WO2021009629A1

WO2021009629A1 - Heat store with phase change material

Info

Publication number: WO2021009629A1
Application number: PCT/IB2020/056477
Authority: WO
Inventors: Roland Diethelm; Erhard Krumpholz; Thomas Schneider; Christian LEFFERING; Renato Götz; Steffen PORSCHE
Original assignee: Zehnder Group International Ag
Priority date: 2019-07-12
Filing date: 2020-07-09
Publication date: 2021-01-21

Abstract

The invention relates to a device (1) for receiving, storing and releasing heat. The device comprises a heat carrier fluid volume region (FV), which can be flowed through by at least one heat carrier fluid (F), and a phase change material volume region (PV), which contains a phase change material (P). At a phase change temperature TW, the phase change material (P) can undergo a reversible phase change between a first state, which exists below the phase change temperature TW, of the phase change material (P) and a second state, which exists above the phase change temperature TW, of the phase change material (P). The heat carrier fluid volume region (FV) adjoins the phase change material volume region (PV) via boundary surfaces (G). The volume regions (FV, PV) are arranged in a container (B) which has a container inner wall (Bi), a container outer wall (Ba) and a thermally insulating installation region (IB) which is arranged between the container inner wall (Bi) and the container outer wall (Ba).

Description

Heat storage with phase change material

The invention relates to a device for absorbing, storing and releasing heat, which comes for example from a solar collector or a power / heat coupling system.

The use of storage tanks to store sensible heat is known. The use of containers filled with water as heat accumulators is particularly popular because of the high heat capacity of water and its low cost and low risk to the environment. The disadvantage here is that the change in temperature of the water in the container is proportional to the amount of heat taken up or given off by the water. If you store larger amounts of heat, the temperature of the storage rises sharply compared to the ambient temperature inside or outside a building, causing high heat losses from the storage

Environment arise through thermal conduction, thermal radiation and convection. Seasonal storage of heat is hardly possible even with a large amount of measures to insulate the storage tank. Only the use of huge bodies of water with the smallest possible surface / volume ratio comes into question.

The use of storage devices for storing latent heat is also known. The use of containers filled with phase change material as heat storage is due to the high

Energy density very interesting. Solid / liquid systems are particularly popular, such as ice stores (frozen / thawed water), wax stores (solidified / melted wax),

Paraffin storage (solidified / melted paraffin), in which the gas phase is negligible in normal operation close to the respective melting temperature of the system due to the usually low vapor pressure there. The melting temperatures or melting temperature ranges of such solid / liquid systems can be adjusted over a wide range through the choice of molecules (length of the carbon chains, degree of branching, presence of polar groups, etc.) or by mixing different types of molecules. For example, melting temperatures, i.e. phase change storage operating temperatures of 0 ° C (ice storage), of around 30 to 60 ° C

(Wax / paraffin storage) or from about 60 to 90 ° C (compared to wax / paraffin even longer molecules or molecules provided with polar groups). These phase change storage systems have a much higher energy storage density than storage of sensible heat. Such phase change storage in buildings, in particular in connection with solar thermal energy and with storage temperatures of on the one hand, for example 30 ° C and on the other hand, for example 80 ° C Heat storage can be used for a period of several weeks. Seasonal storage of heat is only possible here to a limited extent and, if so, then only with a high level of expenditure on heat insulation measures for the storage tank.

The invention is therefore based on the object of enabling long-term, in particular and at least seasonal, storage of heat.

To achieve the object, the invention provides a device for absorbing, storing and releasing heat, wherein the device occupies a volume which

has a heat transfer fluid volume area through which at least one heat transfer fluid can flow and a phase change material volume area containing a phase change material, the phase change material having a reversible phase change between a phase change temperature TW at a phase change temperature TW

existing first state of the phase change material and one above the

Phase change temperature TW can pass through existing second state of the phase change material, and wherein the heat transfer fluid volume area adjoins the phase change material volume area via interfaces, characterized in that the two volume areas are arranged in a container which has a container inner wall facing the volume areas, one of has the outer wall of the container facing away from the volume regions and a thermally insulating insulation region arranged between the inner wall of the container and the outer wall of the container.

The thermal insulation area between the inner wall of the container and the outer wall of the container ensures that between the medium surrounding the device

(typically air) and the phase change material inside the device, only a small amount of thermal energy is exchanged, e.g. through thermal conduction and / or thermal radiation.

The device expediently contains one of a first heat transfer fluid

flow through first volume area, one of a second heat transfer fluid

permeable second volume area as well as a third volume area containing at least one phase change material, the first volume area adjoining the third volume area via first interfaces and the second volume area adjoining the third volume area via second interfaces, the three volume areas being arranged in a container, which one to has the inner wall of the container facing the volume regions, an outer container wall facing away from the volume regions and a thermally insulating insulation region arranged between the inner wall of the container and the outer wall of the container. This enables, on the one hand, a supply or removal of heat through the first boundary surfaces from the first heat transfer fluid in the first volume region to the

Phase change material in the third volume area, and on the other hand a supply or removal of heat through the second interfaces from the second heat transfer fluid in the second volume area to the phase change material in the third volume area. The device can thus be “charged” (heat supply) or “discharged” (heat dissipation).

The isolation area preferably contains an evacuated volume.

This minimizes an uncontrolled supply of heat from outside the device into the phase change material inside the device. This is relevant for the use of the device for cooling when the temperature of the phase change material is lower than the ambient temperature. Also an uncontrolled dissipation of heat from the

Phase change material inside the device minimized to the outside. This is also relevant for the use of the device for heating when the temperature of the phase change material is higher than the ambient temperature.

In the case of the container, at least the inner wall of the container facing the volume areas preferably has a melting temperature (e.g. for metal or thermoplastic) or decomposition temperature (e.g. for thermoset) which is higher than the phase change temperature of the phase change material, preferably more than 20K higher and particularly preferably around more than 40K higher.

This ensures the stability of the inner wall of the container when the store is being loaded and while the load is being held.

The second state of the phase change material is expediently more energetic than the first state of the phase change material.

In a particularly preferred embodiment, the phase change material is in its first state as a solid or in a solidified state and in its second state as a liquid or in a molten state.

During the transition between the first state and the second state, there is only a slight change in volume of the phase change material. Preferably that is used here

Phase change material enclosed in a capsule, the melting temperature of which is above the melting temperature of the phase change material. The cavity of the capsule is preferably only partially filled with the phase change material. This causes a change in volume of the

Phase change material harmless to the capsule during phase change. In a further particularly preferred embodiment, the phase change material is in its first state as a solid with a first material structure or first crystal structure and in its second state as a solid with a second material structure or second crystal structure.

During the transition between the first state and the second state, there is only a very slight change in volume of the phase change material. This can also be used here

Phase change material be enclosed in a capsule, the melting temperature of which is above the phase change temperature of the phase change material. Preferably, the flea space of the capsule is only partially filled with the phase change material, whereby a

Volume change of the phase change material is harmless to the capsule during phase change.

A wall for the material separation of the various volume areas is preferably arranged along the boundary surfaces.

This prevents parts of the phase change material from being flushed out of the third volume area and into the first or into the second volume area by the heat transfer fluid.

The wall is preferably formed from a material whose melting temperature, e.g. in the case of metal or thermoplastic as wall material, or whose decomposition temperature, e.g. in the case of thermosetting plastic as wall material, is higher than the phase change temperature TW of the phase change material.

This ensures that the wall remains stable even after long periods of operation without the device being completely discharged, i.e. while part of the phase change material is retained in its second, more energetic state.

The wall is preferably made of a material with high thermal conductivity, preferably from 30 W / (mK) to 500 W / (mK), and / or has a small wall thickness, preferably from 0.1 mm to 2 mm, particularly preferably from 0.2 mm up to 1.2 mm.

This ensures that the wall's thermal resistance is low. Thus, with a given temperature difference between the heat transfer fluid in the first or second volume area and the phase change temperature TW of the phase change material in the third volume area, a correspondingly high amount of thermal energy per unit of time can be transferred between the heat transfer fluid and the phase change material, which enables a faster charging or discharging of the device becomes.

The wall is preferably formed from a polymer material. With the deliberate acceptance of a low thermal conductivity of the wall material, there is the advantage that the wall material is largely free of corrosion compared to aqueous salt solutions or (practically anhydrous) molten salts as heat transfer fluid or as

Phase change material.

In a particularly advantageous embodiment, the wall is formed from a carbon / polymer composite material, which in its volume or in its polymer matrix contains a proportion of evenly distributed particles of a carbon allotrope such as graphite, in particular expanded graphite, graphene, fullerenes or carbon nanotubes.

Such an admixture of carbon allotrope particles increases the thermal conductivity of the wall material without impairing its mechanical stability and its chemical resistance to salt solutions or molten salts.

The proportion by weight of the carbon allotrope is preferably 2% to 70%, in particular 5% to 50%, of the carbon / polymer composite material.

The particle sizes of the particles of the carbon allotrope, in particular of expanded graphite, are preferably in the range from 1 μm to 500 μm. Typically the particle size distribution is a normal distribution.

The total fraction of the carbon allotrope preferably contains different size-specific fractions, i.e. particle size fractions, the carbon allotrope particles, in particular expanded graphite particles, of a first size-specific fraction having an average particle size which differs from the average particle size of a further size-specific fraction. The mean particle sizes of the two particle size distributions are preferably sufficiently far apart from one another that they form a bimodal distribution with two recognizable maxima in the two adjacent particle size distributions. It is also possible for more than two size-specific proportions to be added to the polymer matrix of the wall material as the respective particle size fraction. Even with such a polydisperse admixture, the mean particle sizes of the multiple particle size distributions are sufficiently far apart that the multiple adjacent particle size distributions form a multimodal distribution with multiple recognizable maxima.

The ratio of the mean particle sizes is preferably two different

size-specific proportions, ie particle size fractions, in the range from 100 to 1 to 10 to 1. The carbon / polymer composite material preferably contains different types of carbon allotrope.

Preferably, the wall is in the form of a line system, which is from a

Heat transfer fluid can flow through and into the phase change material in the

Phase change material volume area is at least partially embedded.

The partial embedding of the line system in the phase change material forms a free volume within the device into which the phase change material can expand when changing to its more voluminous state, so that the device is prevented from inflating or bursting. Preferably, both the phase change material and the line system each form a coherent volume. In the operating state of the device, these are on the one hand the phase change material volume and on the other hand the heat transfer fluid volume.

The line system preferably contains series and / or parallel connections

Pipe register as well as a fluid inlet and a fluid outlet, the fluid inlet being intended for receiving a heat transfer fluid, for example from a solar collector, with a storage charging temperature TL in the line system, the storage charging temperature TL being greater than the phase change temperature TW of the phase change material (TL> TW ).

The line system preferably contains series and / or parallel connections

Pipe register as well as a fluid inlet (FE) and a fluid outlet (FA), the fluid inlet (FE) being intended for receiving a heat transfer fluid from a heating circuit, for example, with a storage discharge temperature TE into the line system, the storage discharge temperature TE being lower than the Phase change temperature TW of the phase change material is (TE <TW).

The pipe registers connected fluidly in series and / or in parallel are preferably

side by side, in particular parallel to each other, arranged as a register package.

This makes the device compact, i.e. a small ratio of the surface area of the device to the volume of the device. As a result, given the type of thermally insulating insulation area between the inner wall of the container and the outer wall of the container, a

uncontrolled supply or removal of heat to the interior or from the interior of the device is minimized.

It is also advantageous if the wall as a plurality of capsule walls of a plurality of

There is phase change material capsules in which the phase change material is encapsulated and which can be flowed around by a heat transfer fluid. The plurality of phase change material capsules (PK) are preferably contained in the container (B) as a solid packing or as a loose bed, which has a fluid inlet (FE ') and a fluid outlet (FA'), the fluid inlet (FE ') for Receipt of a heat transfer fluid (F; Fl, F2) from a solar collector, for example, with a storage charging temperature TL in the container (B) is determined, the storage charging temperature TL being greater than the phase change temperature TW of the phase change material (P) (TL> TW).

The plurality of phase change material capsules (PK) are preferably contained in the container (B) as a solid packing or as a loose bed, which has a fluid inlet (FE ') and a fluid outlet (FA'), the fluid inlet (FE ') for Receipt of a heat transfer fluid (F; Fl, F2) originating from a heating circuit, for example, with a storage discharge temperature TE in the container (B) is determined, the storage discharge temperature TE being less than the phase change temperature TW of the phase change material (P) (TE < TW).

Preferably, the plurality of phase change material capsules contains a first plurality of phase change material capsules having a first capsule size and a second plurality of

Phase change material capsules with a second capsule size.

By selecting the size ratio of the two types of capsules, this enables a denser or less dense packing or bulk of phase change material capsules.

The phase change material capsules preferably have approximately the shape of a sphere, an ovoid, a cylinder, a prism, a cube or a parallelepiped.

By selecting the size ratio and / or the shape of the capsule type or types of capsules, this enables a denser or less dense packing or bulk of phase change material capsules.

The phase change material capsules preferably have a greater average density than the heat transfer fluid.

Thus, the individual phase change material capsules sink down in the container containing the heat transfer fluid and form a bed at the bottom of the container

Phase change material capsules.

In a further particularly advantageous embodiment, the line system contains a first heat pipe with a heat pipe evaporator area, a heat pipe condenser area and a first working fluid, the heat pipe evaporator area being arranged outside the device and the heat pipe condenser area being arranged inside the device. This first heat pipe is used to charge the storage device. This charging heat pipe has a very high thermal conductivity, so you can use it very deep inside the

Phase change material volume (third volume area) heat energy can be entered.

In a further, even more advantageous embodiment, the line system contains a second one

Heat pipe with a heat pipe evaporator area, a heat pipe condenser area and a second working fluid, the heat pipe evaporator area being arranged inside the device and the heat pipe condenser area being arranged outside the device.

This second heat pipe is used to discharge the storage device. This discharge heat pipe has a very high thermal conductivity, so that heat energy can be discharged very deeply from the interior of the phase change material volume (third volume area).

The first working fluid and the second working fluid are expediently the same type of fluid material.

The phase change material can contain an organic material such as wax, paraffin, fatty acid, ester, etc., or an inorganic material, in particular a salt or a salt mixture.

The phase change material preferably contains a paraffin whose chain length is in the range from 20 to 34 carbon atoms.

Such relatively short-chain organic materials have a melting temperature that is well below 100 ° C. This is advantageous for heating domestic water at atmospheric pressure.

The phase change material preferably contains an inorganic salt.

A first particularly preferred phase change material contains one of the following salts:

Na ₂ SO ₄ -10H ₂ O / NaCl-Na ₂ SO ₄ -10H ₂ O / Na ₂ Si0 ₃ -5H ₂ 0.

It is particularly advantageous if the phase change material (P) has an inorganic salt mixture with different anions and / or different cations.

Many (pure) inorganic salts, ie a respective combination of a single type of anions and a single type of cations, have a relatively high melting temperature that is well above 100 ° C. By mixing different such salts, a mixed salt is created which contains different types of anions and cations. In many cases it is the melting temperature such a mixed salt far below the respective melting temperature of the (pure) salts contained in the mixture.

It is particularly advantageous if the phase change material has a salt mixture which contains a combination of at least two of the following salts:

LiNOs / NaNOs / KN0 ₃ / NaN0 ₂ / KNO.

By mixing these salts, a mixed salt can be obtained whose melting temperature is between 50 ° C and 100 ° C. This is beneficial for heating domestic water

Atmospheric pressure.

Further advantages, features and possible applications of the invention emerge from the non-restrictive description / illustration with reference to the drawing, wherein

Fig. 1 is a sectional view of a first embodiment of the device according to the invention;

Figure 2 is a sectional view of a second embodiment of the device according to the invention;

FIG. 3 is an enlarged illustration of the sections A from FIG. 1 and from FIG. 2;

Figure 4 is a sectional view of a third embodiment of the device according to the invention; and

Figure 5 is a sectional view of a fourth embodiment of the device according to the invention.

1 shows a sectional view of a first embodiment of the device 1 according to the invention. The device 1 occupies a volume which has a heat transfer fluid volume area FV through which a heat transfer fluid F can flow and a phase change material volume area PV containing a phase change material P. At a phase change temperature TW, the phase change material P undergoes a reversible phase change between a first state of the existing below the phase change temperature TW

Phase change material P and a second state of phase change material P existing above phase change temperature TW. Heat transfer fluid volume region FV adjoins phase change material volume region PV via interfaces G. The volume areas

FV, PV are arranged in a container B, which is one facing the volume areas

Container inner wall Bi, a container outer wall Ba facing away from the volume areas and a thermally insulating insulation area IB arranged between the container inner wall Bi and the container outer wall Ba, as can be seen in the enlarged section A of

Fig. 3 sees better. The thermal insulation area between the inner wall of the container Bi and the The outer wall of the container Ba ensures that only little thermal energy is exchanged between the medium surrounding the device 1 (typically air) and the phase change material P inside the device 1, for example by conduction and / or thermal radiation. An effort is made to keep the phase change material P in the interior of the device 1 at its "working temperature", ie at its phase change temperature TW, at all times, ie during charging, discharging and holding the charge. This is achieved by always striving for a coexistence of the first state and the second state of the phase change material P.

2 shows a sectional view of a second embodiment of the device 1 'according to the invention. The device 1 ′ comprises a first volume area VI through which a first heat transfer fluid F1 can flow, a second volume area V2 through which a second heat transfer fluid F2 can flow, and a third volume area V3 containing at least one phase change material P. The first volume area VI adjoins the third volume area V3 via first interfaces Gl, and the second volume area V 2 adjoins the third volume area V3 via second interfaces G2. The volume areas VI, V 2, V3 are arranged in a container B, which has an inner container wall Bi facing the volume areas VI, V 2, V3, an outer container wall Ba facing away from the volume areas VI, V2, V3 and an outer wall Ba between the Has the container inner wall Bi and the container outer wall Ba arranged thermally insulating insulation area IB, as can also be seen better in the enlarged section A of FIG. Here, too, the thermal insulation area between the inner wall of the container Bi and the outer wall of the container Ba ensures that between the medium surrounding the device 1 '(typically air) and the phase change material P inside the device 1' there is only little thermal energy, for example through heat conduction and / or heat radiation is exchanged. Here, too, an effort is made to keep the phase change material P inside the device 1 'at its "working temperature" at all times, i.e. during charging, discharging and holding the charge. This is achieved by always having a coexistence of the first state and the second state of the

Phase change material P aims.

FIG. 3 shows an enlarged illustration of the sections A from FIG. 1 and from FIG. 2. One can see a respective section of the container inner wall Bi, the container outer wall Ba and the insulation area IB between the container inner wall Bi and the container outer wall Ba. The isolation area IB forms a fourth volume area V4 of the devices 1, 1 '.

FIG. 4 shows a sectional view of a third embodiment of the device 1 ″ according to the invention. A wall or several walls are used to materially separate the various

Volume areas (cf. FV, PV; VI, V 2, V3 in Fig. 1 and Fig. 2) are provided. The wall or the several walls are in the form of a line system L, which is carried by a heat transfer fluid F can flow through and into the phase change material P in the phase change material

Volume area PV is at least partially embedded. The line system L contains a pipe register or several pipe registers R connected in series and / or parallel in terms of fluid, as well as one

Fluid inlet FE and a fluid outlet FA. The entire device 1 ″ is contained in a container B.

Charging process:

The fluid inlet FE serves to receive a hot heat transfer fluid F, e.g. from a solar collector, with a storage charging temperature TL into the line system L. The storage charging temperature TL is greater than the phase change temperature TW of the phase change material P (TL> TW). The phase change material P is gradually charged, i.e. the phase change into the more energetic state is completed. The fluid outlet FA serves to discharge the heat transfer fluid F which has cooled down after flowing through the device 1 ″.

Unloading process:

The fluid inlet FE serves to receive a cold heat transfer fluid F, e.g. from a heating circuit, with a storage discharge temperature TE into the line system L. The storage discharge temperature TE is lower than the phase change temperature TW of the phase change material P (TE <TW). The phase change material P is gradually discharged, i.e. the

Phase change to the lower energy state completed. The fluid outlet FA is used to discharge the heat transfer fluid F, which has been warmed up after flowing through the device 1 ″.

The dashed line at the upper end of the volume of the phase change material P represents the level of the phase change material. The container B is not completely, in particular between 90% and 95% of the container volume, filled with phase change material P when the phase change material P is less in its state Volume (mostly the volume of the lower energy state). In contrast, the container B is completely or almost completely, in particular more than 95% of the container volume, filled with phase change material P when the phase change material P is in its state with a larger volume (usually the volume of the higher-energy state).

FIG. 5 shows a sectional view of a fourth embodiment of the device 1 "'according to the invention. Here, too, a wall or several walls are provided for the material separation of the various volume areas (cf. FV, PV; VI, V 2, V3 in FIG and Fig. 2) The wall or the plurality of walls lie as a plurality of capsule walls of a plurality of

Phase change material capsules PK before, in which the phase change material P is encapsulated and around which a heat transfer fluid F can flow. The plurality of phase change material capsules PK can be contained in the container B as a solid pack or as a loose bulk.

Charging process:

The container B has a fluid inlet FE 'and a fluid outlet FA', wherein the fluid inlet FE 'is intended to receive a heat transfer fluid F from a solar collector, for example, with a storage charging temperature TL in the container B. The storage charging temperature TL is greater than the phase change temperature TW of the phase change material P (TL> TW). The phase change material P is gradually charged, ie the phase change into the more energetic state is completed. The fluid outlet FA ¹ serves to discharge the heat transfer fluid F. which has "cooled down" after flowing through the device.

Unloading process:

The container B has a fluid inlet FE 'and a fluid outlet FA', wherein the fluid inlet FE 'is intended to receive a heat transfer fluid F, for example from a heating circuit, with a storage discharge temperature TE into the container B, the storage discharge temperature TE being less than the phase change temperature TW of the phase change material P is (TE <TW). The phase change material P is gradually discharged, ie the phase change into the lower-energy state is completed. The fluid outlet FA ¹ is used to deliver the after

Flow through the device "heated heat transfer fluid F.

It can also be seen that the plurality of phase change material capsules PK has a first plurality of large phase change material capsules PK1 and a second plurality of small ones

Has phase change material capsules PK2. The small capsules PK2 are dimensioned so that they fit into the cavities between the large capsules PK1 present as bulk in the container B.

List of reference symbols

1 first version of the device

second embodiment of the device

1 third embodiment of the device

"fourth embodiment of the device

B container

Bi container inner wall

Ba container outer wall

IB isolation area

VI first volume area

V 2 second volume area

V3 third volume area

V4 isolation area, fourth volume area

F heat transfer fluid

Fl first heat transfer fluid

F2 second heat transfer fluid

G interface

Gl first interface

G2 second interface

W wall

W1 first wall

W2 second wall

FV heat transfer fluid volume range

P phase change material

PV phase change material volume range

L piping system

LI first pipeline system

L2 second line system

PK phase change material capsule

PK1 phase change material capsule with first size PK2 phase change material capsule with second size

KW capsule wall

FE fluid inlet

FE 'fluid inlet

FA fluid outlet

FA 'fluid outlet

TL storage tank charging temperature

TE storage tank discharge temperature

R register

S solar radiation

AV expansion volume

FP level level

ST solar thermal panel

Claims

Expectations

1. Device (1;; 1 ";") for absorbing, storing and releasing heat, the device occupying a volume which

a heat transfer fluid volume area (FV) through which at least one heat transfer fluid (F) can flow, and one containing a phase change material (P)

Has phase change material volume region (PV), wherein

the phase change material (P) at a phase change temperature TW a reversible

Phase change between a first state of the phase change material (P) existing below the phase change temperature TW and a second state of the phase change material (P) existing above the phase change temperature TW, and wherein the heat transfer fluid volume area (FV) via interfaces (G) on the phase change material Volume area (PV) is adjacent,

characterized in that the volume areas (FV, PV) are arranged in a container (B) which has a container inner wall (Bi) facing the volume areas, one of the

Volume areas facing away from the container outer wall (Ba) and between the container inner wall (Bi) and the container outer wall (Ba) arranged thermally insulating

Has isolation area (IB).

2. Device according to claim 1, characterized in that it contains a first volume area (VI) through which a first heat transfer fluid (Fl) can flow, a second volume area (V2) through which a second heat transfer fluid (F2) and at least one phase change material (P) can flow third volume area (V3), the first volume area (VI) adjoining the third volume area (V3) via first interfaces (Gl) and the second volume area (V2) adjoining the third volume area (V3) via second interfaces (G2),

characterized in that the volume areas (VI, V 2, V3) are arranged in a container (B) which has a container inner wall (Bi) facing the volume areas, an outer container wall (Ba) facing away from the volume areas and an between the container inner wall (Bi) and the container outer wall (Ba) arranged thermally insulating

Has isolation area (IB).

3. Device according to claim 1 or 2, characterized in that the insulation area (IB) has an evacuated volume (V4).

4. Apparatus according to claim 3, characterized in that in the container (B) at least the container inner wall (Bi) facing the volume areas has a melting temperature (eg for metal or thermoplastic) or decomposition temperature (eg for thermosetting plastics) which is higher than the phase change temperature TW of the phase change material (P) is preferably more than 20K higher and particularly preferably more than 40K higher.

5. Device according to one of claims 1 to 4, characterized in that the second state of the phase change material (P) is more energetic than the first state of the phase change material (P).

6. The device according to claim 5, characterized in that the phase change material (P) is present in its first state as a solid or in a solidified state and is present in its second state as a liquid or in a molten state.

7. The device according to claim 5, characterized in that the phase change material (P) is present in its first state as a solid with a first material structure or first crystal structure and in its second state as a solid with a second material structure or

second crystal structure is present.

8. Apparatus according to claim 6 or 7, characterized in that a wall (W; Wl, W2) for material separation of the various volume areas (FV, PV; VI, V2, V3) is arranged along the boundary surfaces (G; Gl, G2) is.

9. The device according to claim 8, characterized in that the wall (W; Wl, W2) is formed from a material whose melting temperature (e.g. in the case of metal or thermoplastic) or

The decomposition temperature (e.g. with thermosets) is higher than the phase change temperature TW of the phase change material (P).

10. The device according to claim 8 or 9, characterized in that the wall (W; Wl, W2) is formed from a material with high thermal conductivity, preferably from 30 W / (mK) to 500 W / (mK) and / or a small wall thickness, preferably from 0.1 mm to 2 mm, particularly preferably from 0.2 mm to 1.2 mm.

11. Device according to one of claims 8 to 10, characterized in that the wall (W; Wl, W2) is formed from a polymer material.

12. The device according to claim 11, characterized in that the wall (W; Wl, W2) is formed from a carbon / polymer composite material which, in its volume or in its polymer matrix, has a proportion of uniformly distributed particles of a carbon allotrope such as graphite , in particular expanded graphite, graphene, fullerenes or carbon nanotubes contains.

13. The apparatus according to claim 12, characterized in that the weight fraction of the

Carbon allotrope is 2% to 70%, especially 5% to 50%, of the carbon / polymer composite.

14. The device according to claim 12 or 13, characterized in that the particle sizes of the particles of the carbon allotrope, in particular of expanded graphite, are in the range from 1 pm to 500 pm.

15. The device according to claim 13 or 14, characterized in that the total proportion of the carbon allotrope has different size-specific proportions (particle size fractions), the carbon allotrope particles, in particular expanded graphite particles, of a first size-specific proportion having an average particle size, which differs from the mean particle size of a further size-specific fraction.

16. The device according to claim 15, characterized in that the ratio of the mean particle sizes of two different size-specific proportions (particle size fractions) is in the range from 100: 1 to 10: 1.

17. Device according to one of claims 12 to 16, characterized in that the

Carbon / polymer composite material has different types of carbon allotrope.

18. Device according to one of claims 8 to 17, characterized in that the wall (W; Wl, W2) is in the form of a line system (L; LI, L2) through which a heat transfer fluid (F; Fl, F2) can flow and is at least partially embedded in the phase change material (P) in the phase change material volume region (PV; V3).

19. The device according to claim 18, characterized in that the line system (L; LI, L2) has pipe registers (R; RI, R2) connected in series and / or in parallel as well as a fluid inlet (FE) and a fluid outlet (FA), wherein the fluid inlet (FE) is intended to receive a heat transfer fluid (F; Fl, F2) originating from a solar collector, for example, with a storage charging temperature TL in the line system (L; LI, L2), the storage charging temperature TL being greater than the Phase change temperature TW of the phase change material (P) is (TL> TW).

20. The device according to claim 18 or 19, characterized in that the line system (L; LI, L2) fluidly connected in series and / or parallel pipe register (R; RI, R2) and one

Fluid inlet (FE) and a fluid outlet (FA), the fluid inlet (FE) for receiving a heat transfer fluid (F; Fl, F2) originating, for example, from a heating circuit with a storage discharge temperature TE into the line system (L; LI, L2) is determined, wherein the storage discharge temperature TE is less than the phase change temperature TW of the phase change material (P) (TE <TW).

21. Device according to one of claims 8 to 17, characterized in that the wall (W;

Wl, W2) is present as a multiplicity of capsule walls (KW) of a multiplicity of phase change material capsules (PK) in which the phase change material (P) is encapsulated and around which a heat transfer fluid (F; F1, F2) can flow.

22. The device according to claim 21, characterized in that the plurality of

Phase change material capsules (PK) are contained as solid packing or as loose bulk in the container (B), which has a fluid inlet (FE ') and a fluid outlet (FA'), the fluid inlet (FE ') for receiving a e.g. a solar collector originating heat transfer fluid (F; Fl, F2) with a storage loading temperature TL in the container (B) is determined, the

Storage tank charging temperature TL greater than the phase change temperature TW des

Phase change material (P) is (TL> TW).

23. The apparatus of claim 21 or 22, characterized in that the plurality of

Phase change material capsules (PK) are contained as solid packing or as loose bulk in the container (B), which has a fluid inlet (FE ') and a fluid outlet (FA'), the fluid inlet (FE ') for receiving a e.g. a heating circuit originating heat transfer fluid (F; Fl, F2) with a storage discharge temperature TE in the container (B) is determined, the storage discharge temperature TE being less than the phase change temperature TW des

Phase change material (P) is (TE <TW).

24. Device according to one of claims 21 to 23, characterized in that the plurality of phase change material capsules (PK) with a first plurality of phase change material capsules (PK1) with a first capsule size and a second plurality of phase change material capsules (PK2) having a second capsule size.

25. Device according to one of claims 21 to 24, characterized in that the

Phase change material capsules (PK; PK1, PK2) have roughly the shape of a sphere, an ovoid, a cylinder, a prism, a cube or a parallelepiped.

26. Device according to one of claims 21 to 25, characterized in that the phase change material capsules (PK; PK1, PK2) have a greater average density than that

Have heat transfer fluid (F; Fl, F2).

27. Device according to one of claims 18 to 26, characterized in that the

Line system (L; LI, L2) has a first heat pipe with a heat pipe evaporator area, a heat pipe condenser area and a first working fluid, the heat pipe evaporator area being arranged outside the device and the heat pipe condenser area being arranged inside the device.

28. Device according to one of claims 18 to 27, characterized in that the

Line system (L; LI, L2) has a second heat pipe with a heat pipe evaporator area, a heat pipe condenser area and a second working fluid, the heat pipe evaporator area being arranged inside the device and the heat pipe condenser area being arranged outside the device.

29. The device according to claim 28, characterized in that the first working fluid and the second working fluid are the same type of fluid material.

30. Device according to one of claims 1 to 29, characterized in that the

Phase change material (P) comprises an organic material (e.g. wax, paraffin, fatty acid, ester, etc.) or an inorganic material, in particular a salt or a salt mixture.

31. The device according to claim 30, characterized in that the phase change material (P) has a paraffin whose chain length is in the range of 20 to 34 carbon atoms.

32. Apparatus according to claim 30 or 31, characterized in that the

Phase change material (P) has an inorganic salt.

33. The device according to claim 32, characterized in that the phase change material (P) has one of the following salts: I ^ SC 10FhO / NaCl-I ^ SC 10FhO / Na ₂ Si0 ₃ -5H ₂ 0.

34. Apparatus according to claim 32 or 33, characterized in that the

Phase change material (P) has an inorganic salt mixture with different anions and / or different cations.

35. Device according to one of claims 32 to 34, characterized in that the

Phase change material has a salt mixture which contains a combination of at least two of the following salts: LiN0 ₃ / NaN0 ₃ / KN0 ₃ / NaN0 ₂ / KNO.