Heat Storage Applications Research Articles

Shape-stabilized n-heptadecane/polymeric foams with modified iron oxide nanoparticles for thermal energy storage

This study based on design, preparation and characterization of polymerized high internal phase emulsion (poliHIPE) foams as support materials containing iron oxide (Fe3O4) nanoparticles for impregnation of n-heptadecane as phase change material (PCM). The Fe3O4 nanoparticles were synthesized mechanically assisted co-precipitation method and modified for harmonization with the emulsion system. Fe3O4 nanoparticles doped support materials were prepared via emulsion-templated strategy, and the produced polymeric foams used for preparation of shape-stabilized n-heptadecane based composite PCMs. The total latent heat was determined as 99.6 J/g by differential scanning calorimetry (DSC) analysis, while the impregnation ratio of n-heptadecane was found to be 67%. The performances of composites were also investigated via leakage test and heat storage rate measurement. Based on the analysis result, it was determined that shape-stabilized n-heptadecane based composite PCMs are promising energy materials for low temperature latent heat storage applications.

New Insight into Sorption Cycling Stability of Three Al-Based MOF Materials in Water Vapour.

Three porous aluminium benzene-1,3,5-tricarboxylates MIL-96(Al), MIL-100(Al) and MIL-110(Al) materials were studied for their hydrothermal stability. The 40-cycles water vapour sorption experiments for the three samples were performed by varying the temperature between 40 and 140 °C at 75% relative humidity to simulate working conditions for materials used in water sorption-based low-T heat storage and reallocation applications. The materials were characterized by powder X-ray diffraction, N2 physisorption, and Nuclear Magnetic Resonance and Infrared spectroscopies before and after the cycling tests. The results showed that the structure of MIL-110(Al) lost its crystallinity and porosity under the tested conditions, while MIL-96(Al) and MIL-100(Al) exhibited excellent hydrothermal stability. The selection of structures, which comprise the same type of metal and ligand, enabled us to attribute the differences in stability primarily to the known variances in secondary building units and the shielding of potential water coordination sites due to the differences in pore accessibility for water molecules. Additionally, our results revealed that water adsorption and desorption at tested conditions (T, RH) is very slow for all three materials, being most pronounced for the MIL-100(Al) structure.

Melting and Solidification Behaviour of Some Organic Phase Change Materials Applicable to Low Temperature Heat Storage Applications

Melting and Solidification Behaviour of Some Organic Phase Change Materials Applicable to Low Temperature Heat Storage Applications

Use of Low Melting Point Metals and Alloys (Tm < 420 °C) as Phase Change Materials: A Review

Phase Change Materials (PCMs) are materials that release or absorb sufficient latent heat at a constant temperature or a relatively narrow temperature range during their solid/liquid transformation to be used for heating or cooling purposes. Although the use of PCMs has increased significantly in recent years, their major applications are limited to Latent Heat Storage (LHS) applications, especially in solar energy systems and buildings. PCMs can be classified according to their composition, working temperature and application. Metallic PCMs appear to be the best alternative to salts and organic materials due to their high conductivity, high latent heat storage capacity and wide-ranging phase change temperature, i.e., melting temperature and chemical compatibility with their containers. This paper reviews the latest achievements in the field of low-melting point metallic PCMs (LMPM-PCMs), i.e., those with melting temperatures of less than 420 °C, based on Zn, Ga, Bi, In and Sn. Pure LMPM-PCMs, alloy LMPM-PCMs and Miscibility Gap Alloy (MGA) LMPM-PCMs are considered. Criteria for the selection of PCMs and their containers are evaluated. The physical properties and chemical stability of metallic PCMs, as well as their applications, are listed, and new application potentials are presented or suggested. In particular, the novel application of metallic PCMs in casting design is demonstrated and suggested.

Novel Synthesis and Structural Investigations of ZnSO4/MgCl2 Composite Hydrated Salt for Enhanced Thermochemical Heat Storage Applications

Novel Synthesis and Structural Investigations of ZnSO4/MgCl2 Composite Hydrated Salt for Enhanced Thermochemical Heat Storage Applications

Hydrochemical Characterization of Groundwaters’ Fluid Flow through the Upper Mesozoic Carbonate Geothermal Reservoirs in the Geneva Basin: An Evolution more than 15,000 Years Long

Groundwaters circulating in Upper Mesozoic carbonates are of great interest for geothermal heat production and storage applications in the Geneva area. This study aims at providing new insights and proposing new interpretations about the mineral-water reactions and the fluid-flow paths mechanisms across the Geneva Basin (GB). Data from previous studies are combined and improved by new ones collected from cold and hot springs and geothermal exploration wells in 2018 and 2020 in the framework of the GEothermies program and HEATSTORE project. Major ions, trace elements, and the isotopes of Oxygen, Hydrogen, Sulfur, Strontium, and Carbo have been analysed and the results show that the sampled waters have a meteoric origin, the carbonate aquifers act as preferential host rocks for geothermal waters, and partial contribution from the Cenozoic sediments can be observed in some samples. The Jura Mountains and the Saleve Ridge are the main catchment areas and an evolution from a pure Ca-HCO3 footprint for the cold springs, to a Na > Ca-HCO3 and a Na-Cl composutions, is observed at the two geothermal wells. The residence time is in the order of a few years for the cold springs and reaches up to 15–20,000 years for the deep wells.

Hierarchical aluminum fumarate metal-organic framework - alumina host matrix: Design and application to CaCl2 composites for thermochemical heat storage

Aluminum fumarate – porous alumina (AF/Al), synthesized by reactive seeding method, has been used for the first time as a host matrix for CaCl2-based composite sorbents (CSPM) for thermochemical heat storage (TCHS) applications. The porous matrix and composites containing varying amounts of CaCl2 (20–60 wt%) were fully characterized by combining multiple techniques (N2 adsorption/desorption isotherms, powder X-ray diffraction, scanning electron microscopy, elemental analysis). The storage performances of the studied materials have been investigated using thermogravimetry coupled to differential scanning calorimetry (TG/DSC) and a humidity generator. The results show that the hierarchical porous structure of AF/Al impacts the physico-chemical characteristics, water and heat storage performances and water sorption kinetics. The properties of AF/Al, presenting both micro and mesoporosity, as host matrix for CaCl2 have been compared with those of microporous AF and mesoporous Al. It is evidenced that in AF/Al, the presence of micropores arising from the AF membrane enhances the storage capacity of Al by increasing the number of available sorption sites, while the textural mesoporosity of Al offers favorable conditions for water vapor diffusivity, which is crucial for optimal mass and heat transfer. CaCl2–AF/Al composites exhibit enhanced water and heat storage capacities compared to the matrix alone, their performances increasing with the salt content to attain 1930 kJ kg−1 and 0.68 kgH2O kg−1 for 61 wt% of salt. The hydration level at 25 °C and 30%RH did not exceed a maximum of 4.4 nH2O/nanhydrous material, limiting deliquescence and leaching of the salt. A comparative study of the impact of host matrix characteristics on CSPM properties highlights the predominant impact of the salt content on the storage capacity, as well as the influence of porosity on the water vapor sorption behavior.

Sustainable and open sorption system for low‐temperature heat storage applications

In the present study, an open sorption thermochemical energy storage (TCES) system was developed and investigated experimentally for low-temperature heat storage applications using zeolites. Desorption and adsorption experiments were carried out sequentially for 15 cycles to study the energy storage and retrieval characteristics. Further, the performance characteristics were analysed to find the system's suitability for intended applications. The charging and discharging processes were carried out respectively at around 95°C and room temperature, for zeolite 13X and zeolite 4A. Zeolite 13X exhibited better average total energy storage density during the desorption and adsorption and they are respectively 129.4 and 57 kWh/m3. The average cumulative energy storage efficiency for zeolite 13X and zeolite 4A are respectively 44.1% and 24%. Similarly, the average exergy efficiency for zeolite 13X and zeolite 4A are respectively 21.5% and 11%. For the tested thermochemical materials (TCMs), the deviations in mass change due to multi-cycle test-run was small and hence suitable for long-term usage without concern about their stability. The present study has demonstrated the technical competence in utilizing the energy sources (eg, solar energy, industrial waste heat) towards low-temperature heat storage applications, viz. building's space heating and water heating.

Thermal properties of 1-hexadecanol/high density polyethylene/graphene nanoplates composites as form-stable heat storage materials

Composite phase change materials (CPCM) composed of 1-hexadecanol (HD), high density polyethylene (HDPE) and graphene nanoplates (GNP) were synthesized in this work. HD served as phase change material, while HDPE acted as support frame. GNP was introduced to improve thermal conductivity. A number of tests were conducted to acquire physical performances of the CPCM. The chemical components of the materials were obtained from Fourier transformation infrared spectroscope (FT-IR). The crystal structure was illustrated by X-ray diffractometer (XRD). The microcosmic pattern was observed form scanning electronic microscope (SEM). Phase transition characters were analyzed from the data of differential scanning calorimeter (DSC). Thermal stability was shown by thermogravimetric analyzer (TGA). Thermal conductivity of CPCM3 was 1.86 times of HD/HDPE composites (PCM2). The GNP significantly enhanced the thermal conductivity. The latent heat and chemical structure were stable after the thermal cycling experiment. Hence, the CPCM3 is a reliable material in heat storage applications. • 1-Hexadecanol/high density polyethylene/graphene nanoplate composites were prepared. • The CPCM3 melted at 48.53 °C with 146.57 kJ/kg latent heat. • Thermal conductivity of CPCM with 3 wt% GNP is 1.86 times of that of PCM2. • The CPCM behaves good thermal stability and reliability.

Exploration of Highly Porous Biochar Derived from Dead Leaves to Immobilize LiOH·H2O Nanoparticles for Efficient Thermochemical Heat Storage Applications

The inadequate utilization of low‐grade energy from industrial waste heat and solar energy calls for an efficient thermochemical heat storage material. The fabrication of a low‐cost but highly efficient composite comprising highly porous biochar and LiOH·H2O nanoparticles for heat storage applications is reported. The biochar is prepared by the KOH‐assisted pyrolysis of dead banyan leaves, and its microstructure and surface properties can be finely tuned by varying the KOH‐to‐biomass ratio. Such biochar can be mediated to possess a large specific surface area and total pore volume reaching as high as 1255.03 m2 g−1 and 3.65 cm3 g−1, respectively, superior to most previously reported biochar/biocarbon derived from different kinds of waste biomass. Besides, adequate functional groups and a hierarchical porous structure consisting of micropores and mesopores are demonstrated in the prepared biochar. The subsequent hydrothermal reaction with a short duration yields a biochar‐LiOH·H2O composite, where LiOH·H2O can be homogeneously immobilized with a nanoscale size within the porous biochar matrix. Thus, an enormous biochar/LiOH·H2O nanoparticles interface can be obtained, resulting in fast hydration reactions with water molecules. Consequently, a significant heat storage density of as high as 3089.6 kJ kg−1 is achieved within only 10 min, outstripping some recently reported thermochemical heat storage systems.

Mechanical Booster Pump-Assisted Thermochemical Mode for Low-Grade Heat Storage and Upgrading: A Thermodynamic Study

To assure stable and dependable functioning of the thermochemical energy storage (TCES) system under unstable low-grade heat temperatures, three mechanical booster pump-assisted TCES (MBP-assisted TCES) modes operating with SrBr2·H2O/H2O, LiOH/H2O, and CaCl2·H2O/H2O are proposed for the application of heat storage and upgrading. The operating modes are the MBP-assisted charging mode (A mode), MBP-assisted discharging mode (B mode), and MBP-assisted charging and discharging mode (C mode). A thermodynamic model is established to evaluate the influences of condensing temperature, compression ratio, MBP isentropic efficiency, and reaction advancement on the heat source temperature and system performance from both energy and exergy perspectives. The results indicate that compared with the other two modes, the B mode is more effective in reducing the heat source temperature and achieving better system performance. Compared to the conventional TCES mode, the proposed modes can operate at lower heat source temperatures that can be minimized by up to 21∼25°C by employing the B mode with a compression ratio of 3.0 at the condensing temperature of 24°C. The B mode with SrBr2·H2O/H2O exhibits the highest energy and exergy efficiencies that the coefficients of performance based on total energy input and electric power consumed (COPtotal and COPelec), and exergy efficiency varies in the range of 0.53∼0.59, 7.4∼19.6, and 0.78∼0.95, respectively. In contrast, CaCl2·H2O/H2O shows the lowest system performance, but a higher heat output temperature can be required. In addition, to maintain the MBP discharge temperature below 180°C, there is a maximum permitted compression ratio that varies depending on the operating modes, operating conditions, and working pairs. The findings of this research can be used as theoretical references and suggestions for selecting MBP-assisted TCES modes, operating conditions, and working pairs for low-grade heat storage and upgrading.

Encapsulated Copper-Based Phase-Change Materials for High-Temperature Heat Storage.

In this study, a copper-based capsule, encapsulated by a black alumina shell using a simple method, was developed for high-temperature heat storage over 1000 °C. The shell was filled with copper beads (diameter = ∼3 mm), the copper–aluminum (Cu–Al) atomized powder (particle size = 150 μm) was filled in the gap, and then it was heat-treated. This eventually formed a high-density, aluminum-rich network around the Cu beads in the shell. Morphological observations indicated that the corrosion of copper oxide (CuO) on the alumina shell was significantly reduced by mixing Al with Cu. When heat-treated in air at 1100 °C, Cu became CuO, which reacted with Al2O3 to form a new compound, CuAl2O4. Owing to this two-step reaction, the area around the hole provided at the top of the spherical shell gets sealed, thereby suppressing the flow of oxygen into the shell (self-sealing function). The mechanism of in situ sealing was detected using X-ray diffraction and scanning electron microscopy analyses. The Cu–(5–10%) Al capsule could endure a 400 h air exposure test at 1100 °C without leakage or cracking. A low weight increase ratio of 3.5% after the exposure revealed good oxidation resistance of the capsule, whereas the slight damage load change of the capsule after the exposure showed good mechanical stability. The results concluded that a Cu–(5–10%) Al capsule for high-temperature heat storage applications above 1000 °C can be fabricated by a simple process, and it demonstrates excellent durability during the long-term air exposure test. The data obtained in this study can be used as a reference for the design of packed beds in the future.

Advanced diffusion methods for H[formula omitted]O in salt hydrates

A thermochemical heat storage system based on salt hydrates can fulfill a crucial link in a renewable energy society by bridging the gaps between the intermittent heat supply and demand. However, slow diffusion of water through the salt hydrates limit the power output of the storage. Simultaneously, slow water diffusion gives rise to local over-hydrated spots. Recent studies show that cracks and pores in the salt crystal increase the (de)hydration rate. In this sense, we analyzed the diffusion behavior of water in crystalline CaCl2⋅2H2O and around crystal imperfections, like cracks and pores, through reactive force fields molecular dynamics. A Smoluchowski diffusion equation-based method was used to perform this diffusion study. This method enabled the possibility to study a local diffusion behavior instead of the often used global diffusion methods. We found that the diffusion of H2O is extremely low in the crystalline regions of the CaCl2⋅2H2O (<10−10 m2/s), which corresponds with literature for similar salts. However, in cracks, pores, and amorphous regions of the salt, the diffusion is significantly higher (≥10−9 m2/s). Thereby, this enhanced local diffusivity explains why imperfections of the crystalline salt hydrate can improve its characteristics for thermochemical heat storage applications.

Morphological Observation of LiCl Deliquescence in PDMS-Based Composite Foams

The LiCl-based heat storage system exhibits a high-energy density, making it an attractive and one of the most investigated candidates for low-temperature heat storage applications. Nevertheless, lithium chloride, due to its hygroscopic nature, incurs the phenomenon of deliquescence, which causes some operational challenges, such as agglomeration, corrosion, and swelling problems during hydration/dehydration cycles. Here, we propose a composite material based on silicone vapor-permeable foam filled with the salt hydrate, hereafter named LiCl-PDMS, aiming at confining the salt in a matrix to prevent deliquescence-related issues but without inhibiting the vapour flow. In particular, the structural and morphological modification during hydration/dehydration cycles is investigated on the composite foam, which is prepared with a salt content of 40 wt.%. A characterization protocol coupling temperature scanned X-ray diffraction (XRD) and environmental scanning electron microscopy (ESEM) analysis is established. The operando conditions of the dehydration/hydration cycle were reproduced while structural and morphological characterizations were performed, allowing for the evaluation of the interaction between the salt and the water vapor environment in the confined silicon matrix. The material energy density was also measured with a customized coupled thermogravimetric/differential scanning calorimetric analysis (TG/DSC). The results show an effective embedding of the material, which limits the salt solution release when overhydrated. Additionally, the flexibility of the matrix allows for the volume shrinkage/expansion of the salt caused by the cyclic dehydration/hydration reactions without any damages to the foam structure. The LiCl-PDMS foam has an energy density of 1854 kJ/kg or 323 kWh/m3, thus making it a competitive candidate among other LiCl salt hydrate composites.

Microfluidic Production of Monodisperse Biopolymer Microcapsules for Latent Heat Storage.

Microencapsulation of phase change materials in a polymer shell is a promising technology to prevent them from leakage and to use them as a handleable powder state. However, the microencapsulation process is a time-consuming process because the typical shell-forming step requires polymerization or evaporation of the solvent. In this study, we report a simple and rapid flow process to prepare monodisperse biocompatible cellulose acetate (CA) microcapsules encapsulating n-hexadecane (HD) for latent heat storage applications. The microcapsules were prepared by combining microfluidic droplet formation and subsequent rapid solvent removal from the droplets by solvent diffusion. The diameter and shell thickness of the microcapsules could be controlled by adjusting the flow rate and the HD-to-CA weight ratio in the dispersed phase. We found that 1-hexadecanol added to the microcapsules played the role of a nucleation agent and mitigated the supercooling phenomenon during crystallization. Furthermore, cross-linking of the CA shell with poly(propylene glycol), tolylene 2,4-diisocyanate terminated, resulted in the formation of a thin and dense shell. The microcapsules exhibited a 66 wt % encapsulation efficiency and a 176 J g-1 latent heat storage capacity, with negligible supercooling. We believe that this microflow process can contribute to the preparation of environmentally friendly microcapsules for heat storage applications.

Phase change material mixed with chloride salt graphite foam infiltration for latent heat storage applications at higher temperatures and pressures

Phase change material mixed with chloride salt graphite foam infiltration for latent heat storage applications at higher temperatures and pressures

Adsorptive Systems for Heat Transformation and Heat Storage Applications

According to the BP Statistical Review of World Energy 2020 [...]

Effect of Boron Nitride on the Heat Transfer and Heat Storage of Poly(ethylene glycol)/Expanded Vermiculite Composite Phase-Change Materials.

In this work, the expanded vermiculite/poly(ethylene glycol)–boron nitride (E/PB-X) shape-stabilized composite phase-change materials with the encapsulation capacity of ∼66.16 wt % were prepared by a typical vacuum impregnation method to overcome liquid leakage during phase transition and poor thermal conductivity during heat transfer of poly(ethylene glycol). It was found that the boron nitride showed a great influence on the heat transfer and heat storage of E/PB-X. The thermal conductivity of E/PB-X was 0.45–0.49 W/(m·K), indicating that the heat transfer of E/PB-X was significantly enhanced by the dispersed boron nitride fillers, which was mainly attributed to the reduction of interfacial thermal resistance and the formation of rapid thermally conductive channels. However, the latent heat (∼55.76 J/g) of E/PB-X decreased with the increase in the boron nitride content, revealing that the heat storage behavior of E/PB-X was strongly affected by the confinement of surface interactions of boron nitride and expanded vermiculite, which was consistent with the crystallization behavior determined by X-ray diffractometer (XRD) results. Moreover, the spectroscopy (FT-IR) and thermogravimetric analyzer (TGA) results confirmed that E/PB-X exhibited excellent chemical compatibility and thermal stability, respectively, which were conducive to practical heat storage applications.

Synthesis and Adsorbent Performance of Modified Biochar with Ag/MgO Nanocomposites for Heat Storage Application

Heat storage is a major problem in the world. Many research is going on the heat storage application. This research investigates the novel Ag/MgO/biochar nanocomposites for heat storage. Ag/MgO/biochar nanocomposites were fabricated using solvent-free ball milling techniques. According to several analytical measurements, the Ag/MgO nanoparticles in biochar are uniformly dispersed across the carbon interface. This type of adsorbent material has been characterized by different techniques such as X-ray diffraction pattern analysis (XRD), FTIR analysis, scanning electron microscope (SEM), and transmission electron microscope (TEM) as all indicate the surface morphology and successful ball milling synthesis of Ag/MgO nanocomposites. The UV visible spectroscopy wavelength range of AgNPs and MgONPs is 330 nm and 470 nm, respectively. FTIR analysis revealed that different functional groups of modified biochar nanocomposites such as O-H group are 3728 cm-1 and for C-H bond is 932 cm-1, C-O group is 1420 cm-1, and C=O is 1785 cm-1, respectively. Adsorption tests showed that 1.0 gL-1 dosage with 60% phosphate removal, an ion, and 0.2 gL-1 of dosages that had 85% methylene blue decomposition, a charged synthetic dye, were the lowest absorption levels. This research suggests that ball milling offers the advantages of stabilization and chemical adaptability for customized remediation of different atmospheric contaminants. Ball milling is a facile and feasible process to fabricate carbon-metal-oxide nanomaterials.

Assessment of selected salt hydrates for thermochemical energy storage applications

Inorganic salt hydrates are gaining popularity across the heat storage applications due to their good dehydration and hydration characteristics. The present study investigates the dehydration and hydration behaviour of the selected salt hydrates (SrBr2·6H2O, LaCl3·7H2O, MgCl2·6H2O, and MgSO4·7H2O) sequentially for four times using a differential thermogravimetric (DTG-60H) analyzer. The samples were initially heated from room temperature to 600 °C at different heating rates (2, 5, 10 and 20 °C/min) to understand the materials’ behaviour. The dehydration temperatures and the associated enthalpies were observed to increase with the heating rates. For the tested heating rates, the dehydration temperatures and the enthalpies were found to have a range of 142–329 °C and 1420–3050 J/g respectively. The DTG curves suggest that the tested salts lose their water content mostly in the initial phase of heating. The mass loss due to dehydration up to 120 °C when heated at 5 °C/min ranges from 22% to 37%, which can be considered as a good sign for better enthalpies. The changes in mass due to the dehydration and hydration were almost same across the cycles tested, which confirms the materials’ thermal stability. Among the tested salts, LaCl3·7H2O exhibited better hydration enthalpies owing to its higher water vapour absorption capacity, ranging from 107.5 to 215.3 J/g. The present results indicate the materials’ suitability for thermochemical energy storage applications if used with an appropriate temperature program.