ES105 I Fuels Energy sources and uses A Humans first organism to systematically exploit energy reserves 1 First used chemical energy stored in wood prevalent until 1850 2 Kinetic energy of water harnessed about 2000 years ago grind grain in Egypt 3 Wind energy used to grind grain pump water to grind grain perhaps as long ago as 1000 years B Fossil fuels include coal petroleum and natural gas 1 Fuel burns readily to release energy a what type is released Chemical b what is it converted to Mechanical usually 2 fuels are reduced forms of matter a burning oxidizes the material b maximum number of atoms bonded to oxygen C Recall first law of thermodynamics conservation of energy 1 We convert energy from high grade to lower grade forms a Production of fuel means make available for exploitation 1 Oil isn t available until it has been pumped 2 Coal needs to be mined 3 Turbines in dams produce electricity from the kinetic energy of falling water b Consumption of energy is our utilization of the energy source where we convert it from one form to another and reap the rewards of the conversion 1 We put gasoline in our car and convert chemical energy to forward motion 2 We turn on the light switches and convert electrical energy to light D Fossil fuel reserves and consumption 1 Fossil fuels are still being created today at a very slow rate 2 For our purposes the supply of fossil fuels is limited a non renewable b We are depleting our reserves rapidly perhaps half of petroleum has already been burned in about 100 years c Will become prohibitively expensive in the next 100 years Page 1 of 4 E Coal 1 High grade coal is more than 90 carbon anthracite C s O2 g CO2 g 2 Lower grade coal may have less than 70 carbon a Bitumin nearly 90 carbon b Sub bitumin 70 88 c Lignite almost 70 d Peat precursor of coal about 60 3 Coal formed from incompletely decayed plants a Plants usually revert to CO2 upon death b Swamp conditions with standing water reduce decay potential c Plants become buried compressed 1 Cellulose breaks down releasing small molecules containing most of the hydrogen and oxygen 2 Carbon remained as concentrated deposit d Wide expanses of land surface were swamps in late Paleozoic 1 Climate was generally warmer 2 Great land areas existed in tropical regions e Large reserves of coal are present in the United States 1 Must be mined either open pit or underground 2 commonly hauled to coal fired electrical generators to be burned to make steam to turn turbines to generate electricity f the part of coal that is NOT carbon is source of pollutants 1 much coal is high in sulfur from pyrite a creates aerosol sulfuric acid chief component of acid rain b pyrite can be removed by floatation c sulfur bonded to carbon rich molecules can be removed from stack fumes instead of being released 2 other components include nitrates arsenic mercury g coal is a source of other materials 1 heated to make coke a high carbon fuel used in steelmaking 2 byproducts of coke condensed to coal oil and coal tar that are refined into various organic chemicals Page 2 of 4 F Natural Gas mostly methane CH4 2 O2 CO2 2 H2O heat 1 Natural gas is excellent clean burning fuel 2 Also raw material for plastics and other chemicals 3 Natural gas also contains sulfur and nitrogen which can be released to become acid rain 4 from heat and pressure acting on buried organic matter 5 within geologic traps beneath impermeable rock layers G Petroleum 1 replaced coal as primary fuel by about 1950 2 Complex molecules of hydrocarbon probably not derived from plants 3 Fats of planktonic animals in shallow seas a Rain of dead plankton became layers of incompletely decayed organic matter b Heat and pressure of burial changed animal fat into petroleum 4 combustion products are carbon dioxide and water This is the balanced equation for octane a component of gasoline 2C8H18 18 O2 16 CO2 18 H2O a Air contains nitrogen so some is converted in combustion to nitrogen oxides b Petroleum also contains some sulfur compounds also c Burning gasoline leads to smog 5 Origin of petroleum a Zooplankton residue in marine deposits b Burial pressure and proper temperature yields petroleum c Suitable rock with pore space and permeability sedimentary d Presence of trap cap that prevents petroleum from escaping 1 Structural traps folds and faults 2 Stratigraphic traps porous rock contained in impermeable rock a Sand pinches b Lenses c unconformities 6 Petroleum will probably last for another 100 years a Concentration of location of reserves leads to political and economic vulnerability of industrialized nations that do not have vast reserves b US Petroleum Reservoirs 1 Titusville PA 1860s 2 Lucas Dome Spindletop Dome TX 1900s 3 Signal Hill CA 1930s 4 North Slope AK 1980s Page 3 of 4 II Ultimately Earth energy comes from two sources the sun and heat released internally by radioactive decay A Our power ultimately is nuclear 1 Sun s energy is from a fusion reaction a Hydrogen atoms are converted to helium by nuclear fusion 600 million tons s b Heat of fusion of atoms is the radiant energy passed through space that we receive 2 We receive about 1 73 x 1017 watts of energy from Sun 99 a Internal heat is about 3 2 x 1013 watts 0 02 b Tides generated by gravitational pull of Sun and Moon are about 3 x 1012 watts 0 002 c Nearly 30 of Sun s energy is reflected back to space d Energy of fuels such as petroleum or coal is the energy Sun converted to chemical energy by photosynthesis in plants III Photosynthesis A Solar energy absorbed by green plants B Chlorophyll is a catalyst that allows the conversion of radiant energy to glucose a sugar C6H12O6 6 CO2 6 H2O Sun energy C6H12O6 O2 C This reaction actually has produced the levels of oxygen we have in the atmosphere today Ancient algae in the seas created it by photosynthesis D Rare deep sea vent communities not supported by sunlight 1 energy source from the hot water 2 radioactive decay and gravity 3 heating converts seawater sulfates to hydrogen sulfide a Bacteria thrive on the hydrogen sulfide in the hot water b which are consumed by larger organisms c giving rise to an ecosystem National Geographic October 1977 pp 441 453 E Nuclear Energy 1 uranium created by supernova that was source of the solar system nebula 2 fission of uranium a releases energy and byproducts 1 byproducts can be dangerous for millions of years 2 some byproducts can be weapons fuel b heats steam to turn turbines 3 fusion remains elusive Page 4 of 4
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