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Solar Power

Solar Cooker Solar Dehydrator Solar Concentrator Solar Still
Sun Bleaching Heat Sinks Black and White Chlorophyll Collector

Solar Dehydrator

Build this in cardboard or wood.

Materials (for cardboard version):
Large cardboard box
adult wielding a glue gun and a craft knife (but not at the same time!)
black paint
duct tape
wide-width plastic wrap
a liner tray (baking sheet, plastic place mat or similar--the shinier the better!) that is waterproof and fits inside the bottom to catch any stray drips
several feet of fabric elastic (or bare rubber elastic if you have it long enough--you can also loop smaller bands together to make a chain)
2-4 food-safe mesh trays that will fit inside the width of the box (as close to the edges as possible)
optional: screening or netting to cover the ventilation holes and keep out insects

  1. Cut the box with a diagonal line running from the top back of the sides down to a point about eight inches (20 cm) from the bottom of the front of the box. Remove the top and you should have a shape like the one in the photo.
  2. Use scrap cardboard strips to make holders for the trays. Mark spots on either side at 1", 4", and 7" from the bottom of the box. We just glue-gunned either end of the strips onto the sides to make bumps on which the trays sat. Be sure to make the sides level with each other.
  3. Cut out the ventilation holes. A long slit chould be cut at the very bottom of the front of the box (this will also act as a means for removing your drip tray)and another at the very top of the back of the box (but low enought to allow for the plastic overlap). Add two more holes in each side, one at the back near the top, and one at the bottom near the front. If you want, cover the holes with screening or netting and either tape or glue this in place.
  4. Paint the entire box black. We used black tempera paint, but any paint that has low VOCs will work. Let the box dry completely as long as it takes to be sure there will be no paint fume off-gassing. No one wants to eat food that smells and tastes like paint!
  5. Cut the plastic so that it will generously overlap the top of the box. You will need enough overlap so that you can use the elastic around the sides of it to hole it in place. If you have a light-weight sheet of plexiglass that happens to fit the top, you can sit that on the top instead.
  6. Insert your trays and dowble check that everything fits well together.
  7. Add food to dry. Click here for some ideas to get you started.

You can build the same sort of thing in a more sturdy and permanent way using wood and plexiglass.

Solar Concentrator

Ask a responsible adult to supervise you before trying this one, and only do this on a day with little or no wind.

Materials:
a magnifying glass
a heat-proof surface, such as a sidewalk or concrete paving stone
a very small pile of kindling--dry grass, tiny twigs or torn strips of thin paper; the size of this should be about half the size of your fist
a large glass of water
a sunny day

  1. Arrange the kindling in a pile well away from anything else that is flammable (look around and also up to ensure your space is clear).
  2. Use your magnifying glass to shine a concentrated sun beam onto the centre of the kindling pile. You may need to play around with the angle of the glass and the sun to find the right spot.
  3. Hold the beam in place until a thin stream of smoke starts to rise from the pile.
  4. If your adult allow it, continue concentrating the beam. How hot can you make your pile?
  5. Extinguish your pile with the glass of water. To be sure it is out, smother it further by stomping on it.
  6. Large solar concentrators work in a similar way by using mirrors to focus the energy of the sun to heat tubes of water to form steam that can be used to heat buildings or push a turbine to make electricity.

Solar Still

Take advantage of the water cycle to purify (distill) water using solar energy. This experiment could save your life one day!

Materials:
shallow collecting bowl or container
a hole or larger container about 10 cm or more deeper and wider than the collecting dish
a large sheet of plastic wrap that covers the larger hole or container so that the edges extend out around it
several rocks or pebbles or other weights
one small round pebble or marble
"contaminated" water (dirty water, or water with food colouring etc.)--slightly more than the collection bowl can hold
a warm sunny day

  1. Perform this activity in a warm sunny spot that will stay sunny for several hours.
  2. Place your collecting dish in the centre of the hole or larger container.
  3. Choose a larger rock (or a few marbles etc.) to wash thoroughly and place in the centre of the collection bowl (to keep it from floating before it is filled with water).
  4. Pour almost all of the dirty water into the hole or larger container being sure not to get any in the collection bowl.
  5. Cover the hole or larger dish with plastic wrap. Use the rocks to hold the edges down and keep it in place.
  6. Place a small pebble or marble on the centre of the plastic over the collection bowl. This will make the centre of the plastic slightly lower than the rest of the plastic, and help the condensation (aka purified water) to drip into your collection bowl.
  7. Wait. Now wait some more. This step could take several hours depending on the strength of the sun in your area!
  8. When you have some water in your collection bowl, compare it to the remaining dirty water. Take a sip of the distilled water. Do not drink the dirty water unless it only has food colouring in it instead of dirt. As long as your collection bowl, the plastic wrap and the weights you put in the bowl were all clean when you started, the water will be completely safe to drink. How does it taste?

Sun Bleaching

Materials:
several sheets of vivid or dark coloured construction paper--not the kind that is uv resistant
scissors
paper clips--the flat kind work best
optional: tape that will not mark your windows

  1. Cut out some interesting shapes from your construction paper, and lay them on top of other sheets of construction paper. Arrange paper clips to hold these firmly in place
  2. Repeat using a variety of shapes and colours.
  3. Place these on a sunny shelf or window ledge and leave them for a week or longer.
  4. Remove the paper clips and peek inside.
  5. If you wish, you can move the shape and paper clip it to a different overlapping part of the paper and repeat the exercise to make overlapping shadowy shapes and other interesting patterns and designs.

Chlorophyll Collector

You don't have to take the word of your teachers that plants make chlorophyll from the energy of the sun--now you can see it for yourself!

Materials:
a mature tree or large leafy plant with green leaves
paper clips
heavy paper
a mortar and pestle (or other way of grinding a leaf)
filter paper (coffee filters cut into strips work well, as does watercolour painting paper)
rubbing alcohol
a kitchen chair (or any other chair with exposed legs)
string
a small bowl

  1. Choose a leaf from your tree or plant. Leaving the leaf attached to the plant, cover both sides of a portion of the leaf with the paper by folding it around the leaf. Us a paper clip or two to hold this in place. Let it stay this way for at least 2 days.
  2. Take a peek at the section you covered. Do you see any changes? If not, leave it for another day or two.
  3. What do you notice about the colour of the leaf where it was covered?
  4. Remove the paper and note the location of the leaf so you can refer to the same leaf again. Check it in a couple of days. What do you notice? Has it become green again, stayed a different colour, or died?
  5. Now choose a different leaf. Remove it from the plant, cut or rip it into small pieces, then use a mortar (or a rock, or any other way of ginding it that meets with adult approval) and grind it until it becomes well mulched. Add a tablespoon or so of rubbing alcohol and stir.
  6. Now it's time to do a little chromatography to look at the chlorophyll inside the leaf.
  7. Take your chair and string and tie the string to two of the legs to make a hanger for the filter paper. Adjust the height of the string so that when the bowl of leaf mulch is beneath, a strip of filter paper paper clipped to the string can dangle down inside the bowl.
  8. Hang up your filter paper and place the bottom end into the bowl. Watch as the paper absorbs the fluid and the colours begin to separate. How many different colours or strengths of colours separate out?
  9. If you wish, try this again with a different kind of tree or plant, and/or with a leaf from a tree that has changed colour in autumn. Do you notice any differences?



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