An adiabatic supercritical carbon dioxide compression energy storage system

Abstract

The present application relates to supercritical compression carbon dioxide energy storage technical field, the heat insulation supercritical compression carbon dioxide energy storage system includes: compressor unit, expander unit, heat storage tank, in energy storage, the heat storage tank stores the compression heat of supercritical carbon dioxide in high temperature and high pressure state, the supercritical carbon dioxide in high temperature and high pressure state is cooled to the same temperature with high pressure gas chamber, in energy release, the heat storage tank heats the low temperature and high pressure supercritical carbon dioxide discharged by high pressure gas chamber, temperature control system, adjust the cooling medium flow in second heat exchanger, control the compressor inlet temperature, then adjust the inlet temperature of each stage expander, ensure that the inlet position of each stage expander is not lower than the liquefied critical temperature of carbon dioxide, and no large area liquefaction phenomenon appears.The above-mentioned temperature control system can effectively overcome the prior art, carbon dioxide is liquefied when carbon dioxide is at low temperature, and large area condensation phenomenon appears in the expander, thereby ensuring the operation efficiency and energy storage efficiency of the system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of supercritical compressed carbon dioxide energy storage, and particularly relates to an adiabatic supercritical compressed carbon dioxide energy storage system. BACKGROUND

[0002] The supercritical compressed carbon dioxide energy storage system is a high-efficiency energy storage and conversion technology. The working principle is as follows: the supercritical carbon dioxide at low temperature and low pressure is compressed into supercritical carbon dioxide at high temperature and high pressure by a compressor driven by electricity at a low electricity consumption time, and is stored; at a high electricity consumption time, the supercritical carbon dioxide at high temperature and high pressure is sent into an expander, and the expander generates power.

[0003] The compressor is a core component of the supercritical compressed carbon dioxide energy storage system. The compressor not only needs to consume electric energy and compress carbon dioxide, but also needs to store the compression heat of carbon dioxide through a heat exchanger and storage water for heating carbon dioxide at the inlet of the expander in the energy release stage. Therefore, in the conventional design in the field, in order to ensure high efficiency and low power consumption of the compressor, inter-stage cooling of the working medium is needed at the outlet of each compressor to ensure that the temperature of the working medium entering the next stage is low, so as to ensure the 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. 7.38 MPa). Due to the limitations of equipment processing and manufacturing, carbon dioxide properties and other factors, the supercritical carbon dioxide centrifugal compressor has the characteristics of few stages and low single-stage pressure ratio. This characteristic leads to low compression heat temperature of carbon dioxide after inter-stage cooling, which reduces the work capacity of the expander.

[0004] In addition, considering the properties of carbon dioxide, carbon dioxide may be liquefied at a low temperature, which affects the normal work of the carbon dioxide turbine and further affects the normal operation of the expander, and greatly affects the working efficiency of the independent supercritical compressed carbon dioxide energy storage system. Therefore, the technical personnel in the field need a new supercritical compressed carbon dioxide energy storage system to ensure that the temperature of carbon dioxide entering the expander is high, avoid the large-area condensation phenomenon in the expander, and ensure the normal operation of the expander and the operation efficiency and energy storage efficiency of the supercritical compressed carbon dioxide energy storage system. SUMMARY

[0005] Therefore, the technical problem to be solved by the present application is to overcome the problems in the prior art that carbon dioxide is liquefied at a low temperature, a large-area condensation phenomenon occurs in the expander, and the operation efficiency and energy storage efficiency of the system are affected. To this end, the present application provides an adiabatic supercritical compressed carbon dioxide energy storage system, comprising:

[0006] a compressor unit, which compresses low-temperature and low-pressure supercritical carbon dioxide into high-temperature and high-pressure supercritical carbon dioxide by using electricity at low electricity consumption time;

[0007] an expander unit, which generates electricity by using high-temperature and high-pressure supercritical carbon dioxide at electricity consumption peak time;

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

[0009] a low-pressure gas storage chamber, which is connected to the outlet of the expander unit and the inlet of the compressor unit respectively, and is used for storing supercritical carbon dioxide generated by the expander unit during electricity generation;

[0010] a heat storage tank, which is indirectly connected to the outlet of the compressor unit and the inlet of the high-pressure gas storage chamber through a first heat exchanger, and is indirectly connected to the outlet of the high-pressure gas storage chamber and the inlet of the expander unit through a second heat exchanger; during energy storage, the heat storage tank stores compression heat of supercritical carbon dioxide in high-temperature and high-pressure state, and cools supercritical carbon dioxide in high-temperature and high-pressure state to the same temperature as the high-pressure gas storage chamber; during energy release, the heat storage tank heats low-temperature and high-pressure supercritical carbon dioxide discharged from the high-pressure gas storage chamber;

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

[0012] a temperature control system, which adjusts the flow of cooling medium in the second heat exchanger to control the inlet temperature of the compressor, and then adjusts the inlet temperature of each stage of the expander, so that the temperature of the inlet of each stage of the expander is not lower than the critical temperature of liquefaction, and large-area liquefaction does not occur.

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

[0014] the expander unit comprises a first-stage expander and a second-stage expander;

[0015] The first heat exchanger comprises a first inter-stage cooler and a second inter-stage cooler; the outlet of the first stage compressor is connected to the inlet of the first inter-stage cooler, the first inter-stage cooler is connected to the cold storage tank to absorb the compression heat of the first stage compressor by the cooling medium in the cold storage tank; the outlet of the first inter-stage 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 inter-stage cooler, and the second inter-stage cooler is connected to the cold storage tank to absorb the compression heat of the second stage compressor by the cooling medium in the cold storage tank.

[0016] The second heat exchanger comprises a first re-heater and a second re-heater; the first re-heater heats the supercritical carbon dioxide discharged from the high-pressure storage chamber by the heat storage tank; and the second re-heater heats the supercritical carbon dioxide at the outlet of the second stage compressor by the heat storage tank.

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

[0018] During the energy storage process of the system, the adjusting valve of the temperature control system controls the flow of the cooling medium in the first inter-stage cooler to control the temperature of the carbon dioxide at the inlet 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 detecting the temperature of the carbon dioxide at the outlet of the first stage expander and the second stage expander, respectively.

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

[0021] If large-area liquefaction occurs, the controller of the temperature control system adjusts the opening of the adjusting valve to reduce the flow of the cooling medium in the first heat exchanger, so as to increase the temperature of the heat storage water and ensure that the temperature of the carbon dioxide at the last stage of the expander is not lower than the critical temperature.

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

[0023] Assuming that the internal temperature of the i-th stage compressor is The compression process is a polytropic process, and we regard this process as an adiabatic process. Considering the isentropic efficiency, the outlet temperature is:

[0024]

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

[0026] When the 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 upper index in is the component entering the compressor, out is the component from the compressor, the lower index c is the compression charging process, so according to the work 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 heat exchanger of the i th stage, the temperature is The high-pressure carbon dioxide enters the expander; when the unit mass of carbon dioxide enters the i th turbine, the output work is:

[0032]

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

[0034]

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

[0036]

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

[0038]

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

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

[0041] The technical scheme of the present application has the following advantages:

[0042] 1. The heat-insulated supercritical carbon dioxide compression energy storage system provided by the present application comprises:

[0043] a compressor unit, which compresses low-temperature and low-pressure supercritical carbon dioxide into high-temperature and high-pressure supercritical carbon dioxide by using electricity at low electricity consumption time;

[0044] an expander unit, which generates electricity by using high-temperature and high-pressure supercritical carbon dioxide at electricity consumption peak time;

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

[0046] a low-pressure gas storage chamber, which is connected to the outlet of the expander unit and the inlet of the compressor unit respectively, and is used for storing supercritical carbon dioxide generated by the expander unit during electricity generation;

[0047] a heat storage tank, which is indirectly connected to the outlet of the compressor unit and the inlet of the high-pressure gas storage chamber through a first heat exchanger, and is indirectly connected to the outlet of the high-pressure gas storage chamber and the inlet of the expander unit through a second heat exchanger; during energy storage, the heat storage tank stores the compression heat of high-temperature and high-pressure supercritical carbon dioxide, and cools the high-temperature and high-pressure supercritical carbon dioxide to the same temperature as the high-pressure gas storage chamber; during energy release, 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, which is connected to the medium inlet of the heat storage tank through the first heat exchanger, and is connected to the medium outlet of the heat storage tank through the second heat exchanger;

[0049] a temperature control system, which adjusts the flow of cooling medium in the second heat exchanger to control the inlet temperature of the compressor, and further adjusts the inlet temperature of each stage of the expander, so that the temperature of the inlet of each stage of the expander is not lower than the liquefaction critical temperature and no large-area liquefaction phenomenon occurs.

[0050] In the adiabatic supercritical compression carbon dioxide energy storage system, the compressor as the core component is crucial to the overall efficiency of the system, and the centrifugal compressor is most suitable for the adiabatic supercritical compression carbon dioxide energy storage system. The above-mentioned centrifugal compressor not only needs to consume electric energy and compress carbon dioxide, but also needs to store the compression heat of carbon dioxide through the heat exchanger and the heat storage medium for heating the carbon dioxide at the inlet of the expander during the energy release stage. In the prior art, in order to ensure high efficiency and low power consumption of the compressor, inter-stage cooling of the working medium is needed at the outlet of each stage of the compressor to ensure that the temperature of the working medium entering the next stage is low, thereby ensuring the system efficiency. However, in the adiabatic supercritical compression carbon dioxide energy storage system, the low-pressure carbon dioxide is above the supercritical pressure, and the supercritical carbon dioxide centrifugal compressor has the characteristics of few stages and low single-stage pressure ratio due to the limitations of equipment processing and manufacturing, carbon dioxide properties and other factors. The above-mentioned characteristics will result in low temperature of the compression heat of carbon dioxide after inter-stage cooling, thereby reducing the work capacity of the expander. Therefore, considering the properties of carbon dioxide, the low-temperature carbon dioxide will be liquefied during the turbine operation, which affects the normal operation of the expander and seriously affects the working efficiency of the adiabatic supercritical compression carbon dioxide energy storage system.

[0051] In order to solve the above-mentioned problems, the temperature control system is arranged in the present application and cooperates with the heat storage temperature regulation strategy of the adiabatic supercritical compression carbon dioxide energy storage system. In the present application, the temperature control system detects the temperature and liquefaction rate of carbon dioxide at the outlet position of the expander set during the energy release process. The lowest temperature of the high-temperature heat storage medium of the required heat storage tank is calculated, and the heat storage medium flow of the inter-stage cooler of the compressor set is further adjusted and fed back, and the heat storage medium temperature is controlled by adjusting the heat storage medium flow of the inter-stage reheater of the compressor, so that the heat storage medium temperature of the system during the energy storage process can meet the turbine temperature requirement of carbon dioxide in the expander during the energy release process. In the present application, the heat storage medium temperature is controlled by controlling the heat storage medium flow of the inter-stage reheater of the compressor, thereby effectively ensuring the normal operation of the expander set, ensuring the overall efficiency of the system and ensuring the completion of the energy storage and release task of the adiabatic supercritical compression carbon dioxide energy storage system on the basis of sacrificing part of the performance of the compressor set.

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

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

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

[0055] The first heat exchanger comprises a first inter-stage cooler and a second inter-stage cooler; the outlet of the first stage compressor is connected to the inlet of the first inter-stage cooler, the first inter-stage cooler is connected to the cold storage tank to absorb the compression heat of the first stage compressor by the cooling medium in the cold storage tank; the outlet of the first inter-stage 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 inter-stage cooler, and the second inter-stage cooler is connected to the cold storage tank to absorb the compression heat of the second stage compressor by the cooling medium in the cold storage tank.

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

[0057] In the present application, through two-stage compressors, two-stage expanders, and high and low pressure storage tanks and cold and heat storage tanks, the system can effectively enter the energy storage stage when there is excess electric energy, and the supercritical carbon dioxide in the low-pressure gas chamber enters the two-stage compressors, the supercritical carbon dioxide at the outlet of each stage compressor is cooled by cooling water, the carbon dioxide at the outlet of the last stage of the compressor is stored in the high-pressure storage tank after being cooled, and the heat storage water is stored in the heat storage water tank. In addition, the system enters the energy release stage during the peak electricity period, the high-pressure liquid carbon dioxide in the high-pressure storage tank is heated by the heat storage water and then enters the two-stage expanders to expand and do work, the electric energy is fed into the power grid, and the carbon dioxide after the energy release returns to the low-pressure gas chamber. The above-mentioned adiabatic supercritical compressed carbon dioxide energy storage system can effectively ensure the normal operation of the expander set and ensure the overall efficiency of the system.

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

[0059] During the energy storage process of the system, the adjusting valve of the temperature control system controls the flow of the cooling medium in the first inter-stage cooler to control the temperature of the carbon dioxide at the inlet 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 detecting the temperature of the carbon dioxide at the outlet of the first stage expander and the second stage expander, respectively.

[0061] In the system energy release process, the heat storage tank heats the supercritical carbon dioxide at the inlet of the first and second stage expanders 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 large-area liquefaction occurs;

[0062] If large-area liquefaction occurs, the controller of the temperature control system adjusts the opening degree of the regulating valve and reduces the flow of the cooling medium in the first heat exchanger to increase the temperature of the heat storage water and ensure that the temperature of the carbon dioxide at the last stage of the expander is not lower than the critical temperature.

[0063] In the system energy storage process, the temperature of the carbon dioxide at the inlet of the i+1 stage compressor and the temperature of the heat storage water are obtained by detecting the temperature of the carbon dioxide at the outlet of the i stage compressor and adjusting the flow of the cooling water. In the system energy release process, the heat storage water heats the carbon dioxide at the inlet of each stage of the expander, and whether the temperature of the carbon dioxide at the outlet of the expander is lower than the supercritical temperature and whether large-area liquefaction occurs are detected. If so, feedback to the energy storage process to reduce the flow of the cooling water to increase the temperature of the heat storage water, ensure that the temperature of the carbon dioxide at the last stage of the expander is not lower than the critical temperature and large-area liquefaction does not occur. Wherein, i in the above-mentioned i stage is any integer.

[0064] 4. The adiabatic supercritical compressed carbon dioxide energy storage system provided by the present application, 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 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 reducing the temperature of the carbon dioxide at the inlet of the compressor can reduce the power consumption of the compressor.

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

[0071]

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

[0073] However, the design of the adiabatic supercritical compression carbon dioxide energy storage system needs to consider the special properties of carbon dioxide, and there is a condensation problem for the compressor and the expander. Specifically, "due to the local acceleration of the gas flow at the leading edge when entering the impeller, a local low temperature and low pressure area is formed at the leading edge of the suction surface of the main blade and the splitter blade. When the working medium state enters the two-phase region or drops below the critical state, phase change will occur in the channel. This means that the temperature reduction of carbon dioxide entering the compressor and the expander will cause condensation in the compressor and the expander. Therefore, when designing the adiabatic supercritical compression carbon dioxide energy storage system, the temperature of carbon dioxide at the inlet of the compressor and the expander, especially the inlet of the expander, also needs to be considered. BRIEF DESCRIPTION OF DRAWINGS

[0074] In order to more clearly illustrate the technical solutions in the specific embodiments or the prior art of the present application, the drawings needed in the specific embodiments or the prior art description will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0075] Figure 1 The adiabatic supercritical compression carbon dioxide energy storage system structure schematic diagram provided by the present application;

[0076] Figure 2 The adiabatic supercritical compression carbon dioxide energy storage system working process schematic diagram provided by the present application.

[0077] Explanation of reference signs:

[0078] 1-high pressure gas storage chamber; 2-low pressure gas 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 solutions of the present application will be described below in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0080] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0081] Embodiment 1

[0082] Reference Figure 1 , Figure 1 The structure of the supercritical compressed carbon dioxide energy storage system in the embodiment of the present application is shown.

[0083] In this embodiment, an adiabatic supercritical compressed carbon dioxide energy storage system is provided, comprising:

[0084] A compressor set, which uses electricity to compress low-temperature and low-pressure supercritical carbon dioxide into high-temperature and high-pressure supercritical carbon dioxide at low electricity consumption moments; wherein the compressor set comprises a first-stage compressor 5 and a second-stage compressor 6;

[0085] An expander set, which uses high-temperature and high-pressure supercritical carbon dioxide to generate electricity at electricity consumption peaks; the expander set comprises a first-stage expander 7 and a second-stage expander 8;

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

[0087] A low-pressure gas storage chamber 2, which is connected to the outlet of the expander set and the inlet of the compressor set respectively, and is used to store supercritical carbon dioxide generated in the electricity generation of the expander set;

[0088] A heat storage tank 3, which is a heat storage water tank body, indirectly connected to the outlet of the compressor set and the inlet of the high-pressure gas storage chamber 1 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 expander set through a second heat exchanger; in energy storage, the heat storage tank 3 stores the compression heat of high-temperature and high-pressure supercritical carbon dioxide, and cools the high-temperature and high-pressure supercritical carbon dioxide to the same temperature as the high-pressure gas storage chamber 1; in energy release, 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] The cold storage tank 4 is a cooling water tank, which is connected to the medium inlet of the heat storage tank 3 through the first heat exchanger and to the medium outlet of the heat storage tank 3 through the second heat exchanger.

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

[0091] In this invention, such as Figure 1 As shown:

[0092] The first heat exchanger includes: a first-stage intercooler 9 and a second-stage intercooler 10; the outlet of the first-stage compressor 5 is connected to the inlet of the first-stage intercooler 9, and the first-stage intercooler 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-stage intercooler 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-stage intercooler 10, and the second-stage intercooler 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 this invention, such as Figure 1 and Figure 2 As shown, the SC-CCES system is the supercritical compressed carbon dioxide energy storage system of this 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 flow rate of the cooling medium in 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-stage intercooler 9 to control the inlet carbon dioxide temperature of the second-stage compressor 6.

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

[0096] If the large-area liquefaction phenomenon occurs, the controller of the temperature control system adjusts the opening degree of the regulating valve and reduces the flow of the cooling medium in the first heat exchanger, so as to increase the temperature of the heat storage water and ensure that the carbon dioxide temperature at the outlet of the last-stage expander is not lower than the critical temperature.

[0097] In the adiabatic supercritical compression carbon dioxide energy storage system, in order to reduce the power consumption of the compressor set, the carbon dioxide is cooled to 35 DEG C through inter-stage cooling. Table 1 shows the heat storage water temperature, the system energy storage efficiency, and the carbon dioxide temperature at the outlet of the last-stage expander and the liquefaction rate of the supercritical compression carbon dioxide energy storage system under the conditions of normal inter-stage cooling and cooling water flow of the inter-stage cooler being 0. It can be seen from the table that under the condition of normal inter-stage cooling, the carbon dioxide at the outlet of the last-stage expander is liquefied, which significantly reduces the work capacity of the expander and leads to a low system energy storage efficiency; under the extreme condition of cooling water flow being 0, the carbon dioxide temperature at the outlet of the last-stage expander is higher than the critical temperature, and no liquefaction phenomenon occurs, and the system energy storage efficiency is significantly increased.

[0098] Table 1 Influence of cooling water flow of different inter-stage coolers on SC-CCES system

[0099]

[0100] Although the system energy storage efficiency is significantly increased under the condition of cooling water flow of the inter-stage cooler being 0, the CO2 temperature at the outlet of the last-stage expander shows that a part of the waste heat is still wasted. Therefore, based on the two extreme conditions, the above-mentioned regulation and control strategy in the present application is used to ensure that the carbon dioxide temperature at the outlet of the last-stage expander is higher than the critical temperature and no liquefaction phenomenon occurs, and the work of the expander and the power consumption of the compressor are balanced, and the waste heat and the exhaust heat are reduced as much as possible, so that the optimal cooling water flow is sought, and the system energy storage efficiency is optimized. Meanwhile, in combination with the variable operating condition characteristics of the adiabatic supercritical compression carbon dioxide energy storage system, the regulation and control strategy can dynamically regulate and control the cooling water flow, so that the operating efficiency of the system components and the energy storage efficiency are kept in a high-efficiency interval.

[0101] In the present application, the thermodynamic model of the compressor in the compressor set is as follows:

[0102] It is assumed that the internal temperature of the i-th stage compressor is The compression process is a polytropic process, we regard this process as an adiabatic process, and the outlet temperature is calculated according to the isentropic efficiency is:

[0103]

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

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

[0106]

[0107] c p is the specific heat of carbon dioxide at constant pressure, the upper subscript in is the component entering the compressor, and the out is the component from the compressor, and the subscript c is the compression charging process, so according to the work consumed by each stage of the compressor, the total power consumption of the compressor is:

[0108]

[0109] In the present application, the thermodynamic model of the expander in the expander set is:

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

[0111]

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

[0113]

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

[0115]

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

[0117]

[0118] t c is the duration of the energy storage stage, and t e is the duration of the energy release stage.

[0119] Of course, the number of compressors and expanders in the compressor set and the expander set is not limited in the embodiment, and in other embodiments, the compressor set includes at least three compressors, and the expander set includes at least three expanders.

[0120] Of course, the heat storage medium and the cold storage medium in the heat storage tank 3 and the cold storage tank 4 are not limited in the embodiment, and in other embodiments, the heat storage tank 3 and the cold storage tank 4 can also be filled with other materials such as heat conducting oil.

[0121] Obviously, the above embodiments are only examples for clearly illustrating the present application, and are not intended to limit the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. An adiabatic supercritical compressed carbon dioxide energy storage system, characterized in that, include: The compressor unit uses electricity to compress low-temperature, low-pressure supercritical carbon dioxide into high-temperature, high-pressure supercritical carbon dioxide during periods of low electricity usage; the compressor unit includes: a first-stage compressor (5) and a second-stage compressor (6). The expander unit generates electricity using supercritical carbon dioxide at high temperature and high pressure during peak electricity demand. The expander unit includes: a first-stage expander (7) and a second-stage expander (8). The high-pressure gas storage chamber (1) is connected to the outlet of the compressor unit and the inlet of the expander unit, respectively, and is used to store the supercritical carbon dioxide compressed by the compressor unit. The low-pressure gas storage chamber (2) is connected to the outlet of the expander unit and the inlet of the compressor unit, respectively, and is used to store the supercritical carbon dioxide generated by the expander unit in power generation. A 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) via 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 expander unit via a second heat exchanger; during energy storage, the heat storage tank (3) stores the heat of compression of 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 the high-pressure gas storage chamber (1); during energy release, the heat storage tank (3) heats the low-temperature and high-pressure supercritical carbon dioxide discharged from the high-pressure gas storage chamber (1); the first heat exchanger includes: a first-stage intercooler (9) and a second-stage intercooler (10). The cold storage tank (4) is connected to the medium inlet of the heat storage tank (3) through the first heat exchanger and to the medium outlet of the heat storage tank (3) through the second heat exchanger. The temperature control system adjusts the flow rate of the cooling medium in the second heat exchanger to control the compressor inlet temperature, and then adjusts the inlet temperature of each stage expander to ensure that the carbon dioxide temperature at the inlet of each stage expander is not lower than the liquefaction critical temperature and that no large-area liquefaction occurs. The temperature control system includes: a first temperature detector for detecting the outlet carbon dioxide temperature of the first stage compressor (5), a regulating valve for adjusting the flow rate of the cooling medium in the cold storage tank (4), a second temperature detector for detecting the temperature of the medium in the heat storage tank (3), and a third temperature detector for detecting the outlet carbon dioxide temperatures of the first stage expander (7) and the second stage expander (8) respectively. 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 stage intercooler (9) to control the inlet carbon dioxide temperature of the second stage compressor (6); During the system's energy release process, 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 carbon dioxide temperature at the expander outlet is lower than the supercritical temperature and whether a large-area liquefaction phenomenon occurs. If large-scale liquefaction occurs, the controller of the temperature control system adjusts the opening of the regulating valve to reduce the flow rate of the cooling medium in the first heat exchanger, thereby increasing the temperature of the stored hot water and ensuring that the temperature of the carbon dioxide in the final stage of the expander is not lower than the critical temperature.

2. The adiabatic supercritical compressed carbon dioxide energy storage system according to claim 1, characterized in that, The outlet of the first stage compressor (5) is connected to the inlet of the first stage intercooler (9), and the first stage intercooler (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 stage intercooler (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 stage intercooler (10), and the second stage intercooler (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); 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).

3. The adiabatic supercritical compressed carbon dioxide energy storage system according to claim 1 or 2, characterized in that, The thermodynamic model of the compressor in the compressor unit is as follows: Assume the internal temperature of the i-th stage compressor is The compression process is a variable process, which we treat as an adiabatic process. Considering the isotropic efficiency, the outlet temperature is... for: It is the compression ratio of the i-th stage compressor. k It is the specific heat ratio. It refers to the compressor's adiabatic efficiency; When a unit mass of air enters the compressor, the compressor performs the following work: It is the specific heat of carbon dioxide at constant pressure, superscript. in These are the components that enter the compressor. out The components are those coming out of the compressor. The subscript 'c' indicates the compression and charging process. Therefore, based on the work consumed by each stage of the compressor, the total power consumption of the compressor is: 。 4. The adiabatic supercritical compressed carbon dioxide energy storage system according to claim 1 or 2, characterized in that, The thermodynamic model of the expander in the expander unit is as follows: During the energy release stage, after passing through the heat exchanger in stage i, the temperature is... High-pressure carbon dioxide enters the expander; When a unit mass of carbon dioxide enters the i-th stage turbine, the output work is: The air outlet temperature of the i-th stage turbine is: It is the expansion ratio of the i-th stage expander. If the isentropic efficiency of the expander is given, then the total output work during the energy release phase is: 。 5. The adiabatic supercritical compressed carbon dioxide energy storage system according to claim 4, characterized in that, The energy storage efficiency of the adiabatic supercritical compressed carbon dioxide energy storage system is: For the duration of the energy storage phase, This refers to the duration of the energy release phase.

6. 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; the cold storage tank (4) is a cooling water tank.

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