Class18

Class18 - Current Energy Technologies Fossil fuels (coal,...

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Current Energy Technologies
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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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http://resources.edb.gov.hk/biology/english/images/environment/carbon_cycle2.jpg Fossil fuels are produced very slowly (millions of years) by the carbon cycle
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Heat (45%) Transportation (25%) Electricity (30%) There are three broad uses of energy
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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
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Energy can also be obtained from directly or indirectly from biomass by combustion Solar energy Stoker et al, Energy, Scott Foresman,IL, 1975, 285 Advantages Disadvantage (Biomass)
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Tro, 220 1 Natural gas provides the most heat/g of all fossil fuels since it has largest (number 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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http://www.nykline.co.jp/engliSH/seascope/200604/image/photo_01.gif Oil is used for transportation (easy to store) C 1 -C 4 C 5 -C 13 C 10 -C 16 C 15 -C 25 C 20 -C 70 >C 70
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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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http://www.ueet.nasa.gov/StudentSite/engines.html Aircraft burn jet fuel (C10-C16) in jet engine Brings air in Raises air pressure Raises air T and P Provides energy for fan and compressor Adds by- pass air Provides thrust Spark plug ignition
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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 compresses it, and then injects the fuel directly into the combustion chamber (direct injection). Ignition by heat of the compressed air.
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Science for generating electricity Rotation of a wire loop in a magnetic field causes delocalized electrons to move in the loop (conversion of mechanical energy to electrical energy) Electron motion in wire reverses direction every 180º of loop rotation producing alternating current (AC). members.shaw.ca/len92/acdc_inside_generator.gif www.aerospaceweb.org/question/propulsion/jet/generator.jpg Requires energy source to rotate the shaft.
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A simple turbine is a shaft with blades attached to it. Moving fluid causes the blades, shaft, and wire loop to rotate and thus produce AC electricity.
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This note was uploaded on 10/19/2011 for the course CHEM 83 taught by Professor Bonk,j during the Fall '08 term at Duke.

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Class18 - Current Energy Technologies Fossil fuels (coal,...

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