System and method for utilizing geothermal energy

Abstract

A system for utilizing geothermal energy has a storage device equipped to store carbon dioxide present at a first temperature level and a first density level in an underground reservoir; a retrieval device equipped to retrieve carbon dioxide present at a second temperature level higher than the first temperature level and a second density level lower than the first density level from the subterranean reservoir; a heat pump comprising a first heat exchanger equipped to transfer thermal energy of the carbon dioxide downstream of the retrieval device and upstream of the storage device to a process medium of the heat pump, a compressor equipped to compress the process medium downstream of the first heat exchanger, a second heat exchanger equipped to compress the process medium downstream of the storage device, and an expander or throttle valve equipped to restrict the heat energy of the carbon dioxide. The second heat exchanger is equipped to transfer thermal energy of the compressed process medium to a consumer, and the expander or throttle valve is equipped to expand the process medium downstream of the second heat exchanger; and an introduction device equipped to introduce carbon dioxide of the carbon dioxide source downstream of the retrieval device and upstream of the heat pump into the system.

Description

Technical Field

[0001] The present invention relates to systems and methods for utilizing geothermal energy. Background Art

[0002] EP2406562B1 discloses a system for utilizing geothermal energy. The system for utilizing geothermal energy disclosed therein includes a storage device configured to store carbon dioxide present at a first temperature level in an underground reservoir. The system for utilizing geothermal energy disclosed therein also has a retrieval device configured to retrieve carbon dioxide present at a second temperature level from the underground reservoir, wherein the second temperature level is higher than the first temperature level. Additionally, the system for utilizing geothermal energy has an expander, a compressor, and a cooling device. In the expander, the carbon dioxide retrieved from the reservoir by the retrieval device can expand to generate mechanical energy from thermal energy, and the mechanical energy is converted into electrical energy in a generator. The compressor is used to compress the carbon dioxide that has expanded in the expander and to compress the carbon dioxide provided by a carbon dioxide source. The cooling device is used to cool the carbon dioxide in order to store the cooled carbon dioxide in the reservoir again.

[0003] US8316955B2, US8833475B2, and US8991510B2 further disclose the prior art regarding systems for utilizing geothermal energy.

[0004] WO2021 / 013465A1 discloses a system for converting thermal energy into mechanical energy, which can be preferentially utilized in a geothermal power plant. The system disclosed therein has a pump for delivering a flowing medium via an arrangement for converting the flowing medium from a liquid to a gas, a turbine for converting the thermal energy of the flowing medium into mechanical energy, a condenser for condensing the gaseous flowing medium into a liquid, and a cooling unit for cooling the liquid flowing medium.

[0005] There is a need for systems and methods for utilizing geothermal energy that, compared to the prior art, make it possible to increase efficiency and / or increase the utilization rate of heat. Summary of the Invention

[0006] Starting from this, the present invention is based on the object of creating new systems and methods for utilizing geothermal energy. This object is achieved by the system for utilizing geothermal energy according to claim 1 and by the method according to claim 6.

[0007] The system for utilizing geothermal energy according to the present invention includes a storage device configured to store carbon dioxide that exists in an underground reservoir at a first temperature level and a first density level.

[0008] A system for utilizing geothermal energy according to the present invention includes a retrieval device configured to retrieve carbon dioxide present at a second temperature level and a second density level from an underground reservoir, wherein the second temperature level is higher than a first temperature level and the second density level is lower than a first density level.

[0009] A system for utilizing geothermal energy according to the present invention includes a heat pump having a first heat exchanger, a compressor, a second heat exchanger, and an expander or throttle valve, wherein the first heat exchanger of the heat pump is configured to transfer the thermal energy of the carbon dioxide downstream of the retrieval device and upstream of the storage device to the process medium of the heat pump, wherein the compressor of the heat pump is configured to compress the process medium of the heat pump downstream of the first heat exchanger and upstream of the second heat exchanger, wherein the second heat exchanger of the heat pump is configured to transfer the thermal energy of the process medium of the heat pump to a consumer, and wherein the expander or throttle valve of the heat pump is configured to expand the process medium of the heat pump downstream of the second heat exchanger and upstream of the first heat exchanger.

[0010] A system for utilizing geothermal energy according to the present invention includes an introduction device configured to introduce carbon dioxide from a carbon dioxide source downstream of the retrieval device and upstream of the heat pump into the system for utilizing geothermal energy.

[0011] For the present invention presented herein, a system for utilizing geothermal energy includes a heat pump. Through the heat pump, the thermal energy of the carbon dioxide extracted from the underground reservoir can be effectively transferred to the process medium of the heat pump. The process medium of the heat pump can reach a temperature level that can be utilized by at least one consumer, such as for heating energy or process heat. In addition, the efficiency of the geothermal process can be increased, which depends on the temperature difference and density difference of the carbon dioxide between the storage device and the retrieval device.

[0012] Preferably, a system for utilizing geothermal energy includes a turbine configured to expand the carbon dioxide downstream of the retrieval device and upstream of the introduction device and to convert the thermal energy into mechanical energy and / or into electrical energy via a generator driven by the turbine. By incorporating the turbine into the system for utilizing geothermal energy, the geothermal energy can not only be utilized by a consumer, such as for heating energy or process heat, in the area of the heat pump, but the geothermal energy can also be converted into mechanical energy and / or electrical energy. This also serves to increase the efficiency and improve the utilization of geothermal energy.

[0013] Preferably, a system for utilizing geothermal energy includes a separation tank configured to separate liquid from carbon dioxide downstream of a retrieval device and upstream of an introduction device. In particular, the separation tank is connected between the retrieval device and the turbine. By means of the separation tank, it is ensured that the liquid is separated from the carbon dioxide retrieved from the underground reservoir via the retrieval device, so as to deliver only gaseous or supercritical carbon dioxide, particularly in the direction of the turbine. This is also used to improve the efficiency of the system for utilizing geothermal energy. Description of the Drawings

[0014] Preferred further improvements of the present invention are obtained from the dependent claims and the following description. Exemplary embodiments of the present invention are explained in more detail by means of the drawings, but are not limited thereto. Shown in the drawings are:

[0015] Figure 1 : A block diagram of a first system for utilizing geothermal energy according to the present invention,

[0016] Figure 2 : A block diagram of a second system for utilizing geothermal energy according to the present invention. Detailed Description of the Invention

[0017] Figure 1 Highly schematically shown is a system 10 for utilizing geothermal energy and an underground reservoir 11, where carbon dioxide can be stored and heated by geothermal energy. The underground reservoir 11 can be located, for example, at a depth of 1 km to 5 km below the surface 12 of the earth.

[0018] The system 10 for utilizing geothermal energy according to the present invention has a storage device 13 configured to store carbon dioxide present at a first temperature level and a first density level in the underground reservoir 11.

[0019] In addition, the system 10 for utilizing geothermal energy has a retrieval device 14 configured to retrieve carbon dioxide present at a second temperature level and a second density level from the underground reservoir 11. The second temperature level is higher than the first temperature level. Thus, the carbon dioxide retrieved from the underground reservoir 11 via the retrieval device 14 is warmer than the carbon dioxide stored in the underground reservoir 11 via the storage device 13. The second density level is lower than the first density level. Thus, the carbon dioxide to be retrieved in the area of the retrieval device 14 has a lower density than the carbon dioxide to be stored in the underground reservoir 11 in the area of the storage device 13.

[0020] The carbon dioxide retrieved from the underground reservoir 11 via the retrieval device 14 can be guided in the direction of the storage device 13 via a pipeline 15, wherein the system 10 for utilizing geothermal energy has a heat pump 16. The heat pump 16 includes a first heat exchanger 17, a compressor 18, a second heat exchanger 19, andFigure 1 The expander 26 in

[0021] The motor 20 is used to drive the compressor 18 of the heat pump 16. In particular, as Figure 1 shown, when the heat pump 16 includes an expander, mechanical energy is obtained in the expander 19 during the expansion of the process medium of the heat pump 16, and this mechanical energy can be used to drive the compressor 18. In this case, the motor 20 can be disengaged. When there is only a throttle valve instead of the expander 19, all the driving power for driving the compressor 18 of the heat pump 16 must be provided by the motor 20.

[0022] The system 10 for utilizing geothermal energy further includes an introduction device 21 which is equipped to introduce the carbon dioxide of the carbon dioxide source 22 downstream of the retrieval device 14 and upstream of the heat pump 16 into the system 10 for utilizing geothermal energy, that is, into the pipeline 15. A compressor 23 is connected between the introduction device 21 and the carbon dioxide source 22, and this compressor 23 can be driven by a motor 24. By means of the compressor 23, the carbon dioxide of the carbon dioxide source 22 is compressed to a pressure level corresponding to the pressure level of the carbon dioxide in the region of the pipeline 15 downstream of the retrieval device 14 and upstream of the heat pump 16. In addition, Figure 1 a pressure control valve 25 is shown, by means of which the pressure within the pipeline 15 can be directly controlled downstream of the retrieval device 14.

[0023] Figure 2 shown Figure 1 a further development of the system 10, wherein for Figure 2 the system 10 for utilizing thermal energy, the same reference numerals are used for the same components as in Figure 1 . Hereinafter, only the exemplary embodiments of Figure 2 will be discussed in comparison with Figure 1Exemplary embodiments different details. Regarding all remaining details, Figure 2 The exemplary embodiment of Figure 1 corresponds to the exemplary embodiment of Figure 1 such that the explanation regarding the exemplary embodiment of

[0024] In Figure 2 the exemplary embodiment of, the system 10 for utilizing geothermal energy has a turbine 27 which is equipped to expand carbon dioxide downstream of the retrieval device 14 and upstream of the introduction device 21 and thus convert the enthalpy of the carbon dioxide into mechanical energy in order to drive, for example, a generator 28 for generating electrical energy. A compressor 23 then compresses the carbon dioxide from the carbon dioxide source 22 to the pressure level existing downstream of the turbine 27.

[0025] In Figure 2 the exemplary embodiment of, geothermal energy is not only available for consumers in the region of the second heat exchanger 19 of the heat pump 16, but geothermal energy can also be utilized in the region of the turbine 27 and the generator 28 to generate mechanical energy and electrical energy. It is preferred but optional to convert the mechanical energy obtained in the region of the turbine 27 into electrical energy.

[0026] It can be provided that the system 10 includes Figure 1 , Figure 2 a separation tank not shown in. In the separation tank, liquid can be separated from the carbon dioxide retrieved from the underground reservoir 11 via the retrieval device 14. Thus, the efficiency of the system 10 for utilizing geothermal energy can be increased. Thus, the reservoir 11 is dried. Mixing of the carbon dioxide stream with water or other liquids, which would reduce efficiency, can be avoided. Thus, foreign substances are extracted from the carbon dioxide stream for increasing efficiency and maintaining full functionality.

[0027] The positioning of the separation tank depends on the individual components of the system 10. It mainly depends on the corrosiveness and aggregation state of the foreign substances in the carbon dioxide stream and the corresponding corrosion resistance of the components, and in the case of the turbine 27, depends on the tolerance to the liquid components in the substance stream. In the turbine 27, the cavitation effect in the case of the liquid components in the substance stream can significantly reduce the durability of the turbine 27. This depends on the specific design of the turbine 27.

[0028] In the case of corresponding incompatibilities of individual or multiple components within the system 10, it is preferred to place it upstream of the corresponding components. At the same time, separation directly before the storage device 13 and after the turbine 27 and the first heat exchanger 17 increases efficiency because the enthalpy flow of the foreign substances in the turbine 27 and / or the first heat exchanger 17 can be utilized.

[0029] In addition, the system 10 for utilizing geothermal energy may include a pump for carbon dioxide connected between the heat pump 16 (i.e., its first heat exchanger 17) and the storage device 13. Such a pump is optional. Depending on the pressure of carbon dioxide in the area of the storage device 13 and the retrieval device 14 as well as the geometric head and the pressure in the reservoir 11, such a pump may be omitted.

[0030] Furthermore, the invention relates to a method for operating a system 10 for utilizing geothermal energy.

[0031] Via the storage device 13, carbon dioxide present at a first temperature level and a first density level is stored in the underground reservoir 11.

[0032] In the area of the retrieval device 14, carbon dioxide is retrieved from the underground reservoir 11 at a second temperature level and a second density level, wherein the carbon dioxide present in the area of the retrieval device 14 may particularly have a supercritical aggregation state and, if applicable, partially have a gaseous aggregation state.

[0033] Via the first heat exchanger 17 of the heat pump 16, the carbon dioxide is cooled and the density of the carbon dioxide thus increases.

[0034] The invention allows for efficient operation and thus increases the efficiency of the system for utilizing geothermal energy and improves the utilization of geothermal heat.

[0035] List of reference numerals 10 System 11 Underground reservoir 12 Earth's surface 13 Storage device 14 Retrieval device 15 Pipeline 16 Heat pump 17 First heat exchanger 18 Compressor 19 Second heat exchanger 20 Motor 21 Introduction device 22 Carbon dioxide source 23 Compressor 24 Motor 25 Pressure control valve 26 Expander 27 Turbine 28 Generator.

Claims

1. A system for utilizing geothermal energy (10), A storage device (13) is provided, which is equipped for storing carbon dioxide at a first temperature level and a first density level in an underground reservoir (11), A retrieval device (14) is provided, the retrieval device (14) being equipped for retrieving carbon dioxide present at a second temperature level and a second density level from the underground reservoir (11), wherein: the second temperature level is higher than the first temperature level and the second density level is lower than the first density level, A heat pump (16) is provided, the heat pump (16) comprising a first heat exchanger (17), a compressor (18), a second heat exchanger (19) and an expander (26) or a throttle valve, wherein the first heat exchanger (17) of the heat pump (16) is equipped to transfer the thermal energy of the carbon dioxide downstream of the retrieval device (14) and upstream of the storage device (13) to the process medium of the heat pump (16), wherein the compressor (18) of the heat pump (16) is equipped to compress the carbon dioxide in the first heat exchanger (17) and the process medium of the heat pump (16). the process medium of the heat pump (16) downstream of the second heat exchanger (17) and upstream of the second heat exchanger (19), wherein the second heat exchanger (19) of the heat pump (16) is equipped for transferring thermal energy of the process medium of the heat pump (16) to a consumer, and wherein the expander (26) or the throttle valve of the heat pump (16) is equipped for expanding the process medium of the heat pump (16) downstream of the second heat exchanger (19) and upstream of the first heat exchanger (17), There is an introduction device (21) equipped for introducing carbon dioxide from a carbon dioxide source (22) downstream of the retrieval device (14) and upstream of the heat pump (16) into the system (10) for utilizing geothermal energy.

2. The system (10) according to claim 1, Features a turbine (27) equipped to expand the carbon dioxide downstream of the retrieval device (14) and upstream of the introduction device (21) and to convert thermal energy into mechanical energy and / or into electrical energy via a generator (28) driven by the turbine.

3. The system (10) according to claim 1 or 2, Features A separation tank equipped for separating liquid from the carbon dioxide downstream of the retrieval device (14) and upstream of the introduction device (21).

4. The system (10) according to claim 2 and 3, It is characterized in that The separation tank is connected between the retrieval device (14) and the turbine (27).

5. The system (10) according to any one of claims 1 to 4, Features A pump for the carbon dioxide is connected between the heat pump (16) and the storage device (13).

6. A method for operating a system (10) according to any one of claims 1 to 5, comprising the following steps: By means of the storage device (13), gaseous and / or liquid carbon dioxide is stored in the underground reservoir, Retrieving supercritical carbon dioxide from the underground storage tank by means of the retrieval device (14), Supercritical and / or gaseous carbon dioxide is cooled by the first heat exchanger (17) of the heat pump (16).

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