Chapter 14:Chiller Evaluation ProtocolThe Uniform Methods Project: Methods forDetermining Energy Efficiency Savings forSpecific MeasuresCreated as part of subcontract with period of performanceSeptember 2011 – December 2014Alex Tiessen,Posterity GroupOttawa, OntarioNREL Technical Monitor: Charles KurnikNREL is a national laboratory of the U.S. Department of EnergyOffice of Energy Efficiency & Renewable EnergyOperated by the Alliance for Sustainable Energy, LLCThis report is available at no cost from the National Renewable EnergyLaboratory (NREL) at www.nrel.gov/publications.Subcontract ReportNREL/SR-7A40-62431September 2014Contract No. DE-AC36-08GO28308
Chapter 14:Chiller Evaluation ProtocolThe Uniform Methods Project: Methods forDetermining Energy Efficiency Savings forSpecific MeasuresCreated as part of subcontract with period of performanceSeptember 2011 – December 2014Alex Tiessen,Posterity GroupOttawa, OntarioNREL Technical Monitor: Charles KurnikPrepared under Subcontract No. LGJ-1-11965-01NREL is a national laboratory of the U.S. Department of EnergyOffice of Energy Efficiency & Renewable EnergyOperated by the Alliance for Sustainable Energy, LLCThis report is available at no cost from the National Renewable EnergyLaboratory (NREL) at www.nrel.gov/publications.National Renewable Energy Laboratory15013 Denver West ParkwayGolden, CO 80401303-275-3000 www.nrel.govSubcontract ReportNREL/SR-7A40-62431September 2014Contract No. DE-AC36-08GO28308
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AcknowledgmentsThe chapter author wishes to thank and acknowledge Greg McGuire of ICF International for histhoughtful contributions.iiiThis report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
AcronymsANSIAmerican National Standards InstituteBASbuilding automation systemEULeffective useful lifeHVACheating, ventilation, and air conditioningIPMVPInternational Performance Measurement and Verification ProtocolkWhkilowatt-hourM&Vmeasurement and verificationOAToutdoor air temperatureRULremaining useful lifeTMYtypical meteorological yearTRMtechnical reference manualivThis report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
Table of Contents123456Measure Description . 1Application Conditions of Protocol . 2Savings Calculations . 33.1 Determining Baseline Consumption . 3Measurement and Verification Plan . 64.1 Measurement and Verification Method . 64.2 Data Collection . 74.2.1Measurement Boundary . 74.2.2Measurement Period and Frequency . 84.2.3Measurement Equipment . 84.2.4Savings Uncertainty . 94.3 Interactive Effects . 94.4 Detailed Procedures . 94.4.1Chillers . 94.4.2Auxiliary Equipment . 114.5 Regression Modeling Direction . 124.5.1Recommended Method for Model Development . 134.5.2Testing Model Validity . 13Sample Design . 15Other Evaluation Issues . 166.1 Net-to-Gross Estimation . 166.2 Early Replacement . 166.3 Dual-Baseline Realization Rates. 16References . 17Bibliography . 18List of FiguresFigure 1. Dual baseline . 4List of TablesTable 1. Four Common Chiller Types . 1Table 2. Recommended Meter Accuracies . 9Table 3. Chiller M&V Procedures . 10Table 4. Auxiliary Equipment M&V Procedures . 12Table 5. Example of Data Required for Model Development . 13Table 6. Model Statistical Validity Guide . 13vThis report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
1 Measure DescriptionThis protocol defines a chiller measure as a project that directly impacts equipment within theboundary of a chiller plant. A chiller plant encompasses a chiller—or multiple chillers—andassociated auxiliary equipment. This protocol primarily covers electric-driven chillers and chillerplants. It does not include thermal energy storage and absorption chillers fired by natural gas orsteam, although a similar methodology may be applicable to these chilled water systemcomponents. 1Chillers provide mechanical cooling for commercial, institutional, multiunit residential, andindustrial facilities. Cooling may be required for facility heating, ventilation, and air conditioning(HVAC) systems or for process cooling loads (e.g., data centers, manufacturing process cooling).The vapor compression cycle, 2 or refrigeration cycle, cools water in the chilled water loop byabsorbing heat and rejecting it to either a condensing water loop (water cooled chillers) or to theambient air (air-cooled chillers). As listed in Table 1, ASHRAE standards and guidelines definethe most common types of chillers by the compressors they use (ASHRAE 2012).Table 1. Four Common Chiller TypesChiller TypeReciprocating,Screw, andScrollDescriptionReciprocating, screw, and scroll chillers use positive-displacementcompressors. These compressors increase refrigerant vapor pressure byreducing the volume of the compression chamber.CentrifugalReciprocating chillers compress air using pistons; screw chillers compressair using either single- or twin-screw rotors with helical grooves; and scrollchillers compress air through the relative orbital motion of two interfitting,spiral-shaped scroll members.Centrifugal chillers use dynamic compressors. These compressorsincrease refrigerant vapor pressure through a continuous transfer ofkinetic energy from the rotating member to the vapor, followed by theconversion of this energy into a pressure rise. Centrifugal chillers transferthis kinetic energy using impellers similar to turbine blades.Chiller plant auxiliary equipment includes chilled water and condensing water pumps; coolingtower fans and spray pumps (water-cooled chillers); condenser fans (air-cooled chillers), andwater treatment systems.Projects impacting chiller plant equipment generally fall into one of two categories: Equipment replacement. These projects involve replacing a chiller and possiblyreplacing some or all of the auxiliary equipment. Modifications to existing equipment. These projects typically involve adding controlequipment (e.g., adding a variable frequency drive to an existing centrifugal chiller toimprove its part-load efficiency).1As discussed in the section “Considering Resource Constraints” of the Introduction chapter to this report, smallutilities (as defined under U.S. Small Business Administration regulations) may face additional constraints inundertaking this protocol. Therefore, alternative methodologies should be considered for such utilities.2The vapor compression cycle consists of four main components: an evaporator, a compressor, a condenser, and anexpansion valve.1This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
2 Application Conditions of ProtocolA program may address chiller energy-efficiency activities alone, but more often, broadercommercial, multiunit residential, or industrial custom programs will include these activities. Aschiller savings often occur at the same time many jurisdictions experience electricity systempeaks, savings from these projects can have a significant impact on a custom program’s summerpeak-demand savings.Service providers and other stakeholders design energy-efficiency programs to overcome marketbarriers through activities that address the available market opportunities. Chiller programs mayinclude some or all of the following activities: Training. Program administrators sometimes fund or develop training for serviceproviders. For example, in some jurisdictions, service providers do not routinelyundertake detailed common practice, feasibility studies for their customer base. If aprogram is to exploit to the fullest extent the achievable potential in its region, end usersneed to consider early replacement of equipment in their chiller plants. To facilitate thisdecision-making process, service providers may need training on how to conductinvestment-grade energy audits, using recommended practices. Development incentives. Program administrators sometimes provide incentives thatencourage end users to undertake detailed feasibility studies for chiller measures. Ideally,the incentives encourage end users to commission a detailed feasibility study, whichcould result in the development of a business case that would encourage end users tomove forward with a chiller measure. Implementation incentives. Program administrators often provide incentives toimplement chiller measures. Again, ideally, the incentives can encourage end users toinvest more capital upfront to install higher-efficiency equipment or to invest capitalsooner in early replacement projects.This protocol provides direction on how to reliably verify savings from chiller measures using aconsistent approach. It does not address savings achieved through training or through markettransformation activities.2This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
3 Savings CalculationsThis section presents a high-level gross energy savings equation 3 that applies to all chillermeasures. Section 4, Measurement and Verification Plan, provides detailed direction on how toapply this equation.Use the following general equation to determine savings (US DOE FEMP 2008).Equation 1kWh SavingsTotal (kWh SavingsChiller) (kWh SavingsAuxiliary)Where,kWh SavingsTotal First-year energy consumption savingskWhSavingsChiller/Auxiliary 𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝐿𝑜𝑎𝑑 𝑅𝑎𝑛𝑔𝑒 𝑘𝑊ℎ𝐵𝑎𝑠𝑒𝑙𝑖𝑛𝑒 𝑘𝑊ℎ𝑅𝑒𝑝𝑜𝑟𝑡𝑖𝑛𝑔 𝐶𝑜𝑜𝑙𝑖𝑛𝑔 𝐿𝑜𝑎𝑑And,kWhBaseline, Cooling Load Energy required by the baseline equipment (either existing orhypothetical) at a given cooling loadkWhReporting, Cooling Load Energy required by the new equipment at a given cooling loadThe approach for determining demand savings for chiller measures depends on the type of loadbeing served by the chiller plant: HVAC loads. For chillers serving HVAC loads, apply regional load savings profilesbased on regional weather (average daily load profiles for each season), calibratedbuilding simulation models, engineering models targeting peak demand periods, and/orpeak coincident factors to consumption savings data. Process loads. As load savings profiles vary, depending on the process, calculating thedemand savings for chillers serving process loads is not as straightforward as it is forchillers serving HVAC loads. First, produce project-specific load savings profiles andthen apply site-specific coincidence factors to determine coincident peak demandsavings.3.1 Determining Baseline ConsumptionA common issue for many chiller programs is the use of existing equipment in determining thebaseline for establishing project savings claims. The following discussion explains why this isnot always the correct baseline.3As presented in the Introduction, the protocols focus on gross energy savings and do not include other parameterassessments, such as net-to-gross, peak coincidence factors, or cost-effectiveness.3This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
To establish an appropriate baseline, consider three main replacement scenarios (Fagan et al.2011): Early replacement. Existing equipment has a remaining useful life (RUL). Replace-on-burnout. The effective useful life (EUL) of the existing equipment hasexpired. Natural turnover. Replacement of equipment for reasons other than energy savings.For the first scenario (early replacement), apply a dual baseline (Ridge et al. 2011), as shown inFigure 1. For the latter two scenarios, establish a hypothetical baseline that uses a new chillermeeting the applicable energy-efficiency standard 4 for the applicable jurisdiction. Thehypothetical baseline should also consider industry standard practices and the existingequipment, which may set higher efficiency levels than the applicable energy-efficiencystandards.Energy ConsumptionEnergyConsumptionof ExistingEquipmentEnergyConsumptionof HypotheticalEquipmentTimePeriod 1:RULExistingPeriod 2:EULNew - RULExistingFigure 1. Dual baselineAs shown in Figure 1, there are two distinct baseline periods: Period 1. For the duration of the RUL of existing equipment, the existing equipment isthe baseline. Period 2. For the remaining EUL of new equipment, use a hypothetical baseline.4American National Standards Institute (ANSI)/ASHRAE Standard 90.1 is an example of a widely recognizedenergy-efficiency standard.4This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
As available, use the program defined EUL for chiller equipment or consult regional technicalreference manuals (TRM); when program or TRM information is not available, use othersecondary sources. 5 Similarly, use the method defined by the program to determine the RUL ofbaseline chiller equipment. If this has not been previously established, consider defining RUL asthe difference between the EUL and current age of the chiller (or number of years since its lastrebuild) 6.56California’s Database for Energy Efficient Resources suggests an EUL of 20 years for chillers (CPUC 2008).Evaluators should use discretion regarding the scope of the rebuild and how it may impact the RUL of the chiller.5This report is available at no cost from the National Renewable Energy Laboratory (NREL) at www.nrel.gov/publications.
4 Measurement and Verification PlanThis section contains both recommended approaches to determining chiller energy savings andthe directions on how to use the approaches under the following headings: Measurement and verification (M&V) method Data collection Interactive effects Detailed procedures Regression model direction.4.1 Measurement and Verification MethodThis protocol recommends an approach for verifying chiller energy savings that adheres toOption A of the International Performance Measurement and Verification Protocol (IPMVP).Because it is not possible to measure performance data for hypothetical baseline equipment, thisprotocol recommends Option A (retrofit isolation—key parameter measurement) rather thanOption B (retrofit isolation—all parameter measurement).Key parameters that require measurement include cooling load data and independent variabledata, such as outdoor air temperature (OAT). Estimated parameters include manufacturer partload efficiency data. 7In some cases, metered data may be available directly from the facility’s building automationsystem (BAS). 8 Also, if required, the facility can add control points to the BAS, either as part ofthe implementation process or specifically for M&V purposes. Where the BAS cannot provideinformation, the protocol recommends using submeters and data loggers to collect data.To ensure th
2 or refrigeration cycle, cools water in the chilled water loop by absorbing heat and rejecting it to either a condensing water loop (water cooled chillers) or to the ambient air (air-cooled chillers). As listed in Table 1, ASHRAE standards and guidelines define the most common types of chillers by the compressors they use (ASHRAE 2012). Table 1.