1
Feasibility of Retrofitting
Centralized HVAC
Systems for Room-Level
Zoning
Tamim Sookoor
Brian Holben
Kamin Whitehouse
June 7, 2012
International Green Computing Conference (IGCC ’12)
U.S. energy usage*
*U.S. Department of Energy, 2006
1
U.S. residential energy use*
Homes are
~30% vacant
* National Academy of Science, 2006
2
U.S. residential energy use
Homes are
~30% vacant
Smart Thermostat: 28% savings
--Sensys 2010
2
U.S. residential energy use
Homes are
~50% used
when occupied
Our goal:
Occupancy-driven
zoning
2
U.S. residential energy use
Homes are
~50% used
when occupied
Our goal:
Occupancy-driven
Zoning
2
Overview
• Zoning Overview
• Preliminary Studies
• Results
3
Overview
• Zoning Overview
• Preliminary Studies
• Results
3
“Snap-in” zoning retrofit
4
5
“Snap-in” zoning retrofit
• Low cost
• DIY: no configuration
• Focus on forced air
• Other systems are similar
6
7
7
7
7
7
7
7
7
7
7
Snap-in Zoning
Central HVAC
•One sensor
•One air conditioner
Q1:
Q2:
Q3:
Q4:
•K sensors
•
K sensors
•One air conditioner
•K+1 Control Signals •K air conditioners
Zoned HVAC
Does room usage vary?
Can a house be partially conditioned?
Does partial conditioning save energy?
Does leakage reduce efficiency?
8
Overview
• Zoning Overview
• Preliminary Studies
• Results
9
Does room usage vary?
• Smart home data set over 28 days*
Bedroom
Kitchen
Toilet
12AM
3AM
6AM
9AM
12PM
3PM
6PM
9PM
12AM
* Kasteren et al.
10
Can a house be partially conditioned?
• Empirical Study
Office Dining
Room
Living
Room
Kitchen
Bedroo
m
11
Can a house be partially conditioned?
Office
12
Does partial conditioning save
energy?
• EnergyPlus Simulation
System turns
off faster
13
Does leakage reduce efficiency?
35
Insulation Effect
30
Energy (kWh)
25
20
15
10
5
0
4
3
2
1
Number of external walls
14
0
Overview
• Zoning Overview
• Preliminary Studies
• Results
15
Experimental
approach
• Deployed zoning in a 7-room house
• 7 sets of dampers
• 21 thermostats
• Controlled based on temperature
• 20 days of data
• Compared to whole-house conditioning
16
Static Dual-Zone
17
Evaluation method
Dual-Zone
Sun
Mon
Tue
Whole house
18
Wed
Thu
Fri
Sat
…
Energy savings
21%
savings Statistically
significant
at alpha =
0.15
19
Zone airflow
20
Zone airflow
20
Zone airflow
20
Zone airflow
20
Total airflow
21
Conclusions
• “Snap-in” Zoning
• Cheap, easy, & energy saving
• Many challenges have to be overcome
• Equipment safety, occupancy
prediction
• Results indicate potential for energy
savings
22
Credits & Questions
Tamim Sookoor, Brian Holben, Kamin Whitehouse