Solar furnace - what coating, what insulation?

[seb1000]

in fact I did a test Monday morning, it took me suddenly, but I have been thinking about it for at least 1 year.

working time: less than 1h
2 cardboard boxes, one inside the other, very roughly isolated with a few sheets of paper.
the inner cardboard flaps removed, and the top covered with a flexible transparent plastic.
the outer cardboard flaps covered with aluminum and the interior blackened with charcoal.

during the first test my air thermometer arrived at the maximum: 60 ° C in 30 minutes and the water at 50 ° C.
I removed the thermometers, I improved the tightness, and I put back my cup of water and a ramekin with an egg casserole (egg + gruyère): it was 13pm.

at 15 p.m. I ate my egg almost well cooked, the clouds arrived .....


Obviously there are a lot of faults, but it was a test, a draft, just to convince me of the feasibility of the more complex project I had in mind.

[Christophe]

I like this kind of seb test

I too would like to make one for years, I have already found a double glazing recovery and which should be suitable! Go go go!

- glass: single glazing

Precision because may not be clearly visible on the attached image.

In fact this single glazing is "doubled" with a spacing between 25 and 30 mm. We can distinguish the grooves on the image of the Ulog.

[Christophe]

I'll do some pictures tomorrow.

As promised, here are some photos of self-built solar cookers or ovens

[Christophe]

I like this kind of seb test

You inspired me! Here are my tests of the day, in fact it is not a test but a beginning of construction



a) 1 frame double glazing recovery, glass surface 63 * 40 therefore equivalent to an 50 * 50 cm (minimum size recommended in the book)
b) glued synthetic mirror
c) Gardening pan for the 1er tests (it already heats up quite well without any insulation, I made IR thermometer measurements on the 2 pieces of slate between 70 and 75 ° C after 1h)

The synthetic mirror, reflects wonderfully:



By cons I do not know how long it will hold ... we'll be fine. I had paid twenty euros in a brico for 100 * 50 cm.

Advantage is that it is lighter and unbreakable! Before I put the cord, the wind dropped the mirror, with a glass mirror, I do not know if it would still be intact ...

More soon ...

[seb1000]

pretty!

It's motivating. with a little imagination, and recovery, we manage to exceed 60-70 ° C easily.

but at the same time, I think that gaining 10 or 20 ° C when you effortlessly reach 60-70 ° is not difficult.
on the other hand, gaining 10 or 20 ° C when you are already at 100 ° C may be harder.

if all goes well I build and test my parabolic mirror this weekend. I'll keep you posted: in a new post? or as a result of that one?

[Christophe]

Yes it is motivating, it is one of the goals of forums

Well, according to the book (see photo link above) Ulog type ovens can go up, empty, to 160 ° C.

In my case from what I saw today, I have confidence to exceed 120/130 ° C: the tank and the insulation should improve performance! There I had only one stupid tray in pastic (measured at around 55-60 ° C from the outside) then the tray was not inclined enough (therefore drop in radiation).

For your mirror, it will depend on the nature of your tests, if it is the coating, you can post here otherwise a new one would be better.

[dedeleco]

With these devices, some pipes in them, you will be able to test in reduced model heat storage at 60 ° C-120 ° C underground and see if the earth retains heat, its distribution and simulate runoff and drainage !!

One day 30cm and 100days approximately 3m of heat diffusion, as a scale model law.

I prefer the simple: the pseudo parable in cardboard and insulated container with plastic.

[Christophe]

And what about the taz and banana? https://www.econologie.com/forums/cuiseurs-f ... 10742.html

[hic]

in fact I did a test Monday morning, it took me suddenly, but I have been thinking about it for at least 1 year.

working time: less than 1h
2 cardboard boxes, one inside the other, very roughly isolated with a few sheets of paper.
the inner cardboard flaps removed, and the top covered with a flexible transparent plastic.
the outer cardboard flaps covered with aluminum and the interior blackened with charcoal.

during the first test my air thermometer arrived at the maximum: 60 ° C in 30 minutes and the water at 50 ° C.
I removed the thermometers, I improved the tightness, and I put back my cup of water and a ramekin with an egg casserole (egg + gruyère): it was 13pm.

at 15 p.m. I ate my egg almost well cooked, the clouds arrived .....


Obviously there are a lot of faults, but it was a test, a draft, just to convince me of the feasibility of the more complex project I had in mind.

Hi seb1000
Your system is not isolated,
the plastic sheet creates a greenhouse effect but does not isolate

Insulation is the replacement of the sheet with
double / triple glazing / plastic


the Top of the insulation is double glazing VACUUM !!!!!!!!!!!!

example of efficiency!
If you put a TRANSPARENT thermos bottle in full sun,
THE WATER WILL BOIL!
and this without any concentration, without reflector,
nor metallic infrared interceptor as glass !! .
(video view)

R30 or 35 for vacuum
against R 7 for fibers


Another tip:
bring in the energy not the underside,
the hot air rises and this concentrates in height and
may be confined by an opaque insulator with thickness at will,
therefore more efficient, easier to implement.

In this reverse configuration,
The double / triple glazing / plastic being located at the bottom,
the temperature will be a little lower, resulting in better insulation

in these conditions how to control the cooking?
1. ability to lift the opaque bell
2. on the nose
3. electronic thermometer

it will burn

[sherkanner]

I really like the fresnel optical system ^^