Solar Cookies

Saturday May 1, 2010

Can you use the power of the sun without using solar cells? You bet! We’re going to focus the incoming light down into a heat-absorbing box that will actually cook your food for you.


Remember from Unit 9 how we learned about photons (packets of light)?  Sunlight at the Earth’s surface is mostly in the visible and near-infrared (IR) part of the spectrum, with a small part in the near-ultraviolet (UV). The UV light has more energy than the IR, although it’s the IR that you feel as heat.


We’re going to use both to bake cookies in our homemade solar oven. There are two different designs – one uses a pizza box and the other is more like a light funnel. Which one works best for you?


  • Two large sheets of poster board (black is best)
  • Aluminum foil
  • Plastic wrap
  • Black construction paper
  • Cardboard box
  • Pizza box (clean!)
  • Tape & scissors
  • Reusable plastic baggies
  • Cookie dough (your favorite)

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Download Student Worksheet & Exercises


How does that work? Your solar cooker does a few different things. First, it concentrates the sunlight into a smaller space using aluminum foil. This makes the energy from the sun more potent. If you used mirrors, it would work even better!


You’re also converting light into heat by using the black construction paper. If you’ve ever gotten into car with dark seats, you know that those seats can get HOT on summer days! The black color absorbs most of the sunlight and transforms it into heat (which boosts the efficiency of your solar oven).


By strapping on a plastic sheet over the top of the pizza-box cooker, you’re preventing the heat from escaping and cooling the oven off. Keeping the cover clear allows sunlight to enter and the heat to stay in. (Remember the black stuff converted your light into heat?) If you live in an area that’s cold or windy, you’ll find this part essential to cooking with your oven!


Here’s another type of solar cooker that uses a cone design to focus the energy straight to your cookies!



Exercises Answer the questions below:


  1. Name the type of heat energy that the sun provides:
    1. Convection
    2. Conduction
    3. Radiation
    4. Invection
  2. What are some ways that the sun’s energy can be directly harnessed?
  3. Name three of the different parts of the electromagnetic spectrum:

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Solar Boat

Saturday May 1, 2010

expansionpacks_clip_image004_0000Does it really matter what angle the solar cell makes with the incoming sunlight? If so, does it matter much? When the sun moves across the sky, solar cells on a house receive different amounts of sunlight. You’re going to find out exactly how much this varies by building your own solar boat.


We’re going to use solar cells and the basic ideas from Unit 10 (Electricity & Robotics) to build a solar-powered race car.  You’ll need to find these items below.  Note – if you have trouble locating parts, check the shopping list for information on how to order it straight from us.


  • Solar motor
  • Solar cell
  • Foam block (about 6” long)
  • Alligator clip leads
  • Propeller (you can rip one off an old small personal fan or old toy, or find them at hobby stores)

Here’s what you do:


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Download Student Worksheet & Exercises


1. Attach the wires of the solar cell to the motor (one to each motor terminal).


2. Attach the propeller to your motor. If the shaft won’t fit, drill out the center hole. If the hole is too large, use a tiny dab of hot glue on the shaft tip to secure the propeller into place.


3. Stand out in the sun. How do you need to hold your solar cell to make the propellers pin the fastest?


4. Position the motor on a block of foam so that the propeller hangs off the edge and is free to rotate. Hot glue the motor into place, being careful not to get any hot glue near any vents in your motor.


5. Hot glue your solar cell to the foam block. You might want to check the final position in sunlight before attaching it.


6. Optional: Wire up a simple switch (from Unit 10) using paperclips and brass fasteners so you can easily turn your power on and off.


Going further: Using the same solar cell, you can also build a Wind Turbine and a Solar Car.


Exercises Answer the questions below:


  1. What kind of electricity comes from a battery and photovoltaic cell?
    1. Nuclear
    2. Voltaic
    3. Electrochemical
    4. Ionized
  2. Electricity is another name for the free flow of:
    1. Protons
    2. Quarks
    3. Electrodes
    4. Electrons
  3. True or false: Ions are attracted to the same charge.
    1. True
    2. False
  4. Do solar panels work in cloudy climates?
    1. Yes
    2. No

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Solar Car

Saturday May 1, 2010

solarboatSolar energy (power) refers to collecting this energy and storing it for another use, like driving a car. The sun blasts 174 x 1015 watts (which is 174,000,000,000,000,000 watts) of energy through radiation to the earth, but only 70% of that amount actually makes it to the surface. And since the surface of the earth is mostly water, both in ocean and cloud form, only a small fraction of the total amount makes it to land.


A solar cell converts sunlight straight into electricity. Most satellites are powered by large solar panel arrays in space, as sunlight is cheap and readily available out there. While solar cells seem ‘new’ and modern today, the first ones were created in the 1880s, but were a mere 1% efficient. (Today, they get as high as 35%.) A solar cell’s efficiency is a measure of how much sunlight the cell converts into electrical energy.


We’re going to use solar cells and the basic ideas from Unit 10 (Electricity & Robotics) to build a solar-powered race car.  You’ll need to find these items below.  Note – if you have trouble locating parts, check the shopping list for information on how to order it straight from us.


  • Solar cell
  • Solar motor
  • Foam block (about 6” long)
  • Alligator clip leads
  • 2 straws (optional)
  • 2 wooden skewers (optional)
  • 4 milk jug lids or film can tops
  • Set of gears, one of which fits onto your motor shaft (most solar motor kits come with a set), or rip a set out of an old toy

Here’s what you do:


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Download Student Worksheet & Exercises


How does a solar cell work? Solar cells are usually made of silicon. Sunlight is made of packets of energy called photons (we covered this in Unit 9). When photons hit the silicon, one of three things can happen: the photons can pass straight through the silicon if they have a low enough energy; they can get reflected off the surface; or (and this is the fun part) they get absorbed and the electrons in the silicon get knocked out of their shell.


Once knocked out of orbit, the free electrons start flowing through the silicon to create electricity. The solar cells are structured is such a way as to keep the electricity flowing only in one direction. The electron flow created is DC current (refer to Unit 10).


The solar cells you can buy from stores require huge amounts of energy in creating the solar cell, which is the primary downside. You need high temperatures, big vacuum pumps, and lots of people to make a set of solar cells. However, if we focus just on the physics of the solar cell, then we can easily create our own solar battery and other solar cell projects using household items. While these cells won’t look as spiffy as the ones from the store, they still produce electricity from sunlight.


Using the same solar cell, you can also build a Wind Turbine and a Solar Boat.


Exercises Answer the questions below:


  1. Most solar cells are made of what material?
    1. Hydrogen
    2. Aluminum
    3. Silicon
    4. Titanium
  2. Name one benefit of solar cells and one drawback of using them for electricity.
    1. Benefit:
    2. Drawback:
  3. Electrical current begins flowing when:
    1. Sunlight hits an atom
    2. Electrons are knocked out of orbiting atoms
    3. Protons get charged
    4. An atom’s nucleus splits

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Wind Turbine

Saturday May 1, 2010

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Believe it or not, most of the electricity you use comes from moving magnets around coils of wire! Wind turbines spin big coils of wire around very powerful magnets (or very powerful magnets around big coils of wire) by capturing the flow.


Here’s how it works: when a propeller is placed in a moving fluid (like the water from your sink or wind from your hair dryer), the propeller turns. If you attach the propeller to a motor shaft, the motor will rotate, which has coils of wire and magnets inside. The faster the shaft turns, the more the magnets create an electrical current.


The electricity to power your computer, your lights, your air conditioning, your radio or whatever, comes from spinning magnets or wires! Refer to Unit 11 for more detail about how moving magnets create electricity.


We’re going to build a wind turbine that will actually give you different amounts of electricity depending on which way your propeller is facing. Ready?


You’ll need to find these items below.  Note – if you have trouble locating parts, check the shopping list for information on how to order it straight from us.


  • A digital Multimeter
  • Alligator clip leads
  • 1.5-3V DC Motor
  • 9-18VDC Motor
  • Bi-polar LED
  • Foam block (about 6” long)
  • Propeller from old toy or cheap fan, or balsa wood airplane

Here’s what you do:


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Download Student Worksheet & Exercises


Using the same solar cell, you can also build a Solar Car and a Solar Boat.


Exercises


  1. True or false: Electricity in a wind turbine is created by magnets in the turbine:
    1. True
    2. False
  2. What is one advantage of using wind for electricity?
  3.  What might be one problem with constructing wind farms to meet all our energy needs?

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Marshmallow Roaster

Saturday May 1, 2010

Do you like marshmallows cooked over a campfire? What if you don’t have a campfire, though? We’ll solve that problem by building our own food roaster – you can roast hot dogs, marshmallows, anything you want. And it’s battery-free, as this device is powered by the sun.


NOTE: This roaster is powerful enough to start fires! Use with adult supervision and a fire extinguisher handy.


If you’re roasting marshmallows, remember that they are white – the most reflective color you can get.  If you coat your marshmallows with something darker (chocolate, perhaps?), your marshmallow will absorb the incoming light instead of reflecting it.


Here’s what you need to get:


  • 7×10” page magnifier (Fresnel lens)
  • Cardboard box, about a 10” cube
  • Aluminum foil
  • Hot glue, razor, scissors, tape
  • Wooden skewers (BBQ-style)
  • Chocolate, marshmallows, & graham crackers

Here’s what you do:



Download Student Worksheet & Exercises


How does it do that? The Fresnel lens is a lot like a magnifying glass.  In Unit 9, we learned how convex lenses are thicker in the middle (you can feel it with your fingers).  A Fresnel lens (first used in the 1800s to focus the beam in a lighthouse) has lots of ridges you can feel with your fingers.  It’s basically a series of magnifying lenses stacked together in rings (like in a tree trunk) to magnify an image.


The best thing about Fresnel lenses is that they are lightweight, so they can be very large (which is why light houses used these designs). Fresnel lenses curve to keep the focus at the same point, no matter close your light source is.


The Fresnel lens in this project is focusing the incoming sunlight much more powerfully than a regular hand held magnifier. But focusing the light is only part of the story with your roaster.  The other part is how your food cooks as the light hits it.  If your food is light-colored, it’s going to cook slower than darker (or charred) food. Notice how the burnt spots on your food heat up more quickly!


Scientifically Dissecting a Marshmallow

Plants take in energy (from the sun), water, and carbon dioxide (which is carbon and oxygen) and create sugar, giving off the oxygen. In other words: carbon + water + energy = sugar


  1. In this experiment, we will reverse this equation, by roasting a marshmallow, which is mostly sugar.
  2. When you roast your marshmallow, first notice the black color. This is the carbon.
  3. Next notice the heat and light given off. These are two forms of energy.
  4. Finally, put the roasting marshmallow if a mason jar. Notice that condensation forms on the sides. This is the water.

So, by roasting the marshmallow, we showed: sugar = carbon + water + energy!


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Steamboats

Saturday May 1, 2010

In 1920’s, these were a big hit. They were originally called “Putt Putt Steam Boats”, and were fascinating toys for adults and kids alike. We’ll be making our own version that will chug along for hours. This is a classic demonstration for learning about heat, energy, and how to get your kids to take a bath.



Here’s what you need to build your own:


  • Copper tubing (1/8”-1/4” dia x 12” long)
  • Votive candle
  • Foam block
  • Scissors or razor (with adult help)
  • Bathtub

Here’s what you need to do:



Download Student Worksheet & Exercises


  1. Wrap the copper tubing 2-3 times around a thick marker. You want to create a ‘coil’ with the tubing. Do this slowly so you don’t kink the tubing. End with two 3” parallel tails. (This is easier if you start in the middle of the tubing and work outwards in both directions.)
  2. Stick each tail through a block of foam. Bend the wires to they run along the length of the bottom of the boat, slightly pointed upwards. (You can also use a plastic bottle cut in half.)
  3. Position a votive candle on the topside of the boat and angle the coil so it sits right where the flame will be.
  4. To start your boat, fill the bathtub with water. While your tub fills, hold the tubing in the running water and completely fill the coil with water.
  5. Have your adult helper light the candle. In a moment, you should hear the ‘putt putt’ sounds of the boat working!
  6. Troubleshooting: if your boat doesn’t work, it could be a few things:
    1. The tubing has an air bubble. In this case, suck on one of the ends like a straw to draw in more water. Heating an air bubble will not make the boat move – it needs to be completely filled with water.
    2. Your coil is not hot enough. You need the water to turn into steam, and in order for this to happen, you have to heat the coil as hot as you can. Move the coil into a better position to get heat from the flame.
    3. The exhaust pipes are angled down. You want the stem to move up and out of your pipes, not get sucked back in. Adjust the exit tubing tails so they point slightly upwards.

How Do They Work? Your steam boat uses a votive candle as a heat source to heat the water inside the copper tubing (which is your boiling chamber). When the water is heated to steam, the steam pushes out the tube at the back with a small burst of energy, which pushes the boat forward.


Since your chamber is small, you only get a short ‘puff’ of energy. After the steam zips out, it creates a low pressure where it once was inside the tube, and this draws in fresh, cool water from the tub. The candle then heats this new water until steam and POP! it goes out the back, which in turn draws in more cool water to be heated… and on it goes. The ‘clicking’ or ‘putt putt’ noise you hear is the steam shooting out the back. This is go on until you either run out of water or heat.


Bonus! Here’s a video from a member that colored the water inside the pipe so they could see when it got pushed out! Note that the boat usually runs as fast as the first video on this page. The boats here are getting warmed up, ready to go, so they only do one or two puffs before they really start up.



Exercises Answer the questions below:


  1. Name three sources of renewable or alternative energy:
  2. Why is it important to look for renewable sources of energy?
  3. What is one example of a fossil fuel?

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Solar Battery

Saturday May 1, 2010

This is the kind of energy most people think of when you mention ‘alternative energy’, and for good reason! Without the sun, none of anything you see around you could be here. Plants have known forever how to take the energy and turn it into usable stuff… so why can’t we?


The truth is that we can. While normally it takes factories the size of a city block to make a silicon solar cell, we’ll be making a copper solar cell after a quick trip to the hardware store. We’re going to modify the copper into a form that will allow it to react with sunlight the same way silicon does. The image shown here is the type of copper we’re going to make on the stovetop.


This solar cell is a real battery, and you’ll find that even in a dark room, you’ll be able to measure a tiny amount of current. However, even in bright sunlight, you’d need 80 million of these to light a regular incandescent bulb.


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You’ll need to gather these materials together:


  • ½ sq. foot of copper flashing sheet (check the scrap bin at a hardware store)
  • Alligator clip leads
  • Multimeter
  • Electric stove (not gas)
  • Large plastic 2L soda bottle
  • ¼ cup salt
  • Sandpaper & sheet metal shears

Here’s what you need to do:



Download Student Worksheet & Exercises


How does that work? Do you remember learning about the photoelectric effect in Unit 9? This cuprous oxide solar cell ejects electrons when placed in UV light – and sunlight has enough UV light to make this solar cell work. Those free electrons are now free to flow – which is exactly what we’re measuring with the volt meter.


Semiconductors are the secret to making solar cells. A semiconductor is a material that is part conductor, part insulator, meaning that electricity can flow freely and not, depending on how you structure it. There are lots of different kinds of semiconductors, including copper and silicon.


In semiconductors, there’s a gap (called the bandgap) that’s like a giant chasm between the free electrons (electrons knocked out of its shell) and bound electrons (electrons attached to an atom). Electrons can be either free or attached, but it costs a certain amount of energy to go either way (like a toll both).


When sunlight hits the semiconductor material in the solar cell, some of the electrons get enough energy to jump the gap and get knocked out of their shell to become free electrons. The free electrons zip through the material and create a low of electrons. When the sun goes down, there’s no source of energy for electrons to get knocked out of orbit, so they stay put until sunrise.


Does it really matter what angle the solar cell makes with the incoming sunlight? If so, does it matter much? When the sun moves across the sky, solar cells on a house receive different amounts of sunlight. You’re going to find out exactly how much this varies by building your own solar vehicles.


Exercises Answer the questions below:


  1. The sunlight causes the electrons to flow from the cuprous oxide because of:
    1. Photosynthesis
    2. The electromagnetic spectrum
    3. The photoelectric effect
    4. The photochemical principle
  2. What material do most solar cells use instead of copper?
  1. What part of the electromagnetic spectrum is most active in this experiment?
    1. Visible Light
    2. Ultraviolet Light
    3. Gamma Rays
    4. Microwaves
  2. When you read amps, you read:
    1. Current
    2. Voltage
    3. Power Draw
    4. Work

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Crystal Radio

Saturday May 1, 2010

xtal3This project is for advanced students. A crystal radio is among the simplest of radio receivers – there’s no battery or power source, and nearly no moving parts. The source of power comes directly from the radio waves themselves.


The crystal radio turns the radio signal directly into a signal that the human ear can detect. Your crystal radio detects in the AM band that have been traveling from stations (transmitters) thousands of miles away. After working with the electromagnetic spectrum in Unit 9 where we played with frequency and wavelengths of light, you’ll find that you’ve got all the basics for picking up AM radio stations using simple equipment from an electronics store.


The radio is made up of a tuning coil (magnet wire wrapped around a toilet paper tube), a detector (germanium diode) and crystal earphones, and an antenna wire.


One of the biggest challenges with detecting low-power radio waves is that there is no amplifier on the radio to boost the signal strength. You’ll soon figure out that you need to find the quietest spot in your house away from any transmitters (and loud noises) that might interfere with the reception when you build one of these.


One of things you’ll have is to figure out the best antenna length to produce the clearest, strongest radio signal in your crystal radio. I’m going to walk you through making three different crystal radio designs.


Materials:


  • Toilet paper tube
  • Magnet wire
  • Germanium diode: 1N34A
  • 4.7k-ohm resistor
  • Alligator clip test leads
  • 100’ stranded insulated wire (for the antenna)
  • Scrap of cardboard
  • Brass fasteners (3-4)
  • Telephone handset or get a crystal earphone

Here’s what you do:


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Download Student Worksheet & Exercises


The video below shows how to make a slightly different model that uses different parts. If you have the Science Mastery Diamond program, this is the one you have the parts for. The company, GSST sadly has gone out of business, but they gave us permission to use their project guidebook with the video that we made for their kit. Download the project guidebook here and gather your materials!


Materials:


  • 8 steel (unpainted) thumbtacks
  • Toilet paper tube
  • 70 feet of #26-30 magnet wire
  • 1 large paper clip
  • 2 4″ pieces of hook up wire
  • Germanium diode: 1N34A
  • 470 pf disc capacitor
  • 0.01 mf disc capacitor
  • Alligator clip test leads
  • 100’ stranded insulated wire (for the antenna)
  • Scrap of cardboard or wood for your project
  • Crystal earphone

 



Exercises


  1. What are radio waves?
  2. Name some of the parts needed for any radio that we also used in this radio.
  3. What serves as the tuning coil for the crystal radio?
  4. Why do you need a ground for the radio?

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BEAM Robots

Saturday May 1, 2010

This project is for advanced students.This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.


Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We’ll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.


Most BEAM robots use the same solar ‘engine’. The solar cell will convert sunlight into electricity, which will then be stored in our capacitors (think ‘electricity tanks’) until a certain threshold is reached… when the tanks are full, the robot begins to move. This means that you can leave them out all day, and they will sit and collect energy, then turn on by themselves until they run out of juice, then turn off, sit and recharge until they have enough energy to go again… and off they go!


Let’s walk through how to make a BEAM robot. Once you’ve got the hang of it, make a second solar engine from the rest of your parts and add any kind of body you want!


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You’ll need to get the following materials:


Here’s what you do…


Beam Robot:


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Bristle Brush Bot

Saturday May 1, 2010

This is the simplest robot you can make… out of old parts from around the house. While this little robot doesn’t use energy from the sun or wind, we’ve placed it here with other alternative energy projects because the parts come from the trash bin.


This project is an extension of the Jigglebot robot from Unit 10.


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You’ll need to find:


  • Old toothbrush you can destroy
  • Tiny vibrator motor (you can rip one out of an old cell phone) – just make sure it’s got a weight attached to the motor shaft.
  • Small watch battery (make sure it’s around 3V to match the motor)
  • Scissors and/or razor
  • Tape and a hot glue gun
  • Optional: Paper clips for claws and feet

Here’s what you do:



What’s going on? Your BristleBot uses the toothbrush bristles as legs and an eccentric motor to shake and wobble it by tiny amounts to look like a smooth motion. The larger the weight, the more you’ll see the wobbling action. Try making one out of the head of a scrub brush or small broom!


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Stirling Engine

Saturday May 1, 2010

This project is for advanced students.This Stirling Engine project is a very advanced project that requires skill, patience, and troubleshooting persistence in order to work right.  Find yourself a seasoned Do-It-Yourself type of adult (someone who loves to fix things or tinker in the garage) before you start working on this project,  or you’ll go crazy with nit-picky things that will keep the engine from operating correctly.  This makes an excellent project for a weekend.


Developed in 1810s, this engine was widely used because it was quiet and could use almost anything as a heat source. This kind of heat engine squishes and expands air to do mechanical work. There’s a heat source (the candle) that adds energy to your system, and the result is your shaft spins (CD).


This engine converts the expansion and compression of gases into something that moves (the piston) and rotates (the crankshaft). Your car engine uses internal combustion to generate the expansion and compression cycles, whereas this heat engine has an external heat source.


This experiment is great for chemistry students learning about Charles’s Law, which is also known as the Law of Volumes, which describes how gases tend to expand when they are heated and can be mathematically written like this:



where V = volume, and T = temperature. So as temperature increases, volume also increases. In the experiment you’re about to do, you will see how heating the air causes the diaphragm to expand which turns the crank.


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Here’s what you need:


  • three soda cans
  • old inner tube from a bike wheel
  • super glue and instrant dry
  • electrical wire (3- conductor solid wire)
  • 3 old CDs
  • one balloon
  • penny
  • nylon bushing (from hardware store)
  • alcohol burner (you can build one out of soda cans or Sterno canned heat)
  • fishing line (15lb. test or similar)
  • pack of steel wool
  • drill with 1/16″ bit
  • pliers
  • scissors
  • razor
  • wire cutters
  • electrical tape
  • push pin
  • permanent marker
  • Swiss army knife (with can opener option)
  • template
  • HINT: The “circle template” mentioned at 21:57 is actually just a circle traced from the bottom of the soda can onto a sheet of paper

The Stirling heat engine is very different from the engine in your car.  When Robert Stirling invented the first Stirling engine in 1816, he thought it would be much more efficient than a gasoline or diesel engine. However, these heat engines are used only where quiet engines are required, such as in submarines or in generators for sailboats.



Download Student Worksheet & Exercises


Here’s how a Stirling engine is different from the internal-combustion engine inside your car. For example, the gases inside a Stirling engine never leave the engine because it’s an external combustion engine. This heat engine does not have exhaust valves as there are no explosions taking place, which is why Stirling engines are quieter. They use heat sources that are outside the engine, which opens up a wide range of possibilities from candles to solar energy to gasoline to the heat from your hand.


There are lots of different styles of Stirling engines. In this project, we’ll learn about the Stirling cycle and see how to build a simple heat engine out of soda cans.  The main idea behind the Stirling engine is that a certain volume of gas remains inside the engine and gets heated and cooled, causing the crankshaft to turn. The gases never leave the container (remember – no exhaust valves!), so the gas is constantly changing temperature and pressure to do useful work.  When the pressure increases, the temperature also increases. And when the temperature of the gases decreases, the pressure also goes down. (How pressure and temperature are linked together is called the “Ideal Gas Law”.)


Some Stirling engines have two pistons where one is heated by an external heat source like a candle and the other is cooled by external cooling like ice. Other displacer-type Stirling engines has one piston and a displacer. The displacer controls when the gas is heated and cooled.


In order to work, the heat engine needs a temperature difference between the top and bottom of the cylinder. Some Stirling engines are so sensitive that you can simply use the temperature difference between the air around you and the heat from your hand. Our Stirling engine uses temperature difference between the heat from a candle and ice water.


The balloon at the top of the soda can is actually the ‘power piston’ and is sealed to the can.  It bulges up as the gas expands. The displacer is the steel wool in the engine which controls the temperature of the air and allows air to move between the heated and cooled sections of the engine.


When the displacer is near the top of the cylinder, most of the gas inside the engine is heated by the heat source and gas expands (the pressure  builds inside the engine, forcing the balloon piston up). When the displacer is near the bottom of the cylinder, most of the gas inside the engine cools and contracts. (the pressure decreases and the balloon piston is allowed to contract).


Since the heat engine only makes power during the first part of the cycle, there’s only two ways to increase the power output: you can either increase the temperature of the gas (by using a hotter heat source), or by cooling the gases further by removing more heat (using something colder than ice).


Since the heat source is outside the cylinder, there’s a delay for the engine to respond to an increase or decrease in the heat or cooling source. If you use only water to cool your heat engine and suddenly pop an ice cube in the water, you’ll notice that it takes five to fifteen seconds to increase speed. The reason is because it takes time for the additional heat (or removal of heat by cooling) to make it through the cylinder walls and into the gas inside the engine. So Stirling engines can’t change the power output quickly. This would be a problem when getting on the freeway!


In recent years, scientists have looked to this engine again as a possibility, as gas and oil prices rise, and exhaust and pollutants are a concern for the environment. Since you can use nearly any heat source, it’s easy to pick one that has a low-fume output to power this engine. Scientists and engineers are working on a model that uses a Stirling engine in conjunction with an internal-combustion engine in a hybrid vehicle… maybe we’ll see these on the road someday!


Exercises


  1. What is the primary input of energy for the Stirling engine?
  2.  As Pressure increases in a gas, what happens to temperature?
    1. It increases
    2. Nothing
    3. It decreases
    4. It increases, then decreases
  3. What is the primary output of the Stirling engine?

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Fuel Cell Power

Saturday May 1, 2010

41wpr5+y2qLThis project is for advanced students. We’re going to build a car that runs entirely on sunlight and water.  Use energy from the sun, we’ll first use a solar cell to convert sunlight into electricity.


Then we’ll use that electricity to split the water molecule (H2O) into hydrogen and oxygen atoms and store them in separate tanks.


Lastly, we’ll flip the system around to allow the hydrogen and oxygen gases to mix, which will produce the power to run the car and create an exhaust product that’s just plain water.


How does that sound?
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We’re going to use solar cells and the basic ideas from Unit 10 (Electricity & Robotics) and Unit 8: Chemistry to build a fuel cell vehicle.  The fuel cell is reversible, meaning that you can use it to pull apart water molecules into atomic gases, or combine the atomic gases together to make water.


You’ll need to order the Fuel Cell Car Kit (Item# KT-FUELCCK from www.hometrainingtools.com). This kit is a bit expensive, but if you want to build a car that runs entirely from sunlight and water, this is the one you want to get.  The company that makes this particular model also sells the conversion kits for (real!) cars.


Here’s what you do:



How does that work? Molecules can also be split chemically, or by getting hit by a fast-moving particle. When you recombine the hydrogen and oxygen, energy is produced – enough to power a small car. If you guessed that this has to do with Unit 10: Electricity and Unit 8: Chemistry, you’re right! But you might wonder how they work together.


Back in 1800, William Nicholson and Johann Ritter were the first ones to split water into hydrogen and oxygen using electrolysis. (Soon afterward, Ritter went on to figure out electroplating.) They added energy in the form of an electric current into a cup of water and captured the bubbles forming into two separate cups, one for hydrogen and other for oxygen.


It takes energy to split a water molecule. (On the flip side, when you combine oxygen and hydrogen together, it makes water and a puff of energy. That’s what a fuel cell does.)


Back to splitting the water molecule – as the electricity zips through your wires, the water molecule breaks apart into smaller pieces: hydrogen ions (positively charged hydrogen) and oxygen ions (negatively charged oxygen). Remember that a battery has a plus and a minus charge to it, and that positive and negative attract each other.


So, the positive hydrogen ions zip over to the negative terminal and form tiny bubbles right on the wire. Same thing happens on the positive battery wire. After a bit of time, the ions form a larger gas bubble.


If you stick a cup over each wire, you can capture the bubbles and when you’re ready, ignite each to verify which is which. We covered the basics of electrolysis in Unit 8, and now we’re going to show you how to store the energy and use it power a small car in our fuel cell project together.


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BEAM Robot: Solar Roller

Saturday May 1, 2010

Note: Brian Cox has created a BEAM Bot kit as an alternative BEAM project.

Brian's BEAM BOT is modeled after small BEAM projects where parts are soldered to each other, but such projects can be difficult to solder.

BEAM Bot uses a standard Printed Circuit Board (PCB) as the frame thus making it easier to assemble.

You can order Brian's BEAM Bot Kit here: fvresearch.com/product/beam-bot .

Click here for Brian's BEAM Bot instructional video (which can be found under Unit 25).

This project is for advanced students.This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.

Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We'll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.

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To make this project, you'll need to get the Solar Roller kit from Solarbotics. You'll also need your soldering equipment and basic tools, like pliers, wire strippers, scissors, and electrical tape.



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BEAM Robot: Trimet

Saturday May 1, 2010

Note: Brian Cox has created a BEAM Bot kit as an alternative to the Trimet project.

Brian's BEAM BOT is modeled after small BEAM projects where parts are soldered to each other, but such projects can be difficult to solder.

BEAM Bot uses a standard Printed Circuit Board (PCB) as the frame thus making it easier to assemble.

You can order Brian's BEAM Bot Kit here: fvresearch.com/product/beam-bot .

Click here for Brian's BEAM Bot instructional video (which can be found under Unit 25).

This project is for advanced students. This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.

Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We'll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.

You'll need to get the Trimet Kit from Solarbotics. It has everything you need except the tools for the job (soldering iron, pliers, wire strippers, razor) and paperclips.

Here's what you do:

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BEAM Robot: MiniBall

Saturday May 1, 2010

This project is for advanced students.This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.

Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We'll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.

[am4show have='p9;p49;p108;p103;' guest_error='Guest error message' user_error='User error message' ]

You'll need to get the MiniBall Kit from Solarbotics. It has everything you need except the tools for the job (soldering iron, pliers, wire strippers, razor), paperclips, and 80mm plastic ball (the kind found at craft stores for making your own holiday ornaments).

Here's what you do:

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