Energy Efficient Lighting

Overview Fundamentals –Light Quantity –Light Quality –Glare –Energy efficiency –Lighting and Productivity Inside-out Approach to Energy Efficient Lighting –End-Use Maximize daylighting Deliver required quantity of lighting –Distribution Position lights effectively Improve luminaire efficiency –Primary Energy Conversion Install high-efficiency lighting Quantifying Savings

Light Quantity Luminous flux –Quantity of visible light output, lumens, lm. Illuminance –Luminous flux divided by area on which it is incident. –1 footcandle = 1 lm/ft 2 Recommended illuminance increases as size and contrast of visual task decrease.

Light Quality Our eyes evolved to see in natural sunlight; thus, we distinguish colors best in sunlight. Color Rendering Index (CRI) describes the effect of a light source on the color appearance of an object.

HPS and HBF Lights (Same Facility with Same Camera) High Pressure Sodium High Bay Fluorescent Lights CRI = 22 CRI = 85

Glare Glare is very high contrast between lighting levels Avoid glare with parabolic luminairs, light shelves, and reflective blinds.

Energy Efficiency Lighting efficiency = (lm/W) light x (CU) fixture/room Efficient lighting: 1.High lm/W 2.High CU

Characteristics of Superior Lighting Correct Quantity High Quality Minimum Glare Energy efficiency Superior Lighting

Superior Lighting Increases Productivity Superior Lighting Reno post office lighting retrofit. –Energy savings = $22,400 /year –Productivity improvement = $400,000 /year Pennsylvania Power and Light –Energy savings = $2,000 per year –Sick leave decreased from 72 to 54 hours/year Lockheed Martin office with daylighting –Energy savings = 4-year payback –Absenteeism dropping by 15%: 1-year payback California schools –Test scores 20% higher in schools with daylighting Chain of 100+ retail stores –Sales higher in stores with sky lights

Inside-out Approach to Energy Efficient Lighting –End-Use Deliver required quantity of lighting Maximize daylighting –Distribution System Position lights effectively Improve luminaire efficiency –Primary Equipment Install high-efficiency lighting

Utilize Existing Daylighting Wright Brothers Factory, Dayton Ohio

Utilize Existing Daylighting Bureau of Engraving and Printing, Washington D.C.

Utilize Existing Daylighting - By Turning Off Lights Near Windows - Known W MH fixtures near windows operating 6,000 hours/year Action Turn off 10 fixtures for 3,000 hours/yr Savings 10 fix x.465 kW/fix x 3,000 h/yr = 14,000 kWh/yr 14,000 kWh/yr x $0.10 /kWh = $1,400 /yr

Restore Existing Daylighting - By Replacing Discolored Glass and Fiberglass with Corrugated Polycarbonate and Double Pane Lexan - CP costs same as FG, but 10x more light

Install Skylights and Optimize Area Optimum skylight/floor area ratio –Ranges from 1% to 6% –Increases with target lighting level –Decreases as lights are more efficient

Reduce Excess Electric Lighting Known Measured = 50 fc Required = 30 fc Action Disconnect (1- fc req /fc mea ) % of fixtures Savings Disconnect = (1 – fc req / fcmea) = (1 – 30 / 50) = 40% of fixtures

Inside-out Approach to Energy Efficient Lighting –End-Use Deliver required quantity of lighting Maximize daylighting –Distribution System Position lights effectively Improve luminaire efficiency –Primary Equipment Install high-efficiency lighting

Disconnect Blocked Lights

Position Task Lighting Above Work Areas

Reposition Lights Below Scaffolding

Use Reflectors that Push Light Onto Workplane Replace acrylic with aluminum MH reflectors Add reflectors to fluorescent strip lighting

Paint Ceilings White

Install Occupancy Sensors in Seldom Used Areas Known Occupancy sensors cost $15 - $80 each W T12 fixtures operating 6,000 hours/year Action Install occupancy sensors to turn off fixtures for 3,000 hours/yr Savings 10 fix x.237 kW/fix x 3,000 h/yr = 7,110 kWh/yr 7,110 kWh/yr x $0.10 /kWh = $711 /yr

Install Photocells On Outdoor Lights Known Photocell switches cost about $15 each W MH fixtures operating 6,000 hours/year Action Install photocells which turn off fixtures for 3,000 hours/yr Savings 10 fix x.465 kW/fix x 3,000 h/yr = 14,000 kWh/yr 14,000 kWh/yr x $0.10 /kWh = $1,400 /yr

Turn off Lights in Unused Areas

Inside-out Approach to Energy Efficient Lighting –End-Use Deliver required quantity of lighting Maximize daylighting –Distribution System Position lights effectively Improve luminaire efficiency –Primary Equipment Install high-efficiency lighting

Replace Incandescent with Compact Fluorescent Lamps CF lamps Use 75% less energy Last 8-10 times longer Result in less mercury emissions Known W I lamps, life = 1,000 hours, cost = $1, operating 6,000 h/yr Action Replace with 23-W CF lamps, life = 10,000 hours, cost = $5 Savings 100 lamps x ( ) kW/lamp x 6,000 h/yr = 46,200 kWh/yr 46,200 kWh/yr x $0.10 /kWh = $4,620 /yr 100 lamps x 6,000 h/yr x ($1/1,000– $5/10,000) (h- lamp) -1 = $300 /yr $4,620 /yr + $300 /yr = $4,920 /yr

Replace T12 Lamps & Electro-magnetic Ballasts with T8 Lamps & Electronic Ballasts T8 XP lamps with LBF electronic ballasts: Use 42% less energy and put same amount of light on workplane Improve CRI and eliminate flicker Known 100 fixtures with four 34-W T12 lamps and electro-magnetic ballasts operating 6,000 h/yr Action Replace with four 28-W XP T8 lamps and LBF electronic ballasts Savings 100 fix x ( ) kW/fix x 6,000 h/yr = 36,000 kWh/yr 36,000 kWh/yr x $0.10 /kWh = $3,600 /yr

Replace Metal Halide with High Bay Fluorescent Lights High bay fluorescent (HBF) lights: Reduce energy use by 50% or more Improve CRI Reduce maintenance costs Stabilize light level Improve light distribution Can be turned on/off as needed, w/ occupancy or w/photocells

Replace Metal Halide with High Bay Induction Lights HBI uses 50% less energy than MH to produce same illuminance HBI has instant restrike compared to 15-minute for MH HBI CRI = 0.90 compared to CRI = 0.65 for MH HBI lasts 100,000 hours compared to 20,000 hours for MH HBI has reduced lumen degradation compared to MH (90% compared to 70% halfway through rated life) HBI light output is insensitive to temperature

Emerging Lighting Technologies: LEDs Light emitting diodes (LEDs) currently used in: –Computer monitors and televisions –Exit signs, flashlights, etc. Colored LEDs much more efficient than incandescent with colored filters. –California has replaced thousands of 150-W incandescent light bulbs that last about 1 year in traffic lights with red, yellow and green LEDs that consume about 15 W and last about 5 years. White LED efficiency currently between incandescent and T8 fluorescent lights, but: –Efficiency is increasing quickly, theoretical efficiency = 100% –Distribution efficiency ~ 100% –LEDs last about 5 times as long as incandescent lights. LEDs are next lighting revolution

Quantifying Savings 1.Calculate number of proposed lights needed to deliver required footcandles. 2.Calculate annual energy cost savings from replacing the current lights. 3.Calculate annual relamping cost savings, including labor and material costs. 4.Calculate total annual cost savings including energy and relamping savings. 5.Calculate the one-time implementation cost of replacing the current lights. 6.Calculate simple payback of the investment.

Power Input Determined by Ballast – Not Lamp Wattage on lamp is nominal value Power input determined by ballast power Example: 51-W Fluor F32T8 Low Output Electronic Ballast powering 2 x 32 W lamps. –Power input including ballast = 51 W (not 2 x 32 W = 64 W) Example: 465-W MH ballast powering a 400-W MW lamp –Power input including ballast = 465 W (not 1 x 400 W = 400 W)

Luminosity Determined by Lamp and Ballast Mean output of lamp is nominal value Light output = nominal lm/lamp x ballast factor Ballast factor for fluourescents: high output ~1.2; normal output ~0.87, low output ~0.75 Ballast factor for HIDs (MH, HPS)= 1.0 Example: Fluor F32T8 Low Output Electronic Ballast powering 2 x 32 W lamps. –Light output = 2 x 2,710 lm x 0.75 = 4,065 lm Example: MH 400-W lamp with nominal output 23,500 lm –Light output = 1 x 23,500 lm x 1.0 = 4,065 lm

Coefficient of Utilization CU is fraction light emitted by lamps delivered to workplane CU is function of RCR, reflectance of walls, rw, and reflectance of ceiling, rc, and the fixture RCR = 5 x h x (w + l) / (w x l) Reflectance:

Determine Required Number of Lights Illuminance on a workplane, Ew (fc) is Ew (fc) = [LPF(lm/fix) x N(fix)] x CU / Aw(ft2) Thus, N = (Ew x Aw) / (CU x LPF)

Lamp Replacement Costs The number of lamps that must be replaced each year, Nr, can be calculated as: Nr = Num lamps x annual operating hours / lamp lifetime Example: Calculate lamp replacement cost for W MH fixtures if lights operate 8,000 hours per year. The cost of a 400-W MH lamp is about $23.The hourly wage for a skilled-trade electrician is $65 per hour, and it takes 30 minutes to replace a lamp. Nr = 320 lamps x 8,000 hours/year / 20,000 hours = 128 lamps/year Cost = 128 lamps/year x ($23 /lamp + (30/60 hours/lamp x $65 /hour)) Cost = $7,104 /year

Natural Lighting Design Illuminance on a workplane, Ew (fc) is Ew = (Esl x Asl) x skylight x well x CU room / Aw Where, Esl can be calculated from: Esl = Ih (W/ft 2 ) x 110 lm/W (luminous intensity of sunlight)

Natural Lighting Design LightSim Lighting Simulation Software: Uses TMY2, TMY3 or EPW weather data Simulates illuminance on a workplane, Ew (fc) Calculates number of hours and fraction of time that natural lighting exceeds target illuminance.

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