Solar Oven

Light reflects heat; dark absorbs it. Use black outside.

What/where is your heat source?

I'd be more worried about plywood at 250 than PC, but it (PC) might sag if used in the roof. $15.00/sheet for pc is a steal!

Fiberglass insulation.

Unless you will be in the oven during use, don't vent it. Your heat will escape.

Heat source ? The sun. I think you said your in Portland. Do they have, Habitat for humanity stores there ?

That changes a lot.

I'm in the Sonoran Desert in Mesa, AZ.

If I want something to get hot, I put it in the sun.

Solar cookers rely on reflected heat from direct sunlight.

Scale something like this up to suit you.

Or, just put the panels in the sun.

Insulation and all that other stuff only helps if you are adding heat from inside the cooker. Picture a box with heat lamps inside.

Tony: You can use the Lexan sheets for the clear solar inlet windows.

Set your paint drying chamber up to be heated by a convection from heat rising then distributed over the painted surfaces. Natural circulation might work, except you need to make provision for outside air to come into the chamber to carry away solvent.

http://www.iedu.com/Solar/Panels/

Everything you need can be found in the above link that will allow you to make an efficient system.

Hi James Stewart, Thank you for the link on a solar heating box.
It was excellent, very well written and most detailed. (will likely make one.)
However:

Before I do, just one enquiry please? (a niggle in my mind.) If those solar boxes
were replaced with a normal glass window (double glazed if necessary) would not
exactly the same sunshine enter the building and heat the contents?

That is, how does the solar box "increase" the heating effect of the same sunlight?
Maybe I have a mental block on this and, it just bugs me?

Many thanks for your help to explain this to me. (or anyone?)

jt.

A man goes to the registrar and says, "I want to change my name please."
Are you sure? asks the registrar. "Yes, certain he says." Ok, well, what's your name?
"Patrick, Patrick Shithouse" he replies. "And what name would you like?" asks the registrar.
"Michael," he replies.

Think about normal thermal siphon, where the heat enters low and rises, and the cooled liquid returns at the bottom once again. Now think about the heated space as the source, with the sun gone down, and the cold outside, nipping and cooling the liquid in the siphon. The cooled liquid sinks on the outer side, and the warmer liquid rises on the inner side, so it runs backward.

True that you could do with double or triple pane glass, and an absorber material behind that by whatever distance. It will not give as good a result as the other panels that were well thought out.

Obviously, there is a limit on how much sunlight enters through the window in the first place. If someone needs to dry paint, and do this cheap, yeah just go dirt simple, put a window over a box, slide in the painted parts on supports, then use a fan to blow air over the parts.

Hi again, I'm not suggesting the box (as described) does not work, it probably "works"
exceptionally well. But.. How does having the box increase the total heat above that
amount obtained from having a normal double glazed window? i.e. As you say:

" there is a limit on how much sunlight enters through the window in the first place."

If the same area of sunlight enters the building by a glass window (heating the
enclosed air and contents) as does the same amount of sunlight that is absorbed
by using the box (in place of the window) how is this heat "increase" obtained?

That is, if the sunlight, and area of the sunlight, are identical in both cases, then what
provides any "increase" in the heating? (ignoring storage.) The supply is the same?

Sorry if I am missing something here, but I do not want to make a pointless box?

jt.

You are looking at a heat balance. You have energy coming in as sunlight. You have energy coming out as heat. The better the insulation around the box and the lower thermal conductivity of the glass window, then the higher the internal temperature in the box when things balance out.

The "box" does not increase the heat, but the louvers in the heat collecting section may improve transfer of heat and flow to the zones being heated by the box, much more effectively than something like a passive heat wall thermal ballast (for one example).

The design of the box is to totally prevent reverse flow at night that would rob the heated space of the heat delivered during the daylight hours.

Thank you for the explanation. I can see the heat "savings" with the non-return flow.
(which would be advantageous) Also, the protection of the box from night time losses.

This may make it worthwhile to give it a try, thank you.
But I am still unconvinced there would be any increase in the heat obtained.
Maybe the reduced losses would be cumulative, sufficient to make it appear successful.

Many thanks for your help and assurances.

jt.

If you read the piece on fabrication of the absorber, it appears the airfoil parts are needed to break up boundary layer conditions, and produce sufficient mixing of cold and heated air that results in improved heat recovery. Incident energy is the same, recovered is not equal.

Thank you. ( a believer! ) I will try and make time to make one.

jt.

I heat PC to 120 deg C to bend it. Ply is not a good conductor of heat. If you want the sun to heat the outside and warm up the interior i suggest a wire or mesh frame and a cover of builders black plastic. It will eventually break down but is cheap and easy to replace. So cheap that a walk in oven is possible ( timber kiln ). As an aside; I saw a guy on uTube use 50/50 vinegar and water to remove rust. Tried it myself on a VERY rusted welding bench and it works very well. Leaves the steel shiny. BUT it very quickly gets surface rust. I have not yet tried a post wash of soda. The advantage is that vinegar is cheap and comparatively benign. Jim

I don't know the environment where you live? I remember when I painted my car using the sun as the heat source, automotive paints required about 65 to 70 degree F at 50% humidity...on a calm day (not windy day) to cure properly..

The humidity is important to factor in curing the paint! As an environment factor example to consider, the humid Florida weather is very much different to the dry Arizona weather! The quality of paint job, besides the the type of paint is affected by the curing time which in turn is also humidity dependent..

To control humidity, circulated air flow is needed heated naturally or otherwise, and this where you need what type of enclosure is needed...it can be anything just to prevent or minimze outside air influence in the curing process..

Thanks for the comments.

OZ, I use white vinegar, applied full strength to dissolve mineral deposits that have adhered to metal panels or brackets.

I live in southern California, in the summertime it gets hot here, but not as hot as in Mesa,az. I think that is why Lyn goes up north to his red barn in the summertime, over here, we call them, snowbirds.

You can get a lot of information on the cooking variety here:www.solarcookers.orgThey can get up into the 300 degree F range, with good insulation and double glazed glass lids. Using glass is usually recommended because it allows higher energy visible light to enter, and blocks lower energy infra-red from leaving.But hey, you can probably get a big enough container and adequate temperatures by leaving a station wagon in full sunlight with the windows closed.

Is that an offer to donate a station wagon ?

Sorry, mine is in use, but since you were talking about how rednecks do things, I thought I'd suggest the obvious. Look for a yard with a station wagon up on blocks and offer to tow it away for a low fee.

GA Easy solution.