Which perennials (fruit vegetables ...) for a greenhouse?

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Alain G
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by Alain G » 31/03/11, 22:00

Today it's 6 C outside and in the greenhouse in the sun I get 30 C at 15:45 PM, it rises high enough but not enough to heat water using a radiator that will necessarily cool the greenhouse .

Maybe I could make sensors to heat the water to the max!

It bothers me because I could get ahead of production! : Idea:
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cortejuan
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by cortejuan » 31/03/11, 22:27

Re,

It is true that the radiator will cool the greenhouse but at the same time it will increase its efficiency in trapping solar energy. The lower the greenhouse temperature when it is sunny, the more effective the trapping (simply less loss to the outside.)

Yes in your case, a boost from sensors should provide enough energy to maintain the temperature overnight.

the calculation is simple if instead of 5 degrees of difference you go to 10, you get 12 KWh! it's starting to get interesting. I add that good insulation with bubble plastic is necessary to really limit consumption.

cordially
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dedeleco
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by dedeleco » 01/04/11, 00:43

Christophe does not seem to have solved his problem of freezing in winter of his greenhouse to read the posts of 3 pages:
https://www.econologie.com/forums/maintien-h ... t3856.html
who remained without solution !!

I am trying to specify the means to get there, which are a simple version of storing solar heat in the earth to recover for cold periods.

So I think that in winter there are long days and weeks of cold below freezing even in the middle of the day outside, which prevents the greenhouse from heating up on the half day of sun in the mornings so that it stays pretty hot at night.

It would be necessary to know the fluctuations of T observed in its greenhouse and outside next to it during a period of typical cold weather to determine the solution.
During the day, in very cold weather, the air in the greenhouse heats up to T> 0 ° C in the sun at (+ 5 ° C ??), or does it not reach> 0 ° C ??

Indeed, it is necessary to take advantage of the heat stored in the earth at T> 0 ° C to prevent it from freezing at night.
If the greenhouse does not heat enough alone in the sun, to resist night cooling then:
It is necessary to store the heat of the sun better during periods at T> 0 ° C in the soil from morning to night, by improving the greenhouse-to-earth heat exchange and by better insulating the greenhouse (bubble film under the windows in frosty winter) which reduces losses by a factor of 2 to 3.
A circulator between exchangers in the greenhouse and the ground allows this, with sufficient surfaces in between. For example large EPDM in the greenhouse air connected to the same surface of pipes buried in the greenhouse in the lowest possible depth every 20 to 30cm away, fixed by the diffusion speed and the necessary heat flow.
We can even recover the summer heat stored deep in the ground to heat the greenhouse with a deep Canadian well, (at least 3m)
It is necessary to add heat in summer by heating this well with the excess heat from the greenhouse in summer or autumn (which is thus air-conditioned in summer) to find it in winter.
The Canadian well may be far from the greenhouse (with insulated pipes in between).
The depth of the well fixes the duration over which it stores the heat to restore it over the same duration and the volume of heated earth multiplied by its temperature and by its thermal capacity, fixes the quantity of heat recovered.
The diffusivity varies between 0,14 (topsoil) and 1mm / s2 (clay):
http://de.wikipedia.org/wiki/Temperatur ... %A4higkeit
which gives between 37cm and 1m in 1million seconds of diffusion or 11,5 days.
On 1 day it is rac (11,5) = 3,4 times thinner, or about 11 to 30cm.
The earth is the simplest and cheapest in large mass, with a thermal capacity approximately 3 to 4 times weaker than water, but without the need for containers and thick insulators, hardly better in long durations than the compost. arable insulated by thermal diffusion, and much more work to have waterproof and to insulate on the same thicknesses.
So if the cold never lasts more than 12 days and if the soil is organic loose soil with low thermal diffusion (full of organic matter) we can bury plastic exchanger pipes inexpensively every 37cm to 20cm to take advantage of the heat stored before in mild weather and greenhouse, to heat the greenhouse in cold weather. The exchanger in the greenhouse must have approximately the same surface, and the circulator must regulate the flow rate to the minimum to keep the greenhouse a little above 1 ° C, to avoid exhausting the heat stored in the earth .

Finally, the greenhouse can be heated by solar collectors such as EPDM under additional glass or plastic film in the south, which heat the earth of the greenhouse which keeps it not frozen.

If the earth under the greenhouse is warm enough, the greenhouse will not freeze, if outside it is not too cold (not colder long than the earth is hot long, like a day -10 ° C -> + 10 ° C a day in the earth)
Thick plants on the greenhouse floor should not isolate it from the soil.

So if the greenhouse and its complementary solar collectors (to compensate for the absence of afternoon sun) are warmer than the earth, they heat the earth under the greenhouse (to 37cm or more deep) and if the greenhouse is too cold, (close to 1 to 2 ° C), then it heats up with the heat of the earth in depth (other circulator and thermostat in reverse).

With inexpensive pipes (16mm low pressure quite long) and two circulators, thermostats, and valves this system is not expensive and functional.

The duration of very cold weather that can be tolerated without freezing is fixed by the depth, the exchange surface which with the diffusion length gives the stored volume, provided that the heat losses from the greenhouse are less than the heating capacity of the exchanger, which must therefore have a nice surface, comparable to the cooling surface of the greenhouse (to be balanced by the respective delta T if outside it is -18 ° C and the deep earth is at + 10 ° C, then the heating surface in the greenhouse must be at least 18/10 times that of glass in the greenhouse, reduced by the ineffectiveness of thermal convection in the greenhouse, or the insulation of the bubble wrap, which explains the ineffectiveness of the 70l can .)
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bidouille23
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by bidouille23 » 01/04/11, 11:48

Bonjour,


The solution against freezing was given "the culture on hot layer" simple ecological effective since louis 16 in all cases :) .

AlainG, if you grow cucurbits inside you will not have the problem of taste;), and the tomatoes you will grow them after removing manure (which you will have put in your outdoor soup) and put back the earth and mix the all .

http://users.skynet.be/cerclehorticolan ... ouche.html

ecological greenhouse heating, otherwise you make the same system but in a tank and you circulate pipes to prick the heat created inside and take it outside, it should work that right? :)

see you

and bravo Cotejuan superb work
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dedeleco
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by dedeleco » 01/04/11, 12:54

The solution against freezing has been given "the culture on hot layer" simple ecological effective since louis 16 in any case

very well in Brittany and the Paris region not too cold for a long time, but if the cold is long, continental climate, it will be insufficient, and Christophe seems to be colder at 400m above sea level and more to the North East than in Brittany (where his greenhouse would not freeze) and bedding is not enough to prevent freezing. In Russia or in Canada, the culture on layer will not be enough with two months at -18 ° C!
So as long as the average annual temperature is sufficiently positive, and the earth not frozen deep, we can heat with the deep heat of the earth which is in fact the summer heat, kept summer for the winter, provided that the exchangers are of sufficient surface area in relation to the isolation of the greenhouse.

In addition I do not know if Christophe has enough pigs as in Brittany to make a culture on powerful layers ???
Heating the earth in depth when the sun provides enough heat to heat in cold weather, and avoiding the freezing of the greenhouse is a solution, which once installed and functional, does not require any more work, because become perpetual and automatic, after having set the maximum soil and minimum greenhouse temperatures.
It is no longer necessary to stir up manure per m3, with pigs, to prepare the culture on a layer, which will freeze if too cold.
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Alain G
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by Alain G » 01/04/11, 14:21

cortejuan

Do you even leave your bubble wrap in the sun or take it off during the day?
If the light goes well I intend to put it because I already have the components for temperature regulation available.

I use polyethylene construction film which lasts more over time, the greenhouse film is much more expensive and lasts only 2 years while the construction film lasts 5 years, as I leave the film in summer and winter, it requires less of work at a third of the cost and if we take into account the duration it is much higher in relation / quality!


hack

Thank you for your link, very interesting!



Dede

Sending heat to the ground is unthinkable on a small scale and at a shallow depth, my problem is with the ambient air in the greenhouse which can freeze my plants otherwise the soil does not freeze, moreover the film covering the floor keeps heat!

This is why I find the Cortejuan solution interesting!
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dedeleco
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by dedeleco » 01/04/11, 15:10

The bubble wrap works by better insulating and letting the air pass,
but why this statement:
Sending heat to the ground is unthinkable on a small scale and at a shallow depth

because if the ground does not freeze in winter with -18 ° C in Canada, this is what is done spontaneously to keep the strong summer heat for the winter in the ground, which thus does not freeze under the greenhouse and the film on the ground.

With rudimentary solar heat collectors you can increase the solar heat recovered in the ground, as soon as these collectors are warm enough in the sun, winter and summer.
The thermal power available from the ground to keep the air in the greenhouse frost-free will be much higher with warmer soil.
I don't understand that we don't use it anymore !!

Low pressure garden hoses buried under the black collectors and plastic films and 2 circulators on thermostats are sufficient.
Much easier at shallow depth !!
At a greater depth, we can thus find the summer heat as at
http://www.dlsc.ca/DLSC_Brochure_f.pdf
http://www.dlsc.ca

But even at shallow depth we recover the heat from the sun by day for the night, or even over one to two weeks (2cm in topsoil with low thermal diffusivity and high thermal capacity, because humid) !!

I do not understand the difficulty in understanding and realizing it if it is necessary to avoid freezing.

In any case, if the earth does not freeze, Canada is not that cold.
.
Otherwise with this the problem of freezing the air in the greenhouse in winter can be greatly reduced by the installation under the windows in winter of an insulating bubble film at 1,4 € per m2 on the same site:
Bubble wrap for insulation
http://www.serre-jardin.com/equipement/chauffage.asp
which will help keep the heat of the day in the greenhouse.


It arises inside your greenhouse, in glazing, thus making it possible to insulate it and to achieve savings in heating.

Insulates your greenhouse effectively against the cold
Easy and quick to install
Good value for money

Bubble diameter 18 mm
Width 2 meters
Length: per linear meter € 2,8 / m
PVC clips (pack of 50): € 15 *
Film fixing vertically in aluminum grooved profiles

Image
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Alain G
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by Alain G » 01/04/11, 16:13

Dede

You understand that I cannot hope to grow my plants during the winter here in Quebec, I talked about extending the time available for growth!

For the storage of heat in the ground, we can see in your link that it is only possible on a large scale for several dwellings and not very feasible for a single house because the losses in the ground will be too great not to mention the cost!

Currently the earth of my greenhouse is completely thawed because of the sun beating on it but the ground around it is still frozen deep, the frost can reach 1,5 meters here and I still have 40 cm of snow on the ground!

Here we generally plant around the beginning of May but I could be almost 1 month ahead with a system that recovers heat and bubble insulation, that's why I'm interested in the Cortejuan system!

The bubble wrap is not available here but I can use the one provided for the packaging!


Another idea would be to recover the heat from the septic tank or the soil above does not freeze even in winter but that unfortunately will not change the date of planting!
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by dedeleco » 01/04/11, 16:55

Alain G.
I take good note that the ground freezes at 1,5m in your home under normal conditions, which corresponds to at least 2 to 3 months of strong continuous frost of the air, day and night.
But below the earth keeps the positive annual average of temperatures, extremes between summer and winter.

The deep septic tank uses this very deep heat more than it heats strongly, so as not to freeze in winter and this heat comes out on the surface because the soil with a thinner top does not isolate enough by having a higher thermal conductivity.
The septic tank releases an energy of approximately 50 to 200W per inhabitant using the tank (roughly the heat used to live).

Another idea would be to recover the heat from the septic tank or the soil above does not freeze even in winter but that unfortunately will not change the date of planting!


So we can recover this deep summer heat to avoid freezing, as for the septic tank studied not to freeze in winter by having its bottom at much more than 1m deep, which recovers the deep heat kept frost free by the large summer heat which compensates for the cold winter.

If the soil is loose alluvial, drilling is very easy at 3 to 6m with a small auger (50mm) often used for soil studies.
Then exchanger pipes inserted in these holes bring the deep heat to avoid freezing of the soil and the greenhouse, which does the septic tank !! (even very good conductive aluminum or copper rings (or low T heat pipes, with simple volatile acetone) can make this heat exchange between deep and surface that the septic tank performs.

In more maritime France, the soil in winter freezes little (except in rare exceptions as in 1956) it is much easier to achieve a greenhouse freeze.
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Alain G
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by Alain G » 01/04/11, 17:10

Dede

The pit generates more heat than what you cite because you do not take into account the temperature of the water containing a lot of calories which is sent there like the shower dish and washing water, plus the temperature of the water is heated by the house by exchanging pipes with ambient air!
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