Monday, 30 June 2008

Solar Oven Contraption - Half Baked!

This weekend it was really hot! It got up to about 30 C, (86 F) yesterday, which is really too hot for my Canadian self. But I thought it would be a good time to build and test out the simple solar cooker I have been thinking about making for some time.

I wanted to see what could be done with just the stuff I had at home already, so I found two boxes that fit inside eachother, with at least one inch clearance all around. After lining both boxes with tinfoil (shiny side out) I stuffed the space with an assortment of packing material I've collected over the years -- packing peanuts, bubble wrap, sheets of foam, etc. I put black matte corrugated plastic at the bottom of the inner box and after putting my foil-wrapped potatoes into my thrift store black enamel roasting pan, I covered the whole thing with a clear plastic 'oven bag' (which I bought several months ago for this exact purpose). I threw this contraption together in about half an hour -which you can probably tell by looking at the picture! With some glee, I put it outside on the concrete driveway, under the blazing sun.

After about two hours in the sun, I wasn't hearing any sizzling or any other sounds of hotness, so I repositioned the cooker, propped it up at what seemed like a better angle to catch the now lowering sun. It wasn't getting any cooler so I decided I may as well stay outside myself and do some yardwork (the weeding is never ending!). After about two more hours, the sun was going behind the trees and so I figured I would check into the potato situation, seeing as it was now time for supper and I was planning on having baked potatoes after all.

Well, my potatoes were only half-baked. I'm sure that the main reasons for this is that my cooker contraption is slightly half baked as well! The instructions I was using as guidelines say that it helps a great deal if you have a steel plate in the bottom of the inner box, painted matte black. I didn't have a steel plate or any black paint at home though, so I skipped that part. I also didn't seal the plastic oven bag very well over top of the inner box, so I'm sure some heat escaped that wouldn't have otherwise. It would also have been better to have my box lids better angled to reflect the sun into the box. My box lids collected sun, but didn't really direct it inwards. An oven thermometre would also be useful, to see just how hot this thing is really getting.

Despite these shortcomings, I probably would have been able to fully bake those potatoes with another four hours of sunlight. It took me until the afternoon before I was motivated enough to even gather the materials together, so it was after 3 pm before I had the cooker outside. The best cooking sun would have been between 11 and 2.

There is still a lot of summer left though, so I will be trying this again once I get a metal plate of some kind and pick up some matte black paint. I will also keep my eye out for a bigger outer box, and one with a lid that can be cut into a reflector. I'm also seriously considering getting a proper Sun Oven, since I just love the idea of cooking with free energy!

I did get my supper of baked potatoes after all, although I did have to put them in the microwave for another two minutes or so. That's not so bad I guess, since it usually takes about 5 minutes for a potato to bake in the microwave.


Jennifer (of Veg*n Cooking) said...

Aw, too bad the potatoes didn't get fully cooked. Please post again about your next attempt at the solar oven. I have been very interested in building one, as I know that the materials are not that expensive and are made of things we can often find in our homes already. I make my tea by the sun during the summer, why not take advantage for the food too?!

Theresa said...

Jennifer, I think my cooker would have cooked the greens I just had for lunch, even though they didn't cook my potatoes! I was actually quite amazed at how hot the potatoes did still get, even with my very poor design and construction.

Also, for anyone wondering why you can see the potatoes wrapped in foil in the picture, this was before I put the potatoes in the black roasting pan. For the cooking process the potatoes were in the pan, in their foil. For some reason I thought it wouldn't hurt to put the potatoes in the foil, like you do on the barbeque. But it occurs to me that the reason for using the foil in that case is to keep the potatoes from getting burned. In this case the foil may actually have been an extra barrier to the solar heat getting in. When I build Contraption Two I won't do that.

Green Bean said...

Whoa! I can't believe you put all that together - "half baked" or not. That's pretty awesome. I've only vaguely toyed with the idea of a solar oven but I love recharging my batteries with a solar recharging, making sun tea. A cooker is the next logical step. I'll let you figure it out and piggy back on your success. :)