Adiabatic supercritical compressed carbon dioxide energy storage system

Abstract

The invention relates to the technical field of supercritical compressed carbon dioxide energy storage, in particular to an adiabatic supercritical compressed carbon dioxide energy storage system. An expansion unit; during energy storage, the heat storage tank stores compression heat of the supercritical carbon dioxide in the high-temperature and high-pressure state, and the supercritical carbon dioxide in the high-temperature and high-pressure state is cooled to the temperature the same as that of the high-pressure gas storage chamber; during energy release, the heat storage tank heats the low-temperature high-pressure supercritical carbon dioxide discharged from the high-pressure gas storage chamber; the temperature control system adjusts the flow of the cooling medium in the second heat exchanger, controls the inlet temperature of the compressor and further adjusts the inlet temperature of each stage of expansion machine, it is guaranteed that the carbon dioxide temperature of the inlet position of each stage of expansion machine is not lower than the liquefaction critical temperature, and the large-area liquefaction phenomenon does not occur. According to the temperature control system, the phenomenon that in the prior art, when carbon dioxide is at low temperature, carbon dioxide is liquefied, and large-area condensation occurs in the expansion machine can be effectively overcome, and then the operation efficiency and the energy storage efficiency of the system are guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of supercritical compressed carbon dioxide energy storage, and in particular to an adiabatic supercritical compressed carbon dioxide energy storage system. Background Art

[0002] The supercritical compressed carbon dioxide energy storage system is a highly efficient energy storage and conversion technology. Its working principle is: using electricity at low power consumption to drive the compressor to compress low-temperature and low-pressure supercritical carbon dioxide into high-temperature and high-pressure supercritical carbon dioxide and store it; at peak power consumption, the high-temperature and high-pressure supercritical carbon dioxide is sent to the expander, which is used to generate electricity.

[0003] As the core component of the supercritical compressed carbon dioxide energy storage system, the compressor not only needs to consume electrical energy and compress carbon dioxide, but also needs to store the compression heat of carbon dioxide through a heat exchanger and hot water storage water, which is used to heat the carbon dioxide at the inlet of the expander during the energy release stage. Therefore, in the conventional design in this field, in order to ensure high efficiency and low power consumption of the compressor, it is necessary to perform interstage cooling on the working fluid at the outlet of each compressor stage to ensure that the working fluid temperature entering the next stage is low, thereby ensuring efficiency. However, for the supercritical compressed carbon dioxide energy storage system, the medium and low pressure carbon dioxide is above the supercritical pressure (i.e., 7.38MPa). Limited by factors such as equipment processing and manufacturing and the physical properties of carbon dioxide, the supercritical carbon dioxide centrifugal compressor has the characteristics of few stages and low single-stage pressure ratio. This feature results in a lower temperature of the heat of compression obtained after interstage cooling of carbon dioxide, which will reduce the work capacity of the expander.

[0004] In addition, considering the physical properties of carbon dioxide, carbon dioxide liquefaction may occur at lower temperatures, affecting the normal work of the carbon dioxide turbine, and then affecting the normal operation of the expander, which has a greater impact on the working efficiency of the independent supercritical compressed carbon dioxide energy storage system. Therefore, those skilled in the art need a new supercritical compressed carbon dioxide energy storage system to ensure that the temperature of carbon dioxide entering the expander is high, avoid large-scale condensation in the expander, ensure the normal operation of the expander, and ensure the operating efficiency and energy storage efficiency of the supercritical compressed carbon dioxide energy storage system. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problem in the prior art supercritical compressed carbon dioxide energy storage system that carbon dioxide liquefies at low temperatures and condenses over a large area in the expander, thereby affecting the operating efficiency and energy storage efficiency of the system. To this end, the present invention provides an adiabatic supercritical compressed carbon dioxide energy storage system, comprising:

[0006] The compressor unit uses electricity to compress low-temperature and low-pressure supercritical carbon dioxide into high-temperature and high-pressure supercritical carbon dioxide when power is low.

[0007] An expansion unit, which uses high-temperature and high-pressure supercritical carbon dioxide to generate electricity during peak power consumption;

[0008] A high-pressure gas storage chamber, which is respectively connected to the outlet of the compressor unit and the inlet of the expansion unit, and is used to store the supercritical carbon dioxide compressed by the compressor unit;

[0009] A low-pressure gas storage chamber, which is respectively connected to the outlet of the expansion unit and the inlet of the compressor unit, and is used to store supercritical carbon dioxide generated by the expansion unit when generating power;

[0010] A heat storage tank, wherein the heat storage tank is indirectly connected to the outlet of the compressor unit and the inlet of the high-pressure gas storage chamber respectively through a first heat exchanger; the heat storage tank is indirectly connected to the outlet of the high-pressure gas storage chamber and the inlet of the expansion unit respectively through a second heat exchanger; when storing energy, the heat storage tank stores the compression heat of the supercritical carbon dioxide in a high-temperature and high-pressure state, and cools the supercritical carbon dioxide in a high-temperature and high-pressure state to the same temperature as that of the high-pressure gas storage chamber; when releasing energy, the heat storage tank heats the low-temperature and high-pressure supercritical carbon dioxide discharged from the high-pressure gas storage chamber;

[0011] a cold storage tank, connected to the medium inlet of the heat storage tank through the first heat exchanger, and connected to the medium outlet of the heat storage tank through the second heat exchanger;

[0012] The temperature control system adjusts the cooling medium flow in the second heat exchanger to control the compressor inlet temperature, and then adjusts the inlet temperature of each stage of the expander to ensure that the carbon dioxide temperature at the inlet position of each stage of the expander is not lower than the critical temperature of liquefaction and that large-scale liquefaction does not occur.

[0013] Optionally, the compressor unit comprises: a first-stage compressor and a second-stage compressor;

[0014] The expander group comprises: a first-stage expander and a second-stage expander;

[0015] The first heat exchanger includes: a first interstage cooler and a second interstage cooler; the outlet of the first stage compressor is connected to the inlet of the first interstage cooler, and the first interstage cooler is connected to the cold storage tank to absorb the compression heat of the first stage compressor through the cooling medium in the cold storage tank; the outlet of the first interstage cooler is connected to the inlet of the second stage compressor, the outlet of the second stage compressor is connected to the inlet of the second interstage cooler, and the second interstage cooler is connected to the cold storage tank to absorb the compression heat of the second stage compressor through the cooling medium in the cold storage tank;

[0016] The second heat exchanger includes: a first-stage reheater and a second-stage reheater; the first-stage reheater heats the supercritical carbon dioxide discharged from the high-pressure gas storage chamber through the heat storage tank; the second-stage reheater heats the supercritical carbon dioxide at the outlet of the second-stage compressor through the heat storage tank.

[0017] Optionally, the temperature control system comprises: a first temperature detector for detecting the outlet carbon dioxide temperature of the first stage compressor, and a regulating valve for adjusting the cooling medium flow of the cold storage tank;

[0018] During the system energy storage process, the regulating valve of the temperature control system controls the flow rate of the cooling medium in the first inter-stage cooler to control the inlet carbon dioxide temperature of the second stage compressor.

[0019] Optionally, the temperature control system further comprises: a second temperature detector for detecting the temperature of the medium in the heat storage tank, and a third temperature detector for respectively detecting the temperature of the carbon dioxide at the outlets of the first-stage expander and the second-stage expander;

[0020] During the energy release process of the system, the heat storage tank heats the supercritical carbon dioxide at the inlet of the first-stage expander and the second-stage expander respectively; the third temperature detector detects whether the temperature of the carbon dioxide at the outlet of the expander is lower than the supercritical temperature and whether a large-area liquefaction phenomenon occurs;

[0021] If there is a large-scale liquefaction phenomenon, the controller of the temperature control system adjusts the opening of the regulating valve to reduce the flow of the cooling medium in the first heat exchanger to increase the temperature of the stored water and ensure that the temperature of the carbon dioxide at the final stage of the expander is not lower than the critical temperature.

[0022] Optionally, the thermodynamic model of the compressor in the compressor unit is:

[0023] Assume that the internal temperature of the i-th stage compressor is The compression process is a variable process. We regard this process as an adiabatic process. Considering the equal efficiency, the outlet temperature for:

[0024]

[0025] β c，i is the compression ratio of the i-th compressor, k is the specific heat ratio, η cs is the compressor adiabatic efficiency;

[0026] When a unit mass of air enters the compressor, the work done by the compressor is:

[0027]

[0028] c p is the constant pressure specific heat of carbon dioxide. The superscript in is the component entering the compressor, out is the component coming out of the compressor, and the subscript c is the compression charging process. Therefore, according to the power consumed by each stage of the compressor, the total power consumption of the compressor is:

[0029]

[0030] Optionally, the thermodynamic model of the expander in the expander group is:

[0031] In the energy release stage, after passing through the i-stage heat exchanger, the temperature is When the unit mass of carbon dioxide enters the i-th stage turbine, the output work is:

[0032]

[0033] The air outlet temperature of the i-th stage turbine is:

[0034]

[0035] β e，i is the expansion ratio of the i-th stage expander, η ts is the isentropic efficiency of the expander, then the total output work in the energy release stage is:

[0036]

[0037] Optionally, the energy storage efficiency of the adiabatic supercritical compressed carbon dioxide energy storage system is:

[0038]

[0039] t c is the duration of the energy storage phase, t e It is the duration of energy release phase.

[0040] Optionally, the heat storage tank is a hot water storage tank body; the cold storage tank is a cooling water tank body.

[0041] The technical solution of the present invention has the following advantages:

[0042] 1. The adiabatic supercritical compressed carbon dioxide energy storage system provided by the present invention comprises:

[0043] The compressor unit uses electricity to compress low-temperature and low-pressure supercritical carbon dioxide into high-temperature and high-pressure supercritical carbon dioxide when power is low.

[0044] An expansion unit, which uses high-temperature and high-pressure supercritical carbon dioxide to generate electricity during peak power consumption;

[0045] A high-pressure gas storage chamber, which is respectively connected to the outlet of the compressor unit and the inlet of the expansion unit, and is used to store the supercritical carbon dioxide compressed by the compressor unit;

[0046] A low-pressure gas storage chamber, which is respectively connected to the outlet of the expansion unit and the inlet of the compressor unit, and is used to store supercritical carbon dioxide generated by the expansion unit when generating power;

[0047] A heat storage tank, wherein the heat storage tank is indirectly connected to the outlet of the compressor unit and the inlet of the high-pressure gas storage chamber respectively through a first heat exchanger; the heat storage tank is indirectly connected to the outlet of the high-pressure gas storage chamber and the inlet of the expansion unit respectively through a second heat exchanger; when storing energy, the heat storage tank stores the compression heat of the supercritical carbon dioxide in a high-temperature and high-pressure state, and cools the supercritical carbon dioxide in a high-temperature and high-pressure state to the same temperature as that of the high-pressure gas storage chamber; when releasing energy, the heat storage tank heats the low-temperature and high-pressure supercritical carbon dioxide discharged from the high-pressure gas storage chamber;

[0048] a cold storage tank, connected to the medium inlet of the heat storage tank through the first heat exchanger, and connected to the medium outlet of the heat storage tank through the second heat exchanger;

[0049] The temperature control system adjusts the cooling medium flow in the second heat exchanger to control the compressor inlet temperature, and then adjusts the inlet temperature of each stage of the expander to ensure that the carbon dioxide temperature at the inlet position of each stage of the expander is not lower than the critical temperature of liquefaction and that large-scale liquefaction does not occur.

[0050] In the adiabatic supercritical compressed carbon dioxide energy storage system, the compressor is a core component and is crucial to the overall efficiency of the system. Among them, the centrifugal compressor is most suitable for the adiabatic supercritical compressed carbon dioxide energy storage system. The above-mentioned centrifugal compressor not only needs to consume electrical energy and compress carbon dioxide, but also needs to store the compression heat of carbon dioxide through a heat exchanger and a heat storage medium for heating the carbon dioxide at the inlet of the expander in the energy release stage. In the prior art, in order to ensure high efficiency and low power consumption of the compressor, it is necessary to perform interstage cooling on the working fluid at the outlet of each compressor stage to ensure that the working fluid temperature entering the next stage is low and the system efficiency is guaranteed. However, in the adiabatic supercritical compressed carbon dioxide energy storage system, the low-pressure carbon dioxide is above the supercritical pressure. Due to the limitations of equipment processing and manufacturing, the physical properties of carbon dioxide and other factors, the supercritical carbon dioxide centrifugal compressor has the characteristics of a small number of stages and a low single-stage pressure ratio. The above characteristics will result in a lower compression heat temperature obtained by interstage cooling of carbon dioxide, thereby reducing the work capacity of the expander. Therefore, considering the physical properties of carbon dioxide, low-temperature carbon dioxide will have problems such as liquefaction when the turbine is in operation, affecting the normal operation of the expander and seriously affecting the working efficiency of the adiabatic supercritical compressed carbon dioxide energy storage system.

[0051] In order to solve the above problems, the above temperature control system is provided in the present invention and cooperates with the heat storage temperature control strategy of the adiabatic supercritical compressed carbon dioxide energy storage system. The temperature control system in the present invention detects the carbon dioxide temperature and liquefaction rate at the outlet of the expansion unit during the energy release process. The minimum temperature of the high-temperature heat storage medium of the required heat storage tank is calculated, and the heat storage medium flow of the interstage cooler of the compressor unit is further feedback-adjusted. The heat storage medium temperature is controlled by adjusting the heat storage medium flow of the interstage reheater of the compressor, so that the heat storage medium temperature of the system during the energy storage process can meet the carbon dioxide turbine temperature requirement in the expander during the energy release process. In the present invention, the heat storage medium temperature is controlled by controlling the heat storage medium flow of the interstage reheater of the compressor, and then on the basis of sacrificing the performance of part of the compressor unit, the normal operation of the expansion unit is effectively guaranteed, the overall efficiency of the system is guaranteed, and the adiabatic supercritical compressed carbon dioxide energy storage system completes the energy storage and release tasks.

[0052] 2. The adiabatic supercritical compressed carbon dioxide energy storage system provided by the present invention,

[0053] The compressor unit comprises: a first-stage compressor and a second-stage compressor;

[0054] The expander group comprises: a first-stage expander and a second-stage expander;

[0055] The first heat exchanger includes: a first interstage cooler and a second interstage cooler; the outlet of the first stage compressor is connected to the inlet of the first interstage cooler, and the first interstage cooler is connected to the cold storage tank to absorb the compression heat of the first stage compressor through the cooling medium in the cold storage tank; the outlet of the first interstage cooler is connected to the inlet of the second stage compressor, the outlet of the second stage compressor is connected to the inlet of the second interstage cooler, and the second interstage cooler is connected to the cold storage tank to absorb the compression heat of the second stage compressor through the cooling medium in the cold storage tank;

[0056] The second heat exchanger includes: a first-stage reheater and a second-stage reheater; the first-stage reheater heats the supercritical carbon dioxide discharged from the high-pressure gas storage chamber through the heat storage tank; the second-stage reheater heats the supercritical carbon dioxide at the outlet of the second-stage compressor through the heat storage tank.

[0057] In the present invention, through a two-stage compressor, a two-stage expander, as well as high and low pressure storage tanks and cold and heat storage tanks. The system can effectively enter the energy storage stage during the period of surplus electricity. The supercritical carbon dioxide in the low-pressure gas storage chamber enters the two-stage compressor, and the supercritical carbon dioxide at the outlet of each compressor is cooled by cooling water. The carbon dioxide at the outlet of the last stage of the compressor is cooled and stored in the high-pressure storage tank, and the stored hot water is stored in the hot water storage tank. In addition, during the peak power period, the system enters the energy release stage, and the high-pressure liquid carbon dioxide in the high-pressure storage tank is heated by the stored hot water and enters the secondary expander to expand and do work. The electric energy is connected to the power grid, and the carbon dioxide after the energy release is returned to the low-pressure gas storage chamber. The above-mentioned adiabatic supercritical compressed carbon dioxide energy storage system can effectively ensure the normal operation of the expansion unit and ensure the overall efficiency of the system.

[0058] 3. The adiabatic supercritical compressed carbon dioxide energy storage system provided by the present invention, the temperature control system comprises: a first temperature detector for detecting the outlet carbon dioxide temperature of the first stage compressor, and a regulating valve for adjusting the cooling medium flow of the cold storage tank;

[0059] During the system energy storage process, the regulating valve of the temperature control system controls the flow rate of the cooling medium in the first inter-stage cooler to control the inlet carbon dioxide temperature of the second stage compressor.

[0060] The temperature control system further comprises: a second temperature detector for detecting the temperature of the medium in the heat storage tank, and a third temperature detector for respectively detecting the temperature of the carbon dioxide at the outlets of the first-stage expander and the second-stage expander;

[0061] During the energy release process of the system, the heat storage tank heats the supercritical carbon dioxide at the inlet of the first-stage expander and the second-stage expander respectively; the third temperature detector detects whether the temperature of the carbon dioxide at the outlet of the expander is lower than the supercritical temperature and whether a large-area liquefaction phenomenon occurs;

[0062] If there is a large-scale liquefaction phenomenon, the controller of the temperature control system adjusts the opening of the regulating valve to reduce the flow of the cooling medium in the first heat exchanger to increase the temperature of the stored water and ensure that the temperature of the carbon dioxide at the final stage of the expander is not lower than the critical temperature.

[0063] In the energy storage process of the system, the CO2 temperature at the outlet of the i-th compressor is detected, the cooling water flow rate is adjusted to obtain the carbon dioxide temperature at the inlet of the i+1-th compressor, and the temperature of the stored water is obtained. In the energy release process of the system, the stored water heats the carbon dioxide at the inlet of each expander, and detects whether the carbon dioxide temperature at the outlet of the expander is lower than the supercritical temperature and whether large-scale liquefaction occurs. If so, it is fed back to the energy storage process to reduce the cooling water flow rate to increase the temperature of the stored water, ensuring that the carbon dioxide temperature at the last stage of the expander is not lower than the critical temperature and large-scale liquefaction does not occur. Among them, i in the above i-th level is an arbitrary integer.

[0064] 4. The adiabatic supercritical compressed carbon dioxide energy storage system provided by the present invention, according to the energy storage efficiency formula of the adiabatic supercritical compressed carbon dioxide energy storage system:

[0065]

[0066] From the above energy storage efficiency formula, it can be seen that in the adiabatic supercritical compressed carbon dioxide energy storage system, the system efficiency is directly affected by the work done by the expander and the power consumption of the compressor.

[0067] When a unit mass of air enters the compressor, the work done by the compressor is:

[0068]

[0069] From the above compressor work formula, it can be seen that lowering the compressor inlet carbon dioxide temperature can reduce the compressor power consumption.

[0070] Thermodynamic model of the expander in the expander unit. In the energy release stage, after passing through the i-stage heat exchanger, the temperature is When the unit mass of carbon dioxide enters the i-th stage turbine, the output work is:

[0071]

[0072] Through the above expander thermodynamic model, it can be seen that increasing the carbon dioxide temperature at the expander inlet can increase the work capacity of the expander, and there is a restrictive relationship between the two.

[0073] However, when designing an adiabatic supercritical compressed carbon dioxide energy storage system, it is necessary to consider the special physical properties of carbon dioxide, and there is a condensation problem for the compressor and expander. Specifically, "Since the airflow is locally accelerated at the leading edge when entering the impeller, a local low-temperature and low-pressure area is formed at the front edge of the suction surface of the main blade and the splitter blade. When the working fluid state enters the two-phase region or drops below the critical state, a phase change will occur in the channel. This means that the decrease in the temperature of the carbon dioxide entering the compressor and expander will cause condensation in the compressor and expander. Therefore, when designing an adiabatic supercritical compressed carbon dioxide energy storage system, the temperature of the carbon dioxide at the compressor inlet and the expander inlet, especially the expander inlet, also needs to be considered to see if the temperature is appropriate. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0075] Figure 1 A schematic diagram of the structure of the adiabatic supercritical compressed carbon dioxide energy storage system provided by the present invention;

[0076] Figure 2 A schematic diagram of the working process of the adiabatic supercritical compressed carbon dioxide energy storage system provided by the present invention.

[0077] Description of reference numerals:

[0078] 1-high-pressure air storage chamber; 2-low-pressure air storage chamber; 3-heat storage tank; 4-cold storage tank; 5-first-stage compressor; 6-second-stage compressor; 7-first-stage expander; 8-second-stage expander; 9-first-stage intercooler; 10-second-stage intercooler; 11-first-stage reheater; 12-second-stage reheater. DETAILED DESCRIPTION

[0079] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0080] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0081] Example 1

[0082] See also Figure 1 , Figure 1 A schematic structural diagram of a supercritical compressed carbon dioxide energy storage system in an embodiment of the present invention is shown.

[0083] This embodiment provides an adiabatic supercritical compressed carbon dioxide energy storage system, comprising:

[0084] The compressor unit uses electricity to compress low-temperature and low-pressure supercritical carbon dioxide into high-temperature and high-pressure supercritical carbon dioxide when the power is low. The compressor unit includes: a first-stage compressor 5 and a second-stage compressor 6;

[0085] An expansion unit, which uses high-temperature and high-pressure supercritical carbon dioxide to generate electricity during peak power consumption; the expansion unit includes: a first-stage expansion unit 7 and a second-stage expansion unit 8;

[0086] A high-pressure gas storage chamber 1, which is respectively connected to the outlet of the compressor unit and the inlet of the expansion unit, and is used to store the supercritical carbon dioxide compressed by the compressor unit;

[0087] A low-pressure gas storage chamber 2, which is respectively connected to the outlet of the expansion unit and the inlet of the compressor unit, and is used to store supercritical carbon dioxide generated by the expansion unit when generating power;

[0088] The heat storage tank 3 is a hot water storage tank body, and is indirectly connected to the outlet of the compressor unit and the inlet of the high-pressure gas storage chamber 1 respectively through a first heat exchanger; the heat storage tank 3 is indirectly connected to the outlet of the high-pressure gas storage chamber 1 and the inlet of the expansion unit respectively through a second heat exchanger; when storing energy, the heat storage tank 3 stores the compression heat of the supercritical carbon dioxide in a high-temperature and high-pressure state, and cools the supercritical carbon dioxide in a high-temperature and high-pressure state to the same temperature as that of the high-pressure gas storage chamber 1; when releasing energy, the heat storage tank 3 heats the low-temperature and high-pressure supercritical carbon dioxide discharged from the high-pressure gas storage chamber 1;

[0089] A cold storage tank 4, which is a cooling water tank body, is connected to the medium inlet of the heat storage tank 3 through the first heat exchanger, and is connected to the medium outlet of the heat storage tank 3 through the second heat exchanger;

[0090] The temperature control system adjusts the cooling medium flow in the second heat exchanger to control the compressor inlet temperature, and then adjusts the inlet temperature of each stage of the expander to ensure that the carbon dioxide temperature at the inlet position of each stage of the expander is not lower than the critical temperature of liquefaction and that large-scale liquefaction does not occur.

[0091] In the present invention, Figure 1 As shown:

[0092] The first heat exchanger includes: a first interstage cooler 9 and a second interstage cooler 10; the outlet of the first stage compressor 5 is connected to the inlet of the first interstage cooler 9, and the first interstage cooler 9 is connected to the cold storage tank 4 to absorb the compression heat of the first stage compressor 5 through the cooling medium in the cold storage tank 4; the outlet of the first interstage cooler 9 is connected to the inlet of the second stage compressor 6, and the outlet of the second stage compressor 6 is connected to the inlet of the second interstage cooler 10, and the second interstage cooler 10 is connected to the cold storage tank 4 to absorb the compression heat of the second stage compressor 6 through the cooling medium in the cold storage tank 4;

[0093] The second heat exchanger includes: a first-stage reheater 11 and a second-stage reheater 12; the first-stage reheater 11 heats the supercritical carbon dioxide discharged from the high-pressure gas storage chamber 1 through the heat storage tank 3; the second-stage reheater 12 heats the supercritical carbon dioxide at the outlet of the second-stage compressor 6 through the heat storage tank 3.

[0094] In the present invention, Figure 1 and Figure 2 As shown, the SC-CCES system is the supercritical compressed carbon dioxide energy storage system in the present invention. The temperature control system includes: a first temperature detector for detecting the outlet carbon dioxide temperature of the first stage compressor 5, and a regulating valve for adjusting the cooling medium flow of the cold storage tank 4; during the system energy storage process, the regulating valve of the temperature control system controls the cooling medium flow in the first inter-stage cooler 9 to control the inlet carbon dioxide temperature of the second stage compressor 6.

[0095] The temperature control system further includes: a second temperature detector for detecting the temperature of the medium in the heat storage tank 3, and a third temperature detector for respectively detecting the temperature of the carbon dioxide at the outlets of the first-stage expander 7 and the second-stage expander 8; in the energy release process of the system, the heat storage tank 3 heats the supercritical carbon dioxide at the inlets of the first-stage expander 7 and the second-stage expander 8 respectively; the third temperature detector detects whether the temperature of the carbon dioxide at the outlet of the expander is lower than the supercritical temperature and whether a large-area liquefaction phenomenon occurs;

[0096] If there is a large-scale liquefaction phenomenon, the controller of the temperature control system adjusts the opening of the regulating valve to reduce the flow of the cooling medium in the first heat exchanger to increase the temperature of the stored water and ensure that the temperature of the carbon dioxide at the final stage of the expander is not lower than the critical temperature.

[0097] In the adiabatic supercritical compressed carbon dioxide energy storage system, in order to reduce the power consumption of the compressor unit, carbon dioxide will be cooled to 35°C through interstage cooling. Table 1 shows the hot water temperature, system energy storage efficiency, and carbon dioxide temperature and liquefaction rate at the outlet of the final stage of the expander of the supercritical compressed carbon dioxide energy storage system under normal interstage cooling and when the cooling water flow rate of the interstage cooler is 0. It can be seen from the table that under normal interstage cooling conditions, carbon dioxide liquefaction occurs at the final stage of the expander of the supercritical compressed carbon dioxide energy storage system, which significantly reduces the work capacity of the expander and leads to low system energy storage efficiency; under the extreme condition of 0 cooling water flow, the carbon dioxide temperature at the final stage of the expander is higher than the critical temperature, there is no liquefaction phenomenon, and the system energy storage efficiency is significantly increased.

[0098] Table 1 Effect of different interstage cooler cooling water flow rates on SC-CCES system

[0099]

[0100] Although the system energy storage efficiency is significantly increased when the cooling water flow rate of the interstage cooler is 0, the CO2 temperature at the outlet of the final stage of the expander indicates that some of the waste heat is still wasted. Therefore, based on the two extreme working conditions, the above-mentioned control strategy in the present invention is used to ensure that the temperature of the carbon dioxide at the final stage of the expander is higher than the critical temperature and there is no liquefaction phenomenon. The work of the expander and the power consumption of the compressor are weighed, while the goal is to reduce the waste heat and waste heat as much as possible, and seek the optimal cooling water flow rate to optimize the system energy storage efficiency. At the same time, combined with the variable operating characteristics of the adiabatic supercritical compressed carbon dioxide energy storage system, the control strategy can dynamically control the cooling water flow rate, so that the operating efficiency of the system components and the energy storage efficiency remain in the high efficiency range.

[0101] In the present invention, the thermodynamic model of the compressor in the compressor unit is:

[0102] Assume that the internal temperature of the i-th stage compressor is The compression process is a variable process. We regard this process as an adiabatic process. Considering the equal efficiency, the outlet temperature for:

[0103]

[0104] β c，i is the compression ratio of the i-th compressor, k is the specific heat ratio, η cs is the compressor adiabatic efficiency;

[0105] When a unit mass of air enters the compressor, the work done by the compressor is:

[0106]

[0107] c p is the constant pressure specific heat of carbon dioxide. The superscript in is the component entering the compressor, out is the component coming out of the compressor, and the subscript c is the compression charging process. Therefore, according to the power consumed by each stage of the compressor, the total power consumption of the compressor is:

[0108]

[0109] In the present invention, the thermodynamic model of the expander in the expander group is:

[0110] In the energy release stage, after passing through the i-stage heat exchanger, the temperature is When the unit mass of carbon dioxide enters the i-th stage turbine, the output work is:

[0111]

[0112] The air outlet temperature of the i-th stage turbine is:

[0113]

[0114] β e，i is the expansion ratio of the i-th stage expander, η ts is the isentropic efficiency of the expander, then the total output work in the energy release stage is:

[0115]

[0116] In the present invention, the energy storage efficiency of the adiabatic supercritical compressed carbon dioxide energy storage system is:

[0117]

[0118] t c is the duration of the energy storage phase, t e It is the duration of energy release phase.

[0119] Of course, this embodiment does not specifically limit the number of compressors and expanders in the compressor unit and the expander unit. In other embodiments, the compressor unit includes at least three stages of compressors; the expansion unit includes at least three stages of expanders.

[0120] Of course, this embodiment does not specifically limit the heat storage medium and the cold storage medium in the heat storage tank 3 and the cold storage tank 4. In other embodiments, the heat storage tank 3 and the cold storage tank 4 may also be made of other materials such as heat transfer oil.

[0121] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. An adiabatic supercritical compressed carbon dioxide energy storage system, characterized in that: include: The compressor unit uses electricity to compress low-temperature and low-pressure supercritical carbon dioxide into high-temperature and high-pressure supercritical carbon dioxide when power is low. An expansion unit, which uses high-temperature and high-pressure supercritical carbon dioxide to generate electricity during peak power consumption; A high-pressure gas storage chamber (1), which is respectively connected to the outlet of the compressor unit and the inlet of the expansion unit, and is used to store the supercritical carbon dioxide compressed by the compressor unit; A low-pressure gas storage chamber (2), which is respectively connected to the outlet of the expansion unit and the inlet of the compressor unit, and is used to store supercritical carbon dioxide generated by the expansion unit when generating power; A heat storage tank (3), wherein the heat storage tank (3) is indirectly connected to the outlet of the compressor unit and the inlet of the high-pressure gas storage chamber (1) respectively through a first heat exchanger; the heat storage tank (3) is indirectly connected to the outlet of the high-pressure gas storage chamber (1) and the inlet of the expansion unit respectively through a second heat exchanger; when storing energy, the heat storage tank (3) stores the compression heat of the supercritical carbon dioxide in a high-temperature and high-pressure state, and cools the supercritical carbon dioxide in a high-temperature and high-pressure state to the same temperature as that of the high-pressure gas storage chamber (1); when releasing energy, the heat storage tank (3) heats the low-temperature and high-pressure supercritical carbon dioxide discharged from the high-pressure gas storage chamber (1); A cold storage tank (4) is connected to the medium inlet of the heat storage tank (3) through the first heat exchanger, and is connected to the medium outlet of the heat storage tank (3) through the second heat exchanger; The temperature control system adjusts the cooling medium flow in the second heat exchanger to control the compressor inlet temperature, and then adjusts the inlet temperature of each stage of the expander to ensure that the carbon dioxide temperature at the inlet position of each stage of the expander is not lower than the critical temperature of liquefaction and that large-scale liquefaction does not occur.

2. The adiabatic supercritical compressed carbon dioxide energy storage system according to claim 1, characterized in that: The compressor unit comprises: a first-stage compressor (5) and a second-stage compressor (6); The expansion machine group comprises: a first-stage expansion machine (7) and a second-stage expansion machine (8); The first heat exchanger comprises: a first interstage cooler (9) and a second interstage cooler (10); the outlet of the first-stage compressor (5) is connected to the inlet of the first interstage cooler (9), and the first interstage cooler (9) is connected to the cold storage tank (4) so ​​as to absorb the compression heat of the first-stage compressor (5) through the cooling medium in the cold storage tank (4); the outlet of the first interstage cooler (9) is connected to the inlet of the second-stage compressor (6), the outlet of the second-stage compressor (6) is connected to the inlet of the second interstage cooler (10), and the second interstage cooler (10) is connected to the cold storage tank (4) so ​​as to absorb the compression heat of the second-stage compressor (6) through the cooling medium in the cold storage tank (4); The second heat exchanger comprises: a first-stage reheater (11) and a second-stage reheater (12); the first-stage reheater (11) heats the supercritical carbon dioxide discharged from the high-pressure gas storage chamber (1) through the heat storage tank (3); and the second-stage reheater (12) heats the supercritical carbon dioxide at the outlet of the second-stage compressor (6) through the heat storage tank (3).

3. The adiabatic supercritical compressed carbon dioxide energy storage system according to claim 2, characterized in that: The temperature control system comprises: a first temperature detector for detecting the outlet temperature of the carbon dioxide of the first-stage compressor (5), and a regulating valve for adjusting the flow rate of the cooling medium of the cold storage tank (4); During the system energy storage process, the regulating valve of the temperature control system controls the flow rate of the cooling medium in the first inter-stage cooler (9) to control the inlet carbon dioxide temperature of the second stage compressor (6).

4. The adiabatic supercritical compressed carbon dioxide energy storage system according to claim 3 is characterized in that: The temperature control system further comprises: a second temperature detector for detecting the temperature of the medium in the heat storage tank (3), and a third temperature detector for respectively detecting the temperature of the carbon dioxide at the outlets of the first-stage expander (7) and the second-stage expander (8); During the energy release process of the system, the heat storage tank (3) heats the supercritical carbon dioxide at the inlets of the first-stage expander (7) and the second-stage expander (8) respectively; the third temperature detector detects whether the temperature of the carbon dioxide at the outlet of the expander is lower than the supercritical temperature and whether a large-area liquefaction phenomenon occurs; If there is a large-scale liquefaction phenomenon, the controller of the temperature control system adjusts the opening of the regulating valve to reduce the flow of the cooling medium in the first heat exchanger to increase the temperature of the stored water and ensure that the temperature of the carbon dioxide at the final stage of the expander is not lower than the critical temperature.

5. The adiabatic supercritical compressed carbon dioxide energy storage system according to any one of claims 1 to 4, characterized in that: The thermodynamic model of the compressor in the compressor unit is: Assume that the internal temperature of the i-th stage compressor is The compression process is a variable process. We regard this process as an adiabatic process. Considering the equal efficiency, the outlet temperature for: β c，i is the compression ratio of the i-th compressor, k is the specific heat ratio, η cs is the compressor adiabatic efficiency; When a unit mass of air enters the compressor, the work done by the compressor is: c p is the constant pressure specific heat of carbon dioxide. The superscript in is the component entering the compressor, out is the component coming out of the compressor, and the subscript c is the compression charging process. Therefore, according to the power consumed by each stage of the compressor, the total power consumption of the compressor is:

6. The adiabatic supercritical compressed carbon dioxide energy storage system according to any one of claims 1 to 4, characterized in that: The thermodynamic model of the expander in the expander group is: In the energy release stage, after passing through the i-stage heat exchanger, the temperature is The high-pressure carbon dioxide enters the expander; When a unit mass of carbon dioxide enters the i-th stage turbine, the output power is: The air outlet temperature of the i-th stage turbine is: β e，i is the expansion ratio of the i-th stage expander, η ts is the isentropic efficiency of the expander, then the total output work in the energy release stage is:

7. The adiabatic supercritical compressed carbon dioxide energy storage system according to claim 6, characterized in that: The energy storage efficiency of the adiabatic supercritical compressed carbon dioxide energy storage system is: t c is the duration of the energy storage phase, t e It is the duration of energy release phase.

8. The adiabatic supercritical compressed carbon dioxide energy storage system according to claim 1, characterized in that: The heat storage tank (3) is a hot water storage tank body; the cold storage tank (4) is a cooling water tank body.

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