Enterprise-level Carnot battery energy storage system based on reversible screw machine and operation method

Abstract

An enterprise-level Carnot battery energy storage system and operation method based on a reversible screw machine, the system includes a working circuit and a heat storage circuit; the working circuit includes a reversible screw machine, a high-temperature heat exchanger, a low-temperature heat exchanger, a three-way valve, an intermediate air extraction and replenishment branch, an energy storage branch, and an energy release branch; the heat storage circuit includes a high-temperature heat storage circuit and a low-temperature heat storage circuit; the reversible screw machine realizes the switching of compression function and expansion function by changing the direction of the yin and yang rotors and reversing the suction and exhaust positions, and has a variable speed and a variable internal volume ratio, and has multiple air extraction and replenishment orifices, which can realize intermediate air extraction and intermediate air replenishment. The present invention uses a reversible screw machine to couple the energy storage and energy release of the Carnot battery into a system, realizes the switching of the energy storage branch and the energy release branch through a three-way valve, and sets an ejector in the energy storage branch to recover part of the pressure energy, and at the same time, performs medium-temperature heat supplementation and heating through the intermediate air extraction and replenishment orifices of the reversible screw machine, so as to realize the cascade utilization and corresponding output of cold and heat all day long.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage and comprehensive energy utilization, and particularly relates to an enterprise-level Carnot battery energy storage system based on a reversible screw compressor and an operation method thereof. Background Art

[0002] The peak-valley misalignment between the power generation load change characteristics and the power consumption load change characteristics leads to the difference in peak-valley electricity prices. Many large and medium-sized energy-consuming enterprises have greater energy consumption demands during peak electricity periods. At the same time, these enterprises often have comprehensive utilization demands for cooling, heating, power supply, and waste heat utilization in the park, and need an energy storage system and an operation plan that can realize valley electricity used during peak periods, high-efficiency integration, and comprehensive utilization of cooling, heat, and electricity. Compared with other energy storage methods such as water storage energy storage, electrochemical energy storage, and compressed air energy storage, Carnot battery energy storage has the characteristics of high energy storage density and little influence by geographical conditions. Therefore, this technology can be applied to enterprise-level energy storage systems.

[0003] Traditional Carnot battery energy storage systems require two sets of circulation systems for energy storage and energy release to achieve the process of "electricity - heat - electricity", which will increase the construction cost of enterprise-level Carnot battery energy storage systems. At the same time, traditional Carnot battery systems can only rely on the cold sources of the energy storage cycle and the energy release cycle for waste heat utilization and cold and heat supply. When applied to enterprises, other energy utilization technologies need to be combined to achieve all-weather cascade utilization and targeted output of cold and heat. In addition, the energy storage efficiency of traditional large-scale Carnot battery systems is relatively low. When applied to enterprise-level energy storage, the energy storage efficiency needs to be improved. Summary of the Invention

[0004] The purpose of the present invention is to address the above problems in the prior art and provide an enterprise-level Carnot battery energy storage system based on a reversible screw compressor and an operation method thereof. The reversible screw compressor is used to couple the energy storage system and the energy release system of the Carnot battery into one system. The switching of the energy storage branch and the energy release branch is realized through a three-way valve, and an ejector is arranged in the energy storage branch to recover part of the pressure energy. At the same time, medium-temperature heat supply is carried out through the intermediate extraction and compensation air ports of the reversible screw compressor, and all-weather cascade utilization and targeted output of cold and heat are realized on the basis of storing valley electricity and releasing peak electricity.

[0005] To achieve the above object, the present invention has the following technical solutions:

[0006] An enterprise-level Carnot battery energy storage system based on a reversible screw compressor, comprising:

[0007] A working circuit and a heat storage circuit;

[0008] The working circuit includes a reversible screw compressor, a high-temperature heat exchanger, a low-temperature heat exchanger, a three-way valve, an intermediate extraction and compensation air branch, an energy storage branch, and an energy release branch;

[0009] The heat storage circuit includes a high-temperature heat storage circuit and a low-temperature heat storage circuit;

[0010] A reversible screw compressor can switch between compression and expansion functions by changing the rotation direction of the male and female rotors and reversing the suction and discharge positions, has variable speed and variable volume ratio, and has multiple extraction and compensation orifices, enabling intermediate extraction and intermediate gas compensation;

[0011] A high-temperature heat exchanger is connected to the working medium outlet of the reversible screw compressor in its compression function, and includes a sensible heat exchange section and a latent heat exchange section. The sensible heat exchange section is placed in the phase change material, and the latent heat exchange section exchanges heat with the liquid-phase heat storage working medium in the high-temperature heat storage circuit;

[0012] A low-temperature heat exchanger is connected to the working medium inlet of the reversible screw compressor in its compression function, and the internal circulating working medium exchanges heat with the liquid-phase heat storage working medium in the low-temperature heat storage circuit;

[0013] The energy storage branch includes an ejector. The working medium of the ejector is high-pressure liquid phase, the entrained fluid is low-pressure gas phase, and the nozzle position can be adjusted according to the working pressure; the intermediate extraction and gas compensation branch includes a medium-temperature heat exchanger, and the intermediate extraction and gas compensation branch is connected to the extraction and compensation orifices of the reversible screw compressor; the energy release branch includes a working medium pump, and each working medium pump is connected to the high-temperature heat exchanger, the medium-temperature heat exchanger, and the low-temperature heat exchanger through a three-way valve respectively;

[0014] The energy storage branch is connected to the high-temperature heat exchanger, the low-temperature heat exchanger, the reversible screw compressor, and the intermediate extraction and gas compensation branch through a three-way valve, and the intermediate extraction and gas compensation branch is also connected to the working medium pump of the energy release branch through a three-way valve.

[0015] As a preferred solution, the high-temperature heat storage circuit includes a high-temperature heat storage tank group, a first stop valve, and a high-temperature waste heat exchanger. Among them, the first stop valve and the high-temperature waste heat exchanger are placed between the high-temperature heat storage tank group, and the high-temperature heat storage tank group is two heat-insulated heat storage tanks or one heat storage tank with multiple heat-insulated cavities.

[0016] As a preferred solution, the low-temperature heat storage circuit includes a low-temperature No. 1 heat storage tank group, a low-temperature No. 2 heat storage tank group, an eighth three-way valve, a ninth three-way valve, a second stop valve, a third stop valve, a low-temperature No. 1 heat exchanger, and a low-temperature No. 2 heat exchanger. Among them, the second stop valve and the low-temperature No. 1 heat exchanger are placed between the low-temperature No. 1 heat storage tank group, the third stop valve and the low-temperature No. 2 heat exchanger are placed between the low-temperature No. 2 heat storage tank group, the eighth three-way valve and the ninth three-way valve are both connected to the low-temperature heat exchanger, the low-temperature No. 1 heat storage tank group, and the low-temperature No. 2 heat storage tank group, and the low-temperature No. 1 heat storage tank group and the low-temperature No. 2 heat storage tank group are two heat-insulated heat storage tanks or one heat storage tank with multiple heat-insulated cavities.

[0017] As a preferred solution, the energy storage branch includes a first injector, a first gas-liquid separator, a third three-way valve, a second injector, a second gas-liquid separator, a fourth stop valve, a first throttle valve, a second throttle valve, and a fifth three-way valve, wherein the first injector ejection medium inlet is connected to the low-temperature heat exchanger through the left and lower ports of the second three-way valve, the working medium inlet is connected to the high-temperature heat exchanger through the left and right ports of the first three-way valve, the mixed medium outlet is connected to the first gas-liquid separator, and the liquid phase outlet of the first gas-liquid separator is connected to the first throttle valve. Between the second throttle valve, the gas phase outlet is connected to the second ejector induced medium inlet through the left and right ports of the third three-way valve, the lower port of the third three-way valve is connected to the compression function inlet pipeline of the reversible screw machine, the working medium inlet of the second ejector is connected to the middle gas extraction and replenishment branch through the left and lower ports of the fourth three-way valve, the mixed medium outlet is connected to the second gas-liquid separator, the gas phase outlet of the second gas-liquid separator is connected to the compression function inlet pipeline of the reversible screw machine through the fourth stop valve, and the liquid phase outlet is connected to the low-temperature heat exchanger through the first throttle valve and the second throttle valve.

[0018] As a preferred solution, the energy release branch includes a first working fluid pump, a sixth three-way valve, and a second working fluid pump, wherein the first working fluid pump is connected to the low-temperature heat exchanger via the upper and lower ports of the fifth three-way valve, the outlet of the first working fluid pump is connected to the inlet of the second working fluid pump via the right and upper ports of the sixth three-way valve, the left port of the sixth three-way valve is connected to the medium-temperature heat exchanger, and the second working fluid pump is connected to the high-temperature heat exchanger via the left and lower ports of the first three-way valve.

[0019] As a preferred solution, the intermediate air supply branch includes a fourth three-way valve, a sixth three-way valve, a medium-temperature heat exchanger, and a seventh three-way valve, wherein the left port of the seventh three-way valve is connected to the air extraction and supply orifice of the reversible screw machine, and the upper port is connected to the inlet of the second working fluid pump. The external heat source of the medium-temperature heat exchanger includes medium-temperature industrial waste heat and new energy power generation waste heat, and the external cold source includes long-distance heating demand. The right port of the fourth three-way valve is connected between the first gas-liquid separator and the third three-way valve.

[0020] A method for operating the enterprise-level Carnot battery energy storage system based on a reversible screw machine comprises the following steps:

[0021] Energy storage process operation: During the night valley electricity period, the system is put into the energy storage state by adjusting the first three-way valve, the second three-way valve, and the fifth three-way valve. At this time, the circulating working fluid is compressed by the reversible screw machine, releases heat and condenses in the high-temperature heat exchanger, and then enters the energy release branch. The high-pressure condensate recovers part of the pressure energy by ejecting the low-pressure gas in the ejector of the energy release branch, absorbs heat and evaporates in the low-temperature heat exchanger, and is then boosted by the ejector and finally enters the reversible screw machine to form a cycle. Among them, during the energy storage process, the intermediate extraction and makeup air branch has three operating states: extraction for heat supply, makeup air for heat compensation, and no extraction or makeup air. When medium-temperature industrial waste heat and new energy power generation waste heat are input, it is in the makeup air for heat compensation operating state. When supplying heat to a long-distance area is output, it is in the extraction for heat supply operating state. When there is no input or output, it is in the no extraction or makeup air operating state. The switching of the three operating states of the intermediate makeup air circuit during the energy storage process is achieved by adjusting the flow states of the third three-way valve, the fourth three-way valve, the fourth stop valve, and the extraction and makeup air orifices.

[0022] Energy release process operation method: During the day peak electricity period, the system is put into the energy release state by adjusting the first three-way valve, the second three-way valve, and the fifth three-way valve. At this time, the circulating working fluid expands through the reversible screw machine to output technical work, releases heat and condenses in the low-temperature heat exchanger, and then enters the energy release branch. After being compressed by the working fluid pump, the high-pressure liquid evaporates and superheats in the high-temperature heat exchanger and finally returns to the reversible screw machine to form a cycle. Among them, during the energy release process, the intermediate extraction and makeup air branch has three operating states: extraction for heat supply, extraction for heat regeneration, and no extraction. When medium-temperature industrial waste heat and new energy power generation waste heat are input, it is in the no extraction state. When supplying heat to a long-distance area is output, it is in the extraction for heat supply operating state. When there is no input or output, it is in the extraction for heat regeneration state. The switching of the three operating states of the intermediate makeup air circuit during the energy release process is achieved by adjusting the flow states of the sixth three-way valve and the seventh three-way valve and the extraction and makeup air orifices.

[0023] As a preferred solution, the operation method further includes the operation of the high-temperature heat storage circuit: The high-temperature heat storage tank group includes two cavities, a high-temperature cavity and a low-temperature cavity. During the energy storage process, the heat storage fluid in the low-temperature cavity absorbs heat through the high-temperature heat exchanger and enters the high-temperature cavity. During the energy release process, the heat storage fluid in the high-temperature cavity releases heat through the high-temperature heat exchanger and enters the low-temperature cavity. When high-temperature industrial waste heat is input from the outside, the heat storage fluid in the low-temperature cavity enters the high-temperature cavity through the high-temperature waste heat exchanger and the first stop valve.

[0024] As a preferred solution, the operation method also includes operation of a low-temperature heat storage circuit: the low-temperature heat storage tank group No. 1 and the low-temperature heat storage tank group No. 2 each include two cavities, a high-temperature cavity and a low-temperature cavity. During the energy storage process, the fluid in the high-temperature cavity of the low-temperature heat storage tank group No. 2 enters the low-temperature cavity after releasing heat through the low-temperature heat exchanger, and then passes through the third stop valve, and absorbs daytime ambient heat or low-temperature industrial waste heat in the low-temperature heat exchanger No. 2 and returns to the high-temperature cavity. By adjusting the volume ratio of the reversible screw machine, the cold energy is used for short-distance cooling in the park during summer conditions. During the energy release process, the fluid in the low-temperature cavity of the low-temperature heat storage tank group No. 1 enters the high-temperature cavity after absorbing heat through the low-temperature heat exchanger, and then passes through the second stop valve, and absorbs nighttime ambient cold energy in the low-temperature heat exchanger No. 1. By adjusting the volume ratio of the reversible screw machine, the heat is used for short-distance heating in the park during winter conditions.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] The energy storage branch and the energy release branch are switched by a three-way valve, and the energy storage branch and the energy release branch are coupled by a reversible screw machine, which reduces the system construction cost and is more suitable for enterprise-level energy storage. In the energy storage branch, an ejector is introduced to recover the pressure energy in the supercooled liquid to improve the efficiency of the energy storage cycle. Heat exchangers are introduced in the high-temperature heat storage circuit, the medium-temperature air extraction and replenishment circuit, and the low-temperature heat storage circuit to rationally utilize the high-temperature waste heat, medium-temperature waste heat, low-temperature waste heat and the day and night temperature difference in the environment of the enterprise, and realize long-distance heating, short-distance heating, and short-distance cooling at the same time. On the basis of storing valley electricity and releasing peak electricity, all-weather cold and heat cascade utilization and corresponding input and output are realized, the comprehensive energy utilization efficiency of the system is improved, and the efficient integration of the system is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 The overall structural diagram of the enterprise-level Carnot battery energy storage system based on the reversible screw machine of the present invention;

[0029] Figure 2 Schematic diagram of the pumping and energy storage process of the enterprise-level Carnot battery energy storage system based on the reversible screw machine of the present invention;

[0030] Figure 3 Schematic diagram of the energy storage process of the enterprise-level Carnot battery energy storage system based on the reversible screw machine of the present invention without pumping and replenishing gas;

[0031] Figure 4Schematic diagram of the air replenishment energy storage process of the enterprise-level Carnot battery energy storage system based on a reversible screw compressor

[0032] Figure 5 Schematic diagram of the energy release process of the enterprise-level Carnot battery energy storage system based on a reversible screw compressor for extracting heat by pumping air

[0033] Figure 6 Schematic diagram of the energy release process of the enterprise-level Carnot battery energy storage system based on a reversible screw compressor without air extraction and replenishment

[0034] Figure 7 Schematic diagram of the energy release process of the enterprise-level Carnot battery energy storage system based on a reversible screw compressor for extracting heat by pumping air Detailed implementation manners

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0036] As Figure 1 shown, the enterprise-level Carnot battery energy storage system based on a reversible screw compressor in the embodiment of the present invention includes a working circuit and a heat storage circuit. Among them, the working circuit includes a reversible screw compressor 1, a high-temperature heat exchanger 2, a low-temperature heat exchanger 20, a first three-way valve 5, a second three-way valve 21, an intermediate air extraction and replenishment branch, an energy storage branch, and an energy release branch. The heat storage circuit includes a high-temperature heat storage circuit and a low-temperature heat storage circuit.

[0037] The reversible screw compressor 1 can switch between the compression function and the expansion function by changing the rotation direction of the male and female rotors and reversing the suction and exhaust positions, has the functions of variable speed and variable volume ratio, and has multiple air extraction and replenishment orifices, and can realize intermediate air extraction and intermediate air replenishment.

[0038] The high-temperature heat exchanger 2 is connected to the working medium outlet of the compression function of the reversible screw compressor 1, and includes a sensible heat exchange section and a latent heat exchange section. Among them, the sensible heat exchange section is placed in nitrate phase change materials, and the latent heat exchange section exchanges heat with the liquid-phase heat storage working medium in the high-temperature heat storage circuit.

[0039] The high-temperature heat storage circuit includes a high-temperature heat storage tank group 3, a first stop valve 4, and a high-temperature waste heat exchanger 28. Among them, the first stop valve 4 and the high-temperature waste heat exchanger 28 are placed between the high-temperature heat storage tank group 3. The high-temperature heat storage tank group 3 is two heat-insulated heat storage tanks or a heat storage tank with multiple heat-insulated cavities.

[0040] The low-temperature heat exchanger 20 is connected to the working fluid inlet of the reversible screw compressor. During operation, the internal circulating working fluid exchanges heat with the liquid-phase heat storage working fluid in the low-temperature heat storage loop.

[0041] The low-temperature heat storage loop includes a low-temperature first heat storage tank group 22, a low-temperature second heat storage tank group 25, an eighth three-way valve 32, a ninth three-way valve 29, a second stop valve 23, a third stop valve 26, a low-temperature first heat exchanger 24, and a low-temperature second heat exchanger 27. Among them, the second stop valve 23 and the low-temperature first heat exchanger 24 are arranged between the low-temperature first heat storage tank group 22, the third stop valve 26 and the low-temperature second heat exchanger 27 are arranged between the low-temperature second heat storage tank group 25. The eighth three-way valve 32 and the ninth three-way valve 29 are both connected to the low-temperature heat exchanger 20, the low-temperature first heat storage tank group 22 and the low-temperature second heat storage tank group 25. The low-temperature first heat storage tank group 22 and the low-temperature second heat storage tank group 25 are two heat-insulated heat storage tanks or a heat storage tank with multiple heat-insulated cavities.

[0042] The energy storage shunt includes a first ejector 6, a first gas-liquid separator 7, a third three-way valve 8, a second ejector 10, a second gas-liquid separator 11, a fourth stop valve 12, a first throttle valve 18, a second throttle valve 19, and a fifth three-way valve 13. Among them, the working medium of the first ejector 6 and the second ejector 10 is high-pressure liquid phase, and the entrained fluid is low-pressure gas phase, and the nozzle position can be adjusted according to the working pressure. The entrained medium inlet of the first ejector 6 is connected to the low-temperature heat exchanger 20 through the left and lower ports of the second three-way valve 21. The working medium inlet is connected to the above-mentioned high-temperature heat exchanger 2 through the left and right ports of the first three-way valve 5. The mixed medium outlet is connected to the first gas-liquid separator 7. The liquid phase outlet of the first gas-liquid separator 7 is connected between the first throttle valve 18 and the second throttle valve 19. The gas phase outlet is connected to the entrained medium inlet of the second ejector 10 through the left and right ports of the third three-way valve 8. The lower port of the third three-way valve 8 is connected to the inlet pipeline of the compression function of the reversible screw compressor 1. The working medium inlet of the second ejector 10 is connected to the intermediate extraction and gas replenishment shunt through the left and lower ports of the fourth three-way valve 9. The mixed medium outlet is connected to the second gas-liquid separator 11. The gas phase outlet of the second gas-liquid separator 11 is connected to the inlet pipeline of the compression function of the reversible screw compressor 1 through the fourth stop valve 12. The liquid phase outlet is connected to the low-temperature heat exchanger 20 through the first throttle valve 18 and the second throttle valve 19.

[0043] The energy release shunt includes a first working fluid pump 30, a sixth three-way valve 14, and a second working fluid pump 31. Among them, the first working fluid pump 30 is connected to the low-temperature heat exchanger 20 through the upper and lower ports of the fifth three-way valve 13. Its outlet is connected to the inlet of the second working fluid pump 31 through the right and upper ports of the sixth three-way valve 14. The left port of the sixth three-way valve 14 is connected to the medium-temperature heat exchanger 15. The second working fluid pump 31 is connected to the high-temperature heat exchanger 2 through the left and lower ports of the first three-way valve 5.

[0044] The intermediate air supply branch includes a fourth three-way valve 9, a sixth three-way valve 14, a medium-temperature heat exchanger 15, and a seventh three-way valve 16. Among them, the left port of the seventh three-way valve 16 is connected to the air extraction and compensation orifice of the reversible screw compressor 1, the upper port is connected to the inlet of the second working fluid pump 31, and the external heat source of the medium-temperature heat exchanger 15 includes medium-temperature industrial waste heat and new energy power generation waste heat, and the external cold source includes long-distance heating demand. The right port of the fourth three-way valve 9 is connected between the first gas-liquid separator 7 and the third three-way valve 8.

[0045] In addition to the above system, the embodiment of the present invention also provides an operation method for the system, including an energy storage process operation method, an energy release process operation method, a high-temperature heat storage loop operation method, and a low-temperature heat storage loop operation method.

[0046] Example 1: Air extraction energy storage process

[0047] Such as Figure 2As shown in the figure, during the air extraction and energy storage process, the left and right ports of the first three-way valve 5, the third three-way valve 8, the fourth three-way valve 9, the sixth three-way valve 14, and the seventh three-way valve 16 are connected, as well as the left and lower ports of the second three-way valve 21, the eighth three-way valve 32, and the ninth three-way valve 29, and the left and upper ports of the fifth three-way valve 13. The fourth stop valve 12 is opened, and the reversible screw machine 1 is switched to the screw compressor state. In this embodiment, the intermediate air extraction and make-up branch is in the air extraction state and can output medium-temperature heat for long-distance heating. After being compressed by the screw compressor, the superheated gas transfers heat to the heat storage fluid in the high-temperature heat storage loop in the sensible heat section of the high-temperature heat exchanger 2, and transfers heat to the nitrate phase change heat storage material outside the heat exchanger in the latent heat section. The circulating working medium in the high-pressure liquid state after heat exchange enters the working medium inlet of the first ejector 6, mixes with the ejecting medium and then enters the first gas-liquid separator 7. The liquid phase directly enters the pipeline between the first throttle valve 18 and the second throttle valve 19, and the gas phase enters the second ejector 10 as the ejecting medium. On the other side, the intermediate air extraction port of the screw compressor is adjusted to a position matching the air extraction pressure. The extracted medium-pressure superheated gas outputs heat in the medium-temperature heat exchanger 15 for long-distance heating. After the heat exchange, the circulating working medium in the medium-pressure liquid state enters the second ejector 10, mixes with the above-mentioned gas phase and then enters the second gas-liquid separator 11. The liquid phase enters the low-temperature heat exchanger after passing through the first throttle valve 18 and the second throttle valve 19, evaporates after exchanging heat with the liquid heat storage loop in the low-temperature heat storage loop, and enters the first ejector 6 as the ejecting medium, while the gas phase enters the screw compressor through the fourth stop valve 12, thus forming a cycle. In the high-temperature heat storage loop, the heat storage fluid in the low-temperature chamber of the high-temperature heat storage tank group 3 enters the high-temperature chamber after heat exchange in the high-temperature heat exchanger 2. When high-temperature industrial waste heat is input from the outside, the first stop valve 4 can be opened, and the heat storage fluid in the low-temperature chamber can enter the high-temperature chamber after absorbing high-temperature industrial waste heat in the high-temperature waste heat exchanger 28 through the first stop valve 4. In the low-temperature heat storage loop, the fluid in the high-temperature chamber of the low-temperature No. 2 heat storage tank group 25 enters the low-temperature chamber after releasing heat in the low-temperature heat exchanger 20. When the daytime temperature is higher than the set value or low-temperature industrial waste heat is input from the outside, the third stop valve 26 can be opened, so that the fluid in the low-temperature chamber passes through the third stop valve 26 and returns to the high-temperature chamber after absorbing heat in the low-temperature No. 2 heat exchanger 27, thus forming a cycle. Under the summer working condition, by adjusting the volume ratio inside the reversible screw machine, the evaporation temperature of the circulating working medium is reduced. At this time, the fluid in the low-temperature chamber of the low-temperature No. 2 heat storage tank group 25 can be used as a cold source for short-distance cooling in the enterprise park.

[0048] Embodiment 2: Energy storage process without air extraction and make-up

[0049] As Figure 3As shown, during the non-air-extraction energy storage process, the left and right ports of the first three-way valve 5 and the fourth three-way valve 9, the right and lower ports of the third three-way valve 8, the right and upper ports of the seventh three-way valve 16, the left and lower ports of the second three-way valve 21, the eighth three-way valve 32, and the ninth three-way valve 29, and the left and upper ports of the fifth three-way valve 13 are connected. The fourth stop valve 12 is closed, and the reversible screw machine 1 is switched to the screw compressor state. In this embodiment, the intermediate air-extraction and gas-supplying branch is closed, and there is no input or output of medium-temperature heat. Similar to Embodiment 1, the circulating working fluid is compressed by the screw compressor, condensed in the high-temperature heat exchanger 2, and then enters the first ejector 6 as the working medium. After mixing with the entrainment fluid, it enters the first gas-liquid separator 7. Then, since the intermediate air-extraction and gas-supplying branch is closed, the separated liquid phase is throttled and cooled by the second throttle valve 19, absorbs heat and evaporates in the low-temperature heat exchanger 20, and enters the first ejector 6 as the entrainment fluid. The gas phase directly enters the compressor inlet pipeline through the third three-way valve 8, thus forming a cycle. The operation modes of the low-temperature heat storage loop and the high-temperature heat storage loop in this embodiment are the same as those in Embodiment 1.

[0050] Embodiment 3: Gas-supplying Energy Storage Process

[0051] See Figure 4 , during the gas-supplying energy storage process, the left and right ports of the first three-way valve 5, the fourth three-way valve 9, the sixth three-way valve 14, and the seventh three-way valve 16, the right and lower ports of the third three-way valve 8, the left and lower ports of the second three-way valve 21, the eighth three-way valve 32, and the ninth three-way valve 29, and the left and upper ports of the fifth three-way valve 13 are connected. The fourth stop valve 12 is closed, and the reversible screw machine 1 is switched to the screw compressor state. In this embodiment, the intermediate air-extraction and gas-supplying branch is in the gas-supplying state, and medium-temperature industrial waste heat or new energy power generation waste heat needs to be input. Similar to Embodiment 1, the circulating working fluid is compressed by the screw compressor, condensed in the high-temperature heat exchanger 2, and then enters the first ejector 6 as the working medium. After mixing with the entrainment fluid, it enters the first gas-liquid separator 7. Then, the intermediate gas-supplying port of the screw compressor is adjusted to a position matching the gas-supplying pressure. Part of the gas phase in the separator enters the intermediate air-extraction and gas-supplying branch through the fourth three-way valve 9, absorbs medium-temperature heat in the medium-temperature heat exchanger 20, and is then supplemented into the compressor from the gas-supplying port of the screw compressor. The other part directly enters the compressor inlet pipeline through the third three-way valve 8. The liquid phase is throttled and cooled by the second throttle valve 19, absorbs heat and evaporates in the low-temperature heat exchanger 20, and enters the first ejector 6 as the entrainment fluid. The operation modes of the low-temperature heat storage loop and the high-temperature heat storage loop in this embodiment are the same as those in Embodiment 1.

[0052] Embodiment 4: Air-Extraction Heat Supply and Energy Release Process

[0053] As Figure 5As shown, during the air extraction and heat supply energy release process, the left and right ports of the first three-way valve 5, the third three-way valve 8, and the seventh three-way valve 16 are connected, the right and lower ports of the second three-way valve 21 and the fourth three-way valve 9, the upper and lower ports of the fifth three-way valve 13, the left and upper ports of the eighth three-way valve 32 and the ninth three-way valve 29, and the sixth three-way valve 14 is fully opened. The fourth stop valve 12 is closed, and the reversible screw compressor 1 is switched to the screw expander state. In this embodiment, the intermediate air extraction and make-up air branch is in the air extraction state and can output medium-temperature heat for long-distance heat supply. After the circulating working fluid expands through the screw expander, it passes through the second three-way valve 21 and exchanges heat with the heat storage fluid in the low-temperature heat storage loop in the low-temperature heat exchanger 20, and then enters the energy release branch of the system through the fifth three-way valve 13. After being boosted by the first working fluid pump 30 to reach the intermediate pressure level, it comes to the sixth three-way valve 14. On the other side, the intermediate air extraction port of the screw expander is adjusted to a position matching the air extraction pressure. The extracted medium-pressure superheated gas flows out in an unsaturated state after releasing part of the medium-temperature heat in the medium-temperature heat exchanger 15. This two-phase working fluid is mixed and regenerated with the above-mentioned medium-pressure working fluid through the sixth three-way valve 14, and then enters the high-temperature heat exchanger 2 after being boosted by the second working fluid pump 31. It absorbs the phase change latent heat by exchanging heat with the nitrate phase change material in its latent heat section and absorbs the sensible heat by exchanging heat with the high-temperature heat storage fluid in the high-temperature circulation loop in its sensible heat section. After completing the heat exchange, it enters the screw expander to expand in a superheated gas state and outputs technical work, thus forming a cycle. In the high-temperature heat storage loop, the heat storage fluid in the high-temperature cavity of the high-temperature heat storage tank group 3 enters the low-temperature cavity after releasing heat through the high-temperature heat exchanger. When high-temperature industrial waste heat is input from the outside, the first stop valve 4 is opened, and the heat storage fluid in the low-temperature cavity enters the high-temperature cavity after absorbing heat in the high-temperature waste heat exchanger 28 through the first stop valve 4. In the low-temperature heat storage loop, the fluid in the low-temperature cavity of the low-temperature No. 1 heat storage tank group 22 enters the high-temperature cavity after releasing heat through the low-temperature heat exchanger 20. When the night temperature is lower than the set value, the third stop valve 23 is opened, and the fluid in the high-temperature cavity returns to the low-temperature cavity after releasing heat in the low-temperature No. 2 heat exchanger 24 through the third stop valve 23, thus forming a cycle. Under the winter working condition, by adjusting the volume ratio inside the reversible screw compressor, the condensation temperature of the circulating working fluid is increased. At this time, the fluid in the high-temperature cavity of the low-temperature No. 1 heat storage tank group 22 can be used as a heat source for short-distance heat supply within the enterprise park.

[0054] Embodiment 5: Energy release process without air extraction and make-up air

[0055] As Figure 6As shown, during the non-extraction and non-supplementation energy release process, the left and right ports of the first three-way valve 5, the third three-way valve 8, and the sixth three-way valve 14 are connected, the right and lower ports of the second three-way valve 21 and the fourth three-way valve 9, the right and upper ports of the seventh three-way valve 16, the upper and lower ports of the fifth three-way valve 13, and the left and upper ports of the eighth three-way valve 32 and the ninth three-way valve 29 are connected. The fourth stop valve 12 is closed, and the reversible screw machine 1 is switched to the screw expander state. In this embodiment, the intermediate extraction and supplementation branch is in the non-extraction and non-supplementation state, and medium-temperature industrial waste heat or new energy power generation waste heat needs to be input. Similar to Embodiment 4, the circulating working fluid expands through the screw expander and then enters the low-temperature heat exchanger 20 to release heat. After that, it is boosted to the intermediate pressure level by the fifth three-way valve 13 and the first working fluid pump 30. Then, the circulating working fluid enters the medium-temperature heat exchanger 15 through the sixth three-way valve 16 to absorb heat to the saturated liquid state, and after being boosted by the second working fluid pump 31, it enters the high-temperature heat exchanger 2. It absorbs heat in the latent heat section and the sensible heat section respectively and then enters the screw expander in the superheated gas state to expand and output technical work, thus forming a cycle. The operation modes of the low-temperature heat storage loop and the high-temperature heat storage loop in this embodiment are the same as those in Embodiment 4.

[0056] Embodiment 6: Extraction and Regeneration Energy Release Process

[0057] As Figure 7 shown, during the extraction and regeneration energy release process, the left and right ports of the first three-way valve 5 and the third three-way valve 8 are connected, the right and lower ports of the second three-way valve 21 and the fourth three-way valve 9, the upper and lower ports of the fifth three-way valve 13, and the left and upper ports of the eighth three-way valve 32, the ninth three-way valve 29, and the seventh three-way valve 16 are connected. The sixth three-way valve 14 is fully open. The fourth stop valve 12 is closed, and the reversible screw machine 1 is switched to the screw expander state. In this embodiment, the intermediate extraction and supplementation branch is in the extraction and regeneration state, and there is no input or output of medium-temperature heat. Similar to Embodiment 4, the circulating working fluid expands through the screw expander and then enters the low-temperature heat exchanger 20 to release heat. After that, it is boosted to the intermediate pressure level by the fifth three-way valve 13 and the first working fluid pump 30. Then, the intermediate extraction port of the screw expander is adjusted to a position matching the extraction pressure. The extracted medium-pressure superheated gas passes through the seventh three-way valve 16 and then mixes with the above-mentioned medium-pressure subcooled liquid and is regenerated to the saturated liquid state. After being boosted by the second working fluid pump 31, it enters the high-temperature heat exchanger 2. It absorbs heat in the latent heat section and the sensible heat section respectively and then enters the screw expander in the superheated gas state to expand and output technical work, thus forming a cycle. The operation modes of the low-temperature heat storage loop and the high-temperature heat storage loop in this embodiment are the same as those in Embodiment 4.

[0058] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements 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 application, and should all be included in the protection scope of the present application.

Claims

1. An enterprise-level Carnot battery energy storage system based on a reversible screw machine, characterized in that, include: Working circuit and heat storage circuit; The working circuit comprises a reversible screw machine (1), a high-temperature heat exchanger (2), a low-temperature heat exchanger (20), a three-way valve, an intermediate gas extraction and supply branch, an energy storage branch, and an energy release branch; The heat storage circuit includes a high-temperature heat storage circuit and a low-temperature heat storage circuit; The reversible screw compressor (1) realizes the switching between the compression function and the expansion function by changing the direction of the yin and yang rotors and reversing the suction and exhaust positions, has a variable speed and a variable internal volume ratio, and has multiple air extraction and air supply ports, which can realize intermediate air extraction and intermediate air supply; The high-temperature heat exchanger (2) is connected to the outlet of the working medium of the compression function of the reversible screw machine (1), and comprises a sensible heat exchange section and a latent heat exchange section, wherein the sensible heat exchange section is placed in the phase change material, and the latent heat exchange section performs heat exchange with the liquid phase heat storage working medium in the high-temperature heat storage circuit; A low-temperature heat exchanger (20) is connected to the working medium inlet of the compression function of the reversible screw machine (1), and the internal circulating working medium exchanges heat with the liquid phase heat storage working medium in the low-temperature heat storage loop; The energy storage branch includes an ejector, the working medium of the ejector is a high-pressure liquid phase, the ejection fluid is a low-pressure gas phase, and the nozzle position can be adjusted according to the working pressure; the intermediate air extraction and supply branch includes a medium-temperature heat exchanger (15), and the intermediate air extraction and supply branch is connected to the air extraction and supply orifice of the reversible screw machine (1); the energy release branch includes a working fluid pump, and each working fluid pump is respectively connected to the high-temperature heat exchanger (2), the medium-temperature heat exchanger (15) and the low-temperature heat exchanger (20) through a three-way valve; The energy storage branch is connected to the high-temperature heat exchanger (2), the low-temperature heat exchanger (20), the reversible screw machine (1), and the intermediate air extraction and supply branch through a three-way valve, and the intermediate air extraction and supply branch is also connected to the working fluid pump of the energy release branch through a three-way valve; The energy storage branch comprises a first injector (6), a first gas-liquid separator (7), a third three-way valve (8), a second injector (10), a second gas-liquid separator (11), a fourth stop valve (12), a first throttle valve (18), a second throttle valve (19), and a fifth three-way valve (13), wherein the injection medium inlet of the first injector (6) is connected to the low-temperature heat exchanger (20) via the left and lower ports of the second three-way valve (21), the working medium inlet is connected to the high-temperature heat exchanger (2) via the left and right ports of the first three-way valve (5), the mixed medium outlet is connected to the first gas-liquid separator (7), and the liquid phase outlet of the first gas-liquid separator (7) is connected to the first throttle valve (18). Between the second throttle valve (19), the gas phase outlet is connected to the second ejector (10) ejection medium inlet through the left and right ports of the third three-way valve (8), the lower port of the third three-way valve (8) is connected to the compression function inlet pipeline of the reversible screw machine (1), the working medium inlet of the second ejector (10) is connected to the intermediate extraction and replenishment gas branch through the left and lower ports of the fourth three-way valve (9), the mixed medium outlet is connected to the second gas-liquid separator (11), the gas phase outlet of the second gas-liquid separator (11) is connected to the compression function inlet pipeline of the reversible screw machine (1) through the fourth stop valve (12), and the liquid phase outlet is connected to the low-temperature heat exchanger (20) through the first throttle valve (18) and the second throttle valve (19).

2. The enterprise-level Carnot battery energy storage system based on a reversible screw machine according to claim 1, characterized in that, The high-temperature heat storage loop includes a high-temperature heat storage tank group (3), a first stop valve (4), and a high-temperature waste heat heat exchanger (28). Among them, the first stop valve (4) and the high-temperature waste heat heat exchanger (28) are arranged between the high-temperature heat storage tank group (3). The high-temperature heat storage tank group (3) is two heat-insulated heat storage tanks or a heat storage tank with multiple heat-insulated cavities.

3. The enterprise-level Carnot battery energy storage system based on a reversible screw machine according to claim 1, characterized in that, The low-temperature heat storage loop includes a low-temperature first heat storage tank group (22), a low-temperature second heat storage tank group (25), an eighth three-way valve (32), a ninth three-way valve (29), a second stop valve (23), a third stop valve (26), a low-temperature first heat exchanger (24), and a low-temperature second heat exchanger (27). Among them, the second stop valve (23) and the low-temperature first heat exchanger (24) are arranged between the low-temperature first heat storage tank group (22). The third stop valve (26) and the low-temperature second heat exchanger (27) are arranged between the low-temperature second heat storage tank group (25). The eighth three-way valve (32) and the ninth three-way valve (29) are both connected to the low-temperature heat exchanger (20), the low-temperature first heat storage tank group (22), and the low-temperature second heat storage tank group (25). The low-temperature first heat storage tank group (22) and the low-temperature second heat storage tank group (25) are two heat-insulated heat storage tanks or a heat storage tank with multiple heat-insulated cavities.

4. The enterprise-level Carnot battery energy storage system based on a reversible screw machine according to claim 1, characterized in that, The energy release branch includes a first working fluid pump (30), a sixth three-way valve (14), and a second working fluid pump (31). Among them, the first working fluid pump (30) is connected to the low-temperature heat exchanger (20) through the upper and lower ports of the fifth three-way valve (13). The outlet of the first working fluid pump (30) is connected to the inlet of the second working fluid pump (31) through the right and upper ports of the sixth three-way valve (14). The left port of the sixth three-way valve (14) is connected to the medium-temperature heat exchanger (15). The second working fluid pump (31) is connected to the high-temperature heat exchanger (2) through the left and lower ports of the first three-way valve (5).

5. The enterprise-level Carnot battery energy storage system based on a reversible screw machine according to claim 4, characterized in that, The intermediate air replenishment branch includes a fourth three-way valve (9), a sixth three-way valve (14), a medium-temperature heat exchanger (15), and a seventh three-way valve (16). Among them, the left port of the seventh three-way valve (16) is connected to the air extraction and replenishment orifice of the reversible screw compressor (1), and the upper port is connected to the inlet of the second working fluid pump (31). The external heat source of the medium-temperature heat exchanger (15) includes medium-temperature industrial waste heat and new energy power generation waste heat, and the external cold source includes long-distance heating demand. The right port of the fourth three-way valve (9) is connected between the first gas-liquid separator (7) and the third three-way valve (8).

6. An operation method of the enterprise-level Carnot battery energy storage system based on a reversible screw machine according to claim 5, characterized in that, Including the following steps: Energy storage process operation: During the off-peak electricity period at night, the system enters the energy storage state by adjusting the first three-way valve (5), the second three-way valve (21), and the fifth three-way valve (13). At this time, the circulating working fluid is compressed by the reversible screw compressor (1), releases heat and condenses in the high-temperature heat exchanger (2), and then enters the energy release branch. The high-pressure condensate recovers part of the pressure energy through the ejector in the energy release branch by ejecting the low-pressure gas, and after absorbing heat and evaporating in the low-temperature heat exchanger (20), it is boosted by the ejector and finally enters the reversible screw compressor (1) to form a cycle. Among them, during the energy storage process, the intermediate extraction and makeup air branch has three operating states: extraction for heat supply, makeup air for heat compensation, and no extraction and makeup air. When medium-temperature industrial waste heat and new energy power generation waste heat are input, it is in the makeup air for heat compensation operating state. When supplying heat to a remote area, it is in the extraction for heat supply operating state. When there is no input or output, it is in the no extraction and makeup air operating state. The switching of the three operating states of the intermediate makeup air circuit during the energy storage process is achieved by adjusting the flow states of the third three-way valve (8), the fourth three-way valve (9), and the fourth stop valve (12) and the extraction and makeup air orifices. Energy release process operation method: During the peak electricity period during the day, the system enters the energy release state by adjusting the first three-way valve (5), the second three-way valve (21), and the fifth three-way valve (13). At this time, the circulating working fluid expands through the reversible screw compressor (1) to output technical work, releases heat and condenses in the low-temperature heat exchanger (20), and then enters the energy release branch. After being compressed by the working fluid pump, the high-pressure liquid evaporates and superheats in the high-temperature heat exchanger (2) and finally returns to the reversible screw compressor (1) to form a cycle. Among them, during the energy release process, the intermediate extraction and makeup air branch has three operating states: extraction for heat supply, extraction for heat regeneration, and no extraction. When medium-temperature industrial waste heat and new energy power generation waste heat are input, it is in the no extraction state. When supplying heat to a remote area, it is in the extraction for heat supply operating state. When there is no input or output, it is in the extraction for heat regeneration state. The switching of the three operating states of the intermediate makeup air circuit during the energy release process is achieved by adjusting the flow states of the sixth three-way valve (14) and the seventh three-way valve (16) and the extraction and makeup air orifices.

7. The operation method according to claim 6, characterized in that, It also includes the operation of the high-temperature heat storage circuit: The high-temperature heat storage tank group (3) includes two cavities, a high-temperature cavity and a low-temperature cavity. During the energy storage process, the heat storage fluid in the low-temperature cavity absorbs heat through the high-temperature heat exchanger (2) and enters the high-temperature cavity. During the energy release process, the heat storage fluid in the high-temperature cavity releases heat through the high-temperature heat exchanger and enters the low-temperature cavity. When high-temperature industrial waste heat is input from the outside, the heat storage fluid in the low-temperature cavity enters the high-temperature cavity through the high-temperature waste heat exchanger (28) and the first stop valve (4).

8. The operation method according to claim 6, characterized in that, It also includes the operation of the low-temperature heat storage loop: The low-temperature heat storage tank group 1 (22) and the low-temperature heat storage tank group 2 (25) each include two cavities, namely a high-temperature cavity and a low-temperature cavity. During the energy storage process, the fluid in the high-temperature cavity of the low-temperature heat storage tank group 2 (25) enters the low-temperature cavity after releasing heat through the low-temperature heat exchanger (20), and then passes through the third shut-off valve (26) and returns to the high-temperature cavity after absorbing the heat of the daytime ambient environment or low-temperature industrial waste heat in the low-temperature heat exchanger 2 (27). By adjusting the volume ratio inside the reversible screw compressor, the cooling capacity is used for short-distance cooling within the park in summer conditions. During the energy release process, the fluid in the low-temperature cavity of the low-temperature heat storage tank group 1 (22) enters the high-temperature cavity after absorbing heat through the low-temperature heat exchanger (20), and then passes through the second shut-off valve (23) and absorbs the cold of the nighttime ambient environment in the low-temperature heat exchanger 1 (24). By adjusting the volume ratio inside the reversible screw compressor, this heat is used for short-distance heating within the park in winter conditions.

Images