University City MO - Street Light Audit Report

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Bulb Types Ameren owned street lights are furnished with one of three diffeSodium (HPS), Mercury Vapor (MV), or Metal Halide (MH). The factors used to compare energy efficiency are photopic and scotopic luminous efficacy, S/P Ratio, Color Rendering Index (CRI) and bulb lifetime. These are defined as follows: Photopic luminous efficacy: to bright conditions. It is measured in lumens (light output) p (power consumed by the source). Scotopic luminous efficacy to dim conditions. It is measured in lumens (light output) per S/P Ratio: The ratio of scotopic light versus photopic light in a light sou Color Rendering Index (CRI): A measure of the light quality of a light source as compared with sunlight (which is given the maximum CRI value of 100). The closer a light-source's CRI is to 100, the better its ability to show true colors. High Pressure Sodium (HPS) HPS Energy Efficiency HPS bulbs are the main type of Photopic luminous efficacy: 80 150 lm/W bulbs used. 100, 250, and 400 Scotopic luminous efficacy: 30 60 lm/W watt bulbs are used, which S/P Ratio: 0.62 produce 9500, 25,500 and Bulb Lifetime: 24,000 hours or more 50,000 lumens respectively. CRI: 22 2589* of all street lights are HPS have been the most cost/energy efficient bulbs for use in street HPS.lighting in recent years. (NYSERDA, 2002) (LGE Lighting, 2011) (Westside Solutions, 2011) Mercury Vapor (MV) MV Energy Efficiency There are still MV bulbs used Photopic luminous efficacy: 25 60 lm/W although they are being phased Scotopic luminous efficacy: N/A out. 100, 175 and 400 watt S/P Ratio: 0.80 bulbs are used, which produce Bulb Lifetime: 24,000 hours or more; however, light can diminish 3300, 6800 and 20,000 significantly after 12,000 hours. lumens, respectively. 745* of all CRI: 15 street lights are still MV.MV lamps are continuously being replaced with HPS. (NYSERDA, 2002) (Westside Solutions, 2011) Metal Halide (MH) MH Energy Efficiency MH bulbs are only used in flood Photopic luminous efficacy: 60 110 lm/W lights. 400 watt bulbs are used, Scotopic luminous efficacy of 80 150 lm/W which produce 34,000 lumens. S/P Ratio: 1.49 There are 2 MH flood lights.Bulb Lifetime: up to 20,000 hours CRI: 65 or higher Current development in MH lamps, particularly ceramic MH, has shown promise for improving lumen maintenance and lamp life; some mode are surpassing HPS in luminous efficacy and lifetime. (NYSERDA, 2002) (LGE Lighting, 2011) (Westside Solutions, 2011) *Totals do not include 3 unknown bulb types 13 Page