Guidelines for Verifying Existing Building Commissioning Project Savings. Using Interval Data Energy Models: IPMVP Options B and C

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1 Guidelines for Verifying Existing Building Commissioning Project Savings Using Interval Data Energy Models: IPMVP Options B and C

2 2008 California Commissioning Collaborative Acknowledgements The information in this document is drawn from several existing measurement and verification guidelines and research. Efficiency Valuation Organization (EVO), International Performance Measurement and Verification Protocol (IPMVP), Concepts and Options for Determining Energy and Water Savings Volume 1, (April 2007) American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE). Guideline 14, Measurement of Energy and Demand Savings (2002) American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE). Research Project 1050: Development of a Toolkit for Calculating Linear, Change-point Linear and Multiple-Linear Inverse Building Energy Analysis Models, Final Report (November 2002) Prepared by: David Jump, Ph.D., P.E., Quantum Energy Services & Technologies, Inc. (QuEST) Technical Advisor: Ken Gillespie, Pacific Gas & Electric Company Reviewers: Hannah Friedman, P.E., Portland Energy Conservation, Inc. Sami Khawaja, Ph.D., The Cadmus Group Tracy Phillips, P.E., Architectural Energy Corporation Lia Webster, P.E., Portland Energy Conservation, Inc. Project Manager: Kirstin Pinit, Portland Energy Conservation, Inc. Technical Advisory Group: Narendra Amar Amarnani, Los Angeles County Ed Jerome, Cogent Energy James Bryan, Arden Realty Steven Long, Southern California Edison Doug Chamberlin, Cogent Energy Spencer Lipp, Lockheed Martin Business Process Solutions John Cullum, Southern California Gas Company Ann McCormick, Newcomb Anderson McCormick Jim Flanagan, Jim Flanagan Associates Tom Reichert, Engineered Mechanical Services Dakers Gowans, Left Fork Energy Howard Sacks, California Department of General Services Satinder Gulati, California State University Kevin Warren, Warren Energy Engineering The California Commissioning Collaborative is a non-profit corporation with a mission to support and promote the practice of commissioning in California. Its Advisory Council and Board of Directors are made up of utilities, state and federal government, researchers, designers, building owners, and commissioning providers.

3 Guidelines for Verifying Existing Building Commissioning Project Savings Using Interval Data Energy Models: IPMVP Options B and C

4 About this Guideline The Measurement and Verification (M&V) process is an industry accepted process based on measurements before and after an energy management program has been implemented in a facility. Several M&V guidelines exist that describe its application in a wide variety of projects. This guideline describes how to apply these general M&V concepts to existing building commissioning (EBCx) projects and programs. Commissioning existing buildings for the purposes of improving system operations and saving energy has become a widespread practice in recent years. Throughout California, there are several ratepayer funded energy efficiency programs that provide EBCx services to help California achieve its long-term energy efficiency goals. Commissioning practices in existing buildings also help meet requirements for sustainability certifications, such as the U.S. Green Building Council s Leadership in Energy and Environmental Design. This guideline is designed to help commissioning service providers, building owners and managers, and energy efficiency program managers to understand how to manage, design, and complete robust M&V procedures within individual EBCx projects. This Guide: Is written for commissioning service providers and those developing and implementing M&V within their EBCx programs. Provides guidance on designing M&V strategies, identifying and using data resources, selecting methodologies, and scheduling M&V activities. It describes the many synergies between an M&V and an EBCx process. Answers the following questions: o What is M&V and why is it necessary? o How can M&V be applied in an EBCx process? o What are the benefits of applying M&V to an EBCx project or program? The California Commissioning Collaborative (CCC) sponsored this project as part of its on-going effort to develop specific guidance to verify savings in EBCx projects. This guideline represents only one of many methods that may be employed. The CCC plans to develop additional guidance documentation in the near future. Revision Date: November 12, 2008

5 Contents 1. Introduction Purpose of This Guideline General Description of the M&V Process Application in EBCx Projects M&V Approach Option C Whole-Building Approach Option B Retrofit Isolation - Systems Definition Selection of Approach Required Resources Required Energy Metering Required Independent Variables and Sources EMCS as a Source of Data Data Management Analysis Methods Modeling Techniques Alternate M&V Methods Selection of Data Analysis Time Interval Amount of Data to Collect Selecting the Appropriate Model iii

6 5.6 Model Uncertainty Assessment Non-Routine Energy Use Measurement and Verification Process Baseline Period Post-Installation Phase Persistence Phase Demand Savings Average Peak Demand Savings Coincident Peak Demand Savings Appendix A. Empirical Models A.1 1-Parameter Model A.2 2-Parameter Model A.3 3-Parameter Change Point Heating and Cooling Models A.4 4-Parameter Change Point Models A.5 5-Parameter Model A.6 Multivariate Models A.7 Important Statistical Indexes Appendix B. Uncertainty Analysis B.1 Objective B.2 Definition of Uncertainty B.3 Sources of Uncertainty iv

7 B.4 Uncertainty Formulae B.5 Examples Appendix C. Example M&V Plan Biosciences Building C.1 Building Description C.2 Energy Use and Utility Rates C.3 M&V Objectives C.4 Definition of Approach C.5 Documentation of Baseline Conditions C.6 M&V Method and Process C.7 Data Sources and Assumptions C.8 Analysis of Baseline Information C.9 Calculation Method to be Used C.10 Verifying Savings at the Conclusion of Commissioning C.11 Verifying Savings Over Time C.12 Content and Format of All M&V Reports C.13 Responsibilities of Involved Parties C.14 Expected M&V Cost C.15 Schedule for All M&V Activities Appendix D. Example Projects D.1 Example I. Option C Whole Building Approach D.2 Example II. Option B Retrofit Isolation Approach v

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9 Using Interval Data Energy Models: IPMVP Options B and C 1. Introduction 1. Introduction This guideline documents measurement and verification (M&V) procedures based on short time interval energy data collected from existing buildings and their systems that are undergoing a commissioning process. It describes procedures with which commissioning providers may demonstrate realized savings to building owners, program managers, and program evaluators. It shows how integrating these data-driven M&V methodologies into commissioning processes not only supports completion of more robust commissioning projects, but also sustains ongoing energy performance. This guideline is based on the principles and practices of the industry standard International Performance Measurement and Verification Protocol (IPMVP) 1 as well as ASHRAE Guideline Measurement of Energy and Demand Savings. 2 It describes methods that can be applied under an Option C Whole Building approach, or to building systems under an Option B Retrofit Isolation approach. The required data, energy modeling techniques, and procedures to set up and complete Option B and Option C M&V analysis for energy and demand savings are described. This guideline provides additional information to help users with common issues and key concepts, such as selecting the appropriate M&V approach, developing robust baseline energy models, documenting an M&V Plan, and reporting results. To clarify the concepts; figures, definitions, resources, and examples are provided throughout the document. The appendices provide detailed descriptions of energy models, uncertainty analysis, an example M&V Plan, and two examples of M&V applied in existing building Commissioning (EBCx) projects. 1 The International Performance Measurement and Verification Protocol, Concepts and Options for Determining Energy and Water Savings, Volume 1, April 2007, is available from the Efficiency Valuation Organization at: 2 ASHRAE Guideline : Measurement of Energy and Demand Savings, is available at The IPMVP defines four M&V Options (p.21, IPMVP): Option A. Retrofit Isolation, Key Parameter Measurement Savings are determined by field measurement of the key performance parameters which define energy use of affected systems. Parameters not selected for field measurements are estimated. Option B. Retrofit Isolation: All Parameter Measurement Savings are determined by field measurement of the energy use of the affected system. Option C. Whole Facility Savings are determined by measuring energy use at the whole facility or sub-facility level. Option D. Calibrated Simulation Savings are determined through simulation of the energy use of the whole facility or sub-facility. Simulation routines are demonstrated to adequately model actual energy performance measured in the facility. 1

10 Using Interval Data Energy Models: IPMVP Options B and C 1. Introduction Figure 1. Comparison of M&V and EBCx 3 Activities (see sidebar). M&V Process Baseline Period Define Scope of M&V Activity Identify purpose/goals of M&V activity Identify affected systems Design the M&V Process Assess Project & Source of Savings Define Approach Add points & collect data Energy and indep. variable (OAT, etc.) Bldg. level: gas pulse, steam meter, etc. Systems: Chiller kw, other var. loads Document the baseline Equipment inventory and operations Develop baseline energy model Assess baseline model Finalize and Document the M&V Plan Post-Installation Period Verify proper performance Collect post-installation data Develop post-install model Verify savings at conclusion of EBCx Develop savings report Persistence Phase Verify continued equipment performance Establish energy tracking system Provide periodic savings reports 3 Best Practices in Commissioning Existing Buildings, Building Commissioning Association, available at EBCx (RCx) Process Scope of Cx Activity Identify purpose/goals of Cx activity Describe roles of involved parties Identify systems included in Cx process Planning Phase Establish bldg. requirements Review available info./ visit site / interview operators Develop EBCx Plan Document operation conditions Investigation Phase Identify current building needs Facility performance analysis Diagnostic monitoring System testing Create list of findings Implementation Phase Prioritize recommendations Install/Implement recommendations Functionally test recommendations Document improved performance Turnover Phase Update building documentation Develop final report Update Systems Manual Plan ongoing commissioning Provide Training Persistence Phase Monitor and track energy use Monitor and track non-energy metrics Trend key system parameters Document changes Implement persistence strategies In Figure 1, the term Existing Building Commissioning (EBCx) has been used. EBCx is the Building Commissioning Association s (BCA) more generic term than retrocommissioning (RCx) for commissioning existing buildings. The BCA intends this framework to be inclusive of all terms relating to existing building commissioning, including retrocommissioning, recommissioning, and ongoing commissioning. This framework is illustrative of activities in a persistence phase that mirrors activities in long-term M&V processes. Please note that the first four phases of the EBCx process are very similar to the description of RCx in the California Commissioning Collaborative s California Commissioning Guide: Existing Buildings. 2

11 Using Interval Data Energy Models: IPMVP Options B and C 1. Introduction The M&V and EBCx processes have many common steps and activities. Figure 1 shows when M&V-related activities take place during an EBCx project. A more detailed description of the M&V process is provided in Section 6. This guideline helps users identify the many synergies between the two processes, so that users can take advantage of them and minimize additional M&V costs. M&V procedures provide the means to state energy savings within confidence limits. These savings are based on energy measurements before and after an improvement has been made. This is different than savings estimates that are based on data collected only in the baseline period (commonly referred to as ex-ante savings estimates), and engineering calculations and assumptions that vary widely in quality and depth. Savings based on M&V procedures are: independent of prior energy savings estimates. transparent in that their methodologies are well known and publicly documented. repeatable such that they can readily be reviewed and validated by third parties. 1.1 Purpose of This Guideline The purpose of this guideline is to describe practical M&V approaches using mathematical models of energy use developed from interval data (e.g. measured data recorded in short time intervals, typically 15 minutes at the whole-building level) to verify energy and demand savings in EBCx projects. The guideline identifies the large degree of overlap between the commissioning and M&V processes in terms of planning, data collection, analysis, validation, and persistence, and demonstrates the benefits of combining M&V and commissioning processes, thus enabling: Program managers and service providers to report savings based on the most rigorous methods available, which are comparisons of energy use before and after an EBCx project s recommendations have been implemented. 3

12 Using Interval Data Energy Models: IPMVP Options B and C 1. Introduction Feedback on energy performance of building systems, which allows operators to identify and diagnose problems in building operations that adversely affect energy performance. Facilitation of program evaluation by documenting baseline conditions and energy use, and quantifying savings according to common industry standards. Savings uncertainty to be estimated, so that program managers may assess savings risk, and that savings can be stated with a high degree of confidence. Creation and updating of energy baselines from which additional improvements can be quantified. This guideline is organized as follows: In Section 2 the reader is provided with an overview of the M&V process and important notes about applying it in EBCx projects. How to design the M&V process is described in Sections 3, 4, and 5. Section 3 describes how to select an M&V approach. Section 4 identifies the required data resources. Section 5 describes the baseline methodologies to be applied. Section 6 provides a step-by-step description of applying M&V within EBCx projects. Calculating demand savings is described in Section 7. Appendix A provides detailed descriptions of common modeling techniques and Appendix B describes the recommended uncertainty analysis. An example M&V plan for an EBCx project is provided in Appendix C, and Appendix D provides examples of developing baseline energy models under the two M&V approaches described in this guideline. 4

13 Using Interval Data Energy Models: IPMVP Options B and C 2. General Description of the M&V Process 2. General Description of the M&V Process Both the IPMVP and ASHRAE Guideline 14 describe M&V as a procedure to quantify the avoided energy use or demand resulting from energy conservation measures (ECMs). In commercial buildings, ECMs can reduce heating or cooling loads, replace systems and equipment with more efficient versions, add intelligent control systems, or improve system operations through commissioning. While this guideline shows how the M&V process can be integrated with a typical EBCx project, it can also be applied to most commercial building ECMs. Energy savings cannot be directly measured. Simple comparisons of energy use before and after an ECM installation are also insufficient because they do not account for the impacts of routine influencing parameters, such as ambient weather conditions, or building occupancy and schedule. However, M&V provides a means to calculate these realized energy savings through comparisons of energy use or demand before and after ECM installations and making adjustments to account for these influences. This allows a fair comparison of energy use under the same conditions. As will be described, M&V is a process that is based on energy measurements. In commercial buildings, systems and equipment delivering space conditioning, lighting, etc. consume energy in response to building service requirements. Therefore the M&V process is applied to the systems that consume energy, and from which data can be collected. The most common method is to develop a baseline model and project it to post-installation conditions. However, circumstances may dictate that both baseline and post-installation energy use can be projected to some other set of conditions, such as typical meteorological year (TMY) weather conditions. In this case a model of post-installation energy use is also required. Equations 1 and 2 below express this M&V concept mathematically. The Adjustments term in Equation 1 is used to enable the baseline and post-installation energy use to be compared under the same set of conditions. Equation 1 Energy Savings = Baseline Energy Use Post-Installation Energy Use ± Adjustments IPMVP describes the adjustments to energy use as being routine or non-routine. Routine adjustments to energy use are due to the aforementioned parameters that are expected to influence energy use: ambient temperature, occupancy, schedule, production rate, etc. Typically, the routine adjustments to the baseline energy use is represented as a mathematical model, referred to as the Adjusted Baseline Energy Use. Combining 5

14 Using Interval Data Energy Models: IPMVP Options B and C 2. General Description of the M&V Process these terms yields the form that will be used throughout this guideline, as shown in Equation 2. IPMVP describes this as avoided energy use. Equation 2 Energy Savings = Adjusted Baseline Energy Use Post-Installation Energy Use ± Non-Routine Adjustments In Equation 2, the Adjusted Baseline Energy Use is determined from the mathematical model using post-installation conditions. It describes what the baseline energy use would have been without the ECMs. The post-installation energy use is obtained from direct measurements. The non-routine adjustments term in the equation is used to account for unexpected changes that occur from time to time in buildings or systems that affect its energy use. Such changes can include increasing load on the HVAC and electrical systems through the addition of many computers and equipment in a space, or a major renovation project. M&V procedures require that a plan for accounting for non-routine adjustments be developed. Adherence with IPMVP requires that savings (or avoided energy use ) be based on measurements conducted in the reporting period. The reporting period is the post-installation period in which measurements are made, and analysis is completed. IPMVP requires that a full cycle of a building s or system s operation be measured and the data used to develop baseline energy models. To report annual savings, the post-implementation should also span a full cycle. For buildings, this cycle of operation is considered to be one full year. However, due to many circumstances typical to utility energy efficiency programs or RCx projects, neither the baseline nor the reporting period may span an entire year. Thus the first year energy savings often cannot be determined in strict adherence with IPMVP. In these cases, assuming that adequate baseline and post-installation energy models can be developed, the baseline and post-installation energy use can be projected to an annual use by restating or normalizing them to a separate set of full-year conditions (for example typical mean year weather data) in order to determine savings. IPMVP calls savings based on restating baseline and post-installation energy use to a separate set of conditions Normalized Savings. ASHRAE Guideline 14 does not use normalization. 6

15 Using Interval Data Energy Models: IPMVP Options B and C 2. General Description of the M&V Process Figure 2. Projecting Baseline Energy Use into Post-Retrofit Period. 4,500 4,000 Baseline Model: kwh = 79.9*OAT ,500 3,000 Daily kwh Use 2,500 2,000 1,500 Date Break 1, /9/2006 2/11/2006 Baseline Period 2/13/2006 2/15/2006 2/17/2006 2/19/2006 2/21/2006 2/23/2006 2/25/2006 2/27/2006 3/1/2006 3/3/2006 3/5/2006 3/7/ /31/ /2/2006 Date HVAC Daily kwh Usage 11/4/ /6/ /8/ /10/ /12/2006 Baseline Post-Installation Period 11/14/ /16/ /18/ /20/ /22/ /24/ /26/ /28/2006 The IPMVP Option B Retrofit Isolation and Option C Whole Building M&V processes described here require development of a model to predict how these factors affect energy use in the baseline period. The baseline model is then projected into the post-retrofit period so that baseline and post-installation energy use can be compared under the same set of conditions. Figure 2 is a demonstration of this concept. 7

16 Using Interval Data Energy Models: IPMVP Options B and C 2. General Description of the M&V Process 2.1 Application in EBCx Projects M&V is applied where measurements of energy use can be made. Measurements of energy use can be made on individual equipment, 4 on multiple components that make up a system, or collectively on all the systems within a building. For example, an Option B M&V process can quantify the savings of a pump motor retrofit based on measurements of electric energy and water flow rate before and after the retrofit. Option B M&V can also be applied to multiple pieces of equipment that make up a system, such as an air handling unit consisting of a supply and a return fan. Option C M&V is applied at the whole building level. Most ECMs in EBCx projects are corrections to problems in system operations, optimizations of control strategies, or adjustments to mechanical system settings. Because it is common to have multiple ECMs that affect one building system, as well as ECMs that affect multiple systems within a building, it is generally impractical to verify savings of each individual ECM using these methods. For systems or whole buildings where multiple ECMs have been implemented, the Option B or Option C M&V process verifies the cumulative savings of all implemented ECMs. The M&V process utilizing metered energy data described here provides direct feedback on equipment and system energy performance, not individual measure performance, and therefore provides a means for operators and owners to track energy use and make corrections when performance is degrading. This is a primary goal of the EBCx process as well to maintain optimum building system performance long after the EBCx project has been completed. 4 Section 5.2 describes retrofit isolation methods for individual equipment. 8

17 Using Interval Data Energy Models: IPMVP Options B and C 3. M&V Approach 3. M&V Approach As described above, EBCx ECMs are corrections to systems operations, and can affect one or multiple systems within a building. The amount of savings generated by an EBCx project varies widely, with most projects reporting savings between 5 and 15% of the building s annual energy use. 5 Energy use in buildings or systems can vary greatly over the year, and have a degree of randomness that is unexplained by any measurable factors. In order to obtain sufficient resolution, the savings must be much greater than this randomness, or uncertainty, in the data. Several factors affect the resolution of the savings above the uncertainty. One of the most important is the M&V approach, which is the boundary around the affected systems where measurements are made. Other factors include the analysis time interval (hourly or daily) and amount of data. These other factors are discussed later in this guideline. The measurement boundary can be drawn around a single piece of equipment, a system of equipment, multiple systems within a building, or around the whole building. Option B Retrofit Isolation approaches draw the measurement boundary around affected equipment or systems, and Option C Whole Building approaches draw it around the entire building. The measurement boundaries in Figures 3a and 3b illustrate these M&V approaches. Development of a baseline model for M&V purposes is an appropriate method to use in commissioning of complex and dynamic building HVAC systems that serve spaces with varying loads, schedules, and occupancies. Commissioning these systems requires extensive data collection from energy management and control systems (EMCS) and data collected from independently installed loggers. Such data can also be used to develop energy baseline models. 5 Mills, E., et.al., The Cost-Effectiveness of Commercial-Buildings Commissioning, available at: 9

18 Using Interval Data Energy Models: IPMVP Options B and C 3. M&V Approach Figure 3a. Measurement boundary representing Option C Whole Building Approach (blue dashed line). Figure 3b. Measurement boundary representing Option B Retrofit Isolation Approach (red dashed line). The Option B approach isolates the entire HVAC system in the building. Gas Meter DHW Hot Water Plant Chilled Water Plant MCC Gas Meter DHW Hot Water Plant Chilled Water Plant MCC VSD Air Handling Unit VSD Air Handling Unit VSD VSD L P Men Women L P Men Women L P L P L P L P L P Lighting and Plug Load kwh Meter L P Lighting and Plug Load kwh Meter 10

19 Using Interval Data Energy Models: IPMVP Options B and C 3. M&V Approach For each energy source, all energy flows into the boundary are measured and used in the analysis. For the Option C Whole Building approach, the main energy meters are used. There are no correspondingly common energy meters for equipment or systems. The energy flows must be identified and metered in order to use the Option B Retrofit Isolation approach. It is important to note that M&V accounts for energy use by individual energy source. For example, electric savings are verified in a separate M&V process than natural gas savings. The M&V approach is not required to be the same for all energy sources in a building. An Option B Retrofit Isolation approach may be selected to verify electric energy savings while an Option C Whole-Building approach may be used for natural gas savings. There are comparatively fewer end-uses for natural gas than for electricity in a building, and sub-metering natural gas use is often unnecessary. To illustrate how the resolution of savings is enhanced by the selection of the M&V approach, Figure 4 shows baseline and post-installation data and linear models for a building made more energy efficient through an EBCx process. The focus of the EBCx project was on the HVAC systems, which were defined to consist of the chillers, towers, pumps and air-handling units. In Figure 4a, the scatter in the whole-building data obscured the difference between the baseline and post-installation points. This difference, and therefore the savings, is much more distinctive in Figure 4b, which is based on HVAC system data only. Each figure shows the baseline energy models and their confidence limits. Note that the confidence limits have large overlap with postinstallation data in the whole-building approach, and no overlap in the systems-level approach. Results such as these are of course unavailable before an M&V approach is selected. However, the baseline data may be collected and assessed to help users select the most appropriate approach. This assessment is described in Section 5 and Appendix B of this guideline. 11

20 Using Interval Data Energy Models: IPMVP Options B and C 3. M&V Approach Figure 4a. Whole-Building Energy Use Data. 15,000 14,000 Daily kwh Use 13,000 12,000 11,000 10, Ambient Dry-Bulb Temperature Baseline Data Post-Install Data Baseline Model Upper 95% CL Lower 95% CL Figure 4b. HVAC Systems Energy Use Data. 4,500 4,000 Daily kwh Use 3,500 3,000 2,500 2,000 1,500 1, Ambient Dry-Bulb Temperature Baseline Data Post Data Baseline Model Upper 95% CL Lower 95% CL 12

21 Using Interval Data Energy Models: IPMVP Options B and C 3. M&V Approach 3.1 Option C Whole-Building Approach The definition of the Option C Whole-Building measurement boundary is straightforward for a building with only one type of energy source and one meter per source. For a building with multiple energy meters on the same energy source, for example for a building with two electric meters, data from the two meters may be combined before proceeding with analysis, or the approach may be applied to each meter separately. It may also be applied to only the meter serving the systems affected by the EBCx process. If only one of multiple metered energy sources is used, the remaining meters must be analyzed to show that energy use has not increased, or to account for interactive effects. 3.2 Option B Retrofit Isolation - Systems Definition The Option B Retrofit Isolation approach requires a boundary around the equipment or systems to be defined, and all energy flows (of the same energy source) across that boundary measured. The systems should be identified in a way that simplifies measurement or modeling of energy use. It is convenient to define the building s systems similarly to those of the end-use categories of the Commercial End-Use Survey (CEUS). 6 For example, a space heating system may be defined to include all hot water boilers and pumps used to heat and deliver hot water to heating coils throughout the building. Similarly, a space cooling system may be defined to include all chillers, cooling towers, chilled and condenser water pumps, etc. used to deliver chilled water to cooling coils. The energy use of each piece of equipment associated with the defined system must be measured and included in the analysis. For the hot water system there are two energy sources to be measured: electricity and natural gas, while for the chilled water system there is only electric energy to be measured. Defining systems in terms of HVAC and non-hvac systems has advantages in terms of developing energy models. The foremost advantage is that EBCx projects tend to focus CEUS End-Use Categories HVAC Space Heating Space Cooling Ventilation Non-HVAC Cooking Refrigeration Air Compressors Domestic Water Heating Inside Lighting Outdoor Lighting Office Equipment Miscellaneous Equipment Motors 6 Commercial End-Use Survey (CEUS), prepared for the California Energy Commission, available at: 13

22 Using Interval Data Energy Models: IPMVP Options B and C 3. M&V Approach on HVAC and their control systems. Similar to the Option C approach, energy use in HVAC systems is strongly influenced by the ambient air temperature. Thus similar energy modeling techniques can be used. Energy modeling is described in Section 5. Whereas the key independent variable for HVAC systems is ambient air temperature, non-hvac system energy use is more dependent on building schedule or time of day. In defining the building systems under Option B, consideration of the influencing parameters is very important as it can facilitate model development and reduce analysis time. The measurement boundary around building HVAC systems may be defined in more discrete categories, such as chilled water, condenser water, hot water, or air distribution systems. Figure 5a shows the measurement boundary for a chilled water system, and Figure 5b shows it for an air handling system. Table 1a below provides a list of representative equipment that make up electricity consuming systems in a building. Similar definitions can be made for other energy sources, however the list will be much shorter. Systems may also be combined, as shown in Table 1b. Defining systems by the service they provide is advantageous when the EBCx improvements are localized within these systems. As before, the measured energy use of all equipment within the measurement boundary is combined for the purposes of analysis. For example the energy use of the cooling tower fans and condenser water pumps in a condenser water system would be combined. In commissioning projects, there tend to be multiple recommendations that have a high degree of interaction that affect the energy use of the components within a system. Following are common examples. A chilled water system s energy use may be improved with the implementation of a supply water temperature set point reset control sequence, while simultaneously an inoperable coil valve is replaced, and flow in the chilled water bypass is reduced. Correcting each of these measures will result not only in reduced chilled water production and more efficient chiller operation, but also reduced pumping energy. Figure 5. Measurement boundary isolating building systems for Option B. 5a. Chilled water system (green dashed line). CW Pump PCHW Pump Cooling Tower Chiller VSD SCHW Pumps 5b. Air handling system (orange dashed line). VSD CHW 14

23 Using Interval Data Energy Models: IPMVP Options B and C 3. M&V Approach Table 1a. Electric Consuming System Definitions. Table 1b. Combined Systems. System Chilled Water Equipment Chiller(s) Primary Chilled W ater Pump(s) Secondary Chilled Water Pump(s) Combined Systems Combined Chilled Water System Subsystems Chilled Water Condenser Water Chilled Water Condenser Water Air Handling Cooling Tower Fan(s) Condenser Water Pump(s) Supply Fan(s) Return Fan(s) Exhaust Fan(s) HVAC System Water-Cooled DX System Hot Water Condenser Water Air Handling Condenser Water Packaged Air Conditioning Packaged Air Conditioning Air-cooled packaged unit(s) W ater-cooled packaged unit(s) Hot Water (Space Heating) Boiler(s) Hot Water Pump(s) Domestic Hot Water Boiler(s) Hot Water Pump(s) Compressed Air Air Compressor Air Dryer Lighting Interior Exterior Plug Loads Personal Computers/Workstations Copy Machines Problems in a variable air volume (VAV) air handling unit include faulty placement of the duct static pressure sensor, disconnected damper linkages in the VAV terminal units, and non-functional thermostats in some of the zones. Correcting each of these deficiencies will result in much improved supply and return fan modulation. It would also generate chilled water and hot water savings. 15

24 Using Interval Data Energy Models: IPMVP Options B and C 3. M&V Approach The system s energy use defined in this manner is additive. This has advantageous properties: For each energy source, the combined energy use of all the systems adds up to that of the whole building. This can be used as an internal check within the analysis, allows individual system s energy use be benchmarked for comparison, or enables estimation of energy use in systems that cannot be easily measured (for example, if energy use of all HVAC systems and the whole building are measured, but the lighting and plug loads are not, then they can be determined by subtraction). If the commissioning recommendations affect multiple systems, identify the affected systems and collect data and analyze them together to determine the total savings. For example, a variable volume air handling unit with its economizer stuck in the open position and a variable frequency drive in hand mode affects the energy use in the air distribution, chilled, and hot water systems. Combine the energy use from the air distribution, chilled and hot water systems together for analysis, or analyze them separately and combine the results afterward. Some measures may shift load from one system to another. If both systems are included in the data collection and analysis, then there is no need to account for the amount of load shifted. 3.3 Selection of Approach A guiding principle in selecting an M&V approach is to choose the approach that minimizes the amount of expense and effort while providing the necessary resolution in detecting the effect of the energy efficiency improvements. The simplest and most straightforward approach is the Option C Whole-Building approach. Most large commercial buildings in California (over 100,000 ft 2 ) have one or more electric interval data meters. One year of data is usually available from this source, and is enough to generate a baseline model. Interval natural gas data, or other heating source, is far less common but is found frequently on college campuses or in hospitals. If the expected 16

25 Using Interval Data Energy Models: IPMVP Options B and C 3. M&V Approach savings is too small to be detected using only whole-building interval data, for example less than 5%, then an Option B Retrofit Isolation approach should be used. The following factors can help in the selection of the M&V approach. Savings Magnitude. The savings must be large enough to be resolved from the uncertainty in the analysis. As described previously, most EBCx project savings are in the 5 to 15% range. As shown in Appendix B, savings uncertainty depends in large part on modeling uncertainty, which depends on how well the energy use models predict actual energy use. Well behaved buildings can exhibit uncertainties in energy use models as low as 2%, but it is common for building model uncertainties to be greater than 15%. While ASHRAE Guideline compliance criteria states that the level of uncertainty shall not be greater than 50% of the annual reported savings (at the 68% confidence level) for any performance path, 7 the owner or program manager should state their preferred uncertainty criteria, which should be much narrower (either lower uncertainty or higher confidence levels). These criteria should be determined after review of the baseline model uncertainty assessment, and review of costs related to monitoring and analyzing the data. The procedure to assess baseline model uncertainty is described in Appendix B. If the percent savings is not significantly greater than the whole-building baseline model uncertainty, the measurement boundary should be redrawn to isolate the affected systems. This can be achieved if there are multiple energy meters in the building, or by using an Option B approach. The expected savings should be a significant fraction of the system s annual energy use, significantly larger than the combined modeling and measurement uncertainty. Note that if savings are too small, it may be appropriate to use other M&V Options, or an entirely different verification strategy. As these alternate strategies are not yet documented in the CCC s Verification of Savings Project, please refer to the IPMVP descriptions of 7 ASHRAE Guideline , section 3.5.3, p.6. 17

26 Using Interval Data Energy Models: IPMVP Options B and C 3. M&V Approach Option A or Option D, as well as ASHRAE Guideline s Annex E Retrofit Isolation techniques. Systems where EBCx improvements are applied. The scope of the commissioning project may focus on specific systems to be investigated. This supports isolating the affected systems under an Option B approach. Availability of building interval energy metering. Buildings without 15-minute interval energy data are precluded from using the Option C approach, unless interval meters can be installed and enough baseline data gathered before starting the EBCx investigations. Otherwise a systems level approach should be considered. Limited availability of monitored data and storage capabilities. This prevents an Option B approach from being used unless an alternate monitoring system is available. The project team should consider adding the necessary energy use meters or independent variable points with temporary loggers or permanent monitoring equipment, or expanding the energy management and control system (EMCS) capabilities for trending and storing data. These additions should be considered in terms of the owners and program manager s goals in regard to tracking energy use for sustainability or persistence. Points may also be added to the EMCS to monitor the whole building energy use. Cost. There are significant costs associated with the addition of meters and points in the EMCS, independent logging, collecting, cleaning, and analyzing data, and providing M&V plans and savings reports. These costs should also be considered in light of the project s goals. If the expected lifetime of the savings can be increased with the addition of energy tracking capability, the M&V activities will be more cost effective, and the added metering costs can be justified. 18

27 Using Interval Data Energy Models: IPMVP Options B and C 4. Required Resources 4. Required Resources This section describes the basic requirements in preparation of using the data-driven models and analysis techniques for verifying energy and demand savings according to the methods described in this guideline. 4.1 Required Energy Metering Energy and demand data, measured and recorded in short time intervals, are essential to carry out this savings verification analysis. Short time intervals are necessary to obtain an understanding of how energy use is affected as its influencing parameters change over time. The maximum time interval between data points should be no more than one hour. Energy or demand data is often available in 5- or 15-minute intervals. The following sections discuss whole-building and systems energy types and data sources Whole Building Energy Use (Option C) Whole building electric energy or demand. Most utilities with customers in high demand rate categories record the electric energy use or demand from the building s electric meter at 15-minute intervals. Many buildings have multiple electric meters, in which case the energy use should be collected from meters on the circuits that power the subsystems that will be affected by the EBCx process. For example, if one electric meter serves the central plant in a building, and several EBCx operational improvements are made in the chilled water plant, then the data from that electric meter should be used to verify savings. Note that this is not a universal rule: some measures may cause energy penalties in other systems that are connected to other building meters, and these impacts should be determined. In this example, the air handling unit fan energy may increase and if the unit is connected to another meter, its impact should be quantified. Unless the utility electric meters have been recently installed, generally there will be well over a year s worth of whole-building electric interval data available from California Utilities maintain websites were customers with large demand may obtain their 15- minute electric interval data. The Utilities and websites are shown below. PG&E es/demandresponse/tools/ SMUD SCE ess/energymanager/ LADWP SDGE 19

28 Using Interval Data Energy Models: IPMVP Options B and C 4. Required Resources the utility. In California, buildings with loads over 200 kw have real-time electric metering and the data are available through the web sites listed in the sidebar. These data are typically averages over the time interval, not instantaneous readings. Natural gas consumption. Short-term interval data for natural gas consumption in a facility is far less common than whole-building electric interval data. However natural gas interval data can be measured using permanently installed calibrated digital flow meters or pulse counters attached to the gas meter faceplate. Their output is usually in volumetric units, such as cubic feet, and can be monitored by the building s EMCS, or an independent monitoring system. 8 While the pulse counters are also relatively inexpensive, they should be installed by the utility or other licensed contractor. Chilled or hot water use. A building may be connected to a central or district chilled or hot water generation plant. Btu meters are commonly used that have flow meters to measure water flow and temperature sensors that measure the temperatures of the entering and leaving water. The Btu meters calculate instantaneous thermal energy use and the result may be recorded by the EMCS or an alternate system. Alternatively, the measured water flow and temperatures are recorded independently and calculated at a later time. Steam use. A building may also obtain steam from a central plant. At the building, steam is measured using permanently installed steam meters, which measure total pounds of steam entering the building, or steam condensate meters which record the amount of condensed steam returning to the central plant. Condensate meters can be less reliable due to age and corrosion problems, and possible steam system leaks in the building. Coordination with and approval from the local utility is required when needing to add pulse output capability or interval data recording at the utilitysupplied main meters. PG&E s Tool Lending Library has many examples of metering technologies that collect short-term interval data, including: Gas meter faceplate reader/pulse counter Hot and chilled water BTU meters The Library s contents can be found on-line at: /pec/toolbox/tll/ If necessary metering not present consider adding it. Consider goals benefits to adding meters to gain feedback and insure savings persistence. M&V is savings insurance and will be worth the cost. 8 Such as an energy information system (EIS). Such systems are discussed in the LBNL research report Web-based Energy Information Systems for Energy Management and Demand Response in Commercial Buildings, LBNL-52510, available at: 20

29 Using Interval Data Energy Models: IPMVP Options B and C 4. Required Resources Short-term interval data for natural gas, hot or chilled water, or steam are generally not available from their respective utilities or district plants. If these points are available, they are usually connected to the building s EMCS, or to a separate energy monitoring system. The amount of data varies based on each building s resources. A well-written primer on metering technologies, communications, and data storage, is available System Level Energy Use (Option B) For major systems where multiple commissioning improvements will be implemented and the total energy savings resulting from those improvements will be verified, measurements of energy consumption at the system level may be required. Energy meters for directly monitoring energy use at the systems level are limited, and are found on a case by case basis, such as for chillers and motors equipped with variable frequency drives. More common are equipment feedback status signals that can be trended in a building s EMCS. These signals can be converted to energy use data with the aid of power measurements from instruments and independently installed power loggers. More information is provided below: Chiller electric energy. Many chillers are equipped with control panels that provide analog signals of chiller wattage or amps. This data may be recorded by the chiller s own control panel, or independently trended in the building s EMCS. Motors equipped with variable frequency drives (VFD). Many VFD provide analog output signals of motor and inverter wattage or amperage that can be monitored in an EMCS. Often, dip switches or programming on the VFD can be used to select the desired output. Before relying on the VFD output signal data, it should be checked against readings from a reliable watt or amperage meter. Feedback signals. Feedback signals are analog or digital input signals to the EMCS that indicate the status of operating equipment. Generally constant load PG&E s Tool Lending Library has many examples of hand-held instruments and metering technologies that collect short-term interval data. training/pec/toolbox/tll/ SCE also has an instrumentation lending library: signandengineering/instrumentationlendin gprogram/ 9 Metering Best Practices, A Guide to Achieving Utility Resource Efficiency, Federal Energy Management Program (FEMP), US Department of Energy, Energy Efficiency and Renewable Energy, Oct. 2007, available at: 21

30 Using Interval Data Energy Models: IPMVP Options B and C 4. Required Resources equipment is monitored with digital or binary on/off status signals, while variable load equipment are monitored by their variable speed, position, or load signal. o Constant speed fan and pump motors are monitored by signals indicating their on or off status, usually with a 1 or 0, respectively. o An example of a feedback signal for variable load equipment is the actual speed or output frequency of a VFD on a pump or fan motor, or the position of an inlet guide vane on an air handler fan. These variables may serve as proxy variables for energy use if a relationship between the feedback signal and the equipment s energy use can be determined. Figure 6 provides examples of both constant and variable speed feedback signals. o Both constant and variable load feedback signals can be made into proxy variables for energy use. Constant load equipment power can be measured when the equipment is on. Multiple measurements should be made and an average of the power taken. When equipment is on, its power will then be known. Further measurements of power are unnecessary, and only the equipment status signal should be trended. Variable load equipment RMS power consumption must be logged with a true RMS power meter over time as the VFD varies through its range of loads. Usually a few full days of VFD modulation, at 5-minute intervals will suffice to capture data throughout its range of speeds. Simultaneously a characteristic variable load feedback signal for that equipment must be trended. The data is then collected and data sets merged. A relationship between the power and variable load signal is then developed. The form of the relationship between the two variables may be guided by known physical relationships, such as cubic relationship between fan motor power and fan speed for variable speed applications. An example is shown in Figure 7. Fan kw Figure 6. Chart showing examples of timeseries binary and analog feedback signals. Figure 7. Cubic polynomial relationship between fan motor power and speed % /23/2008 3/24/2008 3/25/2008 3/26/2008 AH4.RET INLET VANE %OPEN kw = 2E-05*Speed *Speed *Speed Speed % 3/27/2008 3/28/2008 3/29/ STATUS AH1.RAF.STATUS ON/OFF Actual Cubic Polynomial Fit 22