Solar Cooking

In this lesson, students will build a minimal solar oven that works using two cardboard boxes.

A lesson plan for grades 3–5 Social Studies

By Libby Morrison

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Learning outcomes

Students will:

• build a minimum solar box cooker.
• measure and record the temperature inside the oven over a period of time.
• choose and carry out a cooking project for the solar cooker.

Teacher planning

Time required for lesson

2 hours

Materials/resources

First Activity - Solar Box Cooker

• Two cardboard boxes. One should fit inside the other by at least one-half inch.
• One sheet of cardboard to make the lid somewhat larger than the top of the outside box.
• One small roll of aluminum foil.
• One can of flat-black spray paint (says on can “non-toxic when dry”).
• White glue
• One sheet of clear laminating film for see-through top.

Second Activity - Recording Temperature

• Purchase an inexpensive oven thermometer.
• Solar box cooker
• Pencil and Paper for record-keeping, or log.

Third Activity - Cooking

• Any ingredients for selected cooking project
• Dish or pan and utensils for cooking
• Hot mitts (the oven gets very hot)

Optional Activities

My students also used the oven project to learn about following directions, third world countries (fuel resources, economy, etc.), solar power, scientific method, measuring temperature, measuring ingredients, figuring cost efficiency (see Solar Cooking Archive FAQ section for cost figures), etc.

Technology resources

Computer with Internet access, or copy of printed instructions for minimum solar cooker from Internet site (below).

Pre-activities

First Activity - Solar Box Cooker

Second Activity - Recording Temperature
Third Activity - Cooking

Activities

First Activity - Solar Box Cooker

Second Activity - Recording Temperature
Third Activity - Cooking

Assessment

First Activity - Solar Box Cooker

Second Activity - Recording Temperature
Third Activity - Cooking

Supplemental information

Building the solar oven takes about two hours. Cooperative groups work well with each group completing either the inner or outer box.

My students cooked nachos, smores, and a simple cobbler. The fruit cobbler is very easy. Put canned fruit in your baking dish, peaches work best. You need to drain these somewhat, but some juice is used for cooking. Then sprinkle on a yellow cake mix. Add a few pats of margarine. Place in the sun for cooking. (We started early around 7:30am and it was ready for dessert after lunch, about 11:00am.)

TIP - Put the oven on a stool or chair. (We found it necessary to put the stool legs in cups placed inside water filled larger cups to prevent the ants from seeking out the food.)

ESTIMATING ENERGY DOLLAR SAVINGS-Solar Cooking Survey

The following survey (formula) was devised as a means of estimating energy dollar savings during the summer months from using a solar cooker.

To complete this survey one needs to make some basic assumptions with regards to cooking times (all times are based on averages as observed in Arizona). For the purpose of this survey a full meal is a main course (meat, fish, or poultry) plus rice, steamed vegetable or other side dish. Assume that an average cooking time of two hours for the oven and one hour for the range is necessary to cook a full meal.

A main dish (meat, fish, or poultry) would thus be a partial meal and require only two hours cooking time for the oven.

A side dish (something cooked on the range) would equal one hour cooking time.

Cookies or a snack would require half-an-hour of oven time.

With these definitions, fill out the section below based on your experience with the cooker during the months of June, July and August.

How many full meals did you cook? ________
How many partial meals did you cook? ________

How many side dishes did you cook? ______

How many snacks did you cook? ______

The formula used for determining energy savings is based on how much energy is saved by not using the kitchen oven/range (cooking hours avoided). The amount of time spent solar cooking does not figure into this equation.

Using the numbers previously assigned for cooking times for the four various types of meals, multiply the number of meals by the hours of oven or range time assigned that category. Make sure to keep the oven times separate from the range hours.

__ (number of full meals cooked) x 2 oven hours = ___ hours oven not used

__ (number of full meals cooked) x 1 range hour = ___ hours range not used

__ (number of partial meals . . . ) x 2 oven hours = ___ hours oven not used

__ (number of side dishes . . . . ) x 1 range hour = ___ hours range not used

__ (number of snacks . . . . . . . ) x .5 oven hour = ___ hours oven not used

Because the elements in an electric oven/range heat up and then go on and off as electricity is needed to maintain certain temperatures, energy is not being consumed during
the entire cooking time. Here again one must make another assumption, and figure that the element is drawing electricity only half the time (other formulas that have been published do not include this step, and therefore the results are twice as high). Add all the hours the oven was not used together and divide this number in half. Do the same calculation for the range.

___ total # hours oven not used (full, partial and snacks) divided by 2 = _____

___ total # hours range not used (full, side dishes) divided by 2 = _____

Take the number of hours the heating element for oven and range were not used and plug them into the following equation:

{# of oven cooking hours avoided x 3.2 kW + # of range cooking hours avoided x 1.2 kW} = _____kWh

This equation allows one to determine the number of kilowatt hours saved. To calculate how much money this is equal to one must now take this number and multiply it by the amount the utility company charges its customers per kilowatt hour. In Arizona the average rate is .10/kWh. Thus, the next step would be to take the number of kilowatt hours saved multiplied by the cost.

_____kWh x $0.10/kWh = $ _____

With air conditioning, one earns additional savings. It is estimated that for every dollar spent on cooking (oven/range), an additional $.50 is required to cool and dehumidify an air conditioned home. Solar cookers not only use no electricity or natural gas, but they don’t heat-up the house. The following formula will determine the total dollars saved (cooking and cooling). Enter the amount saved by solar cooking in the first blank and multiply by 1.5. The number 1.5 represents $.50 in cooling cost for every dollar spent on cooking. The answer is the amount of money saved in summer by solar cooking.

$ _____ x 1.5 = $ ______

This is the amount saved by solar cooking during the summer. However, this formula does not apply to solar cooking in the winter time, because the heat from the oven and range could actually lower the heating bill. (from Solar Cooking Archive, June 1996)

Related websites

Solar Cooking Archive - Minimum solar box cooker http://solarcooking.org/minimum.htm

Also of Interest is the Solar Cooking Archive FAQ area http://solarcooking.org/solarcooking-faq.htm

Go to the Documents section at http://solarcooking.org/ for more information.

Comments

This project is limited only by your imagination. It can easily be used across the curriculum, employing mathematics, language arts, reading, etc.

This activity is not limited to elementary grades, but could be used by younger students all the way through twelfth grade and beyond.

The web links were updated 11-02-01.