Project data
Close up of pot holding gimble made from small bike rim and coat hanger wire. Is baking cookies in a small pot on a black dish. Photo Credit:Bart Orlando

The word "Synergy" comes from the Greek words for "to work together". This project combines the existing parabolic shape and comfortable sitting cushion of the Papasan chair with the natural-source energy utilization of the solar cooker. My hope was that, in the spirit of synergy, the whole would be greater than the sum of the parts and that people may find the idea of owning a solar cooker more practical if they can also sit and read a book in it when its not in use. Compared to the traditional mono-functional Parabolic Solar Cooker, this project serves as a chair when not in use, which saves space and is less of a fire hazard than the traditional Parabolic Solar Cooker. It is built mostly from salvaged materials as to not contribute to consumption.

### Bart Orlando

Local Solar Cooking expert and Appropriate Technology innovator Bart Orlando inspired and co-created this project. Bart offered his vision of the papasan chair solar cooker as a class project when he came to speak in front of the class at the beginning of the semester. Bart has been working with students in the Humboldt area for more than 15 years, building and designing pedal powered and solar powered prototypical educational displays. Working with Bart means that this project had the benefit of the innovative design that comes from years of experience. For more information on Bart's projects, visit these [1], [2], and Parabolic basket solar cooker web pages. Bart Orlando's main web page students wishing to start a project with him is entitled Projects With Bart.

Bart with 8' dish.

## Literature Review

• Daniels, Farrington. Direct use of the Suns Energy. New Haven and London: Yale University Press, 1964.

This book contains a brief overview of the applications and constructions of parabolic solar cookers. Also includes information of the many other ways to cook with the sun.

• Halacy, DS Junior. The Coming Age of Solar Energy. New York: Harper and Row, 1963.

Contains an interesting historical overview of small solar projects, including parablolics.

• McDaniels, David K. The Sun, Our Future Energy Source. New York: John Wiley and Sons, Inc, 1979.

A more technical look at the utilization of solar radiation, as well as solar-thermal applications.

Though it was heartening to see that there was literature on solar power, the books I found were not very helpful for this project. What was helpful was these links:

## Criteria

This project was designed with the following Criteria in mind:

Time – Must be able to be designed and constructed within the timeframe of one college semester, or about 4 months of part time labor.

Budget – No set budget, however the more materials that can be salvaged or easily acquired by most people, the better.

Durability – The project must be able to withstand periodic exposure to the elements, especially sun, over the course or years. Also, sitting in the chair must not damage the reflectors.

Portability - The device should be lightweight so that one person could move it without toil, and compact enough to be towed via bike trailer. Rattan, the fiber that many Papasan chairs are made from, is reasonably light weight- making reflector material the key issue in terms of weight.

Design - Should incorporate new improvements or previously not thought of innovations to the solar cooker plan. Should be stable in mild wind.

Synergy/Integration - Should be a multi functional device, capable of easily purifying water as well as cooking food, igniting paper or grass when needed, and still be able to fit easily into an everyday household setting.

Level of embedded energy - Materials should be found or salvaged so that it can be shown that this can be built without industrial equipment.

Ease of use - If multiple parts are to be used, then they should be safe, employ intuitive design, and not require the use of tools for operation.

## Design

### Solar Cooker Background

A solar cooker is used to concentrate sunlight onto a pot or dish. It can be used to bake, fry, make popcorn, cook rice, light fire, sterilize and boil water. This has potentially important applications in sun soaked areas where fuel for cooking is scarce, or where women must travel farther and farther from their villages to gather wood as fuel becomes more scarce. If solar cooking catches on it, it would become a new style of outdoor recreation similar to the barbecue, but one that is directly connected to the world at large (ie the sun) and has no carbon footprint (if people reused their plates and silverware).

There are several shapes a solar cooker can take on, from box-like to parabolic, spherical, funnels and plane mirrors. Each form has different pros and cons in terms of construction, durability, materials, performance, etc. This Wikia page has pictures of all sorts of solar cookers.

### So Why Parabolic?

Parabolic cookers seem to be heavier, and more expensive than the other types of solar cookers. Due to the fact that they focus light to a small area, they require constant tracking in relation to the sun to be effective(adjustments about every 15 minutes.) However, they have the advantage of being able to reach higher temperatures than the other cookers due to the intensity of the precise focus created. Other solar cookers, such as solar ovens use a greenhouse effect to trap heat in an enclosed area, whereas parabolic cookers actually concentrate the sunlight from a larger area into a smaller area.

### Elements of a Parabolic Solar Cooker

#### Frame

This is the backbone of the cooker. It must be:

• Strong enough to support the weight of the reflectors (and possibly the food, depending on the design)
• Stable enough to face moderate winds without the risk of spilling hot/boiling food/liquid on the ground and people
• Light enough to allow frequent adjustments to track the sun.

The frame can be constructed in a variety of ways; it can be cast from a mold, built from salvaged materials, such as satellite dishes, and even blackberry bushes, or be fabricated with new materials especially for the cooker. It can also utilize a pre-existing paraboloid (as in this case).

Papasan chair with cushion removed.
• In this design, a used Papasan Chair provides a sturdy, lightweight, somewhat-stable backbone without the requisite of purchasing new materials. This design method is not available in all areas of the world, butRattan, the material this papasan chair's frame is made from is widespread throughout Asia, Africa, and Australia.

#### Reflector

The reflective surface itself can be a variety of materials. Sometimes a thin metal frame is built around a single piece of cast, polished metal. This table compares different aspects of potential reflectors for the papasan chair solar cooker:

Polished Anodized Aluminum ~95% Light ~$7/square foot Reflective, lightweight, can be salvaged, structurally durable, easily flexed and shaped Easily scratched, not super cheap Mylar >98% Super light$30 for a 4'x'50 roll Super reflective, super light, super cheap Not good at standing up to the elements, forms 'bubbles' if glue starts to give, requires a rigid backing
Aluminum Foil 88% on bright side Super light $3.29 for 1.5'x70' roll Extremely cheap and widely available Not so reflective, corrodes when mixed with acidic juices, structurally weak, would only last one or 2 sessions Can lids 70-80% (my estimate) Light FREE Widely Available, effective, salvageable, did I mention free?! Not super reflective, non-uniform shape is labor intensive to use Acrylic Mirror 99% Medium/Heavy$78 for 1'x4' plane Very reflective, nearly unbreakable Comes in plane, likely very difficult to fit to parabola and still maintain reflectivity, super expensive
Glass Mirror 99% Very heavy At least $100/square foot Super reflective, widespread- meaning it could be salvaged Very expensive new, comes in rigid plane- could be broken to fit paraboloid in mosiac in exchange for a precise focus Astro-foil 76% Light$37 for 1'x50' roll Relatively strong Not so relective
• Many potential materials with high reflectivity and strength are only available by special order from industrial companies. Though I have not tried to order or to ask for a donation of these fine products, the manufacturers usually deal in bulk.

In addition, I am not sure a special-order industrial super-reflector meets this projects criteria of salvageablility and wide availability. That said, a bulk roll of high quality reflective material may be a wise investment for the aspiring do-it-yourself solar technician.

## Discussion

• The Bamboo + bike tube makes an awesome adjustable tripod. Bart mentioned that if we were to use 2" X 10' or bigger poles, the tripod could also function as a tee-pee.
• The chair we used is not a perfect parabola. This means that the focal area is more of a cylinder than a ball, but this may vary from chair to chair. Its possible to graph a parabola and then overlay the graph on a photograph of the chair to see if they line up. However, one would have to guess the coefficient of the parabola. However, this project was a success anyway as the concentrator gets hot enough to to cook with.
• Because of foggy/cloudy Arcata life, testing opportunities were limited, and solar technology in general becomes more of a challenge. However, I don't think this is a bad thing! Maybe it means there are less realistic uses for solar up here, but it also means that we must refine the technology to get better results.
• Actually cooking takes some time to perfect, and is an art unto itself, but in the end its very much worth the effort.

### Does this meet the criteria?

Yes and no, but mostly yes. The hemp, the rattan, the tin can, the bamboo, the discarded bike tube- all super Apprppriate in my mind. These are all sustainable, salvageable or re-used. Then comes the Anodized Sheet of Aluminum Alloy fabricated with high powered industrial machinery. Is that Appropriate? In the absolute? No. In the context of an carbon saving device in a world mostly run on fossil fuels? Yes, I think so, it is Appropriate in that it is a definite step in the direction of do it yourself low-impact living.

Time – Done on time

Budget – Yes, total costs were $15. I was lucky enough to have both chair and sheet metal donated. If one were to purchase a used papasan chair and a used piece of metal that could be cut for free, it would have cost up to$50 more. Still relatively inexpensive.

Durability – Yes. Should last at least 5 years.

Portability - Yes. Easily carried short distances by one or two people, transportable by bike trailer or car.

Design - Yes. It works. Could use a little refining with time.

Synergy/Integration - Yes. Works great as a chair and as a cooker.

Level of embedded energy - Mostly yes. Sheet metal is used, but is a potential salvageable material. Plasma cutters use lots of energy, but not much plasma cutting is required.

Ease of use - Yes. People can be taught the basics in under an hour by somebody who knows what they are doing. Learning curve of a few cooking sessions.