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Calculations kW Savings

= (# fixtures) [(Present input watts/fixture)—(Proposed input watts/fixture)] = (415)[(86 watts/T12 fixture)-(60 watts/T8 fixture)] = 10.8 kW

kWh Savings

= (kW savings)(Annual Operating Hours) = (10.8 kW)(8,760 hours/year) = 94,608 kWh/year

Air Conditioning Savings

= (kW savings)(Air Conditioning Hours/year)(1/Air

Conditioner's COP) = (10.8 kW)(2000 hours)(1/2.6) = 8,308 kWh/year

Additional Gas Cost

= (kW savings)(Heating Hours/year)(.003413 MCF/

kWh)(1/Heating Efficiency)(Gas Cost) = (10.8 kW)(1,500 hours/year)(.003413 MCF/

Lamp Replacement Cost

= [(# fixtures)(# lamps/fixture)][((annual operational hours/proposed lamp life)(proposed lamp cost))— ((annual hours operation/present lamp life)(present lamp cost))]

= [(415 fixtures)(2 lamps/fixture)][((8,760 hours/20,000 hours)($ 3.00/T8 lamp)) - ((8,760 hours/20,000 hours)($ 1.50/T12 lamp))] = $ 545/year

Total Annual Dollar Savings

= (kW Savings)(kW charge)+[(kWh savings)+(Air Conditioning savings)](kWh cost) -(Additional gas cost) - (lamp replacement cost) = (10.8 kW)($ 120/kW year)+[(94,608 kWh)+(8,308 kWh)]($ 0.05/kWh) -($ 276/year) - ($ 545/year) = $ 5,621/year

Implementation Cost = (# fixtures) (Retrofit cost per fixture) = (415 fixtures) ($ 45/fixture) = $ 18,675

Simple Payback

= (Implementation Cost)/(Total Annual Dollar Savings) = ($ 18,675)/($ 5,621/year) = 3.3 years

EXAMPLE 2: REPLACE INCANDESCENT LIGHTING WITH COMPACT FLUORESCENT LAMPS

A power plant has 111 incandescent fixtures which operate 24 hours/day, year round. The incandescent lamps were replaced with compact fluorescent lamps, which saved over 70% of the energy, and last over ten times as long. Because the lamp life is so much longer, there is a maintenance relamping labor savings. Air conditioning savings or heating costs were not included because these fixtures are located in a high-bay building which is not heated or air-conditioned.

Calculations

Watts Saved Per Fixture

= (Present input watts/ fixture) - (Proposed input watts/ fixture)

= (150 watts / fixture) - (30 watts/ fixture) = 120 watts saved/fixture kW Savings

= (# fixtures)(watts saved/fixture)(1 kW/1000 watts) = (111 fixtures)(120 watts/fixtures)(1/1000) = 13.3 kW

kWh Savings

= (Demand savings)(annual operating hours) = (13.3 kW)(8,760 hours/year) = 116,683 kWh/year

Lamp Replacement Cost

= [(Number of Fixtures)(cost per CFL Lamp)(operating hours/lamp life)] - [(Number of existing incandescent bulbs)(cost per bulb)(operating hours/lamp life)] = [(111 Fixtures)($10/CFL lamp)(8,760 hours/10,000 hours)] - [(111 bulbs)($1.93/type "A" lamp)(8,760 hours/750 hours)] = $ - 1,530/year§ §Negative cost indicates savings.

Maintenance Relamping Labor Savings = [(# fixtures)(maintenance relamping cost per fixture)] [((annual hours operation/present lamp life))-((annual hours operation/proposed lamp life))] = [(111 fixtures)($1.7/fixture)][((8,760/750))-

Total Annual Dollar Savings

= (kWh savings)(kWh cost)+ (kW savings)(kW cost) - (lamp replacement cost) + (maintenance relamping labor savings)

Total Implementation Cost

= [(# fixtures)(cost/CFL ballast and lamp)] + (retrofit labor cost)] = (111 fixtures)($45/fixture) = $ 4,995

Simple Payback

= (Total Implementation Cost)/(Total Annual Dollar

EXAMPLE 3: INSTALL OCCUPANCY SENSORS

In this example, an office building has many individual offices that are only used during portions of the day. After mounting wall-switch occupancy sensors, the sensitivity and time delay settings were adjusted to optimize the system. The following analysis is based on an average time savings of 35% per room. Air conditioning costs and demand charges would likely be reduced, however these savings are not included.

Calculations kWh Savings

= (# rooms)(# fixtures/room)(input watts/fixture) (1 kW/1000 watts) (Total annual operating hours)(estimated % time saved/100) = (50 rooms)(4 fixtures/room)(144 watts/fixture)(1/1000)

Total Annual Dollar Savings ($/Year) = (kWh savings/year)(kWh cost) = (40,320 kWh / y ear )($. 05 / kWh) = $ 2,016/year

Implementation Cost

= (# occupancy sensors needed)[(cost of occupancy sen-

sor)+ (installation time/room)(labor cost)] = (50)[($ 75)+(1 hour/sensor)($20/hour)] = $ 4,750

Simple Payback

= (Implementation Cost)/(Total Annual Dollar Savings) = ($ 4,750)/($ 2,016/year) = 2.4 years

EXAMPLE 4: RETROFIT EXIT SIGNS WITH L.E.D.s

An office building had 117 exit signs, which used incandescent bulbs. The exit signs were retrofitted with LED exit kits, which saved 90% of the energy. Even though the existing incandescent bulbs were "long-life" models, (which are expensive) material and maintenance savings were significant. Basically, the hospital should not have to relamp exit signs for 25 years!

Calculations

Input Wattage - Incandescent Signs = (Watt/fixture) (number of fixtures) = (40 Watts/fix) (117 fix) = 4.68 kW

Input Wattage - LED Signs = (Watt/ fixture) (number of fixtures) = (3.6 Watts/fix) (117 fix) = .421 kW

kW Savings

= (Incandescent Wattage) - (LED Wattage) = (4.68 kW) - (.421 kW) = 4.26 kW

kWh Savings

= (kW Savings)(operating hours) = (4.26 kW)(8,760 hours) = 37,318 kWh/yr

Lamp Replacement Cost

= [(Number of LED Exit Fixtures)(cost per LED Fixture)(operating hours/Fixture life)] - [(Number of existing Exit lamps)(cost per Exit lamp)(operating hours/lamp life)] = [(117 Fixtures)($ 60/lamp kit)(8,760 hours/219,000 hours)] - [(234 Exit lamps)($5.00/lamp)(8,760 hours/8,760 hours)] = -$ 889/year§ §Negative cost indicates savings.

Maintenance Relamping Labor Savings = (# signs)(Number of times each fixture is relamped/

yr)(time to relamp one fixture)(Labor Cost) = (117 signs)(1 relamp/yr)(.25 hours/sign)($20/hour) = $585/year

Annual Dollar Savings

= [(kWh savings)(electrical consumption cost)] + [(kW savings)(kW cost)] + [Maintenance Cost Savings]-[lamp replacement cost] = [(37,318 kWh)($.05/kWh)] + [(4.26 kW)($120/kW yr)]+

Implementation Cost

= [# Proposed Fixtures][(Cost/fixture + Installation

Cost/fixture)] = [117][$60/fixture + $5/fixture] = $ 7,605

Simple Payback

= (Implementation Cost)/(Annual Dollar Savings) = ($7,605)/($3,851/yr) = 2 years.

EXAMPLE 5: REPLACE OUTSIDE MERCURY VAPOR LIGHTING SYSTEM WITH HIGH AND LOW PRESSURE SODIUM LIGHTING SYSTEM

A parking lot is illuminated by mercury vapor lamps, which are relatively inefficient. The existing fixtures were replaced with a combination of High Pressure Sodium (HPS) and Low Pressure Sodium (LPS) lamps. The LPS provides the lowest-cost illumination, while the HPS provides enough color rendering ability to distinguish the colors of cars. By replacing the fifty 400 watt Mercury Vapor lamps with ten 250 watt HPS and forty 135 watt LPS fixtures, the company saved approximately $ 2,750/year with an installed cost of $12,500 and a payback of 4.6 years.

EXAMPLE 6:

REPLACE "U" LAMPS WITH STRAIGHT T8 TUBES

The existing fixtures were 2' by 2' Lay-In Troffers with two F40T12CW "U" lamps, with a standard ballast consuming 96 watts per fixture. The retrofit was to remove the "U" lamps and install three F017T8 lamps with an electronic ballast, which had only 47 watts per fixture.

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