This study focuses on the development of a ternary salt-based microencapsulation phase change composite by the sol-gel approach. This composite exhibited a melting temperature range of 150-220 ℃ and could be effectively used for thermal energy storage. The thermophysical properties of the pure ternary nitrate salt were first evaluated. The salt exhibited a melting point of 156.04 ℃, latent heat of 95.5 kJ/kg, and decomposition temperature of 626.3 ℃. Then, the microencapsulated composite was fabricated and investigated based on the results of the pure ternary salt. Various characteristic methods, including scanning electron microscopy with energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry, were employed to evaluate the thermal energy storage performance of the microencapsulated composite. The results indicated that the nitrate salt could be efficiently encapsulated by SiO₂. This resulted in a diameter of 10-40 μm of the composite, endowing it with a great ability to overcome liquid leakage. Meanwhile, the composite exhibited an encapsulation ratio of 90.9%, a latent heat of 86.81 kJ/kg, and a thermal energy utilization efficiency of 78.36%. The results presented in this study demonstrate that the microencapsulated composite achieves excellent thermal energy storage performance and can be an feasible candidate for low and medium thermal energy storage.

Coupling a thermal power plant and its thermal energy storage through a molten-salt Carnot battery energy storage system is an effective retrofit method. The energy storage system uses the abandoned electric or the power to heat molten salt directly or indirectly through the heat-pump cycle, converting electrical energy into high-temperature thermal energy storage. The high-temperature molten salt and the boiler are subsequently used together as a heat source to drive the steam engine to generate electricity, which achieves the purpose of reducing or replacing the boiler. In this report, the pattern of component parameters influencing the efficiency of a molten-salt Carnot battery energy storage system used in retrofitting a thermal power plant is explored. A thermodynamic model of the molten-salt Carnot battery energy storage system is constructed using the Aspen Plus platform; the model consists of a heat-pump cycle, a molten-salt evaporator, and a typical 600 MW subcritical power block. Influence of the cycling medium, regenerative/nonregenerative properties, and component key parameters on the performance of heat pump and overall system are analyzed. The system efficiencies for the system using electric heating and heat-pump heating are compared under variable operating conditions. The results show that the regenerative storage system has a higher coefficient of heat-pump production and higher round-trip efficiency than that for the nonregenerative system. The regenerative storage system requires the lowest return heater heat by using argon as the heat-pump circulating medium and can achieve the highest round-trip efficiency by using helium as the heat-pump circulating medium. When the cold-source temperature is 67 ℃, isentropic efficiency is 0.9, and mechanical efficiency is 1.0, the round-trip efficiency under the rated working condition can reach 61.46%. In addition, the round-trip efficiency at rated operating conditions of the storage system with the heat pump is 45.16% higher than electric heating. These findings can help in the further design and analysis of molten-salt Carnot battery energy storage systems for retrofitting thermal power plants.

The accumulation of industrial waste salts has significantly increased in recent years, resulting in several environmental problems. This study proposes a method to deal with industrial waste salts using NaCl and Na₂SO₄ as the main components (mainly including calcium, magnesium, and potassium impurity ions) and analyzes their thermal properties. These elements comprise sodium-based waste salt as a heat storage material, and its thermal properties are influenced by the existence of several impurity ions, which were discovered through molecular dynamics methods. In addition, binary sodium-based eutectic salts, NaCl-Na₂SO₄ were prepared using a two-step high-temperature melting method with 1% and 5% of KCl added to resemble the waste salts. These results indicated that K⁺ ion enhance the thermal performance of these sodium-based salts. Compared with the latent heat of phase change of binary sodium-based eutectic salts, the latent heat values of mixed molten salts increased by 64% (1%KCl) and 60% (5%KCl). Furthermore, the thermal conductivities of the mixed molten salts were increased by 2—3 times. The results also showd that the presence of K⁺ ions could improve the thermal performance of sodium waste salts, providing a means to reutilize this type of resource.

A composite phase change material (cPCM) was prepared in this study using the melt-blending method. It contained sodium acetate trihydrate as the main phase change material, disodium phosphate dodecahydrate as the nucleating agent, sodium carboxymethyl cellulose as the thickening agent, and expanded graphite as an additive to enhance thermal conductivity. The material properties were characterized and measured using a scanning electron microscope, rheometer, balance, differential scanning calorimeter, and thermal constant analyzer. The thermal cycling stability of the cPCM was evaluated using a thermal cycling system. The results demonstrated that expanded graphite enhanced the thermal conductivity and viscosity of the cPCM. However, it also affected the latent heat and apparent density of the cPCM. As the expanded graphite content increased from 1% to 6%, the thermal conductivity of the cPCM increased from 1.055 to 2.247 W/(m·K), the apparent density decreased from 1.13 to 0.77 g/cm³, and the latent heat decreased from 266.2 to 232.7 J/g. The thermal cycling experiments revealed that the cPCM with 1% expanded graphite exhibited excellent thermal cycling stability, with an effective cycle ratio of >92% and a low supercooling degree (generally <8 ℃) in 530 thermal cycles.

Greenhouses exploit the principle of greenhouse effect to maintain an optimal growth environment for plants. Under intense sunlight, the temperature inside greenhouses may exceed a suitable growth temperature; therefore, appropriate cooling measures must be implemented. In this study, phase-change energy storage technology is applied to greenhouses by exploiting passive temperature control to reduce the peak temperature of the greenhouse and thereby reduce energy consumption. Disodium hydrogen phosphate dodecahydrate (DHPD) was used as the phase change material (PCM). After the addition of nucleating agents and thickeners, a composite PCM was prepared, which exhibited a low supercooling degree and good cycle stability. Its performance was evaluated using the step-cooling curve method, differential scanning calorimetry, and a simultaneous thermal analyzer. Next, the composite PCM was packaged into panels and installed in a greenhouse, and the impact of the phase-change panels on the thermal environment inside the greenhouse under actual sunlight conditions was investigated. The results revealed that sodium metasilicate nonahydrate with a mass fraction of 4% can reduce the supercooling of DHPD from 12 ℃ to 0.5 ℃. Using xanthan gum with a mass fraction of 5% as the thickener, the composite PCM exhibited good cycle stability. The phase change temperature and latent heat of the prepared composite were 34.2 ℃ and 194.5 J/g, respectively, which were found to be suitable for greenhouses. Continuous 24 h temperature detection revealed that the peak temperature of the greenhouse was reduced by 3.5 ℃ in comparison with that of the reference greenhouse without phase change panels. The corresponding peak time was delayed by 32 min. In addition, the total duration of high temperature was significantly shortened in compared to that of the reference. Therefore, the application of the DHPD composite PCM in greenhouses can improve the high-temperature environment of the greenhouse and reduce the energy consumption of cooling.

In this study, a series of composite phase-change materials (CPCMs) were prepared by the melt-blending method using sodium carboxymethyl cellulose as a thickener; disodium hydrogen phosphate dodecahydrate, disodium hydrogen phosphate anhydrous, nano-Al₂O₃, and nano-Al₂O₃ modified by sodium dodecyl sulfate as nucleating agents; and graphite as a thermally conductive enhancer. A comprehensive analysis of the composition, morphology, and thermal properties of CPCMs was performed using an infrared spectrometer, scanning electron microscope, differential scanning calorimeter, and temperature acquisition system. The results show that the addition of 2% sodium carboxymethylcellulose/3% disodium hydrogen phosphate dodecahydrate or 2% sodium carboxymethylcellulose/1% modified nano-Al₂O₃ to sodium acetate trihydrate matrix can effectively solve the problems of SAT phase separation and large supercooling. The DSC analysis results indicate that the enthalpies of phase transition for the CPCMs are maintained at 247.98 J/g and 244.64 J/g. Adding 2% sodium carboxymethyl cellulose/3% disodium hydrogen phosphate dodecahydrate/1% graphite or 2% sodium carboxymethyl cellulose/3% disodium hydrogen phosphate dodecahydrate/1% modified nano-Al₂O₃/1% graphite to the sodium acetate trihydrate matrix enhances the thermal conductivity of the CPCMs without increasing supercooling during rapid-cycling storage. Exothermic experiments were carried out on the CPCMs, and the changes in relative latent heat were calculated using the T-history method. The rate of heat decay was found to increase with the increase in the number of cycles. The first formulation tended to stabilize after reaching 40 cycles, with a heat decay of approximately 23%, whereas the second formulation tended to have an increase in the degree of subcooling after 50 cycles. These results help promote the application of phase-change materials in the field of thermal storage and provide an experimental basis for the development of composite phase-change materials by ensuring the high enthalpy and high stability of sodium acetate trihydrate.

This study focuses on the development and evaluation of a novel inorganic hydrated salt composite phase change mortar for radiant floor heating, utilizing Na₂HPO₄·12H₂O and Na₂SO₄·10H₂O as primary raw materials. The fabrication process involved the preparation of binary mixed molten salt (80%Na₂HPO₄·12H₂O-20%Na₂SO₄·10H₂O) through a physical blending method, adding a nucleating agent (2%Na₂SiO₃·9H₂O) to optimize subcooling. To enhance adsorption and encapsulation, expanded perlite particles (2—2.5 mm) were integrated, resulting in the formation of a stereotyped composite phase change material. This material was seamlessly integrated into the mortar matrix to create the composite phase change mortar. Differential scanning calorimetry tests were conducted on binary molten and binary eutectic salts, as well as stereotyped composite phase change materials, yielding enthalpies of phase change at 229.1, 214.1, and 156.7 J/g, respectively. Scanning electron microscopy revealed excellent compatibility between expanded perlite and eutectic salt phase change materials in the microstructure of the stereotyped composite phase change material. Thermal properties of the developed composite phase change mortar are as follows: 0.63 W/(m·K) thermal conductivity, 1.56 and 1.75 J/(g·K) specific heat capacity in solid and liquid states, and 3.85 W/(m²·K) heat transfer coefficient. To assess the practical impact of the composite phase change mortar, heat storage performance was tested. Comparative analysis with standard mortar demonstrated that the composite phase change mortar significantly mitigates temperature fluctuations. During the heating test with a hot plate at 50 ℃, the peak temperature of the composite phase change mortar at the cold end remained 2.5 ℃ lower than standard mortar. Additionally, the composite phase change mortar exhibited a gradual temperature rate decrease during cooling, indicating robust heat storage capabilities. When applied to intermittent radiant floor heating, the composite phase change mortar effectively stored heat during heating, preventing excessive indoor temperatures. It released heat after heating cessation, slowing down the indoor temperature reduction rate and preventing excessively low indoor temperatures. Using composite phase change mortar ensures indoor thermal comfort and minimizes indoor temperature fluctuations, implementing a heat "peak load shifting" strategy to reduce overall heating energy consumption. In conclusion, this innovative material exhibits significant potential for achieving substantial energy savings in heating systems and contributes to building energy efficiency.

The working temperature range for the battery backplane and the heat storage capacity in solar PV/T systems using phase-change materials need to be improved. In this report, docosane-dodecanol (DE-CP) binary phase-change materials with different mass fractions were prepared using the melt-mixing method, and their latent heat was tested and analyzed. The phase-change temperature range for the binary phase-change material is 20–50 ℃, which essentially covers the working temperature for the battery backplane in the PV/T system. Compared with other binary phase-change materials, the latent heat of the binary phase-change material with 60% DE mass fraction is the largest at 243.8 kJ/kg. Moreover, the high-temperature phase-change peak area for the binary phase-change material with a mass ratio of DE to CP of 6∶4 is larger than the low-temperature phase-change peak area. The distribution of the two phase-change peaks indicates that the binary phase-change material with a DE mass fraction of 60% is more suitable for application in solar PV/T systems. EG (expanded graphite) was then added to the binary phase-change material as a supporting substance to adsorb the material to enhance its thermal conductivity; finally, the composite phase-change material was obtained. The latent heat, compatibility, and thermal conductivity of DE-CP/EG composite phase-change material were measured and analyzed. The results show that the phase-change temperature range for the DE-CP/EG composite phase-change material remains at 20?–?50 ℃. There is good compatibility among the three raw materials, and the thermal conductivity increases from 0.135 W/(m·K) for the original binary phase-change material to 1.383 W/(m·K), which solves the problem of the low thermal conductivity of the phase-change material and provides a reference for the application of the composite phase-change material in solar PV/T systems.

This study presents an electric-thermal phase change energy storage system using Na₂CO₃-K₂CO₃/MgO as the heat storage medium with a heating power of 100 kW, implemented through a modular integration concept. This research involves the development of composite thermal storage materials using physical methods. Characterization analysis techniques, including scanning electron microscopy and differential scanning calorimetry, are employed to examine the composition distribution and thermal storage properties of the composite materials. By analyzing the time-temperature test curve of the heat storage and release process, we introduce the heat storage or release progress function. Investigating the changing trend of the progress function curves in different positions of the system elucidates the dynamic-heat-storage/-release process. Our findings reveal that heat transfer of hot air accumulates from the center of the heat storage module to the top, gradually diffusing to the periphery during the heat storage process. During heat release, cold air absorbs heat successively from the center of the front module, the front module surface, the middle module surface, and the rear module surface along the wind path direction. Heat in the middle and rear thermal storage modules transfers from the center to the bottom, sides, and top surface areas, thereby diffusing to the surrounding areas. A comparative analysis of the progress functions of the heat storage system based on composite phase change material and magnesium iron oxide indicates that the system experiences faster heat storage and release processes when composite phase change material is employed as the heat storage medium. Setting the heating water temperature at 70—80 ℃, the stable heating time of the composite phase change heat storage system is determined to be 1100 min, representing a 37.5% increase compared to the magnesium iron oxide heat storage system. Therefore, this study helps promote the application of phase change thermal storage technology in heating systems and serves as a reference for studying the dynamic heat exchange process in electric heating phase change energy storage systems.

This paper presents a novel structure for a phase change heat storage system incorporating double spiral coils and expanding graphite to enhance heat transfer. A model of the double spiral coil phase change heat storage system is established to simulate the impact of coil pitch and thermal properties of materials on heat storage and release performance. The study delves into the influence of natural convection of phase change materials and the enhancement of material thermal conductivity on heat transfer in confined spaces. Results indicate that reducing the pitch and increasing the number of spiral coils within limited pitch conditions can enhance the heat release performance of the heat storage system. Incorporating expanded graphite boosts the thermal conductivity of phase change materials, albeit with an increase in material viscosity. Consequently, adding the expanded graphite improves the heat transfer and exchange efficiency of the heat storage system, albeit at the cost of suppressing natural convection heat transfer. Comparative analysis reveals that, under confined space conditions, the enhanced heat transfer resulting from material thermal conductivity enhancement compensates for the heat loss attributed to inadequate natural convection heat transfer. This study underscores that the key to controlling heat transfer enhancement in phase change heat storage systems lies in the thermal conductivity enhancement of materials. Drawing on experimental and simulation approaches, this article presents a designed heat storage system structure for heating domestic hot water. The proposed system exhibits excellent heat release performance across a broad range of inlet temperatures and flow rates. When combined with an electric heater, this heat storage system achieves a heating power exceeding 3500 W with electric power consumption below 2200 W, surpassing the power limitations of typical household electric heating equipment.

To achieve sufficient utilization of industrial solid waste and reduce the cost of thermal energy storage (TES) systems, a mixture of alkaline solid waste of carbide slag (CS) and steel slag (SS) is selected at a 1∶1 ratio for CO₂ capture and sequestration. In addition, seven types of carbon-captured shape-stable phase-change composite materials (CCSMs) with different ratios of NaNO₃/CS-SS were prepared by combining CS and SS as the skeleton materials after CO₂ sequestration. Furthermore, thermogravimetric analysis was conducted to characterize the carbon sequestration properties of the CS-SS hybrid materials. Moreover, the TES performance, thermal cycling stability, chemical compatibility, and microstructure of CCS were characterized using differential scanning calorimetry (DSC), high-temperature thermal shock method, X-ray diffraction (XRD) analysis,and scanning electron microscopy. The results indicate that the carbon-sequestration rate of the CS-SS hybrid material is 24.48%. Furthermore, the mass ratio of NaNO₃, CS, and SS in the best thermal performance sample of CC-SC4 was 2∶1∶1, with its thermal storage density reaching 444.2 J/g at a working temperature of 100—400 ℃, thermal conductivity of 1.057 W/(m·K), and chemical compatibility among the components. Sample CC-SC4 exhibited excellent thermal storage performance after 1440 heating/cooling cycles.

Shaped composite phase change materials (SCPCMs) have the advantages of high energy storage density and high thermal stability. However, the internal phase change medium in the molten state is prone to leakage as it continuously absorbs heat during phase changes, resulting in material deformation and corrosion. To overcome this, a high temperature-shaped composite phase change material (HTSCPCM) was prepared using sodium hydroxide-modified fly ash (mFA) as a ceramic matrix and Al-12Si alloy powder as a phase change medium using a hybrid sintering method. Testing and characterization were conducted using scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, fully automated specific surface and porosity analyses, thermogravimetry-differential scanning calorimetry, and thermal conductivity. The results showed that sodium hydroxide-modification of FA resulted in multilevel surfaces and enhanced specific surface area (3.82 to 40.86 cm²/g) and pore volume (0.008 to 0.085 cm³/g). The Al-12Si alloy was shown to be securely bonded to the mFA ceramic matrix. The maximum loading of the matrix to the Al-12Si alloy was 65%, the latent heat of phase transition was 97.76 J/g, and the thermal conductivity was 15.10 W/(m·K). After 100 thermal cycles, the morphology of the AI-12Si/mFA HTSCPCM was unchanged, and no leakage was observed. The latent heat of the phase change was 91.32 J/g, and it decreased by only 6.6% before and after each cycle. The AI-12Si/mFA HTSCPCM prepared in this work has the advantages of a suitable phase transition temperature, high thermal conductivity, high heat storage density, and ease of processing. The results of this study indicate that this AI-12Si/mFA HTSCPCM can be used in the field of high-temperature heat storage.

In order to fully resource the use of waste concrete to capture and store CO₂, this paper utilizes waste concrete for carbon capture, and seven composite phase change heat storage materials with different mass ratios were prepared by using carbon consolidated and unconsolidated waste. Results indicate that the carbon sequestration efficiency of the waste concrete was as high as 24.7% under the specific experimental conditions. The latent heat of melting of the shape-stable phase change composites prepared by carbon sequestration was higher than that before carbon sequestration after adding the same mass fraction of phase change material. The compressive strength of SS2 was as high as 121.54 MPa, and the compressive strengths of both the carbon sequestered waste concrete and shape-stable phase change composites were significantly increased, with the highest thermal conductivity [0.648 W/(m·K)] being lower than that of the un-sequestered sample [0.884 W/(m·K)]. The shape-stable phase change composites before and after carbon sequestration had good chemical compatibility among the components, and the phase change materials were densely bonded with the skeleton materials.

With the continuous increase in the demand for high-quality fruits and vegetables, the cost of cold storage operations has become a significant concern owing to its high energy consumption. To address this issue, phase-change storage technology has been integrated with traditional cold storage to reduce operational costs. Specifically, the cold storage material is charged during off-peak hours using valley power, thereby permitting power-free operation during peak hours. To ensure high quality and safety standards for the preservation process, a low-temperature phase change material with an adjustable phase change temperature is developed. In addition, the effects of the arrangement of cold storage panels and placement of goods on the storage temperature are investigated using numerical simulations, and a cold storage system capable of operating without electricity for 16 hours is designed. The results demonstrate the potential of phase-change storage technology to significantly reduce the energy consumption and costs associated with cold storage operations for preserving fruits and vegetables while simultaneously maintaining product quality and safety.

Considering the high cost and limitations of long-distance offshore wind-power transmission in far-reaching sea, a technical route is proposed herein using ice slurry as a cold storage medium for wind-power elimination in remote offshore spots. Considering a single wind-driven generator in the South China Sea as the research object, performance and economic evaluation models were developed to analyze the cycle coefficient of performance, ice-making speed, unit power consumption, annual cost, and unit ice-making cost. The generator unit was also compared with ice-making machines in shipboard scenarios. The results showed that in the case of water extraction from below the sea surface and replenishing freshwater for ice making, the ice-making speed of the ice-slurry generator unit based on wind power reached 57.18 t/h and the unit power consumption was 39.47 kWh/t. Compared with seawater flake ice-making machines operating at the same power, the ice-making speed was increased by 80.4% and the unit power consumption was reduced by 51.1%. The unit exhibited high production capacity and energy efficiency; the ratio of annual cooling capacity loss from the ice storage tank did not exceed 2.7% of the refrigeration capacity, and it did not exceed 5% when all cooling capacity losses were combined. Moreover, it remained almost unaffected by changes in the seawater flow velocity. The insulation capability of the unit was also excellent. Considering the cooling capacity loss, the annual ice production of the unit reached 951700 tons, which can refrigerate at least 475850 tons of seafood and supply ice to more than 1100 1000-ton fishing ships, indicating that it could meet large-scale ice requirements. The unit's annual cost was 17587000 CNY, and the cost of producing ice slurry was as low as 36.96 CNY per ton, which was 47.3% less than that of a seawater flake ice-making machine in a shipboard scenario. These findings indicate the strong competitiveness and good economic feasibility of the unit.

Phase change cold storage gels have considerable potential for applications in cold chain transportation owing to their good stability. However, their high viscosity and low fluidity inhibit the natural convection during the phase change process, which affect the heat transfer performance of cold storage equipment, thereby reducing the efficiency of cold energy utilization. Herein, a two-dimensional CFD model for tube-fin-type cold storage equipment was established and the influence of the fluidity of phase change cold storage gel on its heat transfer performance was investigated based on the melting-solidification model of FLUENT software. The study compares the cold charging efficiencies of various structural cold storage equipment, introduces the dimensionless number e to represent structural cold charging efficiency, and explores the effect of various structures of cold storage equipment on the cold charging process. Results reveal that the cooling time for cold storage gel with natural convection is 12% shorter than that without natural convection at -5 ℃. Furthermore, under the effectof gravity field, the mobility of cold storage gel varies across different areas and times. Notably, during the early stage of the solidification process and in the cold storage gel above the cold storage equipment, the flow rate of cold storage gel is faster and flow field range is larger, resulting in faster heat transfer. The double-tube structure exhibits a higher cooling efficiency. This study helps to advance the application of cold storage equipment in cold chain transportation and offers a theoretical basis for optimizing the structure of cold storage equipment.

Advanced adiabatic compressed-air energy storage is a method for storing energy at a large scale and with no environmental pollution. To improve its efficiency, an advanced adiabatic compressed-air energy storage system (AA-CAES+CSP+ORC) coupled with the thermal storage-organic Rankine cycle for photothermal power generation is proposed in this report. In this system, the storage of heat from photothermal power generation is used to solve the problem of limited compression heat in the AA-CAES+CSP+ORC, while the medium- and low-temperature waste heat generation in the organic Rankine cycle power generation system further improves the energy storage efficiency. Here, a thermodynamic simulation model of the coupled system was initially constructed using Aspen Plus software, and the influence of two types of concentrated solar heat storage media on system performance was subsequently studied and compared. The results show that compared with thermal oil and solar salt, the system using solar salt as the concentrated solar heat storage medium had a superior performance, and the energy storage efficiency reached 115.9%. The round-trip efficiency reached 68.2%, exergic efficiency reached 76.8%, exergic conversion coefficient reached 92.8%, and energy storage density attained 5.53 kWh/m³. In addition, the study found that low ambient temperature, high inlet temperature, and high air turbine inlet pressure are conducive to improving the energy storage performance of the system.

Solid electric energy storage devices represent a promising avenue for efficient energy consumption. However, traditional methods that rely on resistance heating have inherent shortcomings, including prolonged heating times, uneven temperature distribution, limited lifespan of heating resistance wires, and susceptibility to aging. To significantly improve the performance and heat storage capacity of solid electric energy storage devices, this paper proposes the integration of induction heating technology, known for its rapid and pollution-free heating. We used comprehensive COMSOL simulations to investigate the impact of various current frequencies on the electromagnetic field and temperature distribution of induction heating. We also explored how fluid flow rates influence temperature uniformity within a thermal storage unit. Our findings demonstrate that when cast iron is employed as the thermal storage material and induction heating is adopted, solid electric energy storage devices exhibit superior thermal storage properties. Notably, these devices offer substantially faster initial heating rates (up to 8.5 ℃ per minute) and achieve a higher thermal storage body temperature (900 ℃) compared to traditional resistance-based devices. Moreover, under conditions of a wind speed of 0.05 m/s, the cast iron thermal storage unit exhibited optimal temperature uniformity. This innovative approach not only augments the performance of solid electric energy storage devices but also equips them with flexible and rapid response capabilities, effectively positioning them in the future electricity market.

Latent thermal energy storage (LTES) technology is employed to rectify the imbalance of time and space in the application of low-grade heat and renewable energy in heat pumps (HPs). The adaptive design of cascade latent thermal energy storage (CTS) devices and the improvement in the thermophysical properties of phase change materials (PCMs) have a crucial effect on the stable and efficient operation of coupled HP drying systems. Based on the exergy optimization of multistage heat engines, a CTS device was designed for a solar HP system, and a three-dimensional shell-tube CTS model was established according to the enthalpy method. Physical constraints such as the phase change temperature of the target material and practical application conditions were comprehensively considered, and the theoretical calculation results provided guidance for the selection and improvement of PCMs, in addition to the adjustment of the heat exchanger size. In this study, sodium acetate trihydrate (SAT)-based composite PCMs were used as the filling PCMs with a cascade layout in the CTS device, which were prepared by the addition of different concentrations of acetamide (AC) to adjust the melting temperatures. To investigate the heat-transfer characteristics and thermoregulation performance of the thermal storage processes, three-stage shell-tube CTS device and single-stage LTES device filled with three ratios of SAT/AC were numerically investigated using constant and variable inlet temperatures of solar hot water. The results revealed that the reduction in the heat transfer between the stages of the CTS device could improve the thermal storage capacity. In the latent heat-storage stage of the three-stage CTS device, the average inlet and outlet temperatures decreased by 4.41 ℃, which could adjust the peak temperature by 0.90% and generate a buffering effect on the inlet temperature. Therefore, the operating temperature range of the three-stage CTS device is wider than that of the single-stage heat-storage unit. In addition, the storage density of the three-stage CTS device was 2.39 times than that of a domestic hot-water storage tank of the same volume, which could effectively store heat from the fluctuating heat source generated by the solar collector. The uniformity of the outlet temperature and heat-transfer power of the CTS device was better than that of the single-stage heat-storage unit. This study can provide not only guidance for the preparation of stepwise PCMs but also new ideas for CTS in terms of the coordination and optimization of devices and materials.

Owing to the continuous expansion of the scale of Internet of Things (IoT) nodes, the contradiction between the growing energy consumption of buildings and the limited fossil energy reserves has surged. To facilitate increased applications of environmental thermal energy for power supply and break the bottleneck of node scale and energy consumption of environmentally friendly IoT, in this study, the fin structure of the heat sink in an environmental temperature-difference energy harvesting device based on phase-change annular thermoelectric technology is optimized. Phase-change heat storage technology is coupled the thermoelectric ring topology to exploit its combined advantages. In addition, the structure and parameters of the heat sink fin are optimized; hence, its heat storage capacity and release, as well as the temperature control performance, are enhanced, and the capability of the device to collect and utilize the environmental temperature-difference energy is further strengthened. In addition, the effects of different fin structures and parameters on the heat storage characteristics are investigated, and the heat flow transfer process and energy-harvest performance of the device are analyzed. The results reveal that with an increase in fin density, the volume fraction decreases or the relative height increases, and the heat storage performance and ATEG power generation are improved. Under the boundary conditions of sinusoidal temperature change, the peak power and efficiency of the device reach 31.57 μW and 0.073%, respectively, with a fin efficiency of 0.981. The structure V heat sink exhibits stronger heat storage and release and temperature control performance, and the capacity of the device were calculated to be 0.0453 J, which is 110.4% greater than that of structure I. This study is expected to further improve the heat storage power supply potential of an environmental temperature difference energy self-powered device and provide a foundation for the comprehensive construction of green IoT nodes.

To alleviate the typical high-energy consumption associated with greenhouse heating in winter in northern China, in this study, a greenhouse in Hebei Province is considered as the research object. Based on the existing solar-coupled ground source heat pump heating system in the greenhouse, TRNSYS software is employed to simulate a model of a solar-ground source heat pump phase-change storage heating system driven by low current. In addition, the operation of the system driven by low power is investigated, and the effect of different heat-storage temperatures of the phase-change heat-storage tank on the heating performance of the system is analyzed. Furthermore, the soil heat imbalance problem of the ground source heat pump in the heating of an agricultural greenhouse is investigated, and the economy of the solar-ground source heat pump phase-change heat-storage-heating system is analyzed. The results reveal that the optimum heat-storage temperature of the phase-change heat-storage tank is 44.4 ℃, and the utilization rate of off-peak electricity reaches greater than 98% during the entire heating season. Under the condition that the system has been running for 10 years, the buriedpipe of the solar-coupled ground source heat pump heating system stores 47232 kWh less heat than that stored by the buried pipe to the soil, and the solar-coupled ground source heat pump phase-change heat storage-heating system stores 4487 kWh more heat than that stored by the buried pipe to the soil. The solar-ground source heat pump phase-change storage heating system can better maintain the soil-temperature balance. The solar-coupled ground source heat pump heating system costs 76095 CNY for 15 years of operation, while the solar-ground source heat pump phase-change thermal storage heating system costs 35516 CNY for 15 years of operation; the operating cost is reduced by 53% compared to with that of the solar-coupled ground source heat pump heating system. The comprehensive annual cost of the solar-ground source heat pump phase-change storage heating system and the solar-coupled ground source heat pump heating system are 10890 CNY and 11920 CNY, respectively. The comprehensive annual cost is reduced by 8% in comparison with that of the solar-coupled ground source heat pump heating system, and the solar-ground source heat pump phase-change storage heating system provides better economic benefits.

Thermochemical energy storage with salt hydrates has the advantages of high heat-storage density and nearly zero heat loss in the long storage process; these are of great significance for the efficient utilization of renewable energy. The design and operation control of reactors are crucial for the performance of thermochemical heat storage of salt hydrates. However, multiphysical field-simulation software is widely used for modeling, which is not suitable for long-term research under dynamic conditions. Therefore, in this study, we establish a dynamic simulation model for thermochemical reactors. In addition, sensitivity analysis was conducted to determine the effects of factors such as inlet air temperature, water-vapor partial pressure, flow rate, and reactor size on the outlet parameters. The results show that the airflow rate significantly affected the response time, stable output time, and heat release power. In addition, the partial pressure of water vapor greatly affected the temperature rise, while displaying almost no effect on the total heat release. Finally, by considering a residential building in Changsha as an example, we studied the charging process of the reactor under typical daily meteorological parameters during winter. Compared with the condition without control strategies, the adoption of appropriate control strategies could effectively improve the matching between the heat release power of the reactor and its heat load. The findings of this study could provide a guide for the design and control strategy determination of thermochemical reactors.

Northern weather is characterized by typical cold winters and hot summers, with high light intensity in the summer, which is suitable for the development of solar vegetable greenhouse technology. However, winters are cold, and the use of vegetable greenhouses is subject to seasonal restrictions. To solve the problem of excess heat in summer and the insufficient heating temperature of vegetable greenhouses in winter, Fluent software is employed to simulate the heat storage of ordinary U-shaped buried pipes with a double wing, 90° double wing, four wing, 45° four wing, and six-wing U-shaped buried pipe heat accumulator in the summer, and the effects of different buried pipe structures on the heat storage performance are compared and investigated. The results reveal that the U-shaped buried pipe structure is distributed up and down, and when the fluid is up and down, the liquefaction area of the same wing-type U-shaped buried pipe structure is greater than that when it is finned longitudinally. The temperature of the backfill center position (i.e., x=0 m, y=0 m) reveals that longitudinal winging is greater than transverse winging, whereas lateral winging leads to an increase in the radial temperature. At the same time, the double-winged U-shaped buried pipe exhibits the highest liquid phase rate, while the 45° four-winged U-shaped buried pipe exhibits the lowest liquid phase rate. The six-winged U-shaped buried pipe exhibits the fastest heat storage, whereas the 45° four-winged U-shaped buried pipe exhibits the slowest heat storage. Different U-shaped buried pipe structures located in phase-change backfill materials considerably affect temperature. The heat storage of the winged U-shaped buried pipe is 15—39 MJ greater than that of the ordinary U-shaped buried pipe, the double-winged U-shaped buried pipe structure exhibits the highest heat storage, and the 45° four-wing U-shaped buried pipe exhibits the least heat storage.

Phase change energy storage technology harnesses the unique properties of phase change materials to release or absorb latent heat during phase transitions, enabling energy storage in the form of latent heat. This technology holds promising applications in electric vehicles, renewable energy storage, grid peaking, and smart grids owing to its high energy density, extended lifespan, and high power. It presents a viable solution for energy transition and efficient energy utilization. This paper delves into the advantages, disadvantages, and application scopes of phase change materials within various temperature zones: ultra-low (-190 ℃ to -50 ℃), low (-50 ℃ to 0 ℃), general (0 ℃ to 100 ℃), and high (100 ℃ to 700 ℃) temperatures. This categorization is based on an exploration of the pertinent literature. To enhance phase change material properties, methods including thermal conductivity enhancement, subcooling reduction, phase change temperature regulation, and improvement of cycling stability are discussed in this study. Moreover, it examines the preparation methods of composite phase change materials, introducing microencapsulation, impregnation, sol-gel, and ultrasonic methods, while elucidating the drawbacks of the latter three methods. Finally, it envisions potential future applications of phase change materials, aiming to serve as a reference and guide for further research in the domain of energy storage using phase change energy storage technology.

Shape-stabilized organic phase-change materials have the advantages of low undercooling, low phase segregation, and good chemical stability, with wide application prospects in building-energy saving, battery thermal management, and aviation thermal protection. However, these materials are usually flammable, a property that seriously affects their application safety. Therefore, the flame-retardant properties of such shape-stabilized organic phase-change materials must be studied urgently. This study provides a brief overview on the classification of phase-change materials, the types of flame retardants that can be used, and the flame retardancy mechanisms. In addition, the study details the preparation methods and types of commonly used flame-retardant composites. The effects of various flame retardants on the thermal safety performance of shape-stabilized phase-change heat-storage materials are analyzed based on limiting oxygen index, total heat release rate, and peak heat release rate. In conclusion, the strategies of adding synergistic flame retardants and the chemical modification of phase-change materials are proposed to further enhance the flame retardancy of phase-change materials. The findings of this study are expected to promote the expansion of the application field of shape-stabilized phase-change materials, improve the safety of phase-change energy-storage systems, and help build a safer, environmentally friendly, and efficient energy storage and utilization system

Packed-bed latent thermal energy storage (PLTES) systems enable the reuse of thermal energy and efficient collection of renewable energy, making significant contributions toward achieving carbon neutrality. Considering the intricate transient nature of PLTES systems, this report begins by summarizing the numerical models employed for predicting the thermal performance of these systems. Subsequently, the performance evaluation of PLTES systems is addressed and presented together with the methodology, highlighting the advantages and distinctions between exergy efficiency analysis and energy efficiency analysis. In addition, by analyzing and summarizing the performance optimization methods applied to PLTES systems, cylindrical tanks with an aspect ratio greater than 1 are shown to be usually preferred. According to the selection of practical application scenarios, thermal oil, molten salt, and air are generally used as heat transfer fluids, and shape-stabilized phase-change materials are more promising for application. Subsequently, the report introduces the application of the PLTES system in heat recovery from industrial waste and efficient use of solar energy. Finally, prospects for the future development of PLTES systems are discussed, including areas such as tank design, heat storage unit design, operational strategies, high-temperature environments, and system cost-effectiveness. This discussion aims to provide insights and guidance to promote the development and practical application of PLTES systems.

As a high-temperature heat transfer and storage medium, molten salt is widely used for solar thermal power generation and the flexible transformation of thermal power plants. First, the potential functions of the molecular dynamics of molten salt were summarized and analyzed. This indicated that to reduce simulation errors, the Buckingham potential with coulomb force is more suitable for nitrate and the BMH potential is more suitable for carbonate and chloride salt. Second, an analysis of the thermal properties of molten salt indicated that the addition of Ca²⁺ to solar salt decreased its melting point and increased its viscosity, and the specific heat capacity of nitrate decreased with increasing NO^2- concentration. Increased Li⁺ concentrations increased the specific heat capacity and thermal conductivity of chloride salt but also increased the simulation error; however, with increased K⁺, the specific heat capacity error decreased and the error when calculating residual heat properties increased. The carbonate simulation error was relatively small, which is consistent with experimental results. The simulation errors were large with the addition of K⁺ or Li⁺, and the increased potential energy between ions led to the loss of some particles. It was found that the influence of the boundary effect after the introduction of a boundary condition increased the error; however, the error was reduced by increasing the number of molecules, the potential energy truncation distance correction, and the simulation time step. Currently, studies on the molecular dynamics of molten salt with the same cation and different anions are rare. Exploring the influence of nanofluids on molten salt molecular dynamics, reducing the simulation error of molecular dynamics, and conducting research on the corrosion characteristics of molten salt based on molecular dynamics is the next research direction of molten salt molecular dynamics.

Phase change energy storage materials is a type of energy storage materials that utilize physical phase changes at a specific temperature to achieve energy storage and release. They have the advantages of high heat storage density, fast heat release rate, and uniform distribution of heat storage temperature. In the application of building engineering, it can effectively reduce temperature fluctuations in building structures and achieve the goal of energy conservation and emission reduction. However, there is still a long way to go in the research of its specific application effects. In order to improve the application effectiveness of new phase change energy storage materials in construction engineering, the article conducts research on the characteristics of new phase change energy storage materials based on starch, cellulose, and lignin as carriers. It also analyzes their applications in roof insulation, wall insulation, glass greenhouses, solar photovoltaic power generation, and other fields. It also puts forward prospects and insights for its future development direction. I hope to better promote the integration of new phase change energy storage materials with other building energy-saving technologies, and further enhance the application scope and effectiveness of phase change energy storage materials.

This paper emphasizes the application of phase change thermal storage technology in green buildings and its profound impact on building performance. Through detailed analysis and discussion, we examine the practical implementation of phase change thermal storage technology in building envelope structures, air conditioning systems, and hot water systems, as well as delve into its multifaceted influence on building energy consumption, indoor thermal environment, economy, and environmental friendliness. The findings reveal that phase change thermal storage technology not only significantly reduces building energy consumption and enhances indoor thermal environment but also boosts the economic and environmental sustainability of buildings. However, despite its evident advantages, the technology still encounters certain challenges in practical applications. Looking ahead to future trends, phase change thermal storage technology is expected to play an even more significant role in green buildings. Consequently, we propose pertinent policy suggestions and measures to promote the widespread application of phase change thermal storage technology in green buildings, thereby advancing sustainable development within the construction industry.

This paper delves into the pivotal role of phase change thermal energy storage (PC-TES) technology in global energy and environmental challenges, emphasizing real-world efficiency issues. Through the application of computer technologies such as data collection, artificial intelligence algorithms, and digital twin technology, the PC-TES system achieves comprehensive monitoring, significantly enhancing its energy efficiency. The focus is on the core efficiency issues, including the selection of thermal storage materials and phase change materials, system structural design, heat and mass transfer processes, and thermodynamic cycle efficiency. The paper proposes a series of optimization methods, such as in-depth research into the system's operational principles, exploration of thermal storage material combinations, and optimization of system structural design. The critical nature of performance evaluation and monitoring for PC-TES systems is highlighted, encompassing the role of SCADA systems, real-time monitoring of key parameters, and data analysis supporting decision-making. Lastly, the paper underscores the innovative application of artificial intelligence technology and digital twin technology in PC-TES, providing intelligent and efficient means for system performance enhancement.

The real-time storage power of automotive electric thermal phase-change energy storage system exceeds the preset power value, which will cause excessive transformation of power resources and lead to energy waste. This paper designs a dynamic optimization method for heat storage performance of new energy low-carbon vehicle electric thermal phase change energy storage system. The feasibility of low-carbon mechanism of new energy was analyzed, the objective coordination function of electric heating energy storage was constructed, the active power threshold of phase change energy storage system was set, the power conversion relationship between transformer and electric heater group was combined, the constraint conditions of dynamic heat storage were solved, and the dynamic heat storage performance of automotive electric heating phase change energy storage system was analyzed. Experiments show that the method can avoid the situation that the real-time storage power exceeds the preset power value.

It is the main development direction of thermal storage system to implement high efficiency conversion of heat and avoid energy waste. Computer software is widely used in various fields, and its excellent performance has been consistently praised. How to use the application characteristics of computer software to achieve the purpose of solving energy resources has become an urgent problem to be solved. In view of the above problems, the research of computer software processing technology in thermal energy storage is carried out. Firstly, taking heat pump energy storage and steam drive compressed air thermal energy storage system as examples, the development form of heat storage technology is analyzed. Then, the influence of computer software processing technology on thermal energy storage is determined from two aspects of power mixed distribution and resource integrated scheduling. Finally, software technology is used to adjust the working characteristics of thermal storage system, and the coupling optimization of the system is implemented.