Supercritical carbon dioxide heat storage system heat exchange network optimization method and device based on pinch point optimization

Abstract

The invention provides a supercritical carbon dioxide heat storage system heat exchange network optimization method and device based on pinch point optimization, and the method specifically comprises the following steps: calculating the temperature and flow of a heat storage material corresponding to a heat exchange pinch point according to the working medium flow of a first heat exchanger and the working medium temperature of the assumed heat exchange pinch point; the temperature of inlet and outlet heat storage materials of the first heat exchanger is obtained; determining the working medium outlet temperature of the second heat exchanger by using the first heat exchanger outlet heat storage material temperature and the minimum heat exchange temperature difference; according to the working medium outlet temperature and pressure of the second heat exchanger and heat engine circulation parameters, the working medium inlet and outlet temperature of the third heat exchanger is determined, and the heat storage material temperature, flow and inlet and outlet temperature corresponding to the heat exchange pinch point are calculated; and when the temperatures of the working medium in the fourth heat exchanger and the heat storage material at the outlet of the third heat exchanger meet the minimum temperature difference limit, calculating the round-trip efficiency of the heat storage system at the assumed heat exchange pinch point working medium temperatures of the first and third heat exchangers, and selecting the optimal temperature to complete heat exchange network optimization, thereby improving the heat exchange efficiency of the system.

Description

Technical Field

[0001] The present invention belongs to the field of energy storage technology, and specifically relates to a method and device for optimizing a heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization. Background Art

[0002] With the growing global emphasis on renewable energy, clean energy sources such as wind power and photovoltaics are increasingly contributing to the power grid's share of power. However, these renewable energy sources exhibit significant randomness and volatility, posing significant challenges to grid stability. To effectively balance the temporal and spatial variations in energy supply and demand and improve grid stability and reliability, thermal storage technology has emerged. As a highly efficient energy storage method, thermal storage not only helps regulate grid load and mitigate peak-to-valley fluctuations, but also effectively supports the grid by storing excess energy during peak renewable generation periods and releasing it during peak demand.

[0003] Supercritical CO2 heat pump energy storage technology, an innovative approach to heat storage, utilizes supercritical CO2 (SCO2) as a working fluid, enabling the storage and release of electrical energy through the circulation of heat pumps and heat engines. This technology boasts multiple advantages, including high efficiency, environmental friendliness, and sustainability, and is considered a key development direction in the future of energy storage. However, in practical applications, supercritical CO2 heat pump energy storage systems also face some technical challenges.

[0004] Among them, the most prominent problem is the low heat exchange efficiency between supercritical carbon dioxide and common heat storage materials. Because the specific heat of carbon dioxide in the supercritical state varies significantly with temperature, when it exchanges heat with common heat storage materials such as molten salt, thermal oil, and water, it is prone to a "pinch point" phenomenon. In other words, the minimum heat exchange temperature difference occurs somewhere in the middle of the heat exchanger, rather than at the inlet and outlet ends of the heat exchanger, which seriously affects the heat exchange efficiency. This not only reduces the thermal efficiency of the entire thermal system, but also increases the system's net output power loss and irreversible losses, which in turn has a negative impact on the performance of the entire energy storage system.

[0005] Therefore, it is particularly important to propose a design method for optimizing the pinch point heat exchange network and heat storage temperature zone based on the physical properties of supercritical carbon dioxide, in response to the problems existing in the supercritical carbon dioxide heat pump power storage system. Summary of the Invention

[0006] To address the problems existing in the prior art, the present invention provides a method and device for optimizing the heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization. This method not only helps to improve the heat exchange efficiency of the system, but also further optimizes the performance of the entire energy storage system, thereby promoting the widespread application and development of supercritical carbon dioxide heat pump energy storage technology.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for optimizing a heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization, comprising the following specific steps:

[0008] According to the working fluid flow rate of the first heat exchanger and the working fluid temperature corresponding to the assumed heat exchange pinch point, the temperature and flow rate of the heat storage material corresponding to the heat exchange pinch point are obtained, and the temperatures of the heat storage material at the inlet and outlet of the first heat exchanger are obtained using the temperature and flow rate of the heat storage material;

[0009] The working medium outlet temperature of the second heat exchanger is obtained by using the heat storage material temperature at the outlet of the first heat exchanger and the minimum heat exchange temperature difference;

[0010] Determine the working medium inlet and outlet temperatures of the third heat exchanger based on the working medium outlet temperature and pressure of the second heat exchanger and the operating parameters of the heat engine cycle;

[0011] The working fluid inlet and outlet temperatures of the third heat exchanger and the working fluid temperature corresponding to the assumed heat exchange pinch point are used to obtain the heat storage material temperature and flow rate corresponding to the heat exchange pinch point, and the heat storage material temperatures at the inlet and outlet of the third heat exchanger are obtained using the heat storage material temperature and flow rate;

[0012] When the temperature of the working fluid in the fourth heat exchanger and the heat storage material at the outlet of the third heat exchanger meet the minimum temperature difference constraint, the round-trip efficiency of the heat storage system is calculated under the working fluid temperature conditions corresponding to the assumed heat exchange pinch point of the first and third heat exchangers. The working fluid temperatures corresponding to the assumed heat exchange pinch points of the first and third heat exchangers that optimize the round-trip efficiency of the heat storage system are selected to complete the optimization of the heat exchange network of the heat storage system.

[0013] Furthermore, when the temperature of the working medium in the fourth heat exchanger and the heat storage material at the outlet of the third heat exchanger meet the minimum temperature difference constraint condition, the working medium temperature corresponding to the heat exchange pinch point assumed in the first heat exchanger and the third heat exchanger is excluded and a new assumption is made.

[0014] Furthermore, the steps of obtaining the temperature of the heat storage material at the inlet and outlet of the first heat exchanger are specifically as follows:

[0015] Assuming that the working fluid temperature corresponding to the heat exchange pinch point in the first heat exchanger is between the working fluid inlet and outlet temperatures of the first heat exchanger;

[0016] Combining the minimum heat exchange temperature difference and the working fluid temperature corresponding to the assumed heat exchange pinch point, the heat storage material temperature corresponding to the heat exchange pinch point is obtained;

[0017] Obtaining a heat storage material flow rate according to the working fluid flow rate of the first heat exchanger, the working fluid specific heat corresponding to the heat exchange pinch point, and the specific heat of the heat storage material;

[0018] Taking the heat exchange pinch point as the starting / ending point, the heat exchange process of the first heat exchanger is discretely calculated to obtain the temperature of the heat storage material at the inlet and outlet of the first heat exchanger. The discrete calculation formula is as follows:

[0019] m HTE，HST ·cp HTE，HST ·(T HST，out -T HST，in )=m HTE，CO2 ·(h HTE，CO2，in -h HTE，CO2，out ) (3)

[0020] Where: m HTE,HST is the heat storage material flow rate; cp HTE,HST is the average specific heat of the heat storage material; T HST,in is the inlet temperature of the heat storage material; T HST,out is the outlet temperature of the heat storage material; m HTE,CO2 is the working fluid flow rate; h HTE,CO2,in is the specific enthalpy of the working fluid at the inlet; h HTE,CO2,out is the working fluid outlet specific enthalpy;

[0021] A temperature-heat exchange curve for the heat exchange between the working fluid and the heat storage material is drawn. Based on the curve verification, if the heat exchange pinch point position is consistent with the working fluid temperature corresponding to the assumed heat exchange pinch point and the obtained heat storage material temperature, and meets the set minimum heat exchange temperature difference, the heat storage material temperature corresponding to the heat exchange pinch point in the first heat exchanger is obtained.

[0022] Furthermore, the difference between the temperature of the heat storage material at the outlet of the first heat exchanger and the minimum heat exchange temperature difference is the working medium outlet temperature of the second heat exchanger.

[0023] Furthermore, the working medium side of the third heat exchanger and the working medium side of the second heat exchanger are connected through a heat engine circulation portion, and the steps of determining the working medium inlet and outlet temperatures of the third heat exchanger are specifically as follows:

[0024] The working fluid inlet temperature of the third heat exchanger is obtained according to the working fluid inlet pressure and inlet specific enthalpy of the third heat exchanger. The working fluid inlet specific enthalpy of the third heat exchanger is calculated as follows:

[0025] The working medium outlet temperature and working medium outlet pressure of the second heat exchanger are used to obtain the working medium inlet specific enthalpy of the heat engine turbine;

[0026] The specific enthalpy at the outlet of the heat engine turbine is obtained by using the specific enthalpy at the inlet of the heat engine turbine working medium, the ideal specific enthalpy at the outlet and the isentropic efficiency;

[0027] The working medium inlet specific enthalpy of the third heat exchanger is obtained by using the working medium outlet specific enthalpy of the heat engine turbine, the working medium inlet specific enthalpy of the second heat exchanger, and the working medium outlet specific enthalpy of the heat engine compressor;

[0028] The working medium outlet temperature of the third heat exchanger is obtained according to the working medium outlet pressure and outlet specific enthalpy, wherein the working medium outlet specific enthalpy of the third heat exchanger is equal to the working medium inlet specific enthalpy of the heat engine cooler.

[0029] Furthermore, the steps for obtaining the temperature of the heat storage material at the inlet and outlet of the third heat exchanger are specifically as follows:

[0030] Assume that the working fluid temperature corresponding to the heat exchange pinch point in the third heat exchanger is between the working fluid inlet and outlet temperatures of the third heat exchanger;

[0031] Combining the minimum heat exchange temperature difference and the working fluid temperature corresponding to the assumed heat exchange pinch point, the heat storage material temperature corresponding to the heat exchange pinch point is obtained;

[0032] Obtaining the heat storage material flow rate according to the working fluid flow rate of the third heat exchanger, the working fluid specific heat corresponding to the heat exchange pinch point, and the specific heat of the heat storage material;

[0033] Taking the heat exchange pinch point as the starting / ending point, the heat exchange process of the third heat exchanger is discretely calculated to obtain the temperature of the heat storage material at the inlet and outlet of the third heat exchanger. The discrete calculation formula is as follows:

[0034] m LTE,LST ·cp LTE,LST ·(T LST,out -T LST,in )=m HE,LTE,CO2 ·(h LTE,CO2,in -h LTE,CO2,out )(13)

[0035] Where: m LTE,LST is the heat storage material flow rate; cp LTE,LST is the average specific heat of the heat storage material; T LST,in is the inlet temperature of the heat storage material; T LST,out is the outlet temperature of the heat storage material; m HE,LTE,CO2 is the working fluid flow rate; h LTE,CO2,in is the specific enthalpy of the working fluid at the inlet; h LTE,CO2,out is the working fluid outlet specific enthalpy;

[0036] A temperature-heat exchange curve for the heat exchange between the working fluid and the heat storage material is drawn. Based on the curve verification, if the heat exchange pinch point position is consistent with the working fluid temperature corresponding to the assumed heat exchange pinch point and the obtained heat storage material temperature, and meets the set minimum heat exchange temperature difference, the heat storage material temperature corresponding to the heat exchange pinch point in the third heat exchanger is obtained.

[0037] Furthermore, the supercritical carbon dioxide heat storage system includes a high-temperature heat storage part, a low-temperature heat storage part, a heat engine cycle part, and a heat pump cycle part, wherein:

[0038] High-temperature heat storage part: the outlet of the high-temperature heat storage cold tank is connected to the inlet of the heat storage material of the first heat exchanger, the outlet of the first heat exchanger heat storage material is connected to the inlet of the high-temperature heat storage hot tank, and the working fluid side of the first heat exchanger is connected to the low-temperature heat storage part through the heat pump circulation part;

[0039] The outlet of the high-temperature heat storage tank is connected to the inlet of the heat storage material of the heat engine high-temperature heat exchanger, the outlet of the heat engine high-temperature heat exchanger heat storage material is connected to the inlet of the high-temperature heat storage cold tank, and the working fluid side of the heat engine high-temperature heat exchanger is connected to the low-temperature heat storage part through the heat engine circulation part;

[0040] Low-temperature heat storage part: the outlet of the low-temperature heat storage cold tank is connected to the inlet of the heat storage material of the third heat exchanger, the outlet of the heat storage material of the third heat exchanger is connected to the inlet of the low-temperature heat storage hot tank, and the working fluid side of the third heat exchanger is connected to the high-temperature heat storage part through the heat engine circulation part;

[0041] The outlet of the low-temperature heat storage tank is connected to the heat storage material inlet of the fourth heat exchanger, the heat storage material outlet of the fourth heat exchanger is connected to the inlet of the low-temperature heat storage tank, and the working fluid side of the fourth heat exchanger is connected to the high-temperature heat storage part through the heat pump circulation part;

[0042] The round-trip efficiency of the heat storage system is expressed by the ratio of the work done by the heat engine cycle part during the heat release process to the power consumed by the heat pump cycle part during the heat storage process.

[0043] Furthermore, genetic algorithms, neural networks, particle swarm algorithms and other algorithms are used to assign values ​​to the working fluid temperatures corresponding to the assumed heat exchange pinch points of the first and third heat exchangers, and the working fluid temperatures corresponding to the assumed heat exchange pinch points of the first and third heat exchangers that optimize the round-trip efficiency of the heat storage system are selected to complete the optimization of the heat exchange network of the heat storage system.

[0044] The present invention also provides a supercritical carbon dioxide heat storage system heat exchange network optimization system based on pinch point optimization, including a network optimization module, which runs the steps of the above-mentioned supercritical carbon dioxide heat storage system heat exchange network optimization method based on pinch point optimization.

[0045] The present invention also provides a terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the above-mentioned method for optimizing the heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization are implemented.

[0046] Compared with the prior art, the present invention has at least the following beneficial effects:

[0047] The present invention provides a method for optimizing the heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization. Unlike conventional design methods, this method performs optimization from the perspective of the overall thermal system. It not only focuses on the performance of a single heat exchanger, but considers the entire supercritical carbon dioxide heat storage system as a whole, and optimizes the system performance by optimizing the heat exchange relationship, heat storage temperature zone, and heat exchange pinch point position between each heat exchanger. This holistic optimization method can avoid the problem of overall system performance degradation caused by local optimization, and enables the various parts of the system to coordinate with each other to maximize their efficiency. Through optimization, the adverse effects of the heat exchange pinch point on the system can be minimized. The heat exchange pinch point is the key point of temperature change in the heat exchange process. If it is not handled properly, it will lead to problems such as reduced heat exchange efficiency and increased energy loss. The method of the present invention finds the optimal heat exchange pinch point position through precise calculation and optimization, thereby improving the heat exchange efficiency of the system and reducing energy loss.

[0048] The heat exchange matching relationship between the circulating working fluid and the heat storage material directly affects the heat exchange efficiency and performance of the system. By optimizing this matching relationship, the method of the present invention can reduce irreversible losses during the heat exchange process. Irreversible losses are inevitable energy losses in thermodynamic processes, but they can be minimized through reasonable optimization design. For example, by precisely controlling the working fluid temperature and the heat storage material temperature corresponding to the heat exchange pinch point, and by rationally designing the structure and parameters of the heat exchanger, the working fluid and heat storage material can transfer heat more efficiently during the heat exchange process, reducing energy losses caused by excessive temperature differences or insufficient heat exchange.

[0049] Optimizing the heat exchange matching between the circulating fluid and the heat storage material ultimately improves the performance of the entire heat pump energy storage system. The performance of a heat pump energy storage system is primarily reflected in its heat storage efficiency, heat release efficiency, and round-trip efficiency. By reducing irreversible heat exchange losses and improving heat exchange efficiency, the system can more effectively utilize energy during both the storage and release processes, thereby improving both the storage and release efficiencies. Furthermore, due to the improved overall system performance, the round-trip efficiency of the heat storage system is also optimized, making the system more economical and feasible in the energy conversion and storage process.

[0050] Furthermore, the method of the present invention uses algorithms such as genetic algorithms, neural networks, and particle swarm optimization to assign working fluid temperatures corresponding to the hypothetical heat exchange pinch points of the first and third heat exchangers, and selects the hypothetical temperature that optimizes the round-trip efficiency of the heat storage system. These advanced optimization algorithms possess powerful search and optimization capabilities, enabling rapid identification of optimal solutions within complex parameter spaces. Compared to traditional trial-and-error or empirical design methods, these algorithms can significantly improve the efficiency and accuracy of the optimization process, reducing design time and costs.

[0051] Furthermore, the supercritical carbon dioxide heat storage system targeted by this invention is a complex thermodynamic system, involving interactions among multiple heat exchangers, working fluids, and heat storage materials. Advanced optimization algorithms are capable of handling this complexity, comprehensively optimizing various system parameters by establishing mathematical models and optimizing objective functions. These algorithms also possess excellent adaptability and robustness, capable of handling variations and uncertainties in system parameters, ensuring the reliability and stability of optimization results. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 Schematic diagram of the process of the present invention;

[0053] Figure 2 Schematic diagram of supercritical carbon dioxide heat pump power storage system;

[0054] Figure 3 Comparison of heat exchange matching effects between the method of the present invention and conventional methods;

[0055] In the attached figure: 1. High-temperature heat storage cold tank; 2. High-temperature heat storage hot tank; 3. First heat exchanger; 4. Heat pump compressor; 5. Heat pump regenerator; 6. Heat pump turbine; 7. Fourth heat exchanger; 8. Low-temperature heat storage hot tank; 9. Low-temperature heat storage cold tank; 10. Third heat exchanger; 11. Heat engine cooler; 12. Heat engine compressor; 13. Heat engine regenerator; 14. Heat engine turbine; 15. Heat engine high-temperature heat exchanger; 16. Valve. DETAILED DESCRIPTION

[0056] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0057] like Figure 2 As shown, a supercritical carbon dioxide heat pump power storage system includes: a high-temperature heat storage cold tank 1, a high-temperature heat storage hot tank 2, a first heat exchanger 3, a heat pump compressor 4, a heat pump regenerator 5, a heat pump turbine 6, a fourth heat exchanger 7, a low-temperature heat storage hot tank 8, a low-temperature heat storage cold tank 9, a third heat exchanger 10, a heat engine compressor 12, a heat engine regenerator 13, a heat engine turbine 14, a heat engine high-temperature heat exchanger 15 and a valve 16, wherein:

[0058] The high-temperature heat storage section includes a high-temperature heat storage cold tank 1 and a high-temperature heat storage hot tank 2. These two tanks are connected via a first heat exchanger 3 to form a heat storage cycle. They are also connected via a heat engine high-temperature heat exchanger 15 to form a heat release cycle. During the heat storage phase, the heat storage material in the high-temperature heat storage cold tank 1 enters the first heat exchanger 3 through valve 161 to absorb heat and increase its temperature. The heated heat storage material is then stored in the high-temperature heat storage hot tank 2. During the heat release phase, the heat storage material in the high-temperature heat storage hot tank 2 enters the heat engine high-temperature heat exchanger 15 through valve 162 to release heat and decrease its temperature. The cooled heat storage material is then stored in the high-temperature heat storage cold tank 1.

[0059] The heat pump cycle consists of a first heat exchanger 3, a heat pump compressor 4, a heat pump regenerator 5, a heat pump turbine 6, and a fourth heat exchanger 7. The fourth heat exchanger 7 is connected to a low-temperature heat storage tank 8 and a low-temperature heat storage cold tank 9, absorbing low-temperature heat and raising the temperature of the carbon dioxide working medium. The heat pump regenerator 5, located between the compressor 4 and the fourth heat exchanger 7, recovers and utilizes waste heat from the high-temperature heat exchanger working medium to preheat the working medium entering the compressor, thereby improving system efficiency. The heat pump compressor 4 receives low-pressure, high-temperature supercritical carbon dioxide working medium from the heat pump regenerator 5 and compresses it to further increase its pressure and temperature. The first heat exchanger 3 is connected to a high-temperature heat storage cold tank 1 and a high-temperature heat storage hot tank 2, releasing the heat energy of the carbon dioxide working medium at the compressor outlet and transferring it to the heat storage material. The heat pump turbine 6 receives the carbon dioxide working medium after it has released heat from the heat pump regenerator 5, causing it to expand and produce work, thereby lowering the working medium's temperature.

[0060] The low-temperature heat storage section includes a low-temperature heat storage hot tank 8 and a low-temperature heat storage cold tank 9. These two tanks are connected via a fourth heat exchanger 7 to form a heat release cycle; they are also connected via a third heat exchanger 10 to form a heat storage cycle. During the heat storage phase, the heat storage material in the low-temperature heat storage cold tank 9 enters the third heat exchanger 10 through valve 164 to absorb heat and increase its temperature. The heated heat storage material is then stored in the low-temperature heat storage hot tank 8. During the heat release phase, the heat storage material in the low-temperature heat storage hot tank 8 enters the fourth heat exchanger 7 through valve 163 to release heat and decrease its temperature. The cooled heat storage material is then stored in the low-temperature heat storage cold tank 9.

[0061] The heat engine cycle includes a third heat exchanger 10, a heat engine compressor 12, a heat engine regenerator 13, a heat engine turbine 14, and a heat engine high-temperature heat exchanger 15. The heat engine high-temperature heat exchanger 15 is connected to the high-temperature heat storage cold tank 1 and the high-temperature heat storage hot tank 2. It absorbs heat energy from the hot tanks and transfers it to the working fluid in the heat engine cycle. The heat engine compressor 12, the heat engine regenerator 13, the heat engine turbine 14, and the heat engine high-temperature heat exchanger 15 together constitute the heat engine cycle, which is the reverse process of the heat pump cycle and is typically used to generate electricity.

[0062] The valve 16 includes a first valve 161, a second valve 162, a third valve 163 and a fourth valve 164, which are respectively arranged at the outlets of the high-temperature heat storage cold tank 1, the high-temperature heat storage hot tank 2, the low-temperature heat storage hot tank 8 and the low-temperature heat storage cold tank 9, and are used to control the flow path of the system to ensure that the working medium flows at the correct time and direction.

[0063] The heat pump cycle process is as follows:

[0064] During the heat storage phase, the supercritical carbon dioxide working fluid absorbs heat from the low-temperature heat storage tank 8 and the waste heat of the working fluid at the outlet of the first heat exchanger 3 in the fourth heat exchanger 7 and the heat pump regenerator 5, respectively, to increase its temperature. The working fluid then enters the heat pump compressor 4 for compression, further increasing its temperature and pressure. The compressed working fluid releases heat through the first heat exchanger 3, heating the heat storage material from the high-temperature heat storage cold tank 1, and storing the heated heat storage material in the high-temperature heat storage tank 2, thus storing heat. The working fluid at the outlet of the first heat exchanger 3 is further cooled in the heat pump regenerator 5 and then enters the heat pump turbine 6 for expansion; the expanded low-pressure and low-temperature working fluid absorbs heat energy in the fourth heat exchanger 7, starting a new cycle.

[0065] The heat engine cycle process is specifically as follows:

[0066] The heat engine cycle, the opposite of a heat pump cycle, is typically used to convert thermal energy into electricity. During the heat release phase, the working fluid absorbs heat energy from the high-temperature heat storage tank 2 in the heat engine's high-temperature heat exchanger 15. The working fluid then completes the cycle through the heat engine turbine 14, the heat engine regenerator 13, the third heat exchanger 10, the heat engine cooler 11, and the heat engine compressor 12. In the heat engine turbine 14, the working fluid expands and performs work, outputting mechanical or electrical energy. The expanded working fluid then releases heat energy in the heat engine regenerator 13, the third heat exchanger 10, and the cooler 11, returning to the heat engine compressor 12 to begin the cycle anew.

[0067] like Figure 1 As shown, the present invention provides a heat exchange network optimization method for a supercritical carbon dioxide heat storage system based on pinch point optimization, and the specific steps are as follows:

[0068] S1) Inputting heat pump cycle parameters for the heat storage process, including the inlet and outlet temperatures, pressures, and flow rates of the carbon dioxide working fluid of the heat pump compressor 4, the first heat exchanger 3, the heat pump regenerator 5, the heat pump turbine 6, and the fourth heat exchanger 7;

[0069] S2) Assuming the working fluid temperature corresponding to the heat exchange pinch point in the first heat exchanger 3, and then calculating the inlet and outlet parameters of the high-temperature heat storage material in the first heat exchanger 3, that is, the temperature and flow rate of the high-temperature heat storage cold tank 1 and the hot tank 2;

[0070] S3) Based on the temperatures of the high-temperature heat storage cold tank 1 and the hot tank 2 obtained in step S2, the carbon dioxide working medium inlet temperature of the second heat exchanger 15 is input to calculate the carbon dioxide working medium outlet temperature of the second heat exchanger 15;

[0071] S4) Inputting parameters of the heat engine cycle during the heat release process, including the inlet and outlet temperatures, pressures, and flow rates of the carbon dioxide working fluid of the heat engine compressor 12 and the heat engine cooler 11; and calculating the inlet and outlet temperatures of the carbon dioxide working fluid of the third heat exchanger 10;

[0072] S5) Assuming the temperature of the carbon dioxide working medium corresponding to the heat exchange pinch point in the third heat exchanger 10, calculate the inlet and outlet parameters of the low-temperature heat storage material in the third heat exchanger 10, that is, the temperature and flow rate of the low-temperature heat storage cold tank 9 and the low-temperature heat storage hot tank 8;

[0073] S6) determining whether the heat exchange between the carbon dioxide working fluid and the low-temperature heat storage material in the fourth heat exchanger 7 meets the minimum temperature difference constraint condition. If so, calculating the round-trip efficiency of the heat storage system under the assumed temperature values ​​in this process S2 and S5; if not, the assumed temperature values ​​in this process S2 and S5 do not meet the condition and are excluded;

[0074] S7) Changing the values ​​of the assumed temperatures in S2 and S5 and repeating the calculations in steps S1 to S6, comparing the round-trip efficiency of the heat storage system under different values, and finally obtaining the values ​​of the assumed temperatures in S2 and S5 that maximize the round-trip efficiency, thus completing the heat exchange network optimization.

[0075] In S2, the specific operation process of calculating the inlet and outlet parameters of the high-temperature heat storage material in the first heat exchanger 3 is as follows:

[0076] 1) The inlet temperature T of the supercritical carbon dioxide working medium input to the first heat exchanger 3 HTE,SCO2,in , outlet temperature T HTE,SCO2,ou and flow m HTE,CO2 ;

[0077] 2) Assume that the circulating medium temperature T corresponding to the heat exchange pinch point in the first heat exchanger 3 is pinch,CO2 , where T HTE,CO2,out ≤T pinch,CO2 ≤T HTE,CO2,in ;

[0078] 3) Calculate the heat storage material temperature T corresponding to the heat exchange pinch point position in the first heat exchanger 3 pinch,HST :

[0079] T pinch，HST =T pinch，CO2 -ΔT min (1)

[0080] Where: T pinch,CO2 is the circulating medium temperature corresponding to the heat exchange pinch point position in the assumed first heat exchanger 3; ΔT min is the minimum heat transfer temperature difference / ℃.

[0081] 4) Match the heat storage material flow m HTE,HST :

[0082] m HTE，HST =m HTE，CO2 ·cp HTE，pinch，CO2 / cp HTE，pinch，HST (2)

[0083] Where: cp HTE，pinch，CO2 is the specific heat of carbon dioxide at the heat exchange pinch point / kJ·kg –1 ℃ –1 ;cp HTE，pinch，HST is the specific heat of the heat storage material at the heat exchange pinch point / kJ·kg –1 ℃ –1 ;

[0084] 5) Discretize the first heat exchanger 3 with the pinch point as the starting / ending point, and calculate the inlet and outlet temperatures of the heat storage material of the first heat exchanger 3. For each calculation unit, the inlet and outlet temperatures of the heat storage material can be calculated using the following formula:

[0085] m HTE，HST ·cp HTE，HST ·(T HST，out -T HST，in )=m HTE，CO2 ·(h HTE，CO2，in -h HTE，CO2，out ) (3)

[0086] Where: m HTE,HST is the heat storage material flow in the calculation unit; cp HTE,HST is the average specific heat of the heat storage material in the calculation unit / kJ·kg –1 ℃ –1 ;T HST,in is the inlet temperature of the heat storage material in the calculation unit / °C; T HST,out is the outlet temperature of the heat storage material in the calculation unit / ℃; m HTE,CO2 is the carbon dioxide flow rate in the calculation unit; h HTE,CO2,in is the inlet specific enthalpy of carbon dioxide in the calculation unit / kJ·kg –1 ;h HTE,CO2,out is the specific enthalpy of carbon dioxide outlet in the calculation unit / kJ·kg –1 ;

[0087] 6) Draw the temperature-heat transfer (TQ) curve of the heat exchange between supercritical carbon dioxide working fluid and high-temperature heat storage material, and verify whether the heat exchange pinch point position is consistent with TQ based on the curve. pinch,CO2 and T pinch,HST Consistent, and whether the minimum heat exchange temperature difference meets the setting conditions: If it does, the temperature T of the high-temperature heat storage cold tank (1) and the high-temperature heat storage hot tank (2) can be obtained. HTE,HST,in 、T HTE,HST,out If not, move the heat absorption curve of the heat storage material downward until the constraint is met, and obtain the new temperature of the high-temperature heat storage cold tank 1 and the high-temperature heat storage hot tank 2.

[0088] In S3, the outlet temperature of the carbon dioxide working medium of the second heat exchanger (15) is T HE,HTE,CO2,out The calculation of is as follows:

[0089] T HE,HTE,CO2,out =T HTE,HST,out -ΔT min (4)

[0090] Among them, T HTE,HST,out is the temperature of the heat storage material of the high-temperature heat storage tank (2); ΔT min is the minimum heat transfer temperature difference / ℃.

[0091] In S4, the inlet and outlet temperatures of the carbon dioxide working medium of the third heat exchanger (10) are T HE,LTE,CO2,in 、T HE,LTE,CO2,out calculate:

[0092] h HE,T,in =f(T HE,HTE,CO2,out ,P HE,HTE,CO2,out ) (5)

[0093] h HE,T,out =h HE,T,in -(h HE,T,in -h HE,T,out,is )·η HE,T (6)

[0094] h HE,LTE,CO2,in =h HE,T,out -(h HE,HTE,CO2,in -h HE,C,out ) (7)

[0095] h HE,LTE,CO2,out =h HE,PC,CO2,in (8)

[0096] T HE,LTE,CO2,out =f(P HE,LTE,CO2,out ,h HE,LTE,CO2,out ) (9)

[0097] T HE,LTE,CO2,in =f(P HE,LTE,CO2,in ,h HE,LTE,CO2,in ) (10)

[0098] Where: T HE,HTE,CO2,out is the outlet temperature of the carbon dioxide working medium of the second heat exchanger (15); P HE,HTE,CO2,out is the outlet pressure of the carbon dioxide working medium of the second heat exchanger (15) / kPa, which is calculated by subtracting the pressure loss of the heat engine compressor (12); h HE,T,in is the specific enthalpy at the inlet of the heat engine turbine (14) / kJ·kg –1 ;h HE,T,out is the specific enthalpy at the outlet of the heat engine turbine (14) / kJ·kg –1 ;h HE,T,out,is is the ideal outlet specific enthalpy of the heat engine turbine (14) / kJ·kg –1 ;η HE,Tis the isentropic efficiency of the heat engine turbine (14); h HE,LTE,CO2,in is the inlet specific enthalpy of the carbon dioxide working medium of the third heat exchanger (10) / kJ·kg –1 ;h HE,HTE,CO2,in is the specific enthalpy of carbon dioxide at the inlet of the second heat exchanger (15) / kJ·kg –1 ;h HE,C,out is the outlet specific enthalpy of the working medium of the heat engine compressor (12) / kJ·kg –1 ;h HE,LTE,CO2,out is the specific enthalpy of the carbon dioxide working medium outlet of the third heat exchanger (10) / kJ·kg –1 ;h HE,PC,CO2,in is the specific enthalpy of carbon dioxide at the inlet of the heat engine cooler (11) / kJ·kg –1 ;P HE,LTE,CO2,in is the carbon dioxide working medium inlet pressure of the third heat exchanger (10) / kPa; P HE,LTE,CO2,out is the outlet pressure of the carbon dioxide working medium of the third heat exchanger (10) / kPa;

[0099] The specific operation process of the calculation described in step S5 is as follows:

[0100] 1) The carbon dioxide inlet temperature T of the third heat exchanger (10) is known. HE,LTE,CO2,in , outlet temperature T HE,LTE,CO2,out and flow m HE,LTE,CO2 ;

[0101] 2) Assume that the temperature of the carbon dioxide working medium corresponding to the heat exchange pinch point in the third heat exchanger (10) is T LTE,pinch,CO2 , the assumed carbon dioxide working temperature satisfies: T HE,LTE,CO2,out ≤T LTE,pinch,CO2 ≤T HE,LTE,CO2,in ;

[0102] 3) Calculate the heat storage material temperature T corresponding to the heat exchange pinch point in the third heat exchanger (10) pinch,LST :

[0103] T pinch,LST =T LTE,pinch,CO2 -ΔT min (11)

[0104] Where: ΔT min is the minimum heat transfer temperature difference / ℃.

[0105] 4) Matching heat storage material flow:

[0106] m LTE,LST =m HE,LTE,CO2 ·cp LTE,pinch,CO2 / cp LTE,pinch,LST (12)

[0107] Where: cpLTE,pinch,CO2 is the specific heat of carbon dioxide at the pinch point / kJ·kg –1 ℃ –1 ;cp LTE,pinch,LST is the specific heat of the heat storage material at the pinch point / kJ·kg –1 ℃ –1 ;

[0108] 5) Discretize the third heat exchanger with the pinch point as the starting / ending point, and calculate the inlet and outlet temperatures of the heat storage material in the third heat exchanger. For each discrete calculation unit, the inlet and outlet temperatures of the heat storage material can be calculated using the following formula:

[0109] m LTE,LST ·cp LTE,LST ·(T LST,out -T LST,in )=m HE,LTE,CO2 ·(h LTE,CO2,in -h LTE,CO2,out ) (13)

[0110] Where: m LTE,LST is the heat storage material flow in the calculation unit; cp LTE,LST is the average specific heat of the heat storage material in the calculation unit / kJ·kg –1 ℃ –1 ;T LST,in is the inlet temperature of the heat storage material in the calculation unit / °C; T LST,out is the outlet temperature of the heat storage material in the calculation unit / ℃; m HE,LTE,CO2 is the carbon dioxide flow rate in the calculation unit; h LTE,CO2,in is the inlet specific enthalpy of carbon dioxide in the calculation unit / kJ·kg –1 ;h LTE,CO2,out is the specific enthalpy of carbon dioxide outlet in the calculation unit / kJ·kg –1 ;

[0111] 6) Draw the temperature-heat transfer (TQ) curve of the heat exchange between supercritical carbon dioxide working fluid and low-temperature heat storage material, and verify whether the pinch point position is consistent with the TQ curve. LTE,pinch,CO2 and T pinch,LST Consistent, and whether the minimum heat exchange temperature difference meets the setting conditions: If it does, the temperature T of the low-temperature heat storage cold tank 9 and the low-temperature heat storage hot tank 8 can be obtained. LTE,LST,in 、T LTE,LST,out If not, move the heat absorption curve of the heat storage material downward until the constraint is met, and obtain the new temperature of the low-temperature heat storage cold tank 9 and the low-temperature heat storage hot tank 8.

[0112] In step S6, the round-trip efficiency of the heat storage system is represented by the ratio of the heat engine cycle work in the heat release process to the heat pump cycle power consumption in the heat storage process.

[0113] In step S7, the values ​​of the assumed temperatures in S2 and S5 are assigned using algorithms such as genetic algorithms, neural networks, and particle swarm algorithms.

[0114] Example 1:

[0115] The present invention provides a method for optimizing a heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization, the specific steps of which are as follows:

[0116] Step 1: Input the heat pump cycle parameters for the heat storage process, including the inlet and outlet temperatures, pressures, and flow rates of the carbon dioxide working fluid of the heat pump compressor 4, the first heat exchanger 3, the heat pump regenerator 5, the heat pump turbine 6, and the fourth heat exchanger 7, as shown in the following table:

[0117]

[0118] Step 2: Assume the temperature of the carbon dioxide working medium corresponding to the heat exchange pinch point in the first heat exchanger 3, and then calculate the inlet and outlet parameters of the high-temperature heat storage material in the first heat exchanger 3, that is, the temperature and flow rate of the high-temperature heat storage cold tank 1 and the high-temperature heat storage hot tank 2. The specific operation is as follows:

[0119] 1) The inlet and outlet temperatures and flow rates of the carbon dioxide working fluid in the first heat exchanger 3 are known to be 606°C, 409.3°C, and 295.6 kg / s, respectively;

[0120] 2) Assume that the temperature of the carbon dioxide working medium corresponding to the heat exchange pinch point in the first heat exchanger 3 is 600°C, where 409.3°C ≤ 600°C ≤ 606°C;

[0121] 3) Set the minimum heat exchange temperature difference ΔT min is 6°C, then the calculated temperature of the heat storage material at the pinch point in the first heat exchanger 3 is 594°C;

[0122] 4) Matching the flow rate of heat storage material: The specific heat of high-temperature heat storage material is 1545 J / (kg·°C), and the calculated flow rate of high-temperature heat storage material is 243.3 kg / s;

[0123] 5) Discretize the first heat exchanger with the pinch point as the starting and ending points, and calculate the inlet and outlet temperatures of the heat storage material of the first heat exchanger to be 402.3°C and 600°C respectively;

[0124] 6) Draw the temperature-heat transfer capacity TQ curve of the heat exchange between supercritical carbon dioxide working fluid and high temperature heat storage material, such as Figure 3 a. The heat transfer pinch point position shown in the curve is consistent with the assumption, and the minimum heat transfer temperature difference meets the set conditions: the temperatures of high-temperature heat storage cold tank 1 and high-temperature heat storage hot tank 2 are 402.3℃ and 600℃ respectively.

[0125] Step 3: The temperatures of the high-temperature heat storage cold tank 1 and the high-temperature heat storage hot tank 2 obtained in step 2 are inputted with the carbon dioxide working medium inlet temperature of the second heat exchanger 15 being 328.7°C, and the carbon dioxide working medium outlet temperature of the second heat exchanger 15 is calculated to be 594°C.

[0126] Step 4: Input the parameters of the heat engine cycle during the heat release process, including the inlet and outlet temperatures, pressures, and flow rates of the carbon dioxide working fluid of the heat engine compressor 12 and the heat engine cooler 11, as follows;

[0127]

[0128] The inlet and outlet temperatures of the carbon dioxide working medium of the third heat exchanger 10 are calculated to be 78.85°C and 44.8°C.

[0129] Step 5: Assuming the temperature of the carbon dioxide working medium corresponding to the heat exchange pinch point in the third heat exchanger 10, calculate the inlet and outlet parameters of the low-temperature heat storage material in the third heat exchanger 10, that is, the temperature and flow rate of the low-temperature heat storage cold tank 9 and the low-temperature heat storage hot tank 8. The specific operations are as follows:

[0130] 1) The inlet and outlet temperatures and flow rates of the carbon dioxide working fluid of the third heat exchanger (10) are known to be 78.85°C, 44.8°C and 218.34 kg / s respectively;

[0131] 2) Assume that the temperature of the carbon dioxide working medium corresponding to the heat exchange pinch point in the third heat exchanger (10) is 54.85°C, where 44.8°C≤54.85°C≤78.85°C;

[0132] 3) Set the minimum heat exchange temperature difference ΔT min is 6°C, then the calculated temperature of the heat storage material corresponding to the heat exchange pinch point in the third heat exchanger (10) is 48.85°C;

[0133] 4) Matching the flow rate of heat storage materials: The specific heat of the low-temperature heat storage material is 4181 J / (kg·°C), and the flow rate of the high-temperature heat storage material is calculated to be 114.28 kg / s;

[0134] 5) Discretize the third heat exchanger with the pinch point as the starting and ending points, and calculate the inlet and outlet temperatures of the heat storage material of the third heat exchanger to be 38°C and 68°C respectively;

[0135] 6) Draw the temperature-heat transfer (TQ) curve of the heat exchange between supercritical carbon dioxide working fluid and low-temperature heat storage material, such as Figure 3 (b), the heat transfer pinch point position shown in the curve is consistent with the assumption, and the minimum heat transfer temperature difference meets the setting conditions: the temperatures of the low-temperature heat storage cold tank (9) and the low-temperature heat storage hot tank (8) are 38°C and 68°C respectively.

[0136] Step 6: Determine the heat exchange conditions between the carbon dioxide working fluid and the low-temperature heat storage material in the fourth heat exchanger (7). The inlet and outlet temperatures of the carbon dioxide working fluid are 32°C and 32.56°C respectively, and the inlet and outlet temperatures of the low-temperature heat storage material are 68°C and 38°C respectively, meeting the minimum temperature difference condition. The round-trip efficiency of the system in this case is calculated to be 52.25%.

[0137] Step 7. Use a genetic algorithm (or neural network, particle swarm algorithm, etc.) to assign different assumed temperature values ​​in steps 2 and 5, and compare the round-trip efficiency under different conditions. By comparison, the assumed temperature values ​​that give the highest round-trip efficiency of the system are 600°C and 54.85°C, respectively. In this case, the heat exchange network parameters are the optimal parameters.

[0138] The following are device embodiments of the present invention, which can be used to perform the method embodiments of the present invention. For details not disclosed in the device embodiments, please refer to the method embodiments of the present invention.

[0139] In another embodiment of the present invention, a supercritical carbon dioxide heat storage system heat exchange network optimization system based on pinch point optimization is provided, including a network optimization module, which runs the steps of the above-mentioned supercritical carbon dioxide heat storage system heat exchange network optimization method based on pinch point optimization.

[0140] In another embodiment of the present invention, a terminal device is provided, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be a method for optimizing the heat exchange network of a supercritical carbon dioxide heat storage system based on pinch optimization.

[0141] In another embodiment of the present invention, the present invention further provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a terminal device for storing programs and data. It is understandable that the computer-readable storage medium here can include both the built-in storage medium in the terminal device and, of course, the extended storage medium supported by the terminal device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space. These instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the above-mentioned embodiment regarding a method for optimizing a heat exchange network of a supercritical carbon dioxide heat storage system based on pinch optimization.

[0142] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0143] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the steps in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0144] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0145] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A heat exchange network optimization method for a supercritical carbon dioxide heat storage system based on pinch point optimization, characterized in that: The specific steps are as follows: According to the working medium flow rate of the first heat exchanger (3) and the working medium temperature corresponding to the assumed heat exchange pinch point, the temperature and flow rate of the heat storage material corresponding to the heat exchange pinch point are obtained, and the heat storage material temperature at the inlet and outlet of the first heat exchanger (3) is obtained using the heat storage material temperature and flow rate; The working medium outlet temperature of the second heat exchanger (15) is obtained by using the outlet temperature of the heat storage material of the first heat exchanger (3) and the minimum heat exchange temperature difference; Determining the working medium inlet and outlet temperatures of the third heat exchanger (10) based on the working medium outlet temperature and pressure of the second heat exchanger (15) and the operating parameters of the heat engine cycle; The working medium inlet and outlet temperatures of the third heat exchanger (10) and the working medium temperature corresponding to the assumed heat exchange pinch point are used to obtain the heat storage material temperature and flow rate corresponding to the heat exchange pinch point, and the heat storage material temperature at the inlet and outlet of the third heat exchanger (10) is obtained using the heat storage material temperature and flow rate; When the temperature of the working fluid in the fourth heat exchanger (7) and the heat storage material at the outlet of the third heat exchanger (10) meet the minimum temperature difference constraint condition, the round-trip efficiency of the heat storage system under the working fluid temperature condition corresponding to the heat exchange pinch point assumed by the first heat exchanger (3) and the third heat exchanger (10) is calculated; the working fluid temperature corresponding to the heat exchange pinch point assumed by the first heat exchanger (3) and the third heat exchanger (10) that optimizes the round-trip efficiency of the heat storage system is selected, and the heat exchange network of the heat storage system is optimized.

2. The heat exchange network optimization method for a supercritical carbon dioxide heat storage system based on pinch point optimization according to claim 1, characterized in that: When the temperature of the working medium in the fourth heat exchanger (7) and the heat storage material at the outlet of the third heat exchanger (10) do not meet the minimum temperature difference constraint condition, the working medium temperature corresponding to the heat exchange pinch point assumed in the first heat exchanger (3) and the third heat exchanger (10) is excluded and a new assumption is made.

3. The heat exchange network optimization method for a supercritical carbon dioxide heat storage system based on pinch point optimization according to claim 1, characterized in that: The steps for obtaining the temperature of the heat storage material at the inlet and outlet of the first heat exchanger (3) are as follows: Assuming that the working medium temperature corresponding to the heat exchange pinch point in the first heat exchanger (3) is between the working medium inlet and outlet temperatures of the first heat exchanger (3); Combining the minimum heat exchange temperature difference and the working fluid temperature corresponding to the assumed heat exchange pinch point, the heat storage material temperature corresponding to the heat exchange pinch point is obtained; Obtaining the heat storage material flow rate based on the working fluid flow rate of the first heat exchanger (3), the working fluid specific heat corresponding to the heat exchange pinch point, and the heat storage material specific heat; Taking the heat exchange pinch point as the starting / ending point, the heat exchange process of the first heat exchanger (3) is discretely calculated to obtain the temperature of the heat storage material at the inlet and outlet of the first heat exchanger (3). The formula of each calculation unit after discretization is as follows: m HTE，HST cp HTE，HST ·(T HST，out -T HST，in )=m HTE,CO2 ·(h HTE,CO2,in -h HTE,CO2,out ) Where: m HTE,HST is the heat storage material flow rate; cp HTE,HST is the average specific heat of the heat storage material; T HST,in is the inlet temperature of the heat storage material; T HST,out is the outlet temperature of the heat storage material; m HTE,CO2 is the working fluid flow rate; h HTE,CO2,in is the specific enthalpy of the working fluid at the inlet; h HTE,CO2,out is the working fluid outlet specific enthalpy; A temperature-heat exchange curve of the working fluid and the heat storage material is drawn, and based on the curve verification, if the heat exchange pinch point position is consistent with the working fluid temperature corresponding to the assumed heat exchange pinch point and the obtained heat storage material temperature, and satisfies the set minimum heat exchange temperature difference, the heat storage material temperature corresponding to the heat exchange pinch point in the first heat exchanger (3) is obtained.

4. The method for optimizing a heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization according to claim 1, characterized in that: The difference between the temperature of the heat storage material at the outlet of the first heat exchanger (3) and the minimum heat exchange temperature difference is the working medium outlet temperature of the second heat exchanger (15).

5. The heat exchange network optimization method for a supercritical carbon dioxide heat storage system based on pinch point optimization according to claim 1, characterized in that: The working medium side of the third heat exchanger (10) and the working medium side of the second heat exchanger (15) are connected through a heat engine circulation portion. The steps for determining the working medium inlet and outlet temperatures of the third heat exchanger (10) are specifically as follows: The working medium inlet temperature of the third heat exchanger (10) is obtained based on the working medium inlet pressure and inlet specific enthalpy of the third heat exchanger (10), wherein the working medium inlet specific enthalpy of the third heat exchanger (10) is calculated as follows: The working medium outlet temperature and working medium outlet pressure of the second heat exchanger (15) are used to obtain the working medium inlet specific enthalpy of the heat engine turbine (14); The outlet specific enthalpy of the heat engine turbine (14) is obtained by using the inlet specific enthalpy of the working medium of the heat engine turbine (14), the ideal outlet specific enthalpy and the isentropic efficiency; The working medium inlet specific enthalpy of the third heat exchanger (10) is obtained by using the working medium outlet specific enthalpy of the heat engine turbine (14), the working medium inlet specific enthalpy of the second heat exchanger (15), and the working medium outlet specific enthalpy of the heat engine compressor (12); The working medium outlet temperature of the third heat exchanger (10) is obtained based on the working medium outlet pressure and outlet specific enthalpy, wherein the working medium outlet specific enthalpy of the third heat exchanger (10) is equal to the working medium inlet specific enthalpy of the heat engine cooler (11).

6. The method for optimizing a heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization according to claim 1, characterized in that: The steps for obtaining the temperatures of the heat storage material at the inlet and outlet of the third heat exchanger (10) are as follows: Assuming a working medium temperature corresponding to a heat exchange pinch point in the third heat exchanger (10) between the working medium inlet and outlet temperatures of the third heat exchanger (10); Combining the minimum heat exchange temperature difference and the working fluid temperature corresponding to the assumed heat exchange pinch point, the heat storage material temperature corresponding to the heat exchange pinch point is obtained; Obtaining the heat storage material flow rate based on the working fluid flow rate of the third heat exchanger (10), the working fluid specific heat corresponding to the heat exchange pinch point, and the heat storage material specific heat; Taking the heat exchange pinch point as the starting / ending point, the heat exchange process of the third heat exchanger (10) is discretely calculated to obtain the temperature of the heat storage material at the inlet and outlet of the third heat exchanger (10). The formula of each calculation unit after discretization is as follows: m LTE,LST cp LTE,LST ·(T LST,out -T LST,in )=m HE,LTE,CO2 ·(h LTE,CO2,in -h LTE,CO2,out ) Where: m LTE,LST is the heat storage material flow rate; cp LTE,LST is the average specific heat of the heat storage material; T LST,in is the inlet temperature of the heat storage material; T LST,out is the outlet temperature of the heat storage material; m HE,LTE,CO2 is the working fluid flow rate; h LTE,CO2,in is the specific enthalpy of the working fluid at the inlet; h LTE,CO2,out is the working fluid outlet specific enthalpy; A temperature-heat exchange curve of the heat exchange between the working fluid and the heat storage material is drawn. Based on the curve verification, if the heat exchange pinch point position is consistent with the working fluid temperature corresponding to the assumed heat exchange pinch point and the obtained heat storage material temperature, and satisfies the set minimum heat exchange temperature difference, the heat storage material temperature corresponding to the heat exchange pinch point in the third heat exchanger (10) is obtained.

7. The method for optimizing a heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization according to claim 1, characterized in that: The supercritical carbon dioxide heat storage system includes a high-temperature heat storage part, a low-temperature heat storage part, a heat engine cycle part, and a heat pump cycle part, wherein: High-temperature heat storage part: the outlet of the high-temperature heat storage cold tank (1) is connected to the inlet of the heat storage material of the first heat exchanger (3), the outlet of the heat storage material of the first heat exchanger (3) is connected to the inlet of the high-temperature heat storage hot tank (2), and the working fluid side of the first heat exchanger (3) is connected to the low-temperature heat storage part through the heat pump circulation part; The outlet of the high-temperature heat storage tank (2) is connected to the heat storage material inlet of the heat engine high-temperature heat exchanger (15), the heat storage material outlet of the heat engine high-temperature heat exchanger (15) is connected to the inlet of the high-temperature heat storage cold tank (1), and the working medium side of the heat engine high-temperature heat exchanger (15) is connected to the low-temperature heat storage part through the heat engine circulation part; Low-temperature heat storage part: the outlet of the low-temperature heat storage cold tank (9) is connected to the inlet of the heat storage material of the third heat exchanger (10), the outlet of the heat storage material of the third heat exchanger (10) is connected to the inlet of the low-temperature heat storage hot tank (8), and the working fluid side of the third heat exchanger (10) is connected to the high-temperature heat storage part through the heat engine circulation part; The outlet of the low-temperature heat storage hot tank (8) is communicated with the heat storage material inlet of the fourth heat exchanger (7), the heat storage material outlet of the fourth heat exchanger (7) is communicated with the inlet of the low-temperature heat storage cold tank (9), and the working fluid side of the fourth heat exchanger (7) is communicated with the high-temperature heat storage part through the heat pump circulation part; The round-trip efficiency of the heat storage system is expressed by the ratio of the work done by the heat engine cycle part during the heat release process to the power consumed by the heat pump cycle part during the heat storage process.

8. The method for optimizing a heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization according to claim 1, characterized in that: The working fluid temperature corresponding to the heat exchange pinch point of the first heat exchanger (3) and the third heat exchanger (10) is assigned a value by using algorithms such as genetic algorithms, neural networks, and particle swarms, and the working fluid temperature corresponding to the heat exchange pinch point of the first heat exchanger (3) and the third heat exchanger (10) that optimizes the round-trip efficiency of the heat storage system is selected, thereby completing the optimization of the heat exchange network of the heat storage system.

9. A heat exchange network optimization system for a supercritical carbon dioxide heat storage system based on pinch point optimization, characterized in that: It comprises a network optimization module, which runs the steps of a heat exchange network optimization method for a supercritical carbon dioxide heat storage system based on pinch point optimization according to any one of claims 1 to 8.

10. A terminal device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the processor implements the steps of a method for optimizing a heat exchange network of a supercritical carbon dioxide heat storage system based on pinch point optimization according to any one of claims 1 to 8.

Images