Compressed-air storage power plant and corresponding operating method

Abstract

The invention relates to a compressed-air storage power plant, comprising at least one first compressor (1), at least one compressed-air storage unit (2) and at least one first expander (3), which are connected in series in terms of flow, and a device (4) for supplying heat, said device being suitable for heating the compressed air which is removed from the compressed-air storage unit (2). A heat exchanger (5) is arranged downstream of the at least one expander (3) in the direction of flow, said heat exchanger being designed such that it can absorb residual heat from the exhaust air coming from the expander (3) and deliver it to a subsequent process (6). The invention also relates to a method for operating such a compressed-air storage power plant.

Description

[0001] 2024PF00483

[0002] 1

[0003] Description

[0004] Compressed air storage power plant and method for operating a compressed air storage power plant

[0005] The invention relates to a compressed air storage power plant according to the preamble of independent claim 1 and to a method for operating a compressed air storage power plant according to the preamble of independent claim 6.

[0006] Compressed air energy storage (CAES) systems are energy storage systems based on the principle of compressing, storing, and expanding air. These systems essentially consist of three main steps: compressing the air, storing the compressed air in a compressed air reservoir, and subsequently expanding the air in an expander (air turbine) to generate electrical energy.

[0007] Excess electrical energy, typically from renewable energy sources such as wind or solar power, is used to operate the compressor for compressing the air. The compressed air is then transferred to a

[0008] Compressed air storage systems, such as underground caverns or special pressure vessels, store the air. The exhaust air from the last expander is released into the atmosphere.

[0009] A distinction is made between two different types of CAES processes: adiabatic (A-CAES) and diabatic (D-CAES) processes.

[0010] In diabatic CAES (D-CAES), the heat generated during air compression is not stored but released into the environment. During air expansion, external heat energy, often from the combustion of fossil fuels, is supplied to heat the air and increase process efficiency. A portion of this heat energy is not fully utilized and is released into the environment as residual heat. 2024PF00483

[0011] 2

[0012] In adiabatic CAES (A-CAES), the heat generated during air compression is stored and later reused during expansion. This is achieved through special heat storage devices that absorb the thermal energy and release it as needed. Although the efficiency of A-CAES is higher, some of the thermal energy is still not fully utilized and is released into the environment as residual heat.

[0013] The object of the present invention is to provide a compressed air storage power plant that efficiently utilizes the unused residual heat. Furthermore, it is an object of the invention to provide a method for utilizing the residual heat in such a compressed air storage power plant.

[0014] It should be expressly mentioned at this point that, within the scope of this invention, compressed air is understood to mean not only air in the narrow sense, but also all other suitable gaseous media.

[0015] The problem is solved with regard to the compressed air storage power plant by the features of independent claim 1 and with regard to the method by the features of independent claim 6.

[0016] Further embodiments of the invention, which can be used individually or in combination with each other, are the subject of the dependent claims, the following general description and the description of exemplary embodiments.

[0017] The compressed air storage power plant according to the invention, comprising at least one first compressor, at least one compressed air storage tank, and at least one first expander, which are connected in series in terms of fluid dynamics, as well as a device for supplying heat, which is suitable for heating the compressed air taken from the compressed air storage tank, is characterized in that, in the direction of flow, downstream of the at least one expander, a 2024PF00483

[0018] 3

[0019] A heat exchanger is arranged which is designed to absorb residual heat from the exhaust air coming from the expander and transfer it to a subsequent process.

[0020] The compressed air storage power plant according to the invention thus makes it possible for the first time to supply the heat energy contained in the exhaust air to a subsequent process, thereby significantly increasing the overall efficiency of the compressed air storage power plant.

[0021] One embodiment of the invention provides that the subsequent process is a low-temperature process, wherein the temperature of the low-temperature process is < 300 °C, preferably < 250 °C. Low-temperature processes are particularly advantageous as subsequent processes because the temperature is in a similar range to that of the exhaust air. A low-temperature process such as an ORC (Organic Rankine Cycle) or a low-temperature district heating cycle is particularly suitable.

[0022] A further embodiment of the invention provides that a heat storage unit is arranged between the heat exchanger and the subsequent process. The heat storage unit allows the heat to be released to the subsequent process evenly over a longer period, largely independent of the time of storage.

[0023] The inventive method for operating a compressed air storage power plant, in which the compressed air storage power plant is operated in a discharge mode, is characterized by the following process steps:

[0024] - Extraction of compressed air from the compressed air storage tank

[0025] - Heating the compressed air

[0026] - Releasing the compressed air in the expander

[0027] - Feeding the exhaust air from the expander to a heat exchanger

[0028] - Heat transfer of at least part of the residual heat from the exhaust air to a subsequent process, either directly or indirectly via the heat exchanger. 2024PF00483

[0029] 4

[0030] By utilizing at least some of the residual heat from the exhaust air, the overall efficiency of the process is significantly increased compared to the process described in the prior art.

[0031] One embodiment of the inventive method for operating a compressed air storage power plant, in which a heat storage unit is arranged between the heat exchanger and the subsequent process, is characterized in that the residual heat of the exhaust air is supplied to the heat storage unit, which subsequently releases the heat to the subsequent process.

[0032] The downstream heat storage system allows residual heat to be stored and released evenly and over a longer period of time to the subsequent process as needed, making the subsequent process more predictable.

[0033] A significant advantage of the present invention is that existing systems can also be retrofitted with the heat exchanger and the inventive method can then be carried out.

[0034] Further advantages and embodiments of the invention are explained below using two exemplary embodiments. It shows:

[0035] - Fig. 1 : A compressed air storage power plant according to the invention with an ORC cycle as a subsequent process .

[0036] - Fig. 2 : A compressed air storage power plant according to the invention as shown in Fig. 1 with an additional heat storage unit.

[0037] - Fig. 3 : A compressed air storage power plant according to the invention as shown in Fig. 2 and a low-temperature district heating cycle process as a subsequent process instead of an ORC cycle process.

[0038] The figures show only schematic representations of the invention, in which essentially only those relevant to 2024PF00483 are shown.

[0039] 5

[0040] The components necessary for the invention are shown. Identical or functionally equivalent components are provided with the same reference symbols across all figures.

[0041] Fig. 1 shows a first embodiment of a compressed air energy storage power plant. The compressed air energy storage power plant comprises a compressor 1, which is operated, for example, with surplus electrical energy from renewable energy sources such as wind or solar power. The compressor 1 serves to compress ambient air during storage operation. The compressed air is stored in the compressed air storage tank 2. During discharge operation (discharge mode), the compressed air is extracted from the compressed air storage tank 2 and expanded in an expander 3. A generator for the production of electrical energy can be operated via the expander 3 (not shown in the figures).

[0042] Before entering expander 3, the air must be preheated. Preheating the air is important for several reasons. Firstly, the compressed air cools down significantly during expansion. This cooling can cause moisture in the air to condense and freeze, leading to icing in expander 3. This could impair operation or cause damage. Secondly, efficiency increases because warm air has a higher specific energy, meaning it can perform more work when it expands. Preheating the air thus increases the efficiency of the expansion process and, consequently, the overall efficiency of the power plant. The heat is supplied via a suitable device 4. Such a device 4 could, for example, be a heat exchanger that utilizes the heat generated during the A-CAES process to preheat the air.Such a device can also be a fuel-operated burner or an electric heater. Generally, all devices 4 are suitable for preheating the air if they are capable of heating the air to the required temperature before it enters the compressor 3. 2024PF00483.

[0043] 6

[0044] The exhaust air leaving the expander 3 at the end of the expansion section typically retains sufficient residual heat to be suitable for transferring it to a subsequent process 6 rather than releasing it unused into the environment. To utilize this residual heat, a heat exchanger 5 is provided, allowing it to be transferred to the subsequent process. Suitable subsequent processes include, in particular, all low-temperature processes where the process temperature is < 300 °C, preferably < 250 °C. In the embodiment shown in Fig. 1, the low-temperature process is an ORC cycle. The ORC cycle is a thermodynamic cycle for converting heat into mechanical energy, which can then be converted into electrical energy. It is similar to the classic Rankine cycle but uses organic working fluids (such as silicone oils or refrigerants) instead of water.These media have lower boiling points, which makes the ORC particularly suitable for utilizing low-temperature heat sources such as waste heat. For the sake of simplicity, only the ORC turbine 7 for expanding the working fluid is shown in Fig. 1. The ORC cycle typically includes at least a condenser and a pump that directs the condensate to the heat exchanger (evaporator).

[0045] By using the waste heat from the exhaust air to evaporate the working fluid of the ORC cycle process, a significant increase in the overall process efficiency is achieved, while the plant engineering effort is manageable and the additional costs are low even when retrofitting an existing plant.

[0046] Fig. 2 shows the compressed air storage power plant depicted in Fig. 1 with an additional heat storage unit 8. Since the basic structure remains unchanged, only the differences to the compressed air storage power plant according to Fig. 1 will be discussed below. For the basic structure and operation of the compressed air storage power plant, please refer to the description of Fig. 1. 2024PF00483

[0047] 7

[0048] The additional heat storage unit 8 temporarily stores the thermal energy of the exhaust air and releases it to the ORC cycle process as needed. The heat storage unit 8 enables, in particular, a uniform release of thermal energy over a longer period. In principle, any thermal storage device, such as a salt storage tank, is suitable as the heat storage unit 8. It would also be conceivable to arrange the heat storage unit between the expander 3 and the heat exchanger 5.

[0049] The heat storage unit 8 further expands the application of the invention and enables continuous operation of the low-temperature process even during periods of low wind and calm (weather conditions in which there is little to no wind and the sun shines little or not at all).

[0050] Fig. 3 shows a further embodiment of a compressed air storage power plant according to the invention. The difference to the embodiment according to Fig. 2 is that the low-temperature process is a low-temperature district heating cycle process 6. The other explanations relating to Fig. 2 also apply to the embodiment according to Fig. 3.

[0051] A district heating system is generally a system for the central generation and distribution of heat, which is used to heat buildings and provide hot water. A low-temperature district heating system is a district heating system that circulates heat at lower temperatures than traditional district heating systems. Typically, the flow temperature in such systems is between 30 and 70 degrees Celsius, in contrast to conventional systems, which often use temperatures of 80 to 120 degrees Celsius. The present invention is therefore particularly well suited in combination with such a low-temperature district heating system, since even very small quantities of heat can be used effectively.

[0052] In summary, it can be stated that the compressed air storage power plant according to the invention and the method according to the invention for operating such a 2024PF00483

[0053] 8

[0054] The compressed air storage power plant allows the residual heat from the exhaust air to be used in a subsequent process for the first time, thereby significantly improving the overall efficiency. The invention can be used in new plants as well as integrated into existing plants. The required plant costs and necessary modifications are low.

Claims

2024PF00483 9 Patent claims 1. Compressed air storage power plant, comprising at least one first compressor (1) , at least one compressed air storage (2) and at least one first expander (3) which are connected in series in terms of fluid dynamics, and a device (4) for supplying heat which is suitable for heating the compressed air which is taken from the compressed air storage tank (2) characterized in that in the direction of flow behind the at least one expander (3) a heat exchanger (5) is arranged which is designed to absorb residual heat from the exhaust air coming from the expander (3) and transfer it to a subsequent process (6).

2. Compressed air storage power plant according to claim 1, characterized in that the subsequent process is a low-temperature process, wherein the temperature of the low-temperature process is < 300°C, preferably < 250°C.

3. Compressed air storage power plant according to claim 2, characterized in that the low-temperature process comprises an ORC cycle process.

4. Compressed air storage power plant according to claim 2, characterized in that the low-temperature process comprises a low-temperature district heating cycle process.

5. Compressed air storage power plant according to one of the preceding claims, characterized in that a heat storage unit is arranged between the heat exchanger (5) and the subsequent process. 2024PF00483 10 6. Method for operating a compressed air storage power plant according to claim 1, wherein the compressed air storage power plant is operated in a discharge mode, characterized by the following method steps: - Extraction of compressed air from the compressed air storage tank - Heating the compressed air - Releasing the compressed air in the expander - Feeding the exhaust air from the expander to a heat exchanger - Heat transfer of at least part of the residual heat from the exhaust air to a subsequent process, either directly or indirectly via the heat exchanger.

7. Method for operating a compressed air storage power plant according to claim 6, wherein a heat storage unit is arranged between the heat exchanger ( 5 ) and the subsequent process, characterized in that the residual heat of the exhaust air is supplied to the heat storage unit, which subsequently releases the heat to the subsequent process.

8. Method for operating a compressed air storage power plant according to claim 7, wherein the heat storage unit releases the heat uniformly over a period of time to the subsequent process.

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