Energy Modeling


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The presentation will include the following topics:

- Fundamentals of energy modeling
- Overview of the eQUEST energy modeling program
- Recommendations for integrating energy modeling into the design process
- Brief description of baseline energy modeling using ASHRAE Appendix G
- Recommended strategies for reducing energy use
- How to review energy modeling results
-Common problems and how to avoid them

Energy Modeling

  1. 1. Building Energy Modeling Michael Andelman, P.E. Andelman and Lelek Engineering, Inc.
  2. 2. Learning Objectives Fundamentals of Building Energy Modeling Objectives Available tools Process eQUEST Overview Energy Modeling and the Design Process LEED Energy Modeling and ASHRAE Appendix G Strategies to Reduce Energy Use Reviewing Modeling Results Common Problems and How to Avoid Them
  3. 3. Fundamentals - Objectives Whole building design LEED EA Credit 1 Code compliance analysis Utility Incentives Predict operating costs Federal Tax Credits
  4. 4. Whole building design Right-sizing of mechanical systems/equipment System optimization; comparing alternative building /system designs Building geometry/location/orientation Walls/roofs/windows construction materials HVAC system/equipment Control strategies Lighting and lighting controls Utility selection (electricity, gas, oil, district steam, etc.)
  5. 5. Whole building design (cont’d) Life cycle costing of alternatives Determine interactivity of proposed alternatives
  6. 6. LEED EA Credit 1 Baseline model per ASHRAE App G As-designed model per final construction documents LEED template/ supporting documentation
  7. 7. Code compliance analysis MA Energy Code-Building Design by Systems Analysis ASHRAE Energy Cost Budget Method Pollution generation/reduction analysis
  8. 8. Predict operating costs Entire building Individual building components or end uses (chillers, pumps, lighting system, etc) Seasonal operating costs and patterns Building load analysis Hourly/daily/weekly/monthly load profiles Seasonal/annual load profiles Peak load; design load Individual zones/systems or entire building
  9. 9. Fundamentals- Tools DOE-2 based tools eQUEST VisualDOE Energy-10 Other Energy Plus Design Builder Google sketch-up interface EcoTec Other BLAST Carrier HAP Trane Trace/System Analyzer TRNSYS IES
  10. 10. Fundamentals - Process Define scope and set priorities Gather data Create baseline model Existing building New building – code/ ASHRAE App G base Calibrate model (for existing buildings) Model alternatives
  11. 11. Process - Required Data Architectural Plans Building geometry ACAD floor plan drawings Walls/ windows Elevations/ wall sections Operating Schedules Mechanical Plans HVAC drawings/ system descriptions Equipment schedules and specs Controls specs or interview building operator for existing building Electrical Plans Lighting fixture layout and schedules - COMCHECK or conduct lighting audit of existing facility Lighting controls type/ location
  12. 12. eQUEST Overview DOE2.2 with GUI Hourly building energy simulation Heating/ cooling loads calculated using transfer function methodology Separate calculations for loads, HVAC systems/ central plant equipment, and economics
  13. 13. Loads Building envelope Building location Building geometry Walls/roofs/floors construction materials Windows (glass, frames, exterior or interior shading devices) Large library of manufacturer’s glass selection Infiltration Internal loads Occupants Plug loads Lights Other (manufacturing/process equipment, etc.) Schedules (internal loads, infiltration, shading devices, etc)
  14. 14. Systems HVAC system Type/size/performance – DX/chilled water, constant volume/VAV, terminal units, etc. Control strategies – temperature control, fan control, schedules, setpoints, OA control, etc. Physical plant Equipment selection (type, size, performance) – chillers, boilers, cooling towers, pumps, heat exchangers, district steam/CHW, DHW heaters, etc. Process loads – type (steam, hot water, chilled water, other), size, schedule, etc.
  15. 15. Economics Utility rates/structure Electricity (demand charges, energy charges, summer/winter rates, time-of-use energy charges, ratchets, etc.) Natural gas Fuel oil Purchased steam Purchased chilled water Other Equipment cost – first cost, maintenance cost, major overhaul cost
  16. 16. eQUEST Wizard Up Side Import AUTOCAD floor plans to trace building geometry Screens simplify defining building shell components, schedules, and HVAC systems Create working model in minutes – useful for early schematic phase
  17. 17. eQUEST Wizard (cont’d) Down Side Not all eQUEST options available through Wizard screens Schedules; lighting and equipment power densities based on building type – customizing easier in detailed mode Can’t switch from detail mode back to wizard mode
  18. 18. eQUEST Model Limitations Daylight Analysis No light shelves No internal obstacles No daylight through interior windows Natural Ventilation No interzonal airflow Limited to simple systems Curtain Walls Must fit frame conductance/ width to overall U-value
  19. 19. eQUEST Model Limitations (cont’d) No air stratification Displacement ventilation modeled through work- around Atriums modeled as multiple zones when required No ventilated double skin walls No radiant cooling system (modeled through work-around) One HVAC system per zone
  20. 20. Energy Modeling and the Design Process When to Start Conceptual / early schematic (throw-away) Siting/ building shape analysis Early evaluation of HVAC systems alternatives Design Development Evaluation of building shell/ HVAC system alternatives First pass estimate of LEED credit points Progress/ first final Estimate LEED credit points/ evaluate utility incentives Updating Model Update model as design progresses Check impact of possible changes with model before implementing changes
  21. 21. LEED MODELING & ASHRAE APP-G Create as-design model Create baseline model ASHRAE 90.1 Appendix G Used for LEED analysis Very detailed – many requirements above code Baseline HVAC system Pump power Plant equipment type and number Special requirements for central plant/ cogeneration Schedules same for baseline & as-designed Items to watch Hours loads unmet Heated only spaces Glass overall U-value Utility rates Exceptional method calculations
  22. 22. Recommended Strategies Architectural High performance glass (limit % glass) Passive Solar – south glass w/ shading devices – limited north glazing Mechanical Energy efficient equipment Right sizing equipment Airside heat recovery (heat wheel) for VAV systems w/ ~40% OA or more (application specific) DOA system w/ chilled beams VFDs for fans/ pumps Demand ventilation or occupancy based controls Cogeneration
  23. 23. Recommended Strategies- cont. Electrical High performance lighting T-5 or ‘Super’ T-8 LED downlights High bay T-5 or MH w/ electronic ballast Daylight controls Occupancy controls
  24. 24. Review Results Electric Energy UseComponents Lights Equipment 15% 4% Fans Cooling 68% 1% Heat Rejection 2% Pumps & Aux. 10%
  25. 25. eQUEST Graphic Output
  26. 26. Energy Modeling vs “Common Sense” Lighting energy savings in electrically heated buildings VFDs for hot water pumps Optimizing windows for cooling and heating Low SC reduces passive heating White roofs – minimal impact in this climate Best suited for mild climates where Code insulation is low (e.g. R-10 continuous) Heat Recovery high parasitic losses heating savings for VAV systems can be low if not 100% O.A. at minimum flow interaction with demand ventilation controls DOA Based Systems Sensitive to supply air temperature No airside economizer
  27. 27. Common Problems and how to avoid them Excessive hours outside throttling range Check SS-R reports for problem zones Check reheat and or baseboard heat assigned Check zone cfm Pump/ auxiliary energy too high Check PV-A report for pump sizing Check PS-C report for pump operating hours / part load operation Schedule CHW loop Change pump control to speed if pump has VFD Excessive winter cooling/ summer heating Check if airside economizer is called out Check minimum flow ratio for VAV system Check space temperature are properly applied
  28. 28. Common Problems and how to avoid them Excessive cooling / heating energy use Check PS-C for average equipment performance Resize equipment Change CHW loop/ CW loop controls Change default equipment performance Condensing boilers need custom curves Change boiler aquastat setpoint
  29. 29. Where to Get More Information
  30. 30. Thank you! QUESTIONS?
  31. 31. Michael Andelman, P.E. Andelman and Lelek Engineering, Inc. 1408 Providence Highway Norwood, MA 02062 (781)769-8773 AndelmanLelek