Method for storing energy in a storage device and storage device

Abstract

The invention relates to a method for storing energy in a storage device (10), in which, within an operating temperature range (70), energy is stored in a storage material (20) within the storage device (10) during a charging process (52), and energy in the form of thermal energy is released from the storage material (20) during a discharging process (54) by means of a heat transfer medium, in particular a heat transfer fluid (16). Flexible operating options are achieved by the fact that, during the charging process (52), the storage material (20) undergoes a thermochemical desorption reaction in a first reaction temperature range (72), releasing a reaction fluid, and undergoes a phase transition from solid to liquid state at a higher melting temperature (58).

Description

[0001] The invention relates to a method for storing energy in a storage device, in which, within a working temperature range, energy is stored in a storage material within the storage device during a loading process, and energy is removed from the storage material in the form of thermal energy by means of a heat transfer medium, in particular a heat transfer fluid, during a discharging process. The invention further relates to a storage device with which the method can be carried out.

[0002] The conversion of traditional building heating and hot water systems to CO2-neutral systems requires compact and cost-effective systems for providing thermal energy. Such systems should also be simple in design, flexible, and as economical to operate as possible.

[0003] Systems that combine different storage mechanisms are known. The publication "Palacios, Anabel et al., Hybrid 3 in 1 thermal energy storage system - Outlook for a novel storage strategy, Applied Energy 274 (2020), 115024" describes studies on combining latent, sensible, and thermochemical heat storage in a single system. The specific energy density is comparatively low.

[0004] DE 10 2019 125 540 A1 describes a storage system for the thermochemical storage of energy.

[0005] DE 10 2012 009 696 A1 shows a system for generating and / or storing heat and / or cold comprising several latent heat storage units.

[0006] EP 2 221 568 A1 discloses a method for storing energy in a storage device according to the preamble of claim 1.

[0007] The invention is based on the object of providing a method and a storage device of the type mentioned above which allow flexible operation at high energy density.

[0008] The problem is solved for the method with the features of claim 1 and for the storage device with the features of claim 10.

[0009] The method provides that during the loading process, the storage material undergoes a thermochemical desorption reaction in a first reaction temperature range with release of a reaction fluid and undergoes a phase transition from solid to liquid state at a higher melting temperature.

[0010] The thermochemical desorption reaction is an endothermic, reversible gas / solid equilibrium reaction (chemisorption). By definition, the storage material forms the solid, and the reaction fluid forms the gas of the specific gas-solid material pairing. The reaction proceeds according to an equilibrium characteristic specific to the respective gas-solid material pairing, depending on pressure and temperature. At a given pressure (e.g., essentially ambient pressure), the theoretical reaction temperature at which the desorption reaction takes place is determined by the equilibrium characteristic. In practice, a moderate initial reaction temperature range of, for example, between 10 K and 15 K is usually passed through.

[0011] The released reaction fluid is preferably removed from the storage material, e.g. by suction, and can be condensed and temporarily stored in a storage container until the reverse (sorption) reaction in the discharge process takes place.

[0012] Through the thermochemical desorption reaction and the phase change, energy initially present as thermal energy (possibly after conversion from another energy form) can advantageously be stored as chemical heat and as latent heat within the storage device using at least two different storage mechanisms, namely thermochemical heat storage and latent heat storage, thus enabling flexible operation and a high specific energy density (amount of heat per mass of storage material). Partial loading and / or partial discharging are possible. The storage material preferably consists of a single substance that is also suitable as a thermochemical storage material.

[0013] In a particularly preferred embodiment, the storage material is sensitively heated during the loading process in the remaining operating temperature range, i.e., outside the reaction temperature range and the melting temperature, whereby, in particular, up to three sensitive heat storage phases are passed through: at temperatures below the reaction temperature range, between the reaction temperature range and the melting temperature, and above the melting temperature. Thus, thermal energy can be stored within the storage device by means of a third storage mechanism, sensible heat storage. The combination of three different storage mechanisms results in a flexible process or storage device that can be operated with high energy density.

[0014] Flexible loading options for the storage facility arise when thermal energy is stored during the loading process, which is already present as thermal energy before being introduced into the storage facility (e.g., from an external heat source) and / or which is introduced into the storage facility in another energy form, e.g., in the form of electrical energy, and is converted into thermal energy within the storage facility, e.g., according to the "power-to-heat" approach. The electrical energy can, for example, advantageously come from one or more renewable energy sources.

[0015] According to the invention, electrical energy can be converted into thermal energy by means of a microwave generator within the storage device. The microwave generator comprises, in particular, at least two magnetrons. In this way, for example, heat transfer fluid located in the storage device and / or other material suitable for heating by microwaves can be heated, and the resulting thermal energy can be introduced into the storage material.

[0016] In a preferred embodiment, the storage material undergoes a phase transition, in particular from liquid to solid state, and / or sensible cooling during the discharge process in a first operating mode at the melting temperature. A thermochemical sorption reaction (as a reverse reaction to the desorption reaction) is not undergone. Thus, in the first operating mode, only stored heat is utilized by a maximum of two of three possible storage mechanisms, namely latent heat storage and / or sensible heat storage, with the removal of latent heat and / or sensible heat. The storage material in the desorbed state can be sensitively cooled, for example, to the minimum temperature (ambient temperature) and / or subsequently recharged, for example, to the maximum temperature (with the storage of sensible and / or latent heat).The thermochemical heat is not used and remains stored within the storage facility.

[0017] Preferably, during and / or after the phase transition from liquid to solid state, the porosity of the storage material is increased in the discharge process compared to solidification on a smooth surface. This improves gas exchange between the storage material and the environment, particularly with a gas space in fluid contact with a respective layer, compared to a compact surface of the storage material formed during solidification. The efficiency of the thermochemical reaction (desorption or sorption) with the release or absorption of reaction fluid from or into the storage material is thus increased.

[0018] For this purpose, the storage device preferably has means for increasing the porosity of the storage material in the solid state, compared to a design without such means. The means are designed, for example, as structures present on the upper side of the respective plate, on and / or on which the layer of storage material is arranged. The structure can, for example, be formed by a mechanical (micro)structure that is arranged on the respective upper sides of the plates that support the layers and / or is molded onto them (e.g., monolithically). The (micro)structure can, for example, be an increased surface roughness on the upper side of the plates that support the layers, and / or elevations (e.g., in a rib-like and / or honeycomb-like arrangement). A movable arrangement of parts of the storage device, e.g., the plates that support the layers or parts thereof, would also be possible.

[0019] Preferably, in the discharge process, in a second operating mode, the storage material undergoes a thermochemical sorption reaction (as a reverse reaction to the thermochemical desorption reaction) in a second reaction temperature range, which is in particular below the melting temperature, while absorbing the reaction fluid. The second reaction temperature range, which is passed through during the sorption reaction, can in practice differ from the first reaction temperature range, which is passed through during the desorption reaction. Thus, in addition to the sensible heat and / or the latent heat, the thermochemical heat is stored for use. The reaction temperature range is in particular at a medium temperature level (compared to the melting temperature), so that the second operating mode is particularly suitable when medium-temperature heat is required.

[0020] Advantageous control and regulation variants arise when the thermochemical sorption reaction is initiated within the second operating mode by supplying the reaction fluid to the storage material. This can be done particularly when a suitable temperature prevails (in particular, a temperature within or below the second reaction range).

[0021] If necessary, a more precise adjustment of the temperature level of the stored heat to an external application can advantageously be achieved if the second reaction temperature range (or the temperature level thereof) is determined by a pressure of the reaction fluid, e.g., by its partial pressure in a carrier gas (and / or the absolute pressure within the storage device). This is preferably done while observing physical boundary conditions to avoid adverse changes in the ambient conditions, e.g., condensation of the reaction fluid.

[0022] To achieve an advantageously high energy density of the storage device, which enables a compact design, the storage material is formed exclusively from at least, preferably precisely, one substance suitable for use as a thermochemical storage material. Depending on the boundary conditions or the storage mechanism undergone, the substance can exist in three different states: a solid, sorbed state, a solid, desorbed state, and a liquid, desorbed state. For example, the substance can be formed from a salt hydrate, e.g., copper sulfate, which exists as a hydrate in the sorbed state and as an anhydrate in the desorbed state. Furthermore, the melting point of the storage material lies within the operating temperature range.Thus, the storage material can function simultaneously as a thermochemical, latent, and sensible storage material and can be advantageously used as a "trivalent storage material" for the three different storage mechanisms.

[0023] In an advantageous implementation of the method, the maximum temperature of the operating range is below the decomposition temperature of the storage material, e.g., at a maximum of 500 °C, in particular at a maximum of 450 °C, or preferably at a maximum of 400 °C. At temperatures below 450 °C, for example, the storage device can be designed particularly cost-efficiently by avoiding high-temperature-resistant materials.

[0024] For an advantageous process, the storage material, at least in the desorbed state, e.g., as an anhydrate, can be surrounded by a gas that is inert to the storage material, e.g., a gas mixture such as dry air or nitrogen. For this purpose, a gas space surrounding the storage material is flooded and / or purged with the inert gas when the storage material is in the desorbed state to also remove residues of reaction fluid, e.g., water, from the gas space.

[0025] When filled with the storage material and / or a heat transfer fluid, the storage device is designed to carry out a method according to one of the preceding embodiments. For this purpose, the storage device has a control device and / or is assigned to it, by means of which the execution of the method is controlled and / or regulated. The control device is configured accordingly. The storage device can be thermally coupled or can be coupled to a heat consumer.

[0026] In a preferred embodiment, the storage device comprises a plate heat exchanger having a number of plates, in particular plates which are substantially parallel to one another, between which gap channels are formed, wherein the gap channels are divided into a group of primary gap channels which are fluidically connected in parallel and together form a primary flow channel which is in flow connection with at least one primary inlet / outlet channel of a heat transfer line arrangement for conducting heat transfer medium (in particular heat transfer fluid), and a group of secondary gap channels which are fluidically connected in parallel and together form a secondary flow channel which is in flow connection with at least one secondary inlet / outlet channel of a fluid line arrangement for conducting reaction fluid,The primary gap channels and the secondary gap channels are arranged alternately and are fluid-tight to one another. The plates are made, in particular, of a highly thermally conductive material and / or have a thickness between 0.2 mm and 1.5 mm, preferably between 0.5 mm and 1 mm.

[0027] Preferably, within each of the secondary gap channels, there is a layer of storage material that is in thermal contact with one of the plates, and a gas space that is arranged, in particular, flatly above the storage material. The layer is preferably arranged (directly or indirectly) on the plate that delimits the gap channel from below, over as large an area as possible for effective heat transfer. The gas space is particularly adjacent to a plate that delimits the gap channel from above. The thickness of the layer of storage material is, for example, between 3 mm and 10 mm, in particular between 5 mm and 7 mm, in order to ensure effective gas exchange between the storage material and the gas space. The height of the gas space is, for example, 0.2 to 1 time, e.g.0.5 times the thickness of the layer of storage material in order to achieve an unhindered flow of reaction fluid (with particularly low pressure losses) while maintaining a compact design of the storage device.

[0028] In combination with a microwave generator, according to the invention, means for temperature equalization are in thermal contact with each layer of storage material. Such means can, for example, be highly thermally conductive layers. The highly thermally conductive layers can, for example, be introduced between the upper surfaces of the plates and the layers of storage material and, in particular, can comprise or be formed from a highly thermally conductive material (e.g., with a thermal conductivity of at least 50 W / mK), e.g., graphite and / or copper oxide. The layers of storage material are arranged at least partially indirectly on the plates, with the highly thermally conductive layers interposed. The layers of storage material are, in particular, in thermal contact with the highly thermally conductive layers over their entire surfaces covering the plates.When heat is introduced using microwaves, temperature peaks within the storage material can be avoided.

[0029] The invention will be explained in more detail below using exemplary embodiments with reference to the drawings. They show: Fig. 1 a storage device for storing energy with a plate heat exchanger in a schematic representation and Fig. 2 A, B a Th diagram with an example loading process ( Fig. 2A ) and an example discharge process ( Fig. 2B ) of the storage device.

[0030] Fig. 1 shows a storage device 10 for storing energy in a storage material 20. The storage device 10 is integrated, in particular, for heat dissipation in a peripheral device surrounding the storage device 10 (not shown in detail here) for heat utilization, for example, a heating and / or hot water system of a building. Energy is introduced into the storage material 20 in a loading process 52 (see Fig. 2A ) can be stored, if necessary by converting it into thermal energy, and can be used in a discharge process 54 (cf. Fig. 2B ) in the form of thermal energy by means of a heat transfer medium, in particular a heat transfer fluid 16.

[0031] A housing 40 of the Fig. 1 The storage device 10 shown is shown in parts to show the internal structure of the storage device 10 (see also enlarged detail in Fig. 1 ).

[0032] Within the housing 40, the storage device 10 has a plate heat exchanger 11, which comprises a number of mutually parallel plates 14. The storage device 10 is preferably designed and / or arranged for operation such that the plates 14 extend at least substantially horizontally. As also shown in the enlarged detail in Fig. 1 As shown in more detail, gap channels 12 are formed between the plates 14. The gap channels 12 are divided into two groups, namely a group of primary gap channels 12a and a group of secondary gap channels 12b.

[0033] The individual gap channels 12 of the group of primary gap channels 12a are fluidically connected in parallel to one another and form a primary flow channel for conducting heat transfer fluid 16 through the primary gap channels 12a. For this purpose, the primary flow channel, comprising the individual primary gap channels 12a, is in flow communication with, for example, two primary inlet / outlet channels 32 of the storage device 10. The primary inlet / outlet channels 32 are part of a heat transfer line arrangement 30 for conducting heat transfer fluid 16, which can be assigned, for example, partly to the storage device 10 (in particular the primary inlet / outlet channels 32) and partly to the periphery surrounding the storage device 10 for heat utilization, not shown in detail here.

[0034] The individual gap channels 12 of the group of secondary gap channels 12b are fluidically connected in parallel to one another and form a secondary flow channel for conducting reaction fluid through the secondary gap channels 12b. For this purpose, the secondary flow channel, comprising the individual secondary flow channels 12b, is in flow communication with, here for example, two secondary inlet / outlet channels 36 of the storage device 10. The secondary inlet / outlet channels 36 are part of a fluid line arrangement 34 for conducting reaction fluid, which can be assigned partly to the storage device 10 (in particular the secondary inlet / outlet channels 36) and partly to a periphery surrounding the storage device 10, not shown here, for conducting and / or storing reaction fluid.

[0035] The primary gap channels 12a and the secondary gap channels 12b are arranged alternately with each other and are fluid-tight to each other.

[0036] The storage material 20 is arranged within the secondary gap channels 12b in the form of thin layers 22 (directly or indirectly) on the upper sides and in thermal contact with the plates 14 that define the respective gap channel 12b from below. For effective heat transfer, the respective layers 22 cover at least a large portion of the respective plates 14, due to the (geodetically) horizontal arrangement of the plates 14, even in the liquid state of the storage material 20. A gas space 18 for conducting reaction gas is arranged above the layers 22 in each of the secondary gap channels 12b, in fluid contact with the storage material 20 for gas exchange.

[0037] The thickness of the layer 22 of storage material 20 is, for example, between 5 mm and 7 mm to ensure effective gas exchange between the storage material 20 and the gas space 18. The layer 22 can be arranged on and / or at a structure that improves gas exchange (in Fig. 1 not shown). The structure can be formed, for example, by a mechanical microstructure that is arranged on the respective upper sides of the plates 14 carrying the layers 22 and / or is molded onto them (e.g., monolithically). In particular, the structure is such that, during and / or after the phase change during the discharge process 54, an increased porosity of the storage material 20 is obtained compared to solidification without a structure. This, in particular, improves the transfer of reaction fluid between the storage material 20 and the gas space 18 at the molecular level. The structure can, for example, be an increased surface roughness on the upper side of the plates 14 and / or elevations (e.g., in a rib-like and / or honeycomb-like arrangement).

[0038] The height of the gas space 18 is, for example, between 0.2 and 0.35 times the thickness of the layer 20 of the storage material 20 (20% to 35% of the volume of the storage material 22). In this way, an unhindered flow of reaction fluid (with particularly low pressure losses) can be achieved during operation while maintaining a compact design of the storage device 10.

[0039] The Fig. 1 According to a preferred embodiment, the storage device 10 shown has a heat generation device 42 for converting electrical energy into thermal energy. The heat generation device 42 is designed as a microwave generator, which, for example, comprises two magnetrons 44. In this way, during the loading process 52, energy in the form of electrical energy, for example from renewable energy sources, can be fed into the storage device 10, wherein the microwaves heat the heat transfer fluid 16. Additionally and / or alternatively, thermal energy can be introduced by means of the heat transfer line arrangement 30 and the heat transfer fluid 16.

[0040] In this context, means for temperature equalization are in thermal contact with the respective layers 22 (in Fig. 1 (not shown). Such means can be, for example, highly thermally conductive layers. The highly thermally conductive layers can be introduced, for example, between the upper surfaces of the plates 14 and the layers 22 of storage material 20. The layers 22 are arranged at least partially indirectly on the plates 14, with the highly thermally conductive layers interposed.

[0041] In addition, the storage device 10 comprises a control device which is configured to control and / or regulate the method for storing energy with the storage device 10 (not shown here).

[0042] The operation is explained below using an exemplary embodiment, wherein the storage material 20 is formed by a single substance suitable for use as a thermochemical storage material, which exists as a hydrate in the sorbed state and as an anhydrate in the desorbed state. Copper sulfate, for example, is suitable. The reaction fluid in this material is formed by a gas, namely gaseous water.

[0043] Fig. 2A shows an exemplary endothermic (energy absorbing) loading process 52 and Fig. 2B an exemplary exothermic (energy-releasing) discharge process 54 in a T(temperature in °C) - h(specific enthalpy in kJ / kg) - diagram 50.

[0044] During operation, the temperature in the storage material varies within a working temperature range 70. The working temperature range 70 lies, for example, between ambient temperature as the minimum temperature of the working temperature range 70 and a maximum temperature of the working temperature range 70. The maximum temperature is, in particular, below the decomposition temperature of the storage material 20, preferably at, for example, a maximum of 450 °C, which enables the use of comparatively inexpensive materials for the storage device 10.

[0045] The heat can be introduced in particular as thermal energy by means of the heat transfer fluid 16 from a heat source arranged outside the storage device 10 (cf. Fig. 1 , symbolized by route BD of the heat transfer line arrangement 30). Additionally or alternatively, the heat can initially be introduced into the storage device 10 in another energy form, e.g., as electrical energy, wherein, for example, the electrical energy within the storage device 10 is converted into thermal energy by means of the microwave generator.

[0046] The complete loading process 52 is described below as an example. The loading process 52 can also be carried out in parts (if necessary with partial unloading processes in between).

[0047] During the loading process 52, the temperature of the storage material 20 is increased from the minimum temperature to the maximum temperature of the working temperature range 70. The pressure corresponds, for example, to ambient pressure (at least essentially, e.g., except for a pressure gradient for fluid conveyance). Depending on the temperature and / or the shape of the storage material 20 (sorbed / desorbed or solid / liquid), three different storage mechanisms occur in different heat storage phases within the storage material 20 (referred to as a "trivalent storage material") during the loading process 54.

[0048] How Fig. 2A As shown, the storage material 20 is first sensitively heated by the heat input from state 1, at ambient temperature, to state 2. The storage material 20 is solid and in a sorbed state, here, for example, as a solid hydrate. This represents a first sensible heat storage phase of the process within the storage device 10.

[0049] Between state 2 and state 3, a thermochemical desorption reaction occurs with the release of the reaction fluid, here water (gaseous), from the storage material 20 into the gas space 18. The reaction proceeds at a (theoretical) (de)hydration temperature 56, which is theoretically determined by the equilibrium characteristic at a given pressure (here, for example, essentially ambient pressure). In practice, a moderate first reaction temperature range 72 of, for example, up to 10 K or 15 K is usually passed through (in Fig. 2A not shown).

[0050] During the desorption reaction, the solid hydrate is converted (desorbed) into the solid anhydrate while absorbing heat until the reaction is complete at the (de)hydration temperature 56 or in the reaction temperature range 72. The thermal energy is thus stored in the storage material 20 in the form of chemical heat 60 at a (substantially) constant temperature. This process represents the thermochemical heat storage phase of the process within the storage device 10.

[0051] The released gaseous water is removed from the gas space 18 through the inlet / outlet channels 36 by means of the fluid line arrangement 34 (cf. Fig. 1 , symbolized by outlet F of the fluid line arrangement 34), e.g., sucked off, and, e.g., after condensation, temporarily stored in a storage container (not shown here). The storage container can be assigned to the storage device 10 or arranged separately.

[0052] Subsequently, the storage material 20, which is now present as a solid anhydrate, is further heated sensitively in a second sensible heat storage phase between state 3 and state 4 up to a melting temperature 58.

[0053] At the melting temperature 58, the storage material 20 is completely liquefied between state 4 and state 5, absorbing latent heat 62 from the solid state. This process represents the latent heat storage phase of the process within the storage device 10.

[0054] Subsequently, the storage material 20, now a liquid anhydrate, is further heated sensitively to the maximum temperature of the working temperature range 70, where the loading process 52 comes to an end. This process represents a third sensible heat storage phase. The maximum temperature is below the decomposition temperature of the desorbed, liquid storage material 20 to ensure the reversibility of the process.

[0055] During the unloading process 54 ( Fig. 2B ) heat transfer fluid 16 is passed through the storage device 10 for heat absorption (cf. Fig. 1 , symbolized by route C - D of the heat transfer line arrangement 30). Two different operating modes, operating mode 64 and operating mode 66, can be run through.

[0056] Between state 6 and state 3, in both operating modes 64 and 66, the heat storage phases from the loading process 52 are reversed, with sensible or latent heat being released to the heat storage fluid 16 and stored for use in the storage device 10. During solidification of the storage material 20 with the release of latent heat, for example, the preferably present structure results in increased porosity of the storage material 20 compared to solidification without such a structure.

[0057] In the first operating mode 64, only the latent heat 62 (at the melting temperature 58, a comparatively high temperature) and / or the sensible heat 63 (depending on requirements, also partially, e.g., with subsequent partial reloading) is stored within the operating temperature range 70. The storage material 20, which is in the desorbed, here dehydrated, state (as anhydrate), can be sensitively cooled, if necessary, e.g., to the minimum temperature (ambient temperature). The chemical heat 60 remains stored within the storage device 10. The first operating mode 64 is particularly suitable for covering a high and / or (as a short-term storage) short-term temperature requirement.

[0058] In the second operating mode 66, the chemical heat 60 is also stored, in particular in addition to the latent heat 62 and / or the sensible heat 63. For this purpose, the reaction fluid, here water (gaseous), is supplied to the storage material 20 (cf. Fig. 1, symbolized via an inlet E of the fluid line arrangement 34). At the (de)hydration temperature 56 or in the reaction temperature range 72, the thermochemical sorption reaction then takes place with absorption of the reaction fluid into the storage material 20 (sorption, here hydration) and release of the chemical heat 60 as thermal energy to the heat transfer fluid 16. The second operating mode 66 can be initiated by supplying the reaction fluid to the storage material 20 (when a suitable temperature prevails, in particular a temperature corresponding to the (de)hydration temperature or below). The second operating mode 66 is particularly suitable for covering a medium and / or (as a long-term storage) long-term temperature requirement.

[0059] The second reaction temperature range 72, which is passed through during the sorption reaction, can in practice differ from the first reaction temperature range 72, which is passed through during the desorption reaction. In particular, the reaction temperature range 72 prevailing during the discharge process 54 can also be fixed (controlled and / or regulated) within a certain framework. For this purpose, the pressure of the reaction fluid can be adjusted, for example by controlling / regulating its partial pressure in a carrier gas and / or the absolute pressure within the storage device 10. This allows for a more precise adjustment of the temperature level of the stored heat to an external application, if necessary.

[0060] In particular, to avoid an undesired sorption reaction, the gas spaces 18 can be flushed and / or flooded with a gas (e.g., nitrogen) or gas mixture (e.g., dry air) that is inert to the storage material 20 when the storage material 20 is in a desorbed state (here as an anhydrate). For this purpose, the storage device 10 preferably has a corresponding gas flushing arrangement (not shown here). This can be particularly useful when, for example, the storage device 10 is operated within the first operating mode 64.

[0061] A high specific energy (Wh / kg) can be achieved through the three different storage mechanisms that can be used in the storage device 10, particularly in a single material forming the storage material 20. A theoretical comparison conducted by the inventor using firebricks as a reference storage material results in a 36% higher specific energy that can be stored in copper sulfate as an exemplary trivalent storage material 20 than in the reference storage material. In the comparison, the operating temperature range 70 for the reference storage material was larger, namely between 20°C and 660°C, than for the trivalent storage material 20, which had an operating temperature range 70 between 20°C and 450°C.

[0062] Furthermore, the storage device 10 exhibits a high degree of operational flexibility. For example, the storage device 10 can be operated as a short-term storage device in the first operating mode 64 and / or as a long-term storage device in the second operating mode 66. Depending on the required temperature level, the storage device 10 can also be operated as a high-temperature storage device, a medium-temperature storage device, or a low-temperature storage device.

Claims

1. Method for storing energy in a storage device (10), in which within a working temperature range (70) in a charging process (52) thermal energy is stored in a storage material (20) within the storage device (10) and in a discharge process (54) energy in the form of thermal energy is extracted from the storage material (20) by means of a heat transfer medium, in particular a heat transfer fluid (16), in the charging process (52), the storage material (20) undergoing a thermochemical desorption reaction in a first reaction temperature range (72) with the release of a reaction fluid and undergoing a phase transition from a solid to a liquid state at a higher melting temperature (58), characterized in that during the charging process (52), the thermal energy is introduced into the storage device (10) in the form of electrical energy, the electrical energy being converted into thermal energy by means of a microwave generator within the storage device (10), and in that temperature equalization is achieved by bringing means for temperature equalization into thermal contact with a relevant layer (22) of storage material (20).

2. Method according to claim 1, characterized in that during the charging process (52) in the remaining working temperature range (70) the storage material (20) is heated sensitively, in particular up to three sensitive heat storage phases being passed through.

3. Method according to claim 1 or 2, characterized in that during the charging process (52), thermal energy is stored which is already present as thermal energy before being introduced into the storage device (10) and / or which is introduced into the storage device (10) in another form of energy, e.g. in the form of electrical energy, and is converted into thermal energy within the storage device (10).

4. Method according to any of the preceding claims, characterized in that in the discharge process (54) in a first operating mode (64) the storage material (20) undergoes a phase transition at the melting temperature (58), in particular from a liquid to a solid state.

5. Method according to claim 4, characterized in that in the discharge process (54) during and / or after the phase transition from a liquid to a solid state, the porosity of the storage material (20) is increased compared to solidification on a smooth surface.

6. Method according to any of the preceding claims, characterized in that in the discharge process (54) in a second operating mode (66), the storage material (20), while absorbing the reaction fluid, undergoes a thermochemical sorption reaction in a second reaction temperature range (72), which is in particular below the melting temperature (58), in particular the thermochemical sorption reaction within the second operating mode (66) being initiated by supplying the reaction fluid to the storage material (20).

7. Method according to claim 6, characterized in that the second reaction temperature range (72) is determined by means of a pressure of the reaction fluid, e.g. by means of its partial pressure in a carrier gas.

8. Method according to any of the preceding claims, characterized in that the storage material (20) is formed exclusively from at least, preferably exactly, one substance which is suitable for use as a thermochemical storage material, in particular from a salt hydrate, e.g. copper sulfate, which is present in the sorbed state as a hydrate and in the desorbed state as an anhydrate and / or in that the maximum temperature of the working range (70) is below the decomposition temperature of the storage material (20), e.g. at a maximum of 500°C, in particular at a maximum of 450°C or preferably at a maximum of 400°C.

9. Method according to any of the preceding claims, characterized in that the storage material (20), at least in the desorbed state, e.g. as an anhydrate, is surrounded by a gas that is inert to the storage material (20), e.g. a gas mixture such as dry air or nitrogen.

10. Storage device (10) for receiving a storage material (20), which, when filled with the storage material (20) and / or a heat transfer fluid (16), is designed to carry out a method according to any of the preceding claims, wherein the storage device (10) comprises a plate heat exchanger (11) which has a number of plates (14), in particular plates which are substantially parallel to one another, between which gap channels (12) are formed, wherein the gap channels (12) are divided into a group of primary gap channels (12a) which are connected in parallel in terms of fluid mechanics and together form a primary flow channel which is in fluid connection with at least one primary inlet / outlet channel (32) of a heat transfer conduction arrangement (30) for conducting a heat transfer medium, and a group of secondary gap channels (12b) which are connected in parallel in terms of fluid mechanics and together form a secondary flow channel which is in fluid connection with at least one secondary inlet / outlet channel (36) of a fluid conduction arrangement (34) for conducting reaction fluid, wherein the primary gap channels (12a) and the secondary gap channels (12b) are arranged alternately to one another and are designed to be fluid-tight to one another, wherein means for temperature equalization are in thermal contact with a relevant layer (22), e.g. a highly thermally conductive layer arranged on a relevant plate (14), wherein the storage device (10) comprises a microwave generator.

11. Storage device (10) according to claim 10, characterized in that within the secondary gap channels (12b) there is a layer (22) of storage material (20) in thermal contact with one of the plates (14) and a gas space (18), in particular arranged flatly above the storage material (20),12. Storage device (10) according to claim 11, characterized in that the storage device (10) has means for increasing the porosity of the storage material (20) in the solid state, compared to the design without such means, which are designed in particular as structures, e.g. on the upper side of the relevant plate (14), on and / or at which the layer (22) is arranged in each case.

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