EuroTech PhD summer school

Integrated Approach to Energy Systems

Feb 2nd to 13th, 2015

IntroductiontoDemandResponse

Prof.Jean‐YvesLeBoudecEPFLLaboratoryLCA2

Feb4,2015

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Contents

1.Whatisdemandresponse?

AnillustrationwitheightexamplesAtaxonomy

2.Elementsoftheory

5

WHAT IS DEMAND RESPONSE ? 

6

TerminologyDemand Response (DR)

Demand Side Management (DSM)DemandSideManagement=electricutilitymanipulatesuserapplianceDemandResponse=DemandSideManagementasaresponsetopriceinpracticebothphrasesoftenusedinterchangeably

yearsold(“LoadManagement”,inband tones“ripplecontrol”,AMsignal)

7

A clothes dryer connected to a load control "smart" switch (Wikimedia Commons)

Demand Response (DR)= Demand Side Management 

(DSM)Why invented ?

8

1. Toreducecostsforconsumers

2. Tosaveenergy3. Tooptimizemanagement

oftheelectricalgrid4. Topreventnightoperation

ofnoisyequipment5. Idon’t know

To re

duce

 costs

 for c

onsu

mers

To sa

ve en

ergy

To op

timize

 man

agem

ent o

f...

To pr

even

t nigh

t ope

ratio

n ..

I don

’t kn

ow

12%

0%10%

71%

8%

Solution

electricalsystemsmustbalanceenergyinstantlyenergybalanceinelectricalgridismainlydonebyadjustingsupplytodemand:

schedulingandforecasting+largescaleinterconnection;frequencyresponse;reserves

demandresponse=adjustdemand tosupplyisoneofthetoolsusedtomanagethepowergridenergyefficiency isobtainedbymanagingdemandefficientlybutisoutsidethescopeofthistutorial

9

Examples of Use of Demand Responsepeakshaving

responsetofailures(avoidblackout)mitigatevolatilityofwindandsolarenergymitigatenetworkproblems(congestion,voltage)

10

France’s comsumption on cold and average november week; Xavier Brossat (EDF), Energy Systems Week, 2013

What can be subject to Demand Response ?

Demandresponseappliestoelastic loads(load=consumerofelectricity)Nonelasticloads

lighting,watchingTV,hairdrying

Elasticloadsboiler,carorbicyclebattery,datacenter,fridgesandfreezers,airconditioner,washingmachine

11

Demand Response Example 1Norway’s pilot study [Saele and Grande 2011 ]tariffisincreasedatpre‐definedtimes(8‐10,17‐19)usersmadeawareofhightariffsandtimesInsomehomesheatingisalsodirectlycontrolledstudyconcludesthatitworks

12

Norway’s pilot study [Saele and Grande 2011 ]Demand Response may reduce prices

120EUR/MWh differencebetween2areasinsideNorway[Saele andGrande2011]claimsthatthepricepeakwouldbesuppressedwithdemandresponse

13

A similar example (GulfPower, USA)

14

[Borenstein et al 2002]

Example 2 : Romande Energie

TimeofUsetariffNighttariffislower

InterruptibleSupply:interruptiblesupply(serviceisavailablee.g.20hoursperday)[LeBoudecandTomozei 2011]

15http://www.romande‐energie.ch/images/File/Tarifs/2013_tarifs_RE.pdf

Example 3 :VoltalisWidelydeployedinFranceInterruptibleLoadVoltalis devicestopselectricalresistiveheating/boilerforatmost60mn perdayDevice(«Bluepod»)receivesGSMsignalandstopsthermalloadsNocharge/nopaymentAcceptancebasedon

Voltalis claimsenergyusagereductionGoodcitizens

Similarschemeswithincentivepaymenttousers:PeakSaver(Canada),www.pge.com(USA),NewZealand,NGTfrequencyservice(UK)

16

www.voltalis.com

Example 4: Dynamic Demand

alsocalledfrequencyservicesmartfridges,smartboilers,smartheaters/HVACsrecallthatfrequencyisthefirstsignalofpowerimbalance

17

primaryfrequencycontroltraditionallydonewithdynamicgenerators‐‐ fossilfuelgenerators,usingdroopcontrol

[Molina‐Garcia et al 2011] [Mario Paolone]

Example 4: Dynamic Demanddynamicdemand isanalternativetodynamicgeneratorsHowitworks:(“gridfriendlycontroller”)(underfrequency):fridgedelayscompressorwhenfrequencydropsandanticipateswhenfreq.increases[Molina‐Garciaetal2011]

18

time during which Δ is observed

Is something missing with this algorithm ?

19

1. Nothing2. Timersneedtoberandomized3. Internaltemperatureneedsto

betakenintoaccount4. Outsidetemperatureneedstobe

takenintoaccount5. Idon’t know

Nothing

Timers n

eed to be r

ando

mize

Internal 

tempe

rature nee

ds..

Outsi

de te

mpe

rature nee

ds..

I don

’t kn

ow

0% 2%

23%

48%

27%

SolutionAvoidsynchronized response

[Molina,Garciaetal2011]userandomizedT_

Internal temperature shouldbe accounted for

20

Dynamic DemandSimulationresultsfor[Molina‐Garciaetal2011]with10%ofloadsimplementingdynamicdemandinahypotheticalcountrygrid

dynamicdemand doublesthereserve

21

Dynamic DemandSimulationresultsfor[Molina‐Garciaetal2011]with10%ofloadsimplementingdynamicdemandinahypotheticalcountrygrid– dynamicdemand doublesthereserve

Fridgesasprimary/secondaryresponsecouldprovideca1GWofreservetoUKgrid[Milborrow 2009]

70%ofsecondaryregulationpower(8secto3mn)intheUScanbeprovidedbybuildingairconditioningandheatingfansalone[Hao etal2012]

22

Example 5: Boilers as Tertiary Reserve[Sundstrom et al 2012]

Primaryreserve=realtimeSecondaryreserve=withinminutesTertiaryreserve=startsafter15mnThermalloadscanbeanticipatedordelayedUpperandlowerenergycurvesforoneboilergiveboundsonfeasibleenergyprovisionschedules

23[Sundstrom et al 2012]

upper bound: deliver  3kW for 1.71h then 200 W

lower bound: deliver  0W for 6h then 200 W

Boilers as Tertiary ReserveAssumeoperator(“Serviceaggregator”)controlsalargesetofboilersandcanpredicttheupperandlowerboundsfortheaggregateenergycurves.

Serviceaggregatorcanselectamiddletrajectoryandthereforeobtainsomereservethatcanbesoldtogrid.

Canbeimplementedwithpricingand/orsmartmeters

24

total energydelivered

upper bound

lower bound

time15 mn

grid calls for reserve

4h

300 MW of boilers stop heating for 4 

hours

Example 6: Island with Large Penetration of Renewables

[James‐SmithandTogeby 2007]Bornholm(DK)objectofEcoGridEUprojectElectricity:Peakdemand55MW,Supply30MWwindturbines,60MWACcabletomainland,oneCombinedHeatandPowerplant(coal,35MWtotal)Issue:operationinislandedmodeduetofrequentcablecuts

WindvolatilityGenerationmaybecomelargeCoalplantisnotfastenough3MWofadditionalfastresponse

(within15mn)isrequired25

[James-Smith and Togeby 2007]

Example 6: Findings in[James‐Smith and Togeby 2007]

26

Demandresponseinhomes(heating,hotwater,refrigeratorscanprovide3MWofcapacityinwinterPositivedemandresponse(homes,districtheatingsystem)canavoidspillingwindenergy

[James-Smith and Togeby 2007]

Example 7: Impact of e‐car charging on distribution network [Clement‐Nyns et al 2010] E‐carchargesarehighpower(4kW),stresselectricaldistributionnetwork– peakdemandatnights

27Simulation of 34‐bus residential grid  [Clement‐Nyns et al 2010] 

Scheduled Chargingproblemcanbesolvedbyscheduling theloads(e‐cars),i.e.coordinatetheme‐carscommunicatewithascheduler,throughsmartmeterorothercommunicationmeanscoordinatorsolvesoptimizationproblemandsendsscheduletoe‐carchargers

requires:modelofgrid;ofstateandavailabilityofe‐cars;isfrequentlyrecomputedtoaddressstochasticchanges

28

power loss

power scheduled to car  at time 

Scheduled charging can eliminate need to upgrade distribution network

29

Example 8: Grid Explicit Congestion Notification (GECN) [Christakou et al, 2014]

Goal:solvevoltageandampacityproblemslocallyindistributionnetworksposedbydistributedgeneration(solarPVs,Combinedheatandpower)

30

GECN uses a broadcast explicit congestion control signal

GECNcontrollerbroadcastseveryfewseconds ( ) [−1,1]:

( )isuniqueperMVnetworkbusrateofafewbitspersecond| ( )|:intensityofrequiredresponse

0 means:reduceconsumption0 means:increaseconsumption

AppliancereactsbyreducingorincreasingconsumptionMini‐cycleavoidanceTemperatureconstraints

31

Response of a Refrigerator to GECNWithoutGECN:thethermostatimplementsthedutycycle

WithGECN,forexamplewhensignal isreceivedbyafridgethatisON

Flipafirstcoin:withproba 0.25donothing(i.e.continuethedutycycle),withproba 0.75considerdoingsomethingflipasecondcoinandwithproba

gotoOFFstate

32

0

1

Feedback is implicit, no return channel

33

Implementation:

• Closed loop control

1. Optimalpowerset‐pointsaresolutiontoanoptimization problem2. Theset‐pointsaremapped toGECNsignals andsenttothe

network3. DNOobservesvariationofpowerintheMVbusesviaastate

estimationprocess andadjusts

Optimizationsolved attimet

1 2

3

34

Without any control With GECNVoltage (p.u.)

Taxonomy of Demand ResponseTypeofusercontract

1. Timeofuse(e.g dayversusnight)

2. Controlbytariff(dynamicprices)

3. Controlbyquantity(interruptiblesupply,schedules)Modeofcommunication

1. inband tones(Ripples)2. powerline communication

andsmartmeters3. radiocommunication

Timescaleofoperation1. Static2. Dynamic

5mn‐24hours(smartmeters)

3. Realtime(frequencyresponse,GECN)

GlobalEffect1. Shifttheload(delayor

anticipate)2. Reducedemand

(emergency,shavethepeakonexceptionaldays)

35

Voltalis does not pay nor charge anything to consumers but claims that consumers benefit by seeing a reduced electricity bill. Do you think this 

is true ?

361. 2. 3. 4.

35%

0%

23%

43%

1. Yes,theremustbeareductionintotalenergyconsumed

2. No,therecannotbeanyreductionintotalenergyconsumed

3. Totalenergyconsumedisincreased

4. Idon’tknow

ELEMENTS OF THEORY

1. DemandandSupplyCurves2. Elasticity3. Evaporation

37

1. The Economic Theory of Demand ResponseConsumer Side

TheeconomictheoryofDemandResponseisbasedonthefollowingmodel.Assumeconsumersarewillingtoconsumesomeamountofenergy ataprice ;inagiventimeslot,theutility of isassumedtobemeasurableandequalto ;theconsumerchoosesthevalueof thatmaximizes

38

non elastic load elastic load elastic load with minimum requir’t

The Economic Theory of Demand ResponseSupplier Side

Assumesuppliersusersarewillingtosellsomeamountofenergy ataprice ;inagiventimeslot,the runningcost ofgenerating isassumedtobemeasurableandequalto ;thesupplierchoosesthevalueof thatmaximizes

39

wind supplier flexible supplier flexible supplier with maximum capacity

Demand and Supply CurvesDemandCurve=howmuchconsumeriswillingtobuyatagivenpriceSupplycurve =howmuchsupplieriswillingtosellatagivenprice

Consumermaximizes thereforeSuppliermaximizes therefore

demandcurveis ↦supplycurveis ↦

concave⇒′isdecreasingconvex⇒′isincreasing

40

′

supply curve, flexible supplier

′

elastic load

Market EquilibriumAssumethereisaperfectmarkettofixprices;thesupplierandconsumerpricesareequalPriceandquantityaregivenbyintersectionofsupplyanddemandcurves

41

demand curve

market values  ∗, ∗

supply curve

∗

∗

Supply and Demand Curves Without Demand Response [Kirschen 2003]

Nodemandresponsemeansloadsareinelastic;generationorgridoutagescausepricestosurge

Elasticloadsmayavoidpricepeaks

42

demand curve forflexible load

demand curve forflexible load

Assume some loads disconnect when price becomes Which curve could be a demand curve for the aggregate 

demand  ?

43

1 2 3

1. 2. 3. 4. 5. 6. 7. 8. 9.

3%

34%

18%

0%

5%

8%

16%

13%

3%

1. Curve12. Curve23. Curve34. Either1or25. Either1or36. Either2or37. All8. None9. Idon’t know

Solution

With1thepriceisalways soitdoesnotexpressthedisconnectionWith2,thedemandisinsensitivetopricewhenpriceisbetweeb andWith3,thedemandhasanegativejumpwhenthepriceincreasesto

Correctanswer is 3

44

Norway’s pilot study [Saele and Grande 2011 ]Demand Response may reduce prices

120EUR/MWh differencebetween2areasinsideNorway[Saele andGrande2011]claimsthatthepricepeakwouldbesuppressedwithdemandresponse

45

Supply Curve for Industrial Customers

46

2. Elasticity

47

Do we get this ?

load with demand response

«natural» loadload with demand response

«natural» load

… or that ?

CPP = critical peak pricing

Elasticity and Cross‐ElasticityDemandresponsecausesdemandreductionandtimeshiftingThequantitativeeffectiscapturedby

(self)‐elasticity

andcross‐elasticity ,

definedforexamplefor48

log

log

demand curve in log-log scales

is the elasticity at 

Wikimedia Commons /File:Elasticity‐inelastic.png

Example of Cross‐Elasticity[Kirschen et al 2000]

Usersexpectsomeprices basedonhistoricaldataResultingdemandisassumestwodemandresponsemodelswithcross‐elasticityMarketdecidesfordifferentprices, difference betweenexpectedpriceandactualprice.Demandresponsecauseuserstochangetheirloads.[Kirschen etal2000] assumesthat

,

where , iscalledtheCross‐ElasticityCoefficient(itslightlydiffersfrom ,

, isthefractionoftheloadattime thatismoved

totime duetoachangeinpriceattime

49

Example of Cross‐Elasticity Coefficients

,

[Kirschen etal2000]considerstwopossiblescenariosScenario1: (TimeShifting,“Inflexible”):

, , ,

, , ,

,i.e.changeinpriceat changesloadbyloadistransferredto3hoursbeforeand3hoursafterScenario2: (“Optimizer”):

, , , ,

, ,

,i.e.changeinpriceat changesloadbymostloadistransferredtoearlyandlatehoursoftheday

50

Impact on PriceAssumingnoelasticity,pricesareformedbymatchingdemandlet theprocessofpriceformationwhere

[Kirschen etal2000]studiesacasewithnormaloperationandwithplannedlossofgenerator

51

Supply curve,normal case

modified price

Supply curve,one generator lost

expected price

Impact on Price (continued)Assumenowelasticloadswithknowncross‐elasticity.Theactualloaddependsonthemarketprice:let

betheprocessofloadadaptationAssumemarketaggregatorknowselasticity;shecancomputemarketpricesbysolvingafixedpointproblem

52

[Kirschen et al 2000]

3. EvaporationEvaporation fractionofenergythatissavedduetodemandresponse[LeBoudecandTomozei 2013]

withpuredemandshifting,evaporation=0Ifitistruethatdemandresponsesavesenergy,weshouldseeevaporationWhatdoweexpectingeneral?

53

load with demand response

«natural» load

load with demand response

«natural» load

(Should I keep my chalet warm ?)When I am away I interrupt heating. Does this 

save energy ?

541. 2. 3. 4.

25% 25%25%25%

1. Yes,theremustbeareductionintotalenergyconsumed

2. No,therecannotbeanyreductionintotalenergyconsumed

3. Totalenergyconsumedisincreased

4. Idon’tknow

Evaporation is not the same as “Rebound Effect”

Q1.Doesshuttingdowntheheatingtodayimplyreducingtotalenergyconsumptioncomparedtokeepingtemperatureconstant?=isevaporationpositive?A.wewillseelater.

Q2.Doesshuttingdowntheheatingtoday(andswithing itofftomorrow)implyincreasingtomorrow’senergyconsumption?A.Yes(thisisthereboundeffect).

55

Assumethehousemodelof[McKay2008]

56

leakiness inertia

heat providedto building outside

sumover from to :

efficiency

E, total energy providedachieved t

leakiness inertia

heat providedto building outside

58

efficiency

E, total energy providedachieved t

Scenario No interruption Withinterruption

Buildingtemperature

∗ , 0… , 0… , ∗

Heatprovided ∗ 1

∗ ∗ ∗ 0

∗

Assumeinitialtemperature=finaltemperatureinbothscenarios∗ ∗ .Inthiscaseintegralofenergyfed

intobuilding( ∗ inscenario“Nointerruption”, inscenario“WithInterruption”) isequaltointegralofleakedenergy:

∗ ∗

Itcostsmoreheattokeepthechaletwarmwithoutinterruption.59

The French ADEME agency finds that consumers with Voltalis’s load switching devices save  10% on heating but there is no significant saving on hot water boilers [ADEME 2012]. How do you interpret 

this ?

601. 2. 3. 4. 5.

10%13%

28%

10%

38%

1. Themodelwesawistoosimpleanditsfindingsdonotapply.

2. Boilerleakageissmall,houseleakageisnot.

3. Houseleakageissmall,boilerleakageisnot.

4. Hotwaterboilingisnegligibleconsumptioncomparedtohouseheating

5. Idon’tknow.

SolutionDoesshuttingdowntheheatingtodayimpliesreducingtotalheat consumptioncomparedtokeepingtemperatureconstant?

Answer:yesinallcases

Answer 3is theonly plausible

61

EvaporationResistiveheatingsystemwithpoorlyinsulatedbuilding:heatprovidedisproportionaltoenergyconsumptionevaporationispositive.

Ifheat=heatpump,coefficientofperformance maybevariable.Evaporationmaybepositiveornegative;negativeevaporationispossible(heatpumpoperatingatnightincoldair).

Electricvehicle:weexpectevaporation=0(puretimeshifting).Howeverchargeintensityimpactslosses;fastchargingmayconsumemoreenergy,negativeevaporationispossible.

62

Further ReadingOpenADR:practicalimplementationofDemandResponsebypricehttp://www.openadr.org

Demandresponsebyprice,toolkitforGridOperators:http://www.pjm.com/markets‐and‐operations/demand‐response.aspx

http://www.voltalis.com/bluepod.php

Impactofdemandresponseonrealtimemarketprices[Gast etal,2014]

63

ConclusionDemandresponseaimsatcontrollingdemandtobetterfollowgeneration

Demandresponsecanbeseenasaformofvirtualelectricitystorage

alternativesare:batteries,pump‐hydro,compressedair,etc

DemandresponsecanactonEnergytimescale(15mn ormore)bypriceordirectcontrolSuchsystemsaredeployedtodayPowertimescale(instantly)tocounterbalanceintermittencyofsolarandwindgenerationInthelabs

64

References[Transpower NewZealand2012]http://www.systemoperator.co.nz/presentations/demand‐response‐animation/sampledonMay17,2013[ADEME2012]“Avisdel’ADEME”,8October2012,http://www2.ademe.fr/servlet/getBin?name=133DA6A2F68CD16926D050F0081C36D4_tomcatlocal1349692493746.pdf[Borenstein etal2002]SBorenstein,MJaske,ARosenfeld,“DynamicPricing,AdvancedMetering,andDemandResponseinElectricityMarkets”,ReporttoTheEnergyFoundation,October2002[Christakou etal,2014]Christakou,K.etal.“GECN:PrimaryVoltageControlforActiveDistributionNetworksviaReal‐TimeDemand‐Response”,IEEETransactionsonSmartGrid,2014[Clement‐Nyns etal2010]Clement‐Nyns,K.;Haesen,E.;Driesen,J.,“TheImpactofChargingPlug‐InHybridElectricVehiclesonaResidentialDistributionGrid”,IEEETPS,2010[Gast etal,2014]N.Gast,J.‐Y.LeBoudecandD.‐C.Tomozei. Impactofdemand‐responseontheefficiencyandpricesinreal‐timeelectricitymarkets. e‐Energy'14,Cambridge,UnitedKingdom,2014.[Hao etal,2012]HeHao,TimMiddelkoop,Prabir Barooah andSeanMeyn,“Howdemandresponsefromcommercialbuildingscanprovidetheregulationneedsofthegrid”,50thAllertonConferenceonCommunication,Control,andComputing,2012[Kirschen 2003]Kirschen D.S.“Demand‐SideViewofElectricityMarkets”,IEEETPS2003

65

[James‐SmithandTogeby 2007]E.James‐SmithandM.Togeby “SecurityofSupplyforBornholm”,Ea EnergyAnalysesreport,www.eaea.dk,2007[Kirschen etal2000]DanielS.Kirschen,GoranStrbac,Pariya Cumperayot,andDilemar dePaiva Mendes“FactoringtheElasticityofDemandinElectricityPrices”[leBoudecandThiran2001]LeBoudecJ.Y.andThiranP.,Network Calculus,SpringerVerlag,2001[LeBoudecandTomozei 2011]LeBoudec,J.‐Y.;Tomozei,D.‐C.,“Demandresponseusingservicecurves”ISGTEurope2011[LeBoudecandTomozei 2013]LeBoudec,J.‐Y.;Tomozei,D.‐C.,“StabilityofaStochasticModelforDemand‐Response”,StochasticSystems,vol. 3,2013[Molina‐Garcia2011]Molina‐García,Angel,FrançoisBouffard,andDanielS.Kirschen."Decentralized demand‐side contributiontoprimary frequency control." PowerSystems,IEEETransactionson 26.1(2011):411‐419.[McKay2008]McKay,D.SustainableEnergy‐withoutthehotair,UITCambridge,2008[Milborrow 2009]DavidMilborrow, ”ManagingVariability”,24June2009, AreporttoWWF‐UK,RSPB,GreenpeaceUKandFriendsoftheEarthEWNI )[Saele andGrande2011]H.Saele andOveS.Grande“DemandResponseFromHouseholdCustomers: ExperiencesFromaPilotStudyinNorway”,IEEETSG2011[Sundstrom etal2012]Sundstrom,O.;Binding,C.;Gantenbein,D.;Berner,D.;Rumsch,W.‐C., “Aggregatingtheflexibilityprovidedbydomestichot‐waterboilerstooffertertiaryregulationpowerinSwitzerland”,ISGTEurope2012[Sundstrom andBinding2012]Sundstrom,O.andBinding,C.“FlexibleChargingOptimizationforElectricVehiclesConsideringDistributionGridConstraints”,IEEETSG,2012

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