Th ominant Piece of the T e D
advertisement
The Th e Dominant Dominant Piece of the Energy System: Fossil Fuel elss Prof. William Green MIT Dept. of Chem. Eng. Sustainable Energy class, Fallll 2010 2010 Fossil Fuels DOMINANT for last 100 years EJ/year 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 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. – M Most ost heat used in engines, to make electricity or transportatio transportation n � � � � Electricity, transport from burning fuel in heat engines. Electricity, engines. A simple overall chemical reaction: reaction: – CH2x – (1+x/2) O2 � CO2 + x H2O + he heat h eat at 2 2x x + (1+x/2) – – xx~2 ~2 for natural gas, x~1 for oil, x~0.5 for coal coal – – Almost always (4+2x) N2 molecules molecules co come me in in wi with th th the O2 , go out ut with the CO2 – – 70 to 150 kg of CO2 emit emitte ted per er GJ GJ of of he heat at.. � � Fossil fuels, created over 108 ye year ars by con onve vers rsio ion of pla lant nt material in sediments, will probably be mostly consumed in <103 ye year ars. s. Energy Problem has many Aspects � Sufficient Supply? – Will we exhaust conventional petroleum & gas this century? – Energy supply system robust to natural disasters? � Price P rice / Affordability Affordability – At current prices, energy is u un na affffo orrd da ab blle e to to ma many ny pe peop ople le.. – IIff prices double, world economy crashes! crashes! – Most options significant significantly significantl lyy in incr crea ease se co cost st of of en ener ergy gy. y. � Security Securit y –M Most ost energy resources remote from population centers. centers. –B Blockades, lockades, embargos, upheavals do disrupt supply. supply. –D Diversion iversion of nuclear material to nuclear weapons? weapons? � Environmental E nvironmental & Health Problems Problems – LLocal ocal pollution from energy a major health issue. issue. –S Significant ignificant Water use and Land use issues 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: Lo Long ng Te Term rm is issu sue e – –F Fossil ossil fuels are available now in huge scale scale (unlike most other energy (unlike energy sources) sources) sources) � � G Greenhouse reenhouse Effect on Climate Change is the the Medium­­Te Medium Term rm is issu sue e – – 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. Short­­term Politico Short Politico­­Ec Econ onom omic ic Is Issu sues es � Fossil F ossil Fuels are Cheaper than Alternatives es –W Why hy ~85% of world’s energy from fossil fuels fuels –H How ow to incorporate social cost into price? price? � A few countries hold almost all the world’s world’s oil and gas gas reserves – Security? Balance­ Balance­of­ of­Tr Trad ade? e? De Deve velo lopm pmen ent? t? � Prices P rices fluctuate wildly (inflexible market) market) –A Adds dds to risks for new energy supply ventures ventures � Energy E nergy is lifeblood of economy of economy –G Governments overnments very heavily involved… involved… Pressing Issues, Now to 2025 � ~50% increase in total g gllobal obal energy demand!! – H Hu ug ge e lo long ng­­tte errm me en ne errg gyy iin nffrra assttrru uccttu urre e iin nvve essttm me en nttss – D Do o these investments work for the planet, long term? term? � Engineering & policies for large­ large­s sc ca alle co on ns se errv va attiio on n – E Electricity: lectricity: more efficient production, devices, system system?? – C Capex apex vs. Opex: Doesn’t always favor energy efficiency. efficiency. � Can C an Oil production keep up with demand? demand? – P Probably robably OK until 2020 if Iraq recovers. Doubtful after that… that… – B Better etter recovery from existing fields? Exploit Arctic Ocean? Ocean? – U Unconventional nconventional Oil? Other Sources of Liquid Fuels? Fuels? � ~100% (!) increase in global electricity use. use. –N Natural atural Gas? Price? How to transport it? Security? Security? – Coal? G Greenhouse reenhouse Gases! Feasible to sequester er CO CO2? – Nuclear? R Reduce educe chance of Weapons prolife fera rati tion on?? Facts to Bear in Mind � Energy production and use is capital­ capital­intensive (both renewables and fossil) – –C Capex apex for power plant, oil platform, automobile, or HVA HVAC C system more than single­ single­yye ea arr e en ne errg gyy cco osstt.. – –R Reluctance eluctance to replace equipment until it is worn out out.. – Multi – Mult Mu lti­ i­ye yyear ear ar la llag ag ttimes imes im es in in bu building b uilildi ding ng bi big b ig e energy nerg ne rgy p projects roje ro ject cts. s. � � E Energy nergy conversions and separations cost energy energy – –O Often ften lose a factor of 2 or more in each conversion conversion � � F Fuel uel to electricity electricity � � G Gas as or Coal to liquid fuels fuels – – Separating CO2 or O2 fr from om N2 co cost sts ene nerg rgyy � � Required for CO2 se sequ ques estr trat atio ion. n. Energy E nergy Resource Basics Basics � � Liquid Fuels are much more valuable than Liquid an gases, solids: – – L Liquid iquid Fuel (oil): ~$20.00/MBtu ~$20.00/MBtu � High energy density, easy handling, id idea eal for or tr tran ansp spor orta tati tion on – – N Natural atural Gas: ~ $6.00/MBtu $6.00/MBtu � � H Hard ard to transport: ~100x the volume per carbon. carbon. location dependent price (free at some remote locations) � V Very ery convenient for electricity, buildings buildings – Coal: Coal: Coal: � � � � ~ $1 $1.50/MB $1.50/MB .50/MBtu ttu u Difficult D ifficult to handle or burn cleanly: ash, slag slag Most M ost burned to make electricity electricity Most M ost Hydrocarbon Resources are Solids Solids – – – – – – – – – – – – Coal: 1000 Gton carbon Oil Shale: 500 Gton carbon Tar Sands: 400 Gton carbon Biomass: B iomass: 60 Gton carbon/yr carbon/yr Oil: 300 Gton carbon Natural Gas: >100 Gton carbon ((~ ~1 10 00 ye ea arrs s)) ( ~5 50 0y ye ea arrs s)) ( ~3 30 0y ye ea arrs s)) ( ~3 30 0y ye ea arrs s)) ( ~3 30 0y ye ea arrs s)) 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 H ow to Improve Fossil Fuel Sustainability? Sustainability? – – IImprove mprove Efficiency!! Efficiency!! � Fuels uels llast ast llonger, onger, prices prices lllower, ower, reduce reduce security security concerns concerns � R Reduce educe Health/Environment/Climate Impacts Impacts –S Sequester equester CO2 CO2 � � IImproving mproving Fossil Fuel Production/Supply Production/Supply (but this usually increase increasess CO CO2 emi miss ssio ions ns!) !) –M Make ake Liquid Fuels from Solids, Gas Gas –T Transport ransport Natural Gas Gas –U Use se Difficult Hydrocarbon Resources Resources – LLess ess Destructive/Dangerous Mining Methods 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) – –W Works, orks, but huge capital investment, requires very larg large e gas reserve. Costs a lot of energy, CO2 emissions. � � Gasification then Fischer­ Fischer­Tr Trop opsc sch to die iese sel: l: – –C CH4 H4 + 1/2 O2 = CO + 2 H2 H2 – – n CO + 2n H2 = (CH2)n + n H2O H2O – A lot of chemical energy being converted to heat iin n remote location, often wasted. Big CO2 emissions. emissions. � � O Other ther CH4 reactions?? reactions?? –S Several everal concepts / patents, none successful so far far –G General eneral problem: CH4 is less reactive than products products Local Environmental Impacts � Burning fossil fuels makes local pollution – Air pollution (other than CO2) can de dramatically reduced by emission­­control devices emission � Requires Requires more capital capital � R Requires equires ongoing government oversight oversight � O Often ften reduces energy efficiency efficiency – – S Solid olid waste from impurities in coal coal � � State­of­ State­ of­the­ the­a art rt oil/gas produ production ctio ct io n m minimizes inim in imiz izes es environmental impacts, yet… – – S Significant ignificant CO2 emissions in production. production. – – P Potential otential for large accidental leaks. leaks. – – Work in Arctic and off­ off­ssh ho orre is da an ng ge erro ou uss.. � � Coal and tar production is ve very ry me mess ssyy – – O Often ften big environmental impacts at the mine. mine. – – T Tar ar mining consumes lots of water, energy. energy. – – M Mining ining is dangerous. dangerous. Tar Sands Locations: Canada Canada,, Venezuela, Siberia. � ~85% sand, ~15% hydrocarbon � Highly porous: bitumen will flow out if if T>80 C. H:C ~ 1.5 � Commercial Commercial:: ~2 mbd in Canada. � – Surface mining and hot­ hot­water washing – In In­­situ underground production (inject 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. 1515-20% solid kerogen in impervious mineral 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. Photo by SkyTruth on Flickr. Maybe new in situ method will avoid mining, reduce water use? IIsssues sues with Tar Sands & Shale � Expensive processes – Large Capital Costs – Need lots of Labor in remote arre eas: as: new cities. – Consume huge amount of gas, water. � ~2 barrels water evaporated per barrel of oil mad ade e � ~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) Gr Green eenh house Ga Gass Consider idera atio ion ns Fossi ssill sol solids emit more CO2 tha han n oil – Biom omass ass rou outtes emit lle ess CO2 than oi oill Fossi ssill Solids-to-Liquids conv nve ersi sio on doub ublles CO2 emissi ssio ons Chi hina na is committing he hea avily to Coal – Coal oal--to-Elect ctrrici citty is th the biggest si sin ngle sou sourrce of C CO O2. – Tech chn nology ology to re reduce CO2 emissi ssion ons…at s…at a pr price consu con sum mers in China, India, US will acce accep pt? Some so sorrt of political resp spo onse to Climate Cha hang nge e is coming (probably, event ntua uallly)…. – Car arb bon cap caps s or tta axes? xes? – Tighter effici cie ency regulat atiion ons? s? – Lar arg gescal scale e CO2 cap captture an and d se seq quest strrat atiion on? ?? 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 N N2 2 � – llow ow P CO2 dilute in lots of N2, hard to capture capture � O � Option ption #2: gasify at high pressure (IGCC) (IGCC) 4 CH + O2 + 6 H2O = 4 CO2 + 12 H2 –S Separate eparate O2 from N2, and CO2 from H2 H2 � � O Option ption #3: oxycombustion oxycombustion 2 CH + 2.5 O2 = 2CO2 + H2O –S Separate eparate a LOT of O2 from N2 (~5 N2 per C burned) 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.
