Phase Change Materials For Storage Research Articles

Thermal optimization of PCM‐based heat sink using fins: A combination of CFD, genetic algorithms, and neural networks

AbstractSustainable development requires focusing on renewable energy, such as solar power, due to the limited availability of fossil fuels. Solar energy, available only during daylight, can be stored in thermal batteries using phase change materials (PCM). However, PCM has low thermal conductivity, slowing its melting process. Fins have been added to enhance heat diffusion, but their optimal design requires further study. This research examines an annular chamber with fixed inner and outer wall temperatures and explores fin configurations. Two series of evenly spaced fins (four and five) were analyzed, with melting times calculated using CFD simulations. Larger fins reduce melting time but limit PCM storage. Effectiveness, defined as the PCM space over melting time, was used to evaluate performance. Higher boundary temperatures decreased melting time but did not always increase effectiveness. The study also used artificial neural networks (ANN) combined with a genetic algorithm to predict optimal conditions. The configuration with five fins, a 90°C boundary temperature, a fin length of 45 mm, and a thickness of 5.4 mm achieved the highest effectiveness of 4.7, showing that smaller fins at lower temperatures are more efficient.

Sodium nitrite-sodium nitrate eutectic based composite phase change material (CPCM) for medium-temperature thermal energy storage (TES): Exploring the relationship between microstructures and thermal properties

This paper is concerned with a novel medium-temperature composite phase change material (CPCM). More specifically, the CPCM contains a sodium nitrite‑sodium nitrate phase change material for latent and sensible heat storage, magnesium oxide as a ceramic matrix material for shape-stabilisation and sensible heat storage, and expanded graphite as a thermal conductivity enhancer material (TCEM) to improve heat transfer. The focus is on understanding the relationship between the CPCM microstructures and their thermal properties. This CPCM was found to be unique, exhibiting both a reversible solid-solid transition (≈175 °C) and a reversible solid-liquid transition (≈223 °C), with a total latent heat of fusion of ∼120 J/g. In-depth microstructural characterisation of the CPCM indicated adequate thermal stability during thermal cycling in air up to 350 °C, which was also confirmed by their stable latent heat and thermal conductivity. The results highlighted a correlation between microstructures of the CPCMs and their thermal properties, as well as potential thermal decomposition reactions in high temperature industrial applications of molten salts such as concentrating solar power.

Controllable heat release of supercooled Erythritol-based phase change materials for long-term thermal energy storage

Transeasonal heat storage in organic phase change materials (PCMs) present a promising solution to the intermittent nature of renewable energy. However, PCMs are prone to spontaneous crystallization during storage, leading to the loss of stored latent heat in low-temperature environments. In this study, we incorporated tetrasodium ethylenediaminetetraacetic acid (EDTA-4Na) and superabsorbent polymer (SAP) to erythritol (ERY), referred to as EES-PCMs, to overcome these challenges and achieve more controllable and stable thermal energy storage. The incorporation of EDTA-4Na and SAP into ERY significantly improves the supercooling stability and phase change enthalpy. The optimal ratio (EES-PCMs-2) of phase change enthalpy reaches an impressive 286.62 J/g, with stable performance maintained for 120 days at room temperature. The EES-PCMs-2 exhibits exceptional thermal cycling stability, retaining its properties even after 100 cycles. A novel air-triggered crystallization method is demonstrated, enabling a temperature increase from room temperature to 48.21 °C in 320 s after being exposed to air for long-term storage. This innovative approach effectively overcomes the limitations of traditional triggering mechanisms, providing a straightforward and efficient method for thermal management. The high thermal storage capacity, stability, and controlled exothermic properties of EES-PCMs position them as promising candidates for applications in seasonal solar thermal energy storage.

Electrochemistry of Phase-Change Materials in Thermal Energy Storage Systems: A Critical Review of Green Transitions in Built Environments

This article reviews recent research on phase-change materials (PCMs) used in thermal energy storage systems with the aim of enhancing their performance. The study explores various methods to improve heat transfer in PCMs, such as microencapsulation, infill materials, fins and nanofluids. Additionally, it evaluates techniques to boost heat transfer in latent heat thermal energy storage (LHTES) systems and investigates ways to increase thermal conductivity using porous and low-density materials. PCMs store thermal energy, making them suitable for use in solar energy systems when solar energy is not available. The need for eco-friendly alternatives to conventional heating and cooling in global construction and the significant energy consumption of buildings has driven research on this topic. As such, this study additionally examines current advancements in free cooling systems with latent heat storage to identify the key factors affecting their effectiveness. The findings show that using PCMs for overnight cooling maintains the room temperature within the comfort zone and reduces the cooling loads in various climates. Using machine learning methods, this study also compares recent advancements in the use of PCMs in various solar energy systems, including solar thermal power plants, solar air purifiers, solar water heaters and solar appliances. Results derived feature key factors crucial for the optimal selection of PCMs and the challenges associated with sustainable green transitions in built environments. HIGHLIGHTS This review provides an in-depth examination of PCM thermal energy storage systems. This study investigates the use of fillers, nanofluids, and nanoparticles for enhanced heat transfer. Analytical methods for boosting the PCM thermal conductivity are briefly outlined. Geometric design and thermal conductivity enhancement affect the Latent Heat Thermal Energy Storage (LHTES). The assessment also evaluates advanced free-cooling systems using the LHTES. PCMs help to store heat energy in solar systems and bridge supply gaps. GRAPHICAL ABSTRACT

Numerical investigation of performance enhancement in a PCM-based thermal energy storage system using stair-shaped fins and nanoparticles

This study numerically investigates the melting performance enhancement of phase change material (PCM) in a latent heat thermal energy storage (LHTES) unit using a novel stair-shaped fin and nano-enhanced PCM. Different fin configurations are designed and their thermal performance is compared to traditional straight fins, while the total mass of fins is kept constant. Nano-enhanced PCM is prepared by the inclusion of CuO nanoparticles into RT82 as PCM. The simulation results reveal that the stair-shaped fins can notably enhance the efficiency of phase change compared to the traditional straight fins. The configuration with more extended fin close to the lower zone of the latent heat thermal energy storage unit had the best thermal performance. The full PCM melting time for the most efficient stair-shaped fin configuration is reduced by 52% compared to the straight fins. The combined impacts of the most effective stair-shaped fin design and nanoparticles on the phase change melting performance are evaluated. The inclusion of nanoparticles with volume concentrations of 2% and 5% into the pure PCM leads to 61% and 65% reduction in charge rate, respectively, as compared to the straight fin with pure PCM.

Melting Process Investigation of KCl Salt as a PCM by Enthalpy-Porosity Simulation Model with Temperature-dependent Physical Properties

Salt as a phase change material (PCM) in thermal energy storage (TES) can store solar thermal energy in the form of latent heat by experiencing a process known as the melting process. Recently, the melting process can be observed and investigated using an enthalpy-porosity simulation model. However, the use of enthalpy-porosity simulation model is still focused on constant physical properties, i.e., density and viscosity, of the PCM, and thus, the changes in the physical properties with respect to temperature during the melting process are not included in the simulation process. Therefore, this study aims to use the enthalpy-porosity simulation model with temperature-dependent physical properties of the PCM to investigate the melting process. The salt in this study is Potassium Chloride (KCl), and the computational domain is a concentric tube based on the assumption that the salt is fully contained within the computational domain. The physical properties of the KCl salt (density and viscosity) are set as functions of temperature to include the changes in the physical properties with respect to temperature during the melting process. The simulation results show that the melting process period is 450 s. In addition, the tendency of the melting rate, which is defined as the change in liquid fraction per unit time, is observed to decrease during the melting process. Compared with the constant physical properties of the KCl salt, the melting period of the KCl salt with temperature-dependent physical properties is observed to be shorter, with a deviation of 28.57%.

Exploring the Cutting Process of Coaxial Phase Change Fibers under Optical Characterization Tests

Urban heat islands (UHI) are a growing issue due to urbanization, causing citizens to suffer from the inadequate thermal properties of building materials. Therefore, the need for climate-resistant infrastructure is crucial for quality of life. Phase change materials (PCMs) offer a solution by being incorporated into construction materials for thermoregulation. PCMs store and release heat as latent heat, adjusting temperatures through phase changes. Polymeric phase change fibers (PCFs) are an innovative technology for encapsulating PCMs and preventing leaks. This study produced PCFs via wet-spinning, using commercial cellulose acetate (CA, Mn 50,000) as the sheath and polyethylene glycol (PEG 2000) as the core. The PCFs were cut using a hot-cutting method at three different temperatures and washed with distilled water. Morphological analysis was conducted with a bright-field microscope, and chemical analysis was performed using Fourier transform infrared spectroscopy (FTIR) before and after controlled washing. Additionally, the washing baths were analyzed by UV-visible spectroscopy to detect PEG. The PCFs displayed a well-defined core-shell structure. Although some PEG 2000 leakage occurred in unsuccessful cuts, cuts at 50 °C showed sealed ends and less material in the baths, making it viable for civil engineering materials.

Kinetics study on inhibiting battery thermal runaway using an inorganic phase change material with a super high thermochemical storage capacity

Lithium-ion batteries are susceptible to fires and explosions due to thermal runaway, a serious safety hazard. This study explores the potential of using hydrated inorganic salt (TCM40) composite phase change materials to prevent thermal runaway in battery packs. TCM40 composites stand out due to their exceptional thermochemical heat storage capacity, which allows them to effectively absorb excess heat during runaway events. The research investigates how thermal conductivity, thermal storage capacity, and cell spacing influence the propagation of thermal runaway. The findings demonstrate that TCM40 composites, with a thermal storage density exceeding 1000 kJ/kg, are significantly more effective in preventing thermal runaway compared to traditional latent heat storage phase change materials with lower capacities. To gain a comprehensive understanding of thermal runaway mitigation, a combined thermal management model was developed. This model integrates a battery thermal runaway model with a kinetic model describing the decomposition of TCM40 composites. The analysis reveals that the high heat absorption capability of TCM40 composites minimizes heat transfer to neighboring cells during thermal runaway. Furthermore, the model provides valuable insights into the synergistic effects of thermal conductivity and heat storage capacity on runaway propagation. This knowledge can be directly applied to design safer battery packs, even for compact configurations where cell spacing is less than 2 mm. This study offers significant advancements in both thermal protection materials and design strategies for lithium-ion battery packs. These advancements have the potential to significantly improve battery system safety and minimize the risk of explosions.

A Computational Study on Utilizing Phase Change Material With a Condenser to Improve air Conditioning System Performance

ABSTRACTThe efficacy of employing multiple cylindrical phase change materials (PCM) to enhance the performance of an air conditioning (AC) unit is examined in this study. The objective of the present study is to examine the effects of combining an AC unit with a cylindrical PCM container configuration on the PCM discharge process and the performance of the AC system. The procedure involves the connection of a heat exchanger with a cold energy storage PCM to the condenser of the AC. During the daytime, the warm surrounding air is cooled and then transmitted to the AC unit's condenser. Four different turbulence models, that is, the SST , standard , Realizable and RNG have been considered for the present computational study. The investigation has been performed for different air flow rates, that is, 33.6, 42, and 49 for a constant inlet air temperature of 308.15 K. The present outcomes indicate that as the flow rate rises, the air temperature inside the domain increases and the solid PCM starts melting. It is noted that complete discharging time for multi‐cylindrical PCM reduces as the air flow rate rises which are around 13.36, 11.03, and 9.94 h for airflow rates of 33.6, 42, and 49 , respectively. The maximum achieved increase in the COP is around 94.49%, 88.68%, and 87.57% at airflow rates of 33.6, 42, and 49 L/s, respectively, for the multi‐cylindrical PCM throughout the summer. It is found that for the same temperature, as the airflow rate rises, the consumed power saving rises.

Thermal properties and microstructure of Al–Sn alloys

The Al–Sn alloys feature excellent wear and corrosion resistance, along with good mechanical properties. They are mostly used as bearing materials. However, the application of these alloys as phase change materials (PCMs) for thermal energy storage (TES) has recently been suggested. To assess the adequacy of these alloys in a given area, a detailed evaluation of their thermal properties is required. In the present study, Al–Sn alloys with 11.7, 22.4, 32.8, 41.1, and 53.4 at.% Sn were produced by melting of pure metals. The melt was continuously stirred to avoid segregation, after which casting was carried out in a stainless steel mold. The obtained ingots had a homogeneous microstructure without the appearance of cracks and pores. The thermal diffusivities of the solid Al–Sn alloys in the temperature interval 25–150 °C were measured using the light flash method. The densities at room temperature were measured by the Archimedes method, and the specific heat capacities at different temperatures were calculated using the calculation of phase diagrams (CALPHAD) method. Then the thermal conductivities for studied Al–Sn alloys were obtained by the specific conversion equation. The phase transition temperatures and related heat effects were studied using differential scanning calorimetry (DSC). Variations of thermal conductivity with composition and temperature were determined as well as variation of latent heat of fusion with alloy composition. Moreover, the microstructures and phase compositions of the alloys were examined using scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS). The present research results provide important information on the thermal properties and microstructure of the Al–Sn alloys for designing new PCM for thermal energy storage.

Thermal energy storage, heat transfer, and thermodynamic behaviors of nano phase change material in a concentric double tube unit with triple tree fins

The contribution of this study is the proposal of a synergistic composite enhancement strategy involving tree fins and nanomaterials to improve the low thermal performance of phase change material (lauric acid) in a typical double tube latent heat thermal energy storage unit. The effects of nanoparticle concentrations and tree fin branching angles on the fluid dynamics, melting time, heat transfer, energy storage, and entropy generation characteristics were investigated. By employing tree fins, the melting time was respectively reduced by up to 60.20% and 36.05% compared to the finless case and the rectangular fins, while the energy storage power was respectively boosted by up to 143.36% and 37.45%. The increase of nanoparticle concentration was beneficial for melting heat transfer, and the dendritic fins with a bottom angle of 90° and a top angle of 30° yielded the highest energy storage performance. The total entropy generation of the melting process was mainly governed by the thermal entropy generation, and it showed a decreasing trend with the increase of time. In contrast to the finless configuration, the incorporation of fins diminished the integrated entropy generation value. Similarly, an elevation in nanoparticle concentration also led to a reduction of the integrated entropy generation value.

Thermal Performance Improvement of Composite Phase-Change Storage Material of Octanoic Acid–Tetradecanol by Modified Expanded Graphite

Phase-change cold storage technology is recommended as a solution for energy conservation and carbon neutrality in air conditioning systems of buildings. This study focuses on the development of binary composite phase-change materials comprising octanoic acid–tetradecanol (OA-TD). To enhance its thermal conductivity, expanded graphite (EG) was employed as an additive carrier, and the surface modification of EG particles using hexadecyltrimethoxysilane (HDTMOS) was attempted to make up for the instability and further to improve the performance of OA-TD/EG CPCMs. The OA-TD/EG-HDTMOS CPCMs were synthesized by EG mixed with EG-HDTMOS at a 1:1 mass ratio. The thermal performance and stability of the OA-TD/EG-HDTMOS CPCMs were thoroughly evaluated by multi-cycle melting–solidification and thermal conductivity measurements. The results revealed that the OA-TD mixture, when at a mass ratio of 77:23, exhibited a phase-transition temperature of 11.4 °C and a latent heat ranging from 150 to 155 J/g. Then, the OA-TD/EG-HDTMOS composite material, at a 12:1 mass ratio of OA-TD to EG-HDTMOS, solidified and melted at temperatures of 9.2 °C and 11.2 °C, with a latent heat ranging from 138 to 143 J/g, and significantly improved the thermal conductivity to 0.7 W/(m·K), representing a remarkable 133% increase compared to that of OA-TD alone. Even after undergoing 100 melting–solidification cycles, the OA-TD/EG-HDTMOS maintained superior phase-change thermal performance and stability, making it suitable for cold storage and energy conservation in air conditioning.

Active and hybrid battery thermal management system using microchannels, and phase change materials for efficient energy storage

Efficient battery thermal management (BTM) is key to the safety and performance of Lithium-ion batteries. This study focuses on cooling a module of 15 prismatic Lithium-titanate cells at an 8C discharge rate using finite volume numerical modeling. Initially, the impact of Reynolds numbers and microchannel count on temperature is examined. Then, Phase change materials (PCM) are introduced to increase thermal management efficiency. Three cases for optimizing the hybrid-BTM system are compared: nanoparticles (1%–5% volume fraction), copper foam (93 % porosity), and micro-encapsulated PCM slurry (5%–15 % volume fraction). The results indicate that an increase in microchannels improves the performance evaluation criterion (PEC) by 93.1 %. Additionally, using copper foam increases the PEC by 18.43 %, 17.44 %, 16.53 %, and 16.31 % at Reynolds numbers 800, 1200, 1600, and 2000, respectively. Furthermore, the BTM system using 5 % nanoparticles demonstrates the best performance, reducing the module temperature by 2.41 % in the presence of copper foam and by 1.78 % in the pure state. Moreover, while the MPCM slurry effectively reduces the module temperature to a desirable level, the high pumping costs significantly decrease the PEC. Additionally, the total entropy of the BTM system follows frictional entropy, although thermal entropy effects dominate the PCM.

Experimental investigation on heating performance of long- and short-term PCM storage in Chinese solar greenhouse

Phase change material (PCM) board on north wall of the greenhouses can absorb and store solar heat during the daytime, then releases it at night to provide the thermal environment for crop growth. However, its capability to regulate the greenhouse temperatures in severe winter is limited, necessitating an additional heat source. The heat gap within the greenhouse can be replenished flexibly and promptly by controllable triggering of supercooled salt hydrate for long-term heat storage. This study proposed a synergetic energy storage and release system, combining the short-term storage and passive release of the PCM wallboard with the long-term storage and active triggering solidification of the supercooled salt hydrate in separate storage unit. The temperature regulation effect of this synergetic system was experimentally investigated in a test Chinese greenhouse. The results showed that the combination of the PCM north wallboard with the supercooled salt hydrate storage unit reduced the daytime average temperature by 2.0 °C ~ 3.8 °C compared with the control greenhouse. In sunny days, the PCM north wallboard could meet the nighttime heat demand of the greenhouse with the average temperature rise of 5.2 °C ~ 6.7 °C. In severe weather, by triggering supercooled sodium acetate trihydrate (SAT, CH3COONa·3H2O, Tm = 58.0 °C) at late night, the temperature rose by 5.3 °C in 1 h, effectively heating for 5 h. While supercooled sodium thiosulfate pentahydrate (STP, Na2S2O3·5H2O, Tm = 48.5 °C) was triggered, the temperature rose by 3.3 °C in 1 h, effectively heating for 4 h. Furthermore, the synergetic system was still effective for greenhouses under ventilation and irrigation conditions during the day. This study provides guidance for the development of synergetic PCM systems with long- and short-term solar thermal storage and release for greenhouse heating.

Hydrophobic composite phase change coating: Preparation, performance and application

The utilization of composite phase change materials in energy storage and solar thermal applications is significantly restrained by their inherent non-hydrophobic surfaces and susceptibility to contamination. This study presents a novel synthesis of modified paraffin (Pa) @ silica (SiO2) nanocapsules through an efficient in situ hydrolysis and polycondensation reaction utilizing tetraethyl orthosilicate (TEOS) as the silicon source, paraffin as the phase change material, and hexamethyldisilazane (HMDS) as the surface modifier. These nanocapsules were then employed to formulate a composite phase change coating (PSC-1) by spraying onto a substrate of lithium silicate (Li2SiO3), a green inorganic binder. This coating combines self-cleaning and energy storage functionalities. The thermal characterization of PSC-1 revealed an enthalpy of phase transition of 92.95 J/g at a core-shell ratio of 1.5:1 and an HMDS to TEOS volume ratio of 1:1. Additionally, the thermal conductivity of PSC-1 was measured at 0.505 W/m∙K, which is approximately 53 % higher than that of pure paraffin. PSC-1 also demonstrated superior hydrophobicity, with a static water contact angle of 132.6°. Enhancing its practicality, the coating was subsequently dyed black and assessed for photothermal conversion efficiency, which was determined to be around 68 %. The integration of robust self-cleaning properties and high-efficiency thermal characteristics renders PSC-1 a highly promising material for broad applications in solar energy conversion and storage.

A shape-stable phase change material for high-temperature thermal energy storage based on coal fly ash and Na2SO4-K2SO4

Using coal fly ash (CFA) as the skeleton material and binary sulfates of Na2SO4-K2SO4 as the phase change material (PCM), high-temperature coal fly ash based phase change thermal storage materials (CPCM) were successfully synthesized. The influences of CFA fractions and types on the morphology, physicochemical properties, and thermal characteristics of the composites were intensively investigated. Results show that the heat storage density and thermal conductivity of CPCMs increase with the PCM content. Particularly, the CPCM60-A composite, comprising 60 wt% Na2SO4-K2SO4 eutectic and 40 wt% CFA-A, exhibits excellent chemical compatibility and stable shape retention after sintering. Furthermore, CPCM60-A demonstrates the highest phase change latent heat of 60.43 J/g and thermal conductivity of 0.61 W/(m·K). The influence of CFA types reveals that CFA-A with a higher ratio of SiO2 and Al2O3, lower carbon content, and a rich porous structure is more suitable to fabricate molten salt heat storage materials. This work demonstrates that CFA, a byproduct of coal-fired industry, is a promising skeleton material for the fabrication of high-temperature CPCM composites, offering a novel approach for enhancing the efficiency and cost-competitiveness of solar power and waste heat recovery systems.

A novel approach for solidification enhancement of phase change materials through direct contact with a boiling fluid: An experimental investigation and visualization

Due to their remarkable properties, such as high latent heat and stable temperatures during phase transitions, phase change materials (PCMs) are widely used in thermal energy storage (TES) and thermal management systems (TMSs). However, their low thermal conductivity has limited their broader application across various industries. This study experimentally explores, for the first time, the effects of injecting boiling fluid (BF) into the PCM container as a new method to enhance heat transfer during the solidification process of PCM. To this end, Paraffin wax and acetone with saturation temperature lower than paraffin’s freezing point are selected as PCM and BF, and the influence of four various parameters, namely the initial PCM temperature (75, 85, and 95 °C), the height of the PCM inside the container (15 cm, 25 cm, and 35 cm), the flow rate of the BF (0.32, 0.46, and 0.57 L/min), and the nozzle diameter (2 mm, 3 mm, and 4 mm), on the solidification behavior of PCM, temperature distribution inside the container, and heat transfer enhancement (released energy and Nusselt number) is thoroughly scrutinized. In order to visualize and further evaluate the two simultaneous phase transitions (vaporization of the BF and solidification of the PCM), a Hele-Shaw cell with a height, width, and thickness of 50, 20, and 1 cm is considered as the PCM storage system. The findings indicate that when the BF is injected into the paraffin storage, the high heat transfer coefficient of boiling superbly improves the thermal behavior of PCM, and the solidification process occurs in a much shorter time. Also, boiling of the acetone inside the container and its direct contact with paraffin leads to a significant mixing inside the container and the creation of vortices and turbulent flow in the system, which further improves the freezing phenomenon. Furthermore, it was observed that regardless of other parameters, the flow rate of BF is the most crucial parameter, and after that, the height of the paraffin and the initial temperature have the greatest impact. By employing the highest flow rate, the proposed technique is capable of freezing 0.7, 0.5, and 0.3 L of paraffin in 48, 33, and 18 s, respectively, indicating multiple times of improvement in the full solidification time compared to previous studies.

Capric-lauric & capric-palmitic/modified bentonite composite as phase change materials for thermal energy storage

This paper proposes a new double layer structure shape-stabilized thermal energy storage wallboard (TESW), by employing microwave radiation modified bentonite (Bm) to stabilize capric acid-lauric acid (CA-LA) and capric acid-palmitic acid (CA-PA) as major components of internal and external wallboard. Leakage test showed that CA-LA/Bm and CA-PA/Bm had good morphological stability. The chemical compatibility, phase change behaviors, and microstructure of CA-LA/Bm and CA-PA/Bm were analyzed. The maximal loading capacities of CA-LA/Bm and CA-PA/Bm can be reached 45 % and 50 %, respectively. In addition, the mechanical and thermal performance of CA-LA/Bm and CA-PA/Bm-based thermal energy storage concrete (CL&CP/Bm-TESC) was systematically studied. The Digital Image Correlation (DIC) technology was used to collect and analyze the speckle images of CL&CP/Bm-TESC20 before and after 100 cycles of phase change, determining the evolution of principal strains during the deformation and failure processes. It is worth noting that the numerical simulation results of the designed double layer structure shape-stabilized CA-LA&CA-PA/Bm-based thermal energy storage wallboard (CL&CP/Bm-TESW) show better temperature adjusting performance. These results demonstrate that the prepared composite of CA-LA/Bm and CA-PA/Bm has potential application in the field of thermal energy storage.

Thermal conductivity enhancement of polyethylene glycol/NF composite as stabilized phase change materials for thermal energy storage

Polyethylene glycol (PEG) has the advantages of large latent heat of phase transition, a wide range of phase transition, and cheap price, but the application of PEG in the latent thermal energy storage (TES) systems is hindered due to its lower heat transfer rate and leakage. Porous metal foam has excellent thermal conductivity and high strength, which can effectively improve the problems of PEG. In this study, PEG/nickel foam (NF) composite phase change materials (PCM) were prepared by vacuum molten impregnation method using NF as substrate. It was found that PEG had good compatibility with NF, and the highest impregnation rate of PEG6000/NF reached 85.73 %. The thermal conductivity of PEG2000/NF can be increased to 1.58 1.58 W·m−1 K−1, nearly 4 times larger than that of pure PEG. The phase change temperature range of the composite PCM is 51–63 °C, and the phase change enthalpy is 67.8–126.3 J·g−1. Furthermore, the PEG/NF composite demonstrated outstanding photothermal conversion properties and high thermal stability, which can be widely used in the field of building temperature control and device heat dissipation.

Dynamic simulation of a combined solar system including phase change material storage and its experimental validation

Thermal energy storage is a key issue in efficient energy system applications, especially in renewable energies. In this respect, phase change materials (PCM) have attracted interest as an active solution for efficient energy management, particularly in the building sector. This paper presents a modelling of a PCM thermal battery in solar system assisted by heat pump. The storage stores the heat produced by unglazed solar panels (Batisol®) and releases it into a heat pump. Then this heat is sent to two other PCM storages. In this way, the low-temperature heating and domestic hot water needs of a commercial building in winter are met. The storage consists of a block of PCM contained between two plates of heat transfer fluid. It acts as a plate heat exchanger that can be charged and discharged simultaneously. The objective of the study is to dynamically simulate the thermal behaviour of this storage for different hot inlet temperature profiles. A rectangular profile is used to validate the model using experimental results. Then, a solar system assisted by heat pump and three PCM storages is dynamically simulated. This 2D model would be useful to validate a simpler model for optimising the operational parameters of the system.