developing an open source hourly building energy modelling software tool
DESCRIPTION
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.TRANSCRIPT
Development of an Open Source Hourly Building Energy Modeling Software Tool
! Brittany Hanam MASc EIT
! John Straube PhD P.Eng.
05/12/2011
Agenda
! Energy Modeling and Design ! A New Model
! Case Study
! 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
Building Energy Modeling
! 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
Some Areas for Improvement
! 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
“Building Energy Loads Analysis” (BELA)
Program Structure
Inputs
Inputs Loads Systems
! Canadian Weather for Energy Calculations (CWEC) ! Hourly weather data for a “typical” year
! Temperature, relative humidity, solar radiation, wind
Weather
Inputs Loads Systems
! Lighting ! Plug loads
! Occupancy
! Daily and Weekly
Schedules
Inputs Loads Systems
! Conduction ! Walls, Roof, Foundation, Windows, Doors
! Solar heat gain (windows)
! Infiltration
! Internal Gains: People, Lights, Plug Loads
! Ventilation
Calculation of Loads
Inputs Loads Systems
= 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
! 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)
Thermal Mass
Inputs Loads Systems
! Determine significant loads ! Where to focus efforts for energy upgrades
Display Heating and Cooling Loads
Inputs Loads Systems
Conduction44%
Infiltration50%
Ventilation6%
January Heating LoadsConduction
1% Infiltration4%
Window Solar Heat Gain
30%
Occupants17%
Lights19%
Plug Loads28%
Ventilation1%
August Cooling Loads
Display Heating and Cooling Loads
Inputs Loads Systems
-30
-25
-20
-15
-10
-5
0
5
10
15
Monthly Load Density, kWh/m2
Ventilation
Window SHG
Infiltration
Conduction
Occupants
Plug Loads
Lights
Monthly Load Intensity, kWh/m2
! Determine energy impact of design options
Display Heating and Cooling Loads
Inputs Loads Systems
0
20000
40000
60000
80000
100000
120000
140000
160000
180000
R5 Wall R20 Wall R40 Wall R60 Wall
Load
, kW
hJanuary Heating Loads
Wall Insulation Comparison
Ventilation
Infiltration
Conduction
! BELA currently assumes radiant heating and cooling with Dedicated Outdoor Air System (DOAS) ventilation
Calculation of Systems Energy
Inputs Loads Systems
0
5
10
15
20
25
30
Ener
gy D
ensi
ty {k
Wh/
m2}
Radiant with DOAS Energy Density
Ventilation Distribution
Ventilation Cooling
Ventilation Heating
Space Distribution
Space Cooling
Space Heating
Plug Loads
Lights
Radiant with DOAS Energy Intensity, kWh/m2
! 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
Case Study
! Typical small office building adapted from B.M. Ross 2009 ! Four enclosure assemblies with different levels of thermal
performance, ! Exemplary
! High performance
! Institutional
! Market
Case Study: Small Office Building
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%
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%
Case Study Comparison
Reason for difference?
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%
Case Study Comparison
-3% 24% 6% -15%
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%
Case Study Comparison
-11% 1% 7% 22%
! 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
In Summary
Questions?