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Developing an Open Source Hourly Building Energy Modelling Software Tool

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Energy modelling is an important tool in the design of low energy buildings. It helps evaluate energy savings of various energy efficiency measures and can predict total building energy consumption.

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Developing an Open Source Hourly Building Energy Modelling Software Tool

  1. 1. Development of an Open Source Hourly Building Energy Modeling Software Tool ! Brittany Hanam MASc EIT ! John Straube PhD P.Eng. 05/12/2011
  2. 2. Agenda ! Energy Modeling and Design ! A New Model ! Case Study
  3. 3. Building Energy Modeling ! An important tool in the design of low energy buildings ! Evaluate energy savings of various energy efficiency measures ! Predict total building energy consumption ! Show compliance with standards ! Determine peak loads, size equipment
  4. 4. Some Areas for Improvement ! Energy modeling for architects ! Architects’ design has a significant impact on energy consumption but mechanical engineer or energy modeler runs simulations ! Loads vs. systems energy ! Modeling building energy consumption at early stages of design, when detailed inputs are not known ! Trade-off between accuracy and complexity
  5. 5. “Building Energy Loads Analysis” (BELA) ! Simple, easy to use, flexible program ! Evaluate high-level design options as well as detailed design of new and innovative systems ! Transparent, demonstrate the application of first principles to estimate annual energy consumption
  6. 6. Program Structure
  7. 7. Inputs Inputs Loads Systems
  8. 8. Weather ! Canadian Weather for Energy Calculations (CWEC) ! Hourly weather data for a “typical” year ! Temperature, relative humidity, solar radiation, wind Inputs Loads Systems
  9. 9. Schedules ! Lighting ! Plug loads ! Occupancy ! Daily and Weekly Inputs Loads Systems
  10. 10. Calculation of Loads ! Conduction ! Walls, Roof, Foundation, Windows, Doors ! Solar heat gain (windows) ! Infiltration ! Internal Gains: People, Lights, Plug Loads ! Ventilation Inputs Loads Systems
  11. 11. Thermal Mass ! Transfer function method used in current version ! Apply weighting factor to instantaneous gain or loss ! Better methods available and could be implemented for future versions (eg. Radiant Time Series) = Heating or cooling load at hour θ = Heating or cooling load at hour θ – 1 = Instantaneous heat gains or losses at hour θ = Instantaneous heat gains or losses at hour θ – 1 V0, V1, W1 = Weighting factors Inputs Loads Systems
  12. 12. Display Heating and Cooling Loads ! Determine significant loads ! Where to focus efforts for energy upgrades August Cooling Loads Inputs Loads Systems January Heating Loads Conduction 44% Infiltration 50% Ventilation 6% Conduction 1% Infiltration 4% Window Solar Heat Gain 30% Occupants 17% Plug Loads 28% Lights 19% Ventilation 1%
  13. 13. Display Heating and Cooling Loads Inputs Loads Systems 15 10 5 0 -5 -10 -15 -20 -25 -30 Monthly Load Density, kWh/m2 Ventilation Window SHG Infiltration Conduction Occupants Plug Loads Lights Monthly Load Intensity, kWh/m2
  14. 14. Display Heating and Cooling Loads ! Determine energy impact of design options Inputs Loads Systems 180000 160000 140000 120000 100000 80000 60000 40000 20000 0 R5 Wall R20 Wall R40 Wall R60 Wall Load, kWh January Heating Loads Wall Insulation Comparison Ventilation Infiltration Conduction
  15. 15. Calculation of Systems Energy ! BELA currently assumes radiant heating and cooling with Dedicated Outdoor Air System (DOAS) ventilation Radiant with DOAS Energy Intensity, kWh/m2 Inputs Loads Systems 30 25 20 15 10 5 0 Energy Density {kWh/m2} Radiant with DOAS Energy Density Ventilation Distribution Ventilation Cooling Ventilation Heating Space Distribution Space Cooling Space Heating Plug Loads Lights
  16. 16. Case Study ! Compare results of BELA to eQuest for a small office building ! Reason for this analysis ! To view the differences between results from a simple model built upon fundamental principles to a more developed but less transparent program ! Goal is not to “calibrate” the two models to give the same output ! Similar to a project early in the design stages where detailed inputs are not known ! Programs use similar calculation methods
  17. 17. Case Study: Small Office Building ! Typical small office building adapted from B.M. Ross 2009 ! Four enclosure assemblies with different levels of thermal performance, ! Exemplary ! High performance ! Institutional ! Market
  18. 18. Case Study Comparison Exemplary High Performance Institutional Market BELA eQuest BELA eQuest BELA eQuest BELA eQuest Pump Power 2.1 8.8 2.7 13.3 3.0 11.8 4.1 17.2 Space Heating 72.5 68.7 139.6 164.2 283.0 227.6 452.9 464.7 Space Cooling 29.4 27.4 32.6 26.7 22.9 22.7 23.8 26.8 Fan Power 3.0 8.3 3.0 8.3 3.0 8.3 3.0 8.3 Lights 38.4 41.5 38.4 41.5 38.4 41.5 38.4 41.5 Plug Loads 43.8 47.9 43.8 47.9 43.8 47.9 43.8 47.9 Total 189.3 202.3 260.1 301.9 394.2 359.9 566.0 606.4 Difference -6% -14% 10% -7%
  19. 19. Case Study Comparison Exemplary High Performance Institutional Market BELA eQuest BELA eQuest BELA eQuest BELA eQuest Pump Power 2.1 8.8 2.7 13.3 3.0 11.8 4.1 17.2 Space Heating 72.5 68.7 139.6 164.2 283.0 227.6 452.9 464.7 Space Cooling 29.4 27.4 32.6 26.7 22.9 22.7 23.8 26.8 Fan Power 3.0 8.3 3.0 8.3 3.0 8.3 3.0 8.3 Lights 38.4 41.5 38.4 41.5 38.4 41.5 38.4 41.5 Plug Loads 43.8 47.9 43.8 47.9 43.8 47.9 43.8 47.9 Total 189.3 202.3 260.1 301.9 394.2 359.9 566.0 606.4 Difference -6% -14% 10% -7% Reason for difference?
  20. 20. Case Study Comparison Exemplary High Performance Institutional Market BELA eQuest BELA eQuest BELA eQuest BELA eQuest Pump Power 2.1 8.8 2.7 13.3 3.0 11.8 4.1 17.2 6% -15% 24% -3% Space Heating 72.5 68.7 139.6 164.2 283.0 227.6 452.9 464.7 Space Cooling 29.4 27.4 32.6 26.7 22.9 22.7 23.8 26.8 Fan Power 3.0 8.3 3.0 8.3 3.0 8.3 3.0 8.3 Lights 38.4 41.5 38.4 41.5 38.4 41.5 38.4 41.5 Plug Loads 43.8 47.9 43.8 47.9 43.8 47.9 43.8 47.9 Total 189.3 202.3 260.1 301.9 394.2 359.9 566.0 606.4 Difference -6% -14% 10% -7%
  21. 21. Case Study Comparison Exemplary High Performance Institutional Market BELA eQuest BELA eQuest BELA eQuest BELA eQuest Pump Power 2.1 8.8 2.7 13.3 3.0 11.8 4.1 17.2 Space Heating 72.5 68.7 139.6 164.2 283.0 227.6 452.9 464.7 7% 22% 1% -11% Space Cooling 29.4 27.4 32.6 26.7 22.9 22.7 23.8 26.8 Fan Power 3.0 8.3 3.0 8.3 3.0 8.3 3.0 8.3 Lights 38.4 41.5 38.4 41.5 38.4 41.5 38.4 41.5 Plug Loads 43.8 47.9 43.8 47.9 43.8 47.9 43.8 47.9 Total 189.3 202.3 260.1 301.9 394.2 359.9 566.0 606.4 Difference -6% -14% 10% -7%
  22. 22. In Summary ! Simple energy modeling program developed using fundamental principles ! Transparent, adaptable, suitable for high level design ! Limitations ! Single zone ! Many areas for improvement in accuracy and range of capabilities
  23. 23. Questions?

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