Thermal Energy Storage Materials Research Articles

Crystal Phase Ionic Liquids for Energy Applications: Heat Capacity Prediction via a Hybrid Group Contribution Approach.

In the selection and design of ionic liquids (ILs) for various applications, including heat transfer fluids, thermal energy storage materials, fuel cells, and solvents for chemical processes, heat capacity is a key thermodynamic property. While several attempts have been made to develop predictive models for the estimation of the heat capacity of ILs in their liquid phase, none so far have been reported for the ILs' solid crystal phase. This is particularly important for applications where ILs will be used for thermal energy storage in the solid phase. For the first time, a model has been developed and used for the prediction of crystal phase heat capacity based on extending and modifying a previously developed hybrid group contribution model (GCM) for liquid phase heat capacity. A comprehensive database of over 5000 data points with 71 unique crystal phase ILs, comprising 42 different cations and 23 different anions, was used for parameterization and testing. This hybrid model takes into account the effect of the anion core, cation core, and subgroups within cations and anions, in addition to the derived indirect parameters that reflect the effects of branching and distribution around the core of the IL. According to the results, the developed GCM can reliably predict the crystal phase heat capacity with a mean absolute percentage error of 6.78%. This study aims to fill this current gap in the literature and to enable the design of ILs for thermal energy storage and other solid phase applications.

Preparation of a heat storage material from Nano-SiC based composite carbonate with boosted heat storage density for high temperature thermal energy storage

Heat storage materials for high temperature thermal energy storage, e.g., higher than 500 °C, are rather few and their heat storage density (HSD) are insufficient. Therefore, a novel nano-SiC based composite carbonate heat storage material (Nano-SiC CCHSM) was fabricated in this study. The nano-SiC was innovatively applied to improve the HSD of the CCHSM at high temperature. Results show that the addition of nano-SiC significantly improved the HSD of the base material from 542.7 KJ/Kg to as high as 990.7 KJ/Kg. Optimal addition ratio of nano-SiC was 1 % with the sintering temperature of 550 °C. The nano-SiC mainly contributes to improving the sensible HSD of the CCHSM, especially in the liquid sensible HSD. Deep analysis shows that the correlated reaction mechanism is ascribed to the divergent free energy of liquid-phase ions to the nano-SiC, which leads to the heterogeneous nucleation of molten ions and consequently resulting in the high specific heat capacity of the newly formed protruding nanostructures.

Evaluation of volcanic ash as a low-cost high-temperature thermal energy storage material for concentrated solar power

The integration of renewable energy sources is facilitated by TES because it enables the storage and release of excess clean energy, which improves grid stability. In concentrating solar power plants (CSP), solar molten salt is frequently used since it has some advantages such as good thermal properties. However, certain challenges, such as molten salt corrosion, salt solidification, and high production costs, must be carefully considered. An alternative approach gaining attention involves the use of solid ceramic materials capable of withstanding high temperatures as a potential TES medium without the molten salt drawbacks. Elevating the operating temperature of power conversion processes while concurrently reducing capital costs is a strategic means to enhance the competitiveness of these innovative power plants. This study explores the potential of volcanic ash, a low-cost naturally occurring ceramic material, for TES. The evaluation revealed high-temperature stability up to 750 °C, slight mass gain but stable over time, elevated solar absorption, and excellent thermal and chemical stability, even in the presence of molten salts.

A Mini Review on Sewage Sludge and Red Mud Recycling for Thermal Energy Storage

Sewage sludge and red mud, as common industrial waste, have become a research hotspot in the field of achieving carbon peaking and carbon neutrality, reducing carbon emissions, and solving environmental problems. However, their treatment and disposal have always been a difficult problem in the environmental field. Utilizing these two materials for thermal energy storage can not only improve energy utilization efficiency but also further reduce carbon emissions during their treatment process, providing a new approach for sustainable development in the industrial sector. This article summarizes the research progress for the resource recovery of sewage sludge and red mud for direct thermal energy recovery and composite phase change energy storage. After proper treatment, sludge and red mud can be directly used as energy storage materials. In addition, sludge and red mud can be combined with phase change materials to prepare composite materials with an excellent energy storage performance. This composite has broad application prospects in fields such as solar energy utilization and building energy efficiency. However, there are still some challenges and issues in this resource recovery and utilization, such as potential environmental pollution during the treatment process, the long-term stability of energy storage materials, and cost-effectiveness, which require further research and resolution. The purpose of this paper is to evaluate the potential of sewage sludge and red mud as energy storage materials, to explore their feasibility and advantages in practical applications, and to reveal the research progress, technical challenges, and future development directions of these two materials in the field of thermal energy storage.

Preparation of mono-sized high sphericity Al-Si alloy particles for thermal energy storage materials by pulsated orifice ejection method

The demand for Al-Si particles with high sphericity and narrow size distribution is growing in the field of thermal energy storage. In this study, a novel pulsated orifice ejection method (POEM) was successfully employed to produce different-sized Al-Si alloy particles. The analysis indicates that such particles exhibit high sphericity, with each particle having a sphericity exceeding 0.9. The particles are precisely size-controllable and mono-sized, thereby ensuring that they have the identical thermal history. The combination of cooling rate calculation and particle structure analysis indicates that the particles prepared by POEM exhibit higher cooling rates through rapid solidification, resulting in finer and more uniform microstructures. The thermal analysis results demonstrate that the Al-Si alloy particles prepared in this study have high melting latent heat (approximately 500.87 J/g) and solidification latent heat (approximately 467.26 J/g), showcasing their potential as high-efficiency phase change materials for high-temperature thermal energy storage.

SiO2@Cu core-shell nanostructure impregnation on phase changed material (paraffin) for thermal energy storage

ABSTRACT The present research aims to achieve a shape-stable, and leakage-proof material for thermal energy storage (TES). The leakage analysis of 20 wt.% SiO2@Cu PCM shows 0.05%, as a result, more testing is conducted to assess its morphology, structure, and thermal properties. TGA and DSC studies demonstrated that the latent heat and thermal degradation rate (TDR) has been delayed, with a significant decrease in latent heat of roughly 8.7% compared to pure paraffin. Laser Flash Method (LFA) results revealed that the thermal conductivity (TC) of the PCM composite significantly increased 4.84 times than the paraffin.

Coconut shell-derived activated carbon-enhanced water phase change material for cold thermal energy storage.

In building cooling, the demand for cooling surges during specific times, stressing air-conditioner operation, and additional cooling is often wasted during low-demand periods. Water-phase change material (W-PCM)-based thermal energy storage (TES) allows for load shifting and effective management of peak demand by storing cooling energy when the demand is low. This stored energy can be deployed during peak hours, decreasing energy usage and associated CO2 emissions. However, the use of W-PCMs was hindered by phase separation, slow energy transfer, and high supercooling degree (SCD). We synthesized coconut shell (CNS)-produced activated carbon (ACC) to use as a thermal enhancer in W-PCMs for the first time. First, ACC was synthesized from CNS via steam activation. Then, transmission electron microscopy was used to confirm the pore morphology of the CNS-ACC.The synthesis of the W-PCM with various weight percentages (0.1, 0.6, and 1.2) of CNS-ACC was accomplished in two steps. Zeta potential distribution analysis revealed that the W-PCM with CNS-ACC exhibited colloidal stability. Thermal conductivity (TC) and thermogram analyses revealed that a dose of 1.2 wt% CNS-ACC enhanced liquid and solid TC by 9% and 22%, respectively, despite a 6% and 8% decrease in specific heat and latent heat. More specifically, solidification assessment in a spherical enclosure revealed 100% suppression of SCD with 1.2 wt% CNS-ACC. As a result of this and the enhanced TC, the overall solidification process was accelerated, reducing the overall duration by 18.5%. Thus, the combination of CNS-derived ACC and W-PCM for TES in building cooling could reduce energy consumption and associated CO2 emissions.

Preparation and Thermal Performances of Lauric Acid/Polyvinyl Butyral/Graphene Nanoplates Composite Phase Change Materials

In recent years, there has been significant progress in the development and application of phase change materials (PCMs) for thermal energy storage. The new lauric acid (LA)/polyvinyl butyral (PVB)/graphene nanoplates (GNP) composite phase change materials (CPCM) are prepared using the solution blending method, in which LA acts as PCM, PVB serves as support material, and GNP is used as thermally conductive enhancer. The prepared CPCM with 80 wt% LA can retain stable shape without leakage. The Fourier‐transform infrared and X‐ray diffractometer results indicate that there is no chemical reaction among the various components of the CPCM. The differential scanning calorimeter results show the CPCM3 (with 80 wt% LA and 5 wt% GNP) has melting latent heat of 134.41 KJ Kg−1 with melting temperature of 41.73 °C. The thermal conductivity tests present that thermal conductivity of CPCM3 is 0.689 W (m K)−1, which is 3.83 times that of the PCM2. The thermogravimetric analyzer results verify that the CPCM possess good thermal stability within the operating temperature range of 35–45 °C without any degradation. The thermal cycling tests indicate that CPCM have good thermal reliability. Therefore, it has promising applications in building energy conservation, solar thermal systems, thermal management, and textiles.

Exploring the role of surface roughness in concrete-based thermal energy storage systems: A computational study

This study computationally investigates the effect of thermal energy storage (TES) material surface roughness on heat transfer fluid (HTF) flow dynamics and heat transfer capabilities. The motivation is to further understand systems where concrete as the TES material directly interfaces with air as the HTF, based on previous research suggesting potential benefits of avoiding differential thermal expansion issues associated with metallic tubes. A k-ε turbulence model in COMSOL Multiphysics examined air flow over concrete surfaces with five levels of roughness from 0 to 3 mm peak height. Increasing surface roughness enhances turbulence and significantly improves heat transfer and thermal storage performance, with 7 % higher charging efficiency and energy storage capacity and 55.6 % greater heat transfer rate from 0.3 to 3 mm roughness, despite a 138 % increase in pressure drop. Applying artificial surface modifications like indentations or fins could further optimize efficiency by amplifying heat transfer advantages of increased roughness while moderating pressure losses. This indicates a promising direction for future research on enhancing thermal energy storage through concrete surface optimization and substantiates the potential of concrete as an inexpensive, scalable, high performance TES material.

Biodegradable polylactic acid/polyethylene glycol blends as form-stable phase change materials for thermal energy storage and management

Polyethylene glycol (PEG) is a commonly used phase change material for thermal energy storage. It can store amounts of heat in the process of phase transition, whereas the solid-to-liquid transition requires it to be form-stabilized before application. In this study, a phase change composite with form-stability and processibility is prepared by simply blending PLA with PEG at 180 °C, reaching a maximum PEG loading of 90 wt%. The preparation is easy, cheap, environmental-benign, and scalable. Besides, the obtained PLA/PEG (PLEG) composites are feasible for regulating the thermal behaviors of batteries operated at high rates, providing a low-cost and simple approach to improving the cyclability of fast-charging batteries.

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.

Impact of molten salts composition on the corrosion behavior of NiMoCr and CoNiCrAl coatings on L-PBF 316L stainless steel for CSP plants

The high-temperature corrosion performance of NiMoCr and CoNiCrAl coatings produced by high velocity oxy-fuel (HVOF) on laser powder bed fusion (L-PBF) 316L stainless steel substate has been evaluated in presence of three different molten salts used as thermal energy storage (TES) materials for concentrated solar power (CSP) plants. The coatings have an excellent oxidation resistance at 700 °C, showing a percentage of affected thickness lower than 2 %, due to the formation of a protective layer of Cr2O3 and Al2O3 in both NiMoCr and CoNiCrAl coatings, respectively. The carbonates-based molten salt accelerates the corrosion of the NiMoCr coating, affecting around 43 % of the coating thickness, due to the formation of chromates and the high depletion of Mo in the coating. In contrast, the effective protection shown by the CoNiCrAl coating is explained because the grown LiAlO2 after the lithiation process has a high capacity to act as a strong diffusion barrier for metal ions and inhibited the formation of chromates. In the presence of two different ZnCl2 and MgCl2-rich molten salts, the CoNiCrAl coating behaved worse than NiMoCr coating due to the breakage of the (Al,Cr)-rich oxide layer as a consequence of an active oxidation mechanism and due to the formation of voids along the entire thickness, which were identified in 100 % of the coating thickness. The superior corrosion resistance of the NiMoCr coating in presence of the chloride rich molten salts was attributed to the presence of Mo, which fixed the Cr and inhibited the diffusion of oxygen.

Large supercooling of Al[sbnd]Si alloy in microcapsule composed of Al2O3 shell

Al–Si-based microencapsulated phase change materials (MEPCMs) with a eutectic temperature of 577 °C are promising thermal energy storage (TES) materials owing to their large latent heat. Various preparation methods for Al–Si-based MEPCMs with Al2O3 shells have been reported; interestingly, Al–Si-based MEPCMs have large supercooling that does not depend on the preparation method. Supercooling is an important property of MEPCMs in the engineering aspects of designing a TES system. However, limited studies have reported the mechanism of supercooling in MEPCM. Moreover, the large supercooling of AlSi alloys in microcapsules compared with bulk materials is an interesting phenomenon in the field of physical chemistry. This study investigates the supercooling phenomenon in eutectic, hypoeutectic, and hypereutectic AlSi alloy MEPCMs, that is, AlSi alloys in a microcapsule comprising an Al2O3 shell. For the MEPCM with a hypoeutectic composition, supercooling is not observed because the primary Al acts as a nucleation site. For MEPCMs of eutectic and hypereutectic compositions, supercooling is observed at 25–37 °C. When the MEPCMs are heated to 1000 °C and then cooled, the supercooling degree increases significantly. In MEPCMs with a hypoeutectic composition, the precipitation of primary Al crystals does not occur under these conditions. Such findings contribute to the optimization of the design and operation of TES systems.

Tuning the thermal conductivity of organic-inorganic double-shell thermal storage microcapsules triggered by atomic layer deposition

The regulation of the thermal conductivity of thermal energy storage materials has become a primary challenge to expand the range of utilization for different application scenarios. In this study, organic-shell microcapsule (paraffin@melamine formaldehyde) was initially prepared by in situ polymerization, followed by the deposition of anatase TiO2 on the organic-shell microcapsule using atomic layer deposition (ALD) to form organic-inorganic double-shell microcapsule. The effect of the thickness of the TiO2 shell on the equivalent thermal conductivity of the microcapsules was investigated by utilizing ALD's precise and controllable characteristics for the coating thickness. The obtained double-shell microcapsules indicated a drop in thermal storage capacity, but a substantial boost in thermal stability. Moreover, the thermal conductivity of microcapsules can be tuned in the range between 0.1837 and 0.7529 W m−1 K−1 within 1500 ALD cycle treatment. Furthermore, the parameters of ALD, such as reaction temperature and exposure time, were varied to obtain an amorphous TiO2 shell, and the impacts of different crystal form of TiO2 on the heat transfer properties of microcapsules were concluded by comparison. Double-shell microcapsules exhibited superior mechanical properties compared to single-shell structure. The findings can stimulate significant research interest in broadening the applications of thermal storage microcapsules.

Preparation and characterization of phase change erythritol/expanded graphite@Ag composite materials for thermal energy storage

In this paper, the composite PCMs of Erythritol (ET)/Expanded Graphite (EG)@Ag were prepared by vacuum impregnation method with EG@Ag as matrix and the ET as the phase change material (PCM). The chemical compatibility, thermodynamic properties and thermal stability of composite phase change materials (CPCMs) were systematically examined. The results illustrated that the CPCMs possessed good chemical compatibility with only physical interaction between ET and EG@Ag. The supercooling of ET/EG@Ag-8 wt% reduced by 42.13 °C, which also remain high melting and solidification enthalpy of −258.09 J/g and 187.63 J/g, respectively. The thermal conductivity of ET/EG@Ag-8 wt% reached to 2.87 W/(m·K), which resulted in an enhancement of 463 % in the thermal conductivity of ET. Thermal stability results show that all CPCMs of ET/EG@Ag present good thermal stability below 200 °C. This offers new prospects for the use of ET in the field of medium temperature phase transitions.

مراجعة على التقييم الاقتصادي لدمج المواد المغلفة متغيرة الطور في أغلفة المباني

The worldwide energy crisis has made energy-saving a topic of concern in almost every country. Previous research has explored the use of thermal energy storage materials (TES), such as phase change materials (PCMs), as an effective energy-saving technique. Among various immersion techniques, macro-encapsulation has proven to be efficient, safe, and convenient. However, choosing the right PCM system can be complicated due to the variety of available PCM types, encapsulation materials, and encapsulation shapes. Moreover, while macro-encapsulated PCM systems are efficient, their feasibility depends on several factors, including energy prices, economic situation, and climatic conditions. Therefore, this research aims to provide a comprehensive overview to help create a deeper understanding of the design and application of macro-encapsulated PCM systems. It explains the different types of PCM, encapsulation materials, and encapsulation shapes, guiding the selection for the most appropriate system regarding the surrounding environment. Additionally, it aims to present a guideline for conducting feasibility studies on energy-saving systems such as PCM. A total of 80 research papers covering the intersection between the thermal performance of PCM and the economic assessment have been categorized, studied, and analyzed in order to identify the most accurate method of assessing the system’s feasibility. By providing a base knowledge regarding the various types of each element of the system and the factors that govern the selection of each, this research will help engineers appropriately design the system. In addition, providing a detailed guideline to the assessment of the system shall aid the decision makers in determining the system’s feasibility which encourages its application. Finally, the research investigates and addresses the key issues for future studies. 

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

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

Numerical simulation of various PCM container configurations for solar dryer application

In the context of solar dryers, where drying time is constrained by available sunshine hours and excessive heat during these periods can potentially lead to mineral loss in food, the incorporation of phase change material (PCM) for thermal energy storage emerges as a viable solution. However, the response time of PCMs plays a major role in its charging and discharging in solar dryer performance, prompting extensive research into PCM container configurations to reduce this limitation. Investigations have been conducted through numerical simulations and experimental studies to explore various configurations of PCM. In this study, four distinct container configurations were employed, alongside the introduction of fins, with two variations: solid and hollow. In this regard, Paraffin RT58, with its melting point closely aligned with the operating temperature of the solar dryer, is considered a suitable choice in simulation using ANSYS Fluent. The simulation results revealed that the horizontal rectangles demonstrate the quickest rates for melting and solidification, whereas the cylindrical shape exhibits the most extended durations for these processes. The introduction of fins has a notable impact on reducing both melting and solidification times, with a further decrease observed as the number of fins increases. While solid fins provide slightly superior reductions in melting and solidification times, opting for hollow fins presents benefits in terms of material efficiency, weight reduction, and cost savings.

Tailoring the surface features of CaWO4 by coupling with tubular g-C3N4 for enhanced solar photocatalysis and thermal energy storage

Rising energy and environmental crisis has led researchers to develop novel bifunctional materials. Herein, we report the construction of bifunctional hybrid materials for thermal energy storage and solar photocatalytic systems. Such a novel type of green material including calcium tungstate (CaWO4) and tubular graphitic carbon nitride (g-C3N4) was successfully fabricated via thermal mixing method. X-ray diffraction analysis confirmed the formation of both CaWO4 and g-C3N4 in the composite while morphological analyses verified the successful attachment of CaWO4 particles over the tubular g-C3N4 structure. The wide band gap energy (3.6 eV) of the pristine CaWO4 significantly decreased to 1.85 eV after coupling with g-C3N4. The hybrid catalyst showed superior photocatalytic degradation of Allura red (79.3 % within 120 min) and the rate constant was found 31.3-folds higher compared to pristine CaWO4 (13.3 % removal), which was ascribed to strong light harvesting, increased surface area, smaller crystallite size and fast electron transfer rate. In addition to catalytic functionality, the synthesized pristine and hybrid catalysts were also used in the preparation of lauric acid-based phase change materials (PCMs) and thermal properties of different fillers were examined. The 1 wt% CaWO4/g-C3N4 filler loaded composite displayed 13.03 % increment in heat storage rate (oC/s) when compared with lauric acid, demonstrating the essential role of the hybrid material over the PCM structure. The as-prepared hybrid materials displayed a bifunctional activity derived from incorporation of carbon nitride and thus verified a great potential for different applications due to their enhanced features.

Forum: Pathways toward Critical Advances in the Chemistry of Materials for Thermal Energy Storage

Forum: Pathways toward Critical Advances in the Chemistry of Materials for Thermal Energy Storage