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“Feasibility Study for the use of Solar Powered Street Lights on

Residential Areas”

Prepared by: Sasha Merced

11/14/2008

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Abstract

“Feasibility Study for the use of Solar Powered Street Lights on Residential Areas”

By Sasha Merced

The high price of petroleum and our increasing demand for energy are forcing the

electric rates to go up everywhere in the country. That, added to the fact that petroleum

is a finite resource, made utility companies and consumers realize that we need to look

for alternative sources of power. Solar panels are widely known, but they’re not cost

effective when it comes to supplying large amounts of power. Solar powered lights are

readily available and more affordable, and many people already use them in their yards.

While they are more expensive than regular lights, they save energy, and their LED

bulbs last a long time. Residential electric street light posts are very expensive, need a

lot of maintenance, and do the same job a solar light does. This report studies the

feasibility of using solar powered lights instead of electric street lights on some

residential areas where there’s no need for high power lighting sources.

Keywords: solar power, street lights, energy, utilities, electric rates

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Table of Contents

Abstract............................................................................................................................ ii

Introduction......................................................................................................................1

High Pressure Sodium.....................................................................................................2

Light Emitting Diodes.......................................................................................................4

Should we switch?...........................................................................................................5

Conclusion.......................................................................................................................7

References.......................................................................................................................8

References.......................................................................................................................8

Appendix A.....................................................................................................................10

Appendix B.....................................................................................................................11

Appendix C.....................................................................................................................12

Appendix D.....................................................................................................................13

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Introduction

We are constantly searching for alternative sources of energy. We’ve

experimented with electricity, biofuels, wind power, and solar power, and we’re still

looking for other alternatives. Solar power is the most popular replacement for electric

power, but it’s still not practical or affordable. The panels provide little energy compared

to their size, and solar power is very expensive. The average cost per watt of a solar

panel is $7.00 if it’s installed by you and $9.00 if it’s installed by a contractor. Appendix

A shows how to calculate the cost of switching to 100 percent solar power. In

Jacksonville, the cost of electricity for 1000 kilowatts (kW) is about $.12 per kW after

taxes and surcharges. It would cost around $50,000-60,000 to install solar panels to

provide a house with 1000 kW per month, and it would take 43 years in order for the

system to pay for itself. However, solar lights are becoming very popular because

they’re easy to install, they turn on and off automatically, and they pay for themselves

over a short period of time. These lights are readily available in stores, and come in

many varieties, from path lights, to floodlights. Some even come with remote solar

panels so that you can place the lights wherever you want, regardless of where the sun

hits.

How are solar lights less expensive? They use LED (light emitting diode) lights,

which use less energy than other light bulbs. This allows for the placement of a very

small solar cell to power the lamp.

The following table shows a comparison of LED lights with the most commonly

used light bulbs:

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Comparison between LED, incandescent and fluorescent light bulbs

Incandescent Fluorescent LED

Average Lifespan

(hours)

1500 10,000 60,000

Watts 60 14 6

Cost $1.35 $2.98 $54.95

kWh used (over 60k

hours)

3,600 840 360

Light bulb expense

(over 60k hours)

$81.00 $41.72 $54.96

The technology can easily be applied to other uses as well. LED lights are

already used for traffic lights, and in some cities, for street lights. The only difference is,

unlike our solar patio lights, they’re powered by electricity. The next step in saving

energy would be using solar energy to power the LED street lights. On this report, we’ll

study the feasibility of using solar powered street lights in residential areas.

High Pressure Sodium

Currently, Jacksonville Electric Authority (JEA) uses high pressure sodium (HPS)

street lights on residential areas. The standard HPS street lights vary from 70 to 400

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watts, and the ones used for residential areas are 70 watts. Appendix C shows the

diagram of standard residential street light fixtures. Some mercury vapor street lights

are used, but they are being phased out and replaced with HPS lights. Sodium vapor

lamps use sodium in an excited state in order to produce an orange light. A 70 watt

lamp uses about 36 kW per month and produces about 5,450 lumens. The monthly

electric charge for a 70 watt light is 13.1 cents per kW, not including fuel surcharges or

fees. Underground systems also require additional charges to cover the differential cost

between overhead and underground systems.

The operation of a high-pressure sodium lamp is illustrated in this diagram:

The lamp is powered by an AC voltage that supplies current through the ballast. This

increases the amalgam temperature and the gas (sodium and mercury) pressure,

causing a further increase in current. This cycle keeps repeating until the amalgam is

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fully evaporated about 20,000 hours later. Even though HPS lights are energy efficient,

they create light pollution.

Light Emitting Diodes

Light emitting diodes (LED) are semiconductors that convert electricity into light.

The conductor material is typically aluminum-gallium-arsenide (AlGaAs) that has been

doped so that additional atoms change the balance, either adding free electrons or

creating holes where electrons can go. A semiconductor with extra holes is called P-

type material, and a semiconductor with extra electrons is called N-type material. The

free electrons in the N-type material are repelled by the negative electrode and drawn to

the positive electrode, and the holes in the P-type are repelled by the negative charge

and move the other way, creating a charge that produces the light we see:

LED lights produce about 60 lumens of white light per watt without any light pollution.

When you power the LED light with a solar cell, there’s no electricity being used, which

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helps to preserve our finite energy resources. Appendix D shows some pictures of

installed solar LED street lights.

Should we switch?

LEDs produce less lumens per watt than HPS lights, but their light is much more

efficient and provides better visibility. The following pictures show a street with HPS

lights, and LED lights, respectively:

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The pictures were taken in Oakland, California, as part of an LED light assessment.

There are more pictures of the study in Appendix B.

This shows that you can replace HPS street lights for LED street lights with less

lumens, and, less watts. The currently used 70 watt HPS street lights can be replaced

with a 30-40 watt LCD solar street light. LED lights last twice as much as HPS lights,

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and are more resistant. HPS light bulbs break easily and need constant replacements,

while LEDs are small and harder to break. The following table shows a cost

comparison between HPS and LED lights, using information from previous research:

Comparison of HPS and LED street lights

HPS LED

Initial Cost $400.00, plus electrical

wiring*

$2,000-$4000

Energy cost per year $60.00 0

Maintenance cost per year $24.00 $9.00 (no replacement for

the first 10 years)

Lifespan 30,000 hours (7 years) for

light bulb only, lamp

replaced when other

failures occur as well

60,000 hours (14 years) for

light bulb only,

25+ years for solar cell

Yearly operation cost $144.00 $4.50

*Electrical wiring of underground service

The initial cost of the solar LED street light is larger, but the HPS street light has

a large installation cost for the electric wiring that could go over $40,000 for

underground electric systems. The only installation cost for the LED street light would

be the cost of digging and placing the pole on its designated location. On new

construction, an LED street light might end up being more economical. On areas where

HPS street lights are already in place, changing the lights to LED’s is too costly, and it

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would take about 50 years for the LED light to pay for itself. That is longer than the life

span of the solar cell.

Conclusion

For new construction, solar LED lights would be a great option. They are less

expensive when you factor in the installation costs. They provide better lighting, which

would help reduce crime in some areas. LEDs last twice as much as HPS lights, and

they need less maintenance. They don’t consume any electricity, and they don’t contain

any harmful gases.

Changing current HPS street lights to LED street lights is not feasible because

the upfront cost would be too high. The solar cell would need to be replaced before the

street light pays for itself, adding to the cost. A more suitable option might be to use

electric LED street lights, or to retrofit the HPS street lights to use LED light bulbs. The

state of California saves over $10,000 per year after switching 200,000 old traffic lights

to LED.

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References

Anderson, Neil, et, al. LED’s: New Lighting Alternative for Greenhouses. Department of

Horticultural Science, University of Minnesota.

City of Jacksonville. JEA. Electric Master Catalog. Jacksonville, Fl. November 2008.

City of Jacksonville. JEA. Electric Tariff Documentation, Vol, 1. Jacksonville, FL. June,

2008.

City of Oakland. Prepared for the U.S. Department of Energy and Pacific Gas & Electric

by Energy Solutions. Demonstration Assessment of Light Emitting Diode (LED)

Street Lighting. Oakland, Ca. January 2008.

Harris, Tom. How Light Emitting Diodes ork. October 30, 2008. 08 Nov. 2008.

< http://electronics.howstuffworks.com/led.htm>

JEA Completes Phase I of City Energy Program with Solar at City Hall. May 18, 2004.

10 Nov. 2008. <www.jea.com>

Progress Energy Florida to pilot first LED outdoor area lighting in territory. October 28,

2008. 11 Nov. 2008. < http://www.progress-

energy.com/aboutus/news/article.asp?id=20062>

San Diego Regional Energy Office. Technology Assessment of Light Emitting Diodes

(LED) for Street and Parking Lot Lighting Applications. San Diego, Ca. August

2003.

Solar Street Light. 2008. 10 Nov. 2008. < http://gg-energy.com/Solar_Street_Light.cfm>

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Zavis, Alex. Iraq’s electricity-starved capital turns to   solar. Los

Angeles Times. July, 14, 2008.

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Appendix A

How to figure the cost for 100% solar power

Take number of KWH you use every month. Divide that by 30. That gives you

your average daily usage. So if you use 1000 KWH, that’s 33.3 KWH per day.

Divide it by the number of full sun hours you get per day on a yearly average. So,

if you get 5 hours per day, divide 33.3 by 6, that gives you 5.55 kW, or 5550

watts. Multiply that by 1.15, which gives you 6382 watts of solar panel needed.

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Appendix B

Pictures form a study made in the City of Oakland, California

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Appendix C

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Appendix D

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