Solar Cookers Home Econmics: The Family & Technology

Kendra Wack & Celine Vandale

Solar Cooking

Jewish families celebrate Passover to commemorate the freedom and exodus

of the Israelites (Jewish slaves) from Egypt during the reign of the Pharaoh Ramses

II. When the Pharaoh Ramses II freed the Israelites, they fled so quickly that there

wasn't time to bake their breads. Instead the Israelites packed the raw dough, which

they quickly baked in the hot sun into hard crackers called Matzohs as they fled

through the desert.1 The exodus of the Israelites took place over 3000 years ago, but

the Israelites were not the first to harness solar power for cooking, neither were

they the last. Solar cooking has had a long rich history and has important

implication for the future. Solar cooking is an important link in understanding the

sun’s power, is a sink of innovation and technology, is widely applicable around the

world, has social, economic and ecological benefits, and is the answer to some of the

world’s biggest natural resource shortages. Although, solar cooking is an industry

that has yet to be revolutionized into an efficient home appliance, therefore, there

are many avenues for innovation and technological advancement to be explored.

Horace de Saussure coincidently created the first solar box cooker, although,

because cooking food was not his objective he failed to revolutionize the solar

cooking as an efficient home appliance. Horace de Saussure, “set out to determine

how effectively glass heat traps could collect the energy of the sun.” 2 Horace de

Saussure placed five consecutively smaller open bottomed glass boxes within each

other on a black table, in which he placed a piece of fruit. When this miniature five

walled green house was exposed to the sun, each consecutive glass chamber trapped

warm air and thermal radiation, which are by products of light energy being turned

1 http://www.holidays.net/passover/story.html2 http://solarcooking.org/saussure.htm

into heat. Consequently the innermost glass box became the hottest, a recorded

189.5 degrees Fahrenheit and Horace de Saussure successfully cooked fruit within

this box.3 Cooking was only an experiment used by Horace de Saussure to

understand his greater goal, which was how effectively glass heat traps could collect

the energy of the sun. Although, Horace de Saussure realized the practical

application of his heat trap. Horace de Saussure stated, “someday some usefulness

might be drawn from this device . . . [for it] is actually quite small, inexpensive, [and]

easy to make.”4 Horace de Saussure was correct in stating that solar cooking is

useful, but contrary to his advice the solar cooker failed to be revolutionized into an

efficient home appliance.

In 1976 Barbara Kerr and Sherry Cole developed the simple cardboard solar

box cooker, which ultimately led to the creation of Solar Cookers International, one

hundred years after the end of the industrial revolution.5 Although, examples of

active and passive solar systems like Kerr and Cole’s, were present at conventions

known as “World’s Fairs” during the Guilded Age and Progressive Era, these designs

have only begun to be revolutionized in the mid 20 th century. Kerr and Cole set out

to create solar box cookers to emphasize simplicity in design and construction, to

use appropriate and available materials, to be dependable under a wide variety of

conditions, and to utilize recycled materials and minimal costs.6 Although, they

understand why the solar cooker did not benefit from the industrial revolution,

according to Kerr and Cole, Engineering approaches and available literature often

3 Ibid. 4 Ibid. 5 http://www.solarcooking.org/newsletters/scrjul03.htm#Sport6 http://solarcooking.org/kerr.htm#INTRODUCTION

emphasize maximum solar collection at the expense of simplicity, functionality,

appropriate materials and ease of use. Such designs do not lend themselves to being

used as routine home appliances, nor can they be built without special tools and

skills.7 According to Kerr and Cole, solar cookers have not been revolutionized

because engineers have ruled out the possibility of solar cooking being utilized as an

efficient home appliance.

The contemporaneousness of Kerr and Cole’s invention tells us that the

revolution of the solar cooker is only just beginning, that there are many

technological innovations to be explored before solar cooking can be ruled out as an

efficient home appliance. Currently there are three types of solar cookers that are

being used today, the box cooker, the panel cooker and the parabolic cooker. As

Horace de Saussure documented, a solar box cooker works because the sunlight

entering the solar box through the glass or plastic top is transformed into heat

energy when it is absorbed by the dark absorber plate and cooking pots. This heat

input causes the temperature inside of the solar box cooker to rise until the heat loss

of the cooker is equal to the solar heat gain. Temperatures sufficient for cooking

food and pasteurizing water are easily achieved.8 Roger Bernard developed the

panel cooker, which reflects light into a glass jar containing a cooking pot. Unlike the

box cooker the solar panel cooker does not trap as much thermal radiation or heat

energy, although, the direct heat from the sun is more intensely focused on the

cooking pot. The solar panel cooker is a middle ground between the solar box

cooker and the parabolic cooker. Parabolic cookers are large concave discs that

7 Ibid. 8 http://solarcooking.org/sbcdes.htm

reflect and focus large amounts of light directly onto the bottom of a cooking pot,

but they must be in direct sunlight.

Modern engineers understand why solar cookers have advantages and

disadvantages, but there remains room for innovating an efficient home appliance.

Solar cookers utilize three basic natural laws: (1) when solar radiation (sunlight)

strikes a dark surface it changes to infrared radiation (heat), (2) when light falls on

light-colored or shiny surfaces it reflects and so can be directed to where it is

needed. (3) Solar radiation (sunlight) passes through a transparent window easily,

but infrared radiation (heat) does not, so heat can be trapped.9 Using these three

natural laws solar cookers can maintain temperatures between 250 and 300

degrees Fahrenheit. Food cooks at a mere 190 degrees Fahrenheit and water boils at

212 degrees Fahrenheit, therefore, solar cookers are capable of producing the same

effects of much less efficient, but more popular home appliances such as ovens and

stoves. As we approach the next millennium, such resources as coal, oil and gas,

which is formed from solar grown organic matter and are not renewable, will be

consumed in a tiny fraction of the millions of years required for their formation

leading to resource depletion. Although, solar cookers will always remain a diffuse

resource that will outlast all the fuel resources we now rely on. Therefore, much

more innovative and technological energy must be put into solar cooking to make it

more efficient as a home appliance.

Advocates of solar cooking argue that solar cookers are efficient home

appliances and therefore deserve technological revolutionization. These advocates

9 http://solarcooking.org/kerr.htm#INTRODUCTION

believe the efficiency of the solar cookers is tied to their economic, social and

ecological benefits. Although the economic impact of solar cookers varies between

regions, solar cookers save wood and are an alternative to cooking fuel shortages.

Socially families benefit from solar cooking because they can leave food in the solar

cooker for an infinite amount of time in order to do more economically productive

activities, such as working farming or housework.10 Solar cookers also allowing

families to reduce the amount of time and energy spent collecting or working for

fuel and also encourages health by pasteurizing water making it more sanitary for

consumption and cleansing. And furthermore, solar cookers have an ecologically

beneficial impact by allowing more trees to grow and straw that might have been

cooking fuel to become fertilizer.11

Why has solar cooking not been revolutionized? Historically, solar cooking

advocates think of solar cooking as a simple, low-tech, inexpensive cooking strategy.

These advocates support this stance by stating that, Millions of poor people around

the world, however, still cook over a smoky fire everyday. To find wood for the fire,

they have to walk many hours everyday. Other poor city dwellers don't have access

to wood, so they have to spend up to half of their income on cooking fuel. These

people could never afford an oven made of high-tech materials.12 Contrarily, solar

cooking needs to become more high-tech and revolutionized, in order to replace

conventional cooking appliances. This is important because in some places simple,

low-tech, inexpensive solar cookers may help to offset the expense of fuelwood

collection and cooking fuel costs, but it does little to cut down on the use of non-10 http://www.solarcooking.org/newsletters/scrjul03.htm11 Ibid. 12 http://solarcooking.org/solarcooking-faq.htm

renewable resources in developed countries, like the United States. The United

States consumes the majority of the world cooking fuel and therefore produces a

majority of the pollution. But if solar cookers were revolutionized into high-tech

efficient cookers able to compete with contemporary oven and stoves, that would

make a huge difference in the United States’ overall consumption of natural

resources.

Cooker Design

Solar cookers have the capability to cook food using the suns rays to heat the

oven. The design of the solar cooker has evolved to become more sanitary as well

more efficient. (Wikipedia) Solar cookers are environmentally friendly as well

economically friendly as a cost effective way to safely cook food especially in third-

world countries. Solar cookers can be handmade or bought for commercial cooking

use. (Solar Cooker) Handmade solar cookers are most widely used in lower and seen

as the most popular way to construct a solar cooker. (WikiHow)

Parabolic Cooker

When constructing a solar cooker, there must be thoughtful consideration

put into the use and durability of the cooker. These cookers are shaped into a wide

fan, or bowl like surface area, this must be covered to make a shiny surface to catch

the suns rays. The machine itself may have to have a waterproof cover over the

cooking surface; cooking time may have to be considered as well. (Solar Cooker)

Cookers with larger open reflectors, such as a parabolic cooker quickly and

effectively cook the food. They are not waterproof if not

covered properly. Parabolic cookers are the quickest

solar cookers; they are also the most powerful.

(Inspiration Green) These cookers have the capability to

fry foods. Disadvantages of the parabolic cookers

include having to turn the cooker to ensure that the sun directly hits the panels. This

type of cooker is extremely breakable, because they are most often made of

cardboard. (Solar Cooker) The extreme heat from this type of cooker can be

damaging to the eyes, as well as to harsh to cook certain types of food. (Inspiration

Green) The main advantage of the parabolic cooker is the cooking time; where as

the demanding nature of the cooker may send people towards another cooker. This

cooker is especially fussy because it cannot be used during a windy time, or when

the sun is low. Parabolic cookers must be used in hot climates to ensure the food,

and the surface area maintains and reaches a high enough temperature.

In a classroom situation, a parabolic cooker would not be suitable because of

the cooking time. If parabolic cookers are not covered properly they do not retain

their heat, thus lengthening their cooking time. Although, if constructed properly

with a good quality cover on the cooker these cookers can work at a faster pace.

Parabolic cookers because of their wide spanned cooking area can get extremely

bright and hot to the touch, therefore may not be a suitable cooker to use around

young children or in the classroom.

Box-Style Cookers

Box-style cookers, are by far the easiest to use, and make. These cookers can

cook multiple pots at one time as well, box style cookers are the easiest cookers to

maintain and use. (Solar Cooker) These cookers do not need to be turned during

use, and can be made to any desired size. With the

design of this cooker safety is a large feature,

especially around younger children. (Inspiration

Green) The materials used in this type of cooker

can be as simple as two cardboard boxes and

tinfoil or as elaborate as custom built insulated boxes. These cookers are sturdy

although the larger sizes of these cookers are not easily transported. (Wikipedia)

The box cooker is appropriate the school systems because the materials

needed to build one are easy to obtain. This type of cooker is simple to construct

and the low-risk design helps prevent accidents and burns.

Panel Cookers

Panel style cookers are the most easily transportable cookers; they can be collapsed

and stored. Panel cookers are simple to construct and materials can easily be

obtained. (Solar Cooker) These cookers work best when the temperature is mild and

the sun is not overhead. These ovens can be turned directly

into the sun or slightly away for a higher cooking

temperature. (Wikipedia) This style of cooker has a lengthy

cooking time; as well these cookers cannot be made

waterproof. (Inspiration Green) The materials for this type

of cooker can be as simple as cardboard covered with

tinfoil. (Solar Cooker) Panel cookers are large panels that are constructed in a semi-

circular shape to reflect the sun into the cooking surface. This suns rays that are

reflected into to cooking surface then heat and cook the food that is inside.

There could be use for panel cookers in school because they are easy to

assemble as well as store. The panels can be taken down and the cooker can be laid

flat to store. The construction of panel cookers can be quick and easy for students to

construct. These cookers often are successful although they would need lots of

supervision because of the danger of them. These cookers reflect off bright rays as

well as reach very high temperatures that can cause burns. Therefore must be used

with care, or older students who can properly understand the dangers of solar

cooking.

Description of Cooker Built

Our cooker was a box cooker; the box cooker that we constructed also had

elements of a panel cooker made with the lid flaps from the box. The solar cooker

constructed had layers of household insulation covered with newspaper. These

layers were secured down with large styrofoam meat containers. The cooking

surface of our cooker was made out of a tinfoil tray that was painted black so it

would absorb and attract the heat. Our cooking surface was covered with a glass

cover that helped seal the heat inside to cook the food. The outside of the cooker

was wrapped in pink duct tape to improve the appearance of the cardboard box

underneath. We used a thermal space blanket out a car safety package. The blanket

was secured down with silver furnace ducting tape to ensure we kept the entire

area as a reflector.

HED 313 Solar Cooker Student Evaluation/Reflection Guide Sheet

Name(s)___Celine Vandale & Kendra Wack____

Design Questions

1. Where did you find the design for your cooker?

We found the design for our cooker, our cooker was originally constructed as

a pizza box cooker, although we found that it was not efficient, nor was it visually

appealing. We decided to then go with the box cooker to ensure that it was of good

quality and sturdy for transporting.

2. When you built the cooker, did you include all the components specified by the

design plan?

We used all the components in our design and added more. This cooker

featured panel reflectors to increase heat and reflection capability.

3. Did you make any modifications to the original design and if so, what were they

and why did you make the changes?

We made the modification of adding a thick glass cover on our surface area,

this helped keep the heat enclosed in the cooking area.

4. What effect does wind have on your design?

The wind had very little effect on our design because our cooker was heavier

due to the extra insulation and glass top that sealed the cooking area.

5. Was your solar cooker designed to be economical? Durable? Safe? Portable?

Aesthetically pleasing? Other?

Our solar cooker was designed to be all of the above. Our cooker was

economical because it cooked food quickly and easily. It was durable because of the

box design that we chose to use, also because of the duct tape covering we had on

out cooker it made it more durable. The cooker we made was extremely safe

because the reflections of the sun were reflected downward as well, the heat was

contained within the cooking area. Our cooker was not easily transported although

was able to be transported by foot. Our cooker was also aesthetically pleasing, with

much thought put into the design and construction of the box.

Cooking Questions

1. How does your solar oven cook the food?

Our solar cooker cooked the food by reflecting the heat from the sun

downward and capturing the heat in the cooking area with the glass door. The heat

from the sun cooked to food.

2. Give an example of how a recipe might have to be modified so that it can be

cooked in the solar oven.

We modified the recipe by using mini-marshmallows in our solar oven. This enabled

the surface area of the food to be larger, therefore decreasing cooking time, and

increasing success.

Classroom Use Questions

1. Would the materials that you used to construct your cooker be available to

students building cookers as a classroom project?

In a home ec or practical and applied arts room there would be materials to

make a solar cooker similar to ours. The availability for the silver ducting tape,

space blanket, and glass cover might be difficult to find. However, students could use

tinfoil, clear packing tape, and a glass lid from a pot.

2. What safety issues would you have to clearly explain to your students?

I would have to explain the safety issue of heat and burning, along with safety

dangers to their eyes with the bright rays from the reflecting portions of the cooker.

3. List 5 concepts you could teach to your students using a solar cooker construction

project.

1) Proper cutting and measuring (Practical and Applied Arts)

2) Alternate methods of cooking (Home Economics; Food Studies)

3) Alternate energy sources (Science)

4) Essay portion (English)

5) Group Work and team building

Overall

1. Overall, what went well with this project?

I feel that this project went quite well because our solar cooker was

successful.

2. Overall, what would you change if you were to do it again?

We would change the initial construction of the box. It was difficult to use

although, as everything is it was a learning experience and we wouldn’t change

anything.

3. Overall, what would you change if you were going to assign it to your students?

If I were to assign the solar cooker project I would put students in groups and give

them class time to finish the assignment. I would keep the reflection portion of the

assignment to improve the project further for new classes.

Celine & Kendra’s

Solar Cooker

Field Log #1

Our solar cooker design was originally going to be a pizza box design. This design provided an abundance of instructions on how to make them because they are by far the most popular homemade solar cookers. The pizza box solar cooker was easy to find online as well as they seemed the easiest to make. As we further researched we came to a conclusion that the pizza box oven would not provide enough insulation for our marshmallow to melt to the degree that we had intended.

Field Log #2

We continued to research different ways to construct our solar over. We decided on a box cooker because of the supplies we had on hand. This box was about 12” tall and 12” in length and about 9” inches wide. This box was the box we stuck with although there were many alterations made to it. The original box was fully insulated with household insulation that would be used in walls. And we used 3 separate pans to fully cover the top of our cooker. These pans were silver in color and reflected the light. Saran wrap was used to cover these pans as well; tinfoil was used to wrap the box. This solar cooker did not sufficiently hold heat to melt the marshmallows; it also did not have enough weight to hold itself down if the wind picked up.

Field Log #3

After the first construction of the solar cooker there was major alterations made to it. These alterations consisted of starting from scratch without any previous model to follow. We used common knowledge of hot holding and replica of how an actual oven holds heat. Therefore; we started by using a smaller single tray instead of 3 and we painted it black to make a lower albedo to hold the heat in the tray. We then stuffed the bottom layer of insulation with newspaper, like was instructed with the pizza oven we then covered the newspaper with a bulk ground beef Styrofoam container that was flipped upside down. We then layered the insulation on top of the Styrofoam container and covered it again with a ground beef container. I then cut a hole in a ground beef container and fit the hot holding tray in the ground beef container. The extra space on either side was filled with extra insulation, stuffed tightly and sealed with duct tape.

Field Log #4

We noticed a loss of heat in our first model; we predicted this was because of the saran wrap being incapable of holding heat and insulating the box properly. I bought a picture frame and removed the glass from it, we then used that as our cover of the pan. With the first model we continually had issues with the tinfoil tearing and being difficult to work with. Instead of tinfoil we decided to use an insulating car blanket. This car blanket was easy to work with as well was much shinier and reflective than tinfoil. Our solar over was sealed duct tape, and then covered with a much shinier tape used for sealing heating ducts. We made each of the flaps alterable and did not secure them because of the ever-changing position of the sun. We decided to make the make the outside of the box cosmetically appealing and engaging for students and other viewers. We made out oven look like a retro pink oven with and industrial looking back and a silver window and silver knobs.

Field Log #5

We went out and bought mini marshmallows with chocolate chips and graham wafer crackers to make our smores. Before even trying out these ingredients, we realized that we should probably go out and buy the mini, mini size of these ingredients. We also made sure that our ingredients were very fresh. We decided that this would be the most efficient way to make sure that our smores would cook quickly.

Field Log #6

It was a very sunny day so we decided to go outside with all of our class to test out our solar cookers. We found the best spot to test our solar cooker was in a spot that was very sunny and had no wind at all. The wind this day was a very cold wind and would of delayed our cooking. We lifted up the glass to put our graham cracker, mini marshmallows, and mini chocolate chips inside. We placed two side by side so that we were each able to try them when they were finished cooking. We then waited to see what would happen.

Field Log #7

The time in which we put our smores in the solar cooker was 10:45. We checked on the smores every 5 minutes to see if they were starting to melt. Our smores were completely melted and ready to eat at 11:15. We then took them out and we each ate one; they were delicious. We then thought that we had enough time to make another one, so we did. We were very excited about how our solar cooker worked so well. We agreed that it worked so well due to the fact that it was insulated and constructed so well. This project of the solar cooker was a lot of fun and we both learned a lot about the process involved in making a solar cooker.