Smart Grids Versus the Achilles' Heel of Renewable Energy

12 Pages·2014·1.23 MB·English

CONTRIBUTED
P A P E R
Smart Grids Versus the Achilles’
Heel of Renewable Energy:
Can the Needed Storage
Infrastructure Be Constructed
Before the Fossil Fuel Runs Out?
This paper summarizes the need for large-scale investments in energy storage with a
view on the long term wherein significant energy needs of the world are met by
renewable energy sources.
ByWilliam F. Pickard, Life Fellow IEEE
ABSTRACT|Inthispaper,primafacieevidenceispresentedto must next be stored so as to be available in
demonstratethat,bythecloseofthiscentury:1)theworldwill time’’VReginald A. Fessenden, 1910 [1].
beapproachingexhaustionofitssupplyofrecoverable fossil
fuel;2)theenergyshortagesengenderedtherebycanreliably This truism was beautifully illustrated in a recent
be avoided only if immediate massive steps are taken to modeling exercise by Budischak et al. [2] who analyzed
actualize the development and manufacture of important, as fouroperatingyearsofa72-GWAmericangridsystemand
yet unproven, components of a global smart energy system; showed that, with rare exceptions, it could have been
and3)theworldover,thereislittleevidence(asmeasuredby powered solely by a mix of photovoltaics, offshore wind,
funding committed for development and demonstration) that andinlandwindif:1)therenewablegenerationwassized
thekeygovernmentsareseriouslyconcerned. to be approximately 200 GWpeak; and 2) the grid was
buffered by approximately 875 GWh of energy storage
KEYWORDS|Massiveenergystorage;renewableenergy;smart capacity.Thatis,eachgigawattofgeneratingcapacityhad
grid tobebackedby12GWhofstoragecapacity;and,evenso,
there were five brief periods when the renewable genera-
tionwouldhaverequiredsignificantfossilbackup.Never-
I. INTRODUCTION
theless, this exercise did show that a renewably powered
grid, which made no pretense of being ‘‘smart,’’ could be
‘‘The problem of the commercial utilisation, for
successfully operated given massive energy storage. It is
the production of power, of the energy of solar
only reasonable toassumethat asmart grid could beope-
radiation, the wind and other intermittent natural
ratedevenbetter.Thisisgoodnewsforordinarycitizens,
sources is a double one. The energy of the sources
for pundits who comment on energy questions, and also
mustfirstbechangedsoastobesuitableinform;it
for fossil-fuel geologists who keep predicting imminent
supply shortages. But it leaves policy makers a bit up in
the air.
ManuscriptreceivedJuly20,2013;revisedApril4,2014;acceptedApril4,2014.Dateof First, a grid (smart or otherwise) that requires fossil
publicationMay16,2014;dateofcurrentversionJune16,2014. backup for its reliable performance is neither renewable
TheauthoriswiththeDepartmentofElectricalandSystemsEngineering,Washington
University,SaintLouis,MO63130USA(e-mail:[email protected]). nor sustainable. And a nation that opts also for essential
DigitalObjectIdentifier:10.1109/JPROC.2014.2316359 fossil-fuel backup while claiming to make a green
0018-9219(cid:2)2014IEEE.Personaluseispermitted,butrepublication/redistributionrequiresIEEEpermission.
Seehttp://www.ieee.org/publications_standards/publications/rights/index.htmlformoreinformation.
1094 Proceedings of the IEEE|Vol.102,No.7,July2014
Pickard:SmartGrids Versus the Achilles’Heel of Renewable Energy
Table1PredictedWorldProductionofFossilFuel.SevenIndependentResearchGroupsWereSelectedforInclusion;TheyPresentedTheirPredictions
Differently
transition, may not be taking its task seriously enough. If not occur until the latter half of the century. By contrast,
thefossilbackupisnotCO neutral,thenemployingitmay industrial or agency projections seem more optimistic:
2
simultaneously drive climate change and invalidate the 1) BP’s ‘‘Energy Outlook 2030’’ [3] foresees increasing
model used to predict the renewable generation. If the worldproductionofpetroleumliquids(p.34),naturalgas
fossilbackupisassumedtocomewithcarboncaptureand (p.44),andcoal(p.56)overtheperiod2010–2030;2)the
storage (CCS), then a major development effort for CCS U.S. Energy Information Agency’s ‘‘Annual Energy Out-
will be needed; and this could negatively impact the re- look’’ [4] foresees monotonically increasing production of
sourcesavailabletodevelopthemassiveenergy/electricity petroleumliquids(Fig.19)overtheperiod2010–2035;and
storage(MES)thatwillbeessentialtomatchintermittent 3)theInternationalEnergyAgency’s(IEA’s)‘‘WorldEner-
renewable generation to variable consumer demand. gy Outlook’’ [5] foresees modest production increase in
Second, no one knows for sure when fossil-fuel pro- petroleum liquids(Fig. 3.15), modest production increase
ductionwillhavedroppedcatastrophicallyandaswitchto innaturalgas(Table4.4),and,barringCO amelioration,a
2
renewable energy become unavoidable.1 However, in the significantincreaseincoalproduction(Table5.4)by2035.
past several years, there have been made a number of in- Thesetwosetsofpredictionsarenotinblatantcontradic-
dependent scholarly studies of anticipated depletion tion because the first focuses on the latter half of this
scenarios: seven of these are summarized in Table 1. The centurywhilethesecondworriesonlyaboutthenext20or
clear message of these projections is that annual world soyears.Infact,virtuallyeveryoneagreesthatfossilfuel’s
outputsofcoal, oil, and natural gasare now nearing their daysarenumbered,andeventheIEA’sguardedoptimismis
peaks but that really serious constrictions in supply may qualified by a realistic ‘‘the rate of oil production has ex-
ceededthatofdiscoveriesbyawidemarginformanyyears’’
1Nuclear energy will not, in this contribution, be considered [5,p.105].2Whatuncertaintythereisliesinknowingthe
renewableeventhough,withreprocessingandbreederreactors,itmight precisedateby which aswitchtorenewablesshouldhave
prospectivelybecomepartiallysoandprovidemanycenturiesofbase-load
been completed. Section II discusses the obligations this
power.ThisdecisionwasbaseduponthefailureoftheUnitedStatesto
develop tested, functioning, permanent repositories for civilian nuclear uncertaintyplacesupongridplanners.
wasteVdespitethefactsthattheneedhasbeenclearformorethan60
yearsandthat,undertheguidelinesoftheInternationalAtomicEnergy
Agency, it issupposedto doso. Additionally, barring asyet prospective 2Where appropriate, pointers will be given to page (p.), section
output-agile fission generators, matching generator output to consumer (Sec.),chapter(Ch.),equation(eq.),figure(Fig.),table(Table),appendix
demandcouldstillrequirevastMES. (App.),orexperiment(Exp.)ofthepertinentreference.
Vol.102,No.7,July2014|Proceedings of the IEEE 1095
Pickard:SmartGrids Versus the Achilles’ Heel of Renewable Energy
Third, massive electricity/energy storage (MES) does backup that a major catastrophe merits are unavailable.
notatpresentexistonthescaleneeded.Tobeginwith,the Nor do present-day grids fragment gracefully into smart
scale needed is unclear. Will it entail, as envisioned by microgrids, each with its own robust supply of massive
Armaroli and Balzani [6], a world largely powered by energy/electricity storage (MES).
electricity?Orwillitinstead,asenvisionedbyAhlgren[7], In the envisioned smart grid of the future, supply and
leavetransportationlargelypoweredbysyntheticcombus- demand will be matched by balancing renewable gener-
tibles?Andwillitbeaworldoflowenergyintensityanda ation, consumer demand, and colossal MES.
modest total population or an overcrowded world charac- 1) Renewable generation is unlike fossil-fuel gener-
terized by profligate energy use? To be optimistic, let us ation.Onceitsgeneratorsareinplace,theydonot
assume that it will it be an affluent but frugal society in have to be fueled by the utility. Sunshine, wind,
which10kAy(cid:2)1ofgrossdomesticproduct(GDP)requires tidal flow, and their ilk are fluxes of energy not
a metric tonne of oil equivalent energy (toe), rather like produced by man, but ratherintercepted by man.
what might be the case for the European Union in 2035 If man does not intercept them and capture their
[5, Fig. 2.4].3 Then, a 50 kAy (cid:2)1 per person GDP must energy,thatenergypassesonandbecomesoppor-
be backedbyanaverageper-personrenewablegeneration tunitylost.Becausein-placerenewablegeneration
of 5 toe y(cid:2)1 )6.6 kW(cid:3)5 kW. And, as the results of has but minor operating costs yet yields valuable
Budischaketal.reveal[2],thisshouldbebufferedatarate energy,itsoperatorhasastrongmotiveforcaptur-
somewhatabove12kWhofstorageperkilowattofaverage ing and selling as much as possible given the
generation to compensate for source intermittency. How- available generating capacity.
ever,inthe United States,lengthygrid outagesarerather 2) Consumer demand has some flexibility. To be
morefrequentthanthepublicgrasps[8];sosimplecaution sure,theconsumerhaspreferences;buthecanbe
might suggest storing at least 48 kWh of energy for each bribed/coercedbysuitablepricingoptionstoshift
kilowattofaveragegenerationused,justincase.Thisthen thatdemandintime,andeventoinstallpersonal
means that each affluent member of an equitable world energy storage or to do without the desired ener-
societycouldneeddirect-plus-indirectunderpinningbyas gy.Commonlyviewedasintolerable,however,are
muchas5kW ofsteadyenergysupplyplusitsbackup at power outages that take down hospitals or police
avg
48 kWh/kW [8] for perhaps 240 kWh ¼ 10kWdof communications or a major semiconductor fabri-
avg
energy storage.4 In Section III, this assertion will be cation facility and do so independently of the
discussedinmuchgreaterdetailandillustrations given of consumers’momentarywillingnesstopay.Thatis,
just how daunting this task promises to be. smart control seems likely to compensate for a
Today,agridlabeled‘‘smart’’canshedload,encourage host of minor mismatches, but not for essential
conservation, protect critical uses, make sensible choices, demandsthatdonotabateduringprolongedshort-
andinformthepublicoflessobviousconsequencesoftheir fallsofrenewablegeneration.
energychoices.Butitdoesnot,initspresentincarnations, 3) Massive energy/electricity storage5 for backstop-
providetrulymassivequantitiesofenergystoragetheway ping renewable generation is only somewhat like
thecoalpilebehindthegeneratingplantusedto.Whena thehugepileofcoalbehindthepowerstation[9].
brief outage occurs today: 1) uninterruptible power sup- When the MES is exhausted, then we have to
pliescomeonlineandprotectdatasystemsforminutesto awaitthenaturalresumptionofrenewablegener-
hours;and2)emergencygeneratorscometolifeandkeep ation,whereas,todate,diminishedcoalpileshave
a home, or a hospital, or even the cooling pumps at a always been replenished with cheap shipments
nuclearpowerplantrunninguntilthegridreturnsortheir from the mines, and natural processes have en-
dieselfuelrunsout.Currently,however,themanydaysof dowed the mines with years (even decades) of
reserves, exploitation of which can generally be
3Thereaderisremindedthatlongtraditionwithintheenergyindustry accessed by emergency measures. Coal piles be-
makesfreeuseofmanynon-SIenergyunits,andthattheseunitsarenot hind power stations are only simple heaps of
always precisely defined. A good introduction to this uncertainty of
crushed rock on bare ground, are cheap to
conversion is provided by the American Physical Society at their Web
site http://www.aps.org/policy/reports/popa-reports/energy/units.cfm. construct compared to the cost of the coal, and
The ‘‘quad’’ is one quadrillion British thermal units or 1.055 (cid:4)1018 J.
The‘‘tonneofoilequivalent’’(‘‘toe’’)is1010caloriesor41.868(cid:4)109J.The 5MESasdefinedinconnectionwiththesmartgridcommonlyrefers
‘‘barrelofoilequivalent’’(‘‘boe’’)is(cid:3)6.12GJ.The‘‘standardcubicfoot(of tothestorageanddischargecapabilitiesofthelocalsmartgridasawhole
naturalgas)’’(‘‘SCF’’)is1000Btuor1.055(cid:4)106J. ratherthantheaverage5kWavgofpowerand10kWdofstorageneeded
4Thereaderisremindedthat,bytheFirstLawofThermodynamics, byeachpersonusingthatgrid.OfficialthresholdsforMEShavenotyet
energy is always conserved. However, by the Second Law of Thermo- beenestablished forMESon agridscale. However,a credibleestimate
dynamics,notallformsofenergyareequallyusefulforpoweringalltasks. can be obtained by studying the limitations of present pumped hydro
Forexample,theportionoftheenergyinasystemthatcanbeconverted storagefacilitiesintheUnitedStates:thesetopoutaround1GWpeakwith
into mechanical work is frequently referred to as the ‘‘exergy’’ of the 1 GWd maximum capacity [19, Table 1], but none have been built in
system,andisregardedasenergyofhighquality.The5kWavgperperson recentyears.Aserviceablelowerboundon‘‘massive’’mightthereforebe
figure given above pessimistically assumes that high-quality pure-exergy 1 GWpeak ((cid:3)0.5 GWavg) and 1 GWd; such a facility could service
electricitywouldbeneeded,andthuserrsonthesideofcaution. (cid:3)100000people.
1096 Proceedings of the IEEE|Vol.102,No.7,July2014
Pickard:SmartGrids Versus the Achilles’Heel of Renewable Energy
can, at little cost, be generously sized to outlast onnonrenewableenergysupplieswilloccur;and7)that,if
probable supply disruptions, such as strikes or the necessary renewable energy supplies are not yet
delivery postponement due to severe weather. In available when the crunch does occur, severe societal
contrast, development of MES infrastructure is dislocations could well result. Because all seven of the
expected to be significantly more expensive per recentstudiessummarizedinTable1predictsignificantly
kilowatthourthanthesimplepilingofpulverized constrictedsuppliesoffossilfuelsbytheendofthepresent
coal.BothMESandcoalpilingaregambler’sruin century,itseemsonlyprudenttocommenceanimmediate
problemsinwhichthegambler’spocketsmustbe reconfiguration of the world’s energy infrastructure to a
deep enough to outlast a run of bad luck. The sustainable renewable basis.
differencebetweenthemistheconstructioncosts, Mistakes will be made during this restructuring; and
which assure that the MES gambler will almost resources will be wasted. This is only to be expected be-
always have the shallower pockets. Of course, cause mankind has never before made a comparably ex-
when the coal runs out, the MES gambler will treme transition on such short notice. For example, the
have the only pocketsVa thought which those periodrequiredforcoaltogofrom1%ofAmerica’ssupply
who might wish to put off MES would do well to ofprimarypowerto50%wasontheorderof50years,and
contemplate. the same was true as coal was displaced by oil/gas [10].
Inasmartgridfuture,thesmartgrid,howeversophis- Now,asTable1reveals,mankindhasaslittleas50yearsto
ticated, will not work unless undergirded by both ample switch energy sources. Only this time the switch will not
renewable generation and ample massive energy storage. bevoluntary:thistime mankind willhave nochoice.And
Thebalanceamongabundanceofgeneration,flexibilityof thenewtechnologyneeded,thoughenvisioned,isnotyet
demand,andmassivenessofstorageremainstobeworked well developed. In such circumstances, society’s leaders
out. That will be a function of economic realities not yet have an obligation to behave proactively rather than hop-
comprehensible because the technologies that determine ingforthebestwhilelettingmatterstaketheircourse.Itis
them have yet to be developed, much less evolved to a simple matter of intergenerational equity: the present
maturity. doesnothavearightknowinglytobeggarthefuture[11].6
Acautionarytaleofcostlyproactive preparationisthe
following. In the 1920s and the early 1930s, the distri-
II. THE OBLIGATIONS OF UNCERTAINTY
butionofarmamentsamongtheindustrializednationswas
It was argued above that each resident of an equitable loosely regulated by international treaties, in no small
sustainable society would have to be the recipient of pri- measure to avoid the destabilizing effects of a renewed
mary energy equivalent to as much as 5 kW of steadily arms race such as that which preceded the Great War. As
suppliedrenewablepower.Thisisinnowayanoutlandish former allies, Japan and the United States were allowed
estimate, because already the Earth’s population of about roughparityinaircraftcarriers.However,shortlyafterthe
7.1 billion people is consuming a gross primary energy of onsetoftheGreatDepression,theriseofNaziGermanyin
roughly 14 Gtoe y(cid:2)1 ) 2.0 toe person(cid:2)1y(cid:2)1 ) 84 GJ Europe and Japan’s territorial ambitions on the Chinese
person(cid:2)1y(cid:2)1 [5, Table 2.1]; and this leads to an average mainland provoked international unease. The subsequent
current power consumption of 2.7 kW person(cid:2)1. action–reaction,showninTable2,thenoccurredbetween
If we make it a humanity-wide goal to grow coupled theUnitedStatesandJapan[12].Inthemiddle1930s,the
generationandconsumptiontoreachthe5.0kWperson(cid:2)1 Japaneserampedupacarrierbuildingprogram,whilethe
goalin50years,thatisanetgrowthof1.25%ayearinthe United Statesfocused upon itsmassiveinternaleconomic
availablepercapitapower.Ifpopulationgrowthisfigured catastrophe and did not react obviously until 1941. Even
in, then the growth in total power generated could pro- then isolationism was rampant within the American
bablybecloserto31%–4%;andgrowthatsucharapidpace electorate, and rearmament was far from popular. World
2
has, in fact, been envisioned by the U.S. Energy Infor- WarIIachievedfullscaleinlate1941,withJapanandthe
mation Administration [9, Ch. 5]. However, it is by no United States having rough parity in carriers. 1942 was a
means certain that mankind absolutely positively must tough year, and it ended with Japan enjoying two-to-one
have any particular per capita supply of renewable power superiorityincarriers.FortunatelyfortheUnitedStates,it
by any particular date. What is difficult to deny are the hadalotofunderutilizedproductionpotentialandturned
propositions: 1) that the supply of fossil fuels is finite; thingsaround.But,ifithadnotstartedlayingdowncarrier
2)thattheproblemofpermanentCO disposalhasnotyet keels in 1941, World War II could have had a rather
2
beenresolvedunequivocally;3)thatthesupplyoffission- differentcourse.Naturallythisanalogyfromhistoryisnot
able materials is finite; 4) that the permanent disposal of
massive quantities of fission waste has not yet been re- 6This laststatement isobviously amoral or philosophical judgment
solved unequivocally; 5) that adequate sustainable power thatcannotbefalsifiedbyreplicableexperiment.Rawls[11]discussesin
detail the ‘‘veil of ignorance’’ test that might be used to support it.
supplied from renewable sources is not yet available;
Presumably, most readers would prefer not to find themselves in a
6)thatnooneknowsforsurewhentheinevitablecrunch beggaredfuture.
Vol.102,No.7,July2014|Proceedings of the IEEE 1097
Pickard:SmartGrids Versus the Achilles’ Heel of Renewable Energy
Table2AnatomyofanArmsRace.TheNumberofMajorAircraftCarriers the 10 kWd person(cid:2)1 (240 kWh person(cid:2)1) of energy
LaidDown,Launched,andDeployedintheRun-UpandProsecutionof storage seem out of line because it backs up the resident
WorldWarII.DataAreforYear’sEnd
foronlytwodays,andbecauseoutagesoftwoormoredays
inlengtharepartofthememoriesofmostadults,middle-
aged and older [8].8
Remembering that the chemical energy in combusti-
blesmustbeheavilydiscountedifitistobeconvertedinto
usefulwork,approximatelywhatdoes10kWd(¼864MJ
(cid:3)1GJ)ofexergystoragelooklikeinpracticalterms?Inthe
following,foursimpleillustrationswillbeprovidedforthe
case in which the captured renewable energy is immedi-
atelyconvertedintoelectricityfordistributionorstorage.9
A) Iso-octane has a higher heat value of approxi-
mately 32.9(cid:4)109 Jm(cid:2)3 [16]. If it can be turned
back into exergy with an efficiency of 1/3, about
79Lwillbeneededforeachcitizen.Thus,astor-
agetankwiththevolumeoftheGreatPyramidof
Giza (2.48(cid:4)106 m3 [17, p. 456]) should suffice
for 31.5(cid:4)106 people.
B) A large industrial battery (GNB model GX6000)
wasarbitrarilyselected[18].Nominalspecifications
are: voltage, 4 V; capacity, 6000 A h ) 86.4 MJ;
volume, 417 L; mass, 894 kg. Ten such massive
batteries will be needed for each citizen, a total
volume of 4.17 m3. But a Great Pyramid of such
all that similar to the present energy challenges because batteriesshouldsufficeforonly0.59(cid:4)106 people.
everynationontheplanethadalotofexperiencewithwar C) 250 m3 of dry air, isothermally compressed to a
and the United States knew how to build weapons of war volumeofonly1m3,holdsamechanicalenergyof
that worked. Whereas, today, nobody has had experience 140MJ;therefore,6.17m3ofsuchcompressedair
with a catastrophic exhaustion of fossil-fuel reserves, no- will be needed. And a pressure chamber the
body knows what the correct trajectory is to achieve re- volume of a Great Pyramid would suffice for but
newablefueling,andnobodyknowswhichmassiveenergy 0.40(cid:4)106 people.
storage strategies are the correct ones. D) Acubicmeterofwaterelevated750matstandard
Therefore, it seems prudent to invoke some sort of gravity has a potential energy of 7.35 MJ; there-
precautionary principle7 and mandate remedial action: fore,118m3 perpersonwillbeneeded.But,since
precaution is, after all, a standard response to uncertainty two reservoirs are needed in a pumped storage
[13]–[15];anditwasenjoineduponusfromearliestyouthin scheme (one upper and one lower [19]), a Great
suchaphorismsas‘‘anounceofpreventionisworthapound Pyramidofreservoirwouldhandleonly10.5(cid:4)103
ofcure’’orfablessuchasTheAntandtheGrasshopper. people.
The reader will observe that these per-person energy
storage volumes span the range 0.079–236 m3, a ratio of
III. THE MONSTROUS SIZE OF THE MES
roughly 1 : 3000. Moreover, the absolute quantities that
Inanimaginedaffluentworldofthefuture,eachresident ultimately will be required are unknown because future
(cf. Section I above) could need as much as 5 kW of con- population growth is unknown. Nevertheless, current
tinuousenergybufferedby10kWdofenergystorage.The predictions of world population in 2100 call for roughly
5 kW is by no means a farfetched estimate because, in
2011, (cid:3)312 million residents of the United States con-
sumed97.30quads(102.7(cid:4)1018 J)ofprimaryenergy[4] 8Take note that the 10 kWd person(cid:2)1 takes cognizance only of
‘‘normal’’short-termweathervariationsandgridfailures.Itdoesnotfactor
or10.4kWperson(cid:2)1:thepresumptionof5kWperson(cid:2)1in
intrans-seasonalloadshiftingforwinterheatingorsummercooling.
factassumessignificantenergyconservation.Neitherdoes 9For simplicity, the only storage modes discussed are a typical
hydrocarbon and those modes that the Electricity Storage Association
7In modern ecological or political thinking, a precautionary frame- currentlyrecommendsfordecouplingfromenergyusethegenerationand
workmakesitasocialresponsibilityofpolicymakerstoprotectthepublic stationary storage of massive quantities of electrical energy (http://
fromsignificantharmwhenthereiscrediblescientificevidenceofsuch www.electricitystorage.org/technology/storage_technologies/technology_
harmbeingapttoarisefromaparticularcourseofaction,whetherthat comparison).Ifnoneofthesecomeclosetosufficing,thenslimarethe
course is optional, mandatory, or quite unpredictable. Moreover, it is chancesofmankindexitingthiscenturyincontrolofitsenergyfuture.It
common to regard as unwise the postponement of proactive precaution shouldbenotedthatthefourhavebeenroughlyorderedbytheper-person
becausethereisnotyetfullscientificcertaintyofthatharm. volumeofenergystoragerequired.
1098 Proceedings of the IEEE|Vol.102,No.7,July2014
Pickard:SmartGrids Versus the Achilles’Heel of Renewable Energy
ten billion people, give or take a factor of two.10 The au- over a century without a major breakthrough in energy
thor, who has been much impressed by the huge drops in density and may have ‘‘hit the wall’’; second, they tightly
birthrate that frequently follow universal education and couple together storage capacity and maximum power
readilyavailablecontraception,willuse5.00(cid:4)109people output;andthird,theymaynotdeliverthelongandrobust
for population projections in this document. But ‘‘only‘‘ service lives that utility customers expect.12 Thinking
fivebillionisstillahugenumberwhoseenergyneedswill ‘‘outside the box’’ seems called for.
havetobemetwithrenewablesoncefossilfuelsandother Outside the box is, for example, redox flow batteries,
nonrenewables have been exhausted. wherein output current is intrinsically decoupled from
totalenergystored[29],[30].Suchbatteriesarenowina
phase of intense development.
IV. ARE THESE FOUR OBVIOUS Outside the box is metal–air batteries, which offer
STORAGE STRATEGIES ADEQUATE seductively large theoretical (as contrasted with currently
FOR THE WORLD’S NEEDS? practical) energy densities [31].
Outside the box is new electrolytes, such as are found
What will now be shown is that each of these strategies
in the burgeoning field of metal-based ionic liquids
offers some prospect of being able to surmount the inter-
(MetILs), e.g., [32] and [33].
mittency challenge (i.e., the task of storing sufficient
‘‘Outside the box,’’ as illustrated above, also means
energytomatchcapriciouslyvaryingrenewablegeneration
‘‘under development.’’ And ‘‘under development’’ is of
to mankind’s changing needs). This disconnect between
little use for massive electricity storage until the new
supply and demand has justly been described as the
technologieshavebeenfieldtested,thebugswrungoutof
Achilles’heelofrenewableenergy[20].Yet,ithasstillnot
their production, robustness demonstrated, end-of-life
beenunequivocallyneutralized.Andresearchrelatedtoit
issues resolved, and the new batteries are flooding into
has been quietly neglected.11
the market by the boxcar.
CaseA).Thispossibilitydependsuponusingrenewably
Case C). Compressed air energy storage (CAES),
generated electricity to drive the synthesis of inorganic
whetheradiabaticorisothermal,hasbeenrecentlyfigured
and organic fuels from water (provides H) and air
prominently in the energy policy literature, e.g., [34]–
(providesC,N,andO).Thiscouldyieldgaseoushydrogen
[38].Moreover,therealsoseemstobearespectableliter-
[21],ammonia[7],methane[7],[22]–[24],simplealcohols
ature on the physical and engineering underpinnings of
[7], [22], [23], and liquid hydrocarbons [7], [22], [23],
CAES, e.g., [39]–[44]. What seems to be missing is
[25], [26]. Because the atoms constituting the fuels are
evidence for a single major instance in which CAES was
continuously recycled, the supplies of synthesizing con-
actually built and successfully used for operation of an
stituentsaresustainable.Andthefeasibilityoftheprocess
expander train to generate electricity directly. The com-
should depend largely 1) upon the sustainability of cata-
monly cited plants in Huntorf, Germany and McIntosh,
lysts for the syntheses; and 2) upon the realities of both
AL, USA [43] use compressed air as a way of reducing
energyeconomicsandfinancialeconomics.Untilsynthetic
compressor costs in natural-gas-fired power plants; such
fuel synthesizing systems are scaled up enormously and
use isnot sustainable because natural gas isan unsustain-
their technology allowed to mature, accurate economic
able,finite,fossilresource.Nomajornewplantshavebeen
predictions about this form of storage are unlikely.
builtindecades;andfewarebeingwidelytoutedas‘‘under
CaseB).Thispossibilitydependsuponusingrenewably
construction.’’ If built, for example, advanced adiabatic
generatedelectricitytomanufactureandchargebatteries,
CAES might prove a viable storage solution. But until
of which there is a plethora of types. It has already been
designed,built,tested,debugged,andreliablyoperatedat
shownthattheplanet’sleadreservesareseeminglyinade-
reasonable cost, it ought not be counted upon to meet
quate to sustain massive electricity storage with lead acid
future MES needs.
batteries for a world population of even five billion [27],
Case D). Pumped hydro storage works well and is
[28].Ifbatteriesaretobeused,today’sfamiliarfamiliesof
backed by generations of experience [45], [46]. Indeed,
secondarybatterieswill,foranumberofreasons,probably
approximate calculations of various strategies that might
never suffice for massive energy storage: first, they have
be employed have already been made [19], [47], [48] and
been subjected to intense incremental improvement for
will be adapted here to the problem as posed by Murphy
10A search of the Web yields many interesting charts, all of which [47] for the United States: roughly, store enough
pointtothisoutcomeandmostofwhicharebasedonthe2010revisionof gravitational potential in elevated water to provide 2 TW
theUnitedNations’ProbabilisticPopulationProjectionshttp://esa.un.org/ ofelectricpowerfor7days)336TWh)336(cid:4)109kWh
unpd/ppp/index.htm.
11Modernscienceissovibrantthatsomewheresomeoneisdiligently )1.21(cid:4)1018 J (cid:3)1 EJ.
exploringalmostanytopicofpossibleconcern.Whatmattersiswhether
effective action is being taken on those rare problems whose predicted 12Thisismemorablydescribedintherecentscathingessay‘‘Battery
onsets1)arerelativelysoon;2)couldwellbecatastrophicasopposedto performance deficit disorder’’ by Prof. Thomas W. Murphy of the
merely inconvenient; 3) are not already being circumvented; and 4) do University of California at San Diego (http://physics.ucsd.edu/do-the-
notyethavewelltestedandverifiedsolutions. math/2012/08/battery-performance-deficit-disorder/)
Vol.102,No.7,July2014|Proceedings of the IEEE 1099
Pickard:SmartGrids Versus the Achilles’ Heel of Renewable Energy
Murphy [47] proposed damming valleys in mountain- V. CAN THE NECESSARY
ous terrain to provide the upper and lower reservoirs and INFRASTRUCTURE BE CREATED
estimated that: 1) 170 stations each storing (cid:3)7(cid:4)1015 J IN THE TIME REMAINING?
would be needed; 2) in aggregate, an area rather larger
thanLakeErie(onlydeeper)wouldbedrowned; and3)a A. Introduction
stupendous quantity of concrete would be required. The take home message of Section I was that recent
By contrast, Pickard [19] favored many smaller mod- projections of fossil-fuel supplies are strongly pessimistic:
ular facilities built upon non-arable flatland, each with a by 2070, mankind will probably be well beyond peak
hydraulic head of 750 m, an excavated underground re- fossil fuel.
servoir of roughly 25(cid:4)106 m3, and an upper reservoir The claim of Section II was that, if mankind expects
roughly 1 km2 in area and 30 m deep, formed on the seriousenergyshortagesinagenerationorso,thenit has
surfaceandringedbyspoilfromtheexcavation;eachsuch an obligation to protect future generations by moving
module would store roughly 0.2(cid:4)1015 J. In all, roughly forthwith to counter those shortages, even if doing so is
5000 of these smaller units would be needed; but they devilishly inconvenient. It is just not right to place the
couldbeplaced,largelyunnoticed,onlandoflowagricul- burden of our life styles upon the shoulders of our
tural, commercial, and scenic value. descendents.
Last, Slocum et al. [48] have proposed storing the InSectionIII,itwasshownthatdauntinglylargeisthe
energyinpartiallyevacuatedhollowspheresrestingonthe amountofmassiveenergystorageneededtosmoothoutall
seabednearoffshorewind-turbinegenerators.Whenthere of the intermittencies that characterize common renew-
isashortageofelectricpower,seawaterwouldbeadmitted able sources.
tothespherebywayofaFrancisturbinedrivingasuitable In Section IV, it was asserted that none of the likely
generator; and the resulting electricity would be fed into technologiesneededtomakesuchmassivestorageareality
the grid. When there is a surplus of electric power, the cantodaybeobtainedofftheshelfatknownspecifications,
Francis turbine would be run backwards by some of that cost, reliability, and lifetime.
surplus,andthewaterinsidethespherewouldbepumped In this section, it will be argued that revising the
into the sea. world’senergyinfrastructuretorunreliablywithamixof
Obvious though these three pumped hydro schemes largely intermittent renewable sources is apt to take at
may appear, they are all outside the boundaries of tried least 50 years [10], [50], [51].
and tested technology. They should work, except that
the history of technology is littered with the ruins of B. Previous Transitions in Primary Energy Sources
major projects that failed because of unanticipated Whatwewillherefocusuponisstoredenergythatcan
contingencies. be transformed to do useful work. The history of such
Economic feasibility and turnaround efficiency. The rea- energy in the service of man can be summarized in the
sonableness of an energy project’s cost is situationally nine transitions of Table 3.
determined [49], as is the cost itself. Here, buffering the Untilcoalwasaddedtotheenergymix,primaryenergy
renewable generation is presumed essential: what remain was neither conveniently nor infinitely dispatchable; cf.,
to be determined are the magnitude of the buffering and [52] and [53]. Humans could work only so hard and then
the timing of its addition to the project. Both are in- only so many hours a day: you either accepted this and
fluenced by the anticipated (though unpredictable) gyra- livedwithitoryouworkedpeopletodeath,inwhichcase
tions of the cost. you lost a most useful source of intelligent energy; more-
Turnaround efficiency of a storage system over a spe- over, humans tended to be stubbornly diurnal. The envi-
cified interval of time isthe ratio {totalamount ofenergy ronment, like humans, could be exploited only so
of a particular type extracted from the system}/{total vigorously; and therefore the supply of biomass, whether
amountofenergyofthesametypeaddedtothesystem},it gathered or farmed, was limited and perhaps seasonal.
beingassumedthattheinitialandfinalstatesofthesystem Animals, like humans, could be worked only so many
are the same. Normally, higher efficiencies are preferred hoursaday,andprovideddispatchableenergyonlyifem-
strongly. ployed in shifts. Wind is notoriously fickle; and its users,
Summary. There are lots of clever, though untried, whethersailorsormillers,acceptedthisintermittencybe-
strategiesthatmightmeettheworld’srapidlyapproaching causeintermittentwindwasalotbetterthanrowingaboat
need for energy storage in stupendously massive quanti- or pushing on a capstan mill. Hydro, whether by falling
ties.Someofthem,perhapsmostofthem,mayultimately waterorbyflowingwaterorbywaves,wasonlysomewhat
fail to work satisfactorily. And those that finally do prove dispatchable, and was apt to be seasonal. Coal opened a
out,mayfailtodosoinatimelyfashion.Presumably,the wholenewenergy terrain:itstoredenergydensely,could
mostprudentpathtosuccessinmassiveenergystoragelies be accumulated locally in enormous piles, and yielded as
intestingstraightwayalloftheaboveschemesinfull-scale muchenergyasneededbythesimpleexpedientofshovel-
demonstration projects. ingharder.Oilwasalotlikecoal.Andgasisalotlikecoal
1100 Proceedings of the IEEE|Vol.102,No.7,July2014
Pickard:SmartGrids Versus the Achilles’Heel of Renewable Energy
Table3NineEnergyTransitionsThatCharacterizetheDevelopmentof C. Massive Energy Storage Is Different
Mankind.TheLastTwoAreStillUnderWay;and,FromFoodThrough Itisdifferentbecausedispatchabilityofmassivepowers
Solar;EachofthePrimaryEnergySourcesEmployedbyMankindWaxes
hasbecomepossibleonlysincemankindgraduallybecame
andWanesWithHumanDevelopment
dependent upon fossil fuels and developed life styles that
dispatchability made possible. And only when fossil fuels
become scarce is dispatchability likely to become recog-
nized as the daunting desideratum that it is. Without
dispatchability,ourtechnicalcivilizationcouldwelltrans-
form into an under-resourced variety of global refugee
camp.
Puttingitdifferently,mankindhasalwaysbeendepen-
dentuponenergyderivedfromtheenvironment.Thishas,
however, been sharply recognized only recently. The
history of civilization can now be regarded as one long
storyofextractinggreaterabsolutequantitiesofenergy,of
employing energies of higher quality, and of employing
those energies more effectively [52]. Migration to follow
food resources (i.e., edible fuel) is prehuman. Storage of
food surpluses is prehuman. The origins of stockpiling
andoil:itisconvenientlystored;anditsenergycan,with nonfoodchemicalfuelsarelostinhistory;andourpresent
some forward planning, be dispatched on demand in vir- day proficiency at it is the result both 1) of gradual unre-
tually any quantity desired. marked trial and error, and, more recently, 2) of preme-
Nuclearenergy, althoughstoredatafarhigherenergy ditated scientificdesign.Wheremankindcomesupshort,
density than the chemical energy of oil, may have repre- however, is on massively and efficiently storing energy in
sented a step backward in three ways First, it is not, as nonfoodnoncombustibleforms.Therefore,whensupplies
presently configured, dispatchable because of the slow of fossil fuels become meager, our technical civilization
thermalresponsetimesofpresentlyavailableplants;gene- enters uncharted waters.
rationIVnuclearplants,nowintheplanningstage,might
possibly circumvent this [54]. Second, it is not, sensu D. What History Tells Us About the Rapidity of
stricto,renewablebecausetheavailableresourcesoffissile PreviousTransitionsintheSupplyofPrimaryEnergy
nuclei (though large) are limited; however, fertile nuclei and What We Should Expect During the Transition
are in much greater supply and could perhaps extend From Fossil Fuels to Renewable Ones
greatlyanageoffissionfuel;cf.,[49].Third,despitebeing Historically, such transitions have taken generations,
twogenerationsintoitsnuclearfuture,mankindhasyetto severaldecadestocenturies[52],[53];and50yearsshould
produce a demonstrably effective method of storing the beconsideredaroughlowerlimitfortransitionsthatwere
nuclear waste from power reactors [55]; but, here too, drivenbyeconomicconsiderationsofafreemarketwithin
generation IV reactors might be of help; cf., [54]. The astablesocialmilieu[10].Hence,technically,itshouldbe
difficulty is that delivery of generation IV reactors is not possible to shift to renewables before 2070, the putative
envisioned until the 2030s, and could well be delayed by exhaustionmilestoneforfossilfuels(cf.,Table1).Butthis
unforeseen difficulties. Therefore, one should not count time could be different.
too heavily upon nuclear powering the postcarbon world: First, what are the immediate benefits that might en-
because, despite our being 60 years into the touted ticeanationhastilytochangeitsprimarysourcesofenergy
Atomic Age, nuclear has yet to fulfill the hopes once before it has to? Probably none, whereas past switches
vested in it. weremotivatedbytheprospectofnear-termgain.Within
Before being accumulated and stored by man, solar the ambit of the Organization for Economic Co-operation
energymustfirstbeanthropogenicallycapturedandtrans- and Development (OECD): 1) the economies of its mem-
formed [1]. The good news about solar is that there is a ber nations are today mostly delicate, so that any major
great deal of it reallocation of priorities/expenditures might pit immedi-
What does seem likely as the century progresses is: ately baleful consequences against major but prospective
1) that Earth’s dowry of those three bulwarks of nonre- gainsinadistantfuture;2)today,rightnow,governmental
newable(buthighlydispatchable)storedenergy(CþOþ units are having a hard time balancing their budgets and
G) will soon be greatly depleted; and 2) that the dis- governmentfinancialobligationsarebecomingmorediffi-
patchable energy we take for granted will become some- cult to honor; 3) even cherished social programs are be-
thingofagoldenlegendfrombygonedaysVunless,thatis, coming stressful to sustain; and 4) today, right now, civil
massive energy storage grows in synchrony with energy infrastructure is in need of costly repair, refurbishing,
generation by intermittent renewables. and replacement. Therefore, there will be relentless
Vol.102,No.7,July2014|Proceedings of the IEEE 1101
Pickard:SmartGrids Versus the Achilles’ Heel of Renewable Energy
temptationtoletrenewabletechnologydevelopquietly,to rently,windenergyaveragesabout$2pernameplatewatt,
avoid rocking the energy boat, and to await more installed [63]; or, at a cautious capacity factor of 1/4,
propitiouseconomictimesbeforetryingtoswitchsources roughly $8 per average watt. Thus, the raw generation to
of primary energy. take the United States green could cost (cid:3)$13 trillion.13
Anyway,second,isthegrowthofrenewablegeneration Suppose, as presumed above, that this power flow should
reallyinatightracewiththeexhaustionoffossilfuels?Isa be backed up by one week of MES; then on the order of
sense of urgency about switching fuels truly justified? (cid:3)1.01(cid:4)1018 J¼281(cid:4)109 kWh¼1670gigawatt-weeks
Renewable generation clearly is becoming better every will be needed. It has been estimated that underground
year;meanwhile,thejuryisoutonjustwhenthesupplies pumped hydro MES would cost about a third of lead-
of fossil fuel will get really, really tight. Moreover, in acid battery MES and come in around $4 per watt-day ¼
lightoftheFreeWorld’sproductionmiracleduringWorld 167 $/kWh [16], [19], [64];14 this works out to a storage
WarII,doesitnotseemlikelythata‘‘fossil-fuelexhaustion investment by the United States of (cid:3)$47 trillion, which
crunch’’ would simply motivate mankind to belt-tighten suggests trying to make do with two days rather than a
and,inonlyafewyears,buildtherenewableenergygene- week of MES. Finally, a crude ballpark figure is needed
ration, actualize the low-loss immensely-flexible smart for the cost of 200 000 km of (cid:5)750-kV HVDC backbone
grid,andprovideallthemassiveenergystoragesuchagrid for a nation-spanning smart grid; because the cost per
will need to operate flawlessly? Arguably, maybe. kilometerofsuchastructureissohighlydependentupon
But, third, remember that the technology to accom- the local circumstances of each link, a pessimistic flat
plishmuchoftheabovehasthusfaronlybeenenvisioned cost of $2 million km(cid:2)1 will be assumed (cf., [65]),
andconceptualized.Callupanyenergy-relevantindustrial thereby yielding a total cost of (cid:3)$0.4 trillion and empha-
organization and ask for firm price, delivery, and speci- sizing that the installation costs of transmission will be
fications on several gigawatts of immediately connected minor compared to those of generation and storage.
sustainableconcentrated-solar-power(CSP)generationor If then the decision is made to dial back storage
a gigawatt-week of turnkey flow battery MES. The author capability to only two days, the total cost will be
presumesthatyouwillbetoldthatthisisnotoff-the-shelf (cid:3)$28trillion(giveortakeafactorof2),slightlylessthan
technology and that lengthy development will be neces- two years of America’s recent Gross Domestic Product
sary; also, the ultimate price may be painfully less attrac- (GDP)of(cid:3)$15trillion.Spreadover50ybetweennowand
tive than envisioned. Indeed, engineering history is 2070,thiswouldrequire(cid:3)$0.6trilliony(cid:2)1.Thisisonly4%
littered with technical marvels that did not quite work of the GDP, roughly twice what was spent building rail-
out as confidently (even reasonably) expected. The roadsandcanalsinthedecadesimmediatelyprecedingthe
Maginot Line was built more or less on schedule, except Civil War; only America’s economy is much more mature
that its designers failed to get it right the first time, and nowthanthen.Moreimportantly,that4%ismarkedlyless
therewasnosecondchance[56].TheAtomicAge,withits thanthe7.6%ofGDPthatAmerica’sbusinessesallocated
envisioned ‘‘electrical energy too cheap to meter [57],’’ to capital expenditures in the peri-recession year of 2010
nevercametopass;whilethesafeandpermanentdisposal [66],[67];and,ifitweretobephasedinoverafewyears,
of its toxic waste remains an unresolved problem to this the economy would probably adjust unremarkably. But it
day [55]. Likewise, antiballistic missile defense systems bearsnotingthatthelongertheUnitedStatesdithersonthe
have been under development by the United States since renewable energy issue, the bigger will be the fraction of
1945, with the first of many major efforts commencing the GDP required: 4% will become 6%, will become 8%,
in1957[58];despiteperiodicpublicityandsignificantex- etc.; and, before you know it, the fraction needed will be
penditures, these programs have limped along for over disastrouslylarge.
50years[59],withmodestinterceptionsuccessoccurring
only in the past five [60], [61]. F. A Somewhat Pessimistic Interpretation
AlthoughtheUnitedStatesmaynottodayhaveinplace
E. Can the Envisioned Smart Grid Be Afforded? as appropriate a STEM and manufacturing complex as it
Whereas we have but little experience with large-area hadinplaceatthestartofWorldWarII,therestillmaybe
full-blownmultigigawattsmartgrids,whereasexamplesof
theirancillarylow-lossrobusttransmissionbackbonesare 13Infact,recentdatafromtheNationalRenewableEnergyLaboratory
(MichiganWindWorkingGroup,‘‘Newwindmapsandresourcepotential
notyetavailableforstudy,andwhereascopiousharddata
estimatesfortheUnitedStates,’’March31,2010)indicatethatthewind
on gigawatt-week energy storage do not exist, be it there- from only prime locations within the United States ought to be able to
forerecognizedthatentrepreneuriallyreassuringcostesti- deliverthreetimesthe50quadneeded.
14Ifthisseemsinsanelyexpensive,pleasenotethatthisisequivalent
matescannotbemade.Atbest,analystsmustmakedowith
toabout46$/MJofturnkeyMES.Bycomparison,atypical12-Vstorage
Fermi calculations; cf., [62]. battery(asforanautomobile)turnsouttocostaround50$/MJ,butone
Suppose,asaconcreteexample,thattheUnitedStates thenhastoexpendmuchmoneybuyingandinstallingtheelectronicsfor
monitoring and recharging. The reputed cost of battery storage to be
reduces its primary energy demand to only (cid:3)50 quad
installedonHokkaido(Japan)isapproximately$204millionfor60MWh,
y(cid:2)1 ) (cid:3)52.8 (cid:4) 1018 Jy(cid:2)1 ) (cid:3)1.67 (cid:4) 1012 Wavg. Cur- orabout950$/MJ.
1102 Proceedings of the IEEE|Vol.102,No.7,July2014
Pickard:SmartGrids Versus the Achilles’Heel of Renewable Energy
time for it to react to the approaching end of the Age of investment in energy, especially renewable energy, is
FossilFuel.Withthetimeavailable,itmightyetbepossi- widespread throughout the world [76]–[78]. Yet, without
ble to clarify the technical issues and create a sustainable realtestdatafromreallarge-scaledemonstrationprojects,
smart grid with renewable generation, robust and deftly neithertheUnitedStatesnortheworldcanmakesensible
managedtransmission,andampleMES.Anditdoesseem strategic decisions on our energy future. And without
as if the economic demands of the task, though onerous, those sensible decisions, the world will risk terrible eco-
could be metVby the United States.15 This accords with nomicharmwhenfossilfuelbecomesscarceandabidding
other recent studies, e.g., [6] and [68]–[71], but is at va- war ensues for that which is left.
riancewiththerarermorepessimisticones,e.g.,[72]–[74].
However, despite an infectious gee-whiz enthusiasm
VI. CONCLUSION
for smart grids, there islittle compelling evidence for the
politicalwillneededactuallytoputinplacepolicieslikely The data and derivations set forth in this contribution
to result in the final development and deployment of the constituteatleastseveralscintillaeofevidence,probablya
building blocks that might be used in a nation-spanning preponderance of evidence, and possibly even prima facie
smart grid.16 Unfortunately, once the oil shocks of the evidencethat,bythecloseofthiscentury:1)theworldwill
1970s had passed, funding for energy research, develop- be approaching exhaustion of its recoverable fossil-fuel
ment,anddemonstrationfellsharplyintheUnitedStates supplies; 2) the energy shortages engendered thereby can
and has not yet recovered [75]. Currently, similar under- reliably be avoided only if immediate massive steps are
takentoactualizethedevelopmentandmanufactureofthe
15Howwelltheburdensofgoinggreencouldbebornebylessaffluent
many unproven components of a global smart energy sys-
nationsisamatterofspeculation,asiswhatwillhappentothosenations
thatneglecttosomuchastry. tem;and3)theworldover,thereispreciouslittleevidence
16Publicperceptionofthepresentenergysituationwasevaluatedon (as measured in G$ y(cid:2)1 of new funding for development
April4,2014,byaGooglesearchofthefollowingtermsforitemsupdated
and demonstration) that world governments are seriously
duringthepastmonth:‘‘fuelprice,’’69(cid:4)103hits;‘‘smartgrid,’’139(cid:4)103
hits;‘‘massiveenergystorage,’’31hits. concerned. h
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