Solid-liquid Phase Change Materials Research Articles

Double-network aerogel-based eutectic composite phase change materials for efficient solar energy storage and building thermal management

Phase change materials (PCMs) have shown great promise in solar energy storage and thermal management of buildings. Nevertheless, the solid-liquid PCMs currently used in these applications face multiple challenges that need to be addressed, such as inadequate solar absorption capacity, leakage issues, and low phase change enthalpy. In this research, urea and sodium acetate trihydrate (SAT) were employed as the main PCMs, while disodium hydrogen phosphate dodecahydrate (DHPD) served as the nucleating agent. Additionally, we used polyvinyl alcohol/silica (PVA/SiO2) aerogel as a porous support structure. Carbon nanotubes (CNTs) were also introduced as photothermal conversion materials to fabricate a photothermal conversion-type double-network aerogel-based eutectic composite PCM (ECPCM). The prepared ECPCM exhibited excellent shape stability, high mechanical strength, and outstanding photothermal conversion performance. Moreover, the ECPCM demonstrated good flame retardancy, low supercooling, and the absence of phase separation issues. Furthermore, the ECPCM demonstrated efficient solar energy storage capacity and outstanding performance in building thermal management. This study offers a new perspective on the advancement of ECPCMs in solar energy storage and thermal management of buildings.

Silica-based aerogels encapsulate organic/inorganic composite phase change materials for building thermal management

Phase change energy storage materials are widely used in thermal management because they reduce energy consumption and effectively address issues such as energy supply and demand mismatches. However, challenges such as leakage in solid-liquid phase change materials (PCMs), flammability in organic solid-liquid PCMs, and supercooling and phase separation in inorganic solid-liquid PCMs still need to be resolved for their practical applications. In this study, we used methyl palmitate, dodecahydrate disodium hydrogen phosphate, and decahydrate sodium carbonate as the main PCMs, sodium carboxymethyl cellulose as an emulsifier and thickener, and silica aerogel as the encapsulating material to successfully prepare a novel shape-stabilized organic/inorganic composite PCM (CPCM). The prepared CPCM exhibits excellent shape stability and flame retardancy without supercooling or phase separation issues. In addition, the prepared CPCM has a high latent heat value (174.1 J/g) and a suitable phase transition temperature (22.9 °C), and its thermal performance remains basically unchanged after 100 heating/cooling cycles. Furthermore, this CPCM also demonstrates exceptional performance in building thermal management. This study provides a new solution to the problems of flammability, supercooling, phase separation and easy leakage of CPCM currently used in the field of building thermal management.

Confined Crystallization Polyether-Based Flexible Phase Change Film for Thermal Management.

Phase change materials (PCMs) possess the potential to regulate temperature by utilizing their thermal properties to absorb and release heat. Nevertheless, the application of PCMs in thermal management is constrained by issues such as liquid leakage and limited flexibility. In this study, we propose a novel approach to address these challenges by incorporating a pore structure within nanofibers to confine the crystallization of phase change molecules, thereby enhancing the flexibility of the composite material. Additionally, inspired by the adaptive mechanisms observed in plants, we have developed a form stable PCM based on polyether, which effectively mitigates the issue of liquid leakage at higher temperatures. Despite being a solid-liquid PCM at its core, this material exhibits molecular-scale flow and macroscopic shape stability as a result of intermolecular forces. The composite film material possesses remarkable flexibility, efficient thermal management capabilities, adjustable phase transition temperature, and the ability to undergo repeated processing and utilization. Consequently, it holds promising potential for applications in personal thermal energy management.

Confined Crystallization Polyether-Based Flexible Phase Change Film for Thermal Management.

Phase change materials (PCMs) possess the potential to regulate temperature by utilizing their thermal properties to absorb and release heat. Nevertheless, the application of PCMs in thermal management is constrained by issues such as liquid leakage and limited flexibility. In this study, we propose a novel approach to address these challenges by incorporating a pore structure within nanofibers to confine the crystallization of phase change molecules, thereby enhancing the flexibility of the composite material. Additionally, inspired by the adaptive mechanisms observed in plants, we have developed a form stable PCM based on polyether, which effectively mitigates the issue of liquid leakage at higher temperatures. Despite being a solid-liquid PCM at its core, this material exhibits molecular-scale flow and macroscopic shape stability as a result of intermolecular forces. The composite film material possesses remarkable flexibility, efficient thermal management capabilities, adjustable phase transition temperature, and the ability to undergo repeated processing and utilization. Consequently, it holds promising potential for applications in personal thermal energy management.

Self-healing, adaptive and shape memory polymer-based thermal interface phase change materials via boron ester cross-linking

Addressing the thermal resistance between rough interfaces without applying pressure to the interfacial sandwich has been a challenge. Herein, a thermal interface phase change material (TIPCM) is designed to realize a 3D support skeleton with a dynamic crosslinking network by introducing a boron ester crosslinking backbone into paraffin wax (PW) and ethylene-octene copolymer (EOC), thus enabling the TIPCM to ensure mechanical integrity without leakage even above the melting temperature of EOC. The chemical cross-linking between the organic solid–liquid phase change material (PCM) and the polymer realizes thermally triggered self-healing and adaptive shape memory properties. The phase transition of PW leads to a decrease in the modulus of TIPCM and activates the ester exchange of the dynamic covalent bonding of boron esters, which allows TIPCM to self-heal and self-adapt to a variety of object surfaces. These enabled the TIPCM to fill the interface gaps through small stress deformations, forming an interlocking structure that reduces contact thermal resistance and promotes heat transfer. The obtained TIPCM achieves excellent chip thermal management performance, cooling the analog CPU temperature by 67 °C at 5 V. In conclusion, this study provides a potential strategy for redesigning TIPCMs with high latent heat and special physical properties for thermal management.

Self-healing, adaptive and shape memory polymer-based thermal interface phase change materials via boron ester cross-linking

Addressing the thermal resistance between rough interfaces without applying pressure to the interfacial sandwich has been a challenge. Herein, a thermal interface phase change material (TIPCM) is designed to realize a 3D support skeleton with a dynamic crosslinking network by introducing a boron ester crosslinking backbone into paraffin wax (PW) and ethylene-octene copolymer (EOC), thus enabling the TIPCM to ensure mechanical integrity without leakage even above the melting temperature of EOC. The chemical cross-linking between the organic solid–liquid phase change material (PCM) and the polymer realizes thermally triggered self-healing and adaptive shape memory properties. The phase transition of PW leads to a decrease in the modulus of TIPCM and activates the ester exchange of the dynamic covalent bonding of boron esters, which allows TIPCM to self-heal and self-adapt to a variety of object surfaces. These enabled the TIPCM to fill the interface gaps through small stress deformations, forming an interlocking structure that reduces contact thermal resistance and promotes heat transfer. The obtained TIPCM achieves excellent chip thermal management performance, cooling the analog CPU temperature by 67 °C at 5 V. In conclusion, this study provides a potential strategy for redesigning TIPCMs with high latent heat and special physical properties for thermal management.

Boosting thermal energy transport across the interface between phase change materials and metals via self-assembled monolayers

Thermal energy storage using phase change materials (PCMs) has great potential to reduce the weather dependency of sustainable energy sources. However, the low thermal conductivity of most PCMs is a long-standing bottleneck for large-scale practical applications. In modifications to increase the thermal conductivity of PCMs, the interfacial thermal resistance (ITR) between PCMs and discrete additives or porous networks reduces the effective thermal energy transport. In this work, we investigated the ITR between a metal (gold) and a polyol solid–liquid PCM (erythritol) at various temperatures including temperatures below the melting point (300 and 350 K), near the melting point (390, 400, 410 K, etc) and above the melting point (450 and 500 K) adopting non-equilibrium molecular dynamics. Since the gold-erythritol interfacial thermal conductance (ITC) is low regardless of whether erythritol is melted or not (<40 MW m−2 K−1), self-assembled monolayers (SAMs) were used to boost the interfacial thermal energy transport. The SAM with carboxyl groups was found to increase the ITC most (by a factor of 7–9). As the temperature increases, the ITC significantly increases (by ∼50 MW m−2 K−1) below the melting point but decreases little above the melting point. Further analysis revealed that the most obvious influencing factor is the interfacial binding energy. This work could build on existing composite PCM solutions to further improve heat transfer efficiency of energy storage applications in both liquid and solid states.

CFD simulation of solid/liquid phase change in commercial PCMs using the slPCMlib library

Modelling the solidification and melting behavior of phase change materials (PCMs) can present several challenges, including non-isothermal phase change, multi-step transitions, complex enthalpy-temperature relations and convective heat transfer. To tackle these challenges, this study proposes a novel numerical method based on real experimental data for modelling complex phase change behavior of commercial PCMs in Ansys Fluent CFD software. The phase transition of PCMs is simulated with the apparent heat capacity (AHC) method, which is implemented as a User-Defined Function (UDF). Heat convection is simulated with the Boussinesq approximation. The method is validated by comparing to the Ansys Fluent built-in Solidification and Melting (S&M) model for the case of piecewise constant heat capacity. The results show that AHC method provides excellent agreement with S&M model for a piecewise constant heat capacity model. In addition, the AHC method solves convergence problems even for narrow phase change temperature ranges when a smooth heat capacity function is assumed. Finally, the AHC model is also tested on a set of commercial PCMs exhibiting complex phase change behavior. Temperature dependent specific heat capacities are determined from heat capacity data provided by PCM manufacturing companies and are imported as cubic Hermite spline functions from the solid-liquid phase change material library slPCMlib available at https://slpcmlib.ait.ac.at/. From the presented case study and tested PCMs it can be concluded that the AHC method is numerically robust when used with sufficiently smooth heat capacity functions, and it can be recommended for the analysis of heat transfer with PCMs showing a complex phase change behavior.

Thermal management of high-powered short-duration electronics aided by a phase change material thermal energy storage

Quantifying the performance of phase change materials (PCMs) for thermal energy storage in high-power short-duration electronics applications requires performing tests that push the material to its limit. This involves designing experiments to test solid-liquid PCMs in near real-world thermal load conditions to test its performance. Conventional cooling methods are sized to manage the maximum loading the cooling system will be subjected to in its operation, even if this loading occurs for a short period of time. This design ethos is inefficient and results in heavy and expensive equipment being used in an application where it will be underutilized most of its useful life. In this work, a PCM thermal energy storage (TES) device was built using a plate-and-frame heat exchanger and investigated to determine the suitability of this system to manage the temperature of high-power electronics with a low duty cycle. These experiments showed how a PCM-TES can be used in conjunction with conventional temperature management equipment to create a reliable cooling solution while allowing the conventional cooling components to be decreased in size and capacity. This work shows that, for a given application, a cooling system can be more efficiently designed with the use of a PCM-TES and opens the door to additional research on this topic.

Phase Engineered Composite Phase Change Materials for Thermal Energy Manipulation.

Phase change materials (PCMs) present a dual thermal management functionality through intrinsic thermal energy storage (TES) capabilities while maintaining a constant temperature. However, the practical application of PCMs encounters challenges, primarily stemming from their low thermal conductivity and shape-stability issues. Despite significant progress in the development of solid-solid PCMs, which offer superior shape-stability compared to their solid-liquid counterparts, they compromise TES capacity. Herein, a universal phase engineering strategy is introduced to address these challenges. The approach involves compositing solid-liquid PCM with a particulate-based conductive matrix followed by surface reaction to form a solid-solid PCM shell, resulting in a core-shell composite with enhanced thermal conductivity, high thermal storage capacity, and optimal shape-stability. The core-shell structure designed in this manner not only encapsulates the energy-rich solid-liquid PCM core but also significantly enhances TES capacity by up to 52% compared to solid-solid PCM counterparts. The phase-engineered high-performance PCMs exhibit excellent thermal management capabilities by reducing battery cell temperature by 15°C and demonstrating durable solar-thermal-electric power generation under cloudy or no sunshine conditions. This proposed strategy holds promise for extending to other functional PCMs, offering a compelling avenue for the development of high-performance PCMs for thermal energy applications.

Solid–liquid phase transition simulated by the lattice Boltzmann model: from pore scale to representative elementary volume scale

Purpose This paper aims to establish a lattice Boltzmann (LB) method for solid-liquid phase transition (SLPT) from the pore scale to the representative elementary volume (REV) scale. By applying this method, detailed information about heat transfer and phase change processes within the pores can be obtained, while also enabling the calculation of larger-scale SLPT problems, such as shell-and-tube phase change heat storage systems. Design/methodology/approach Three-dimensional (3D) pore-scale enthalpy-based LB model is developed. The computational input parameters at the REV scale are derived from calculations at the pore scale, ensuring consistency between the two scales. The approaches to reconstruct the 3D porous structure and determine the REV of metal foam were discussed. The implementation of conjugate heat transfer between the solid matrix and the solid−liquid phase change material (SLPCM) for the proposed model is developed. A simple REV-scale LB model under the local thermal nonequilibrium condition is presented. The method of bridging the gap between the pore-scale and REV-scale enthalpy-based LB models by the REV is given. Findings This coupled method facilitates detailed simulations of flow, heat transfer and phase change within pores. The approach holds promise for multiscale calculations in latent heat storage devices with porous structures. The SLPT of the heat sinks for electronic device thermal control was simulated as a case, demonstrating the efficiency of the present models in designing and optimizing SLPT devices. Originality/value A coupled pore-scale and REV-scale LB method as a numerical tool for investigating phase change in porous materials was developed. This innovative approach allows for the capture of details within pores while addressing computations over a large domain. The LB method for simulating SLPT from the pore scale to the REV scale was given. The proposed method addresses the conjugate heat transfer between the SLPCM and the solid matrix in the enthalpy-based LB model.

Design and Construction of a Rapid Milk Chiller Using Cold Energy Storage System in the Context of Bangladesh

Milk is a highly sensitive product that must be collected and cooled within a few hours to reduce losses due to chemical spoilage and to preserve quality. As milk production is often remote from markets and processing facilities, milk chillers using thermal energy storage (TES) units provide the means for preserving quality through chilling during a power cut and hygienic storage before onward transportation to processing facilities and operation of the chiller at maximum thermal efficiency. This study gives an overview of thermal energy storage (TES) base rapid milk chiller. A review of TES for cold storage applications utilizing solid-liquid phase change materials has been done. Various perspectives were focused on the different stages of the work: phase change materials (PCMs), exemplification, improvement in exchange of heat, and the impact of the whole process on the quality of the milk Materials used as potential PCMs by specialists at low temperatures (less than 4 °C) are condensed and a portion of their thermo-physical properties are accounted for. The concept of planning and measuring procedures based on the determined load profile for structure day is introduced. In this design of a milk chilling unit using thermal energy storage, two cycles have been combined to get the desired cooling temperature. One is the vapor compression cycle, which can also be called the ice storage cycle. Another one is the milk chilling cycle. The main purpose of the milk chilling cycle is to keep the milk temperature between 2°C to 4°C. The comparison of using cold water with ethylene glycol (PCM) as a storage source of refrigeration for the milk cooling process based on the compressor capacity, ice storage box volume, and power consumed at the variable of cooling load is presented. Also, the effect of using cold storage to reduce the refrigeration capacity and energy saving is presented. The time duration of the milk chiller’s capacity to keep a specific amount (20 liters) of milk cool has been calculated to determine the variance and efficiency of the system compared to other milk chilling processes. Some suggestions concerning the planning of milk chiller hardware are given. Unique consideration was paid to the examination of explicit highlights of heat transfer phenomena in ice storage boxes including the appraisal of the length and the rate of ice arrangement and dissolution. The approach of estimating parts of the ice storage capacity framework incorporated into the milk chilling framework arranged in hot, wet, and dry atmospheres is exhibited. In light of the hourly cooling burden figuring that was completed utilizing Carrier’s Hourly Analysis Program, estimating the ice thermal capacity framework for various working procedures including full, chiller priority, and ice priority storage tasks for the design are displayed. At last, an examination of some operational qualities of the framework is broken down.

Bidirectional anisotropic bacterial cellulose/polyvinyl alcohol/MXene aerogel phase change composites for photothermal conversion enhancement

The issues of inherent low thermal conductivity, slow heat transport rate and easy leakage are critical challenges for accelerating solar-thermal energy harvesting and storage for organic solid-liquid phase change materials (PCMs). Aerogel carriers with thermal conductivity enhancement based on ice temple methods show favorable potential for PCMs solar thermal applications. Comparing with disordered and unidirectional freezing, bidirectional freezing can assemble efficiently in multiple dimensions and result in long-range ordered structures. In this paper, bacterial cellulose/polyvinyl alcohol/MXene aerogels were constructed by bidirectional freezing. The anisotropic PCMs composites were from vacuum impregnation PEG into aerogel networks. By controlling crystallization and growth of ice crystals through the dual temperature gradients, the PCMs composites obtained enhanced heat transfer efficiency in horizontal and vertical directions. Bidirectional aligned PCMs with PDMS wedge angle of 0° and 20° exhibit high thermal conductivity of 0.716 W m−1 K−1 and 0.768 W m−1 K−1, which were 184% higher than that of PEG, and photothermal conversion efficiency of 55.17% and 76.91%. Remarkably, the PCMs composites with a 20° PDMS wedge angle also exhibited a high PCM loading capacity (96.3%) and a high enthalpy (157.7 J/g). The results show that bidirectional anisotropic PCMs composites have excellent overall performance and are expected to improve solar thermal application.

Hydrophilicity regulation of carbon nanotubes as phase-change materials for thermal energy storage

Solid-liquid phase-change materials (PCMs) offer exciting prospects for thermal energy conservation, whose performance is greatly affected by the carrier materials. Using expanded vermiculite (EV) as frameworks, carbon nanotube arrays (CNTs) were grown between EV layers by chemical vapor deposition (CVD). Then, the paraffin (PA) was loaded on the EV@CNTs composite by vacuum impregnation to prepare composite PCMs (PA/EV@CNTs), where the PA is organic carrier and the EV@CNTs acts as porous supports with high structural strength. The loading capacity of PA is further regulated by the hydrotropism of CNTs which effectively prevents the leakage of molten PA. The in-situ grown CNTs significantly improves the thermal conductivity of PCMs, improving the efficiency of energy conversion. With maximum PA loading capacity of 95 wt%, the thermal conductivity of PA/EV@CNTs-95% reaching 0.7176 W/mK, which was 1.73 and 2.96 times higher than that of pristine EV and PA. The phase change latent heat of PA/EV@CNTs-95% was measured to be 168.54 J/g, which is 1.48 times higher than that of PA/EV. After 100 cycles, the PA/EV@CNTs still maintains excellent thermal stability, and the enthalpy retention rate is 98.73%. The incorporation of high thermal conductivity amphipathicity CNTs in these PCMs makes them promising candidate for various applications such as energy-efficient buildings, thermal management in electronic devices, and self-cleaning materials.

Melting performance analysis of finned metal foam thermal energy storage tube under steady rotation

The latent heat thermal energy storage (LHTES) technology based on solid-liquid phase change material (PCM) is of great significance for the efficient utilization of thermal energy. To address the issues of slow thermal response and non-uniform melting of the LHTES technology, a hybrid heat transfer enhancement method combined with finned metal foam and steady rotation is proposed in this work. An enthalpy-porosity model considering non-Darcy porous effects and mechanical rotation is established based on the local thermal equilibrium assumption and the fixed grid system. Four different structures (uniform metal foam, graded metal foam, finned metal foam with uniform porosity, and finned metal foam with graded porosity) are investigated firstly to identify the optimal structural arrangement under the same volume of PCM. Numerical results demonstrate that the LHTES units strengthened by the finned metal foam with graded porosity achieve the shortest melting time and largest thermal energy storage rate (TESR). The graded porous structure reduces thermal resistance, rotation enhances flow and heat transfer inside the container, and the fins expand the heat source area. Moreover, the effect of different fin types, graded porosities, and rotational speeds are further considered. The findings suggest that the increase of these three parameters does not correspond to better thermal performance; instead, there is an optimal value. Compared with the base case, the optimal configuration (fin length of 20 mm, fin width of 1.5 mm, porosity gradient of 2%, and rotational speed of 0.5 rpm) can shorten the melting time by 46.68%, increase the TESR and Nu by 74.06% and 69.02%, respectively. This paper validates the feasibility of the hybrid heat transfer enhancement method with finned metal foam and steady rotation, which can offer new insights into the engineering practice of the LHTES technology.

Eco-Friendly Flame-Retardant Phase-Change Composite Films Based on Polyphosphazene/Phosphorene Hybrid Foam and Paraffin Wax for Light/Heat-Dual-Actuated Shape Memory.

Multiactuated shape memory materials are a class of promising intelligent materials that have received great interest in the fields of self-healing, anticounterfeiting, biomedical, soft robotic, and smart thermal management applications. To obtain a light/heat-dual-actuated shape memory material for thermal management applications in fire safety, we have designed a type of halogen-free flame-retardant phase-change composite film based on polyaryloxyphosphazene (PDAP)/phosphorene (PR) hybrid foam as a support material and paraffin wax (PW) as a phase-change material (PCM). PDAP was synthesized as a flexible foam matrix through the ring-opening polymerization of hexachlorocyclotriphosphazene, followed by a substitution reaction of aryloxy groups. The porosity of the PDAP foam is improved by introducing PR nanosheets, facilitating a high latent heat capacity of the PDAP-PR/PW composite films for thermal management applications. The PDAP-PR/PW composite films can implement rapid shape recovery within 65 s in the heating process, which is much shorter than that of the corresponding film without PR nanosheets (185 s). Furthermore, the PDAP-PR/PW composite films also exhibit light-actuated shape memory behavior thanks to their good solar-to-thermal energy absorption and conversion contributed by PR nanosheets as a highly effective photothermal material. More importantly, the presence of PR nanosheets imparts an excellent flame-retardant property to the PDAP-PR/PW composite films. The PDAP-PR/PW composite film can be self-extinguished within 2 s after the flame. Through an innovative integration of flexible polyphosphazene foam, PR nanosheets, and solid-liquid PCM to obtain a sensitive actuating response to light and heat, this study offers a new approach for developing multiactuated and eco-friendly flame-retardant shape memory materials to meet the requirement of applications with a requirement of fire safety in soft actuators, thermal therapy, control devices, and so on.

A review of the application of solid-liquid phase change materials in water heaters

This paper reviews the stability, heat transfer efficiency and photothermal conversion efficiency optimization studies of solid-liquid phase change materials (PCM) applied to water heaters. Suggestions and prospects were proposed. The study shows that the solid-liquid PCM are mostly filled in the water tank, thermal storage devices or solar thermal collector heater system with paraffin wax, and the addition of solid-liquid PCM can significantly improve the water heater performance. Further in-depth research is needed on PCM dosage and system economics of their application in heat pump water heaters, and the application of photothermal conversion PCM in solar water heater systems.

Improving heat storage performance of shell-and-tube unit by using structural-optimized spiral fins

Spiral fins have been widely used to enhance the heat transfer of latent heat thermal energy storage (LHTES) systems. However, owing to the inhomogeneous melting of solid-liquid phase change materials (PCMs) driven by convective heat transfer, the uniform spiral fins always have poor enhancing performance. In the present work, we proposed structural-optimized spiral fins, including optimized fin thickness, optimized fin height, and optimized fin pitch, to uniformly and efficiently transfer the heat from fins to PCM. By comparing their melting results with the original-uniform model, we found that negative models with larger fin volume at the bottom are more efficient in accelerating the melting process, and they can maximally reduce the complete melting time of PCM by 15.01% compared with the original one. On the contrary, the positive model with a smaller fin volume at the bottom slows down the melting of the LHTES unit. The heat transfer mechanism along the whole melting process is analyzed by comparing the thermal parameters (including liquid fraction, average temperature, average liquid velocity, and heat flux) of the original and optimized models. The enhancements of the negative models are owing to their benefits to the developments of convective heat transfer in the top region and conductive heat transfer at the bottom. According to the results of this paper, researchers can design novel high-performance LHTES systems using optimized spiral fins.

Double-layered phase change materials featuring high photothermal conversion for stable thermoelectric power generation

Organic solid-liquid phase change materials have attracted great attention in the field of photothermal conversion and energy storage due to their advantages such as high latent heat, low subcooling, stable chemical properties, and constant temperature during the phase change process. However, preparing organic composite phase change materials (CPCMs) with multiple desirable properties such as good shape stability, high thermal conductivity, high enthalpy, and excellent photothermal conversion efficiency, remains a challenge. Herein, using a rapid melt blending of expanded graphite (EG) into lauric acid (LA) and cold pressing technique, we constructed double-layered and shape-stabilized D-LA/EG composites. The upper layer consists of 20 wt% EG and 80 wt% LA, while the lower layer 6 wt% EG and 94 wt% LA. It was found that the prepared D-LA/EG exhibited good shape stability, high thermal conductivity, high enthalpy, and excellent photothermal conversion efficiency. More interestingly, when applied as a heat source for an all-solid-state thermoelectric generator in a photo-thermal-electric conversion system, a stable output voltage of 315 mV is generated after the light is ceased, which is attributed to the release of the heat stored in the CPCMs. This work provides a simple and economical strategy to synthesize and balance the above four properties CPCMs, which has potential applications in photo-thermal-electric conversion and solar energy utilization.

A novel bio-based composite phase change material with excellent photo-thermal conversion capability for solar energy harvesting and energy storage

Organic solid-liquid phase change materials (PCMs) have been widely studied in the field of photo-thermal conversion and thermal energy storage. However, problems such as easy leakage and low efficiency of photo-thermal conversion limit their applications. To solve these problems, this study developed a shape-stable composite phase change material (CPCM) using sponge tissue of discarded corn stem (STCS), polyethylene glycol (PEG), pyrrole (Py), and multi-walled carbon nanotube (MWCNT). PPy and MWCNT enable the CPCM to have excellent photo-thermal conversion capability and thermal conductivity. With 0.2 % MWCNT content, the CPCM achieved a thermal conductivity of 0.4609 W/m·K and a photo-thermal conversion efficiency exceeding 95.3 %. It also demonstrated high enthalpy and relative enthalpy efficiency (152.2 J/g, 96.01 %). Moreover, the CPCM exhibited remarkable shape and thermal stability, with no pyrolysis below 340 °C and nearly unchanged enthalpy after 100 cycles. Meanwhile, this CPCM also showed excellent ability in promoting seawater desalination. This work provides a new idea for recycling of agricultural waste and storage of solar energy as well as desalination of seawater.