Method for storing thermal energy and thermal energy store

Abstract

The invention relates to a method for storing thermal energy by means of at least two containers, each of which is filled with a solid filling material, a thermal storage medium for storing and / or releasing thermal energy being introduced into and / or discharged from the containers in sequence, a temperature storage being carried out in a temperature stratified manner by means of the solid filling material in the respective container, and the heat storage medium is used for a heat transfer process during storage and / or release of (thermal energy). The invention also relates to a corresponding thermal energy store.

Description

Technical Field

[0001] This invention relates to a method for storing thermal energy using at least two containers, each filled with a solid filler. Furthermore, this invention also relates to a thermal energy storage device. Background Technology

[0002] Energy storage is advantageous in order to compensate for fluctuations in power generation and consumption. In particular, energy storage and backup are key components of the energy transition in the context of climate change, especially when using different renewable energy sources.

[0003] Energy can be stored in energy storage devices, such as known chemical or electrical storage devices. Furthermore, thermal storage devices are also known, offering advantages over chemical or electrical storage devices, particularly in terms of cost per unit of energy and the total amount of energy stored.

[0004] For thermal energy storage, existing technologies include, for example, solid-state or liquid storage. For temperature ranges from 90°C to 400°C, temperature-stratified energy storage based on thermal oil (Thermoöl) is also advantageous. Unlike water-based energy storage, the internal pressure caused by saturated vapor can be disregarded. Temperature stratification, in particular, prevents mixing losses, more precisely, "exergieverlust" (exergieverlust). Furthermore, if appropriate filling and emptying of the energy storage device is implemented, long-term extraction at high temperature levels can be ensured.

[0005] To input energy into the energy storage device, the device must be filled. Here, as is known in the prior art, thermal oil is introduced into the energy storage device from above, allowing hot thermal oil to flow downwards. To extract energy from the energy storage device, it must be discharged. In this case, cold thermal oil is introduced into the container from bottom to top.

[0006] Because thermal oil is expensive, inexpensive solid fillers, such as gravel, can be introduced into the storage container to reduce costs. This can replace a portion of the volume of the expensive thermal oil. In the prior art, storage containers in which solid fillers occupy 60% to 70% of the volume and can provide approximately 60% to 80% of the heat capacity are particularly known.

[0007] Thermal oils cost several times more than solid fillers, for example, ten to twenty times more, especially for the same heat capacity. Therefore, it is desirable to further reduce the demand for thermal oils. Specifically, it is necessary to continue to achieve temperature stratification in energy storage devices. Summary of the Invention

[0008] In this context, the object of the present invention is to provide an improved method for storing thermal energy and an improved thermal energy storage device.

[0009] According to the present invention, this objective is achieved by a method having the features of claim 1 and / or by a thermal energy storage device having the features of claim 13.

[0010] According to this regulation:

[0011] A method for storing thermal energy using at least two containers, each filled with a solid filler, wherein a heat storage medium for storing and / or releasing thermal energy is sequentially introduced into and / or drawn out of the containers, wherein temperature storage is performed through temperature stratification by the solid filler in the respective containers, and the heat storage medium is used for heat transfer processes during storage and / or release (thermal energy).

[0012] A thermal energy storage device, particularly for performing the method according to the invention, has at least two containers, each filled with a solid filler, wherein the containers are connected by at least one conduit such that a thermal storage medium for storing and / or releasing thermal energy can be sequentially introduced into and drawn out of the containers, wherein temperature storage is performed through the solid filler.

[0013] The present invention is based on the understanding that thermal energy can be stored, wherein the energy storage task can be mainly undertaken by solid fillers.

[0014] The present invention is based on the concept of using the heat storage medium primarily for heat transfer during storage or release. According to the invention, this is achieved, in particular, by using multiple small containers that can be filled or discharged sequentially. Thus, the storage volume used for the filling or discharging process can be kept small, thereby reducing the volume fraction of the required heat storage medium (especially thermal oil).

[0015] The entire thermal energy storage device is divided into at least two containers, which can be sequentially filled with heat storage medium. Thus, each container has a small volume relative to the total energy storage. Correspondingly, less heat storage medium is required to fill or empty the "small" containers (i.e., so-called sub-containers) of the entire thermal energy storage device. According to the invention, costs can be significantly reduced here, particularly because the cost of the heat storage medium is low due to the small volume share of the so-called "sub-volumes" of the containers.

[0016] A container can be understood as a divided volume fraction containing solid filler. The at least two containers may share a common partition wall, allowing sub-containers to be created within a larger container by dividing it into different sub-volumes. Furthermore, these containers can be arranged side-by-side, independently of each other, to form an energy storage device.

[0017] Solid filler can fill most of the volume of each container. Specifically, the entire container is filled with solid filler. For example, gravel can be used as solid filler. Alternatively, different storage materials can be used, such as porous and / or cavity-containing materials. In particular, the solid filler is formed by spaced-apart objects, allowing the heat storage medium to reach the surface of each unit of the solid filler.

[0018] In particular, thermal oil can be used as a heat storage medium or heat transfer medium. Other fluid media capable of storing energy can also be envisioned.

[0019] Temperature stratification in storage specifically refers to a temperature gradient within each container, from the upper to the lower region. In particular, the storage medium (e.g., especially solid fillers) has a higher temperature in the upper region of the container than in the lower region.

[0020] Advantageous design options and improvements are derived from the remaining dependent claims and the description in conjunction with the accompanying drawings.

[0021] Before energy is stored, each container is at a particularly low temperature level and does not have a significant amount of heat storage medium.

[0022] In a preferred embodiment, to store heat energy in a temperature-stratified manner into the first container, a heat storage medium can be introduced into the container from below until a certain liquid level is reached, and subsequently, a hot heat storage medium can be introduced into the container from above. When filling the container from below, a cold heat storage medium, especially a cold thermal oil, is particularly preferred. Using a cold heat storage medium particularly avoids mixing losses. These losses are especially important to avoid when the container is not completely filled. In this case, the lower portion of the solid filler may have already heated up, resulting in unused heat input. Using a cold heat storage medium from below also prevents or reduces the generation of thermal stress during container filling.

[0023] The process of filling the cold heat storage medium from below continues until the hot heat storage medium, especially the hot thermal oil, can flow in properly and with low eddy current from above.

[0024] Therefore, in a preferred embodiment, the heat storage medium can be supplied with heat uniformly and with low eddy currents. Specifically, it is supplied to the container from above. This is particularly advantageous for achieving temperature stratification within the container. Temperature-stratified storage is thus possible, wherein the container is specifically filled with a solid filler and the heat storage medium. In this case, the interior of the container, especially the upper region, has a higher temperature than the lower region.

[0025] In a preferred embodiment, after thermal energy is stored in the solid filler, the heat storage medium can be discharged downwards from the container. Since the heat storage medium is discharged from the container after filling, it can be used for filling the next container of the energy storage device.

[0026] In a preferred embodiment, the heat storage medium can thus be introduced from the first container into the second container to initiate the storage process in the second container. The filling schedule for the second container follows the filling process described for the first container. Multiple containers can thus be filled sequentially, with the same heat storage medium used for each container. Therefore, thermal energy can be stored in a large volume using only a relatively small volume of heat storage medium.

[0027] In a preferred embodiment, the heat storage medium can remain in the container after it has been initially filled with heat energy. Therefore, emptying the container can be cancelled, and the container can be said to remain in standby mode.

[0028] In a preferred embodiment, to release heat energy from the first container, a heat storage medium can be introduced into the container from below until it reaches an outlet opening disposed at the top of the container, whereby the hot heat storage medium is discharged from the container from above. Specifically, a cold heat storage medium is introduced into the container from below to release heat energy. This particularly allows the release process to begin immediately. Advantageously, a corresponding temperature gradient is maintained because the fully heated energy storage is filled with the cold medium. Therefore, the temperature difference between the introduced heat storage medium and the fully heated energy storage should not be chosen to be too large. In a feasible embodiment, a certain amount of heat storage medium can be stored at the bottom of the container. Additionally or alternatively, at the start of the release process, a heat storage medium at a moderate temperature can be introduced from below.

[0029] In a preferred embodiment, the supply of the heat storage medium can be carried out uniformly and with low eddy currents. This ensures, in particular, that temperature stratification within the container is maintained. After the heat storage medium is supplied from above in a low-eddy current manner, the heat storage medium is heated from above, especially from within the container. This allows energy to be released from the container.

[0030] In a preferred embodiment, after the heat energy is released from the solid filler, the heat storage medium can be discharged downwards from the container. Therefore, the heat storage medium can be used for the release from another container.

[0031] In a preferred embodiment, a heat storage medium can be introduced from a first container into a second container to initiate a release process in the second container. The release process in the second container can be performed as described for the first container. This allows for sequential discharge from multiple containers of the energy storage device, thus requiring only a small amount of heat storage medium.

[0032] In a preferred embodiment, venting is performed between the containers and / or using at least one temporary storage device during storage and / or release. Specifically, volume compensation, or more precisely, venting, may be required when the container is filled from below with a cold thermal storage medium during storage. Similarly, volume compensation, or more precisely, air intake, may be required when the thermal storage medium is discharged downwards after thermal storage is complete during storage. During release, volume compensation, or more precisely, venting, may be required when the container is filled from below with a thermal storage medium. Similarly, volume compensation, or more precisely, air intake, may be required when the thermal storage medium is discharged downwards after thermal release is complete.

[0033] For intake, exhaust, and / or volume compensation, a protective gas can be used, for example. Nitrogen can be used in particular to prevent oxidation of the heat storage medium or other structural components. Alternatively or additionally, a gaseous phase may be formed from a portion of the evaporated heat storage medium. This gaseous phase can be discharged from the corresponding container. In one embodiment, volume compensation can be performed, for example, between containers, which are specifically connected by piping. In another embodiment, a compensation container or reserve container may be provided alternatively or additionally, which can temporarily store the heat storage medium. Thus, depending on the state of the energy storage, the protective gas can be kept, for example, under pressure or overpressure. Thus, the closed system can be in a loaded or discharged state, thereby keeping the protective gas under pressure or overpressure.

[0034] In a preferred embodiment, at least one container may be partially thermally filled, wherein the upper portion of the solid filler has a higher temperature than the lower portion of the solid filler, and the container does not have a heat storage medium. This stratification limits convection compensation losses. In this state, the heat storage medium is specifically discharged downwards from the container.

[0035] The present invention also relates to a thermal energy storage device. This thermal energy storage device can be used in particular to implement the method according to the invention. Therefore, the features and advantages described with respect to the method also apply to this thermal energy storage device.

[0036] In a preferred embodiment of the thermal energy storage device, the container may have an inflow region filled with a minimum amount of the heat storage medium, and / or include a mixing region in which the temperature transition of the heat storage medium from cold to hot is achieved. This, in particular, prevents the unwanted formation of temperature stress inside the container.

[0037] In a preferred embodiment, a separation device can be provided in the outflow region of at least one container, allowing separation between the liquid and gas phases. Thus, a pipeline can be provided in the upper region of the container, branching off to allow the liquid phase to be discharged on one branch and the gas phase on the other. Appropriate valves installed in the pipeline can be used in this case. Therefore, a subsystem for controlling the input or output of the protective gas can be specifically provided, such as having at least one compressor or fan, a piping system, and at least one compensation container.

[0038] The container preferably has insulation to limit heat loss.

[0039] In a preferred embodiment, at least two containers can be connected in their respective lower regions via a first piping system, allowing cold heat storage medium to be sequentially introduced into the containers from below; and / or can be connected in their respective upper regions via a second piping system, allowing hot heat storage medium to be introduced or released, wherein a connection to a temporary storage device is formed, particularly in the upper region. Valves can be provided in the respective piping systems to allow or prevent inflow or outflow to the respective containers. Furthermore, at least one pump can be provided to enable the flow of the heat storage medium. A heat exchanger may also be provided.

[0040] The above-described design schemes and improvements can be combined arbitrarily with each other, as long as it is meaningful. Other feasible design schemes, improvements, and implementations of the present invention include combinations not explicitly mentioned in the features of the invention described above or after in conjunction with the embodiments. In particular, those skilled in the art will also add individual aspects as improvements or supplements to the corresponding basic forms of the present invention. Attached Figure Description

[0041] The present invention will now be explained in detail with reference to the embodiments shown in the accompanying drawings. The drawings are shown here:

[0042] Figure 1 One implementation of the container is shown;

[0043] Figure 2 Another implementation of the container is shown;

[0044] Figure 3 A container with a possible temperature distribution is shown;

[0045] Figure 4 This illustrates the possible heat flow during container filling;

[0046] Figure 5 This illustrates the possible heat flow during container discharge;

[0047] Figure 6 One possible implementation of a thermal energy storage device is shown. Detailed Implementation

[0048] The accompanying drawings are intended to provide a further understanding of embodiments of the invention. These figures illustrate embodiments and are used to explain the principles and solutions of the invention in conjunction with the description. Other embodiments and many mentioned advantages can be derived by referring to the drawings. Elements in the drawings are not necessarily shown to scale relative to each other.

[0049] In the accompanying drawings, elements, features, and components that are identical, have the same function, or perform the same purpose are labeled with the same reference numerals, unless otherwise specified.

[0050] Figure 1 One embodiment of container 1 is shown. Container 1 is, for example, in... Figure 6 This is part of the thermal energy storage 7 described herein. Container 1 is therefore designed as a sub-storage of the energy storage 7 and is filled with solid filler 2. Preferably, container 1 is substantially completely filled with solid filler 2. A conduit 8 is shown in the lower region of container 1, through which container 1 can be filled. An outlet opening 5 is provided in the upper region of container 1, thereby forming an outflow region 10. This outflow region can also be connected to the conduit 8. A liquid level 4 is exemplarily shown in the middle region of container 1, representing the liquid level of the thermal storage medium 3. Therefore, the thermal storage medium 3 can be filled into or emptied from container 1 through the openings in the upper and lower regions. Thermal energy can thus be stored in or released from container 1.

[0051] exist Figure 2 Another embodiment of container 1 is shown. A pipe 8 can be seen in the upper region of container 1, which branches into two sub-pipes. This forms a separation device 11, allowing the liquid phase 12 and the gas phase 13 to be discharged from container 1 through different sub-pipes. This is particularly useful for intake, exhaust, and volume compensation when using, for example, a protective gas. In this case, exhaust or intake of container 1 can be achieved during storage or release. An inflow region 9 is provided in the lower region of container 1. The figure shows a minimum liquid level 4 in container 1, where the heat storage medium 3 exists only in the lower region of container 1. This indicates its possible state before storage or release.

[0052] Figure 3A container 1 with a possible temperature distribution T is shown. In the schematic diagram, the temperature distribution T is shown from the lower region L of container 1 to the upper region H. The lower region of container 1 has a lower temperature than the upper region of container 1. The entire container 1 can be filled with a solid filler 2. By targeted filling, a mixing region, indicated by the dashed lines inside container 1, can be achieved, for example, in which a gradual temperature transition from a cold temperature to a hot temperature can be achieved in the heat storage medium 3. Therefore, even when the heat storage medium 3 is discharged from container 1, the solid filler 2 can still have the temperature gradient shown. Thus, temperature-stratified storage and release can be achieved by means of the heat storage medium 3.

[0053] Figure 4 The diagram illustrates the possible heat flow during filling of container 1. At this point, the liquid level 4 of the heat storage medium 3 first rises to the upper region of container 1. Subsequently, warm or hot heat storage medium is filled into the container from above. This generates a heat flow Q, during which the container first heats up more intensely from the upper region H. The liquid level 4 can then be lowered to the reference level shown on the right side of the diagram. In this case, the heat storage medium 3 can be discharged downwards from container 1.

[0054] exist Figure 5 The diagram illustrates the possible heat flow during discharge from container 1. Container 1 is initially filled with the heat storage medium 3 from below until it reaches the upper region H, from which the heated medium 3 can be discharged. As the heated medium 3 is discharged from the upper region H, a heat flow Q is generated in the direction of the upper region H, as indicated by the arrow. During this process, the interior of the container is cooled. After the discharge process is complete, the heat storage medium is drawn downwards, reaching the liquid level 4 shown on the right side of the diagram.

[0055] Figure 6 A possible implementation of the thermal energy storage device 7 is shown. In this implementation, the thermal energy storage device 7 has four containers 1a to 1d. Containers 1a to 1d are connected in the lower region via a first piping system 8a. In the upper region, the containers are connected via a second piping system 8b. This allows for the implementation of so-called cold branches (which connect the containers 1 to each other primarily in the lower region) and hot branches (which connect the containers 1 to each other primarily in the upper region). Various valves can be installed in the piping 8 to allow the heat storage medium 3 to flow into and out of the containers 1. Furthermore, the valves can allow the input and output of protective gases to achieve intake or exhaust.

[0056] exist Figure 6In the upper region 15, the piping system 8b is subjected to high temperatures. Pipeline 8b leads to a temporary storage tank 6b, which can be configured as a compensation container for protective gas handling. In this case, at least one compressor or fan can be installed in the upper region.

[0057] exist Figure 6 In the lower region 14, the piping system 8a is subjected to low temperatures. A subsystem for filling or emptying the heat storage medium can be implemented in the lower region. For this purpose, a pump 16 can be installed, which can be used to transport the heat storage medium 3. This allows for the transport of the heat storage medium 3 from the first container 1a to the second container 1b, and subsequently to the third container 1c and the fourth container 1d. Figure 6 The left side shows another temporary storage 6a, which in one embodiment can be implemented as a volume compensation system for the heat storage medium 3. This temporary storage 6a can also be connected to the piping system 8a via a pump.

[0058] exist Figure 6 The right side illustrates the possibility of storing heat energy into or releasing heat energy from the system or heat storage device 7. In the illustrated embodiment, a pump 16 and a heat exchanger are provided. The hot heat storage medium 3 can be guided to the heat exchanger via pipes 8a and 8b, and can be exported from or imported into the system.

[0059] Although the present invention has been fully described above with reference to preferred embodiments, the invention is not limited thereto and can be modified in various ways. In particular, the number of containers 1 in the thermal energy storage 7 can be different. Figure 6 The implementation shown in the figure. For example, it can be set with only two containers, or more than four containers, especially four to ten containers.

Claims

1. Method for storing thermal energy by means of at least two containers (1), which are filled with a solid filling (2) respectively, wherein, A heat storage medium (3) for storing and / or releasing heat energy is sequentially introduced into and / or drawn out from the container (1), wherein temperature storage is performed by temperature stratification through solid fillers (2) in the respective container (1), and the heat storage medium (3) is used for heat transfer processes during storage and / or release (heat energy).

2. The method of claim 1, wherein, In order to store thermal energy into the first container (1a) in a temperature-stratified manner, the heat storage medium (3) is introduced into the container (1a) from below until a certain liquid level (4) is reached, and then the hot heat storage medium (3) is introduced into the container (1a) from above.

3. The method of claim 2, wherein, A heat storage medium (3) that supplies the heat uniformly and with low eddy currents.

4. The method according to any of the preceding claims, characterized in that, After the heat energy is stored in the solid filler (2), the heat storage medium (3) is discharged downward from the container (1a).

5. The method according to any of the preceding claims, characterized in that, The heat storage medium (3) is introduced from the first container (1a) into the second container (1b) to initiate the storage process in the second container (1b).

6. The method according to any of the preceding claims, characterized in that, The heat storage medium (3) remains after being stored in the container (1) which is first filled with heat energy.

7. The method according to any one of the preceding claims, characterized in that, In order to release heat energy from the first container (1a), the heat storage medium (3) is introduced into the container (1a) from below until the heat storage medium (3) reaches the outlet opening (5) arranged on the top of the container (1a), so that the hot heat storage medium (3) is discharged from the container (1a) from above.

8. The method according to claim 7, characterized in that, The heat storage medium (3) is supplied uniformly and with low eddy current.

9. The method according to any one of the preceding claims, characterized in that, After the heat energy is released from the solid filler (2), the heat storage medium (3) is discharged downward from the container (1a).

10. The method according to any one of the preceding claims, characterized in that, The heat storage medium (3) is introduced from the first container (1a) into the second container (1b) to initiate a release process in the second container (1b).

11. The method according to any one of the preceding claims, characterized in that, During storage and / or release, venting is performed between containers (1a, 1b) and / or using at least one temporary storage (6).

12. The method according to any one of the preceding claims, characterized in that, At least one container (1a, 1b) is only partially geothermally filled, wherein the upper portion of the solid filler (2) has a higher temperature than the lower portion of the solid filler (2), and the container (1a, 1b) does not have a heat storage medium (3).

13. A thermal energy storage device (7), particularly for performing the method according to any one of the preceding claims, the thermal energy storage device having at least two containers (1a, 1b), each container being filled with a solid filler (2), wherein, The containers (1a, 1b) are connected by at least one pipe (8) so that a heat storage medium (3) for storing and / or releasing heat energy can be sequentially introduced into and drawn out of the containers (1a, 1b), wherein temperature storage is performed by the solid filler (2).

14. The thermal energy storage device (7) according to claim 13, characterized in that, The containers (1a, 1b) have an inflow region (9) filled with the minimum filling degree of the heat storage medium (3), and / or include a mixing region in which the temperature transition of the heat storage medium from cold to hot is realized.

15. The thermal energy storage device (7) according to claim 13 or 14, characterized in that, A separation device (11) is provided in the outflow area (10) of at least one container (1a, 1b), which allows for the separation between the liquid phase (12) and the gas phase (13).

16. The thermal energy storage device (7) according to any one of claims 13 to 15, characterized in that, The at least two containers (1a, 1b) are connected in their respective lower regions by a first piping system (8a) so that cold heat storage medium (3) can be sequentially introduced into the containers (1a, 1b) from below; and / or connected in their respective upper regions by a second piping system (8b) so that hot heat storage medium (3) can be introduced or released, wherein, particularly in the upper region, a connection to a temporary storage device (6) is formed.

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