developing an open source hourly building energy modelling software tool

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


!   Lighting !   Plug loads

!   Occupancy

!   Daily and Weekly

Schedules


!   Conduction !  Walls, Roof, Foundation, Windows, Doors

!   Solar heat gain (windows)

!   Infiltration

!   Internal Gains: People, Lights, Plug Loads

!   Ventilation

Calculation of Loads


= 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


!   Determine significant loads !  Where to focus efforts for energy upgrades

Display Heating and Cooling Loads


Conduction44%

Infiltration50%

Ventilation6%

January Heating LoadsConduction

1% Infiltration4%

Window Solar Heat Gain

30%

Occupants17%

Lights19%

Plug Loads28%

Ventilation1%

August Cooling Loads



-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



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


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




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?




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%


-3% 24% 6% -15%




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%


-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?

developing an open source hourly building energy modelling software tool

Engineering