power density targets for efficient lighting of interior ... · power density targets for efficient...
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april 2007 Laboratorium voor Lichttechnologie
Power Density Targets for Efficient Lighting of Interior
Task Areas
P Hanselaer, C Lootens, W Ryckaert, G Deconinck, P Rombauts
To be published LR&T 2007
april 2007 Laboratorium voor Lichttechnologie
2 [ / .100 /100 ]sysfinTA
PNPD W m lux W lm= =
Φ
.fin finTA TA TAA EΦ =
Normalized Power Density NPD
2
finTA
: Task Area (m )
E : maintained mean illuminance ( )TAA
lux
finTA : maintained luminous flux on TA ( )lumenΦ
: installed power for lightingsysP
april 2007 Laboratorium voor Lichttechnologie
NPD
• A measure of the efficiency to illuminate a specific task area
• It is not a measure of energy consumption, which depends on illumination levels, switch-on time, dimming, . . .
april 2007 Laboratorium voor Lichttechnologie
Actual criteriumNPD< 2.0 à 2.5 (W/m2.100 lux)
1. Based on best practice
Theoretical basis?
Non-standard task areas
EN 12464
shops, classrooms, musea?
2. Standard task area: floor (edge zone in-or excluded)
april 2007 Laboratorium voor Lichttechnologie
Purpose:determine a target NPD value
• lighting task as a starting point
• allowing arbitrary task areas;
• valid for a wide range of applications like offices, shops,
work areas, classrooms;
• simple and easy-to-use while being accurate and
reproducible;
• independent of a specific light calculation software and
related input and output parameters;
• visual comfort requirements are included
april 2007 Laboratorium voor Lichttechnologie
• efficiency to power the light source
• efficiency of converting electrical power to light
• efficiency of the luminaire
• efficiency of directing the luminous flux to the task area
• efficiency of maintaining the initial luminous flux.
sysfinTA
PNPD =
ΦsysP
.fin finTA TA TAA EΦ =
april 2007 Laboratorium voor Lichttechnologie
efficiency to power the light source
sysfinTA
PNPD =
ΦsysP
.fin finTA TA TAA EΦ =
lampgear
sys
PP
η =
april 2007 Laboratorium voor Lichttechnologie
efficiency of converting electrical power to light
sysfinTA
PNPD =
ΦsysP
.fin finTA TA TAA EΦ =
inilamp
lamplampP
ηΦ
=
april 2007 Laboratorium voor Lichttechnologie
efficiency of the luminaire (Light Output Ratio)
sysfinTA
PNPD =
ΦsysP
.fin finTA TA TAA EΦ =
inilum
inilamp
LOR Φ=Φ
april 2007 Laboratorium voor Lichttechnologie
efficiency of directing the luminous flux to the task area:
utilance (LDF, spacing, room reflectance)
sysfinTA
PNPD =
ΦsysP
.fin finTA TA TAA EΦ =
iniTAinilum
U Φ=Φ
april 2007 Laboratorium voor Lichttechnologie
efficiency of maintaining
the initial luminous flux:
maintenance factor
sysfinTA
PNPD =
ΦsysP
.fin finTA TA TAA EΦ =
finTAiniTA
MF Φ=Φ
april 2007 Laboratorium voor Lichttechnologie
Combining efficiencies
100. . . .
sysfinTA lamp gear
PNPD
MF U LORη η= =Φ
Minimal values:Selecting the best?
Eliminating the worst?
Maximum value
april 2007 Laboratorium voor Lichttechnologie
0.85gearη >
70 /lamp lm Wη >
0.75LOR >
0.75MF >
U > ???
Proposal:
april 2007 Laboratorium voor Lichttechnologie
Target value for utilance
Different methods (ray-tracing, point-by-point, flux transfer) with room reflectance and room index K as parameter and . . . standard task area
horizontal area .vertical area .( )
l wKh l w
= =+
april 2007 Laboratorium voor Lichttechnologie
Luminous flux on total room area:2 ...
2. 0.5
.
1
iniinilum
iniinilumlum
linilum um
with
ρ
ρ
ρ
ρ
Φ + + +
Φ= Φ <
<
>=− < >
< > Φ> Φ
april 2007 Laboratorium voor Lichttechnologie
Check: room: 6x6x3
=11 442 inilum lmΦ 0.5 / 0.5 / 0.5ρ = 0.7 / 0.5 / 0.3ρ =
A(m2) ( )E lux ( )ini lmΦ ( )E lux ( )ini lmΦ
Ceiling 36 103 3 708 76 2 736
Walls 72 146 10 530 128 9 216
Floor 36 237 8 532 231 8 316
Total 22 770 20 268
TA
0.5 could be too optimistic for downlighters0.5
ρρ< >=
=
april 2007 Laboratorium voor Lichttechnologie
2. . .inilum TA TA nTA nTAA E A EΦ = +
The luminous flux on total room areacan also written as
high: U will be low, low efficiency
low: U will be high, low lighting comfort nTA
nTA
E
E
2
1 .nTA nTA
TA TA
UE AE A
=+
april 2007 Laboratorium voor Lichttechnologie
0.5nTA TAE E<CIBSE, Luminance criteria
2
1 0.5 nTA
TA
U AA
>+
LE
ρπ
=
0.7
0.50.2
ceiling TA
wall TA
floor TA
L L
L LL L
=
=
=
april 2007 Laboratorium voor Lichttechnologie
0.85gearη >
70 /lamp lm Wη >
0.75LOR >
0.75MF >
Proposal:
2
1 0.5 nTA
TA
U AA
>+
april 2007 Laboratorium voor Lichttechnologie
Target value
2( / .100 ) (1.5 0.75 )nTA
TA
W m luxANPDA
< +
Task area!
april 2007 Laboratorium voor Lichttechnologie
(Non-)Task areaEdge zone included in task area (EN12464)
april 2007 Laboratorium voor Lichttechnologie
Test 1: standard task area
21nTA
TA
AA K
= +
1.5(2.25 )NPDK
< +
april 2007 Laboratorium voor Lichttechnologie
2
2.5
3
3.5
4
4.5
5
5.5
0 1 2 3 4 5 6
K
NPD
(W/1
00 lm
)
The formula offers theoretical basis for actual targets with standard task area!
april 2007 Laboratorium voor Lichttechnologie
Test 1: standard task area
– K=5 – U > 1.18– NPD < 2.55W/m².100lux
Large landscape office (30x30x3)
april 2007 Laboratorium voor Lichttechnologie
Test 1: standard task area
Indoor sport (44x23x8m)
– K= 1.888– U> 0.99– NPD< 3 W/m².100lux
april 2007 Laboratorium voor Lichttechnologie
Room: 6x6x3
Desk: 2x2
ATA=3x3=9
AnTA= 135
U>0.24
NPD < 12.8 W/m².100lux or maximum 115W/100 lux
Test 2: non-standard task area
april 2007 Laboratorium voor Lichttechnologie
Test 2: software calculations
385
40 !!!!
iniTAininTA
E lux
E lux
=
=
2
Three T5 lamps, 24 W, above deskPsys = 88 WU= 0.71 >>> 0.24
88NPD= 3.4 12.8 (target)9 .(2.9)
Wm
= <<
april 2007 Laboratorium voor Lichttechnologie
Test 3: software calculations
46 !!!!
131 !!!!
iniTAininTA
E lux
E lux
=
=
2
Three T5 lamps, 24 W, cornerPsys = 88 WU= 0.085 <<< 0.24
88NPD= 28 12.89 .(0.35)
Wm
= >>
april 2007 Laboratorium voor Lichttechnologie
Conclusions2( / .100 ) (1.5 0.75 )nTA
TA
W m luxANPDA
< +
• Easy, independent of software calculations
• In accordance with actual criterium for standard task areas
• Non – standard task areas: needs further testing
• Fine tuning for target values is possible
Thank you!