Get our free book (in Spanish or English) on rainwater now - To Catch the Rain.

Changes

Jump to: navigation, search

Papasan Chair Solar Cooker

3,026 bytes added, 00:04, 8 July 2012
m
External links
{{305inprogress|May 15, 2008}}
[[Image:PCSC_-_low_setting_front.jpg|frame|center|Ready to cook!]]
[[Image:new_gimble.jpg|frame|center|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 ]]
{{TOCright}}==Concept==
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===
[[Image:PCSC - Bart.jpg|thumb|left|Bart with 8' dish.]]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 technologiesprototypical 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 [http://wwwfriends.humboldtccathsu.educom/%7Eccatbart/pedalpower/inventions/frames_final_htm..htm pedal power], [http://wwwfriends.humboldtccathsu.educom/~ccatbart/solarcooking/parabolic/paraboliccookerwebsection-pg1.htm parabolic solar cooker], and [[parabolic_Basket_Solar_Cookerparabolic_Basket_Solar_Cooker_-_Engineering_305| 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]].
==Literature Review==http://solarcooking*Daniels, Farrington.wikia''Direct use of the Suns Energy.'' New Haven and London: Yale University Press, 1964.com/wiki/Compendium_of_solar_cooker_designs
• http://solarcookingThis book contains a brief overview of the applications and constructions of parabolic solar cookers.org/http://wwwAlso includes information of the many other ways to cook with the sun.fsec.ucf.edu/en/research/solarthermal/solar_cooker/documents/reflectivematerialsreport.pdf
==Criteria==*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:
 
* http://solarcooking.wikia.com/wiki/Compendium_of_solar_cooker_designs - A massive list of different solar projects. Lots of pictures. Good wikia, tons of info.
 
*http://solarcooking.org/ - Good resource over all. Designs, pictures, info, tips, etc.
 
 
*http://www.fsec.ucf.edu/en/research/solarthermal/solar_cooker/documents/reflectivematerialsreport.pdf - An exhaustive, though somewhat disorganized list of reflective materials. The chart in the [[Papasan_Chair_Solar_Cooker#Reflector|reflector]] section is based on this.
 
== Criteria ==
This project was designed with the following Criteria in mind:
'''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).
*'''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 [http://www.appropedia.org/[Parabolic_Basket_Solar_Cooker_-_Engineering_305 |blackberry bushes]], or be fabricated with new materials especially for the cooker. It can also utilize a pre-existing paraboloid (as in this case). [[Image:PCSC_CHAIR_NAKED.JPG|thumb|right|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, but[http://en.wikipedia.org/wiki/Rattan Rattan], the material this papasan chair's frame is made from is widespread throughout Asia, Africa, and Australia.
[[Image:HotPot-cooking-vessel.jpg|thumb|none| The HotPot cooking vessel consists of a dark pot suspended inside a clear pot with a lid]]
*A gallon sized tin can painted with black tempura tempera paint. A wire coat hanger with a paper base can be unhooked from the paper, revealing a perfect holder for a gallon sized can. 2 holes are punctured in the can at 180 degree angles 1" from the top, and the coat hanger is hooked inside. This proved to be a good method for testing the cooker, however the inside of the can may possibly off-gas small amounts of toxic chemicals. To avoid this, fill 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 a matching-sized pot lid (no plastic) or aluminum foil. This will use the double-boiler effect and not toxify your food. This is the most easily salvageable/reusable design.[[Image:PCSC_-_mason_jar_in2.jpg|thumb|left|Using a mason jar inside of a tempura tempera painted can.]][[Image:PCSC - mason far lid on.jpg|thumb|none|Tempura Tempera painted can with pot lid.]]
*A black stainless steel or cast-iron cooking pot with lid and suspension hooks would also be appropriate. No plastic can be present on the pot.
====Suspension====
The suspension mechanism holds the food over the focus from above while the cooker is being used.
We wanted a suspension mechanism that could be:[[Image:PCSC_-_inner_tube_tie.jpg|thumb|right|Top end of suspension with inner tube tied around bamboo and chain.]]
*Easily adjusted
*Lightweight
We went with a tripod constructed of bamboo and a bike inner tube, with a 1/2" width chain for suspension. The bamboo should be a least 1" thick for durability and strength. In addition to being a fascinating organism, [http://en.wikipedia.org/wiki/Bamboo Bamboo] is a choice building material for sustainability.
==Fun Math stuff==* In math, a parabola is a conic section with the graph (y=x²) on a Cartesian plane. If that 2 dimensional image were to be "spun" around the origin in the 3rd dimensiony-axis, 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 single point (or sphere, in the case of a paraboloid) known as the focus. There are numerous [http://en.wikipedia.org/wiki/Parabola#Parabolas_in_the_physical_world examples of parabolas in the natural world.]
*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 and accidentally burn things or people.
* Area of circle in m<sup>2</sup> * 1000 watts/m<sup>2</sup> = Ideal power output in W (m<sup>2</sup> cancel out)
1530 1.53 m<sup>2</sup> * 1000 W/m2 m<sup>2</sup> = 1530W
* Ideal power output in W * Reflectivity coefficient of anodized aluminum = Reality-adjusted power output in W
*Diffusion of light from scratched/dirty facets (Bart estimates that the reflectivity for this project is more along the lines of 90%)
==Implementation==
Since we were designing this project as we built it, our time frame was on the order of weeks and months, but this could feasibly be built in one to two days once all materials have been acquired.
*one piece of paper, black
Materials for the food holding device are not included, because there are several options. To view these, [http://www.appropedia.org/[Papasan_Chair_Solar_Cooker#Food_holding_device|click here]].
===Reflector===
*To cut your reflector from a sheet of anodized aluminum, you will want to first measure the radius of the chair, from the center point to the rim. It is important that the measurement of the radius includes the 3-dimensionality of the curve of the chair. Use this measurement to make triangles with 2 of the sides the length of the radius plus one inch and the 3rd side around 8 inches long. Take care to draw an extra space at [[Image:PCSC - parabolic sheet.jpg|thumb|right| This shows a material-saving layout for cutting the point of sections. Note that the triangle triangles don't terminate at a point, so that a 1/4" mounting bolt will fit through it.[mirror_measure.jpg] This shows a material-saving layout for cutting the sections. ] You may want to measure how many times the 3rd (8") side of the triangle will fit along the circumference of the chair to see how many facets to cut. Since people are going to be sitting on the chair, take care to round any sharp edges to a curve, and to sand any burrs.[[Image:PCSC - shear resized.jpg|thumb|right| Students using a beverly shear to cut aluminum facets.]]
*Once the pieces are cut, gently flex them to fir the curved shape of the chair frame. Aluminum will maintain this shape once bent. First practice bending one to see how breakable it is before bending the rest.
*Now is time to use the drill. Measure in about 1/2" in and down from the corner of both sides of the 8" length of each facet, and drill a 1/8" hole. This is where the string goes to mount the facet.
*Stack all of the facets on top of one another and make a mark on the end piece you made for the bolt. Have someone with a steady hand press down on the facets so they don't slide and drill through the facets with your 1/4" drill bit. This will be easier than you'd expect, due to the softness of aluminum. Slide the bolt through and nut it so that the facets are like a fan.[[Image:PCSC - bolt picture.jpg|thumb|right|The bolt is used to hold all of the facets together.]]
*With the 1/4" bit, drill a small depression into the round circle of wood beneath where the cushion sits in the middle of your chair, so that the facets can sit in the center of the chair.
*Now it is time to spread out the facets and tie them down to the outer rim of the chair with the hemp twine. Be sure that they are flexed to shape of the chair before tying them down so that you can get an accurate parabolic focus later on. [tying[Image:PCSC - aim no shadow.jpg|thumb|right|Note how the facets are tied down to the rim.]]
NOTE: It may be advisable to drill an additional hole 2/3 down the length of each mirror corresponding to where the frame lies under it, so that the mirrors can be tied close to the fameframe. This may facilitate a tighter focus. However, the chair we used was not a perfect parabola and it turned out that '''not''' having the additional ties allowed for a better focus.
===Suspension===
This part of the project is amazingly easy. [[Image:PCSC - inner tube tie.jpg|thumb|none| The top part of the tripod. With inner tube and chain.]]
*Lay your 3 poles on the ground so that they are lying parallel next to each other. Spread your length of chain so that it too is parallel with the poles and has a few extra inches on one end of the poles. On this end, bundle the poles together so that the chain lies in the middle of all 3 of them.
*You may want a 3rd hand here to hold the poles with the chain in the middle while you wrap the tube around them once, about 6 inches from the ends of the poles. Tie the wrapping so it is tight, and then tightly wrap the rest of the length of tube around the poles, taking case to tie it so that it will not come undone.
*Stand the poles up with the tie assembly facing up. Take a big breath and unfold it into the tripod that you just created!Make sure the chain can support the weight of a good tug without slipping. If it does not seem strong, take extra measures to make sure it is. Remember this will be holding boiling water! 
===Testing the focus with aiming device===
Now, look at the the facets; do they lie close to the frame? Does it look parabolic? Are the mirrors clean? If the facets float above the frame and look uneven, you may want to try the extra tie technique mentioned in the above "Reflector" section. This will allow for a better focus. If the mirrors are dirty, try using a small amount of citra-solv natural solvent and water on a rag to clean them.
*Fabricate the aiming device by inserting the chopstick into the ratchet head on the end where the ratcheter usually goes. Plug this onto the nut in the center of your facets. This creates a sundial. Now you will be able to tell when the cooker is facing the sun because the chopstick will cast no shadow. [picture[Image:PCSC - aim shadow.jpg|thumb|Note the shadow cast by the chopstick. This means the cooker is not aimed properly.]] [picture[Image:PCSC - aim no shadow.jpg|thumb| Now it is centered on the sun, and the stick casts no shadow.]] (Note- If your chopstick catches on fire, it is probably well aimed.)
[cd - practising aiming]
When it is aimed, and your mirrors are well shaped, a ball of concentrated light about 6inches in diameter should appear a few inches below the rim plane. Wearing your UV protected sunglasses, test this by placing your hand in the center till you find the hot spot. When you think your dish is well focused, try rolling the piece of black paper into a cylinder and float it in the hotspot. It should start to smoke and burst into flames within 30 seconds. If not, make sure your mirrors are clean and are forming a tight focus. Paper burns at 451 degrees farenheightFahrenheit, so if your cooker can ignite paper it can boil water, fry, and cook. In other words, it passes the test. [[Image:PCSC - smoke.jpg|thumb|left|Testing the focus by trying to burn black paper. Theres smoke...] [Image:PCSC - fire!.jpg|thumb|none|Theres fire!]]
Now you are ready to cook! Your project should resemble this photo: [taco[Image:PCSC Standing hot.JPG|frame|none]]
*Besides posing a threat to the stability of your setup, Wind also has the potential to greatly reduce the temperature of your cooking pot. If this is an issue, try finding a wind-shaded area or using a dead-air-space design for your cooking pot, like the HotPot mentioned [http://www.appropedia.org/Papasan_Chair_Solar_Cooker#Food_holding_device|here].
==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 sure to use ''''ALWAYS USE SUNGLASSES with WITH UV protection 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==
{| border="1" cellspacing="0" cellpadding="2" align="center"
! Quantity !! Material !! Source !! Cost ($) !! Total ($)
|align="right"| Free
|-
| 1oz || Black Tempura Tempera Paint || HSU Child Development Center
|align="right"| Donated
|align="right"| Free
|}
==Discussion==  *The Bamboo + bike tube = makes an awesome standAnother question was 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 was 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. Bart says that However, this project was a close success anyway as the concentrator gets hot enough to 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 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? ===
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.
==Picture Gallery==
<gallery>
Image:PCSC CHAIR NAKED.JPG|The frame of the chair pre-mirror
Image:PCSC - low setting side.jpg|Low sun mode from the side
Image:PCSC tying down mirrors.JPG|Using hemp twine to tie the mirrors to the frame
Image:PCSC_-_mason_jar_in2.jpg|Using a mason jar inside of a tempura tempera painted canImage:PCSC - mason far lid on.jpg|Tempura Tempera painted can with pot lid
Image:PCSC - bolt.jpg|The bolt used to tie all of the mirror facets together
Image:PCSC - inner tube tie.jpg|Bamboo poles with chain in the middle tied with inner tube
</gallery>
==See also==
* [[Compound parabolic concentrators]]
* [[Compound parabolic reflectors for solar cookers]]
* [[Parabolic solar cookers]]
==External Linkslinks ==[http://solarcooking.wikia.com/wiki/Compendium_of_solar_cooker_designs An Excellent Overv Overview]
{{Solar navbox}}
[[Category:Engr305Appropriate Technology]][[ImageCategory:Parabolic solar cookers]][[ImageCategory:Example.jpg]]Solar cooking]]
1,022
edits

Navigation menu