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Solar oven interior: black or reflective?

 
Posts: 12
Location: Missouri
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Does anyone know or have an opinion about which interior will be more effective in generating heat: a black painted solar oven interior or a reflective interior?  Black will absorb energy and keep it from being lost back through the window, but reflective would hopefully redirect the energy toward the cooking vessel for absorption (with the risk of losing some back through the window).  Thoughts? Experience?
 
Posts: 710
Location: In the woods, West Coast USA
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There are two types of solar ovens.

A box with sides and a glass lid holds the heat in, so flat black interior.   Also use black cookware in it as well, so it absorbs the heat.

If you are thinking of the satellite-style that is silver and holds a pot up off the center of it, that focuses the heat on one point, which hopefully, when done right, is under the pot.  It's tricky to move this one and keep it focused, especially if you are on rough ground.  It's more dangerous to kids/animals because the heat source is open, the surface is shiny and kids want to put their hands on it, which is a serious mistake if it is up in the 350 F range.  And small kids, or kids playing ball around it can back into it, or hit it with a ball, and it's quite vulnerable.

We use a box style for picnics and keeping food warm, and that's where it's important to keep people away from it.

Both styles need to be tipped up into the sun at the angle of the season, and both need to be moved every so often to follow the sun across the sky, otherwise they lose heat.  
 
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I used a box style oven with pieces of slate lining the bottom for thermal mass. Cooked the food in a cast iron skillet or dutch oven & a glass lid. Or a Mason jar painted black. It worked amazingly well. Gave that one away but starting v2.0 soon.
 
Alicia Donathan
Posts: 12
Location: Missouri
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Thanks, Cristo.  I'm building the box style.  Too many kids to try the other version.  
 
Alicia Donathan
Posts: 12
Location: Missouri
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Mike, what temps do you reach inside your slate-lined oven?
 
Mike Barkley
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I don't recall the internal temps. That was a few years ago in Texas. Plenty hot for sure. I used it mostly for stew type meals. Loaded it up in the morning & it would be done by supper time. It had a tempered glass top with a foam rubber seal. 3/4" plywood. Very basic design. It also worked fairly well as a dehydrator if the lid was left partly open so it wouldn't reach max temp.

Giant fresnel lens + sun = spontaneous combustion to almost anything placed at the focal point. Using that to heat an off grid hot tub next year. Solar heat is good!
 
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