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Calibration of the AJLC Annex Sunroom Model in Oberlin, Ohio
Samina Ali, Kristin Braziunas, Lora DiFrancoSystems Modeling Final Presentation
Spring 2007
Background
• AJLC Annex history
• Original model by John Petersen & Alfredo Fernandez (AS5)
• Focus on winter months
• Building characteristics
Now that the sunroom is completed…•Test the model!•Temperature sensors
Objectives
• Compare new and observed data
• Calibrate & perform sensitivity analysis
• Validate using April data• Sunroom as a heat source
Main question: Does the current model correctly predict the temperature of a sunroom given building specifications, irradiance, and outside temperature?
SunRoom Air Temperature
Exchange Slab To Outside
Internal Gain to Air
Gradient Based Exchange
UA Slab to exteriorT Outside
Q Internal
Number human occupants
Daily internal heat gain
one minus
South shadingSouth wall window Area
SHGC
Solar Gain To Air
Heater On\Off Switch
Thermostat Setpoint
Diurnal Heat Capacity Room
Slab Temperature
Exchange With Slab
Exchange With Slab 2
Q From Room To Slab
U base between room and slab
Radiation Vertical
Q Solar totalQ solar south
Diurnal Heat Capacity Slab
Heater Output
UA room to slab
Pct solar to air
Decrease exchange
Q Solar total
Pct solar to slab
Pct solar to slab
Solar Gain To SlabAuxiliary Heating
Q Gradient Total
Model Structure:Major Stocks and Flows
SunRoom Air Temperature
Slab Temperature
Assumptions
• No solar gain through west- or east-facing windows– Trial and error
• No interaction with the house– “door open” problem
Methods: Data Collection
• 6 Temperature Sensors– 2 measure sunroom air
temperature– 4 measure slab temperature
9:21 PM Mon, May 07, 2007
Sunroom Temperature
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1: Actual Average Room Temp in degrees F 2: SunRoom Air Temperature
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Methods: Calibration March 2007
Initial run without variable changes
Sunroom Air Temperature
Difference Range: -30 to +35 degrees F
9:13 PM Mon, May 07, 2007
Slab Temperature
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1: Actual Average Slab Temp in … 2: Slab Temperature 3: Actual Upper Slab Temp TC03…
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“Upper” Slab Temperature used for calibration
Methods: Calibration March 2007
Initial run without variable changes
Slab Temperature
Difference Range: -23 to +57 degrees F
Sunroom Temperature, predicted by Upper Slab Temperature
9:21 PM Mon, May 07, 2007
Sunroom Temperature Predicted by Empirical Slab Temperature
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Conclusion: problems in predicting slab temperature
Methods: Calibration March 2007
Initial run without variable changes
Difference Range: -27 to +10 degrees F
Methods: Calibration Calibrating the Slab, Main Stocks and Flows
• Values added– Solar Heat Gain Coefficient
• Values to mess with– Diurnal Heat Capacity Slab– Solar Gain to Slab
• Pct Solar to Slab• South Shading
Exchange Slab To Outside
UA Slab to exteriorT Outside
one minus
South shadingSouth wall window Area
SHGC
Solar Gain To Air
Heater On\Off Switch
Thermostat Setpoint
Slab Temperature
Exchange With Slab
Exchange With Slab 2
Q From Room To Slab
U base between room and slab
Radiation Vertical
Q Solar totalQ solar south
Diurnal Heat Capacity Slab
Heater Output
UA room to slab
Pct solar to air
Decrease exchange
Q Solar total
Pct solar to slab
Pct solar to slab
Solar Gain To SlabAuxiliary Heating
Methods: Calibration Calibrating the Slab, Physical Characteristics
• Values Added– Passive Solar Enhancement
• “depth of slab”
UA Slab to exterior
Passive Storage Enhancement
Depth of slab
U base between room and slab
SunRoom Air Temperature Slab Temperature
U effective room to slab
Active Storage Enhancement
UA room to slab
Floor AreaSlab Volume
Slab exterior Area R Slab
East wall width Slab Depth
Diurnal Heat Capacity Slab
Unit DHC concrete
South wall width
Methods: Calibration March 2007
Calibrating the Slab
9:34 PM Tue, May 08, 2007
Untitled
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Difference Range: -15 to +18 degrees F
9:34 PM Tue, May 08, 2007
Untitled
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Methods: Calibration March 2007
Calibrating the Sunroom Air
Difference Range: -25 to +24 degrees F, mostly due to outliers
Validation Results• April 1st – 5th: Heater Off
• slab temperature
Difference range: 2 to 14 deg F
4:44 PM Sun, May 06, 2007
Slab temp predicted vs. actual upper slab temp
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April 1st – 5th: heater offSunroom temperature
Difference range: -4 to 16 deg F
4:44 PM Sun, May 06, 2007
Predicted sunroom temp compared with the actual sunroom temp
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April 7th- 30th: Heater Onslab temperature
Difference range: 5 to 21 deg F
5:04 PM Sun, May 06, 2007
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April 7th- 30th: Heater Onsunroom temperature
Difference range: -5 to 7 deg F• Noise: The days with the sunroom door open
5:04 PM Sun, May 06, 2007
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Take home points• If predicted slab temp oscillation > actual slab
temp oscillation, use dampening variables-
- increase slab volume
- decrease the inflow to the slab from the sun
• West and East heat gain may not be very significant
Future Research• Heat exported into the house (ex – fan)• Standard model: Include east and west component for
heat gain and loss• Increase Heat flow into the slab (ex- fan)• What if there are different kinds of thermal mass?
- DHC- Volume - Position of the mass (trombe wall, water bed,
water drums)• Plants in the sunroom
- plant volume * plant conversion coefficient etc.• Improving the sunroom: South overhang, Reflectors