Energy Resources Alternative Sources Chapter 14. Figure 14.1.
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<ul><li><p>Energy ResourcesAlternative SourcesChapter 14</p></li><li><p>Figure 14.1</p></li><li><p>Figure 14.2</p></li><li><p>Figure 14.3</p></li><li><p>Figure 14.4</p></li><li><p>Nuclear Power - FissionFission splitting apart the atom releases energyCurrently commercially feasibleUranium-235 fuels most fission reactorsA controlled chain reaction occurs with continuous and moderate release of energyThe energy release heats water within the core of a reactorThis heat is transferred through heat exchangers to outer loops where steam generation is possible for generating power or propulsion</p></li><li><p>Figure 14.5 U-235 Nuclear fission and chain reaction</p></li><li><p>Figure 14.6 Conventional nuclear fission reactor</p></li><li><p>Geology of Uranium95% of uranium found in sedimentary (or metasedimentary) rocksGenerally found in sandstonesUranium is weathered from other rocks and deposited by migrating ground waterMinor amounts of uranium are present in many crustal rocksGranitic rocks and carbonates may be rich in uraniumUranium oxide (U3O8): yellowcake</p></li><li><p>Extending the Nuclear Fuel SupplyUranium-235 is not the only fuel useful for fission-reactorsIt is the most plentiful naturally occurring oneUranium-238 can absorb a neutron and converts to plutonium-239 and is fissionableU-238 makes up 99.3% of natural uraniumUsed for over 90% of reactor grade enriched uraniumBreeder reactor can maximize the production of other radioactive fuelsExpensive and complex</p></li><li><p>Figure 14.7 the nuclear fuel cycle</p></li><li><p>Concerns Related Nuclear Reactor SafetyNuclear reactor safety is a serious undertakingControlled release of very minor amounts of radiation occurMajor concerns are with accidents and sabotageLoss of coolant in the core could produce a core meltdownThis event could allow the fuel and core materials to melt into an unmanageable mass and then migrate out of the containment structureCould result in a catastrophic release of radiation into the environmentReactors must be located away from active faults</p></li><li><p>Figure 14.8 Three Mile Island Reactors</p></li><li><p>Concerns Related to Fuel HandlingMining and processing of uranium ore is a radioactive hazardMiners are exposed to higher levels of radioactivity than the general populationTailings piles are exposed to weather and the uranium is mobilized into the environmentPlutonium is both radioactive and chemically toxicEasy to convert into nuclear weapons materialUranium (enriched) is serious security problem</p></li><li><p>Figure 14.9 Locations of U.S. uranium reserves</p></li><li><p>Radioactive WastesEnergy produced by nuclear fission produces radioactive wastesDifficult to treatNo long-term, permanent storage or disposal sites in operationNuclear power plants are decommissioned once operations ceaseExpensive to decommission these plantsAbundant radioactive contaminated material associated with these plants that must be permanently stored somewhere and safely</p></li><li><p>Figure 14.10</p></li><li><p>Risk Assessment and Risk ProjectionNo energy source is risk-free with acceptable risk</p><p>8% of U.S. energy is supplied by nuclear power in 2002</p><p>Nuclear-plant cancellation is not without its costs</p><p>Nuclear plants have lower fueling and operating costs than coal-fired plants</p><p>Reliance on nuclear power varies widely</p><p>Different people weigh the pros and cons of nuclear fission power in different ways</p></li><li><p>Figure 14.11 U.S. nuclear power plants</p></li><li><p>Figure 14.12 Percentage of electricity generated by nuclear fission varies greatly by country</p></li><li><p>Nuclear Power - FusionNuclear fusion is the opposite of nuclear fissionSun is a gigantic fusion reactorFusion is a cleaner form nuclear power than fissionFusion involves combining smaller nuclei to form larger onesCan produces abundant energyHydrogen is plentiful and is the raw material requiredFusion difficult to achieve given current technology Theoretical not yet economically attained</p></li><li><p>Figure 14.13 One nuclear fusion reaction</p></li><li><p>Solar EnergyAbundant solar energy reaches the earths surfaceBe dissipated in various waysSolar energy is free, clean, and a renewable resourceLimitations are latitude and climateSolar HeatingPassive solar heating: no mechanical assistanceActive solar heating: mechanical circulation of solar-heated waterSolar ElectricityPhotovoltaic cells</p></li><li><p>Figure 14.14 Distribution of solar energy</p></li><li><p>Fig. 14.15 Solar heating</p></li><li><p>Figure 14.16 A solar cell for the generation of electricity</p></li><li><p>Figures 14.17 a and b</p></li><li><p>Figures 14.18 a and b</p></li><li><p>Geothermal PowerThe earth contains a great deal of heat, most of it left over from its early history, some generated by decay of radioactive elements in the earthInterior of the earth is very hotAbundant source of heat and hot waterMagma rising into the crust bring abundant heat up into the crust as geothermal energyHeat escaping from the magma heats water and the water convectively circulates</p></li><li><p>Figure 14.19 Geothermal energy</p></li><li><p>Figure 14.20 Lone Star Geyser, Yellowstone</p></li><li><p>Figure 14.21 Geothermal power plants worldwide</p></li><li><p>Geothermal PowerApplications of Geothermal EnergyCirculating geothermal water (not steam yet) through buildings to heat themUse the hot geothermal water to raise the temperature of other water to reduce cost of heating that waterGeothermal water (stream) can be used to run electric generatorsEnvironmental ConsiderationsSome locations have sulfur gases in the geothermal fluidsOther chemical (caustic) elements may be present that can clog geothermal circulation systems</p></li><li><p>Figure 14.22 The Geysers geothermal power complex </p></li><li><p>Figure 14.23 Mammoth Terraces, Yellowstone</p></li><li><p>Limitations on Geothermal PowerFirst, most geothermal fields have limited life times and taper offSecond, geothermal fields are stationary not mobileThird, not many geothermal sites are suitable for energy production</p></li><li><p>Alternative Geothermal SourcesMany areas away from plate boundaries have high geothermal gradientsThese areas contain hot-dry-rock type geothermal resourcesDeep drilling into such rocks may produce appreciable amounts of geothermal energy</p></li><li><p>Figure 14.24</p></li><li><p>HydropowerFalling or flowing water has long been used to produce energy for humansHydroelectric power produces less than 5% of U.S. energy requirementTypically, a stream is dammed and the discharge is regulated to produce electricityHydropower is clean and non-pollutingHydropower is renewable as long as streams have water flowing in them</p></li><li><p>Figure 14.25</p></li><li><p>Figure 14.26</p></li><li><p>Figure 14.27</p></li><li><p>Limitations on Hydropower DevelopmentReservoirs tend to:Silt upIncrease surface area exposed to evaporationDestroy habitatsEncourage earthquakesExpensive to buildReservoirs are stationary power sources</p></li><li><p>Tidal Power and Ocean Thermal Energy ConversionLimited energy production possibleNot enough difference in high-tide versus low-tide displacement of water (only about 1 meter difference)Most economic potential requires about 5 meters differenceOcean thermal energy conversion (OTEC) is another clean, renewable technology. It exploits the temperature difference between warm surface water and the cold water at depth</p></li><li><p>Figure 14.28 Tidal-power generation</p></li><li><p>Figure 14.29 Ocean thermal energy conversion</p></li><li><p>Wind EnergyThe winds are ultimately powered by the sun, and thus wind energy can be viewed as a variant of solar energyClean and renewable energy resourceMany technological improvements have increased the energy production from windmillsAreas of best wind generation potential tend to be far from population centers that would benefit from themWind Farms are large scale operations producing about 1 megawatt per windmillAbundant small scale windmills involve small wind turbines lifting water on a ranch or farm</p></li><li><p>Figure 14.30 The windiest places in the United States</p></li><li><p>Figure 14.31 Art driven by wind, Palm Springs, California</p></li><li><p>Figure 14.32 Wind power capacity</p></li><li><p>BiomassBiomass refers to the total mass of all the organisms living on earthBiomass energy uses discarded waste material that is burned as a fuel to produce energy Biomass fuels include wood, paper, crop waste, and other combustible wasteAlcohol, as a fuel, is produced from grains, such as cornMixed with gasoline to form gasoholQualifies as a renewable resource</p></li></ul>
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