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Feasibility of Retrofitting

Centralized HVAC Systems for Room-

Level ZoningTamim Sookoor

Brian HolbenKamin Whitehouse

June 7, 2012International Green Computing Conference (IGCC ’12)

U.S. energy usage*

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*U.S. Department of Energy, 2006

U.S. residential energy use*

Homes are ~30% vacant

* National Academy of Science, 2006

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U.S. residential energy use

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Homes are ~30% vacant

Smart Thermostat: 28% savings--Sensys 2010

U.S. residential energy use

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Homes are ~50% usedwhen occupied

Our goal:Occupancy-driven

zoning

U.S. residential energy use

Homes are ~50% usedwhen occupied

Our goal:Occupancy-driven

Zoning

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Overview

•Zoning Overview

•Preliminary Studies

•Results

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Overview

•Zoning Overview

•Preliminary Studies

•Results

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“Snap-in” zoning retrofit

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“Snap-in” zoning retrofit

•Low cost

•DIY: no configuration

•Focus on forced air

•Other systems are similar

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Central HVAC

•One sensor

•One air conditioner

Snap-in Zoning

Zoned HVAC

•K sensors

•K air conditioners•K+1 Control Signals

•One air conditioner

•K sensors

Q1: Does room usage vary?Q2: Can a house be partially conditioned?Q3: Does partial conditioning save energy?Q4: Does leakage reduce efficiency?

Overview

•Zoning Overview

•Preliminary Studies

•Results

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Does room usage vary?

•Smart home data set over 28 days*

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Bedroom

Kitchen

Toilet

12AM 3AM 6AM 9AM 12PM 3PM 6PM 9PM 12AM

* Kasteren et al.

Can a house be partially conditioned?

•Empirical Study

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Living Room

Kitchen

DiningRoom

Office

Bedroom

Can a house be partially conditioned?

Office

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Does partial conditioning save energy?

System turns off faster

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•EnergyPlus Simulation

Does leakage reduce efficiency?

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4 3 2 1 0Number of external walls

0

5

10

15

20

25

30

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Energ

y (

kWh)

Insulation Effect

Overview

•Zoning Overview

•Preliminary Studies

•Results

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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

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Static Dual-Zone

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Evaluation method

Sun Mon Tue Wed Thu Fri Sat …Dual-Zone

Whole house

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Energy savings

21% savings Statisticall

y significant at alpha = 0.15

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Zone airflow

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Zone airflow

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Zone airflow

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Zone airflow

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Total airflow

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Conclusions

•“Snap-in” Zoning

•Cheap, easy, & energy saving

•Many challenges have to be overcome

•Equipment safety, occupancy prediction

•Results indicate potential for energy savings

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Credits & Questions

Tamim Sookoor, Brian Holben, Kamin Whitehouse