A phase change cold storage type freezing point fresh-keeping warehouse refrigeration system and a regulation and control method

Abstract

The application provides a phase change cold storage type freezing point fresh-keeping store refrigeration system and a regulation and control method, and relates to the technical field of refrigeration systems.The system comprises a control unit, a vapor compression type refrigeration unit, a phase change cold storage unit and a glycol coolant circulation unit electrically connected with the control unit, the vapor compression type refrigeration unit is cyclically connected with the phase change cold storage unit and the glycol coolant circulation unit, the glycol coolant circulation unit is cyclically connected with a cold store, the cold store is connected with the phase change cold storage unit, and the phase change cold storage unit is connected with the glycol coolant circulation unit.The application fuses compression refrigeration, phase change cold storage and regulation and control technologies, realizes effective reduction of electricity cost by relying on a peak-valley electricity price differentiation control strategy, realizes stable control of the temperature in the cold store by regulating the cold supply temperature, solves the industry pain point that the cold cost and temperature control of the cold store are difficult to balance, and realizes energy-saving, high-efficiency and precise temperature control operation of the cold store system.

Description

Technical Field

[0001] This invention relates to the field of refrigeration system technology, and more particularly to a phase change cold storage type ice point preservation refrigeration system and control method. Background Technology

[0002] With the rapid development of the cold chain logistics industry, the market demand for cold storage facilities, as an important facility for preserving agricultural products, continues to rise. Traditional cold storage facilities generally rely on the national power grid for power supply and use vapor compression refrigeration technology as the core cooling method. Although they can meet basic refrigeration needs, many problems have been exposed during operation.

[0003] On the one hand, traditional cold storage facilities lack targeted power utilization strategies. Peak-hour electricity demand leads to high electricity prices, significantly increasing costs for continuous cold storage operation. Conversely, while electricity is cheap during off-peak hours, the lack of effective energy storage methods results in substantial waste of power resources and low energy efficiency. On the other hand, the refrigeration temperature and the cold storage supply temperature in cold storage facilities are inconsistent. Switching between these two cooling methods causes significant temperature fluctuations and low temperature control accuracy, making it difficult to meet the stringent storage requirements of perishable foods like fruits and vegetables. Furthermore, the cold storage process typically uses intermediate fluids, making the system complex and resulting in energy losses, hindering technology adoption.

[0004] Based on this, the present invention proposes a phase change cold storage type freezing point preservation refrigeration system and control method. By using off-peak electricity cold storage and peak electricity cold release operation strategy to balance the impact of peak and off-peak electricity prices, and by controlling the cold supply, constant temperature storage of cold storage is achieved. This reduces electricity costs while improving temperature control accuracy, taking into account both the economy and practicality of cold storage operation. Summary of the Invention

[0005] To address the aforementioned technical issues, a phase change cold storage type ice point preservation refrigeration system and its control method are provided.

[0006] The technical means employed in this invention are as follows: A phase change cold storage refrigeration system includes: a control unit and a vapor compression refrigeration unit, a phase change cold storage unit, and an ethylene glycol refrigerant circulation unit electrically connected to the control unit. The vapor compression refrigeration unit is cyclically connected to the phase change cold storage unit and the ethylene glycol refrigerant circulation unit, respectively. The ethylene glycol refrigerant circulation unit is cyclically connected to the cold storage. The cold storage is connected to the phase change cold storage unit, and the phase change cold storage unit is connected to the ethylene glycol refrigerant circulation unit.

[0007] Furthermore, the vapor compression refrigeration unit includes a compressor, a condenser, and an expansion valve, and the ethylene glycol refrigerant circulation unit includes a buffer tank, which stores a 30% ethylene glycol solution. The compressor is connected to the buffer cabinet via a first pipeline, and the buffer cabinet is connected to the compressor via a second pipeline. The condenser and the expansion valve are both installed on the first pipeline. The condenser is located between the compressor and the expansion valve. A second shut-off valve is also installed on the first pipeline, and a first shut-off valve is also installed on the second pipeline.

[0008] Furthermore, the phase change cold storage unit includes a cold storage cabinet, the interior of which contains phase change cold storage material. The cold storage cabinet is connected to the first pipeline via a third pipeline and to the second pipeline via a fourth pipeline. One end of the third pipeline is connected to the first pipeline between the condenser and the second shut-off valve, and one end of the fourth pipeline is connected to the second pipeline between the compressor and the first shut-off valve.

[0009] Furthermore, the buffer cabinet is connected to the cold storage via a fifth pipeline, and the cold storage is connected to the buffer cabinet via a sixth pipeline. A first delivery pump is installed on the fifth pipeline, and a fifth shut-off valve is installed on the sixth pipeline.

[0010] Furthermore, the cold storage cabinet is connected to the sixth pipe via the seventh pipe and to the buffer cabinet via the eighth pipe; wherein, one end of the seventh pipe is connected between the cold storage and the shut-off valve five, and the seventh pipe is equipped with a second delivery pump and a sixth shut-off valve, the sixth shut-off valve being located between the second delivery pump and the cold storage cabinet, and the eighth pipe is equipped with a seventh shut-off valve.

[0011] Furthermore, the freezing point of the phase change cold storage material is -10.2℃, and the phase change cold storage material is composed of sodium chloride, sodium carboxymethyl cellulose and water, wherein the mass concentration of sodium chloride is 15% and the mass concentration of sodium carboxymethyl cellulose is 1%.

[0012] This invention also provides a control method using the above-mentioned phase change cold storage freezing point preservation refrigeration system, comprising: S1, Off-peak electricity hours: During off-peak electricity hours, the system's core cold storage phase involves providing immediate cooling to the cold storage facility on demand, fully utilizing low-priced electricity to reduce overall system electricity costs. Under this condition, the compressor starts, and the vapor compression refrigeration cycle operates normally: low-temperature, low-pressure gaseous refrigerant is compressed by the compressor into high-temperature, high-pressure gaseous refrigerant, which then enters the condenser to release heat through heat exchange, condensing into medium-temperature, high-pressure liquid refrigerant. This liquid refrigerant is then throttled and depressurized by the expansion valve, forming a low-temperature, low-pressure gas-liquid mixture. Simultaneously, the cold storage facility's cooling or cold storage is completed by regulating the shut-off valves, specifically by opening shut-off valves one and two. The system supplies cooling to the buffer cabinet for cold storage; or it opens shut-off valves three and four to supply cooling to the cold storage cabinet for cold storage. During off-peak hours, the compressor operates at full power. The temperature sensor in the buffer cabinet monitors the ethylene glycol outlet temperature within the range of -12℃±2℃. If the temperature is below this range, the vapor compression refrigeration unit supplies cooling to the cold storage cabinet; if the temperature is above this range, the vapor compression refrigeration unit supplies cooling to the buffer cabinet. The system also opens transfer pump one and shut-off valve five, and closes transfer pump two, shut-off valve six, and shut-off valve seven to supply cooling to the cold storage through the buffer cabinet. S2, Peak Power Hour: During peak electricity hours, electricity prices are high, and compressors operate at low power. The cooling capacity going to the cold storage comes from the cooling capacity released by the cold storage cabinet, reducing the electricity consumption of the grid during peak hours and lowering electricity costs. Shut-off valves three and four are closed, and shut-off valves six and seven are opened to supply cooling to the buffer cabinet. Shut-off valve five is closed, transfer pumps one and two are started, and shut-off valves six and seven are opened to form a cooling cycle of ethylene glycol solution. The phase change cold storage material in the cold storage cabinet releases cold capacity, and the cooled ethylene glycol solution is transported to the buffer cabinet for further cooling to -12℃±2℃ by the vapor compression refrigeration unit, and then transported to the cold storage end for cooling. The ethylene glycol solution returns to the circulation after heat exchange, ensuring continuous cooling of the cold storage during peak electricity hours. S3, Grid Parity Electricity Hours: During periods of affordable electricity, the system, based on real-time temperature feedback data inside and outside the cold storage, as well as weather forecast data, adjusts the compressor, delivery pump, and shut-off valves to achieve flexible switching and coordinated supplementary cooling between direct cooling via compression refrigeration and cold storage cooling. Simultaneously, it regulates the temperature inside the cold storage by controlling the flow rate of the ethylene glycol solution. In normal weather, the cold storage is cooled by the vapor compression refrigeration unit. In extreme weather, when the vapor compression refrigeration unit's cooling capacity is insufficient to maintain the cold storage temperature, the vapor compression refrigeration unit will operate at full power before the day's temperature reaches high temperatures to maintain the cold storage temperature and simultaneously perform cold storage. During periods of high temperatures, the cold storage capacity supplements the compression refrigeration shortfall.

[0013] Compared with the prior art, the present invention has the following advantages: 1. Significantly reduce electricity costs: By adopting the operation strategy of "storing cold energy during off-peak hours and releasing cold energy during peak hours", most of the high-energy-consuming operations are shifted to low-electricity-price periods, effectively avoiding peak electricity prices and significantly reducing overall electricity costs.

[0014] 2. Achieve reliable temperature control: The phase change cold storage unit does not directly release cold energy into the cold storage for cooling. Instead, it serves as an intermediate cold source, working together with the cooling capacity of the compression refrigeration unit to cool the cold storage, ensuring stable and reliable temperature control of the ethylene glycol solution entering the cold storage. Combined with real-time feedback from temperature sensors in the buffer cabinet and within the cold storage of the ethylene glycol refrigerant circulation unit, a closed-loop control system is formed, effectively reducing temperature fluctuations within the cold storage, improving temperature uniformity, and achieving constant temperature control of the cold storage from -2℃ to 7℃.

[0015] 3. Improve system reliability and energy efficiency: Vapor compression refrigeration units store cold for phase change cold storage units, reducing the involvement of intermediate working fluids, increasing the temperature difference between the refrigerant evaporation temperature and the cold storage unit, improving the COP of vapor compression refrigeration units, and reducing the volume of phase change cold storage units.

[0016] Furthermore, the system's cold storage characteristics help with peak shaving and valley filling in the power grid; it reduces the compressor's operating power during peak hours, indirectly reducing carbon emissions; and the use of ethylene glycol solution as a refrigerant reduces the amount of refrigerant required in long-distance pipelines and the risk of potential leakage. The control unit can be programmed strategically (using existing programming) according to different electricity pricing policies, weather forecasts, and cargo storage requirements, making it highly adaptable and easy to promote in different regions and application scenarios.

[0017] Based on the above reasons, this invention can be widely promoted in fields such as cold storage and cooling. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a diagram of the ethylene glycol refrigerant circulation system of the ice storage air conditioning system of the present invention.

[0020] In the diagram: 1. Cold storage; 2. Cold storage cabinet; 3. Buffer cabinet; 4. Compressor; 5. Condenser; 6. Transfer pump one; 7. Transfer pump two; 8. Expansion valve; 9. Shut-off valve one; 10. Shut-off valve two; 11. Shut-off valve three; 12. Shut-off valve four; 13. Shut-off valve five; 14. Shut-off valve six; 15. Shut-off valve seven. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0025] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms 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, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0026] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0027] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0028] Example 1 Fruit and vegetable preservation typically requires temperatures between -2℃ and 7℃, and demands high precision in temperature control. This invention aims to address the problems of high electricity costs during peak hours and wasted electricity resources during off-peak hours in traditional cold storage, as well as the low temperature control precision and poor energy efficiency of cold storage systems. This invention integrates compression refrigeration, phase change cold storage, and regulation technologies. It leverages a differentiated peak-valley electricity pricing strategy to effectively reduce electricity costs and achieves stable temperature control within the cold storage by regulating the supply temperature of cold energy. This solves the industry pain point of balancing cooling costs and temperature control in cold storage, enabling energy-efficient, high-performance, and precisely temperature-controlled cold storage systems.

[0029] This invention provides a phase change cold storage refrigeration system for ice point preservation, which is a cold storage temperature control system based on phase change cold storage. The system mainly includes a control unit and a vapor compression refrigeration unit, a phase change cold storage unit, and an ethylene glycol refrigerant circulation unit electrically connected to the control unit. The vapor compression refrigeration unit is cyclically connected to the phase change cold storage unit and the ethylene glycol refrigerant circulation unit, respectively. The ethylene glycol refrigerant circulation unit is cyclically connected to the cold storage unit 1. The cold storage unit 1 is connected to the phase change cold storage unit, and the phase change cold storage unit is connected to the ethylene glycol refrigerant circulation unit.

[0030] The vapor compression refrigeration unit consists of core components such as compressor 4 (inverter compressor), condenser 5, and expansion valve 8, providing basic cooling capacity for cold storage 1. The ethylene glycol refrigerant circulation unit consists of buffer tank 3 (storing 30% ethylene glycol solution, i.e., a mixture containing 30% ethylene glycol and 70% water), transfer pump, pipelines, and shut-off valves. It serves as an intermediate medium for cooling capacity transfer, delivering the cooling capacity generated by the refrigeration unit or the cooling capacity released by the phase change cold storage unit to cold storage 1. Compressor 4 is connected to buffer tank 3 through a first pipeline, and buffer tank 3 is connected to compressor 4 through a second pipeline. Condenser 5 and expansion valve 8 are both installed on the first pipeline, with condenser 5 located between compressor 4 and expansion valve 8. Shut-off valve 2 10 is also installed on the first pipeline, and shut-off valve 1 9 is also installed on the second pipeline.

[0031] The phase change cold storage unit includes a cold storage cabinet 2 and phase change cold storage material inside the cold storage cabinet 2, used to store cold energy during periods of low electricity prices. The freezing point of the phase change cold storage material is -10.2℃, and the phase change cold storage material includes, but is not limited to, sodium chloride, sodium carboxymethyl cellulose, and water, wherein the mass concentration of sodium chloride is 15%, the mass concentration of sodium carboxymethyl cellulose is 1%, and the remaining 84% is water. The cold storage cabinet 2 is connected to the first pipe through a third pipe and to the second pipe through a fourth pipe; one end of the third pipe is connected to the first pipe between the condenser 5 and the second shut-off valve 10, and one end of the fourth pipe is connected to the second pipe between the compressor 4 and the first shut-off valve 9.

[0032] The buffer cabinet 3 is connected to the cold storage 1 via the fifth pipeline, and the cold storage 1 is connected to the buffer cabinet 3 via the sixth pipeline. A delivery pump 6 is installed on the fifth pipeline, and a shut-off valve 13 is installed on the sixth pipeline.

[0033] The cold storage cabinet 2 is connected to the sixth pipe via the seventh pipe and to the buffer cabinet 3 via the eighth pipe. One end of the seventh pipe is connected between the cold storage 1 and the shut-off valve 13. The seventh pipe is equipped with a second pump 7 and a shut-off valve 14. The shut-off valve 14 is located between the second pump 7 and the cold storage cabinet 2. The eighth pipe is equipped with a shut-off valve 15.

[0034] The aforementioned control unit controls the opening and closing of various valves, the start and stop of the delivery pump, and the operation of the compressor 4 based on real-time electricity price signals, temperature sensor data inside the cold storage 1, and preset programs (currently available in the control unit), thereby achieving the switching of the system's operating modes.

[0035] The core of this invention lies in the following: During off-peak electricity hours, the compressor operates simultaneously for refrigeration and to charge the phase change energy storage unit as much as possible, making full use of low-priced electricity. During peak electricity hours, the compressor operates at low power, relying on the phase change energy storage unit's cold release and compression refrigeration for coordinated cooling, using ethylene glycol circulation to cool the cold storage, thus reducing high-priced electricity consumption. During periods of grid parity, the compressor refrigeration or coordinated cooling mode is flexibly adopted according to the real-time temperature requirements of the cold storage, achieving stable temperature control. Ultimately, this achieves the dual goals of energy saving and cost reduction, as well as temperature control.

[0036] This invention, by combining phase change cold storage, ethylene glycol refrigerant circulation, and regulation technologies, designs a phase change cold storage freezing point preservation refrigeration system, namely a phase change cold storage temperature-controlled cold storage system. This system has significant beneficial effects in reducing electricity costs, improving temperature control accuracy, and optimizing energy utilization efficiency. 1. Significantly reduce electricity costs: By adopting the operation strategy of "storing cold energy during off-peak hours and releasing cold energy during peak hours", most of the high-energy-consuming operations are shifted to low-electricity-price periods, effectively avoiding peak electricity prices and significantly reducing overall electricity costs.

[0037] 2. Achieve reliable temperature control: The phase change cold storage unit does not directly release cold energy into the cold storage for cooling. Instead, it serves as an intermediate cold source, working together with the cooling capacity of the compression refrigeration unit to cool the cold storage, ensuring stable and reliable temperature control of the ethylene glycol solution entering the cold storage. Combined with real-time feedback from temperature sensors in the buffer cabinet and within the cold storage of the ethylene glycol refrigerant circulation unit, a closed-loop control system is formed, effectively reducing temperature fluctuations within the cold storage, improving temperature uniformity, and achieving constant temperature control of the cold storage from -2℃ to 7℃.

[0038] 3. Improve system reliability and energy efficiency: Vapor compression refrigeration units store cold energy for phase change cold storage units, reducing the involvement of intermediate working fluids, increasing the temperature difference between the refrigerant evaporation temperature and the phase change cold storage unit, improving the COP of vapor compression refrigeration units, and reducing the volume of cold storage units.

[0039] In addition, the system's cold storage characteristics help the power grid "peak shaving and valley filling," reducing the compressor's operating power during peak hours and indirectly reducing carbon emissions; ethylene glycol solution, as a refrigerant, reduces the amount of refrigerant charged in long-distance pipelines and the risk of potential leakage; the control unit can be programmed strategically (using existing programming) according to different electricity pricing policies, weather forecasts, and cargo storage requirements, making it highly adaptable and easy to promote in different regions and application scenarios.

[0040] This invention utilizes phase change cold storage and regulation technology to reduce electricity costs and control the internal temperature of cold storage. Throughout the system operation, the controller (existing controller) controls the opening and closing of various shut-off valves, the start and stop of various delivery pumps, and the operating status of compressor 4 based on peak and off-peak electricity pricing periods and temperature data collected by sensors within the cold storage. The target storage temperature within cold storage 1 is -2 to 7°C. The specific implementation method is as follows: Off-peak electricity hours (cold storage and cooling mode): Compressor 4 operates at full power, and the vapor compression refrigeration cycle operates normally to generate cooling capacity. At the same time, the shut-off valve is adjusted to deliver the cooling capacity to the cold storage cabinet 2 for storage. If the cold storage 1 has an immediate cooling demand during off-peak electricity hours, the shut-off valve can be adjusted to allow the vapor compression refrigeration unit to supply cooling to the buffer cabinet 3 and provide cooling to the cold storage end, making full use of low-priced electricity.

[0041] During peak power periods (cold release and cooling mode): Compressor 4 operates at low power, adjusting the shut-off valve to form a cold release circulation loop centered on the cold storage cabinet 2. Transfer pump 7 is started, allowing the ethylene glycol solution to flow through the cold storage cabinet 2, exchanging heat with the phase change cold storage material to obtain a low temperature. It is then transported to the cold storage 1 via buffer cabinet 3 for cooling. This mode achieves low power consumption and high-precision temperature control during peak power periods.

[0042] During periods of affordable electricity (hybrid control mode): When cooling demand is within permissible limits, the vapor compression refrigeration unit supplies cooling to cold storage unit 1. In extreme high-temperature weather, cold storage is pre-stored, and the cold storage unit 2 releases cold to supplement the cooling capacity gap.

[0043] Through the above implementation methods, the system of the present invention realizes control from energy cost optimization to terminal temperature management, and is suitable for modern cold storage scenarios with high standards for both energy consumption costs and storage quality.

[0044] Example 2 like Figure 1 As shown, the refrigeration system of this invention integrates phase change cold storage technology with 30% ethylene glycol solution refrigerant circulation technology. It effectively reduces electricity costs by relying on the differentiated control strategy of peak and off-peak electricity prices. At the same time, through the regulation of pipeline shut-off valves and delivery pumps, combined with the stable cold release characteristics of phase change cold storage materials, the temperature in the cold storage is controlled.

[0045] The core of the system consists of a vapor compression refrigeration unit, a phase change cold storage unit, an ethylene glycol refrigerant circulation unit, and a control unit. The core components include a compressor 4, a condenser 5, an expansion valve 8, a cold storage cabinet 2 (with built-in phase change cold storage material), a buffer cabinet 3 (filled with 30% ethylene glycol solution), a first transfer pump 6, a second transfer pump 7, and shut-off valves 9, 10, 11, 12, 13, 14, and 15. All components are connected by pipelines to form a closed-loop circulation system integrating refrigeration, cold storage, and cold release. By controlling the start and stop of each transfer pump and shut-off valve, efficient storage and on-demand supply of cold energy are achieved.

[0046] The present invention provides a control method using the aforementioned phase change cold storage freezing point preservation refrigeration system, the specific working principle of which is as follows: 1. Off-peak electricity hours: During off-peak electricity hours, the system's core cold storage phase occurs, simultaneously providing on-demand cooling for cold storage unit 1, fully utilizing low-priced electricity to reduce overall system electricity costs. Under this condition, compressor 4 starts, and the vapor compression refrigeration cycle operates normally: low-temperature, low-pressure gaseous refrigerant is compressed by compressor 4 into high-temperature, high-pressure gaseous refrigerant, which then enters condenser 5 to release heat through heat exchange, condensing into medium-temperature, high-pressure liquid refrigerant. This liquid refrigerant is throttled and depressurized by expansion valve 8, forming a low-temperature, low-pressure gas-liquid mixture. Simultaneously, by controlling the shut-off valves, cold storage unit 1 is cooled or its cold storage capacity is stored. Specifically, shut-off valves 1-9 and 2-10 are opened to supply cooling to buffer tank 3, thus cooling cold storage unit 1; or shut-off valves 3-11 and 4-12 are opened to supply cooling to cold storage tank 2, used for cold storage. The aforementioned gaseous refrigerant refers to the circulating refrigerant in the vapor compression refrigeration unit. The liquid refrigerant, after passing through expansion valve 8, becomes a gas-liquid mixture and then turns into a gaseous state after flowing through the evaporator (buffer tank 3) or cold storage tank 2. During off-peak electricity hours, compressor 4 operates at full power. The temperature sensor (an existing sensor) in buffer cabinet 3 monitors the ethylene glycol outlet temperature within the range of -12℃ ± 2℃. If the temperature is below this range, the vapor compression refrigeration unit supplies cooling to cold storage cabinet 2; if the temperature is above this range, the vapor compression refrigeration unit supplies cooling to buffer cabinet 3. Transfer pump 6 and shut-off valve 13 are activated, while transfer pump 7, shut-off valve 14, and shut-off valve 15 are closed, supplying cooling to cold storage 1 through buffer cabinet 3.

[0047] 2. Peak power periods: During peak electricity hours, electricity prices are high, and compressor 4 operates at low power. The cooling capacity going to cold storage 1 mainly comes from the cooling capacity released by the cold storage cabinet 2 (temperature around -10℃), reducing the electricity consumption of the grid during peak hours and lowering electricity costs. Shut-off valves 31 and 42 are closed, while shut-off valves 9 and 10 are opened to supply cooling to buffer cabinet 3. Shut-off valve 513 is closed, transfer pumps 16 and 27 are started, and shut-off valves 614 and 715 are opened, forming a cooling cycle of the ethylene glycol solution. The phase change cold storage material in the cold storage cabinet 2 releases its cooling capacity. The cooled ethylene glycol solution is then transported to buffer cabinet 3 for further cooling to -12℃±2℃ by a vapor compression refrigeration unit before being transported to cold storage 1 for cooling. This completes the ethylene glycol solution recirculation cycle after heat exchange, ensuring continuous cooling for cold storage 1 during peak electricity hours.

[0048] 3. Hours of electricity pricing: During periods of subsidized electricity, the system, based on real-time temperature feedback data from inside and outside cold storage 1 (temperature sensors are installed both inside and outside cold storage 1, and all temperature sensors use existing structural types), and weather forecast data, adjusts compressor 4, delivery pump, and shut-off valve to achieve flexible switching and coordinated supplementary cooling between direct cooling via compression refrigeration and cooling from the cold storage unit. Simultaneously, it regulates the temperature inside cold storage 1 by controlling the flow rate of the ethylene glycol solution (flow control is achieved through pump speed or valve opening; additionally, conventional flow meters can be installed on the pipeline to display real-time flow, depending on actual usage requirements). To save on initial equipment investment, the equipment power is calculated based on the ambient temperature (e.g., 30℃). Therefore, below 30℃, from the cold storage perspective, the cooling capacity comes from the compression refrigeration system, or from the cold storage system and a small amount of compression refrigeration. In normal weather, cold storage 1 will be cooled by a vapor compression refrigeration unit. In extreme weather, the refrigeration capacity of the vapor compression refrigeration unit cannot maintain the temperature of cold storage 1. Therefore, before the temperature reaches its high point, the vapor compression refrigeration unit will operate at full power to maintain the temperature of cold storage 1 and simultaneously perform cold storage. During high-temperature periods (generally in July and August, from 12 PM to 4 PM), the cold storage capacity will supplement the compression refrigeration shortfall. Since 30℃ is a common summer high temperature, it serves as a dividing line: below 30℃ is considered normal weather, and above 30℃ is considered extreme weather. When selecting refrigeration equipment for cold storage 1, the cooling capacity requirement of cold storage 1 at 30℃ will be considered. Therefore, when the temperature exceeds 30℃, the refrigeration equipment will not be able to meet the cooling capacity demand, requiring a combination of cold storage and maximum compression refrigeration power for combined cooling.

[0049] The off-peak, peak, and parity electricity periods vary from region to region. For example, in a certain region, the local electricity pricing mechanism is as follows: peak electricity periods are 6:00-8:00 and 18:00-23:00 (7 hours in total), parity electricity periods are 23:00-6:00 the next day, 8:00-10:00, and 16:00-18:00 (11 hours in total), and off-peak electricity periods are 10:00-16:00 (6 hours in total).

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A phase change cold storage type ice point preservation refrigeration system, characterized in that, include: The control unit and a vapor compression refrigeration unit, a phase change cold storage unit and an ethylene glycol refrigerant circulation unit electrically connected to the control unit, wherein the vapor compression refrigeration unit is cyclically connected to the phase change cold storage unit and the ethylene glycol refrigerant circulation unit respectively, the ethylene glycol refrigerant circulation unit is cyclically connected to the cold storage (1), the cold storage (1) is connected to the phase change cold storage unit, and the phase change cold storage unit is connected to the ethylene glycol refrigerant circulation unit.

2. The phase change cold storage refrigeration system for ice point preservation warehouse according to claim 1, characterized in that, The vapor compression refrigeration unit includes a compressor (4), a condenser (5) and an expansion valve (8), and the ethylene glycol refrigerant circulation unit includes a buffer cabinet (3), which stores a 30% ethylene glycol solution. The compressor (4) is connected to the buffer cabinet (3) through the first pipeline, and the buffer cabinet (3) is connected to the compressor (4) through the second pipeline. The condenser (5) and the expansion valve (8) are both installed on the first pipeline. The condenser (5) is located between the compressor (4) and the expansion valve (8). A second shut-off valve (10) is also installed on the first pipeline, and a first shut-off valve (9) is also installed on the second pipeline.

3. The phase change cold storage refrigeration system for ice point preservation warehouse according to claim 2, characterized in that, The phase change cold storage unit includes a cold storage cabinet (2), the interior of which contains phase change cold storage material. The cold storage cabinet (2) is connected to the first pipeline through a third pipeline and to the second pipeline through a fourth pipeline. One end of the third pipeline is connected to the first pipeline between the condenser (5) and the second shut-off valve (10), and one end of the fourth pipeline is connected to the second pipeline between the compressor (4) and the first shut-off valve (9).

4. The phase change cold storage refrigeration system for ice point preservation warehouse according to claim 3, characterized in that, The buffer cabinet (3) is connected to the cold storage (1) through the fifth pipeline, and the cold storage (1) is connected to the buffer cabinet (3) through the sixth pipeline. A delivery pump (6) is installed on the fifth pipeline, and a shut-off valve (13) is installed on the sixth pipeline.

5. The phase change cold storage refrigeration system for ice point preservation warehouse according to claim 4, characterized in that, The cold storage cabinet (2) is connected to the sixth pipe through the seventh pipe and to the buffer cabinet (3) through the eighth pipe; wherein, one end of the seventh pipe is connected between the cold storage (1) and the shut-off valve five (13), the seventh pipe is equipped with the second pump (7) and the shut-off valve six (14), the shut-off valve six (14) is located between the second pump (7) and the cold storage cabinet (2), and the eighth pipe is equipped with the shut-off valve seven (15).

6. The phase change cold storage refrigeration system for ice point preservation warehouse according to claim 3, characterized in that, The phase change cold storage material has a freezing point of -10.2℃ and is composed of sodium chloride, sodium carboxymethyl cellulose and water, wherein the mass concentration of sodium chloride is 15% and the mass concentration of sodium carboxymethyl cellulose is 1%.

7. A control method, using the phase change cold storage freezing point preservation refrigeration system as described in claim 5, characterized in that, include: S1, Off-peak electricity hours: During off-peak hours, the system's core cold storage phase is implemented, providing immediate cooling to the cold storage (1) on demand, fully utilizing low-priced electricity to reduce the overall electricity cost of the system. Under this condition, the compressor (4) starts, and the vapor compression refrigeration cycle operates normally: the low-temperature, low-pressure gaseous refrigerant is compressed by the compressor (4) into a high-temperature, high-pressure gaseous refrigerant, which enters the condenser (5) to release heat through heat exchange and condenses into a medium-temperature, high-pressure liquid refrigerant. This liquid refrigerant is throttled and depressurized by the expansion valve (8) to form a low-temperature, low-pressure gas-liquid mixture. At the same time, the cold storage (1) is cooled or stored by regulating the shut-off valves. Among them, the shut-off valves 1 (9) and 2 (10) are opened to supply cooling to the buffer cabinet (3), thus providing cooling to the cold storage (1). ) Refrigeration; or open stop valve three (11) and stop valve four (12) to supply cold storage cabinet (2) for cold storage; during off-peak hours, compressor (4) is in full power operation state, and monitors the ethylene glycol outlet temperature in buffer cabinet (3) within the range of -12℃±2℃ through temperature sensor in buffer cabinet (3). If the temperature is lower than this range, vapor compression refrigeration unit supplies cold storage cabinet (2); if the temperature is higher than this range, vapor compression refrigeration unit supplies cold to buffer cabinet (3); turn on transfer pump one (6) and stop valve five (13), and turn off transfer pump two (7), stop valve six (14) and stop valve seven (15) to supply cold storage (1) through buffer cabinet (3); S2, Peak Power Hour: During peak electricity hours, the price of electricity is high, and the compressor (4) operates at low power. The cooling capacity going to the cold storage (1) comes from the cooling capacity released by the cold storage cabinet (2), which reduces the electricity consumption of the power grid during peak electricity hours and lowers the cost of electricity. Close the stop valve three (11) and the stop valve four (12), and open the stop valve (9) and the stop valve (10) to supply cooling to the buffer cabinet (3). Close the stop valve five (13), start the transfer pump one (6) and the transfer pump two (7), and open the stop valve six (14) and the stop valve seven (15) to form a cooling cycle of ethylene glycol solution. The phase change cold storage material in the cold storage cabinet (2) releases the cooling capacity. The cooled ethylene glycol solution is transported to the buffer cabinet (3) and further cooled to -12℃±2℃ by the vapor compression refrigeration unit, and then transported to the end of the cold storage (1) for cooling. The ethylene glycol solution refrigeration cycle after heat exchange is completed, ensuring that the cold storage (1) continues to supply cooling during peak electricity hours. S3, Grid Parity Electricity Hours: During the period of affordable electricity, the system, based on the feedback data of the real-time temperature inside and outside the cold storage (1) and the weather forecast data, adjusts the compressor (4), the delivery pump and the shut-off valve to achieve flexible switching and coordinated cooling between direct cooling by compression refrigeration and cooling by cold storage cabinet release. At the same time, the temperature inside the cold storage (1) is adjusted by controlling the flow rate of the ethylene glycol solution. In normal weather, the cold storage (1) is cooled by the vapor compression refrigeration unit. In extreme weather, the cooling power of the vapor compression refrigeration unit cannot maintain the temperature of the cold storage (1). The vapor compression refrigeration unit will run at full power in advance before the temperature of the day rises to high temperature to maintain the temperature of the cold storage (1) and carry out cold storage at the same time. During high temperature periods, the cold storage capacity is used to supplement the compression refrigeration gap.

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