying geothermal reservoirs, different reservoir types yield correspondingly different conceptual models.Keywords
EGS; Geothermal gradient; Geothermal reservoir; HDR; Heat conduction; History of geothermal use; Mantle flow; Plate tectonics; Terrestrial heat-flowOutline1.1 Introduction 1.2 The Nature and Origin of Geothermal Energy 1.3 Geothermal Reservoirs References1.1. Introduction
Geothermal Energy is energy contained within the high temperature mass of the Earth's crust, mantle, and core. Since the Earth's interior is much hotter than its surface, energy flows continuously from the deep, hot interior up to the surface. This is the so-called terrestrial heat-flow. The temperature of the Earth's crust increases with depth in accordance with Fourier's law of heat conduction. Thus the energy content of a unit of mass also increases with depth.All of the Earth's crust contains Geothermal Energy, but Geothermal Energy can only be recovered by means of a suitable energy-bearing medium. To be practical, the energy-bearing media must be: hot enough (high-specific energy content), abundant enough, easily recoverable, inexpensive, manageable, and safe. Water satisfies these requirements perfectly. The specific heat of water is 4.187
eBook - PDF- David R. Boden(Author)
- 2016(Publication Date)
- CRC Press(Publisher)
1 1 An Overview of Energy KEY CHAPTER OBJECTIVES • Describe and contrast nonrenewable and renewable sources of energy. • Identify characteristics that make Geothermal Energy distinctive from other forms of renewable energy and describe how temperature affects how geo-thermal energy is utilized. • Recognize the difference between energy and power and apply the terms in the correct context. • Discuss the attributes of Geothermal Energy in terms of fuel source, emis-sions, and baseload. Succinctly, Geothermal Energy is heat from the Earth that can be harnessed and used for the benefit of society. Geothermal Energy is below us everywhere and is available all the time, unlike other forms of renewable or alternative energy, such as solar and wind. And, yet, in many ways geothermal is overlooked because peo-ple are not able to see it like sunshine or feel it like wind. Geothermal, unlike solar and wind energy, is a baseload energy resource capable of providing power 24 hours a day all year long, similar to traditional fossil-fuel-fired power plants. This chapter provides a cursory overview of all forms of energy to provide a perspec-tive of how Geothermal Energy fits into the energy milieu. Also, key concepts on energy and power are reviewed so the reader understands how energy and power are related and measured. BASIC TERMINOLOGY OF ENERGY AND POWER Energy comes in many forms, including kinetic (energy of motion), potential (the ability to deliver energy), chemical (energy in fossil fuels, such as gasoline and natu-ral gas), and of course thermal or heat energy. The heat energy of the Earth is enor-mous and so is its ability to do work. Examples of Earth’s work include moving huge pieces of the Earth’s crust and uppermost mantle a few centimeters every year, the eruption of volcanoes, and the episodic lurching and shaking during an earthquake.
eBook - ePub- W Shepherd, D W Shepherd(Authors)
- 2014(Publication Date)
- ICP(Publisher)
CHAPTER 7
Geothermal Energy
7.1.Physical Basis of Geothermal Energy
Geothermal Energy is thermal energy stored in the sub-surface of the earth. It is not a renewable source because prolonged exploitation can exhaust a particular site. Nevertheless, the vast extent of energy potentially available is such that many references refer to it as if it was infinitely renewable. Energy is stored in natural underground reservoirs of steam and/or hot water, known as aquifers, and also in more solid “hot sediments” that are buried at depth or adjacent to hot spots.Heat energy flows outwards from within the earth at the average rate of 0.063W/m2 . The total outward flow amounts to 32 × 1012 W, as shown in Fig. 2.1 of Chapter 2 . It is of interest that the amount of interior heat flux flowing outwards is only about one-thousandth the value of the solar energy flux falling from space onto the same area [1 , 2 ]. The surface geothermal heat distribution is too small and too diffuse to be exploited, except in concentrated hot spots such as geysers or volcanoes.7.2.Geological Structure of the Earth
The geological structure of the earth is illustrated in Fig. 7.1 [3 ]. It is believed to approximate to five concentric spheres. From the outside proceeding inwards these are the atmosphere, crust, mantle, liquid outer core (magma) and solid inner core. As one proceeds inwards the temperature and density increase. For non-volcanic (i.e. non-seismic) areas the average geothermal gradient is between 17°C and 30°C per kilometre of depth (50°−87°F per mile). In volcanic areas the temperature gradient is much higher.The earth’s crust, composed of basalt, silicate rocks, is not of uniform thickness. Under the oceans the crust is about 15 km thick and consists of porous rock. Under the continental land masses the crust is about 35 km thick (Fig. 7.2 ) and the proportion of porous rock probably increases with depth. Between the continental land mass and the ocean, the continental shelf contains a great thickness of sedimentary rocks such as sandstone or limestone [4
eBook - PDF- Sunggyu Lee, James G. Speight, Sudarshan K. Loyalka, Sunggyu Lee, James G. Speight, Sudarshan K. Loyalka(Authors)
- 2014(Publication Date)
- CRC Press(Publisher)
At a depth of about 6 mi. from the earth’s surface, the temperature is higher than 100°C; thus, the total amount of Geothermal Energy in storage far exceeds, by several 551 Geothermal Energy orders of magnitude, the total thermal energy accountable in all forms of nuclear and fossil fuel resources of this planet. Solar energy is the only comparable resource in terms of such vast quantities. Therefore, it is very logical, if not imperative, that our energy priorities incorporate a vital resource such as Geothermal Energy. 17.2.2 R ENEWABILITY AND S USTAINABILITY OF G EOTHERMAL E NERGY The US Department of Energy (DOE) classifies Geothermal Energy as renewable . Its source is the continuously emanating thermal energy generated by the earth’s core. Each year, rainfall and snowmelt maintain the supply of requisite water to geother-mal reservoirs, and production from individual geothermal fields can be sustained for decades and perhaps centuries. An accurate prediction of the sustainable service life of each field is, however, very difficult. 17.2.3 O CCURRENCE OF G EOTHERMAL E NERGY The occurrence of geothermal heat (also known as geoheat) can be explained by one of the following theories: 3 1. The first theory is that about 6 billion years ago, the earth was a hot molten mass of rock, and this mass has been cooling through the epochs of time, with the outer crust formed as a result of a faster cooling rate. 2. The second theory presupposes that the earth is like a giant furnace. The decaying of radioactive material within the earth provides a constant heat source. 3. The third theory is based on the presumption that geothermal heat origi-nates from the earth’s fiery consolidation of dust and gas over 4 billion years ago. Even though a generally agreed-on explanation for the natural occurrence of Geothermal Energy is unavailable, a combination of the aforementioned theories is widely offered.
eBook - ePub- Farshid Zabihian(Author)
- 2021(Publication Date)
- CRC Press(Publisher)
15Geothermal Energy
AbstractWe will first learn about the origin of Earth, its different inners layers and their characteristics, and the sources of its energy. We will then discuss how Geothermal Energy can be assessed. We will take a look at Geothermal Energy applications, particularly for heating purposes either directly or via heat pumps. Next, we will briefly review the history of Geothermal Energy utilizations and their current status. We will discuss different types of geothermal resources and their characteristics. Then, we will learn about various methods employed to find geothermal resources followed by a discussion on the drilling process to access Geothermal Energy resources and equipment used for this purpose. Next, we will study how Geothermal Energy is converted to electricity in power generation units. We will discuss about vapor-dominated, liquid-dominated, and binary cycles. Finally, we will learn about enhanced or engineered geothermal systems (EGS). We will conclude the chapter with a brief review of the environmental impacts of Geothermal Energy systems.Learning Outcomes
After successful completion of this chapter, you will be able to- explain the origin of Earth, its inner structure, and its energy
- describe the application of Geothermal Energy for heating purposes either directly or via heat pumps
- characterize geothermal resources
- identify various methods used in the exploration of geothermal resources
- describe drilling methods and equipment to access geothermal resources
- explain different types of power generation units for the conversion of Geothermal Energy to electricity (vapor-dominated, liquid-dominated, and binary cycles)
- explain enhanced or engineered geothermal systems (EGSs)
- identify the environmental effects of geothermal power generation systems
15.1 Introduction
Geothermal Energy is a source of thermal energy provided by the inner core of Earth. Unlike most other energy sources, particularly renewable energy sources, this energy is not originated from the Sun. This characteristic of Geothermal Energy provides a unique advantage for geothermal-based energy systems that other renewable energy systems may find hard to compete. Geothermal Energy sources are not intermittent, and unlike many other renewable energy sources, they do not suffer from daily, seasonal, and unpredictable variations. They are available around the clock all year. As a result, they can be used as baseload power generation units with a capacity factor of typically between 70% and 90%.
eBook - PDF- Frank R. Spellman(Author)
- 2014(Publication Date)
- CRC Press(Publisher)
247 6 Geothermal Energy The U.S. Geological Survey has calculated that the heat energy in the upper 10 kilome-ters of the Earth’s crust in the U.S. is equal to over 600,000 times the country’s annual non-transportation energy consumption. Probably no more than a tiny fraction of this energy could ever be extracted economically. However, just one hundredth of 1% of the total is equal to half the country’s current non-transportation energy needs for more than a century, with only a fraction of the pollution from fossil-fueled energy sources. McLarty et al. (2000) Geothermal heat is the only renewable energy source created naturally by the Earth itself. —Kimberly K. Smith, Carlton College If we utilize waste biomass, solar (passive and thermal), wind (on shore), photovoltaic, geothermal, and other renewable resources available to us in the United States, we would exceed the demand (what we need) by at least five times as much energy as we need, all from clean, renewable sources. —Frank R. Spellman On May 30, 2009, at 5:00 p.m., a worker of Terra-Gen Operating Company LLC was seriously injured with second- and third-degree burns to his body while at the com-pany’s remote worksite near Inyokem, California, performing his regular assigned duties as an operation supervisor at the geothermal electric power generation facil-ity. The worker observed a leak of 150 to 160°F geothermal water coming from a temporary diesel engine-powered pump and piping system at a collection pond. He shut off the diesel engine of one of the five temporary pumps at the site, then turned around to walk away. After rotating his body he fell into a pool of heated water. The pressurized water from the leak gouged out an approximately 2-foot-deep depression in the sand and gravelly desert soil. He radioed a coworker and alerted him of the incident. The company’s emergency action plan was implemented. The worker was airlifted to Fresno Regional Medical Center to receive treatment.
eBook - PDFGeothermal Energy
Renewable Energy and the Environment, Second Edition
- William E. Glassley(Author)
- 2014(Publication Date)
- CRC Press(Publisher)
15 2 Sources of Geothermal Heat The Earth as a Heat Engine The earth gives the impression that it is dependably constant. Over the timescale of a human lifetime, little seems to change, as John Burroughs noted when he wrote of, “the unshaken permanence of the hills” of Ireland (John Burroughs 1876, Winter Sunshine, vol. II). The reality, however, is quite contrary to that experience. Every cubic centimeter of the earth is in motion and has been since the earth was formed 4.5 billion years ago. Indeed, the earth is a profoundly dynamic entity. On the timescale of seconds, earthquakes jar the earth; over the time span of a few years, volcanoes appear and grow; over millennia, landscapes slowly evolve; and over millions of years, the continents rear-range themselves on the planet’s surface. The energy source to drive these processes is heat. Although the extrusion of molten rock at volcanoes is perhaps the most dramatic evidence that heat energy exists in the earth’s interior, there is, in fact, a constant flux of heat from every square meter of the earth’s surface. The aver-age heat flux for the earth is 87 mW/m 2 (Stein 1995; see Sidebar 2.1 for a discussion of the units). For a total global surface area of 5.1 × 10 8 km 2 , this heat flux is equivalent to a total heat output of more than 4.4 × 10 13 W. For comparison, it is estimated that the total power consumed by all human activity in 2006 was approximately 1.57 × 10 13 W (US Energy Information Agency 2008). Clearly, heat in the earth has the potential to significantly contribute to satisfying human energy needs. This heat is the source of Geothermal Energy. The remainder of this chapter will consider the origin, distribution, and properties of that heat. ORIGIN OF THE EARTH’S HEAT In order to intelligently use the heat available in the earth, it is important that the sources of that heat be understood.
eBook - PDFGeothermal energy
Utilization and technology
- Dickson Mary H., Fanelli Mario(Authors)
- 2003(Publication Date)
- UNESCO(Publisher)
AIMS 1. To define what is meant by the term Geothermal Energy , and the relationship between Geothermal Energy and geological phenomena of a planetary scale; to evaluate how much of this energy could be recovered and exploited by humankind. To identify the main physical mechanisms occurring in the shallowest parts of the Earth’s crust, how these mechanisms can be harnessed to allow us to extract the Earth’s heat, and the main methods of research that can be used. 2. To show how Geothermal Energy can be utilized in numerous applications, from electricity generation to a wide range of direct heat uses, and the benefits that can be gained from these uses. 3. To emphasize the relatively minor impact of Geothermal Energy on the environment, without underestimating the risks that effectively do exist. 4. Finally, to demonstrate the potential benefits – to a community and/or to a nation – of exploiting indigenous geothermal resources, with emphasis on the importance of first making careful assessments of each specific situation, especially as regards quality of the resource and socio-economic conditions, and also of defining the programme of action. OBJECTIVES When you have completed this chapter you should be able to: 1. define the nature of the Earth’s heat, the phenomena related to the latter and how these phenomena influence the distribution of the geothermal areas in the world 2. define geothermal systems and explain how they function 3. define the main categories of Geothermal Energy 4. discuss the present status of the development of Geothermal Energy in the world 5. discuss the main research methods used in areas of potential geothermal interest 6. discuss the major forms of geothermal utilization 7. discuss the potential impact on the environment of Geothermal Energy. 1 C H A P T E R 1 Geothermal Background Mary H. Dickson and Mario Fanelli Istituto di Geoscienze e Georisorse, CNR, Pisa, Italy
eBook - PDF- Vaughn C. Nelson, Kenneth L. Starcher(Authors)
- 2015(Publication Date)
- CRC Press(Publisher)
253 11 Geothermal Energy 11.1 INTRODUCTION The temperature gradient in the Earth’s crust is 17 ° C–30 ° C per kilometer of depth. For example, deep mines are hot, and most need cooling for the miners. Plumes of magma ascend by buoyancy and force themselves into the crust, generally along the edges of tectonic plates (Figure 11.1), which results in volcanoes. There are huge regions of subsurface hot rocks with cracks and faults that allow water to seep into the reservoir, which then results in hot springs, geysers, mud pots, and fumaroles. Two famous examples are Yellowstone Park and Iceland, which is an exposed sec-tion of the Mid-Atlantic Ridge. Geothermal Energy is not renewable in the same sense as solar, wind, and hydro energy, and the average heat flow of the Earth is a thousand times less than the low-density solar insolation. Another major difference is that solar and wind energy are vari-able on short time periods, and hydro is variable by season; however, Geothermal Energy only declines as heat is taken out, with lifetimes of 100 or more years. Even though the heat flow is small, there are many locations in the world with reservoirs of hot rock with water and steam that can be used for heating and for the generation of electricity. These regions have average heat flow around 300 mW/m 2 compared with a global average of 60 mW/m 2 . In the generation of electricity, the heat flow of the Earth is much less than the removal of energy from the hot rock reservoirs, so it is similar to mining. But the geothermal reservoirs are large, and they will produce energy for years, although some fields have declined and are being recharged with water or new wells with fracking. Other geothermal fields need energy for pumping the fluids from the reservoir.
eBook - PDFOcean Energies
Environmental, Economic and Technological Aspects of Alternative Power Sources
- R.H. Charlier, J.R. Justus(Authors)
- 1993(Publication Date)
- Elsevier Science(Publisher)
38 1 Chapter 9 Geothermal Energy ... there is some encouragement that in the reflection that Oceanography has usually only ruined the reputations of people who dared to speculate too little and thought on too small a change. She has smiled most benignly on those who backed the most daring and outraging possibility. The Great Ocean Business, Brenda Horsfield and Peter Bennet Stone Geothermal Energy A certain amount of thermal energy can be extracted from the earth and used economically to produce electricity. This has been done for some time, including by the United States. Geothermal resources are either submarginal or paramarginal: the first group includes resources whose recovery would cost more than twice as much as the price of other energy sources, and the second group those recoverable at a cost one to two times that price. Geothermal resources exist in hydrothermal convection systems, either vapor dominated or hot water systems; hot igneous systems, either partly molten or hot dry rocks; and conduction-dominated areas, like the Gulf of Mexico geopressured system (Fig. 9.1). BACKGROUND Geothermal means literally heat of the earth, a term coined from the Greek words yq (the earth) and Bt-ppos (heat). This source of heat was in use in ancient Rome to heat villas: the Romans tapped the naturally warm waters and established spas of hot mineral baths throughout their empire as far north as Bath (England) and Trier (Germany). They were not alone in tapping the medicinal properties of such hot springs, Babylonians and Greeks and later the Japanese, also did so. The use of thermal springs was somehow lost during subsequent eras, though in France such resorts as Dax, Ax-les-Thermes, Plombikres, and Chaudes-Aigues boast of continued usage. The Habsburg dynasty founded hydrothermal spas such as Marienbad in Bohemia (now Czechoslovakia), and the Hungarians sank a well to secure natural mineral waters.
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