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Making personal comfort the basis for efficient buildings Edward Arens
Center for the Built Environment University of California at Berkeley
November 12 2013, ARPA-E Workshop
Outline of Talk
Energy savings from personal comfort systems (PCS) Energy savings come only from freeing up interior setpoints PCS devices must themselves be efficient (no 1KW heaters)
How good PCS works Thermal physiology and perception The most promising approaches Example designs
Linking PCS to the building’s control system How to generalize this relationship
Adoption in practice: ‘Tech-push’ versus ‘demand-pull’ Needs and warnings
November 12 2013, ARPA-E Workshop
Two sides to PCS
Building+control system
One-off assemblage, many functions, little generality
Specialized device developed for large-scale manufacturing
November 12 2013, ARPA-E Workshop
Energy savings from PCS
Hoyt, T., H.L. Kwang, H. Zhang, E. Arens, T. Webster, 2009, “Energy savings from extended air temperature setpoints and reductions in room air mixing.” International Conference on Environmental Ergonomics 2009
Energy savings come from expanding the range of ambient air temperature setpoints Secondary effects:
• Enable less-controlled or slowly-responding systems by assuring comfort, e.g., naturally ventilated buildings or radiantly cooled buildings
• Serve as sensors for central HVAC
PCS
PCS
November 12 2013, ARPA-E Workshop
Extending the warm side setpoint
DPR: a net-zero naturally-ventilated building in Phoenix!
Uses ceiling fans
Interior temperature maintained at 82oF (28oC)
Standard 55 (since 2010) says this is comfortable
Is it?
Photos courtesy of DPR
November 12 2013, ARPA-E Workshop
Thermal satisfaction rating, CBE Survey
Mean Scores - Thermal ComfortLEED (n=31) compared to CBE database (n=257)
-3
0
3
0% 25% 50% 75% 100%
Percentile Rank
Mea
n Sa
tisfa
ctio
n Sc
ore
leed median: 0.42db median: -0.13
mixed mode median: 0.62
LEED (n=31), mixed mode (n=5) compared to CBE database (n=257)
Data for evolving green building design criteria
DPR
DPR mean: 0.97
November 12 2013, ARPA-E Workshop
Thermal acceptability unchanged
Right now, how acceptable is the thermal environment at your workspace?
November 12 2013, ARPA-E Workshop
Measured power savings
0
2
4
6
8
10
12
70 No PCS 70 68 67 66
Pow
er [k
W]
Heating Setpoint oF
Foot Warmer Computer & Monitor Reheat Heating
November 12 2013, ARPA-E Workshop
0
5
10
15
20
25
30
35
40
14:52 15:00 15:07 15:14 15:21 15:28 15:36
Skin
Tem
pera
ture
(°C
)
-4
-3
-2
-1
0
1
2
3
4
Back Temperature overall_sensation back_sensation
Back coolingTroom = 28.2°C
Back cooling, warm environment
November 12 2013, ARPA-E Workshop
Local cooling/heating devices for offices For cold conditions For warm conditions
Heated keyboard Palm warmer
Foot warmer
Head cooling device
Hand cooling device
November 12 2013, ARPA-E Workshop
Lab studies of PCS
Comfort Various configurations of
local heating and cooling Perceived air quality
Effect of air movement on body plume
November 12 2013, ARPA-E Workshop
PCS: fans and footwarmer
105 PCS units assembled, Funded by PIER/CEC and CBE
air temperature sensor occupancy sensor
USB to workstation computer
occupancy sensing pressure plate
Fan unit
Footwarmer unit
Control and monitoring software, database design air temperature speed and warmth choices occupancy
November 12 2013, ARPA-E Workshop
control panel and occupancy sensor
• Powered by rechargeable battery • 2 – 4 days operation between charges • Maintains comfort between 60.5 and 85 F
• Max heating power 14 W • Max cooling power 3.6 W
PCS: heated/cooled chair
November 12 2013, ARPA-E Workshop
PCS contributing to building controls
Add to PCS: • Wireless communications • Intelligence; report:
• Environment • Controls status • Occupancy • Interpreted data
• Occupant identification by cellphone, RFID; customization of settings.
• Measuring occupant thermal status; extremity temperature gradienting
November 12 2013, ARPA-E Workshop
Hardware for sensing, actuating, communications
• Traditionally, sensing has been difficult in buildings ~ $1000/point for wired sensors
• The future will be small and mass-produceable; PCS can help here
November 12 2013, ARPA-E Workshop
Our sensing ideal?
Miniature sensor of: Temperature Humidity CO2
Occupancy Specialized Inexpensive Scalable
Mosquito
November 12 2013, ARPA-E Workshop
Software for linking to HVAC: simplifying measurement and actuation
www.cs.berkeley.edu/~stevedh/smap2/
e.g., sMAP • Time-series
database • Many data
streams • Interpretive
tools • Supports
interaction between PCS and system
November 12 2013, ARPA-E Workshop
Apps to gain personal control from central HVAC
Occupant interaction with local zone control; sMAP
November 12 2013, ARPA-E Workshop
Adoption in practice 1: ‘technology-push’
• PCS level • Make it efficient • Make it effective—more comfortable than ‘neutral’ • Add sensors and intelligence • Make it economical for the various stakeholders
• HVAC systems level: • Communicate PCS data to central system • Need open source communications protocols that
combine many data streams, access BACNET ports and control systems, and communicate back to PCS
November 12 2013, ARPA-E Workshop
Adoption in practice 2: ‘demand-pull’
Two benefits: • Comfort for more people • Improved building energy efficiency Building stakeholders: • Occupant • Tenant (employer) • Operator • Owner Who benefits? Who pays?
November 12 2013, ARPA-E Workshop
Overall discomfort dictated by local discomfort: in warm environments
Head is most important in warm environments
November 12 2013, ARPA-E Workshop
Overall discomfort dictated by local discomfort: In cold environments
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