Internet Version [Naruhodo no Mori] Vol.58

by Yumiko Mori

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Vol.58   July 15th, 2001

Cooking Onsen Eggs with Solar Energy

EcoEnergy

Home science experiments for mothers of elementary school children

Mom an Toshi, who is now a high school student, sit on the deck.
There's no sign of rain, but Mom opens an umbrella and put it upside down on the deck.
Mom has prepared cardboard sheets which have aluminum foil attached on one side. She puts these cardboard sheets on the inner side of the umbrella. Then she attaches a can to the tip of the umbrella pole and put an egg into the can.

Toshi: "Now it is ready. We just have to wait until the egg is cooked."
Mom: "I wonder it's going to work. I hope we can eat this egg at lunch time."

One hour later, we take the egg out from the can and crack it open.
Mom: "It's cooked. Toshi, this is Onsen egg."
Toshi: "How can we eat this egg?"
Mom: "We can cool down this egg and later eat with sauce."
Toshi: "But I realized we are waisting so much."
Mom: "What do you mean?"
Toshi: "We are wasting a lot of solar energy. It can make this can so hot. We should use solar energy for other purposes."
Mom: "That's right. You can invent something. And you may win a Novel prize!"
Toshi: "Mom, you are asking too much."

Note: 'Onsen' eggs are half cooked eggs with soft yolk. The name 'onsen' means hot spring, in which 'onsen' eggs were originally cooked.

Materials

Eggs

An aluminum can

A can opener, a black marker, wire, and a pair of pliers

An umbrella

Cardboard sheets

Aluminum foil

A cutter and a Scotch tape

If available, a thermometer

How to make an 'onsen' egg

Required time: 2 hours

1. Using cardboard sheets, make light reflectors.
   Prepare 25 cm x 50 cm cardboard sheets and cut corners as illustrated.
   Make 8 copies of the shaped cardboard sheets.
   

2. Cover one side of the sheets (1) with aluminum foil. Tape the aluminum foils on the back of the sheets.
   

3. If the can's top lid is still on, remove its top rid using a can opener.
   Paint the outer surface of the can with black marker.
   Insert an egg into the can and fill water until the egg is covered.
   

4. Choose sunny area. Put the umbrella upside down and point its pole toward the sun. If necessary, add support (chairs or other furniture) to stabilize the umbrella.
   Place the reflector sheets on the inner side of the umbrella.
   Attach the can to the umbrella pole with wire, as illustrated below.
   

5. Expose the umbrella under the sun for 1 hour. Remove the can from the pole. Be careful. The can and water inside is probably very hot.

* Be careful on a windy day. The umbrella could fall down or the reflectors may fly off.

* The optimum condition for 'onsen' eggs is to maintain the eggs at 65-70 centigrade degree for 30 minutes.

EcoEnergy

In this experiment, we experienced real ecoenergy. We have to appreciate the existence of the sun. We can say the sun is the earth's mother. If the sun didn't exist, we wouldn't have been born. I heard many of today's children have never seen the sunset or the sunrise. I hope the sun doesn't become too distance existence for them.