Abstract: An arrangement for storing thermal energy, including a shaft (1) and at least one tunnel (2), the shaft (1) and the tunnel (2) being in fluid communication with each other. The tunnel (2) includes at least a first (2a), a second (2b), and a third (2c) tunnel section. The second tunnel section (2b) is arranged between and connected to the first (2a) and third (2c) tunnel sections. The second tunnel section (2b) is sealed off at an end (4) connected to the third tunnel section (2c), and the third tunnel section is further connected the shaft (1). The shaft (1) and first (2a) and third (2c) tunnel sections hold fluid for thermal storage. The second tunnel section (2b) is an expansion space should a volume of the fluid expand beyond a volume of the shaft (1) and the first (2a) and third (2c) tunnel sections.

Abstract: An arrangement for storing thermal energy has at least two tunnels (1a, 1b) for holding a fluid. The tunnels (1a, 1b) are connected to each other by at least one channel (2), such that fluid communication is allowed between the tunnels (1a, 1b). Each of the inner tunnel (1a) and the outer tunnel (1b) is configured as a helix, the inner tunnel (1a) forming an inner helix and the outer tunnel (1b) forming an outer helix.

Abstract: An arrangement for storing thermal energy, having at least one subterranean chamber for holding a first fluid is provided. A passage holding a second fluid is extended outside at least a part of the chamber. At least one channel is arranged to allow fluid communication of the first fluid between different sections of the chamber, and/or allow fluid communication of the second fluid between different sections of the passage.

Abstract: A method for operating an arrangement (1) for storing thermal energy where the arrangement (1) includes an energy storage (2) having a temperature gradient. The method involves retrieving energy at a first temperature (T1) from the energy storage (2) for use in a first heat-absorbing system (3), such that free space is created in the energy storage (2) for energy at a second temperature (T2). The second temperature (T2) is higher than the first temperature (T1).

Abstract: The present invention relates to a thermal energy storage system comprising an energy storage (2) having a vertical temperature gradient and an internal combined heating and cooling machine (15). The internal combined heating and cooling machine (15) is adapted for retrieving energy having a first temperature from the energy storage, while simultaneously returning heated energy having a second higher temperature and cooled energy having a third lower temperature. The invention also relates to a method for using the thermal energy storage system.

Abstract: The present invention relates to an arrangement for storing thermal energy, comprising a shaft (1) and at least one tunnel (2), the shaft (1) and the at least one tunnel (2) being in fluid communication with each other. The tunnel (2) comprises at least a first (2a), a second (2b), and a third (2c) tunnel section. The second tunnel section (2b) is arranged between and connected to the first (2a) and third (2c) tunnel sections. The second tunnel section (2b) is sealed off at an end (4) connected to the third tunnel section (2c), and the third tunnel section is further connected the shaft (1). The shaft (1) and first (2a) and third (2c) tunnel sections are adapted for holding fluid for thermal storage. The second tunnel section (2b) is adapted for use as an expansion space should a volume of the fluid expand beyond a volume of the shaft (1) and the first (2a) and third (2c) tunnel sections.

Abstract: The present invention relates to a thermal energy storage system comprising an energy storage (2) having a vertical temperature gradient and an internal combined heating and cooling machine (15). The internal combined heating and cooling machine (15) is adapted for retrieving energy having a first temperature from the energy storage, while simultaneously returning heated energy having a second higher temperature and cooled energy having a third lower temperature. The invention also relates to a method for using the thermal energy storage system.

Abstract: The invention relates to a method for operating an arrangement (1) for storing thermal energy. The arrangement (1) comprises an energy storage (2) having a temperature gradient. The method comprises retrieving energy of a first temperature (T1) from the energy storage (2) for use in a first heat-absorbing system (3), such that free space is created in the energy storage (2) for energy of a second temperature (T2). The second temperature (T2) is higher than the first temperature (T1).

Abstract: The present invention relates to an arrangement for storing thermal energy, comprising at least two tunnels (1a, 1b) for holding a fluid. The tunnels (1a, 1b) are connected to each other by at least one channel (2), such that fluid communication is allowed between the tunnels (1a, 1b). Each tunnel (1a, 1b) extends at least partially along a respective circular arc.

Abstract: An arrangement for storing thermal energy, having at least one subterranean chamber for holding a first fluid, wherein a passage holding a second fluid is extended outside at least a part of the at last one chamber. The at least one channel is arranged to allow fluid communication of the first fluid between different sections of the chamber, and/or in that at least one channel is arranged to allow fluid communication of the second fluid between different sections of the passage. A method is also disclosed for improving an arrangement for storing thermal energy having the steps of providing at least one channel within the arrangement.