Large-scale heat energy incremental storage and flexible regulation power supply system

Abstract

The utility model provides a kind of large-scale heat energy increment storage and flexible regulation and control energy supply system, including low-temperature stage heat pump, medium-temperature phase change heat storage unit, high-temperature stage heat pump, low-temperature stage heat pump and environmental heat source or industrial waste heat heat exchange, for absorbing the heat released by low-grade heat source, medium-temperature phase change heat storage unit is used to store the heat released by low-temperature stage heat pump, high-temperature stage heat pump and user end heat exchange connection, for output hot water or steam to user end.The utility model is through two-stage compression to share temperature rise technical path, realizes increment heat storage and energy quality regulation and control function, in heat storage mode, low-temperature stage heat pump absorbs heat from environment or industrial waste heat and improves quality and is stored in phase change heat storage unit;In heat release mode, high-temperature stage heat pump further improves the quality of heat storage energy and outputs high-grade heat energy, breaks through the theoretical limit of traditional electric heating equivalent conversion, has peak clipping and on-demand flexible heating capacity, can be widely applied in building heating, industrial process heat and other fields.

Description

Technical Field

[0001] This utility model relates to the field of thermal energy storage and heat pump technology, specifically to a large-scale incremental thermal energy storage and flexible control energy supply system. Background Technology

[0002] Under the "dual carbon" context, the deep decarbonization of building heating and cooling systems faces numerous challenges, especially the increase in peak grid load and decrease in system stability brought about by the large-scale deployment of heat pumps. With the increasing proportion of renewable energy, the power grid faces increasingly severe peak-shaving pressure, urgently requiring flexible and adjustable energy storage methods to smooth load fluctuations. Simultaneously, the construction of new energy systems such as zero-carbon parks and low-carbon industrial parks requires the on-site consumption of renewable energy within these parks, full utilization of waste heat resources, and multi-energy synergy of cooling, heating, and power, placing higher demands on thermal energy storage and flexible control technologies.

[0003] Thermal energy storage (TES) technology can effectively decouple heat load from power supply in time and space, supporting peak shaving and valley filling of the power grid and the consumption of renewable energy. However, current integrated heat pump-thermal storage (HP-TES) systems generally lack systematic design and quantitative evaluation of the functions of "incremental energy storage" and "energy quality regulation".

[0004] Electrically driven vapor compression heat pumps are a highly efficient heat energy generation technology, with an energy output-to-input ratio greater than 1, superior to electrothermal technology. However, existing technologies mainly suffer from the following problems: First, traditional heat storage and release methods rely on the cascaded utilization of thermal energy, often releasing heat at a temperature 5-10°C lower than the storage temperature. This cascaded utilization is constrained, often requiring the search for phase change materials with phase change temperatures higher than the user's heating temperature. This significantly increases the constraints on the selection of phase change thermal storage materials (phase change temperature, phase change enthalpy, storage density, performance stability, material toxicity and safety, and economics).

[0005] Secondly, in response to the challenges of highly volatile supply and demand in future energy systems, thermal energy storage systems must not only fulfill the basic function of thermoelectric decoupling but also possess higher-level regulation capabilities. Specifically, by absorbing low-temperature ambient heat sources or industrial waste heat through heat pump systems and raising their temperature for storage, "incremental thermal energy storage" can be achieved by using limited electrical energy to obtain higher thermal storage capacity.

[0006] Third, in high-temperature-rise heat pump systems, single-stage compressors face severe performance degradation. The industrial sector possesses a large amount of recoverable low-grade waste heat resources, including cooling tower circulating water (30~50℃) and air compressor cooling water (40~50℃) from industries such as petrochemicals, steel metallurgy, and electronics manufacturing. Simultaneously, various environmental heat sources above -25℃, such as air sources, surface water sources, groundwater sources, soil sources, and sewage sources, also have enormous potential for utilization. These low-grade heat sources generally have temperatures in the range of -25~50℃, making them difficult to utilize directly.

[0007] Fourth, user-side heating demand exhibits diverse characteristics, with significant differences in heating temperature requirements across different application scenarios. For hot water demand of 60-90℃, a single-stage heat pump can provide direct supply; for low-pressure steam demand of 120℃ and below, high-temperature heat pump technology can achieve direct steam supply; however, for medium- and high-pressure steam demand of 120-150℃ or even higher, such as heat used in food processing, chemical reactions, and textile printing and dyeing processes, a two-stage steam compression or multi-stage cascade heat pump system is required. Existing single-stage heat pump systems, when handling high temperature rise conditions, suffer from excessively high single-stage compression ratios. This leads to excessive exhaust temperature, a sharp drop in compressor efficiency, and a significant reduction in the system's coefficient of performance, making it difficult to meet practical application needs. This is because the temperature difference between the low heat source temperature (-25-50℃) and the high heat demand temperature (80-150℃) can reach 100-175℃.

[0008] Therefore, it is necessary to develop a large-scale thermal energy storage and conversion control system that can achieve "incremental thermal energy storage" and "flexible energy quality control". Through two-stage or multi-stage compression, the system can reasonably share the temperature rise, realize the efficient recovery and utilization of low-grade waste heat and environmental heat sources, and output hot water or steam at different temperature levels as needed. At the same time, it can also have the ability to peak shaving and valley filling, support grid peak regulation, and promote the consumption of renewable energy, so as to improve resource utilization efficiency, support multi-energy synergistic optimization and flexible system operation, and provide technical support for the construction of zero-carbon parks and low-carbon industrial parks. Utility Model Content

[0009] In view of the deficiencies in the existing technology, the purpose of this utility model is to provide a large-scale incremental thermal energy storage and flexible energy supply system.

[0010] The large-scale incremental thermal energy storage and flexible control energy supply system provided by this utility model includes a low-temperature heat pump, a medium-temperature phase change thermal energy storage unit and a high-temperature heat pump connected in sequence by heat exchange. The low-temperature heat pump is connected to an external environmental heat source or a low-grade heat source of industrial waste heat at -25~50℃ for heat exchange. It is used to absorb the heat released by the low-grade heat source, upgrade it to 50~70℃ through a low-temperature thermodynamic cycle, and release it to the medium-temperature phase change heat storage unit. The medium-temperature phase change heat storage unit is used to store the heat released by the low-temperature stage heat pump and release the stored heat to the high-temperature stage heat pump. The high-temperature heat pump is connected to the user end for heat exchange. It is used to absorb the heat released by the intermediate heat storage unit, upgrade the heat through a high-temperature thermodynamic cycle, and output hot water at 60~90℃ or steam at 100~150℃ to the user end.

[0011] Preferably, the low-temperature stage heat pump includes a low-temperature stage evaporator, a low-temperature stage compressor, a low-temperature stage condenser, and a low-temperature stage expansion valve; The low-temperature stage evaporator, low-temperature stage compressor, low-temperature stage condenser and low-temperature stage expansion valve are connected in sequence to form a low-temperature stage circuit, and the low-temperature stage circuit stores the low-temperature stage working fluid. The low-temperature stage evaporator is connected to an external low-grade heat source at -25~50℃ for heat exchange. The low-temperature stage working fluid absorbs heat from the external low-grade heat source in the low-temperature stage evaporator and evaporates into a low-temperature low-pressure gas. The low-temperature low-pressure gas is compressed by the low-temperature stage compressor to form a high-temperature high-pressure gas. The high-temperature and high-pressure gas enters the low-temperature stage condenser, where it condenses and releases heat, transforming into a high-temperature and high-pressure liquid. The high-temperature and high-pressure liquid expands through the low-temperature stage expansion valve, forming a low-temperature and low-pressure two-phase fluid, which then flows back to the low-temperature stage evaporator, completing the low-temperature stage heat pump cycle. The low-temperature stage condenser is heat exchanged with the medium-temperature phase change thermal storage unit, and the low-temperature stage working fluid in the low-temperature stage condenser is used to release the upgraded heat to the medium-temperature phase change thermal storage unit.

[0012] Preferably, the high-temperature heat pump includes a high-temperature evaporator, a high-temperature compressor, a high-temperature condenser, and a high-temperature expansion valve; The high-temperature evaporator, high-temperature compressor, high-temperature condenser and high-temperature expansion valve are connected in sequence to form a high-temperature circuit, and the high-temperature working fluid is stored in the high-temperature circuit. The high-temperature evaporator is heat-exchange connected to the medium-temperature phase change heat storage unit. The high-temperature working fluid absorbs the heat released by the medium-temperature phase change heat storage unit in the high-temperature evaporator and evaporates into a low-temperature, low-pressure gas. The low-temperature, low-pressure gas is compressed by the high-temperature compressor to form a high-temperature, high-pressure gas. The high-temperature and high-pressure gas enters the high-temperature stage condenser, where it condenses and releases heat, transforming into a high-temperature and high-pressure liquid. The high-temperature and high-pressure liquid expands through the high-temperature stage expansion valve, forming a low-temperature and low-pressure two-phase fluid, which then flows back to the high-temperature stage evaporator, completing the high-temperature stage heat pump cycle. The high-temperature stage condenser is connected to the user end for heat exchange, and the high-temperature stage working fluid in the high-temperature stage condenser is used to output the upgraded heat to the user end.

[0013] Preferably, the medium-temperature phase change thermal energy storage unit includes a phase change thermal energy storage device, a thermal energy storage medium circulation pump, an electric three-way valve, and a thermal energy storage medium circulation pipeline; The heat storage medium circulation pipeline is installed in the phase change heat storage device. The heat storage medium circulation pipeline contains heat storage medium for heat exchange with the phase change heat storage material inside the phase change heat storage device. The heat storage medium circulation pump and the electric three-way valve are both installed on the heat storage medium circulation pipeline. The heat storage medium circulation pipeline has a heat storage side loop and a heat release side loop. The heat storage side loop is connected to a low-temperature heat pump for heat exchange, and the heat release side loop is connected to a high-temperature heat pump for heat exchange. The electric three-way valve is used to control the selective conduction of the heat storage side loop and the heat release side loop.

[0014] Preferably, the phase change thermal storage material includes one or more of sodium acetate trihydrate, sodium thiosulfate pentahydrate, disodium hydrogen phosphate dodecahydrate, sodium sulfate decahydrate, paraffin materials, stearic acid, and lauric acid.

[0015] Preferably, the high-temperature stage heat pump further includes an economizer, which is connected to the high-temperature stage circuit and is used for intermediate gas replenishment; The evaporation temperature of the economizer is the midpoint between the evaporation temperature and the condensation temperature of the high-temperature working fluid.

[0016] Preferably, the cryogenic working fluid is one or more of R134a, R1234ze, R1233zd, R290, R32, ammonia, and carbon dioxide; The evaporation temperature of the low-temperature working fluid is -10~30℃, and the condensation temperature is 50~70℃.

[0017] Preferably, the high-temperature working fluid is one or more of R245fa, R1234yf, R1233zd, water vapor, and R600a; The evaporation temperature of the high-temperature working fluid is 40~60℃, and the condensation temperature is 90~120℃.

[0018] Compared with the prior art, the present invention has the following beneficial effects: 1. This utility model overcomes the technical bottleneck of the sharp decline in efficiency of single-stage heat pumps when the temperature rise is large by adopting a two-stage compression technology to share the temperature rise. Traditional single-stage heat pumps have problems such as excessively high compression ratio leading to excessive exhaust temperature and reduced compressor efficiency when dealing with large temperature rise conditions (such as rising from -25℃ to 120℃, a temperature difference of 145℃). However, this utility model rationally distributes the temperature rise task to two-stage compressors, with the temperature rise of each stage controlled within 70℃, avoiding the performance degradation of single-stage compression and enabling the system to maintain high operating efficiency over a wide range of operating conditions.

[0019] 2. This utility model realizes the function of "incremental heat storage", which has a fundamental advantage over the traditional electrothermal conversion method. The traditional resistance heating method is constrained by the second law of thermodynamics, and the ideal efficiency limit is 1.0. However, this utility model uses the reverse Carnot cycle principle to absorb additional heat from the outside and store it with improved quality by utilizing low-grade environmental heat sources or industrial waste heat. This achieves a "magnification effect" of greater heat storage capacity under the drive of unit electrical energy. Theoretical analysis shows that under typical operating conditions, the system's comprehensive energy efficiency coefficient η can reach 1.5~2.0, that is, 1.5~2.0 kWh of heat energy can be stored for every 1 kWh of electrical energy consumed, breaking through the theoretical limitations of traditional electrothermal conversion.

[0020] 3. This utility model achieves the "energy quality regulation" function through an intermediate phase change thermal storage unit, solving the technical limitation of fixed heat release temperature in traditional thermal storage systems. Conventional thermal storage and release are based on the cascade utilization of thermal energy, and the temperature of released heat energy is often 5-10℃ lower than the thermal storage temperature, which imposes many constraints on the selection of phase change thermal storage materials. This utility model, through the coordinated control of two-stage heat pumps, can output hot water or steam at different temperature levels of 80-120℃ as needed, realizing precise adjustment and flexible supply of thermal energy quality, and meeting various heat needs such as building heating and industrial steam.

[0021] 4. This utility model has significant peak shaving and valley filling functions for the power grid, effectively mitigating the impact of renewable energy fluctuations on the power grid. Through the timing operation strategy of "valley power thermal storage - peak power thermal supply", the power load can be transferred from peak hours to valley hours, reducing the pressure of peak-valley difference in the power grid. The phase change thermal storage technology, through a flexible thermal storage and release regulation mechanism, can effectively mitigate the impact of intermittent energy or extreme operating conditions on system operation and improve system operation stability.

[0022] 5. This utility model adopts medium-temperature phase change thermal storage technology, which has obvious advantages in safety and economy compared with high-temperature thermal storage systems. Medium-temperature thermal storage has low operating pressure and high safety, avoiding the high pressure risks and material constraints faced by high-temperature thermal storage systems. The phase change materials have a wide range of choices, low cost, high chemical stability, and environmental friendliness, making them suitable for large-scale engineering applications.

[0023] 6. This utility model constructs an integrated platform for large-scale incremental thermal energy storage and flexible control, organically integrating functions such as thermal energy recovery, incremental storage, quality improvement, and flexible control. The modular design of the system facilitates engineering implementation and can adapt to application scenarios of different scales. It has broad application prospects in multiple fields such as building heating, industrial process heat, and regional energy systems, and provides an important technical path for achieving the goal of carbon neutrality. Attached Figure Description

[0024] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is the operating diagram of this utility model; Figure 3 This is the TS diagram of the operation of this utility model; Figure 4 This is a structural diagram of a specific device in an embodiment of this utility model; Figure 5 This is a schematic diagram of the operation control process of this utility model.

[0025] The diagram shows: Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0027] This utility model discloses a large-scale incremental thermal energy storage and flexible energy supply system. Through a two-stage compression technology to share the temperature rise, it achieves the functions of "incremental thermal energy storage" and "energy quality regulation": In thermal energy storage mode, the low-temperature stage heat pump absorbs heat from the environment or industrial waste heat and stores it in the phase change thermal energy storage unit after upgrading it; In heat release mode, the high-temperature stage heat pump further upgrades the stored thermal energy and outputs high-grade thermal energy. The system breaks through the theoretical limitation of traditional equal conversion of electricity and heat, and has the ability to peak shaving and valley filling and flexible on-demand heating. It can be widely used in building heating, industrial process heat and other fields.

[0028] This invention, based on the core concepts of "incremental thermal storage" and "energy quality regulation," constructs an innovative thermal energy storage and conversion system architecture. "Incremental thermal storage" refers to the use of a heat pump system to absorb additional heat from the environment or industrial waste heat and improve its heat quality for storage, achieving a "magnification effect" of storing a larger amount of thermal energy per unit of electrical energy. Its comprehensive energy efficiency coefficient η is defined as the ratio of stored heat to total input electrical energy. "Energy quality regulation" refers to the efficient coupling between the thermal storage unit and the heat pump system's front and back ends, outputting thermal energy of different heat qualities as needed, achieving flexible regulation functions for multiple scenarios.

[0029] Traditional electrothermal conversion methods are strictly constrained by the second law of thermodynamics, with an ideal efficiency limit of 1.0. This invention, however, overcomes this theoretical limitation by utilizing a low-grade environmental heat source based on the reverse Carnot cycle principle. System thermodynamic performance analysis shows that, with a high-efficiency compressor, the coefficient of performance (COP) of the low-temperature stage heat pump can reach 2.5–4.5, and the COP of the high-temperature stage heat pump can reach 3–5. The thermodynamic perfection (the ratio of actual COP to Carnot COP) of both stages can be maintained at a high level of around 50%, significantly superior to traditional single-stage high-temperature-rise heat pump systems.

[0030] The large-scale incremental thermal energy storage and flexible control energy supply system provided by this utility model includes a heat pump system including, but not limited to, a low-temperature heat pump 1 subsystem, a medium-temperature phase change thermal energy storage unit, a high-temperature heat pump 7 subsystem, and an intelligent control system. The low-temperature heat pump 1 includes a low-temperature evaporator 2, a low-temperature compressor 3, a low-temperature condenser 4, and a low-temperature expansion valve 5, which are connected to the medium-temperature phase change thermal energy storage unit via pipelines. Its evaporation temperature range is -10 to 30°C, and its condensation temperature range is 50 to 70°C. The high-temperature heat pump 7 includes a high-temperature evaporator 8, a high-temperature compressor 9, a high-temperature condenser 10, and a high-temperature expansion valve 11, which are connected to the medium-temperature phase change thermal energy storage unit via pipelines. Its evaporation temperature range is 40 to 60°C, and its condensation temperature range is 90 to 120°C.

[0031] The medium-temperature phase change thermal energy storage unit mainly includes a phase change thermal energy storage unit 6, a thermal energy storage medium circulation pump, an expansion tank, a temperature sensor, an electric three-way valve, and a thermal energy storage medium circulation pipeline. The phase change thermal energy storage unit 6 is filled with phase change material with a phase change temperature in the range of 40~70℃, possessing high thermal energy storage density characteristics, and a thermal energy storage capacity of 50~120 kWh. The electric three-way valve controls the flow direction of the thermal energy storage medium between thermal energy storage mode and thermal energy release mode, realizing intelligent adjustment of the system operation mode.

[0032] Specifically, the heat storage medium circulation pipeline is installed in the high-temperature stage evaporator 6 of the phase change heat storage device. The heat storage medium circulation pipeline contains heat storage medium for heat exchange with the phase change heat storage material inside the high-temperature stage evaporator 6. The heat storage medium circulation pump and the electric three-way valve are both installed on the heat storage medium circulation pipeline. The heat storage medium circulation pipeline has a heat storage side loop and a heat release side loop. The heat storage side loop is heat exchanged with the high-temperature stage evaporator 1 of the low-temperature stage heat pump, and the heat release side loop is heat exchanged with the high-temperature stage evaporator 7 of the high-temperature stage heat pump. The electric three-way valve is used to control the selective conduction of the heat storage side loop and the heat release side loop.

[0033] Among them, the phase change materials and their operating parameters used in the phase change thermal storage unit 6 are: sodium acetate trihydrate (phase change temperature 58℃), sodium thiosulfate pentahydrate (phase change temperature 48℃), disodium hydrogen phosphate dodecahydrate (phase change temperature 44℃), sodium sulfate decahydrate (phase change temperature 32℃), paraffin wax (phase change temperature 41~44℃), stearic acid (phase change temperature 53℃), lauric acid (phase change temperature 42℃), etc., with phase change temperatures in the range of 40~60℃, and their composite materials. The thermal storage capacity is 50~120kWh, and the thermal storage and release power is 5~50kW, depending on the operating conditions and compressor specifications.

[0034] The refrigerant configuration is as follows: the low-temperature stage working fluid is one or more of R134a, R1234ze, R1233zd, R290, R32, ammonia, and carbon dioxide; the high-temperature stage working fluid is one or more of R245fa, R1234yf, R1233zd, water vapor, and R600a; the low-temperature stage evaporation temperature is -10~30℃, and the condensation temperature is 50~70℃; the high-temperature stage evaporation temperature is 40~60℃, and the condensation temperature is 90~120℃.

[0035] The control system adopts a hierarchical control architecture, including: an equipment layer, which includes compressor frequency conversion control, electric valve switching control, and circulating pump frequency conversion control; a control layer, which includes a PLC controller, temperature, pressure, and flow acquisition modules, and a communication module; and a monitoring layer, which includes a touch screen human-machine interface and a remote communication interface.

[0036] Furthermore, the system is equipped with comprehensive safety protection measures, including: pressure protection, which includes high and low pressure protection switches and safety valves; temperature protection, which includes compressor overheat protection and antifreeze protection; flow protection, which includes a water flow switch and minimum flow protection; and electrical protection, which includes phase loss protection, overload protection, and short circuit protection.

[0037] Furthermore, the system employs a two- or multi-stage compression technique to share the temperature rise, effectively avoiding the sharp efficiency drop caused by excessively high compression ratios in single-stage heat pumps under high temperature rise conditions. The low-temperature stage heat pump 1 is responsible for raising the low-grade heat source (-25~50℃) to a medium-temperature level (55~65℃), with a temperature rise range of 20~70℃; the high-temperature stage heat pump 7 is responsible for further raising the medium-temperature stored heat energy to a high-grade level (80~120℃), with a temperature rise range of 30~70℃. Through reasonable temperature rise distribution, the system can maintain high operating efficiency under various operating conditions.

[0038] Furthermore, the system can flexibly output heat in various forms. For hot water demand of 60~90℃, the system can directly supply it through the high-temperature heat pump 7; for low-pressure steam demand of 100~120℃ (corresponding to saturation pressure of 0~0.1 MPa), the system heats the water to saturation and generates steam by condensing the working fluid in the high-temperature condenser 10; for medium-high pressure steam demand of 120~150℃ (corresponding to saturation pressure of 0.1~0.4 MPa), the system can adopt two-stage steam compression technology, and achieve higher temperature steam output by configuring two high-temperature heat pumps 7 in series or by using an economizer to supplement gas.

[0039] Based on the above energy supply system, this utility model also provides an operation control method for a large-scale incremental thermal energy storage and flexible regulation energy supply system. Based on the time-of-use electricity pricing mechanism and the supply and demand matching principle, the control steps are as follows: In the first stage of incremental thermal storage control, the system monitors electricity price signals, ambient temperature, and the temperature of the phase change thermal storage unit 6. When the electricity price is at its lowest point (typically 10:00 PM to 8:00 AM the next day) and the thermal storage unit temperature is below the set value, the low-temperature heat pump 1 subsystem is activated for incremental thermal storage. The low-temperature heat pump 1 absorbs heat from an ambient heat source above -25°C or a waste heat source below 50°C, upgrades it to 50~70°C through a thermodynamic cycle, and stores it in the phase change thermal storage unit 6. The thermal storage power is controlled by adjusting the frequency of the low-temperature compressor 3. The thermal storage power can be adjusted within the range of 30%~100% of the rated power, achieving precise control of the thermal storage process.

[0040] The second stage of energy-quality regulated heating involves activating the high-temperature heat pump 7 subsystem for energy-quality regulated heating when electricity prices are at their peak and there is demand for heating. The high-temperature heat pump 7 uses the phase change thermal storage unit 6 as its heat source, further upgrading the medium-temperature stored thermal energy to a high-grade level of 80-120℃ (which can be increased to 150℃ by adding steam compression) to meet the heating needs of different users. By adjusting the frequency of the high-temperature compressor 9 and the heating circulation flow rate, flexible adjustment of heating temperature and power can be achieved, with the heating power adjustment range being 20% ​​to 100% of the rated power.

[0041] Furthermore, the system possesses peak shaving and valley filling capabilities, effectively alleviating the pressure of peak-valley differences in the power grid. By storing heat during off-peak hours and supplying heat during peak hours, the grid load is effectively transferred. Based on the time-of-use electricity price difference (typically 0.3~0.8 yuan / kWh), the system's annual operating cost can be reduced by 20%~40%.

[0042] The above are the basic embodiments of this utility model. The following will further describe the solution of this utility model with reference to the accompanying drawings and through preferred embodiments. Example 1 This embodiment discloses a large-scale incremental thermal energy storage and flexible energy supply system, such as Figure 1 As shown, the system consists of three core modules: a low-temperature compression heat pump, a high-temperature compression heat pump, and a medium-temperature phase change heat storage unit. The overall system includes two independent refrigerant circulation loops and two water-side heat exchange circulation loops. Both the low-temperature stage heat pump 1 and the high-temperature stage heat pump 7 are water-source heat pumps. The intermediate heat storage unit is thermally coupled to the low-temperature stage condenser 4 of the low-temperature stage heat pump 1 and the high-temperature stage evaporator 8 of the high-temperature stage heat pump 7 through water circulation loops, thereby completing energy transfer and regulation across temperature zones.

[0043] Regarding the cryogenic compression heat pump cycle, in this cycle, the cryogenic working fluid (such as R134a or R1234ze(E)) absorbs heat from an external low-grade heat source (such as industrial waste heat or ambient heat) in the cryogenic evaporator 2 and evaporates into a cryogenic, low-pressure gas. This gas is then compressed by the cryogenic compressor 3 into a high-temperature, high-pressure gas, which enters the cryogenic condenser 4 to condense and release heat, transforming into a high-temperature, high-pressure liquid. Subsequently, the working fluid expands through the cryogenic expansion valve 5, forming a cryogenic, low-pressure two-phase fluid, which flows back to the cryogenic evaporator 2, completing the cryogenic heat pump cycle.

[0044] Regarding the high-temperature compression heat pump cycle, in this cycle, the high-temperature working fluid (such as R245fa or HP-1) absorbs heat from the intermediate heat storage unit in the high-temperature evaporator 8 and evaporates into a low-temperature, low-pressure gas. After being compressed by the high-temperature compressor 9, the working fluid is transformed into a high-temperature, high-pressure gas, which enters the high-temperature condenser 10 to release heat and condense into a high-temperature, high-pressure liquid. Then, it is throttled by the high-temperature expansion valve 11 to become a low-temperature, low-pressure two-phase state, flowing back to the high-temperature evaporator 8, thus completing the high-temperature heat pump cycle. This process achieves a rise in heat from a medium-temperature level to a high-temperature level, providing users with high-quality hot water or steam at 80~120℃.

[0045] Regarding the intermediate-temperature phase change thermal energy storage unit, it utilizes phase change materials (such as hydrated salts and organic acids) to achieve high-density energy storage in the form of latent heat through solid-liquid phase change within a specific temperature range. In storage mode, the water-side circulation loop transfers the heat released from the low-temperature condenser 4 to the storage unit, where the storage material undergoes a transformation from solid to a solid-liquid coexistence state and finally to a liquid state, completing large-scale thermal energy storage. In release mode, the storage unit releases heat to the high-temperature evaporator 8 through water circulation, where the storage material undergoes a transformation from a liquid to a solid-liquid coexistence state and finally to a solid state, achieving stable heat release. This unit features high energy density, low heat loss, and strong operational stability.

[0046] Under design conditions, the low-temperature stage operates with R134a / R1234ze(E) as the working fluid, with an evaporation temperature of -10 to 30°C and a condensation temperature of 50 to 70°C. The temperature rise range of the heat storage material is approximately 40°C to 75°C, corresponding to a heat storage capacity of 90 to 110 kWh. The COP of the low-temperature stage can reach 3 to 5. The high-temperature stage operates with R245fa / HP-1 as the working fluid, with an evaporation temperature of 40 to 60°C and a condensation temperature of 90 to 120°C. The heat release reaches 70 to 90 kWh, and the final heat supply reaches 100 to 120 kWh. The COP of the high-temperature stage reaches 3 to 5, and the temperature of the heat storage material drops from 65 to 70°C to 50°C. The comprehensive performance is evaluated using the comprehensive energy efficiency coefficient η, defined as the ratio of the cumulative heat release at the high-temperature end to the total electrical energy consumed by the compressor and water pump, i.e., the ratio of total output heat to total power consumption. Calculations were performed on the system under different operating conditions, and the overall performance coefficient of the system remained at 1.7~2.0, which is similar to the efficiency of cascade heat pump systems in the same temperature range. This verifies the feasibility and high efficiency of the system in terms of incremental thermal energy storage and flexible energy quality control.

[0047] Multi-source incremental thermal energy storage mode during off-peak electricity periods: During off-peak electricity periods (e.g., 10:00 PM to 8:00 AM the next day), the low-temperature stage heat pump 1 starts to perform incremental thermal energy storage. The low-temperature stage working fluid absorbs low-grade heat from environmental heat sources (air source, water source, geothermal, etc.) or industrial waste heat (e.g., cooling tower circulating water, air compressor cooling water, etc.) within the range of -25 to 50°C in the low-temperature stage evaporator 2. After compression, it releases heat in the low-temperature stage condenser 4 and is transferred to the medium-temperature phase change thermal energy storage unit through the water loop, realizing large-scale energy storage in the form of latent heat. This process converts low-priced electrical energy into high-density thermal energy, completing the solid-to-liquid transformation process within the phase change material, thereby realizing the energy transfer strategy of "off-peak electricity thermal energy storage - peak electricity thermal energy release". Theoretical calculations show that under typical operating conditions with a COP of 3 to 4 for the low-temperature stage heat pump, 3 to 4 kWh of thermal energy can be stored for every 1 kWh of off-peak electricity consumed, achieving a significant incremental thermal energy storage effect. Compared with direct utilization of waste heat, heat pump-based heat storage can increase the utilization rate of waste heat by more than 50%.

[0048] The hot water supply operates on the following heat release mode: The thermal storage unit releases latent heat, which is transferred to the high-temperature evaporator 8 via water circulation. The high-temperature working fluid absorbs heat and evaporates, then is compressed to a high-temperature and high-pressure state. It condenses and releases heat in the high-temperature condenser 10, providing users with hot water at 60~90℃. This mode is suitable for centralized building heating and large-scale domestic hot water supply scenarios. The system can flexibly adjust the heating power and outlet water temperature according to the end-user demand, thereby ensuring the continuity and comfort of heating.

[0049] Steam supply heat release mode: When there is a demand for low-pressure steam at 100~120℃ on the user side (such as in food processing, textile printing and dyeing industries), the heat storage unit releases latent heat. The heat is transferred to the high-temperature stage evaporator 8 through the water-side circulation loop. The high-temperature stage working medium absorbs heat and vaporizes in it. After being compressed by the high-temperature stage compressor 9, it releases heat in the high-temperature stage condenser 10, so that the working medium on the water side of the condenser reaches a saturated state and produces saturated steam at a maximum pressure of about 0.1MPa, which is output to the user end, replacing the traditional gas or coal-fired boiler steam supply and realizing green and low-carbon industrial heat energy supply. For medium- and high-pressure steam demand at 120~150℃ (such as chemical reactions, high-temperature sterilization, etc., corresponding to pressures of 0.1~0.4MPa), the system can adopt two-stage steam compression technology or economizer gas injection technology. By connecting two high-temperature heat pumps 7 in series, the first stage raises the heat storage temperature to 90~100℃, and the second stage further raises it to 120~150℃; or an economizer is set in a single high-temperature heat pump 7 to improve the system's operating efficiency under high pressure ratio conditions, thereby achieving higher temperature steam output. The economizer evaporation temperature is the midpoint between the condensation temperature and the evaporation temperature, and the economizer heat exchange accounts for 15~25% of the total heat exchange. A main circuit electronic expansion valve and an auxiliary circuit electronic expansion valve are provided to control the main circuit and the economizer circuit respectively.

[0050] This utility model system can effectively solve the problem of peak load impact on the power grid caused by large-scale distributed heating of air source heat pumps, and achieve spatial and temporal decoupling of supply and demand through thermal storage units; it can replace traditional fossil energy cogeneration systems and decentralized gas boilers, and provide a clean and efficient multi-energy synergistic solution for zero-carbon parks and low-carbon industrial parks; it can promote the local consumption of renewable energy during off-peak hours and improve the overall efficiency and flexibility of the energy system.

[0051] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0052] The specific embodiments of this utility model have been described above. It should be understood that this utility model is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the substantive content of this utility model. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A large-scale incremental thermal energy storage and flexible control energy supply system, characterized in that, It includes a low-temperature heat pump (1), a medium-temperature phase change heat storage unit, and a high-temperature heat pump (7) connected in sequence for heat exchange. The low-temperature heat pump (1) is heat exchanged with a low-grade heat source of external environmental heat source or industrial waste heat at -25~50℃. It is used to absorb the heat released by the low-grade heat source, upgrade it to 50~70℃ through a low-temperature thermodynamic cycle, and release it to the medium-temperature phase change heat storage unit. The medium-temperature phase change heat storage unit is used to store the heat released by the low-temperature heat pump (1) and release the stored heat to the high-temperature heat pump (7). The high-temperature heat pump (7) is connected to the user end for heat exchange. It is used to absorb the heat released by the intermediate heat storage unit, upgrade it through a high-temperature thermodynamic cycle, and output hot water at 60~90℃ or steam at 100~150℃ to the user end.

2. The large-scale incremental thermal energy storage and flexible control energy supply system according to claim 1, characterized in that, The low-temperature heat pump (1) includes a low-temperature evaporator (2), a low-temperature compressor (3), a low-temperature condenser (4), and a low-temperature expansion valve (5). The low-temperature stage evaporator (2), low-temperature stage compressor (3), low-temperature stage condenser (4) and low-temperature stage expansion valve (5) are connected in sequence to form a low-temperature stage circuit, and the low-temperature stage circuit stores the low-temperature stage working fluid. The low-temperature stage evaporator (2) is connected to an external low-grade heat source at -25~50℃ for heat exchange. The low-temperature stage working fluid absorbs heat from the external low-grade heat source in the low-temperature stage evaporator (2) and evaporates into a low-temperature low-pressure gas. The low-temperature low-pressure gas is compressed by the low-temperature stage compressor (3) to form a high-temperature high-pressure gas. The high-temperature and high-pressure gas enters the low-temperature stage condenser (4) to condense and release heat and is converted into a high-temperature and high-pressure liquid. The high-temperature and high-pressure liquid is throttled and expanded by the low-temperature stage expansion valve (5) to form a low-temperature and low-pressure two-phase fluid, and flows back to the low-temperature stage evaporator (2) to complete the low-temperature stage heat pump cycle. The low-temperature stage condenser (4) is heat exchanged with the medium-temperature phase change heat storage unit. The low-temperature stage working fluid in the low-temperature stage condenser (4) is used to release the upgraded heat to the medium-temperature phase change heat storage unit.

3. The large-scale incremental thermal energy storage and flexible control energy supply system according to claim 1, characterized in that, The high-temperature heat pump (7) includes a high-temperature evaporator (8), a high-temperature compressor (9), a high-temperature condenser (10), and a high-temperature expansion valve (11). The high-temperature evaporator (8), high-temperature compressor (9), high-temperature condenser (10) and high-temperature expansion valve (11) are connected in sequence to form a high-temperature circuit, and the high-temperature working fluid is stored in the high-temperature circuit. The high-temperature evaporator (8) is heat exchanged with the medium-temperature phase change heat storage unit. The high-temperature working fluid absorbs the heat released by the medium-temperature phase change heat storage unit in the high-temperature evaporator (8) and evaporates into a low-temperature low-pressure gas. The low-temperature low-pressure gas is compressed by the high-temperature compressor (9) to form a high-temperature high-pressure gas. The high-temperature and high-pressure gas enters the high-temperature stage condenser (10), where it condenses, releases heat, and transforms into a high-temperature and high-pressure liquid. The high-temperature and high-pressure liquid expands through the high-temperature stage expansion valve (11) to form a low-temperature and low-pressure two-phase fluid, which then flows back to the high-temperature stage evaporator (8) to complete the high-temperature stage heat pump cycle. The high-temperature stage condenser (10) is connected to the user end for heat exchange, and the high-temperature stage working fluid in the high-temperature stage condenser (10) is used to output the upgraded heat to the user end.

4. The large-scale incremental thermal energy storage and flexible control energy supply system according to claim 1, characterized in that, The medium-temperature phase change thermal storage unit includes a phase change thermal storage device (6), a thermal storage medium circulation pump, an electric three-way valve, and a thermal storage medium circulation pipeline. The heat storage medium circulation pipeline is installed in the phase change heat storage device (6). The heat storage medium circulation pipeline contains a heat storage medium for heat exchange with the phase change heat storage material inside the phase change heat storage device (6). The heat storage medium circulation pump and the electric three-way valve are both installed on the heat storage medium circulation pipeline. The heat storage medium circulation pipeline has a heat storage side circuit and a heat release side circuit. The heat storage side circuit is heat exchanged with a low-temperature heat pump (1), and the heat release side circuit is heat exchanged with a high-temperature heat pump (7). The electric three-way valve is used to control the selective conduction of the heat storage side circuit and the heat release side circuit.

5. The large-scale incremental thermal energy storage and flexible control energy supply system according to claim 4, characterized in that, The phase change thermal storage material includes one of the following: sodium acetate trihydrate, sodium thiosulfate pentahydrate, disodium hydrogen phosphate dodecahydrate, sodium sulfate decahydrate, paraffin materials, stearic acid, and lauric acid.

6. The large-scale incremental thermal energy storage and flexible control energy supply system according to claim 3, characterized in that, The high-temperature stage heat pump (7) also includes an economizer, which is connected to the high-temperature stage circuit and is used for intermediate gas replenishment; The evaporation temperature of the economizer is the midpoint between the evaporation temperature and the condensation temperature of the high-temperature working fluid.

7. The large-scale incremental thermal energy storage and flexible control energy supply system according to claim 2, characterized in that, The cryogenic working fluid is one of R134a, R1234ze, R1233zd, R290, R32, ammonia, and carbon dioxide. The evaporation temperature of the low-temperature working fluid is -10~30℃, and the condensation temperature is 50~70℃.

8. The large-scale incremental thermal energy storage and flexible control energy supply system according to claim 3, characterized in that, The high-temperature working fluid is one of R245fa, R1234yf, R1233zd, water vapor, and R600a; The evaporation temperature of the high-temperature working fluid is 40~60℃, and the condensation temperature is 90~120℃.

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