GEOTHERMAL ENERGY. Andrea Galvez, Julie Hirschi, Richard Knight, Paris Kralik, Tyler Gross March 23, Physics 1010

Transcription

1 Physics 1010 GEOTHERMAL ENERGY Andrea Galvez, Julie Hirschi, Richard Knight, Paris Kralik, Tyler Gross March 23, 2015 Physics 1010

2 GEOTHERMAL ENERGY Group eportfolio Project By: Andrea Galvez, Julie Hirschi, Richard Knight, Paris Kralik, Tyler Gross Abstract Thesis: Geothermal energy is an underutilized renewable energy source that is clean and sustainable which could help lessen the world s dependence on coal and oil. This paper will outline the important aspects of geothermal energy today and why it should be used in place of coal and fossil fuels, as fossil fuels pollute and are a finite resource. Geothermal energy is an energy source produced from the earth itself. It is seen in natural occurrences such as geysers to the manmade power plants that harness that energy. The source of that energy comes from deep beneath the surface of the earth from the radioactive decay that slowly generates heat and energy through nuclear fission and fusion processes. Not only are there natural occurrences that display nature s energy but there are many commercial and modern applications that are currently in use from Iceland to California. In Utah, there are also geothermal systems in operation today. Though there are many obstacles to overcome, geothermal could be used as a primary clean energy source. Introduction This paper will discuss the benefits and practicalities of geothermal as a clean alternative energy source to coal and fossil fuels. The following specific topics about geothermal energy will be covered, such as its status as a natural energy source, its historical influence, its sources and the physics behind it, the commercial and modern applications currently in use today in Iceland and California, and the future of where it is heading, specifically in Utah. 1 G e o t h e r m a l

3 Figure 1 - Old Faithful Geothermal as a Natural Energy Source Geothermal is nature s own pressure cooker of energy. The word geothermal means heat from the earth, referring to energy harvested from the earth itself. The most popular and widely viewed examples of geothermal power that occur naturally are the geysers of Yellowstone National Park, such as Old Faithful (Figure 1). The word geyser comes from the Icelandic name for gushing. A geyser is a column of water that is heated below the earth s surface at temperatures above 100 C. At deeper levels, the boiling point of water is higher than at the surface. Deeper water is heated to boiling, at which point it turns to steam and expands, pushing the column of water above it out the geyser opening with great force (Hewitt, 2014). Old Faithful s eruption of steam and water reaches a maximum height of 184 feet in the air, approximately every 35 to 120 minutes every day. Though this is not the largest geyser in the world, it is the one that is most recognized for its consistency, given its name and history, it is the most faithful (Yellowstone National Park, n.d.). The largest active geyser in the world is also in Yellowstone, called the Steamboat Geyser, which produces an eruption of force up to 300 to 400 feet in the air, but its eruptions are rare and not as predictable. The largest recorded geyser in history was the Waimangu Geyser in New Zealand. In the early 1900 s it was said to have erupted with a height of 1,500 feet. With that type of natural force underground, it makes sense that there is potential for energy harness and production (Steamboat Geyser in Yellowstone National Park, n.d.). 2 G e o t h e r m a l

4 Historical Importance The first known use of geothermal energy began more than 10,000 years ago with the Paleo-Indians. They used geothermally heated water, known as hot springs, as a source of warmth, cleaning, and healing (Figure 2). The Romans and Chinese also have many recorded uses of thermal heated pools for bathing, cooking, and cleaning, dating back centuries. Still in use today are many hot springs. People travel all over to obtain the benefits that the minerals of hot springs are said to provide. Three in Utah that people visit regularly are Crystal Hot Springs in Honeyville, Mystic Hot Springs in Monroe, and the Homestead Crater in Midway. Figure 2 - Maori women cooking at Whakarewarewa Many areas with geothermal sources are found in places such as Iceland, Italy, Kenya, New Zealand, Mexico, and the United States. In Boise, Idaho, the first district heating system from a hot springs pumped into town buildings was in use as early as About 30 years later Boise was also the first to commercially use geothermal energy to operate a greenhouse. In the early 1900 s Italy was the first to generate electricity by using a geothermal power plant. In the 1950 s, the first large scale geothermal power plant in the United States was built at The Geysers in California. In 1984, Utah began generating geothermal power from the Roosevelt Hot Springs, now called the Blundell Power Plant near Vernal (Department of Energy, n.d.). 3 G e o t h e r m a l

5 The Source of Geothermal Energy The Earth s Zones and Compositions The earth's layers are broken up into five distinct sections, each with its own unique function and composition (Figure 3). These layers are the crust and the outer most sections. Underneath the crust is the upper mantle followed by the lower mantle. The core of the earth has two sections; the outer core is believed to be molten while the inner core is believed to be in a solid state (HowStuffWorks, n.d.). The crust is the earth s thinnest layer which is comprised up of two types. The first type is continental crust or land; at its thinnest it is only 8 km and at its thickest it is 70 km. This layer is mostly made up of a material called granite. The second type of crust is called oceanic crust which is mostly made up of a type of rock called basalt. At the oceanic crusts thickest point it only measures roughly 8 km. Figure 3 - Formation of Geothermal Energy The upper mantle rests 670 km below the earth s surface. It is comprised mostly of iron, oxygen, silicon, magnesium, and aluminum. In the lower part of the upper mantle is a 4 G e o t h e r m a l

6 combination of solid and melted rock. In the upper part of the upper mantle it consists more of solid materials because it is at a much cooler temperature. The mantle is separated into two sections because of one difference. The lower mantle is made up of solid material, although it is a higher temperature than the upper mantle. This is caused by the immense pressure in which the material is able to stay in a solid form. The temperature in the outer core is between 4,000 C - 6,000 C. It is made up of iron and magnesium, and flows around the outside of the inner core. This flow is said to be the reason for the earth s magnetic field. The inner core is believed to be solid due to the extreme pressure of the planet. It is made up mainly of iron and has a temperature of over 5,000 C. This ball of iron is approximately 2,500 km wide. Extracting heat from the mantle is restricted to areas where the mantle is close to the surface. Areas are restricted not necessarily by law but by our ability to drill at such depths. We are limited in the areas where the crust is thinner to allow for our drills to puncture through the earth s crust to reach this geothermal energy. Volcanoes, earthquakes, geysers, hot pots, and warm springs occur in areas where the mantle is closest to the surface. The immense power contained in the earth is the cause of volcanoes, earthquakes, geysers, and warm springs. All of these are signs of a thinned crust in the area and this power has broken through to the surface. Earthquakes are the shifting of the plates which result in large areas of thinned crust causing more geothermal activity (National Geographic Kids, n.d.). Figure 4 - Map of Geothermal Resources in the US 5 G e o t h e r m a l

7 There are many geothermal plants in California (Figure 4). Here in Utah we have two plants now and with the increase need for power and electricity plans to open and install more plants here are on their way (Scientific American, n.d.). Currently most of the western United States is a pot of gold at the end of a rainbow. There is more geothermal activity in the United States than anywhere else, and just like our oil, it is an untapped resource (Department of Energy, n.d.) (Geothermal Energy vs Fossil Fuels Energy, n.d.). The Physics of Geothermal Energy Primordial Heat and Radioactive Decay The two primary sources of geothermal heat are primordial heat and radioactive decay (Figure 5). Primordial heat is the heat left over from the creation of the earth. The earth was created 4.5 billion years ago when energy and mass of cosmic matter collided. The collision of cosmic matter made earth a large hot piece of space debris. The outside of the earth cooled insulating the heat in the middle. At its core, the earth continues to retain a large amount of its primordial heat (Haven Earth: Geothermal Energy, n.d.). Figure 5 - Heat created in the earth's interior by radioactive decay Some of the elements of earth s original composition were radioactive (Figure 6). They slowly decay generating thermal energy and heat. Most of the radiogenic heat produced comes 6 G e o t h e r m a l

8 from decays of daughter nuclei in the decay chains of uranium-238 and thorium-232, and potassium-40 (Physicsworld.com, n.d.). The current total heat flux from the earth to space is about 44.2 terawatts. Scientists have concluded that half of this heat comes from radioactive decay and half is derived from primordial heat (Video Dailymotion, n.d.). Figure 6 - Basics of Radioactive Decay Nuclear Fission A more descriptive name for radioactive decay is nuclear fission. Nuclear fission is, The splitting of the nucleus of a heavy atom, such as uranium-235, into two smaller nuclei, accompanied by the release of much energy (Hewitt, 2014). Nuclear forces dominate the nuclei of elements. However, the domination of nuclear forces in the nucleus of uranium is fragile. If a uranium nucleus absorbs a neutron, it becomes elongated. The uranium nucleus may continue to elongate due to electrical forces. Once the elongation passes a critical point, the nucleus will separate due to electrical forces and produce smaller nuclei (Hewitt, 2014). 7 G e o t h e r m a l

9 Essentially, one neutron begins the fission process and two or three neutrons are released as a result of fission (Figure 7). The released neutrons can cause other fissions which result in neutrons being released in an avalanche-like fashion. This sequence is called a chain reaction and typically releases 200,000,000 electron volts of energy. The energy released by fission is a million times greater than that released in chemical reactions, but lower than the energy released by nuclear fusion (Hewitt, 2014). The amount of energy released by fission is a million times greater than the amount of energy released in chemical reactions but lower than the energy released in nuclear fusion. Two conditions need to be satisfied in order for a fission reaction to occur. Firstly, the critical mass of the substance needs to be reached. Critical mass is the minimum amount of fissile material needed for a sustained nuclear chain reaction. Secondly, a relatively slow neutron is required in order to initiate the process (Difference and Comparison Diffen, n.d.). Fission occurs mainly for the rare uranium isotope U-235. Scientists separate U-235 from the more common uranium isotope U-238. Although U-238 will absorb neutrons created by fission of U-235, it doesn t undergo fission. For this reason, U-235 is separated from U-238 and it can be a challenging task. In fact, it took two years for enough U-235 to be separated from uranium ore in order to create the fission bomb (otherwise known as the atomic bomb) that was detonated at Hiroshima in 1945 (Hewitt, 2014). Slow neutrons are more likely to be captured by U-235 than by U-238 even though U- 238 are more abundant. The neurons released by fission of U-235 are very fast. U-235 is not able to capture these fast neutrons and so chain reactions don t usually take place in natural uranium. If neutrons could be slowed, U-235 would capture them and the likelihood of a chain reaction occurring in pure natural uranium would increase (Hewitt, 2014). 8 G e o t h e r m a l Figure 7 - Nuclear Fission Process

10 Nuclear Fusion The opposite of nuclear fission is a process called nuclear fusion. Nuclear fusion is, The combination of light atomic nuclei to form heavier nuclei, often with the release of much energy (Hewitt, 2014). The light we see and warmth we feel from the sun are results of fusion. Fusion occurs in the sun s core. It is when hydrogen nuclei collide and fuse into heavier helium atoms. A great amount of energy is released and the temperatures in the core of the sun can reach 15,000,000 Celsius. The fusion of two hydrogen atoms produces helium, which is a heavier element than hydrogen (Figure 8). However, the helium atom s mass isn t exactly equal to the sum of the two hydrogen atoms. This is because a lot of energy has been gained and mass has been lost in the fusion process. This event is described by Einstein s formula E=mc². The energy created equals the mass multiplied by the speed of light squared (ITER - the way to new energy, n.d.). It takes high levels of energy in order for two protons to get close enough together so that nuclear forces can overcome electrostatic repulsion. In the sun s core, high levels of energy are abundant allowing fusion to occur naturally. However, in order to replicate fusion on the earth in a nuclear power plant has not proven to be energy efficient up to this point. This is because of the high level of energy needed in order to push two protons together allowing fusion to occur. In contrast, little energy is needed in order to split atoms in the fission process. The energy released in fusion is at least three times more than the energy fission releases (Difference and Comparison Diffen, n.d.). Figure 8 - Nuclear Fusion Process 9 G e o t h e r m a l

11 Commercial and Modern Applications Iceland Iceland is recognized around the world as a leader in harnessing and utilizing geothermal energy. The largest component in the direct use of geothermal heat in Iceland is space heating. Similarly, space heating is the largest component in the direct use of geothermal resources around the world. Space heating accounts for 37 percent of all direct use development around the world, whereas in Iceland, space heating accounts for 45 percent of all direct use development (Figure 9). Temperatures above 50 C are generally required for space heating. However with the use of geothermal heat pumps, space heating is a practical option at temperatures below 10 C. Currently, 89 percent of Iceland s population warms their households with geothermal space heat. This percentage is expected to rise to 92 percent as more of the population is slowly turning towards geothermal energy. In Iceland, there is only about a one percent share of oil for heating and the share of electric heating is 10 percent. Iceland has been able to import less fuel because such a large percentage of the population is using space heating. In addition, the heating prices in Iceland have dropped. (National Energy Authority of Iceland, n.d.). Utilization of Geothermal Energy in Iceland 2013 Figure 9 - Geothermal Energy in Iceland Iceland is using geothermal resources to generate electricity. About 40 percent of all direct use development in Iceland is being used to generate electricity. In addition, geothermal electricity makes up 24.5 percent of Iceland s total electricity production (Figure 10). The 10 G e o t h e r m a l

12 generation of geothermal electricity has increased in recent years. This is a result of the expansion in Iceland s energy intensive industry. In 2011, the aluminum production industry used 70 percent of the electricity generated in Iceland that year, which is a very high electric energy consuming process. (National Energy Authority of Iceland, n.d.). Power Intensive Industries in Iceland 2011 Figure 10 - Electricity Consumption in Iceland One of most visited places in Iceland is a geothermal spa called the Blue Lagoon (Figure 11). The Blue Lagoon is located in a lava field on the Reykjanes Peninsula in southwestern Iceland. The lagoon was built close to a geothermal power plant. After generating electricity with water that runs near a lava flow, the water is fed into the lagoon and is a byproduct of the power plant. The water is rich in minerals and is thought to help people with skin conditions. The water is renewed every two days and is very clean. The geothermal spa is famous for its recreational and medicinal purposes. (Wikipedia, the free encyclopedia, n.d.). Figure 11 - Iceland's Blue Lagoon Hot Springs 11 G e o t h e r m a l

13 Cal Energy Geothermal energy is also a major supplier of renewable energy in California (Figure 12). California possesses twenty five major geothermal plants within its state, fourteen of which can attain heat beginning at 300 degrees Fahrenheit. The heat from the fourteen plants comes from water underground. The hot water or steam is what creates the electricity inside of these large power plants. The main types of geothermal power plants are dry steam, flash or double flash, and binary cycle power plants. (Background on Geothermal Energy in California, n.d.) Figure 12 - The Geysers Power Plant at Cal Energy Enhanced Geothermal Systems (EGS) is another geothermal resource that can be used to produce electricity. EGS are geothermal reservoirs. They have the potential to create thousands of extra megawatts of electricity in California. It is mechanically produced to create energy. They are used mainly to acquire heat from rocks rather than from water or steam. Figure 13 - Areas in California that use Geothermal Energy 12 G e o t h e r m a l

14 In California s 58 counties, 46 of them have reduced temperature means for direct-use geothermal (Figure 13). Many cities in California have taken advantage of direct-use of geothermal energy. San Bernardino City is known for using the most amount of direct geothermal energy than anywhere else in North America. Imperial Valley and Coso Hot Springs is said to have the potential for more than 4,000 megawatts of power from the plants. When added together, California's geothermal power plants have the installed capacity of about 2,030 megawatts. They produced 4.8 percent of California's total electricity in (Geothermal Energy, n.d.). Modern Applications In Utah, there are multiple geothermal systems in operation. There are three applications of geothermal harvesting that are used which function differently from typical systems. The three types of systems are direct use, heating pumps, and power plants. All geothermal systems work the same way; by extracting the thermal energy underneath the surface of the earth. (Department of Energy, n.d.). The direct use of geothermal energy involves thermally induced water below the earth s surface (Figure 14). A water reservoir a few hundred feet below the earth s surface is usually hot enough for industrial, greenhouse, and aquaculture processes (Renewable Energy World, n.d.). The water is pulled through a well where its heated water is used directly. Direct use geothermal heating is atypical in the state of Utah, with a few minor operations being used in greenhouses and fish farms. 13 G e o t h e r m a l Figure 14 - Diagram of major parts of geothermal power plant

15 Ground source heating and cooling pumps have a higher capacity for energy because, unlike direct use, its energy is powered by using a pump. This method allows energy to flow in and out of whatever is being heated. The two common ways to use a pump are by using a horizontal closed-loop pump and a vertical closed-loop pump. They both operate by utilizing the heat directly under the surface of the earth, which holds constant temperature throughout winter and summer, by pumping that energy through buildings. Horizontal systems are ideal for small buildings and homes because they only take up four feet below the earth s surface while vertical systems are installed about 200 feet below the surface. The most common commercial use of this technology in Utah is vertical heat pumps used to heat schools. Geothermal injection is what is called an open loop systems. It is when water from a reservoir underground is used and water is pumped out and fed into a heating system either in a residential or commercial area. The most powerful method of harvesting geothermal energy is a geothermal power plant. Essentially, it runs like a typical power plant, but uses geothermal energy to run the turbines (Figure 15). Pockets of hot water are being heated by the liquid hot magma below the earth s surface and then pumped up to the surface to turn into electricity. The first step is to drill a hole down to the heated water below and pump the heated water up to the surface as steam. The steam then turns a turbine that powers a generator making an electrical current to provide energy. The water is then pumped into a cooling tower to release off steam and cools to be pumped into an injection well back into the earth to repeat the process. Figure 15 - Diagram of Geothermal Power Plant 14 G e o t h e r m a l

16 There are a few power plants in Utah, all running under one of the following plant types; binary, dry stream or flash. Of all types of energy used in Utah, geothermal renewable energy is one of the lowest producers of electricity comprising 0.6 percent in all. A typical problem with this method of harvesting power is that its production is miniscule, never producing more or less that it currently does. In short, the energy output is directly related to the temperature gradient of the earth below operation. The second problem has to do with efficiency. One could, in theory, produce more energy by digging closer and closer to the earth s core. Geothermal plants are able to deal with plasma, which is an incredible feat in itself. But if too much of this plasma is injected in the turbines, you re looking at melted equipment. The western region of the United States has some of the greatest landscape for geothermal technology. New England is too populated and the southern region has airy soil. The potential of geothermal in Utah in particular lies in that much of the population is condensed along the Wasatch Front leaving the desert, the area that is perfect for geothermal, untapped. In general, the more offset from a tectonic plate a location is, the more heat it will have. While Utah is a better spot for generating geothermal energy than Colorado, California is the best of the three because of its high gradient. Geothermal gradients are higher when you can only dig a few feet and achieve a higher temperature. California is closer to the core of the earth (sea level) and thus has a high gradient. Colorado, which is on a plateau, has a lowest gradient. You might think that an area like Yellowstone may be the greatest place to do this, but while the output of heat is high, it is also inconsistent and occasionally too high. What is the reason for Utah s high potential of geothermal energy use and its low production of this renewable energy? Geothermal sites in Utah, either suitable or potentially suitable for electric power generation, are limited in number given current economics and technology. It s very simple. It all comes down to money. With the fall of the United States economy and shift in the flow of money, geothermal plants have a high initial cost to manufacture but the return rate on profits is high. As for the technology, we currently are developing ways to drill deeper such as the use of plasma drills in order to stretch deeper into the earth s crust and reach the higher geothermal energy. 15 G e o t h e r m a l

17 Conclusion The problem with geothermal power is that it's relatively weak and doesn t work economically on the large scale, like coal; however, its energy tap is constant and its payoff is determined on how much other energy supplies suffer, while coal prices may go up, geothermal prices are set. Also, unlike coal, the output and byproduct are cleaner and healthier to breath. Using heat pumps is the most available and effective form of geothermal energy at this time. As oil reserves throughout the world deplete, geothermal and other natural energy use will increase. Prior to the recession, the United States produced most of the geothermal energy in the world, but since the recession this has slowed. East Africa, Central America, and Asia have taken the lead due to economic growth of these countries. As the United States continues to grow economically, the increase of geothermal energy plants production is inevitable. Money needs to be put into researching better ways to harness the energy of the earth in a less hazardous way than coal and oil. In Utah, though there are many obstacles to overcome, geothermal could be used as a primary clean energy source to replace coal and fossil fuel energy plants, to provide for a cleaner, energy efficient means of supplying power to homes and businesses around the state. 16 G e o t h e r m a l

18 References Background on Geothermal Energy in California. (n.d.). Retrieved from Blue Lagoon (geothermal spa) - Wikipedia, the free encyclopedia. (n.d.). Retrieved March 22, 2015, from Can Geothermal Power Compete with Coal on Price? - Scientific American. (n.d.). Retrieved from Consumer Energy Center - Geothermal Energy. (n.d.). Retrieved from Difference Between Geothermal Energy and Fossil Fuels Energy Difference Between Geothermal Energy vs Fossil Fuels Energy. (n.d.). Retrieved from Earth Heated by Nuclear Energy - Video Dailymotion. (n.d.). Retrieved from Geothermal Basics Department of Energy. (n.d.). Retrieved from Geothermal FAQs Department of Energy. (n.d.). Retrieved from Haven Earth: Geothermal Energy. (n.d.). Retrieved from 17 G e o t h e r m a l

19 Hewitt, P. G. (2014). Conceptual physics: Books a la carte edition (12th ed.). S.l.: Addison- Wesley. A History of Geothermal Energy in America Department of Energy. (n.d.). Retrieved from How Does Geothermal Compare to Other Energy Sources? - HowStuffWorks. (n.d.). Retrieved from ITER - the way to new energy. (n.d.). Retrieved from National Geographic Kids Structure of the Earth. (n.d.). Retrieved from Nuclear Fission vs Nuclear Fusion - Difference and Comparison Diffen. (n.d.). Retrieved from Old Faithful Geyser - Yellowstone National Park. (n.d.). Retrieved from Radiogenic heat in the Earth - physicsworld.com. (n.d.). Retrieved from Renewable Energy World - Renewable Energy News, Jobs, Events, Companies, and more. (n.d.). Retrieved from Space Heating Direct Utilization Geothermal National Energy Authority of Iceland. (n.d.). Retrieved from World's Tallest Geyser Steamboat Geyser in Yellowstone National Park. (n.d.). Retrieved from 18 G e o t h e r m a l

20 Figures 1-15 Background on Geothermal Energy in California. (n.d.). Retrieved from Careers in Geothermal Energy. (n.d.). Retrieved from Distinguished Professors. (n.d.). Retrieved from Electricity Generation Geothermal National Energy Authority of Iceland. (n.d.). Retrieved from Energy Generation in Iceland: Part I Geothermal :: GBIG Insight. (n.d.). Retrieved from Geothermal Energy A Student's Guide to Global Climate Change US EPA. (n.d.). Retrieved from Geothermal energy Renewables and energy security British Geological Survey (BGS). (n.d.). Retrieved from How does Geothermal Energy Work. (n.d.). Retrieved from Iceland Is Pushing Geothermal Boundaries With Magma-Generated Power. (n.d.). Retrieved from ITER - the way to new energy. (n.d.). Retrieved from 19 G e o t h e r m a l

21 Māori women cooking at Whakarewarewa Geothermal energy Te Ara Encyclopedia of New Zealand. (n.d.). Retrieved from Nonrenewable Energy Source: Nuclear - Fission. (n.d.). Retrieved from Old Faithful Geyser - Old Faithful Yellowstone. (n.d.). Retrieved from Radioactive Decay - High School Online Collaborative Writing. (n.d.). Retrieved from THE ENERGY STORY: Chapter 4 - Geothermal Energy. (n.d.). Retrieved from 20 G e o t h e r m a l