Solar Cooker

Legg Middle School Planetarium

The Solar Cooker

What is the Solar Cooker?

The experiment to see if the Solar Cooker worked.

How does the Solar Cooker work?

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What is the Solar Cooker?

Do you know what this thing is? We didn't for a long time. Thanks to some knowledgeable planetarians around the world, we now have answered the mystery.

This Red Thing was found while cleaning a corner of the planetarium. We were removing some old materials that had accumulated over the years and the Red Thing was being used as a garbage heap. The people who have been around the building longer than me were not sure what it was (or should be).

The Solar Cooker stands 1.4 m (~ 4 ft 6 in) tall and is 1 m (~ 3 ft 3 in) wide. The cooker can be spun just above the base to face any direction.

The parabolic dish has a diameter of 90 cm (~ 3 ft) and is about a 20 cm (~ 4 in) deep at its center. The parabolic dish pivots on a horizontal axis and is covered with a shiny aluminum paper.

The focus ring on the Solar Cooker is 48 cm (~ 19 in) above the center of the dish. This is the point where the light is concentrated and converted to heat energy.

How does is the Solar Cooker work?

The Solar Cooker works on the basic principle of reflection. The sun's light rays are collected by the parabolic bowl and are bounced off the shiny aluminum that covers the dish. These light rays reflect at various angles and are concentrated to a single point. When an object (such as a marshmallow or hot dog) is placing at the focus point, it will heat up and cook. The light rays are converted in to heat energy. The darker the object (like a black pot) placed at the focus point, the better the light is converted to heat.

The experiment to see if the Solar Cooker worked.

On a pleasant spring day (31 March 1999), a marshmallow "Peep" was set up to be roasted with the Solar Cooker. The parabolic dish was covered with aluminum foil and taped in place. The helpless, yellow Peep was carefully placed on the cooker's focus point and the dish was aimed at the sun. After things were set, it was up to the Sun to finish the job. The experiment was carried out by two sixth grade students. I helped them write up an activity before the Peep was sacrificed.

What is a marshmallow Peep?

A marshmallow Peep is a chick shaped marshmallow coated with yellow dyed sugar. The Peep is a flightless newborn chick and is a treasured Easter treat for the sons and daughters of dentists across the US.

The particulars of a marshmallow Peep:

feather color	yellow #5
eye color	brown
age	just hatched
height	about 3.5 centimeters	about 1.25 inches
width	about 4 cm	about 1.5 in
depth	about 5 cm	about 2 in
mass	about 10 grams	0.35 ounces
place of birth	Bethlehem, Pennsylvania, USA

The experiment results.

The Solar Cooker was place in on open area and carefully aimed at the sun. The temperature on this day was 22º C (72º F). No control marshmallow Peep was set up, the sole purpose of the experiment was to roast a single helpless Peep. The trial was not a success. The Peep should have been reduced to a marshmallow goo. The two students plan on attempting this experiment again after Spring Break. The students came up with the following possible reasons way the Peep was unaffected:

1) the wind changed the shape of the reflector.
2) the dish was not aimed exactly at the sun.
3) the wind cooled down the Peep and it could not heat up.

air temperature	22º C (72º F)
start time	10:45 am
finish time	did not cook, stopped at 2:30 pm
cooking time	did not cook
focus temperature	25º C (77º F)
conditions	windy with a few cloud in the sky.
problems	the wind kept blowing under the aluminum foil causing it to lose its shape.

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Legg Middle School 175 Green St. Coldwater, MI 49036 517-279-5940 (fax) 517-279-5945