High Latent Heat Storage Research Articles

Optically triggered cascade heat releasing from leakage-proof hydrate salt for intelligent thermal energy storage

Hydrate salts are promising phase change materials for energy storage and conversion due to their safety, large latent heat and low cost. However, leakage during melting and supercooling in solidification are two main obstacles limiting their practical application. Herein, sodium sulfate decahydrate (SSD) was encapsulated with silica shell and further modified to be highly hydrophobic thus to achieve leakage-proof. Furthermore, azobenzene was introduced with delicate design to conduct isomerization under light illumination, the heat of which triggered solidification of supercooled SSD thus forming a cascade heat release process. The encapsulated SSD possesses high latent heat (123 J/g) and energy storage efficiency (80 %), and maintains shape-stable at 25 °C above SSD's m.p. More importantly, introduction of Azo can release heat stored in SSD promptly with temperature increased by 12 °C. This study paves the way for designing an intelligent thermal energy storage method by optically triggering cascade heat releasing from a stably stored phase change materials composite.

Preparation and characterization of Kevlar nanofiber based composite phase change material with photo/electro-thermal conversion properties

To develop phase change material suitable for multi-energy complementary applications, nanofibrous Kevlar aerogel containing paraffin and then deposited with polypyrrole (PPY-KNF/PF) were fabricated. The structure, morphology and photo/electro-thermal conversion ability of PPY-KNF/PF, especially the effect of confinement on the latent heat storage capacity of composites without PPY (KNF/PF) were investigated. The results showed that PF was induced to the interface of nanofibers, then intercalated into the nanosheets during self-assembly of KNF and formed three-dimensional porous structure. The maximum latent heat of KNF/PF with PF fraction of 78.7 % is 117.2 J·g−1 without leakage. Due to the confinement effect, the actual enthalpies of KNF/PF are all lower than the theoretical latent heats, and the difference between the actual and theoretical values enlarges with the increase of PF percentage. The deposition of PPY has no effect on the structure and morphology of KNF/PF and the PPY-KNF/PF80 displays good shape stability and high latent heat storage ability (101.9 J·g−1). Moreover, the composite was endowed with multi-properties of electrothermal and active photothermal conversion, which makes it more suitable for use in the case of insufficient solar energy. This work demonstrated an effective strategy to fabricate composite PCMs with electro/photo-thermal conversion devoting to energy conversion, storage and complementary utilization.

KARAKTERISTIK PENYIMPAN KALOR LATEN PADA PARABOLIC MIRROR DISH

Storing heat in the form of latent heat is a good method, because it is able to store a large amount of heat energy with a small volume of storage media. The use of paraffin as a heat storage medium has many advantages, including thermal stability, non-toxicity, no degradation, and high latent heat storage capacity. This study uses a parabolic mirror dish as a collector of solar thermal energy, equipped with a hinged holder that can be adjusted so that it points to the sun's position from morning to evening, the collected energy is stored in thermal storage using paraffin as a storage medium. The research was conducted from 09.00 WIB to 24.00 WIB, the research location was on the Ronggolawe College of Technology campus. The results showed that the highest temperature obtained in paraffin as a heat storage was 112 oC, while the duration of storing until 24.00 WIB was still able to maintain the temperature at 36 oC.

Water-resistant gum-based phase change composite for thermo-regulating insulation packaging

The world's current energy crisis calls for green energy solutions that can preserve energy while incorporating renewable. As such, we have developed a leakage-proof phase change material (PCM) embedded in a biopolymeric matrix as a lightweight yet strong bio-based phase change composite (PCC) for passive energy storage and insulation purposes in packaging. This bio-based composite consists of gum tragacanth (GT) biopolymer and polyethylene glycol (PEG) PCM. It is further incorporated with biochar (BC) or mineral additive, i.e., Cloisite Na+, to enhance its mechanical strength and thermal stability, which are among the main challenges for insulation materials. A hydrophobic layer of octadecyl isocyanate (ODI) is developed on the surface of the composite to increase its water resistance. The composite provides a hydrophobic surface with a minor water uptake capacity of 3.6 ± 0.3 % after one-week immersion in the water. It shows high latent heat storage up to 160 J g−1 and a stable phase change behavior, as demonstrated by over 100 differential scanning calorimetry heating-cooling cycles. It also possesses notable compressive mechanical properties, which were improved significantly after incorporating BC and Cloisite Na+. The thermal conductivity of the composite is as low as 0.035 W m−1 K−1 manifesting in better thermal regulation compared with commercial polyethylene foams. This energy-positive bio-based solution combines the advantages of excellent insulation as a highly porous, lightweight, and strong composite with the latent heat and thermal inertia of PCM, making it suitable for transportation packaging of temperature-sensitive products.

Improving the Heat Transfer of Phase Change Composites for Thermal Energy Storage by Adding Copper: Preparation and Thermal Properties

Phase change materials (PCMs), as an effective thermal energy storage technology, provide a viable approach to harness solar heat, a green energy source, and optimize energy consumption in buildings. However, the obstacle preventing widespread practical use of PCM is its poor performance in terms of heat transfer and shape stabilization. This article focuses on the application of the shape stabilization method. To improve the thermal conductivity of organic PCMs (hexadecane), copper microparticles are added to form phase change composites (PCC). This process allows an enhanced PCM (75 wt%) that distributes effective thermal storage capabilities while maintaining low cost. SEM, FTIR, ATG, infrared thermography (IRT), and DSC were used to characterize the composites’ micromorphology, chemical composition, thermal degradation stability, and thermal energy storage capabilities. DSC results showed that a proportion of 75 wt% phase change material with 15 wt% Cu had excellent thermal stability and high energy storage density per unit mass. In light of its high latent heat storage capacity of 201.32 J/g as well as its ability to prevent Hexadecane exudation, PCC ensures higher thermal conductivity and shape stability during phase transition than ordinary PCM. The incorporation of Cu to paraffin causes delay in PCM phase transformation, leading it to respond to rapid charging and discharging rates and, consequentially, to challenges in temperature control, as shown by IRT. The new PCCs had favorable thermal stability below 100 °C, which was advantageous for practical application for thermal energy storage and management, and notably for solar thermal energy storage.

Design optimization and thermophysical characteristics of NaF–KCl reciprocal salts by theoretical predictions and experimental measurements for the high latent heat storage

Design optimization and thermophysical characteristics of NaF–KCl reciprocal salts by theoretical predictions and experimental measurements for the high latent heat storage

Phase-Change Microcapsules with a Stable Polyurethane Shell through the Direct Crosslinking of Cellulose Nanocrystals with Polyisocyanate at the Oil/Water Interface of Pickering Emulsion.

Phase-change materials (PCMs) attract much attention with regard to their capability of mitigating fossil fuel-based heating in in-building applications, due to the responsive accumulation and release of thermal energy as a latent heat of reversible phase transitions. Organic PCMs possess high latent heat storage capacity and thermal reliability. However, bare PCMs suffer from leakages in the liquid form. Here, we demonstrate a reliable approach to improve the shape stability of organic PCM n-octadecane by encapsulation via interfacial polymerization at an oil/water interface of Pickering emulsion. Cellulose nanocrystals are employed as emulsion stabilizers and branched oligo-polyol with high functionality to crosslink the polyurethane shell in reaction with polyisocyanate dissolved in the oil core. This gives rise to a rigid polyurethane structure with a high density of urethane groups. The formation of a polyurethane shell and successful encapsulation of n-octadecane is confirmed by FTIR spectroscopy, XRD analysis, and fluorescent confocal microscopy. Electron microscopy reveals the formation of non-aggregated capsules with an average size of 18.6 µm and a smooth uniform shell with the thickness of 450 nm. The capsules demonstrate a latent heat storage capacity of 79 J/g, while the encapsulation of n-octadecane greatly improves its shape and thermal stability compared with bulk paraffin.

Preparation and performance of reversible thermochromic phase change microcapsules based on negative photochromic spiropyran

Thermochromic phase change materials have been widely studied for their importance in energy-efficient buildings, thermal control clothing, and low-temperature energy storage. Herein, we successfully designed and synthesized a spiropyran compound with negative photochromic properties in a solid matrix, 3-(3′,3′-dimethyl-6,8-dinitrospiro[chromene-2,2′-indolin]−1′-yl) propyl methacrylate (SPMA), as a thermochromic dye. The synthesized spiropyran was copolymerized with methyl methacrylate (MMA) using photoinitiation, and then n-octadecane was encapsulated by the copolymer to prepare reversible thermochromic phase change microcapsules (TC-microPCMs) through the solvent evaporation technique. The encapsulation efficiency of n-octadecane by copolymers prepared with different photoinitiator concentrations was also investigated. According to the results of SEM, particle size analysis (DLS), and DSC, the copolymer prepared at 3% concentration possessed the best encapsulation effect on n-octadecane, and the melting enthalpy of the microcapsules reached 168.7 J/g and the encapsulation ratio was 89.5%, which was not significantly different from that of microcapsules without the addition of thermochromic dyes. This di-functionalization process effectively avoids the "impurity effect" of dye addition. In addition, the homogeneous spherical structure and stable chemical composition of the microcapsules are the key factors to achieve a fully reversible thermochromic behavior. What's more, the functionalized film based on TC-microPCMs, TC-microPCMs@PVA, was used to explore the potential for applications in thermal storage and temperature sensing. The results demonstrated that the composite film has excellent reversible thermochromic performance, high latent heat storage performance, and good cycling durability, which make the bifunctional microcapsules highly promising candidates for thermal sensors, solar energy storage, and smart textiles.

A thermodynamic framework to identify apposite refrigerant former for hydrate-based applications

High latent heat storage capacity with naturally assisted salt rejection makes the clathrate compounds appropriate for applications towards load management and desalination processes. Adding to these energy savings are the ease of operations provided by water and the mild conditions at which the refrigerant hydrates are occurred. A direct comparison between these hydrates becomes unfeasible due to the scattered experimental data. Though thermodynamics can streamline this dispersed data, they are currently limited to being a proof of concept most accurately representing the experimental observations. We address this critical deficit of phase assessment and identify, from among R13, R14, R22, R23, R125, R134a and R152a, the most suitable hydrate former for the concerned application. An approach based on van der Waals and Platteeuw model is undertaken and the estimates are quantified in terms of percent average absolute relative deviations (% AARD). An average AARD of 1.75% and 2.68% is observed in pure and aqueous electrolytic phase of NaCl, KCl, CaCl2 and MgCl2, respectively. The model predictions are then estimated at temperature/salinity of 281 K/0 wt% and 284 K/3.5 wt%. Together with the qualitative assessment of the hydrate phase, viz, vapor pressure, compressibility and dissociation enthalpy, R152a refrigerant is observed to be the appropriate former for applications to both load management and desalination.

Enhanced energy management performances of passive cooling, heat storage and thermoelectric generator by using phase change material saturated in metal foam

In this study, a thermal energy management system that combines passive cooling, heat storage and electrical energy harvest is proposed by using foam/PCM composite and thermoelectric generator (TEG), which are separately fixed upon and under the heat source as the coolers of heat source. Foam/PCM composite is also aimed to enhance the latent-heat energy storage and passive cooling. Results show that the control case of using solitary metal foam harvests the most thermoelectric energy, but has the risk of leading heat source to thermal failure. Using pristine PCM can reduce the wall temperature and prolong the thermal management time during phase change. However, the intrinsic low thermal conductivity of pure PCM still results in high temperature of heat source when the PCM is in solid stage. Attributed to high thermal conductivity and latent heat storage, the foam/PCM composite presents the lowest heat-source temperature, but at the cost of delivering the least thermoelectrical power.

Numerical and experimental studies of microcapsules phase change material in a pulsating fluidized bed as an energy storage medium

Phase change materials (PCMs) and particularly microencapsulated phase change materials (MPCM) have introduced new ways to enhance the energy storage capacity of a system due to the high latent heat and high storage density of these materials. This experimental and numerical research aims to investigate the process in a pulsating fluidized bed with MPCMs operating as an energy storage device. Experiments were carried out with MPCM (PX52) in a pulsating fluidized bed with the 0.2 m ID and 1 m height. Numerical simulation was performed using the Eulerian-Lagrangian approach in a symmetric two-dimensional model. Pulsating gas flow at a temperature of 60 °C with a frequency range of 1–10Hz for 200 μm mean diameter was used in the experiment and simulation. The effect of pulsating on the efficiency of the energy storage was examined at 1.5, 2, and 2.5 of the minimum fluidization velocity (Umf). Also, simulation and experiment were performed in the continuous mode for comparison with the published research of others. Results of simulation and experimental data of this study and others were noticed in close agreement. The simulation and experimental results revealed an optimal pulsating frequency, at which the energy storage in the fluidized bed is highest for 2 Umf in 7Hz, which is 92% for pulsating and 64% for continuous flow. Besides, using 7Hz and 10Hz frequencies enhanced the charging time with higher efficiency and reached the stabilized temperature in a shorter time.

Dual-encapsulated multifunctional phase change composites based on biological porous carbon for efficient energy storage and conversion, thermal management, and electromagnetic interference shielding

The development of broadening the adaptability of applications is critical to the growth of phase change materials (PCMs) in the future. A novel multifunctional shape-stable phase change composite (PCC) with paraffin (PA) impregnated into biological porous carbon scaffold and followed by coating a polyurethane (PU) layer comprised of Fe3O4 nanoparticles was explored by a dual-encapsulation strategy. The biological porous carbon was made from the loofah sponge (LS) through immersion in the phenolic resin (PR) solution followed by carbonization. The structural morphology, shape and thermal stabilities, thermal energy storage, temperature regulation, photo/electro to thermal conversion properties，as well as electromagnetic interference (EMI) shielding of fabricated PCCs were explored. The results revealed that the LS maintained the original shape with 3-dimensional structure and natural honeycomb-like porous of single fiber after carbonization, which would offer sufficient mechanical support and highly efficient leakage-proof performance in collaborating with PU coating. The fabricated composites exhibited high latent heat storage density (up to 155.2 J/g), superior temperature regulation performance, and great thermal stability and reliability. The synergetic effect between enhanced thermal conductivity of biological porous carbon scaffold and effective photon trapping performance of Fe3O4 nanoparticles led to a photothermal conversion efficiency up to 76 %. Additionally, the obtained PCCs possessed satisfactory electrothermal conversion, storage effects and strong EMI-shielding (up to 32 dB). Predictably, this innovative type of PCCs had opened up creative routes for energy storage and conversion materials, which would have a potential value in various fields such as electronic protection, military stealth, energy-saving buildings, and solar thermal energy utilization.

Two-dimensional lamellar phosphogypsum/polyethylene glycol composite PCM: Fabrication and characterization

In this work, a nanocomposite phase change material (PCM) has been designed by combining two-dimensional lamellar anhydrous calcium sulfate with polyethylene glycol (PEG). We report a facile strategy to controllably fabricate two-dimensional lamellar anhydrous calcium sulfate (LAH) with the average thickness of 28.63 nm from phosphogypsum (PG) through ethylenediamine tetraacetic acid disodium (Na2EDTA) induction in glycerol and ethylene glycol solutions at 98 °C. The obtained 2D lamellar CaSO4 was a slit-type mesoporous material stacked by the nanosheet of calcium sulfate. It has a specific surface area of 70.02 m2/g, which is 10 times larger than phosphogypsum. Na2EDTA acts as a crystal habit-directing agent to regulate crystal morphology through nonclassical nanoparticle-mediated crystallization processes, resulting in the crystalline morphology tending to be lamellar. Lamellar anhydrous calcium sulfate phase change composites (LAHPCMs) were prepared with 2D lamellar anhydrous nano-CaSO4 and polyethylene glycol (PEG). The LAHPCMs had a high latent heat storage capacity (92.99 J/g). Lamellar anhydrous calcium sulfate phase change composites have good thermal stability and durability, structure stability, and good liquid leakage resistance. These results provide the possibility for phosphogypsum to be used for energy storage and thermal insulation.

A Novel Layered Double Hydroxide and Dodecyl Alcohol Assisted PCM Composite with High Latent Heat Storage Capacity and Thermal Conductivity

A Novel Layered Double Hydroxide and Dodecyl Alcohol Assisted PCM Composite with High Latent Heat Storage Capacity and Thermal Conductivity

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.

Polynorbornene-based bottlebrush polymers confining phase change materials for ultra-stable latent heat storage derived from solar irradiation

Converting abundant solar energy into latent heat stored by organic phase change materials (PCMs) can effectively overcome the intermittency and instability of solar irradiation and improve energy utilization efficiency. However, facile fabrication of form-stable PCMs (FSPCMs) to realize simultaneously energetic solar-thermal conversion and storage in broad-scale practical applications remain a formidable challenge. Here we offer an appealing solar-thermal energy conversion and storage system that utilizes paraffin (PW) as latent heat storage units, sulfur treated nickel foams (S–Ni foams) as solar-thermal conversion materials and polynorbornene-based bottlebrush polymers (PNb22C) as gelators, which can self-assemble into 3D supporting scaffolds, to confine the paraffin in small nanometer-scale spacing. Novel FSPCMs demonstrate no paraffin leakage, high latent heat storage capacity (172.1 J/g) and ultra-stable thermal cycling durability during the 500 times thermal cycling tests. In addition, owning to powerful solar-thermal conversion of S–Ni foams, the developed FSPCMs can energetically convert solar energy into latent heat storing by paraffin with reversible solar-thermal energy storage and release during the 200 cycling tests, providing universal potential opportunities for practical applications in solar energy utilization system, etc.

Aluminum doping of mesoporous silica as a promising strategy for increasing the energy storage of shape stabilized phase change materials containing molten NaNO3: KNO3 eutectic mixture

Efficient thermal energy storage at high temperature is necessary for both industrial waste heat utilization and continuous solar power generation. Shape-stabilized phase change materials containing mesoporous aluminosilicates and eutectic NaNO3: KNO3 (1:1 mol) molten salt mixture were obtained at 90% wt. salt. The influence of aluminum doping was studied for the first time. All samples show thermal stability up to 550 °C and two distinct phase transitions corresponding to the melting/freezing of nanoconfined and interparticle salt phases. The radius and spherical shape of the nanoconfined phase were determined from the melting and freezing point depressions with respect to bulk. The enthalpy decrease was quantified in terms of surface tension and the contributions of a non-melting fraction of surface adsorbed ions. SBA-15 type aluminosilicates matrices yield composites with high latent heat storage of 76–77 Jg−1, of which 8 Jg−1 for the nanoconfined phase and good thermal reliability. Aluminum doping is a simple and promising strategy for obtaining high temperature, efficient thermal energy storage materials due to a lack of non-melting salt fraction. The resulting shape-stabilized PCMs have a higher operating temperature range and latent heat storage, offering a 36% increase in total heat capacity over the pristine salt.

Multifunctional Phase Change Composites Based on Elastic MXene/Silver Nanowire Sponges for Excellent Thermal/Solar/Electric Energy Storage, Shape Memory, and Adjustable Electromagnetic Interference Shielding Functions.

Multifunctional phase change materials (PCMs) are highly desirable for the thermal management of miniaturized and integrated electronic devices. However, the development of flexible PCMs possessing heat energy storage, shape memory, and adjustable electromagnetic interference (EMI) shielding properties under complex conditions remains a challenge. Herein, the multifunctional PCM composites were prepared by encapsulating poly(ethylene glycol) (PEG) into porous MXene/silver nanowire (AgNW) hybrid sponges by vacuum impregnation. Melamine foams (MFs) were chosen as a template to coat with MXene/AgNW (MA) to construct a continuous electrical/thermal conductive network. The MF@MA/PEG composites showed a high latent heat (141.3 J/g), high dimension retention ratio (96.8%), good electrical conductivity (75.3 S/m), and largely enhanced thermal conductivity (2.6 times of MF/PEG). Moreover, by triggering the phase change of the PEG, the sponges displayed a significant photoinduced shape memory function with a high shape fixation ratio (∼100%) and recovery ratio (∼100%). Interestingly, the EMI shielding effectiveness (SE) can be adjusted from 12.4 to 30.5 dB by a facile compression-recovery process based on shape memory properties. Furthermore, a finite element simulation was conducted to emphasize the advantage of the MF@MA/PEG composites in the thermal management of chips. Such flexible PCM composites with high latent heat storage, light-actuated shape memory, and adjustable EMI shielding functions exhibit great potential as smart thermal management materials in military and aerospace applications.

Development of advanced multifunctional façade systems: Thermo-acoustic modelling and performance

The development of lightweight and multifunctional curtain wall systems, which integrate different technological solutions, is aimed at achieving increasingly higher requirements related to energy efficiency as well as indoor environmental quality in non-residential buildings. On one hand lightweight and thin façade elements present several advantages (such as construction time, space, and transportation savings, less weight on primary structure etc.), while facing the challenge of guaranteeing the required thermal and acoustic performance and achieving legislative compliance on the other. In the framework of the Horizon 2020 Project Powerskin+ a new concept of multifunctional façade, which combines high performance insulation, energy harvesting, heating system, and latent heat storage capabilities is under development. Within the design process of the different sub-modules (opaque and transparent), performance calculations are carried out by means of existing simulation tools, or ad-hoc developed models for more complex systems. In this study, the authors present the main steps required to accelerate the simulation-based design process and the future thermal and acoustic optimization of the novel lightweight and multifunctional façade element.

Analysis of Heat Transfer and Natural Convective of a Phase Change Material

A phase-change material (PCM) is a substance with a high latent heat storage capacity which on melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Various PCM like Paraffin wax, stearic acid are considered which are used to absorb heat from the coolant water from the engine. The conduction and convection criterion of heat transfer enable the PCM to store this heat as latent heat. The amount of convection and temperature change brought about due to the heat flux has been simulated and studied in detail using FLUENT. The thermal energy storage device (TESD) works on the effect of absorption and rejection of heat during the solid-liquid phase change of heat storage material. The overall function of the TESS is dominated by the PCM. The PCM material should be selected considering the application and the working conditions. Depending on the applications, the PCMs should first be selected based on their melting temperature for heat recovery system.