Reminder Electric Lighting Design Analysis Tools

Transcription

1 ELECTRIC LIGHTING DESIGN METHODS Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 1 Reminder Electric Lighting Design Analysis Tools Look-ups: pre-canned solutions provided by product manufacturers to speed adoption of solutions (and products) in graphic or tabular format Correlations: product-generic methods such as the zonal cavity method applicable to many situations First principles: employing basic physics relationships such as the point-to-point method Computer simulations: to tap the data storage and number crunching capabilities of computers often coupled with rendering routines Analog mock-ups: not common except for proof-ofconcept demonstrations Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 2 1

2 Illuminances of Concern Design illuminance = design criterion The target or benchmark that defines success Initial illuminance = the illuminance experienced upon first operating a system (space and equipment are new) LLF is set to 1.0 to estimate initial illuminance Maintained illuminance = the illuminance found in a space after some defined time (perhaps 2, 4, 5 years) Condition that occurs when LLF assumes a real value Maintained illuminance must equal or exceed design illuminance in a successful system Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 3 Design Tool: Lookup Tables product driven and for a specific lamp-luminaire combination in this case a recessed can-type downlight Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 4 2

3 Design Tool: Sample Layout Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 5 Design Tool: Comparative Layouts Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 6 3

4 Design Tool: Zonal Cavity Method this method applies ONLY to uniform illuminance situations and is embodied in a worksheet >> we will look at this method because it explains what happens to light in a room Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 7 # luminaires = Zonal Cavity Method: The Bottom Line (illuminance) (area) (lumens per luminaire) (CU) (LLF) where, illuminance = design illuminance CU = coefficient of utilization LLF = light loss factor area = task plane (lighted) area lumens per luminaire = lamp lumens x lamps per fixture Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 8 4

5 Zonal Cavity Method: A Second Bottom Line maintained illuminance = (# luminaires)(lumens per luminaire)(cu)(llf) (area) where, # luminaires = a realistic design luminaire count lumens per luminaire = lamp lumens x lamps per fixture CU = coefficient of utilization LLF = light loss factor area = task plane area Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 9 Zonal Cavity Method: An Unstated Bottom Line initial illuminance = (# luminaires)(lumens per luminaire)(cu)(1) (area) where, # luminaires = a realistic design luminaire count lumens per luminaire = lamp lumens x lamps per fixture CU = coefficient of utilization LLF has been set to 1.0 area = task plane area Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 10 5

6 Zonal Cavity Method: Key Metrics CU = coefficient of utilization -- the likely efficiency (lumens/lumens) of a particular luminaire installed in a particular space in delivering light from lamps to task -- is dimensionless (decimal value) means 65% of lamp light reaches task (the other 35% is absorbed in the luminaire and by room surfaces before it can reach task plane) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 11 Zonal Cavity Method: Key Metrics LLF = light loss factor(s) -- LLF collectively represents several factors that will cause a deviation between initial and maintained illuminance -- dimensionless (decimal value) LLF means a 25% loss -- total LLF = product of individual LLFs Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 12 6

7 Light Loss Factors Fixed (non-recoverable) factors Non-standard voltage Non-standard ballast Non-standard ambient temperature these factors essentially adjust lamp/ballast performance to account for non-catalog conditions they are design correction factors; these effects are generally constant over time (they don t escalate; and they can t be mitigated by normal maintenance) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 13 Light Loss Factors Progressive (recoverable) factors Burnouts Lamp lumen depreciation Luminaire dirt depreciation Room surface dirt depreciation Luminaire surface depreciation these factors adjust illuminance estimates to account for wear and tear on the lighting system over time; the effects change over time (and can generally be reversed at the cost of appropriate maintenance) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 14 7

8 Zonal Cavity Method general data correlators LLFs calculations Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 15 Zonal Cavity Walkthrough start with design illuminance; a lamp selection (perhaps a trial selection); and an appropriate luminaire selection (likely also a trial selection) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 16 8

9 Zonal Cavity Walkthrough lamp selection results in design lamp data find lamp data; from generic tables or manufacturer s catalog information for zonal cavity method need initial lumens and lumen maintenance (lamp LLF) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 17 Zonal Cavity Walkthrough lamp selection will inform luminaire selection (as to basic type match); consider efficacy in selection of both lamp and luminaire Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 18 9

10 Zonal Cavity Walkthrough luminaire selection may be challenging simply due to the wide variety of fixtures available Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 19 Zonal Cavity Walkthrough define space geometry and reflectances, calculate the correlation variables (cavity ratios and effective reflectances); determine the CU value Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 20 10

11 Zonal Cavity Walkthrough start with space dimensions (L, W, and H of three cavities ) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 21 Zonal Cavity Walkthrough calculate cavity ratios for three cavities using above equations (or look-up tables) a non-existent cavity has a ratio of 0 (h = 0) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 22 11

12 Zonal Cavity Walkthrough cavity ratios can be calculated for non-rectilinear spaces using a more basic equation Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 23 Zonal Cavity Walkthrough rho w = (rho 1 )(area 1 ) + (rho 2 )(area 2 ) + area1 + area2 + wall reflectance (rho w ) is the weighted average reflectance of wall surfaces rho = visible reflectance (%) area = surface area 1, 2, are different finishes or materials in the cavity being considered Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 24 12

13 Zonal Cavity Walkthrough establish effective cavity reflectances for ceiling and floor cavities using this chart; ceiling/floor reflectance, wall reflectance, and cavity ratio are variables Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 25 Zonal Cavity Walkthrough CU adjustment factors are used if floor cavity reflectance (rho fc ) is not 20% Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 26 13

14 Zonal Cavity Walkthrough after selecting a luminaire (from IESNA Lighting Handbook, textbook, or manufacturer s web site); find CU data for the fixture this requires that the correlating factors are available Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 27 Zonal Cavity Walkthrough the IESNA Lighting Handbook has typical CU data (and more information) for many generic fixture types; manufacturers web sites will have specific fixture CU data Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 28 14

15 Zonal Cavity Walkthrough photometrics basic properties cross section CU values initial luminaire selection will be based upon meeting some design criteria; these criteria can be roughly evaluated from sample luminaire data Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 29 Zonal Cavity Walkthrough extracting CU values to do so you need to know RCR, rho cc, and rho w (rho fc is assumed to be 20%) see next slides Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 30 15

16 Zonal Cavity Walkthrough spacing criterion is the maximum distance luminaires may be spaced apart (usually taken as center line to center line) if illuminance is to be reasonably uniform; given as a multiple of mounting height above task CU values are extracted from data tables on the basis of rho cc, rho w, and RCR in this case from manufacturer s catalog data note the spacing criterion (SC) value (near top of table) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 31 Zonal Cavity Walkthrough establish LLF values LLF total = (LLF 1 ) (LLF 2 ) ( ) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 32 16

17 Zonal Cavity Walkthrough Lamp Lumen Depreciation Generic: select a reasonable value for the chosen lamp type Specific: obtain from manufacturer s catalog Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 33 Zonal Cavity Walkthrough Luminaire Dirt Depreciation a multi-step process first, establishing categories luminaires (fixtures) will get dirty (collect dust / attract grime) over time; such dirtiness will reduce the performance of the luminaire; different fixtures do better or worse at staying clean resulting in a particular LLF value Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 34 17

18 Zonal Cavity Walkthrough Luminaire Dirt Depreciation (continued) then, establishing environmental dirt conditions Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 35 Zonal Cavity Walkthrough Luminaire Dirt Depreciation (continued) another way of establishing environmental dirt conditions Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 36 18

19 Zonal Cavity Walkthrough Luminaire Dirt Depreciation (continued) select a reasonable value for chosen luminaire type (category), considering environmental dirt conditions (VC to VD) and cleaning schedule (months) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 37 Zonal Cavity Walkthrough substantial effect little effect System Voltage Effect (LLF) establishing building voltage impact on lamp output Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 38 19

20 Zonal Cavity Walkthrough crunch numbers a) theoretical # fixtures required b) actual # fixtures desired c) maintained illuminance d) initial illuminance Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 39 Zonal Cavity Walkthrough theoretical analysis (first cut) yields the precise number of fixtures needed to deliver maintained illuminance this may be 24.7 (not possible) or 11 (not symmetrical) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 40 20

21 Zonal Cavity Walkthrough select an architecturally-desired number of fixtures and recalculate illuminance Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 41 A Different Design Tool The Point-to-Point Method Used with the local or supplemental illuminance approach Requires access to luminous intensity data from manufacturer s catalog (specific) common from lighting handbooks (generic) less common Requires no information about materials in the space (considers direct illuminance only) Requires information about the source-task arrangement Should include LLF for lamp lumen degradation and luminaire dirt depreciation Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 42 21

22 Point-to-Point Method E = (I) (cos Θ) (LLF) / (d 2 ) where, E = illuminance I = luminous intensity in direction D Θ = angle of incidence LLF = light loss factor d = distance (source to task) see next slide for illustration Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 43 Design Analysis Point-to-Point Method establish situational geometry then find d (between source and P) and find Θ P is the illuminated point of interest Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 44 22

23 Point-to-Point Method E = (I) (cos Θ) (LLF) / (d 2 ) involves the cosine law same quantity of light spreads over a greater area as the angle of incidence increases; reducing the density of light [illuminance]) (cos 0 = 1.0; cos 90 = 0) and involves the inverse square law (same quantity of light spreads over a greater area as distance d increases; reducing illuminance) photonicswiki.org Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 45 Design Analysis: Point-to-Point Method select luminaire/lamp, then find luminous intensity (candlepower) data at appropriate angles (those of interest to design) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 46 23

24 there are several formats for luminous intensity data full polar plot on this slide quadrant plot on previous slide Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 47 LED phosphor white LED spectrum (wikimedia) LED is NOT repeat, NOT energy efficient in most applications just yet. There are a few efficient LED products like the CREE downlight and a lot of mediocre, inefficient stuff. Be very selective and don t believe the marketing hype. A good place to learn more about the problems of current LED products is the US DOE s CALIPER reports. James Benya-SBSE listserve (7 Nov 2008) Ball State Architecture ENVIRONMENTAL SYSTEMS 2 Grondzik 48 24