Phase-change material for controlling temperature of cold fresh warehouse and preparation method of phase-change material

Abstract

The invention discloses a phase-change material for controlling the temperature of a cold fresh warehouse and a preparation method thereof, the phase-change material comprises the following components in percentage by weight: 10-12% of calcium chloride hexahydrate, 5-7% of ammonium chloride, 5-7% of strontium chloride hexahydrate and the balance of carboxymethyl cellulose, and the urea accounts for 10-12% of the weight of the calcium chloride hexahydrate. The strontium chloride hexahydrate accounts for 3%-5% of the weight of the calcium chloride hexahydrate, and the carboxymethyl cellulose accounts for 2%-4% of the weight of the calcium chloride hexahydrate. The phase-change material module is installed on the top and the side face of the cold fresh storage to absorb heat or release heat under the action of the heat exchange device through the change of the solid state and the liquid state, so that the temperature in the cold fresh storage is adjusted, and the blank in the engineering application of the phase-change material cold chain in the prior art is filled up.

Description

Technical Field

[0001] The present invention relates to a cold chain storage technology, and more specifically, to a phase change material for temperature control in a cold storage and a preparation method thereof. Background Art

[0002] Cold storage, as a key facility in the cold chain, is widely used in food preservation, particularly for perishable products like meat, fruits, and vegetables. The temperature inside the cold storage facility must be maintained between 0°C and 4°C to inhibit microbial growth and slow metabolic rates, thereby extending shelf life and maintaining product quality. Traditional cold storage primarily relies on mechanical refrigeration systems (such as compressors and refrigerant cycles). While these systems enable precise temperature control, they suffer from high energy consumption, complex equipment, and high maintenance costs. Furthermore, the reliance on a continuous power supply limits the application of mechanical refrigeration systems in remote areas or environments with unstable power grids. Therefore, the development of low-energy, sustainable cold storage technologies has become a research hotspot in recent years.

[0003] Phase change materials (PCMs), due to their ability to absorb or release large amounts of latent heat during phase change, are increasingly considered an ideal choice for thermal energy storage and temperature control. In practical applications, the performance of PCMs is closely linked to their integration with thermal management systems. In recent years, the integration of renewable energy and PCMs has provided a new development direction for cold storage technology. However, despite progress in theoretical research and initial applications of PCMs in cold storage, existing technologies still suffer from the following shortcomings: First, insufficient system integration: Most research focuses on PCM formulation and performance optimization, lacking systematic installation and configuration solutions tailored to the specific temperature range of cold storage (0°C to 4°C). Second, energy dependence: Traditional cold storage systems rely on grid power, and most applications combining solar energy with PCMs are small-scale or experimental designs, lacking large-scale validation in fixed cold storage. Third, a lack of engineering application: Existing literature rarely addresses the specific layout of PCM modules within cold storage, the matching of heat exchange devices, and the optimization of operating modes, resulting in a unclear path from laboratory to practical application. Therefore, it is necessary to conduct further research and improvement on the cold storage system for the integrated and industrial application of phase change materials. Summary of the Invention

[0004] One of the purposes of the present invention is to address the above-mentioned shortcomings and provide a phase change material and a preparation method for temperature control of a cold fresh storage, in the hope of solving the technical problems in the prior art that the cold fresh storage relies on power supply from the power grid, has high energy consumption and is restricted in use, and similar phase change materials have insufficient performance in terms of latent heat, supercooling and cycle stability.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: On the one hand, the present invention provides a phase change material for temperature control of a cold storage, wherein the phase change material comprises calcium chloride hexahydrate, urea, ammonium chloride, strontium chloride hexahydrate and carboxymethyl cellulose, wherein urea accounts for 10%-12% of the weight of the calcium chloride hexahydrate, ammonium chloride accounts for 5%-7% of the weight of the calcium chloride hexahydrate, strontium chloride hexahydrate accounts for 3%-5% of the weight of the calcium chloride hexahydrate, and carboxymethyl cellulose accounts for 2%-4% of the weight of the calcium chloride hexahydrate.

[0006] Another aspect of the present invention provides a method for preparing a phase change material for temperature control in a cold storage, the method comprising the following steps: Step A: Weigh a target amount of calcium chloride hexahydrate and place it in a stirring container, then weigh urea, ammonium chloride, strontium chloride hexahydrate and carboxymethyl cellulose according to the weight ratio of claim 1.

[0007] Step B: adding urea and ammonium chloride in proportion to a stirring container and stirring and mixing with calcium chloride hexahydrate to obtain a uniform and transparent solution; Step C, adding strontium chloride hexahydrate and carboxymethyl cellulose in proportion to the uniform transparent solution, stirring and mixing, to obtain a uniform viscous mixed solution; Step D: adding the uniform and viscous mixed solution into a forming mold to obtain a phase change material module.

[0008] Preferably, a further technical solution is: the above method also includes adding the uniform viscous mixed solution into a molding mold, smoothing its surface with a scraper, and then allowing the uniform viscous mixed solution to solidify in an environment of -1-1 degrees Celsius, and then sealing the molding mold to obtain a phase change material module for temperature control of a cold storage.

[0009] A further technical solution is that the forming mold is a plate-shaped or tubular polyethylene network mold.

[0010] A further technical solution is that the phase change material module is installed on the top of the inner wall of the cold storage and / or on the side wall close to the entrance door.

[0011] A further technical solution is: the preparation environment temperature of the method is 20-25 degrees Celsius.

[0012] The above-mentioned phase change material module and heat exchange device are integrated into the cold storage, and effective heat transfer and storage are achieved through scientific layout; the photovoltaic power supply system is used to realize automatic operation of active heat absorption during the day and passive heat release at night; the system operation is optimized through temperature monitoring and control units to ensure temperature stability and energy utilization efficiency.

[0013] The systems used in the phase change material module mainly include: a phase change material module, which uses a calcium chloride hexahydrate-based composite material with a phase change temperature of 2°C±0.2°C and a latent heat of 120-127 J / g, and is installed on the inner wall or top of the cold storage; a photovoltaic power supply system with a power of 0.2 kW per cubic meter of storage capacity, which drives the heat exchange device through solar power generation during the day and is powered by energy storage batteries at night; a heat exchange device, which can be pipeline-type (copper serpentine pipe, refrigerant water / ethylene glycol solution) or fan-type (axial fan, wind speed 1-3 m / s) to achieve efficient heat transfer; a temperature monitoring system equipped with high-precision digital sensors (accuracy ±0.1°C), three for every 5 cubic meters of storage capacity, for real-time monitoring of temperature distribution; an intelligent control system using an ARM Cortex-M4 microprocessor, which dynamically adjusts operating parameters through a PID algorithm, supports switching between daytime, nighttime and emergency modes, and fault diagnosis and remote control functions to ensure system reliability.

[0014] The present invention uses a photovoltaic power module to drive a heat exchange device, absorbing heat during the day and releasing heat at night, achieving stable temperature control of the cold storage in a low-energy, modular manner, filling the gap in the existing technology in the engineering application of phase change materials in the cold chain. Compared with traditional mechanical refrigeration systems, the present invention does not require continuous electricity to drive the refrigeration compressor, reducing energy consumption by about 50%, and replacing power grid power with solar energy to reduce operating costs. In response to the specific temperature requirements of 0°C to 4°C for fixed cold storage, an engineered installation and configuration solution is provided, avoiding the limitations of portable design, and has significant practical value and promotion potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 FIG. 1 is a DSC graph of a phase change material for illustrating an embodiment of the present invention.

[0016] Figure 2 A comprehensive comparison diagram of phase change material performance for illustrating an embodiment of the present invention.

[0017] Figure 3 A system flow chart for illustrating an embodiment of the present invention.

[0018] Figure 4 The figure is a system advantage comparison curve diagram for illustrating an embodiment of the present invention.

[0019] exist Figure 4 The three sub-graphs in the figure illustrate the significant advantages of this patented system in temperature stability, energy consumption reduction, and emergency response capabilities, making it suitable for precise temperature control between 0°C and 4°C in cold storage. The graphs are based on experimental data (72-hour test, 10 m³ storage capacity, 5 kg of pork + 10 kg of apples, freshness retention rate >95%).

[0020] Figure 4 son Figure 1 The system demonstrates temperature variations within the warehouse over a 24-hour period compared to a traditional mechanical refrigeration system. This system utilizes phase change material (PCM, latent heat 120-127 J / g) in conjunction with a photovoltaic-powered heat exchanger (refrigerant flow rate 0.1-0.5 L / min or wind speed 1-3 m / s) to maintain a stable warehouse temperature of 0-4°C, with a fluctuation range of ≤±0.8°C. Traditional systems, due to their reliance on continuous electricity for mechanical refrigeration, experience large temperature fluctuations (±1.5°C, standard deviation 0.5°C), often exceeding the target range of 0-4°C (minimum -1°C, maximum 6°C).

[0021] Figure 4 son Figure 2 This paper compares the daily energy consumption of this system with that of a traditional system over a seven-day period. This system utilizes photovoltaic power (0.2 kW / m³, conversion efficiency 18-20%) and phase change material energy storage (cold release rate 0.1-0.2 J / g / min), achieving a stable daily energy consumption of 1.2 kWh (experimental results: 72 hours of power consumption: 3.6 kWh, daily average 1.2 kWh, fluctuation ±0.05 kWh). The traditional system's energy consumption fluctuated between 2-5 kWh (average 3.5 kWh, standard deviation 1.0 kWh, compressor power 1.5 kW).

[0022] Figure 4 son Figure 3 The system demonstrated its ability to maintain temperature in emergency mode during a power outage (PV output <100 W / m², battery charge <10%). PCM modules (6 kg / 10 m³, latent heat 120-127 J / g) maintained the room temperature at 3-4°C for 12 hours via natural convection (heat loss through the insulation layer <0.1 W / m²). The experiment involved heating the room from 3°C to 3.8°C over 12 hours at a rate of 0.067°C / h, with a fluctuation of ±0.1°C. DETAILED DESCRIPTION

[0023] The system's fresh food storage temperature control system, based on proprietary phase change materials (PCM), integrates a photovoltaic power module, a heat exchanger, an insulation layer, a temperature control system, and an intelligent control unit. This system achieves precise temperature control between 0°C and 4°C, making it particularly suitable for preserving perishable foods such as meat, fruits, and vegetables. Through its modular design, intelligent control, and efficient energy storage, the system ensures low energy consumption, high stability, and suitability for use in remote areas or environments without a stable power grid.

[0024] The phase change material unit includes multiple phase change material modules, each designed to be installed on the inner wall of a fresh food storage facility. The phase change material module utilizes solid-liquid phase transition to absorb heat from the fresh food storage facility and release cooling energy at night, maintaining the temperature within the facility between 0°C and 4°C, with a fluctuation of ≤±1°C. This inhibits microbial growth and extends the shelf life of food (e.g., extending the shelf life of fresh meat to 30 days and reducing nutrient loss in fruits and vegetables by 20%-30%). It can be implemented in a variety of forms, such as a plate (50 cm × 30 cm × 2 cm, weighing 1 kg), suitable for large heat-loaded areas (such as the storage ceiling). Alternatively, a tube (5 cm in diameter, 50 cm in length, weighing 0.8 kg) is suitable for installation in confined spaces or on sidewalls. The packaging material for the phase change material module can be a food-grade polyethylene mesh (pore size 0.5 mm, thickness 2 mm, tensile strength >10 MPa). Its porous structure enhances heat conduction and prevents leakage, complying with the GB 4806.7-2016 food safety standard.

[0025] The properties of the phase change material used in the present invention are as follows: Phase transition temperature: 2°C ± 0.2°C (determined by differential scanning calorimetry, DSC).

[0026] Latent heat of fusion: 120-127 J / g, ensuring long-term temperature maintenance.

[0027] Supercooling: <0.5℃ (determined by cooling curve method), fast response.

[0028] Thermal conductivity: 0.33 W / m·K (standard configuration), meeting the heat dissipation requirements of cold storage.

[0029] Cyclic stability: >500 freeze-thaw cycles, latent heat decay <5% after 50 cycles.

[0030] Phase separation degree: <0.02, ensuring liquid homogeneity.

[0031] This invention utilizes a proprietary phase change material (PCM) formula based on calcium chloride hexahydrate (CaCl2·6H2O, purity ≥99%, food grade). The PCM exhibits a phase change temperature of 2°C ± 0.2°C, a latent heat of 120-127 J / g, a thermal conductivity of 0.33 W / m·K, a supercooling of <0.5°C, and a cycling stability of >500 cycles. A melting point modifier and stabilizer are added to the aforementioned base material.

[0032] Melting point modifiers are urea and ammonium chloride. Urea (purity ≥99%, food grade) accounts for 10%-12% of the weight of calcium chloride hexahydrate, lowering the melting point from 29°C to 2°C through a eutectic system and increasing the latent heat by approximately 15 J / g. Ammonium chloride (NH4Cl, purity ≥99%, food grade) accounts for 5%-7% of the weight of calcium chloride hexahydrate, enhancing thermodynamic stability and optimizing melting point accuracy (±0.2°C).

[0033] The stabilizers are strontium chloride hexahydrate and carboxymethyl cellulose. Strontium chloride hexahydrate (SrCl2·6H2O, purity ≥98%, food grade) accounts for 3%-5% of the weight of calcium chloride hexahydrate and acts as a nucleating agent, reducing the supercooling to 0.4-0.5°C (2-3°C when not optimized). Carboxymethyl cellulose (CMC, food grade, viscosity 500-1000 mPa·s) accounts for 2%-4% of the weight of calcium chloride hexahydrate and acts as a thickener, preventing liquid phase separation and reducing the phase separation degree to 0.02 (0.15 when not optimized).

[0034] Based on the above-mentioned self-developed phase change material (PCM) formula, the phase change material module is prepared using the following process: Step 1: Base Material Mixing Equipment: 500 mL stainless steel stirring vessel (corrosion-resistant, equipped with a constant temperature jacket), magnetic stirrer (power 100 W).

[0035] Process: Weigh 100g of CaCl2·6H2O and place it in a stirring container. Add 11g of urea and 6g of ammonium chloride. Stir at 300rpm for 30 minutes at 25℃±2℃ (stirring paddle diameter 5cm) to form a uniform transparent solution (pH 6.5-7.0).

[0036] Inspection: Take samples with a glass rod and observe that there are no solid particles and the solution is clear.

[0037] Step 2: Stabilizer addition Process: Slowly add 4 g of SrCl2·6H2O (3 times, 1.33 g each time, with an interval of 2 minutes), then add 3 g of CMC (2 times, 1.5 g each time), and continue stirring at 300 rpm for 20 minutes to obtain a viscous light white mixture (viscosity about 800 mPa·s).

[0038] Inspection: Use spectrophotometer (wavelength 550 nm) to detect no precipitation and no separation of the mixture.

[0039] Step 3: Encapsulation Equipment: Automated filling machine (accuracy ± 0.1 g), polyethylene network mold (pore size 0.5 mm, volume 100-200 g).

[0040] Process: Pour the mixture into the mold at a flow rate of 5g / s, smooth the surface with a scraper (flatness error <1 mm), place it in a cold storage at 0℃±1℃ for 2 hours to solidify (cooling rate 0.5℃ / min), and heat seal the mold (120℃, pressure 0.2 MPa).

[0041] Inspection: After curing, the hardness of the module is >2 MPa, without bubbles or cracks.

[0042] Step 4: Storage Process: The packaged module is placed in a -5℃±1℃ freezer and sealed (relative humidity <50%). The package integrity is checked with an X-ray detector before use.

[0043] Cycle: Storage period ≤ 6 months, regular sampling and testing of latent heat (decay < 1%).

[0044] The DSC curve of the phase change material obtained by the above method is as follows: Figure 1 shown.

[0045] In a preferred embodiment of the present invention, 6-12 plate-shaped modules or 8-15 tubular modules are installed for 10 m³ of storage capacity. Meat is provided with 1 kg / m³ (high heat load), while fruits and vegetables are provided with 0.7 kg / m³. Preferably, based on the heat load distribution within the storage (COMSOL Multiphysics simulation), the top configuration density is increased by 20% (to address hot air accumulation, accounting for 40% of the heat load).

[0046] refer to Figure 3 As shown in the figure, a comprehensive comparison of the latent heat value, thermal conductivity, supercooling and phase separation, and thermal stability of the phase change material of the present invention and the materials reported in literature [1], [2], and [3] is shown. The figure contains four sub-graphs and uses the same material for comparison. The latent heat value of the present invention is 120-127 J / g, the thermal conductivity is 0.33-0.35 W / m·K, the supercooling degree is 0.4-0.5℃, the phase separation is 0.02, and the latent heat remaining after the cycle is 95%, based on experimental verification.

[0047] The phase-change material module contacts the heat exchange device via thermal grease (0.1 mm thick, thermal conductivity >2 W / m·K). Contact here means the two can exchange temperatures. To avoid mutual influence, the two are typically kept 1-2 cm apart, achieving a heat transfer efficiency >90%. The phase-change material module absorbs heat when changing from solid to liquid, rapidly lowering the cold storage temperature to 0-4°C. When changing from liquid to solid, it releases 2°C of latent heat, maintaining the cold storage temperature at 0-4°C.

[0048] During the day, the photovoltaic power module generates solar power (12-24 V) to power the heat exchanger, intelligent control unit, and auxiliary components. This power supply also charges the battery pack during the night. The battery pack also powers the aforementioned components in an emergency mode, ensuring reliability in off-grid environments.

[0049] The photovoltaic power module consists of a photovoltaic panel, a battery pack, and a power management module. The photovoltaic panel uses polycrystalline silicon solar panels with a conversion efficiency of 18-20% and weather resistance that meets the IEC 61215 standard. The battery pack uses lithium iron phosphate (LiFePO4) batteries with a cycle life of >2000 cycles and an operating temperature range of -20°C to 60°C. The power management module can be integrated into an intelligent control unit and includes an inverter (efficiency >95%, sinusoidal output), a DC-DC converter (supporting 12 / 24 V switching), and an MPPT controller (efficiency >95%).

[0050] In a preferred application scenario of the present invention, the photovoltaic panels generate 0.2 kW per cubic meter of storage capacity (400 W per 10 m³ of storage capacity, 2 m² of area, four 100 W panels connected in series and parallel). The energy storage battery has a capacity of 500 Wh (10 m³ of storage capacity, 12 V, 42 Ah), supporting eight hours of nighttime operation (average power of 60 W). The power management module has an output power range of 10-2000 W, with a dynamic allocation accuracy of ±5%, and a standby power consumption of <0.5 W.

[0051] The photovoltaic panels can also be equipped with a dust-proof coating (reducing dust accumulation by 10%) and an adjustable support frame, allowing the panels to tilt by ±10° at latitudes of ±5°, e.g., 30° at 30° latitude, to accommodate seasonal changes in sunlight. The battery pack has a built-in BMS (Battery Management System) that monitors voltage, current, and temperature in real time (with an accuracy of ±0.1 V) to prevent overcharge and over-discharge and extend battery life. The power management module prioritizes the allocation of battery power (heat exchange device > intelligent control unit > auxiliary components). When the battery pack charge drops below 30%, the power of non-essential loads (such as the LCD backlight) is reduced by 20%. When the charge drops below 10%, emergency mode is triggered.

[0052] The photovoltaic panels and battery pack are connected to the intelligent control unit's built-in power management module (RS485 / USB interface, 5m waterproof cable, loss <0.5%). The heat exchanger and temperature sensor are also connected to the intelligent control unit, enabling real-time monitoring of photovoltaic output and battery charge. When the storage temperature exceeds 4°C, 90% of the power is allocated to the heat exchanger, and the battery pack charge drops below 10%. The intelligent control unit enters emergency mode, supporting only the temperature sensor (power consumption <0.5W).

[0053] The heat exchange device includes a power unit and a heat exchange medium channel, which is in contact with the phase change material module. Specifically, the heat exchange device efficiently transfers heat from the cold storage to the phase change material module, or assists the phase change material module in releasing 2°C of cooling energy into the cold storage, ensuring a heat transfer efficiency of >90%, maintaining a storage temperature of 0-4°C with a temperature difference of <1°C.

[0054] In different embodiments of the present invention, both ducted and fan-type systems can be used. The ducted system is suitable for medium- to large-sized warehouses (>10 m³), ​​where refrigerant circulation evenly distributes heat. The fan-type system is suitable for small warehouses (≤10 m³), ​​where air convection can be flexibly arranged. The ducted system has a polished interior (roughness Ra < 0.4 μm) to reduce refrigerant resistance, and the pump is equipped with a flow sensor (accuracy ±0.01 L / min). The fan-type system has adjustable blade angles (15-30 degrees) and is equipped with a dust screen (pore size 1 mm), which requires monthly cleaning. The pore size of the dust screen is 1 mm. If a plate-type phase change material module is used, a convection fan is generally provided for every two modules.

[0055] The heat exchanger's power unit is regulated by an intelligent control unit, which adjusts the flow rate and speed based on temperature sensor feedback (sampling at 1 Hz). For example, if the top temperature exceeds 4°C, the flow rate is increased to 0.5 L / min or the speed is reduced to 80% (1200 rpm); if the bottom temperature is less than 0.5°C, the flow rate is reduced to 0.1 L / min or the speed is reduced to 50% (500 rpm). The intelligent control unit records heat transfer efficiency (>90%) and detects faults such as flow rate <0.05 L / min or speed deviation >10% (alarm <100ms).

[0056] This system also features an insulation layer, installed between the cold storage's inner wall and the phase change material module. This layer reduces heat transfer from outside the cold storage, achieving a heat loss rate of less than 0.1 W / m², reducing the load on the heat exchanger and extending the emergency mode temperature maintenance period (12-15 hours). The primary material is polyurethane foam, which has a thermal conductivity of 0.025 W / (m·K), a density of 35 kg / m³, and a flame retardant rating of B1. A proportional limiter (with a thermal conductivity of 0.03 W / (m·K)) is used as a backup for local reinforcement. Sealing is achieved using a double-layer rubber sealing strip (2-3 mm thick, 2 MPa elastic modulus), and thermal bridges are filled with 5 cm thick insulation foam (with a thermal conductivity of 0.035 W / (m·K)).

[0057] The insulation layer is 8cm thick, with thermal bridges (such as door frames) increasing to 10cm. When the temperature difference between inside and outside the warehouse is 20°C, heat loss is less than 0.1W / m² (GB / T 13475 test). The airtightness of the door gap is less than 0.1 m³ / (m·h), meeting the GB 50072 cold storage standard.

[0058] The optimized design of the insulation layer utilizes a high-pressure sprayer (0.5 MPa) for application, ensuring uniform foaming (density tolerance <5%) and a flatness tolerance <2 mm. Thermal bridges are addressed by installing 2 cm thick, 0.03 W / (m·K) thermal insulation sleeves through the wall. Magnetic sealing strips are installed at the door seams, improving airtightness by 10%. Maintenance requires annual inspection of the sealing strips (tensile strength degradation <10%) and replacement every three years. The insulation layer, combined with the heat exchanger, reduces heat loss by 20% in emergency mode, extending cooling capacity. An intelligent control unit monitors temperature differences and issues warnings for heat losses exceeding 0.15 W / m².

[0059] In the present invention, the above-mentioned system also includes a temperature control system, which includes an intelligent control unit and multiple temperature sensors. The temperature sensors are all connected to the intelligent control unit. The temperature sensors are used to be installed in the cold storage to collect real-time temperature values ​​at various positions in the cold storage and transmit them to the intelligent control unit; the power device of the heat exchange device is also connected to the intelligent control unit. The intelligent control unit is used to adjust the output power of the power device according to the real-time temperature value to ensure that the fluctuation is ≤±1°C and generate a temperature curve for optimized operation.

[0060] The temperature sensor can be digital (DS18B20 or PT100, accuracy of ±0.1°C, response time <1 s), operating in a -20°C to 50°C range. The intelligent control unit integrates a data acquisition module and a transmission module. The data acquisition module supports 8-channel input, samples at 1 Hz, and can store 1 GB (30 days of data). The transmission module uses Wi-Fi (2.4 GHz, 50 m range) or RS485 (1000 m range).

[0061] Temperature sensors are arranged with three sensors for every 5 m³ of storage capacity, and six for a 10 m³ storage area (two at the top, 0.810 cm from the module, two in the middle, 1 / 2 the height, and two at the bottom, 1 / 4 the height). This allows the top of the storage area to monitor hot air (40% heat load), the middle area to reflect the average temperature, and the bottom to monitor cold air. This arrangement is optimized based on CFD simulation. The temperature sensors can be mounted using a stainless steel bracket (adjustable in height, capable of bearing a load of >0.5 kg). The temperature sensors are factory calibrated and recalibrated annually to an accuracy of ±0.1°C. One spare sensor is provided for each area, with a switching time of <5 seconds. Data processing filters out deviations >3σ to ensure accurate feedback.

[0062] The intelligent control unit can integrate data from the photovoltaic power system, heat exchange device, and temperature sensors, dynamically adjust operating parameters, and automatically switch modes (daytime / nighttime / emergency), achieving temperature stability (±1°C), energy consumption optimization (30% during the daytime, 20% at nighttime), and remote management. It includes: Microprocessor: ARM Cortex-M4 (100 MHz, 512 KB RAM), RTOS, dual-core redundancy (switching < 50 ms, MTBF > 50,000 hours).

[0063] Data acquisition module: 8-channel ADC (16-bit, sampling 1 Hz), storage 1 GB (30 days of data).

[0064] Power management module: inverter (efficiency > 95%), DC-DC converter (MPPT), distribution accuracy ±5%.

[0065] Communication module: Wi-Fi (IEEE 802.11b / g / n, 50 m), Bluetooth (5.0, 10 m).

[0066] User Interface: 4-inch LCD touchscreen (800x480, IPS, anti-glare film, viewing angle >160°), displays temperature (±0.1°C), battery level (±1%), mode, and alarm.

[0067] Backup power: Lithium battery (3.7 V, 2000 mAh), 24 hours of operation without power.

[0068] The microprocessor adjusts the heat exchanger's power (flow rate 0.1-0.5 L / min, speed 500-1500 rpm) using a PID algorithm (Kp=0.5, Ki=0.1, Kd=0.05, response time <100 ms). It switches between daytime, nighttime, and emergency modes. In daytime mode, if the PV output exceeds 100 W / m², the heat exchanger (10-2000 W) is prioritized and the battery pack is simultaneously charged. In nighttime mode, the battery pack provides power (10-50 W). Normal operation occurs when the battery level exceeds 20%, while an alarm is triggered when the battery level falls below 20%. In emergency mode, if the PV output falls below 100 W / m² or the battery level falls below 10%, only the temperature sensor (<0.5 W) is activated. The intelligent control unit monitors pump blockage (flow rate <0.05 L / min), fan failure (speed deviation >10%), and temperature sensor failure (timeout >5 s), sending alerts (LCD, app, <100 ms) and recording up to 1000 records. Through data analysis, linear regression + time series prediction of temperature trends (error <0.2°C) is performed to optimize cooling release (e.g., temperature drop >0.3°C / h, flow rate reduction by 10%).

[0069] The intelligent control unit connects the heat exchange device and temperature sensor via RS485 / USB, integrates data stream (sampling 1Hz), and performs PID regulation (response <100ms) to ensure fluctuation ≤±1°C and failure rate <0.1%.

[0070] The phase change material-based cold storage temperature control system provided by the present invention, its various components, and the phase change material produced by the method are installed as follows: Phase change material module installation: Position: Fixed on the top of the cold storage (heat load 40%) or the side wall of the door (heat load 20%), 8 cm above the top of the storage (heat convection speed 0.2-0.5 m / s, COMSOL simulation).

[0071] Fixing: Use 304 stainless steel brackets (quick lock, load > 2 kg / module, installation < 5 min / module), with a spacing of 8-10 cm (resistance < 0.1 Pa, CFD optimized).

[0072] Quantity: 6-12 plate-shaped or 8-15 tubular modules per 10 m³ storage capacity (1 kg / m³ for meat, 0.7 kg / m³ for fruits and vegetables, with a 20% increase in top density).

[0073] Protection: 0.1 mm polyethylene coating (moisture resistance >95%), protected from sunlight (irradiance <100 W / m²), X-ray inspection package.

[0074] Optimization: module numbering (A1-A12), bracket quick lock.

[0075] Photovoltaic power system installation: Photovoltaic panels: fixed on the south side of the 6061 aluminum alloy bracket (load bearing > 50 kg / m²), with an inclination of ±5° (latitude 30°, inclination 30°), 1.2 m above the ground, and dust-proof coating (cleaned monthly, efficiency degradation < 2%).

[0076] Battery pack: Placed in an IP54 ventilation box (0-40°C, air volume 50 m³ / h, thermal insulation coating reflectivity >80%), with a 5 m waterproof cable (2.5 mm², loss <1%).

[0077] Intelligent control unit: fixed to the inner wall of the warehouse (1.2 m from the ground, with anti-vibration bracket), LCD facing the operation area, 2000 mAh backup battery.

[0078] Optimization: Angle adjuster (5° steps).

[0079] Heat exchange device installation: Pipeline type: The serpentine pipe of the heat exchange medium channel is fixed under the phase change material module (1-2 cm away, 0.1 mm thermal grease), the pump is placed in the corner (anti-vibration pad, noise <30 dB), and the flow sensor is (±0.01 L / min).

[0080] Fan type: The fan is fixed below the phase change material module (2-3 cm away, wind direction module 001), PWM interface, dustproof net (1mm).

[0081] Commissioning: Test refrigerant circulation (pressure 0.2 MPa), air velocity 1-3 m / s (TSI VelociCalc, ±0.1 m / s), efficiency >90%.

[0082] Optimized: Quick-release connector (<10 min), blade angle 15-30°.

[0083] Thermal insulation and monitoring system installation: Insulation layer: 8-10 cm polyurethane foam sprayed (density error <5%), magnetic sealing strip for door gaps (air tightness <0.1 m³ / (m·h)), thermal bridge filled with 5 cm insulation cotton.

[0084] Temperature sensor: fixed on top / middle / bottom (6 sensors per 10 m³ storage), stainless steel bracket (±10 cm), IP67 housing, calibration error <±0.1°C.

[0085] Optimization: Infrared detection heat loss (per year), backup sensor switching <5.

[0086] Intelligent control unit installation: Position: Fixed on the inner wall of the storage (>50 cm away from the heat exchange device, with shock-proof bracket).

[0087] Connection: RS485 / USB interface, 5m waterproof cable, connecting module heat exchange module and temperature sensor.

[0088] Debugging: Target temperature 2°C (±1°C), test mode switching, APP control (delay <1s), alarm (<100ms).

[0089] Optimization: LCD anti-glare film, OTA upgrade (6 months / time).

[0090] refer to Figure 3 As shown, the system of the present invention has three operating modes, which are switched by the intelligent control unit, namely daytime operating mode, nighttime operating mode and emergency mode.

[0091] Daytime operation mode: Mechanism: Module 007 generates electricity (0.2 kW / m³, 12-24 V) to drive the heat exchanger's power unit. Refrigerant circulation (0.2-0.5 L / min) or air convection (1-3 m / s) transfers heat to the phase change material module.

[0092] Process: The phase change material module absorbs heat (120-127 J / g) and changes from solid to liquid, and the temperature of the cold storage drops from 6°C to 4°C (4-6 hours, rate 0.5°C / h).

[0093] Control: The intelligent control unit analyzes temperature sensor data (1 Hz) using a PID algorithm (Kp=0.5, Ki=0.1, Kd=0.05, response time <100 ms): When the top temperature exceeds 4°C, the flow rate is adjusted to 0.5 L / min and the rotation speed to 80% (1200 rpm). When the top temperature differs from 4°C by more than 1°C, the heat exchanger speed is increased by 10%. When the top temperature approaches 4°C, the flow rate is adjusted to 0.2 L / min and the rotation speed to 50% (600 rpm), resulting in a 30% energy saving. Data: Temperature curves, power allocation (±5%), and photovoltaic output are stored to optimize next-day operation (prediction error <0.2°C).

[0094] Night operation mode: Mechanism: The battery pack supplies power (10-50 W), and the phase change material module releases latent heat (0.1-0.2 J / g / min), maintaining the cold storage temperature at 0-4°C (fluctuation ±0.8°C).

[0095] Process: At this time, the phase change material module changes from liquid to solid, and the intelligent control unit adjusts the release of cold.

[0096] Control: The intelligent control unit uses a PID algorithm to prevent freezing: When the temperature inside the storage tank is less than 0.5°C, the flow rate is 0.05 L / min and the rotation speed is 500 rpm. When the temperature inside the storage tank is greater than 3.5°C, the flow rate is 0.3 L / min and the rotation speed is 1000 rpm. When the battery pack charge is less than 20%, the power is reduced to 10% of the original power, entering early warning emergency mode.

[0097] Data: Predicted temperature drop (error <0.1℃ / h), energy saving 20%.

[0098] Emergency Mode: Trigger: Photovoltaic <100 W / m² or battery pack charge <10% (detected by the intelligent control unit).

[0099] Mechanism: The heat exchange device is turned off, allowing the phase change material module to form natural convection and reduce heat loss through the insulation layer (heat loss <0.1 W / m²).

[0100] Aging: 6 kg PCM (10 m³) maintained at 3-4°C for 12-15 hours (latent heat 120-127 J / g).

[0101] Regulation: The temperature sensor continues to operate (<0.5 W), and the intelligent control unit sends an alarm to the external control system (delay <1s).

[0102] As can be seen from the above, based on the application of phase change materials (PCM) in cold storage temperature control, the present invention proposes the following innovations to solve the problems of high energy consumption and strong dependence on the power grid in traditional cold storage systems, as well as the lack of systematic design of PCM applications.

[0103] For example, this invention utilizes the phase change material's liquefaction to absorb heat, while the process of solidification releases 2°C of heat energy. This 2°C of heat release influences the temperature inside the fresh-keeping room at night, maintaining a constant temperature of 0-4°C. This collaborative operation mode, where photovoltaic power generation actively drives the heat exchange device to absorb heat during the day and the phase change material's latent heat releases cooling energy at night, achieves dynamic and stable control of the storage temperature between 0°C and 4°C. Compared to traditional mechanical refrigeration, which relies on continuous electricity, this invention utilizes renewable energy (photovoltaic power generation, with an efficiency of 18-20%) to actively regulate the phase change material's heat absorption and release processes, enabling mode switching (daytime / nighttime / emergency) through an intelligent control system. The specific mechanism is as follows: during the day, the photovoltaic panels (0.2 kW per m³ storage capacity) output 12-24 V to drive the heat exchange device (refrigerant flow rate 0.2-0.5 L / min or wind speed 1-3 m / s), transferring the heat in the storage to the phase change material (latent heat 120-127 J / g). At night, the energy storage battery (500 Wh / 10 m³) supplies power, and the phase change material releases cooling energy (0.1-0.2 J / (g·min)) to maintain the storage temperature.

[0104] For example, this invention proposes a standardized installation method for phase change material modules (50 cm × 30 cm × 2 cm plates or 5 cm × 50 cm tubes, with 8 cm spacing), as well as precise placement of heat exchange devices (pipes 1-2 cm from the modules, fans 2-3 cm from the modules). This modular design and strategic layout optimize heat transfer efficiency (>90%). Modular brackets (aluminum, with a load capacity >2 kg per module) and thermal grease (0.1 mm thickness, thermal conductivity >2 W / m·K) ensure uniform heat absorption and release from the PCM, avoiding localized temperature fluctuations (temperature differences <1°C). The installation height (8 cm from the roof) and spacing (8 cm) were determined based on thermal convection simulations (COMSOL Multiphysics, air velocity 0.2-0.5 m / s), prioritizing placement in high-heat-load areas (top accounts for 40% of heat, door sidewalls account for 20%). The heat exchange device uses a variable frequency pump (20-50 W, flow rate 0.1-0.5 L / min) or a PWM fan (10-50 W, 500-1500 rpm), which is coordinated with the phase change material module to improve heat transfer efficiency by 10%.

[0105] For example, this invention incorporates an intelligent control unit (ARM Cortex-M4, 100 MHz, RTOS). Through temperature monitoring (accuracy ±0.1°C), real-time feedback, and automated regulation, it achieves seamless switching between daytime heat absorption and nighttime heat release. It also features an emergency mode without power supply, maintaining the storage temperature for 12-15 hours. This intelligent control system integrates sensors (three per 5 m³, located on the top, middle, and bottom), photovoltaics (MPPT efficiency >95%), and a heat exchanger (PWM regulation), enabling dynamic power allocation (accuracy ±5%) and fault diagnosis (pump blockage, fan failure, sensor malfunction). In emergency mode, the heat exchanger is shut down (power consumption is reduced to <0.5 W), and the PCM releases cooling energy (120-127 J / g) through natural convection. The insulation layer (0.025 W / (m·K)) maintains a temperature of 3-4°C. The control system supports remote monitoring (Wi-Fi / Bluetooth, app latency <1 second), enhancing user convenience.

[0106] This invention optimizes the phase change material module configuration (0.5-1 kg / m³, latent heat 120-127 J / g), photovoltaic power (0.2 kW / m³), heat exchange efficiency (>90%), and thermal insulation performance (heat loss <0.1W / m²) for the narrow 0-4°C temperature range of cold storage, creating a complete engineering solution to meet the needs of meat, fruits, and vegetables. The proprietary phase change material formula (CaCl2·6H2O 78 wt%, urea 11 wt%, NH4Cl 6 wt%, SrCl2·6H2O 4 wt%, CMC 3 wt%) achieves a melting point of 2°C ± 0.2°C, a latent heat of 120-127 J / g, and a supercooling of <0.5°C. System parameters were designed based on experiments and simulations (CFD, COMSOL), such as the temperature sensor layout (3 per 5 m³, temperature difference <1°C) and the insulation layer thickness (8 cm, thermal conductivity 0.025 W / (m·K)), ensuring a fluctuation of ±1°C.

[0107] The present invention brings significant advantages in temperature stability, energy saving, environmental adaptability, economy and environmental friendliness, and is particularly suitable for cold chain storage scenarios in remote areas or without a stable power grid.

[0108] Excellent temperature stability: Through the synergistic effect of a photovoltaic-driven heat exchanger (efficiency >90%) and a proprietary phase-change material module (latent heat capacity 120-127 J / g), the system rapidly absorbs heat during the day (from 6°C to 3°C in 4-6 hours at a rate of 0.5°C / h) and steadily releases heat at night (releasing 0.1-0.2 J / (g·min) of cooling capacity), maintaining a storage temperature of 0-4°C with a fluctuation of ≤±1°C (experimental data: 72-hour test, 10 m³ storage, fluctuation of ±0.8°C). The intelligent control system utilizes a PID algorithm (response <100 ms) and real-time feedback from six sensors (accuracy ±0.1°C) to dynamically adjust the flow rate (0.05-0.5 L / min) or rotation speed (500-1500 rpm) to ensure temperature uniformity (temperature difference <1°C). High-precision temperature control inhibits microbial growth (for example, reducing E. coli proliferation in meat by 90%) and enzyme activity (reducing fruit and vegetable metabolic rates by 30%), extending the shelf life of fresh pork to 30 days (compared to 15-20 days), reducing moisture loss in apples to less than 5% (compared to 10%), and reducing nutrient loss (vitamin C) by 20%-30%. Suitable for small and medium-sized cold chain businesses and farmers, this system improves storage quality by 10%-15%. Three sensors per 5 m³, CFD-optimized layout, and thermal insulation (0.025 W / (m·K)) synergistically adapt to seasonal temperature fluctuations (-10°C to 40°C). Experimental data (5 kg of pork and 10 kg of apples, 72 hours) confirms the absence of freezing or rotting, maintaining intact quality.

[0109] Significant energy savings: Compared to traditional mechanical refrigeration (average annual power consumption of 5,000 kWh / 10 m³, compressor power of 1.5 kW), this system utilizes photovoltaic power (0.2 kW / m³, efficiency of 18-20%) and phase change material latent heat storage (120-127 J / g), reducing annual power consumption to 2,000 kWh (experimental results: 72-hour power consumption of 3.6 kWh, daily average of 1.2 kWh), representing energy savings exceeding 50%. During the day, photovoltaic power generation (2 kW / 10 m³) eliminates grid costs, while at night, battery power (500 Wh) is used (power of 10-50 W). An intelligent control system optimizes energy allocation (accuracy of ±5%, energy savings of 30% daytime and 20% nighttime). Operating costs are reduced by 60% (conventional costs approximately 5,000 yuan / year, compared to approximately 2,000 yuan / year for a 10 m³ warehouse), making this system particularly suitable for small and medium-sized cold storage facilities (5-50 m³) and users in remote areas. The average annual electricity savings are approximately 3,000 yuan per 10 m³, with a payback period of less than three years (initial cost 5,000-7,000 yuan). The photovoltaic system's MPPT controller (efficiency >95%) and PCM's high latent heat capacity (>120 J / g) reduce energy waste. The intelligent control system predicts temperature drops (with an error of <0.1°C / hour) and dynamically reduces power (e.g., if the temperature drops >0.3°C / hour at night, the flow rate is reduced by 10%). Experimental verification (10 m³ reservoir, 72 hours) has shown stable power consumption and an 8-hour battery life.

[0110] Excellent and robust environmental adaptability: The system does not require a stable power grid. Its photovoltaic system (2kW / 10 m³) and battery pack (500Wh) support 24 / 7 operation. In emergency mode, natural convection from phase change material (6kg / 10 m³, latent heat 120-127 J / g) maintains a storage temperature of 3-4°C for 12-15 hours (experimental simulation: rainy day, storage temperature rise 0.8°C in 12 hours). An insulation layer (8cm, 0.025W / (m·K)) reduces heat loss to <0.1W / m². An intelligent control system monitors power consumption (triggering an emergency when power consumption <10%), ensuring safe storage even on consecutive rainy days (sunlight <100W / m²). This system is suitable for rural areas without power grids (such as fruit and vegetable distribution centers in remote mountainous areas), reducing food losses caused by power outages by 10%-15% (compared to traditional losses of 20-30%). For example, a 50kg container of vegetables (spinach and apples) showed no decay after 48 hours, with a freshness rate exceeding 95%. The system operates in environments ranging from -10°C to 40°C, making it suitable for a wide range of global climates. The phase change material's cycling stability (>500 cycles, attenuation <5%) and the insulation's airtightness (<0.1 m³ / (m·h)) ensure long-term reliability. The intelligent control unit's remote alarm (app, with a delay of <1 second) enhances emergency response. Experiments (500L storage, 50kg of vegetables) demonstrated a 48-hour stability of 2-2.6°C.

[0111] Economical and Easily Deployable: The system features standardized components (phase change material modules, photovoltaic panels, and control systems), with an initial investment of approximately 5,000-7,000 yuan per 10 m³ (compared to 8,000-10,000 yuan traditionally, a 30% reduction). Annual maintenance costs average 200 yuan (compared to 500 yuan traditionally, a 60% reduction). Modular installation (locking brackets, <5 minutes per module) shortens construction time (2-3 days for a 10 m³ warehouse, compared to 5-7 days traditionally). The automated intelligent control system (no professional maintenance required) lowers the technical requirements. A pilot program (2.5 days for a 10 m³ warehouse) validated construction efficiency. Suitable for small and medium-sized cold chain enterprises (5-50 m³) and individual farmers, the system generates an average annual economic benefit of approximately 3,000 yuan per 10 m³ (saving electricity and reducing losses). The modular design supports expansion (adding new modules takes less than one day), allowing expansion into developing countries' cold chain markets to increase coverage by 20%. For example, annual losses at fruit and vegetable distribution centers in remote areas have been reduced from 15% to 5%. Standardized phase change material modules (plate / tube, mold accuracy ±0.1 mm), fast photovoltaic panel installation (angle adjustment, <1 hour), and control system OTA upgrades (once every 6 months) reduce maintenance costs. Experiments (20kg of vegetables + 10kg of fish, 48 hours) verified the preservation effect and reduced costs by 55%.

[0112] Environmentally friendly: The system reduces the use of traditional refrigerants (CFCs). Its photovoltaic power supply (2 kW / 10 m³) and PCM energy storage (120-127 J / g) reduce carbon emissions by approximately 1.5 tons of CO₂ / year / 10 m³ (compared to 3 tons traditionally, a 50% reduction). Pollution-free operation (PCM, food-grade, polyethylene encapsulation) meets green and low-carbon requirements (carbon neutrality goals). Experimental results (10 m³ storage, 2000 kWh annual power consumption) validated the carbon reduction. This system provides a sustainable path for the cold chain industry, reducing reliance on fossil fuels (80% of the traditional power grid is coal-fired), supporting the development of green cold chains in remote areas, and reducing annual CO₂ emissions by approximately 500 kg per 10 m³ user. It complies with global low-carbon policies (such as the EU's 2030 emission reduction targets). The photovoltaic system (18-20% efficiency) and PCM (>500 cycles) are environmentally friendly throughout their lifecycle. The intelligent control system optimizes energy consumption (prediction error <0.2°C) and reduces inefficient operation by 10%. The experiment (72 hours, power consumption 3.6 kWh) verified the low-carbon effect.

[0113] To demonstrate the feasibility and technical effectiveness of this invention, the inventors describe in detail the installation, configuration, and operation of a cold storage temperature control system based on their proprietary phase change material (PCM) using three specific application examples. These examples, targeting small (10 m³), ​​medium (50 m³), ​​and large (100 m³) cold storage facilities, demonstrate how the system works at different scales. The following application examples are based on actual test data and simulation results (COMSOL Multiphysics and CFD) to ensure thorough and repeatable descriptions.

[0114] Application Example 1: System Installation and Operation of a Small Cold Storage (10m³) 1. System Configuration (1) Phase change material module: Eight plate-shaped phase change material modules (50 cm × 30 cm × 2 cm, 1 kg per module, total weight 8 kg) were selected. The self-developed PCM formula is as follows: 78 wt% calcium chloride hexahydrate (CaCl2·6H2O, purity ≥99%, food grade), 11 wt% urea (purity ≥99%), 6 wt% ammonium chloride (NH4Cl, purity ≥99%), 4 wt% strontium chloride hexahydrate (SrCl2·6H2O, purity ≥98%), and 3 wt% carboxymethyl cellulose (CMC, viscosity 800 mPa·s). Performance: Phase transition temperature 2.1°C (DSC measurement), latent heat 125 J / g, supercooling 0.4°C, thermal conductivity 0.33 W / m·K, and cycle stability >500 cycles (4.2% attenuation after 50 cycles). The module is encapsulated with food-grade polyethylene network (pore size 0.5mm, thickness 2mm, tensile strength>10MPa, in compliance with GB 4806.7-2016), and the surface is coated with a 0.1mm thick polyethylene-based coating (waterproof, anti-corrosion, moisture resistance>95%).

[0115] (2) Photovoltaic power system: Equipped with 2m² polycrystalline silicon photovoltaic panels (power 400W, efficiency 18.5%, four 100W panels connected in series and parallel, IEC 61215 certified), 500Wh lithium iron phosphate batteries (12V, 42Ah, cycle life >2000 times, BMS monitoring accuracy ±0.1V), power management module including MPPT controller (efficiency >95%) and inverter (12 / 24V sine wave, efficiency >95%).

[0116] (3) Heat exchange device: 2 axial flow fans (20 W, air volume 150 m³ / h, wind speed 1-3 m / s, PWM speed regulation 500-1500 rpm, noise <38 dB), equipped with dust screen (aperture 1 mm), adjustable blade angle (15-30°).

[0117] (4) Insulation layer: 8 cm polyurethane foam (thermal conductivity 0.025 W / (m·K), density 35 kg / m³, flame retardant B1) is sprayed on the outer wall, 2 mm double-layer magnetic sealing strip (elastic modulus 2 MPa, air tightness <0.1 m³ / (m·h)) is added to the door gap, and 5 cm thermal insulation cotton (thermal conductivity 0.035 W / (m·K)) is filled in the thermal bridge (such as pipes passing through the wall), and the heat loss is <0.1 W / m².

[0118] (5) Temperature monitoring system: 6 digital sensors (DS18B20, accuracy ±0.1℃, response <1 s, operating temperature -20℃ to 50℃), arranged at the top (2, 10 cm away from the module, monitoring hot air), middle (2, 1 / 2 of the warehouse height, average temperature), and bottom (2, 1 / 4 of the warehouse height, cold air), with 1 spare sensor in each area (switching <5 s), Wi-Fi connection (2.4GHz, 50 m range).

[0119] (6) Intelligent control unit: ARM Cortex-M4 microprocessor (100 MHz, 512 KB RAM, RTOS), 4-inch LCD touch screen (800x480, IPS, anti-glare film, viewing angle >160°), 1 GB storage (30 days of data), Wi-Fi / Bluetooth (5.0, 10 m range), PID algorithm (Kp=0.5, Ki=0.1, Kd=0.05, response <100 ms), supports fault diagnosis (pump blockage, fan failure, sensor failure, alarm <100 ms), data analysis (temperature prediction, error <0.2°C), remote control (APP, delay <1 s), power consumption <5 W, IP65 protection, equipped with 2000 mAh backup battery (24 hours of power outage operation).

[0120] 2. Installation steps (1) Phase change material modules: 6 modules were fixed to the inner wall of the warehouse roof (heat load 40%, CFD simulation), and 2 modules were located near the door side wall (heat load 20%), 8 cm above the warehouse roof (heat convection velocity 0.2-0.5 m / s, COMSOL optimization), and 8 cm apart (resistance <0.1 Pa, air velocity 0.3 m / s). 304 stainless steel brackets (modular, quick-lock, load >2 kg / module, installation <5 min / module) were used. Modules were numbered A1-A8 (for easy maintenance and tracking). Before installation, the modules were protected from sunlight (irradiance <100 W / m²). The packaging was inspected by X-ray to ensure no cracks. Construction time: 4 hours (2 people).

[0121] (2) Photovoltaic system: The photovoltaic panels are fixed to the roof outside the south side of the reservoir (6061 aluminum alloy bracket, load-bearing capacity >50 kg / m²), with an inclination angle of 35° (latitude 33°, sunlight efficiency >90%), 1.2 m above the ground, and equipped with a dust-proof coating (cleaned monthly, efficiency degradation <2%). The batteries are placed in an IP54 ventilation box (0-40°C, air volume 50 m³ / h, thermal insulation coating reflectivity >80%), and connected to the intelligent control unit via a 5 m waterproof cable (2.5 mm², loss <1%). The intelligent control unit is fixed to the inner wall of the reservoir (1.2 m above the ground, shock-absorbing bracket with shock absorption rate >80%), with the LCD facing the operation area. Construction time: 3 hours (2 people).

[0122] (3) Heat exchange device: Two fans are fixed to the bracket below the module (2 cm from the surface, with airflow directed into the storage room), equipped with PWM interfaces and dust screens. After installation, wind speed was tested (1-3 m / s, instrument: TSI VelociCalc, accuracy ±0.1 m / s), and noise level was <38 dB (test distance 1 m). Installation time: 1 hour (1 person).

[0123] (4) Insulation and monitoring: 8 cm of polyurethane foam was sprayed on the exterior wall (high-pressure spraying, 0.5 MPa, density error <5%, flatness error <2 mm). Magnetic sealing strips were added to the door gaps (air tightness test: GB / T 13475, <0.1 m³ / (m·h)). Thermal bridges were filled with insulation cotton (5 cm thick). The sensor was fixed to a stainless steel bracket (height adjustable ±10 cm, IP67 housing) and calibrated (JJF1101-2019, error <±0.1°C). Construction time: 6 hours (2 people).

[0124] (5) Intelligent control unit: Fixed to the inner wall of the storage (>50 cm from the fan, with anti-vibration bracket), RS485 interface for connecting photovoltaic, battery, fan, and sensor (5 m waterproof cable, loss <0.5%). Commissioning: Set target temperature to 2°C (±1°C), test mode switching (day / night / emergency), app control (delay <1 s), fault alarm (response <100 ms). Construction time: 2 hours (1 person).

[0125] (6) Total construction time: 16 hours (2-3 days, 3 people).

[0126] 3. Operation process (1) Daytime mode (8:00-14:00): Photovoltaic panels generate electricity (400W, 12V, MPPT efficiency>95%), driving fans (40W, wind speed 2m / s). The initial room temperature is 6.2℃, and it drops to 3.0℃ in 4 hours (at a rate of 0.55℃ / h, Figure 4 ). PCM absorbs heat (125J / g), changes from solid to liquid, and stores 1000kJ of heat. The intelligent control unit monitors the top temperature (>4℃ increases the speed to 80%, 1200rpm), increases the wind speed by 10% when the temperature difference is >1℃, and reduces the speed to 50% (600rpm, energy saving 30%) when the temperature is close to 3℃. Dynamic process: 8:00-10:00, the temperature drops to 4.5℃ (rate 0.85℃ / h), 10:00-12:00, stable at 3.5-4.0℃, 12:00-14:00, reaches 3.0℃ (fluctuation ±0.8℃). Temperature curve ( Figure 4 ) shows a fluctuation of ±0.8℃, and the energy consumption curve shows a peak value of 40 W and an average of 20 W.

[0127] (2) Night mode (18:00-2:00): Battery powered (40 W, BMS monitored), PCM releases cooling capacity (0.15 J / (g·min)), and the room temperature is maintained at 1.2-3.2°C. The intelligent control unit reduces the speed to 500 rpm based on the bottom temperature (<0.5°C to prevent freezing), and increases to 1000 rpm at the top temperature >3.5°C. Dynamic process: Maintain 1.5-2.5°C from 18:00-22:00, and stabilize at 2.0-3.2°C (fluctuation ±0.8°C) from 22:00-2:00. The energy consumption curve shows a stable 20 W, and the battery power is consumed by 40% (200 Wh).

[0128] (3) Emergency mode: Simulates a rainy day (PV <100 W / m², battery <10%), fans off, PCM natural convection (insulation heat loss <0.1 W / m²), and the storage temperature rises from 3.0°C to 3.8°C over 12 hours (0.067°C / h). The intelligent control unit operates only the sensor (power consumption <0.5 W), sends alerts to the app (delay <1 s), and records temperature changes (1 GB storage). The temperature curve shows a gentle temperature rise over 12 hours, with a fluctuation of ±0.5°C.

[0129] 4. Test Results (1) Temperature stability: 72 hours operation, storage temperature 0.8-3.8℃, fluctuation ±0.8℃ (sensor data, Figure 4 ). Top / middle / bottom temperature difference <1℃ (CFD verification).

[0130] (2) Energy consumption: Total power consumption is 3.6 kWh (daily average 1.2 kWh, traditional 2-5 kWh, energy saving > 50%), energy consumption curve ( Figure 4 ) shows 20-40W during the day and 20W at night.

[0131] (3) Freshness preservation effect: Storing 5kg of fresh pork + 10kg of apples without freezing for 72 hours, the water loss is 4.8% (conventional 10%), the vitamin C loss is 18% (conventional 30%), and the freshness preservation rate is >95% (microbiological test: Escherichia coli proliferation rate <10 4 CFU / g).

[0132] (4) Heat transfer efficiency: 92% (GB / T 21001 test, wind speed 2 m / s).

[0133] (5) Environmental adaptability: The test environment is 25°C (summer, humidity 70%), the storage temperature is stable, and there is no condensation on the insulation layer. Low temperature test (-10°C, winter), battery efficiency> 90%.

[0134] (6) Operating parameters: Fan speed 500-1500 rpm, heat transfer 1000 kJ (daytime), cooling capacity 720 kJ (nighttime). Fault diagnosis: Detect fan speed deviation >10% (alarm <100 ms).

[0135] (7) Dynamic process: Temperature curve ( Figure 4 ) shows that the temperature dropped by 3.2℃ in 4 hours during the day, maintained at 1.2-3.2℃ for 8 hours at night, and rose by 0.8℃ in 12 hours of emergency; the energy consumption curve shows that the total power consumption is 3.6 kWh and the peak is 40 W.

[0136] Application Example 2: System Expansion for a Medium-Sized Cold Storage (50 m³) 1. System Configuration (1) Phase change material module: 30 tubular phase change material modules (5 cm diameter, 50 cm length, 0.8 kg per module, total weight 24 kg) were selected. The formulation was the same as in Application Example 1, with the addition of 0.5 wt% nano-alumina (Al2O3, 50 nm, food grade). Performance: phase change temperature 2.0°C, latent heat 122 J / g, supercooling 0.5°C, thermal conductivity 0.35 W / m·K, and attenuation of 4.5% after 50 cycles. Packaging was the same as in Application Example 1, with mold heat sealing (120°C, 0.2 MPa).

[0137] (2) Photovoltaic power system: 10 m² photovoltaic panels (2 kW, 8 250 W panels, 19% efficiency), 2500 Wh battery (12 V, 208 Ah, BMS monitoring), intelligent control unit is the same as in Application Example 1, with the addition of a dual-core processor (master / backup, switching < 50 ms), and OTA upgrade (6 months / time).

[0138] (3) Heat exchange device: copper serpentine pipe (inner diameter 8 mm, wall thickness 0.5 mm, roughness Ra < 0.4 μm, total length 20 m), refrigerant water / ethylene glycol (1:1, freezing point -15 °C), variable frequency pump (30 W, flow rate 0.1-0.5 L / min, head 3 m), equipped with flow sensor (±0.01 L / min).

[0139] (4) Insulation layer: 10 cm polyurethane foam (thermal conductivity 0.025 W / (m·K)), 3 mm magnetic sealing strip, thermal bridge filled with 5 cm insulation cotton, heat loss < 0.08 W / m².

[0140] (5) Temperature monitoring system: 15 sensors (PT100, accuracy ±0.1°C), 5 at the top (10 cm away from the phase change material module), 5 in the middle (1 / 2 of the warehouse height), 5 at the bottom (1 / 4 of the warehouse height), 2 spare sensors, RS485 connection (1000 m range).

[0141] (6) Intelligent control unit: Same as application example 1, with the addition of cloud platform storage (1 year of data), support for multi-user APP management (up to 5 users), and fault log recording (time, type, parameters).

[0142] 2. Installation steps (1) Phase change material modules: Arranged vertically along both sides of the storage chamber (15 modules per side, 30% heat load), with 10 cm spacing (resistance <0.08 Pa, CFD optimized), and 20 cm above the ground (where cold air falls). Use modular brackets (quick-lock, <5 minutes per module). The molds were X-ray inspected. Construction time: 10 hours (3 people).

[0143] (2) Photovoltaic system: Photovoltaic panels are placed on the roof (inclination angle 33°, latitude 32°, angle adjustment step 5°), the battery box is coated with thermal insulation (reflectivity > 80%), and the intelligent control unit is installed in the operating room (LCD anti-glare). Construction time: 6 hours (2 people).

[0144] (3) Heat exchange device: Pipes are placed at the bottom of the module (1 cm distance, 0.1 mm thermal grease), pumps are placed in corners (vibration pads, noise <30 dB), and refrigerant circulation is tested (pressure 0.2 MPa, flow rate 0.3 L / min). Construction time: 3 hours (2 people).

[0145] (4) Insulation and monitoring: 10 cm foam spraying (density error <5%), magnetic sealing of door gaps, and sensor bracket height adjustment (±10 cm). Construction time: 12 hours (3 people).

[0146] (5) Intelligent control unit: RS485 / USB connection, debugging and fault diagnosis (pump blockage alarm <100 ms), cloud platform data synchronization. Construction time: 3 hours (1 person).

[0147] (6) Total construction time: 34 hours (4-5 days, 4 people).

[0148] 3. Operation process (1) Daytime mode (9:00-15:00): Photovoltaic power generation (2 kW, MPPT efficiency > 95%), driving pump (30 W, flow rate 0.3 L / min). The storage temperature dropped from 7.0°C to 4.0°C (6 hours, rate 0.5°C / h). PCM absorbs heat (122 J / g), storing 3660 kJ. The intelligent control unit adjusts the flow rate (increases to 0.5 L / min at the top > 4°C, and drops to 0.2 L / min near 4°C, saving 25% energy). Dynamic process: drops to 5.5°C (rate 0.75°C / h) from 9:00-11:00, stabilizes at 4.5-5.0°C from 11:00-13:00, and reaches 4.0°C (fluctuation ±0.6°C) from 13:00-15:00. Temperature curve ( Figure 4 ) shows a fluctuation of ±0.6℃, and the energy consumption curve shows a peak value of 60W and an average of 30W.

[0149] (2) Night mode (18:00-4:00): Battery powered (30 W), phase change material releases cooling capacity (0.12 J / (g·min)), storage temperature 2.0-4.0°C. The intelligent control unit reduces the flow rate to 0.1 L / min based on the bottom temperature (<0.5°C), and increases it to 0.3 L / min at the top (>3.5°C). Dynamic process: Maintain 2.2-3.0°C from 18:00-22:00, and stabilize at 2.5-4.0°C (fluctuation ±0.6°C) from 22:00-4:00. The energy consumption curve shows an average daily value of 2.5 kWh, and the battery consumption is 50% (1250Wh).

[0150] (3) Emergency mode: The pump was turned off, and the PCM module operated in natural convection. The storage temperature rose from 4.0°C to 4.9°C over 15 hours (0.06°C / h). The intelligent control unit issued an alarm and recorded data. The temperature curve showed a gentle rise, with a fluctuation of ±0.4°C.

[0151] 4. Test Results (1) Temperature stability: 72 hours operation, storage temperature 1.8-4.9℃, fluctuation ±0.6℃ ( Figure 4 ). Temperature difference <0.8℃ (CFD verification).

[0152] (2) Energy consumption: Total power consumption is 7.5 kWh (daily average 2.5 kWh, traditional 5-8 kWh, energy saving >55%), and the energy consumption curve shows 30-60 W during the day and 30 W at night.

[0153] (3) Freshness preservation effect: 20 kg of vegetables (spinach) + 10 kg of fish were stored without rotting for 48 hours, with a water loss of 4% (conventional 10%) and a freshness preservation rate of >95% (microbial test: total colony count <10 5 CFU / g).

[0154] (4) Heat transfer efficiency: 94% (flow rate 0.3 L / min).

[0155] (5) Environmental adaptability: Test environment: 30°C (tropical, 80% humidity), stable storage temperature, no condensation on the insulation layer. Cold test (0°C), battery efficiency >85%.

[0156] (6) Operating parameters: Flow rate 0.1-0.5 L / min, heat transfer 3660 kJ (daytime), cooling release 2880 kJ (nighttime). Fault diagnosis: Detection flow rate <0.05 L / min (alarm <100 ms).

[0157] (7) Dynamic process: Temperature curve ( Figure 4 ) shows that the temperature dropped by 3.0℃ in 6 hours during the day, maintained at 2.0-4.0℃ for 10 hours at night, and rose by 0.9℃ in 15 hours of emergency; the energy consumption curve shows a total power consumption of 7.5 kWh and a peak of 60 W.

[0158] Application Example 3: System Expansion for Large Cold Storage (100 m³) 1. System Configuration (1) Phase change material module: 60 plate-shaped phase change material modules (50 cm × 30 cm × 2 cm, 1 kg per module, total weight 60 kg) were selected. The formulation was the same as that in Application Example 1. Performance: phase change temperature 2.1°C, latent heat 124 J / g, supercooling 0.4°C, thermal conductivity 0.33 W / m·K, and attenuation of 4.0% after 50 cycles.

[0159] (2) Photovoltaic power system: 20 m² photovoltaic panels (4 kW, 16 panels of 250 W, 19% efficiency), 5000 Wh battery (24 V, 208 Ah), intelligent control unit as in Application Example 2, with an additional redundant power supply (4000 mAh, 48 hours of operation in the event of a power outage).

[0160] (3) Heat exchange device: copper pipe (inner diameter 10 mm, wall thickness 0.5 mm, total length 40 m), refrigerant water / ethylene glycol (1:1), two variable frequency pumps (50 W, flow rate 0.2-0.5 L / min, head 4 m), equipped with two flow sensors (±0.01 L / min).

[0161] (4) Insulation layer: 10 cm polyurethane foam (thermal conductivity 0.025 W / (m·K)), 3 mm magnetic sealing strip, thermal bridge filled with 5 cm insulation cotton, heat loss < 0.08 W / m².

[0162] (5) Temperature monitoring system: 30 sensors (PT100, accuracy ±0.1°C), 10 on the top, 10 in the middle, 10 on the bottom, 4 spare sensors, RS485 connection.

[0163] (6) Intelligent control unit: Same as application example 2, with the addition of multi-zone management (divided into 4 zones, each zone independently adjusted), and support for 10-user APP management.

[0164] 2. Installation steps (1) Phase change material modules: 40 modules fixed to the roof (heat load 45%), 20 modules along the side walls (heat load 25%), 10 cm apart and 8 cm from the roof. Quick-lock brackets (<5 minutes / module). Construction time: 20 hours (4 people).

[0165] (2) Photovoltaic system: Photovoltaic panels are placed on the roof (30° inclination, 30° latitude), the battery box is equipped with a temperature-controlled fan (100 m³ / h), and the intelligent control unit is installed in the control room. Construction time: 10 hours (3 people).

[0166] (3) Heat exchange device: Pipes were placed at the bottom of the module (1 cm away), two pumps were connected in parallel (with anti-vibration pads), and the flow rate was tested (0.3 L / min). Construction time: 6 hours (3 people).

[0167] (4) Insulation and monitoring: Spray 10 cm of foam, with adjustable sensor bracket height. Construction time: 20 hours (4 people).

[0168] (5) Intelligent control unit: Debug multi-zone management and test fault diagnosis (flow deviation alarm <100 ms). Construction time: 4 hours (2 people).

[0169] (6) Total construction time: 60 hours (7-8 days, 5 people).

[0170] 3. Operation process (1) Daytime mode (8:00-16:00): Photovoltaic power generation (4 kW), driving pump (100W, flow rate 0.4L / min). The storage temperature dropped from 8.0℃ to 4.0℃ (8 hours, rate 0.5℃ / h). The phase change material module absorbs heat (124 J / g), storing 7440 kJ. The intelligent control unit adjusts the flow rate (increases to 0.5 L / min at the top >4℃, and drops to 0.2L / min near 4℃, saving 30% energy). Dynamic process: drops to 5.5℃ from 8:00-12:00, and stabilizes at 4.0-4.5℃ from 12:00-16:00 (fluctuation ±0.5℃). Temperature curve ( Figure 4 ) shows a fluctuation of ±0.5℃, and the energy consumption curve shows a peak value of 120 W and an average of 60 W.

[0171] (2) Night mode (18:00-6:00): Battery powered (100W), phase change material releases cooling capacity (0.13 J / (g·min)), storage temperature 1.8-4.0°C. The control system adjusts the flow rate (reduced to 0.1 L / min at the bottom when the temperature is <0.5°C, and increased to 0.3 L / min at the top when the temperature is >3.5°C). Dynamic process: maintained at 2.0-3.0°C from 18:00-24:00, and stabilized at 2.5-4.0°C (fluctuation ±0.5°C) from 24:00-6:00. The energy consumption curve shows an average daily consumption of 5.0 kWh, and the battery consumption is 60% (3000Wh).

[0172] (3) Emergency mode: The pump is turned off, the phase change material is allowed to flow naturally, and the storage temperature rises from 4.0°C to 5.0°C over 18 hours (0.056°C / h). The control system sends an alarm and records data. The temperature curve shows a fluctuation of ±0.4°C.

[0173] 4. Test Results (1) Temperature stability: 72 hours operation, storage temperature 1.8-5.0℃, fluctuation ±0.5℃ ( Figure 4 ). Temperature difference <0.7℃.

[0174] (2) Energy consumption: Total power consumption is 15 kWh (daily average 5.0 kWh, traditional 10-15 kWh, energy saving >60%), and the energy consumption curve shows 60-120 W during the day and 60 W at night.

[0175] (3) Insurance effect: Storing 50 kg of vegetables and 20 kg of fish, no decay for 72 hours, water loss of 3.8% (conventional 12%), freshness rate> 96% (total colony <10 4 CFU / g).

[0176] (4) Heat transfer efficiency: 95% (flow rate 0.4 L / min).

[0177] (5) Environmental adaptability: The test environment was 35°C (tropical, 85% humidity), the storage temperature was stable, and there was no condensation on the insulation layer. In the extreme cold test (-20°C), the battery efficiency was >80%.

[0178] (6) Operating parameters: flow rate 0.2-0.5 L / min, heat transfer 7440 kJ (daytime), cooling release 5760 kJ (nighttime). Fault diagnosis: Pump flow deviation >10% (alarm <100 ms).

[0179] (7) Dynamic process: Temperature curve ( Figure 4 ) shows that the temperature drops by 4.0℃ in 8 hours during the day, maintains 1.8-4.0℃ for 12 hours at night, and rises by 1.0℃ in 18 hours of emergency; the energy consumption curve shows a total power consumption of 15 kWh and a peak of 120 W.

[0180] Figure 4 The references shown in are: [1] Chuanchang Li, Mu Li, YaxiLi, Tailored calcium chloridehexahydrate as a composite phase change material for cold storage. Journal ofEnergy Storage. Volume 56, Part A, 1 December2022, 105798. [2] Babu Natarajan a, AravindChellachi Kathiresan b, Senthil KumarSubramanium, Development and performance evaluation of a hybrid portable solar cold storage system for the preservation of vegetables and fruits inremote areas. Journal of Energy Storage. Volume 72, Part A, 15 November 2023,108292. [3] -50℃-0℃ PCM Phase Change Materials For Cooling PlatesFor FoodAnd All Biological Indicators. In addition to the above, it should be noted that references to "one embodiment," "another embodiment," "an embodiment," and the like throughout this specification refer to specific features, structures, or characteristics described in conjunction with that embodiment as included in at least one embodiment generally described herein. The appearance of the same term in multiple places in this specification does not necessarily refer to the same embodiment. Furthermore, when a specific feature, structure, or characteristic is described in conjunction with any embodiment, it is intended that such feature, structure, or characteristic, when implemented in conjunction with other embodiments, also fall within the scope of the present invention.

[0181] Although the present invention has been described herein with reference to a number of illustrative embodiments thereof, it will be understood that numerous other modifications and implementations may be devised by those skilled in the art that fall within the scope and spirit of the principles disclosed herein. More specifically, within the scope of the present disclosure, the drawings, and the claims, numerous variations and modifications may be made to the components and / or layout of the subject combination arrangement. In addition to variations and modifications to the components and / or layout, other uses will also be apparent to those skilled in the art.

Claims

1. A phase change material for temperature control of cold storage, characterized in that The phase change material includes calcium chloride hexahydrate, urea, ammonium chloride, strontium chloride hexahydrate and carboxymethyl cellulose, wherein the urea accounts for 10%-12% of the weight of the calcium chloride hexahydrate, the ammonium chloride accounts for 5%-7% of the weight of the calcium chloride hexahydrate, the strontium chloride hexahydrate accounts for 3%-5% of the weight of the calcium chloride hexahydrate, and the carboxymethyl cellulose accounts for 2%-4% of the weight of the calcium chloride hexahydrate.

2. A method for preparing a phase change material for temperature control of a cold storage, characterized in that The preparation method comprises the following steps: Weighing a target amount of calcium chloride hexahydrate and placing it in a stirring container, and then weighing urea, ammonium chloride, strontium chloride hexahydrate and carboxymethyl cellulose according to the weight ratio of claim 1; Add urea and ammonium chloride in proportion to a stirring container and stir with calcium chloride hexahydrate to obtain a uniform and transparent solution; adding strontium chloride hexahydrate and carboxymethyl cellulose in proportion to the uniform transparent solution, stirring and mixing, to obtain a uniform viscous mixed solution; The uniform and viscous mixed solution is added into a forming mold to obtain a phase change material module.

3. The method for preparing a phase change material for temperature control of a cold storage according to claim 2, characterized in that: The method also includes adding the uniform viscous mixed solution into a forming mold, smoothing its surface with a scraper, and then allowing the uniform viscous mixed solution to solidify in an environment of -1-1 degrees Celsius, and then sealing the forming mold to obtain a phase change material module for cold storage temperature control.

4. The method for preparing a phase change material for temperature control of a cold storage according to claim 2 or 3, characterized in that: The forming mold is a plate-shaped or tubular polyethylene network mold.

5. The method for preparing a phase change material for temperature control of a cold storage according to claim 2 or 3, characterized in that: The phase change material module is installed on the top of the inner wall of the cold storage and / or on the side wall close to the entrance door.

6. The method for preparing a phase change material for temperature control of a cold storage according to claim 2, characterized in that: The preparation environment temperature of the method is 20-25 degrees Celsius.

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