Download Automatic Lighting Control for Enegy Savings

Automatic Lighting Control for
Energy Savings
ncontrolled lighting wastes
energy. By installing an
automatic lighting control system, your lights will be on only when
necessay, or will be dimmed for certain times of the day and types of
activities. The system can help yeduce energy costs and increase lamp
life. In this Technology Update,
you will leam more about various
automatic lighting control systems
and the benefits they provide.
U
Backgrou nd
Automatic lighting control systems are now available that will economically provide light when and where it is needed (Figure 1).
Electronic sensors and microprocessor-based energy controllers
will contribute to cost savings by regulating light output according
to available daylight and lamp aging.
Energy savings of 50 percent to 65 percent can be obtained using
this equipment. The total initial electrical installation cost for new
office buildings with automatic fluorescent dimming systems will
be 10 to 12 percent higher than with conventional line voltage
switching systems. The additional expense will be recovered in approximately 5 years through energy and operating cost savings.
Figure 1. Typical energy savings with automatic lighting control
nergy use with
circuit breaker switching
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Energy use with
automatic lighting control
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midnight 6 am.
noon
6 p.m.
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midnight
Time
Energy saved by using
people presence sensors
Toll-free Hotline 1-800-872-3568
Bonneville
POW E R A D MI N ISTRATI 0 N
m
Energy saved by
takhg advantage of
dMbt
FAX 1-800-872-3882
Energy saved by
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to task
Electronic Bulletin Board 1-800-762-3319
Figure 2. Ceiling mounted
electronic sensor
H The area or zone where the
activity is carried out
H The time of day
Lampaging
People
For many lighting installations
there is no need to activate artificial lighting unless people are
in the area. An electronic sensor (Figure 2) may be used to
detect human presence and
switch lighting through an automatic control system. The sensor will ensure that lights are
automatically turned off in unoccupied areas.
lnstallina Automatic
Lighting3ontrol
Automatic lighting control systems are available that will
adjust artificial lighting according to these variables:
The presence of people
The activity or "task" being
performed
The contribution available
from daylight
Task
Lighting needs vary according
to the activity being performed.
What people are doing in an
area will affect illumination
level requirements.
A level of 70 footcandles may be
required for continuous office
work (Figure 3), but after normal working hours the cleaning
staff may need only 28 footcandles to perform its work. Combining human presence sensors
with dimming controllers that
have time-of-day capabilities
will provide this control alternative.
For office areas, fluorescent and
incandescent dimming equipment will provide lighting control according to task. For
industrial areas and recreational
facilities, the high intensity
discharge (mercury vapor, metal halide, high pressure sodium)
automatic energy control system shown in Figure 4 may be
used to vary lighting levels.
For example: An automatic energy control system can vary
the lighting levels in an ice
arena according to the use of the
ice. Low levels of light may be
used for figure skating, public
skating, and ice cleaning, while
a higher level would be used for
recreational hockey, and the full
design level would be used for
competitive hockey. The light-
Figure 3. Lighting level controlled by work performed, time of day, and human presence
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28 footcandles for cleaning tasks
70 footcandles for off ice tasks
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ing controls would provide a
Figure 4. Automatic energy control system for use in recreational facilities
pre-set proper level of dimming and industrial areas
for the activity scheduled for
that time of day, combining dimming and a time clock.
System input from
lighting transformer
Facility operators may use a
wall-mounted control station to
adjust lighting levels according
to area use. Additional savings
can be obtained by supplementing the system with timing controls to dim lighting during
lunch and break periods, and
for janitorial and security work
after hours.
Day1ig ht
A fluorescent energy management lighting controller automatically adjusts lights in
response to changes in daylight
while maintaining constant illumination on the work surface.
required ligl,til,g level may
be set manually or changed by
automatic timers or programs.
Figure 5.
Monitor/co nt rol
station
-i'here are many periods when
perimeter areas in an office
building are adequately illuminated by daylight. Automatic
fluorescent dimming systems
controlled by photocells (Figure
5 ) can take advantage of this
"free" lighting.
Fluorescent energy management lighting controller
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The area shown as Zone 1 in Figure 6 is approximately onethird of the total floor area and
receives, on a yearly average,
enough daylight to supply as
much as 30 percent of the required lighting. A 10 percent
overall saving can be achieved
using a fluorescent dimming
system that takes advantage of
daylight. For an office building
this represents a minimum saving of a proximately 0.62
kWh/ft /yr. At 5c/kWh the
minimum annual cost saving
will be $30.79 for each 1,000 ft2
of office space.
Y
Zone
using the dimming systems just
described each lighting zone in
an officebuilding can be maintained at the recommended
light level for the type of work
being performed. Savings may
be maximized by reducing light
levels for 'Ones needing Only
low levels of illumination.
Using the zoning pattern shown
in Figure 7, an automatic
lighting control system can provide low levels of illumination
for hallway and service areas
and higher levels for accounting, typing, and drafting areas.
Time
Programmable time controllers
are available to independently
switch several lighting circuits
on a 7-day, time-of-day, on-off
schedule. A calculator-type
keyboard (Figure 8) is used to
program the controller for a
normal daily schedule and a
holiday schedule 7 days in advance.
Similar controllers are available
that can transmit power line carrier signals on the standard electrical wiring circuits. These
devices do not require col,trol
wiring for light switching.
Lamp Aging
An automatic dimming system
controlled by a photocell will
correct for lamp aging and depreciation.
Figure 6. Plan view of off ice floor showing zone 1,
which will benefit from daylighting
l~
Standard lighting design practices are based on maintaining
the required illumination levels
throughout the life of a lamp.
To compensate for aging and depreciation, a higher initial illumination must be accepted for a
standard fluorescent lighting
system.
For a lighting task requiring 70
footcandles, Figure 9 shows that
102 footcandles will be provided in the first year of fluorescent lamp life. The lighting
level in the second year will be
approximately 84 footcandles.
Only in the third year of lamp
life will the lighting level drop
to the specified 70 footcandles.
Energy has been wasted in
maintaining excessive lighting
levels in the first 2 years of lamp
life.
An automatic fluorescent dimming system will ensure that
the required 70 footcandles is
maintained throughout the life
of the lamps. The graph on the
left in Figure 10 shows a
Figure 7. Office floor layout
Zone 1I perimeter daylighting
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1
buildinm envelope
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zone4
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Figure 8. Calculator type keyboard
for programming schedules
Using the zone control switch ,
on-off switching or multilevel
switching can be provided for
lighting zones using a low voltage remote switching system.
Programmable
Lighting ControlIers
lighting level with a standard
system varying from 102 footcandle to 70 footcandles. The energy use is 100 percent for the
3-year period.
The graph on the right shows 70
footcandles maintained over 3
years with a dimming system
that will reduce relative energy
use to 70 percent at the beginning of the period and will
gradually increase use to
100 percent in the third year.
The central controller (Figure
12), containing a microprocessor and logic circuitry, can be
programmed to provide discretionary control and to override
functions by keyboard entry.
Programs can also be entered
on data cards to take account of
seasonal factors, vacation shutdown, and other variables. The
controller can also be equipped
with an optional CRT display or
printer to provide status readout.
Advantages of Automatic Lighting Control
Systems
Using an automatic lighting
control system to increase levels
when required and reduce levels or switch lights when a
higher level is not needed produces lighting that is more effective and energy efficient.
The following major advantages
may be obtained from automatic
lighting control.
Energy Cost Savings
Total savings of 50 to 65 percent
are obtainable. Dollar figures
shown in Table 1 are based on
an energy cost of 5 cents/kWh.
Figure 9. Lamp aging pattern using a standard fluorescent switching system
Low Voltage Remote
Switching Systems
Lighting may be controlled to
various light levels by wiring
fluorescent luminaires as shown
in Figure 11. Low voltage remote switching relays are used
to control levels. Three-lamp
lighting fixtures can be controlled to three levels. Two or four
lamp fixtures can be controlled
to two levels.
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Figure 10. Variation in lighting level and power consumption
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70 footcandles required liahtinq level
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00
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Years
100% - ,
Years
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1
Standard system
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2
3
Years
1
Years
1
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2
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3
Dimming system
loo%-.
3
1
2
Standard system
Reduction of Energy Used for
Air Conditioning
Energy savings from daylight
and air conditioning are complementary. Daylight is at a maxiOne watt of air conditioning
load is required to remove every mum on sunny days when the
potential for air conditioning
two or three watts of heat load
produced by lighting. Reducing savings highest.
lighting energy use through
Although lighting makes a conautomatic COntrOlS Will reduce
tribution to the heating of a
air conditioning energy use.
building, the annual energy reduction from air conditioning
Figure 11. Multiple level fixtures using low voltage relays, ballasts not
hown
A
..
B
A+B
.
None
6
33%
SSYO
100%
_.
0%
2
Dimming system
savings is generally greater than
energy contributed by lighting
during the heating season.
Increased Lamp and
Ballast Life
Reducing the operating hours of
lamps and ballasts will increase
their productive life. Decreasing the total hours of lamp operation from 5,000 to 4,000
hours per year will increase the
life of fluorescent lamps (rated
at 20,000 hours lamp life) from
4 years to 5 years.
Compatible with Energy
Management and Building
Control Systems
Automatic dimming systems
and low voltage remote switching relays may be integrated
with microprocessor-based
small-user energy management
systems that incorporate peak
demand control and time-ofday control of heating and ventilation systems.
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Figure 12. Programmable lighting control schematic
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Photocontrol
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Automatic lighting control may
also be integrated with computerized building control systems
that have energy management
functions in addition to fire and
security system functions. Elec-
cording to zone and light level
tronic sensors used to detect
human presence for lighting con- requirements using computerized building control systems.
trol may be used as inputs for
central computerized security
systems. Security lighting may
also be centrally controlled acTable 1. Energy Cost Savings
Type of Control Action
Energy Saving** Annual Cost Saving ***
(kWh/ft2/year)
($/I,OOO ft2/year)
Reduction*
(%)
Detecting presence of people
25
1.5
75
Dimming to reduce effect of
compensating for lamp aging,
lens depreciation, and dirt
depreciation
15
0.9
45
Dimming to take advantage
of daylight
10
0.6
30
Matching lighting to
task and person
15
0.9
45
Totals
65
3.9
$195
.
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.
*Theestimates listed are the savings in lighting energy use.
**Energysavings are based on 5,000 hr/year operation.
***Airconditioning savings will accrue in proportion to the reduction in lighting energy use. When office lighting energy use is reduced by 50 to
65 percent, annual air conditioning operating cost reductions in the order of $75 to $85 per 1,000 ft2 will generally be achieved.
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v The Electric Ideas Clearinghouse is
a comprehensive infomation
source for commercial and industrial energy users. It is operated
by the Washington State Energy
Offzce and is part of the Electric
Ideas technology transfer program
sponsored by participating utilities
and the Bonneville Power Administration.
Electric Ideas Clearinghouse
P.O. Box 43171
Olympia, WA 98504-3171
v Technology Update CH-32
Toll-free Hotline: 1-800-872-3568
Fax: 1-800-872-3882
Electronic Bulletin Board:
1-800-762-3319
Adapted from B.C. Hydro. Automatic Lighting
Control for Energy Savings. Guides to Energy
Management. GEM No. L108. January 1990. With
permission from B.C. Hydro, Vancouver, British
Columbia
DOE/BP-3 983 3 -2 3
March 1993
15C
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