MIT22_081JF10_lec11b

MIT22_081JF10_lec11b - The Dominant The Dominant Piece of...

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Unformatted text preview: The Dominant The Dominant Piece of the Energy System: Fossil Fuels els Prof. William Green MIT Dept. of Chem. Eng. Sustainable Energy class, Fall 2010 ll 2010 Fossil Fuels DOMINANT for last 100 years World primary energy supply 1850-2000 500 450 400 350 300 250 200 150 100 50 0 1 EJ = 1018J = 0.948 Quads Gas Oil Coal Nuclear Hydro + Biomass EJ/year 1850 1875 1900 1925 1950 1975 2000 Year We live in a fossil-fuel dominated world (80+% of supply in 2000) E.M Drake US Energy System 2002: consume 1020J/yr, ~85% fossil U.S. consumption per capita ~60% higher than most developed countries Fossil Fuels Basics Dig carbon out of the ground, burn it to make heat + CO2. Some heat used directly to heat buildings, reactors. Most heat used in engines, to make electricity or transportation Most transportation Electricity, Electricity, transport from burning fuel in heat engines. engines. A simple overall chemical reaction: reaction: CH2x + (1+x/2) O2 CO2 + x H2O + heat (1+x/2) heat heat 2x 2x x~2 for natural gas, x~1 for oil, x~0.5 for coal x~2 coal Almost always (4+2x) N2 molecules come in with the O2 , go out molecules come in with th ut with the CO2 70 to 150 kg of CO2 emitted per GJ of heat. emitte er GJ of heat. Fossil fuels, created over 108 years by conversion of plant year onversio l an t material in sediments, will probably be mostly consumed in <103 years. years. Energy Problem has many Aspects Sufficient Supply? Will we exhaust conventional petroleum & gas this century? Energy supply system robust to natural disasters? Price Affordability Price / Affordability At current prices, energy is unaffordable to many people. unaffordable to many people. If prices double, world economy crashes! If crashes! Most options significantly increase cost of energy. significantly significantly increase cost of energy y. Security Security Most energy resources remote from population centers. Most centers. Blockades, embargos, upheavals do disrupt supply. Blockades, supply. Diversion of nuclear material to nuclear weapons? Diversion weapons? Environmental Environmental & Health Problems Problems Local pollution from energy a major health issue. Local issue. Significant Water use and Land use issues Significant issues Global Climate Change from CO2 Why & Why Not use Fossil Fuels? Finite but Very Large Amount of Fossil Fuel We are definitely going to run out of fossil fuel energy... in a century or two: Long Term issue Long Term issue Fossil fuels are available now in huge scale Fossil scale (unlike (unlike most other energy sources) energy sources) sources) Greenhouse Greenhouse Effect on Climate Change is the the MediumTerm issue MediumTerm issue We'll "run out of atmosphere" to hold the CO2 before we run out of fossil fuel. Might even run out of capacity to store CO2 2 underground or in ocean... ocean... One Proposal to stabilize CO2: Efficiency+Biofuel+CO2 CCS Courtesy of Ronald Prinn. Used with permission. Short Shortterm PoliticoEconomic Issues PoliticoEconomic Issues Fossil Fossil Fuels are Cheaper than Alternatives es Why ~85% of world's energy from fossil fuels Why fuels How to incorporate social cost into price? How price? A few countries hold almost all the world's world's oil and gas reserves gas Security? BalanceofTrade? Development? BalanceofTrade? Development? Prices Prices fluctuate wildly (inflexible market) market) Adds to risks for new energy supply ventures Adds ventures Energy Energy is lifeblood of economy of economy Governments very heavily involved... Governments involved... Pressing Issues, Now to 2025 ~50% increase in total global energy demand!! global Huge longterm energy infrastructure investments Huge longterm energy infrastructure investments Do these investments work for the planet, long term? Do term? Engineering & policies for largescale conservation largescal onservation Electricity: more efficient production, devices, system? Electricity: system? Capex vs. Opex: Doesn't always favor energy efficiency. Capex efficiency. Can Can Oil production keep up with demand? demand? Probably OK until 2020 if Iraq recovers. Doubtful after that... Probably that... Better recovery from existing fields? Exploit Arctic Ocean? Better Ocean? Unconventional Oil? Other Sources of Liquid Fuels? Unconventional Fuels? ~100% (!) increase in global electricity use. use. Natural Gas? Price? How to transport it? Security? Natural Security? Coal? Greenhouse Gases! Feasible to sequester CO2? Greenhouse er CO Nuclear? Reduce chance of Weapons proliferation? Reduce feration? Facts to Bear in Mind Energy production and use is capitalintensive capital (both renewables and fossil) Capex for power plant, oil platform, automobile, or HVAC Capex HVAC system more than singleyear energy cost. singleyear energy cost. Reluctance to replace equipment until it is worn out. Reluctance out. Multi year lag times in building big energy projects. Multiyear lag times in building big energy projects. Multiyear la imes building bi nerg rojects Energy Energy conversions and separations cost energy energy Often lose a factor of 2 or more in each conversion Often conversion Fuel to electricity Fuel electricity Gas or Coal to liquid fuels Gas fuels Separating CO2 or O2 from N2 costs energy from cost nergy Required for CO2 sequestration. sequestration. Energy Energy Resource Basics Basics Liquid Liquid Fuels are much more valuable than an gases, solids: Liquid Fuel (oil): ~$20.00/MBtu Liquid ~$20.00/MBtu High energy density, easy handling, ideal for transportation idea or transportation Natural Gas: Natural ~ $6.00/MBtu $6.00/MBtu Hard to transport: ~100x the volume per carbon. Hard carbon. location dependent price (free at some remote locations) Very convenient for electricity, buildings Very buildings Coal: Coal: Coal: ~ $1.50/MBtu $1.50/MBtu $1.50/MBtu Difficult Difficult to handle or burn cleanly: ash, slag slag Most Most burned to make electricity electricity Most Most Hydrocarbon Resources are Solids Solids Coal: 1000 Gton carbon Oil Shale: 500 Gton carbon Tar Sands: 400 Gton carbon Biomass: Biomass: 60 Gton carbon/yr carbon/yr Oil: 300 Gton carbon Natural Gas: >100 Gton carbon (~100 years) (~10 ears) ( ~50 years) 50 years) ( ~30 years) 30 years) ( ~30 years) 30 years) ( ~30 years) 30 years) Making Fossil Fuels Less Unsustainable Fossil Fuels are THE REALITY until 2050 Biofuels can substitute for some fossil fuel (but not enough biomass on earth to replace even 50% of current fossil fuel usage). How How to Improve Fossil Fuel Sustainability? Sustainability? Improve Efficiency!! Improve Efficiency!! Fuels last longer, prices lower, reduce security concerns uels last longer, prices l lower, reduce security concerns Reduce Health/Environment/Climate Impacts Reduce Impacts Sequester CO2 Sequester CO2 Improving Improving Fossil Fuel Production/Supply Production/Supply (but this usually increases CO2 emissions!) increases CO missions!) Make Liquid Fuels from Solids, Gas Make Gas Transport Natural Gas Transport Gas Use Difficult Hydrocarbon Resources Use Resources Less Destructive/Dangerous Mining Methods Less Methods Presentation Order Rest of this lecture: Fossil Fuels other than Oil CO2 capture (for sequestration) overview Later in the Course: More on Oil, Liquid Fuels for Transportation Biomass to Liquid Fuels Energy security, environment, economics often in conflict Please see slide 5 in McRae, Gregory. "Cost Modeling and Comparative Performance of Coal Conversion Systems." MIT Energy Short Course, June 14, 2006. Natural Gas is a great fuel... but most is located far from consumers Price recently collapsed in USA due to new production technology W.F. Banholzer, DOE workshop Aug 2007 No one has yet invented a cost - effective way to make gas into a shippable liquid transportation fuel. Courtesy of William F. Banholzer. Used with permission. Technical Challenge: Converting Natural Gas to Liquids Refrigerate to liquified natural gas (LNG) Works, but huge capital investment, requires very large Works, large gas reserve. Costs a lot of energy, CO2 emissions. Gasification then FischerTropsch to diesel: FischerTropsc iesel: CH4 + 1/2 O2 = CO + 2 H2 CH4 H2 n CO + 2n H2 = (CH2)n + n H2O H2O A lot of chemical energy being converted to heat in in remote location, often wasted. Big CO2 emissions. emissions. Other Other CH4 reactions?? reactions?? Several concepts / patents, none successful so far Several far General problem: CH4 is less reactive than products General products Local Environmental Impacts Burning fossil fuels makes local pollution Air pollution (other than CO2) can de dramatically reduced by emission emissioncontrol devices Requires more capital Requires capital Requires ongoing government oversight Requires oversight Often reduces energy efficiency Often efficiency Solid waste from impurities in coal Solid coal Stateoftheart Stateoftheart oil/gas production minimizes production minimizes ctio inimizes environmental impacts, yet... Significant CO2 emissions in production. Significant production. Potential for large accidental leaks. Potential leaks. Work in Arctic and offshore is dangerous. offshor angerous. Coal and tar production is very messy very messy Often big environmental impacts at the mine. Often mine. Tar mining consumes lots of water, energy. Tar energy. Mining is dangerous. Mining dangerous. Tar Sands Locations: Canada, Venezuela, Siberia. Canada, ~85% sand, ~15% hydrocarbon Highly porous: bitumen will flow out if if T>80 C. H:C ~ 1.5 Commercial: ~2 mbd in Canada. Commercial: Surface mining and hotwater washing hot Insitu underground production (inject In steam). Coke/Hydrotreat to make liquid, remove S. Canadian Tar Sands: World's largest earthmoving operation Truck is bigger than a house, costs $5M. ~5 tons of sand and peat moved and ~1 barrel of wastewater produced per barrel of oil. Photo by Alex Abboud on Flickr. At 2 mbd, that is a lot of polluted water! In-situ production from tar sands Diagram of steam-assisted gravity drainage removed due to copyright restrictions. Oil Shale Locations: USA, Brazil. Colorado's Green River formation is most valuable. 15-20% solid kerogen in impervious 15mineral matrix. Does not flow... Pyrolysis of crushed shale T~500 C converts 2/3 of kerogen to heavy oil. Upgrade to remove N,S, reduce viscosity. H:C ~ 1.6 similar to diesel. Mining Oil Shale in the Colorado Rockies ~8 tons of rock mined and ~3 tons of water consumed per ton of oil produced. Maybe new in situ method will avoid mining, reduce water use? Photo by SkyTruth on Flickr. Issues Issues with Tar Sands & Shale Expensive processes Large Capital Costs Need lots of Labor in remote areas: new cities. reas: Consume huge amount of gas, water. ~2 barrels water evaporated per barrel of oil made ade ~100% of Mackenzie Delta gas will soon be used for tar sands production. Environmental impacts CO2 emissions (~30% energy consumed to produce) Waste water (comparable volume to oil made) Waste solids (comparable volume to oil made, unless ss produced in situ) Greenhouse Gas Considerations Greenh Gas idera ion Fossil solids emit more CO2 than oil ssil sol han Biomass routes emit less CO2 than oil omass out le oil Fossil Solids-to-Liquids conversion doubles CO2 ssil nve sio ubl emissions ssio China is committing heavily to Coal hina hea Coal-to-Electricity is the biggest single source of CO2. oalctr cit th sin sour CO Technology to reduce CO2 emissions...at a price chnology re ssions...at pr consum consumers in China, India, US will accept? accep Some sort of political response to Climate Change sor spo hange is coming (probably, eventually).... ntual Carbon caps or taxes? arb caps taxes? Tighter efficiency regulations? cie ations? Largescale CO2 capture and sequestration?? arg scale capt and seq stration? CO2 capture and underground sequestration is possible, but significantly increases both capital & operating costs Please see slide 22 in McRae, Gregory. "Cost Modeling and Comparative Performance of Coal Conversion Systems." MIT Energy Short Course, June 14, 2006. Public acceptance and unresolved policy issues even more problematic CO2 Sequestration Projects Sleipner, Statoil, Norway Courtesy of Statoil. Used with permission. In Salah/Krechba, BP, Algeria Courtesy of BP. Used with permission. Technical Challenge: CO2 capture Option #1: CO2 capture from smokestack 2 CH + 2.5 O2 + 10 N2 = 2 CO2 + H2O +10 N2 N2 low P CO2 dilute in lots of N2, hard to capture low capture Option Option #2: gasify at high pressure (IGCC) (IGCC) 4 CH + O2 + 6 H2O = 4 CO2 + 12 H2 Separate O2 from N2, and CO2 from H2 Separate H2 Option Option #3: oxycombustion oxycombustion 2 CH + 2.5 O2 = 2CO2 + H2O Separate a LOT of O2 from N2 (~5 N2 per C burned) Separate burned) Please see slide 21 in McRae, Gregory. "Cost Modeling and Comparative Performance of Coal Conversion Systems." MIT Energy Short Course, June 14, 2006. Integrated Gasification Combined Cycle Source: Botero, MIT Sustainable Energy Fall 2010 Fossil Fuels I 29 Courtesy of Cristina Botero. Used with permission. Please see slide 30 in McRae, Gregory. "Cost Modeling and Comparative Performance of Coal Conversion Systems." MIT Energy Short Course, June 14, 2006. MIT OpenCourseWare http://ocw.mit.edu 22.081J / 2.650J / 10.291J / 1.818J / 2.65J / 10.391J / 11.371J / 22.811J / ESD.166J Introduction to Sustainable Energy Fall 2010 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. ...
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