Intro. to Commercial Building Control Strategies

8/13/2019 Intro. to Commercial Building Control Strategies

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IntroductiontoCommercialBuildingControlStrategiesand

TechniquesforDemandResponse

NaoyaMotegi

MaryAnnPiette

DavidS.Watson

SilaKiliccote

PengXu

LawrenceBerkeleyNationalLaboratory

MS90R3111

1CyclotronRoad

Berkeley,California94720

May22,2007

ThisworkdescribedinthisreportwascoordinatedbytheDemandResponseResearch

CenterandfundedbytheCaliforniaEnergyCommission,PublicInterestEnergy

ResearchProgram,underWorkforOthersContractNo.50003026andbytheU.S.

DepartmentofEnergyunderContractNo.DE-AC02-05CH11231.

LBNLReportNumber59975


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i

Acknowledgements

Theworkdescribed in thisreportwascoordinatedby theDemandResponseResearch

CenterandfundedbytheCaliforniaEnergyCommission(EnergyCommission),Public

InterestEnergyResearch(PIER)Program,underWorkforOthersContractNo.50003

026

andby

the

U.S.

Department

of

Energy

under

Contract

No.

DE

AC02

05CH11231.

Theauthorswishtothanktheengineersandstaffateachbuildingsite. Specialthanksto

RonHofmann forhis conceptualizationof thisprojectandongoing technical support.

Thanks also to Laurie ten Hope, Mark Rawson, and Dave Michel at the California

Energy Commission. Finally, thanks to the Pacific Gas and Electric Company who

fundedtheAutomatedCPPresearch.

We appreciate the helpful comments providedby the peer reviewers of this report:

Douglas B. Nordham (EnerNOC), Austen DLima (San Diego Gas and Electric

Company),SteveGreenbergandBarbaraAtkinson(LBNL).

Pleasecite

this

report

as

follows:

Motegi,N.,M.A.Piette,D.S.Watson,S.Kiliccote,P.Xu.2006.IntroductiontoCommercial

Building Control Strategies and Techniques for Demand Response. California Energy

Commission,PIER.LBNLReportNumber59975.


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Preface

The Public Interest Energy Research (PIER) Program supports public interest energy

research and development that will help improve the quality of life in Californiaby

bringingenvironmentallysafe,affordable,andreliableenergyservicesandproductsto

themarketplace.

The PIER Program, managed by the California Energy Commission (EnergyCommission),annuallyawardsupto$62milliontoconductthemostpromisingpublic

interestenergyresearchbypartneringwithResearch,Development,andDemonstration

(RD&D)organizations,includingindividuals,businesses,utilities,andpublicorprivate

researchinstitutions.

PIERfundingeffortsarefocusedonthefollowingsixRD&Dprogramareas:

BuildingsEndUseEnergyEfficiency

Industrial/Agricultural/WaterEnd

Use

Energy

Efficiency

RenewableEnergy

EnvironmentallyPreferredAdvancedGeneration

EnergyRelatedEnvironmentalResearch

EnergySystemsIntegration

WhatfollowsisthefinalreportfortheStatewideAutoDRCollaborationProject,50003

026, conducted by Lawrence Berkeley National Laboratory. The report is entitled

Introduction toCommercialBuildingControlStrategiesandTechniques forDemand

Response.ThisprojectcontributestotheEnergySystemsIntegrationProgram.

FormoreinformationonthePIERProgram,pleasevisittheEnergyCommissionsWeb

site at: http://www.energy.ca.gov/research/index.html or contact the Energy

CommissionsPublicationsUnitat9166545200.


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TableofContents

ExecutiveSummary..................................................................................................................... 1

1. Introduction ......................................................................................................................... 1

1.1. BackgroundandOverview........................................................................................ 1

1.2. Objectives ..................................................................................................................... 1

1.3. ResearchScope ............................................................................................................ 11.4. BenefitstoCalifornia .................................................................................................. 3

1.5. ReportOrganization ................................................................................................... 3

1.6. BuildingOperationandEnergyManagementFramework .................................. 4

1.7. TermsandConceptsforDRStrategies .................................................................... 6

2. DemandResponseStrategyOverview ......................................................................... 10

2.1. HVACSystems.......................................................................................................... 10

2.2. LightingSystems....................................................................................................... 14

2.3. MiscellaneousEquipment........................................................................................ 16

2.4. NonComponentSpecificControlStrategies........................................................ 16

2.5. StrategiesUsedinCaseStudies .............................................................................. 16

3. DemandResponseStrategyDetail................................................................................ 19

3.1. HVACSystems.......................................................................................................... 19

3.1.1. Globaltemperatureadjustment...................................................................... 20

3.1.2. Passivethermalmassstorage ......................................................................... 25

3.1.3. Ductstaticpressuredecrease.......................................................................... 26

3.1.4. Fanvariablefrequencydrivelimit................................................................. 27

3.1.5. Supplyairtemperatureincrease .................................................................... 28

3.1.6. Fanquantityreduction .................................................................................... 29

3.1.7. Coolingvalvelimit........................................................................................... 30

3.1.8. Chilledwatertemperatureincrease............................................................... 31

3.1.9. Chillerdemandlimit........................................................................................ 32

3.1.10. Chillerquantityreduction............................................................................... 34

3.1.11. Reboundavoidancestrategies........................................................................ 36

3.2. LightingSystems....................................................................................................... 37

3.2.1. Zoneswitching ................................................................................................. 37

3.2.2. Luminaire/lampswitching.............................................................................. 38

3.2.3. Steppeddimming ............................................................................................. 41

3.2.4. Continuousdimming....................................................................................... 42

3.3. MiscellaneousEquipment........................................................................................ 43

3.4. NonComponentSpecificStrategies ...................................................................... 45

3.4.1. Demandlimitstrategy ..................................................................................... 45

3.4.2. Pricelevelresponsestrategy .......................................................................... 46

4. ImplementationofDRStrategies.................................................................................. 47

4.1. DRStrategyDevelopmentandCommissioning................................................... 47


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ListofFigures

Figure1.Examplesofloadshapes ............................................................................................. 6

Figure2.HVACDRstrategydecisiontree ............................................................................. 11

Figure3.LightingDRstrategydecisiontree .......................................................................... 15

Figure4.FrequencyofDRstrategies....................................................................................... 18

Figure5.Temperature

drift

rate

allowed

under

ASHRAE

Standard

55 .......................... 218

Figure6.Zonesetpointsdeadband.......................................................................................... 22

Figure 7. Conceptual diagram of demand savings for typical HVACbased demand

responsestrategy ............................................................................................................... 24

Figure8.Luminaireswitchingalternaterowsofluminaires ............................................ 39

Figure9.Luminaireswitchingeveryotherluminaireineachrow.................................. 39

Figure10.Lampswitching middlelampsofthreelampfixtures..................................... 40

Figure11.Lampswitchinglampsineachluminaire ......................................................... 40

Figure12.Exampleofpricelevelzonesetpointcontrol....................................................... 46

Figure13.Demandsavingsintensitybyshedstrategy(W/ft2)............................................ 51

Figure14.OATvs.averagedemandsavings ......................................................................... 52

Figure15.Wholebuildinghourlydemandvs.OATanddemandsheds .......................... 54

ListofTables

Table1.Demandsidemanagementterminologyandbuildingoperations......................... 4

Table2.BuildingHVACtypes ................................................................................................. 11Table3.HVACdemandresponsestrategies .......................................................................... 12

Table4.DRstrategiesusedinLBNLAutoDRstudies(fullyautomated) ........................ 17

Table5.DRstrategiesusedincasestudies(manualorsemiautomated) ......................... 18

Table6.Conditionsforglobaltemperatureadjustment(GTA)........................................... 20

Table7.Conditionsforpassivethermalmassstorage.......................................................... 25

Table8.Conditionsforductstaticpressuredecrease ........................................................... 26

Table9.Conditionsforfanvariablefrequencydrivelimit .................................................. 27

Table10.Conditionsforsupplyairtemperaturereset ......................................................... 28Table11.Conditionsforfanquantityreduction.................................................................... 29

Table12.Conditionsforcoolingvalvelimit........................................................................... 30

Table13.Conditionsforchilledwatertemperatureincrease .............................................. 31

Table14.Conditionsforchillerdemandlimit........................................................................ 32

Table15.Conditionsforchillerquantityreduction............................................................... 34

Table16.Conditionsforzoneswitching................................................................................. 37

Table17.Conditionsforluminaire/lampswitching.............................................................. 38

Table18.Conditionsforsteppeddimming ............................................................................ 41Table19.Conditionsforcontinuousdimming....................................................................... 42

Table20.Recommendeddatacollectionpoints ..................................................................... 49

Table21.Demandsavingsinfluencefactors........................................................................... 51


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Table22.StatisticalsignificanceofOATvs.demandsavings.............................................. 53


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Abstract

Demand Response (DR) isa setof timedependentprogramactivitiesand tariffs that

seektoreduceelectricityuseorshiftusagetoanothertimeperiod. DRprovidescontrol

systems thatencourage load sheddingor load shiftingduring timeswhen theelectric

grid is near its capacity or electricity prices are high. DR helps to managebuilding

electricitycostsandtoimproveelectricgridreliability.

This report provides an introduction to commercial building control strategies and

techniquesfordemandresponse.Manyelectricutilitieshavebeenexploringtheuseof

critical peak pricing (CPP) and other demand response programs to help reduce

summer peaks in customer electric loads. This report responds to an identified need

amongbuildingoperatorsforknowledgetouseDRstrategiesintheirbuildings.These

strategiescanbeimplementedusingeithermanualorautomatedmethods.

The

report

compiles

information

from

field

demonstrations

of

DR

programs

in

commercialbuildings. The guide provides a framework for categorizing the control

strategies that have been tested in actual buildings. The guides emphasis is on

characterizinganddescribingDRcontrolstrategiesforairconditioningandventilation

systems.Thereisalsogoodcoverageoflightingcontrolstrategies. Theguideprovides

someadditionalintroductiontoDRstrategiesforothermiscellaneousbuildingenduse

systemsandnoncomponentbasedDRstrategies.

The core information in this report isbased on DR field tests in 28 nonresidential

buildings,mostofwhichwere inCalifornia,and the restofwhichwere inNewYorkState. The majority of the participatingbuildings were officebuildings. Most of the

Californiabuildingsparticipatedinfullyautomateddemandresponsefieldtests.


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ExecutiveSummary

Introduction


seek toreduceorshiftelectricityusage to improveelectricgridreliabilityandmanage

electricity costs. DR strategies provide control methodologies that enhance load

shedding or load shifting during times when the electric grid is near its capacity orelectricitypricesarehigh.Manyelectricutilitieshavebeenexploringtheuseofcritical

peakpricing(CPP)andotherdemandresponseprogramstohelpreducesummerpeaks

incustomerelectric loads.Recentevaluationshaveshown thatcustomershave limited

knowledgeofhow tooperate theirfacilities toreduce theirelectricitycostsunderCPP

(QuantumandSummitBlue2004).

Purpose

Thepurpose

of

this

report

isto

provide

an

introduction

to

commercial

building

control

strategiesandtechniquesfordemandresponse.Whileenergyefficiencymeasureshave

been widely understood by many audiences including facility managers, building

owners, control contractors, utility program managers, auditors, and policy makers,

therearenotmanydocumentsintroducingframeworksorguidelinesformeasuresand

strategiestoparticipateindemandresponseprograms.

Commercialbuildingshavebeenonlyminorparticipantsindemandresponseprograms.

This report is designed tobe an initial introduction to the technical capabilities of

existingbuildingequipmentandsystemsandtheirabilitytoprovidedemandresponsecontrolstrategies.WhilethefocusoftheguideisonDR,wehavefoundthattheprocess

ofdevelopingDRcontrolstrategiescanalsohelpidentifystrategiesforenergyefficiency

duringdailybuildingoperations.

ProjectObjectives

Thereportisauniqueguidethatcompilesinformationfromactualfielddemonstrations

of DR programs in commercialbuildings. The guide providesbackground technical

information

necessary

to

identify

and

enable

demand

response

control

strategies.

The

guideisintendedforusebybuildingprofessionalsincludingfacilitymanagers,building

owners,controlcontractors,buildingengineers,utilitypersonnel,andauditors.

ProjectOutcomes

Theguideprovidesa framework forcategorizing thecontrolstrategies thathavebeen

testedinactualbuildings.TheguidesemphasisisoncharacterizinganddescribingDR

control strategies for airconditioning and ventilation systems, plus lighting control

strategies. Theguideprovidessomeadditional introduction toDRstrategies forother

miscellaneousbuildingendusesystemsandnoncomponentbasedDRstrategies.Thesestrategiescanbeimplementedusingeithermanualorautomatedmethods.


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The core information in this report isbased on DR field tests in 28 nonresidential

buildings,mostofwhichwere inCalifornia,and the restofwhichwere inNewYork

State. The majority of the participatingbuildings were officebuildings. Most of the

Californiabuildingsparticipatedinfullyautomateddemandresponsefieldtests.

Heating, Ventilating, and Air Conditioning (HVAC). HVAC systems can be an

excellent resource for DR savings for the following reasons. First, HVAC systems

compriseasubstantialportionoftheelectricloadincommercialbuildings.Second,thethermal flywheel (thermal storage) effect of indoor environments allows HVAC

systems to be temporarily unloaded without immediate impact on the building

occupants. Third, it is common for HVAC systems tobe at least partially automated

withenergymanagementandcontrolsystems (EMCS).Toprovidereliable,repeatable

DRcontrol,itisbesttopreplanandautomateoperationalmodesthatwillprovideDR

savings.TheuseofautomationreducesthelaborrequiredtoimplementDRoperational

modeswhentheyaresignaled.

HVACbased DR strategies recommended for a given facility varybased onbuildingtypeandcondition,mechanicalequipment,andEMCS.Basedonthesefactors,thebest

DR strategies are those that achieve the aforementioned goals of meeting electricity

demandsavings targets while minimizing negative impacts on the occupants of the

buildings or the processes that they perform. This guide discusses the following DR

strategiesforHVACsystems,whicharebestsuitedtoachievethesegoals:

GlobalTemperatureAdjustmentofZones,and

SystemicAdjustmentstotheAirDistributionand/orCoolingSystems.

It is often difficult to estimate the demand savings achieved by HVAC strategies,

because the buildings HVAC electric load is dynamic and sensitive to weather

conditions, occupancy, and other factors. However, previous research has found that

HVAC demand as well as demand savings tend to have positive correlation with

outsideairtemperature(OAT).

Lighting.DRstrategiesforlightingcanalsobeeffectiveinreducingpeakdemand.Ona

hotsummerdaywhendaylightisinabundance,daylitand/oroverlitbuildingsarethe

best candidates for lighting demand savings. Since lighting produces heat, reducing

lighting levelswillalsoreduce thecooling loadwithin thespace (SezgenandKoomey

1998). Lighting DR strategies tend tobe simple and depend widely on wiring and

controls infrastructures. However, since lighting has safety implications and the

strategies tend tobe noticeable, they shouldbe carried out selectively and carefully,

considering the tasks in the spaceand ramificationsof reduced lighting levels for the

occupants.

DRcontrol

capability

of

lighting

systems

isgenerally

determined

by

the

characteristics

of the lighting circuit and the control system. Following is the list of lighting DR

strategiesdiscussedinthisguideinincreasingorderofsophistication:

Zoneswitching


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Fixtureswitching

Lampswitching

Steppeddimming

Continuousdimming

Miscellaneous Equipment. There is also demand savings potential for certain other

equipment inboth commercialand industrialbuildings.Equipmentorprocesseswith

thedemand savingpotentialsdiscussed in this reportare fountainpumps,antisweatheaters, electric vehicle chargers, industrialprocess loads, cold storage, and irrigation

waterpumps.

NonComponentSpecific Strategies. Other effective DR strategies focus on controls

settings rather than on specific equipment. Such strategies highlighted in this report

includedemandlimitstrategyandsignallevelresponsestrategy.

Conclusions

HVAC systems canbe an excellent resource for DR shed savingsbecause; 1) HVACsystems create a substantial electric load in commercial buildings, 2) the thermal

flywheel effect of indoor environments allows HVAC systems to be temporarily

unloadedwithoutimmediateimpacttothebuildingoccupants,and3)itiscommonfor

HVACsystemstobeatleastpartiallyautomatedwithEMCSsystems.

ForHVACDRstrategies,globaltemperatureadjustmentofzonesistheprioritystrategy

thatbestachievestheDRgoal.Incontrast,systemicadjustmentstotheairdistribution

and/orcoolingsystemscanbedisruptivetooccupants. DRstrategiesthatslowlyreturn

the system to normal condition (rebound avoidance) shouldbe considered to avoid

unwanteddemandspikescausedbyanimmediateincreaseofcoolingload.

Lighting DR strategies tend tobe simple and provide constant, predictable demand

savings.Since lightingproducesheat, reducing lighting levelsmay reduce thecooling

load and/or increase the heating load within the space. The resolution of lighting

controlstendstobelowerthanthatofHVACcontrols. Alsolightingsystemsareoften

not automated with EMCS. These issues canbe major obstacles for automation of

lightingDRstrategies.

IfaDRstrategycanbeachievedwithoutanyreductioninservice,thestrategyshouldbe

considered as permanent energy efficiency opportunity rather than a temporary DR

strategy. That is, it shouldbe performed on nonDR days as well. The process of

commissioning shouldbe applied to each phase of DR control strategy application,

including planning, installation, and implementation to make sure the goal of DR

controlisachieved.

Recommendations

The information in this report should be disseminated to key personnel who are

involved inDR implementation including facilitymanagers,buildingowners,controls

contractors,andauditors.Disseminating this informationwillhelpprovideacommon

understanding of DR control strategies and development procedures to enable these


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strategies.The report isnotanexhaustive listofallDR strategies.Further research is

needed tobetterunderstand the peak demand reduction potential and capabilitiesof

thesestrategiesforvariousbuildingtypesindifferentclimatesandoccupancypatterns.

One specific technical development needed is to explore the design and operation of

simplifiedpeakelectricdemandsavingsestimationmethodsandtools.Currentauditors

and building engineers have widely varying methods to estimate peak demand

reductions

for

various

strategies.

BenefitstoCalifornia

This guide isbased primarily on case studies in California and is intended to help

streamline the DR control strategy implementation process and increase successful

participation in DR programs in California. Peak demand reduction and demand

responsearekeypartsofthestatesenergypolicies.


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1. Introduction

1.1. Background and Overview


seek toreduceorshiftelectricityusage to improveelectricgridreliabilityandmanage

electricity costs. DR strategies provide control methodologies that enhance load

shedding or load shifting during times when the electric grid is near its capacity or

electricitypricesarehigh.Manyelectricutilitieshavebeenexploringtheuseofcritical

peakpricing(CPP)andotherdemandresponseprogramstohelpreducesummerpeaks

incustomerelectric loads.Recentevaluationshaveshown thatcustomershave limited

knowledgeofhow tooperate theirfacilities toreduce theirelectricitycostsunderCPP

(QuantumandSummitBlue2004).

1.2. Objectives

Thepurposeofthisreportistoprovideanintroductiontocommercialbuildingcontrol

strategiesandtechniquesfordemandresponse.Whileenergyefficiencymeasureshave

been widely understood by many audiences including facility managers, building

owners, utility program managers, auditors, and policy makers, there are not many

documents introducing frameworks or guidelines for measures and strategies to

participateindemandresponseprograms.Commercialbuildingshavebeenonlyminor

participants in demand response programs. This report is designed tobe an initial

introduction to the technical capabilities of existingbuilding equipment and systems

andtheirability toprovidedemandresponsecontrolstrategies.Whilethe focusof the

guideisonDR,wehavefoundthattheprocessofdevelopingDRcontrolstrategiescan

alsohelpidentifystrategiesforenergyefficiencyduringdailybuildingoperations.

Thisreportwillhelpunderstandtechnicalaspectsofdemandresponsecontrolstrategies.

HVAC systems are often complex combinations of components with minimal sensor

points, limited trend logging, and poorlycommissioned sequences of operation. The

processofdevelopingDRcontrolstrategieswillprovidevaluablepeakdemandsavings

in

addition

to

new

insights

for

improving

energy

efficiency

during

dailybuilding

operations. The report is the first guide that compiles information from actual field

demonstrations of DR programs in commercial buildings. The guide provides the

technical information necessary to install demand response control strategies for

audiencesincludingfacilitymanagers,buildingowners,andauditors.

1.3. Research Scope

This report provides an introduction to commercial building control strategies for

demand response that havebeen fieldtested in actual commercialbuildings. Thesestrategiescanbeimplementedusingeithermanualorautomatedcontrolmethods.The

authorscompiledinformationfromactualfielddemonstrationsincommercialbuildings

that have participated in DR programs in California and New York. Thus, the guide


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providesaframeworkforcategorizingcontrolstrategiesthathavebeentestedinactual

buildings.Theguideemphasizesstrategiesforairconditioningandventilationsystems.

There is also ample coverage of lighting control strategies. In addition, the guide

provides some introduction toDR strategies forotherbuilding enduse equipment. It

alsodiscussesnoncomponentbasedDRstrategies.

Thereportisauniqueguidethatcompilesinformationfromactualfielddemonstrations

of DR programs in commercialbuildings. The guide providesbackground technicalinformationnecessary to identifyandenabledemandresponsecontrolstrategies. The

guideisintendedforusebybuildingprofessionalsincludingfacilitymanagers,building

owners,controlcontractors,buildingengineers,utilitypersonnel,andauditors. Itmay

alsobeofinteresttoresearchers,energyplanners,andpolicymakers.

Thedemandresponsecontrolstrategiesdiscussedinthisguidewouldberecommended

foreithersemi orfullyautomatedDR,thoughtheymaybeusedformanualDRaswell.

SeeSection1.6onLevelsofAutomationforDRfordefinitionsofDRautomationtypes.

LawrenceBerkeleyNationalLaboratory(LBNL)hasbeenconductingaseriesofresearchprojectsanddemonstrationsoffullyautomatedDRstrategies(referredtoasLBNLAuto

DR) (Piette et al. 2005a, 2005b, and 2006). This report is based on the cumulative

experiencesandfindingsfromtheLBNLAutoDRdemonstrationstudiesalongwiththe

othercasestudiesreferencedinthisreport.

The core information in this guide isbased on DR field tests in 28 nonresidential

buildings, most of which were in California. DRdata from the Energy Commissions

EnhancedAutomationcasestudiesinCaliforniawerealsoevaluated(CEC2006a),along

with case studies from New York (NYSERDA 2006). Case studies to date have

emphasized certain types ofbuildings, while otherbuilding types have not yetbeen

studied. The majority of the participants havebeen officebuildings. Otherbuilding

typesincludeseveralretailsites,asupermarket,publicassemblybuildings,acafeteria,a

postoffice,amuseum,ahighschool,datacenters,andlaboratorybuildings.Thesample

didnot includeanyhotelorhealthcarebuildings,butmanyofthestrategiesdiscussed

maybeapplicabletothesebuildingtypes.MostoftheCaliforniabuildingsparticipated

infullyautomateddemandresponsefieldtests.

It is also important to consider the HVAC systems that the case studies and

demonstrationbuildingsused.Builtupvariableairvolume(VAV)systemswithcentral

coolingplantsdominatethesample,althoughmanyofthesmallerbuildingsuserooftop

packagedunitsystems.ManyofthelesscommonHVACsystemswerenotincludedin

thecasestudies.Thisreportdidnotidentifyanywatersourceheatpumporgascooling

sitesthathaveimplementedDRstrategies.

Thisguidefocusesonsummerpeakdemandreductionstrategies,althoughlightingDR

strategies can be utilized to reduce winter demand as well. Most of the examplesintroducedinthisreportarebasedoncasestudiesinthenorthernorcentralCalifornia

region,whichhasamildorhotanddry climate.This reportdoesnot include careful

considerationoftheapplicationofDRtofacilitiesinhotandhumidclimates.


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This guide is intended as a starting point for organizing and presenting such

information.Although the information isbasedona limitednumberofbuildings, the

authors compiled the existing case study data because of the need for organized

informationonthissubject.Theinformationinthisguidehasbeenevaluatedbyseveral

professionalengineersandenergyanalyststobringbuildingHVACandcontrolstheory

intothediscussionofDRstrategies.

1.4. Benefits to California

This guide isbased primarily on case studies in California and is intended to help

streamline the DR control strategy implementation process and increase successful

participation in DR programs in California. Peak demand reduction and demand

responsearekeypartsofthestatesenergypolicies.

1.5. Report Organization

Thissectiondiscussestheguidesbackground,objectives,organization,anddefinitions,

terms, and concepts.Section 2provides anoverviewof the characteristics ofdemand

response control strategies. These control strategies are presented in four categories:

HVAC, lighting, miscellaneous equipment, and nonendusespecific measures. In

Section 3, ten HVAC strategies, four lighting strategies, six miscellaneous equipment

strategies, and two nonendusespecific strategies are described in detail along with

their system requirements and sequences of operation. The appendices provide more

detailed descriptions and case study examples of each strategy. Section 4 discusses

commissioningandtheEMCSdatacollectionprocedure;measurementandverificationofdemandresponsestrategiesisveryimportanttoachievesuccessfuldemandresponse.

StatisticalfindingsfromtheDRstrategycasestudiesarealsointroducedinthissection.

ThisreportreviewedDRstrategiesthathavebeendemonstrated inactualbuildings in

previousresearchactivities,including;

EnhancedAutomation CaliforniaEnergyCommission(CEC2006a)

RealTime Price Response Program Independent System Operator New

England(ISONewEngland2003) AutomatedDemandResponse LawrenceBerkeleyNationalLaboratory(LBNL)

(Piette2005a,2005b)

AutomatedCriticalPeakPricing LBNL(Piette2006)

DemandShiftingwithThermalMass LBNL(Xu2004,2006)

Peak Load Reduction Program New York State Energy Research and

DevelopmentAuthority(NYSERDA2006andSmith2004)

NewYorkTimes LBNLandNewYorkTimes(Kiliccote2006)

DemandResponse

Program

Evaluation

Quantum

Consulting

and

Summit

Blue

Consulting(QuantumandSummitBlue2004)


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1.6. Bui lding Operation and Energy Management Framework

Thissectionprovidesbackground information forvariousenergyanddemandcontrol

activities.Italsoprovidesdefinitionsoftermsandconceptsusedinthisguide.

During the past few decades, knowledge and use of practices to minimize energy

consumption in commercial building design and operations has been improved to

achievegreater

levels

of

energy

efficiency.

Related

to

reduction

of

energy

use

isenergy

cost minimization. Electricity cost minimization inbuilding operations requires close

attentiontothestructuresofelectricitytariffs,whichconsiderthetimeandthequantity

ofelectricityused.Electricitypricing structurescanbecomplex, including timeofuse

charges, demand ratchets, peakdemand charges, and other related features. New

demand response programs and tariffs that utilities or independent system operators

(ISO) offer provide greater incentives to consider the use of sophisticated building

operationaland control strategies that reduceelectricityuseduringoccasionalevents.

Following are three definitions forbuilding design and operational control strategies.

Table 1 provides insight into the motivations, design, and operation of these three

strategies(Kiliccote2006).

Energy Efficiency and Conservation: Energy efficiency lowers energy use while

providing the same levelof service.Energy conservation reducesunnecessaryenergy

use. Both energy efficiency and conservation provide environmental protection and

utilitybillsavings.Energyefficiencymeasurescanpermanentlyreducepeakdemand

byreducingoverallconsumption.Inbuildingsthisistypicallydonebyinstallingenergy

efficientequipment

and/or

operating

buildings

efficiently.

Energy

efficient

operations,

a

key objective of newbuilding commissioning and retrocommissioning (for existing

buildings),requirethatbuildingsystemsoperateinanintegratedmanner.

Table 1. Demand side management terminology and building operationsEfficiencyandConservation

(Daily)

PeakLoadManagement

(Daily)

DemandResponse(Dynamic

EventDriven)

Motivation

EconomicEnvironmentalprotectionResourceavailability

TOUsavingsPeakdemandcharges

Gridpeak

Price(economic)Reliability

Emergencysupply

DesignEfficientshell,equipment,systems,andcontrolstrategies

LowpowerdesignDynamiccontrolcapability

OperationsIntegratedsystemoperations

DemandlimitingDemandshifting

DemandsheddingDemandshiftingDemandlimiting

Initiation Local Local Remote

Peak Load Management: Daily peak load management hasbeen conducted in many

buildingstominimizetheimpactofpeakdemandchargesandtimeofuserates.Typical

peak load management methods include demand limiting and demand shifting.


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Demand Limiting refers toshedding loadswhenpredeterminedpeakdemand limits

areabouttobeexceeded.Demandlimitscanbeplacedonequipment(suchasachiller

or fan), systems (such as a cooling system), or a wholebuilding. Loads are restored

whenthedemandissufficientlyreduced.Thisistypicallydonetoflattentheloadshape

when the monthly peak demand is predetermined. Demand shifting is achievedby

changing the time that electricity isused. Thermal energy storage is an example of a

demand

shifting

strategy.

Thermal

storage

can

be

achieved

with

active

systems

such

as

chilled water or ice storage, or with passive systems such as precooling ofbuilding

mass.InCalifornia,timedependentvaluation(TDV)1isalsoinuseforbuildingenergy

code compliance calculations requiredby the statebuilding energy code (Title 24) to

take into account the time that electricity is used during the year (CEC 2005). TDV

acknowledgesthatsomeefficiencymeasuresreducesummerpeakelectricdemandmore

thanothers.

DemandResponse:Demandresponseisdynamicandeventdrivenandcanbedefined

asshorttermmodifications incustomerenduseelectric loads in response todynamicprice and reliability information. Demand response programs may include dynamic

pricing and tariffs, priceresponsive demand bidding, contractually obligated and

voluntarycurtailment,anddirectloadcontrolorequipmentcycling.Asdiscussedabove,

Demand limiting and shifting canbe utilized for demand response. DR can alsobe

accomplishedwithdemandshedding,whichisatemporaryreductionorcurtailmentof

peakelectricdemand.Ideallyademandsheddingstrategywouldmaximizethedemand

reductionwhileminimizinganylossofbuildingservices.

Figure 1 illustrates concept of typical electric load shapes for each energy/demandcontrolactivitydescribedabove.

1Time dependent valuation (TDV) is an energy cost analysis methodology that accounts for

variationsincostrelatedtotimeofday,seasons,geography,andfueltype. InCalifornia,under

TDV thevalueofelectricitydiffersdependingon timeofuse (hourly,daily, seasonal)and the

valueofnaturalgasdiffersdependingonseason.TDVisbasedonthecostforutilitiestoprovide

theenergyatdifferenttimes.


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6

0

1

2

3

4

5

6

7

8

9

10

1:00

2:00

3:00

4:00

5:00

6:00

7:00

8:00

9:00

10:00

11:00

12:00

13:00

14:00

15:00

16:00

17:00

18:00

19:00

20:00

21:00

22:00

23:00

0:00

Time of day

Buildingdemand

Baseline

Energyefficiency

Demandlimiting

Demand

shedding

Demandshifting

*Thischartisconceptual;thedataarenotfromactualmeasurements.

Figure 1. Examples of load shapesLevelsofAutomation forDR:Varying levelsofautomation forDRcanbedefinedas

follows. Manual Demand Response involves a laborintensive approach such as

manually turning off or changing comfort set points at each equipment switch or

controller. SemiAutomated Demand Response involves a preprogrammed load

sheddingstrategyinitiatedbyapersonviacentralizedcontrolsystem.FullyAutomated

DemandResponsedoesnotinvolvehumanintervention,butisinitiatedbyanEnergy

ManagementControlSystem(EMCS)inahome,building,orfacilitythroughreceiptof

anexternalcommunicationssignal,receiptofwhichinitiatespreprogrammedsheddingstrategies.

Recent evaluations have shown that customers have limited knowledge of how to

operatetheirfacilitiestoreducetheirelectricitycostsundercriticalpeakpricingorCPP

(Quantum and Summit Blue 2004). While lack of knowledge of how to develop and

implementDRcontrolstrategies isabarrier toparticipation inDRprograms likeCPP,

anotherbarrieristhelackofautomationinDRsystems.MostDRactivitiesaremanual

andrequirepeopletofirstreceiveemails,phonecalls,andpagersignals,andsecondly

forpeopletoactonthesesignalstoexecuteDRstrategies(Piette2006).

1.7. Terms and Concepts for DR Strategies

Thetermsdefinedbelowdescribekeyconceptsofdemandresponsecontrolstrategies.

Thesetermsareusedthroughoutthisreport.

Reductioninservice:Demandresponsestrategiesachievereductionsinelectricdemand

by temporarilyreducing the levelofservice in the facility.HVACand lightingare the

systemsmost commonlyadjusted toachievedemand response savings in commercialbuildings.Thegoalofdemandresponsestrategiesistomeetthedemandsavingstargets

while minimizing any negative impacts on the occupants of the buildings or the

processesthattheyperform.


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7

Occupant satisfaction: Occupant satisfaction shouldbe maintainedby adjusting DR

strategies tominimizethereduction inservice,so that theoccupantsdonotnotice the

changeinservice(detectability),oratleastsothattheoccupantscanacceptthechanges

(acceptability). Many studies have addressed the effect of temperature changes or

lighting changes on occupant detectability, acceptability, and task performance.

Newsham et al. conducted an extensive literature search on these studies (Newsham

2006).

OnecommonquestionregardingDRstrategies is: Ifyoucanuseastrategy forashort

period,whynotuseitallthetime?Eveniftheoccupantsdonotnoticethereductionin

service,theoccupantsproductivitymaybehigherwhenthespaceconditionsarecloser

to the occupants desirable conditions. Differencesbetween the impacts of shortterm

and longterm space condition changes are yet unknown. Daily demand savings

associatedwithreductioninserviceshouldbeconsideredcarefully.SeeLinkstoretro

commissioningbelowfordiscussionofrelatedtopics.

Sharedburden:DRstrategies thatshare theburdenevenly throughout the facilityare

least likely to have negative effects onbuilding occupants. For example, if it were

possibletoreducelightinglevelsthroughoutanentirefacilityby25%duringaDRevent,

impacts tooccupantsmightbeminimal.However, turningoff allof the lights inone

quadrantofanoccupied spacewouldnotbeacceptable. InHVAC systems, strategies

thatreduceloadevenlythroughoutallzonesofafacilityaresuperiortothosethatallow

certainareas(suchasthosewithhighsolargains)tosubstantiallydeviatefromnormal

temperature ranges. By combining demand savings from shed in each component of

HVAC and lighting systems (and other loads, if available), the impact on eachcomponentisminimizedandthedemandsavingspotentialisincreased.

Closedloop control: Comfort is maintained in modernbuildings through the use of

closed loop controls. Sensors are used to measure important parameters such as

temperature,andactuatorsadjustdampersorvalvestomaintainthedesiredsetpoints.

Theeffectofthevalveoractuatoronthecontrolledzoneorsystemismeasuredbythe

sensor, hence closing the (control) loop. Control subsystems for which there is no

feedbackfromsensorsareknownasopenloopcontrols.

TomaintainpredictableandmanagedreductionsofserviceduringDRevents,strategies

shouldmaintaintheuseofclosedloopcontrolwhereverpossible.However,closedloop

control may become an obstacle to achieve demand savings when the final target

parameter cannotbe changed through centralized control. (For example, pneumatic

control systems cannot change zone setpoints from centralized control, while typical

directdigitalcontrolsystemscan.)Forinstance,ifsupplyairtemperatureisraisedina

closedloopcontrolsystemtoreducechillerdemand,thefanspeedsuptodelivermore

air to satisfy the zone setpoints and fails to shed HVAC demand, unless the zone

setpointsareincreased.

Granularity of control: For the purposes of DR control inbuildings, the concept of

granularityreferstotheamountoffloorareacoveredbyeachcontrolledparameter(e.g.


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8

temperature).Ifthespacehasmanyzonesthatcanbeseparatelycontrolled,thecontrol

strategyisconsideredhighlygranular.InHVACsystems,theabilitytoeasilyadjustthe

temperaturesetpointofeachoccupiedspace isahighlygranularwaytodistribute the

DR shed burden throughout the facility. Less granular strategies such as making

adjustments tochillersandothercentralHVACequipmentcanprovideeffective shed

savings,butcancausetemperatureinsomezonestodriftoutofcontrol.Granularityof

control

can

also

allow

building

operators

to

create

DR

shed

behaviors

that

are

customized for their facility.Anexamplewouldbe to slightly increasealloffice zone

temperaturesetpoints,butleavecomputerroomsetpointsunchanged.

Resolutionofcontrol:Higherresolutionofcontrolincreasestheflexibilitytoadjustthe

levelofDRcontrolwithinadesirablerange.Higherresolutionofcontrolalsoenhances

thecapabilityoframpingup thechangeofDRcontrolparameters.HVACparameters

canoftenbecontrolledwithhighresolution;inmanysystemstemperaturesetpointscan

beadjustedbyas littleas0.1F.Although somemodern fluorescentdimmingballasts

can adjust individual lamps light output in 1% increments, most commercial lampballastsareonlycapableofturninglampsonoroff.

Rebound: At the end of each DR event, the affected systems must return to normal

operation.When lighting strategies areused forDR,normaloperation is regainedby

simplyreenablingall lightingsystems totheirnormaloperation.Lightscomebackon

as commandedby time clocks, occupancy sensors, or manual switches. There is no

reasonforlightingpowertojumptolevelsthatarehigherthannormalforthatperiod.

However, without special forethought, HVAC systems tend to use extra energy

followingDReventstobringsystemsbacktonormalconditions.Extraenergyisusedto

removeheatthatistypicallygainedduringthereducedservice levelsoftheDRevent.

ThispostDReventspikeisknownasrebound. Tominimizethechanceofhighdemand

chargesandtoreducenegativeeffectstotheelectricgrid,reboundshouldbeminimized

throughuseofagracefulreturntonormalstrategy.ThesimplestcaseiswheretheDR

eventendsorcanbepostponeduntilthebuildingisunoccupied.Ifthisisnotpossible,

strategies that allow HVAC equipment to slowly ramp up or otherwise limit power

usageduringthepostDRperiodshouldbeused.

Links to retrocommissioning:Assuming theHVACand lightingsystemsarealready

operatedtoachieveoptimaloccupantsatisfactionandminimizeenergyconsumptionin

their normal operation, the implementation of DR may cause a reduction in service.

However,therearemanycasesinrealitywherethesystemsarenotoperatedoptimally.

Inthesecases,itmaybepossibletoreduceelectricdemandwithoutreductioninservice.

Ifafacilityfindssuchastrategy,itshouldbeconsideredapermanentenergyefficiency

opportunityratherthanatemporaryDRstrategy,andshouldbeperformedonnonDR

daysaswell.

Planning a DR strategy can be a good opportunity to examine the sequence and

parameters of building control. While facility managers may be concerned about

deviations from current operation only for energy efficiency, they may be more


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9

motivated if the goal isboth energy efficiency and DRbecause the occupants canbe

morepermissiveunderaDRsituationinmanycases.Onceconfirmedthatthestrategy

doesnotnegatively impactthelevelofservice,thestrategycanbeoperatedonadaily

basis.

TheLBNLAutoDRstudies foundseveralcaseswhereDRstrategiesmerely impacted

thelevelofserviceandincorporatedthestrategiesintheirdailyoperation(Pietteetal.

2005a,2005b,2006).Inoneexample,aductstaticpressureresetstrategywasusedforabuildingwithpneumaticzone controls.Through thiseffort todevelop shorttermDR

strategies,theductstaticpressurewasresettooperatelowerduringalloperatinghours.

In another case, reduction in service actually improved occupant comfort or

productivityinsomezonesthatwereovercooledduringnormaloperation.Thesecases

can be viewed as classic retrocommissioning opportunities, identified through the

processofdevelopingDR strategies. Inother instances,when examining electric load

shapes, the team found equipment, such as fans or process equipment, running

unnecessarilyatnight.Inaddition,ifsystemsinafacilityareoperatingpoorlyduetodesignorcommissioning

issues, it maybe more difficult to implement effective DR strategies. For example, if

zones are overcooled due to excessive minimum airflows or low supply air

temperatures, raising zone temperature setpoints during a DR event will not save

energy.

DRstrategycommissioning:Theprocessofcommissioningshouldbeapplied toeach

phase of DR control strategy application including planning, installation, and

implementationtomakesurethatthegoalofDRcontrol tomaximizedemandsavings

andminimizeimpacttooccupants isachieved.Thecommissioningprocedureandkey

issuesaredescribedinSection4.1.

DesignofDRcontrol strategieswould ideally takeplaceduring thenewconstruction

commissioning phase and be incorporated into the commissioning process. A

demonstrationof this concept isbeingplannedat theNewYorkTimesHeadquarters

building(Kiliccoteetal.2006).


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10

2. Demand Response Strategy Overview

This section provides an overview of demand response control strategies. These

strategies are categorized into four areas: HVAC, lighting, miscellaneous equipment,

andnoncomponentspecificmeasures.Thedetailsofeachstrategyaredescribedinthe

followingsection.

2.1. HVAC Systems

HVAC systems canbe an excellent resource forDR shed savings for several reasons.

First,HVACsystemscreateasubstantialelectricdemandincommercialbuildings,often

more thanone thirdof the totaldemand.Second, the thermalflywheeleffectof indoor

environments allows HVAC systems tobe temporarily unloaded without immediate

impacttothebuildingoccupants.Third,itiscommonforHVACsystemstobeatleast

partiallyautomatedwithEMCS.

However,therearesignificanttechnicalchallengestousingcommercialHVACsystemstoprovideDRsavings.Thesesystemsaredesigned toprovideventilationandthermal

comfort to the occupied spaces. Operational modes that provide reduced levels of

service or comfort are rarely included in the original design of these facilities. To

provide reliable, repeatable DR sheds it isbest to preplan and automate operational

modes that will provide DR savings. The use of automation reduces labor costs

associatedwiththeimplementationofDRoperationalmodes.

HVACbasedDRstrategiesrecommendedforagivenfacilityvarybasedonthetypeand

conditionofthebuilding,mechanicalequipment,andEMCS.Basedonthesefactors,thebestDR strategiesare those thatachieve theaforementionedgoalsofmeetingelectric

demand savings targets while minimizing negative impacts on the occupants of the

buildingsortheprocessesthattheyperform.ThefollowingDRstrategiesareprioritized

toachievethesegoals:

GlobalTemperatureAdjustmentofZones

SystemicAdjustmentstotheAirDistributionand/orCoolingSystems

It is often difficult to estimate the demand savings that willbe achievedby HVACstrategies,becauseHVACcoolingloadisdynamicandsensitivetoweatherconditions,

occupancy, and other factors. However, previous research has found that the HVAC

demand and its demand savings tend to have positive correlation with outside air

temperature(OAT).

In all field tests that used HVACbased DR strategies, upon initiation of DR events,

temperatures in occupied zones drifted from normal levels at rates well within the

acceptablerateofchangespecificationallowedinASHRAEStandard552004(ASHRAE

2004).DRstrategiesused toreturnHVACsystemstonormaloperationshouldalsobe

designed to limit the rate of temperature change so as to not exceed the ASHRAE

standard. DR strategies that slowly return the system to normal condition have the

additionalbenefitoflimitingrebound.


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11

HVAC strategies canbe categorizedby the system targeted for control modification.

Theseincludezonecontrol,airdistribution,andcentralplant,inorderofrecommended

priority. Where practical, DR strategies that use temporary modifications to zone

temperaturesetpointsarerecommended.Thisrecommendationisbasedonmaximizing

DRshedsavingseffectivenesswhileminimizingthepotentialforoccupantdiscomfort.

Figure2showsthebasicconceptoftheHVACDRstrategydecisiontree.

START

Zone

control

DDC zone

control?

Y NDDC zone

control?

Y N

Central plant

control

Air

distribution

control

Air distribution

System DDC?

Y NAir distribution

System DDC?

Y N Central plant

DDC?

Y NCentral plant

DDC?

Y N

Do not try DR

at this time

Figure 2. HVAC DR strategy decision tree

BuildingHVACtypes

Building HVAC types are characterized using the following four primary system

attributesand the secondaryattributes listed inTable2.Theprimaryattributes are (1)

constant air volume (CAV) or variable air volume (VAV), and (2) central plant with

chilled water system or packaged units. Applicable DR strategies depend on these

system types. Applicability based on these attributes is described in each strategy

section.Manyofthe lesscommonHVACsystems, includingwatersourceheatpumps

andgascoolingsystems,arenotincludedinthisstudy.

Table 2. Bui lding HVAC typesType Primarysystemattribute Secondarysystemattribute

TypeACAVsystemwithcentralplant(CAVCentral)

Singlezone/multizoneSingleduct/dualductWithreheat/withoutreheatTypeofchiller

TypeBVAVsystemwithcentralplant(VAVCentral)

Singleduct/dualductWithreheat/withoutreheatTypeofchiller

TypeCCAVsystemwithpackageunits(CAVPackage)

Singlezone/multizoneSingleduct/dualductWithreheat/withoutreheat

TypeD

VAVsystemwithpackageunits(VAVPackage) Singleduct/dualductWithreheat/withoutreheat

CAV:Constantairvolume VAV:Variableairvolume


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12

Table3provides shortdefinitionsofDR strategies and theirapplicabilitybybuilding

HVAC type.Onecan findabuildingHVAC type that is theclosest toonesbuilding,

andlookforthosestrategiesthatareappropriate.EveniftheHVACtypematches,the

strategieslistedheremayormaynotbefeasible,dependingonthecontrolattributesof

yourbuilding.

Table 3. HVAC demand response strategies

Category

DRStrategy

Definition

A

B

C

D

Globaltemperature

adjustment

Increasezonetemperaturesetpointsforan

entirefacilityX X X X

Zone

control Passivethermal

massstorage

Decreasezonetemperaturesetpointspriorto

DRoperationtostorecoolingenergyinthe

buildingmass, andincreasezonesetpointsto

unloadfanandcoolingsystemduringDR.

X X X X

Ductstaticpressure

decrease

Decreaseductstaticpressuresetpointsto

reducefanpower.X X

Fanvariable

frequencydrivelimit

Limitordecreasefanvariablefrequencydrivespeedsorinletguidevanepositionsto

reducefanpower.

X X

Supplyair

temperatureincrease

IncreaseSATsetpointstoreducecooling

load.X X X X

Fanquantity

reduction

Shutoffsomeofmultiplefansorpackage

unitstoreducefanandcoolingloads.X X X X

Air

distribution

CoolingvalvelimitLimitorreducecoolingvalvepositionsto

reducecoolingloads.X X

Chilledwater

temperatureincrease

Increasechilledwatertemperaturetoimprovechillerefficiencyandreducecooling

load.

X X

Chillerdemandlimit Limitorreducechillerdemandorcapacity. X X

Central

plant

Chillerquantity

ReductionShutoffsomeofmultiplechillerunits. X X * *

SlowrecoverySlowlyrestoreHVACcontrolparameters

modifiedbyDRstrategies.** ** ** **

Sequential

equipmentrecovery

RestoreHVACcontroltoequipment

sequentiallywithinacertaintimeinterval. **

**

** **

Rebound

avoidance

ExtendedDRcontrol

Period

ExtendDRcontrolperioduntilafterthe

occupancyperiod.** ** ** **

*Thestrategycanbeappliedtopackagesystemsbyreducingshuttingoffsomeofthecompressors.

**ApplicabilityofreboundavoidancestrategiesisdeterminedbytheDRstrategiesselected.

ZonecontrolstrategiesGlobalTemperatureAdjustment

This strategy requires zone level direct digital control (DDC) that can be easily

programmedtorespondgloballytodemandresponsecommands.Somecontrolsystem

manufacturersprovideproducts thatenable thezonesetpointsofall thermostats tobe

changed globally by one parameter. This software feature is known as global

temperatureadjustment(GTA).ForcontrolsystemsthatdonotofferGTAasastandard

feature,itcanusuallybeprogrammedduringtheinstallationorretrofitprocess,atacost


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somewhathigher than if itwereastandard feature.Thisstrategyhasproven tobean

effectiveandminimallydisruptivetechniqueforachievingHVACdemandresponse.

Airdistributionstrategies

Insystemsforwhichglobaltemperatureadjustmentofzones isnotanoption(suchas

those that are not DDC), strategies that make temporary adjustments to the air

distributionormechanicalcoolingsystemscanbeemployedtoenabledemandresponse.

IftheHVAC(fans,chillers,orboth)isaconstantvolumesystem(withoutVAV),direct

controloftheequipmentmaybeconsidered.

If the HVAC system is VAV, a combination of multiple parameter controls canbe

considered.Within a closed loop system, fansand chillers always try tomaintain the

required set points by changing HVAC parameters. For example, a supply air

temperature(SAT)increasemightreducechilledwaterflowtosavecoolingenergy,but

fanpowermightrisetoincreaseairflowtomaintaincoolingzonesetpointsattheVAV

boxes

(which

try

to

compensate

for

warmer

supply

air

by

supplying

more

air).

To

achieve a demand reduction, the fan and chiller control strategies may require

simultaneous modifications. One may want to limit or fix the chilled water supply

temperature, and simultaneously limit or fix the variable frequency drive (VFD)

percentagetoreducefanpower.

While effective in achieving load reductions, the use of systemic adjustments to air

distribution systems and/or mechanical cooling systems for DR purposes has some

fundamental drawbacks. In these strategies, the DR burden is not shared evenly

between all the zones. Centralized systemic HVAC DR shed strategies can allowsubstantialdeviations in temperature,airflow,andventilationrates insomeareasofa

facility.Centralizedsystemicchanges to theairdistributionsystemand/ormechanical

cooling systems allow zones with low demand or those that are closer to the main

supply fan to continue to operate normally and hence these zones do not contribute

towardloadreductioninthefacility.Zoneswithhighdemand,suchasthesunnysideof

thebuildingorzonesattheendsoflongductruns,canbecomestarvedforair.Aftera

VAV box is fully opened, its zone setpoint is no longer under control. Increased

monitoringof

occupied

areas

should

be

conducted

when

using

these

strategies.

Coolingstrategies

Most modern centrifugal, screw, and reciprocating chillers have the capability of

reducing theirpowerdemands.This canbedoneby raising the chilled water supply

temperature setpoint orby limiting the speed, capacity, number of stages, or current

drawofthechiller.Thenumberofchillersrunningcanalsobereducedinsomeplants.

As mentioned above, reducing the central plant load can typically achieve larger

demand savings than canbe achievedby reducing the air distribution load. These

strategiesmaycausesomeairdistributionload increases,whichareusuallymorethan

compensatedforbycentralplantloadreductions.


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14

Reboundavoidancestrategies

As mentioned in section 1.7, HVAC systems tend to experience rebound, using extra

energy following DR events in order tobring systemsback to normal conditions. To

minimize the chance of high demand charges and to reduce negative effects on the

electric grid, rebound shouldbe minimized through use of a gradual return to the

normalstrategy.ThesimplestcaseiswheretheDReventendsorcanbepostponeduntil

thebuildingisunoccupied.Ifthisisnotpossible,strategiesthatallowHVACequipmentto slowly rampup or otherwise limit power usage during the return to normal state

shouldbeused.

2.2. Lighting Systems

Onahotsummerdaywhendaylight isabundant,daylitand/oroverlitbuildingsare

thebest candidates for demand reduction using the lighting system. Since lighting

producesheat,reducinglightinglevelswillalsoreducethecoolingloadwithinthespace

and allow the HVAC strategies to work for extended periods of time. Research has

shownthateachkWhoflightingsavingscanalsoprovideadditionalcoolingsavingsby

reducing the cooling load. This savings varies in quantity by building type and

characteristics,climatezone,andseasonoftheyear.AnLBNLstudyestimatedthat,ona

nationalannualaverage,1kWh lightingsavings induces0.48kWhcoolingsavings for

existingcommercialbuildings(SezgenandKoomey1998).

Lightingdemandshedstrategies tend tobesimpleanddependwidelyonwiringand

controlsinfrastructures.However,sincelightingistypicallyassociatedwithhealthand

safetyandtheshedstrategiestendtobevisible,theyhavetobecarriedoutselectively

andcarefullyconsideringthetasksperfomedinthespaceandramificationsofreduced

lightingfortheoccupants.Typically,theresolutionoflightingcontrolstendstobelower

thanthatofHVACcontrols.Also,lightingsystemsareoftennotautomatedwithEMCS.

These issuescanbemajorobstacles forautomationof lightingDRstrategies,although

lightingstrategiesarepopularlyusedinmanualDR.

Estimating the demand savings potential of lighting strategies depend on how the

demandsavings

are

achieved.

Demand

response

control

capability

of

lighting

systems

is

generallydeterminedbythecharacteristicsoflightingcircuitandcontrolsystem.There

are two ways to implement demand response control with lighting, absolute reduction

and relative reduction. Absolute reduction is achievedby programmingpreset lighting

level for times when demand response is required. This maybe configured in many

differentwaysbasedonthelightingcontrolstrategies,i.e.halfthefixtureson,onethird

ofthelampsineachfixtureon,oralllampsat70%offulllightoutput.

Theproblemwithanabsolutereductionapproachisthatitdoesnotyieldanysavingsor

mayevenincreaselightingelectricityconsumptionifthelightinglevelsarethesameasor lower than the preset levels at the time demand response is initiated. Therefore,

althoughthisapproach iseasyto implementwithcurrent lightingcontrolsystems,the

demandsavingsestimatevariesdependingonthebuildinguseandoccupancy.


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15

Relativereductionmeansreducingloadswithrespecttotheleveloflightingatthetime

ofdemand response. Insteadof reducing toapreset level,acertainpercent reduction

over the current value is achieved during a demand response event. Implementation

requires that the light output from the lamp or power output from the ballast is

communicatedback to the lighting control system, so central closed loop control is

required.Systemswithsuchsophisticatedcontrolstendtobenewerandmoreexpensive.

The

decision

to

implement

absolute

or

relative

lighting

reduction

depends

on

the

buildinglightinginfrastructure,thelightinguse inthebuilding,andthecapabilitiesof

theinstalledlightingcontrolsystem.

FollowingisalistoflightingDRstrategiesinincreasingorderofsophistication.

Zoneswitching

Fixtureswitching

Lampswitching

Steppeddimming

Continuousdimming

START

Central lighting

control?

Y NCentral lighting

control?

Y N

Dimmable

ballast?

Y NDimmable

ballast?

Y N

Zone

switching

Zone

switching?

Y NZone

switching?

Y N

Bi-level

switching?

Y NBi-level

switching?

Y N

Do not try DR

at this time

Fixture

switching

Continuous

dimming

Lamp

switching

Stepped

dimming

Bi-level

infrastructure?

Y NBi-level

infrastructure?

Y N

Step dimming

capability?

Y NStep dimming

capability?

Y N

Figure 3. Light ing DR strategy decision tree

Figure 3 presents a decision tree to assist in strategy development. Each strategy isdescribedindetailinsection3below.

Controlstrategyplanningprocedure

While the decision tree in Figure 3 shows the decision process, within a facility it is

common to find various vintage of equipment and control systems for lighting, as

retrofits tend to happen in stages depending on the varying tasks and their lightingrequirementswithinthespaces.Itisimportanttostartwiththereflectedceilingplanof

a facility tounderstand the zones, circuits, and control infrastructures. Granularityof

controlsdescribeshowmuchfloorareaiscoveredbyagivencontrolparametersuchas


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16

a photosensor. Less granular strategies affect more occupants and tend tobe more

disruptive. More granular strategies require welldesigned and wellimplemented

infrastructuresandallowoccupantstobetteracceptDRstrategyimplementation.

2.3. Miscellaneous Equipment

DR can target other equipment besides HVAC and lighting. If the equipment is

independentfromanycriticaloperation,thesequenceofcontroldoesnotrequiresuchcareful consideration. One issue of shedding miscellaneous equipment is that this

equipment is often not connected to the EMCSbut rather isoperated standalone. In

commercialbuildings,thedemandresponsepotentialofmiscellaneousequipmentshed

is usually insignificant compared to HVAC or lighting shed. On the other hand, in

industrialsites,significantdemandreductioncanbeachievedbytemporallyunloading

processloadswithoutjeopardizingtheprocessorproductquality

2.4. Non-Component-Specific Control Strategies

The demand response control strategies mentioned above can be controlled in a

sophisticatedmannerwiththeuseofanadvancedEMCS.CombinationofDRstrategies

are programmed in the EMCS to coordinate appropriate strategiesbased on various

conditionalparameterssuchasoutsideair temperature,wholebuildingdemand level,

orelectricitypricelevel.Thesestrategiesmayrequireahighlevelofprogrammingeffort.

2.5. Strategies Used in Case Studies

Table4andTable5summarizetheDRstrategiesusedduring4yearsintheLBNLAuto

DRstudiesand theothercasestudies.The listcontains56participants(35commercial

and 9 industrialbuildings). All 40 LBNL project sites implemented the strategies as

fullyautomatedDR,whiletheothercasestudiesusedeithermanualorsemiautomated

DR.


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17

Table 4. DR strategies used in LBNL Auto-DR studies (fully-automated)

Building use 20

03

20

04

20

05

20

06

Globaltemp.adjustment

Du

ctstaticpres.

Increase

SA

TIncrease

Fa

nVFDlimit

CH

Wt

emp.

Increase

Fa

nqty.reduction

Pre-cooling

Co

olingvalvelimit

Bo

ilerlockout

Fa

n-coilunitoff

Electrichumidifieroff

Ch

illerdemandlimit

Slowrecovery

Ex

tendedshedperiod

Co

mmonarealightdim

Officearealightdim

Tu

rnofflight

Dimmableballast

Bi-levelswitching

An

ti-sweatheatershed

Fo

untainpumpoff

No

n-criticalprocessshed

Office X

Office X

Office X X

Office X

Office X X X X X

Office X X X X X

Office X X

Office X X

Office X

Office X X

Hi-tech office X X X X X X X X

Hi-tech office X

Office, data center X X X X X

Office, data center X X

Office, lab X X X X X X

Office, lab X X X X X X X

Office, lab X X

Office, lab X X

Research facility X X

Cafeteria, auditorium X

Archive storage X

Library X X X

Highschool X X

Junior Highschool X X

Detention facility X

Retail X X X X

Retail X X

Retail X X

Retail X X

Furniture retail X

Furniture retail X

Supermarket X X X

Supermarket X

Supermarket X

Supermarket X

Museum X X

Distribution center X X

Manufacture, office X X

Bakery X

Material process X

Participation HVAC Lighting Other

*Somesitesparticipatedin2003or2004studystoppedduetoineligibilitytoparticipateinCPP.

*IntheParticipationcolumn, indicatestheyearofparticipation,andindicatesthatthesite

wasintheprocessofdevelopingtheDRstrategiesindicatedincolumnstotheright.


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Table 5. DR strategies used in case studies (manual or semi-automated)

Building useRerefenced

studies Globaltemp.adjustment

Duct

staticpres.Increase

SAT

Increase

FanVFDlimit

CHW

temp.Increase

Fanqty.reduction

Pre-cooling

Fan-coilunitoff

Chillerdemandlimit

Chillerqty.reduction

Commonarealightdim

Officearealightdim

Turn

offlight

Dimm

ableballast

Bi-levelswitching

Non-

criticalprocessshed

Elevatorcycling

Shut

offcoldstorage

Wwa

terpumppeakshift

Office Quantum X X X

Office Quantum X X X X X X X

Food process Quantum X X X

Glass process Quantum X

Chemical repackage Quantum X X X

Packing & cold storage Quantum X X X X

Packing & cold storage Quantum X X

Retail NYSERDA X X

Cement process NYSERDA X

Office NYSERDA X X X

Irrigation NYSERDA X

Lumber process SCE X

Office SCE X X

Office DOE Project X X X X X X X X

Library ISO New England X X

HVAC Lighting Other

Figure4illustratesthenumberofsitesforeachstrategyused.Themostpopularstrategy

usedwasglobal temperatureadjustment,ofwhichnearlyhalfof the listed sitesused.

DuctstaticpressureincreaseandSATincreasewerethesecondmostpopularstrategies.

0 5 10 15 20 25

Global temp. adjustment

Duct static pres. Increase

SAT Increase

Fan VFD limit

CHW temp. Increase

Fan qty. reduction

Pre-cooling

Cooling valve lim it

Turn off light

Dimmable ballast

Bi-level switching

# of sites

Fully-Automated Manual or Semi-Automated

Figure 4. Frequency of DR strategies


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3. Demand Response Strategy Detail

Thissectiondescribesthedetailsofthesystemoperationmethodsofdemandresponse

strategies.Eachstrategy isexplainedwithsystemrequirements,sequenceofoperation

andspecific issues toconsider.The information is firstsummarized in table formand

thenexplainedbelow.

3.1. HVAC Systems

ThissectiondescribesthedetailsofHVACDRcontrolstrategies.Table6throughTable

15summarizethekeyinformationonthestrategy,andthedetailsareexplainedbelow

thetable. Definitionsofitemsinthetablearelistedbelow,

DefinitionBriefdefinitionoftheDRcontrolstrategy.

HVACtypeApplicableHVACtypesasdefinedinTable2.

Target loads HVAC system component or equipment whose electric load is

targetedtobereducedbytheDRstrategy.

Category DR approach: demand shed, demand shift, or demand limit as

definedinSection1.6.

System applicabilityHVACorcontrolsystemcharacteristicsrequired touse

theDRstrategy.

Sequence

of

operation

Detailed

sequence

of

operation

used

to

program

the

EMCStoimplementtheDRcontrolstrategy.

EE potentialPotentialofachievingsavings fromenergyefficiencyaswellas

DRbyapplyingtheDRstrategyduringregularpracticeoutsideofDRevents.

ReboundRiskof reboundpeakandnecessityof reboundavoidancestrategy

fromapplyingtheDRstrategy.

Cautions Miscellaneous issues to be considered when the DR strategy is

appliedto

mitigate

and

avoid

any

risks.

Applied sites Number andbuilding type of the LBNL AutoDR participant

sites that applied the DR strategy. None indicates the DR strategy was not

implemented at the LBNL AutoDR sites, but was used in some other case

studiesoratan excandidate site that implemented the strategybut couldnot

automateit.


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3.1.1. Global temperature adjustment

Table 6. Condi tions for g lobal temperature adjustment (GTA)

Definition Increasezonetemperaturesetpointsforanentirefacility.

HVACtype All

Targetloads Airdistribution,cooling

Category

Demandshed

System

applicability

1.DDCzonecontrol

2a.Globaltemperatureadjustment(GTA)capabilityatzonelevel,or

2b.CapabilitytoprogramGTAateachVAVbox.

Option1:Absolutesetpointadjustment

Globallyadjust(increase)allzonecoolingsetpointstoacommon

value(e.g.76F),TcF

Globallyadjust(decrease)orleaveunchangedallzoneheating

setpointstoacommonvalue(e.g.68F),ThF

(Tc:DRmodecoolingsetpoint,Th:DRmodeheatingsetpoint)Sequenceof

operationOption2:Relativesetpointadjustment

Globallyadjust(increase)allzonecoolingsetpointsbyacommon

differentialtemperaturefromtheirpriorsetpoint(e.g.2F),TcF

Globallyadjust(decrease)orleaveunchangedallzoneheating

setpointsbyacommondifferentialtemperaturefromtheirprior

setpoint(e.g.2F),ThF

(Tc:DRmodecoolingsetpoint,Th:DRmodeheatingsetpoint)

EEpotentialSomeoccupantsmaybemorecomfortableduringDRevents. This

wouldindicatemakingpermanentchangestothesetpoints.

Rebound Reboundavoidancestrategyrequired.

CautionsAdjustzonetemperaturesetpointsinmultiplestepsifalongshed

durationisrequired.

Appliedsites

15officebuildings,6retailstores,2laboratoryfacilities,2schools,

1manufacturingfacility,1museum,1archivestorage,1detention

facility

Global Temperature Adjustment (GTA) of occupied zones is a strategy that allows

commercialbuildingoperators toeasily adjust the space temperature setpoints for an

entirefacilitybyonecommandfromonelocation.Typically,thisisdonefromascreen

onthehumanmachineinterface(HMI)totheEMCS.Infieldtests,GTAwasshowntobe

the most effective and least objectionable strategy of the HVAC DR strategies tested

(Pietteetal.2005a,2005b,and2006).Itismosteffectivebecauseitreducestheloadofall

associatedairhandlingandcoolingequipment.Itisleastobjectionablebecauseitshares

the

burden

of

reduced

service

level

evenly

between

all

zones.

GTA

based

DR

strategies

can be implemented either automatically based on remote signals or manually by

buildingoperators.


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thesevendorsprovidedsomeofthelargestshedsandrequiredtheleastamountofset

uplabor.

For sites that have EMCS controlled space temperature zones,but lack GTA, it can

typically be added in the field. To add GTA to an existing site, each EMCS zone

controllermustbeprogrammedtolistenforaglobalGTAcommandfromthecentral

EMCS system. In addition, the central system must be programmed to send GTA

commandstoallrelevantzonecontrollersontheEMCSdigitalnetwork.TypicallyGTAcommandsaresentinaglobalbroadcasttoallcontrollerssimultaneously.

Manufacturersofferdifferent typesofVAVzone setpointconfigurationmethods.The

followingtwoexamplesarecommonVAVzonesetpointconfigurations.

1. Definezonecoolingsetpointsandzoneheatingsetpointsseparately.

2. Definethemidpointbetweenzonecoolingsetpointsandzoneheatingsetpoints

andthewidthofthedeadband.2Increasingthedeadbandmakescoolingsetpoints

higher and heating setpoints lower. Raising the midpoint makesboth coolingandheating setpointshigher.Figure 6 shows the change in thedeadband and

required airflow change in a VAV system.3 Increasing the cooling setpoints

reducestherequiredairflow.

Heating

setpoint

Cooling

setpoint

Min

CFM

AirflowCFM

Deg-FThNew

setpoint

TcNew

setpoint

Original

deadband

New deadband

ThTh TcTc

Setpoint-airflow relationship

with original deadband

Setpoint-airflow relationship

with new deadband

Figure 6. Zone setpoints deadband

2Deadband in thecontextofzone temperaturecontrolhas twodefinitions;1) the temperature

range between actuation and deactuation of the cooling or heating system, and 2) the

temperature range where no cooling or heating (beyond that required to provide freshair) is

provided.Although the firstdefinitionhasbeenhistoricallyused, theseconddefinition isalsocommonlyused.Thisreportusestheseconddefinition.

3 Figure 5 shows proportional control for illustrative purposes. Most zone controllers use

proportionalandintegralcontrolalgorithms.


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IfGTAofzonesisavailable,itistherecommendedHVACDRstrategyforcommercial

buildings.Infieldtests,sitesthatusedHVACDRstrategiesotherthanGTAusuallydid

sobecausethatfeaturewasnotavailableatthesite.ReasonsthatGTAwasnotavailable

include:1)Space temperaturewasnotcontrolledby theEMCS (e.g.useofpneumatic

controlsinoccupantzones),and2)SpacetemperaturewascontrolledbytheEMCS,but

thespacetemperaturecontrollersdidnotincludetheGTAfeature.

WhiletheGTAstrategyreducestheserviceleveloftheoccupiedspaces,itdoessousinga closedloop control strategy in a highly granular fashion. This causes the DR shed

burden tobeevenlysharedbetweenallbuildingoccupantsandkeepsallzonesunder

control.Sincenoneof thezonesare starved forairflow, there isno riskofventilation

ratesdroppingbelowspecifieddesignlevels.

SometimesiftheHVACsystemsareoversizedandthechillersarenotcontrolledbythe

percentage of zones asking for cooling, the GTA strategy has tobe combined with

supplyair temperature reset.One typicalexample isabuildingwithmultiple rooftop

units,wherethecompressorsarecontrollednotbyhowmanyzonesaredirectlyaskingfor cooling, but by meeting the supply air temperature setpoints. If the units are

oversizedortheminimumsupplyairflowrateistoohigh,GTAmaynotworkandthe

zone temperatures will not follow the new setpointsbecause of the excessive cooling

providedby theminimumair flow. In thatcase, theSATsetpointhas tobe increased

about3~5oFintheGTAperiodtoreducetheminimumcoolingdeliveredbytheHVAC

system.

TheGTA strategyworkswellwithmostbuiltupHVAC systems,where typically the

chillersshutoffifthepercentageofzonesthataskforcoolingislessthanapredefined

threshold.InGTA,ifnozonesaskforcoolingoncethenewsetpointisabovethecurrent

zone temperatures, thechillersnormally shutoffautomatically.Sometimes, insteadof

being completely shut off, the chillers will onlybe reduced to a partial capacity, to

maintaincoolingforsomehotspotsthatarepoorlybalancedorotherwiseoverloaded.

Thermalzonesthatarepoorlydesignedorpoorlybalancedcanalsoposechallengesdue

to overcooling. If minimum fresh air requirements are overcooling many zones, shed

savingsfrom

aGTA

DR

strategy

alone

may

not

be

effective.

This

problem

can

be

solved

by increasing the supply air temperature in addition to raising the zone temperature

setpoints.

DemandsavingscomponentsofGTA

Demand savingsby theGTA strategy consistsof twoparts, steadystate savingsand

transientsavings. Whenzonesetpointsareraised,coolingisturnedofforreducedtoits

minimaloperationuntilzonetemperaturesreachthenewsetpoints(transientsavings).

After zone temperatures are stabilized at the new setpoints, the cooling load is still

lowerthanthebaselinecoolingloadduetoasmallerdifferencebetweenzonesetpoints

andOAT(steadystatesavings).


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Transient savings can be achieved by the thermal mass storage effect of building

structuremass,includingfloorslabandinteriorandexteriorwalls,furniture,andother

materials. When zone setpoints are increasedby the GTA strategy, the thermal mass

componentshave stored coolingenergy.The thermalmass coolsdown the indoorair

anddisplaces the cooling loaduntil it runsoutof stored cooling energy.Durationof

transient savings can widely vary depending on factors includingbuilding structure,

outside

air

flow

rate,

internal

heat

gain,

and

solar

heat

gain

through

windows.

Figure7 illustratesaconceptualdiagramofdemandsavings (notactual fielddata)by

theGTAstrategywithzonesetpoint(ZTsetpoint)increasefrom72Fto76F. Thezone

temperture (ZT read) is also shown. A case study of this strategy is introduced in

AppendixA,sectionA.1.

0

100

200

300

400

500

11

:00

11

:30

12

:00

12

:30

13

:00

13

:30

14

:00

14

:30

15

:00

15

:30

16

:00

16

:30

17

:00

17

:30

18

:00

18

:30

19

:00

Time

WholeBuildingPower[kW]

70

75

80

85

90

95

Temperature[F]

Baseline DR demand ZT SP ZT read

Transient Savings

Steady-State Savings

Figure 7. Conceptual d iagram of demand savings for typical HVAC-based demand

response strategy


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3.1.2. Passive thermal mass storage

Table 7. Conditions for passive thermal mass storage

DefinitionDecreasezonetemperaturesetpointsduringoffpeakhourspriortoacurtailmentto

storecoolingenergyinthebuildingmass,andthenincreasezonesetpointstounload

fanandcoolingsystemduringacurtailment.

HVACtype All

Targetloads Airdistribution,cooling

Category

Demandshiftordemandshed

System

applicability

1.DDCzonecontrol

2a.Globaltemperatureadjustment(GTA)capabilityatzonelevel,or

2b.CapabilitytoprogramGTAateachVAVbox.

3.Mediumtohighbuildingmass.

Sequenceof

operation

DecreasezonetemperaturesetpointsbyTc1Fpriortoacurtailment.

IncreasezonetemperaturesetpointsbyTc2Fduringacurtailment.

EEpotentialOccasionallyproducestotalenergyusagesavingsinmildclimates,especiallywhen

nighttimefreeventilationcoolingisused. However,totalenergyusagemayincrease

dependingonclimate,buildingtype,andprecoolingschedule.Rebound Reboundavoidancestrategyrequired.

Cautions

ThisstrategyisapplicabletodayaheadDRprograms,wheretheeventnotificationis

sentonthedaybefore. Iftheeventnotificationisonthesameday,thereisnot

sufficienttimetostoreenoughcoolingenergy. Thepassivethermalmassstorage

controlisverycomplicatedandhastobedoneproperly. Testing,adjusting,and

balancingcontrolschedulesarerecommendedinthepreparationphase.Avoidover

coolingduringtheprecoolingperiodtopreventcoldcomplaintsfromoccupants.

Appliedsites 1officebuilding,1museum

Precooling the thermalmassof thebuildingcanbeused toreduce thepeak load.Forexample,insummer,thebuildingmasscanbecooledduringnonpeakhourstoreduce

thecoolingloadinthepeakhours.Asaresult,thecoolingloadisshiftedintimeandthe

peak demand is reduced. Thebuilding mass canbe cooled most effectively during

unoccupiedhoursbecauseitispossibletorelaxthecomfortconstraints.

Thermalmasscontrolstrategiesdiffer in theway theystoreandreleaseheat from the

mass.Thebuildingmassmaybecooledbynaturalormechanicalventilation,withor

withoutmechanicalcooling.Precoolingcanbeperformedeitherduringtheunoccupied

hoursorduringtheoccupiednonpeakhours,usuallyinthemorning.Inclimateswitha

large diurnal temperature swing, it may be possible to precool the building mass

withoutmechanicalcooling.

Ifthereissufficientprecoolingandthedaytimecoolingloadisrelativelylow,itmaybe

possible for the indoorair temperature toremainwithin thecomfortrangeduring the

peakhourswithoutanymechanicalcooling.Coolingenergystored inthemasscanbe

dischargedduringthepeakhoursbyeitherzonaltemperatureresetordemandlimiting

thecooling

plant

and

distribution

system

(Xu

2004).

Adetailed

simulation

study

of

the

passivethermalmassstoragestrategyissummarizedinAppendixA,sectionA.2(Braun

etal.2001).


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3.1.3. Duct static pressure decrease

Table 8. Conditions for duct static pressure decrease

Definition Decreaseductstaticpressure(DSP)setpointstoreducefanpower.

HVACtype B(VAVCentral),D(VAVPackage)

Targetloads Airdistribution,cooling(occasionally)

Category Demandshed

System

applicability

1.AllzonecontrolsystemsincludingpneumaticandDDC

2.DDCforairhandlingunit

Sequenceof

operationLowerDSPsetpointsbyX%.

EEpotentialTuningDSPsetpointscansavefanpowerconsistentlywithouta

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