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RoomZoner : Occupancy-based Room-Level Zoning of a Centralized HVAC System

RoomZoner : Occupancy-based Room-Level Zoning of a Centralized HVAC System. Tamim Sookoor and Kamin Whitehouse April 11, 2013 4 th International Conference on Cyber-Physical Systems (ICCPS). US Residential Energy Use*. *US Energy Information Administration. US Residential Energy Use*.

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RoomZoner : Occupancy-based Room-Level Zoning of a Centralized HVAC System

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  1. RoomZoner: Occupancy-based Room-Level Zoning of a Centralized HVAC System Tamim Sookoor and Kamin Whitehouse April 11, 2013 4th International Conference on Cyber-Physical Systems (ICCPS)

  2. US Residential Energy Use* *US Energy Information Administration

  3. US Residential Energy Use* Homes are ~30% vacant Smart Thermostat: 28% Savings --Sensys 2010 *US Energy Information Administration

  4. US Residential Energy Use* Homes are ~50% used when occupied Our goal: Occupancy-driven zoning *US Energy Information Administration

  5. Related Work HVAC Co-design ICCPS 2013 POEM IPSN 2013 PreHeat UbiComp 2011

  6. RoomZoner • Retrofit centralized HVAC for room-level zoning • Low cost DIY installation • Ensure safety of HVAC system 69°F 69°F 72°F 69°F 69°F 72°F 69°F

  7. Outline • Zoning Overview • Challenges • Approach • Evaluation

  8. DIY Zoning Retrofit

  9. 69°F

  10. 64°F 72°F 71°F 72°F 70°F 71°F 64°F 70°F 69°F 72°F 65°F 71°F 70°F 69°F 63°F 68°F

  11. Outline • Zoning Overview • Challenges • Approach • Evaluation

  12. Zoning With a Central HVAC System RoomZoner • Central HVAC • One sensor • One heater/cooler • Zoned HVAC • N sensors • N heaters/coolers • N sensors • One heater/cooler • N + 1 control signals • Can a central HVAC system safely be used for zoning? • Can it be implemented with COTS components?

  13. Backpressure

  14. Backpressure

  15. Backpressure

  16. Short Cycling 73°F 72°F 71°F 70°F 69°F

  17. Temperature Estimation What temperature to use for control decisions? 78°F 74°F 76°F 65°F 69°F 70°F 69°F

  18. Temperature Estimation Occupied rooms? 78°F 74°F 76°F Low system stability 65°F 69°F 70°F 69°F

  19. Temperature Estimation House average? 78°F 74°F 77°F Average = 72°F 65°F 70°F Slow reaction 71°F 69°F

  20. Occupancy Assessment 78°F 67°F 66°F 65°F 77°F 72°F 70°F 72°F 69°F

  21. Outline • Zoning Overview • Challenges • Approach • Evaluation

  22. Tackling the Challenges Challenge Approach Dump Zones Conservative Averaging Occupancy Characterization • Equipment Safety • Temperature Estimation • Occupancy Assessment

  23. Dump Zone Selection 78°F Which additional rooms should you condition? 74°F 77°F 65°F 70°F 71°F 69°F

  24. Dump Zone Selection 78°F 74°F 77°F 65°F 70°F 71°F 69°F

  25. Dump Zone Selection 78°F How many rooms should be in the dump zone? 74°F 77°F 65°F 70°F 71°F 69°F

  26. Building a Airflow Model Exponential Measurements

  27. Building a Conservative Airflow Model 2N Measurements

  28. Conservative Airflow

  29. Estimating Total Airflow + + > T + + + +

  30. Conservative Temperature Averaging 78°F Heating: Max Cooling: Min 74°F 77°F 65°F Trade-off comfort for stability 70°F 72°F 69°F

  31. Occupancy Characterization • Analyze Historical Occupancy Data • Find sensor firing frequencies that identify • Stable occupancy • Start of long-term usage • End of long-term usage • Transitional occupancy • Start of temporary usage • End of temporary usage

  32. Occupancy Characterization • Exhaustive search over frequencies • Minimize total occupancy time Sensor frequencies

  33. Outline • Sensor Design • Topological Constraints • Search • Evaluation

  34. Mon Tue Wed Thu Fri Sat Experimental Approach • Deployed RoomZoner in a 7-room house • 13 registers • 12 temperature sensors • 42 days (21 RoomZoner/ 21 whole house) RoomZoner … Sun Whole house

  35. Response to Temperature

  36. Energy Savings ~14% less energy

  37. Limitations and Future Work • Current system built using an ad-hoc approach • Use a control-theoretic approach such as MPC • Current evaluation limited in scope • Evaluate system in multiple houses • Extend evaluation period

  38. Conclusions • Centralized HVACs can be retrofitted for zoning • Low-cost DIY installation • Saves energy • Requires incorporation of prediction • Predict room-level occupancy (POEM?) • Predict room temperature changes (Matchstick?) • One step towards residential room-level zoning of centralized HVAC systems

  39. Feedback or Questions?

  40. Backup Slides

  41. Implementation

  42. Challenges to Central HVAC Zoning • Equipment safety • Backpressure • Short-cycling • Temperature estimation • N sensors  1 Heater/Cooler • Occupancy assessment • Passageway rooms • Short-term room usage • Multi-room usage

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