FR2461897A2 - Seasonal heat storage below ground - uses summer solar heat to provide winter heating stored in pipework in sand mass - Google Patents

Abstract

The underground heating store consists of an inner hot circuit and a peripheral cool circuit which provides a screen for, and reduces the losses from the inner circuit. The heat to these circuits is provided by solar panels in the summer and a stock of heat is built up underground to be reclaimed in the winter with the aid of a heat pump. The buried pipe network is buried in a mass of material which is "fluid" and has a high conductivity, such as sand. The sand bed (5) will be in direct contact with the ground and be covered with insulation (58).

Description

The purpose of this addition is to describe a number of
of improvements brought to the main patent improvements for
so much respectively on
a layout of pipelines intended for the storage and destocking of
heat in the ground, a layout particularly suitable for small and medium-sized buildings (claims 1, 2, 3 and 12 of the patent, in particular);
various arrangements of the basement, intended to optimize exchanges
and storage, and to limit losses (claims 12 2, 3 and 12 of
patent, in particular);
the possibility of using water without antifreeze, even in very large
cold (claims 7, 10 and 11 of the patent, in particular) ;;
the possibility of reducing the storage temperature in the soil,
by associating with the ground another seasonal storage device (return
dictions 1 and 11 of the patent, in particular);
the possibility of improving the average performance of the
heat using a stored or storable make-up (claims 9, -
10 and 11 of the patent, in particular).

In a small or medium-sized kid, with
a small volume storage area in the soil, losses may
to be, relatively, more important, and a layout of pipes creating
in the peripheral parts of the basement, indoors or outdoors
of the building, a storage temperature lower than that which rt-
gene in the center limits losses OR An example is described by
figure 7 (In order to avoid any risk of confusion, the figures in the pre
sente addition are numbered ia following those of the patent, these
being from 1 to 6).

FIG. 7 represents a plot which can be adopted for
a rectangular building whose walls and floor are
figured in 30. The floor level (31) in the crawl space will be established
so that an intervention remains possible, in the event of an incident on a cana
The heat transfer fluid arrives, during storage, through a
tube 32 and a distributor 34, then to the exchange surfaces 36, symbo-
read here by eight symmetrical tubes, buried in the central part
The tubes 37 then convey it to the surfaces of
change 38 placed so as to "wrap" the hottest areas of the
underground, by creating a transition temperature region.
fluid, which flows in the direction of the arrows is then brought back towards the
return 33 by the collector 35.In winter, heat recovery is
obtained by reversing the direction of circulation of the fluid in the network, (inlet at 33, outlet at 32), so that the recovery fluid (which can come from the evaporator of a heat pump) cools the region in. device, thus eliminating any subsequent risk of heat loss, and even allowing, possibly, to collect heat on the soil outside the storage, if its temperature drops below 180 the subsequent course of the recovery fluid allows it to reheat iron again, and be used with or without reheating.

FIG. 8 is a variant of FIG. 7, in which the hot network is located close to the surface of the ground (in the basement 3 and the warm network outside the building, the two installations are not necessarily Iiees.ma@s @@ insta @@ a @@ we have other characteristics.

The tubes of the hot network are embedded in a "diffusion layer" 57 added above the floor of the crawl space 31, and surmounted by an efficient heat insulation 58. One of the difficulties encountered in the storage of heat directly in the ground resides in fact, in the risk of drying the soil around the hot pipes, drying which can cause the separation of the soil from the pipe, and, in addition, a significant reduction in the heat transmission coefficient. The diffusion layer overcomes this risk.

It could be constituted, for example, by a particularly fluid product to dry (in particular dry) whose contact with the ground will be perfect, and whose contact with the tube will remain satisfactory.-The product will be chosen taking into account its conduction coefficient , as high as possible. The layer could, on the contrary, be carried out using 1d1a product whose contact. intimate with the tube is assured and reliable, (vibrated concrete coating the tube). The cnotact with the ground will then have to be optimized, thanks to the shape or to the fragmentation of the diffusion layer. Although the figure indicates it not, the "lukewarm" network can also be treated in this way.

Furthermore, the installation shown in FIG. 8 could be improved by the direct placement, in the ground, of sachets of special products whose phase changes are obtained at a fixed and moderate temperature, with absorption (or release). a significant amount of heat (Calcium chloride hexahydrate, for example, the phase change of which is 27/280). The location of this product, figured by the number 59, should be the subject of '' a study specific to each case, taking into account, in particular, its characteristic temperature.

 The circuit described in the patent (figure implies an interpenetration of its various elements which requires the use of a single fluid, the overall volume of which will necessarily be significant, in particular because of the reservoir. In winter, this fluid will circulate in the solar collectors and must then be protected against the risk of frost. The solutions are known. In this case, they would be costly and complicated. The risk of frost can be eliminated by using the heat contained in the air extracted from the building to reheat the circuit water when it passes through the solar collectors in winter, and this, according to various methods, three of which are described below.

FIG. 9 shows the possibility of directly heating the water before it enters the collectors.

The water arrives by a tube 39 in a reheating battery 40 @@ @ @ @ temperature is re @ evee, par @@ empre, ue @@ @@, @@@ @@@@@@@ of the building arrives by a sheath 42 and is rejected to the outside after having been cooled, for example, from 20 to 8. As it leaves the battery, a pipe 41 conducts the water to the solar collectors;
This device, if kept permanently, causes some heat loss, during periods when, simultaneously, the solar radiation is zero, and the outside temperature below 70 (in the example). However, any system addition of antifreeze, or automatic emptying is eliminated; furthermore, the installation is always in working order and the slightest radiation is captured as soon as it appears. It will finally be easy to regulate the temperature of the water in the sensors at the lowest level compatible with safety, either by acting on the air flow in the battery, or by heating only part of the water.

In the variant of FIG. 10, the water is heated during its passage through the collectors. These comprise, between the collecting element 44 and the heat insulator 45, an empty space 46 constituting a plenum, in which the air circulates. (42) extracted from the building. This air reaches it through a sheath 47 and connections 48 and leaves it through the outlets 49; collected by a sheath 50 which remains outside. The plenum 46 is designed so that the exchange is optimal, and that the exhaust air is as completely cooled as possible. This plenum can also be replaced by exchange surfaces of any shape, and in particular by simple round ducts. It is also possible ensure perfect air cooling using a battery mounted on the air, in series or in parallel with the sensors.

FIG. 11 shows another embodiment, in the case of a sensor mounted by components, in an attic, for example.
closed by a torture 52, comprises, on the southern slope, a glazed opening 53 through which the solar radiation strikes a non-glazed sensor 54. The extracted air is then used in order to re-heat the roof, and in particular the area 55 between the glass and the sensor.

The air (42) arrives through a sheath 56, which distributes it above all of the captors, and exits from below, either to be directly discharged to the outside, or to enter dissipated in the attic before expulsion.

The risk of condensation, on the pane 53 in particular, must be analyzed in each case, and is linked to the outside temperature but also to the configuration of the attic and the building.

 Lowering the storage temperature in the ground may be necessary, in certain cases, due to the configuration of the buildings and the relative importance of the heat requirements. The area of collectors required is a direct function of the requirements of winter, and is limited to the strict minimum by the high cott. It can then prove to be insufficient, in summer, to carry out the necessary contribution of heat in the ground in winter, if the losses are too important i.e. say if the storage temperature is too high. It must also be taken into account that a reduced high storage temperature, either the yield of the collectors or the yield 'changes in the ground.

But the lowering of the storage temperature leads to the use of heat pumps, and the coefficient of performance of these is related to the temperature-evaporation.Any action on it é ~; As difficult, it is desirable to work on lowering the condensation temperature. This can be achieved by using a storage tank closely associated with storage in the ground, tank in which the temperature would be equal to the maximum temperature required - at the start of heating (Figure 4 of the patent). However, it is also possible to use the tank 16 of the
Figure 6 of the patent.

 your explanations given below take into account the reference outside temperatures and the operating temperatures of the heating, which it is useful to specify beforehand. It was admissible for a clean climate, the reference outside temperature was -40, and that the heating operating temperature was then 360 at the start, for 200 at the return. For a temperature of + 40, the heating temperatures would be 30 and 20. If an accessory storage makes it possible to face the excess requirements between -4 and +40.11 it is possible to set the heat pump to 30 with condensation and to limit its power to the corresponding level. When the outside temperature requires it, the condenser setting temperature pass @ to 36, but the supply temperature of this condenser being increased by the same amount, the existing power will be sufficient, and the energy absorbed by the compressor will be increased only slightly (due to the decrease in the coefficient of p The average performance of the installation will remain excellent.

 Figure 12 shows the possibility of using the reservoir 16, successively, as daily regularization storage, and as seasonal storage. This latter use leads to an increase in its capacity, so that it meets the increase in needs, when the outside temperature will be below +4.

During normal periods (regularization storage), the pump 21 draws water through the piping 60, the valve 61 being closed, and the three-way valve 62 blocked in the corresponding position. The water is reheated in the condenser from 20 to 30 (for example) and returns via pipes 63 and 64, valve 65 open and valve 66 closed. The tank is kept at constant temperature; space heating is conventional, with regulation by the three-way valve 15, itself controlled by a reference system. In periods of extreme cold, the requirements exceeding the power of the heat pump, the diagram is different. Valve 15 is blocked on the hot water supply, valve 69 being closed. Valve 71 is closed and valve 66 open. Three-way valve 62 is put into service and controlled by the chosen reference system. Valve 61 is open and valve 65 closed. Heating is directly controlled by the pump. with heat, this being then no longer supplied with water at 200 as previously (bottom of the tank), but in heated water thanks to a mixture between the bottom and the top of the tank, mixture whose temperature is modulated by the valve 62 according to the heating needs. The heat pump, without significant increase in power , goes from the temperature range 20/30 to a maximum range 26/360, and can meet requirements up to -4. Its coefficient of performance then drops a little, but it remains excellent, on average, over the whole winter
FIG. 13 is a variant of the previous one. The reservoir 16 is separated into two distinct reservoirs: 151 daily, of small volume, and 16 seasonal, of capacity adapted to: needs.

at
The regulation of the heating remains permanently ensured by the three-way valve 15. The temperature of the tank 161 remains permanently, at the top, equal to the set temperature of the heat pump. , from 30 ju @ to +4 outside, then raised according to the needs below +4.

 In the first case, the three-way valve 72 is blocked, the water being able to come only from 161. In the second, it is put into service and controlled in order to maintain, at the top of the tank 161 the set temperature of the heat pump. Valve 74 is open, valve 76 remaining closed. Resupply of tank 162 is carried out normally thanks to the return of the heating installation. The temperature in tank 162 is much higher than 20, the heat taken from the seasonal tank is added to that which continues to be supplied by the heat pump.

 Storage in the seasonal tank can be effectively achieved by using the latent heat of a product such as that which has already been mentioned, stored in sachets or sealed tubes and around which the water will circulate. few annual changes of state.

The heat stock will be reconstituted in summer, or even during a period of softening of the temperature: three-way valve 72 blocked in the direction of valve 74, itself open, as well as valve 76, valve 75 being closed, during this operation.

 The use of auxiliary energy, preferably storable, is often recommended in solar heating. It allows, like the previous solutions, to reduce the power of the properly solar installation. Figure 14 shows the use of a source of particular heat, with this in mind.

 Most dwellings, and more particularly individual houses, have an open fire, generally fueled by wood. There are commercially available devices which allow central heating to be combined with an open fire, that This replaces a boiler. This equipment has had little success, since the easements for supplying wood to an open fire are not very compatible with the current concept of central heating, and the comfort that it implies.

Such a device, however inexpensive, adapts, on the contrary remarkably, in order to ensure the response to peaks, in the case of solar heating. In the case of the climate already mentioned, the heating is- normally calculated for +160 (200 taking into account so-called free heat) by -4 or a difference of 200.I1 would be possible to calculate solar heating by + 4O or by 00, or with a difference of 16 or even 120 depending on the The power saving is then 20 or 40% and it becomes possible to choose the materials, and not @ m @ ent @@ heat pump, dan @ a sone of power such that it @ works with a ren - dement maximum.With a base of 0 (saving 20%) it will be theoretically necessary to call on @ ppoint only one day in @ average per year, which is better than acceptable, and the periods lasting cold below 0 occurs only very rarely (one winter in ten, for example) and will be overcome at the cost of an effert of a few days. ptée is + 40, this results in a minimal power of 40%, and can allow relaising unthinkable installations otherwise, it will be necessary to operate the wood fire for seven to eight days a year, which is still very acceptable .The association "solar + wood" can therefore constitute a remarkable solution
Figure 14 shows a series connection, with bypass.

 The heating element 77 is shown above the hearth. It could just as easily constitute a chimney or chenille plate. It will be compulsory to provide a safety device preventing the bypass valve from closing during the operation of the fire. Of wood.

 mounting in series is not a necessity, but allows you to make the most of the advantages of the system, since the wood fire provides not only the heat, but the flow temperature of the heating water. poesible, but would have the disadvantage of reducing the volume of water passing through the body 77 and increasing the risk of wear due to fire.

The installation of a wood fire is generally. considered, in itself, as a comfort factor. The device described can therefore be applied in all small or medium-sized installations where an addition to gas or fuel would lead to an overly complex installation, and where an additional to electricity would entail a risk for the future, the cold days being for EDF peak days,
the use of electricity indeed Joule so much to proscribe, in any event.

Claims (11)

CLAIMS 10- Device according to claims 1, 2, 3 and 12 of the patent, in which the exchange surfaces are -constituted by two successive networks, mounted in series, with or without collector (s) interposed between the two networks, one of the networks being located in the central area of the basement or the crawl space of heated buildings, the other network, in which water, like the surrounding scl, is at a lower temperature, being located at the periphery of the batime @ ts, inside or outside thereof, and / or partially below the first network and thus uses to create a screen for heat losses from the hottest icon. 20 - Device according to claim 1 above, wherein the pipes or elements constituting the exchange surfaces are embedded in a special layer intended for the diffusion of heat, this layer being produced using materials having a good thermal conductivity and improving the thermal bond between the exchange surfaces and the ground.  3 - Device according to claims 1, and 2 above, wherein the material constituting the diffusion layer is chosen for  its plasticity (sand, for example) which guarantees the permanence of the con  tacts between the diffusion layer, the exchange surfaces, and the ground.  4 - Device according to claims 1 and 2 above, in which the product constituting the diffusion layer is chosen for the quality and reliability of its thermal connections with the exchange surfaces (cement concrete, vibrated, coating piping, for example  ple) and for its own conductivity qualities.  5 - Device according to claims 1, 2 and 3 of the patent, wherein the ground for the storage of heat is lined with masses of chemical product @ high latent heat by phase change, these masses being arranged so as to brake the diffusion of heat towards the periphery of the buildings, and to increase the thermal inertia of the ground, in particular during the interseason.  6 - Device according to Claims 10 and 11 of the patent, in which the risk of freezing in the solar collectors is avoided, during the winter thanks to the use of the heat contained in the extracted air  heated buildings. - / 7 - Device according to claim 6 above, wherein the water intended to pass through the sensors passes through, beforehand, in totali or partially, a battery heated thanks to the passage of the extracted air, in whole or in part, with the possibility of slaving the level of heating to the water temperature in or at the output of sensors.  8 - Device according to claim 6 above, wherein the extracted air heats up, using appropriate exchange surfaces, the  rear side of the collectors, which thus become usable for capturing both the solar heat and that of the extracted air, with the possibility of limiting or interrupting the passage of air, the rear thermal insulation of the collectors, behind the passage of air, which can be maintained, reduced, or even removes.  9 - Device in accordance with claim 6 above in which the extracted air is used to heat the room where the solar collectors are arranged, with the possibility of adjusting the air flow rate. 10 - Device according to: claims 6 and 9 above, wherein the sensor itself being separated from the glazing, which separates the room from the outside, the flow of extracted air is directed between the sensor and the vitrage.de high are low. 11 - Device according to claims 10 and 11 of the patent, in which the heat reservoir is used successively, either normally as a daily regulation reservoir, or as a seasonal reservoir, a set of fittings then making it possible to separate the reservoir from the circuit d 'heating supply e to empty it more or less completely of the available heat it contains, this arrangement making it possible to decrease the power of the basic installation and improve the average efficiency of the installation.  120- Device according to claims 10 and 11 of the patent, in which the heat reservoir described in the patent is supplemented by a seasonal heat reservoir (sensible or latent heat) intended to meet the excess heat requirements of very cold oracle days to the modulated use of the stored heat and its temperature level, this arrangement making it possible to reduce the power of the installation and thus improve its average efficiency. 13 - Device according to claim 11 of the patent, in which a water heating system, obtained by means of suitable exchange surfaces placed in the enclosure of an open fire, supplied with wood or similar fuels, allows, by its association with solar-based heating, to reduce the installed power thereof, to reduce the cost, to improve the average efficiency, the use of the installation made in the chimney (or in a suitable similar device) allowing the cold peaks to pass thanks to the added heat and the increased temperature.