ENSURING A PRODUCTIVE ENERGY MODELING PROCESS

Transcription

1 ENSURING A PRODUCTIVE ENERGY MODELING PROCESS ASHRAE Rocky Mountain Technical Conference April 15, 2011 Kendra Tupper, P.E. (RMI) Sue Reilly, P.E., BEMP (Group 14) Michael Brendle, FAIA (RNL)

2 OVERVIEW Energy modeling as part of an integrated design process How to use modeling effectively at different design phases Quality control practices Case Study

3 Modeling Within an Integrated Design

4 OPTIMAL USE OF MODELING Typical Design Process: ENERGY MODELING ACCOUNTING TOOL Energy Modeling SHOULD Informs Design Facilitates LCCA Provides Recommendations that t are Implemented Ensures Achievement of Project Goals

5 CHOOSING AN ENERGY MODELER Licenses BEMP (ASHRAE) BESA (AEE) P.E. Project Experience Professional recommendations Past reports Technical Knowledge HVAC systems Specific experience for given project Where does the model fall within the design team structure? Independent energy analysis (Contracted by owner vs the architect vs the MEP) MEP design firm does energy modeling in house

6 EARLY DECISIONS A M I ARE THE MOST IMPORTANT HIGH Typical energy modeling timeframe Leve el of Effo ort LOW Project Start Time Project Finish

7 Modeling Throughout the Design Phases

8 MODELING AND THE BUILDING LIFE CYCLE How is energy modeling best utilized during each phase? What are the key steps to be followed during each phase?

9 CONCEPT PHASE MODELING OVERVIEW Activities Build 1st model to focus efforts Goal Setting Technical Potential Modeling Objectives Align team around energy-related goals Make design recommendations EARLY to increase potential for impact Identify where efforts should be focused to maximize energy savings and equipment downsizing Maximize opportunity for energy efficiency

10 CONCEPT PHASE MODELING BUILD PRELIMINARY MODEL Take what you know (footprint, building type, etc.) and construct a model Document all assumptions, note values to be validated Evaluate the end-use breakdown to identify major savings opportunities Evaluate peak heating and cooling load contributions to identify ways to downsize mechanical systems Analyze certain measures that are early design decisions and will be difficult to change later Determine the technical potential for reduced energy consumption to challenge the actual design

11 CONCEPT PHASE MODELING G S GOAL SETTING Use Energy Modeling to Quantify Targets Goal Setting Charrette kbtu/sf/yr Types of Goals Overall Target Comparative Certifications Values 55% better than LEED Platinum EISA 2007 ASHRAE Energy Star score EUI < 35 kbtu/sf/yr Lowest EUI of any ASHRAE Building U.S. museum Net Zero operating Energy Quotient carbon 80% water reduction from Living Building Demand < 3 W/sf current use Challenge % reduction below ASHRAE 90.1 No mechanical cooling End-Use Specific 80% reduction in lighting g energy from natural daylight 100% of heating from waste heat and solar thermal

12 CONCEPT PHASE MODELING TECHNICAL POTENTIAL WHAT IS IT?? The minimum level of energy consumption possible for a building, given today s technology (excluding renewables) WHY DO WE CARE? Challenges conventional ways of thinking Not limited by industry benchmarks/norms Leads to more aggressive design targets Explicitly determines where ground has been lost HOW DO WE DETERMINE THIS? Start with a baseline or current design Removes the losses and inefficiencies with best available technology

13 CONCEPT PHASE MODELING OUTPUTS AND COMMUNICATION Peak Cooling Load Contributions Potential Cooling Load Reduction Evaluate heating and cooling load breakdowns to identify impactful load reduction measures.this is how you can downsize HVAC systems! ** Use Design Day Feature

14 SCHEMATIC DESIGN ENERGY MODELING ITERATIVE ANALYSIS PROCEDURE Optimize Load Reduction Strategies Use LCCA to Evaluate Options Resize and Reselect Mechanical Equipment Compare Metrics to Benchmarks and Goals

15 SCHEMATIC DESIGN ENERGY MODELING MEASURES TO ANALYZE EARLY ON Building siting and orientation Geometry Massing and program layout Passive strategies Glazing size and location Shading and daylighting strategies

16 SCHEMATIC DESIGN ENERGY MODELING LIFE CYCLE COST ANALYSIS Include all cash flows Identify business as usual baseline Packages of measures Downsize HVAC equipment Identify packages that meet various goals Ne et Present Value of Measures Package $40,000,000 $30,000,000 $20,000,000 $10,000,000 $0 ($10,000,000) ($20,000,000) 15-Year NPV of Package versus Cumulative CO2 Savings NPV Max NPV Mid NPV Neutral 0 20,000 40,000 60,000 80, , , , ,000 Cumulative Metric Tons of CO2 Saved over 15 Years Max CO2 Reduction

17 SCHEMATIC DESIGN ENERGY MODELING Supplementary Analysis Key Outputs Spreadsheet Analysis Thermal Energy Storage Daylighting Energy Model Thermal Comfort Renewable Energy Production Recommended package of efficiency measures Comparison to baseline and goals Present economic results in a compelling business case Computational Fluid Dynamics

18 DESIGN DEVELOPMENT FOCUS OF ENERGY MODELER Evaluate specific design options by updating the energy and LCCA models (defend against value engineering); Periodically review the design for variations from recommendations and project goals; Suggest specific products or manufacturers that can achieve SD recommendations; Optimize control strategies; Ensure that all thermal comfort and indoor air quality criteria are being satisfied, and Revisit how measures are modeled in the software programs to improve the model accuracy.

19 DESIGN DEVELOPMENT MODELING QUALITY CONTROL Verify all loads are being met Use ASHRAE Fundamentals to check sqft/ton Cfm/sqft Cfm/ton Exterior Lighting 3% Interior Lighting 20% DHW 1% Misc. Plug Loads 11% Compare energy model results Pumps Fans to CBECs data 15% 5% Space Heating 7% Space Cooling 38% * Find EUI and end use breakdown by climate zone and building type / / /

20 CONSTRUCTION DOCUMENTS ENERGY MODELING OBJECTIVES Document Modeling Assumptions Ensure project efficiency strategies remain in the building design Finalize Performance and Savings Estimates Document savings for LEED / EPACT / other

21 CONSTRUCTION DOCUMENTS DOCUMENT MODELING APPROACH Basic site info; Conditioned and total square footage; Description of baseline used (i.e. ASHRAE ); Actual site location and weather files used for energy model; Detailed list of inputs and assumptions for Proposed and Baseline models - note when external calculations were required; Description and visuals of thermal zoning; Detailed description of HVAC systems and how they were modeled; Explanations of workaround used; Description of EEMs and related assumptions; and What is included under each end use category for the model.

22 MODELING PROCEDURES POST OCCUPANCY Modeling is used during post occupancy. To inform benefits: Measurement and Verification (compare to predicted performance) To make the business case for existing building retrofits As a tool for continuous commissioning and building operation M&V is part of a performance feedback loop that benefits: Facility Managers Designers Energy Modelers

23 MODELING PROCEDURES POST OCCUPANCY LEED NC EAc5 Intent Requirements Provide for ongoing accountability of energy consumption over time M&V Plan Option B, D savings method 2, Vol. III 1 Year M&V Period Process for corrective action Optio on D Pro ocedures Develop M&V Plan Ensure sufficient metering Gather and check data Calibrate Calculate verified savings

24 Quality Control Procedures

25 GENERAL PRINCIPLES 1.Be knowledgeable of the inner workings of the simulation tool 2.Be knowledgeable of the technologies being modeled 3.Follow modeling procedures that facilitate quality assurance

26 GENERAL PRINCIPLES KNOWLEDGE OF INNER WORKINGS Consider the capabilities and limitations of the tools, such as. Weighting factors or transfer functions? Does it calculate surface temps and thermal comfort? How does it model airflow between zones? Are lightshelves handled sufficiently? Perform test runs Check standard reports Create and compare hourly output data Review documentation User support groups, forums and list serves

27 GENERAL PRINCIPLES KNOWLEDGE OF TECHNOLOGIES Colleaguesg Manufacturers / Distributors Technical Journals and Conference Proceedings DOE Building Technologies Program website Energy Design Resources website Design Guidelines: HVAC Simulation Guidelines Design Guidelines: Advanced Variable Air Volume (VAV) Systems Design Guidelines: CoolTools Chilled Water Plant

28 GENERAL PRINCIPLES FACILITATE QUALITY ASSURANCE Checking model input: Document assumptions and input values Use pre-processing tools/spreadsheets to convert component descriptions into modeling input values Import input file segments for complex components modeled often in projects RMI EMIT Tool Make design changes incrementally in the model

29 GENERAL PRINCIPLES FACILITATE QUALITY ASSURANCE Checking model output: Develop a review checklist Extract data for evaluating reasonableness of results Key output values Metrics, back-of-the-envelope calculations, hourly data Extract results from output files and report sideby-side Evaluate against rules-of-thumb metrics RMI Model Evaluate against performance of actual buildingsmanager Evaluate against each run is the change as expected? Tool

30 GENERAL PRINCIPLES FACILITATE QUALITY ASSURANCE PARTIAL CHECKLIST Input ASHRAE climate zone Weather data file Output Zone and plant loads met Building EUI Effective underground R-value Building plugs W/ft 2 Overall window U-value Building lighting W/ft 2 Plug loads Building occupant density System type, plant type Cooling - design ft 2 /ton, kw/ton, loading Baseline fan per PRM Cooling loop gpm/ton VAV - min box turn down, central Heating - Btu/ft 2, average efficiency, heating coil loading Outside air - fixed, % supply or cfm/person, DCV; off at night Controls SAT reset, humidity, loop temp resets Supply air - design cfm/ft 2 Ventilation air - % design flow, cfm/ft 2

31 GENERAL PRINCIPLES FACILITATE QUALITY ASSURANCE KEY M METRICS* * Metric Units Low Medium High Building EUI kbtu/ft 2 yr Cooling Design ft 2 /ton Cooling Design kw/ton Cooling Loop gpm/ton Heating Design Btu/ft Fans kw/cfm Supply Air cfm/ft Ventilation Air cfm/ft Lighting W/ft Plugs W/ft *T i l f ffi b ildi l ffi i t di d hi h i ti *Typical of office buildings: low very energy efficient; medium code; high existing buildings

32 Case Study

33 Eastside Human Services; a case study

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48 Baseline Annual Energy Costs by End Use Cooling $8,247 11% $77,000 Fans $4,829 6% Heating $36,957 48% Equipment $11,928 15% Ext Lighting $408 1% Interior Lighting g $14,064 18% Water Heating $446 1%

49 Envelope Exterior walls: R 19 batt in studs with R 4 c.i. R 20 minimum roof insulation Windows: North Low E, Argon filled IGU (U 0.25, SHGC 0.38) Windows: non North Low E, low SHGC Argon filled IGU (U 0.25, SHGC 0.28) Exterior shading devices on south, east and west facing windows

50 Lighting Average building lighting power density of 0.66 W/sf Occupancy sensors in most spaces. Daylight dimming controls in perimeter and second floor core office spaces.

51 HVAC Core: Underfloor air distribution system serving core zones with 60 F supply air, economizer with dual temperature control, indirect direct evaporative cooling, and enthalpy energy recovery wheel Perimeter: Fan coil units served by variable refrigerant flow system with EER 12.6, HSPF 8. Demand controlled ventilation controlled by zone CO 2 sensors

52 Annual Energy Costs by End Use $0 $10,000 $20,000 $30,000 $40,000 $50,000 $60,000 $70,000 $80,000 $90,000 Equipment 1 Ext Lighting Interior Lighting Water Heating Heating 2 Cooling Fans Pumps