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Background

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. The opportunity to work with Bart Orlando means that this project can benefit from innovative design that comes from years of experience. It is built mostly from salvaged materials as to not contribute to consumption.

Literature Review

http://solarcooking.wikia.com/wiki/Compendium_of_solar_cooker_designs

http://solarcooking.org/ http://www.fsec.ucf.edu/en/research/solarthermal/solar_cooker/documents/reflectivematerialsreport.pdf

Criteria

These are the criteria that the project was designed to meet.

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. 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 their shape, they require constant tracking in relation to the sun (adjustments about every 15 minutes.) However, they have the advantage of being able to reach higher temperatures than the other cookers due to the precise focus created. So there is some trade off.


Fun math stuff

  • In math, a parabola is a conic section with the graph (y=x²) on a Cartesian plane. If that 2-D image were to be "spun" around the origin in the 3rd dimension, the resulting shape would be a paraboloid, the shape used by this cooker. Both parabolas and paraboloids have the effect of concentrating energy waves to a point known as the focus. There are numerous examples of parabolas in the natural world[1].
  • [2] is a great tool for watching incoming rays focus to a point on a parabolic graph.
  • On a typical day of full sun, it is commonly approximated that a flat surface facing the sun will receive 1000 Watts of power per square meter. The chair is approximately 4 feet in diameter and 18 inches deep. To calculate the surface area of a paraboloid requires calculus, which I do not know, but I can surmise that the combined area of the 2-D triangular facets its close.

Times reflectivity of anodized aluminum. Should equal the amount of power in watts. Convert that to joules, and then the average output of a stove. 40 minutes to cook rice = natural gas saved.

  • A deep focused parabola is one that contains the focus within the form. A shallow focus parabola projects the focus outside of the form. For this reason, deep focused parabolic cookers are much safer than shallow because they don't project balls of incendiary light outside of the rim plane.

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 possible the food, depending on the design), stable enough to face moderate winds, yet 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, or be fabricated especially for the cooker. or utilize a pre-existing paraboloid (as in this case).

In this design, a used Papasan Chair provides a sturdy lightweight backbone without having to purchase new materials. This method is not available in all areas of the world, it is possible that old satellite dishes to provide cookers for a significant part of the population.

Reflector

The reflective surface itself can be Mylar, glass, or steel, aluminum, each varying in weight, price and availability used. sometimes a thin metal frame is built around a single piece of metal that is the reflector.

====Food holding device==== - could be a cross bar, or suspension. suspension is much easier to integrate into a device that also functions as a chair. The suspension mechanism is a breeze to manufacture, all that is needed is bamboo poles, and a discarded inner tube. Poles should be at least 1" thick to ensure stability and longevity.

Suspension

3 possiblities

  • hot pot by Gaiam. unfortuntely, this costs $99 as the hotpot cannot be purchased from the company without also purchasing a small solar cooker. This exemplifies a good solar
  • gallon sized tin can + tempura paint- good for testing, though it may possibly off-gas small amounts of toxic chemicals. avoid this by filling the tin can with water, placing your food in a small or medium sized mason jar (with lid) inside of the tin can, and then cover the tin can with foil. This will use the double-boiler effect and not toxify your food.


3' feet chain mason jar tinfoil or cover for tin can

  • bike rim

bike rim with hooks at 120 degree angles. This is measured by simply measuring a length of string to fit the circumference of the rim and then folding the string into three equal lengths. These lengths now measure to one third of the circumference. Re-fit the string to the rim, measuring off

Food Holding Device

PCSC - pyrex.jpg Table for reflector materials

[Image:PCSC - pyrex.jpg| A homemade insulated cooking vessel from Solarcooking.Wikia.com]

Implementation

1000watts/Msquared X area of cooker. (math)

Always over-build

Tied in back

Bike Rim Suspension for Frying Pan - Picture

Ideally-

The HotPot cooking vessel consists of a dark pot suspended inside a clear pot with a lid

Safety

  • As with any type of concentrated energy this has the potential to be dangerous and must be respected. Solar cookers can easily reach temperatures above 450 degrees Fahrenheit. Care must be taken around small children and animals, especially when hot food or liquid is suspended from a tripod.
  • Solar Cookers have the potential to start fires if left unattended in the sun. This is easily avoidable with this project, just put the cushion on when the Cooker is not in use.
  • Be SURE to use SUNGLASSES with UV protection when cooking/testing/adjusting your cooker! Concentrated sunlight is even more damaging to the eyes than the regular kind... And if you are wearing cheap sunglasses that only protect against visible light, you will be more comfortable than usual when staring at concentrated UltraViolet radiation that you can't see. This radiation is even more damaging to the eyes than visible light. UV protection!!

Cost

Papasan Chair - Donated

4 X 8 Anodized Aluminum Sheet - Donated*

Ball of Hemp Twine - $3.50

Pliers - borrowed

3 Bamboo poles sized 8' by 1 - mad river garden supply - $3

9' Length of chain - ace hardware - $9.00

1" long 5/16th bolt/nut - donated

1 bicycle inner tube with puncture - donated

1 small container Citra-Solv natural de-greaser - $3

1 gallon size tin can

pot lid - free

(make table)



  • Notes on reflector

From working with Bart Orlando, I had the opportunity to

Discussion

The Bamboo + bike tube = awesome stand Another question was if the chair was a perfect parabola. 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. Bart says that a close enough to cook with. though focus is a little wide.

Because of foggy/cloudy Arcata life, testing opportunities were limited, and solar technology in general become more of a challenge. 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.

External Links

http://solarcooking.wikia.com/wiki/Compendium_of_solar_cooker_designs An Excellent Overv [[Image:Example.jpg]]

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