Insulation; Apparently a Must Have for a Solar Cooker

While I scour the internet looking for resources of cheap ideas to get my solar oven cranked up as high as she can go, one common topic keeps popping up; Insulation.

Now insulation is something that I naively ignored in my very basic solar oven, assuming that with the summer temps here in the desert, it would not be an issue. It appears I was dead wrong. As soon as the sun drifts behind the shade of a tree in the late afternoon - BAM! the temp in my solar oven drops below the 150 degree (F) bottom end threshold for my thermometer.

A simple foil lined outer box seems to be sufficient, with at least a 1/2 in gap between the inner and outer boxes (bottom too). Air alone seems to work just fine, but others have filled the gap with sand, dry soil, newspaper and "gasp", Styrofoam.

My mission as it stands right now will continue to be to see how hot we can crank up this solar oven, and I believe the next upgrade will be fitting a "Heaven's Flame" style reflector to it..

But food for thought .... if you intend to do any real cooking beyond reheating, the consensus seems to be that insulation is of the utmost importance. Funny how right now that still appears to be last on my list.

More Minor Changes to the (still) Basic Solar Cooker

So, i took a quick peek and at around noon the solar over I have so unceremoniously plopped in the sunniest part of my back yard. Guess what? 225 degrees F, just like yesterday.

(outside temp 102 F)

Again, the components of my solar cooker so far have included a cardboard box, a picture frame with the included glass, a little foil on the inner box sides, a black t-shirt, a $5 oven thermometer from the grocery store ... and not much else.

So I took 10 minutes on my lunch break and tried to fashion some sort of gasket to make up for the hastily cut edges of the cardboard box. The solution I came up with was simply building each of the cardboard walls up a bit with some duct tape, and hoping that by laying the glass on top there would be enough pressure to for a bit of a seal. Was there? I can't really say.

The verdict? No change. Now I'm torn .... I'm not so convinced there was a whole lot of loss there anyway ... but I'm also not so confident that if there was any loss, that this may have actually remedied it.

On another note, though - while contemplating what I could use that was made of metal and a dark color to line the bottom (as opposed to the tee shirt) I came up with what I thought was genious. (other opinions may vary) It just so happens that the top of the broiler pan (you know, the part with the slots cut in it) is a perfect fit.

It's been in there now for about 15 minutes and we've already broken that pesky 225 degree ceiling we have been up against. Sure, it's only at about 230 degrees (F), but that's promising. I like to see at least a little progress each time I fiddle with the solar oven.

(update, it's been an hour now, no measurable improvement. Maybe it's just too late in the day. I'll check again tomorrow when the broiler pan has a running start at the midday sun.)

Baby Steps .. My Solar Oven's Minor First Upgrade

Just to keep you up to date, the solar oven mentioned below had a little more testing today.

Outside temp; 100 degrees F.

So last night I did a pretty lazy job of covering the interior walls with foil, applied simply and not so elegantly with a little of my 5 year old's Elmer's glue. I had originally intended to make some reflectors, but a half-hearted search didn't unearth my tape measure, so the interior would have to do.

I put the solar oven back in the yard for some testing this morning. After a few hours with lackluster results, in lieu of black paint ( I simply didn't have any) I folded up an old black tee shirt to line the bottom surface of the cooker.

The results ... well it's about 2:30 pm and the solar oven has reached neighborhood of about 225 degrees. That's a 25 degree improvement that I attribute much more to the black bottom than the foiled sides.

Other things to note: .

My box cutting job wasn't even close to perfect, so, I'm sure that along with the loss from the glass, there's probably quite a bit of loss where the glass rests along the cut top of the box. I'll need to fashion some sort of gasket to seal that up a little better.

So the black t-shirt worked out, but I'ld really like to try a fitted, flat black piece of scrap metel in there for not only attracting the heat, but holding it in as well.

I'll also have to look a little more into the options for insulating the box. With summer temps here in the desert, that's probably last on the list.

Once I find one of my dang tape measures I'll see how much heat we can generate by adding some reflectors to the solar cooker.

I'm really trying to see how close I can get to the 360 - 400 degrees F boasted by the $300 commercial versions I have seen online - but, in reality, I'd be pretty darn happy with 300 degrees, only because that is a temperature I am famiar with from the gas oven in my home.

and that's that...

So, I Thinks it's About time I Look into This Solar Cooking Stuff

Well, I have been looking into the whole solar cooking thing for a while - reading the blogs, looking at the pictures (both the DIY and "professional grade" versions) watching the youtube videos ... well you get the point.

It usually boiled down to the same old excuse ... who has the time.

But, now it's summer in the desert. I'm a cheap S.O.B,and when it's over 100 degrees outside, I feel a little silly at dinner time when my oven and my AC just seem to be duking it out ... and the loser is usually my wallet.

Oh yeah, and then I saw this ...

That's my grill before noon on a late June day here in Nevada ... over 120 degrees... and, in case you're wondering, no, it's not on.

Crazy, right?

So after a quick refresher of some online DIY solar ovens - I started with a serrated knife, a cardboard box and a picture frame what already had glass in it, all found in my garage- Literally a couple of minutes later I had the beginnings of a solar oven.

I had to wait a couple of hours to grab the thermometer on our family grocery shopping trip to see what was what.

Of course there's a bit more to do, but I was/am curious what happens if I approach this a single step at a time. I like to think we're off to a good start.

I checked it about an hour/ hour and a half after tossing the thermometer in there and, frankly, I was a little surprised.

Just in case you can't read it, that's 200 degrees - and it's just a regular old box and a pane of glass. So we're all on the same page, it's 99 degrees outside right now, but I'm still pretty excited.

Next up we'll try painting the inside black, and/ or adding some cardboard and aluminum foil reflectors. Let's see how how we can get this solar oven!