A pressurized water reactor thermal energy storage peak shaving system

Abstract

The application discloses a pressurized water reactor heat storage energy peak shaving system, and belongs to the field of reactor engineering and energy storage technology. The system comprises a pressurized water reactor secondary loop, a carbon dioxide energy storage loop and a carbon dioxide power generation loop. At the electricity trough of the power grid, the pressurized water reactor secondary loop drives a steam turbine with excess steam, the turbine is coaxially connected with a compressor of the energy storage loop, so that the excess electric energy is converted into heat energy and stored in a high-temperature molten salt tank, and domestic hot water is supplied at the same time. At the electricity peak of the power grid, the steam turbine in the pressurized water reactor secondary loop generates power at full load, and the power generation loop generates power by using the stored molten salt heat energy, and provides low-temperature heat energy required for the next cycle of the energy storage loop. In the application, molten salt and water are combined as heat storage medium, and through multi-loop coupling and key equipment optimization, efficient, compact and flexible heat storage energy and peak shaving are realized, the application is suitable for energy storage reconstruction of nuclear power plants, and has the advantages of high energy density, small land occupation, low investment cost and environmental friendliness.

Description

Technical Field

[0001] This invention relates to the fields of reactor engineering and energy storage technology, specifically to a pressurized water reactor thermal energy storage peak shaving system. Background Technology

[0002] Nuclear energy, as a baseload energy source with high energy density, cleanliness, low carbon emissions, and stable operation, occupies an important strategic position in my country's energy and power system. Among them, pressurized water reactor (PWR) technology, due to its mature technology and high safety, has become the dominant reactor type in my country's operating and under-construction nuclear power plants. However, due to multiple considerations such as nuclear safety, fuel management, and equipment lifespan, PWR nuclear power plants are usually designed to operate continuously for a long period at a constant or near-constant power (i.e., baseload). Their power regulation capability is relatively limited, and they generally do not have the rapid and large-scale load-following capability similar to coal-fired or gas-fired power plants.

[0003] This "constant power generation" operating mode inherently contradicts the actual load demand of the power grid. Power grid load exhibits significant peak-valley variations, typically peaking during the day and evening and declining at night. The constant power output of nuclear power plants results in a large surplus of unabsorbed electricity during off-peak periods, wasting valuable clean energy; conversely, during peak periods, the lack of flexible power generation capacity can exacerbate grid pressure. This supply-demand mismatch not only reduces the overall economic benefits of nuclear power generation but also poses a challenge to the stable and efficient operation of the power grid.

[0004] To enhance the operational flexibility and grid adaptability of nuclear power units, enabling them to participate in grid peak shaving, the construction of efficient and reliable energy storage systems is considered a key technological approach. Through energy storage systems, excess electricity generated by nuclear power plants can be stored during off-peak hours and released for power generation during peak hours, thereby achieving decoupling and rematching between the output power of nuclear power units and grid demand.

[0005] However, applying existing mature energy storage technologies to nuclear power plant scenarios faces numerous severe challenges. First, while large-scale physical energy storage technologies, such as pumped hydro storage and compressed air storage, are relatively mature, their construction and operation heavily rely on specific geographical and geological conditions (such as elevation differences in mountains and underground caves), and require vast land areas. Nuclear power plants are typically located in specific coastal or riverside areas with extremely limited available land resources, making it difficult to provide the space and natural conditions necessary for constructing such large-scale energy storage facilities. Second, while electrochemical energy storage technologies, such as various types of battery storage, offer flexible deployment options, their scale, lifespan, safety, and cost are still insufficient to meet the long-term, large-capacity energy storage requirements of nuclear power plants. Therefore, developing a new technological solution suitable for the space and environmental constraints of nuclear power plants and capable of meeting large-scale energy storage needs has become an urgent requirement for the industry.

[0006] In recent years, thermal energy storage and power generation technologies, especially systems combined with supercritical carbon dioxide power cycles, have attracted widespread attention due to their advantages such as high energy density, compact system design, and high efficiency potential. Some studies have proposed conceptual ideas for coupling thermal energy storage systems with nuclear power plants. However, these existing solutions mostly remain at the principle or conceptual level and often suffer from one or more of the following prominent problems: First, the system coupling methods are crude, lacking specific and feasible engineering interface design schemes. Many schemes do not explain in detail how to achieve efficient and reliable heat and power exchange between the nuclear island secondary loop system and the external energy storage / power generation system without affecting the original safe operation of the nuclear power plant.

[0007] Secondly, the system integration is low, with many energy conversion stages and significant losses. Some solutions design energy storage and release processes as relatively independent systems, failing to achieve the sharing and integration of key equipment (such as regenerators and thermal storage tanks), resulting in a large system footprint, high equipment investment, and limited overall cycle efficiency.

[0008] Third, the selection of the working fluid and medium did not fully consider the special characteristics of nuclear power plant applications. The failure to comprehensively assess the thermophysical properties, safety, economy, and compatibility with existing materials in nuclear power plants cast doubt on the engineering feasibility of the proposed solution.

[0009] Fourth, the lack of detailed thermal design and parameter optimization that match the actual operating conditions of nuclear power plants (such as secondary loop steam parameters, equipment operating limitations, etc.) results in insufficient economic efficiency and modifiability of the scheme. Summary of the Invention

[0010] To address the aforementioned shortcomings of existing technologies, this invention aims to propose a pressurized water reactor thermal energy storage peak-shaving system. This system solves the problem that existing pressurized water reactor nuclear power plants, operating at constant power, struggle to adapt to peak-valley load variations in the power grid, leading to energy waste during off-peak hours and high power supply pressure during peak hours. Furthermore, it addresses the pain points of existing energy storage peak-shaving systems, such as low energy quality, low overall energy conversion efficiency, extensive modifications, and large land area requirements.

[0011] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A pressurized water reactor thermal energy storage peak-shaving system is provided, which includes a pressurized water reactor secondary loop, a carbon dioxide energy storage loop, and a carbon dioxide power generation loop; The pressurized water reactor secondary loop includes a steam generator, a main steam turbine, a condenser, and a main steam pipeline connecting the outlet of the steam generator and the inlet of the main steam turbine; an auxiliary steam-water separator reheater is connected to the main steam turbine; the main steam turbine is connected to the main generator via drive shaft D; The carbon dioxide energy storage circuit includes a compressor, a molten salt heat exchanger A, a high-temperature molten salt tank, and a low-temperature molten salt tank. The outlet of the compressor is connected to the cooling side inlet of the molten salt heat exchanger A via a pipeline. The carbon dioxide power generation circuit includes a molten salt heat exchanger B, a turbine, a main compressor, an auxiliary compressor, and a generator B. The cooling side inlet of the molten salt heat exchanger B is connected to the outlet of the high-temperature molten salt tank via a pipeline. The pressurized water reactor secondary loop also includes a branch line connected in parallel to the main steam pipeline. The branch line is equipped with an electric branch valve and an auxiliary steam turbine. The output shaft of the auxiliary steam turbine is connected to the input shaft of the compressor of the carbon dioxide energy storage loop through a first transmission mechanism to drive the compressor. The auxiliary steam turbine is equipped with a main steam-water separator reheater. The outlet of the high-temperature molten salt tank is also connected to the cooling side inlet of the molten salt heat exchanger B via a pipeline, the outlet of the low-temperature molten salt tank is connected to the heating side inlet of the molten salt heat exchanger A via a pipeline, and the inlet of the low-temperature molten salt tank is connected to the cooling side outlet of the molten salt heat exchanger B via a pipeline, thereby forming a molten salt thermal energy storage cycle that connects the energy storage circuit and the power generation circuit. The carbon dioxide energy storage circuit and the carbon dioxide power generation circuit share at least one regenerative heat exchanger. Pressurized water reactor thermal energy storage peak-shaving system includes energy storage peak-shaving mode and combined power generation mode; The energy storage peak shaving mode is as follows: when the grid load is low, the electric diversion valve is controlled to allow some steam to enter the diversion branch to drive the auxiliary steam turbine, which in turn drives the compressor to run, so that the carbon dioxide energy storage circuit works and converts electrical energy into heat energy stored in the high-temperature molten salt tank. The combined power generation mode is as follows: during peak grid load, the electric diversion valve is controlled to close the diversion branch, allowing all steam to enter the main steam turbine for power generation. At the same time, the heat energy stored in the high-temperature molten salt tank is used to drive the carbon dioxide power generation circuit to generate additional electricity.

[0012] The technical principle of the pressurized water reactor thermal energy storage peak-shaving system in this invention is as follows: it consists of a pressurized water reactor secondary loop, a carbon dioxide energy storage loop, and a carbon dioxide power generation loop. Flexible allocation of nuclear steam power is achieved by connecting parallel branch lines (including electrically operated branch valves and auxiliary turbines) on the main steam pipeline of the secondary loop. The auxiliary turbine directly drives the compressor in the energy storage loop, converting excess electrical energy (in the form of steam kinetic energy) during off-peak periods into thermal energy, which is stored in a high-temperature molten salt tank via a molten salt heat exchanger. During peak periods, the stored thermal energy drives the power generation loop, which uses carbon dioxide as the working fluid, to generate electricity. The two carbon dioxide loops share a regenerative heat exchanger and are thermally coupled through the molten salt tank loop.

[0013] The pressurized water reactor thermal energy storage peak-shaving system in this invention, through the regulation of an electrically operated diversion valve, flexibly adjusts the power input to the main generator without changing the reactor power, while simultaneously storing or releasing energy, enabling the nuclear power plant to track grid load. It utilizes a carbon dioxide heat pump cycle to achieve the conversion and storage of electrical energy into high-temperature thermal energy, and a carbon dioxide Brayton cycle to achieve efficient conversion of thermal energy into electrical energy, resulting in high overall electro-thermal-electrical conversion efficiency.

[0014] Furthermore, the first transmission mechanism is a transmission shaft A, through which the output shaft of the auxiliary steam turbine is directly connected to the input shaft of the compressor. This transmission method is direct, efficient, has low mechanical loss, fast response speed, avoids additional energy conversion links, improves the energy transmission efficiency from nuclear steam to compression work, and has a simple and reliable structure.

[0015] Furthermore, the carbon dioxide energy storage circuit also includes a secondary turbine and a primary turbine, which are coaxially arranged and jointly drive generator A through drive shaft B. This "one shaft driving two turbines to drive one generator" layout enables direct energy transfer and aggregation within the turbine unit, reducing mechanical losses and investment costs associated with multiple shafts and generators, and improving system compactness and power generation efficiency.

[0016] Furthermore, the output shaft of the turbine in the carbon dioxide power generation circuit is simultaneously connected to the input shafts of the auxiliary compressor, the main compressor, and the generator B via drive shaft C. This integrated design of "one shaft driving three machines" directly utilizes the expansion work to drive the compression and power generation processes required by the circuit, minimizing losses from multiple conversions between mechanical energy and electrical energy, significantly improving net cycle efficiency and system integration, and reducing equipment investment.

[0017] Furthermore, the shared regenerative heat exchanger includes a high-temperature printed circuit board heat exchanger and a low-temperature printed circuit board heat exchanger. In the carbon dioxide energy storage loop, the cooling side outlet of the molten salt heat exchanger A is connected to the cooling side of the high-temperature printed circuit board heat exchanger through a pipeline, and then splits into two paths. One path is connected to the cooling side of the low-temperature printed circuit board heat exchanger and the inlet of the main turbine in sequence, and the other path is connected to the inlet of the auxiliary turbine. In the carbon dioxide power generation loop, the turbine outlet is connected sequentially to the cooling side of the high-temperature printed circuit board heat exchanger and the cooling side of the low-temperature printed circuit board heat exchanger via pipelines. It then splits into two paths: one path connects sequentially to the cooling side of the water heat exchanger B and the inlet of the main compressor; the other path connects to the inlet of the auxiliary compressor. A shared regenerative heat exchanger serves both the carbon dioxide energy storage loop and the carbon dioxide power generation loop, significantly reducing the number of heat exchangers and lowering investment costs and floor space requirements.

[0018] Furthermore, the pressurized water reactor thermal energy storage peak-shaving system also includes a water thermal energy storage circulation system, which includes a high-temperature water tank, a low-temperature water tank, a water heat exchanger A, and a water heat exchanger B; The outlet of the high-temperature water tank is connected to the cooling side inlet of the water heat exchanger A via a pipeline, and the cooling side outlet of the water heat exchanger A is connected to the inlet of the low-temperature water tank or the domestic hot water supply network. The outlet of the low-temperature water tank is connected to the heating side inlet of the water heat exchanger B via a pipeline, and the heating side outlet of the water heat exchanger B is connected to the inlet of the high-temperature water tank. The heating side of the water heat exchanger A is connected in series in the carbon dioxide energy storage circuit on the pipeline after the outlet of the main turbine; the cooling side of the water heat exchanger B is connected in series in the carbon dioxide power generation circuit on the pipeline after the outlet of the cooling side of the low-temperature printed circuit board heat exchanger.

[0019] The water-based thermal energy storage system incorporates high- and low-temperature water tanks and associated heat exchangers. The carbon dioxide energy storage loop utilizes water as a low-temperature heat source, heating the water while simultaneously cooling the working fluid; the carbon dioxide power generation loop uses water as a cooling source, cooling the working fluid while being heated. Hot water from the high-temperature tanks can supplement the heat source for the energy storage loops and provide domestic hot water, improving overall energy efficiency and economy, and contributing to the system's stable operation and efficiency maintenance under different operating conditions.

[0020] Furthermore, the molten salt heat exchanger A, molten salt heat exchanger B, water heat exchanger A, and water heat exchanger B are all shell-and-tube heat exchangers. Shell-and-tube heat exchangers are a mature technology with a robust structure, high reliability, and strong pressure resistance. They can adapt to the temperature, pressure, and physical property requirements of molten salt and water, and have relatively low manufacturing costs and are easy to maintain, ensuring the long-term stable operation of key heat exchange links in the system.

[0021] Furthermore, the compressor is a centrifugal compressor. Centrifugal compressors are suitable for high flow rates and high pressure ratios, and have high isentropic efficiency, which can effectively improve the coefficient of performance (COP) of the heat pump cycle, thereby directly improving the energy conversion efficiency of the entire energy storage process.

[0022] Furthermore, both the carbon dioxide energy storage circuit and the carbon dioxide power generation circuit use carbon dioxide as the working fluid. Carbon dioxide has a low critical temperature (31°C) and a moderate critical pressure (7.38 MPa), making it easy to achieve a supercritical state in the cycle and obtain superior flow and heat transfer characteristics.

[0023] Furthermore, the pressurized water reactor secondary loop also includes a condensate pump, a low-pressure heater, a feedwater pump, and a high-pressure heater, which are sequentially connected to the condenser outlet via the main steam pipeline. The high-pressure heater is connected to the feedwater inlet of the steam generator, forming a feedwater regenerative subsystem. The outlets of the main turbine and auxiliary turbine are connected to the inlets of the low-pressure heater and the high-pressure heater, respectively. This configuration retains a mature feedwater regenerative cycle, utilizing the turbine to increase the feedwater temperature and ensuring the thermal efficiency of the pressurized water reactor secondary loop itself.

[0024] Compared with existing pressurized water reactor nuclear power plants, the beneficial effects of this invention are as follows: This invention provides a pressurized water reactor (PWR) thermal energy storage and peak-shaving system capable of storing and releasing energy 24 / 7, independent of geographical conditions, and adaptable to nuclear power plant site selection, while also meeting real-time grid needs. The working fluid for both the energy storage and power generation loops is transcritical or supercritical carbon dioxide, achieving a small overall system footprint. Shared regenerative equipment further reduces footprint and investment costs, resulting in a compact and efficient system. In this PWR thermal energy storage and peak-shaving system, energy storage and release are achieved through the coupling of three loops. By referencing existing PWR secondary loop design parameters, the form and parameters of each loop in this system are rationally designed, and the selection and use of various equipment are optimized, significantly improving the electrothermal energy conversion rate. This results in a PWR thermal energy storage and peak-shaving system characterized by high energy density, small footprint, and high flexibility. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a pressurized water reactor thermal energy storage peak-shaving system in Example 1.

[0026] Figure 2 This is a schematic diagram of a pressurized water reactor thermal energy storage peak-shaving system in Example 2.

[0027] The components include: 1. Steam generator; 2. Electric diverter valve; 3. Main steam turbine; 4. Auxiliary steam-water separator reheater; 5. Auxiliary steam turbine; 6. Main steam-water separator reheater; 7. Condenser; 8. Condensate pump; 9. Low-pressure heater; 10. Feedwater pump; 11. High-pressure heater; 12. Low-temperature molten salt tank; 13. Molten salt heat exchanger A; 14. High-temperature molten salt tank; 15. Molten salt heat exchanger B; 16. High-temperature water tank; 17. Water heat exchanger A; 8. Low-temperature water tank; 19. Water heat exchanger B; 20. Compressor; 21. Auxiliary turbine; 22. Main turbine; 23. Generator A; 24. Turbine; 25. Auxiliary compressor; 26. Main compressor; 27. Generator B; 28. High-temperature printed circuit board heat exchanger; 29. ​​Low-temperature printed circuit board heat exchanger; 30. Drive shaft A; 31. Drive shaft B; 32. Drive shaft C; 33. Drive shaft D; 34. Main generator. Detailed Implementation

[0028] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0029] Example 1, Reference Figure 1 As shown, the present invention provides a pressurized water reactor thermal energy storage peak-shaving system, including a pressurized water reactor secondary loop, a carbon dioxide energy storage loop and a carbon dioxide power generation loop, and further includes a molten salt thermal energy storage cycle and a water thermal energy storage cycle system.

[0030] Specifically, the pressurized water reactor (PWR) secondary loop is an integrated modification of the existing PWR nuclear power plant secondary loop. Its core connection is as follows: the main steam generated by steam generator 1 is transported through the main steam pipeline. A branch line is connected in parallel on the main steam pipeline. This branch line is equipped with an electric branch valve 2 and an auxiliary turbine 5. The auxiliary turbine 5 is equipped with a main steam-water separator reheater 6. The un-branched steam enters the main turbine 3 along the original main steam pipeline. The main turbine 3 is equipped with an auxiliary steam-water separator reheater 4. The main turbine 3 drives the main generator 34 to generate electricity via drive shaft D33. The exhaust steam from both the main turbine 3 and the auxiliary turbine 5 enters the condenser 7 for condensation. The condensate, after being pressurized by the condensate pump 8, flows sequentially through the low-pressure heater 9, the feedwater pump 10, and the high-pressure heater 11, finally returning to the feedwater inlet of steam generator 1, completing the feedwater reheat cycle. Steam extracted from the main turbine 3 and auxiliary turbine 5 is directed to the low-pressure heater 9 and high-pressure heater 11 as a heat source. The output shaft of the auxiliary turbine 5 is directly connected to the input shaft of the compressor 20 in the carbon dioxide energy storage circuit via drive shaft A30, realizing the direct transmission of mechanical work.

[0031] The carbon dioxide energy storage loop uses carbon dioxide as the working fluid, and its main function is to convert mechanical work into thermal energy storage during grid off-peak periods. Its core connection is as follows: the outlet of compressor 20 (preferably a centrifugal compressor) is connected to the cooling side (carbon dioxide side) inlet of molten salt heat exchanger A13. The cooling side outlet of molten salt heat exchanger A13 is sequentially connected to the cooling side of high-temperature printed circuit board heat exchanger 28 and the cooling side of low-temperature printed circuit board heat exchanger 29. Before the cooling side inlet of low-temperature printed circuit board heat exchanger 29, the pipeline splits into two paths: the main path connects to the cooling side of low-temperature printed circuit board heat exchanger 29, and the branch path connects to the inlet of auxiliary turbine 21. The main turbine 22 and auxiliary turbine 21 are arranged coaxially and jointly drive generator A23 via drive shaft B31. The outlet of main turbine 22 is connected to the heating side (carbon dioxide side) of water heat exchanger A17, after which the carbon dioxide working fluid returns to the inlet of compressor 20, completing the cycle.

[0032] The carbon dioxide power generation circuit also uses carbon dioxide as the working fluid, and its main function is to convert stored thermal energy into electrical energy during peak grid periods. Its core connection is as follows: the outlet of the heating side (carbon dioxide side) of the molten salt heat exchanger B15 is connected to the inlet of the turbine 24. The outlet of the turbine 24 is sequentially connected to the cooling side of the high-temperature printed circuit board heat exchanger 28 and the cooling side of the low-temperature printed circuit board heat exchanger 29. At the cooling side outlet of the low-temperature printed circuit board heat exchanger 29, the pipeline splits into two paths: the main path connects to the cooling side inlet of the water heat exchanger B19, and the branch path connects to the inlet of the auxiliary compressor 25. After the outlets of the main compressor 26 and the auxiliary compressor 25 merge, the carbon dioxide working fluid returns to the heating side inlet of the molten salt heat exchanger B15. The output shaft of the turbine 24 is connected to the input shafts of the auxiliary compressor 25, the main compressor 26, and the generator B27 simultaneously via the drive shaft C32, realizing power distribution.

[0033] The molten salt thermal energy storage cycle is as follows: the outlet of the low-temperature molten salt tank 12 is connected to the heating side (molten salt side) inlet of the molten salt heat exchanger A13, and its heating side outlet is connected to the inlet of the high-temperature molten salt tank 14. The outlet of the high-temperature molten salt tank 14 is connected to the cooling side inlet of the molten salt heat exchanger B15, and its cooling side outlet is connected to the inlet of the low-temperature molten salt tank 12. Thus, the molten salt circulates between the high-temperature and low-temperature tanks, serving as the medium connecting the energy storage circuit (thermal storage) and the power generation circuit (heat release). Specifically, a molten salt pump can be used to achieve the molten salt circulation.

[0034] The water-based thermal energy storage system includes a high-temperature water tank 16, a low-temperature water tank 18, a water heat exchanger A17, and a water heat exchanger B19. Specifically, the outlet of the high-temperature water tank 16 is connected to the cooling side (water side) inlet of the water heat exchanger A17, and its cooling side outlet can be connected to the domestic hot water network or the low-temperature water tank 18. The outlet of the low-temperature water tank 18 is connected to the heating side inlet of the water heat exchanger B19, and its heating side outlet is connected to the inlet of the high-temperature water tank 16. The water circuit provides a low-temperature heat source (through water heat exchanger A17) for the energy storage circuit and a cooling source (through water heat exchanger B19) for the power generation circuit, while also producing domestic hot water.

[0035] The pressurized water reactor thermal energy storage peak-shaving system in this invention includes an energy storage peak-shaving mode and a combined power generation mode.

[0036] Energy storage peak-shaving modes (during periods of low grid load) include: 1. Power Regulation and Diversion: The power grid dispatch command requires the nuclear power plant to reduce its output power. The control system regulates the electric diversion valve 2 to divert a portion (e.g., 25%) of the main steam to the diversion branch.

[0037] 2. Main circuit power generation: The remaining 75% of the steam drives the main steam turbine 3 to operate at reduced power, and drives the main generator 34 to generate electricity through the drive shaft D33.

[0038] 3. Driving the heat pump energy storage: The diverted steam drives the auxiliary steam turbine 5 to do work. Its output power directly drives the compressor 20 through the drive shaft A30, providing power for the energy storage circuit, thereby converting the surplus electrical energy of the grid (manifested as the mechanical energy of steam) into heat energy.

[0039] 4. Thermal energy storage: In the energy storage circuit, after carbon dioxide is compressed and heated, it transfers heat to molten salt in molten salt heat exchanger A13. The heated high-temperature molten salt is stored in high-temperature molten salt tank 14, completing the storage of electrical energy into high-temperature thermal energy.

[0040] 5. Energy Recovery and Hot Water Supply: In the energy storage loop's own circulation, the main turbine 22 and auxiliary turbine 21, which perform expansion work, drive the generator A23 through the drive shaft B31 to recover part of the energy. At the same time, the loop releases heat at the water heat exchanger A17 to heat the water in the water loop, producing domestic hot water at >60°C.

[0041] Combined generation modes (during peak grid load periods) include: 1. Main circuit full power generation: The control system closes the electric diversion valve 2, and all the main steam enters the main steam turbine 3, restoring it to full power operation, and the main generator 34 outputs rated power.

[0042] 2. Heat release for power generation: At the same time, the high-temperature molten salt flowing out from the high-temperature molten salt tank 14 heats the carbon dioxide working fluid in the power generation circuit in the molten salt heat exchanger B15.

[0043] 3. Combined power generation: High-temperature and high-pressure carbon dioxide drives turbine 24 to perform work. The power output from the turbine simultaneously drives generator B27 to generate electricity (providing additional peak-shaving power) through drive shaft C32, and drives auxiliary compressor 25 and main compressor 26 to maintain cyclic operation.

[0044] 4. Heat source replenishment: The waste heat from the power generation circuit is released in the water heat exchanger B19 to heat the water in the water circuit, replenishing the heat of the high-temperature water tank 16 and providing a preheating heat source for the next energy storage cycle of the energy storage circuit.

[0045] Example 2, Reference Figure 2 As shown, the present invention also provides another embodiment of a pressurized water reactor thermal energy storage peak-shaving system. This system also includes a pressurized water reactor secondary loop, a carbon dioxide energy storage loop, a carbon dioxide power generation loop, and molten salt thermal energy storage and water thermal energy storage systems, but some equipment layouts and connections have been changed to further improve the system's compactness and operational flexibility.

[0046] Specifically, the pressurized water reactor secondary loop still revolves around steam generator 1. Steam from steam generator 1 is transported to main turbine 3 via main steam pipeline. Main turbine 3 drives main generator 34 via drive shaft D33 and is directly connected to the input shaft of compressor 20 in the carbon dioxide energy storage loop. Condenser 7, condensate pump 8, low-pressure heater 9, feedwater pump 10, and high-pressure heater 11 constitute the feedwater regenerative subsystem, forming a closed loop with steam generator 1. Steam extracted from the main and auxiliary turbines is still used to heat the feedwater.

[0047] In the carbon dioxide energy storage loop, the outlet of compressor 20 is sequentially connected to the cooling side (carbon dioxide side) of molten salt heat exchanger A13, the cooling side of high-temperature printed circuit board heat exchanger 28, and the cooling side of low-temperature printed circuit board heat exchanger 29. The subsequent piping splits into two paths: one leads to the main turbine 22, and the other to the auxiliary turbine 21. The two turbines are coaxially connected and jointly drive generator A23 via drive shaft B31. The outlet of the main turbine 22 is connected to the heating side of water heat exchanger A17, after which the working fluid returns to the inlet of compressor 20.

[0048] In the carbon dioxide power generation circuit, the heating side outlet of the molten salt heat exchanger B15 is connected to the inlet of the turbine 24. The turbine 24 outlet passes sequentially through the cooling side of the high-temperature printed circuit board heat exchanger 28 and the cooling side of the low-temperature printed circuit board heat exchanger 29, before splitting into two paths: one path enters the main compressor 26 via the cooling side of the water heat exchanger B19, and the other path directly enters the auxiliary compressor 25. The output shaft of the turbine 24 simultaneously drives the auxiliary compressor 25, the main compressor 26, and the generator B27 via the drive shaft C32.

[0049] Molten salt thermal storage cycle connection method and Figure 1 The implementation is consistent: low-temperature molten salt tank 12 → molten salt heat exchanger A13 (heating side) → high-temperature molten salt tank 14 → molten salt heat exchanger B15 (cooling side) → low-temperature molten salt tank 12, forming a closed molten salt cycle.

[0050] The water storage heat circulation system is the same as in the previous embodiment: high temperature water tank 16 → water heat exchanger A17 (cooling side) → domestic hot water pipe network / low temperature water tank 18 → water heat exchanger B19 (heating side) → high temperature water tank 16.

[0051] This embodiment and Figure 1 The main difference between the embodiments lies in the different spatial layout of the equipment and the routing of the pipelines, specifically reflected in: Compact equipment layout: The high-temperature printed circuit board heat exchanger 28 and the low-temperature printed circuit board heat exchanger 29 are stacked vertically or arranged side by side in space to reduce the length of connecting pipes and reduce pressure loss and heat loss.

[0052] Simplified transmission system: Drive shafts A30, B31, and C32 all adopt a short-shaft direct-drive design, reducing the number of support bearings and improving transmission efficiency and system rigidity.

[0053] Optimized pipeline routing: The main high-temperature and high-pressure pipelines in the carbon dioxide circuit adopt the shortest path design, and the key bends adopt a large curvature radius design to reduce local resistance and erosion wear.

[0054] This system also features energy storage peak-shaving mode and combined power generation mode, and its workflow is consistent with the aforementioned embodiments: Energy storage and peak shaving mode: Steam drives the main steam turbine 3 or the auxiliary steam turbine 5 to drive the compressor 20 to operate, converting electrical energy into heat energy and storing it in the high-temperature molten salt tank 14. At the same time, the water circuit can supply domestic hot water.

[0055] Combined power generation mode: The main steam turbine 3 generates electricity at full load, the high-temperature molten salt drives the carbon dioxide power generation circuit to operate, the generator B27 outputs additional electrical energy, and the water circuit provides preheating for the energy storage circuit.

[0056] This embodiment optimizes equipment layout and piping design, further improving the system's space utilization and operational reliability while maintaining the system's functional integrity. It is suitable for nuclear power plant retrofit scenarios with more limited space (such as small modular reactors).

[0057] In summary, the pressurized water reactor thermal energy storage peak-shaving system provided by this invention, without interfering with the nuclear reactor power, uses steam to drive a steam turbine. The turbine and the compressor in the energy storage loop are coaxially connected, directly driving the compressor in the energy storage loop to store excess electrical energy as heat in a high-temperature molten salt tank, thus completing the storage of high-grade thermal energy. The stored high-grade thermal energy is then used to generate electricity through a power generation loop, thus releasing the energy. This system enables the nuclear power plant to become a flexible regulating power source for the grid, achieving flexible peak-shaving.

Claims

1. A pressurized water reactor thermal energy storage peak-shaving system, characterized in that, This includes a pressurized water reactor secondary loop, a carbon dioxide energy storage loop based on the reverse Carnot cycle, and a carbon dioxide power generation loop based on the Carnot cycle. The pressurized water reactor secondary loop includes a steam generator (1), a main steam turbine (3), a condenser (7), and a main steam pipeline connecting the outlet of the steam generator (1) and the inlet of the main steam turbine (3); an auxiliary steam-water separator reheater (4) is connected to the main steam turbine (3); the main steam turbine (3) is connected to the main generator (34) through a drive shaft D (33); The carbon dioxide energy storage circuit includes a compressor (20), a molten salt heat exchanger A (13), a high-temperature molten salt tank (14), and a low-temperature molten salt tank (12). The outlet of the compressor (20) is connected to the hot side inlet of the molten salt heat exchanger A (13) through a pipeline. The carbon dioxide power generation circuit includes a molten salt heat exchanger B (15), a turbine (24), a main compressor (26), an auxiliary compressor (25), and a generator B (27). The hot side inlet of the molten salt heat exchanger B (15) is connected to the outlet of the high-temperature molten salt tank (14) through a pipeline. The pressurized water reactor secondary loop also includes a branch line connected in parallel to the main steam pipeline. The branch line is equipped with an electric branch valve (2) and an auxiliary steam turbine (5). The output shaft of the auxiliary steam turbine (5) is connected to the input shaft of the compressor (20) of the carbon dioxide energy storage loop through a first transmission mechanism to drive the compressor (20). The auxiliary steam turbine (5) is equipped with a main steam-water separator reheater (6). The outlet of the high-temperature molten salt tank (14) is also connected to the hot side inlet of the molten salt heat exchanger B (15) through a pipeline. The inlet of the low-temperature molten salt tank (12) is connected to the cold side outlet of the molten salt heat exchanger A (13) through a pipeline. The outlet of the low-temperature molten salt tank (12) is connected to the cold side inlet of the molten salt heat exchanger B (15) through a pipeline, thereby forming a molten salt thermal energy storage cycle that connects the energy storage circuit and the power generation circuit. The carbon dioxide energy storage circuit and the carbon dioxide power generation circuit share at least one regenerative heat exchanger. The carbon dioxide energy storage circuit and the carbon dioxide power generation circuit can be selectively in transcritical or supercritical operating states. Pressurized water reactor thermal energy storage peak-shaving system includes energy storage peak-shaving mode and combined power generation mode; The energy storage peak shaving mode is as follows: when the grid load is low, the electric diversion valve (2) is controlled to allow some steam to enter the diversion branch to drive the auxiliary steam turbine (5), which in turn drives the compressor (20) to run, so that the carbon dioxide energy storage circuit works and converts electrical energy into heat energy stored in the high temperature molten salt tank (14). The combined power generation mode is as follows: during peak grid load, the electric diversion valve (2) is controlled to close the diversion branch, so that all the steam enters the main steam turbine (3) to generate electricity. At the same time, the heat energy stored in the high-temperature molten salt tank (14) is used to drive the carbon dioxide power generation circuit to generate additional electricity.

2. The pressurized water reactor thermal energy storage peak-shaving system according to claim 1, characterized in that, The first transmission mechanism is a transmission shaft A (30), and the output shaft of the auxiliary steam turbine (5) is directly connected to the input shaft of the compressor (20) through the transmission shaft A (30).

3. The pressurized water reactor thermal energy storage peak-shaving system according to claim 1, characterized in that, The carbon dioxide energy storage circuit also includes a secondary turbine (21) and a main turbine (22), which are coaxially arranged and drive the generator A (23) together through the transmission shaft B (31).

4. The pressurized water reactor thermal energy storage peak-shaving system according to claim 3, characterized in that, The output shaft of the turbine (24) in the carbon dioxide power generation circuit is connected to the input shaft of the auxiliary compressor (25), the main compressor (26) and the generator B (27) through the transmission shaft C (32).

5. The pressurized water reactor thermal energy storage peak-shaving system according to claim 1, characterized in that, The shared regenerative heat exchangers include a high-temperature printed circuit board heat exchanger (28) and a low-temperature printed circuit board heat exchanger (29). In the carbon dioxide energy storage circuit, the cooling side outlet of the molten salt heat exchanger A (13) is connected to the cooling side of the high temperature printed circuit board heat exchanger (28) through a pipeline, and then splits into two paths. One path is connected to the cooling side of the low temperature printed circuit board heat exchanger (29) and the inlet of the main turbine (22) in sequence, and the other path is connected to the inlet of the auxiliary turbine (21). In the carbon dioxide power generation circuit, the outlet of the turbine (24) is connected in sequence to the cooling side of the high temperature printed circuit board heat exchanger (28) and the cooling side of the low temperature printed circuit board heat exchanger (29) through pipelines, and then splits into two paths. One path is connected in sequence to the cooling side of the water heat exchanger B (19) and the inlet of the main compressor (26), and the other path is connected to the inlet of the auxiliary compressor (25).

6. The pressurized water reactor thermal energy storage peak-shaving system according to claim 1, characterized in that, It also includes a water storage heat circulation system, which includes a high-temperature water tank (16), a low-temperature water tank (18), a water heat exchanger A (17), and a water heat exchanger B (19). The outlet of the high-temperature water tank (16) is connected to the cooling side inlet of the water heat exchanger A (17) via a pipeline, and the cooling side outlet of the water heat exchanger A (17) is connected to the inlet of the low-temperature water tank (18) or the domestic hot water supply network. The outlet of the low-temperature water tank (18) is connected to the heating side inlet of the water heat exchanger B (19) via a pipeline, and the heating side outlet of the water heat exchanger B (19) is connected to the inlet of the high-temperature water tank (16). The heating side of the water heat exchanger A (17) is connected in series in the carbon dioxide energy storage circuit on the pipeline after the outlet of the main turbine (22); the cooling side of the water heat exchanger B (19) is connected in series in the carbon dioxide power generation circuit on the inlet pipeline of the main compressor (26).

7. The pressurized water reactor thermal energy storage peak-shaving system according to claim 1, characterized in that, The molten salt heat exchanger A (13), molten salt heat exchanger B (15), water heat exchanger A (17) and water heat exchanger B (19) are all shell and tube heat exchangers.

8. The pressurized water reactor thermal energy storage peak-shaving system according to claim 1, characterized in that, The compressor (20) is a centrifugal compressor.

9. The pressurized water reactor thermal energy storage peak-shaving system according to claim 1, characterized in that, The working medium in both the carbon dioxide energy storage circuit and the carbon dioxide power generation circuit is carbon dioxide.

10. The pressurized water reactor thermal energy storage peak-shaving system according to claim 1, characterized in that, The pressurized water reactor secondary loop also includes a condensate pump (8), a low-pressure heater (9), a feedwater pump (10) and a high-pressure heater (11) that are sequentially connected to the outlet of the condenser (7) via the main steam pipeline. The high-pressure heater (11) is connected to the feedwater inlet of the steam generator (1) to form a feedwater regeneration subsystem. The outlets of the main steam turbine (3) and the auxiliary steam turbine (5) are connected to the inlets of the low-pressure heater (9) and the high-pressure heater (11).

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