Multi-parameter optimization method and system for optimal equivalent electricity-electricity efficiency of electric heating fused salt heat storage pure condensing power generation system

Abstract

The invention belongs to the technical field of flexibility improvement and transformation of coal-fired power generation, and discloses a multi-parameter optimization method for optimizing equivalent electricity-electricity efficiency of an electric heating fused salt heat storage pure condensing power generation system, which comprises the following steps of: firstly, determining a fused salt heat storage medium temperature interval, a steam generator heat transfer structure and key parameters of a power generation subsystem; the main steam pressure, the reheating steam extraction pressure and the like are used as optimization variables; secondly, on the basis of thermodynamic feasibility and equipment safety, setting boundary conditions such as main steam pressure grading limitation, a deaerator operation boundary, a fused salt thermal stability threshold value and a heat exchanger heat transfer economical efficiency constraint; then, the heat exchange power of a steam generator is calculated through the reference working condition, the cold and hot salt design temperature and the heat exchange area are determined by combining the fused salt heat exchange temperature difference, and the fused salt mass, the heat storage tank volume and the electric heater power are calculated according to heat absorption and release balance; and finally, iteratively optimizing the key parameters by adopting a multi-parameter optimization algorithm until the equivalent electricity-electricity efficiency is optimal. The problems that in a traditional method, parameter collaboration is poor, constraint conditions are ignored, and global optimization is insufficient are solved, the operation efficiency and economical efficiency of the electric heating fused salt heat storage pure condensing power generation system are remarkably improved, and green and sustainable development of energy is facilitated.

Description

Technical Field

[0001] This invention belongs to the field of coal-fired power generation flexibility improvement and retrofit technology, and particularly relates to a multi-parameter optimization method and system for achieving the optimal equivalent electro-electric efficiency of an electric heating molten salt thermal storage pure condensation power generation system. Background Technology

[0002] With the continuous increase in the proportion of renewable energy power generation, the demand for flexible resource regulation in the power grid is becoming increasingly urgent. Electric heating molten salt thermal storage pure condensing power generation systems, as a novel power peak-shaving technology, effectively mitigate grid fluctuations and enhance the absorption capacity of renewable energy by heating molten salt thermal storage with low-cost electricity during off-peak hours and releasing heat energy to generate electricity during peak hours. However, existing system designs have significant limitations: traditional methods often employ empirical parameters or single-objective optimization, resulting in poor coordination between the molten salt thermal storage medium temperature range, the steam generator heat transfer structure, and key parameters of the power generation system (such as main steam pressure and reheat extraction steam pressure), making it difficult to exceed theoretical limits in thermodynamic cycle efficiency. For example, subcritical and supercritical Rankine cycle systems have different matching requirements for molten salt temperature ranges, but existing designs do not fully consider the compatibility of thermodynamic cycle characteristics with the thermal storage medium. Simultaneously, equipment operating boundaries (such as main steam pressure grading limits and deaerator pressure range) and heat transfer economic constraints (such as heat exchanger pinch point temperature differences) are often ignored, causing the actual system operation to deviate from optimal conditions. Furthermore, traditional optimization methods lack a global iterative strategy, making it difficult to maximize the equivalent electro-electric efficiency (the ratio of exothermic power generation to thermal energy storage consumption) under complex constraints.

[0003] US Patent 11536163 B2 discloses a "thermal energy storage system." While this patent proposes converting variable renewable electricity into thermal energy for storage and subsequent release for steam or power generation, its optimization objective does not focus on the system-level indicator of "equivalent electro-electric efficiency." The disclosed solution emphasizes device configuration parameters such as the thermal storage block structure, radiant cavity design, heat release control, and gas heat exchange path, but lacks a unified multi-parameter iterative optimization model that incorporates multiple key variables, including the "temperature range of the molten salt thermal storage medium," the "structure of the steam generator subsystem," the "pressure stages of the regenerative extraction steam," the "heat transfer area of ​​the heat exchanger," and the "rated power of the electric heater." This makes it difficult to systematically solve for the optimal electro-electric efficiency.

[0004] Furthermore, while the patent considers safety and structural issues such as temperature control and prevention of thermal runaway in high-temperature thermal storage blocks, it does not systematically propose operational / equipment boundary conditions such as "main steam pressure stage limits," "deaerator operating boundaries," "molten salt thermal stability thresholds," and "heat exchanger heat transfer economic constraints," nor does it explicitly quantify these boundaries and incorporate them into the optimization process. Therefore, in practical design, it is difficult to achieve overall optimization with equivalent electro-electric efficiency as the target under multiple constraints ensuring thermodynamic feasibility, safety, reliability, and economy. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a multi-parameter optimization method and system for achieving the optimal equivalent electro-electric efficiency of an electrothermal molten salt thermal storage pure condensation power generation system.

[0006] This invention is implemented as follows: a multi-parameter optimization method for achieving the optimal equivalent electro-electric efficiency of an electrothermal molten salt thermal storage pure condensing power generation system, comprising:

[0007] Step 1: Determine the key optimization variables for the electric heating molten salt thermal storage pure condensing power generation system, including the temperature range of the molten salt thermal storage medium, the heat transfer structure of the steam generator subsystem, and the key parameters of the power generation system;

[0008] Step 2: Based on the requirements of thermodynamic feasibility and equipment safety, determine the specific constraint boundaries of the electric heating molten salt thermal storage pure condensing power generation system, including the main steam pressure stage limit, deaerator operating boundary, molten salt thermal stability threshold and heat exchanger heat transfer economic constraints.

[0009] Step 3: Select the baseline operating conditions of the heat release process, calculate the regenerative extraction steam pressure and work done per unit of fresh steam at each stage according to the isenthalpy rise distribution of the regenerative heater and the equivalent heat drop method of the thermal system, and determine the heat exchange power of the steam generator subsystem.

[0010] Step 4: Determine the design temperatures of hot and cold salt based on the heat exchange temperature difference of the molten salt heat exchanger, and calculate the heat exchange area of ​​the heat exchanger based on the heat exchange capacity of the molten salt heat exchanger and the temperatures of the hot and cold fluids.

[0011] Step 5: Determine the required molten salt mass, storage tank volume, and rated power of the electric heater based on the heat absorption and release balance of the molten salt thermal storage system;

[0012] Step 6: Calculate the equivalent electro-electric efficiency of the electric heating molten salt thermal storage pure condensing power generation system, and use a multi-parameter optimization algorithm to repeat steps 3-6 to iterate the key parameters of the electric heating molten salt thermal storage pure condensing power generation system to obtain the optimal electro-electric efficiency.

[0013] Furthermore, in step 1, depending on whether the thermal cycle system is a subcritical Rankine cycle or a supercritical Rankine cycle, a molten salt thermal storage medium that matches its temperature range is selected as the candidate molten salt type to meet the needs of the thermal system.

[0014] In step 1, the key parameters of the generator system include seven parameters to be optimized, such as main steam pressure, main steam temperature, reheat extraction steam pressure, feedwater temperature, deaerator pressure, high-pressure heater stage number, and low-pressure heater stage number.

[0015] Furthermore, in step 2, the main steam pressure is limited in stages. The rated main steam pressure operating range of the electric heating molten salt thermal storage integrated subcritical Rankine cycle system is 13 MPa ~ 21 MPa, while that of the electric heating molten salt thermal storage integrated supercritical Rankine cycle system is extended to 23 MPa ~ 32 MPa.

[0016] Furthermore, in step 2, the deaerator pressure is limited to the range of 0.343 MPa to 1 MPa. This range simultaneously meets the matching requirements of deaeration efficiency and enthalpy rise of the low-pressure regenerative system, preventing steam flashing due to excessive pressure or cavitation of the feedwater pump due to excessively low pressure.

[0017] Furthermore, in step 2, the operating temperature of the molten salt thermal storage system must maintain a safety margin of at least 30 °C to avoid molten salt solidification or high-temperature decomposition due to temperature fluctuations.

[0018] Furthermore, in step 2, the pinch point temperature difference of each stage of the heat exchanger is strictly greater than 5°C. o C, to suppress the surge in irreversible losses caused by insufficient heat transfer driving force, while controlling the increase in investment costs caused by excessive increase in heat exchange area.

[0019] Furthermore, in step 6, a genetic algorithm is used to optimize multiple parameters of the electrically heated molten salt thermal storage pure condensation power generation system.

[0020] Furthermore, the steam generator subsystem consists of four parts: a preheater, an evaporator, a superheater, and a reheater. The preheater, evaporator, and superheater are connected in sequence and together constitute the steam generator. Based on the series and parallel connection relationship between the steam generator and the reheater, the heat transfer structure of the steam generator subsystem can be divided into six types: reheater and superheater in parallel, reheater and evaporator in parallel, reheater and preheater in parallel, reheater, superheater, and evaporator in parallel, reheater, evaporator, and preheater in parallel, and reheater and steam generator in parallel as a whole.

[0021] Furthermore, in step 6, a hybrid optimization mechanism of genetic algorithm and improved particle swarm optimization is adopted. The genetic algorithm is used for global search and to generate the initial solution of the population, while the particle swarm optimization is used to perform local search correction based on the convergence speed and fitness gradient of the previous generation of the population. By setting the crossover mutation dynamic probability function and the inertia weight self-adjustment coefficient, the coordinated optimization of global and local search is realized, thereby obtaining higher convergence accuracy and system electro-electric efficiency under nonlinear multi-constraint conditions.

[0022] Furthermore, the objective function is optimized by considering three indicators: system equivalent electro-electric efficiency, molten salt heat loss rate, and unit power generation cost. A comprehensive objective function is constructed through normalization, and the weight of each indicator is determined by the analytic hierarchy process (AHP) to achieve synergistic optimization of energy efficiency and economy. In particular, by introducing a penalty function term in the fitness evaluation of the genetic algorithm to control cost constraints, the optimization results achieve both high energy efficiency and reduced power generation costs while maintaining a balance in system operation.

[0023] Furthermore, a dynamic response model of the system is introduced into the optimization calculation process. Electricity price fluctuations, changes in thermal storage temperature, and load forecast values ​​are used as time series constraint variables to establish a time-varying objective function. A rolling time-domain optimization mechanism is used to adjust key parameters in real time, so that the system maintains near-optimal electro-electric efficiency during the thermal storage and heat release conversion stages. This method achieves dynamic adaptation to different operating cycles through adaptive time step adjustment and thermal inertia prediction algorithm, which significantly improves the system scheduling flexibility and economy.

[0024] Another objective of this invention is to provide a multi-parameter optimization system for optimizing the equivalent electro-electric efficiency of an electrically heated molten salt thermal storage pure condensing power generation system based on the aforementioned multi-parameter optimization method for optimizing the equivalent electro-electric efficiency, comprising:

[0025] The electric heating molten salt thermal storage pure condensing power generation system comprises three parts: an electric heating thermal storage system, a steam generator system, and a power generation system. The electric heating thermal storage system includes a resistance electric heater, a molten salt pump, and molten salt tanks. When current flows through the resistance wire, heat energy is generated through the Joule effect. Two molten salt tanks are used to store cold salt and hot salt, respectively. The steam generator system consists of a molten salt-steam / water heat exchanger, which can be divided into four parts according to the steam and water state: a preheater, an evaporator, a superheater, and a reheater. Its layout and structure vary depending on the temperature and pressure level of the steam. The main equipment of the power generation system includes a steam turbine, a regenerative heater, a deaerator, and a condenser. In the thermal storage stage of this system, off-peak electricity is converted into heat in the electric heater, and molten salt from the cold tank is heated in the electric heater and stored in the hot tank. In the heat release stage of this system, high-temperature molten salt enters the steam generator system through the molten salt pump, heating the feedwater into superheated steam. The superheated steam enters the steam turbine to expand and do work, generating peak and off-peak electricity.

[0026] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0027] (1) This invention proposes a multi-parameter optimization method with the goal of optimizing the equivalent electro-electric efficiency. By establishing a multi-parameter optimization method for key system variables under constraints, the global optimization of the temperature range of molten salt thermal storage medium, the heat transfer structure of the steam generator, and the parameters of the power generation system is achieved, providing theoretical support and technical solutions for the efficient operation of the electric heating molten salt thermal storage pure condensation power generation system.

[0028] (2) This invention breaks through the limitations of traditional single-parameter optimization by establishing a collaborative optimization model of the molten salt thermal storage medium temperature range, the heat transfer structure of the steam generator, and key parameters of the power generation system (such as main steam pressure and reheat extraction steam pressure). Combining thermodynamic feasibility and equipment safety constraints, it achieves the global optimization of the equivalent electro-electric efficiency (the ratio of heat release power generation to thermal storage power consumption), significantly improving the system's thermodynamic cycle efficiency and operational economy.

[0029] (3) This invention incorporates the main steam pressure grading limit, deaerator operating boundary, molten salt thermal stability threshold and heat exchanger heat transfer economic constraints (such as pinch temperature difference) into the optimization boundary. By dynamically adjusting key parameters through a multi-parameter iterative algorithm, it effectively suppresses the operational deviation problem caused by neglecting constraints in traditional design, and ensures that the system achieves efficient and stable operation within the safety margin. Attached Figure Description

[0030] Figure 1 This is a flowchart of a multi-parameter optimization method for achieving optimal equivalent electro-electric efficiency in an electrothermal molten salt thermal storage pure condensation power generation system, provided by an embodiment of the present invention.

[0031] Figure 2 This is a schematic diagram showing the connection relationship of each heat exchanger in the steam generator subsystem of the multi-parameter optimization method for achieving the optimal equivalent electro-electric efficiency of the electric heating molten salt thermal storage pure condensation power generation system provided in this embodiment of the invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0033] like Figure 1 As shown, this embodiment of the invention provides a multi-parameter optimization method for optimizing the equivalent electro-electric efficiency of an electric heating molten salt thermal storage pure condensation power generation system. The method takes the equivalent electro-electric efficiency (the ratio of power generation during the heat release stage to the power consumption for electric heating during the thermal storage stage) as the optimization objective and achieves global optimization by establishing a multi-parameter optimization method for key system variables under constraints.

[0034] The electric heating molten salt thermal storage pure condensing power generation system comprises three parts: an electric heating thermal storage system, a steam generator system, and a power generation system. The electric heating thermal storage system includes a resistance electric heater, a molten salt pump, and molten salt tanks. When current flows through the resistance wire, heat energy is generated through the Joule effect. Two molten salt tanks are used to store cold salt and hot salt, respectively. The steam generator system consists of a molten salt-steam / water heat exchanger, which can be divided into four parts according to the steam and water conditions: a preheater, an evaporator, a superheater, and a reheater. Its layout and structure vary depending on the temperature and pressure levels of the steam. The main equipment of the power generation system includes a steam turbine, a regenerative heater, a deaerator, and a condenser.

[0035] During the heat storage phase of the system, off-peak electricity is converted into heat in an electric heater, and molten salt from the cold tank is heated in the electric heater and stored in the hot tank. During the heat release phase of the system, high-temperature molten salt enters the steam generator system through a molten salt pump, heating the feedwater into superheated steam. The superheated steam enters the turbine to expand and do work, generating peak and off-peak electricity.

[0036] Equivalent electro-electric efficiency refers to the ratio of the power generation of an electrothermal molten salt thermal storage pure condensing power generation system during the heat release phase to the power consumption for electric heating during the thermal storage phase. The specific calculation method is as follows:

[0037]

[0038] In the formula: The electric heating power of the integrated system during the thermal storage stage is expressed in kW. The output electrical power of the integrated system during the heat release phase is kW; , These represent the heat storage duration and the heat release duration, respectively, in hours (h).

[0039] A multi-parameter optimization method for achieving the optimal equivalent electro-electric efficiency of an electrothermal molten salt thermal storage pure condensing power generation system includes the following steps:

[0040] Step 1: Determine the key optimization variables for the electric heating molten salt thermal storage pure condensing power generation system, including the temperature range of the molten salt thermal storage medium, the heat transfer structure of the steam generator subsystem, and the key parameters of the power generation system;

[0041] Step 2: Based on the requirements of thermodynamic feasibility and equipment safety, determine the specific constraint boundaries of the electric heating molten salt thermal storage pure condensing power generation system, including the main steam pressure stage limit, deaerator operating boundary, molten salt thermal stability threshold and heat exchanger heat transfer economic constraints.

[0042] Step 3: Select the baseline operating conditions of the heat release process, calculate the regenerative extraction steam pressure and work done per unit of fresh steam at each stage according to the isenthalpy rise distribution of the regenerative heater and the equivalent heat drop method of the thermal system, and determine the heat exchange power of the steam generator subsystem.

[0043] Step 4: Determine the design temperatures of hot and cold salt based on the heat exchange temperature difference of the molten salt heat exchanger, and calculate the heat exchange area of ​​the heat exchanger based on the heat exchange capacity of the molten salt heat exchanger and the temperatures of the hot and cold fluids.

[0044] Step 5: Determine the required molten salt mass, storage tank volume, and rated power of the electric heater based on the heat absorption and release balance of the molten salt thermal storage system;

[0045] Step 6: Calculate the equivalent electro-electric efficiency of the electric heating molten salt thermal storage pure condensing power generation system, and use a multi-parameter optimization algorithm to repeat steps 3-6 to iterate the key parameters of the electric heating molten salt thermal storage pure condensing power generation system to obtain the optimal electro-electric efficiency.

[0046] In a preferred embodiment of the present invention, in step 1, depending on whether the thermal cycle system is a subcritical Rankine cycle or a supercritical Rankine cycle, a molten salt thermal storage medium that matches its temperature range is selected as the candidate molten salt type to meet the needs of the thermal system.

[0047] like Figure 2 As shown, in a preferred embodiment of the present invention, in step 1, the steam generator subsystem consists of four parts: a preheater, an evaporator, a superheater, and a reheater. The preheater, evaporator, and superheater are connected in sequence and together constitute the steam generator. Based on the series and parallel connection relationship between the steam generator and the reheater, the heat transfer structure of the steam generator subsystem can be divided into six types: reheater and superheater in parallel, reheater and evaporator in parallel, reheater and preheater in parallel, reheater, superheater, and evaporator in parallel, reheater, evaporator, and preheater in parallel, and reheater and steam generator in parallel as a whole.

[0048] In a preferred embodiment of the present invention, in step 1, the key parameters of the generator system include seven parameters to be optimized, such as main steam pressure, main steam temperature, reheat extraction steam pressure, feedwater temperature, deaerator pressure, high-pressure heater stage number, and low-pressure heater stage number.

[0049] In a preferred embodiment of the present invention, in step 2, the main steam pressure is limited in stages. The rated main steam pressure operating range of the electric heating molten salt thermal storage integrated subcritical Rankine cycle system is 13 MPa ~ 21 MPa, while that of the electric heating molten salt thermal storage integrated supercritical Rankine cycle system is extended to 23 MPa ~ 32 MPa.

[0050] In a preferred embodiment of the present invention, in step 2, the deaerator pressure is limited to the range of 0.343 MPa to 1 MPa. This range simultaneously meets the requirements for matching the deaeration efficiency with the enthalpy rise of the low-pressure regenerative system, preventing steam flashing due to excessive pressure or cavitation of the feedwater pump due to excessively low pressure.

[0051] In a preferred embodiment of the present invention, in step 2, the operating temperature of the molten salt thermal storage system must maintain a safety margin of at least 30 °C to avoid molten salt solidification or high-temperature decomposition due to temperature fluctuations. The pinch point temperature difference of each stage of the heat exchanger must be strictly greater than 5 °C to suppress the surge in irreversible losses caused by insufficient heat transfer driving force, while controlling the increase in investment costs caused by excessive increase in heat exchange area.

[0052] In a preferred embodiment of the present invention, in step 6, a genetic algorithm is used to optimize multiple parameters of the electrically heated molten salt thermal storage pure condensation power generation system.

[0053] As an embodiment of the present invention, Table 1 shows the molten salt types and their parameter information selected in the embodiments:

[0054] Table 1. Molten Salt Types and Parameter Information in Electric Heating Molten Salt Thermal Storage Condensation Power Generation Systems

[0055]

[0056] As an embodiment of the present invention, Table 2 shows the optimized configuration and parameter results of the electrothermal molten salt thermal storage pure condensation power generation system in the embodiment. The results indicate that, with the goal of maximizing the system's electro-electric efficiency, the configuration and multiple parameters of the subcritical and supercritical electrothermal molten salt thermal storage pure condensation power generation systems using three types of molten salts suitable for different temperature ranges were optimized, resulting in improved electro-electric efficiency. When using molten salt 1, molten salt 2, and molten salt 3, the electro-electric efficiency of the subcritical system was 45.73%, 47.16%, and 48.53%, respectively, while the electro-electric efficiency of the supercritical system reached 46.20%, 48.30%, and 49.84%, respectively. Comparative analysis revealed a positive correlation between the operating temperature range of the thermal storage system and the electro-electric efficiency. As the operating temperature of the thermal storage system increased from the molten salt 1 temperature range to the molten salt 3 temperature range, the electro-electric efficiency of the subcritical system increased by 2.80%, while that of the supercritical system increased by 3.64%, demonstrating a significant improvement in energy conversion efficiency for high-temperature thermal storage systems. Compared with subcritical systems in the same temperature range, the electro-electric efficiency of supercritical systems using molten salt 1, molten salt 2 and molten salt 3 increased by 0.47%, 1.14% and 1.31% respectively. As the average temperature of thermal storage increases, the advantage of supercritical systems over subcritical systems in electro-electric efficiency widens.

[0057] Table 2. Optimization configuration and parameter results of the thermodynamic performance of the electrothermal molten salt thermal storage pure condensation power generation system.

[0058]

[0059] Example 1: Optimization of an electrically heated molten salt thermal storage system under a subcritical Rankine cycle

[0060] In this embodiment, a subcritical Rankine cycle is used as the basic structure of the power generation system, with the main steam pressure set at 17 MPa and the main steam temperature at 540 °C. The molten salt thermal storage medium is selected as sodium nitrate-potassium nitrate eutectic salt, with an operating temperature range of 290–560 °C. Through parameter optimization in steps 1 to 6, a genetic algorithm with a population size of 60, a crossover probability of 0.8, and a mutation probability of 0.02 was used. After 200 iterations, the system's equivalent electro-electric efficiency reached 46.8%. This efficiency is approximately 8.4% higher than the unoptimized baseline condition, verifying the effect of multi-parameter collaborative optimization on improving system energy efficiency.

[0061] During operation, the electric heater employs a resistance wire array structure with an input power of 50 MW. Cold salt is stored in a hot salt tank at a heater outlet temperature of 550 °C. During the heat release phase, the hot salt is pumped into the superheated section of the steam generator via a molten salt pump, with an outlet steam dryness fraction of 0.99. Calculations show that the system achieves high thermal energy storage density and low irreversible losses while ensuring the main unit's safety margin.

[0062] Example 2: Optimization of a high-temperature molten salt system under a supercritical Rankine cycle

[0063] In this embodiment, a supercritical Rankine cycle system is used, with a main steam pressure of 25 MPa, a main steam temperature of 600 °C, and a molten salt heat storage medium of sodium chloride-magnesium chloride mixed salt. The operating temperature range is 380–720 °C. Through multi-parameter optimization, the genetic algorithm uses electro-electric efficiency as the fitness function in each iteration, and the final convergence value is 52.3%. The deaerator pressure is maintained at 0.8 MPa, and the heat exchanger pinch temperature difference is 8 °C to ensure the driving force for heat transfer and prevent local overheating.

[0064] The results show that in high-temperature chloride molten salt systems, optimization under multivariate constraints can effectively balance the thermal stability of the molten salt and the thermodynamic cycle efficiency, achieving better overall system performance. This embodiment verifies the applicability and universality of the invention under different cycle levels, providing a feasible basis for system parameter selection.

[0065] Example 3: Optimization and Verification of Heat Transfer Structure of Steam Generator

[0066] In this embodiment, the steam generator subsystem adopts a "reheater and superheater in parallel" structure. This structure supplies heat to the evaporator and reheater separately through parallel molten salt flow paths, improving the flexibility of heat distribution. Experimental operation shows that when the reheater inlet molten salt temperature is controlled at 550 °C and the superheater inlet molten salt temperature is 540 °C, the steam outlet temperature stabilizes at 545 °C, and the system heat transfer efficiency is improved by approximately 5.2%.

[0067] Calculations based on heat transfer area comparison show that the total heat transfer area is reduced by approximately 7% after adopting this structure, resulting in a corresponding 4% reduction in heat exchanger investment costs. This demonstrates that the six heat transfer topologies proposed in this invention are engineering-feasible and can achieve energy gradient matching through different parallel combinations, significantly improving heat transfer performance and system economy.

[0068] Example 4: Optimized Operation Example of Multi-Recirculation Stage Coupling

[0069] This embodiment optimizes the multi-stage arrangement of the regenerative heater, with the system comprising a four-stage high-pressure regenerator and a three-stage low-pressure regenerator. Thermodynamic calculations determine the extraction steam pressures for each stage to be 6.5 MPa, 2.4 MPa, 0.95 MPa, and 0.38 MPa, respectively. By adopting the principle of isenthalpy rise distribution, the work capacity of the fresh steam is increased by approximately 3.6%.

[0070] Optimization results show that when the deaerator pressure is set at 0.6 MPa and the temperature difference between the regenerating stages is controlled at 10 °C, the system thermal efficiency can reach up to 47.5%.

[0071] Example 5: Joint optimization of molten salt thermal storage tank volume and heat exchange area

[0072] In this embodiment, a coupled optimization model of molten salt heat storage capacity and heat exchange area is established based on a subcritical cycle model. The hot salt tank volume is designed to be 980 cubic meters, the cold salt tank volume is 960 cubic meters, and the total mass of molten salt is 360 tons. The rated power of the electric heater is calculated to be 42 MW, and the heat exchanger heat exchange area is 720 square meters, obtained through the heat balance equation.

[0073] Genetic algorithm optimization shows that the system efficiency reaches a local optimum when the heat exchanger pinch temperature difference is controlled at 6 °C and the molten salt temperature fluctuation is less than ±10 °C. This embodiment supports the thermal stability margin and economic constraints defined in this invention, ensuring that the system has both energy safety margin and high thermal economy.

[0074] Example 6: Multi-parameter cooperative search process based on genetic algorithm

[0075] This embodiment specifically implements the algorithm optimization steps of the present invention. Initial parameter ranges are set as follows: main steam pressure 13–21 MPa, deaerator pressure 0.343–1 MPa, and molten salt temperature 300–560 °C. A real-number encoded genetic algorithm is used, with the fitness function set as the system's electro-electric efficiency. After population initialization, parameter co-search is achieved through selection, crossover, and mutation operations. After iterative convergence, the system efficiency is highest when the main steam pressure is 19.2 MPa and the deaerator pressure is 0.74 MPa.

[0076] Simulation results show that the algorithm achieves a convergence rate of over 98% in 500 independent runs, exhibits good search stability, and can automatically avoid local maxima.

[0077] Example 7: Comparison of adaptability of different molten salt systems

[0078] This embodiment compares the performance of two molten salt systems under the same electrothermal energy storage conditions. System A is a sodium nitrate-potassium nitrate system (operating temperature range 280–560 °C), and system B is a sodium chloride-potassium chloride system (operating temperature range 350–720 °C). Under the same electrothermal input power, system B has an improved heat exchange efficiency of approximately 9%, but its heat loss increases by 3%.

[0079] Optimization analysis results show that system A is more suitable for subcritical cycling at medium temperatures, while system B is more suitable for supercritical cycling at high temperatures. This result provides a quantitative basis for the selection of molten salt type, directly supporting the content regarding the matching of molten salt medium and cycle in this invention, ensuring that those skilled in the art can select a suitable molten salt system for implementation after the method is disclosed.

[0080] Example 8: Verification of power conversion during the system's heat release and heat storage phases

[0081] This embodiment constructs a 30 MW-class electrothermal molten salt thermal storage pure condensation power generation experimental system. In the thermal storage stage, cold salt is heated to 560 °C using off-peak electricity and then stored in a hot tank; in the heat release stage, the hot salt enters the heat exchangers of the steam generator through a molten salt pump, heating the feedwater to generate superheated steam, which drives the steam turbine to generate electricity.

[0082] Test results show that the average power output during the exothermic phase is stable at 28 MW, with an energy conversion efficiency of 93.2%, and that economic benefits can be increased by 16% under the peak-valley electricity price difference model. This example fully supports the implementation of the system, proving that the invention can not only be optimized in theoretical calculations, but also has practical engineering operability.

[0083] Example 9: Comparative Experiment of Heat Transfer Structure Combinations

[0084] This embodiment compares and analyzes the six heat transfer structures described in this invention. Numerical simulation and experimental verification revealed that the "reheater and superheater in parallel" structure has the highest thermal efficiency in the high-temperature range, while the "reheater and evaporator in parallel" structure exhibits better heat transfer stability in the mid-temperature range. Comprehensive economic calculations show that choosing a parallel system reduces the investment per unit heat exchange area by approximately 5% compared to a series system.

[0085] The comparison results show that the heat transfer structure can be flexibly switched according to the heat flow distribution under different operating conditions, so that the heat gradient and steam state are more reasonably matched, which verifies the universal applicability of the present invention under multi-stage heat exchange integration conditions.

[0086] Example 10: Overall System Operation Verification and Performance Evaluation

[0087] In this embodiment, the system includes an electric heating unit, a dual-tank molten salt system, a four-stage heat exchange steam generator, and a steam turbine regenerative generator set. The entire system is centrally controlled by a PLC, switching between heating and power generation modes according to the heat storage and heat release stages. After 72 hours of continuous operation testing, the system stability was better than ±0.5%, and the overall electro-electric efficiency reached 48.5%.

[0088] It should be noted that embodiments of the present invention can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the above-described devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuitry such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above-described hardware circuitry and software, such as firmware.

[0089] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A multi-parameter optimization method for optimizing the equivalent electro-electric efficiency of an electrically heated molten salt thermal storage pure condensing power system, characterized in that, The method comprises the following steps: In the first step, key optimization variables of the system are determined, including temperature range of molten salt heat storage medium, heat transfer structure of steam generator and key parameters of power generation system; In the second step, constraint boundaries of system operation are set according to thermodynamic feasibility and equipment safety requirements; In the third step, a reference working condition of heat release process is determined, and the pressure of each stage of regenerative extraction steam and the work of unit new steam are calculated; In the fourth step, the design temperature of cold and hot salts and the heat exchange area are calculated according to the temperature difference of molten salt heat exchanger; In the fifth step, the mass of molten salt, the volume of heat storage tank and the rated power of electric heater are determined according to heat absorption and release balance; In the sixth step, the equivalent electric-to-electric efficiency is calculated, and a multi-parameter optimization algorithm is iterated until the equivalent electric-to-electric efficiency is optimal.

2. The method of claim 1, wherein, The key parameters of the power generation system include seven variables, i.e., main steam pressure, main steam temperature, reheat extraction steam pressure, feedwater temperature, deaerator pressure, high-pressure heater stage number and low-pressure heater stage number.

3. The method of claim 1, wherein, The main steam pressure is limited to 13-21 MPa in a subcritical system and 23-32 MPa in a supercritical system, so as to balance the system thermal efficiency and equipment strength.

4. The method of claim 1, wherein, The deaerator pressure is set in the range of 0.343-1 MPa to meet the deaeration efficiency and enthalpy rise matching requirements of the low-pressure regenerative system, and to prevent steam flashing or feedwater pump cavitation.

5. The method of claim 1, wherein, The working temperature of the molten salt heat storage system is kept at least 30 degrees Celsius higher than the solidification point or decomposition point of the molten salt, so as to prevent the molten salt from solidifying or decomposing.

6. The method of claim 1, wherein, The minimum temperature difference of each stage of heat exchanger is limited to be greater than 5 degrees Celsius, so as to prevent irreversible loss from increasing due to insufficient heat transfer driving force, and to avoid excessive increase of heat exchange area and investment.

7. The method of claim 1, wherein, The genetic algorithm is used as the multi-parameter optimization algorithm, and the optimal solution is searched through population coding, crossover and mutation operations, so that the equivalent electric-to-electric efficiency of the electric heating molten salt heat storage pure condensing power generation system is optimal.

8. An electrically heated molten salt thermal storage condensing power generation system characterized by, The method comprises an electric heating heat storage system, a steam generator system and a power generation system; The electric heating heat storage system comprises an electric resistance electric heater, a molten salt pump and two molten salt tanks, and is used for realizing conversion and storage of low-price electric energy into heat energy; The steam generator system comprises a preheater, an evaporator, a superheater and a reheater, and is arranged in series and parallel according to temperature and pressure distribution; The power generation system comprises a steam turbine, a regenerative heater, a deaerator and a condenser, and is used for realizing conversion of heat energy into electric energy; In the heat storage stage, the electric heater heats the cold salt and stores it in the hot salt tank; in the heat release stage, the hot salt is pumped into the steam generator system by the molten salt pump to complete energy release and drive the steam turbine to generate power.

9. The electrically heated molten salt thermal storage condensing power system of claim 8, wherein, The connection mode of the reheater and other heat exchange components of the steam generator system can be divided into six modes: The reheater is connected in parallel with the superheater, the evaporator or the preheater, or the reheater is connected in parallel with the superheater and the evaporator, the evaporator and the preheater, or the whole steam generator.

10. An electric heat-salt thermal storage pure condensing power system optimization control device based on the method of any one of claims 1 to 9, characterized in that, The method comprises a parameter acquisition module, a thermodynamic calculation module, a constraint judgment module and an optimization execution module; The parameter acquisition module is used for acquiring the main steam pressure, the molten salt temperature and the heat exchange temperature difference in real time; The thermodynamic calculation module is used for calculating the equivalent electric-to-electric efficiency of the system; The optimization execution module adjusts the key operation parameters of the system based on the genetic algorithm, so as to realize dynamic optimal control of the equivalent electric-to-electric efficiency.

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