edward arens center for the built environment university

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


Two sides to PCS

Building+control system

One-off assemblage, many functions, little generality

Specialized device developed for large-scale manufacturing


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


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


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


Extending the cold side setpoint


Thermal acceptability unchanged

Right now, how acceptable is the thermal environment at your workspace?


Measured power savings

0

2

4

6

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12

70 No PCS 70 68 67 66

Pow

er [k

W]

Heating Setpoint oF

Foot Warmer Computer & Monitor Reheat Heating


Cooling/heating tests, 19 body segments


Face cooling, warm environment


0

5

10

15

20

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40

14:52 15:00 15:07 15:14 15:21 15:28 15:36

Skin

Tem

pera

ture

(°C

)

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-2

-1

0

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Back Temperature overall_sensation back_sensation

Back coolingTroom = 28.2°C

Back cooling, warm environment


Warming feet, cool environment


Local cooling/heating devices for offices For cold conditions For warm conditions

Heated keyboard Palm warmer

Foot warmer

Head cooling device

Hand cooling device


Lab studies of PCS

Comfort Various configurations of

local heating and cooling Perceived air quality

Effect of air movement on body plume


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

Bancroft Library, UCB


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


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


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


Our sensing ideal?

Miniature sensor of: Temperature Humidity CO2

Occupancy Specialized Inexpensive Scalable

Mosquito


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


Apps to gain personal control from central HVAC

Occupant interaction with local zone control; sMAP


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


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?


Questions?


Overall discomfort dictated by local discomfort: in warm environments

Head is most important in warm environments


Overall discomfort dictated by local discomfort: In cold environments


0

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15:36 15:43 15:50 15:57 16:04 16:12 16:19 16:26 16:33

Tem

pera

ture

(°C

)

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Finger Temperature overall_sensation left_hand_sensation

Hand Cooling

Hand cooling in warm environment (C

)

edward arens center for the built environment university

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