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| body | <h1><span style="color: #003366;">Build the Initial Energy Model</span></h1><hr /><p><span style="color: #003366;">Building an initial baseline energy model starts with commonly available energy information such as that found on monthly utilities bills. Combining that information with Building Management System (BMS) data allows one to develop insights about the building's operation and energy usage. </span></p><p><span style="color: #003366;"><strong>INPUTS</strong></span></p><p><span style="color: #003366;"><span class="TextRun SCXW256333377 BCX0"><span class="NormalTextRun SCXW256333377 BCX0">Inputs for this task include the well-organized compilation of information and data collected during the Discovery Phase. Please refer to the “Learn the Building” section for specific information of what should be collected. </span></span><span class="EOP SCXW256333377 BCX0"> </span></span></p><p><strong>OUTPUTS</strong> </p><p><span>Deliverables from the baseline energy model work include the following:</span><span> </span></p><ul><li><span>Building Energy Consumption and Detailed End Use Breakdowns </span><span>[Graphic]</span><span> </span></li><li><span>Documented Baseline System Assumptions</span></li></ul><p><strong>ACTIVITIES</strong></p><p><strong><span><span style="color: #ff9900;">Define and Understand the Purpose of the Energy Model</span></span></strong></p><p><span>The purpose of energy modeling in this context is to provide high-accuracy estimates of potential energy, cost and carbon savings for energy conservation measures (ECMs) under consideration. The energy model should incorporate site weather data for a typical year as well as detailed information about building geometry, building construction, systems, operations, and occupancy. The energy model will use this information to simulate the building’s energy consumption for every hour of the year. </span><span> </span></p><p><span>Code or LEED energy models that may have been created for the building during its initial design and construction should not be used in deep energy retrofit study efforts because they do not reflect the actual performance of the building under study.</span><span> </span></p><p><em><span style="color: #ff00ff;">The goal at this phase of the project is not to create an exact replica of the building—doing so would require modeling effort and investment in building metering that does not yield improvements in model accuracy that will improve decision making. Instead, energy models routinely include simplifications that maintain fidelity to metered data and an appropriate level of detail to form a basis of comparison for ECMs under consideration </span>- <span style="color: #ff00ff;">Italics: FOR DISCUSSION</span></em></p><p><span style="color: #003366;"><strong> <em> </em><span style="color: #ff9900;">Create the Baseline Model </span><span style="color: #ff9900;"> </span></strong></span></p><p><span>The baseline model represents the current systems and operations of the building. Energy savings for all proposed ECMs will be calculated relative to the baseline model performance. </span><span> </span></p><p><span>The baseline energy model should be informed by the information collected during the Discovery and Investigation Phase. In instances where data is not available, the energy modeler will need to make assumptions based on the building program, systems, or a basic understanding of building operation. Temporary, representative monitoring can also be applied to test assumptions. Together this information can be used to allocate energy consumption to specific systems and inform control sequences and operating schedules used in the baseline model. </span><span> </span></p><p><em><span style="color: #ff00ff;">The energy modeling effort should be focused on refining the load breakdown and end uses relative to one another rather than on modeling each floor and system explicitly. Certain simplifications can be made to accurately model the usage pattern without modeling specifics – this allows baseline systems, ECMs, and any future modifications to be modeled more quickly. Instead of modeling each room and tenant floor explicitly, spaces with similar functions (internal loads and schedules), exposures (envelope loads), and system types can be grouped together</span>. <span style="color: #ff00ff;">Italics: FOR DISCUSSION- leave or remove; is this too technical?</span></em></p><p><span style="color: #003366;"><strong><span style="color: #ff9900;">Make Necessary Adjustments to the Baseline Model</span> </strong></span></p><p><span>The baseline model energy consumption should be adjusted to account for the following:</span><span> </span></p><ul><li><strong><em><span>Weather</span></em></strong><span> - Typical weather data for the site can be modeled using </span><a href="https://data.nrel.gov/submissions/156"><span>TMY3 data files</span></a><span>, which capture and compare typical performance and eliminate any extreme weather event effects that may have occurred in the baseline year. TMY3 files are produced by the National Renewable Energy Laboratory and can be freely accessed and downloaded from the </span><a href="https://energyplus.net/weather"><span>EnergyPlus website.</span></a><span> </span></li><li><strong><em><span>Occupancy (Lease Turnover or COVID) </span></em></strong><span>- The baseline energy model should be adjusted to account for any fluctuations in building occupancy that are expected to occur over the study period. For example, tenant lease turnover schedules should be collected during the Discovery Phase and accounted for in the baseline model. Similarly, any disruptions to building occupancy, such as those experienced during the COVID 19 global pandemic, should be captured in the baseline model. In order to understand the full magnitude of ECM impacts, it is important to separate energy reductions resulting from ECMs versus those resulting from lower occupancy levels.</span><span> </span></li><li><strong><em><span>Planned Upgrades – </span></em></strong><span>The baseline model should be adjusted to account for any planned projects that will impact the building’s energy consumption. By capturing these savings in the baseline model, the project team will avoid projecting ECM savings that are no longer available because they have already been captured by planned projects. </span><span> </span></li></ul><p><span style="color: #003366;"><strong><span style="color: #ff9900;"> Document Assumptions and Review Initial Results With Greater Project Team</span> </strong> </span></p><p><span style="color: #003366;"><span class="TextRun BCX0 SCXW220830082"><span class="NormalTextRun BCX0 SCXW220830082">After the initial baseline model has been built and adjusted, the energy modeler should review his/her/their assumptions and the resulting load breakdowns with the project team. The modeler should then solicit feedback from the engineers and building operators who have greater insight into the current building operation and systems design. Feedback should be incorporated into the next iteration of baseline model. The feedback loop between the energy modeler and the building team will be an iterative process that will continue throughout the duration of the project as more information is collected from the building.</span></span><span class="EOP BCX0 SCXW220830082"> </span></span></p><p><br /></p><p><span style="color: #003366;"><strong>LESSONS LEARNED & KEY CONSIDERATIONS </strong></span></p><ul><li><span style="color: #003366;"><strong> <em>Determine Energy Model Level of Detail and Input Assumptions</em> - </strong></span>Some of the most important decisions to be made during this stage include determining the appropriate level of modeling detail and making a judgement on how to best model the building features to facilitate future modifications. While these decisions will primarily be made by the energy modeler given their expertise, engineers may provide valuable input by highlighting systems of interest and potential ECMs. Where modeling assumptions are made due to a lack of input information, these should be shared with the engineers so that they may be reviewed and corrected as the engineers familiarize themselves with the existing building systems and operations. This line of communication is critical for ensuring that the final modeled savings are reasonably accurate and are neither over nor underestimated.</li></ul><ul><li><span style="color: #003366;"><strong> <em>Invest in the Calibration of the Baseline Model - </em></strong></span>It is very difficult to establish where you want to go without understanding where you are now. It is important not to undervalue or gloss over the initial data collection phase, testing, and on-the-ground observations for the following reasons: </li></ul><ol><li style="list-style-type: none;"><ol><li><span style="color: #003366;">The energy model outputs are only as good as the inputs, so the less assumptions that are input into the model, the more accurate energy, cost, and CO<sub>2</sub> emission savings will be. For example, in energy simulations for new buildings the total energy consumption is highly sensitive to operating schedules which are a constant between baseline and proposed models. Together with weather data, assumed operating schedules and use intensities are a key variable energy modelers use to calibrate the baseline model. </span></li><li><span style="color: #003366;">It is an important step to determine ECMs. We typically find easy and financially attractive ECMs from analyzing data and just getting to know how each system is “actually” operating. </span></li><li><span style="color: #003366;">Learning more about your building is never a wasted effort and can minimize maintenance costs in the future. </span></li><li><span style="color: #003366;">While team members’ heuristics can be immensely helpful, cognitive bias can lead to inappropriate extrapolation or focusing on a familiar or well understood, but fundamentally less significant aspect of the building’s operations or performance. A mechanical engineer might focus on heating system decarbonization since they know how to solve that problem, but cutting unoccupied IT plug loads—a problem a mechanical engineer is less familiar with—might have a more significant carbon emissions impact. </span></li></ol></li></ol><ul><li><span style="color: #003366;"><strong><em>Sync Energy Modeling Assumptions with Site Observations - </em></strong></span>Even in well-maintained buildings with stringent base-building and tenant standards, expect to uncover exceptions and anomalies. Sometimes equipment is shut off and sequences are manually overwritten because the system was never properly commissioned, integrated with the BMS, or simply due to a lack of understanding of the whole system impact. This is especially true for older existing buildings that have had operations team turnover resulting in a loss of institutional knowledge over the years. For the energy model to accurately capture savings for ECMs, the baseline model must reflect real-life operation. Design documents—even as-built—only provide a starting point for the model. </li></ul><ul><li><span style="color: #003366;"><strong> <em>Understand that Baseline Model Calibration is an Iterative Process - </em></strong></span>Given that the baseline energy model calibration is a continuous and iterative process that will evolve with ECM development and site observations, the following should be considered during the initial modeling: </li></ul><ol><li style="list-style-type: none;"><ol><li><span style="color: #003366;">Keep the energy model flexible (simple inputs, controls, schedules) so that if changes are needed, the model can be adapted and adjusted quickly. </span></li><li><span style="color: #003366;">Accept that perfection is the enemy of good progress. Model calibration is guaranteed to change as more information about the building becomes available. Welcome iteration. Set reasonable expectations for level of modeling and calibration effort aligned with the project schedule and status. While not directly applicable to BIM LOD statements can provide guidance on how to conceptualize these expectations.</span></li></ol></li></ol> |
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