Solar Cooker

B

Bowie Mike

Joined
Sep 30, 2006
Messages
118
Not exactly W&S Skills - but I have been wanting to try improving on heating up my lunch with the sun. I have reached that point where eating sandwiches every day has become a little old (you know you've been there) so I've been trying canned soup and ravioli.

I don't have a way to heat it up so I've been heating it on the dash of my truck, using just the sun to warm the can. It generally works - not really hot, more like warm, but it beats the heck out of the dry sandwich.:barf:

Today I used a stainless steel mixing bowl. I put the can of soup (the complete can, unopened) in the bowl, covered it with plastic wrap, added a rubber band to secure the plastic, and set it on the dash.

It was about 80 degrees today and the ravioli was noticably warmer by reflecting the sun back onto the can. The bowl was used and scratched on the inside, so I probably didn't get optimum reflection from the sun - but it worked.:thumbup:

I thought about lining a carboard box with aluminum foil, but I figured it wouldn't last very long - getting knocked around in the truck. Plus it didn't require any time or effort to cover the bowl with plastic.

I may try polishing the bottom of the bowl, or lining it with aluminum foil to improve the heat reflection.
 
We had some special wax that would start to melt at 150 F .It was in the trunk of a white car in the sun, air temperature 70 F. It melted !! If you are driving you can heat things with the engine or exhaust manifold heat. ..I don't think your reflector did much for you.
 
mete said:
If you are driving you can heat things with the engine or exhaust manifold heat.
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I've actually seen that done on two different cooking shows! In one show, chef Ming Tsai prepared some sort of baked fish in aluminum foil using this technique. The foil packets were wedged tight against the manifold. Unfortunately, when it comes to the manifold, it looks like some experimentation is in order, as it's not really calibrated for cooking.

I really do like the idea of driving to a picnic spot and having lunch cooked just as you pull into a parking area.

...back to the topic at hand...A long time ago I read a book where solar power was featured. There was one design using corrugated cardboard to create the frame for a parabolic mirror (aluminum foil, shiny side out, was used as the reflector) and some sort of tripod to support a pot to cook food. For scale, the size of the reflector was about the size of a medium sized umbrella. I've also seen some commercial designs where the actual cooker folded down, similar in the way an umbrella does.

I've never actually tried this design myself, but it's supposed to work very well in bright sun, and a good pair of sunglasses were suggested, as well as oven mitts, and all metal cooking pots(plastic handles were likely to melt).
 
I wonder if a flat (non-glossy) black surface wouldn't get hotter than a shiny surface on a box or other container to warm your soup can in. I guess I'm weird, but I even like "C B-A-D" ravioli at room temperature. Same with Campbell's Chunky clam chowder or plain old chicken noodle soup. Shake 'em up first, though! What about setting a can of something yummy on the engine after you get to work in the morning? Unless it's really cold outside it might be pretty warm at lunch time. Throw an old folded towel over it maybe to help hold the heat in.
 
How about using the cigarette lighter for the soup lol. Im dorming in a cooridor style dorm where my kitchen is down the hall (and since im in a cooking dorm its not that bad since other buildings all share a kitchen in the basement) and there have been plently of times where its 3 in the morning and I dont feel like walking down to the kitchen to heat up the soup. Not to mention the clean up after. Well, pepsi can stove to the rescue next semester lol. I find some kind of chowder is the best cold because the fat doesnt bunch up together like in regular soup. Ive also used my desk lamp to heat up leftover pork chops in a plastic container. Keep the lamp around an inch over the container an hr before you want to eat and it works fairly well.

ANYWAYS back to the topic at hand. The thing with solar cookers is that you have to make sure the item you want to heat up is in the focal point of it. Those who have math or physics experiance should prob remember parabolas where waves going parallel into the curvature will all reflect off to one point. A great example is a huge metal bowl. If you stand in front of it and someone else says something, you wont be able to hear it well if you arent in the focal point. Now once you adjust yourself to that point, the voice of the person talking sounds magnified.

Heres a quick description I guess:
http://www.cockeyed.com/incredible/parabola/parabola.html

That being said, I dont think itll be that feasable because to heat food up, your going to need a pretty big dish.

Well, I guess you could warm up food, but keeping it in the car during a hot day can do that. But really hot soup? Forget it.
 
All of you make good points. I think my mixing bowl is a little too small to do much good...but it's working a little.


I might try wrapping the can of ravioli in a black trash bag and setting that on the dash.

It's all just experimentation through lunch - as long as it tastes good, I'm in.
 
Why not get a small backpacking stove? The type that screws onto a isobutane canister? They are great! I have one that packs into a little billy pot with the gas canister. If you have the bowl already, heating up ravioli and soup for a hot lunch is a snap. The amount of gas required to heat that stuff is so small one canister would last a while. You could also brew tea or coffee right on the spot! A good thing to have in the car/truck anyway . . . .
 
Christopher Nyerges book, "How To Survive Anywhere" details how to make a solar oven. Involves two carboard boxes, paper, aluminum foil, and a piece of glass - not really practical for a vehicle unless you have lots of room.

Back in the day, I too used the exhaust manifold of my truck to heat spaghetti-Os for a warm lunch when dog hunting. Leave them in the can, peel the label, and set-em on the exhaust manifold. Worked rain or shine!
 
http://www.solarcooking.org/plans/

Googled "solar oven" and found that page with all kinds of different plans.

I met someone a few years ago on a camping trip (car camping) who had a solar oven that seemed to work pretty well as long as it wasn't too cloudy. I'm not sure if it was worth the trouble though. . . it was kind of a PITA to set up and she had to go re-orient the reflector periodically as the sun moved.
 
Salamander42 said:
http://www.solarcooking.org/plans/

Googled "solar oven" and found that page with all kinds of different plans.

I met someone a few years ago on a camping trip (car camping) who had a solar oven that seemed to work pretty well as long as it wasn't too cloudy. I'm not sure if it was worth the trouble though. . . it was kind of a PITA to set up and she had to go re-orient the reflector periodically as the sun moved.
Click to expand...

There are two basic designs for solar cookers. Solar ovens work like your car's interior. The glass lets infrared radiation in to heat the interior surfaces which then radiate UV radiation which cannot escape through the glass. For this design, a dark interior is more efficient at converting IR to UV. Cooks by contained heat.

Solar condensers focus the sun's IR energy into a specific area. This is most efficient with a parabolic reflector (like your bowl) and don't rely on trapped heat so the cover isn't necessary. Be careful with this design, tho', bigger is actually more dangerous! My college physics prof had a 6' diamater parabolic reflector that would ignite dry wood in under a second!

I've seen pretty effective condensers made of corrugated cardboard painted with bumper paint. Boil a can of spaghetti-o's in 5 minutes. (This is a common engineering/physics project)

J-
 
I had JUST such a project in one of my freshman engineering classes: a solar powered oven.

The rules were simple: you had to bake chocolate chip cookies with an oven that was designed and built yourself. You were not allowed to buy ANYthing for the project; only salvaged material and garbage were allowed to be used, and it actualy had to bake the cookies.

We used a large cardboard box with a much smaller box nested inside. The space betweene was stuffed with wadded up newspaper. The small internal box was fitted with a black disposable baking tray, cut to size, to abzorb more light. a glass lenze helps insulate the oven.

Next problem is how to collect the sunlight. We built large arms covered with aluminum foil as make-shift mirrors to focus sunlight onto the cookies.

IF you were to use REAL foam insulation for the box to retain more heat, and use REAL mirrors for the collectors you should have no problem not only re-heating foot, but actualy cooking it from scratch.
 
I used to put the gas station cheeseburgers and such on the dash of my car. When it was real sunny and hot they would get hot enough you could not hold them. I knew a guy that did the little stove thing. His fuel canisters lasted a month he said heating up a can of soup everyday.
 
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