Device for generating energy from compressed air, system comprising such a device and method for operating the system

Abstract

Device for generating energy from compressed air, comprising an air turbine (16) which is designed to expand gaseous air from a first pressure level to a second pressure level and in the process to obtain first energy, comprising a combustion chamber (17) which is designed to receive the air expanded in the air turbine and to burn fuel therein, and comprising an exhaust gas turbine (18) which is designed to expand exhaust gas produced during the combustion of the fuel in the combustion chamber (17) and in the process to obtain second energy, wherein at least the air turbine and the exhaust gas turbine have a common housing.

Description

The invention relates to an apparatus for generating energy from compressed air, to a system comprising such an apparatus and to a method for operating the system.Liquid air energy storage (LAES) devices and compressed air energy storage (CAES) devices are known in practice in order to store energy and subsequently use the energy. Thus, in a liquid air energy storage device, liquid air is stored in a memory, which can be evaporated in an evaporator. The vaporized air is then passed over an air turbine to be expanded in the air turbine to generate mechanical energy, which may then be used, for example, to drive a generator or other machine to generate electrical energy. In a compressed air energy storage device, compressed gaseous air is stored, which can likewise be guided via an air turbine in order in turn to obtain mechanical energy in the air turbine, which can be used, for example, to drive a generator and thus to obtain electrical energy. Liquid air energy storage (LAES) devices known from practice and compressed air energy storage (CAES) devices have a limited efficiency. There is a need for a compressed air energy generation apparatus that has higher efficiency.Proceeding from this, the object of the invention is to create a novel device for generating energy from compressed air, a system with such a device and a method for operating the system.This object is achieved by a compressed air energy generating apparatus according to claim 1, a system according to claim 10 or according to claim 11 and a method according to claim 13.The device for generating energy from compressed air has an air turbine which is designed to expand gaseous air from a first pressure level to a second pressure level and in the process to obtain first energy.The apparatus for generating energy from compressed air further comprises a combustion chamber configured to receive the air expanded in the air turbine and combust it in the same fuel.The device for generating energy from compressed air further comprises an exhaust gas turbine which is configured to expand exhaust gas formed during the combustion of the fuel in the combustion chamber and thereby to obtain second energy.At least the air turbine and the exhaust gas turbine have a common housing.With the aid of the device according to the invention for generating energy from compressed air, energy can be obtained with high efficiency from compressed air, which is provided, for example, by a liquid air energy storage (LAES) device or a compressed air energy storage (CAES) device. In this case, the compressed air is firstly expanded in the air turbine to a first pressure level and subsequently fed to the combustion chamber, in which, in the presence of the air expanded to the first pressure level, a fuel is burned and exhaust gas is thus generated, which is fed via an exhaust gas turbine in order thus to generate further energy. Energy is therefore generated both in the air turbine and in the exhaust gas turbine, namely mechanical energy which can be used, for example, to drive a generator for generating electrical energy.Compared to a simple air turbine, more than twice the useful power can be generated with the device according to the invention. Energy can thus be obtained at high efficiency from compressed air.Preferably, the air turbine, the combustion chamber and the exhaust gas turbine have the common housing. Alternatively, the air turbine and the exhaust turbine have the common casing and the combustor have a separate casing. If the air turbine, the combustion chamber and the exhaust gas turbine have a common housing, the device can be designed to be particularly compact with a smaller installation space requirement and a low weight. As a result, the arrangement of air turbine, combustion chamber and exhaust gas turbine can then be positioned particularly flexibly in a liquid air energy storage (LAES) device or a compressed air energy storage (CAES) device. If the combustion chamber is arranged in a separate housing, the installation space requirement and the weight of the device are increased, but thermal stresses on the common housing of the air turbine and of the exhaust gas turbine can be reduced.The device for generating energy from compressed air preferably has a first heat exchanger connected between the air turbine and the combustion chamber, via which heat exchanger, on the one hand, the air expanded in the air turbine and to be supplied to the combustion chamber and, on the other hand, the exhaust gas expanded in the exhaust gas turbine can be conducted in order to heat the air expanded in the air turbine upstream of the combustion chamber. The temperature of the air expanded in the first air turbine is increased by the first heat exchanger, as a result of which the required fuel quantity in the combustion chamber can be reduced. Thus, the efficiency of the device according to the invention can be further increased.The device for generating energy from compressed air preferably has a second heat exchanger, which is connected upstream of the air turbine and via which, on the one hand, the air to be expanded in the air turbine and, on the other hand, the exhaust gas expanded in the exhaust gas turbine can be conducted in order to heat the upstream of the air turbine to be expanded in the air turbine. The efficiency of the device for generating energy from compressed air can also be further increased by means of the second heat exchanger upstream of the air turbine. Thus, by increasing the temperature of the air to be expanded in the air turbine, more energy can be obtained in the air turbine.Preferably, the air turbine and the exhaust turbine are oriented in a back-to-back arrangement such that the inlet sides of the two turbines are directed away from each other and the outlet sides of the two turbines face each other. The back-to-back arrangement of the two turbines allows an advantageous thermal compensation of the common housing of at least air turbine and exhaust gas turbine to form a shaft which is driven by the air turbine and exhaust gas turbine. Alternatively, the air turbine and exhaust turbine are aligned in an inline arrangement such that an exit side of one of the two turbines faces an entry side of another of the two turbines.A system according to the invention has the device according to the invention for generating energy from compressed air and preferably a liquid air energy storage (LAES) device which has a storage for storing liquid air and an evaporator for evaporating the liquid air, wherein the evaporated air can be supplied to the air turbine as gaseous, compressed air. The device according to the invention for generating energy from compressed air is particularly preferably used in combination with a liquid air energy storage (LAES) device in order to generate energy from liquid air.As an alternative to a liquid air energy storage (LAES) device, the system according to the invention can also have a compressed air energy storage (CAES) device.Preferred developments of the invention are evident from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail with reference to the drawings, without being restricted thereto. The following shows: FIG. 1 shows a first system with a first device according to the invention for generating energy from compressed air, FIG. 2 shows a second system with a second device according to the invention for generating energy from compressed air, FIG. 3 shows a third system with a third device according to the invention for generating energy from compressed air.The invention relates to an apparatus 10 for generating energy from compressed air. FIG. 1 shows the device 10 according to the invention in connection with a liquid air energy storage (LAES) device 11 and an electric machine 12.The LAES device 11 has a storage 13 for storing liquid air. Furthermore, in the exemplary embodiment shown, the LAES device 11 has a pump 14, which is configured to provide the liquid air to an evaporator 15 of the LAES device 11. In the evaporator 15, the liquid air can be evaporated in order to provide compressed gaseous air, from which energy can then be obtained with the aid of the device 10, which is used in FIG. 1, for example, to drive the electric machine 12.The pump 14 is optional in a LAES device 11. The liquid air can also be taken from the storage 13 in another way and fed to the evaporator 15. If a pump 14 is present, it can be designed as a cryopump.The device 10 according to the invention for generating energy from compressed air has an air turbine 16. The air turbine 16 is configured to expand the compressed air from a first pressure level to a second pressure level and thereby to obtain first energy.Furthermore, the device according to the invention for generating energy from compressed air has a combustion chamber 17. The combustion chamber 17 is configured to receive the air expanded in the air turbine 16 and combust a fuel therein in the presence of the air, thereby generating exhaust gas. The fuel to be burned is ignited in the combustion chamber 17.The device 10 according to the invention for generating energy from compressed air furthermore has an exhaust gas turbine 18. The exhaust gas turbine 18 is configured to expand the exhaust gas produced during the combustion of the fuel in the combustion chamber 17 and thereby to obtain second energy.Preferably, the air turbine 16 and the exhaust turbine 18 drive a common shaft 22 and, via the common shaft 22, drive the electric machine 12 together. In this case, the electric machine 12 is preferably operated in a generator mode in order to provide electrical energy in this way.According to FIG. 1, liquid air L 1 is therefore taken from the reservoir 13 by means of the pump 14, which is provided as liquid air L 2 from the pump 14 to the evaporator 15. Downstream of the evaporator 15 there is gaseous compressed air L3 flowing over the air turbine 16, the air turbine 16 leaving gaseous air L4 expanded to the second pressure level. The air L4 at the second pressure level is supplied to the combustion chamber 17, namely together with fuel K, wherein during the combustion of the fuel K, exhaust gas is formed, which leaves the combustion chamber 17 as exhaust gas A1 and is expanded in the exhaust gas turbine 18. Expanded exhaust gas A 2 is discharged from the exhaust gas turbine 18.In FIG. 1, the device 10 comprises a first heat exchanger 19 which is connected between the air turbine 16 and the combustion chamber 17. Via this first heat exchanger 19, on the one hand, the air L 4 expanded in the air turbine 16 and, on the other hand, the exhaust gas A 2 expanded in the exhaust gas turbine 18 are guided in order to transfer thermal energy of the exhaust gas A 2 to the expanded air L 4 and thus to increase the temperature of the expanded air upstream of the combustion chamber 17. As a result, the efficiency of the device 10 according to the invention for generating energy from compressed air can be increased.FIG. 2 shows a block diagram of a second device 10 according to the invention for generating electrical energy from compressed air again together with the LAES device 11, wherein the same reference numerals are used for the same assemblies as in FIG. 1 to avoid unnecessary repetitions in FIG. 2 and reference is made to the relevant explanations relating to FIG. 1. Only those details will be discussed below in which the exemplary embodiment of FIG. 2 differs from the exemplary embodiment of FIG. 1.In FIG. 1, the air turbine 16, the exhaust gas turbine 18, the combustion chamber 17 and the first heat exchanger 19 have a common housing 20. This allows a particularly compact, space-saving and weight-reduced design to be ensured. In FIG. 2, however, only the air turbine 16, the exhaust gas turbine 18 and the combustion chamber 17 have the common housing 20, the first heat exchanger 19 is not integrated into the common housing 20, but rather is designed as a separate assembly with a separate housing.A further difference of FIG. 2 from FIG. 1 is that the exhaust gas A 2 which has been expanded in the exhaust gas turbine 18 and is guided via the first heat exchanger 19 is subsequently guided as exhaust gas A 3 via a second heat exchanger 21 which is arranged upstream of the air turbine 16 as seen in the flow direction of the air to be expanded in the air turbine 16. Via this second heat exchanger 21, on the one hand, the compressed, gaseous air L 3 and, on the other hand, the exhaust gas A 3 are guided in order to heat the air L 3 to be expanded in the air turbine 16 upstream of the air turbine 16. The efficiency can also be further increased as a result.A further device 10 according to the invention for generating energy from compressed air is shown in FIG. 3, wherein the LAES device 11 is again shown in FIG. 3 and the same reference numerals are used for the same assemblies to avoid unnecessary repetitions as in FIG. 1 and only those details will be discussed below by which the exemplary embodiment of FIG. 3 differs from the exemplary embodiment of FIG. 1.In the exemplary embodiment of FIG. 3, only the air turbine 16 and the exhaust gas turbine 18 have a common housing 20. In FIG. 3, both the first heat exchanger 19 and the combustion chamber 17 are not integrated into the common housing 20, but rather are designed as a separate assembly with a separate housing. As a result, the common housing 20 of the air turbine 16 and the exhaust gas turbine 18 is exposed to a lower thermal load than in FIG. 1 and also than in FIG. 2, so that thermal deformations can be reduced. This is advantageous for the shaft 22 driven by the two turbines 16, 18, via which the electric machine 12 is driven.In the present invention, compressed, gaseous air L 3, which is provided by the LAES device 11 in the exemplary embodiment shown, is accordingly expanded to a pressure level of a combustion chamber pressure of the combustion chamber 17.In contrast to the exemplary embodiments shown, the compressed, gaseous air can also be provided by a compressed air energy storage (CAES) device.In a CAES device, the evaporator 15 is omitted. Instead of the pump 14, a compressor may be present in a CAES device.The air supplied to the combustion chamber 17 is used to combust fuel K in the combustion chamber 17, wherein the exhaust gas A 1 is thereby produced in the combustion chamber 17, which exhaust gas is conducted via the exhaust gas turbine 18 for expansion. Both in the air turbine 16 and in the exhaust gas turbine 18, mechanical energy is accordingly obtained in each case, which is used to drive an electric machine 12, preferably in a generator mode, via a preferably common shaft 22, in order to generate electrical energy in this way.Thermal energy is accordingly supplied to the air expanded in the air turbine 16 by the combustion of the fuel K, wherein the exhaust gas A 1 is expanded to ambient pressure in the exhaust gas turbine 18. Residual heat of the exhaust gas A 2 can be used in at least one heat exchanger 19, 21 in order to heat the air L 4 expanded in the air turbine 16 and / or the air L 3 to be expanded in the air turbine 16.With the invention, significantly more power can be output than can a pure air turbine in conjunction with a LAES device or CAES device. Thus, approximately more than twice the power can be delivered.The heat of the exhaust gas can be used in the exemplary embodiments of FIGS. 1 to 3 for preheating the fuel K.Alternatively or additionally, it is also possible to guide the exhaust gas which leaves the exhaust gas turbine 18 via the evaporator 15 in a LAES device 11 in order to thus use heat of the exhaust gas in the region of the evaporator 15.Then, when a LAES device 11 is present, the liquid air may be used to cool assemblies such as the combustion chamber 17 to allow for a higher combustion temperature or operating temperature. Alternatively or additionally, liquid air may be utilized to regulate air or exhaust temperatures or mass flows and / or to optimize combustion of the fuel and / or reduce emissions.Preferably, the air turbine 16 and the exhaust turbine 18 are oriented in a back-to-back arrangement such that the inlet sides of the two turbines 16, 18 are directed away from one another and the outlet sides of the two turbines 16, 18 face one another. This back-to-back arrangement of the two turbines 16, 18 is not shown in FIGS. 1 to 3, and it allows an advantageous thermal compensation of the common housing of at least air turbine 16 and exhaust gas turbine 18 to form a shaft 22, which is driven by the air turbine 16 and exhaust gas turbine 20.The invention enables energy to be obtained with high efficiency from compressed air.The invention further relates to a method for operating the system comprising the apparatus 10, the CAES device or LAES device 11 and the electric machine 12 which is coupled to an electrical power grid.If the grid frequency of the electrical power grid is less than a setpoint value, the electrical machine 12 is operated in a generator mode for grid stabilization of the electrical power grid 12. In this case, for the purposes of grid stabilization, mechanical energy obtained in a production phase of electrical energy in the apparatus 10 is converted into electrical energy and fed into the power grid. In this case, the CAES device or LAES device 11 is connected to the apparatus 10.Then, if a grid frequency of the electrical power grid is greater than a setpoint value, the electrical machine 12 is operated by motor for grid stabilization of the electrical power grid. In this case, electrical energy is converted into power loss for grid stabilization. In this case, the CAES device or LAES device 11 is preferably separate from the apparatus 10. When the CAES device or LAES device 11 is separated from the apparatus 10, the electric machine 12 is preferably operated at minimum rotational speed in order to change over to a next production phase of electrical energy within the shortest time.The invention accordingly also relates to the use of the system comprising the apparatus 10, the CAES device or LAES device 11 and the electric machine 12 for network stabilization of an electric power network to which the electric machine 12 is connected.List of reference characters10 Device 11 LAES device 12 electric machine 13 storage 14 pump 15 evaporator 16 air turbine 17 combustion chamber 18 exhaust gas turbine 19 first heat exchanger 20 housing 21 second heat exchanger 22 shaft

Claims

Device for generating energy from compressed air, having an air turbine (16) which is designed to expand gaseous air from a first pressure level to a second pressure level and in this case to obtain first energy, having a combustion chamber (17) which is designed to receive the air expanded in the air turbine and to combust it in the same fuel, having an exhaust gas turbine (18) which is designed to expand exhaust gas which is produced during the combustion of the fuel in the combustion chamber (17) and in this case to obtain second energy, at least the air turbine (16) and the exhaust gas turbine (18) having a common housing (20).Device according to Claim 1, characterized in that the air turbine (16), the combustion chamber (17) and the exhaust gas turbine (18) have the common housing (20).Device according to claim 1, characterised in that the air turbine (16) and the exhaust gas turbine (18) have the common housing (20), and in that the combustion chamber (17) has a separate housing.Device according to one of Claims 1 to 3, characterized bya first heat exchanger (19) connected between the air turbine (16) and the combustion chamber (17), via which, on the one hand, the air expanded in the air turbine (16) and to be supplied to the combustion chamber (17) can be conducted and, on the other hand, the exhaust gas expanded in the exhaust gas turbine (18) can be conducted in order to heat the upstream of the combustion chamber (17) expanded in the air turbine (16).Device according to one of Claims 1 to 4, characterized bya second heat exchanger (21) which is connected upstream of the air turbine (16) and via which, on the one hand, the air to be expanded in the air turbine (16) and, on the other hand, the exhaust gas expanded in the exhaust gas turbine (18) can be conducted in order to heat the air to be expanded in the air turbine (16) upstream of the air turbine (16).Device according to Claims 4 and 5, characterized in that the first heat exchanger (19) is designed to receive the exhaust gas expanded in the exhaust gas turbine (18) and then to make it available to the second heat exchanger (21).Device according to claim 4, 5 or 6, characterised in that the first heat exchanger (19) is arranged in the common housing (20).Device according to one of Claims 1 to 7, characterized in that the air turbine (16) and the exhaust gas turbine (18) are oriented in a back-to-back arrangement in such a way that the inlet sides of the two turbines (16, 18) are directed away from one another and the outlet sides of the two turbines (16, 18) face one another.Device according to one of Claims 1 to 8, characterized in that the air turbine (16) and the exhaust gas turbine (18) are oriented in an inline arrangement in such a way that an outlet side of one of the two turbines (16) faces an inlet side of another of the two turbines (18).System comprising an apparatus (10) according to one of Claims 1 to 9 and comprising a liquid air energy storage device (11) which has a store (13) for storing liquid air and an evaporator (15) for evaporating the liquid air, wherein the evaporated air can be fed to the air turbine (16).System comprising an apparatus (10) according to one of Claims 1 to 9 and comprising a compressed air energy storage device which has a store for storing compressed gaseous air, wherein the compressed gaseous air can be fed to the air turbine.System according to Claim 11, characterized byan electric machine (12) which is coupled to the device (10) according to one of Claims 1 to 9 and can be operated by motor and generator.Method for operating a system according to Claim 12, wherein, for the purposes of network stabilization of an electrical power network coupled to the electrical machine (12), the electrical machine (12) is operated by motor when a network frequency of the electrical power network is greater than a setpoint value, or the electrical machine (12) is operated by generator when a network frequency of the electrical power network is less than a setpoint value.

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