Carnot battery system coupled with uninterrupted low-temperature heat source and integrated optimization method of Carnot battery system

Abstract

The invention discloses a Carnot battery system coupled with an uninterrupted low-temperature heat source and an integrated optimization method of the Carnot battery system. The Carnot battery system comprises a high-temperature heat pump system, a heat storage system and a power circulation system, in the charging process, the high-temperature heat pump system operates, and waste heat of the uninterrupted low-temperature heat source module is improved into high-grade heat energy to be stored in the heat storage system through renewable energy source electric power; in the discharging process, the power circulation system operates, gradient utilization is conducted on heat energy stored in the heat storage system and an uninterrupted low-temperature heat source in the discharging stage, and generated mechanical energy is converted into electric energy through a generator and output to a power grid. The system configuration does not depend on the working medium type, and the comprehensive utilization rate of the uninterrupted low-temperature heat source and the back-and-forth efficiency of the Carnot cell are improved; according to the integrated optimization method, the working medium is coded to become a continuous variable capable of being synchronously optimized, and the optimal charge-discharge cycle working medium combination and system operation parameters suitable for different operation conditions can be obtained only through one-time optimization.

Description

Technical Field

[0001] The present invention relates to the field of novel thermomechanical energy storage technology, and in particular to a Carnot battery system coupled with an uninterrupted low-temperature heat source and an integrated optimization method thereof. Background Art

[0002] In the context of the rapid development of renewable energy, combining energy storage systems with renewable energy generation can effectively solve the volatility of renewable energy and the instability of the power system. In particular, as the proportion of renewable energy generation continues to increase, the role of energy storage systems becomes increasingly important. Carnot battery is a very promising energy storage technology, consisting of an electric heating system, a heat storage system and a thermal power generation system. During the charging stage, the heat pump system is driven by wind abandonment, solar abandonment or low-valley cheap electricity, and the generated heat energy is stored through a heat storage medium. When the power grid is at peak load and the electricity price is high, the heat engine cycle is used to convert the heat energy back into electrical energy and return it to the grid. Carnot battery has the advantages of flexible deployment, no geographical restrictions and high energy density. At present, the traditional system form has a low utilization rate of uninterrupted heat sources, lacks system configuration suitable for different working fluid types and operating conditions, and has no effective working fluid and parameter collaborative optimization method, which hinders the improvement of the comprehensive performance of Carnot battery and its promotion and application.

[0003] The Chinese invention patent application with publication number CN117346581A proposes a waste heat utilization system based on Carnot batteries, which realizes the recovery and utilization of high-temperature thermal energy by inputting high-temperature waste heat into a high-temperature heat storage device. However, the energy release mechanism of this system is complex, which will lead to poor economy and adjustability.

[0004] The Chinese invention patent application with the announcement number CN118599500A proposes a mixed working fluid and its system and method for low-temperature waste heat Carnot battery energy storage system, which achieves efficiency improvement by setting a regenerator and a waste heat preheater in the power cycle, but the system only considers subcritical operation, and there is a functional conflict between the configuration of the regenerator and the preheater. In addition, the system working fluid needs to be given in advance, and parameter optimization under the conditions of each working fluid cannot achieve global performance optimization in one step. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a Carnot battery system coupled with an uninterrupted low-temperature heat source and an integrated optimization method thereof. The system can effectively improve the comprehensive utilization rate of the uninterrupted low-temperature heat source and the round-trip efficiency of the Carnot battery by coupling with the uninterrupted low-temperature heat source during the two periods of charging and discharging. The integrated optimization method proposed in the present invention encodes the working fluid to make it an optimizable continuous variable, and only one optimization is required to obtain the optimal charge and discharge cycle working fluid combination and system operating parameters suitable for different operating conditions.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A Carnot battery system coupled with an uninterrupted low-temperature heat source comprises three subsystems: a high-temperature heat pump system, a heat storage system and a power cycle system, wherein the heat energy outlet of the high-temperature heat pump system is connected to the heat energy inlet of the heat storage system, and the heat energy outlet of the heat storage system is connected to the heat energy inlet of the power cycle system; the heat energy inlets of the high-temperature heat pump system and the power cycle system are respectively connected to the waste heat outlet of the uninterrupted low-temperature heat source module 1, the electric energy inlet of the high-temperature heat pump system is connected to the electric energy outlet of the renewable energy power generation module 14, the power output shaft of the power cycle system is connected to the power input shaft of the generator 16, and the electric energy outlet of the generator 16 is connected to the electric energy inlet of the power grid 15;

[0008] During the charging process, the high-temperature heat pump system operates, using renewable energy electricity to upgrade the waste heat of the uninterrupted low-temperature heat source module 1 into high-quality thermal energy and store it in the heat storage system; during the discharging process, the power cycle system operates, and the thermal energy stored in the heat storage system and the uninterrupted low-temperature heat source in the discharging stage are utilized in a cascade manner, and the generated mechanical energy is converted into electrical energy through the generator 16 and output to the power grid 15.

[0009] The high-temperature heat pump system includes a heat pump evaporator 2, a regenerator 3, a compressor 4, a heat pump condenser 5, and a throttle valve 6; the waste heat outlet of the uninterruptible low-temperature heat source module 1 is connected to the low-temperature side inlet of the heat pump evaporator 2, and the low-temperature side outlet of the heat pump evaporator 2 is connected to the waste heat inlet of the uninterruptible low-temperature heat source module 1, and the heat from the uninterruptible low-temperature heat source module 1 is input into the heat pump evaporator 2, so that the circulating working fluid in the heat pump evaporator 2 absorbs heat and evaporates; the low-temperature side outlet of the heat pump evaporator 2 is connected to the low-temperature side inlet of the regenerator 3, and the circulating working fluid is further heated by the regenerator 3; the low-temperature side outlet of the regenerator 3 is connected to the inlet of the compressor 4, and the power inlet of the compressor 4 is connected to the power outlet of the renewable energy power generation module 14, and the compressor 4 consumes the power generated by the renewable energy module 14 to heat up the circulating working fluid. pressure; the outlet of the compressor 4 is connected to the high-temperature side inlet of the heat pump condenser 5, and the circulating working fluid in the high-temperature and high-pressure state flows through the heat pump condenser 5, exchanges heat with the heat storage medium from the heat storage system, and releases heat; the high-temperature side outlet of the heat pump condenser 5 is connected to the high-temperature side inlet of the regenerator 3, and heat is exchanged and cooled with the circulating working fluid at the low-temperature side outlet of the heat pump evaporator 2 through the regenerator 3; the high-temperature side outlet of the regenerator 3 is connected to the low-temperature side inlet of the heat pump evaporator 2 through the throttle valve 6, and the low-temperature side outlet of the heat pump evaporator 2 is connected to the waste heat inlet of the uninterruptible low-temperature heat source module 1, and the circulating working fluid after cooling is throttled and expanded through the throttle valve 6 and then enters the heat pump evaporator 2 to absorb the heat of the uninterruptible low-temperature heat source. The low-temperature heat source in the heat pump evaporator 2 is cooled by the circulating working fluid after absorbing heat, and then is input into the uninterruptible low-temperature heat source module 1 to be heated again.

[0010] The heat storage system adopts a double-tank sensible heat storage form, including a high-temperature heat storage tank 7 and a low-temperature heat storage tank 8. During the charging process, the outlet of the low-temperature heat storage tank 8 is connected to the low-temperature side inlet of the heat pump condenser 5, and the low-temperature side outlet of the heat pump condenser 5 is connected to the inlet of the high-temperature heat storage tank 7. The heat storage medium flows from the low-temperature heat storage tank 8 through the heat pump condenser 5 into the high-temperature heat storage tank 7, and exchanges heat with the high-temperature heat pump circulating working fluid in the heat pump condenser 5 to increase the temperature, and the heated heat storage medium is stored in the high-temperature heat storage tank 7. During the discharging process, the outlet of the high-temperature heat storage tank 7 is connected to the high-temperature side inlet of the heat engine evaporator 9, and the high-temperature side outlet of the heat engine evaporator 9 is connected to the inlet of the low-temperature heat storage tank 8. The heat storage medium flows from the high-temperature heat storage tank 7 through the heat engine evaporator 9 into the low-temperature heat storage tank 8, and exchanges heat with the power circulating working fluid in the heat engine evaporator 9 to reduce the temperature, and the cooled heat storage medium is stored in the low-temperature heat storage tank 8, and then the cycle is repeated.

[0011] The power cycle system includes a heat engine evaporator 9, a turbine expander 10, a heat engine condenser 11, a working fluid pump 12, and a preheater 13; the low temperature side outlet of the heat engine evaporator 9 is connected to the inlet of the turbine expander 10, the power output shaft of the turbine expander 10 is connected to the power input shaft of the generator 16, the power outlet of the generator 16 is connected to the power inlet of the power grid 15, the circulating working fluid entering the heat engine evaporator 9 exchanges heat with the heat storage medium in the heat engine evaporator 9 to absorb heat, and the high temperature and high pressure working fluid enters the turbine expander 10 to expand and work, driving the generator 16 to rotate and generate electricity, and the generated electricity is transmitted to the power grid 15; the outlet of the turbine expander 10 is connected to the high temperature side inlet of the heat engine condenser 11 to cool the expanded working fluid exhaust gas; the heat engine condenser 11 The high temperature side outlet is connected to the inlet of the working fluid pump 12, the outlet of the working fluid pump 12 is connected to the low temperature side inlet of the preheater 13, the waste heat outlet of the uninterruptible low temperature heat source module 1 is connected to the high temperature side inlet of the preheater 13, the high temperature side outlet of the preheater 13 is connected to the waste heat inlet of the uninterruptible low temperature heat source module 1, and the low temperature side outlet of the preheater 13 is connected to the low temperature side inlet of the heat engine evaporator 9; the power cycle working fluid cooled by the heat engine condenser 11 is compressed and pressurized by the working fluid pump 12 and then input into the preheater 13, preheated by the waste heat of the uninterruptible low temperature heat source module 1 in the discharge stage and heated, and then enters the heat engine evaporator 9 to absorb the heat energy stored in the high temperature heat storage tank 7 for heating and evaporation, and the waste heat in the preheater 13 is absorbed by the power cycle working fluid and cooled and then returned to the uninterruptible low temperature heat source module 1.

[0012] The circulating working fluids in the high-temperature heat pump system and the power cycle system are all one of six low global warming potential organic working fluids or a mixed working fluid formed by one of six low global warming potential organic working fluids and carbon dioxide, and the six organic working fluids are R1234yf, R1234ze(E), R1234ze(Z), R1224yd(Z), R1233zd(E), and R1336mzz(Z);

[0013] The heat storage medium in the heat storage system is pressurized water or heat transfer oil. The heat storage temperature of the high-temperature heat storage tank 7 is 110-140°C, and the heat storage temperature of the low-temperature heat storage tank 8 is lower than 100°C and slightly higher than the temperature of the uninterrupted low-temperature heat source.

[0014] The compressor 4 of the high-temperature heat pump system adopts a screw compressor or a centrifugal compressor, and the turbine expander 10 of the power cycle system adopts an axial flow turbine expander; when a single organic working fluid is used, the heat pump evaporator 2, the regenerator 3, the heat pump condenser 5, the heat engine evaporator 9, the heat engine condenser 11 and the preheater 13 all adopt plate heat exchangers; when a mixed working fluid of organic working fluid and carbon dioxide is used and the mass mixing ratio of carbon dioxide is relatively high so that the circulation high pressure exceeds 3.5MPa, the heat pump condenser 5, the heat engine evaporator 9 and the preheater 13 all adopt printed circuit board heat exchangers, and the heat pump evaporator 2, the regenerator 3 and the heat engine condenser 11 all adopt plate heat exchangers.

[0015] The uninterrupted low-temperature heat source is industrial waste heat, data center liquid cooling waste heat, regional heating network or geothermal heat.

[0016] The present invention also provides an integrated optimization method for a Carnot battery system coupled with an uninterrupted low-temperature heat source, comprising the following steps:

[0017] Step 1: By encoding the working fluids of the high-temperature heat pump system and the power cycle system, the discrete working fluid types in the high-temperature heat pump system and the power cycle system are converted into corresponding continuous variables, which are called working fluid selection factors;

[0018] Step 2: Input the working fluid selection factor and system operation parameters of step 1 into the Carnot battery system integrated model for calculation, and output the thermal economy evaluation index of the Carnot battery system;

[0019] The system operation parameters include the high temperature heat storage temperature of the high temperature heat storage tank 7, the low temperature heat storage temperature of the low temperature heat storage tank 8 and the pinch point temperature difference of six heat exchangers, the six heat exchangers are heat pump evaporator 2, regenerator 3, heat pump condenser 5, heat engine evaporator 9, heat engine condenser 11, preheater 13; the thermal economy evaluation index includes round-trip efficiency, energy storage density and levelized energy storage cost;

[0020] Step 3: Use the thermal economy evaluation index obtained in step 2 as the optimization objective function, solve the multi-objective optimization problem based on the multi-objective intelligent optimization algorithm, and obtain the Pareto frontier; determine the weights of round-trip efficiency, energy storage density and levelized energy storage cost according to different application scenarios, and determine the optimization result on the Pareto frontier.

[0021] The process of working fluid coding is as follows:

[0022] Through the piecewise function method, the discrete types of organic working fluids are converted into continuous optimizable variables, and fair screening is achieved by ensuring that each organic working fluid has the same search interval through uniform intervals.

[0023] The working fluid coding expression is as follows:

[0024]

[0025] Among them, WF is the working fluid, and numbers 1-6 correspond to six organic working fluids respectively; WFS is the working fluid selection factor, and its interval is set to (1,7), that is, the selection interval length of each organic working fluid is 1; when the working fluid selection factor is in different intervals, it corresponds to different types of organic working fluids.

[0026] The expression of the multi-objective optimization problem in step 3 is as follows:

[0027]

[0028] Where RTE is the round trip efficiency, VED is the volume energy density, LCOS is the levelized energy storage cost, x is the decision variable, T HST is the high temperature heat storage temperature of the high temperature heat storage tank 7, T CST is the low-temperature heat storage temperature of the low-temperature heat storage tank 8, and PPTD×6 is the pinch point temperature difference of the six heat exchangers in the Carnot battery system.

[0029] Compared with the prior art, the advantages of the present invention are:

[0030] 1. The Carnot battery system proposed in the present invention makes full use of the uninterrupted low-temperature heat source during the charging and discharging stages, that is, the high-temperature heat pump circulation system of the Carnot battery uses the uninterrupted low-temperature heat source to increase the evaporation temperature during the charging stage, and the power circulation system uses the uninterrupted low-temperature heat source for preheating during the discharging stage, which effectively improves the comprehensive utilization effect of the uninterrupted low-temperature heat source and the round-trip efficiency of the electric energy of the Carnot battery.

[0031] 2. The Carnot battery system proposed in the present invention adopts a regenerator in the high-temperature heat pump system to further improve the performance of the high-temperature heat pump. In the power cycle system, the secondary coupling uninterrupted low-temperature heat source is used for preheating, which improves the performance of the power cycle while eliminating the regenerator in the power cycle system in the prior art, effectively reducing the heat exchanger area and investment cost, and improving the economy. In addition, the reasonable configuration of the above two subsystems makes the entire Carnot battery system independent of the working fluid type of the high-temperature heat pump system and the power cycle system, and the use of different working fluids can make the Carnot battery system operate efficiently.

[0032] 3. The Carnot battery system proposed in the present invention uses low global warming potential organic working fluids and carbon dioxide as alternative working fluids. One of the organic working fluids or a mixture of one of the organic working fluids and carbon dioxide can be selected as the working fluid of the high-temperature heat pump system and the power cycle system, thereby ensuring the thermal performance and making the entire Carnot battery a sustainable energy storage system.

[0033] 4. The present invention proposes an integrated optimization method for the working fluid and operating parameters of the Carnot battery system. By encoding the working fluid, it becomes an optimizable continuous variable, and can simultaneously optimize and determine the optimal working fluid and the corresponding system operating parameters of the high-temperature heat pump system and the power cycle system at one time, saving computing resources and time. The global optimality of the system's comprehensive performance can be achieved in one step of optimization.

[0034] 5. The Carnot battery system proposed in this power generation is not only suitable for industrial waste heat, but can also be applied to data center liquid cooling waste heat, regional heating network, geothermal and other scenarios.

[0035] In summary, compared with the prior art, the present invention can effectively improve the comprehensive utilization rate of the uninterrupted low-temperature heat source and the round-trip efficiency of the Carnot battery by coupling with the uninterrupted low-temperature heat source during the two periods of charging and discharging; the integrated optimization method proposed in the present invention encodes the working fluid to make it an optimizable continuous variable, and only one optimization is required to obtain the optimal charge and discharge cycle working fluid combination and system operating parameters suitable for different operating conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of the Carnot battery system coupled with an uninterrupted low-temperature heat source of the present invention.

[0037] In the figure: uninterrupted low-temperature heat source module 1, heat pump evaporator 2, regenerator 3, compressor 4, heat pump condenser 5, throttle valve 6, high-temperature heat storage tank 7, low-temperature heat storage tank 8, heat engine evaporator 9, turbine expander 10, heat engine condenser 11, working fluid pump 12, preheater 13, renewable energy power generation module 14, power grid 15, generator 16.

[0038] Figure 2 A flow chart of the calculation method of the Carnot battery system integration model provided by the present invention.

[0039] Figure 3 This is a Pareto frontier comparison diagram of the Carnot battery system integration optimization method proposed in the present invention and the traditional enumeration method, where: Figure 3 (a) is the traditional enumeration method, Figure 3 (b) is the method of the present invention. DETAILED DESCRIPTION

[0040] The structural features and effects achieved by the present invention will be clearly and completely described below in conjunction with the accompanying drawings.

[0041] like Figure 1As shown, a Carnot battery system coupled with an uninterruptible low-temperature heat source includes three subsystems: a high-temperature heat pump system, a heat storage system and a power cycle system. The heat energy outlet of the high-temperature heat pump system is connected to the heat energy inlet of the heat storage system, and the heat energy outlet of the heat storage system is connected to the heat energy inlet of the power cycle system; the heat energy inlets of the high-temperature heat pump system and the power cycle system are respectively connected to the waste heat outlet of the uninterruptible low-temperature heat source module 1, the electric energy inlet of the high-temperature heat pump system is connected to the electric energy outlet of the renewable energy power generation module 14, the power output shaft of the power cycle system is connected to the power input shaft of the generator 16, and the electric energy outlet of the generator 16 is connected to the electric energy inlet of the power grid 15;

[0042] During the charging process, the high-temperature heat pump system operates, using renewable energy electricity to upgrade the waste heat of the uninterrupted low-temperature heat source module 1 into high-quality thermal energy and store it in the heat storage system; during the discharging process, the power cycle system operates, and the thermal energy stored in the heat storage system and the low-temperature heat source in the discharging stage are utilized in a cascade manner, and the generated mechanical energy is converted into electrical energy through the generator 16 and output to the power grid 15.

[0043] The uninterrupted low-temperature heat source is a low-temperature heat source condition that provides continuous heating throughout the day, specifically industrial waste heat, data center liquid cooling waste heat, regional heating network or geothermal energy.

[0044] The high-temperature heat pump system includes a heat pump evaporator 2, a regenerator 3, a compressor 4, a heat pump condenser 5 and a throttle valve 6; the waste heat outlet of the uninterrupted low-temperature heat source module 1 is connected to the low-temperature side inlet of the heat pump evaporator 2, and the heat from the uninterrupted low-temperature heat source module 1 is input into the heat pump evaporator 2, so that the circulating working fluid in the heat pump evaporator 2 absorbs heat and evaporates; the low-temperature side outlet of the heat pump evaporator 2 is connected to the low-temperature side inlet of the regenerator 3, and the circulating working fluid is further heated by the regenerator 3; the low-temperature side outlet of the regenerator 3 is connected to the inlet of the compressor 4, and the power inlet of the compressor 4 is connected to the power outlet of the renewable energy power generation module 14, and the circulating working fluid is heated and pressurized by the electric energy generated by the renewable energy module 14 consumed by the compressor 4; the outlet of the compressor 4 is connected to the heat pump condenser 5, the circulating working fluid in the high temperature and high pressure state flows through the heat pump condenser 5, exchanges heat with the heat storage medium from the heat storage system, and releases heat; the high temperature side outlet of the heat pump condenser 5 is connected to the high temperature side inlet of the regenerator 3, and exchanges heat and cools down with the circulating working fluid at the low temperature side outlet of the heat pump evaporator 2 through the regenerator 3; the high temperature side outlet of the regenerator 3 is connected to the low temperature side inlet of the heat pump evaporator 2 through the throttle valve 6, and the low temperature side outlet of the heat pump evaporator 2 is connected to the waste heat inlet of the uninterruptible low temperature heat source module 1, and the circulating working fluid after cooling is throttled and expanded through the throttle valve 6 and then enters the heat pump evaporator 2 to absorb the heat of the uninterruptible low temperature heat source; the low temperature heat source in the heat pump evaporator 2 is input into the uninterruptible low temperature heat source module 1 for reheating after the circulating working fluid absorbs heat and cools down.

[0045] The heat storage system adopts a double-tank sensible heat storage form, including a high-temperature heat storage tank 7 and a low-temperature heat storage tank 8; during the charging process, the outlet of the low-temperature heat storage tank 8 is connected to the low-temperature side inlet of the heat pump condenser 5, and the low-temperature side outlet of the heat pump condenser 5 is connected to the inlet of the high-temperature heat storage tank 7, and the heat storage medium flows from the low-temperature heat storage tank 8 through the heat pump condenser 5 into the high-temperature heat storage tank 7, and heat exchanges with the high-temperature heat pump circulating working fluid in the heat pump condenser 5 to increase the temperature, and the heated heat storage medium is stored in the high-temperature heat storage tank 7; during the discharging process, the outlet of the high-temperature heat storage tank 7 is connected to the high-temperature side inlet of the heat engine evaporator 9, and the high-temperature side outlet of the heat engine evaporator 9 is connected to the inlet of the low-temperature heat storage tank 8, and the heat storage medium flows from the high-temperature heat storage tank 7 through the heat engine evaporator 9 into the low-temperature heat storage tank 8, and heat exchanges with the power circulating working fluid in the heat engine evaporator 9 to reduce the temperature, and the cooled heat storage medium is stored in the low-temperature heat storage tank 8, and then the cycle is repeated;

[0046] The power cycle system includes a heat engine evaporator 9, a turbine expander 10, a heat engine condenser 11, a working fluid pump 12, and a preheater 13; the low temperature side outlet of the heat engine evaporator 9 is connected to the inlet of the turbine expander 10, the power output shaft of the turbine expander 10 is connected to the power input shaft of the generator 16, and the power outlet of the generator 16 is connected to the power inlet of the power grid 15; the circulating working fluid entering the heat engine evaporator 9 exchanges heat with the heat storage medium in the heat engine evaporator 9 to absorb heat, and the high temperature and high pressure working fluid enters the turbine expander 10 to expand and work, driving the generator 16 to rotate and generate electricity, and the generated electricity is transmitted to the power grid 15; the outlet of the turbine expander 10 is connected to the high temperature side inlet of the heat engine condenser 11 to cool the expanded working fluid exhaust gas; the heat engine condenser 11 The high temperature side outlet is connected to the inlet of the working fluid pump 12, the outlet of the working fluid pump 12 is connected to the low temperature side inlet of the preheater 13, the waste heat outlet of the uninterruptible low temperature heat source module 1 is connected to the high temperature side inlet of the preheater 13, the high temperature side outlet of the preheater 13 is connected to the waste heat inlet of the uninterruptible low temperature heat source module 1, and the low temperature side outlet of the preheater 13 is connected to the low temperature side inlet of the heat engine evaporator 9; the power cycle working fluid cooled by the heat engine condenser 11 is compressed and pressurized by the working fluid pump 12 and then input into the preheater 13, preheated by the waste heat of the uninterruptible low temperature heat source module 1 in the discharge stage and heated, and then enters the heat engine evaporator 9 to absorb the heat energy stored in the high temperature heat storage tank 7 for heating and evaporation, and the waste heat in the preheater 13 is absorbed by the power cycle working fluid and cooled and then returned to the uninterruptible low temperature heat source module 1.

[0047] The high temperature heat pump system is one of six low global warming potential organic working fluids or a mixture of one of six low global warming potential organic working fluids and carbon dioxide; the circulating working fluid in the power cycle system is one of six low global warming potential organic working fluids or a mixture of one of six low global warming potential organic working fluids and carbon dioxide; the six organic working fluids are R1234yf, R1234ze(E), R1234ze(Z), R1224yd(Z), R1233zd(E), and R1336mzz(Z). The heat storage medium in the heat storage system is pressurized water or heat transfer oil, the heat storage temperature of the high temperature heat storage tank 7 is 110-140°C, and the heat storage temperature of the low temperature heat storage tank 8 is lower than 100°C and slightly higher than the temperature of the uninterrupted low temperature heat source.

[0048] The equipment of the system is selected according to the power and operating pressure of the system: the compressor 4 of the high-temperature heat pump system adopts a screw compressor or a centrifugal compressor according to the capacity, and the turbine expander 10 of the power cycle system adopts an axial flow turbine expander; the six heat exchangers, namely the heat pump evaporator 2, the regenerator 3, the heat pump condenser 5, the heat engine evaporator 9, the heat engine condenser 11 and the preheater 13 adopt plate heat exchangers or printed circuit board heat exchangers according to the operating pressure. When a single organic working fluid is used, the six heat exchangers all adopt plate heat exchangers; when a mixed working fluid of organic working fluid and carbon dioxide is used and the mass mixing ratio of carbon dioxide is relatively high so that the circulating high pressure exceeds 3.5MPa, the heat pump condenser 5, the heat engine evaporator 9 and the preheater 13 all adopt printed circuit board heat exchangers, and the heat pump evaporator 2, the regenerator 3 and the heat engine condenser 11 all adopt plate heat exchangers.

[0049] An integrated optimization method for a Carnot battery system coupled with an uninterrupted low-temperature heat source comprises the following steps:

[0050] Step 1: By encoding the working fluids of the high-temperature heat pump system and the power cycle system, the discrete working fluid types in the high-temperature heat pump system and the power cycle system are converted into corresponding continuous variables, which are called working fluid selection factors;

[0051] The process of working fluid coding is as follows:

[0052] Through the piecewise function method, the discrete organic working fluid types are converted into continuous optimizable variables, and fair screening is achieved by ensuring that each organic working fluid has the same search interval through uniform intervals.

[0053] The working fluid coding expression is as follows:

[0054]

[0055] Among them, WF is the working fluid, and numbers 1-6 correspond to six kinds of organic working fluids respectively; WFS is the working fluid selection factor, and its interval is set to (1,7), that is, the selection interval length of each organic working fluid is 1; when the working fluid selection factor is in different intervals, it corresponds to different types of organic working fluids;

[0056] Step 2: Input the working fluid selection factor and system operation parameters of step 1 into the Carnot battery system integrated model for calculation, and output the thermal economy evaluation index of the Carnot battery system;

[0057] The system operation parameters include the high temperature heat storage temperature of the high temperature heat storage tank 7, the low temperature heat storage temperature of the low temperature heat storage tank 8 and the pinch point temperature difference of the six heat exchangers, the six heat exchangers are respectively the heat pump evaporator 2, the regenerator 3, the heat pump condenser 5, the heat engine evaporator 9, the heat engine condenser 11, and the preheater 13; the thermal economy evaluation index includes the round-trip efficiency, the energy storage density and the levelized energy storage cost;

[0058] like Figure 2 As shown, the calculation process of the Carnot battery system integration model is as follows:

[0059] First, the working fluid selection factor, system operating parameters and boundary conditions of step 1 are input into the Carnot battery system integrated model, and the heat storage temperature and heat storage efficiency after standing are calculated according to the thermal insulation performance of the heat storage system; the boundary conditions include ambient temperature, efficiency of the turbo expander 10, the generator 16 and the working fluid pump 12, charging and discharging time, electricity price, temperature of uninterrupted low-temperature waste heat, thermal insulation performance of the high-temperature heat storage tank 7 and the low-temperature heat storage tank 8, equipment price, operation and maintenance cost, and the life of the Carnot battery system;

[0060] Then, the heat storage temperature is input into the high-temperature heat pump system model, and the superheat and condensation pressure are assumed to calculate the compression, i.e., isentropic efficiency, find the pinch point between the heat storage medium and the high-temperature heat pump working fluid in the heat pump condenser 5, calculate the pinch point temperature difference of the heat pump condenser 5, and make the pinch point temperature difference of the heat pump condenser 5 converge to the design value by iterating the condensation pressure; continue to calculate the pinch point temperature difference of the regenerator 3, and make the pinch point temperature difference of the regenerator 3 converge to the design value by iterating the superheat, and then calculate the performance coefficient and equipment cost of the high-temperature heat pump system;

[0061] Input the heat storage temperature into the power cycle system model, assume the condensation pressure, find the pinch point between the cooling water in the heat engine condenser 11 and the power cycle working fluid, calculate the pinch point temperature difference of the heat engine condenser 11, and make the pinch point temperature difference of the heat engine condenser 11 converge to the design value by iterating the condensation pressure; assume the evaporation pressure, find the pinch point between the heat storage medium and the power cycle working fluid in the heat engine evaporator 9, calculate the pinch point temperature difference of the heat engine evaporator 9, and make the pinch point temperature difference of the heat engine evaporator 9 converge to the design value by iterating the evaporation pressure, and then calculate the power generation efficiency and equipment cost of the power cycle system;

[0062] Finally, the thermal economic evaluation index of the Carnot battery system is calculated and output based on the performance coefficient and equipment cost of the high-temperature heat pump system and the power generation efficiency and equipment cost of the power cycle system;

[0063] Step 3: Using the thermal economic evaluation index obtained in step 2 as the optimization objective function, the multi-objective optimization problem is solved based on the multi-objective intelligent optimization algorithm to obtain the Pareto frontier; the weights of round-trip efficiency, energy storage density and levelized energy storage cost are determined according to different application scenarios, and the optimization result is determined on the Pareto frontier;

[0064] The expression of the multi-objective optimization problem is as follows:

[0065]

[0066] Where RTE is the round trip efficiency, VED is the volume energy density, LCOS is the levelized energy storage cost, x is the decision variable, T HST is the high temperature heat storage temperature of the high temperature heat storage tank 7, T CST is the low-temperature heat storage temperature of the low-temperature heat storage tank 8, and PPTD×6 is the pinch point temperature difference of the six heat exchangers in the Carnot battery system.

[0067] By setting appropriate variable optimization intervals and using multi-objective intelligent optimization algorithms (such as NSGA-Ⅱ), the Pareto frontier can be obtained. Since the high-temperature heat pump system and the power cycle system of the Carnot battery system can use different working fluids, when there are n alternative working fluids, the working fluid combination is n. 2 The traditional optimization method needs to optimize each working fluid combination once, which consumes a lot of time and computing resources. The integrated optimization method proposed in the present invention includes a working fluid coding method, which makes the working fluid an optimization variable and is automatically optimized by the optimization algorithm. Therefore, only one optimization is needed to obtain the best working fluid combination and the corresponding system parameters at the same time.

[0068] like Figure 3 As shown in (a), when there are four alternative working fluids, the traditional enumeration method requires four optimizations; Figure 3 As shown in (b), when there are four alternative working fluids, the integrated optimization method proposed in the present invention only requires one optimization, saving a lot of time and computing resources.

Claims

1. A Carnot battery system coupled with an uninterrupted low temperature heat source, characterized in that: The invention comprises three subsystems: a high-temperature heat pump system, a heat storage system and a power cycle system. The heat energy outlet of the high-temperature heat pump system is connected to the heat energy inlet of the heat storage system, and the heat energy outlet of the heat storage system is connected to the heat energy inlet of the power cycle system. The heat energy inlets of the high-temperature heat pump system and the power cycle system are respectively connected to the waste heat outlet of the uninterrupted low-temperature heat source module (1), the electric energy inlet of the high-temperature heat pump system is connected to the electric energy outlet of the renewable energy power generation module (14), the power output shaft of the power cycle system is connected to the power input shaft of the generator (16), and the electric energy outlet of the generator (16) is connected to the electric energy inlet of the power grid (15); During the charging process, the high-temperature heat pump system operates, using renewable energy electricity to upgrade the waste heat of the uninterrupted low-temperature heat source module (1) into high-quality thermal energy and store it in the thermal storage system; during the discharging process, the power circulation system operates, and the thermal energy stored in the thermal storage system and the uninterrupted low-temperature heat source in the discharging stage are utilized in a cascade manner, and the generated mechanical energy is converted into electrical energy through the generator (16) and output to the power grid (15).

2. A Carnot battery system coupled with an uninterrupted low temperature heat source according to claim 1, characterized in that: The high-temperature heat pump system comprises a heat pump evaporator (2), a regenerator (3), a compressor (4), a heat pump condenser (5), and a throttle valve (6); the waste heat outlet of the uninterrupted low-temperature heat source module (1) is connected to the low-temperature side inlet of the heat pump evaporator (2), and the heat from the uninterrupted low-temperature heat source module (1) is input into the heat pump evaporator (2), so that the circulating working fluid in the heat pump evaporator (2) absorbs heat and evaporates; the low-temperature side outlet of the heat pump evaporator (2) is connected to the low-temperature side inlet of the regenerator (3), and the circulating working fluid is further heated by the regenerator (3); the low-temperature side outlet of the regenerator (3) is connected to the inlet of the compressor (4), and the power inlet of the compressor (4) is connected to the power outlet of the renewable energy power generation module (14), so that the compressor (4) consumes the power generated by the renewable energy module (14) to increase the temperature and pressure of the circulating working fluid; the outlet of the compressor (4) is connected to the heat source module (14), and the outlet of the compressor (4) is connected to the heat source module (14). The high-temperature side inlet of the heat pump condenser (5) is connected, and the circulating working fluid in a high-temperature and high-pressure state flows through the heat pump condenser (5) to exchange heat with the heat storage medium from the heat storage system to release heat; the high-temperature side outlet of the heat pump condenser (5) is connected to the high-temperature side inlet of the regenerator (3), and heat is exchanged and cooled with the circulating working fluid at the low-temperature side outlet of the heat pump evaporator (2) through the regenerator (3); the high-temperature side outlet of the regenerator (3) is connected to the low-temperature side inlet of the heat pump evaporator (2) through a throttle valve (6), and the low-temperature side outlet of the heat pump evaporator (2) is connected to the waste heat inlet of the uninterruptible low-temperature heat source module (1), and the circulating working fluid after cooling is throttled and expanded through the throttle valve (6) and then enters the heat pump evaporator (2) to absorb the heat of the uninterruptible low-temperature heat source, and the low-temperature heat source in the heat pump evaporator (2) is input into the uninterruptible low-temperature heat source module (1) to be heated again after the circulating working fluid absorbs heat and cools it.

3. A Carnot battery system coupled with an uninterrupted low temperature heat source according to claim 1, characterized in that: The heat storage system adopts a double-tank sensible heat storage form, comprising a high-temperature heat storage tank (7) and a low-temperature heat storage tank (8); during the charging process, the outlet of the low-temperature heat storage tank (8) is connected to the low-temperature side inlet of the heat pump condenser (5), and the low-temperature side outlet of the heat pump condenser (5) is connected to the inlet of the high-temperature heat storage tank (7); the heat storage medium flows from the low-temperature heat storage tank (8) through the heat pump condenser 5 into the high-temperature heat storage tank (7), exchanges heat with the high-temperature heat pump circulating working fluid in the heat pump condenser (5) to increase the temperature, and the heated heat storage medium is heated to The medium is stored in a high-temperature heat storage tank (7); during the discharge process, the outlet of the high-temperature heat storage tank (7) is connected to the high-temperature side inlet of the heat engine evaporator (9), and the high-temperature side outlet of the heat engine evaporator (9) is connected to the inlet of the low-temperature heat storage tank (8). The heat storage medium flows from the high-temperature heat storage tank (7) through the heat engine evaporator (9) into the low-temperature heat storage tank (8), exchanges heat with the power cycle working fluid in the heat engine evaporator (9) to reduce the temperature, and the cooled heat storage medium is stored in the low-temperature heat storage tank (8), and then the cycle is repeated.

4. A Carnot battery system coupled with an uninterrupted low temperature heat source according to claim 1, characterized in that: The power cycle system comprises a heat engine evaporator (9), a turbine expander (10), a heat engine condenser (11), a working fluid pump (12), and a preheater (13); the low temperature side outlet of the heat engine evaporator (9) is connected to the inlet of the turbine expander (10), the power output shaft of the turbine expander (10) is connected to the power input shaft of the generator (16), the power outlet of the generator (16) is connected to the power inlet of the power grid (15), the circulating working fluid entering the heat engine evaporator (9) exchanges heat with the heat storage medium in the heat engine evaporator (9) to absorb heat, the high temperature and high pressure working fluid enters the turbine expander (10) to expand and work, driving the generator (16) to rotate and generate electricity, and the generated electricity is transmitted to the power grid (15); the outlet of the turbine expander (10) is connected to the high temperature side inlet of the heat engine condenser (11), cooling the working fluid exhaust gas after expansion; the heat engine condenser (11) ) is connected to the inlet of the working fluid pump (12), the outlet of the working fluid pump (12) is connected to the low-temperature inlet of the preheater (13), the waste heat outlet of the uninterruptible low-temperature heat source module (1) is connected to the high-temperature inlet of the preheater (13), the high-temperature outlet of the preheater (13) is connected to the waste heat inlet of the uninterruptible low-temperature heat source module (1), and the low-temperature outlet of the preheater (13) is connected to the low-temperature inlet of the heat engine evaporator (9); the power cycle working fluid cooled by the heat engine condenser (11) is compressed and pressurized by the working fluid pump (12) and then input into the preheater (13), preheated by the waste heat of the uninterruptible low-temperature heat source module (1) in the discharge stage and then heated, and then enters the heat engine evaporator (9) to absorb the heat energy stored in the high-temperature heat storage tank (7) to heat up and evaporate, and the waste heat in the preheater (13) is absorbed by the power cycle working fluid and cooled and then returned to the uninterruptible low-temperature heat source module (1).

5. A Carnot battery system coupled with an uninterrupted low-temperature heat source according to any one of claims 1 to 4, characterized in that: The circulating working fluids in the high-temperature heat pump system and the power cycle system are all one of six low global warming potential organic working fluids or a mixed working fluid formed by one of six low global warming potential organic working fluids and carbon dioxide, and the six organic working fluids are R1234yf, R1234ze(E), R1234ze(Z), R1224yd(Z), R1233zd(E), and R1336mzz(Z); The heat storage medium in the heat storage system is pressurized water or heat transfer oil, the heat storage temperature of the high-temperature heat storage tank (7) is 110-140° C., and the heat storage temperature of the low-temperature heat storage tank (8) is lower than 100° C. and slightly higher than the temperature of the uninterrupted low-temperature heat source.

6. A Carnot battery system coupled with an uninterrupted low temperature heat source according to claim 5, characterized in that: The compressor (4) of the high-temperature heat pump system adopts a screw compressor or a centrifugal compressor, and the turbine expander (10) of the power cycle system adopts an axial flow turbine expander; when a single organic working fluid is used, the heat pump evaporator (2), the regenerator (3), the heat pump condenser (5), the heat engine evaporator (9), the heat engine condenser (11) and the preheater (13) all adopt plate heat exchangers; when a mixed working fluid of an organic working fluid and carbon dioxide is used and the mass mixing ratio of the carbon dioxide is relatively high so that the circulating high pressure exceeds 3.5 MPa, the heat pump condenser (5), the heat engine evaporator (9) and the preheater (13) all adopt printed circuit board heat exchangers, and the heat pump evaporator (2), the regenerator (3) and the heat engine condenser (11) all adopt plate heat exchangers.

7. A Carnot battery system coupled with an uninterrupted low temperature heat source according to claim 6, characterized in that: The uninterrupted low-temperature heat source is industrial waste heat, data center liquid cooling waste heat, regional heating network or geothermal heat.

8. An integrated optimization method for a Carnot battery system coupled with an uninterrupted low-temperature heat source, characterized in that: The steps include: Step 1: By encoding the working fluids of the high-temperature heat pump system and the power cycle system, the discrete working fluid types in the high-temperature heat pump system and the power cycle system are converted into corresponding continuous variables, which are called working fluid selection factors; Step 2: Input the working fluid selection factor and system operation parameters of step 1 into the Carnot battery system integrated model for calculation, and output the thermal economy evaluation index of the Carnot battery system; The system operation parameters include the high-temperature heat storage temperature of the high-temperature heat storage tank (7), the low-temperature heat storage temperature of the low-temperature heat storage tank (8), and the pinch point temperature difference of six heat exchangers, wherein the six heat exchangers are respectively a heat pump evaporator (2), a heat regenerator (3), a heat pump condenser (5), a heat engine evaporator (9), a heat engine condenser (11), and a preheater (13); the thermal economy evaluation index includes round-trip efficiency, energy storage density, and levelized energy storage cost; Step 3: Use the thermal economy evaluation index obtained in step 2 as the optimization objective function, solve the multi-objective optimization problem based on the multi-objective intelligent optimization algorithm, and obtain the Pareto frontier; determine the weights of round-trip efficiency, energy storage density and levelized energy storage cost according to different application scenarios, and determine the optimization result on the Pareto frontier.

9. The integrated optimization method of a Carnot battery system coupled with an uninterrupted low-temperature heat source according to claim 8, characterized in that: The process of working fluid coding is as follows: Through the piecewise function method, the discrete types of organic working fluids are converted into continuous optimizable variables, and fair screening is achieved by ensuring that each organic working fluid has the same search interval through uniform intervals. The working fluid coding expression is as follows: Among them, WF is the working fluid, and numbers 1-6 correspond to six organic working fluids respectively; WFS is the working fluid selection factor, and its interval is set to (1,7), that is, the selection interval length of each organic working fluid is 1; when the working fluid selection factor is in different intervals, it corresponds to different types of organic working fluids.

10. The integrated optimization method of a Carnot battery system coupled with an uninterrupted low-temperature heat source according to claim 8, characterized in that: The expression of the multi-objective optimization problem in step 3 is as follows: Where RTE is the round trip efficiency, VED is the volume energy density, LCOS is the levelized energy storage cost, x is the decision variable, T HST is the high temperature heat storage temperature of the high temperature heat storage tank 7, T CST is the low-temperature heat storage temperature of the low-temperature heat storage tank 8, and PPTD×6 is the pinch point temperature difference of the six heat exchangers in the Carnot battery system.

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