Publisher’s version / Version de l'éditeur: Electrical Equipment News, June, p. 11,16, 1992-06
READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.
https://nrc-publications.canada.ca/eng/copyright
Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la
première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.
Questions? Contact the NRC Publications Archive team at
PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.
NRC Publications Archive
Archives des publications du CNRC
This publication could be one of several versions: author’s original, accepted manuscript or the publisher’s version. / La version de cette publication peut être l’une des suivantes : la version prépublication de l’auteur, la version acceptée du manuscrit ou la version de l’éditeur.
Access and use of this website and the material on it are subject to the Terms and Conditions set forth at
Reducing energy wastage from desktop computers
Newsham, G. R.; Tiller, D. K.
https://publications-cnrc.canada.ca/fra/droits
L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.
NRC Publications Record / Notice d'Archives des publications de CNRC: https://nrc-publications.canada.ca/eng/view/object/?id=83aa7224-f2f2-4bdd-b260-4c01a09a36ce https://publications-cnrc.canada.ca/fra/voir/objet/?id=83aa7224-f2f2-4bdd-b260-4c01a09a36ce
S e r
TH1 National Research Conseil national
N21
dkm
council Canada de recherches Canadano, 1 8 2 1
c 0
2
Institute for lnstitut deB L D G
-. Research in recherche enConstruction construction
Reducing Energy Wastage From
Desktop Computers
by Guy R. Newsham, Ph.D., and Dale K. Tiller, D.Phil
ANALYZED
Appeared in
Electrical Equipment News June 1992
pages 1 1 and 16 (IRC Paper No. 1821)
mc-asn
llRC
L I B R A R Y
APR P.V R5
fc%BIBLLL
id E Q U E
l R C
C W r X - m1
Reprinted with permission from
Southam Business Communications Inc.
Reducing
energy
wastage from
Electronic office equipment is expected to have the highest growth rate of all the end-uses
of energy in the North American commercial sector. Researchers are obtaining data on
- .actual computer use profiles to make more realistic estimates of the energy and cost
savings that can be achieved
by
tailoring electricity consumption to actual computer use
BY GUY R. N E W S H A M , PH.D., AND DALE K. TILLER, D.PHIL.D
esktop coknputers and associated peripherals often remain switched on when they are not in use. Electrical energy is therefore wasted in two ways: directly by unnecessarily powering com- puters and peripherals; and indirectly through the increased load on the building cooling system. The Institute for Research in Construction of the National Research Council of Canada (lRC/NRC) is studying the magnitude of this waste, and identifying cost-effective ways to ensure that equipment is switched off when not in use.Electronic office equipment is expected to have the highest growth rate of all the end-uses of energy in the North American commercial sector. By 1995 there will be up to 65 million personal computers in the United States alone. Estimates for office equipment electric- ity use for the same year range from 25 TWh to 130 TWh (1 TWh = 1 billion k ~ h ) l . Although newer
equipment consumes less power, the total energy consumption by electronic office equipment is expected to rise throughout the nineties.
There are no reliable data on current electricity loads or operating profiles for statistically sampled sets of computers and peripherals. The relatively high estimated power density typical of current use (10 to 20 W/mZ), along with the possibility of explosive future demand, suggests a detailed study of loads and oper- ating profiles is appropriate. If necessary, cost-effec- tive means to manage the load should be identified.
Rated vs. plug loads
The measured power consumption of electronic office equipment is often considerably lower than its name plate rating. Therefore, any assessment of energy con- sumption (and cooling load) based on nameplate rat- ings may be an overestimate.
We measured the idling power consumption of almost 500 personal computers, monitors, and print- ers. Figure 1 (on page 16) shows that for computers only (monitors and all other peripherals were discon- nected except in the case of the Mac SE, which has a built-in monitor), the ratio of rated power consumption to measured power consumption was about 3-4 to 1. The error bars represent the standard deviation of the measured power consumption. AT-286's and AT386's, made by a number of different manufacturers, showed considerable variation in measured power consump tion. Even computers from the same manufacturer, for example the Mac SE, showed some variation.
The ratio of rated power consumption to measured power consumption was around 2 to 1 for monitors, and as high as 20 to 1 for printers.
Idling power consumption is a good estimate of average power consumption for computers and mon- itors. The power used by computers did not increase significantly when accessing a disk or running a pro- gram nor did the power used by monitors decrease significantly when "screen saver" programs were used. However, printer power consumption rises sig- nificantly during operation. Consequently, the aver- age power consumption of a printer will vary with the frequency of use.
Knowing the average power consumption we can predict the energy savings that would result from switching off computers and peripherals when they are not in use. (See sidebar.)
Real use p d l e s
We are currently obtaining data on actual computer use profiles, using a sample of about 150 computers.
lge pow
c t ener;
station
rn *
> > > > > > > > > < >
M
easured avera rer consumptic: )m@$ec+t+&d pera"phera1s can be used to predil gy savings for ed @& g&&9&3&s. In an extreme case, a 150W
work! (comprising cs :~~&hj%ex.r and printer) usedfor!
only
4.5 hours per warmng day but always lenQ$n.*iding
nights and weekends),uses
about I310k W
of electricd energy pea if &*re switched off whennot
used, consumption could
be
as low as 1 72 kwhp&$&r,
me laeat generated whtlcthe computer is running but not used adds to t h e cooling load. further &f?m
increasing electrical energy consumption. Table 1 > > , > c > , two
different operating schedules. and three charge rate+ : : ; : : : : ' ' - > ,
~ s t s for
I
Tabk I-
E s h n a h d e M t i t y corn(ddIam
per yeu~-1br
a 7 50 W personal computersyskm opemting under )wo d i h ~ n b schedules
Operating Computer W A C Use*" Total Electricity Cost
Schedule*
I
*
Use@wwYo
rnW54
B 3 cents/kWh 8 6 cents/kWfi Q 12 cents/kWh1310 528 $55 $110 $221 F
1 = Power to computer 24 hrslday, 7 days/wk 2 = Power to computer 4.5 hrslday, 5 days/
**WAC use dculated for an interior office lding thermal simulatf
in warmer and/or ml
rnent, the putential savings More efficient computer
:onsum I j b j j l I j I > i < >ill><>< I<>><>>>>< !es far 6: st
exam
ore hunELECTRICAL EQUIPMENT NEWS JUNE 1992
niques, utilities might wish to consider These profiles will allow us to make real- offering financial incentives to encour- istic estimates of the energy and cost age the use of energyefficient equipment savings that can be achieved by tailoring and practices, similar to the incentives electricity consumption to actual com- offered for energy-efficient lighting. puter use. We have developed software, Many users leave their computers on
Figure I
-
Idling power consumption vs. rated power consumption for computers
-
"
0
50
100
150
200
250
300
RATED POWER CONSUMPTION, W
Many examples of each computer type were measured, the bars represent the standard deviation in these measurements.
installed on a computer's hard disk, to at all times because they fear hardware monitor keyboard activity. failures associated with power cycling.
Thus, we can identify periods when Manufacturers of computer chips, moni- the computer was switched on but there tors and hard drives report that new was no keyboard activity. For most equipment should experience no reduc- users, this implies that the computer was tion in life expectancy due to power not being used, and so, if the computer cycling, provided correct shutdown p r e and peripherals were switched off, cedures are followed.
energy savings would accrue. In addi- We believe the issues raised in this tion, we will be able to correlate com- article are extremely important in a puter use to time of day, enabling us to world where the environmental and analyze the effects of computer use on political costs of power generation are peak demand. coming to the fore. We wish to acknowl- edge the funding provided for this pro-
Tailoring power consumption ject by the Canadian Electrical Associa-
to actual use tion and Energy, Mines and Resources
The final phase of the project will exam- Canada.
ine ways of ensuring that computers and Guy Newsham & Dale Tiller are with the
peripherals are switched off when not in Institute forResearch in Conshuction ofthe
use. We are considering two possibili- National Research Council o f Canada in
ties: lacing stickers on or near worksta- Ottawa. 0
tions' remiiding users to switch equip-
ment off
successful
in encouraging Footnotes equipment: the impact o f market trends and :] L. Norford et al. Electronic oficepeople to zwitch off lights when leaving technolorn on end-use demand for electricify. the office)'; and a device that selectively ~1ecfriciK Lund University Press, Sweden, pp.
powers down equipment after a desig- 427-460(1989).
nated period of inactivity.
we
plan to try 2 M.S. Rea et al. The effectiveness o f lightswitch reminders in reducing light usage. -&L
both on user samples and assess their in, Research and Technoloa 19, pp, a1-85 effectiveness using the monitoring soft- (1987). . .
ware described above. If significant sav-
