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ATI_SDM_2010_Jun
- 1. Adaptive Optimal Designof Active Thermally Insulated (ATI) Windows Using Surrogate Modeling Junqiang Zhang, Achille Messac, Souma Chowdhury, and Jie Zhang Rensselaer Polytechnic Institute Department of Mechanical, Aerospace, and Nuclear Engineering Multidisciplinary Design and Optimization Laboratory 6th AIAA Multidisciplinary Design Optimization Specialist Conference April 2010, Orlando, FL
- 2. 2 Outline •Motivation • Active Window Technology Overview • ATI Window Design • Modeling • Adaptive Optimization • Surrogate Model of Optimal Operations • Results and Comparisons • Concluding Remarks
- 3. 3 Motivation 53%energy consumed by HVAC systems in residential buildings 44% energy consumed by HVAC systems in commercial buildings • Windows occupy only 10% to 15% of the wall area • Windows can contribute 25% to 30% of the heat gain Department of Energy, “Buildings Energy Data Book”, 2005, http://buildingsdatabook.eere.energy.gov/ Energy Information Administration, “Commercial Buildings Energy Consumption Survey”, 2003, http://www.eia.doe.gov/emeu/cbecs/
- 4. 4 Types ofActive Windows Heat extraction double skin facades Absorb the sun’s heat outside Switchable window coatings Change optical properties to limit solar heat gain Active control of shading systems Block incident sunlight to limit solar heat gain Thermoelectric Windows Outside Inside
- 5. 5 Thermoelectric (TE)Units • TE Units can be very small and operate with no moving parts, making them ideal to fit inside building envelopes or in the small space of the window frames. • A TE unit will form hot and cold sides when subjected to electric current. Melcor Center Hole Series Thermoelectric Cooler Hot Side Cold Side Heat Flow
- 6. 6 ATI WindowDesign Window Front View Cross Section of Side View 6 Side Channel Clear glass Side Channel Fans Heating air flow in Winter 1 m .5 m TE Units & Fin Dividing Wall 6 mm Air Clear Glass Tinted pane 24 mm Out In 12 mm Inner Pane Middle Pane Outer Pane
- 7. 7 ATI WindowDesign • Thermometer, anemometer, and solar radiation sensor are used to detect weather conditions. • Thermostat receive signals from the sensors and adjust the electric power supplies of TE units and fans according to different weather conditions. • Actively regulate the overall thermodynamic properties of the air in the gap between the inner pane and the middle pane to benefit the building occupants.
- 8. 8 Modeling •Motivation • Active Window Technology Overview • ATI Window Design • Modeling • TE models • CFD Model • Outside Heat sinks • Thermostats and weather condition sensors • Optimization • Surrogate Model of Optimal Operation • Comparison of Energy Efficiency • Concluding Remarks
- 9. 9 TE UnitsAnalysis • The cold side absorbs heat based on the number of TE units, Nte, the electrical current, Ite, the cold side temperature, Tc, and the temperature difference, DTte • The hot side releases the heat absorbed from cold side and the heat converted from the electric power Peltier effect: induce heat flow in the direction of electric current Joules effect: heat generated because of electrical resistance Conduction: heat transfer because of temperature gradient
- 10. Computational Fluid Dynamics(CFD) Model • A CFD model is meshed by Gambit • A steady-state heat transfer process is simulated in FLUENT • The outer pane, the middle pane, and the air gap between them, are modeled as an equivalent thermal resistance. • Solar heating of the panes is modeled as volumetric heat generation. • The air flow and associated heat flux in the ATI window are evaluated • Qconv: the heat flux through the inner pane 10
- 11. Solar Insolation •Accounting for the thermal heat flux, Qconv , from FLUENT, and the solar heat, Qsolar , the total heat gain is QATI Cross Section Reflected SR Absorbed SA Solar radiation Esky 11 • The incident solar radiation is reflected from the outer pane, absorbed by the panes, or transmitted into the room
- 12. Heat Sink Analysis • Pin spacing is defined by the equation below. • Pin diameter is 2.5 mm Stanescu, G., Fowler, A. J., and Bejan, A., “The optimal spacing of cylinders in free-stream cross-flow forced convection,” International Journal of Heat and Mass Transfer, Vol. 39, No. 2, 1996, pp. 311–317 12 A p S d W TE Units H L
- 13. Fan Model 13 Top Left Top Right Bottom Left Bottom Right Left Most Center Right Center Left Right Most
- 14. Fan Model 14 The Pressure Gradients of Fans Δpavg : average pressure gradient produced by fans k : the slope of the pressure gradients • A linear pressure gradient profile is assumed. • The total electric power consumption of all fans is less than 6% of that of the TE units. It is not minimized.
- 15. Control Systems TEUnits 15 Outside Temperature Wind Speed Solar Radiation Thermometer Anemometer Light Sensor Thermostat Processor Memory TE Units Power Controller Fan Power Controller Fans • Thermometer, anemometer, and light sensor are used to sense outside temperatures, wind speeds, and intensity of solar radiation. • Thermostat is used to control electric power supplied to TE units and fans.
- 16. Weather Conditions 16 Indoor weather conditions: • Indoor temperature: 75 ℉ (297 K) • Indoor heat transfer coefficient: 3.6 W/m2 Outside weather conditions: • Outside temperature: 7 to 97 ℉ (259 to 309 K) • Wind speed: 0 to 21.5 m/s • Solar radiation: 0 to 1000 W/m2 • Number of weather conditions: 10 x 3 (the small set population size) • Combinations: Sobol’s Quasirandom sequence generator algorithm Heating condition: Outside T < Inside T (usually in winter) Cooling condition: Outside T > Inside T (usually in summer) “Comparative Climatic Data for the United States through 2008,” Tech. rep., http://www.noaa.gov. Colaco, M. J., Dulikravich, G. S., and Sahoo, D., “A response surface method-based hybrid optimizer”, Inverse Probl Sci Eng, Vol. 6, No. 16, 2008, pp. 717– 7S4o1bol, I. M., “Uniformly Distributed Sequences with an Additional Uniform Property,” USSR Computational Mathematics and Mathematical Physics, Vol. 16, 1976, pp. 236–242.
- 17. 17 Adaptive OptimizationProblems Heating Cooling
- 18. Approximation of CFDModel • Local surrogate models are built during the optimization to reduce computational time. • Trust region method is used to manage the approximation • Surrogate model was created using extended radial basis functions (ERBF) 18
- 19. Weather Conditions andOptimization Results 19 No. 1 2 3 4…… 28 29 30 Outside T (K) 284.0 296.5 271.5 277.8…… 298.8 273.8 280.1 Outside T (℉) 51.5 74.0 29.0 40.3…… 78.2 33.2 44.5 Wind speed (m/s) 10.75 5.38 16.13 8.06…… 0.34 11.09 3.02 Solar radiation (W/m2) 500 750 250 625…… 359 859 234 Vte (V) 1.14 0.97 3.28 1.34…… 1.37 1.86 1.84 Δpavg (Pa) 0.96 0.95 1.77 1.00…… 1.75 1.89 2.00 k 0.07 0.07 0.02 0.08…… 0.01 0.01 0.02 Red: heating conditions (Outside T < Inside T) Blue: cooling conditions (Outside T > Inside T)
- 20. Optimization Convergence History 20 Convergence History of f(x) under Weather Condition 2 70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 Number of Function Evaluations
- 21. Surrogate Models ofOptimal Operations 21 Quadratic Response Surface Method Optimal
- 22. Surrogate Models ofOptimal Operations • The three functions are stored in the memories of the thermostats • With the inputs from the sensors, the thermostat evaluates Vte , Δpavg, and k. • Within the defined ranges of weather conditions, the operation of ATI 22 windows is optimal. Outside Temperature Wind Speed Solar Radiation Surrogate Model (Thermostat) Inputs Vte Δpavg k TE Units Power Controller Fan Power Controller Power of TE Units Power of Fans Outputs
- 23. Comparison with PassiveWindows 3-Pane 23 • Calculate the amounts of heat transferred through passive 3- pane window in the same weather conditions by WINDOW software. • WINDOW is a software developed by Lawrence Berkeley National Laboratory to analyze window thermal and optical performance. Clear Glass Air Gap Bronze Glass
- 24. Comparison of HeatFlux 24 Heating conditions (higher is better) Convective Heat (W) Weather Condition Number +: Out -> In − : In -> Out
- 25. 25 Comparison ofHeat Flux Cooling Conditions (lower is better) Convective Heat (W) Weather Condition Number +: Out -> In − : In -> Out
- 26. Comparison of EnergyEfficiency 26 Coefficient Of Performance (COP) is a measurement of energy efficiency. The COP of a standard HVAC system is about 3. The COP of an ATI window, COPATI, is defined as how much heat flux is reduced, compared with a passive window with the same structure, divided by the electric power used.
- 27. Comparison of EnergyEfficiency 27 45 40 35 30 25 20 15 10 5 3 0 COP of ATI Window COP of HVAC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Weather Condition Number Heating conditions: COP of the ATI windows is generally higher.
- 28. 28 Concluding Remarks • Adaptive optimization is performed to optimize the performance of the ATI window under different weather conditions. • Provide active control of the ATI window to adapt to different weather conditions using surrogate modeling. • High energy efficiency is generally achieved under heating conditions.
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Editor's Notes
- #4 Current energy production methods are unsustainable. Comment on the demand side.
- #5 These are four types of active windows. These are others efforts to decrease the energy lost through windows.
- #6 We chose thermoelectric units for our system because they are very small and are solid state.
- #8 We sought to design a window system that will compensate for all of the heat gained through the glass and maintain a thermal balance. This is our window design that improves upon the current passive window model.
- #9 Introduce the heat sinks. Start with heat sinks, then move to single TE units, then to cascades of units