Kitchen in the

Therese Peffer

We've all heard the saying about too many cooks in the kitchen. But what happens when you move your kitchen into the sun? You get a myriad of solar cooker designs, great food, and lots of fun in the sun. We found this out recently at Home Power's 2nd Annual Solar Cooking Contest.

Last February, we offered a challenge to our readers: design and build a simple, cheap, and easy to use solar cooker that works well. The rules were simple: the cooker had to cook, meaning it should boil water. The cooker should use common tools and materials appropriate to your area. Durability and easy duplication would score high points.

And our readers responded. We received twelve cooker designs for the contest. Of these twelve, three contestants sent their cookers. Two cookers arrived at the contest with their designers. We built three designs for a total of eight entries in the contest. (We built the designs appropriate to the contest — original designs that were easy to duplicate with complete instructions).

The day of the contest

Saturday, July 31, dawned clear and bright — a beautiful day for the cooking contest. By nine am, solar cookers covered a fair portion of Camp Creek campground. Besides the eight contestants, we had eleven other solar ovens smiling at the sun. Jim Shoemaker from Redding brought his cardboard and foil Sun Star type cooker. The Solar Man himself, Phil Wilcox, brought two solar ovens. One small commercial cooker, a Sunspot, could easily fit into a backpack; the other design was part of a U.S. Air Force survival pack in the '50s! Yes, solar cooking has been around for awhile. We also had four Sun Ovens, a Sun Chef, and three other homemade models cooking ribs, peach cobbler and other tasty goodies.

By ten o'clock, we placed a cup of pre-soaked pinto beans and a cup of rice in each of the contesting cookers. One result of having this number of solar cooks — you get an incredible variety of cookers! Each cooker reflected the designer's carefully spent time, creativity and imagination; no two were alike. Walking around the cookers, you could hear how the cookers sparked the imagination of all those who came. We looked, appreciated, and used other's creations as a stepping stone for our own solar cooker dreams.

The Contestants

Unfortunately, we don't have the space to fully cover the designs for every cooker. What will have to suffice is a brief description, photographs and the designer's name and address (at the end of the article). So take a close look at the photos and be inspired by the ingenuity of the designers! Keep in mind next year's contest As with last year's contest, the first place cooker design is described in full.

The parabolic cookers added a new dimension to the contest — they really cook! Two cookers used parabolic dishes to reflect and focus the sun's energy onto a cooking pot.

Jack Thompson from San Diego, California sent a design that used a cardboard-ribbed foil-covered parabolic dish. A galvanized pipe frame held the dish and cooking pot. Kathleen and Bob-O built this cooker from Jack's plans and "rib" template.

The other parabolic design arrived with David Baty and Cody Brewer, who hail from Berkeley, California. Their cooker consists of a four foot diameter sand & cement dish that rests in an old car tire. They used aluminum flashing for the reflective interior. David and Cody had already impressed us the day before by making espresso in their parabolic cooker. On contest day, their rice and beans kept boiling over and needed additional water a few times. Both parabolic cookers cooked the rice and beans to perfection in less than two hours. This left plenty of sun time for a solar cooker first for all of us at the contest — solar popped popcorn!

Lu Yoder from Albuquerque, New Mexico sent a simple design that used two 2 foot by 3 foot cylindrical concentrators. His plans called for a flexible substrate such as hard plastic, thin plywood or masonite covered with a reflective material, such as polished aluminum cans. The panels were curved to concentrate the sun's energy on a cooking pot that sat on an insulated box on the ground. We made the cooker with masonite and aluminum litho sheets from our local newspaper.

Dan Freeman sent his cooker from his home in Peoria, Arizona. Dan's creative portable design used aluminized bubble pack material (similar to Reflectix) as both reflector and insulation. This material was velcroed to a folding aluminum frame. His cooking box sported a unique curved parabolic-section shape.

We were thrilled to receive an international entry. Rodrigo Carpio from Cuenca, Ecuador sent beautifully detailed designs in Spanish for his rugged, but surprisingly lightweight box type cooker. Bill Battagin and I built the cardboard and plywood cooker from Rodrigo's design. The cooker walls consisted of 2x2 wood frames covered with cardboard and then wrapped in foil — light, sturdy insulation. We screwed the walls together to form a box, and finished the outside with X inch plywood. The plans called for the walls to lie inside the box for storage — in storage mode, the cooker was only half the height! We didn't have the materials to finish the box with aluminum sheeting as per plans, so we painted the outside instead. Quite a weatherproof design. The wide flat interior of this box cooker is especially suited for climates near the equator.

From Las Vegas, Nevada came a cooker designed by Bohuslav Brudik. This clever design used a store-bought rectangular bamboo basket, insulated with cotton batting and rags and covered with cardboard painted black. Bohuslav used plexigass for glazing and fashioned reflectors from flattened honey cans supported by dowels. Simple and worked great!

Peter Pearl drove from Bisbee, Arizona to share his solar cooker design and other great ideas. His compact solar cooker had a black beveled steel interior in a small wooden box with a single polished reflector.

And finally, Jay Campbell, who won first place in last year's contest, sent another original cooker from Albuquerque, New Mexico. He designed the cooker using a washtub, insulated with straw, with a box interior. Jay made foldable reflectors of foil-covered masonite. The cheery green cover added to the festive atmosphere at the contest.

The envelope please...

Now the toughest job of all. Six judges walked around the cookers to judge the performance, buildability, ruggedness and beauty of design of each entry (see sidebar for details). Anita Jarmann, Sherri Reiman, Selina S-Wilcox, Karen Perez, Kathleen Jarschke-Schultze, and Dan Lepinski spent a few hours studying the cookers, sampling their fares, and marking numbers on their detailed sheets. Most cookers had no problem with the rice, but the beans presented a challenge. We decided the point system would allow impartial judging. (After sampling the espresso, Karen was a bit biased towards the cement parabolic cooker. As it is, that cooker now resides at HP Central. If you want your own too, see directions on page 34 this issue.)

When the judging was finished and the numbers tallied, we had our winners. Cookers were ranked by total number of points from all judges. Jay Campbell won a Solarex MSX-60 photovoltaic panel for first place with his washtub design. Peter Pearl will be installing a PowerStar 200 watt inverter for winning second place. David Baty and Cody Brewer shared the solar/dynamo radio for winning third place with their cement parabolic cooker. Finally, time to eat rice, beans, salsa, guacamole, hot dogs, ribs, peach cobbler

Judging the Cookers

Each judge carried a judging sheet for each of the eight contestants. The cookers were given points in four categories: Performance, Buildability, Ruggedness, and Beauty of Design. The four categories in turn consisted of two to five subcategories, worth 15 to 25 points.

Performance of the cooker included how well it cooked, high temperature reached, ease of use, and ease of set-up. Each subcategory here was worth up to 25 points for a total of 100 points for this category.

Elements of buildability consisted of clarity of instructions, easy of assembly, imaginative use of materials, amount of tools needed for construction, and common skills needed for assembly. The subcategories here were worth up to 15 points each, a total of 75 points.

In the ruggedness category, points were given for portability, wind resistance, site preparation needed and moisture resistance. Up to 20 points each were allotted for these subcategories for a total of 80 points.

And finally, beauty of design included physical appearance of the cooker and originality of design, worth up to 25 points each — 50 points total. The most points possible from each judge was 305.

While sometimes it can be difficult to assign numbers to different qualities, we think it allows for easy and fair judging since all the cookers were judged in the same fashion. The details of the judging are provided for those of you interested in entering the contest next year. And, (ahem) we've asked Jay to be a judge next year

And now as promised, are the details of the winning design by Jay Campbell.

The Winning Design — the Navahorno

This year, I chose to work with a developing country right in my own back yard. I designed and built a solar oven based on the needs, foods and materials common to the Navajo Nation. This stunning land spreads across 24,000 square miles of New Mexico, Arizona and Utah, and is home to more than 175,000 people. Of the 500+ tribes in the United States, the Navajo tribe is the largest, and their landholdings the most extensive. They were chosen for this project not for their size, however, but for their need.

Despite the beauty of the land, life on the reservation is hard. Much of the tribe has never been on the grid, so

The Winning Cooker!

Jay Campbell, Albuquerque, NM

the concept of going off it is meaningless. Wood and propane supply the primary sources of household energy. The climate and terrain of the Navajos are typical of many tribes in the area. The air is dry, vegetation is sparse and the sun shines brightly. Wood is not available in many areas, so it is hauled in from the distant mountains. The tribal government has been promoting solar electricity for some time now, funding small systems at remote sites, and encouraging members to utilize this abundant resource. They will play a key role in the promotion of this oven.

This project would have been impossible without many consultations with JoAnn Willie, a lifelong resident of the rural Navajo land. She is also a graduate student in Mechanical Engineering at the University of New Mexico. Her combination of skills was invaluable in the development, testing and promotion of this oven. The information she gave on materials, foods, cookware and eating habits was all blended into this design, and its ultimate success is hers to enjoy.

The Oven

The oven is built around several common items in rural Navajo life. The outer box consists of a two foot diameter galvanized washtub, commonly used for washing kids, clothes and produce. When they no longer hold water, they are used to feed animals, store wood, and haul whatever needs hauling. These are truly a ubiquitous item in daily living. They are common, abundant, durable and used ones can be found for next to nothing.

Solar Cooking

Materials and Tools for Jay's Navahorno



One 2 foot diameter washtub

6.5 ft. old garden hose

1/10 bale straw

Two small hinges with screws wood saw measuring tape paintbrush hammer razor knife

C clamps also leather strips, white glue, 3/4 in. nails, and aluminum foil

The insulation used is straw. The dry land doesn't provide sufficient grass for grazing, so hay, alfalfa and straw are widely used for fodder. This oven requires about X0 of a bale of straw, costing about a quarter.

The inner box is sized around the most common types of cookware — enameled steel stew pots. The volume is large enough to feed a family of six. All other materials are made from commonly available items, down to using leather for hinges and weatherstripping. A piece of garden hose, split lengthwise, is used to seal the inner and outer boxes together.

The collapsible reflectors reduce storage space requirements when not in use. The exposed surfaces are either painted or galvanized, helping to assure a long life. For outdoor storage, however, a cover would be recommended. A door on top swings open for access to the hot section. The reflectors are mounted securely to the door, and have withstood winds of up to 30 mph. The leatherwork is oiled, to protect it from the elements. The colors of this oven represent something the Navajos are world famous for — their turquoise and silver jewelry.

A set of cardboard risers is included to size the cooking space for the cookware. The appropriate riser is placed into the oven, and then covered with a black cardboard square. This way, the food can be raised to the hottest part of the oven, regardless of the cookware.

The highest temperature achieved was 330°F (165°C). The time required to boil one liter of 20°C water was 56 minutes at this elevation (about 6000 feet). The total cost as built is $10.83, assuming a used washtub. A new one would add about $10 to that price. About 6 hours was spent on the actual construction; this could be reduced significantly for any future copies.


Gather tools and materials. Measure and cut wooden pieces (right). Put together the inner box, top, glass frame, and reflectors, then assemble these together.

Cut the following out of plywood:






0 0

Post a comment