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| INTERACTIVE PHYSICAL SCIENCE |
| LESSON TWO: ENERGY SOURCES |
This lesson identifies the different types of fossil fules and describes how they are used in the production of usable energy |
| Section Theme: Overview |
| What is A Fossil Fuel? You discover that the most commonly used energy source today is supplied by burning three major fossil fuels, coal, petroleum, and natural gas. They are called fossil fuels because they are formed from plant and animal material that was buried in sediment millions of years ago. As time passed, bacterial action, heat, and pressure converted these fossils into hydrocarbons, molecules consisting of carbon and hydrogen. When hydrocarbons are burned, they release heat, water, carbon dioxide, and some pollutants. |
| Nonrenewable resources are those that cannot be replaced after they are used. |
| To get a short introduction to energy sources we have prepared a short movie for you to watch. |
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| To go to your movie on Energy Sources. |
| After you have studied this site and visited each link you may answer questions by: |
| Natural Gas The third fossil fuel is natural gas. Natural gas is a colorless gas consisting mostly of methane (CH4). Methane is commonly found with petroleum deposits, but it is also found by itself. Like deposits of petroleum, natural gas deposits are reached by drilling wells. Natural gas is an important fuel because it is relatively easy to collect from the earth, and, compared with some other fossil fuels, it produces little pollution when burned. It is collected and transported by pipelines to processing plants and then distributed to consumers. Natural gas is most often used for heating and generating electricity. Although natural gas has traditionally been considered a fossil fuel, some scientists have recently challenged this classification. These scientists now hypothesize that natural gas comes from the rocks and dust from which the earth was originally made. The facts that some meteorites contain hydrocarbons and that simple hydrocarbons like methane have been discovered in interstellar space are used as evidence to support this hypothesis. One prediction from the hypothesis is that there are huge quantities of natural gas deep in the earth, much deeper than levels where fossils are found. |
| Coal Coal is a dark brown or black rock that can be burned to release energy. It is used most commonly as a fuel for electric energy plants and for industrial processes, such as iron smelting, that require high temperatures. Coal is found in layers of sedimentary rock thought to be the sites of old peat bogs that were covered with earth and compressed for millions of years. When the layers in coal are split, fossils of plants and animals are often found. Coal is found in many areas of the United States in layered deposits called seams. Coal is removed by two principal methods, depending on the location of the seam in the earth. The first method, strip mining, is used if the seam is near the surface. Strip mining involves stripping away the top layer of soil and then removing the layers of coal underneath. This leaves huge scars on the earth�s surface and should be but most often isn�t followed by reclamation. Reclamation is the process of restoring the land to its original fertile condition. Coal located deeper in the earth is removed by deep mining, the second method of removing coal. In this process, deep shafts are dug into the earth to reach the coal. The specialized machinery shown in this picture is used to dig tunnels directly into the seam. As the coal is dug away, it is taken to the surface of the mine. |
| Petroleum The second fossil fuel you research is petroleum. Black gold is one name for petroleum. It is also called crude oil, or simply oil. Petroleum is a dark brown, thick liquid found in underground pools. These pools are located within layers of porous sedimentary rock, such as sandstone. Oil is collected by drilling wells down to the deposits and pumping the oil to the surface. Some oil wells are drilled as deep as seven kilometers into the earth. Unlike coal, oil cannot be easily used in the same form in which it is taken from the earth. It must first be taken to a refinery a large industrial plant that separates crude oil into products such as gasoline, diesel fuel, heating fuel, petroleum jelly, and asphalt. Oil is separated into various products in a fractionation tower, as shown in this drawing. Within a fractionation tower, the petroleum undergoes fractional distillation. The oil is heated into a gas, which rises in the fractionation tower. Since the products contained in the crude oil vapor have different boiling points, they condense back to a liquid state at different temperatures and levels in the tower. Each product is then pumped from its condensation level in the tower to a separate holding tank. During the distillation process, many petroleum products undergo still another process called cracking. In this process, heat and chemicals are used to break apart the most dense mol-ecules. This process is used primarily to produce more gasoline than is possible through fractional distillation alone. |
| Review Fossil Fules To review your readings on fossil fuels watch the following movie |
| Fossil Fule Link Two |
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| Solar Energy Energy from the sun is called solar energy. Solar energy is a renewable resource. It travels through space as sunlight and provides the earth with both light and heat. Solar energy drives the winds. Solar energy is responsible for the water cycle (the evaporation and precipitation of water that results in rain and snow) that eventually drives hydroelectric generators. |
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| Created by Waller Junior High: 2001 |
| Solar Heating Humans can harness solar energy for many uses. One major use of solar energy is for heating homes and buildings. Many different systems for converting sunlight to heat are now in operation. Most of the systems use either passive solar heating or active solar heating. These two systems differ in the ways that they collect and transfer heat. |
| Homes that are heated as a result of the simple absorption of solar energy use passive solar heating. In this method of heating, no mechanical devices are used to transfer heat from one place to another. |
| More complex solar-heating systems use active solar heating. This method of heating uses mechanical devices such as fans to move heat from one place to another within a building. Most active solar-heating systems include solar collectors, which are devices that gather sunlight and convert it into heat. |
| Wind Turbines The energy, of wind can be converted into electricity with wind turbines. A typical wind turbine consists of a fanlike turbine attached to an electric generator. When wind strikes the turbine, the wind makes the turbine spin. This spins the generator to produce electricity. |
| Geothermal Energy In some places, geological forces push large masses of melted rock, or magma, to within four to six kilometers of the earth�s surface, forming geothermal hot spots. As water seeps down to these hot spots, the water becomes very hot. Sometimes this hot water forces its way back to the earth�s surface, forming geysers or hot springs. |
| Turbines Powered by Steam In most cases, the fluid that turns generator turbines is steam made by boiling water. The fuel used to boil the water is most often a fossil fuel. In some cases the fuel is a nuclear fuel such as uranium. The steam turbines in electric generating plants work just as well on steam from under the earth�s surface as they do on steam from a boiler. Therefore, if steam is released from hot spots, electricity can be generated. In some cases, hot spots do not already contain water and steam. In these situations, water is pumped down to the hot spots to produce the necessary steam to operate the turbines. Geothermal Electric Plants Many countries, including the United States, the Commonwealth of Independent States, Italy, Australia, Japan, and Iceland, already have electric plants that operate on geothermal energy. Some countries, such as Iceland, use geothermal energy directly rather than converting it to electricity. Such direct uses include heating homes, buildings, and household water. The hot water from the earth is even used to heat swimming poois. Like solar or wind energy, geothermal energy is free, if you don�t count the cost of trapping and processing it. Unfortunately, it is only available in a limited number of locations. Many of these are not near places where many people wish to live. Also, the water from some hot spots contains high concentrations of dissolved minerals that are slightly radioactive. This radioactive water is less dangerous than spent fuel from a nuclear reactor, but it must be disposed of carefully. Mining the Earth�s Heat If geothermal energy is to be used as a future energy resource, hot spots must be close enough to the surface to allow inexpensive mining� of the earth�s internal heat. This occurs most commonly where tectonic plates push into each other or pull apart. |
| Hydroelectric Energy In areas where deep bodies of water are collected behind dams, the fluid turning the turbine is water falling through a dam. Electricity produced in this fashion is called hydroelectric energy. The drawing on this page shows the basic arrangement of a hydroelectric dam. Ocean Tide Energy Water flowing down a river can be used to produce hydroelectric energy if that river can be trapped behind a dam. However, this is not the only way to use the energy of moving water. Another method involves the ocean tides, which also represent large masses of moving water. In a few locations on Earth, dams can be used to trap water within a bay area during high tide. Then at low tide, the water is allowed to drain through turbines located in the dams to produce hydroelectric energy. Water Temperature Energy? The oceans also represent a source of energy that is not based on water movement. Instead, this energy source is based on water temperature. The water at the surface of the oceans absorbs large amounts of solar energy. As a result, surface water is much warmer than deeper water. You have probably experienced this difference while swimming. You can even feel it in a swimming pool as you dive to the bottom. A process that uses the differences in ocean water temperature to produce electricity is called ocean thermal energy conversion, or OTEC. |
| Read more about fossil fuel by clicking on Link One and Two |
| Fossil Fule Link One |
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| Solar Energy Link Two |
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| Solar Energy Link One |
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| Read more about solar energy by clicking on Link One and Two |
| Read more about Wind Energy by clicking on Link One and Two |
| Wind Energy Link One |
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| Wind Energy Link Two |
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| Read more about Geothermal Energy by clicking on Link One, Two & Three |
| Geothermal Energy Link One |
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| Geothermal Energy Link Two |
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| RESEARCH OCEAN ENERGY |
| RESEARCH HYDROELECTRIC ENERGY |
| Turbines Powered by Steam Link Three |
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| Nuclear Energy Nuclear energy is very concentrated, but it is also very hard to release in a controlled fashion. Complex devices called nuclear reactors are used to convert nuclear energy into heat. The heat from nuclear energy is used to boil water into steam. The steam is then used to spin a generator turbine that produces electricity. Splitting Up All operating nuclear energy plants use nuclear fission. Fission means �splitting.� In nuclear fission, the nucleus of a uranium or plutonium atom splits when a free neutron crashes into it. When each nucleus is split, it releases heat energy, smaller atoms, and additional neutrons. The addi-tional neutrons go on to split other nuclei to cause a chain reac-tion. This chain reaction must be carefully regulated to keep it under control. Nuclear reactors are designed in many different ways. A simple diagram of one kind of nuclear reactor is shown on this page. Most reactors, regardless of their design, contain the same basic parts. The nuclear chain reaction takes place and is controlled within the reactor core. The reactor core contains uranium (or plutonium) fuel pellets that have been sealed inside long rods called fuel rods. The uranium inside these rods is the fuel for the entire nuclear reactor. Another set of rods is also located inside the reactor core. These rods are called control rods be-cause they are designed to control the nuclear chain reaction. The control rods are filled with materials such as boron and cadmium that can absorb free neutrons. When the control rods are lowered into the reactor core, more neutrons are absorbed, so a smaller number of nuclei are split. This, in turn, slows the chain reaction, and less heat is produced. When reactor technicians �power up� or �power down� a nuclear reactor, they are raising or lowering the control rods. The Moderator In addition to fuel rods and control rods, the reactor core also contains a moderator. The moderator is a substance such as water or graphite that can slow down the speed of free neutrons. If neutrons are moving too fast, they will not cause the urani-um or plutonium nuclei to split. In order to have many of the neutrons travel slowly enough to cause fission, they must bounce off something that can absorb some of their kinetic energy. Neutrons transfer some of their kinetic energy to the atoms of a moderator in collisions. Most commercial nuclear energy reactors in the United States use water as a moderator. The water in nuclear reactors also acts as a coolant. It flows around the fuel rods, where it absorbs heat. If left uncooled, the reactor core could get so hot that it would actually melt, causing radiation to escape. This situation is called a meltdown. Partial meltdowns have occurred at Chernobyl in the Ukraine and at Three Mile Island in Pennsylvania. Reactors also contain shielding to prevent radia-tion from escaping the core. Some shielding materi-als reflect stray neutrons back into the core. Others absorb radiation to protect the structure of the reac-tor and to keep radiation from escaping. Radiation can cause biological damage to the people who work at the reactor. The containment dome, which covers the entire reactor, is designed to prevent radiation from escaping into the environment even if an accident occurs in the reactor. The Three Mile Island accident caused little damage to the environment because the radiation was held in the reactor by the containment dome. By contrast, the Chernobyl reactor did not have a containment dome, and the Chernobyl accident released large quantities of radiation into the environment. |
| Read more about Nuclear Energy by clicking on Link One & Two |
| Nuclear Energy Link One |
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| Nuclear Energy Link Two |
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| Waller Junior High School |