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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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

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Difference Range: -15 to +18 degrees F

9:34 PM Tue, May 08, 2007

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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

Future Audience• Future Systems

Modeling students

• Modelers, designers - to evaluate the performance of their sunrooms or greenhouses, using the standard model

• Designers - to better design a sunroom before it has been built.

We are the best calibration crew!!! EVER!