An underground cavity storage system and a method for controlling the injection 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 temperature sensor (14, 16) is configured to detect at least one temperature (Tg, Tw) at the underground cavity gas storage (2); At least one compressor (18) is configured to generate a gas flow (f) of the gas (4) to be injected in the underground cavity gas storage (2) based on the at least one detected temperature (Tg, Tw) at the underground cavity gas storage (2); and at least one heat exchanger (12) is configured to reduce or increase the temperature (Tg) of the gas (4) based on the at least one detected temperature (Tg, Tw) at the underground cavity gas storage (2). The disclosure further relates to a method comprising the steps of controlling (s102) the at least one compressor (18) for generating a gas flow (f) of the gas (4) to be injected in the underground cavity gas storage (2) 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 there on the computer program.

Description

[0001] An underground cavity storage system and a method for controlling the injection 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 solutions of the prior art is that underground cavity storage system lacks operational temperature management.

[0009] A further 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.

[0010] A further problem with the solutions of the prior art is that the temperature in the ambient mass is expected to increase after several storage cycles, which make the recirculation system less needed to prevent low temperatures.

[0011] There is thus a need for an improved underground cavity storage system and a method, which comprises operational temperature management. There is a further need for an improved underground cavity storage system and a method, which reduce costs

[0012] There is further a need for an improved underground cavity storage system and a method in which the temperature of the gas to be injected into the underground cavity gas storage is controlled.

[0013] There is further a need for an improved underground cavity storage system and a method in which the temperature of an ambient mass surrounding the underground cavity gas storage is controlled.

[0014] 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.

[0015] It 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.

[0016] A further objective is to provide a system and an operational method for an underground cavity storage system that relies on preheating surrounding mass to prevent freezing temperatures, which can lead to wall damage in an underground cavity storage.

[0017] This is solved by an underground cavity storage system, a method, a computer program and a computer-readable medium having stored there on the computer program according to the appended claims.

[0018] According to a first aspect there is provided an underground cavity storage system comprising of a control device connected to the system; an underground cavity gas storage for storing the gas in an interior volume thereof, at least one compressor, which is fluidly connected downstream of a gas source and which compressor is configured to generate pressurized gas; at least one heat exchanger arranged downstream of the at least one compressor, which at least one heat exchanger is configured to reduce or increase the temperature of the gas injected in the underground cavity gas storage; 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 compressor is configured to generate a gas flow of the gas to be injected in the underground cavity gas storage based on the at least one detected temperature at the underground cavity gas storage; and that the at least one heat exchanger is configured to reduce or increase the temperature based on the at least one detected temperature at the underground cavity gas storage.

[0019] 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.

[0020] 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 a shaped cavity in a rock mass, rock salt mass or stiff soil. The underground cavity gas storage may be provided with a liner. The gas may be stored in the underground cavity gas storage as 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. A gas circulation device may be arranged for generating a mixing gas flow of the gas in the underground cavity storage system. The gas circulation device may be arranged for generating a mixing gas flow of the gas in the underground cavity storage system based on the detected temperature downstream of the at least one compressor. The gas circulation device may be controlled for increasing the mixing gas flow f of the gas. The gas circulation device may be controlled for increasing the mixing gas flow of the gas if the detected temperature downstream of the at least one compressor 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 compressor and upstream of the at least one heat exchanger. The gas circulation device may be a fan, pump and / or a compressor.

[0021] 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 may be a surrounding rock mass, 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.

[0022] According to a second aspect there is provided a method, performed by a control device, for controlling the injection 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 compressor, which is fluidly connected downstream of a gas source and which compressor is configured to generate pressurized gas; at least one heat exchanger arranged downstream of the at least one compressor, which at least one heat exchanger is configured to reduce or increase the temperature of the gas injected in the underground cavity gas storage; 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 compressor for generating a gas flow of the gas to be injected in the underground cavity gas storage based on the at least one detected temperature at the underground cavity gas storage; and controlling the at least one heat exchanger based on the at least one detected temperature at the underground cavity gas storage.

[0023] 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. The underground cavity gas storage may be a shaped cavity in a rock mass, rock salt mass or stiff soil. 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.

[0024] The injection and withdrawing flows may, in addition to internal factors such as pressure and temperature of the gas, be determined by external factors such as gas market conditions and connected process requirements.

[0025] 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 compressor for generating a gas flow of the gas to be injected in the underground cavity gas storage based on the at least one detected temperature at the underground cavity gas storage may be performed for injection of the gas into the underground cavity gas storage. Compressing the gas by the compressor increases the temperature of the gas. Injecting warm gas into the underground cavity gas storage may increase the temperature in the underground cavity gas storage. The heat in the underground cavity gas storage may be transferred into the ambient mass surrounding the underground cavity gas storage. The step of controlling the at least one heat exchanger based on the at least one detected temperature at the underground cavity gas storage. In order to avoid overheating the underground cavity gas storage during injection of gas, the compressed and heated gas may be cooled in the heat exchanger.

[0026] The step of detecting the 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.

[0027] The step of detecting the 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 surrounding the underground cavity gas storage. The ambient mass may be a rock salt mass, stiff soil or concrete.

[0028] The step of detecting the 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 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.

[0029] The step of controlling the compressor for generating a gas flow of the gas to be injected in the underground cavity gas storage based on the at least one detected temperature at the underground cavity gas storage comprises controlling the at least one compressor for increasing the gas flow of the gas if the at least one detected temperature at the underground cavity gas storage decreases below a threshold temperature. Increasing the gas flow by the compressor may increase the temperature of the gas to be injected into the underground cavity gas storage. Further, the injection may be determined by external factors such as gas market conditions and connected process requirements. The step of controlling the compressor for generating a gas flow of the gas to be injected in the underground cavity gas storage based on the at least one detected temperature at the underground cavity gas storage comprises controlling the compressor for increasing the pressure of the gas to be injected in the underground cavity gas storage based on the at least one detected temperature at the underground cavity gas storage. The compressor may increase the temperature of the gas by compressing the gas. Heat is developed when the gas is compressed. Further, the injection may, be determined by external factors such as gas market conditions and connected process requirements.

[0030] The step of controlling the at least one heat exchanger based on the at least one detected temperature at the underground cavity gas storage comprises controlling the at least one heat exchanger for increasing the temperature of the gas downstream of the at least one heat exchanger if the at least one detected temperature at 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 wall of the cavity may be damaged if the temperature drops below 0° C due to freezing of water. Further, if the ambient mass surrounding the underground cavity gas storage is a rock mass, rock salt mass, stiff soil or concrete, cracks 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 adjusted to a suitable temperature. The increased temperature of the injected gas may heat the underground cavity gas storage. Further, the temperature of the ambient mass and the flow rate of the gas flow in to 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.

[0031] The step of controlling the at least one heat exchanger based on the at least one detected temperature at the underground cavity gas storage comprises controlling the at least one heat exchanger for decreasing the temperature of the gas downstream of the at least one heat exchanger if the at least one detected temperature of the underground cavity gas storage increases above a threshold temperature. The temperature in the underground cavity gas storage may increase during injection of compressed gas into the underground cavity gas storage. Gas injected at higher temperatures 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.

[0032] The method comprises the further step of: controlling a gas circulation device for generating a mixing gas flow of the gas in the underground cavity storage system based on the detected temperature downstream of the at least one compressor. The gas circulation device may be a fan, pump or a compressor. The compressed gas may reach high temperatures. The temperature of the compressed gas can be decreased by mixing the compressed gas with gas stored in the underground cavity storage. The gas in the underground cavity gas storage may have a lower temperature than the compressed gas from the compressor. The size of the gas circulation device together with piping can be reduced, or even disregarded, which can compensate in costs for the decreased storage capacity resulting from higher operational temperatures.

[0033] The step of controlling the gas circulation device for generating a mixing gas flow of the gas in the underground cavity system based on the detected temperature downstream of the at least one compressor comprises controlling the gas circulation device for increasing the mixing gas flow of the gas if the detected temperature downstream of the at least one compressor increases above a threshold temperature. If the temperature of the compressed gas downstream of the compressor is above threshold temperature, the gas circulation device may be activated for mixing the gas from the underground cavity gas storage with the compressed gas downstream of the compressor. The result is that the temperature of the gas to be injected into the underground cavity gas storage decreases to an acceptable temperature, which may not damage the underground cavity storage.

[0034] The step of controlling the gas circulation device for generating a mixing gas flow of the gas in the underground cavity system based on the detected temperature downstream of the at least one compressor comprises controlling the gas circulation device 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 compressor and upstream of the at least one heat exchanger. The temperature of the gas at the top of the underground cavity gas storage may be lower than the temperature of the gas at the bottom of the underground cavity gas storage. Gas injected to the underground cavity gas storage may be injected at the bottom of the underground cavity gas storage. 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.

[0035] Brief of the

[0036] 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.

[0037] Fig. 1 schematically illustrates in a section view, an underground cavity storage system according to an example,

[0038] Fig. 2 schematically illustrates in a section view, an underground cavity storage system provided with a gas circulation device according to an example,

[0039] Figures 3a and 3b 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,

[0040] Fig. 4 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,

[0041] Fig. 5 shows a flowchart of a method according to an example, and

[0042] Fig. 6 schematically illustrates a control device according to an example.

[0043] Detailed description

[0044] 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.

[0045] 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 gas 4 in an interior volume V thereof. At least one compressor 18 is fluidly connected downstream of a gas source 20. The compressor 18 is configured to generate pressurized gas. At least one heat exchanger 12 is arranged downstream of the at least one compressor 18. The at least one heat exchanger 12 is configured to reduce or increase the temperature Tg of the gas 4 injected in the underground cavity gas storage 2. At least one temperature sensor 14, 16 is arranged at the underground cavity gas storage 2. The at least one temperature sensor 14, 16 is configured to detect at least one temperature Tg, Tw at the underground cavity gas storage 2. The compressor 18 is configured to generate a gas flow f of the gas 4 to be injected in the underground cavity gas storage 2 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 based on the at least one detected temperature Tg, Tw at the underground cavity gas storage 2. The temperature can be detected by a temperature detector 26 downstream of the compressor 18. The heat exchanger 12 may be configured to reduce or increase the temperature Tg of the gas 4 based on the temperature can be detected by a temperature detector 26 downstream of the compressor 18. The heat exchanger 12 can be connected to a district heating system 21

[0046] 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, The at least one distance dl, d2, , dn is within the range of 0 m - 100 m. The ambient mass 6 surrounding the underground cavity gas storage 2 may be a rock mass, a rock salt mass, stiff soil or concrete surrounding the underground cavity gas storage 2.

[0047] Fig. 2 schematically illustrates in a section view, an underground cavity storage system according to an example. The underground cavity storage system 1 comprises the features of fig. 1 and also the following features. A gas circulation device 10 is arranged for generating a mixing gas flow of the gas 4 in the underground cavity storage system 1 based on the detected temperature downstream of the at least one compressor 18. The gas circulation device 10 withdraws the gas 4 from a position at a top of the underground cavity gas storage 2 and injecting the withdrawn gas 4 to a position downstream of the at least one compressor 18 and upstream of the at least one heat exchanger 12. The temperature can be detected by a temperature detector 26 downstream of the compressor 18. The gas circulation device 10 may be controlled for increasing the mixing gas flow f of the gas 4 if the detected temperature downstream of the at least one compressor 18 increases above a threshold temperature Ttt. The circulated gas 4 withdrawn from the underground cavity gas storage 2 is mixed with the injected gas 4 at a position downstream of the temperature detector 26. An additional temperature detector 28 is arranged downstream of the position where the circulated gas 4 withdrawn from the underground cavity gas storage 2 is mixed with the injected gas 4.

[0048] Figures 3a and 3b schematically illustrate in section views, how heat energy and temperature in the underground cavity gas storage 2 and in the ambient mass 6 interact 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. 3a 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. 3a. Injected gas 4 may be circulated within the underground cavity storage 2, which is illustrated with arrows 4' in fig. 3a. In fig. 3b the gas 4” is withdrawn from the volume V of 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. 3b.

[0049] Fig. 4 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 cavity heat is transferred from the gas 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 surrounding ambient mass 6 is transferred from the surrounding ambient mass 6 to the gas 4 in the underground cavity gas storage 2 during withdrawal of the gas 4, which results in a temperature increase of the gas 4 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.

[0050] Fig. 5 shows a flowchart of a method according to an example. The method is performed by a control device 200, for controlling the mixing of gas 4 from an underground cavity gas storage 2 of an underground cavity storage system 1 with compressed gas from a gas source 20. The method relates to the underground cavity storage system 1 shown in figures 1 and 2. The underground cavity storage system 1 thus comprising a control device 200 connected to the system 1. An underground cavity gas storage 2 is arranged for storing gas 4 in an interior volume V thereof. At least one compressor 18 is fluidly connected downstream of the gas source 20. The compressor 18 is configured to generate pressurized gas. At least one heat exchanger 12 is arranged downstream of the at least one compressor 18. The at least one heat exchanger 12 is configured to reduce or increase the temperature Tg of the gas 4 injected in the underground cavity gas storage 2. At least one temperature sensor 14, 16 is arranged at the underground cavity gas storage 2. The at least one temperature sensor 14, 16 is configured to detect at least one temperature Tg, Tw at the underground cavity gas storage 2. The compressor 18 is configured to generate a gas flow f of the gas 4 to be injected in the underground cavity gas storage 2 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 based on the at least one detected temperature Tg, Tw at the underground cavity gas storage 2.

[0051] 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 compressor 18 for generating a gas flow f of the gas 4 to be injected in the underground cavity gas storage 2 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. The step of detecting slOl the temperature 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 temperature 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 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 compressor 18 for generating a gas flow f of the gas 4 to be injected in the underground cavity gas storage 2 based on the at least one detected temperature Tg,Tw at the underground cavity gas storage 2 comprises controlling the at least one compressor 18 for increasing the gas flow f of the gas 4 if the at least one detected temperature Tg,Tw at the underground cavity gas storage 2 decreases below a threshold temperature Ttt. The step of controlling sl02 the compressor 18 for generating a gas flow f of the gas 4 to be injected in the underground cavity gas storage 2 based on the at least one detected temperature Tg,Tw at the underground cavity gas storage 2 comprises controlling the compressor 18 for increasing the pressure of the gas 4 to be injected in the underground cavity gas storage 2 based on the at least one detected temperature Tg,Tw at the underground cavity gas storage 2. 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 at least one detected temperature Tg,Tw at the underground cavity gas storage 2 decreases below a threshold temperature Ttt. 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 at least one detected temperature Tg,Tw of the underground cavity gas storage 2 increases above a threshold temperature Ttt. The method comprises the further step of: controlling sl04 a gas circulation device 10 for generating a mixing gas flow of the gas 4 in the underground cavity storage system 1 based on the detected temperature downstream of the at least one compressor 18. The step of controlling sl04 the gas circulation device 10 for generating a mixing gas flow f of the gas 4 in the underground cavity system 1 based on the detected temperature downstream of the at least one compressor 18 comprises controlling the gas circulation device 10 for increasing the mixing gas flow f of the gas 4 if the detected temperature downstream of the at least one compressor 18 increases above a threshold temperature Ttt. The step of controlling sl04 the gas circulation device 10 for generating a mixing gas flow f of the gas 4 in the underground cavity system 1 based on the detected temperature downstream of the at least one compressor 18 comprises controlling the gas circulation device 10 for withdrawing the gas 4 from a position at a top of the underground cavity gas storage 2 and injecting the withdrawn gas 4 to a position downstream of the at least one compressor 18 and upstream of the at least one heat exchanger 12. Fig. 6 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. 5 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 compressor (18), which is fluidly connected downstream of a gas source (20) and which compressor (18) is configured to generate pressurized gas; at least one heat exchanger (12) arranged downstream of the at least one compressor (18), which at least one heat exchanger (12) is configured to reduce or increase the temperature (Tg) of the gas (4) injected in the underground cavity gas storage (2); and at least one temperature sensor (14, 16) arranged at the underground cavity gas storage (2), characterized in that the at least one temperature sensor (14, 16) is configured to detect at least one temperature (Tg, Tw) at the underground cavity gas storage (2); that the at least one compressor (18) is configured to generate a gas flow (f) of the gas (4) to be injected in the underground cavity gas storage (2) 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) 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 (14,16) 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. A method, performed by a control device (200), for controlling the injection 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 compressor (18), which is fluidly connected downstream of a gas source (20) and which compressor (18) is configured to generate pressurized gas; at least one heat exchanger (12) arranged downstream of the at least one compressor (18), which at least one heat exchanger (12) is configured to reduce or increase the temperature (Tg) of the gas (4) injected in the underground cavity gas storage (2); and at least one temperature sensor (14, 16) 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 compressor (18) for generating a gas flow (f) of the gas (4) to be injected in the underground cavity gas storage (2) 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).

4. The method according to claim 3, wherein the step of detecting (slOl) the temperature at the underground cavity gas storage (2) comprises detecting the temperature (Tw) of a wall (8) of the underground cavity gas storage (2).

5. The method according to any one of the claims 3 and 4, wherein the step of detecting (slOl) the temperature at the underground cavity gas storage (2) comprises detecting the temperature (Tw) of an ambient mass (6) surrounding the underground cavity gas storage (2).

6. The method according to claim 5, wherein the step of detecting (slOl) the 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.

7. The method according to any one of the claims 3 - 6, wherein the step of controlling (sl02) the at least one compressor (18) for generating a gas flow (f) of the gas (4) to be injected in the underground cavity gas storage (2) based on the at least one detected temperature (Tg,Tw) at the underground cavity gas storage (2) comprises controlling the at least one compressor (18) for increasing the gas flow (f) of the gas (4) if the at least onedetected temperature (Tg,Tw) at the underground cavity gas storage (2) decreases below a threshold temperature (Ttt).

8. The method according to any one of the claims 3 - 7, wherein the step of controlling (sl02) the at least one compressor (18) for generating a gas flow (f) of the gas (4) to be injected in the underground cavity gas storage (2) based on the at least one detected temperature (Tg,Tw) at the underground cavity gas storage (2) comprises controlling the at least one compressor (18) for increasing the pressure of the gas (4) to be injected in the underground cavity gas storage (2) based on the at least one detected temperature (Tg,Tw) at the underground cavity gas storage (2).

9. The method according to any one of the claims 3 - 8, 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 at least one detected temperature (Tg,Tw) at the underground cavity gas storage (2) decreases below a threshold temperature (Ttt).

10. The method according to any one of the claims 3 - 8, 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 at least one detected temperature (Tg,Tw) of the underground cavity gas storage (2) increases above a threshold temperature (Ttt).

11. The method, according to any one of the claims 3 - 10, comprising the further step of: controlling (sl04) a gas circulation device (10) for generating a mixing gas flow of the gas (4) in the underground cavity storage system (1) based on the detected temperature downstream of the at least one compressor (18).

12. The method according to claim 11, wherein the step of controlling (sl04) the gas circulation device (10) for generating a mixing gas flow (f) of the gas (4) in the underground cavity system (1) based on the detected temperature downstream of the at least one compressor (18) comprises controlling the gas circulation device (10) for increasing the mixinggas flow (f) of the gas (4) if the detected temperature downstream of the at least one compressor (18) increases above a threshold temperature (Ttt).

13. The method according to any one of the claims 11 and 12, wherein the step of controlling (sl04) the gas circulation device (10) for generating a mixing gas flow (f) of the gas (4) in the underground cavity system (1) based on the detected temperature downstream of the at least one compressor (18) comprises controlling the gas circulation device (10) for withdrawing the gas (4) from a position at a top of the underground cavity gas storage (2) and injecting the withdrawn gas (4) to a position downstream of the at least one compressor (18) and upstream of the at least one heat exchanger (12).

14. 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 3 - 13.

15. A computer-readable medium (202) having stored there on the computer program of the claim 14.

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