Craig Wray, Jessica Granderson, Guanjing Lin, Xiufeng Pang

A Conceptual Plan for
Energy-Related Measurement
& Verification of Advanced
Retro-Commissioning Technology Demonstration Projects

Craig Wray, Jessica Granderson, Guanjing Lin, Xiufeng Pang

Building Technology and Urban Systems Division

Lawrence Berkeley National Laboratory

Prepared for:

DOE Building Technologies Office

June 25, 2015

DISCLAIMER

This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California.

ACKNOWLEDGEMENT

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Building Technology of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Much of the material in this document is derived from or was provided bythe International Performance Measurement and Verification Protocol, and documents published by the Federal Energy Management Program (FEMP) of the U.S. Department of Energy, and Quantum Energy Services and Technology (QuEST).

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TABLE OF CONTENTS

1.Introduction

2.Measurement and Verification: An Overview

3.M&V Options: Summary of Approaches

3.2 Option B: Retrofit Isolation With All Parameter Measurement

3.2.1 Approach to Option B

3.3 Option C: Whole-Building Data Analysis

3.3.1 Approach to Option C

3.3.2 Data Collection

3.4 Option D: Calibrated Simulation

3.4.1 Approach to Option D

3.4.2 Simulation Software

3.4.3 Model Calibration

4.Developing Regression Models for M&V

4.1 Independent Variables

4.2 Choosing a Model

5.Selecting an M&V Approach: IPMVP Options A-D

5.1 M&V Considerations for Option A

5.2 M&V Considerations for Option B

5.3 M&V Considerations for Option C

5.4 M&V Considerations for Option D

6.Developing an M&V Plan

7.Considerations for Technology Demonstration Projects

References

List of Acronyms

Other References

Bibliography

Appendix A: Site Selection Questionnaire

Appendix B: M&V Data Analysis Tool

Integration with Universal Translator

Modeling Method

Uncertainty Method

Other Tool Algorithms and Routines

Summary

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1.Introduction

Building commissioning is a systematic process that can be used to reduce building energy use and to improve indoor environmental conditions for occupants. Retro-commissioning (RCx) is specific to existing buildings and includes identifying performance goals as well as deficiencies and improvement opportunities. It also includes implementing changes through tuning, low cost repairs, and more capital-intensive retrofits as needed; and using measurement and verification (M&V) techniques to verify that changes indeed improve building operation. Examples of advanced strategies and technologies include using utility data to identify candidate buildings, integrating building automation systems with fault detection tools to inform stakeholders of opportunities, and implementing automated control system adjustments.

This document describes a conceptual approach for validating the benefits of RCx-related technology innovations relative to current practice, which can be used as a foundation for developing subsequent site-specific M&V plans. More specifically, it provides an overview of M&V practices that could be used to assess energy savings associated with implementing these technologies and includes a methodology for comparing post-installation performance to baseline data. It also includes project hypotheses, technical objectives, specific indicators of success, and criteria needed to select optimum implementation sites for technology demonstrations. Specific criteria include at least the following: facility size and characteristics, number of locations required to develop generalizable conclusions, and required performance data. A demonstration site questionnaire that addresses these criteria is included as an Appendix to support follow-on site selection efforts.

2.Measurement and Verification: An Overview

Energy savings themselves cannot be measured directly because they represent the absence of energy use. Instead, savings are determined by comparing the energy use before and after the installation of energy conservation measure(s).The “before” case is called the baseline; the “after” case is called the post-installation or performance period. Proper determination of savings includes adjusting for changes that affect energy use, but that are not caused by the implemented measure(s). Such adjustments account for changes in weather, occupancy, or other such factors that might differ between the baseline and performance periods. Equation 1 describes the general equation used to calculate savings:

Savings = (Baseline Energy - Post Installation Energy) ± Adjustments Eqn. 1

Equation 1 can be restated so that no adjustments need be made for the post-installation energy measurements. In that case, a regression model is developed from baseline energy use measurements and independent variables are used to determine “what baseline energy use would have been” under post-installation conditions.Similarly, both baseline and post-installation energy use may be restated to some set of conditions other than baseline or post-installation conditions.

M&V protocols to determine savings in energy conservation projects have existedsinceabout 1995. Notable protocols include the International Performance Measurement and Verification Protocol (IPMVP) – Volume I, the Federal Energy Management Program (FEMP) M&V Guidelines for Federal Energy Projects, and ASHRAE Guideline 14.

IPMVP Volume I(2014) provides guidance in the form of a conceptual framework for measuring, computing, and reporting savings achieved by energy or water efficiency projects in buildings. It defines key terms and outlines issues that must be considered when developing an M&V plan, but does not provide details for specific measures or technologies. Developed through a collaborative effort involving industry, government, financial, and other organizations, the IPMVP document provides four M&V options, and addresses issues related to the use of M&V in third-party-financed and utility projects.

The FEMP M&V Guideline (2008) contains specific procedures for applying concepts originating in the 2007 version of IPMVPVolume I. The Guideline represents a specific application of the IPMVP for federal projects. It outlines procedures for determining M&V approaches, evaluating M&V plans and reports, and establishing the basis of payment for energy savings during the contract. These procedures are intended to be fully compatible and consistent with the IPMVP document.

ASHRAE Guideline14 (2002) is a reference for calculating energy and demand savings associated with M&V activities. In addition, it sets forth instrumentation and data management guidelines and describes methods for accounting for uncertainty associated with models and measurements. It specifies three engineering approaches to M&V. Compliance with each approach requires that the overall uncertainty of the savings estimates be below prescribed thresholds. The three approaches presented in Guideline 14 are closely related to and support the options provided in IPMVPVolume I. Guideline 14, however, does not discuss issues related to performance contracting.

In general, M&V activities include site surveys, metering energy and independent variables, engineering calculations, and reporting. How these activities are applied to determine energy savings depends on characteristics of the energy conservation measures (ECMs) being implemented and balancing accuracy in energy savings estimates with the cost of M&V itself.

IPMVP Volume Ilists four M&V protocol optionsthatenable one to apply a range of suitable techniques for a variety of applications(summarized in Section 3 of this document, withexcerpts from Chapter 4 of the FEMP Guideline):

• Option A (Retrofit Isolation with Key Parameter Measurement).
• Option B (Retrofit Isolation with All Parameter Measurement).
• Option C (Whole Building).
• Option D (Calibrated Simulation).

A simple graphical representation of the savings impact demonstrated throughapplication of M&V is shown in Figures1 and 2. These data were collected as part of a monitoring-based commissioning project (MBCx) at UC Berkeley’s Soda Hall. In this IPMVP Option B approach, energy use by the HVAC systems (chillers, pumps, air handlers) was measured for three months prior to improving the operational efficiency of these systems. As Figure 1 shows, a baseline energy model was developed with a simple linear regression of daily energy use versus ambient dry-bulbtemperature.

Figure 1. Scatter plot of daily HVAC energy use vs.
ambient temperature (2-parameter model).

The resulting statistical indices (i.e. root-mean square error - RMSE) are shown in Figure 2. Ambient temperature and energy use data continued to be collected in the post-installation period, and the baseline energy use projected into the post-installation period using the model. Figure 2 shows the savings over the post-installation measurement period as the difference between the projected baseline model and the measured post-installation use.

Figure 2 is a powerful visualization of the M&V concept, and highlights its strengths in demonstrating savings to project and program sponsors. It is simple to understand, and provides several useful insights into the HVAC system energy use:

• Demonstrates the dependence of HVAC energy use with ambient temperature.
• Demonstrates magnitude of energy savings each day.
• Creates new baselines for additional projects.
• Compares post-installation model (orange line in post installation period) with post-installation energy use to provide an indication when energy performance is slipping, and can be used for on-going tracking purposes.

Figure 2. Representation of the M&V concept over time.

3.M&V Options: Summary of Approaches

M&V approaches are divided into two general types. One type (retrofit isolation)considers only the affected equipment or system independent of what occurs in the rest of the building. The other type (whole-building) considers the total energy use and de-emphasizes specific equipment performance. IPMVP Options A and B are retrofit isolation methods; Option C is a whole-building method; Option D can be used as either, but is usually applied as a whole-building method. One primary difference between these approaches is where the boundary of the ECM is defined. All energy used within the boundary must be considered.

The four generic M&V options are summarized in Table 1. Each option has advantages and disadvantages based on site-specific factors and the needs and expectations of the stakeholders.

Retro-commissioning efforts (RCx) usually focus on HVAC operations (although lighting is sometimes included), with improvements spanning many pieces of equipment, and have been shown to generate median savings of 16%. Therefore, IPMVP Options B, C, and D are most useful for quantifying RCx energy savings. If lighting measures are implemented, Option A is often used to determine end-use specific savings.

Table 1: IPMVP M&V Options

M&V Option / Performance and Usage Factors / Savings Calculation
Option A:
Retrofit Isolation with Key Parameter Measurement / This option is based on a combination of measured and estimated factors when variations in these factors are not expected. Measurements are spot or short-term and are taken at the component or system level, both in the baseline and post-installation cases. Measurements should include the key performance parameter(s) that define the energy use of the ECM. Estimated factors are supported by historical or manufacturer’s data. Savings are determined by means of engineering calculations of baseline and post-installation energy use based on measured and estimated values. / Direct measurements and estimated values, engineering calculations, and/or component or system models are often developed through regression analysis. Adjustments to models are not typically required.
Option B:
Retrofit Isolation with All Parameter Measurement / This option is based on periodic or continuous measurements of energy use taken at the component or system level when variations in factors are expected. Energy or proxies of energy use are measured continuously. Periodic spot or short-term measurements may suffice when variations in factors are not expected. Savings are determined from analysis of baseline and reporting period energy use or proxies of energy use. / Direct measurements, engineering calculations, and/or component or system models often developed through regression analysis. Adjustments to models may be required.
Option C:
Utility Data Analysis / This option is based on long-term, continuous, whole-building utility meter, or sub-metered energy data. Savings are determined from analysis of baseline and reporting period energy data. Typically, regression analysis is conducted to correlate with and adjust energy use to independent variables such as weather, but simple comparisons may also be used. / Based on regression analysis of utility meter data to account for factors that drive energy use. Adjustments to models aretypically required.
Option D:
Calibrated Computer Simulation / Computer simulation software is used to model energy performance of a whole-building (or sub-building). Models must be calibrated with actual hourly or monthly billing data from the building. Implementation of simulation modeling requires engineering expertise. Model inputs include building characteristics; performance specifications of new and existing equipment or systems; engineering estimates, spot-, short-term, or long-term measurements of system components; and long-term whole-building utility meter data. After the model has been calibrated, savings are determined by comparing a simulation of the baseline with either a simulation of the performance period or actual utility data. / Based on computer simulation model (such as EnergyPlus) calibrated with whole-building or end-use metered data or both. Adjustments to models are required.

3.2 Option B: Retrofit Isolation With All Parameter Measurement

M&V Option B uses periodic or continuous metering of all energy quantities, or all parameters needed to calculate energy, during the performance period. This approach provides the greatest accuracy in the calculation of savings, but increases the performance-period M&V cost.

Option B is typically used when any or all of the following conditions apply:

• For simple equipment replacement projects with energy savings that are less than 20% of total facility energy use as recorded by the relevant utility meter or sub-meter (Option C is not applicable).
• When energy savings values per individual measure are desired.
• When interactive effects can be estimated using methods that do not involve long-term measurements.
• When the independent variables that affect energy use are not complex andexcessively difficult or expensive to monitor.
• When operational data on the equipment are available through control systems.
• When sub-meters already exist that record the energy use of subsystems under consideration (e.g., a separate sub-meter for HVAC systems).

3.2.1Approach to Option B

Option B procedures rely on the physical assessment of equipment change-outs to ensure that the installation meets specifications. The potential to generate savings is verified through observations, inspections, and spot/short-term/continuous metering of energy or proxies of energy use (e.g., using variable frequency drive speed as a proxy for motor power). Baseline models are typically developed by correlating metered energy use or proxies with key independent variables. Depending on the ECM, spot or short-term metering may be sufficient to characterize the baseline condition, and the continuous metering of one or more variables may occur after retrofit installation. It is appropriate to use spot or short-term measurements in the performance period to determine energy savings when variations in performance are not expected, and may support some normalized savings approaches though adjustments to the baseline and/or the performance period model(s). When variations are expected, as in the case of retrocommissioning, it is appropriate to measure factors continuously. Continuous monitoring of information also can be used to improve or optimize equipment operation over time, thereby improving the performance of the retrofit.

3.3 Option C: Whole-Building Data Analysis

Energy savings under Option C are estimated by developing statistically representative models of whole-building or sub-metered energy consumption (i.e., therms and/or kWh). This method confirms total energy savings, but does not measure the savings from individual components.

In general, Option C should be used with complex equipment replacement and controls projects for which predicted savings are relatively large, i.e., greater than about 10% to 20% of the building’s energy use, on a monthly basis. Depending on the building’s predictability, availability of more granular interval meter data, and uncertainty requirements, savings of less than 10% may be measurable using Option C. Option C regression methods are valuable for measuring interactions between energy systems or determining the impact of projects that cannot be measured directly, such as insulation or other building envelope measures. Regression analysis requires experienced, qualified analysts, and Option C methods should be employed only for projects that meet the following requirements:

• Savings are predicted to be greater than about 10% to 20% of the overall consumption measured by the utility or sub-meter.
• At least 12 and preferably 24 months or more of pre-installation data are used to calculate a baseline model.
• At least 9 and preferably 12 months of performance period data are used to calculate annual savings.
• Adequate data on independent variables are available to generate an accurate baseline model, and procedures are in place to track the variables required for performance period models.
• Significant operational or other changes are not planned for the facility during the performance period, and procedures are in place to document changes that do occur at the site.

Again, these guidelines may be relaxed if interval meter data are available, and depending on building predictability, and project uncertainty requirements.

3.3.1Approach to Option C

With Option C, regression models are developed to predict energy use based on the appropriate independent variables for the project. Although simple mathematical techniques utilizing utility bill comparison are sometimes used, they tend to be unreliable and are not recommended. Regression models can account for impacts of weather and other independent variables on energy use, whereas simple utility bill comparison techniques cannot.