Efficient Thermal Energy Research Articles

Performance Evaluation of Nano-Enhanced Phase Change Materials for Thermal Energy Storage: An Experimental Study

In rapidly developing economies, the increasing energy demand and fossil fuel consumption have made the need for renewable energy sources and efficient thermal energy storage (TES) solutions more urgent than ever. This study focuses on enhancing the thermal energy storage capabilities of paraffin-based phase change materials (PCMs) by incorporating Al2O3, MgO, and CuO nanoparticles. The evaluation of nano-enhanced PCMs focused on their melting temperatures, thermal storage capacities, thermal conductivities, and charge/discharge times. The experimental results revealed significant changes in the thermal properties of the nano-enhanced PCMs compared to pure paraffin. The melting temperature was raised by 2°C due to Al2O3 nanoparticles, whereas CuO and MgO nanoparticles decreased it by 1.7°C and 1.8°C, respectively. Compared to pure paraffin, Al2O3-PW, MgO-PW, and CuO-PW exhibited improvements of 13%, 39%, and 48% in thermal conductivities, respectively. CuO-doped paraffin showed an 11.8% decrease in discharge time, suggesting its suitability for rapid heat transfer applications like defrosting systems or thermal management in electronics. On the other hand, paraffin doped with MgO showed a minimal 2.24% reduction in discharge time, indicating its effectiveness in applications requiring heat retention, particularly for improved thermal insulation in building materials. The results highlighted the potential of nano-enhanced PCMs in energy storage and construction is underlined, offering a sustainable approach to improving energy efficiency in various sectors.

Optimizing of partial porous structure for efficient heat transfer and thermal energy storage of phase change material in a rectangular cavity

Optimizing of partial porous structure for efficient heat transfer and thermal energy storage of phase change material in a rectangular cavity

Analysis of various system designs for adsorption cycle in building heating applications

Buildings are major energy consumers, highlighting the need for efficient thermal energy storage to reduce reliance on non-renewable sources. Adsorption-based systems offer significant energy savings for heating applications. This research compares four critical adsorption-based cycles: adsorption thermal energy storage, adsorption heat transformer, adsorption mass recovery with heating and cooling, and a novel combined cycle. The study uncovers new insights into temperature and pressure control challenges through lumped parameter modeling. These dynamic modeling results advance our understanding and optimization of adsorption systems, enhancing their feasibility and efficiency for building heating. The adsorption mass recovery cycle demonstrates superior energy storage density (289 kW h/m³) compared to the adsorption heat transformer cycle (240 kW h/m³) and the adsorption thermal energy storage cycle (157 kW h/m³). It also has the highest water uptake (0.56 kg/kg), surpassing the other two cycles. Despite its pressure fluctuations and temperature instability challenges, the adsorption mass recovery cycle outperforms the adsorption heat transformer and adsorption thermal energy storage cycles in energy storage density. The novel combined cycle optimizes heat storage and release, achieves the highest energy storage density (302 kW h/m³), and outperforms the individual cycles. The combined cycle's performance was evaluated in a home in South Korea, revealing significant energy savings and proving an effective solution for enhancing energy efficiency in building heating systems. This research addresses a crucial gap and provides a foundation for future advancements in thermal energy storage.

Nanofluidic Thermoelectric Transducer with Ultrahigh and Tunable Sensitivity.

Thermosensitive transient receptor potential (thermoTRP) ion channels can transduce external thermal stimuli to neural electrical signals, allowing organisms to detect and respond to changes in environmental temperature. Reproducing such ionic machinery holds promise for advancing the design of highly efficient low-grade thermal energy harvesters and ultrasensitive thermal sensors. However, there still exist challenges for artificial nanofluidic architectures to achieve comparable thermoelectric performance. Here, we report nanofluidic thermoelectric transducers with ultrahigh and tunable sensitivities controlled by electrostatic gating in graphene nanochannels. The equivalent Seebeck coefficient can be significantly boosted and reaches 1 order of magnitude higher than the current state of the art, even beyond thermoTRP ion channels. The improvement is attributed to substantial slippage on the highly charged graphene surface, leading to enhanced electrokinetic ion transport inside the graphene channel, which is confirmed by a scaling theory for thermoelectric coupling as well as molecular dynamic simulations. The dependence of the nanofluidic thermoelectric on the concentration, channel size, and cation types is also investigated to further clarify the underlying mechanism.

Enhancing thermal conductivity of novel ternary nitrate salt mixtures for thermal energy storage (TES) fluid

Efficient thermal energy storage (TES) is crucial for concentrated solar power (CSP) plants, necessitating the exploration of advanced heat transfer fluids with enhanced thermal conductivity. Conventional binary nitrate salt mixtures have limitations in thermal performance, prompting research into ternary mixtures and nanoparticle additives. This study investigates novel ternary nitrate salt mixtures comprising potassium nitrate (KNO₃), lithium nitrate (LiNO₃), and magnesium nitrate hexahydrate (Mg(NO₃)₂·6 H₂O) as high-performance TES fluids during the during the heat absorption phase. Seven different salt compositions were synthesized and characterized using the laser flash technique to evaluate their thermal conductivity over 100–400°C. Results revealed a significant influence of composition on thermal conductivity, with maximum values during melting ranging from 0.0777 W/m·K to 0.7373 W/m·K. Melting points varied from 335 K to 340.39 K, demonstrating tailorability through compositional adjustments. Furthermore, incorporation of 0.5 wt% aluminum oxide (Al₂O₃) nanoparticles resulted in substantial thermal conductivity enhancements, with the most significant increase observed in TSF10 (from 0.0777 W/m·K to 0.491 W/m·K). These improvements are attributed to enhanced phonon transport, increased surface area, and Brownian motion facilitated by Al₂O₃ nanoparticles. The study provides a comprehensive cost analysis, including raw material costs, and discusses the potential efficiency gains for CSP applications. The findings contribute to the development of high-performance and cost-effective TES fluids, advancing the efficiency and viability of sustainable energy generation.

Compressor‐Driven Titanium and Magnesium Hydride Systems for Thermal Energy Storage: Thermodynamic Assessment

ABSTRACTMetal hydrides enable excellent thermal energy storage due to their high energy density, extended storage capability, and cost‐effective operation. A metal hydride‐driven storage system couples two reactors that assist in thermochemical storage using cyclic operation. Metal hydride reactors, operating at both low and high temperatures, serve for the storage of hydrogen and thermal energy, respectively. The integration of efficient thermal energy storage technology is known to enhance the efficiency of solar thermal systems. In this regard, during the peak hours of solar energy, the high‐temperature supply heat can be utilized to store hydrogen gas in the low‐temperature reactor, which simultaneously facilitates energy storage in the high‐temperature reactor. Moreover, the temperature and energy released from the reactors are highly dependent on the pressure of the gas. As a result, installing a compressor between the low and high‐temperature metal hydride reactors can help generate additional outputs, such as a cooling effect. This paper conducts a thermodynamic analysis to assess the system's performance, considering parameters such as thermal storage efficiency, coefficient of performance (COP), and COPCCH (combined cooling and heating based COP). Moreover, the performance analysis was carried out for two cases, that is, high‐temperature titanium hydride (TiH2) and magnesium hydride (MgH2). The results show that MgH2 and TiH2 achieve a maximum COPCCH of 1.08 and 0.9, respectively, and system storage efficiency of 76.15% and 74.34%, respectively. In spite of having lower efficiency than MgH2, the TiH2‐based system has the ability to recover heat at a very high temperature.

Anisotropic and shape-stable sugarcane-based phase change composites in the application of solar thermal energy storage

The study of anisotropically thermal conductive phase change composites (PCCs) with shape-stability is of great importance to improve the intermittent issues in solar thermal utilization, while some drawbacks like the high cost, low thermal conductivity, and poor durability of current PCCs restrains their practical applications. Herein, a cheap and scalable biomass-based PCC containing carbonized sugarcane (CSC), polyethylene glycol (PEG), and graphene (GF) is proposed. The abundant vessels inside CSC result in a high PEG loading rate of 82.48 %. The naturally occurring anisotropic structure inside CSC can drive GF to be oriented along the lengthwise direction, which gives PCC a high thermal conductivity anisotropy degree of 1.45. The prominent anisotropy improves the lengthwise thermal diffusion and restrains the transverse heat leakage to the environment. Besides, the loaded GF can further enhance the light absorption of PCC to 98 %. As a result, the prepared PCC can achieve high solar-thermal energy storage efficiencies of 79.3–91.7 % with variable solar intensity from 1 to 2 suns. Meanwhile, good anti-leakage and durability performances promote the practical utilization of PCCs. The present work paves a promising road for manufacturing biomass-based anisotropic PCCs in efficient solar thermal energy storage.

Okra functional biomimetic composite phase change materials integrated with high thermal conductivity, remarkable latent heat, and multicycle stability for high temperature thermal energy storage

High-temperature phase change materials (h-PCMs) offer viable solutions for efficient thermal energy storage systems within large-scale industrial facilities. However, h-PCMs still face enormous challenges owing to low thermal conductivity and restricted thermal storage efficiency. Herein, we report okra functional biomimetic high-temperature composite phase change materials (h-CPCMs) that exhibit excellent comprehensive thermal storage properties and operational reliability, inspired by the okra seed storage process. The okra biomimetic SiC ceramic skeleton, featuring unique macropores and crosslinked axially fibrous thermal transfer pathways, significantly boosts the thermal storage efficiency of loaded molten-salt-based h-PCMs. The resulting h-CPCMs exhibit excellent thermal conductivity with a maximum value of 31 W/(m·K) accompanied by a notable latent heat of 207 J/g. Of note, the h-CPCMs with high porosity maintain superior thermal storage properties after 500 cycles. The overall thermal storage performance under 400–700 °C outperformed that of h-CPCMs reported in previous works. Furthermore, utilizing a self-designed thermal storage performance testing device, the thermal storage power density of h-CPCMs performs a 101 % enhancement compared to pure h-PCMs, suggesting a significant improvement in thermal storage efficiency. This work provides valuable insights and advancements for the further design of highly performance h-CPCMs.

Study of a Novel Updraft Tower Power Plant Combined with Wind and Solar Energy

This study presents a novel solar updraft tower power plant (SUTPP) system, which has been designed to achieve the simultaneous utilization of solar and wind energy resources in desert regions, in response to the pressing demand for sustainable and efficient renewable energy solutions. The aim of this research was to develop an integrated system that is capable of harnessing and converting these abundant energy sources into electrical power, thereby enhancing the renewable energy portfolio in arid environments. The methodology of this study involved the design and construction of a prototype SUTPP, comprising a 53 m high tower, a 6170 m2 collector, five horizontal-axis wind turbines, and a thermal energy storage layer made up of pebbles and sand. The experimental setup was meticulously detailed, and experiments were conducted to collect data on the system’s performance under various environmental conditions. Subsequently, three-dimensional numerical simulations were performed to explore the effects of ambient wind speed and solar radiation on the output power of the SUTPP. The results indicate that the output power of the system increases with the increase in ambient wind speed and solar radiation. The impact of solar irradiation on output power was observed to diminish as ambient wind speeds increased. Notably, as the inlet wind speed rose from 4 m/s to 12 m/s, the output power showed a substantial increase of 727%. The numerical simulations revealed that ambient wind speed has a more pronounced effect on power output compared to solar radiation. Furthermore, it was found that the influence of solar radiation is significant at low wind speeds, with its impact decreasing as wind speed increases. This research provides essential guidance for the design and engineering of highly efficient solar thermal energy utilization projects, representing a significant advancement in the field of renewable energy technology deployment in desert environments.

Finite element method-based investigation of heat exchanger hydrodynamics: Effects of triangular vortex generator shape and size on flow characteristics

Heat exchangers (HEs) play a critical role in numerous industrial and engineering applications by facilitating efficient thermal energy transfer. In the pursuit of enhancing the performance of such systems, this study focuses on the hydrodynamic effects of two distinctive vortex generators (VGs) within a turbulent airflow channel, operating under steady-state conditions. Arranged in a staggered manner, the first vortex generator (VG) adopts a rectangular structure positioned in the upper section, while the second VG, triangular in shape, is situated on the opposing wall at varying heights, ranging from 40 to 80 mm in 10 mm increments. A further examination of the triangular VG includes two cases, one featuring an inclined front-face and the other showcasing an inclined rear-face. The turbulent airflow within the channel is accurately represented using the Newtonian fluid model and the standard k-epsilon turbulence model, while the governing equations are solved through the finite element method. A non-uniform mesh, consisting of triangular and square elements with a specific focus on refining the mesh near walls, is designed to capture boundary layer effects and effectively resolve intricacies in near-wall flow dynamics. The investigation unveils dynamic responses within the channel, characterized by notable flow distortions and prominent regions of recirculation, demonstrating the effectiveness of both rectangular and triangular VGs. Importantly, the analysis shows that tilting the triangular VG’s back-face notably improves the hydrodynamic structure of the HE channel, leading to enhanced recirculation cells and substantially increased performance. In particular, increasing the height of triangular VGs significantly enhances flow velocity within the channel. For instance, the axial velocity increased by 33.8% when the VG height was raised from 40 to 80 mm in the first triangular case, while an increase of about 37.9% was observed in the second triangular case at the lowest inlet velocity of 7.8 m/s. In addition, triangular VGs with an inclined back-surface achieved higher axial velocities compared to those with an inclined front-surface, with a 13.5% increase at the smallest height and a 17.0% increase at the maximum height. Furthermore, increasing the inlet velocity to 9.8 m/s resulted in a 17.1% higher axial velocity in the second model, reaching 55.4 m/s compared to 47.3 m/s in the first model. These findings underscore the importance of optimizing the triangular VG shape, height, and inlet conditions to maximize the hydrodynamic performance of HE systems, leading to potential energy savings and improved efficiency.

Enhancement of Thermo-Physical Properties of Form-Stable Nano-Enhanced Phase Change Materials: Advancing Maritime Sustainability

This paper explores the application of novel, form-stable eutectic mixtures in thermal energy storage systems for maritime environments. These advanced materials present a significant leap forward, addressing critical challenges faced by conventional phase change materials (PCMs) in marine environments. The stability, eliminating leakage and fluidity issues encountered with liquid PCMs are ensured by incorporating 2-hydroxypropyl ether cellulose (HPEC) as a gelling agent. Additionally, the thermal properties and heat transfer capacities were significantly enhanced, and eventually, overall system efficiency improved by including nano-graphene platelets (NGPs). Notably, NGPs effectively suppress supercooling, minimizing energy losses and guaranteeing consistent performance at elevated temperatures. Further, the eutectic mixture demonstrates exceptional durability through an accelerated thermal reliability test, guaranteeing optimal performance over a projected seventy-year lifespan. This enhanced thermal performance, and enduring stability combination establishes the form-stable eutectic mixture with NGPs as an up-and-coming solution for diverse maritime applications requiring efficient and reliable thermal energy storage. This research provides a compelling case for implementing form-stable eutectic mixtures with NGPs in maritime thermal energy storage systems. Its superior performance and sustainability offer significant advantages for diverse shipboard and offshore applications, contributing to improved energy efficiency, environmental sustainability, and operational resilience within the maritime sector.

Enhancing the phase change material based shell-tube thermal energy storage units with unique hybrid fins

The poor thermal conductivity of phase change material (PCM) has limited its application to thermal energy storage system. The present work aims to improve the performance of PCM in a vertical shell-tube energy storage unit through unique hybrid fins. The enthalpy-porosity approach is used to numerically investigate the phase change phenomenon. Based on the straight and spiral fin results, the novelty designs of double side spiral fin and hybrid fins, i.e. spiral/straight hybrid fin and straight/spiral hybrid fin, are proposed to further optimize the PCM charging process. The effects of different fin structure, hybrid fin proportion and spiral fin angle on the liquid fraction, temperature and average thermal energy storage rate are discussed. The fin structures can reduce the melting time of PCM up to 100% compared to the no-fin case. Although double side spiral fin outperforms the straight fin for the PCM melting behavior, the hybrid fin configurations shows the best enhancement, especially for the straight/spiral hybrid fin. The optimal fin design for the straight/spiral hybrid fin case is that with 0.7 fin proportion and 180° spiral angle, with up to 11.8% reduction of the melting time compared to the designs of other fin proportions and spiral angles. This work demonstrates the potential of this unique hybrid fin to be integrated with PCM for efficient thermal energy storage.

A comprehensive review on integration of receiver geometries, nanofluids, and efficient thermal energy storage for solar parabolic dish collectors

A comprehensive review on integration of receiver geometries, nanofluids, and efficient thermal energy storage for solar parabolic dish collectors

Evaluation of wavy wall configurations for accelerated heat recovery in triplex-tube energy storage units for building heating applications

Efficient thermal energy storage (TES) is crucial for integrating intermittent renewable energy sources and managing fluctuations in energy supply and demand. Among TES methods, latent heat TES (LHTES) using phase change materials (PCMs) is highly promising due to its high energy storage density and nearly isothermal operation during phase transitions. However, the inherently low thermal conductivity of PCMs hinders heat transfer rates, negatively impacting charging and discharging performance. This study investigates novel wavy channel geometries for the PCM container in a triplex-tube LHTES unit to enhance heat transfer and improve solidification rates during the discharge process. A comprehensive computational model based on the enthalpy-porosity method is developed to simulate the PCM (paraffin wax RT35) solidification inside wavy channels with sinusoidal, zigzag, and step-function profiles. The effects of channel geometry, heat transfer fluid (HTF) velocity, and inlet temperature on solidification rate and heat recovery are systematically evaluated. Results demonstrate that the step-function geometry significantly accelerates solidification compared to straight channels, reducing discharge time by 65.1 % and increasing heat recovery rate by 147.9 %. Decreasing waviness width from 15 mm to 5 mm further reduces solidification time by 70.1 %, while increasing waviness height from 5 mm to 15 mm leads to a 74.4 % reduction. Moreover, increasing HTF flow from Re = 250 to 1000 enhances heat recovery by 92.3 %, and lowering inlet temperature from 20 °C to 10 °C improves it by 76.9 %. The findings provide valuable insights for designing efficient LHTES units with wavy channel geometries for renewable energy integration and thermal management applications.

Enhanced solar energy utilization of thermal energy storage tanks with phase change material and baffle incorporating holes

In response to the pressing need for more efficient thermal energy storage solutions, this study investigates the strategic implementation of baffles in phase change material (PCM) tanks to enhance thermal performance. PCM offers a promising solution for efficient thermal energy storage (TES); however, ensuring uniform temperature distribution inside the tanks remains challenging. Horizontal baffles with holes of varying diameters were introduced in Tanks 02, 03, and 04, while an inclined baffle with holes was used in Tank 05. The Tank 06 benefitted from an inclined baffle with holes of different diameters. A comprehensive analysis of all Tanks was evaluated by assessing PCM and water heat flux, PCM and water static enthalpy, Richardson number, velocity vectors, temperature, and liquid fraction contours. The results demonstrated that significant improvements were achieved with the addition of baffles. Tank 01, without a baffle, exhibited a melting time of 2860 s. However, the introduction of baffles resulted in reduced melting times for Tanks 02 to 06: 2360 s (17.48 %), 2350 s (17.83 %), 2400 s (16.08 %), 2320 s (18.88 %), and 2240 s (21.67 %), respectively; which led to enhance TES efficiency, and a quicker energy storage process. The study also includes a comprehensive economic analysis, evaluating the total cost (Ctotal) and performance-economic ratio (Pc). Tank 06 shows superior economic performance, with a Pc value of 0.26 despite a slightly higher cost than Tank 01 by $2 USD. These findings highlight the baffle design’s effectiveness in achieving better heat transfer and uniform temperature distribution within PCM tanks, making them more efficient for TES applications.

Modeling heat and mass transfer in granular flows between vertical parallel plates

Gravity-driven granular flows between vertical parallel plates at elevated temperatures are integral in the development of the next generation of particle-based heat exchangers for concentrated solar power. Efficient modeling methodologies that accurately captures the heat transfer mechanisms of temperature-dependent granular flows are essential to effectively design and evaluate these heat exchangers. Transient, pseudo-one-dimensional heat and mass transfer models were developed for inlet flow temperatures between 473 and 1073 K. The mass transfer models for the granular flows were resolved using discrete element method simulation, providing detailed temporal and spatial distributions of flow parameters in good agreement with experimental measurements. The heat transfer model employed a one-dimensional, two-phase, continuum approach, and a system of non-linear differential equations was solved via finite difference method. The particle-to-wall contact heat transfer was determined with an effective thermal conductance model. Radiative heat transfer between particles and walls was also considered. The predicted particle and wall temperatures for two different channel widths of 6.4 and 2 mm were well-correlated to previously obtained experimental measurements with Pearson’s correlation coefficients greater than 0.91. A significant disparity in particle temperature of up to 72 K was observed when radiative heat transfer was omitted, and a maximum temperature difference of 11 K was observed when temperature-dependent granular flow properties were not considered. The model revealed that radiative heat transfer potentially contributed to > 30 % of heat losses in wider channels at high inlet temperatures, and conduction was the dominated heat transfer mechanisms in narrower channels (∼70 %) due to increased particle-to-wall contact. This accurate model, leveraging discrete element method in a streamlined approach, advances the understanding and modeling of heat transfer in granular flows at elevated temperatures, enabling more efficient and reliable solar thermal energy storage and transport.

Thermal performance augmentation of honeycomb metal matrix embedded phase change material in shell-tube latent heat storage unit

Due to the global warming challenge, there is a transition from the utilization of fossil fuels to harvesting new and renewable energy sources globally. Solar energy, being the infinite source with easy accessibility, leads the race among other allied sources. However intermittent nature of it demands an efficient thermal energy storage system. In the present experimental study, an innovative heat transfer augmentation technique i.e. aluminium honeycomb grill and fine mesh embedded in PCM is demonstrated. Both visualization of PCM melt fraction and capture of temperature contour complemented each other to identify the honeycomb version (HC-LHSU) as substantially better (43 % improvement in charge period) than the base model (BM-LHSU). On the other side, due to fine pores (porosity = 95 %), the fine meshmodel (FM-LHSU) yielded poorer results than BM-LHSU. Even the temperature gradient that exists during the charge or discharge period is gauged and recognized HC-LHSU as the best, followed by BM-LHSU and FM-LHSU. Since the onset of the phase transition zone reflects heat storage rate, the same is identified, and the charge period (sensible heat + latent heat) assessed to be 8000 s, 10000 s, and 12,000 s for HC-LHSU, BM-LHSU, and FM-LHSU, respectively. Further, an improvement in the average Nusselt number by 74 % and 67 % during the charge and discharge period respectively compared to the base model justified the honeycomb grill's role in augmenting the energy storage unit's performance.

Advancing Thermal Performance in PCM-Based Energy Storage: A Comparative Study with Fins, Expanded Graphite, and Combined Configurations

Phase Change Material (PCM) thermal energy storage systems have emerged as a promising solution for efficient thermal energy storage from low to very high-temperature applications. This paper presents an investigation into the utilization of medium temperature range PCM-based systems for domestic hot water application, focusing on different techniques to overcome the low thermal conductivity of the PCM. Five shell and tube heat exchangers were fabricated employing different heat transfer enhancement methods including fin, expanded graphite (EG), and a combination of fin and EG. The combination of EG and circular fins exhibited the best performance in terms of charging and discharging, maintaining a uniform temperature distribution throughout the system due to extensive conductive network provided by the combination of EG and circular fins. When the PCM/EG/fin heat exchanger system is fully charged, the energy stored in the system is 109% higher than that of the PCM heat exchanger at the same elapsed time. Furthermore, the PCM/EG/fin system demonstrated a faster discharging response compared to other thermal energy storage (TES) configurations, with over 160% higher discharging power than a system without any enhancement methods. These findings emphasize the practical viability of integrating PCM/EG composite materials into thermal energy storage systems, offering a viable solution for meeting high heat demand requirements in domestic hot water applications. Furthermore, the enhanced discharging response observed in the PCM/EG/fin system has significant implications for improving energy efficiency and reducing operational costs in real-world applications.

Improving phase change heat transfer in an enclosure partially filled by uniform and anisotropic metal foam layers

Anisotropic metal foams exhibit exceptional potential for improving the efficiency of latent heat thermal energy storage (LHTES) units by enhancing heat transfer and thermal energy storage rates. This study explores the largely uncharted area of thermal behavior of anisotropic metal foams in varied configurations and enclosure designs. The research focuses on an LHTES unit with a specific channel configuration, constructed using copper and containing three layers of copper metal foam, one of which is anisotropic and infused with paraffin wax. The finite element method was utilized to manage the complexities emerging from phase change, and the anisotropic angle varied from 0 to 90° in three different placements of the AMFL: top, middle, or bottom of the enclosure. The ideal design was achieved with an AMFL in the middle with a 0°angle, resulting in a 3.7 % reduction in melting time and approximately a 2.3 % reduction in solidification time. However, AMFL designs at the middle placement with a 75° anisotropic angle were less effective, hampering the melting and solidification processes, thus potentially extending charging and discharging times. The study concludes that the placement and angle of the AMFL layer are vital for the heat transfer capabilities of phase change materials. AMFL at the middle with a 0° angle optimally leverages temperature gradients, enhancing heat transfer compared to other investigated cases. An AMFL in the middle with a 0° angle exhibits approximately 7.1 % and 6.3 % improvements for melting fractions of 0.9 and 0.95, respectively, underscoring its potential for efficient thermal energy storage.

Vertically aligned montmorillonite aerogel–encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage

Vertically aligned montmorillonite aerogel–encapsulated polyethylene glycol with directional heat transfer paths for efficient solar thermal energy harvesting and storage