Robert A. Huggins Energy Storage Fundamentals, Materials and Applications Second Edition 123 Energy Storage Robert A. Huggins Energy Storage Fundamentals, Materials and Applications Second Edition RobertA.Huggins DepartmentofMaterialsScience andEngineering StanfordUniversity Stanford,CA,USA ISBN978-3-319-21238-8 ISBN978-3-319-21239-5 (eBook) DOI10.1007/978-3-319-21239-5 LibraryofCongressControlNumber:2015945958 SpringerChamHeidelbergNewYorkDordrechtLondon ©SpringerInternationalPublishingSwitzerland2010,2016 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilarmethodologynowknownorhereafterdeveloped. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publicationdoesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexempt fromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. Thepublisher,theauthorsandtheeditorsaresafetoassumethattheadviceandinformationinthis book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, express or implied, with respect to the material contained hereinorforanyerrorsoromissionsthatmayhavebeenmade. Printedonacid-freepaper Springer International Publishing AG Switzerland is part of Springer Science+Business Media (www.springer.com) Preface Introduction Energyisnecessaryforanumberofreasons;themostbasicandobviousinvolvethe preparationoffoodandtheprovisionofheatinordertomakelifecomfortable,orat least, bearable. Subsequently, a wide range of technological uses of energy have emergedandbeendeveloped,sothattheavailabilityofenergyhasbecomeacentral issueinsociety. Theeasiestwaytoacquireusefulenergyistosimplyfinditinnatureaswoodor as a hydrocarbon fossil fuel. But it is advantageous to simply convert what is available in nature into more useful forms. The processing and conversion of raw materials,especiallypetrochemicals,hasbecomeaverylargeindustry. Wood Woodhasbeenusedtoprovideheatformillennia.Itcanbeacquiredasneededby foraging or cutting. When it is abundant, there is relatively little need for it to be stored.However,manysocietieshavefounditdesirabletocollectmorewoodthan isimmediately neededduringwarmperiodsduringtheyear,andtostore itupfor useinthewinter,whentheneedsaregreater,oritscollectionisnotsoconvenient. Onecanstillseethisinsomelocations,suchasthemoreremotecommunitiesinthe Alps.Onemightthinkofthisastheoldestandsimplestexampleofenergystorage. It was discovered long ago that it is possible to heat wood under oxygen-poor conditionssothatsomeofitsvolatileconstituentsaredrivenoff,leavingahighly porous carbon-rich product called charcoal. Charcoal has a higher heating value per unit weight than the wood from which it was produced, approximately 30,400kJkg(cid:2)1,insteadof14,700kJkg(cid:2)1.Thusitismoreefficienttostoreandtouse v vi Preface toproduceheat.Thisisanexampleoftheconversionofasimplefuelintoonewith ahigherenergyvaluebeforestorage. In the nineteenth century 84 % of the energy worldwide, roughly 1018 megajoules, or about 1 yottajoule (YJ) was supplied by wood, charcoal, and crop residues. Coals Naturaldepositsofcarbonwerealsodiscoveredlongago;itwasfoundthattheycan likewisebe readily burnedto produce heat. These solid, carbon-rich materials are oftendescribedasvarioustypesofcoal,withdifferentenergycontents.Thelowest energy content form is called peat, followed by lignite (brown coal), sub-bituminous coal, and hard coal (or anthracite). Their approximate specific energycontentsareshowninFig.1. Fig.1 Energycontentandcarbon,andoxygencontentsofthedifferenttypesofcoal.Basedon USDOEdata Preface vii Theharderformshavesufficientenergycontentsthatitiseconomicaltonotonly store them, but also transport them to other locations. Coals constitute the largest fossil fuel resource in the world, about 5.3 YJ, and are now the most important energy source in a number of places. Where it is available, coal is the least expensivefuel,lessthanoilornaturalgas. As in the case of wood, coals can be heated in an air-poor environment to produceamorevaluableproduct,calledcoke.Cokecanthenbeburnedtoproduce moreheatperunitweightandvolumethanthecoalfromwhichitwasmade,while alsoproducingverylittlesmoke.Becauseofitsporosity,relativelyhighhardness, and higher energy content, coke is used in blast furnaces to reduce iron oxide to molteniron,anearlystepintheproductionofsteel. There is anincreasingconcernabout the toxic contaminants that are originally contained as minor constituents in coals. Because of the concern about such particles getting into the atmosphere, they are often trapped in equipment that is designed to reduce air contamination from coal-burning power plants. They also appear in the coal ash, the non-combustible components in the coal, that are generally stored in open surface ponds or landfills. About 130 million tons of coalashareproducedperyearintheUnitedStates. Other Possible Solid Petrochemical Energy Sources In addition to coal and oil, other related natural carbon sources are known, and some are evidently very abundant in selected locations. These include large tar sandandoil-containingshaledepositsinCanada.Thepursuitofthepossibilityof their extraction and use has elicited strong, and sometimes politically charged, emotions. OneoftheissueshasbeenthedesiretotransporttheproductsacrosstheUnited StatestotheGulfCoast,wheretheywouldberefined,andthenshipped overseas, ratherthanbeingmadeavailableforconsumptiondomestically. These are comparatively dilute sources of carbon, and their extraction and conversion into useful fuels is relatively expensive. In addition, they involve the use and consumption of other materials, such as natural gas and water, in the conversionprocess. Althoughverylargeamountsofthisfamilyofsolidhydrocarbonsareknownina numberofplaces,itmustberecognizedthattheyarealsodepletableresources.The timerequiredfortheirregenerationinnatureisimmense,sotheycanalsoonlybe countedupononce. viii Preface Crude Oil Petroleum,orcrudeoil,isalsoafossilfuel,similartocoal;butithastheadvantage thatitisliquid.Thismakesitmuchmoreversatileforanumberofapplications.The majoruseintheUnitedStatesatthepresenttimeisfortransportation.Itisreadily transportedusingvehicles(ships,trucks,andrail),aswellaspipelines,anditcanbe easily stored in tanks. For a number of years it has been less expensive to extract crude oil, rather than coal, from the earth, although this disparity has varied with both location and time. As readily extracted natural crude oil supplies are con- sumed,itisgenerallynecessarytodigeverdeeper,withgreaterassociatedcosts. Thespecificenergyoftypicalcrudeoilisabout42KJkg(cid:2)1.Thisishigherthan anyotherfossilfuel.Ithasbecomeaworld,commodity,andisshippedalloverthe world. Refineries convertittoa variety ofproducts,such asheavy fuel oil,diesel fuel, gasoline, kerosene, etc. Subsequently, significant amounts of these liquid materialsarealsoconvertedintoavarietyofsolidplastics. Mankind’s use of petrochemical fuels based on crude oil as energy sources is actuallyonlyquiterecent.Table1listsanumberofthemajorcrudeoildiscoveries andtheirdates.Thesehavealloccurredinthelastcenturyandahalf.Thusthe“oil age”hasbeenjustarecentepisodeinthehistoryofmoderncivilization. Table1 Thediscoveryofoil—locationsanddates Earlydiscoveries NearBakku,ontheCaspianSea About1849 Bend,NorthofBucharest,Rumania 1857 OilSprings,Ontario,Canada 1858 DrakewellnearTitusville,PA,USA 1859 Firstmajoroilfieldsdiscovered Spindletop,nearBeaumont,TX,USA 1901 OthersinOklahomaandCalifornia,USA Shortlythereafter DiscoveriesintheMiddleEast Bahrain 1920 KirkukinIraq 1927 GachsaraninIran 1935 DammaminSaudiArabia 1938 AbqaiqinSaudiArabia 1940 GhawarinSaudiArabia 1948–1949 Alaska,USA PrudhoeBay 1968 NorthSeaareas Forties,UK 1970 Ekofisk,Norway 1971 Brent,UK 1971 SouthAmerica Venezuela 1988 Preface ix The Problem of the Depletion of Fossil Fuels As mentioned earlier, fossil fuels are not infinitely available, and the sources that arefoundbecomedepletedastheircontentsareremoved.Itwaslongthoughtthat thiswouldnotbecomeaproblem,fornewoilfieldswouldbefoundtoreplacethose that became depleted. Contrary to this, M. King Hubbert published predictions of futureoilproductioninboththeUnitedStates[1]andtheworld[2]thatindicated that annual oil production would follow bell-shaped curves, reaching a peak, followedbydeclineineachcase. His predictions were not taken very seriously for some time, all seemed to be going well,with oilproductiongrowingeveryyear.ButUSproductionpeakedin 1970anddecreasedasexistingfieldsdepletedfasterthantherateofdiscovery. This is depicted in Fig. 2, which compares actual production to the 1956 prediction by Hubbert that US production would peak about 1970. It is seen that thecorrespondenceisremarkable.Obviously,theUnitedStateswouldbemoreand more dependent upon imported oil, not just because of its increasing energy demand,butalsothedeclineinitsdomesticproduction. Fig.2 Relationship 4 betweenactualannualoil productionandthe predictionmadebyHubbert ar) e in1956.Adaptedfrom[4] y er s p 3 el arr b n o billi 2 n ( o cti u d o Pr Oil 1 S. U. 0 1950 2000 Year