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Lecture1910fb - Chemistry 83 11/09/10 Current Energy...

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Chemistry 83 11/09/10 1 Current Energy Technologies http://www.countercurrents.org/world_energy.jpg Fossil fuels (coal, oil, natural gas) serve as the source for ~88% of current world energy production
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Chemistry 83 11/09/10 2 Heat (45%) Transportation (25%) Electricity (30%) There are three broad uses of energy Heat is produced when fossil fuels react with oxygen (called combustion) Solar energy Stoker et al, Energy, Scott Foresman,IL, 1975, 285 Advantages Disadvantage Carbon Geochemical Cycle
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Chemistry 83 11/09/10 3 Science for production of heat from fossil fuels • Combustion is reaction with O 2 • Combustion converts chemical energy to heat energy: Fossil fuel + O 2 CO 2 + H 2 O; H H = BE(reactants) - BE(products) • Highlighted term always dominates since the products of combustion each have two strong bonds: CO 2 (2BE C=O = 374 kcal) and H 2 O (2BE O-H = 220 kcal) H < 0 for combustion of all fossil fuels making them good sources for heat energy • Average H for fossil fuels is -9 kcal/g Tro, 220 1 Natural gas provides the most heat/g of all fossil fuels since it has largest ratio of (C-H bonds/C): C n H 2n+2 ; (2n+2)/n = 2+2/n 2 Hydrogen is likely replacement for fossil fuels for storing energy due to high heat of combustion (3 times that of natural gas). 1 2
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Chemistry 83 11/09/10 4 Energy from any source can be stored and used on demand with hydrogen cycle technology Stoker et al, Energy, Scott Foresman,IL, 1975, 285 Store until needed 2H 2 + O 2 2H 2 O Energy input from any source: 2H 2 + O 2 2 H 2 O http://library.thinkquest.org/29033/voyages/shuttle.jpg Combustion reaction in space Combustion reaction: 2H 2 + O 2 2H 2 O + heat Space shuttles also generate electricity from hydrogen using a fuel cell
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Chemistry 83 11/09/10 5 http://www.nykline.co.jp/engliSH/seascope/200604/image/photo_01.gif Oil is the major energy source for transportation C 1 -C 4 C 5 -C 13 C 10 -C 16 C 15 -C 25 C 20 -C 70 >C 70 http://www.howstuffworks.com/engine.htm Mixture of gasoline (C5- C13 and air is ignited by a spark from spark plug (K). Explosion forces piston downward and causes crankshaft and ultimately the car wheels to rotate. Technology: internal combustion engine converts chemical energy heat energy mechanical energy
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Chemistry 83 11/09/10 6 http://auto.howstuffworks.com/diesel.htm Trucks and trains burn diesel fuel (C15- C25) explosively in diesel engine Diesel engine has no spark plug. Intakes air and
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This note was uploaded on 12/19/2010 for the course CHEM 83 taught by Professor Bonk,j during the Fall '08 term at Duke.

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Lecture1910fb - Chemistry 83 11/09/10 Current Energy...

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