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Lab Manual : Do-it-Yourself Solar LED Lantern Kit

(For use with Sundance Solar item No. 900-10017-35)

Welcome to the kit that will help you store sunshine in a jar! You are also helping

the earth by reusing a glass or plastic jar, which could take hundreds to millions of

years to decompose if it were thrown away. This solar lantern kit also helps to

support the creation of solar lanterns to help those who live without electricity

(more on that later).

Your first task is to find a container with a wide lid, such as a peanut butter or

mayonnaise jar. If you want, you could even get more creative: what other

objects would you want to glow at night? Ask your parents for permission first!

The solar lantern you create will charge itself during the day, and will light up at

night. The next day, the lantern will charge itself again. This is because energy

can be changed from one form to another. The sun’s energy (which comes from

the fusion or combining of atoms) releases light energy, which is turned into

electrical energy in the solar panel. The electrical energy from the solar panel is

stored in the batteries in the form of chemical energy. At night, the chemical

energy in the batteries is changed back into electrical energy, which feeds into the

LEDs, causing them to release light energy.

DAYTIME NIGHTIME

light

SUN SOLAR PANEL BATTERY LED

sunlight electricity electricity

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Table of Contents

How it Works: Solar Cells……………………………………………………………………………….. page 3

Intro to Circuits…….………………………………………………………………………………………… page 4

Giving the LEDs More Power: Adding Solar Panels……………………………….………. page 6

Putting it All Together…………………………………………………………………………….………. page 7

Assembly Instructions and Pictures…………………………………………………………………. page 8

Solar Insolation Maps and Recharge Times……………………………………………………… page 9

Challenge: Developing Solar Lanterns for South Africans………………………..……… page 11

Glossary………………………………………………………………………………………………………….. page 12

Solar Jar Light Kit Materials List

In each of the 15 solar jar kits:

1 - 3V 70mA polycrystalline solar panel with wires

1 - Circuit board (pcb) with dusk/dawn operation with 2 LED’s

1 – Battery holder for 2 AAA batteries

2 – AAA NiMH rechargeable batteries

4 – Grey wire nuts

Required for the Optional “Time Out and Try Its”: plastic combs,

balloons, aluminum soda cans, red LEDs, 3V coin cell batteries, extra

copper wire, earphones, pennies, aluminum foil, a small cup (like a

medicine cup), and warm salt water.

Not included: Mason jars or other “containers” for your solar lantern, electric drill and drill bits,

silicon adhesive and/or hot glue gun (use adult supervision)

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How it Works: Solar Cells

Photovoltaic (fo-to-vol-ta-ik) panels are solar panels that produce electricity directly from

sunlight. The term "photo" means “light”. "Voltaic" is named after Alessandro Volta (1745-

1827), a pioneer in the study of electricity. Photovoltaics, then, means "light electricity."

Photovoltaic panels produce clean, reliable electricity without consuming any fossil fuels. They

are being used in a wide variety of applications, from providing power for watches, highway

signs, and space stations, to providing for a household's electrical needs.

How Does a Solar Cell Work?

An atom (the smallest unit of matter) has three atomic particles: the proton (red in the

diagram below) with a positive charge, the neutron (green in the diagram below) with no

charge, and the electron (yellow in the diagram below). Atoms have the capability to lose

electrons, which can flow from atom to atom in the form of electricity. Some types of atoms

‘give up’ their electrons easily, while other atoms tend to ‘hold on’ to their electrons. The

atoms that make up solar panels are made of mostly silicon, but have other atoms (such as

boron and phosphorus) which are set up in a way so that an electric field is created that

‘pushes’ the electrons to the bottom of the solar panel.

electrons

A photon (a unit of light coming from the sun) can strike an electron at the bottom of the solar

panel, giving it enough energy to ‘boost’ it back up to the top of the solar panel. The electrons

flowing to the top of the panel are collected in a wire called a terminal. Since electrons have a

negative charge, the terminal at the top of the panel is the negative terminal. In electronics,

the black wire is usually connected to the negative terminal, and the red wire is connected to

the positive terminal.

The electrons at the negative terminal, however, cannot create a current (or get the electrons

to ‘flow’) unless they are hooked to a ‘loop’ which feeds back to the positive end of a solar

panel. The closed loop through which electricity flows is called a circuit.

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Optional “Time Out and Try It”: Electric Fields

Charged objects create an invisible electric force field around themselves. These

electric fields are essential to solar cells. One of the simplest ways to show the forces of

electric fields is with static electricity. For the following activities, you’ll need a dry

plastic comb, a faucet, balloons, and an aluminum soda can.

“Bending” Water with a Comb

1. Turn on a faucet and slowly turn down the water until you have a VERY thin

stream of water flowing.

2. Take the plastic comb and brush it through your hair ten times.

3. Now slowly bring the comb close the flowing water, (without actually touching the

water). If all goes well, the stream of water should bend towards the comb! That’s

because the comb collects electrons from the hair, and the trickle of water has a

more positive charge.

“Rolling” a Can:

1. Place the can on its side on a flat smooth surface like a table or a smooth floor.

2. Rub the blown up balloon back and forth through your hair really fast.

3. Now the fun part: Hold the balloon close to the can without actually touching the

can. The can will start to roll towards the balloon without you even touching it!

That’s because when you rub the balloon through your hair, invisible electrons build

up on the surface of the balloon. The electrons have the power to pull very light

objects (with a positive charge) toward them - like the soda can.

Intro to Batteries

The energy from the solar panels needs to be ‘stored’ in the batteries so that the energy can be

used to create light at night. The chemical reactions in the battery causes a buildup of

electrons at one end (making it negatively charged), and a loss of electrons at the other end

(making it positively charged). A fluid inside the battery allows the electrons to flow from its

negative to its positive end. But the electrons in the negative end of battery will not ‘flow out’

of the battery unless they are connected by a wire which touches the positive end of the

battery. This wire ‘loop’ will allow for the electrons to flow in a circuit.

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Optional “Time Out and Try It”: Making a Simple Coin Battery

With a little time and preparation, you can make your own battery and ‘hear’ the

electricity coming out of it! You will need a small medicine cup, warm salt water, copper coins,

aluminum foil, two copper wires, and an earphone.

1. Tape one copper wire to a coin, and place the coin wire side down in a small cup. Make sure the

copper wire is leading out of the cup. Then layer a piece of paper towel (the size of the penny) on top

of the coin. Then put a piece of aluminum foil (the size of the coin) on top of the paper towel.

2. Layer the coins, paper towel circles, and aluminum foil circles in the same repeating order until you

get at least 5 layers. The more layers the better!

3. Tape another copper wire onto the topmost layer (which should be a foil circle). The top copper wire

should also lead out of the cup. Then cover the coin/paper/foil stacks in the cup with warm salt

water.

4. Wrap one of the copper wires leading outside the cup around an earpiece or earphone. Scrape the

other copper wire leading outside the cup against the first. Did you hear a ‘static’ sound? Then you

made electricity with your ‘battery’!

Intro to Circuits

Electricity flows in circuits: closed paths through which electrons flow. Within these circuits or

“loops” in which the electricity travels, one needs to incorporate an energy source, switches,

and loads (something that the current feeds into - in this case, it is the LEDs). The solar panel

provides the energy, and the battery stores the energy. Switches will allow one to disconnect

the circuit at will. The LEDs (which stands for Light Emitting Diodes) will emit light. In the case

of solar panels, the electricity flows in only one direction, which is called direct current. All the

experiments we are doing in this kit involve direct current. But the electricity used in our

houses runs on alternating current, which regularly changes its forward and backward direction

in the circuit many times a second. So if you hook solar panels up to a house, you will need to

use a special device called an inverter to change the energy from direct current to alternating

current.

Optional “Time Out and Try It”: Making a Circuit with a Battery

and an LED

Get a 3 volt coin battery and an LED from your instructor. Your first “challenge” will be to

light up the LED using only the coin battery.

The reason why the LED works in only one direction is because it is a diode (it only works in

one direction only). Which end of the LED is positive? Which end of the LED is negative?

Label on the picture to the right.

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Giving the LEDs More Power: Adding Solar Panels

Solar panels can be connected in order to produce more voltage (the ‘push’ of electrons in a

circuit) or more current (the amount of electrons ‘flowing’ through a circuit). The unit for

voltage is the volt, and the unit for current is the amp. If you multiply voltage times current,

you get power (in units called watts). You can increase the power of multiple solar panels by

connecting them in certain ways. Connecting solar panels ‘end to end’ will increase the voltage

of the circuit. Connecting solar panels ‘side by side’ will increase the current in a circuit. This

way, you can ‘step up’ the current or voltage to what is needed.

Optional “Time Out and Try It”: Making a Two Panel Circuit

Let’s try hooking up two solar panels ‘end to end’. In electronics, this is called a

series circuit. Get together with another group and connect your two solar panels

together using wire nuts, like the picture below:

Now shine a light on both solar panels, and connect an LED to the leftover black and

red wires. Does the LED light up when the solar panels are lit? Does it stay lit if the

solar panels are taken away?

Disconnect the two solar panels and connect an LED to a single panel. Again, shine

a light on the panel. Does the LED light up? How bright is it compared to being

connected to two solar panels?

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Putting it All Together…

So why are we using LEDs, and not a different kind of bulb? That’s because

LEDs don't get especially hot, and they are much more energy efficient than

any other commonly used light bulb. They can be made to be quite small

and bright. They are also frequently used in all kinds of devices, including

remote controls, digital clocks, traffic lights, watches, and ‘on’ lights on

appliances and electronics. They are the base of the thinnest flat screen

televisions and computer monitors on the market today.

So how is a rechargeable battery different from the non-rechargeable kind,

and why do we need to use a rechargeable one? Either type of battery creates

a voltage by introducing two chemical reactions which create separate

negative and positive terminals. In a standard battery, the chemical reaction

will eventually reach a limit where no more electrons can be produced, and

the battery is dead. In a rechargeable battery like the one in this kit, the

chemical reaction is reversible, so that electrical energy from the solar panel

can recharge the battery, and the battery will refill itself if it gets enough

sunlight.

Making a working ‘dusk to dawn’ lantern is more complicated than just connecting the solar

panel to the batteries and the LEDs. The electricity has to be blocked from leaving the batteries

when they are charging, and an automatic switch needs to turn the LEDs ‘off’ during the day

and ‘on’ at night. Each of these jobs requires a separate component on the circuit board:

� The printed circuit board (pcb) contains all the circuits that makes the

lantern work, and acts like the ‘brain’ of the lantern

� Diodes are used in the circuit board to make ‘one way streets’, so the

electricity only travels in one direction

� A transistor helps to ‘direct traffic’ like a traffic signal. During the day,

they give the ‘green light’ for electricity from the solar panels to fill the

batteries. At night, they give the ‘green light’ for the electricity

generated by the batteries to light the batteries.

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Assembly Instructions

1. Using a grey wire nut, connect the two red wires

together from the battery holder to the circuit board

(marked BATTERY on the circuit board in small white

letters). Repeat with 2 black wires from the battery

holder to the circuit board.

2. Using a grey wire nut, connect the two red wires

together from the solar panel to the circuit board

(marked SOLAR on the circuit board in small white

letters). Repeat with the two black wires from the solar

panel to the circuit board.

3. You can now test your light. If the LEDs do not turn on,

check the switches for the battery pack and the LEDs

(the ‘on’ position for the LEDs is toward the center of

the green ‘chip’ called the printed circuit board or PCB).

Now check to see how the LEDs respond when in bright

or dark light. The LEDs should light when the solar panel

is not in bright light and should turn off automatically

when it is in bright light.

4. You can now install your LED light in a wide-mouthed

canning jar or a recycled jar (peanut butter or

mayonnaise jars work well – you need a rather wide lid).

Disconnect the wire nuts connecting the wires to the

solar panel. Drill 2 holes in the top of your jar and lead

the wires through with the solar panel on top of the lid.

If you have a metal lid, use electrical tape to make sure

that the solder contacts do not touch the lid, causing

your solar panel to ‘short out’. You may want to wrap or

tidy up the wires with electrical tape. Use hot glue or

silicon sealant to adhere the solar panel above and

battery pack/PCB/LED complex under the lid.

OPERATION…The solar garden light should get as much sun as possible. When the solar panel is

covered or when it is dark, turn on inner switches for the LEDs until they light. If you take the

lantern back out into the sun, the LEDs will go off. At night, the LEDs will turn back on

automatically. Have fun! ☺

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Solar Insolation Maps and Recharge Times

So if you place your solar lantern outside in direct sun, how long will it take to fully charge the

batteries, if they were empty? To do this, follow the steps below:

A. Find the total number of peak sun hours per day at your location: __________ peak

sun hours per day

B. Find the maximum current that the solar module will produce during these peak sun

hours: ____________ mA (which stands for milliamps – the number is printed on a label on the

back of the solar panel)

C. Multiply your answer in A times your answer in B: ______________ mAh/day (which

stands for milliamp hours per day)

D. Find the capacity of the rechargeable battery: _________________ mAh (which stands

for milliamp hours – it’s written on the side of the rechargeable battery)

E. Divide your answer in D by your answer in C, and you will get the number of days

needed to fully charge the rechargeable batteries if they started out empty. You

may get a decimal Write your answer in the line below –

__________ days to fully recharge the empty batteries

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This calculation is just an estimate, because the true number of peak sun hours of an area vary

by month, the batteries are usually not empty at the start, the sun is not always directly over

top of the panels, and the weather may not be clear and sunny.

In practice, we found out that the solar lanterns work more dependably when left out in the sun to

charge for 1 or 2 full days BEFORE turning the LED lights on. This seems to match with the numbers that

we calculated above.

Solar insolation maps can be found online on different web sites, but the most common site is

http://www.nrel.gov/gis/solar.html.

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Developing Solar Lanterns for South Africans

Excerpt from Pamela Ulicny, Biology and Environmental Science teacher in Tri-Valley Jr/Sr High School in

Hegins, Pennsylvania:

“The inspiration for developing this solar-powered lantern was originally sarted by Mark

Gamble, CEO of Educo Africa. I was lucky enough to be granted a educational trip to South

Africa through the Toyota International Teacher Program, funded by Toyota Motor Sales and the

Institute for International Education. The trip was the experience of a lifetime and a wonderful

experience to share with my students. But I was also saddened to see so much poverty there.

Mark Gamble explained how his organization called Educo Africa helps South African youth from

disadvantaged communities. The solar-powered lanterns were designed with the eventual

purpose of teaching South Africans science, technology, math, sustainability, and job skills as

they are trained to build their own solar-powered lanterns. Educo Africa would help their youth

build and sell solar lanterns to those who do not have electricity in their homes. This would help

families in poverty who currently use kerosene lanterns. Kerosene lanterns are a fire hazard and

have already resulted in severe burns, fatalities, and the destruction of many homes. The cost

of buying kerosene over a long time is more expensive than the cost of a solar-powered lantern.

Additionally, the kerosene lanterns create as much smoke as two packs of cigarettes a day.

Kerosene smoke also increases the chance of cataracts, respiratory infections, tuberculosis or

lung and throat cancers.”

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Glossary:

alternating current - An electric current that reverses its direction many times a second at regular

intervals, typically used in power supplies.

atom – the smallest part of matter.

current – A flow of electric charge. It is how ‘crowded’ the electrons are as they flow in a circuit. The

unit that measures the amount of current or ‘electrical flow’ going through a material is called an amp

(ampere, Amp or I).

diode – A semiconductor device with two terminals, typically allowing the flow of current in one

direction only.

direct current - An electric current flowing in one direction only.

electron – a negatively charged particle in an atom. Electricity is caused by the flow of electrons.

LED – Light Emitting Diode - A semiconductor diode that converts applied voltage to light and is used in

lamps and digital displays.

neutron – an uncharged charged particle in an atom; it is neither negatively or positively charged.

parallel circuit - a closed circuit in which the current divides into two or more paths before recombining

to complete the circuit. This type of circuit adds current but does not add voltages.

photon - A particle representing a unit of light or other electromagnetic radiation, also defined as a

“packet” of solar energy of a particular wavelength.

photovoltaic effect – the creation of voltage or electric current in a material upon exposure to light.

power - is the rate of doing work, measured in watts, and represented by the letter P. It is the product

of voltage times current.

proton – a positively charged particle in an atom.

series circuit - An electric circuit connected so that current passes through each circuit element in turn

without branching. This type of circuit adds voltages but does not add current.

transistor - A small electronic device containing a semiconductor and having at least three electrical

contacts, used in a circuit as an amplifier, detector, or switch.

voltage - electric potential or potential difference expressed in volts. A volt (V) is a unit that measures

the amount of ‘push’ that moves the electrons in a circuit.

watt – the standard unit for measuring power (P).

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References and Further Reading

http://science1.nasa.gov/science-news/science-at-nasa/2002/solarcells/ - How Do Photovoltaics Work?

http://science.howstuffworks.com/environmental/energy/solar-cell.htm - How Solar Cells Work

http://electronics.howstuffworks.com/led.htm - How Light Emitting Diodes Work

http://phet.colorado.edu/en/simulation/photoelectric - PhET: an interactive simulation of the

photoelectric effect

http://electronics.howstuffworks.com/everyday-tech/battery5.htm - How Batteries Work

http://electronics.howstuffworks.com/transistor.htm - How Transistors Work

http://www.youtube.com/watch?v=IcrBqCFLHIY – Video: How Does a Transistor Work?

http://www.nrel.gov/gis/solar.html - National Renewable Energy Laboratory: Solar Insolation Maps

Pre-wired kits are available here:

http://store.sundancesolar.com/sunbender-do-it-yourself-solar-led-jar-light-kit-pre-wired-no-soldering/

Contact sales@sundancesolar.com for classroom pricing.

Kits are also available with soldering required and a curriculum manual is available for high school

students.

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A portion of the sale of these solar lantern kits will be donated to Educo Africa in Cape Town, so

that we can do our part to put an end to energy poverty. Our dream is to offer a safe and

sustainable light source so that disadvantaged students get a greater chance to read, study,

complete their homework and chores, and achieve their goals. If your school, club, or religious

organization would like to learn more, please contact Pam Ulicny or Ed Bender (contact

information below) and ask about the “This Little Light of Mine” fundraiser.

Questions & comments:

Ed Bender ed@sundancesolar.com

Pam Ulicny psu@tri-valley.k12.pa.us