Optimized air compressor unit and compressed air energy storage system

Abstract

The application relates to the technical field of compressed air energy storage, and provides an air compressor unit with optimized configuration and a compressed air energy storage system.The air compressor unit comprises multistage air compressors in series, the variable compression efficiency of each stage of the air compressors is sequentially reduced, and the process parameter configuration of each stage of the air compressors satisfies the following condition: the air compressor unit with optimized configuration and the compressed air energy storage system provided by the application can realize the optimal combination of the compression exhaust temperature of each stage and the total compression power by reasonably configuring the exhaust temperature parameter configuration between the air compressors of each stage, so that the overall energy efficiency of the system is improved.

Description

Technical Field

[0001] This invention relates to the field of compressed air energy storage technology, and in particular to an optimized configuration of an air compressor unit and a compressed air energy storage system. Background Technology

[0002] Advanced insulated compressed air energy storage, as a large-scale, long-term energy storage technology, has been successfully demonstrated in engineering projects of varying capacity levels in China. When absorbing energy, the compressed air energy storage system utilizes surplus electricity from renewable energy sources, thermal power plants, or off-peak electricity from the grid to drive an air compressor to compress ambient air, obtaining high-temperature, high-pressure compressed air. This compressed air then exchanges heat with a heat transfer medium, absorbing and storing the thermal energy. After releasing heat and cooling, the air enters the storage device, thus storing electrical energy using both the heat transfer medium and compressed air as carriers. When releasing energy, the stored compressed air again exchanges heat with the stored heat transfer medium, absorbing heat and heating up before entering an air expander to depressurize and perform work, driving a generator to generate electricity. Simultaneously, the cooled heat transfer medium is stored, thus achieving the regeneration of electrical energy.

[0003] Based on the working principle of compressed air energy storage power generation systems, the compression process has a dual impact on the overall energy storage characteristics of the system. First, the exhaust temperature during compression determines the system's heat storage temperature, which in turn determines the intake temperature during expansion. According to classical thermodynamics, the intake temperature is positively correlated with the output power during expansion. Therefore, increasing the compressor exhaust temperature will increase the output power during expansion, which, under the condition of constant compression power, contributes to improving the overall energy efficiency of the system. However, according to classical thermodynamics, while the exhaust temperature increases, the power output during compression also increases, thus having an opposite effect on the overall energy efficiency of the system compared to the exhaust temperature.

[0004] As shown above, the exhaust temperature and compression power consumption during the compression process have both positive and negative impacts on the energy efficiency of compressed air energy storage systems. Optimization is needed to determine the optimal combination of exhaust temperature and compression power consumption for each stage of the compressor, thereby maximizing the overall system energy efficiency. Currently, there are no specific process design and optimization methods for advanced adiabatic compressed air energy storage air compressor units. Summary of the Invention

[0005] This invention provides an optimized configuration of an air compressor unit and a compressed air energy storage system to address the shortcomings of low energy efficiency in existing compressed air energy storage systems and improve the energy efficiency of compressed air energy storage systems.

[0006] This invention provides an optimized configuration of an air compressor unit, comprising: a multi-stage air compressor connected in series, wherein the variable compression efficiency of each stage of the air compressor decreases sequentially, and the process parameters of each stage of the air compressor are configured to satisfy the following conditions:

[0007]

[0008]

[0009] Where, m ci and m ci+1 These are the flow air mass flow rates of the air compressors at stage i and stage i+1, respectively. and These are the variable compression efficiencies of the air compressors at stage i and stage i+1, respectively. C is the compression and exhaust temperature of the air compressor of stage i. ci and C ci+1 These are the polynomials of the air compressor at stage i and stage i+1, respectively, with respect to the above parameters.

[0010] According to the optimized configuration of the air compressor unit provided by the present invention, the air compressor is provided with an inlet guide vane valve on the inlet side.

[0011] According to the optimized configuration of the air compressor unit provided by the present invention, the air compressor is provided with an outlet throttle valve on the outlet side.

[0012] The optimized configuration of the air compressor unit provided by the present invention further includes a flow detection device suitable for monitoring the flow rate of the air compressor.

[0013] The optimized configuration of the air compressor unit provided by the present invention further includes a temperature detection device suitable for monitoring the compressed exhaust temperature of each stage of the air compressor.

[0014] Another aspect of the present invention provides a compressed air energy storage system, comprising: an air compressor unit, a heat storage module, an expander unit, and an air storage device as described in any of the preceding claims;

[0015] The air compressor unit is connected to the air storage device, the air storage device is connected to the expander unit, and the heat storage module is connected to both the air compressor unit and the expander unit.

[0016] According to the compressed air energy storage system provided by the present invention, the air compressor unit includes at least one constant pressure air compressor and at least one non-constant pressure air compressor, the constant pressure air compressor is connected to the heat storage module, and the non-constant pressure air compressor is connected to the air storage device.

[0017] The compressed air energy storage system provided by the present invention further includes a cooling device connected to the non-constant pressure air compressor.

[0018] The compressed air energy storage system provided by the present invention further includes a first heat exchanger, wherein the constant pressure air compressor is connected to the first heat exchanger, and the first heat exchanger is connected to the heat storage module.

[0019] The compressed air energy storage system provided by the present invention further includes a second heat exchanger, wherein the heat storage module is connected to the second heat exchanger, and the second heat exchanger is connected to the expander unit.

[0020] The optimized configuration of the air compressor unit and compressed air energy storage system provided by this invention can achieve the best combination of compressed exhaust temperature and compressed power by reasonably configuring the exhaust temperature parameters between each stage of the air compressor, thereby improving the overall energy efficiency of the system.

[0021] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of one embodiment of the optimized configuration air compressor unit provided by the present invention;

[0024] Figure 2 This is a schematic diagram of a second embodiment of the optimized configuration air compressor unit provided by the present invention;

[0025] Figure 3 This is a schematic diagram of an embodiment of the compressed air energy storage system provided by the present invention.

[0026] Figure label:

[0027] 1. Heat storage module; 2. Gas storage device; 3. Constant pressure air compressor; 4. Non-constant pressure air compressor; 5. First heat exchanger; 6. Second heat exchanger; 7. Cooling device; 8. Expander. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present invention based on the specific circumstances.

[0030] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0031] In view of the shortcomings of existing compressed air energy storage systems, the present invention provides an optimized configuration of an air compressor unit and a compressed air energy storage system.

[0032] The following is combined Figures 1 to 3 This invention describes an optimized configuration of an air compressor unit and a compressed air energy storage system.

[0033] It should be noted that the air compressor unit provided by this invention has two application scenarios: one is for design scheme optimization in the system design phase, and the other is for operation scheme optimization in the actual operation phase. The following details specific embodiments of the air compressor unit provided by this invention applied to design scheme optimization in the system design phase and operation scheme optimization in the actual operation phase.

[0034] Design scheme optimization applied in the system design phase

[0035] like Figure 1The diagram shown is a schematic representation of one embodiment of the optimized configuration of the air compressor unit provided by the present invention. In this embodiment, the constant pressure section air compressor unit includes multiple air compressors A1 to An connected in series. The variable compression efficiency of each air compressor decreases sequentially. Heat exchangers B1 to Bn are provided between adjacent air compressors. Each heat exchanger uses a low-temperature heat transfer medium to exchange heat with the air compressor exhaust, reducing the air compressor exhaust temperature to the ambient temperature level before it enters the next stage air compressor. At the same time, gas-liquid separators S1 to Sn are provided between adjacent air compressors. The gas-liquid separators are used to separate the liquid water generated by the condensation of compressed air after cooling, preventing the liquid water from entering the subsequent process flow. Therefore, the mass flow rate of the air entering the next stage air compressor will be less than that of the previous stage air compressor. Thus, the process parameter configuration of each stage air compressor satisfies the following conditions:

[0036]

[0037]

[0038] Where, m ci and m ci+1 These are the mass flow rates of the air passing through the i-th and i+1-th air compressors, respectively. and These are the polytropic compression efficiencies of the i-th and i+1-th stage air compressors, respectively. Let C be the compression and discharge temperature of the i-th stage air compressor. ci and C ci+1 These are the polynomials of the i-th and i+1-th stage air compressors with respect to the above parameters, respectively.

[0039] The above formula shows that when the ratio of the polynomials of two adjacent air compressor stages... In When m is between 1 and 1, the overall energy efficiency of the compressed air energy storage system reaches its optimal level. However, during actual operation, m... ci , and Since parameters can change dynamically, this invention optimizes the parameter ratio between different levels of air compressors through the above methods, enabling the overall energy efficiency of the compressed air energy storage system to reach the optimal level under dynamic system operation conditions.

[0040] Due to gas-liquid separation, the mass flow rate of the air passing through each stage of the air compressor is not equal. In this case, attention should be paid to the product of the mass flow rate of the air passing through each stage of the air compressor and the compressed exhaust temperature, and then to the ratio of the variable compression efficiency of each stage of the air compressor.

[0041] like Figure 2The diagram shown is a schematic representation of a second embodiment of the optimized configuration of the air compressor unit provided by the present invention. In this embodiment, the constant pressure section air compressor unit includes multiple air compressors A1 to An connected in series. The variable compression efficiency of each air compressor decreases sequentially. Heat exchangers B1 to Bn are provided between adjacent air compressors. Each heat exchanger uses a low-temperature heat transfer medium to exchange heat with the exhaust gas of the air compressor, reducing its temperature to the ambient temperature level before it enters the next stage air compressor. When the air contains no moisture or has low humidity, a gas-liquid separator is not required. At this time, the air flow mass flow rate of each air compressor is equal, and the process parameter configuration of each air compressor satisfies the following conditions:

[0042]

[0043]

[0044] Similarly, and These are the polytropic compression efficiencies of the i-th and i+1-th stage air compressors, respectively. Let C be the compression and discharge temperature of the i-th stage air compressor. ci and C ci+1 These are the polynomials of the i-th and i+1-th stage air compressors with respect to the above parameters, respectively.

[0045] In other words, under ideal conditions, since there is no gas-liquid separation, the mass flow rate of the air passing through each stage of the air compressor is equal. At this time, it is only necessary to pay attention to the ratio of the compression and discharge temperature of each stage of the air compressor to the variable compression efficiency of each stage of the air compressor.

[0046] Optimization of operation plan during actual operation phase

[0047] Even if the multi-stage air compressor unit meets the above-mentioned optimized configuration conditions under the design conditions, the actual operating parameters of each stage of the air compressor may deviate from the predetermined configuration due to interference factors such as the actual operating environment and pipeline resistance. By measuring the flow air mass flow rate, compressed exhaust temperature and variable compression efficiency of each stage of the air compressor, it is possible to quickly and conveniently determine whether there is a deviation in the actual operating parameters of each stage of the air compressor based on the above-mentioned optimized configuration conditions.

[0048] In some embodiments, if the actual operation deviates from the optimal configuration conditions, the exhaust pressure of each stage of the air compressor can be adjusted by setting an outlet throttle valve and / or an inlet guide vane valve on the air compressor, while meeting the safety operation constraints of the air compressor module. Simultaneously, the flow rate, exhaust temperature, and variable compression efficiency of each stage of the air compressor can be monitored in real time using flow detection devices, temperature detection devices, etc., and calculations can be performed to determine whether the above-mentioned optimal configuration conditions are met or as close as possible to being met.

[0049] The air compressor unit provided by this invention can achieve the optimal combination of exhaust temperature of each stage of the compressor and total compression power by reasonably configuring the exhaust temperature parameters between each stage of the air compressor, thereby improving the overall energy efficiency of the system.

[0050] like Figure 3 As shown, another aspect of the present invention provides a compressed air energy storage system, comprising: an air compressor unit, a heat storage module 1, an expander unit, and an air storage device 2 as described in the above embodiment; the air compressor unit is connected to the air storage device 2, the air storage device 2 is connected to the expander unit, and the heat storage module 1 is connected to both the air compressor unit and the expander unit.

[0051] The air compressor unit includes at least one constant-pressure air compressor 3 and at least one non-constant-pressure air compressor 4. For example... Figure 3 As shown, in this embodiment, the constant pressure air compressor 3 is exemplified by two stages, while the non-constant pressure air compressor 4 is exemplified by one stage, and the non-constant pressure air compressor 4 is the final stage compressor.

[0052] Specifically, in this embodiment, it also includes a first heat exchanger 5, a second heat exchanger 6, and a cooling device 7. A two-stage constant-pressure air compressor 3 is connected to the first heat exchanger 5, the first heat exchanger 5 is connected to the heat storage module 1, the heat storage module 1 is connected to the second heat exchanger 6, the second heat exchanger 6 is connected to the expander unit, and a non-constant-pressure air compressor 4 is connected to the cooling device 7. Each stage of the constant-pressure air compressor 3 is connected to the heat storage module 1 via the first heat exchanger 5, and the non-constant-pressure air compressor 4 is connected to the air storage device 2.

[0053] The cooling device 7 can be driven by a cooling tower to cool the high-temperature air discharged from the non-constant pressure air compressor 4.

[0054] In this embodiment, the expander unit includes two-stage expanders 8. Both expanders 8 are connected to the heat storage module 1 through a second heat exchanger 6, which can use the heat stored in the heat storage medium in the heat storage module 1 to heat the air, and then pass the heated air into the expander to expand and do work.

[0055] The compressed air energy storage system provided by this invention is applicable to non-constant pressure systems (referring to systems that simultaneously possess constant pressure air compressors and non-constant pressure air compressors). In this case, the gas storage device uses a constant volume method for gas storage. Therefore, during the gas filling process, the pressure inside the gas storage device rises, and the exhaust pressure of the last-stage air compressor in the compressor unit rises, resulting in unstable air compressor operation and unstable exhaust temperature, which is not conducive to the collection of compressed heat energy. Therefore, when the gas storage device 1 is a constant volume gas storage device, in order to achieve efficient storage of compressed heat energy, this embodiment divides the air compressor unit into a constant pressure section (constant pressure air compressor 3, the same below) and a non-constant pressure section (non-constant pressure air compressor 4, the same below). The exhaust pressure and exhaust temperature of the constant pressure section are stable, and the exhaust after the stage exchanges heat through the first heat exchanger 5, storing the heat energy in the form of a heat storage medium in the heat storage module. The exhaust pressure of the non-constant pressure section increases with the increase of the gas storage pressure by adjusting the speed of the air compressor. A cooling device is set after the non-constant pressure section to dissipate the heat, thereby reducing the air temperature entering the next stage compressor or gas storage device.

[0056] In some embodiments, the non-constant pressure air compressor 4 may also be a multi-stage series, with cooling devices provided between stages.

[0057] The working principle of the compressed air energy storage system provided by this invention is as follows:

[0058] During the system's air-filled energy storage, the system utilizes surplus electricity from renewable energy sources, thermal power generation, or off-peak electricity from the power grid to drive the air compressor unit to continuously compress air. The exhaust from the constant-pressure air compressor 3 first passes through the first heat exchanger 5 to exchange heat with the heat transfer medium and cool down before entering the non-constant-pressure air compressor 4 for further compression. The air compressed by the non-constant-pressure air compressor 4 then enters the air storage device 2 through pipelines for storage and backup.

[0059] When the system releases gas to generate electricity, the compressed air enters the second heat exchanger 6 from the gas storage device 2 to exchange heat with the heat storage medium flowing out of the heat storage module 1, raising its temperature. The compressed air, after absorbing heat and being heated, enters the expander 8 to expand and do work.

[0060] In practice, a throttling valve can be installed on the outlet pipe of the gas storage device 2 to stabilize the pressure of the discharged air at a certain set value before it enters the expander unit.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An optimized configuration air compressor unit, characterized in that, include: In a multi-stage air compressor connected in series, the polytropic compression efficiency of each stage decreases sequentially, and the process parameters of each stage of the air compressor are configured to meet the following conditions: Where, m ci and m ci+1 These are the flow air mass flow rates of the air compressors at stage i and stage i+1, respectively. and These are the variable compression efficiencies of the air compressors at stage i and stage i+1, respectively. C is the compression and exhaust temperature of the air compressor of stage i. ci and C ci+1 These are the polynomials of the air compressor at stage i and stage i+1, respectively, with respect to the above parameters.

2. The optimized configuration air compressor unit according to claim 1, characterized in that, The air compressor is equipped with an inlet guide vane valve on the inlet side.

3. The optimized configuration air compressor unit according to claim 1, characterized in that, The air compressor is equipped with an outlet throttle valve on its outlet side.

4. The optimized configuration air compressor unit according to claim 1, characterized in that, It also includes a flow detection device suitable for monitoring the flow rate of the air compressor.

5. The optimized configuration air compressor unit according to claim 1, characterized in that, It also includes a temperature detection device suitable for monitoring the compressed exhaust temperature of the air compressors at all levels.

6. A compressed air energy storage system, characterized in that, include: The air compressor unit, heat storage module, expander unit, and gas storage device as described in any one of claims 1 to 5; The air compressor unit is connected to the air storage device, the air storage device is connected to the expander unit, and the heat storage module is connected to both the air compressor unit and the expander unit.

7. The compressed air energy storage system according to claim 6, characterized in that, The air compressor unit includes at least one constant-pressure air compressor and at least one non-constant-pressure air compressor. The constant-pressure air compressor is connected to the heat storage module, and the non-constant-pressure air compressor is connected to the air storage device.

8. The compressed air energy storage system according to claim 7, characterized in that, It also includes a cooling device connected to the non-constant pressure air compressor.

9. The compressed air energy storage system according to claim 7, characterized in that, It also includes a first heat exchanger, the constant pressure air compressor is connected to the first heat exchanger, and the first heat exchanger is connected to the heat storage module.

10. The compressed air energy storage system according to any one of claims 6 to 9, characterized in that, It also includes a second heat exchanger, the heat storage module is connected to the second heat exchanger, and the second heat exchanger is connected to the expander unit.

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