Liquid carbon dioxide energy storage system based on heat pump energy storage system

Abstract

The invention relates to the technical field of energy storage, in particular to a liquid carbon dioxide energy storage system based on a heat pump energy storage system, which comprises a wind power plant, a liquid carbon dioxide storage module connected with the wind power plant, a heat pump energy storage module connected with the wind power plant, and an energy release module connected with the liquid carbon dioxide storage module and the heat pump energy storage module. In the low-load period of the power grid, surplus electric energy of the wind power plant is converted into pressure energy, heat energy and cold energy to be stored; and in the high-load period of the power grid, the stored pressure energy, heat energy and cold energy are converted into electric energy to be transmitted to the power grid. The utilization rate of renewable energy sources is improved, the phenomenon of wind curtailment is reduced, and the impact of renewable energy source grid connection on a power grid is reduced.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technology, and in particular to a liquid carbon dioxide energy storage system based on a heat pump energy storage system. Background Art

[0002] In recent years, my country has vigorously developed renewable energy, and the installed capacity of renewable energy has continued to increase. Due to the intermittent and volatile characteristics of renewable energy, its large-scale grid connection has brought huge challenges to the safe and stable operation of the power grid. Energy storage systems can decouple the power generated by renewable energy from time, improve the stability of renewable energy, reduce the impact of renewable energy grid connection on the power grid, and improve the utilization rate of renewable energy.

[0003] The heat pump energy storage system is an energy storage technology developed based on heat pump cycle technology and thermal energy storage technology. It uses a heat pump cycle to convert the electricity from new energy sources that cannot be connected to the grid into heat energy and cold energy during low-load periods of the power grid and store it in a heat storage medium to achieve energy storage. During high-load periods of the power grid, the stored cold energy and heat energy are converted into electrical energy and provided to the power grid to achieve energy release. Because it uses thermal energy storage to store energy, compared with other energy storage methods, it has the advantages of high energy storage density, no geographical restrictions, and flexible application.

[0004] However, the heat pump energy storage system currently proposed does not make effective use of the stored cold energy, and in the energy release stage, a compressor / pump is still required to transport the working fluid, which to a certain extent reduces the electric energy delivered to the power grid in the energy release stage of the system. The present invention uses the cold energy stored in the energy storage stage to condense the turbine exhaust in the energy release stage, reducing the turbine exhaust pressure and improving the turbine's working capacity. In the energy storage stage, the liquid carbon dioxide in the low-pressure storage tank is pumped into the high-pressure storage tank using the surplus electric energy of the power grid to provide the working fluid for the energy release stage. Therefore, the cycle does not require pumps / compressors or the like to transport the working fluid in the energy release stage. In addition, since the carbon dioxide in the system proposed in the present invention is stored in a liquid state in the storage tank, compared with other energy storage methods, it has the advantages of high energy storage density, no geographical restrictions, and flexible application. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above-mentioned problem that when the grid load is not high, the electric energy generated by the wind farm cannot be fully connected to the grid, and the surplus electric energy cannot be stored efficiently, the present invention is proposed.

[0007] Therefore, an object of the present invention is to provide a liquid carbon dioxide energy storage system based on a heat pump energy storage system.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions: a liquid carbon dioxide energy storage system based on a heat pump energy storage system, comprising a wind farm; a liquid carbon dioxide storage module connected to the wind farm, the liquid carbon dioxide storage module comprising a low-pressure storage tank, a carbon dioxide pump, and a high-pressure storage tank; a heat pump energy storage module connected to the wind farm, the heat pump energy storage module comprising a compressor, a thermal oil cooling tank, a first heat exchanger, a thermal oil hot tank, a first heat regenerator, a cooler, an expander, a refrigerant hot tank, a second heat exchanger, and a refrigerant cold tank; and a liquid An energy release module connected to the liquid carbon dioxide storage module and the heat pump energy storage module, the energy release module includes a second regenerator, a third heat exchanger, a turbine, and a condenser; the liquid carbon dioxide storage module is used to convert the electric energy that the wind farm cannot be connected to the grid into the pressure energy of liquid carbon dioxide for storage, the heat pump energy storage module is used to convert the electric energy that the wind farm cannot be connected to the grid into the thermal energy of the heat transfer oil and the cold energy of the refrigerant for storage, and the energy release module is used to utilize the pressure energy of liquid carbon dioxide, the thermal energy of the heat transfer oil and the cold energy of the refrigerant to generate electricity and provide it to the grid during high-load periods of the power grid.

[0009] As a preferred solution of the liquid carbon dioxide energy storage system based on the heat pump energy storage system described in the present invention, the wind farm is connected to two motors, one motor is connected to the liquid carbon dioxide storage module, and the other motor is connected to the heat pump energy storage module, and the motors use the surplus electric energy of the wind farm to drive each module.

[0010] As a preferred solution of the liquid carbon dioxide energy storage system based on the heat pump energy storage system described in the present invention, the output end of the low-pressure storage tank is connected to the input end of the high-pressure storage tank, and the liquid carbon dioxide transportation power is provided between the low-pressure storage tank and the high-pressure storage tank through a carbon dioxide pump, and the carbon dioxide pump is driven by an electric motor.

[0011] As a preferred solution of the liquid carbon dioxide energy storage system based on the heat pump energy storage system described in the present invention, the first heat exchanger, the second heat exchanger, the third heat exchanger, the first heat regenerator and the second heat regenerator are all provided with a cold side and a hot side, and the cold side and the hot side are respectively provided with an input end and an output end.

[0012] As a preferred solution of the liquid carbon dioxide energy storage system based on the heat pump energy storage system described in the present invention, wherein: the hot side input end of the first heat exchanger is connected to the compressor outlet, the hot side output end of the first heat exchanger is connected to the hot side input end of the first heat regenerator, the cold side input end of the first heat exchanger is connected to the outlet of the thermal oil cold tank, and the cold side output end of the first heat exchanger is connected to the inlet of the thermal oil hot tank.

[0013] As a preferred solution of the liquid carbon dioxide energy storage system based on the heat pump energy storage system described in the present invention, the cold side output end of the first heat regenerator is connected to the inlet of the compressor, the cold side input end of the first heat regenerator is connected to the cold side of the second heat exchanger, and the hot side output end of the first heat regenerator is connected to the cooler.

[0014] As a preferred solution of the liquid carbon dioxide energy storage system based on the heat pump energy storage system described in the present invention, the output end of the cooler is connected to the input end of the expander, the output end of the expander is connected to the cold side input end of the second heat exchanger, the hot side input end of the second heat exchanger is connected to the refrigerant hot tank outlet and the hot side output end of the second heat exchanger and the refrigerant cold tank inlet.

[0015] As a preferred solution of the liquid carbon dioxide energy storage system based on the heat pump energy storage system described in the present invention, the hot side input end of the second heat regenerator is connected to the turbine outlet, the cold side input end of the second heat regenerator is connected to the high-pressure storage tank outlet, the cold side output end of the second heat regenerator is connected to the cold side of the third heat exchanger, and the hot side output end of the second heat regenerator is connected to the condenser.

[0016] As a preferred solution of the liquid carbon dioxide energy storage system based on the heat pump energy storage system described in the present invention, the turbine exhaust is connected to the hot side input end of the second regenerator, and the turbine is connected to a generator for generating electricity.

[0017] Beneficial effects of the present invention: Through the above structure, the present invention converts the surplus electric energy of the wind farm into pressure energy, heat energy and cold energy for storage during the period of low load of the power grid; during the period of high load of the power grid, the stored pressure energy, heat energy and cold energy are converted into electric energy and transmitted to the power grid. The utilization rate of renewable energy is improved, the occurrence of "wind abandonment" phenomenon is reduced, and the impact on the power grid is reduced. The present invention rationally utilizes the heat energy and cold energy stored in the heat pump energy storage module in the energy storage stage, rationally utilizes the heat energy stored in the energy storage stage to heat the working fluid of the energy release module, increases the turbine inlet temperature of the energy release module, and improves the output and efficiency of the system. The cold energy stored in the energy storage stage is used to condense the turbine exhaust of the energy release module into liquid, which reduces the turbine exhaust pressure, improves the output and efficiency of the system, and realizes the liquid storage of low-pressure carbon dioxide, reduces the floor space occupied by the energy storage system, and saves the floor space cost of the energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0019] Figure 1This is an overall schematic diagram of a liquid carbon dioxide energy storage system based on a heat pump energy storage system. DETAILED DESCRIPTION

[0020] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0023] Secondly, the present invention is described in detail with reference to the schematic diagram. When describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0024] Example 1

[0025] Reference Figure 1 , is an embodiment of the present invention, which provides a liquid carbon dioxide energy storage system based on a heat pump energy storage system, including a wind farm F; a liquid carbon dioxide storage module 100 connected to the wind farm F, the liquid carbon dioxide storage module 100 including a low-pressure storage tank 101, a carbon dioxide pump 102, and a high-pressure storage tank 103; a heat pump energy storage module 200 connected to the wind farm F, the heat pump energy storage module 200 including a compressor 201, a thermal oil cold tank 202, a first heat exchanger 203, a thermal oil hot tank 204, a first regenerator 205, a cooler 206, an expander 207, a refrigerant hot tank 208, a second heat exchanger 209, and a refrigerant cold tank 210; an energy release module 300 connected to the liquid carbon dioxide storage module 100 and the heat pump energy storage module 200, including a second regenerator 301, a third heat exchanger 302, a turbine 303, and a condenser 304;

[0026] The system works in two phases: energy storage phase and energy release phase;

[0027] Energy storage stage: When the power grid is in a low-load period, the wind farm has surplus electricity that cannot be connected to the grid. The energy storage system is in the energy storage stage. The electricity that the wind farm F cannot connect to the grid is used to drive two motors M. The two motors M provide the required power for the liquid carbon dioxide storage module 100 and the heat pump energy storage module 200 respectively. The liquid carbon dioxide storage module 100 is used to convert the electricity that the wind farm F cannot connect to the grid into the pressure energy of liquid carbon dioxide for storage, and the heat pump energy storage module 200 is used to convert the electricity that the wind farm F cannot connect to the grid into the heat energy of the heat transfer oil and the cold energy of the refrigerant for storage.

[0028] The specific working process is: when the power grid is in a low-load state, the surplus electricity of the wind farm F is used to drive the carbon dioxide pump 102 to pump the liquid carbon dioxide flowing out of the low-pressure storage tank 101 to the high-pressure storage tank 103, thereby realizing the conversion of electrical energy into pressure energy storage.

[0029] Surplus electric energy from wind farm F is used to drive compressor 201 to compress carbon dioxide to a high-temperature and high-pressure state. The high-temperature and high-pressure carbon dioxide at the outlet of compressor 201 exchanges heat with the low-temperature thermal oil stored in the thermal oil cold tank 202 in the first heat exchanger 203. The high-temperature and high-pressure carbon dioxide transfers heat to the thermal oil. The thermal oil that has completed the heat exchange becomes high-temperature thermal oil and is stored in the thermal oil hot tank 204, thereby realizing the conversion of electrical energy into thermal energy storage.

[0030] The high-pressure carbon dioxide that has completed heat exchange enters the first regenerator 205 for heat recovery and transfers heat to the low-pressure carbon dioxide flowing out of the cold side of the second heat exchanger 209 to improve system efficiency. The high-pressure carbon dioxide that has completed heat recovery enters the cooler 206 and is cooled to room temperature by water. The cooled high-pressure carbon dioxide enters the expander 207 for expansion and work. In the present invention, the motor M, the compressor 201, and the expander 207 are coaxial. The expander 207 provides part of the energy for driving the compressor 201, and the remaining energy for driving the compressor 201 is provided by the motor M. The low-temperature and low-pressure carbon dioxide that has completed expansion and work exchanges heat with the refrigerant stored in the refrigerant hot tank 208 in the second heat exchanger 209, and the cold energy it carries is transferred to the refrigerant. The refrigerant that has completed heat exchange is stored in the refrigerant cold tank 210. The low-pressure carbon dioxide that has completed heat exchange enters the first regenerator 205 and is heated by the high-pressure carbon dioxide flowing out of the first heat exchanger 203. The heated low-pressure carbon dioxide enters the compressor 201 and is compressed to a high-temperature and high-pressure state. At this point, the energy storage process of the heat pump energy storage module 200 is completed, and the surplus electric energy of the power grid is converted into the heat energy of the heat transfer oil and the cold energy of the refrigerant for storage.

[0031] Energy release stage: When the power grid is in a high load period, the energy storage system is in the energy release stage.

[0032] The specific working process is: when the power grid is in a high-load period, the high-pressure liquid carbon dioxide stored in the high-pressure storage tank 103 exchanges heat with the exhaust gas of the turbine 303 in the second regenerator 301, and the high-pressure liquid carbon dioxide absorbs the heat of the exhaust gas of the turbine 303 to become a high-pressure carbon dioxide gas with a certain degree of superheat. Then, the high-pressure carbon dioxide gas exchanges heat with the high-temperature thermal oil stored in the thermal oil hot tank 204 in the third heat exchanger 302, and the high-temperature thermal oil transfers the heat it carries to the high-pressure carbon dioxide gas. The high-temperature thermal oil becomes low-temperature thermal oil and is stored in the thermal oil cold tank 202. The high-pressure carbon dioxide gas that completes the heat exchange becomes high-temperature and high-pressure carbon dioxide gas, and then the high-temperature and high-pressure carbon dioxide gas enters the turbine 303 to do work, driving the generator G to generate electrical energy for transmission to the power grid. The exhaust gas of the turbine 303 that has completed work in the turbine 303 enters the second regenerator 301, and transfers its own heat energy to the high-pressure liquid carbon dioxide that enters the second regenerator 301 from the high-pressure storage tank 103. The exhaust gas of the turbine 303 that has completed heat exchange in the second regenerator 301 enters the condenser 304, and the refrigerant stored in the refrigerant cold tank 210 enters the condenser. The exhaust gas of the turbine 303 is condensed into liquid by using the cold energy of the refrigerant. The low-pressure liquid carbon dioxide is stored in the low-pressure storage tank 101, and the refrigerant is stored in the refrigerant hot tank 208. During the high-load period of the power grid, the energy release module 300 converts the pressure energy stored in the liquid carbon dioxide storage module 100 and the heat energy and cold energy stored in the heat pump energy storage module 200 in the energy storage stage into electrical energy and transmits them to the power grid through the above working process.

[0033] Table 1 is a table of key node status parameters of the present invention:

[0034] Temperature / ℃ Pressure / MPa Flow rate / kg / s Compressor 201 inlet 250 1 10 Compressor 201 outlet 647 18 10 Expander 207 inlet 20 18 10 Expander 207 outlet -40 1 10 Turbine 303 entrance 639 25 9.34 Turbine 303 outlet 404 3 9.34

[0035] Table 2 is a table of system performance data of the present invention:

[0036] project unit Numeric Energy storage time Hour 10 Energy release time Hour 10 Compressor 201 power MW 4.41 Expander 207 power MW 0.24 Motor power MW 4.19 Carbon dioxide pump 102 MW 0.21 Turbine 303 power MW 2.48 Charge capacity MW·h 44 Discharge MW·h 24.8 Round trip efficiency ％ 56.4％

[0037] It can be seen from the above table that the charging capacity of the present invention is 44MW·h, the discharging capacity is 24.8MW·h, and the round-trip efficiency is 56.4%. Compared with the heat pump energy storage system in the prior art, the present invention has the advantages of large charging and discharging capacity and high round-trip efficiency. In addition, in the energy release stage of the present invention, the carbon dioxide working fluid is stored in a storage tank in liquid form, which has the advantage of large energy storage density. And the present invention uses a carbon dioxide pump to convert low-pressure liquid carbon dioxide working fluid into high-pressure liquid carbon dioxide working fluid in the energy storage stage to provide pressure energy for the working fluid in the energy release stage. The power of the carbon dioxide pump 102 is only 0.21MW. Compared with the prior art solution of using a compressor to provide pressure energy for the working fluid in the energy release stage, the use of a working fluid pump has the advantages of high system stability, low cost and high efficiency. In summary, the present invention has the advantages of large charging and discharging capacity, high round-trip efficiency, large energy storage density, high system stability and low cost.

[0038] Importantly, it should be noted that the construction and arrangement of the present application shown in a plurality of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values ​​(e.g., temperature, pressure, etc.), installation arrangement, use of materials, color, directional changes, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, the element shown as integrally formed can be composed of multiple parts or elements, the position of the element can be inverted or otherwise changed, and the nature or number or position of the discrete element can be changed or changed. Therefore, all such modifications are intended to be included in the scope of the present invention. The order or sequence of any process or method steps can be changed or reordered according to alternative embodiments. In the claims, any "device plus function" clause is intended to cover the structure of performing the function described herein, and is not only structurally equivalent but also equivalent structure. Without departing from the scope of the present invention, other replacements, modifications, changes and omissions can be made in the design, operating conditions and arrangement of the exemplary embodiments. Therefore, the invention is not limited to a specific embodiment, but extends to several modifications still falling within the scope of the appended claims.

[0039] Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention) may not be described.

[0040] It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

[0041] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A liquid carbon dioxide energy storage system based on a heat pump energy storage system, Features: Including wind farms (F); A liquid carbon dioxide storage module (100) connected to a wind farm (F), the liquid carbon dioxide storage module (100) comprising a low-pressure storage tank (101), a carbon dioxide pump (102), and a high-pressure storage tank (103); A heat pump energy storage module (200) connected to a wind farm (F), comprising a compressor (201), a heat transfer oil cold tank (202), a first heat exchanger (203), a heat transfer oil hot tank (204), a first heat regenerator (205), a cooler (206), an expander (207), a refrigerant hot tank (208), a second heat exchanger (209), and a refrigerant cold tank (210); An energy release module (300) connected to the liquid carbon dioxide storage module (100) and the heat pump energy storage module (200), comprising a second regenerator (301), a third heat exchanger (302), a turbine (303), and a condenser (304); The liquid carbon dioxide storage module (100) is used to convert the electric energy of the wind farm (F) that cannot be connected to the grid into the pressure energy of liquid carbon dioxide for storage, the heat pump energy storage module (200) is used to convert the electric energy of the wind farm (F) that cannot be connected to the grid into the heat energy of heat transfer oil and the cold energy of refrigerant for storage, and the energy release module (300) generates electricity using the pressure energy of liquid carbon dioxide, the heat energy of heat transfer oil and the cold energy of refrigerant.

2. The liquid carbon dioxide energy storage system based on the heat pump energy storage system according to claim 1, Features: The wind farm (F) is connected to two motors (M), one motor (M) is connected to a liquid carbon dioxide storage module, and the other motor (M) is connected to a heat pump energy storage module (200), and the motor (M) uses surplus electric energy of the wind farm (F) to drive each module.

3. The liquid carbon dioxide energy storage system based on the heat pump energy storage system according to claim 2, Features: The output end of the low-pressure storage tank (101) is connected to the input end of the high-pressure storage tank (103), and the low-pressure storage tank (101) and the high-pressure storage tank (103) are provided with liquid carbon dioxide transportation power through the carbon dioxide pump (102), and the carbon dioxide pump (102) is driven by an electric motor (M).

4. The liquid carbon dioxide energy storage system based on the heat pump energy storage system according to claim 3, Features: The first heat exchanger (203), the second heat exchanger (209), the third heat exchanger (302), the first heat regenerator (205) and the second heat regenerator (301) are all provided with a cold side and a hot side, and the cold side and the hot side are respectively provided with an input end and an output end.

5. The liquid carbon dioxide energy storage system based on the heat pump energy storage system according to claim 4, Features: The hot side input end of the first heat exchanger (203) is connected to the outlet of the compressor (201), the hot side output end of the first heat exchanger (203) is connected to the hot side input end of the first heat regenerator (205), the cold side input end of the first heat exchanger (203) is connected to the outlet of the heat transfer oil cold tank (202), and the cold side output end of the first heat exchanger (203) is connected to the inlet of the heat transfer oil hot tank (204).

6. The liquid carbon dioxide energy storage system based on the heat pump energy storage system according to claim 5, Features: The cold side output end of the first heat regenerator (205) is connected to the inlet of the compressor (201), the cold side input end of the first heat regenerator (205) is connected to the cold side output end of the second heat exchanger (209), and the hot side output end of the first heat regenerator (205) is connected to the input end of the cooler (206).

7. The liquid carbon dioxide energy storage system based on the heat pump energy storage system according to claim 6, Features: The output end of the cooler (206) is connected to the input end of the expander (207), the output end of the expander (207) is connected to the cold side input end of the second heat exchanger (209), the hot side input end of the second heat exchanger (209) is connected to the outlet of the refrigerant hot tank (208), and the hot side output end of the second heat exchanger (209) is connected to the inlet of the refrigerant cold tank (210).

8. The liquid carbon dioxide energy storage system based on the heat pump energy storage system according to claim 7, Features: The cold side input end of the second heat regenerator (301) is connected to the outlet of the high-pressure storage tank (103), the hot side input end of the second heat regenerator (301) is connected to the outlet of the turbine (303), the cold side output end of the second heat regenerator (301) is connected to the cold side input end of the third heat exchanger (302), and the hot side output end of the second heat regenerator (301) is connected to the inlet of the condenser (304).

9. The liquid carbon dioxide energy storage system based on the heat pump energy storage system according to claim 8, Features: The exhaust gas of the turbine (303) is connected to the hot side input end of the second heat regenerator (301), and the turbine (303) is connected to a generator (G) for generating electricity.

Images