Double Solar Oven

Anyone who's done much with solar ovens already knows that almost every design hits a limit on how hot it can get. It seems like most of the ones I have dealt with max out somewhere between 200 and 275 no matter what you do. This assumes a perfectly clear and sunny summer day too. I was thinking about it today and wondered to myself if anyone has ever tried a double solar oven.

That is to say, a standard solar oven that also includes a solar panel attached to a heating element and small blower/fan. Something where it would augment the direct solar heat with solar powered heat. It seems like this would really go a long way to cook items that just don't work with a low and slow cooking style. So has anyone tried this at all?

D. Logan : Two things, you can explore using a fresnel lens from the front of a DEAD big screen TV, as a concentrator, Or anything that can be cooked

in a Crock Pot can be started in a Solar Cooker and when it is up to temperature switched to a hay box or fireless cooker, you can still find cookbooks

from the 30s and 40s touting this useful technique ( On really good solar cooking days you can start then transfer several dishes to a hay box and

depending on ingredients, have them held ready at the same time ) Here is a pretty fancy commercial model- link below :


http://www.hiwtc.com/photo/products/29/06/44/64400.jpg

For the Good of the Craft ! Big AL

How about an oven within an oven? Would that work?

D. Logan;
Have you tried simply building with more collector area?

I have not yet put together a finished oven, so I'm not pretending I know the answer, but when I look at all the cardboard and tinfoil plans out there, I go out on recycling day and score a few more of those chipped, 1'x4' mirrors that are always on one sidewalk or another, and at some point, I will start framing them up, and pointing them at a 'box' until I see some temps I can work with. Like any solar, I have to think it's just a numbers game, ultimately just adding more surface area than one would initially expect.

I've gutted an old microwave for my future oven, BTW, and will be focusing my mirrors (which are bendable, so they will each get focused down to about a 1' patch) on the sheet metal at the rear and underside of this oven, mounting it onto a rolling BBQ grill frame for convenient work height and portability. The mirrors will store on the cart, but be set up on a stand just north of the Oven, where they will track the sun with an arduino or similar micro-control circuit. Finally, the oven will have some baffles that fold open so you aren't getting blinded or flashed by the mirror array.

That's the plan for now, anyway. I'm currently building a custom cellulose blower and will have to wait for the bake projects..

Right, we ended up not really using our solar box ovens because they can't bake anything nicely if it isn't sweet, and we don't really eat much cake here. Anyway, they are too small for our school feeding over 40 people every day, often 100. An English volunteer recently had fun making cake several times a week, though.

We use solar cookers successfully though, which are called Scheffler cookers. They are parabolic reflectors made of small normal mirrors for the primary reflector, and aluminum or broken mirror bits for the secondary reflector that is inside the kitchen, under the pot. They get very hot -- when showing them to visitors we like to show off by holding a twisted newspaper in front for a few seconds until it bursts into flame.

These are not ovens, but I can imagine an adjustment putting an oven box instead of the secondary reflector. I think it would have to be rotatable to allow even baking.