Simple multi-layer greenhouse

Here are the results of my simple multi-layer greenhouse experiment, conducted in December when the weather was hot and stable, not mild and rainy as it is now. The experimental setup is shown below, with two laboratory thermometers, and a mercury one to check. One sensor was attached to a 6in black tile sitting on the EPS box, the other on the glass surface. On top were up to 5 alternating layers of EPS and picture glass, as shown below.

dsc02878

The temperatures are in C, and were measured by recording the maximum temperature over the period. As far as possible, I tried to obtain measurements on a clear calm day. The location is on the tropic of Capricorn in December, so the sun was virtually overhead.

Time	Layers	Tile	Glass

12:00	5	116	50
12:30	5	110	49
12:45	3	110	49
12:50	2	106.9	52.2
1:00	1	110.1	60.1
1:10	4	104.6	46.6
1:25	5	102.9	46.5

Below is a graph of the data above. Its fairly clear that the number of layers has very little effect on the temperature of the black tile. The temperature of the external glass layer does decrease however, with more layers. This I would think is due to the increased heat losses from the sides of the stack of alternating glass and EPS blocks.

image001

Once again, conducting this with precision outside is not possible without better equipment. As I reported with an earlier post, the temperature of the tile was beginning to melt the EPS foam.

The same result, of little change in the temperature of the tile with additional layers, was reported in a post by JQ Public:

My son and I repeated the experiment as mentioned and we the same results. We then used two glass jars, one as a control and one with water vapor and got the same results. We tried the two jar experiment again, but his time we stayed indoors and used a heat lamp and got the same results. In our fourth experiment we use one jar as a control and added vinegar and baking soda to the second jar to produce CO2. After and hour into the experiment we added even more vinegar and backing soda to create even more CO2 and yet again the temperature did not increase. The mean control jar temperature was 34.87 while the experimental jar was 35.43. The mean humidity for the control was <20% (we could not measure below 20%) and the mean humidity of the experimental jar was 42.73%.

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0 thoughts on “Simple multi-layer greenhouse

  1. David,
    In your first post about these experiments, you said that you were looking for a Miskolczi maximum of about 57 C (330K). “From the fourth root of 3/2 we get 1.107, meaning a maximally developed greenhouse effect on earth would increase temperatures by 10.7%. The temperature of the experiment in degrees Kelvin was 299.3K, meaning an increase of 31.4 degrees was possible. The increase achieved was only 23.6 degrees, 75% of the maximum, but approaching that figure.”

    Are you still looking for a maximum?

  2. David,
    In your first post about these experiments, you said that you were looking for a Miskolczi maximum of about 57 C (330K). “From the fourth root of 3/2 we get 1.107, meaning a maximally developed greenhouse effect on earth would increase temperatures by 10.7%. The temperature of the experiment in degrees Kelvin was 299.3K, meaning an increase of 31.4 degrees was possible. The increase achieved was only 23.6 degrees, 75% of the maximum, but approaching that figure.”

    Are you still looking for a maximum?

  3. jae: Yes ambient was 36C and steady.
    Nick: I am looking for a maximum, but I think Arthur was right about how to calculate it.

  4. CoRev: It helped me get a feel for these physics. Practical experiments. But right now, though I would like to put a simple model together, its a bit beyond me. Perhaps someone could suggest one. My guess is that it doesn’t confirm or deny M’s theory, but I don’t know why the temperatures seem constant despite the number of layers. This is not the homeostasis in M’s theory. It probably can be attributed in large part to the emissivity of the materials.

    A better statement of the earthly greenhouse principle to me would be that it is warmer due to the emissivity of the insulated materials involved. Suppression of convection, the usual explanation, doesn’t include suppression of conduction, nor help you work out what the temperature should be.

    Thoughts? Models?

  5. CoRev: It helped me get a feel for these physics. Practical experiments. But right now, though I would like to put a simple model together, its a bit beyond me. Perhaps someone could suggest one. My guess is that it doesn’t confirm or deny M’s theory, but I don’t know why the temperatures seem constant despite the number of layers. This is not the homeostasis in M’s theory. It probably can be attributed in large part to the emissivity of the materials.

    A better statement of the earthly greenhouse principle to me would be that it is warmer due to the emissivity of the insulated materials involved. Suppression of convection, the usual explanation, doesn’t include suppression of conduction, nor help you work out what the temperature should be.

    Thoughts? Models?

  6. CoRev: I think I can see why there would be no difference in tile and glass temperatures no matter what is between them, how many layers. The temperature of the tile is determined by the fraction of SW absorbed, not what is above it. The temperature of the outer glass is determined by the fraction of IR absorbed, and it doesn’t matter to it whether the tile is below, or another pane of glass, its all the same IR.

    So to a degree, I can see how the intuition that the extra layers would make the tile warmer is wrong. To the extent that that might be similar to extra CO2 not making the atmosphere or the surface of the earth warmer, that sounds like many of the arguments I have heard here. But I am not at all sure.

  7. CoRev: I think I can see why there would be no difference in tile and glass temperatures no matter what is between them, how many layers. The temperature of the tile is determined by the fraction of SW absorbed, not what is above it. The temperature of the outer glass is determined by the fraction of IR absorbed, and it doesn’t matter to it whether the tile is below, or another pane of glass, its all the same IR.

    So to a degree, I can see how the intuition that the extra layers would make the tile warmer is wrong. To the extent that that might be similar to extra CO2 not making the atmosphere or the surface of the earth warmer, that sounds like many of the arguments I have heard here. But I am not at all sure.

  8. Michael L: That article is on Icecap, also. Unfortunately, it has some serious errors in it that will probably be used to try to discredit the whole thing. Especially the stuff about Neils Bohr. Wrong wavelength regions.

  9. Michael L: That article is on Icecap, also. Unfortunately, it has some serious errors in it that will probably be used to try to discredit the whole thing. Especially the stuff about Neils Bohr. Wrong wavelength regions.

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