greenhouse heating heat buffer

Solar thermal energy in all its forms: solar heating, hot water, choosing a solar collector, solar concentration, ovens and solar cookers, solar energy storage by heat buffer, solar pool, air conditioning and solar cold ..
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cortejuan
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Re: greenhouse heating heat buffer




by cortejuan » 20/11/17, 13:07

Hello,

You confirm my observations: without a dynamic exchange system it does not work, therefore the water reserves in buckets, various containers have no effect because as you say the losses are such that the exchange is tight-- > exterior is 100 times more violent than the basin -> greenhouse exchange.

On my remark, I don't remember which one you are talking about because I totally agree with your comment: the greater the difference between the interior and the exterior, the greater the losses, it is a "beast" law of thermodynamics. So we always have an interest in correcting the excesses in the greenhouse by lowering the temperature.

Regarding the exchange in your greenhouse, you can without introducing a pump "simply" correct the temperature by installing in your reserve a coil connected either to a car radiator or other, or to run, as I did, copper tubes along your shelves connected to the coil.

The confirmation in my case is that the temperature in my bin under the greenhouse has quickly dropped to 10 degrees, which is about the greenhouse set temperature. It was initially at 18 degrees so the exchange took place. But without a pump, the exchange is much slower than when the water is in circulation.

cordially
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cortejuan
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Re: greenhouse heating heat buffer




by cortejuan » 25/03/18, 17:16

Hello,
feedback after this winter.

On the one hand, I decided to abandon the wood heating because too restrictive even if the system was effective. In very cold weather, -10 degree for example, I had to make an outbreak every day, when I say outbreak, it's a euphemism, in fact I spent half the day to reload the boiler.

So exit the wood heating. While waiting for affordable photovoltaic panels, I used propane (yes, I know green question is questionable ...) to make up for the lack of sun, especially during December and January.

From February, my thermal storage partially took over with some efficiency. For example, for an outside temperature of 5 degree on average (in recent days) I gained, during the day (actually during 4 at 5 hours), between 2 and 3 degrees of temperature in my 2900 liters of water this which makes a stored energy of just over 8 kWh (for an average increase of 2,5 degrees). It is not so bad. returned at night it largely maintains the temperature 10 degrees even if it is cold.

Another advantage, in the morning, the water is 9-10 degrees, the conversion is even better and the greenhouse much less hot day.

Finally, it is especially the piloting of the PWM fans that makes all the difference (variable speed all the more high that the difference between the set temperature and that of the greenhouse is large). As the amount of energy contained in the air is low (despite the impression of heat), it requires a significant renewal to recover the maximum calories hence the interest of the variable speed.

So storage in water with a good conversion efficiency remains an interesting solution especially for photovoltaics that will overcome the storage battery (expensive, not sustainable and not really green).

This is my future job.

But it would be nice if we could delete the two months of December and January, those who will always ask me problem ...

cordially
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lilian07
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Re: greenhouse heating heat buffer




by lilian07 » 26/03/18, 14:11

Hello,
Nice work of experimentation, measurement and feedback.
For my part, I am sizing a project for a greenhouse of 100 m2 and we are focusing on a land storage type BTES with its significant constraints (concurrent site APPER).
In your situation you are trying to clip the cycle day night from which the idea of ​​water stock that remains formidable in this case.
I did not read the whole job but I have some questions:
1) Why not insulate with inexpensive greenhouse insulation "2 euros / m2" in winter during December-January periods
2) Why not use "low cost solar thermal solar panels under polycarbonate" thermal collectors to recharge your water tanks?
3) Why consider photovoltaics to heat water.

Your research is interesting.
cordially
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cortejuan
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Re: greenhouse heating heat buffer




by cortejuan » 14/08/19, 23:14

Hi,

With considerable delay, I answer the questions. It's never too late...

On the insulation, of course I use 3 bubble-greenhouse layers placed at 2cm windows.

I continue to explore and I am moving towards solar thermal with a heat exchanger Hrale type but the fluid is less manipulable than the electron that does not need pumps.

cordially
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izentrop
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Re: greenhouse heating heat buffer




by izentrop » 27/09/19, 02:01

Chinese bioclimatic greenhouses, with wall trombe, buried 1 / 3, oriented south, cover unrolled at night http://www.pierre1911.fr/2017/04/serres ... ation.html

Image
result:
Image
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cortejuan
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Re: greenhouse heating heat buffer




by cortejuan » 20/11/19, 10:48

Hello,

I will redetect again, I should have been a gravedigger ...

I still have not decided between solar photovoltaic and solar thermal. The first is simple because I know how to transport the electrons that never freeze in the wires, the second is more efficient ...

That said, prices have actually decreased in photovoltaics, we can find 2kW for a little over 2000 euros (autocono without battery) so I continue to scratch my head. Especially since there seems to be a lot of scammers in the field.

Thermal or photovoltaic? Do you have an idea ? Not your feeling but tangible data for one or the other?

I am surprised that the thermal storage of electricity is so little suggested. A tank of water of only 10 m3 passing from 50 degrees to 20 degrees it is already a packet of KWh (about 350 kWh except error) with the advantage that the efficiency of the conversion photons / electrons is independent of the temperature of the tank. Well it is true, user of this solution to put my greenhouse frost, I am not completely impartial.
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lilian07
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Re: greenhouse heating heat buffer




by lilian07 » 11/01/20, 10:57

if you want to use photovoltaic then you have to associate it with a small heat pump system to make hot water in buffer.
The advantage is that in case of need (no solar you can always have a backup system to avoid losing all of your plant production.
Otherwise there is a lot of optimization to be achieved with the tornado wall or indoor culture tanks to better manage heat losses and improve the culture.
You should still accept the simple hydraulic system to have an efficient system.
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cortejuan
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Re: greenhouse heating heat buffer




by cortejuan » 13/12/20, 16:16

Hello,

I continue my reflection and given the fall in the prices of photovoltaic panels, I think I will try the experience of converting electrical energy into heat via a plunging resistance to supply my thermal buffer, which is inefficient in the middle of winter .

So basically, I equip myself with 3 or 4 panels of 300 W 12 volts each connected in parallel to the others so I have to get about 1000 W theoretical. If I plug in a simple 600W 12 volt resistor, that should work right? The assembly is very simple and does not require a converter, voltage regulator.

What is your opinion other than "uses thermal panels". I have my reasons for preferring electrons which do not freeze in the wires and remain there wisely ...
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dede2002
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Re: greenhouse heating heat buffer




by dede2002 » 14/12/20, 14:46

Hello,

It is doable but it would still require a voltage regulation system.
Otherwise, as soon as the voltage of the panels drops the power becomes ridiculous.
We can make simple by coupling or uncoupling several resistors, according to the voltage of the panel under load.
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cortejuan
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Re: greenhouse heating heat buffer




by cortejuan » 15/12/20, 20:30

Thank you for the answer,

I am not sure what a voltage regulator will bring. If the voltage drops, solar energy is decreasing. I have the impression that a voltage regulator will not be able to play its role because if the power drops, the heating resistance being constant, the voltage at its terminals will have to collapse anyway. I think so, but I am not an expert in this kind of problem.

Finally, I try to do something simple that requires minimal intervention. This was not the case with my super-efficient boiler but also super boring to feed every two days ...
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