Solar cooker

Know of a stove that has some Character about it for one reason or another, post it here.
churro
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Joined: Tue Feb 17, 2015 12:00 pm

Re: Solar cooker

Postby churro » Fri Apr 17, 2015 3:26 pm

I haven't forgotten this project. It's still coming...

In the meantime, I found this website by the inventor of the fun-panel cooker:

http://sunnycooker.webs.com/

Seems he has several other designs. He makes them out of cardboard, but I like the idea of using other materials that are waterproof (corrugated plastic, closed cel foam, etc.). I'd love to hear some suggestions about other materials I could use. His website deserves a read, especially the comparison tests using metal vs. glass lids, with and without the oven bags.

realityguy
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Joined: Tue Feb 24, 2009 2:20 am
Location: slightly north of Seattle,WA

Re: Solar cooker

Postby realityguy » Fri Apr 17, 2015 5:31 pm

I saw a bunch of the white corrugated plastic signboards at the thrift shop for $1.99 each(about 2'x3') but when I went back the next day someone had bought all of them..about 10... :roll:
To me they appeared to be a nice lightweight exterior structure for whatever foil or covering you put on them..and would probably fold if you creased them..like cardboard..Do you think the plastic would melt?..my biggest concern...
The views and opinions expressed by this person are his own and not the general consensus of others on this website.Realityguy

churro
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Re: Solar cooker

Postby churro » Fri Apr 17, 2015 10:05 pm

@ Realityguy- Most of the heat is inside the oven bag. The reflector itself stays cool, provided the pot is somehow lifted off the surface. I use a cookie cooling rack inside the oven bag, below the pot. The one I made from corrugated plastic did melt a little (just warped) the one time I set the pot directly on it while cooking pulled pork for about 6 hours. Still works fine, though, and the reflector is always outside the oven bag, so no fumes in the food.

The corrugated plastic bends best if you cut halfway through the thickness of it from the outside or the bend. Then it makes a really rigid reflector. I highly recommend you make one from cheap or free materials first (cardboard and foil come to mind- use white glue diluted with an equal volume of water on the dull side of the foil). Not only will you be convinced that it works, but you can work out the kinks before you spend any money on more expensive materials.

BTW, corrugated plastic is most commonly used for zoning and liquor license notices. These have to be posted for some period of time, then the owner of the establishment will usually give them to you. I think I used one sheet of standard-sized plastic for mine. The mylar decals I got from the auto parts store were expensive, and seem to be no better than aluminum foil or tape (though lighter), but the foil or tape are hardier and can be polished or cleaned if need be.

realityguy
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Joined: Tue Feb 24, 2009 2:20 am
Location: slightly north of Seattle,WA

Re: Solar cooker

Postby realityguy » Sat Apr 18, 2015 5:09 pm

I found a good-sized roll of the reflective metal tape at the local thrift store for a couple bucks..add that price to a couple of those signs and it would probably have made a nice cheap,lightweight, but durable fold-flat cooker for about $6-8...
I'm thinking trailwise :roll: ..maybe a platform of three small rocks to keep the pot off the plastic cooker might work well...Hey!What can I say..I'm cheap! :lol: :lol: :lol:
The views and opinions expressed by this person are his own and not the general consensus of others on this website.Realityguy

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zelph
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Re: Solar cooker

Postby zelph » Sat Apr 18, 2015 6:01 pm

An umbrella with 4-6 sections only. Attach aluminized emergency blanket material to individual sections of umbrella. Do away with extra handle length if necessary........................it was just a thought :idea:
http://www.woodgaz-stove.com/

churro
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Re: Solar cooker

Postby churro » Mon Apr 20, 2015 2:54 pm

I decided to play around with one of my solar cookers. Since I have never tried this cast iron pot with a pyrex lid, I just boiled up 3 cups of water to see how long it would take. 20 minutes of pre-heating the empty pot got it too hot to touch, then I added the water. 35-40 minutes later it was at a rolling boil. When I opened it up, the condensation on the inside of the bag sizzled aggressively when it dripped onto the pot.

Here it is set up:
IMG_4810.JPG


And here are the parts. The stainless trivet thing came from a counertop appliance that somebody gave me. The bag is a turkey roasting bag.
IMG_4812.JPG


I've been contemplating using the wool from my sheep to make an insulated box that would accommodate this pot with a cast iron lid underneath. The idea would be to pre-heat the lid in one cooker, cook the food in the other, then transfer both to the box to keep warm/finish cooking for dinner time. This should let me cook in the middle of the day when the sun is best, then serve in the evening.

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zelph
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Re: Solar cooker

Postby zelph » Mon Apr 20, 2015 3:31 pm

How often do you have to reposition the oven towards the sun?

Is the turkey bag strong enough to lift the loaded pot?

Take a look a this pot design made for a crock pot. It has a twist lock lid that you can lift up the pot via the lid.

http://www.ebay.com/itm/Rival-Crock-Pot ... 6089&rt=nc
http://www.woodgaz-stove.com/

churro
Posts: 208
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Re: Solar cooker

Postby churro » Mon Apr 20, 2015 11:34 pm

zelph wrote:How often do you have to reposition the oven towards the sun?

Is the turkey bag strong enough to lift the loaded pot?

Take a look a this pot design made for a crock pot. It has a twist lock lid that you can lift up the pot via the lid.

http://www.ebay.com/itm/Rival-Crock-Pot ... 6089&rt=nc

I usually start with it pointed a little ahead of the sun, then reposition every forty minutes to an hour.

The turkey bag is strong enough to lift the pot. Sometimes I lift the bag and rotate 180 degrees to ensure even cooking. Be careful with bags that have been used more than a few times, though.

Neat crockpot! Would probably be handy for this.

churro
Posts: 208
Joined: Tue Feb 17, 2015 12:00 pm

Re: Solar cooker

Postby churro » Mon Apr 20, 2015 11:46 pm

I finally got around to making a closed-cell foam mattress into a cooker. I stretched the emergency blanket out and taped it flat with blue painter's tape. Then I sprayed both the emergency blanket and the foam with spray adhesive, let it get tacky, then pressed the foam onto the blanket. Here's how it looks:
IMG_4814.JPG

The fact that the surface is not smooth doesn't seem to matter. It gather's enough light.
I drew the fold lines on the back and used a box cutter to cut about 1/3 of the way through the foam, from the back, to establish the crease lines.
IMG_4818.JPG

A few tabs of velcro allowed me to set it up:
IMG_4821.JPG

I might try spanish rice in it tomorrow.
A few thoughts, though. I put a pot in it and placed my head where the sun ought to be. The reflection of the pot did not fill the panels, suggesting that the pot is too small for this reflector. Not a problem, really, unless this is to be a backpacking setup meant for a small pot (which it is). I'm carrying enough reflector to cook for 6-8 people. It'll work fine with a smaller pot, but a smaller reflector makes more sense, if only to lighten my load.

Also, the reflective surface on this emergency blanket (Sol brand, I believe) seems kind of fragile. When I was smoothing the blanket down I noticed that the surface seemed to transfer to my hands as a grey dust. Next time, I'll try mylar and see if it's more durable.

All in all, this concept is viable. The foam seems to be a perfect substrate to fold into a reflector, though I need to experiment with materials to surface it with and methods for joining them to ensure durability.

churro
Posts: 208
Joined: Tue Feb 17, 2015 12:00 pm

Re: Solar cooker

Postby churro » Tue Apr 21, 2015 12:24 am

The blue pad I started with measured 20 1/4" x 72" when I started. I used the full width, but removed about 6" of the length to make the geometry work out. I think that for the smallish pots backpackers use, the pad could easily have been cut down to 18" x 48", offering a reasonable 3/4 length pad for sleeping. When deployed as a solar reflector, this should be adequate to bake or cook in dark pots inside of turkey roasting bags up to about 32-40 ounces.

I think a few grommets, strategically placed, would allow the whole thing to be staked and tethered to counteract wind.

One nice thing about solar cooking is that it's hard to burn anything. The temps are relatively low (though above boiling temp, so safe) and the sun moves, tuning the heat down gradually, if you wander off and forget you are cooking. I have set mine in the morning to the part of the sky where the sun will be at 2 pm, and eaten at 4 pm, no hassle.


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