I fiddled around with parabolic dishes and fresnel lenses but in terms of cooking, I couldn't do much more than fry an egg or boil a couple cups of water. So I decided to take a shot at a more efficient way of solar cooking reasonable amounts of food like cakes and poultry. To do so, I chose a box design with reflectors placed all around it to gather more light and energy into the cooking area. It was a relatively easy build and it cost me no more than 30$ and I was thrilled by the results it gave me!
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A large mojority of the materials I used were gathered from friends who had them lying around or who wanted to dispose of them.
What I used:
Tools
What I used:
Tools
- A circular saw and its guiding rail
- A glass cutter
- A jigsaw (with metal cutting blade)
- A compact drill
- A grinder
- 8 mm thick plywood
- 18 mm thick plywood
- glass pane from a picture frame
- Glass or arcylic or stainless steel mirror
- Silicone caulk
- Metal bars
- Screws
- 2*4 or other wood pieces
- A length of seal (strip seal for doors)
- High termerature black spray paint
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At intro you says that parabolic gave poor results, but I think you didn't insist enough with it. I have cooked meat, noodles, fruit, hamburgers and sausage using a mirrors array of about 1m2. All in quantities enough for 3 or 4 persons.
The advantage of parabolic is that you can roast food, not only boil it. A small disadvantage is you need reorient it each 10 or 15 minutes, except that you have a solar seeker.
1. Double or even triple glaze your door - you were already on this track. Multiple glazing will do two things: It will help keep heat inside the oven and therefore speed-up your cooking. The innermost glazing will attain a much higher temperature and therefore any moisture in the air will struggle to condense on it.
2. Cook your food inside an oven bag; keep the moisture contained :-)
Cheers.
On another note. I am looking to build a large solar oven. I was given a large double pained piece of glass from a window. It has a blue tint to it and I am not sure if it is a true tint to block the sun or if it is just a glaze. I can't peel it off.
Do you think it will work?
1. Technical Response
From my high school physics days... the 'colour' or 'color' of anything, including your blue-tinted window, is dependent on the wavelength / frequency of light being REFLECTED off it. Your glass appears to be 'blue-tinted' because it's reflecting the blue wavelengths of the white light that is being shone on it.
Your eyes pick up these reflections, and your brain says "that glass is 'blue'". Something that appears to be 'white' is actually reflecting all visible light, and something that appears to be 'black' is actually absorbing all visible light (i.e. NO visible light is being reflected).
In order for a solar oven to work, the glass being used MUST allow infra-red light (aka 'heat') to pass through it and be absorbed by the black box enclosure, which then re-radiates that infra-red light or heat, heating the air inside the box.
infra-red light is near (actually outside of) the red-end of the visible spectrum, whereas blue light is towards the other end of the visible spectrum (remember 'ROY G BIV' for the colours of the rainbow). Therefore, in theory, there is a REASONABLE chance your glass will work.
2. Practical Response
Get a cardboard box and paint the inside of it black. Put the open cardboard box directly behind the blue-tinted glass, just like you were building a solar oven, and put the whole lot outside in direct sunlight. OR, even simpler, place the glass between something that is already black or near black in colour and direct sunlight.
If the blue-tinted glass allows infra-red light or heat to pass through it then your cardboard box enclosure, or your black object, should get warm/hot.
Cheers.
I may be wrong here...
Clearly you were paying attention in Physics. In my (limited) defence, it's been many years since I took Physics classes, although it's coming back to me... :-)
GeorgeP4,
While my general comments about why your eyes / brain perceives an OPAQUE object as being of a particular colour is correct (i.e. due to reflected light), I haven't followed the physics / logic through when it comes to semi-transparent objects such as coloured / tinted glass.
If an object appears blue in colour, then all visible light other than blue light is being absorbed by that object. The blue-coloured light is being reflected off the surface of the object AND, with blue-coloured but otherwise transparent objects, is passing right through the object.
The mistake I made was assuming that with semi-transparent objects, such as tinted-glass, the colours you can't see (i.e. the colours that aren't being reflected) are passing right through the object. As Gael has pointed out, the light you can't see is being ABSORBED (by the tint). Only the colour you can see is being reflected off, or passing right through, the tinted glass.
Therefore, in theory, your blue-tinted glass is likely to be at the wrong end of the (electromagnetic) spectrum and there is a REASONABLE chance your glass will NOT work, in not allowing infra-red light or heat to pass through it...:-(
The above said, given you've already got the glass and it's pretty easy to test, forget 'the theory' and give it a go.
OK, so that's two bum steers from me now!
Cheers.
I see you're using imperial measurements for your window size, so I assume you're living somewhere in the States. If you're living in an area that sees extreme temperatures (e.g really hot or really cold, or both) then there's a fair chance the glazing is designed to stop heat either entering or leaving your house (which is no good for a solar oven). Tinted-glass for houses is generally designed to reduce glare, keep heat inside or outside the house, and/or keep UV light outside the house (UV light fades curtains, lounge suites etc.).
I'm only using light theory to GUESS what the glass is likely to do, which I originally screwed-up in any event, so go figure. Even if I do know, or think I know, the theory, I usually test to confirm.
It's a relatively simple thing to test so, if it was me, I'd Nike it.
Hope this helps.
Cheers.
Gael
Alternatively, a water scavenger, like damp rid (aka calcium chloride) could work. If you don't want to buy something, you can turn a non-toxic hydrate, like epsom salt or even baking soda, into a anhydrous form by baking at the appropriate temperature (wikipedia can be a good info source for this). Leave the anhydrous form in an open dish in the oven when you cook, and it should dehydrate the air fairly well.