Stable Phase Change Materials Research Articles

Insights into effect of lignocellulosic biomass framework types on bio-based shape stable composite phase change materials

The utilization of biomass waste as framework materials to inhibit the leakage of phase change material (PCMs) has gained widespread attention. In this work, three new kinds of shape stable composite phase change materials (sscPCMs) were prepared which combined with stearic acid (SA) and peanut shell powders (PSP), poplar wood powders (PWP), and corn straw powders (CSP), respectively. The influence of lignocellulosic biomass types on the thermal energy storage performance of sscPCMs was studied by comparing three types of sscPCMs. The research results indicated that SA/CSP exhibited superior properties in terms of load capacity and thermal energy storage performance. According to leakage experiments the load capacity of SA/PSP, SA/PWP and SA/CSP was 31.67 %, 44.69 %, and 50.09 %, respectively. The phase change latent heat of SA/PSP, SA/PWP, and SA/CSP was 55.78, 84.27 and 98.47 J/g, respectively. In addition, the relationship between biomass component content and load rates was studied. The results showed that there was a positive correlation between the loading rates of SA and the ratio of holocellulose (cellulose + hemicellulose) to lignin. The results provided a promising approach for the selection of lignocellulosic biomass framework materials.

The preparation and selection process for a new form stable phase change material (FSPCM) intended for use as thermal storage in applications at intermediate temperatures

There is a greater focus on solar energy since the food processing business requires a lot of thermal energy to remove moisture from agricultural products. This study thoroughly explains how to choose Phase Change Materials (PCMs) within a specific temperature range. The best PCM is selected from the Multiple Criteria Decision Making (MCDM) procedures based on a few characteristics. Based on the results of the MCDM method, the eutectic of paraffin and palmitic acid is chosen. PCM is bound, and FSPCM is formed using clay. The method of preparation of Clay-based FSPCM is described in detail. The amount of clay materials and different clay percentage combinations are chosen from the leakage experiment. Kaolin has the least amount of leakage out of all the clay materials tested. Kaolin-based FSPCM Exhibits improvement in thermal conductivity compared to Pure PCM.

Development and preparation of novel nano-enhanced organic eutectic phase change materials for low-temperature solar thermal applications

ABSTRACT Thermally reliable and stable eco-friendly Phase change materials are of significant aid in thermal energy storage technology, leading to improved energy utilization and reliability of the system. This study develops two novel organic eutectic PCM of Lauric acid – Margaric acid (LM) and Myristic acid – Margaric acid (MM), which are chemically stable and thermally compatible for latent heat energy storage. LM eutectic mixture had a melting temperature of 52.66°C with a latent heat of 163.68 J/g, and MM eutectic mixture had its melting temperature at 44.79°C and a latent heat of 197.31 J/g. The phase change temperatures were favorable for low temperature solar thermal applications with good latent heat capacity. The thermal characteristics of these eutectic mixtures are further enhanced with the dispersion of highly conductive Multi walled carbon nanotubes (MWCNT) at three different mass fractions (.5%, 1% and 1.5% by weight). Nano enhancement could achieve exceptional thermal conductivity enhancement in MM eutectic mixture by 110.6% and 83.73% in LM eutectic mixture. Thermogravimetric analysis and Fourier-transform infrared spectroscopy analysis ensured the thermal and chemical stability of the eutectic mixtures. The optical absorption characteristics were extensively enhanced with nano particle addition, which is highly preferable in solar thermal applications.

Harnessing leather waste in polymer matrix for sustainable smart shape‐stable phase change materials

AbstractThe utilization of leather waste (LW) in a polyurethane (PU) matrix makes a smart and novel shape stable phase change material (SSPCM). This is essential for sustainability as it reduces landfill waste after use. The PU is synthesized in bulk with a 90% yield, using biodegradable polycaprolactone diol and bio‐based polyol (castor oil), along with tolylene‐2,4‐diisocyanate. PL and PLG composites are prepared by blending of constituent components PU (P), LW (L), and poly(glycidyl methacrylate) (PGMA, G), as specified by their code names. Role of LW (hydrogen bonding and chemical crosslinking) and morphology are elucidated by FTIR and SEM, respectively. Self‐healing time (2 h), shape fixity ratios (Rf) (PL: 60–80% and PLG: 60–70%) and shape recovery ratios (Rr) (100% for both) are determined at 60°C. PLG displays faster shape recovery in water (<30 s) compared to air (>300 s). Shape stability and thermal properties of the SSPCM are examined using the temperature responsive leakage study, TGA, and DSC. This research introduces a new approach for using leather waste (LW) in SSPCM, with self‐healing and 100% Rr. This material may find application where SSPCM with high durability and flexibility is essential such as textile and footwear materials.

Physical-Entanglements-Supported Polymeric Form Stable Phase Change Materials with Ultrahigh Melting Enthalpy.

With the rapid development of new energy and the upgrading of electronic devices, structurally stable phase change materials (PCMs) have attracted widespread attentions from both academia and industries. Traditional cross-linking, composites, or microencapsulation methods for preparation of form stable PCMs usually sacrifice part of the phase change enthalpy and recyclability. Based on the basic polymer viscoelasticity and crystallization theories, here, a kind of novel recyclable polymeric PCM is developed by simple solution mixing ultrahigh molecular weight of polyethylene oxide (UHMWPEO) with its chemical identical oligomer polyethylene glycol (PEG). Rheological and leakage-proof experiments confirm that, even containing 90% of phase change fraction PEG oligomers, long-term of structure stability of PCMs can be achieved when the molecular weight of UHMWPEO is higher than 7000kg mol-1 due to their ultralong terminal relaxation time and large number of entanglements per chain. Furthermore, because of the reduced overall entanglement concentration, phase change enthalpy of PCMs can be greatly promoted, even reaching to ≈185 J g-1, which is larger than any PEG-based form stable PCMs in literatures. This work provides a new strategy and mechanism for designing physical-entanglements-supported form stable PCMs with ultrahigh phase change enthalpies.

A graphene-CuNWs@PAMPS mixed aerogel for composite phase change materials with high thermal conductivity and excellent solar-thermal to electrical conversion

Phase change materials could store and release heat energy through phase change. However, the shortcomings of low thermal conductivity in the photothermal conversion process and easy leakage in the solid-liquid conversion seriously hinder the application of heat energy utilization. Graphene had high thermal conductivity, and it was an ideal material for improving the solar absorption, solar energy conversion and thermal conductivity of phase change materials. In this paper, a graphene aerogel composed of copper nanowires (CuNWs)/2-acrylamide-2-methylpropanesulfonic acid (AMPS) was designed. The thermal conductivity and shape stability of phase change materials for solar-thermal-electrical conversion applications were enhanced by composite CuNWs. Furthermore, PAMPS was coated on the surface of copper nanowires to avoid the oxidation of copper nanowires, and the sulfonic acid group of PAMPS was used to induce CuNWs to disperse uniformLy on the graphene sheets, which further constructed a good conductive network. After vacuum impregnation of PW, the best thermal conductivity phase change composite (PW-CuNWs@PAMPS-GA(1:1)) was obtained. The PCC loaded with CuNWs with the same graphene content achieved a thermal conductivity of 1.46 W/(m·K) and a high latent heat of 206.8 J/g. The latent heat retention rate was as high as 99.57 %. The photothermal conversion efficiency of PW-CuNWs@PAMPS-GA(1:1) was remarkable at 96.4 %. Due to its excellent solar-thermal-electrical conversion efficiency, the output voltage and output current were 800.8 mV and 85.8 mA, respectively, at a solar analog intensity of 5 kW/m2. Even after the sunlight was stopped, the voltage output could be maintained for a while by releasing the heat energy stored in the phase change composite.

Nanoscale Stabilization Mechanism of Sodium Sulfate Decahydrate at Polyelectrolyte Interfaces.

Sodium sulfate decahydrate (SSD) is a low-cost phase-change material (PCM) for thermal energy storage applications that offers substantial melting enthalpy and a suitable temperature range for near-ambient applications. However, SSD's consistent phase separation with decreased melting enthalpy over repeated thermal cycles limits its application as a PCM. Sulfonated polyelectrolytes, such as dextran sulfate sodium (DSS), have shown great effectiveness in preventing phase separation in SSD. However, there is limited understanding of the stabilization mechanism of SSD by DSS at the atomic length and time scales. In this work, we investigate SSD stabilization via DSS using neutron scattering and molecular dynamics (MD) simulations. Neutron scattering and pair distribution function analysis revealed the structural evolution of the PCM samples below and above the phase change temperatures. MD simulations revealed that water from the hydrate structure migrates from the hydrate crystal to the SSD-DSS interfacial region upon melting. The water is stabilized at this interface by aggregation around the hydrophilic sulfonic acid groups attached to the backbone of the polyelectrolyte. This architecture retains water near the dehydrated sodium sulfate, preventing phase separation and, consequently, stabilizing SSD rehydration. This work provides atomistic insight into selecting and designing stable and high-performance PCMs for heating and cooling applications in building technologies.

A novel cement mortar comprising natural zeolite/dodecyl alcohol shape stable composite phase change material for energy effective buildings

Investigations into Phase Change Materials (PCMs) for heat storage in facilities have gained significance, contributing to indoor temperature regulation, decreased energy usage, and improved building efficiency, thereby supporting sustainability initiatives. However, the issue of PCM leakage during the heating phase has constrained its thermal energy storage (TES) prospective at large scaled-practices. Addressing this concern, the present study emphases on elimination of the leakage problem of dodecyl alcohol (DA) as a PCM with appropriate melting temperature for building TES request by its impregnating into the natural zeolite (NZ) as a low cost host matrix. In the second stage of the work, using the developed shape stable-NZ/DA (SS-NZ/DA) composite PCM in cement mortar instead of sand, novel cementitious mortars with enhanced thermal properties were created by incorporating different weight percentages (25 %, 50 %, 75 %, and 100 %) compared to the mortar comprising NZ. Experimental works were carried out to analyze the shape-stability, TES features, cycling TES stability and thermal endurance of the SS-NZ/DA composite as well the physical properties, mechanical strength, and solar temperature regulation performance of the SS-NZ/DA included mortars. The SS-NZ/DA demonstrated the melting enthalpy of 107.5 J/g at 19.47 °C and a freezing enthalpy of 106.1 J/g at 19.86 °C. The performance test results obtained under real weather conditions indicated that the integration of SS-NZ/DA into mortar presented maximum drop of 10 % and 9.26 % in peak indoor temperature at the SS-CPCM slab surface and the center of SS-CPCM slab-cabin, respectively, accompanied by an approximate 3-hour time delay. Mortars with SS-NZ/DA composite PCM exhibited a decreased dry unit weight (1189 kg/m3) and thermal conductivity (0.394 W/mK) while experiencing a moderate strength loss (4.5 MPa). These favorable physico-mechanical properties, TES characteristics and thermal management capability make the novel cementitious mortar containing composite PCM as an energy-efficient material for creating thermo-regulative building components. In this study, the natural, economical, and environmentally friendly nature of the NZ material used for PCM impregnation, its ability to contain a high percentage of PCM (up to 45 %) without any leakage issues, is the most fundamental and important characteristic of the composite used. The most unique feature of this composite mortar is the ability to achieve sufficient mechanical and thermal properties in cementitious mortars produced using this composite material without any leakage problems.

Phase change materials encapsulated in a novel hybrid carbon skeleton for high-efficiency solar-thermal conversion and energy storage

Phase change materials (PCMs) with high energy density and stationary transition temperature are now considered promising solar energy storage mediums. However, their intrinsic poor light absorption, thermal conductivity and stability severely impede their potential applications. In this study, a novel carbonized hybrid aerogel (CHA) structure was firstly constructed by incorporating MXene and carbon nanofibers (CNFs) into a continuous phase polyamic acid salt (PAAS) aqueous solution, followed by directional freezing, vacuum drying, imidization, and carbonization processes. Finally, the composite PCMs (CPCMs) were fabricated by vacuum impregnation of PCMs into the CHAs. The CPCM, of which CHA consists of 20 wt% MXene and 10 wt% CNF@PDA, demonstrates high solar-thermal conversion efficiency (>91 %), improved thermal conductivity of 0.40 W·m−1·K−1, great thermal stability (enthalpy loss < 0.19 % after 100 cycling tests with no obvious leakage). The introduction of MXene and CNFs endows PCM with broader light absorption spectrum range. The skeleton matrix embedded with bonded MXene sheets and CNFs provides more thermal pathways, light absorption sites and carrying capacity, improves the thermal conductivity, solar-thermal conversion property and stability of PCM. In addition, CPCM also exhibits outstanding EMI SE (95 dB). The multifunctional and high-performance CPCMs shows potential to realize the effective capture and utilization of solar energy. This work provides a new strategy to construct stable and multifunctional hybrid carbon skeleton for high-efficiency solar-thermal conversion and energy storage.

Multistage Porous Carbon Derived from Enzyme-Treated Waste Walnut Green Husk and Polyethylene Glycol for Phase Change Energy Storage.

The thermal storage performance, cost, and stability of phase-change materials (PCMs) are critical factors influencing their application in the field of thermal energy storage. Porous carbon, with its excellent support, thermal conductivity, and energy storage properties, is considered one of the most promising support matrix materials. However, the simple and efficient synthesis of high-performance and highly active bio-based materials under mild conditions still faces challenges. In our work, a novel method for preparing new functional composite phase-change materials based on enzyme treatment technology and using waste walnut green husk biomass and polyethylene glycol as raw materials was developed. The enzymatic treatment method exposes the internal structure of the walnut green husk, followed by the adjustment of the calcination temperature to increase the adsorption sites of the biochar, thereby stabilizing polyethylene glycol (PEG). The porous properties of walnut green husk biochar effectively regulate the phase-change behavior of polyethylene glycol. In the biochar carbonized at 600 °C, the PEG loading reached 72.09%, and the absorption heat of the solid-solid phase-change material (SSPCM) reached 194.76 J g-1. This work not only enriches the application of biomass in heat storage but also demonstrates the broad prospects of SSPCMs in solar thermal utilization.

Solar to thermal energy storage performance of composite phase change material supported by copper foam loaded with graphite and boron nitride

Phase Change Materials (PCM) have emerged as one of the potential candidates for solar Thermal Energy Storage (TES) because of their high energy density, low volume change, and easy availability in varying temperature ranges. However, PCM suffers from a few critical drawbacks such as leakage during phase transformation, low thermal conductivity, and poor photothermal energy conversion performance. In this study, shape-stable composite PCM loaded with varying percentages of Graphite (GR) and Boron Nitride (BN) were prepared. Copper foam of 96 PPI was used as 3-dimensional skeleton support to provide shape stability to the eutectic mixture of Lauric Acid (LA)-Myristic Acid (MA). Shape stable composite PCM CF/LA-MA/GR with 0 %, 5 %, 15 %, 25 %, and 35 % of GR and CF/LA-MA/BN with 0 %, 5 %, 15 %, 25 %, and 35 % of BN were prepared and characterized for thermal, physical, and photothermal energy conversion performance. A maximum loading percentage of 67 % of LA-MA in CF without leakage was obtained. The PCM composites show excellent thermal stability at elevated temperatures and suitable TES parameters for solar thermal storage applications. Among all the prepared samples, CF/LA-MA/GR35% shows a maximum rise of 76.1 % in heating rate and 81.2 % in photothermal energy conversion efficiency in comparison with CF/LA-MA/GR0%. In addition, CF/LA-MA/GR35% shows a maximum of 1.08 W/m-K of thermal conductivity at a melting enthalpy of 95.36 J/g. The shape-stable composite PCM shows a stable physical structure along with good surface morphology.

Synthesis and properties of biomass derived carbon/PEG composite as photothermal conversion effective phase change material for functional concrete

Mixing phase change material (PCM) into concrete is a practical strategy for functionalizing concrete as an energy-storage unit. This study aims to invent an efficient photo-thermal conversion type PCM for the manufacturing energy storage functional concrete, which meet the needs of hydration heat storage and thermal storage in service. To solve the liquid leakage problem of PCM, a novel bamboo-based hydrothermal carbon sphere (HCS) with unique mesoporous structure was prepared to pack polyethylene glycol (PEG) to make shape stable PCM. The photo-thermal material nano-Ag was successfully introduced into the composite PCM through a high-voltage electrostatic field. To understand the stability and performance of the PCM for concrete use, the structural composition and thermal storage efficiency of Ag@HCS-CNTs/PEG in simulated concrete pore solution (a highly alkaline solution containing potassium, sodium, and calcium cations) were systematically studied via multiple characterization methods. After being soaked in concrete pore solution for 7 days, the PCM shows outstanding thermal storage density (147 J/g), photo-thermal conversion efficiency (110.6%), and resistance to Na+, Mg2+, Cl− and SO42−. In addition, the biomass subtracted PCM preparation has low energy consumption and low carbon emission features. These open a window of realistic PCM application in the structural concrete, insulation porous walls and energy storage buildings.

Novel Sodium Chloride/Aluminum Oxide Powder-Composite Structure with High Shape-Retention Performance for the Encapsulation of a High-Temperature Phase-Change Material

Inorganic phase-change materials (PCMs) with high melting points have great potential for thermal energy storage systems. Sodium chloride (NaCl) has a high melting point (801 °C) and high latent-heat-storage density (482 kJ/kg). However, it is difficult to encapsulate NaCl using a sintered ceramic shell because of its good wettability against ceramics and high volume-expansion capacity during melting. In this study, a novel NaCl/Al2O3 powder-composite structure was developed as highly stable PCM core material for highly stable encapsulation. The shape-retention performance and the mechanism of NaCl/Al2O3 powder-composite structure during melting were investigated. We have successfully fabricated a NaCl/Al2O3 powder-composite structure, which has a higher NaCl volume ratio of 80 vol% than conventional techniques. The gel-like network structure of Al2O3 particles in molten NaCl was a key structure to keep the shape of the composite ball and to prevent the evaporation of molten NaCl.

High value utilization of waste peanut shell: Prepared novel shape stable composite phase change materials with high thermal conductivity

To address the leakage and low thermal conductivity issues of phase change materials (PCMs), this study aims to prepare high thermal conductivity shape stable composite phase change materials (sscPCMs) using waste peanut shell. Employing pyrolysis technology, waste peanut shell has been successfully converted into high-performance framework materials. In addition, it also compared the thermal energy storage performance of shape stable composite stearic acid/peanut shell biochar (ss-cSA/PSC) with that of shape stable composite stearic acid/peanut shell (ss-cSA/PS). Excitingly, the thermal energy storage performance of ss-cSA/PSC has been significantly improved. Specifically, the thermal conductivity of ss-cSA/PSC reached 0.527 W/(m·K), which is 3.2 times higher than that of pure SA and 2.4 times higher than that of ss-cSA/PS. In addition, the phase change latent heat of ss-cSA/PSC can reach 70.59 J/g, which is 27.2% higher than that of ss-cSA/PS. The high thermal conductivity and phase change latent heat highlighted its significant superiority in the field of thermal energy storage. Furthermore, ss-cSA/PS and ss-cSA/PSC have been characterized by SEM, FTIR, XRD, and TGA. The results indicated that both two kinds of sscPCMs have excellent chemical compatibility, thermal reliability, and thermal stability. In summary, PSC is an economical, environmentally friendly, and sustainable framework material which used to prevent the leakage of PCMs and improve the thermal performance.

Shape stable composite phase change material with improved thermal conductivity for electrical-to-thermal energy conversion and storage

Limited thermal conductivity and leakage of phase change material (PCM) are among the most challenging obstacles that impede their effective applications in real-world scenarios. This study focussed on enhancing the thermal conductivity (TC), address leakage issues and incorporate thermoelectric conversion capabilities by using a single multifunctional scaffold. The shape stable PCM (ss-PCM) composite has been prepared using medium temperature range (~46 °C) commercial grade paraffin wax (PW) as organic PCM while expanded graphite (EG) as an encapsulating scaffold. The composite was prepared using vacuum impregnation method, incorporating various weight percentages (wt.%) of EG. In particular, the three wt.% of EG that has been used to encapsulate PCM are 5 % (ss-PCM1), 10 % (ss-PCM2) and 15 % (ss-PCM3). Then the composite was evaluated for its thermal stability, potential chemical interactions, leakage prevention, optical properties, thermal conductivity and thermo-electric conversion capability. Results revealed that the incorporation of 15 wt% EG in PCM (ss-PCM3) demonstrated no traces of leakage even after heating the composite at 60 °C. In addition, a significant increment of 447 % in thermal conductivity and 98 % in light absorbance has been observed. However, the composite showed a slight decrement of 13.83 % in latent heat related to base PCM. Finally, ss-PCM3 was put through to 500 heating-cooling cycles to evaluate its reliability and potential defects due to thermal fatigue. The characterization results of the composite were in close agreement before and after the thermal cycling, indicating its potential for practical applications. The electro-thermal conversion measurement findings indicate that the ss-PCM3 can achieve a conversion ability of 61.89 % when operated at 4.8 V. Several potential applications for this composite include energy-efficient buildings, infrared thermal concealment, solar energy utilization, and heat insulation.

Effect of CNTs length on thermophysical properties of paraffin/CNTs/graphene aerogel nanocomposite as a shape stabilized phase change material

In this work, paraffin/carbon nanotubes/graphene aerogel (Pa/CNTs/GA) nanocomposite with different CNTs lengths were synthesized. CNTs' length was changed by refluxing them in a mixture of acids for different times, by which the initial micrometer length of CNTs was reduced to 1200 and 205 nm after 0.5 and 1 h refluxing. To complete dispersing CNTs in paraffin, they were functionalized for the second time using dodecylamine. By inserting paraffin composites into the aerogel using vacuum impregnation, the thermal conductivity of the aerogel increases greatly. Melting and freezing latent heat of both samples of graphene aerogel composite containing 0.5 and 1 h refluxed CNTs was reduced compared to that of the pure paraffin and Pa/CNTs composite. The specific heat of the Pa/CNTs/GA composite containing 1 h refluxed CNTs was reduced compared to that of the Pa/CNTs (1 h refluxed) composite, but it was increased for the samples containing 0.5 h refluxed CNTs. Also, Pa/ZnO, Pa/TiO2, and Pa/Al2O3 composites were prepared and their thermophysical properties were compared with those of Pa/CNTs composites.

Advances in phase change building materials: An overview

Abstract Efficient and sustainable thermal management of buildings is critical since the building sector is considered as the largest energy contributor contributing around 40% of the total energy consumption which is responsible for about 38% of greenhouse gas emission. Utilisation of phase-change material (PCM) in building energy systems can enhance the overall energy performance of buildings, thereby making drastic reduction in greenhouse gas emissions. The major shortcoming of organic PCM is their leakage problem; however, this can be overcome through the employment of either encapsulation or shape stabilisation technology. Numerous papers have prepared unlimited number of form stable PCMs for various applications ranging from textiles to thermal energy storage (TES); however, the factors to consider when selecting PCM for an intended application are not clear and the influence of synthesis techniques and processing parameters on the performance of stabilised PCM is yet to be understood. Also, majority of the publications have focused mainly on the encapsulation of paraffins for TES by employing different encapsulation techniques. Therefore, selecting a suitable technique for the synthesis of form stable PCM is the most challenging. This review aims at providing a comprehensive database addressing these issues, focusing mainly on PCMs, processing techniques, performance of encapsulated and composite PCMs, and phase change building materials prepared in previous studies, since this is the most critical information required to widen the potential usage of PCM technology in building applications. A concise summary of environmentally friendly poly(ethylene glycol)-based composite PCMs is also included.

Activated carbon foam composite derived from PEG400/ Terminalia Catappa as form stable PCM for sub-zero cold energy storage

A novel form-stable phase change material (FSPCM) for cold energy storage has been developed using sea almond (SA) (Terminalia catappa) derived supporting matrix and polyethylene glycol 400 (PEG 400) as the basic phase change material (PCM) for energy storage. A two-step method based on pyrolysis followed by KOH activation was implemented to produce activated carbon (SAS-AC) from the sea almond shell, an agricultural waste. The SAS-AC possessed a high specific surface area and a total pore volume of 1842.6 m2/g and 0.9275 cm3/g, respectively. The Activated carbon foam (SAS-ACF) was used as the supporting matrix for the PCM. Good chemical compatibility observed between the PCM and the SAS-ACF was validated using Fourier transform infrared analysis. The contact angle of 46.6o found between PEG 400 and SAS-ACF confirmed excellent wettability. The thermal conductivity of the FSPCM was found to be 0.411 W/m K, which was 82.66% higher than that of pristine PEG 400 (0.225 W/m K). A melting temperature and an enthalpy of −6.87 °C and 26.53 J/g were obtained for the FSPCM. Thermogravimetric analysis (TGA) proved the excellent thermal stability of FSPCM. The performance of the FSPCM was analyzed using a custom made experimental setup. All the results indicated that the developed FSPCM has a great potential to be used as a cold energy storage medium.

An experimental investigation on kinetic analysis of thermal degradation of shape stable composite phase change materials and adaptive neuro fuzzy inference system modeling for predicting mass loss

An experimental investigation on kinetic analysis of thermal degradation of shape stable composite phase change materials and adaptive neuro fuzzy inference system modeling for predicting mass loss

N-doped EG@MOFs derived porous carbon composite phase change materials for thermal optimization of Li-ion batteries at low temperature

Electric vehicles often encounter the challenge of battery capacity reduction in cold environments. Existing thermal conductive patches and partial short-circuiting for electrical heating can address the above issues. In this paper, a method to increase battery capacity was proposed by phase change material (PCM) assisted heating. Specifically, a nitrogen-doped hierarchical porous carbon (NPC) was synthesized through a combination of “low-temperature calcination + concentrated nitric acid treatment” to treat the chrysanthemum-shaped MOF-199@EG, and impregnated with stearic acid (SA) to form a stable composite PCM. With its well-developed pore structure and N-adsorbed active sites, the NPC prevents the leakage of molten SA, maintains stability effect and significantly improves the thermal properties of SA composites. The SA/NPC has a loading rate of 80.15 wt%, closely approaching the theoretical values of latent heat (137.89 J·g-1). It also demonstrates enhanced thermal conductivity (1.873 W·m-1·K-1) and thermal diffusivity (1.024 mm2·s-1). Thermal conductivity and thermal diffusivity of SA/NPC are 8.56 times and 14.06 times higher, respectively, than those of SA. Furthermore, when the lithium-ion battery is discharged 2C at −20 °C, the utilization of SA/NPC as an insulation material can increase the discharge energy by 7.89 %. Consequently, this novel composite PCM holds significant promise for the thermal optimization of batteries at low temperature.