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Note on estimating fixture power total fixture power

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Unformatted text preview: (F32T8) with magnetic ballast: with electronic ballast: 70 W 62 W fixture power consumption Typically power consumption for T8 lamps with electronic ballasts will be around 30 - 35% lower than that for T12 lamps with magnetic ballasts--for approximately the same lighting level. Note on Estimating Fixture Power Total fixture power for particular combinations of lamps and ballasts can usually be estimated by referring to manufacturer’s data. e.g. ballast manufacturer’s catalogs will provide estimated fixture power for certain lamp and ballast combinations. “Luminaire Efficiency” The ratio of the total light output (lumens) from a luminaire to the total output from the lamps fitting into it. lamps Luminaire Efficiency Luminaire (cross-section) = lens lumens out lumens out lamp lumens Light Distribution in a Space… • Some light leaving the luminaire will be absorbed (by walls, furnishings, etc) before it reaches the intended surface. • Paint colours, surface reflectances, and other factors have a large impact on how much light is absorbed. “Quality” of Lighting There are many aspects that affect the perceived “quality” of lighting… • Illuminance levels • “Contrast ratios” / glare / uniformity / distribution • Lighting “colour” / colour rendition A careful lighting design can achieve high quality illumination with low energy use… For Aspects of Lighting System design: Energy Design Resources “Design Brief: Efficient Lighting Systems” For Aspects of Lighting Controls design: Energy Design Resources “Design Brief: Lighting Controls” Some useful reference documents… For General Aspects of Lighting Equipment: Hydro One “Lighting Energy Efficiency Reference Guide” “Lighting Power Density” (LPD) • Total installed lighting electrical power per unit of floor area • Measured in “watts/m2” or “watts/ft2” Example of resulting LPD’s according to “Good Practice” for a new installation… ANSI/ASHRAE/IESNA Standard 90.1 “Energy Standard for Buildings Except Low-Rise Residential Buildings” Evolution of “Good Practice” Maximum Allowable Lighting Power Density (for select Space Types) Space Type MNECB (1997) ASHRAE 90.1-2007 19 – 23 12 Classroom 21 15 Corridor 9 5 30 – 35 18 25 13 – 18 Office (enclosed) Retail Manufacturing On Previous Slide: “MNECB” = Model National Energy Code of Canada for Buildings 1997 • “Good Practice” circa mid-1990’s for illuminance levels, with lighting primarily by T12’s with magnetic ballasts. “ASHRAE 90.1-2007” • Modern “Good Practice” for illuminance levels, with lighting primarily by T8’s/T5’s with electronic ballasts. Note: Modern “Best Practice” will provide good quality illumination at even lower LPD’s. General guideline for good practice…. Resulting LPD’s for good practice design that achieves required illuminance levels (e.g. ASHRAE 90.1) c c Good practice for illuminance levels (e.g. IESNA) c Heat Gains from Lighting Equipment Lights can have an important impact on building energy use in at least two ways: 1. Direct electricity consumption (i.e. to produce light) 2. Indirectly can affect HVAC energy (i.e. the heat produced by the lights affects heating and cooling loads) Electrical power in Radiant heat (including visible light) Eventually absorbed by a surface (adding heat to the surface), or a small amount might “escape” (e.g. through a window) 60 W Convective heat (e.g. heats room air) Radiant + Convective = Power in = 60 W Typical assumptions for approximate radiative/convective split: Fluorescent: 60% radiative, 40% convective Incandescent: 80% radiative, 20% convective (From McQuiston, Parker, and Spitler, “Heating, Ventilating, and Air Conditioning”, Sixth Edition.) Typical thermal storage effect on heat gain from lights (e.g. fluorescent) lighting power consumption power “stored heat” cooling load (e.g. rate of heat addition to room air) lights on lights off stored heat removed time (Diagram adapted from “2009 ASHRAE Handbook – Fundamentals”, Chapter 18.) Location of luminaire will affect where heat gains appear... Air Handling Unit Fan To other HVAC zones Cooling Heating Coil Coil Supply Duct Supply Duct Ceiling Space Luminaire Luminaire Grille Return Air Duct From other HVAC zones Supply Air Suspended Ceiling T Thermostat Supply Air Some other “heat sources”… (heat) useful illumination lamp + ballast losses (heat) luminaire losses (heat) space excess illumination losses (heat) (heat) Energy Balance Example on Room? (Conceptual Example 1) 0 HVAC System 400 W 300 W 20 ? T 80 W 40 W 120 W 20 W 1000 W 300 W Energy Balance Example on Room? (Conceptual Example 2) 15 100 W 75 W HVAC System 20 ? 40 W 250 W T 80 W 120 W 700 W 75 W Building Energy Performance – Spring 2012 - Topic 6 - Energy Flow through Building Envelope (Part 1) Extract from Model National Energy Code of Canada for Buildings 19...
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This note was uploaded on 10/04/2012 for the course ME 760 taught by Professor Davidmather during the Spring '12 term at Waterloo.

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