Storage (buffer) in the soil by thermal rollers?

[dedeleco]

This site indicated by Aumicron is really very good, a teaching model, clear and it is essential to learn well and understand all the information given even for ordinary insulation, to avoid mistakes.
At the end, it offers natural convection air circulation to recover summer heat and to reuse it in winter without any fan. This is much more difficult than a fan or heat transfer fluid and they do not hide the difficulty with its limitation to a single climate.
Nevertheless, they end up on a finding that we must change the regulations too restrictive on a single solution that forgets the others.

Here we are at the end of this journey to the perfectly passive bioclimatic dwelling. As you can imagine, such a home does not really resemble the usual idea of ​​a house, and that is why it is difficult to build in France today because:

* Planning regulations prohibit it
* Companies do not have the skills to build this kind of buildings
* Banks do not finance
* The insurances do not insure, because the constructions are out-of-norms and outside DTU
* And most importantly, citizens do not really want to build a house that does not look like a house ...

In my opinion with exchangers with central heating type water, drilling 3 6m and simple solar thermal panels, it is possible to transform an ordinary house by changing little, almost passive house, especially if we can use a garden , which allows to increase the storage volume without spending too much to reduce the thermal losses of the house.
Instead of trying to remove the last calories lost at a very high cost (to the point that we give up old houses), it seems cheaper to use a summer heat storage optimized to limit its cost.

[Aumicron]

For those interested in natural convection soil storage without the aid of a fan, see this topic:

https://www.econologie.com/forums/petite-que ... t9597.html

[Aumicron]

On an other subject, minguinhirigue wrote :

dedeleco, I see you're very active on the subject of inter-seasonal storage, I'm a little busy right now but I'm trying to redo a point this weekend on documents and sites that I have in my possession at this time. topic

An overview of an intervention by minguinhirigue on the subject here:

https://www.econologie.com/forums/stocker-de ... tml#136865

[minguinhirigue]

Hello everyone, Hi Aumicrons, I had indeed made different interventions on the forum Speaking of inter-seasonal storage (3 to 6 months):
- liabilities based on the links wiki et earthshelters
- aerolics, relying on the Built and functional pebble tunnels in southern France, and the Swiss experiments and studies for the storage of thermal energy in Canadian wells: http://www.unige.ch/cuepe/html/biblio/p ... me_jmz.pdf ; http://www.unige.ch/cuepe/html/recherch ... .php?id=10 ; http://www.unige.ch/cyberdocuments/thes ... these.html
- hydraulic, illustrating it with very large installations in Germany: http://www.solarge.org/uploads/media/1_ ... angold.pdf

If the pebble tunnel is the subject of the discussion, what interests us is the aerodynamic questions.

On the house Brugeille post a solar house with almost autonomous thermal bufferThe architect "CRETE" presents a roller tunnel system:
- 3 roller tunnels, to 2m50 under the DRC slab, 80 cm high, 5ml, or about 6m3 (total roll control is 12m3 (increased volume, or other use position, it does not specify).
- 125m2 surf area
- SOUTH oriented veranda with a developed surface (roof + vertical walls SE and SO) = 36 m2
- Variable airflow from 150 to 1200m3 / h: night time = VMC flow;
the day in full sun = direct heating OR storage between 600 and 1200m3 / h in loop between veranda and storage or inside

It covers 30% of heating needs and 50% of air conditioning needs with this device.

Germs and dust of all kinds are regulated with a geotextile (in the tunnel) and the appropriate filters, but it is also possible to put a heat exchanger to eliminate any health risk (for those worried about clean air).

The roller tunnels act as heat exchangers with the median:
- 300 m² of dry land under the house.
- heats the summer, from 14-17 ° C to 26-28 ° C (thanks to the hot air at the top of the greenhouse (sometimes more than 40 ° C))
- cools in the winter from 26-28 ° C to 14-17 ° C (partly via tunnel air, partly through the migration of heat into the earth layer around the tunnel, the heat wave goes back as far as at the slab on land-full non-insulated 3 months (about 84 cm traversed by a heat wave in a dry clay massif (diffusivity = 0,0020 m² / h), 114 cm in a dry sand and gravel massif ( diffusivity = 0,0037 m² / h)
- parasitic losses occur on the outskirts of the house: considering the peripheral earth as an infinite medium of constant temperature in sand and gravel, we see that the heat wave of the tunnels reaches less than 3 meters over the year. First approximation from the simple diffuse formula).

This system has the advantage of being more compact than a Canadian well (less piping), of being theoretically more efficient, of being relatively simple to install (excavation work at the same time as foundations, plans of ducts relatively simple), and to be simple maintenance once installed.

There are, however, relatively few examples of functional achievements, (apart from that of the architect above, I know only a few very large tunnels for ecological buildings demonstrators!), And thermal losses in use. can overcome the economic interest in other conventional systems if significant foundation work is not required. Moreover, the physical study of the devices based on inter-seasonal phased-out systems, a serious study of dimensioning involves new tools for building thermists (calculation of dynamic variations of the temperature conditions at the border between the roller tunnel and the median, and the ground and the slab of the DRC.). It is not insurmountable, but not frequent either.

The Swiss studies presented above deal with similar issues:
- Air / ground heat exchangers : the air entering in winter comes out with the calories of the summer ... but their results give important dimensions (100 to 500 m) because the exchanger is only a wall in concrete or in PVC (less effective than the roller tunnel). See interesting application to greenhouses in Seville or Geneva.
- cooling of buildings by controlled thermal phase shifter : the air entering in winter comes out with the calories of the summer ... there, the theoretical dimensions of the tunnels are gigantic (several km) for the annual phase shift, because the thermal exchanges with the environment are not considered.

[minguinhirigue]

There is of course also the passive technique, which does not heat transmission through the air (convection), but does everything by conduction, directly from the living rooms.

The principle is to have a house designed so that without heating, the average annual temperature is between 18 and 23 ° C, which exchanges this temperature freely with the basement on which it is built.

It can be a BBC home, but also a simple solar house (temperature amplitude day / night more important).

The first hot summer days, the house heats the heat exchanger with the ground, still in the shade and all fresh out of the first building site, it is between 15 and 20 ° when outside he types 26 ° C and 36 ° under the greenhouse (see Canadian well temperatures)!
The wall heats all summer, and it gradually transmits the heat received to the earth stored under the house ... It never exceeds the average summer temperature (between night and day: 24 ° C in a well-designed house, well ventilated , and not too far south!)

The wall having warmed, winter is coming, it is around 24 ° C. Reverse phenomenon, the heat migrates, it returns from the depths of the earth to heat a house which as soon as the sun falls pass under 18 ° C minimum ... If the house is well designed, the average temperature in winter will never go down under 18 ° (solar contributions, and personal, low losses ...). The thermal storage either ... 18 ° C at the end of the winter, perfect to clog the first heat of the summer!

This system can be made with soil, pebbles, sand, embankments, but being careful not to leave materials too porous (convection). The element is to prevent the infiltration of water into the thermal stock.

Small illustration, taking the formula of penetration of an annual sinusoidal thermal signal ("heat wave") in a massive semi-continuous medium using the diffusivity of:
1 - the earth: 0,0011 m² / h
2 - porous natural stones: 0,0018 m² / h
3 - non-porous natural stones: 0,0040 m² / h
4 - solid concrete: 0,0028 m² / h
5 - moist earth: 0,0050 m² / h

Approximate depths of penetration of the heat wave into the soil are obtained:
1 - Earth: 1,24 m
2 - porous natural stone: 1,58 m
3 - non-porous natural stone (granites): 2,36 m
4 - solid concrete: 1,97 m
5 - moist earth: 2,64 m

The author of earthshelter therefore advises with good reason to cover the floor overflowing the house to avoid humidifying the "thermal stock".