Advanced Thermal Energy Research Articles

Thermally enhanced flexible phase change materials for thermal energy conversion and management of wearable electronics

The developing trend of miniaturization and integration for electronics imposes challenges of efficient heat dissipation technology, where novel materials with advanced thermal energy conversion and management are urgently needed. In this work, we propose an emerging phase change material (PCM) system with polyvinyl alcohol/expanded graphite network loading paraffin wax (PE-PW), which exhibits superb flexibility, thermal energy storage capacity and thermal conductivity. The phase change enthalpy is from 115.61 J/g to 168.93 J/g without any leakage, which can be maintained even after 500 thermal cycles. The thermal conductivity can reach 1.46 W/mK, 484% enhanced compared with that of pure PCM. Meanwhile, the thermal management test indicates that the PE-PW composites can quickly absorb and store the generated heat to achieve temperature control, thus protecting the system from overheating and indicating excellent thermal management capacity. This flexible PE-PW system has broad application prospects in the field of thermal energy conversion and management for wearable electronics.

Multi-perspective analysis of adiabatic compressed air energy storage system with cascaded packed bed latent heat storage under variable conditions

Adiabatic compressed air energy storage (A-CAES) with advanced thermal energy storage systems has enormous potential in applications. In particular, the extent of thermal energy utilization determines the comprehensive performance of an A-CAES system. In this paper, a cascaded latent heat packed bed storage system is used as a thermal energy storage under variable conditions of A-CAES. The transient thermal characteristic of the packed bed under variable conditions are further studied. Moreover, the key parameters that affect the thermal energy utilization of the system are also parametrically investigated. The results show that the proposed system has a roundtrip efficiency of 63.42 %, an exergy efficiency of 66.58 %, and a payback period of 4.63 years. The economic analysis shows that the proposed system is more advantageous in comparison with A-CAES with heat transfer oil as heat storage system.

Advanced thermal energy storage made of a ternary CPCM with two phase change temperatures in building walls

This paper introduces a ternary composite phase change material (CPCM) comprising three phase change materials, with a eutectic mixture as the low phase change temperature (PCT) component. The thermal performance and stability of the CPCM are rigorously evaluated through simulations and experiments including step cooling curves, differential scanning calorimetry (DSC), thermal cycling, and Fourier-transform infrared (FTIR) spectroscopy. The ternary CPCM CA/C18-TD (2.0:8.0) exhibits superior latent heat storage—224.53 J/g compared to 143.83 J/g for the binary CA-TD (3.0:7.0)—and maintains stability without supercooling after 300 thermal cycles. It also proves cost-effective compared to its components. In building applications, walls integrated with the CPCM CA/C18-TD (2.0:8.0) exhibited significantly enhanced thermal regulation properties, including longer thermal delay times and reduced attenuation factors across both winter and summer conditions. Specifically, the CPCM wall reduced temperature fluctuations by up to 31.91 % in comparison to ordinary wall and 21.63 % against single PCM wall in winter, 54.51 % and 44.22 % lower than the ordinary and single PCM walls respectively in summer. These walls also showed a remarkable reduction in heat flow density by up to 17.49 W/m2 and 5.41 W/m2 compared to ordinary wall under summer and winter conditions, respectively. This means that the CPCM has superior insulation performance and reduces susceptibility to external environmental changes. These findings confirm CA/C18-TD (2.0:8.0) as an optimal CPCM for seasonal thermal energy storage in energy-efficient PCM wall.

Experimental and numerical assessment of thermal characteristics of PCM in a U-shaped heat exchanger using porous metal foam and NanoPowder

The utilization of Latent Heat Thermal Energy Storage (LHTES) has gained significant attention to address the disparity between energy supply and demand. One of the key advantages lies in the use of phase change materials (PCM). The purpose of this research is to overcome this obstacle by focusing on enhancing the thermal efficiency of an advanced thermal energy storage system specifically designed for solar domestic and industrial application. to overcome this obstacle by focusing on enhancing the thermal efficiency of an advanced thermal energy storage system specifically designed for solar domestic and industrial application. Through computational and experimental studies, a novel and small LHTES system with parallel U-shaped heat exchanger (USHX) has been created and investigated. To improve performance, two approaches are employed: optimizing thermal efficiency by dispersing nano-sized graphite powders into the paraffin material, and/or incorporating metal foams. The PCM is RT35HC, and the hot/cold heat transfer fluid is H2O, which travels via the U-shaped tube. The model incorporates the enthalpy-porosity technique to account for phase change phenomena. After comparing the numerical outcomes with the experiments herein run, data are shown in terms of liquid fraction, temperature evolution, stored energy, and a dimensionless parameter that characterizes the phase change process. The findings suggest that the proposed methods for enhancing heat transfer can enhance the thermal efficiency of systems. The outcomes illustrate that by addition of all methods, reduces the melting time by 13.39 %, 60.77 %, and 71.93 %, when compared to system with pure PCM.

Thermodynamics analysis of fins integration in sono-PCM reactor: Sonic power influence

This research presents a novel approach of integrating fins into a sonochemical phase change material (PCM) reactor to tackle the challenge of low PCM thermal conductivity, with a focus on cooling the ultrasonic reactor. Through comprehensive numerical simulations using a Fluent-based CFD code, we analyze the thermal performance of the sono-PCM system with and without fins under varying power densities (45.5 and 85.6 kW/m3) and operating times (up to 1 h). Our results highlight the remarkable advantage of fins in accelerating the heat transfer and melting process, reducing the time for a 50% PCM melt by 28.1 and 45.2% for power densities of 45.5 and 85.6 kW/m3, respectively. Enthalpy analysis further confirms the efficiency of the fins, demonstrating a reduction of ∼19% in water enthalpy after 1 h for both power densities. Moreover, the presence of fins significantly enhances the heat recovery by the PCM, leading to 20.1 and 73.2% increase in PCM enthalpy for power densities of 45.5 and 85.6 kW/m3, respectively. These enhancements are attributed to the increased surface area of contact provided by fins, which facilitate efficient heat dissipation within the bulk PCM. This study not only provides crucial insights into PCM systems with fins but also opens up avenues for advanced thermal energy management strategies, revolutionizing heat storage and transfer processes across various engineering applications.

High performance composite phase change materials enhanced via evaporation-induced hydrogen bond network refactoring

Composite phase change materials (CPCMs) with real-time thermal harvesting are in high demand in the solar-thermal energy conversion industry. However, poor heat conduction, lack of strength and leakage problem severely restrict its availability. In this study, we develop an evaporation-inspired, facile, and versatile strategy for manufacturing shape stable CPCMs from organohydrogels with enhanced thermal performances for advanced thermal energy storage and management. Organohyodrogels contained with graphene nanoplatelets (GNPs) served as the template. By oven-drying the organohydrogel, hydrogen bonding reconstruction would assist in the formation of a dense polymer layer to encapsulate PCMs, forming the non-leakage CPCMs. The strong capillary force generated during the oven-drying process would induce the alignment of GNPs, forming thermal conduction pathways. The as-prepared composite exhibits a high thermal conductivity (1.25 W m-1K−1), satisfactory latent heat storage (171.5 J g−1) and excellent Young’s modulus (8.3 MPa). When subjected to solar radiation, solar energy is converted to heat and stored inside the material, with a conversion efficiency as high as 95.8 %. The robust composite with high performance is expected to be an efficient and reliable thermal management material in solar-thermal energy conversion.

Repurposing coal plants—regional economic impacts from low carbon generation

Repurposing coal power plants in the United States may provide significant opportunities to incentivize low-carbon and renewable electricity generation created by the Inflation Reduction Act (IRA). Re-using coal sites for their existing electric grid interconnections and infrastructure could reduce costs and provide benefits to coal-based communities experiencing energy transitions. This study estimates local employment, labor income, and tax revenue effects from renewable and low-carbon generation options repurposing coal power plants and meeting their economic impacts at existing coal plant sites in North Carolina. The study bridges gaps in energy transition studies by including site feasibility assessment of advanced reactors for former coal power plant sites, renewable electricity generation, and thermal energy storage. It also considers cost advantages of reusing existing power plant interconnections, IRA discounts, and generation technology economic impacts using IMPLAN. A least-cost quadratic optimization model considers different site-specific electricity generation portfolios to analyze site-based economic impacts and associated technology costs meeting or exceeding site-based coal generation and its economic impacts. This study finds that replacing coal generation costs less than maintaining the current coal fleet, a technology-inclusive portfolio provides the least-cost pathway, and benefits may exceed site-based impacts of existing coal plants. Local tax revenues from advanced reactors and thermal energy storage systems may increase revenues by at least $28 million. Across all repurposing scenarios, replacing existing coal plants with energy storage, renewable, and low-carbon generation leads to net employment growth and tax revenues, indicating further benefits to a rapid and more equitable decarbonization through economic development.

Ice templated honeycomb-like porous copper foam to improve the anisotropic thermal transfer property of phase change composites

This study explores the use of copper foam (CF) as a thermally conductive scaffold for phase change materials (PCMs), enhancing shape stability. Employing the ice template method (ITM), we fabricate a CF with a low-density, honeycomb structure and anisotropy from flake copper powders. The resulting phase change composites (PCCs), infused with paraffin wax (PW), showcase high thermal conductivity and shape retention compared to pure PW, with anisotropic heat flow due to directional channels in the CF. With a 34.4 wt% filling ratio, the PCCs achieve axial and lateral thermal conductivities of 2.85 W m−1 K−1 and 1.51 W m−1 K−1, respectively, and a thermal storage enthalpy of 158.18 J g−1. This work presents a novel method for advanced thermal energy storage and management, indicating the promise of ITM-derived CF in high-performance PCCs for diverse applications.

Production and assessment of UV-cured resin coated stearyl alcohol/expanded graphite as novel shape-stable composite phase change material for thermal energy storage

Expanded graphite-phase change materials (PCM) structures are reinforced to polymers with various methods to fabricate advanced thermal energy storage materials. However, these methods still suffer from processing time and product efficiency challenges. In this study, the UV-curing method was used to produce shape-stable EG-PCM-reinforced resin composites with fast curing and low process temperature of the resin. The composite material, comprising UV-curable resin (30 %), stearyl alcohol (65 %), and Expanded graphite (5 %), was synthesized. This synthesis aimed to address the limitations of traditional PCMs, such as low thermal conductivity and leakage. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the materials' phase change behavior and thermal stability. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) analyses were conducted to elucidate the microstructure and crystallinity of composite materials. The composites, exhibiting near-perfect impermeability with leakage as minimal as 0.89 %, not only enable the attainment of cooler environments by 2–3 °C under hot air conditions but also demonstrate exceptional thermal stability up to 207 °C, as evidenced by TGA results. Additionally, they offer a remarkable melting enthalpy value of 153.1 J/g. These composites, with their shape-retention ability during phase transitions and high thermal energy storage capacity, are a versatile and efficient option for sustainable energy management. This research contributes to the development of innovative materials for renewable energy integration and reducing carbon emissions.

Enhancing sustainability with waste hemp-shive and phase change material: Novel gypsum-based composites with advanced thermal energy storage properties

This study addresses the rising demand for sustainable construction by introducing composite materials from natural and renewable resources: gypsum, hemp, and phase change materials (PCMs). These materials cater to the growing preference for eco-friendly building solutions. Incorporating hemp enhances sustainability while integrating PCMs into the porous hemp structure ensures adequate thermal energy storage and release without leakage. Firstly, the agricultural waste hemp shives and lauryl alcohol (LA) PCM were mixed to create shape-stabilized hemp/PCM composites. The highest PCM ratio was determined in shape-stabilized composites exhibiting non-leakage properties, which was 45 wt %. These composites were then incorporated into gypsum materials at loadings of 7.5 %, 15 %, 22.5 %, and 35 wt % to produce the final composites. Morphological, thermal, and chemical characteristics of shape-stabilized composites were examined using SEM, TGA, and DSC, while the solar thermoregulation tests assessed the gypsum matrix composites. The phase change temperature of PCM was determined as 20.24 °C with a melting enthalpy value of 224.4 J/g. The hemp/PCM shape-stabilized composites demonstrated an impressive melting enthalpy value of 100.2 J/g, with only a slight reduction to 99.5 J/g after 750 test cycles. When the ambient temperature exceeded 50 °C, the central temperature of the cabins containing PCM composites was found to be at least 4 °C cooler than those containing only gypsum. Conversely, when the ambient temperature dropped to around 20 °C, it was observed that the central temperature of the cabins with PCM composites was approximately 2 °C warmer than those with only gypsum. This study introduces a novel approach to creating environmentally friendly gypsum/hemp/PCM composites for thermal energy storage systems.

Effect of nanocavity geometry on nanoscale nucleate boiling heat transfer

In recent years, surfaces with nanocavities have been identified to considerably improve boiling heat transfer, that is highly promising for advanced thermal energy systems. To boost developments in nanostructured boiling surfaces, effects of nanocavity geometry on nucleate boiling at the nanoscale are systematically studied for the first time by utilizing molecular dynamics simulation. Three typical nanocavities with rectangular, semicircular, and triangular cross-sectional shapes are constructed, which have the identical width and depth (8 nm and 4 nm). Moreover, three representative wetting conditions corresponding to different solid-liquid interaction strengths are further considered to provide a comprehensive understanding of geometry effects. The results manifest that nanocavity geometry effect on nucleate boiling can be attributed to the differences in their solid-liquid contact area and solid-liquid interactions play a vital role in reinforcement effectiveness. When the solid-liquid interaction is sufficiently strong (energy coefficient equals 1.5, termed ultra-superhydrophilicity), variations in nanocavity geometries will induce remarkable effects on boiling performance. Among three geometric configurations, the rectangular nanocavity exhibits the highest heat transfer efficiency and achieves maximum boiling enhancement, including significant improvements in bubble nucleation and growth, as well as critical heat flux. This study provides an essential insight into nanoscale boiling reinforcement mechanism.

Enhanced Gypsum Boards with Activated Carbon Composites and Phase Change Materials for Advanced Thermal Energy Storage and Electromagnetic Interference Shielding Properties

This work presents the development of novel gypsum board composites for advanced thermal energy storage (TES) and electromagnetic interference (EMI) shielding applications. Activated carbon (AC) derived from spent coffee with a high surface area (SBET = 1372 m2/g) was used as a shape stabilizer, while the commercial paraffin, RT18HC, was used as organic encapsulant phase change material (PCM). The AC showed a remarkable encapsulation efficiency as a shape stabilizer for PCM, with ~120.9 wt% (RT18HC), while the melting enthalpy (ΔHm) of the shape-stabilized PCM was 117.3 J/g. The performance of this PCM/carbon nanocomposite as a thermal energy storage material was examined by incorporating it into building components, such as gypsum wallboards. The microstructure of these advanced panels, their density, and their dispersion of additives were examined using X-ray microtomography. Their thermal-regulated performance was measured through a self-designed room model with a similar homemade environmental chamber that was able to create a uniform temperature environment, surrounding the test room during heating and cooling. The measurements showed that the advanced panels reduce temperature fluctuations and the indoor temperature of the room model, in comparison with normal gypsum panels, by a range of 2–5%. The investigated gypsum board composite samples showed efficient electromagnetic shielding performance in a frequency range of 3.5–7.0 GHz, reaching an EMI value of ~12.5 dB, which is adequate and required for commercial applications, when filled with PCMs.

High-entropy Ti-Zr-Hf-Ni-Cu alloys as solid-solid phase change materials for high-temperature thermal energy storage

High-performance high-temperature solid-solid phase change materials (SS-PCMs) are urgently demanded for thermal energy storage and thermal management at elevated temperatures in the rapidly developing energy and information industries. Here, we report a novel class of Ti-Zr-Hf-Ni-Cu high-entropy alloys showing high thermal-energy-storage performance at elevated temperatures, which are a robust candidate for high-temperature SS-PCMs. Notably, the figure-of-merit values of these Ti-Zr-Hf-Ni-Cu SS-PCMs are an order of magnitude higher than that of traditional SS-PCMs, due to their much higher thermal conductivity and satisfactory volumetric energy storage capacity as compared to traditional SS-PCMs. Furthermore, the phase transition temperatures of these SS-PCMs can be easily and precisely tuned by composition change, in a wide high-temperature range of 300–470 °C. These high figure-of-merit SS-PCMs with high thermal conductivity have extremely promising prospects for advanced thermal energy storage and compact high-power-density electronic cooling applications. This work opens a new field for exploring high-entropy alloys as solid-solid thermal-energy-storage phase change materials.

Impact of Convection and Rotation on Advanced Thermal Energy Storage Using Nanoencapsulated Phase Change Materials in Wavy Enclosures

Free convection heat transfer in hybrid nanofluids in a differentially heated wavy enclosure is studied. The wavy enclosure moves at a constant counterclockwise rotational speed along its longitudinal axis. The enclosure is filled with a hybrid nanofluids consisting of water (H2O) and nanoencapsulated phase change materials (NEPCMs). These NEPCMs consist of a polyurethane coating and a core of N‐nonadecane, which undergoes a phase transition and has the capacity to retain or emit a significant quantity of latent heat. The dimensionless forms of the governing equations have been solved using finite element method. The validity of the present code is demonstrated by comparing its predictions with published results. The governing parameters under consideration are the corrugated number, 0 ≤ N ≤ 3, the volume fraction of hybrid nanoparticles, 0.0 ≤ ϕ ≤ 0.05, the Taylor number, 8 × 102 ≤ TaH2O ≤ 2 × 104. Changing the rotation speed is found to alter the melting and solidification zones in terms of pathways and size zones. The melting zone has a large size at moderate wave number, and its size shrinks and shifts downward as the wave number increases. An increase in the heat transfer rate values up to 38% is obtained when the concentration is adjusted from 1% to 5% for N = 1.

Review of recent advancement in performance, and thermal energy storage studies on indirect solar dryers for agricultural products.

Efficient drying methods and post-harvest processes are crucial to reduce waste in fruits, vegetables, and agricultural products. Factors like moisture-related deterioration, climate change, mishandling, delayed shipping, improper storage, and sales delays contribute to post-harvest losses and quality degradation. Solar dryers, especially indirect-type solar dryers, provide a practical and environmentally friendly way to preserve these goods. In comparison to other types of solar dryers, indirect-type dryers have a number of advantages. This review focuses on evaluating the performance of different configurations of Indirect-type solar dryers in terms of drying time, maximum air temperature, drying efficiency for collectors, and overall dryer efficiency. The influence of various operating conditions on the thermal efficiency of Indirect-type solar dryers is also investigated. The study provides detailed information on the sensible and latent storage units and materials used in Indirect-type solar dryers, including those operating through natural or forced convection. The review also explores the utilization of advanced technologies, such as desiccant systems, recycling processes, the use of Nano fluids and nanoparticles, and thermal energy storage, to enhance the thermal performance of solar dryers. Additionally, the paper examines potential difficulties and suggestions for selecting, using, and testing thermal storage for indirect-type solar dryers. In summary, this review provides a comprehensive examination of indirect-type solar dryers, and their performance. It highlights the potential for improving drying efficiency through the integration of advanced technologies and thermal energy storage.

Hybrid MWCNT/TiO2 nanoparticles based high-temperature quinary nitrate salt mixture for thermal energy storage applications

This study developed an advanced thermal energy storage (TES) material consisting of a quinary nitrate salt mixture doped with hybrid MWCNT/TiO2 nanoparticles. The structural, morphology, and thermophysical properties of hybrid MWCNT/TiO2 and hybrid MWCNT/TiO2 doped quinary nitrate salt mixture was characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), laser flash analysis (LFA), viscosity measurement, X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy and Field environmental scanning electron microscopy and Energy dispersive X-ray (FESEM-EDX) analysis. Furthermore, levelized cost of electricity (LCOE) of concentrated solar power (CSP)-parabolic trough collector (PTC) power plant using the optimized sample as the TES materials were calculated using the “physical trough model” in system advisor model (SAM) software. Based on the result, 0.05 wt% dosage of hybrid MWCNT/TiO2 nanoparticles in the quinary nitrate salt mixture has the most favorable thermophysical properties, with 17.655 % enhancement in average specific heat capacity, 37.769 % enhancement in latent heat, 25.412 % enhancement in average thermal conductivity and 94.77 % decrement in viscosity. Furthermore, SAM simulation studies also showed that the developed TES material could reduce LCOE of the CSP power plant by 1.29 % to 0.1687 USD/kWh. Therefore, in the efforts of replacing the coal-fired electricity generation with the CSP-PTC power plants, it is also possible to achieve a potential annual saving of up to 552 million USD compared to commercial TES materials.

Heat transfer characteristics of fluids containing paraffin core-metallic shell nanoencapsulated phase change materials for advanced thermal energy conversion and storage applications

The influence of heat transfer characteristics of fluids filled with paraffin core-metallic shell nanoencapsulated phase change material (PCM) on photothermal conversion and storage in a volumetrically heated solar system is numerically analysed. The results show that nanoencapsulated paraffin/Al, paraffin/Au, paraffin/Ag, and paraffin/Cu filled heat transfer fluids enhance the energy storage by 68, 73, 92 and 86 %, respectively as compared with the water-based Al, Au, Ag and Cu nanofluids. It is found that the phase change slurry (PCS) improves the temperature and storage gain, as the utilization of nanoencapsulated PCM and the rise in PCM mass concentration enhance the solar energy absorption power of the slurry. The maximum enhancement in stored energy is also observed for paraffin/Cu PCM filled slurry for a particle diameter of 15 nm. The enhancement in mass concentration of paraffin from 5 to 20 %, improves the thermal performance from 312 to 554 % compared to pure water, respectively. Increasing the size of the core/shell architecture of the PCM, however, reduces the surface area-to-volume ratio of the capsule, causing aggregation of the particles and decreasing the heat transfer between the capsule and the host fluid. This in turn results in decrease in temperature gain. Furthermore, it is noticed that the merger of mono- and hybrid- nanoparticles augments the thermal performance of the PCS. The findings of the study indicate that the paraffin core-metallic shell nanoencapsulated PCMs would significantly enhance the performance of advanced photothermal energy conversion and storage devices.

Advanced Phase Change Materials from Natural Perspectives: Structural Design and Functional Applications.

Phase change materials have garnered extensive interest in heat harvesting and utilization owing to their high energy storage density and isothermal phase transition. Nevertheless, inherent leakage problems and low heat storage efficiencies hinder their widespread utilization. Nature has served as a great source of inspiration for addressing these challenges. Natural strategies are proposed to achieve advanced thermal energy management systems, and breakthroughs are made in recent years. This review focuses on recent advances in the structural design and functions of phase change materials from a natural perspective. By highlighting the structure-function relationship, advanced applications including human motion, medicine, and intelligent thermal management devices are discussed in detail. Finally, the views on the remaining challenges and future prospects are also provided, that is, phase change materials are advancing around the biomimicry design spiral.

PREFACE: ADVANCED THERMAL MANAGEMENT, ENERGY CONVERSION, AND STORAGE TECHNOLOGIES

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Natural zeolites as host matrices for the development of low-cost and stable thermochemical energy storage materials

Advanced thermal energy storage technologies based on physical adsorption and chemical reactions of thermochemical materials (TCMs) are capable of storing large shares of renewable energy with high energy density. Further research and development is required to improve the performance and reduce the cost of these materials. A promising approach to developing low-cost TCM is to use natural zeolite adsorbents as host matrices in the development of salt-loaded composite TCM. In this study, the thermal properties of various species of low-cost zeolites from natural deposits across Canada were investigated. Two high purity crystal (HPC) zeolites from the Trans Canada (TC-HPC) and Juniper Creek (J-HPC) deposits in British Columbia were determined to have the highest water uptake capacity (0.145 g/g and 0.113 g/g, respectively) and enthalpy of adsorption (408 J/g and 304 J/g, respectively). Despite having approximately half of the water uptake capacity and adsorption enthalpy of the commercially available synthetic zeolite 13X, the cost of thermal energy storage ($CAD/kWhth) of the natural zeolites was determined to be 72–79% lower than that of the synthetic zeolite. Repeated adsorption and desorption experiments demonstrated the hydrothermal stability of the HPC zeolites over multiple charge and discharge cycles. Overall, the experimental results and cost analysis indicate that Canadian HPC zeolites are promising alternatives to synthetic zeolites in the pursuit of low-cost and stable TCM.