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In keeping with the grand tradition of creating ways to warm my lunch at work with readily available office supplies, I present for your review, dear reader The Office Worker's Portable Solar Oven.
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Signing UpStep 1The Situation
Due to circumstances beyond my control, my cubicle at work is close to both the break room and a small loading area on the second floor. Because of this I usually have a wall of boxes filled with copier paper situated somewhere behind me. Aside from this being a nuisance when it comes to concentrating on my job it also affords me the opportunity to scavenge as many copier boxes that a man can get his hands on.
This is a perfect situation to improve upon my earlier solar cooking ideas.
See here: http://www.instructables.com/id/Dashboard-Chilli/
This is a perfect situation to improve upon my earlier solar cooking ideas.
See here: http://www.instructables.com/id/Dashboard-Chilli/
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I would like to echo what Haw1horne said: Heating plastic is a bad idea unless it is designed for heating. You may not see or taste the outgassed products, but they are there. Other sites also say that if you can't use glass then the baking bags will work. I think a layer on the inside of the cover sealed with a cardboard edge, and another layer on the outside of the cover also sealed. Of course, pull tight to reduce diffraction.
An aside to the previous; careful what paint you use. Some are not safe to be heated. Look for those labeled as non-toxic stove paint.
A glass top would help keep the lid sealed because of its additional weight. If you go with the turkey bag window route, I'm thinking paperclip and rubber band anchoring system around the outside would keep things tight and allow for less heat loss. My guess is this is where your heat loss came from.
An angled lid lined with foil (aluminum, tin, lead, mylar, whatever) would catch more light and protect the works when all finished and folded down.
I'll start my oven tomorrow. Again, fantastic job with this and thank you so much for your time and effort.
have a nice day
I always call aluminum foil "tin foil" though, just like my father always called the refrigerator the "ice box."
Good lunch warmer, Z0rb. We get lots of sun here. It will work well.
http://solarflower.blogspot.com/2009_09_01_archive.html#6825927391729345306
It's a compound parabolic concentrator. If you scaled it up a bit, insulated it and put your food in a black container at the focus it would act as an oven.
The angle range will give you about 4 hours without having to reposition and the degree of concentration is about 10 times when it's pointed directly at the sun, down to about 6 two hours either side.
I spent quite a bit of time with a cad package, this is the most efficient design I could come up with.
And use reflective mylar, you can get it cheap from hydroponics stores and is about 50% more reflective than tinfoil.
Instead of cooking food, it might accelerate microbial growth! ICK! lol
Dude, I really gotta say (in somewhat paraphrased agreeance wth fishhead445 had to say), I thoroughly enjoyed this entry! Clear, concise, highly informative, well documented data, and witty as alll freakin' hell! THANX! ^_^
HAIL!!!! ^_~
The real trick here, I suspect, is maximising insulation on all sides and the area of the window, while minimising total volume. Afterall, the more air inside, the more air to heat up.
I wonder how much light gets lost from diffusion by the trash bag, too. Probably not much, but it would be interesting to compare it with glass. (There's gotta be a broken flatbed scanner around the office somewhere...)
But yeah, what with the way a Fresnel lens focuses light into a concentrated beam (much as lighthouses do), so does the heat concentrate, as well. Like with one of those Fresnel lens panels that can be gotten through Edmund Scientifics that can melt asphalt, for instance. As far as a focal point, with a Fresnel lens, it's a beam (again, like with lighthouse lenses, which are of the Fresnel type), so there's not much as far as spacial restrictions go, I would imagine. But I could be wrong. I'm no scientist lol
True that, on the insulation... but with a focused beam (as opposed to an apex/singular focal point) and spacially-throughout-heat-intensity, there *may* be a need for more heat resistant materials... hmmm... insulative fiberglass, perhaps? Like the kind one can find in one's attick? Maybe...
you should see if you can finish it. they're awesome! especially when they're cheap;)
hey that rhymes!
There's 3 complications with your implementation of the solar box oven (variation of the Kerr/Cole Oven patented in the 1980s)
One is the plastic glazing. If the oven did get hot enough, that sheet would very likely melt, warp, and/or outgas. This could be bad for your lunch! In any event, its probably not a food-safe grade of plastic if you found it around the work place. One work around is to use food-grade turkey bag plastic. Stretch it tight across a frame, and mount the frame in the lid.
Second is the plastic glazing. Yes, I know that sounds redundant. The biggest source of heat leaking is going to be out through that plastic. You can improve this by either using glass or lexan for the glazing, or by creating a double layer of food-grade plastic with a 1/4" gap in between the layers.
Third, most box ovens made for climates outside the Tropics have an additional reflector to help boost the heat up to cooking temperatures. Cookers that don't have the additional reflector are (1) Made for the tropics (2) Use double glazing (3) Use high-R polyisocyanurate insulation in the walls.
also painting the interior black might help, as would raising your food container so that the light reflected off of the foil will hit all sides of the container