Dimmable lighting: energy savings and occupant satisfaction

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Dimmable lighting: energy savings and occupant satisfaction

Newsham, G. R.; Birt, B.; Laouadi, A.; Atif, M. R.

Benjamin Birt, Aziz Laouadi and Guy Newsham

Dimmable Lighting:

Energy Savings and

Occupant Satisfaction

Electricity Use in Canada



Natural Resources Canada data 2006/2000

Residential

28.9%

Industrial

45.3%

Transportation

0.2%

Commercial /

Institutional

25.7%

Water

Heat

6%

_Cooling

10%

Heating

29%

Other

39%

Commercial /

Institutional

What is a Dimming Ballast?

Overview



Research studies addressing:

•

Personal dimming control

•

Daylight harvesting

•

Occupancy sensors

•

Demand response

What is Daylight Harvesting?

http://windows.lbl.gov/daylighting/designguide/dlg.pdf

Photosensor

Task light (undershelf)

Indirect (partition-mounted)

Direct parabolic

(ceiling centre)

Direct parabolic

(ceiling perimeter)

Personal control, no daylight



First laboratory experiment

Personal control, no daylight

(cont’d)



Chosen

illuminance

•

Individual

preferences vary

•

Mean ~425 lx …

•

… therefore,

energy saving

15%

Typical

recommended

practice

100

200

300

400

500

600

700

Desktop illuminance (lux)

F

re

q

u

e

n

c

y

30

25

20

15

10

5

0

Personal control, no daylight

(cont’d)



Satisfaction benefits

•

Within 100 lx of your own preference

DIFF SAME

DIFF SAME

DIFF SAME

DIFF SAME

Personal control, no daylight

(cont’d)

Rated comfortable by 70%

Rated comfortable by 90%

more sustained motivation

Typical practice:

recessed parabolic, grid

Workstation specific,

Personal control, with daylight



Laboratory experiment

•

40 participants

•

Prompted every 30 minutes

to adjust electric light

•

20% transmission window

–

Maximum daylight: ~500 lx

13

Personal control, with daylight

(cont’d)



Chosen illuminance

•

Individual preferences vary

•

Not constant throughout day

0

200

400

600

800

1000

1200

Participants

T

otal

des

k

illuminanc

e

,

lux

Participants

Personal control, with daylight

(cont’d)



Energy savings

25% 38%

E

nergy

use/day

(k

Wh)

from

ele

ctr

ic

choi

ce

t

p

h

o

to

s

Field study of

personal

lighting controls,

occupancy sensors and daylight harvesting

Field Study

Field Study

(cont’d)



Workstation specific, direct-indirect lighting



Data for 80+ occupants

•

~65 with system of interest

Field Study

(cont’d)



Data collection

•

March 12th and October 2nd, 2005

•

Energy and control use data every 15 minutes

•

Occupants surveyed:

–

office and lighting appraisals

–

environmental satisfaction

Field Study

(cont’d)



Energy savings

0.02 manual control

actions/person/day

(~ x2 during Phase 1,

when DH deactivated)

Field Study

(cont’d)



Power reduction

LPD, W/m

2

Conventional

10

Studied system

5.6

Studied system (effective)

2.7

ture

avg

.

po

w

er

de

man

d

(W

atts)

Payback

2

– 4 years, new installation

4

– 12 years, retrofit

Commissioning and Maintenance Issues



123 sidelit spaces with photocontrols

in California



52% not functioning …



… other 48% saving half of expected



Many intentionally disabled due to

occupant complaints

Heschong Mahone Group, Sidelighting Photocontrols Field Study, Commercial

Market Research Report #06-152, for the Northwest Energy Efficiency Alliance

(2006).

http://www.nwalliance.org/research/reports/152.pdf

Comparison of Control Types for Offices

Energy

Savings

Effect on

People

Cost

Occupancy

Sensors

+ + +



$

Daylight

Harvesting

+ +



$ $ $

Personal

Control

+



$ $

Conclusions



Dimming ballasts enable:

•

Substantial energy savings

•

Peak load reduction

•

Improved occupant satisfaction

Getting there from here



More expensive

•

3% of commercial buildings (7% of floor space),

have “advanced” lighting controls

•

7% (31% of floor space) have energy

management and control systems (EMCS)

for HVAC

Getting there from here



Utility incentives



Price will come down with volume

•

1 in 20 conventional commercial buildings

in Pacific NW had daylight harvesting;

•

2 in 3 LEED-certified commercial buildings

had them



Value of improved occupant satisfaction?



Committed and trained facility managers



Software tools

Baylon & Storm, P. (2008). ACEEE Summer Study on Energy

Efficiency of Buildings: 4/1 to 4/12.

www.nrc-cnrc.gc.ca/irc