An underground cavity storage system and a method for controlling the circulation of gas in an underground cavity gas storage

Abstract

The disclosure relates to an underground cavity storage system (1) comprising a control device (200) connected to the system (1); an underground cavity gas storage (2) for storing the gas (4) in an interior volume (V) thereof. At least one gas circulation device (10) is configured to generate a circulating gas flow of the gas (4) in the underground cavity storage system (1). At least one heat exchanger (12) is arranged downstream of the at least one gas circulation device (10). At least one temperature sensor (14) arranged at the underground cavity gas storage (2). The disclosure further relates to a method performed by a control device (200), for controlling the circulation of gas (4) in an underground cavity gas storage (2) of an underground cavity storage system (1). The method comprises the steps of detecting (s101) at least one temperature (Tg, Tw) at the underground cavity gas storage (2); controlling (s102) the at least one gas circulation device (10) for generating a circulating gas flow of the gas (4) in the underground cavity storage system (1) based on the at least one detected temperature (Tg, Tw) at the underground cavity gas storage (2); and controlling (s103) the at least one heat exchanger (12) based on the at least one detected temperature (Tg, Tw) at the underground cavity gas storage (2). The disclosure further relates to a computer program and a computer- readable medium (202) having stored thereon the computer program.

Description

[0001] An underground cavity storage system and a method for controlling the circulation of gas in an underground cavity gas storage

[0002] Technical field

[0003] The present disclosure relates to an underground cavity storage system, a method, a computer program and a computer-readable medium having stored thereon the computer program.

[0004] Background art

[0005] Underground cavity storage systems have been implemented in the form of lined rock caverns and salt caverns. The rock caverns have been used for depth in the order of 100 m and the salt caverns have been used for a depth of about 1000 m. The gas is stored at high pressures of above 150 bar and at temperatures between 0°C to 80°C. The cavern gas tightness is maintained by a steel lining or impermeable salt formation.

[0006] Document US6374844B1A discloses an operation method of cavern storage using gas recirculation system. This gas recirculation system aims to prevent lining damage because of freezing temperatures during withdrawal and allows more storage capacity by decreasing maximum temperatures during storage filling.

[0007] Summary

[0008] A problem with the solutions of the prior art is that the recirculation systems add large costs to the cavern storage operation which may not compensate for the addition in storage capacity.

[0009] A further problem with the solutions of the prior art is that the temperature in the rock is expected to increase after several storage cycles, which make the recirculation system less needed to prevent low temperatures.

[0010] There is thus a need for an improved underground cavity storage system and a method, which reduce costs for operating the underground cavern storage system.

[0011] There is further a need for an improved underground cavity storage system and a method in which the temperature in the ambient mass is not expected to increase after several storage cycles, which make a recirculation system necessary to prevent low temperatures in the underground cavity storage system. There is further a need for an improved underground cavity storage system and a method for storing of hydrogen gas or other fluids (for example methane, carbon dioxide and ammonia), for applications of, e.g., balancing renewable energy production variability and direct reduction of iron for fossil-free steel making process. The operation of such as storage may therefore be determined by external factors such as market conditions and process operations.lt is an objective of the present disclosure to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages in the prior art and solve at least the above-mentioned problem.

[0012] A further objective of is to provide a system and an operational method for an underground cavity storage system that relies on preheating surrounding ambient mass to prevent freezing temperatures, which can lead to wall damage in an underground cavity storage.

[0013] This is solved by an underground cavity storage system, a method performed by a control device, for controlling the circulation of gas in an underground cavity gas storage of an underground cavity storage system, a computer program and a computer-readable medium having stored thereon the computer program according to the appended claims.

[0014] According to a first aspect there is provided an underground cavity storage system comprising a control device connected to the system; an underground cavity gas storage for storing the gas in an interior volume thereof, at least one gas circulation device for generating a circulating gas flow of the gas in the underground cavity storage system at least one heat exchanger arranged downstream of the at least one gas circulation device, which at least one heat exchanger is configured to reduce or increase the temperature of the gas circulated by the at least one gas circulation device; and at least one temperature sensor arranged at the underground cavity gas storage. At least one temperature sensor is configured to detect at least one temperature at the underground cavity gas storage; that the at least one gas circulation device is configured to generate a circulating gas flow of the gas in the underground cavity storage system based on the at least one detected temperature at the underground cavity gas storage; and that the heat exchanger is configured to reduce or increase the temperature of the gas circulated by the at least one gas circulation device based on the at least one detected temperature at the underground cavity gas storage.

[0015] The ambient mass surrounding the underground cavity gas storage acts as a thermal storage, with heat capacities larger than the ones of the stored gas. Gas is injected at higher temperatures into the underground cavity gas storage to build up heat in the ambient mass, such that the maximum temperature in the underground cavity gas storage at maximum pressure should not exceed a maximum operational limit temperature, e.g. 80°C. The required injecting gas temperature, which may be estimated from numerical or empirical methods, is obtained by cooling the compressed gas outside of the underground cavity gas storage, with the possibility of mixing with some cooler storage gas. Controlling the temperatures, pressures and flows in the underground cavity gas storage may be read from detecting devices, such as sensors. For rapid withdrawals, freezing temperatures in the cavity may be avoided without recirculation of gas into the underground cavity gas storage.

[0016] Components of the underground cavity storage system may be arranged underground or above ground. The control device may be connected to the components of the system by wire. The control device may be wireless connected to the components of the system. The underground cavity gas storage may have any shape. The underground cavity gas storage may be arranged in a surrounding rock mass or rock salt mass, concrete, stiff soil or similar. The underground cavity gas storage may be a shaped cavity in a rock mass or rock salt mass, concrete, stiff soil or similar. The underground cavity gas storage may be provided with a liner. The gas may be stored in the underground cavity gas storage in gas or liquid form. The interior volume of the underground cavity gas storage may have any shape. The heat exchanger may be connected to a community heating system. The heat exchanger may reduce or increase the temperature of the gas based on at least one detected temperature at the underground cavity gas storage. The temperature at the underground cavity gas storage may be detected by a temperature sensor. The temperature sensor may be arranged at the underground cavity gas storage for detecting the at least one detected temperature at the underground cavity gas storage. The detected temperature at the underground cavity gas storage is a temperature in the underground cavity gas storage, at a wall of the underground cavity gas storage, outside of the underground cavity gas storage or a temperature at a distance from the underground cavity gas storage.

[0017] A gas circulation device may be arranged for generating a circulating gas flow of the gas in the underground cavity storage system. The gas circulation device may be arranged for generating a circulating gas flow of the gas in the underground cavity storage system based on the at least one detected temperature at the underground cavity gas storage. The gas circulation device may be controlled for increasing the circulating gas flow of the gas. The gas circulation device may be controlled for increasing the circulating gas flow of the gas if the detected temperature at the underground cavity gas storage increases above a threshold temperature. The gas circulation device may be controlled for withdrawing the gas from a position at a top of the underground cavity gas storage. The gas circulation device may be controlled for withdrawing the gas from a position at a top of the underground cavity gas storage and injecting the withdrawn gas to a position upstream of the at least one heat exchanger. The gas circulation device may be a fan, pump and / or a compressor.

[0018] The at least one temperature sensor is arranged in an ambient mass surrounding the underground cavity gas storage on at least one distance from a wall of the underground cavity gas storage, wherein the at least one distance is within the range of 0 m - 100 m. The ambient mass is the surrounding rock mass or rock salt mass, concrete, stiff soil or similar. The temperature sensor may be arranged on the wall of the underground cavity gas storage. The temperature sensor may be arranged far away from the wall of the underground cavity gas storage. A number of temperature sensors with a distance from each other may be arranged in the range of 0 meters to 100 meters. Arranging the temperature sensors in this way results in an indication about the heat distribution at the underground cavity gas storage and a distance from the wall of the underground cavity gas storage.

[0019] The at least one gas circulation device is at least one pump, fan and / or compressor. The gas circulation device may circulate the gas from an outlet to an inlet of the underground cavity gas storage. The circulation may be performed at low pressure and at a variable gas flow rate. The circulation may alternately be performed at a high pressure at a high or low gas flow rate.

[0020] According to a second aspect there is provided a method, performed by a control device, for controlling the circulation of gas in an underground cavity gas storage of an underground cavity storage system, the underground cavity storage system comprises the control device connected to the system; the underground cavity gas storage for storing the gas in an interior volume thereof, at least one gas circulation device for generating a circulating gas flow of the gas in the underground cavity storage system; at least one heat exchanger arranged downstream of the at least one gas circulation device, which at least one heat exchanger is configured to reduce or increase the temperature of the gas circulated by the at least one gas circulation device; and at least one temperature sensor arranged at the underground cavity gas storage. The method comprises the steps of: detecting at least one temperature at the underground cavity gas storage; controlling the at least one gas circulation device for generating a circulating gas flow of the gas in the underground cavity storage system based on the at least one detected temperature at the underground cavity gas storage; and controlling the heat exchanger based on the at least one detected temperature at the underground cavity gas storage.

[0021] Components of the underground cavity storage system may be arranged underground, partly over the ground and / or on the ground. The control device may be connected to the components of the system by wire. The control device may be wireless connected to the components of the system. The underground cavity gas storage may have any shape, such as cylinder or spherical like shape. The underground cavity gas storage may be a cavity in a rock mass or rock salt mass, concrete, stiff soil or similar. The underground cavity gas storage may be provided with a liner. The gas may be stored in the underground cavity gas storage in gas or liquid form. The interior volume of the underground cavity gas storage may have any shape. The heat exchanger may be connected to a community heating system. The heat exchanger may reduce or increase the temperature of the gas based on at least one detected temperature at the underground cavity gas storage. The gas circulation device may be arranged for generating a circulating gas flow of the gas in the underground cavity storage system based on the at least one detected temperature at the underground cavity gas storage. The gas circulation device may be controlled for increasing the circulating gas flow f of the gas. The gas circulation device may be controlled for increasing the circulating gas flow of the gas if the detected temperature at the underground cavity gas storage increases above a threshold temperature. The gas circulation device may be controlled for withdrawing the gas from a position at a top of the underground cavity gas storage. The gas circulation device may be controlled for withdrawing the gas from a position at a top of the underground cavity gas storage and injecting the withdrawn gas to a position downstream of the at least one heat exchanger. The gas circulation device may be a fan, pump and / or a compressor. The temperature at the underground cavity gas storage may be detected by a temperature sensor. The temperature sensor may be arranged at the underground cavity gas storage for detecting the at least one detected temperature at the underground cavity gas storage. The detected temperature at the underground cavity gas storage is a temperature in the underground cavity gas storage, at a wall of the underground cavity gas storage, outside of the underground cavity gas storage or a temperature at a distance from the underground cavity gas storage. The step of detecting at least one temperature at the underground cavity gas storage may be performed by detecting the temperature by the temperature sensor arranged in the underground cavity gas storage. The step of controlling the at least one gas circulation device for generating a circulating gas flow of the gas in the underground cavity storage system based on the at least one detected temperature at the underground cavity gas storage. The gas circulation device may be controlled for increasing the circulating gas flow of the gas. The gas circulation device may be controlled for increasing the circulating gas flow of the gas if the detected temperature in the underground cavity storage system increases above a threshold temperature. The gas circulation device may be controlled for withdrawing the gas from a position at a top of the underground cavity gas storage. The gas circulation device may be controlled for withdrawing the gas from a position at a top of the underground cavity gas storage and injecting the withdrawn at the bottom of the underground cavity gas storage. The gas circulation device may be a fan, pump and / or a compressor. The step of controlling the heat exchanger based on the at least one detected temperature at the underground cavity gas storage may be performed by heating or cooling the gas in the heat exchanger. The heat exchanger is configured to reduce or increase the temperature of the gas circulated by the at least one gas circulation device based on the at least one detected temperature at the underground cavity gas storage. The method is thus useful for tuning or controlling the temperature of the walls of the underground cavity gas storage and the temperature of the ambient mass surrounding the underground cavity storage. The method also ensures that the temperature of the walls of the underground cavity storage and the temperature of the ambient mass may not fall below a threshold temperature.

[0022] The step of detecting the at least one temperature at the underground cavity gas storage comprises detecting the temperature of a wall of the underground cavity gas storage. The temperature sensor may be arranged on the wall of the underground cavity gas storage. The temperature sensor may be arranged on the inside wall of the underground cavity gas storage. The temperature sensor may be arranged on the outside wall of the underground cavity gas storage. A number of temperature sensors may be arranged on different positions on the wall of the underground cavity gas storage.

[0023] The step of detecting the at least one temperature at the underground cavity gas storage comprises detecting the temperature of an ambient mass surrounding the underground cavity gas storage. The ambient mass may be a rock mass or rock salt mass, concrete, stiff soil or similar surrounding the underground cavity gas storage.

[0024] The step of detecting the at least one temperature at the underground cavity gas storage comprises detecting the temperature of the ambient mass surrounding the underground cavity gas storage on at least one distance from a wall of the underground cavity gas storage, wherein the at least one distance is within the range of 0 m - 100 m. The temperature sensor may be arranged far away from the wall of the underground cavity gas storage. A number of temperature sensors with a distance from each other may be arranged in the range of 0 meters to 100 meters. Arranging the temperature sensors in this way results in an indication about the heat distribution at the underground cavity gas storage and a distance from the wall of the underground cavity gas storage.

[0025] The step of controlling the at least one gas circulation device for generating a circulating gas flow of the gas in the underground cavity storage system based on the at least one detected temperature at the underground cavity gas storage comprises controlling the at least one gas circulation device for increasing the circulating gas flow of the gas if the detected temperature at the underground cavity gas storage decreases below a threshold temperature. Increasing the gas flow and the increasing the temperature in the heat exchanger results in that a large mass flow of heated gas may enter the underground cavity gas storage.

[0026] The step of controlling the at least one gas circulation device for generating a circulating gas flow of the gas in the underground cavity storage system based on the at least one detected temperature at the underground cavity gas storage comprises controlling the at least one gas circulation device for increasing the pressure of the gas to be injected in the underground cavity gas storage based on the detected temperature at the underground cavity gas storage. Increasing the pressure of the gas may increase the temperature of the gas. The circulation device may be a compressor. This results in that heated gas may enter the underground cavity gas storage and thus increase the temperature of the underground cavity gas storage.

[0027] The step of controlling the heat exchanger based on the at least one detected temperature at the underground cavity gas storage comprises controlling the heat exchanger for increasing the temperature of the gas downstream of the heat exchanger if the detected temperature of the gas in the underground cavity gas storage and the at least one temperature of the wall of the underground cavity gas storage decreases below a threshold temperature. During withdrawal of gas from the underground cavity gas storage the pressure in the underground cavity gas storage decreases, which results in a temperature drop in the underground cavity gas storage. The temperature in the wall of the cavity may be damaged if the temperature drops below 0° C due to freezing damages. Further, if the ambient mass surrounding the underground cavity gas storage is a rock mass, cracks in the rock may arise due to freezing. The threshold temperature of the at least one detected temperature at the underground cavity gas storage may thus be above 0° C in order to prevent freezing. By controlling the gas flow created by the compressor and controlling the heat exchanger for heating the gas flowing through the heat exchanger the temperature of the gas to be injected can be increased to a suitable temperature. The recirculated gas of increased temperature may heat the underground cavity gas storage. Further, the temperature of the ambient mass and the flow rate of the gas flow into the underground cavity gas storage may affect the temperature development within the underground cavity gas storage during injection of gas. For rapid withdrawals of gas, freezing temperatures in the underground cavity gas storage may be avoided.

[0028] The step of controlling the heat exchanger based on the at least one detected temperature at the underground cavity gas storage comprises controlling the heat exchanger for decreasing the temperature of the gas downstream of the heat exchanger if the detected temperature of the gas in the underground cavity gas storage and the at least one temperature of the wall of the underground cavity gas storage increases above a threshold temperature. The temperature in the underground cavity gas storage may increase during circulation of compressed gas. Gas at higher temperatures, which is recirculated into the underground cavity gas storage may build up heat in the ambient mass. However, the temperature in the underground cavity gas storage should not increase above a threshold temperature. The threshold temperature underground cavity gas storage may be 80° C. Thus, the maximum temperature in the cavity at maximum pressure may not exceed a maximum operational limit temperature, e.g. 80° C.

[0029] The step of controlling the at least one gas circulation device for generating a circulating gas flow of the gas in the underground cavity storage system based on the at least one detected temperature at the underground cavity gas storage comprises controlling the gas circulation device for withdrawing the gas from the underground cavity gas storage and injecting the withdrawn gas to the underground cavity gas storage after the withdrawn gas has passed the at least one heat exchanger. The gas circulation device may be controlled for circulation the gas stored in the underground cavity gas storage. The gas is circulated in the in the underground cavity storage system. During circulation the gas flows from the underground cavity gas storage, through the gas circulation device, through the heat exchanger and further into the circulation cavity gas storage. The gas circulation device may be controlled for circulating the gas at different flow rates and at different pressures depending on the condition of the gas, the condition of the underground cavity gas storage and / or the condition of the ambient mass. The heat exchanger may be controlled for heating or cooling the circulated gas at different temperatures depending on the condition of the gas, the condition of the underground cavity gas storage and / or the condition of the ambient mass. The present disclosure also relates to a computer program stored on a computer- readable medium and comprising instructions, which when the program is executed by a data processing unit of a control device of an underground cavity storage system, cause the control device to carry out the method according to the second aspect. The disclosure further relates to a computer-readable medium having stored thereon the computer program. The method may be comprised in pre-programmed software, which may be implemented into a production unit suitable for utilizing the method. The pre-programmed software may be stored in the control device. Alternatively, or in combination, the software may be stored in a memory or in a computer at a distance from the control device.

[0030] Brief of the

[0031] The above objects, as well as additional objects, features and advantages of the present disclosure, will be more fully appreciated by reference to the following illustrative and non-limiting detailed description of example embodiments of the present disclosure, when taken in conjunction with the accompanying drawings.

[0032] Fig. 1 schematically illustrates in a section view, an underground cavity storage system according to an example,

[0033] Figures 2a and 2b schematically illustrate in section views, how the temperatures in the underground cavity gas storage and in the ambient mass interacts during filling and withdrawal of the gas,

[0034] Fig. 3 shows a diagram for temperature measurements in the storage changing with time, and average temperature at distance from the cavity wall during gas storage operation,

[0035] Fig. 4 shows a flowchart of a method according to an example, and

[0036] Fig. 5 schematically illustrates a control device according to an example.

[0037] Detailed description

[0038] The present disclosure will now be described with reference to the accompanying drawings, in which preferred example embodiments of the disclosure are shown. The disclosure may, however, be embodied in other forms and should not be construed as limited to the herein disclosed embodiments. The disclosed embodiments are provided to fully convey the scope of the disclosure to the skilled person. Fig. 1 schematically illustrates in a section view, an underground cavity storage system 1 according to an example. The underground cavity storage system 1 comprising a control device 200 connected to the system 1. An underground cavity gas storage 2 is arranged for storing the gas 4 in an interior volume V thereof. A gas circulation device 10 is arranged for generating a circulating gas flow of the gas 4 in the underground cavity storage system 1. A heat exchanger 12 is arranged downstream of the at least one gas circulation device 10, which heat exchanger 12 is configured to reduce or increase the temperature Tg of the gas 4 circulated by the at least one gas circulation device 10. Temperature sensors 14, 18 are arranged at the underground cavity gas storage 2, which temperature sensors 14 are configured to detect at least one temperature Tg, Tw at the underground cavity gas storage 2. The gas circulation device 10 is configured to generate a circulating gas flow of the gas 4 in the underground cavity storage system 1 based on the at least one detected temperature Tg,Tw at the underground cavity gas storage 2. The heat exchanger 12 is configured to reduce or increase the temperature Tg of the gas 4 circulated by the at least one gas circulation device 10 based on the at least one detected temperature Tg,Tw at the underground cavity gas storage 2. The heat exchanger 12 is connected to a heat source 20. The gas circulation device 10 is a pump, fan and / or compressor. Some of the temperature sensors 14 are arranged in an ambient mass 6 surrounding the underground cavity gas storage 2 on at least one distance dl, d2, , dn from a wall 8 of the underground cavity gas storage 2, at distance dl, d2, . , dn in the range of 0 m - 100 m. A temperature sensor 18 is arranged in the underground cavity gas storage 2 for detecting the temperature Tg of the gas 4. The temperature sensor 18 can also be configured to detect the pressure of the gas 4 within the underground cavity gas storage 2. A gas source 22 may be fluidly connected to the underground cavity gas storage 2. A gas sink 24 may be fluidly connected to the underground cavity gas storage 2.

[0039] Figures 2a and 2b schematically illustrate in section views, how the temperatures Tg, Tw in the underground cavity gas storage 2 and in the ambient mass 6 interacts during filling and withdrawal of the gas 4, 4”. The ambient mass 6 is a rock mass, a rock salt mass, stiff soil or concrete surrounding the underground cavity gas storage 2. In fig. 2a the gas 4 is injected into the volume V of the underground cavity gas storage 2. Before injected into the underground cavity gas storage 2, the gas 4 may be heated in the heat exchanger 12 (see fig. 1). Heat from the gas 4 is transferred to the ambient mass 6 during filling of the gas 4. Heat from the gas 4 transferred to the ambient mass 6 is illustrated by arrows At in fig. 2a. Injected gas 4 may be circulated within the underground cavity storage 2, which is illustrated with arrows 4' in fig. 3a. In fig. 2b the gas 4” is withdrawn from the underground cavity gas storage 2. During withdrawal of the gas 4” from the underground cavity gas storage 2, the temperature Tg in the underground cavity gas storage 2 decreases due to pressure drop in the underground cavity gas storage 2. Heat stored in the ambient mass 6 is transferred from the ambient mass 6 to the underground cavity gas storage 2 during withdrawal of the gas 4”. Heat stored in the ambient mass 6 is transferred from the ambient mass 6 to the underground cavity gas storage 2 is illustrated by arrows At in fig. 2b.

[0040] Fig. 3 shows a diagram for temperature measurements in the cavity 2 changing with time, and average temperature at distance from the wall 8 of the underground gas storage in the ambient mass 6 during gas storage operation. A comparison between conventional operation and operation with heated ambient mass is shown. By heating the ambient mass temperature, the temperature in the cavity increases and can be kept within acceptable operational limits. During gas injection into the underground cavity gas storage 2 heat is transferred from the gas 4 in the underground cavity gas storage 2 to the ambient mass 6. During withdrawal of the gas 4 from the underground cavity gas storage 2 the temperature in the underground cavity gas storage 2 decreases. Heat stored in the ambient mass 6 is transferred from the ambient mass 6 to the underground cavity gas storage 2 during withdrawal of the gas 4 resulting in a temperature increase in the underground cavity gas storage 2. The temperature in the ambient mass 6 decreases with the distance from the wall 8 of the underground cavity gas storage 2. On the left-hand side in Fig. 3 the temperature inside the underground cavity gas storage 2 is illustrated. The temperature inside the underground cavity gas storage 2 depends on the injection of gas to the underground cavity gas storage 2 and withdrawal of the gas from underground cavity gas storage 2, and also on the temperature in the ambient mass 6. On the right hand side of Fig. 3 the average temperature in the ambient mass 6 is illustrated. The dashed line illustrates how the temperature in the ambient mass 6 decreases with the distance from the wall 8 of the underground cavity gas storage 2. The solid lines represent the temperatures in a conventional situation when the transfer of heat between the underground cavity gas storage 2 and the ambient mass 6 is not used.

[0041] Fig. 4 shows a flowchart of a method according to an example. The method is performed by a control device 200, for controlling the circulation of gas 4 in an underground cavity gas storage 2 of an underground cavity storage system 1. The method relates to the underground cavity storage system 1 shown in fig. 1. The underground cavity storage system 1 thus comprises the control device 200 connected to the system 1. The underground cavity gas storage 2 is arranged for storing the gas 4 in an interior volume V thereof. At least one gas circulation device 10 for generating a circulating gas flow of the gas 4 in the underground cavity storage system 1. At least one heat exchanger 12 arranged downstream of the at least one gas circulation device 10, which at least one heat exchanger 12 is configured to reduce or increase the temperature Tg of the gas 4 circulated by the at least one gas circulation device 10. At least one temperature sensor 14 is arranged at the underground cavity gas storage 2.

[0042] The method comprises the steps of: detecting slOl at least one temperature Tg, Tw at the underground cavity gas storage 2; controlling sl02 the at least one gas circulation device 10 for generating a circulating gas flow of the gas 4 in the underground cavity storage system 1 based on the at least one detected temperature Tg, Tw at the underground cavity gas storage 2; and controlling sl03 the heat exchanger 12 based on the at least one detected temperature Tg, Tw at the underground cavity gas storage 2.The step of detecting slOl the at least one temperature Tg, Tw at the underground cavity gas storage 2 comprises detecting the temperature Tw of a wall 8 of the underground cavity gas storage 2. The step of detecting slOl the at least one temperature Tg, Tw at the underground cavity gas storage 2 comprises detecting the temperature Tw of an ambient mass 6 surrounding the underground cavity gas storage 2. The step of detecting slOl the at least one temperature Tg,Tw at the underground cavity gas storage 2 comprises detecting the temperature Tw of the ambient mass 6 surrounding the underground cavity gas storage 2 on at least one distance dl, d2, , dn from a wall 8 of the underground cavity gas storage 2, wherein the at least one distance dl, d2, , dn is within the range of 0 m - 100 m. The step of controlling sl02 the at least one gas circulation device 10 for generating a circulating gas flow of the gas 4 in the underground cavity storage system 1 based on the at least one detected temperature Tg, Tw at the underground cavity gas storage 2 comprises controlling the at least one gas circulation device 10 for increasing the circulating gas flow f of the gas 4 if the detected temperature Tg, Tw at the underground cavity gas storage 2 decreases below a threshold temperature Ttt. The step of controlling sl02 the at least one gas circulation device 10 for generating a circulating gas flow of the gas 4 in the underground cavity storage system 1 based on the at least one detected temperature Tg, Tw at the underground cavity gas storage 2 comprises controlling the at least one gas circulation device 10 for increasing the pressure of the gas 4 to be injected in the underground cavity gas storage 2 based on the detected temperature Tg, Tw at the underground cavity gas storage 2. The step of controlling sl03 the heat exchanger 12 based on the at least one detected temperature Tg, Tw at the underground cavity gas storage 2 comprises controlling the heat exchanger 12 for increasing the temperature of the gas 4 downstream of the heat exchanger 12 if the detected temperature of the gas Tg in the underground cavity gas storage 2 and the at least one temperature Tw of the ambient mass 6 of the underground cavity gas storage 2 decreases below a threshold temperature Ttt. The step of controlling sl03 the heat exchanger 12 based on the at least one detected temperature Tg, Tw at the underground cavity gas storage 2 comprises controlling the heat exchanger 12 for decreasing the temperature of the gas 4 downstream of the heat exchanger 12 if the detected temperature of the gas Tg in the underground cavity gas storage 2 and the at least one temperature Tw of the ambient mass 6 of the underground cavity gas storage 2 increases above a threshold temperature Ttt. The step of controlling sl02 the at least one gas circulation device 10 for generating a circulating gas flow f of the gas 4 in the underground cavity storage system 1 based on the at least one detected temperature Tg, Tw at the underground cavity gas storage 2 comprises controlling the gas circulation device 10 for withdrawing the gas 4 from the underground cavity gas storage 2 and injecting the withdrawn gas 4 to the underground cavity gas storage 2 after the withdrawn gas 4 has passed the at least one heat exchanger 12.

[0043] Fig. 5 schematically illustrates a control device 200 of the indoor climate system 1 according to an example. The control device 200 comprises at least one data processing unit 201 and a computer-readable medium 202. The control device 200 may be configured to perform the method as described in fig. 4 upon execution of a computer program P by the at least one data processing unit 201. The computer program P comprises computer-readable instructions that may be stored in the computer-readable medium 202, such as a non- transitory hardware memory device of the control device 200.

Claims

CLAIMS1. An underground cavity storage system (1) comprising a control device (200) connected to the system (1); an underground cavity gas storage (2) for storing the gas (4) in an interior volume (V) thereof, at least one gas circulation device (10) for generating a circulating gas flow of the gas (4) in the underground cavity storage system (1) at least one heat exchanger (12) arranged downstream of the at least one gas circulation device (10), which at least one heat exchanger (12) is configured to reduce or increase the temperature (Tg) of the gas (4) circulated by the at least one gas circulation device (10); and at least one temperature sensor (14) arranged at the underground cavity gas storage (2), characterized in that the at least one temperature sensor (14) is configured to detect at least one temperature (Tg, Tw) at the underground cavity gas storage (2); that the at least one gas circulation device (10) is configured to generate a circulating gas flow of the gas (4) in the underground cavity storage system (1) based on the at least one detected temperature (Tg, Tw) at the underground cavity gas storage (2); and that the at least one heat exchanger (12) is configured to reduce or increase the temperature (Tg) of the gas (4) circulated by the at least one gas circulation device (10) based on the at least one detected temperature (Tg, Tw) at the underground cavity gas storage (2).

2. The system (1) according to claim 1, wherein the at least one temperature sensor (14) is arranged in an ambient mass (6) surrounding the underground cavity gas storage (2) on at least one distance (dl, d2, , dn) from a wall (8) of the underground cavity gas storage (2), wherein the at least one distance (dl, d2, , dn) is within the range of 0 m - 100 m.

3. The system (1) according to any one of the claims 1 and 2, wherein the at least one gas circulation device (10) is at least one pump, fan and / or compressor.

4. A method, performed by a control device (200), for controlling the circulation of gas (4) in an underground cavity gas storage (2) of an underground cavity storage system (1), the underground cavity storage system (1) comprises the control device (200) connected to the system (1);the underground cavity gas storage (2) for storing the gas (4) in an interior volume (V) thereof, at least one gas circulation device (10) for generating a circulating gas flow of the gas (4) in the underground cavity storage system (1) at least one heat exchanger (12) arranged downstream of the at least one gas circulation device (10), which at least one heat exchanger (12) is configured to reduce or increase the temperature (Tg) of the gas (4) circulated by the at least one gas circulation device (10); and at least one temperature sensor (14) arranged at the underground cavity gas storage (2), the method is characterized by the steps of: detecting (slOl) at least one temperature (Tg, Tw) at the underground cavity gas storage (2); controlling (sl02) the at least one gas circulation device (10) for generating a circulating gas flow of the gas (4) in the underground cavity storage system (1) based on the at least one detected temperature (Tg, Tw) at the underground cavity gas storage (2); and controlling (sl03) the at least one heat exchanger (12) based on the at least one detected temperature (Tg, Tw) at the underground cavity gas storage (2).

5. The method according to claim 4, wherein the step of detecting (slOl) the at least one temperature (Tg,Tw) at the underground cavity gas storage (2) comprises detecting the temperature (Tw) of a wall (8) of the underground cavity gas storage (2).

6. The method according to any one of the claims 4 and 5, wherein the step of detecting (slOl) the at least one temperature (Tg,Tw) at the underground cavity gas storage (2) comprises detecting the temperature (Tw) of an ambient mass (6) surrounding the underground cavity gas storage (2).

7. The method according to claim 6, wherein the step of detecting (slOl) the at least one temperature (Tg,Tw) at the underground cavity gas storage (2) comprises detecting the temperature (Tw) of the ambient mass (6) surrounding the underground cavity gas storage (2) on at least one distance (dl, d2, , dn) from a wall (8) of the underground cavity gas storage (2), wherein the at least one distance (dl, d2, , dn) is within the range of 0 m - 100 m.

8. The method according to any one of the claims 4 - 7, wherein the step of controlling(sl02) the at least one gas circulation device (10) for generating a circulating gas flow of the gas (4) in the underground cavity storage system (1) based on the at least one detected temperature (Tg,Tw) at the underground cavity gas storage (2) comprises controlling the at least one gas circulation device (10) for increasing the circulating gas flow (f) of the gas (4) if the detected temperature (Tg,Tw) at the underground cavity gas storage (2) decreases below a threshold temperature (Ttt).

9. The method according to any one of the claims 4 - 8, wherein the step of controlling (sl02) the at least one gas circulation device (10) for generating a circulating gas flow of the gas (4) in the underground cavity storage system (1) based on the at least one detected temperature (Tg,Tw) at the underground cavity gas storage (2) comprises controlling the at least one gas circulation device (10) for increasing the pressure of the gas (4) to be injected in the underground cavity gas storage (2) based on the detected temperature (Tg,Tw) at the underground cavity gas storage (2).

10. The method according to any one of the claims 4 - 9, wherein the step of controlling (sl03) the at least one heat exchanger (12) based on the at least one detected temperature (Tg,Tw) at the underground cavity gas storage (2) comprises controlling the at least one heat exchanger (12) for increasing the temperature of the gas (4) downstream of the at least one heat exchanger (12) if the detected temperature of the gas (Tg) in the underground cavity gas storage (2) and the at least one temperature (Tw) of the ambient mass (6) of the underground cavity gas storage (2) decreases below a threshold temperature (Ttt).

11. The method according to any one of the claims 4 - 9, wherein the step of controlling (sl03) the at least one heat exchanger (12) based on the at least one detected temperature (Tg,Tw) at the underground cavity gas storage (2) comprises controlling the at least one heat exchanger (12) for decreasing the temperature of the gas (4) downstream of the at least one heat exchanger (12) if the detected temperature of the gas (Tg) in the underground cavity gas storage (2) and the at least one temperature (Tw) of the ambient mass (6) of the underground cavity gas storage (2) increases above a threshold temperature (Ttt).

12. The method according to any one of the claims 4 - 11, wherein the step of controlling (sl02) the at least one gas circulation device (10) for generating a circulating gas flow (f) of the gas (4) in the underground cavity storage system (1) based on the at least one detected temperature (Tg,Tw) at the underground cavity gas storage (2) comprises controllingthe gas circulation device (10) for withdrawing the gas (4) from the underground cavity gas storage (2) and injecting the withdrawn gas (4) to the underground cavity gas storage (2) after the withdrawn gas (4) has passed the at least one heat exchanger (12).

13. A computer program comprising instructions, which when the program is executed by a data processing unit (201) of a control device (200) of an underground cavity storage system (1), cause the control device (200) to carry out the method according to any one of the claims 4 - 12.

14. A computer-readable medium (202) having stored thereon the computer program of the claim 13.

Images