Heat accumulator

heat storage

The invention relates to a heat accumulator comprising a large-volume reservoir for storing a storage medium, in particular hot water, as well as methods for its production.

The operation of a heating system or the provision of hot water is often performed by means of heat storage. In principle, a thermal storage heat record from a heat source such as a solar energy system and long-term storage. If needed, the stored energy can be extracted from the heat store again and used for example for heating.

From DE 2005 037 997 Al a heat accumulator is known, which comprises at least one storage container arranged in the ground, wherein the storage container is formed of a pressure-resistant material and surrounded by a thermally insulating, pressure-resistant material. One possibility for the construction of heat storage is, the heat storage to construct such that they comprise an inner container, an outer container and disposed between the inner and the outer container thermal insulation. The inner container is formed such that it can withstand the damage caused by the picked storage medium in the heat accumulator internal pressure. The thermal insulation is placed without pressure to the inner container. Neither the thermal insulation or the serving as a protective sleeve outer container take on a significant portion of the internal pressure. The internal pressure is thus almost entirely absorbed by the inner container. If the inner container made of plastic, so it must have a very large wall thickness in order to have sufficient strength to withstand the internal pressure permanently. The necessary wall thickness is greater, the higher the temperature of the stored heat in the memory storage medium. From a resistance to internal pressure diagram of a thermoplastic material can be seen that on the timeline depends on the temperature decreases the comparison voltage. The higher the temperature is, the lower is the comparison voltage with the same service life. The resulting necessary large wall thickness of the inner container are disadvantageous because the weight of the heat accumulator is thereby increased, which makes handling more difficult and the transport costs are increased, caused by the higher material consumption higher costs and thus also the outer diameter of the heat accumulator is relatively large. If the heat storage system for use in a house determines it must not mountaineering Ü its outer diameter advantageously integrated door width of 79 cm. A large wall thickness thus causes the inner diameter of the heat container is reduced and therefore the maximum volume of the heat accumulator is limited. The object of the invention to provide a large volume Wärniespeicher which is inexpensive in construction and relatively easy to manufacture and can ignore efficiently store heat over a longer period.

This object is solved by the features of claim 1. Advantageous developments of the invention are specified in the dependent claims.

According to the invention, the large-volume storage tank of the heat accumulator an inner container and an outer container wherein the inner container made of a temperature-resistant thermoplastic material formed and the outer container is made of a pressure-resistant thermoplastic. In an intermediate space between the inner container and the outer container a pressure-resistant, heat-insulating material is arranged.

It is advantageous if the wall thickness of the outer container is greater than the wall thickness of the inner container. In particular, it is advantageous if the outer container, the inner container and the wärmeisolϊerende material are configured such that a pressure applied to the heat accumulator pressure is substantially absorbed by the outer container. With such a force exerted on the heat accumulator pressure is, in particular to a pressure exerted by the recorded medium in the heat storage memory internal pressure. Alternatively or additionally, an external pressure can act on the heat store. This is especially the case, when the heat accumulator is accommodated in the ground and is not filled or only partly with a storage medium. Characterized in that the pressure is substantially of the outer container and not or only to low levels through the inner container and the thermal insulation Rende material is taken, it is achieved that the sum of the wall thicknesses of the outer container and the inner container is lower than if the pressure would only be taken up by the inner container. A resistance to internal pressure diagram of a thermoplastic material it follows that the lower the temperature is, a smaller wall thickness is required to receive the same pressure. Since the inner tank has almost the temperature of the storage medium, the outer container but on the other hand, only the room temperature or the temperature of the soil in which it is arranged has, the required wall thickness accumulated is smaller. The reduced wall thickness summed weight of the heat accumulator is reduced and reduced material costs. Here, the material cost can be reduced to about 50%. Furthermore, such thinner walls allow manufacturing technology easier to control and the transport and the related transport costs are facilitated due to the low weight. Further, a low cooling of the inner and outer container is achieved in the manufacturing process.

Furthermore, it is advantageous that the plastic from which the outer container is formed is suitable to be received in the ground. This allows the heat sinks are arranged in a space-saving manner in the ground.

A particular advantage of the inventive heat accumulator is that the reservoir in a particularly simple and inexpensive way to produce, since the production of the storage tank, to be formed of an inexpensive, thermoplastic, reading a relatively simple feasible B can be carried out molding process. In an advantageous development of the invention the storage container substantially has the shape of a sphere, an ellipsoid of revolution or a cylinder. Preferably, the spherical shape is to be selected when used in the soil, as a result of the ratio of surface area to volume, the ball can be expected the lowest heat losses and the ball can show a high compressive strength simultaneously.

In the temperature-resistant plastic of the inner container it is preferably polypropylene (PP) or polyethylene (PE), as PP or PE has a heat resistance up to 95 ° C and is thus adapted to the temperature conditions of the storage medium when the internal container, for example for receiving serving of hot water. This has the advantage that in the manufacture of the inner container, the wall thickness of the inner container may be selected to be relatively thin and thus material cost can be saved.

In the pressure-resistant plastic material of the outer container it is preferably polyethylene (PE), a duroplatischen plastic or glass fiber reinforced plastic (GRP).

In the heat-insulating, pressure-resistant material of the intermediate layer between the outer container and the inner container is a rigid foam, preferably polyurethane (PU)₅ as polyurethane may have a strength which is adapted to the pressure conditions in the inner container which are in the range of 100 to 200 kPa

Further, it is advantageous that the outer container comprises at least a first part and a second part. It is particularly advantageous if these parts have a maximum dimension in one direction is less 79 cm, for example, are each a maximum of 79 cm long. In this way the parts of the outer container can be transported in a simple manner through a standard door having a width of 79 cm. Through the construction of the outer container of several parts a greater filling volume of the heat accumulator can be realized and this heat storage are transported nonetheless easily in interiors.

Another aspect of the invention relates to a method for producing a large volume memory element for storage of heat energy, in which in a blow-molding an inner container is manufactured from thermoplastic material. In a further blow molding an outer container with a larger diameter is formed as the inner container of thermoplastic material. The outer container is divided into at least two parts. These parts are arranged at a predetermined distance from the outer surface of the inner container with space therebetween. Subsequently, the parts of the outer container are connected to each other and the space between the inner container and outer container is filled with plastic foam material.

Another aspect relates to another method for producing a large volume storage tank for the storage of thermal energy, in which in a blow-molding an inner container is manufactured from thermoplastic material and in a further blow molding process at least two parts of an outer container having a larger diameter than the inner containers are made of thermoplastic material , On the inside of the parts of the outer container, which faces the inner container in the assembled state, a layer of plastic foam material is applied in each case in a foaming process, is the dimensionieret such that an intermediate region between the inner container and the outer container is at least partially filled by this layer. The parts of the outer container are disposed about the inner container and subsequently interconnected.

It is particularly advantageous if the inner container and the parts of the outer container are separately transported to the place where the storage container is to be placed and assembled only there. In this way, the transport of the heat accumulator or of the individual components of the heat accumulator is simplified and the parts can be easily transported through doors or other smaller openings.

The parts of the outer container are preferably connected to each other via at least one formed by at least one external thread and at least one internal thread screw connection. The thread can be molding forming process with a simple way in the manufacture of parts in the blow. Furthermore, can such screw connection with the dismantling of a heat accumulator solve nondestructively.

Alternatively, the parts of the outer container may be interconnected by a clamping ring.

The method of claims relate to production processes for the various products according to the invention, as defined in the claims based on structural and functional characteristics. To specify the manufacturing steps for different product examples of these features can be included. The invention will be explained with reference to embodiments in conjunction with drawings. In which:

1 shows a simplified sectional view of a disposed in the ground heat accumulator,

Figure 2 is a detailed sectional view of the heat accumulator of Figure 1 in a neck portion,

3 shows a simplified sectional view of three heat store different volumes,

4 shows a simplified sectional view of a heat accumulator for the aerial application of a first embodiment of the invention,

5 shows a simplified sectional view of a heat accumulator for the aerial application of a second embodiment of the invention,

Figure 6 is a simplified sectional view of a heat accumulator for the aerial application of a third embodiment of the invention,

Figure 7 is a simplified sectional view of a heat accumulator for the aerial application of a fourth embodiment of the invention, and Figures 8 to 10 examples of a three-layered wall structure for the inner container.

1 shows in a simplified sectional view of a spherical heat accumulator 10 with a storage container 12 which comprises an inner container 14 and an outer container sixteenth The storage tank 12 is disposed in this example, in use in the soil. The inner container 14 is made in a blow molding and is made of a temperature-resistant thermoplastic plastic, preferably of solid (ie unfoamed) polypropylene (PP) formed. The inner container 14 can be filled for example with hot water as a storage medium 18th The material of the inner container 14 is chosen so that a durability of the material to the operating temperature of the storage medium 18, in this case, hot water, of up to 95 ° C is ensured. The capacity of the storage tank 14 is in this embodiment, approximately 3000 1, which corresponds to a diameter of the spherical storage container 12 of approximately 2.10 to 2.20 m. The outer container 12 is also formed of plastic. The size and weight of the storage tank 14 are thus for a load carrier of the storage container 14, for example, for transport over long distances in a truck, well suited.

The outer container 16, which is also read in the B is made molding process consists of a pressure-resistant thermoplastic plastic, preferably of solid polyethylene (PE), in order to achieve a sufficiently high resistance of the outer container 16 against the externally acting earth pressure of the soil. Characterized a particularly high stability of the storage tank 12 is achieved. A gap 20 is formed between the inner container 14 and outer container 16 which is filled with a thermally insulating, pressure-resistant rigid foam, preferably polyurethane (PU). The intermediate space 20 is charged by the pressure of water present in the hot water Irmenbehälter 14 eighteenth By filling the gap 20 with the heat-insulating, pressure-resistant rigid foam is achieved that the heat losses of the storage medium are minimized 18 in the inner container 14, wherein simultaneously pressing together of the gap 20 by the internal pressure of the inner container 14, which is in the range of 100 to 200 kPa (about 10 to 20 m water column), avoided.

The storage tank 12 includes upward pressure resistant with a pressure cap 22 of steel from which the pressure lid 22 is removable for possible inspection of the inner container 14th The heat accumulator 10 is provided with a power transmission system (not shown) coupled with a tube 24 is provided in the storage container 12 for a discharge of the storage medium 18 and a further pipe 40 for delivery of the storage medium 18th An assembly housing 26 which is formed for example of a plastic cylinder is disposed in a neck region 28 of the storage container 12 and lies with its underside on the outer container 16. It may be there is welded to the outer container 16th This mounting housing 26, which comprises an insulating ring 30, the protection of which is arranged in a mounting area for connections 32 functions (not shown here) fittings from rain water and earth. Insulating ring 30 is made of insulating plastic material, such as polyurethane (PU), and protects against heat loss, which can occur in the area 22 of the pressure lid, since there is a thermally conductive bridge yet. Figure 2 is a detailed sectional view of the neck portion 28 of the storage container 12 of Figure 1. In this embodiment, a tube is provided by leadership 34 on the neck 36 of the reservoir 12 for the supply and / or removal of the storage medium 18th The tube 24 is 34 fixed to the inner wall of the inner container 14 in the area of ​​pipe penetration for better sealing by means of a weld 44th The tube 24 is 34 of the outer container 16 is flanged in the area of ​​the duct by means of a flange 46th A clamping ring 42 is used for locking the pressure lid 22 above the pressure lid 22 is another cover 38. This lid 38 is formed of a thermally insulating plastic and is used for heat insulation of the storage container 12 in the area of ​​the pressure lid 22 which is formed from steel.

Figure 3 shows a sectional view of three heat storage 10a, 10b, 10c, which are distinguished by their different capacity of each inner container 14 and in this embodiment, have a capacity of 2000, 3000 and 4000. 1 The first heat storage 10a with the capacity of 2000 1 includes a spherical inner container 14a₅ having a diameter of 1.60 m and a spherical outer container 16a which has a diameter of 1.80 m. The second heat storage 10b has the capacity of 3000 1 and comprises an inner container 14b with the diameter of 1.80 m and an outer container 16b with a diameter of 2.00 m. The third heat storage 10c with the capacity of 4000 1 includes an inner container 14c with the diameter of 2.00 m and an outer container 16c with the diameter of 2.20 m. The respective inner container 14 and the respective outer container 16 of the spherical heat accumulator 10 are, as already mentioned, produced in the blow molding process.

The blow molding process is used to manufacture the respective inner container 14 or the outer container 16 made of plastic. In this blow molding is first plastic granulate, which forms the basis of the thermoplastic material melted in an extruder and it is a hot plastic tube through a die into an open blow mold. Subsequently, the blow mold is closed and the enclosed plastic tube inflated with compressed air and pressed against the contours of the blow mold. Through the cold surface of the blow mold the plastic tubing cools rapidly, whereby the plastic has adapted to the shape of the blow mold is tight. By varying the material thickness in the plastic tube can be the thickness of the walls of the hollow body control. Upon completion of the cooling operation, the hollow body can be removed from the blow mold.

The storage container 12 can be manufactured in a simple manner by mixing in a blow molding process as described above, the inner container 14 is made of a thermoplastic plastic and is manufactured in a further blow molding process, the outer container 16 of thermoplastic material, wherein the outer container 16 each have a larger diameter than the inner container 14 has. Subsequently, the outer container 16 is divided into at least two parts and the divided parts of the outer container 16 arranged at a predetermined distance from the outer surface of the inner container 14, wherein the parts of the outer container 16 connected by means of a welding process with each other are the and the gap 20 is filled between the inner container 14 and outer container 16 with plastic foam material.

When B las molding process are for producing the inner container or the outer container, different blow molding needs. This blow molding are relatively expensive to produce and are expensive. Therefore, the blow molding can be designed so that the same blow molding are used for the production of several storage containers having different volumes for the required inner container and the outer container. The storage container 10a according to Figure 3 with small volume having an outer container 16a, which was prepared with the aid of a blow mold with an outer diameter of 1.80 m. The same blow mold can be used for the storage container 10b of medium volume, in order to manufacture the inner container 14b from another plastic material. The blow mold for the outer container 16b may be used for the storage vessel 10c to make the inner container 14c. In order to produce the three illustrated in Figure 3 storage container 10a, 10b, 10c, not six blow molding are required, but only four. The diameter of the outer container and the inner container must be adapted to one another accordingly, so that the same blow mold can be used once for an outer container and an inner container for once. Analogously, it can be continued for a larger number of storage tanks.

4 shows a simplified sectional view of a heat accumulator 50 is shown for the overground use in a first embodiment of the invention. Elements of the same design or the same function have the same reference numerals. The heat accumulator 50 is mainly used in heating systems in conjunction with solar thermal systems, heat pumps, solid fuel boilers, boilers and gas boilers. The heat accumulator 50 is filled with a storage medium 18th The task of the heat accumulator 50 is to store the heat of the storage medium 18 over a long period.

As the certain for use in ground heat storage 10 according to Figures 1 to 3 includes the above-ground heat storage 50 to 4 a in a B las inner container molding process produced 14 and also read in a B outer container molding process produced 16. The inner container 14 is , in particular polypropylene manufactured from plastic. The outer container is made of a thermoplastic plastic, in particular polyethylene, polypropylene or a thermosetting plastic. The outer diameter of the inner container 14 is less than the inner diameter of the outer container 16. The space thus formed between the inner vessel 14 and outer vessel 16 is provided with a heat-insulating, pressure-resistant rigid foam, preferably rigid polyurethane filled. Through the use of plastics is achieved that the heat of the storage medium 18 for a long time can be saved. The thermal conductivity of plastic materials is much lower than the heat conductivity of metallic materials, so that the heat losses are lower.

The outer container 16 has a largest dimension of an outer diameter of not more than 79 cm. In this way it is achieved that the heat accumulator 50 can be easily transported by standard doors with a width of 80 cm, so that the heat accumulator 50 in a simple Manner, without having to be disassembled into its component parts have to be built up in houses, especially in basements. The heat storage unit 50 has a capacity of about 400. 1

The bottom 15a of the inner container 14 is formed into a hemispherical shape. Likewise, the bottom 15a of the opposite segment 15b, in which the opening portion of the inner container 14 is formed is hemispherical. The intermediate area 15c between the bottom 15a and the segment 15b is cylindrical. By this geometrical configuration of the inner container 14 is a high pressure resistance is achieved. The outer container 16 has approximately the same shape as the inner container 14. The bottom 17 of the outer container 16 is not completely hemispherically shaped, but flattened, so that the heat accumulator 50 can safely stand upright on this flattened bottom in use.

Alternatively, both the inner container 14 and the outer container 16 may be completely formed spherical. In this way a very high compressive strength of the heat accumulator 50 is reached.

The heat storage unit 50 has at the bottom side opposite the container opening, which is closed pressure-tight by means of a pressure cap 58th The pressure cap 58 includes a plurality of apertures 60, 62, through the various components, in particular heat exchangers, temperature sensor, filling lines and / or discharge lines, can be introduced. Furthermore, the opening of the heat accumulator 50 and the discharge cover 58 are covered by a pot-shaped insulating hood 64th The insulating cap 64 comprises an insulating washer and two interconnected semi-annular elements which surround the insulating disk. The ϊsolierhaube 64 serve on the one hand to protect through the openings 60, 62 incorporated components and for the isolation of the heat accumulator 50th

The outer container 16 includes a first part 52 and a second part 54 which are connected to each other through a welded connection 56th The welded connection 56 is preferably arranged in the cylindrical intermediate portion of the outer container sixteenth

Through the storage medium 18, an internal pressure in the heat accumulator 50 is applied. By the inner pressure of the heat accumulator 50 is loaded by a circumferential tension. The internal pressure is to be incorporated in particular through the inner container 14, the outer container 16 and the foam insulation. From a creep internal pressure diagram for the plastics used can be determined for a desired service life and the corresponding operating temperature of the components, the maximum tolerable voltage reference. The components have to be dimensioned such that the internal pressure caused by circumferential tension is less than or equal to said determined comparison voltage. Is the actual stress occurring is greater than the comparison voltage, the desired service life is not achieved at the operating temperature. The higher the internal pressure, the greater needs to be chosen the wall thickness of the component, so that the comparison voltage is not exceeded. The comparison voltage is lower, the higher the temperature of the component. The heat accumulator 50 is dimensioned such that a large part of the load caused by the internal pressure is absorbed by the outer container sixteenth The outer container 16 has substantially a temperature of room temperature, ie approximately 2O⁰C corresponds. The average temperature of the inner container 14, however, is due to the warm storage medium 18 significantly higher. The storage medium has a temperature of 95⁰C, so the average temperature of the inner container 14 between 60 to 70⁰C. The outer container 16 thus requires a much smaller wall thickness than the inner container 14 to withstand the same internal pressure. The sum of the wall thickness of the inner container 14 and the wall thickness of the outer container 16 of the heat accumulator 50 is substantially less than the summed wall thickness of an inner container and an outer container in a heat accumulator in which the caused by an internal pressure load is absorbed by the inner container substantially. In this way savings of up to 50% of the material. Further, the heat accumulator 50 is thereby more easily, so it is easier to handle and can be transported more cost effective. Likewise, the cooling time is significantly reduced when blow through the lower wall thickness.

In the invention, the wall thickness of the outer container 16 is by a factor of 1.5 to 2.5 greater than the wall thickness of the inner container 14 for all examples.

Advantageously, the inner container 14 and foam insulation are constructed such that they have Langzeitkriechverhalten that are coordinated so that a minimum residual maturity is guaranteed. Further, it is advantageous that the outer container 16 has a strength that is sufficient to achieve this minimum remaining time to receive the complete caused by the internal pressure load.

5 shows a simplified sectional view of a heat accumulator 70 is shown for the overground use in a second embodiment of the invention. Compared to the heat shown in Figure 4 Memory 50, the cylindrical intermediate region of the heat accumulator 70 longer, so that the heat accumulator 70 according to Figure 5 has a larger volumetric capacity than the heat storage 50 of FIG. 4 When using the heat storage 70 stands upright on the floor 16a.

The respective inner container 14 and outer container 16 of the heat accumulators 50, 70 are according to the figures 4 and 5, as already mentioned, produced in a blow molding process. The heat storage 50, 70 according to figure 4 and 5 can be manufactured in a simple manner by the method described in connection with the particular for use in the ground heat-storage 10 in the description of FIG. 3

Figure 6 shows a simplified sectional view of a heat accumulator 80 for the aerial application according to a third embodiment of the invention. The outer diameter of the inner container 14 is approximately 79 cm. The outer container 16 comprises two parts 52, 54. The two parts 52, 54 of the outer container 16 are dimensioned such that they do not exceed respectively a maximum dimension in a direction of 79 cm. In this way it is achieved that both the inner container 14 as well as the two parts 52, 54 of the outer container 16 in a simple manner can be individually transported through a standard door having a width of about 80 cm, whereby the setting up of the heat accumulator 80 in homes , especially in cellars, in a simple manner is possible.

The first part 52 of the outer container 16 and the second part 54 of the outer container 16 are connected together via a screw connection. To this end, comprises one of the two parts 52, 54 an internal thread 82 and the other part 52, 54 a to the inner thread 82 complementary external thread 84. By screw connecting the two parts 52, 54 of the outer container 16 when setting up the Wärmespeϊchers 80 are connected at its destination in a simple manner. Likewise, the two parts can be 52, 54 separated during disassembly easily without destruction of one another. By locking screw connection, the heat losses are reduced.

Alternatively, the parts can be 52 and 54 connected together by a clamping ring.

7 shows a simplified sectional view of a heat accumulator 90 is shown for the overground use in a fourth embodiment of the invention. The heat accumulator 90 comprises an inner container 14 having a diameter of about 79 cm. The outer container 16 is divided into three parts 92, 94, 96th The three parts 92, 94, 96 are dimensioned such that they do not exceed a length of 79 cm each. The first part 92 is connected via a first threaded connection 98 with the second part 94 and the second part 94 is connected via a second screw connection 100 with the third part 96th The screw 98, 100 are each formed by an internal thread and a complementary to this internal thread external thread.

Both the external and the internal thread are formed during blow molding of the parts 92, 94, 96 with. Through the multi-part design of the heat accumulator 90 has a larger volume is achieved.

In alternative embodiments of the invention the heat accumulator 90 can also be made of more than three parts, for example consist of four parts, whereby a larger volume of the heat accumulator is reached, and / or the size of the components is reduced, so that the heat accumulator can be transported also by smaller doors or other openings.

The storage tank 12 of the heat accumulator 80, 90 according to Figures 6 and 7 can be manufactured in a simple manner with the aid of a blow molding process. For this purpose, the inner container is in a first blow-molding process, as described in connection with Figure 3, 14 is made of thermoplastic material. In another blow molding the individual parts 52, 54, 92, 94, 96 of the outer container 16 are produced, the respective female and male threads 82, 84 are formed directly. In the next step, the foam insulation is applied to the individual parts 52, 54, 92, 94, 96th The parts 52, 54, 92, 94, 96 of the outer container 16 are for this purpose filled by means of foaming molds, each having an inner core of which the diameter corresponds to the outer diameter of the inner container 14 with rigid foam material. In this process, the parts 52, 54, 92, 94, 96 respectively, the outer shape and the inner cores of the foaming molds form the corresponding internal shape. The space between the parts 52, 54, 92, 94, 96, and the inner cores is in each case filled with the insulating foam, so that the insulation is formed. The foam insulation is maintained even after removal of the inner cores of the parts 52, 54, 92, 94, adhere 96th The inner container 14 and the parts 52, 54, 92, 94, 96 of the outer container are separately transported to the installation site of the heat accumulator 80, 90 and mounted only at the site by the parts 52, 54, 92, 94, 96 on the inner container 14 be slipped and are connected by means of the screw formed by the internal and external threads 82, 84 firmly together. The heat storage 50, 70, 80, 90 described in Figures 4-7 is set up for upright operation, that its longitudinal axis is vertical. The outer parts 52, 54, 92, 94, 96 and the associated rigid foam insulation thus have horizontal rules, which entails significant technical advantages. A vertical separation of the insulation and the outer parts leads to a relatively long separating line. Now, when the inner container 14, a compressive force is applied to the outer shell due to its internal pressure on the foam insulation, so a gap increases along this dividing line between the parts and it will increase the output via this gap heat loss. In the present invention, in particular in a screw connection of the parts, relatively short separation distances and a better sealing can be achieved, so that the heat loss is reduced.

In the previous embodiments, the inner container 14 is a single layer of solid PE or PP. In order to improve the property of the heat storage even further, the inner container 14 may have a three-layered wall construction. The examples of Figures 8, 9 and 10 show such embodiments of an inner container 14 having an inner layer 102, a middle layer 104 and an outer layer 106. Preferably, the inner layer 102 comprises solid PP or massive PE and the outer layer 106 solid PP or massive PE. The middle layer 104 comprises foamed PP or foamed PE (Figure 8).

A development showing the example of Figure 9, in which the middle layer 104 is made of solid or foamed PP or PE and an additional reinforcement made of glass fiber 108 includes 108th In this way, the pressure stability of the inner container 14 can be further improved. Optionally, to further increase the compressive strength is also a outer glass fiber reinforcement 110 of the outer layer 106 may be provided with polyester resin or epoxy resin. Example 9 may be modified so that the ϊnnenschicht 102 and the outer layer 106 made of solid PE or PP and the middle layer 104 is made of foamed PE or PP. The outer layer 106 then includes a glass fiber reinforcement 110. In such a structure results from the foamed middle layer 104 to improve the heat insulation and the glass fiber reinforcement 110 an improvement in the compressive strength.

A high priority in heating technology has the oxygen diffusion. This should be below a limit value, in order to ensure high corrosion resistance of the heating pipes. For this DIN is to meet 4726th In the examples according to the invention, the ratio of tank volume to the container surface is relatively large and the wall thickness of the inner container 14 is large, so that only an extremely small oxygen diffusion can occur. A further improvement can be achieved by an oxygen-barrier layer in the inner container fourteenth In the example of Figure 10 is as a middle layer 112, a barrier layer, known as EVOH (ethylene-vinyl cleaner-alcohol) or Selar (product name) used. This layer 112 may also be combined with the middle layer 104 according to the examples of FIGS. 8 and 9 Alternatively or additionally, an outer fluorination and / or an inner fluorination of the inner container be made fourteenth LIST OF REFERENCE NUMBERS

10, 10a, 10b, 10c, 50, 70, 80, 90 heat storage

12, 12a, 12b, 12c reservoir

14, 14a, 14b, 14c inside container

16, 16a, 16b, 16c outer container

18 storage medium, hot water

20 clearance

22 pressure cap

24 outlet

26 mounting housing

28 neck

30 insulating ring

32 mounting area for connections

34 pipe penetration

36 neck

38 End cover

40 inlet pipe

42 clamping ring

44 weld

46 flange

52, 54, 92, 94, 96 parts of the outer container

56 S ch white verb indung

58 pressure cap

60, 62 holes

64 insulation hood

82, 84 threaded

98, 100 V ery aub connection

102 inner layer 104 middle class

106 outer layer

108 glass fiber reinforcement

110 glass fiber reinforcement

1 12 barrier layer