Search

Photovoltaic technology plays a crucial role in harnessing renewable energy. While photovoltaic panels directly convert solar energy into electricity, more than 50% of solar radiation is lost as waste heat, diminishing the overall efficiency of the panels. This study reviews various cooling technologies for photovoltaic systems, focusing on the use of phase change materials for cooling in photovoltaic systems. Phase change materials, known for their high latent heat capacity, are extensively used in thermal energy storage applications. Incorporating phase change materials in photovoltaic systems can increase thermal storage potential by 30–50% compared to conventional systems, leading to a 70% extension in heat storage duration and various levels of enhanced power output. The main purpose of the article is to review the advantages and disadvantages of various technologies, determine the research direction of phase change materials for cooling systems in photovoltaics, and ensure the reliability of this technology. [ABSTRACT FROM AUTHOR]

In order to solve the phase separation problem of Na2S2O3·5H2O–CH3COONa·3H2O PCM (phase change material), sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), xanthan gum (XG), sodium polyacrylate (PAAS) and polyacrylamide (PAM) were selected as additives. The effects of different proportions of the above thickeners on the supercooling degree, phase separation, phase change temperature and latent heat of Na2S2O3·5H2O–CH3COONa·3H2O system were studied by using the cooling curve and DSC, so as to screen the best thickener for eutectic PCM. The experimental results show that CMC, XG and PAAS can eliminate the phase separation of Na2S2O3·5H2O–CH3COONa·3H2O. Among them, the optimal ratio of CMC, XG and PAAS is 3 mass%, 3 mass% and 1 mass%, respectively. From the perspective of heat storage performance, PAAS is the optimal thickener for Na2S2O3·5H2O–CH3COONa·3H2O. The phase change temperature is 40.5 °C. The subcooling degree is about 14.7 °C, and the latent heat is about 221 J g−1. The melting time is 15 min. Only PAAS can make Na2S2O3·5H2O–CH3COONa·3H2O eutectic PCM completely exothermic at room temperature, which can not only play the role of thickener to eliminate phase separation, but also is a nucleating agent. After 100 melting-solidification cycles, the change rate of latent heat value was only 5%, and the change rate of phase transition temperature was less than 1%. Considering heat storage performance and cyclic stability, PAAS is the optimal thickener for Na2S2O3·5H2O–CH3COONa·3H2O PCM. [ABSTRACT FROM AUTHOR]

Summary: In order to find phase change materials that can be better applied in the field of solar collectors, the phase change heat storage properties of urea (U) and ammonium bromide (AB) were studied. The eutectic ratio of UAB was found by the Edison method, and different additives were added to UAB by dipping and mixing. The structure and property of the composites were characterized by X‐ray powder diffraction (XRD), scanning electron microscope (SEM), differential scanning calorimetry (DSC), and TG/TGA, respectively. The results showed that the eutectic ratio of UAB was 6:3; it was weakly acidic after melting not layered. When 6‐wt% EG and 1‐wt% nanometer titanium dioxide (TiO2) were added, the thermal conductivity of the material increased by 3.62 times; the thermal diffusivity was increased by 6.77 times. When the mass fraction of EG is between 1% and 6%, the larger the mass fraction of EG, the greater the thermal conductivity of the material. After 1000 cycles, the composite material performance was stable; at the same time, the used materials can be used as fertilizers to solve the problem of material pollution, which indicated that the prepared UAB/TiO2/EG composite PCMs had great application prospect in the field of solar collectors. [ABSTRACT FROM AUTHOR]

Summary: Composite expended graphite (EG)/Ba(OH)2·8H2O form‐stable phase change material (PCM) is prepared with porous adsorption method in this study to solve the problem of the leakage risk in the application process based on barium hydroxide octahydrate. In addition, the thermal properties and stability have been measured and verified. Thermal conductivity of each group composite material was enhanced by about two to four times, while the addition has little negative effect on the other properties. With microscopic features being characterized by scanning electron microscope (SEM), the experimental result demonstrates that the composite material with 7 wt% of EG is optimal to be a saturated state between two phases. After the thermal cyclings of 100, 300, and 500 times, thermal properties did not change dramatically, which can be used as an ideal material for solar thermal storage system within finite thermal cyclings. In order to simulate the operating condition of solar energy or waste heat storage, the composite material was encapsulated in the heat storage unit with pipe bundle, and heat storage/release experiences were performed to test the performance of the material and hot water supply. The results indicate that the composite material is qualified to storage and release sufficient heat. The experimental data can provide necessary technical reference for engineering design and effect prediction in practical application. [ABSTRACT FROM AUTHOR]

[Display omitted] • The PCM used to control the chip temperature is summarized. • The research methods and results of PCM being encapsulated in chip modules are reviewed. • The standard for selecting chip-level PCM is proposed. • A structure to solve the PCM leakage problem and a theory of selecting PCM on the micro-scale are introduced. With the rapid development of integrated circuits, chips are gradually miniaturized, but the number of transistors inside them increases exponentially, which increases the complexity and power density of the chip. The increase in power density makes the peak temperature of the chip higher, which reduces the chip's performance and shortens its life. Heat management using the latent heat storage(LHS) technique is nowadays employed to reduce the chip's temperature peak. This paper reviews the theoretical basis of phase change materials(PCMs) applied to chip thermal management technology and summarizes the application progress of PCMs in electric chip thermal management through the research of recent related literature. This paper is composed of three parts. The first part introduces different types of PCMs used in the field of chip thermal management, especially composite PCMs. The second part discusses non-embedded cooling solutions, focusing on analyzing the effect of using thermal conductivity enhancers (TCE) to improve the thermal performance of the PCM heat sink. The third part is a pioneering review of the research methods and conclusions of embedded cooling, showing that the application of PCM on the micro-scale has an important effect on suppressing the temperature peak of electronic chips. [ABSTRACT FROM AUTHOR]

Calcium ions can react with polyethylene glycol (PEG) to form a form-stable phase change material, but the low thermal conductivity hinders its practical application. In this paper, hydroxylated multi-walled carbon nanotubes (MWCNTs) with different mass are introduced into PEG1500·CaCl2 form-stable phase change material to prepare a new type of energy storage material. Carbon nanotubes increased the mean free path (MFP) of phonons and effectively reduced the interfacial thermal resistance between pure PEG and PEG1500·CaCl2 3D skeleton structure. Thermal conductivity was significant improved after increasing MWCNTs mass, while the latent heat decreases. At 1.5 wt%, composite material shows the highest phase change temperature of 42 °C, and its thermal conductivity is 291.30% higher than pure PEG1500·CaCl2. This article can provide some suggestions for the preparation and application of high thermal conductivity form-stable phase change materials. [ABSTRACT FROM AUTHOR]

With the rapid increase of the thermal power of electronic devices, phase change material(PCM) have shown great application prospects in the field of electronic thermal management. However, due to the irregular surface of the electronic device, PCM can only act on the back of the component or the outside of the package, which leads to the occurrence of heat transfer hysteresis. In order to reduce the heat transfer distance between the heat source and PCM, a new type of ER/SAT/DSP composite functional material with thermal control function was prepared in this paper to solve the key technical problem of fluid seamless packaging thermal control. The composite material is encapsulated in a fluid state and will no longer melt after solidification. Through thermophysical experiments and morphological characterization, the results show that when the mass fraction of PCM is 35%, the composite material has the best physical properties and application performance. And after 200 thermal cycles, the leakage rate is only 3.7%. Through the PTC thermal control experiment, the results show that the maximum temperature at different positions of the device for pouring the new composite was reduced by 7.4 °C and 8.1 °C, respectively, and the operation time corresponding to different temperatures was increased by 5.76 times, 5.80 times and 6.98 times, respectively. Therefore, the composite material shows a good thermal control ability for electronic components of any surface shape. [ABSTRACT FROM AUTHOR]

In order to alleviate the contradiction between the growing energy demand and the limited fossil energy, intensifying research and development of application technologies that utilize renewable energy is necessary. Energy storage technology using PCMs is a frontier research field with great application prospect. As a kind of phase change energy storage materials, organic PCMs (OPCMs) have been widely used in solar energy, building energy conservation and other fields with the advantages of appropriate phase change temperature and large latent heat of phase change. However, low thermal conductivity and liquid leakage problem restrict the further application of OPCMs. Compounding organic materials with other materials can effectively improve this situation. This paper focuses on the compound types of organic PCMs and the principles of various composite technologies. And the development direction of organic composite PCMs in the future and the improvement of composite technology are discussed in the end of the paper. • The types of various organic composite PCMs are reviewed. • The principle of compound ratio between organic phase change materials is reviewed. • The technology and principle of preparing organic shape setting materials by porous materials are reviewed. • The principle of microencapsulation technology in the modification of organic phase change materials is reviewed. • Suggestions for wider application of organic composite PCMs are listed. [ABSTRACT FROM AUTHOR]

• The research progress of flexible composite phase change materials in BTMS applications is integrated. • The methods of PCM to enhance heat transfer performance and safety performance are summarized. • The flexible mechanism of FCPCM in BTMS is discussed in terms of molecular structure, interactions and mechanistic aspects. • The challenges of FCPCM in inorganic material development, recyclability and protection performance are presented. The trend for electric vehicles to replace traditional fuel vehicles is becoming increasingly apparent with the global tendency towards carbon peaking and carbon neutrality. As the core of electric vehicles, the working safety of lithium-ion batteries is becoming more and more important. This review presents an overview of the battery thermal management system (BTMS) based on flexible composite phase change materials (FCPCM), which discusses the flexibility generation mechanism of FCPCM for BTMS in terms of molecular structure, interactions and mechanistic aspects. Before introducing FCPCM, this review summarizes the approaches of phase change materials (PCM) in enhancing thermal conductivity, anti-leakage performance and safety performance. However, there are still defects such as strong rigidity and poor mechanical strength. The inclusion of flexible matrix could effectively improve the flexibility. Microscopically, flexibility is enhanced by the creation of the flexible structure. At the contact interface, the enhanced flexibility increases the interfacial wettability, thus reducing the contact thermal resistance between the PCM and the cell, and enabling the heat transfer performance to be improved. Due to the different flexible materials added, the microscopic mechanisms vary, including flexible structural support, physical cross-linking of microscopic molecular chains and chemical bonding cross-linking between molecules. Thermal induced flexibility enhances the packaging performance of FCPCM. Furthermore, FCPCM offers considerable improvement in mechanical and shape memory properties due to inter-molecular interactions. This review provides a timely introduction to the emerging advantages of FCPCM over traditional composite PCMs for BTMS applications. Finally, the challenges and difficulties encountered in the application of FCPCM in batteries are pointed out, and an outlook on future research directions is given. [ABSTRACT FROM AUTHOR]

Molten barium hydroxide (BHO) with strong alkalinity will absorb CO 2 in the air and denaturing part of BHO, so it is very important to treat it with liquid seal. In this paper, the effects of liquid seals with different cooling methods and white suspended substances on the phase change process of BHO were compared for phase change experiments, so as to study the influencing factors of powdery expansion of BHO and the crystal crystallization mode. The experimental results show that the probability of powdery expansion of BHO increases with the decrease of cooling rate. Liquid paraffin and high temperature silicone oil can play the role of air insulation, but will make BHO supercooling and powder expansion probability increase, some white powder suspended between molten BHO and liquid sealing material (BaCO 3 attached to tiny bubbles) has a certain promoting effect on nucleating crystallization of BHO, and the supercooling degree of BHO without white powder will increase again, the surface of the BHO crystal shows a tight structure around the loose and porous center, known as a branch cavity structure, which becomes apparent as the cooling rate increases. This experiment provides a reference for the study of phase change materials in the field of phase change energy storage. • The cause and influencing factors of powdered expansion of BHO were discovered. • The effect of liquid seal on the phase transformation process of barium hydroxide octahydrate was discovered. • The crystallization mode and macroscopic crystal structure of barium hydroxide octahydrate were discovered. [ABSTRACT FROM AUTHOR]