Solar Oven With Tracking...

Whilst surfing the net one day I came across a site that showed you how to make simple solar cookers. The next day I made one out of cardboard and tin foil. I was amazed at how well it worked. After a lot more surfing and learning I came up with this design that any handyman with basic electrical skills could make.
What makes it really easy is there are no elaborate electronics with lots of components and circuit boards. You just need a small battery, couple of small solar panels, a motor and a switching device. Your comments are most welcome so please feel free to praise or criticize. Suggestions most welcome...

Step 1 Constructing and insulating the box...

I am lucky enough to have a nail gun so that made building a lot easier. So most of it is built with nails and wood glue. I built the two sides separate and filled them with corrugated cardboard which I already had. I made the walls about 80mm (3") thick for good insulation.

(Unfortunately the image notes are not working so please ask if anything is not clear)

Comments

[killerjackalope]

The method of tracking here is genius - it's incredibly simple but self regulating, great job...

[stringstretcher]

Nicely done! I have been goofing around with this kind of tracker, wondering how to switch more current with it... didn't think to do it mechanically. I have used the method to construct a leave-me-alone box (about 5 or 10 in fact). Thanks for sharing!
jim in sweden

[Ben082]

Your design seems really simple and effective. The thermometer showed that it reached a good temperature. I will definitely try this maybe on a smaller scale and keeping an eye on cost. Thanks for the instructable.

[Lorddrake]

brilliant work.

[Misac-kun]

your sun tracking system is very simple and clever, i just imagine how much it will heat on desert areas, like mojave :D

[gentlegreen]

Are glass-faced optical mirrors really a good choice ?

I would have thought aluminized mylar would be more efficient reflectors as well as lighter and less prone to being ruined by water ingress.

[SolarPoweredGardener]

Maybe... I did not go that far into it... I just wanted the maximum reflection I could get and these work really well...

I got it out the garage earlier this week after winter... It worked first time, did not even have to charge the battery... Cooked a whole chicken in about six hours...

Am looking at a smaller version using cool room panels....

[gentlegreen]

It's a bit of a myth that because you can see your face in it, it must be an efficient reflector - the light has to pass through the glass twice. I made that mistake in a makeshift greenhouse when I first started gardening.

I'm inspired to have a go with aluminized mylar food packaging - it works very well as a reflector for my bike light. I'm told emergency blankets are a good cheap option - perhaps I'll hang around next time they hold a road race in my City. :)

[Jonesy Boogieman]

What kind of paint did you use? Wouldn't the heat generated in the box during use make the paint and glue off-gas and get absorbed by the food?

[SolarPoweredGardener]

I used a heat resistant paint that can stand temperatures up to 300c (570f). It is called 'Pot Belly Black' and can be used on barbecues etc. I would suggest that anyone using it to operate the oven empty a few times as it did release a strong smell when heated in the confined space of the oven at first...

[steveo625c6]

How exactly do the mirrors benfit this? From the looks of it the angles don't add up to anything that would make it into the box.

[SolarPoweredGardener]

The mirrors are set at that angle so that when they are facing directly at the sun its rays are deflected directly onto, and through the glass. Lets say the sun is hitting the glass at 30 degrees Celsius. It will be hitting the mirrors the same, but because of the deflection about 10% of heat is lost when reflected to the glass. So the mirrors are sending about 27 degrees Celsius. So you have 30+27+27 = 84 degrees Celsius hitting the glass.

I am not sure where you get the box thing from. If you are referring to what some call box cookers I believe that refers more to the cooking chamber itself. It is a box shape usually with a closed top (as mine is) instead of an open type surrounded with reflectors where to cooking pot needs to be put in some sort of green house effect. Usually an oven cooking bag. That was my first solar cooker and they work very well. A little tip for anyone using these I found the cooking bags very awkward. So what I used was a plastic dome I got from a gardening shop what they use to protect new plants from the frost etc.

If you are suggesting the mirrors would work more efficient at right angles to the glass, only a small percent would reflect directly onto the glass The rest may get to the glass after a zig-zag effect bouncing from one mirror to the other. Not very efficient as you loose about 10% of heat each bounce...

I hope this has answered your question. It is only my way of seeing it and I stand to be corrected by anyone who knows a lot more about it than I do....

Thanks for your comment Steve...

[drbill]

Great I'ble.

I like the recycling of the Baxter boxes. I get a butt load of them every 2 weeks.

I would like to see a use for all the tubing that comes with them. We use the 5000mL stuff.

[SolarPoweredGardener]

I used to get a monthly delivery of the boxes. Fortunately that has stopped now as I was lucky enough to get a transplant last November... I used some tubing to set up a automatic watering system for my seed trays...

Thanks for all the positive support guys. Glad to hear it's encouraging others...