Method for transferring thermal energy, and device for carrying out the method

Abstract

The invention relates to a method for transferring thermal energy and to a device for carrying out the method, wherein a working medium is provided, the temperature of which changes in the event of a change in state. In a first step, the state of the working medium is changed by increasing the temperature thereof; in a second step, the working medium is cooled by dispensing heat to a first system; in a third step, energy is additionally dispensed in order to further cool the working medium; in a fourth step, the working medium is further cooled by changing the state of the working medium while reducing the temperature thereof; in a fifth step, the working medium is heated by absorbing heat from a second system; and in a sixth step, energy is additionally absorbed in order to heat the working medium.

Description

[0001] METHOD FOR TRANSFERRING THERMAL ENERGY AND DEVICE FOR CARRYING OUT THE METHOD

[0002] The invention relates to a method for transferring thermal energy and a device for carrying out the method.

[0003] Heat pumps are known to absorb heat from a lower-temperature source and transfer it to a higher-temperature source. The efficiency of heat pumps is expressed by the coefficient of performance (COP), which is the ratio of the heat output to the electrical power input. The efficiency of heat pumps depends on the temperature difference between the heat source and the heat sink. The greater the temperature difference, the lower the efficiency.

[0004] The use of so-called shape memory materials, such as nitinol, in solid-state heat pumps and cooling systems is known from the general state of the art. These systems operate based on the elastocaloric effect, allowing heat to be exchanged via a change in the shape of the shape memory materials. Such systems represent a promising alternative to conventional compressor technology. Other systems, for example, are based on the magnetocaloric effect.

[0005] DE 10 2015 121 657 A1 describes a method for operating cycle-based systems with a hot-side reservoir and a cold-side reservoir for a fluid and at least one heat exchanger unit with mechanocaloric material, wherein heat transfer takes place between the mechanocaloric material and the fluid. It is essential that the heat transfer between the mechanocaloric material and the fluid occurs essentially by means of latent heat transfer. A corresponding heat exchanger unit and a corresponding device are also described.

[0006] EP 3 862 658 A1 discloses a method for stabilizing and / or controlling the operating temperature of a cycle-based system comprising at least one heat exchanger unit with at least one calorific material element, in which a base temperature of the calorific material element is controlled by means of a cooling fluid. A heat exchanger unit, a refrigeration machine, and a heat pump are also described.

[0007] CN 116 202 242 A describes an elastic heat compression cooling and cold storage system and a control method therefor. The system comprises a conveyor device, an elastic heating unit, a compression device, an elastic heat exchange device, a cooling device, and a refrigerator. The conveyor device drives the elastic heating unit to reciprocate between the compression device and the elastic heat exchange device; the compression device is used to compress the elastic heating unit on the conveyor device. The elastic heating unit adopts a shape memory alloy tube assembly, and the shape memory alloy tube assembly is transformed from austenite to martensite under the load of compressive stress to release heat to the environment.The elastic heating unit allows the shape memory alloy tube assembly to remain in a compressed state after being compressed by a self-locking structure. The elastic heat exchange device can relieve the compression state of the shape memory alloy tube assembly, so that the shape memory alloy tube assembly transforms from martensite to austenite after the compression stress is relieved and the temperature is reduced. The elastic heat exchange device drives the fluid to flow between the elastic heating unit and the heat load, thus reducing the temperature of the heat load. The requirement for instant application with low temperature and large cooling capacity can be met.

[0008] CN 106 016 819 A relates to the technical field of magnetic refrigeration and discloses an efficient heat exchanger cold storage bed system for a magnetic refrigerator.The system comprises a cold storage bed I, a cold storage bed II, a heat exchange water tank, and a heat exchanger, wherein the cold storage bed I and the cold storage bed II are filled with porous magnetic coolants; magnetic fields for magnetizing and demagnetizing the magnetic coolants are arranged on the outer sides of the cold storage bed I and the cold storage bed II; a valve set A and a valve set B are respectively arranged at two ends of the cold storage bed I; a valve set C and a valve set D are respectively arranged at two ends of the cold storage bed II; each of the valve sets A, B, C, and D includes a one-way magnetic flow valve and a one-way shut-off valve, respectively; a water pump is arranged at a water outlet of the heat exchange water tank; and the heat exchange water tank, the cold bed I, the cooling bed II, and the heat exchanger are filled with heat exchange media.According to the efficient heat exchange cooling bed system for the magnetic refrigerators, low temperature heat exchange media and high temperature heat exchange media are circulated in a unique way and cannot be mixed with each other, so the cooling effect can be improved.

[0009] The object is to provide a method for transferring thermal energy and a device for carrying out the method with a higher level of efficiency than the prior art. This object is achieved by a method for transferring thermal energy, wherein a working fluid is provided whose temperature changes upon a change of state, comprising at least the following steps:

[0010] (i) in a first step, a change in the state of the working medium occurs when its temperature is increased within a first temperature range,

[0011] (ii) in a second step, the working medium is cooled by releasing heat to a first system within the first temperature range,

[0012] (iii) in a third step, additional energy is released to further cool the working medium, so that the working medium is transferred from the first temperature range to a second temperature range,

[0013] (iv) in a fourth step, further cooling of the working medium takes place by a change in state of the working medium when its temperature is reduced within the second temperature range, (v) in a fifth step, heating of the working medium takes place by absorption of heat from a second system within the second temperature range, and (vi) in a sixth step, additional absorption of energy for heating the working medium takes place, so that the working medium is transferred from the second temperature range back to the first temperature range, wherein the energy released in the third step and the energy absorbed in the sixth step is at least partially recuperable.

[0014] The efficiency of thermal energy transfer depends, among other things, on the temperature difference between the two systems. One aspect of the invention is to carry out the change of state of the working medium in a first temperature range and a second temperature range, each of which is adapted to the temperature of the first system and the second system, which can be selected differently, since in a further step an additional absorption or release of heat energy takes place in a recuperable manner to generate a temperature difference. The released heat energy is stored and later returned to the working medium. Consequently, the temperature difference of the working medium can be selected to be smaller than the temperature of the first system and the second system, so that the procedure according to the invention enables a higher efficiency compared to the prior art.Since such processes for transferring thermal energy are typically applied in a cyclic process, the subsequent steps of additional energy absorption and release can be carried out with minimal loss, as the amount of energy to be transferred is approximately the same in both steps. The change in state of the working fluid is typically a crystalline phase transformation, in which the working fluid cools or heats accordingly. The process according to the invention can exchange thermal energy between both systems, with one of the two systems usually acting as a reservoir and being represented, for example, by the ambient air. The other system is typically an interior space to be air-conditioned or heated.

[0015] In an embodiment of the method according to the invention, the additional release of energy for recuperation takes place in the third step by transferring heat to an energy storage device and the additional absorption of energy takes place in the sixth step by transferring heat from the energy storage device.

[0016] Particularly preferably, both the additional release and the additional absorption of energy are carried out by means of the energy storage device. In this way, the temperature difference to the temperature of the first system or the second system is reduced both during cooling and during heating of the working medium, wherein at the same time the energy released or absorbed during cooling and during heating is temporarily stored in the energy storage device. In this way, the additional release or absorption of energy can be designed with low losses with regard to the energy balance of the overall system. In a further embodiment of the method according to the invention, the energy storage device has a fluid with a temperature gradient that is adapted to the heat transfer in the third and sixth steps.

[0017] A particularly efficient form of energy transfer from the working medium to the energy storage device can be achieved by means of a fluid, for example water, which has a temperature gradient, so that depending on the desired transfer direction, the working medium is connected to either the cold or the warm side of the energy storage device and the fluid is guided past the working medium so that the desired heat transfer takes place via thermal contact.

[0018] In a further embodiment of the method according to the invention, the energy content of the energy storage device exceeds the heat stored in the working medium by several times.

[0019] To prevent or mitigate the temperature levels between the energy storage unit and the working fluid from equalizing, it is planned to select an energy content of the energy storage unit that is significantly greater than the heat stored in the working fluid. An excess of this by a factor of, for example, between 5 and 10 should be sufficient in this case.

[0020] In a further embodiment of the method according to the invention, the energy storage device is an elongated reservoir filled with water.

[0021] In an elongated reservoir filled with water, the temperature gradient can be easily generated and maintained, and by determining the volume of the elongated body, the energy content of the energy storage device can be adapted to the heat quantity of the working fluid. This enables a simple and cost-effective implementation of an efficient energy storage device for transferring heat to the working fluid.

[0022] In a further embodiment of the method according to the invention, the energy storage device has a plurality of PCM elements arranged in a gradient.

[0023] Instead of a fluid-filled reservoir, a latent heat storage device can also be used, which has a large number of storage elements whose temperature is selected relative to the respective neighboring elements in such a way that an overall temperature gradient is established.

[0024] In a further embodiment of the method according to the invention, the second and third steps and / or the fifth and sixth steps are carried out simultaneously, at least in sections.

[0025] The energy delivery to the first system and the additional energy delivery, for example, to the energy storage device, can be carried out simultaneously or in sections with overlapping timing. This way, the duration of the consecutive process steps can be reduced. Likewise, the energy absorption from the second system and the additional energy absorption, for example, from the energy storage device, can also be carried out in this way.

[0026] In a further embodiment of the method according to the invention, the first to sixth steps are carried out to transfer heat from the second system to the first system. According to this procedure, the method according to the invention is used to heat the first system. The first system is, for example, an interior space of a building. The second system is typically a reservoir surrounding the building, so that, for example, heat is transferred from the ambient air into the interior space.

[0027] In a further embodiment of the method according to the invention, the first to sixth steps are carried out to transfer heat from the second system to the first system.

[0028] According to this approach, the method according to the invention is used to cool the second system. In this case, the first system would form a reservoir surrounding the building, and the second system would correspond, for example, to the interior.

[0029] In a further embodiment of the method according to the invention, the change in state of the working medium occurs barocalorically, elastocalorically, magnetocalorically or electrocalorically.

[0030] The change in state of the working medium occurs through a crystalline phase transition and can be induced in various ways. In addition to electrical or magnetic activation, mechanical activation of the working medium through tensile or compressive forces is particularly possible.

[0031] In a further embodiment of the method according to the invention, the working fluid is a shape memory material that is converted between an austenitic and a martensitic state. Such materials have already been successfully used in solid-state heat pumps, thus enabling a simple and cost-effective implementation of the method according to the invention without the need for extensive material development.

[0032] In a further embodiment of the method according to the invention, the first to sixth steps are carried out in reverse order.

[0033] In principle, it is also conceivable to carry out the procedural steps in a different order and, in particular, in reverse.

[0034] In a further embodiment of the method according to the invention, the first to sixth steps are repeated cyclically.

[0035] In particular, when the process is applied in a heat pump for heating or air conditioning, the individual process steps are repeated, with the typical duration of a process step being in the range of seconds.

[0036] In a further embodiment of the method according to the invention, the cycle time is adapted to the thermal conductivity of the working medium.

[0037] In order to achieve heat transfer from the working medium to one of the two systems, the cycle time must be selected so that it is adapted to the thermal conductivity of the working medium in order to utilize the energy contained therein.

[0038] This object is also achieved by a device for carrying out a method as described above, which device has at least one strip of a shape memory material which is connected at one end to a pressure stamp and is arranged in a holding body which has fluid channels for heat dissipation or heat absorption which are connected to the first or the second system or an energy storage device.

[0039] While electrical or magnetic activation of the working medium is possible, mechanical activation of the working medium through tensile or compressive forces is particularly easy to implement. It is also possible to provide multiple pressure plungers in parallel, possibly with a phase shift.

[0040] Below, some examples are explained in more detail using the drawings. They show:

[0041] Figure 1 shows a diagram of an embodiment of a first method step,

[0042] Figure 2 shows a diagram of an embodiment of a second method step,

[0043] Figure 3 shows a diagram of an embodiment of a third method step,

[0044] Figure 4 shows a diagram of an embodiment of a fourth method step,

[0045] Figure 5 shows a diagram of an embodiment of a fifth method step,

[0046] Figure 6 shows a diagram of an embodiment of a sixth method step, Figure 7 shows a schematic view of an apparatus for carrying out the method,

[0047] Figure 8 shows a detail of a device for carrying out the method,

[0048] Figure 9 shows a further detail of a device for carrying out the method,

[0049] Figure 10 shows a further detail of a device for carrying out the method, and

[0050] Figure 11 shows a diagram of a first simulation calculation, and

[0051] Figure 12 shows a diagram of a second simulation calculation.

[0052] In the figures, identical or functionally equivalent components are provided with the same reference numerals.

[0053] An exemplary embodiment of the method according to the invention will first be explained with reference to Figures 1 to 6. In Figures 1 to 6, the illustration is based on a diagram in which tensile stress is plotted against temperature. The following explanation is based on a shape memory material that is converted between an austenitic state "A" and a martensitic state "M". The region between the two states is marked "M - A" in the figures. The lines shown correspond to the change of state due to the crystalline phase transition in the shape memory material. The device provided for carrying out the method is then described with reference to Figures 7 to 10. Examples of a simulation for calculating the achievable efficiency are given in Figures 11 and 12.

[0054] Figure 1 shows a first process step in an exemplary embodiment. Starting at position P1, the tensile stress is increased, resulting in a phase transition from the austenitic state "A" to the martensitic state "M" at position P2. Due to the elastocaloric effect, the working fluid reacts with an increase in temperature, resulting in a shift to position P3. Thus, in the first step, a change in the state of the working fluid occurs as its temperature increases.

[0055] In the next process step, shown in Figure 2, the working fluid is cooled by utilizing the heat. The reduction in temperature results in a shift from position P3 to position P4. The utilization of the heat can, for example, be achieved by acquiring the room air in a building with heat transfer from the working fluid to the room air in a room air conditioning unit. In the second step, the working fluid is cooled by dissipating heat to a first system.

[0056] Figure 3 shows the third process step. Here, the working medium is cooled further by additional heat being released, for example to an energy storage device. In this way, the temperature in the working medium is reduced further, whereby the temperature change in the third step can be greater than in the second step. The further reduction in temperature results in a shift from position P4 to position P5. In the third step, additional energy is released to further cool the working medium. Examples of an energy storage device for additional energy release are given below. In Figure 4, the working medium is cooled further by the elastocaloric effect returning to the initial state, i.e. from the martensitic state “M” to the austenitic state “A”.During the phase transition, a shift occurs between position P5 and position P6. With further reduction of the tensile stress, the operating point shifts to position P7. In the fourth step, the working fluid cools further due to a change in state of the working fluid as its temperature decreases.

[0057] The fifth process step is shown in Figure 5. Here, the working fluid is heated by an external heat source from a second system, thus reducing the temperature. A shift from position P7 to position P8 occurs. This step can, for example, involve the use of outside air with a heat transfer to the working fluid. In this example, the second system would be the outside air, which acts as a reservoir. In the fifth step, the working fluid is heated by absorbing heat from a second system.

[0058] Figure 6 shows the sixth process step. This involves further heating of the working fluid, for example, using the energy storage device, so that the temperature is transferred to the initial state shown in Figure 1. As a result, a shift from position P8 to position P1 is achieved, allowing the cycle to be repeated. Therefore, in the sixth step, additional energy is absorbed to heat the working fluid.

[0059] Position P3 defines an upper limit and positions P1 and P4 respectively define a lower limit of a first temperature range. Position P7 defines a lower limit of a second temperature range, the upper limit of which is given by P5 and P8 respectively. In a conventional heat pump using a shape memory material, the first temperature range and the second temperature range follow one another directly. In contrast, the invention separates the two ranges by additional heat being dissipated in the third step (from P4 to P5) and this heat then being fed back in as completely as possible in the sixth step (from P8 to P1).Intermediate storage of this heat with as little loss as possible enables correspondingly loss-free recuperation when shifting the temperature levels, so that the temperature difference of the working medium can be selected to be smaller than the temperature of the first system and the second system in order to achieve a higher efficiency compared to the state of the art.

[0060] The process steps shown in Figures 1 to 6 could also be varied. For example, it would be conceivable to expand or relax the working fluid in the third and / or sixth steps in addition to the temperature change. Furthermore, the change in state does not necessarily occur suddenly across the entire working fluid, so in reality, thermal and calorific effects can overlap.

[0061] Figure 7 schematically shows a device 10 with which the method according to Figures 1 to 6 can be carried out. The working medium 12 is connected via the connection 14 and a first multi-way valve 16 both to the first system 20 via the connection 18 and to the energy storage device 24 via the connection 22. Furthermore, the working medium 12 is connected via the connection 26 and a second multi-way valve 28 both to the second system 32 via the connection 30 and to the energy storage device 24 via the connection 34. In this way, it is possible to exchange heat both between the working medium 12 and the first system 20 or the second system 32 and between the working medium 12 and the energy storage device 24. The first multi-way valve 16 and / or the second multi-way valve 28 can be designed such that heat can be transferred simultaneously to the energy storage device 24 and the first system 20 or the second system 32.

[0062] An important aspect of the invention is the additional release of energy in the third step by transferring heat from the working medium 12 to the energy storage device 24 and the additional absorption of energy in the sixth step by transferring heat from the energy storage device 24 to the working medium 12. In this way, the temperature difference is reduced both during cooling and during heating of the working medium 12, while at the same time the energy released or absorbed during cooling and during heating is temporarily stored in the energy storage device 24.

[0063] The energy storage device 24 can be easily formed using a fluid, such as water, that has a temperature gradient. Depending on the desired transfer direction, the working medium 12 is then connected to either the cold or the warm side of the energy storage device 24, so that the desired heat transfer takes place via thermal contact. The energy storage device 24 is preferably an elongated reservoir filled with water, since, on the one hand, the temperature gradient can be easily generated and maintained, and, on the other hand, by determining the volume of the elongated body, the energy content of the energy storage device 24 can be adapted to the amount of heat in the working medium 12.

[0064] The device 10 can be used to transfer heat from the second system 32 to the first system 20. The first system 20 is, for example, an interior space of a building. The second system 32 is typically a reservoir surrounding the building, so that, for example, heat from the ambient air is transferred into the interior space. However, the device 10 can also be designed to transfer heat from the second system 32 to the first system 20. The method according to the invention is thus used to cool the second system 32. In this case, the first system 20 would form a reservoir surrounding the building, and the second system 32 would correspond, for example, to the interior space.

[0065] Particularly when the method is applied in a heat pump as a device 10 for heating or air conditioning, the individual process steps are applied repeatedly, with the typical duration of a process step being in the range of seconds. The cycle time is adapted to the thermal conductivity of the working medium 12.

[0066] Figure 8 shows a detail of the device 10 in a cross-sectional view. In the upper region of the device 10 is a pressure stamp 40, which is guided in a stop limit 42. Between an upper housing plate 44 and a lower housing plate 46 is the working medium 12, which is held between an upper receptacle 48 connected to the pressure stamp 40 and a lower receptacle 50 arranged on the lower housing plate 46. The working medium 12 is in this case designed as a strip of a shape memory material. Adjacent to the main surfaces of the strip-shaped working medium 12 are a left-hand holding body 52 and a right-hand holding body 54, which are provided with semicircular fluid channels 56 on their side facing the strip-shaped working medium 12. Detail A is shown again in an enlarged view in Figure 9.

[0067] In Figure 9, the fluid channels 56 between the left-hand holding body 52 and the right-hand holding body 54 are clearly visible. A gap is formed between the holding bodies 52, 54 in the region of the strip-shaped working medium 12, which gap is selected to be slightly wider than the thickness of the strip-shaped working medium 12. Heat can be supplied or removed via the fluid channels 56. For this purpose, the fluid channels 56 open into common supply lines so that they can be connected to a fluid circuit via the connections 14 and 28 according to Figure 7, for example, to the first system 20 or the second system 32 and the energy storage device 24 via the multi-way valves 16 and 18 described above.

[0068] As shown in Figure 10, the concept can also be extended to include multiple parallel pressure stamps 40. As described above, the second and third steps, as well as the fifth and sixth steps, can be carried out simultaneously. This reduces the number of process steps to four. Advantageously, the parallel pressure stamps 40 are driven by a camshaft (not shown in Figure 10), which can provide a phase shift of the individual pressure stamps 40 by 90°. The rotational speed of the camshaft corresponds to the cycle time, which is typically in the range of seconds. In this way, a compact device 10 can be created that can be used as a heat pump for heating or cooling.

[0069] Of course, it is also possible to provide more pressure stamps 40 operated in parallel. Furthermore, the inventive concept can also be readily transferred to other materials in which the change in state of the working medium can occur barocalorically, elastocalorically, magnetocalorically, or electrocalorically. The change in state of the working medium occurs through a crystalline phase transition and can be brought about in different ways. In addition to electrical or magnetic activation, mechanical activation of the working medium through tensile or compressive forces is particularly possible. With reference to Figure 11, the use of a shape memory material in a simulation calculation is described in detail below. The shape memory material used here is a nickel-titanium alloy, which in this composition is commonly referred to as nitinol and is known as a pseudo-elastic material.In contrast to the representation in Figures 1 to 6, here the temperature is plotted against the entropy in a diagram and a cyclic process with a temperature increase between 10 °C and 30 °C is simulated using field lines 60 to 66. The change in state of the shape memory material through relaxation at field line 60 or stretching at field line 62 occurs isothermally, with additional heat being released or absorbed by the first or second system, respectively, so that the isothermal course is idealized.

[0070] The simulation calculation refers to an ideal Nitinol, without considering hysteresis effects. Between the isothermal curves 60 and 62, regeneration occurs through cooling at field line 64 and heating at field line 66, respectively. At the same time, heat is dissipated to the working fluid at the energy storage device 24 and absorbed from the energy storage device 24, respectively, as described above in connection with Figure 7. Field line 64 corresponds to a state with high tensile stress of 1000 MPa, while field line 66 is a state without tensile stress.

[0071] This simulation results in a maximum efficiency of 87% compared to a Carnot cycle. A curve in which the two field lines 64 and 66 are arranged parallel or almost parallel would represent the ideal state of a Carnot cycle. If the curves are not completely parallel, the heat energy supplied to the energy storage device and the heat energy released by the energy storage device do not match, which results in a loss. Figure 12 shows a simulation calculation for a magnetocaloric material. In the simulation using field lines 70 to 76, gadolinium is considered in a cycle with a temperature range between 5 °C and 25 °C. In the representation in Figure 12, the temperature is plotted against entropy in a diagram, simulating a cycle.The change of state of the magnetocaloric material by demagnetization at field line 70 or magnetization at field line 72 is assumed to be isothermal, whereby additional heat is released or absorbed to the first or second system, respectively, so that the isothermal course is idealized.

[0072] Between the isothermal curves 70 and 72, regeneration occurs through cooling at field line 74 and heating at field line 76, respectively. At the same time, heat is dissipated to the working fluid at the energy storage device 24 and absorbed from the energy storage device 24, respectively, as described above in connection with Figure 7. Field line 74 corresponds to a state with magnetization, while field line 76 corresponds to a state without magnetization. Within the scope of this simulation calculation, an efficiency of 65% is obtained for a Carnot cycle.

[0073] The efficiency is reduced compared to the previous example, which is likely due to the kink in the field line 76. However, the achievable efficiencies are very good for both examples and enable a wide range of possible applications.

[0074] It is to be expected that electrocaloric materials will perform even better, since the field lines of regeneration in electrocaloric materials tend to run parallel compared to field lines 64 and 66 or 74 and 76. The features stated above and in the claims, as well as those shown in the figures, can be advantageously implemented both individually and in various combinations. The invention is not limited to the described embodiments, but can be modified in many ways within the scope of expert knowledge.

[0075] List of reference symbols:

[0076] 10 Device

[0077] 12 Working medium

[0078] 14 Connection

[0079] 16 multi-way valve

[0080] 18 Connection

[0081] 20 systems

[0082] 22 Connection

[0083] 24 energy storage units

[0084] 26 Connection

[0085] 28 Multi-way valve

[0086] 30 connection

[0087] 32 systems

[0088] 34 Connection

[0089] 40 printing stamps

[0090] 42 Stop limit

[0091] 44 Housing plate

[0092] 46 Housing plate

[0093] 48 recording

[0094] 50 recordings

[0095] 52 holding bodies

[0096] 54 holding bodies

[0097] 56 fluid channels

[0098] 60 - 66 field lines

[0099] 70 - 76 field lines

Claims

Claims:

1. A method for transferring thermal energy, wherein a working medium is provided whose temperature changes upon a change of state, comprising at least the following steps: (i) in a first step, a change in the state of the working medium occurs when its temperature is increased within a first temperature range, (ii) in a second step, the working medium is cooled by releasing heat to a first system within the first temperature range, (iii) in a third step, additional energy is released to further cool the working medium, so that the working medium is transferred from the first temperature range to a second temperature range, (iv) in a fourth step, further cooling of the working medium takes place by a change in state of the working medium while reducing its temperature within the second temperature range, (v) in a fifth step, heating of the working medium by heat absorption from a second system takes place within the second temperature range, and (vi) in a sixth step, additional energy is absorbed to heat the working medium, so that the working medium is transferred from the second temperature range back to the first temperature range, wherein the energy released in the third step and the energy absorbed in the sixth step is at least partially recuperable.

2. Method according to claim 1, in which for recuperation the additional release of energy in the third step takes place by transferring heat to an energy storage device and / or the additional absorption of energy in the sixth step takes place by transferring heat from an energy storage device.

3. The method according to claim 2, wherein the energy storage device comprises a fluid with a temperature gradient adapted to the heat transfer in the third step and in the sixth step.

4. Method according to one of claims 2 or 3, wherein the energy content of the energy storage device exceeds the heat stored in the working medium by a multiple.

5. Method according to one of claims 2 to 4, wherein the energy storage device is an elongated reservoir filled with water.

6. Method according to one of claims 2 to 4, wherein the energy storage device comprises a plurality of PCM elements arranged in a gradient.

7. Method according to one of claims 1 to 6, wherein the second and third steps and / or the fifth and sixth steps are carried out at least partially simultaneously.

8. A method according to any one of claims 1 to 7, wherein the first to sixth steps are performed to transfer heat from the second system to the first system.

9. A method according to any one of claims 1 to 7, wherein the first to sixth steps are performed to transfer heat from the second system to the first system.

10. A method according to any one of claims 1 to 9, wherein the working medium is a shape memory material that can be converted between an austenitic and a martensitic state.

11. Method according to claim 10, wherein in the third step and / or in the sixth step, in addition to the temperature change, an expansion or relaxation of the working medium takes place.

12. The method according to any one of claims 1 to 11, wherein the first to sixth steps are carried out in reverse order.

13. The method according to any one of claims 1 to 12, wherein the first to sixth steps are repeated cyclically.

14. The method according to claim 13, wherein the cycle time is adapted to the thermal conductivity of the working medium.

15. Method according to one of claims 1 to 14, in which the change in state of the working medium occurs barocalorically, elastocalorically, magnetocalorically or electrocalorically.

16. Device for carrying out the method according to one of claims 1 to 14, which has at least one strip of a shape memory material which is connected at one end to a printing unit and is arranged in a housing which has fluid channels for heat dissipation or heat absorption.

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