Sentinel: Occupancy Based HVAC Actuation using Existing WiFi Infrastructure within Commercial Buildings

Transcription

1 Sentinel: Occupancy Based HVAC Actuation using Existing WiFi Infrastructure within Commercial Buildings Bharathan Balaji, Jian Xu, Anthony Nwokafor, Rajesh Gupta, Yuvraj Agarwal University of California, San Diego Carnegie Mellon University

2 Occupancy-driven Building HVAC Room Wi-Fi Client Access Point Vacant Occupied Occupant HVAC: Heating, Ventilation and Air Conditioning HVAC Control (via BACnet) 2

3 Outline Overview Motivation WiFi Based Sensing Challenges Implementation Results Conclusion 3

4 Outline Overview Motivation WiFi Based Sensing Challenges Implementation Results Conclusion 4

5 Why is HVAC Efficiency Important? US Energy Consumption 1 Commercial Buildings Energy Breakdown 1 29% 19% Commercial Residential Industrial 17% 20% Lights HVAC Plug loads Misc 22% Transportation 23% 30% 40% 36% electricity 39% carbon emissions Static Control Occupancy Based Control Occupancy based control of HVAC can provide 15% 40% energy savings! 2 1. Building Energy Data Book OBSERVE: Occupancy-Based System for Efficient Reduction of HVAC Energy - Erickson et al. IPSN

6 Occupancy Based HVAC Control Static Occupancy Schedule 6:00AM HVAC ON 10:00PM Actual Occupancy Commercial Building Vacant Occupied HVAC Zone Building partitioned to zones Independent control of each zone Occupancy can be used to turn off unused zones 1. Duty-Cycling Buildings Aggressively: The Next Frontier in HVAC Control. Agarwal et al. IPSN

7 Existing Occupancy Solutions Modern buildings use motion sensors Cannot detect stationary occupants 2 Expensive to install in existing buildings Wireless sensors based solutions Use of camera 1 or combination of sensors 2 Hard to deploy and maintain at scale 3 Leverage existing infrastructure Accurate, scalable WiFi Inexpensive, easy to maintain 1. POEM: Power-Efficient Occupancy-Based Energy Management System. Erickson et al. In IPSN Duty-Cycling Buildings Aggressively: The Next Frontier in HVAC Control. Agarwal et al. IPSN 2011 Insights from a large, long-lived appliance energy WSN. Dawson-Haggerty et al. In IPSN

8 Outline Overview Motivation WiFi Based Sensing Challenges Implementation Results Conclusion 8

9 WiFi Based Sensing Lobby ACCESS POINT Conference Room Self-calibrated indoor localization not accurate More accurate solutions require war driving, complex client apps Locate up to 1000 devices in real-time Significant energy savings even with coarse grained localization Printer Room ZONE OF DETECTION Real Location Occupant s 1. On the Empirical Performance of Self-Calibrating Wifi Location Systems. Turner et al. IEEE LCN

10 WiFi Based Sensing Lobby ACCESS POINT SHARED SPACE Conference Room Assume visitor cannot enter without owner present Division of spaces into personal and shared Assume person in office whenever within vicinity Sacrifice savings when occupant is just outside office PERSONAL Printer Room SPACE Real Location Possible Location Assumed Location 10

11 Outline Overview Motivation WiFi Based Sensing Challenges Implementation Results Conclusion 11

12 Partitioning the Building Lobby Zone 3 Zone 1 Zone 2 SHARED SPACE PERSONAL SPACE Conference Room Zone 4 Zones may consist of more than one room Zone contain both personal and shared spaces Some personal spaces converted to shared spaces Zone Type Area Electric Power Personal 37.50% 63.90% Shared 58.30% 66.90% Printer Room Zone 5 Contribution of each type of space to area and electricity in our building testbed Max savings of 33.1% 12

13 Challenges with Using WiFi for Occupancy Sensing Occupant does not use WiFi Device battery may run out Phone forgotten at home Need to lend office to visitor Solution: Provide web based manual HVAC override 13

14 Leveraging WiFi Connectivity for Occupancy Sensing Assumption: WiFi radio is always connected Reality: WiFi radio duty cycled to save power Android, Windows Phone: Can change settings iphone: Not possible to change settings Change settings to fetch mail every 15 mins May impact battery life Smartphone app for reduced battery impact 14

15 Outline Overview Motivation WiFi Based Sensing Challenges Implementation Results Conclusion 15

16 Building Testbed CSE, UCSD Built in 2004, 145,000 sq ft, 5 floors HVAC: VAV with reheat coil, 237 zones Occupants: Faculty, staff and students 16

17 Collecting WiFi Data Authentication Server Mirror Traffic Proxy RADIUS Server 802.1X/RADIUS Access Point Wi-Fi Client Authentication packets contain: Client MAC, AP MAC, client username Book keeping information: Start, stop, hand-off and periodic liveness packets 17

18 Acquiring Metadata Information Mapping of occupant offices from HR manager Room Occupant User identity from WiFi logs Location of AP from network manager Identify smartphone from hand-offs WiFi Devices Connectivity info from WiFi logs Access Point 18

19 Occupancy Based HVAC Control Three modes of operation in each zone Occupied (Weekdays 6am 6pm) Adequate ventilation, 4⁰F band (e.g. 70⁰F 74⁰F) Standby (Weekdays 6pm 10pm) Minimum ventilation, 8⁰F band (e.g. 68⁰F 76⁰F) Unoccupied (Nights & Weekends) Minimum ventilation, 12⁰F band (e.g. 66⁰F 78⁰F) When we turn Off HVAC, we go into Standby mode 19

20 DAMPER HOT WATER PIPE % HVAC Electrical Power HVAC Working & Savings AHU: Air Handler Unit VAV: Variable Air Volume AHU CENTRAL PLANT SUPPLIES HOT AND COLD WATER VAV COLD AIR HOT WATER COLD WATER Electrical power is cubic proportional to occupancy Only essential ventilation at 0% occupancy RETURN AIR REHEAT COIL SUPPLY AIR % Occupancy HVAC ZONE 20

21 Sentinel: Overall Architecture BACnet Connector HTTP BACnet/IP Building Management System BuildingDepot 1 MySQL Cassandra Storage HTTP HTTP HVAC Actuation Server Occupancy Inference Server AAA Authentication Server 1. BuildingDepot: An Extensible and Distributed Architecture for Building Data Storage, Access and Sharing. Y. Agarwal, R. Gupta, D. Komaki, and T. Weng. In BuildSys

22 Outline Overview Motivation WiFi Based Sensing Challenges Implementation Results Conclusion 22

23 Number of People Results User Study Survey of 187 out of 415 building occupants 61% users always connected to WiFi Reasons for not using WiFi: Poor WiFi coverage Good cellular data plan Device connectivity problems with WPA Unknown Cellular N/W Guest N/W Device Problems Sometimes Connected Always Connected Android iphone Windows Feature Others N/A 23

24 Number of Occupants Number of Errors Results Accuracy 116 occupants, 10 days, 436 events Ground truth collected manually 86% accuracy, 6.2% false negatives False Negative False Positive Inherent Error System Error WiFi Connectivity Unknown Occupancy Trends Across a Week for 38 Participants March 18 24,

25 Number of Occupants Electrical Power (kw) Temperature (F) Results Energy Savings Electricity - Typical Day Electricity - Sentinel Day Temperature Typical Day Temperature Sentinel Day Typical Day: March 22, 2013 Sentinel Day: March 26, Occupancy across Sentinel Day - Mar 26, 2013 Control of 55 out of 237 HVAC zones for 1 day 17.8% HVAC electrical energy savings 25

26 Conclusion Occupancy information is crucial to effective use of HVAC in commercial buildings. It is possible to use existing WiFi infrastructure for occupancy detection in building spaces. Our occupancy model applies to personal spaces. Shared spaces are currently not subject to HVAC control. 86% detection accuracy using WiFi, 6.2% false negatives WiFi connectivity issues lead to inaccuracies 23% of building area controlled using Sentinel 17.8% HVAC electrical energy savings for 1 day 26

27 Thank You! Questions? Acknowledgements: Thomas Weng, Hidetoshi Teraoka, Du Li, UCSD Facilities Management, UCSD Academic Computing Services, Anonymous reviewers 27

28 Extra Slides

29 Detailed Error Analysis Unknown System Error people Error Zone of Detection Incorrect Device Device Error ios Stop ios Start False Negative False Positive 29

30 HOT WATER SUPPLY Domestic Water Heat Exchanger HOT WATER RETURN HOT WATER SUPPLY* HOT WATER PUMP HVAC Heat Exchanger Air Mixer HOT WATER RETURN* Outside Air Relief Air COLD WATER SUPPLY* Cooling Coil COLD WATER RETURN* COLD WATER PUMP SUPPLY FAN Supply Air Return Air CRAC RETURN FAN *CENTRAL PLANT SUPPLIES HOT AND COLD WATER

31 HOT WATER SUPPLY HOT WATER RETURN Reheat Valve Supply Air VAV Supply Fan Damper Reheat Coil Flow sensor Return Air Exhaust Fan T Room 1 Room 2 Zone Temperature Thermostat Adjust HVAC Zone

32 Impact on Battery Life 3 day usage study across 20 smartphone users 32