The Experiments
1. Sundial
Clamp it to the table so it won't move. Inside with the lights turned down move a light past the sundial to illustrated how the shadow moves as the sun moves. Introduces the concept that the sun moves through the southern sky in winter.
To do: - Check the time when you start and kids will come back and check it again later.
- Copy the face of a sundial onto paper and the kids can make their own.
2. Black absorbs light, white reflects
- Materials: - Two pieces of copper, about six inches square, one painted black, the other white. If you have trouble finding copper or brass aluminum or steel will also get the point across.
- Digital thermometer is nice but not necessary
To do: -When you set these in the sun, kids easily feel how much more heat black absorbs than white.
-Check the temperature difference with the thermometer.
3. Same as #2, but with two 2-pound coffee cans filled with water, and one painted black, the other white.
To do: -Same as #2 above
4. Hot water rises
This experiment shows what happens inside the pipes of a solar water heater.
Materials:
- One clear plastic 1-gallon jar
- 4 oz artichoke hearts jar: drill two holes in the lid and glue in two pieces of drinking straws in the holes so they stick out 1/4" above and below the lid
- food coloring
To do: Fill the big jar with cold water. Fill the small jar with hot water (solar heated of course), add food coloring to the hot water, put the lid on, and set the small jar inside the large jar. The colored water being hotter, takes up more space than the same number of cold water molecules, and rises up, through a straw, out of the little jar to the top of the cold water in the big jar. Like smoke coming out of a chimney.
5. Cardboard box heater
Materials:
- shallow cardboard box with a lid, approximately 12" X 18"
- Flat black paint
- Piece of plastic sheeting or thin Plexiglass, 10" X 16"
- Duct tape
- Digital thermometer
This is a basic box heater. Cut a hole in the lid almost to the edges. Use duct tape to fasten the plastic sheet over this hole. Paint the inside of the box black.
To do: -Stick the thermometer inside the box. How hot does it get? Mine approaches 200 degrees F.
-Cut a small hole in the end of the box and stick your fingers down inside. Hot?
-Would painting the outside of the box increase the temperature inside the box?
-How could you make this heater work better?
6. A hot water heater
This is the combination of experiments 2, 4, and 5. See Daniel's Direct Use of the Sun's Energy, chapter 6, for details of water heater construction.
Description: A 2' X 4' box framed with 1" x 4". The back is 1/4"plywood. The inside of the box is insulated with 1/2" foam board, painted black with high temperature flat black paint and contains a framework of copper tubing (see drawing). The top of the box is covered with clear plastic. The top of the copper grid is connected to the top of a three-gallon plastic paint pail. The bottom of the grid is connected to the bottom of the plastic paint bucket. The water flows through the copper pipe, rising, gaining heat, into the water tank. The cooler water settles to the bottom of the tank and then flows to the bottom of the collector.
To do: - Stick your hand in the water, carefully. It's hotter than you think.
- Look for the hot water where it comes out of the hose from the copper pipe. You will see it shimmer, like heat waves coming off hot pavement.
- With a piece of surgical tubing and large syringe, inject some water with food coloring in it into the tank drain that feeds back to the bottom of the collector. .
- Measure the temperature difference between the top and bottom of the tank.
- How could this water heater be made to work better?
- Comment on how inventions are often a combination two or three ideas known to most people but put together in a clever and simple way. In this case: Black absorbs heat, hot water rises and a box with a clear lid combine to become a hot water heater.
7. Solar-heated kid warmer
I built this for those chilly days in the fall and spring. It really works and my preschool kids love it. It is just a big box heater.
Materials: - Large cardboard dryer box
- Duct tape
- Flat black paint
- 3" X 4" piece of Visqueen
Directions: Cut a large hole in the side of a dryer box. Cover this hole with plastic sheeting using duct tape around the edges. In the opposite side from the window cut a small door. Paint the box black and face towards the sun.
To do: - Kids can hide inside this cozy space to warm up on chilly days.
8. Small solar oven (make or buy)
I got a small cardboard oven (the sun spot) for $20. There are good plans in the book Heaven's Flame by Joseph Radabaugh. You can buy more expensive ovens from Kansas Wind Power or Real Goods.
To do: -I always make cookies (even if they are small) and put them in the oven before we start.
-After the cookies are finished baking, the kids can put their hands in the oven to feel the power of the sun.
9. Solar Hot Dog cooker (see plans below)
This is a parabola shaped frame that holds a plastic mirror. The parabola focuses the sunlight on the hot dog and will burn it if the hot dog is not rotated. The plastic mirror (available at glass stores) works a lot better than aluminum foil and it is easier to clean. This rather silly device I've used in my summer class and it is definitely an attention getter.
To do: - Have the kids two or three at a time put their hand at the focal point if they want to. It is hot.
-Cut the hot dogs in half and let the kids cook their own.
10. Umbrella lined with aluminum foil (pseudo-parabolic reflector)
Materials: - old umbrella
- Aluminum foil
- metal cup painted black
- bailing wire, pliers
Cut off the handle at the focal point and make a wire stand to hold a black cup. Mine took about 15 minutes to heat a cup of water.
To do: - Put your hand quickly in and out of the focal point to feel the heat
- Heat water for tea or hot chocolate
11. Fresnel lens cooker
Materials: - 1 X 6 Lumber
- Approximately 18 square feet of plastic mirror
- a stand to hold the cooking pot
- Pan painted black
I made this from VITA plans. It is about 4' in diameter and has four steps, each 6 1/2" wide, aimed at the focal point. It heats a quart of water to near boiling in 15-20 minutes.
To do: - Heat water for tea or hot chocolate
- cook soup or rice
- Keep the collector aimed at the sun so the focal point will remain on the item being cooked
12. Solar cells
This is an old 30-watt ARCO panel connected through a volt and ammeter to a rubber bladed 2-speed fan.
To do: - This is a good demonstration to teach that blocking the sun blocks the energy. People often stand in front of the cells and ask why they don't work.
- Use the fan for air conditioning
- Hook up another electrical device, a pump, motor or light
13. A race against solar cells, using an old war surplus hand crank generator
This machine will put out about 50 watts, but it is hard to keep up for long.
To Do: -Kids crank to see how many watts they can produce and compare their output to the output of the solar cells.
14. Books, magazines and plans
Direct use of the Sun's Energy, Heaven's Flame, The 12 Volt Bible for Boats, the latest Popular Science on solar cells and power plants, plans for a solar furnace made from beer cans and other miscellaneous stuff from my solar file.
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