Development and thermophysical analysis of binary eutectics phase change materials for solar drying application

Keywords Eutectic, Phase change materials, Non-paraffins, Thermal energy storage, Solar dryer ALL Metrics - Views Downloads How to cite this article Pandey S, Anand A, Buddhi D and Sharma A. Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.12688/f1000research.127268.3) NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article. Export Citation Sciwheel EndNote Ref. Manager Bibtex ProCite Sente Select a format first ▬ ✚ Research Article Revised Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved] Saurabh Pandey https://orcid.org/0000-0001-6946-3642 1, Abhishek Anand https://orcid.org/0000-0002-3593-7907 1, Dharam Buddhi2, Atul Sharma https://orcid.org/0000-0002-3754-8550 1Saurabh Pandey https://orcid.org/0000-0001-6946-3642 1, Abhishek Anand https://orcid.org/0000-0002-3593-7907 1, Dharam Buddhi2, Atul Sharma https://orcid.org/0000-0002-3754-8550 1 PUBLISHED 06 Aug 2025 Author details Author details 1 Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Jais, Amethi, UP, 229304, India 2 Uttaranchal University, Dehradun, Uttarakhand, 248007, India 2 Uttaranchal University, Dehradun, Uttarakhand, 248007, India Saurabh Pandey Roles: Conceptualization, Data Curation, Formal Analysis, Methodology, Software, Writing – Original Draft Preparation Roles: Conceptualization, Data Curation, Formal Analysis, Methodology, Software, Writing – Original Draft Preparation Abhishek Anand Roles: Formal Analysis, Software Roles: Formal Analysis, Software Dharam Buddhi Roles: Investigation, Project Administration, Validation, Visualization Roles: Investigation, Project Administration, Validation, Visualization Atul Sharma Roles: Data Curation, Formal Analysis, Funding Acquisition, Project Administration, Resources, Supervision, Validation, Visualization, Writing – Review & Editing Roles: Data Curation, Formal Analysis, Funding Acquisition, Project Administration, Resources, Supervision, Validation, Visualization, Writing – Review & Editing OPEN PEER REVIEW REVIEWER STATUS This article is included in the Uttaranchal University gateway. This article is included in the Energy gateway. This article is included in the International Conference on Clean Energy Systems and Technologies collection. In the past 30–40 years, conflicts over limited conventional energy sources and the negative climate change caused by them have attracted researchers and analysts to new, clean, and green energy technologies. Thereby reducing the consumption of conventional fuel and the negative impact on the climate. The production of alternative energy in the form of thermal energy storage using phase change materials (PCMs) is one of the techniques that not only reduces the gap between the supply and demand of energy but also increases the stability of the energy supply. The tendency of PCMs to melt and solidify over a wide temperature range makes them more attractive for use in many applications. The effective and efficient storage of solar energy by PCM has the potential to significantly advance the use of renewable energy. Organic non-paraffin compound beeswax (BW) mixed with other non-paraffin compounds stearic acid (SA), Palmitic acid (PA), Myristic acid (MA), and Lauric acid (LA) in different compositions with the help of magnetic stirrer at 50–60°C for 3–4 hours to prepare BWSA, BWPA, BWMA, and BWLA eutectic PCM. Prepared eutectics melt and solidify in the temperature range 36–56°C and with latent heat in the range of 155–211 kJ/Kg, and they are thermally Stable around 200-250 °C. Due to suitable temperature and good latent heat storage range, it is a good choice as thermal energy storage, for solar drying applications. Eutectic, Phase change materials, Non-paraffins, Thermal energy storage, Solar dryer Corresponding Author(s) Saurabh Pandey ([email protected]) Grant information: The author (Saurabh Pandey) would like to thank the Rajiv Gandhi Institute of Petroleum Technology (RGIPT) for providing the Institute Fellowship. Copyright: © 2025 Pandey S et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. How to cite: Pandey S, Anand A, Buddhi D and Sharma A. Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.12688/f1000research.127268.3) First published: 09 Nov 2022, 11:1277 (https://doi.org/10.12688/f1000research.127268.1) Latest published: 06 Aug 2025, 11:1277 (https://doi.org/10.12688/f1000research.127268.3) In this revised version (Version 2), significant modifications have been made based on the suggestions and comments provided by the reviewers. Key improvements include the addition of a comprehensive discussion on the selection and formulation of eutectic phase change materials (PCMs), focusing on various ratios of beeswax (BW) blended with fatty acids such as stearic acid (SA), palmitic acid (PA), myristic acid (MA), and lauric acid (LA). The rationale behind selecting specific combinations and proportions has been elaborated to highlight their influence on thermal properties. Detailed analysis of the Differential Scanning Calorimetry (DSC) results has been incorporated, addressing both the phase change temperatures and enthalpies. The discussion section has been expanded to interpret the thermal behaviour and to provide a comparative assessment of the different PCM formulations. Thermogravimetric analysis (TGA) has been included to evaluate the thermal stability and degradation behaviour of the eutectic PCMs. Discussion on the application section has been added to demonstrate the potential uses of the developed eutectic PCMs in thermal energy storage systems. In this revised version (Version 2), significant modifications have been made based on the suggestions and comments provided by the reviewers. Key improvements include the addition of a comprehensive discussion on the selection and formulation of eutectic phase change materials (PCMs), focusing on various ratios of beeswax (BW) blended with fatty acids such as stearic acid (SA), palmitic acid (PA), myristic acid (MA), and lauric acid (LA). The rationale behind selecting specific combinations and proportions has been elaborated to highlight their influence on thermal properties. Detailed analysis of the Differential Scanning Calorimetry (DSC) results has been incorporated, addressing both the phase change temperatures and enthalpies. The discussion section has been expanded to interpret the thermal behaviour and to provide a comparative assessment of the different PCM formulations. Thermogravimetric analysis (TGA) has been included to evaluate the thermal stability and degradation behaviour of the eutectic PCMs. Discussion on the application section has been added to demonstrate the potential uses of the developed eutectic PCMs in thermal energy storage systems. See the authors' detailed response to the review by Deepika P. Joshi See the authors' detailed response to the review by Abuelnuor Abdeen Ali Abuelnuor Modern civilization has grown and developed mostly as a result of energy, which has always been important from the perspective of the development of the global economy. However, along with increased efficiency in the energy sector, significant barriers must also be overcome, including the creation of conventional energy sources, reducing the use of fossil-based fuels, as well as reducing greenhouse gas emissions i.e., CO2 (carbon dioxide), SOX (oxides of sulfur), CH4 (methane), NOX (nitrogen oxides).1 Researchers around the world have been looking for new technologies in the last 30–40 years that will reduce the use of fossil fuels and, lessen the detrimental effects that energy production has on the climate and environment. A practical way of using alternative energy is through energy storage, in addition to conserving energy, energy storage also improves the stability and quality of the energy supply and reduces the variation between supply and demand. One of the popular techniques of energy storage is thermal energy storage (TES), which can be classified as2: i) Latent heat storage and ii) sensible heat storage. Latent heat storage is reliant on heat absorption or release phenomenon, during the phase transition of material from solid to liquid or liquid to gas or vice versa. These materials involved in phase transition are known as phase change materials (PCMs). Whereas in sensible heat storage, energy is stored by increasing the temperature of liquid or solid. In the charging and discharging process, a sensible heat storage system makes use of the material's heat capacity and temperature variation. Stored heat in materials depends on the amount of storage material, the specific heat of the medium, and the temperature change.3 Due to applied thermal energy, some materials change their state by storing some amount of latent heat during the state/phase transition, such materials are known as PCMs. During the transition from solid to liquid or from liquid to solid, thermal energy is transferred. These solid-liquid PCMs function initially like traditional storage materials, as they absorb heat, their temperature increases, but release heat at a practically constant temperature, in contrast to conventional (sensible) storage materials.4 PCMs use chemical bonds for energy storage and release. Although in a sense every material is a PCM, the materials are only categorized as PCM if they have some characteristics of energy storage. High thermal conductivity and significant latent heat should be present in phase transition materials used for energy storage. Additionally, the materials melting points should be within a practical application range; materials should melt consistently with the least amount of supercooling and should be chemically stable. The materials should not be toxic, or chemically corrosive, and should be economical for practical applications.5 PCMs are often divided into three groups i.e., organic, inorganic, and eutectics, which is the combination of two or more materials. This group of PCMs is divided into salt hydrates and metallics. Due to their low cost, better thermal conductivity, cost-effectiveness, and minor volumetric changes for storage, salt hydrates are very appealing materials for phase change energy storage. Salt hydrates are a typical crystalline solid that are a mixture of water (H2O) and inorganic salts and is written as AB.nH2O. Salt hydrates can change from a solid to a liquid state by dehydrating or hydrating the salt, even though this process thermodynamically mimics melting or freezing. Generally, a salt hydrate melts into water, and salt hydrate6 i.e., Most salt hydrates have the problem of incongruent melting. The hydrate crystals disintegrate into anhydrous salt and water, or a lower hydrate and water, at the melting point. The fact that the water released during crystallization is insufficient to completely dissolve all of the solid phases present causes incongruent melting, which is one issue with the majority of salt hydrates. The lower hydrate (or anhydrous salt), due to the density difference, descends to the bottom of the container. Many salt hydrates also have weak nucleating capabilities, which causes the liquid to supercool before crystallization starts. The addition of a nucleating agent, which supplies the nuclei on which crystal formation is started, is one approach to solving this issue. Another option is to keep some crystals in a small, cold area so they can act as nuclei. Some of the salt hydrates with their latent heat of fusion and melting point are listed in Table 1. Most of the metal eutectics and low melting metals come under the inorganic metallic PCM category, but due to their heavy weight, metallics have not been given substantial consideration for PCMs. They are reasonable candidates when the volume is taken into account due to the high latent heat of fusion output per unit volume. The employment of metallics brings forth a variety of peculiar technical issues. The strong heat conductivity of the metallics distinguishes them significantly from other PCMs.8 Organic PCMs are divided into the paraffin and non-paraffin subgroups. Without any loss in their latent heat of fusion and phase segregation, these materials have the property of congruent melting i.e., repeatedly melting and freezing. It also exhibits the property of non-corrosiveness and self-nucleation. Paraffin is mostly made up of an alkanes chain (CH3–CH2–CH3…), and the crystallization of these chains generates a significant amount of latent heat. In general, paraffin is stable below 500°C, and there are no significant changes in the volume on their melting; also they have low vapor pressure while melting.9 The melt-freeze cycle of paraffin is often relatively long. With more carbon atoms present, alkane has a higher melting point. The fact that paraffin is accessible in a wide range of temperatures is the primary factor in its qualification as an energy storage material. Along with other beneficial traits like consistent melting and good nucleating qualities, paraffin has several other advantages.10 They have a few unfavorable characteristics, including low thermal conductivity, incompatibility with plastic containers, and considerable flammability. By slightly modifying the wax and the storage unit, all these negative effects can be somewhat removed. Some of the most desirable and moderate desirable paraffin are shown in Table 2. Of all phase transition materials, non-paraffin organics are the most prevalent and have the widest range of features.11 Unlike paraffin, which has extremely comparable properties, each of these materials will have unique characteristics. This is the broadest group of potential PCMs. After conducting a thorough analysis of organic materials, Buddhi and Sawhney found several esters, fatty acids, alcohols, and glycols that might be useful as energy storage materials.12 Fatty acids and other non-paraffin organic compounds are other subgroups of these organic molecules. Due to their flammability, fatty acids and non-paraffin organic materials cannot be subjected to extreme heat, flames, or oxidizing agents. Compared to paraffin, fatty acids have high heat of fusion and have repeatable behavior in their melting and freezing. Fatty acids also freeze without supercooling. All fatty acids are described by the chemical formula CH3(CH2)2n.COOH. Their main disadvantage is that they are 2–2.5 times more expensive than technical-grade paraffin. They are also barely corrosive. Some of the non-paraffin compounds are listed in Table 3 with their melting point and latent heat of fusion. A minimal-melting composition of at least two or more materials is known as a eutectic, and during crystallization, each of these materials melts and freezes concurrently to form a mixture of the material crystals.13 Because they freeze to a close-knit combination of crystals, eutectic materials rarely melt or freeze without the components segregating. Both components simultaneously liquefy when heated, making separation unlikely. Since they are minimum melting, some segregated PCM compositions have been wrongly referred to as eutectics. But it would be more accurate to refer to them as peritectic as they undergo a peritectic reaction during phase change. Some of the compositions of the eutectics are shown in Table 4.11 Now, if there is a discussion on the merits and demerits of the three types of PCMs mentioned above (inorganic, organic, and eutectic), there are many discrepancies, some of which are listed in Table 5. The rationale for mixing organic non-paraffin compounds such as beeswax (BW) with fatty acids like stearic acid (SA), palmitic acid (PA), myristic acid (MA), and lauric acid (LA) is to tailor the thermal properties particularly the melting point and latent heat of fusion of the resulting eutectic phase change materials (PCMs) for targeted thermal energy storage applications. Eutectic mixtures typically melt at temperatures lower than their individual components, enabling precise tuning of phase change behavior to the desired range of 50–60°C, suitable for applications such as solar water heating, building thermal management, and electronics cooling. Beeswax, a complex blend of long-chain esters, acids, and hydrocarbons, contributes high thermal stability and reduced subcooling, while the fatty acids offer chemical renewability and high latent heat but may suffer from issues like subcooling or phase separation. By carefully selecting compositions near the eutectic point such as BW:SA (20:80) or BW:PA (40:60) the mixtures form homogenous, stable PCMs that melt sharply and perform consistently over thermal cycles. Other than the listed eutectic PCMs, many more eutectic mixtures were prepared with the good latent heat of fusion and melt-freeze cycle. In this series, beeswax-Stearic (BWSA), beeswax-Palmitic (BWPA), beeswax-Myristic (BWMA), and beeswax-Lauric (BWLA) are prepared and tested. These four prepared eutectic mixtures are a composition of organic non-paraffin PCMs. Organic non-paraffin compound beeswax (BW) in different compositions mixed with another organic non-paraffin compound, Palmitic (PA), Myristic (MA), and Lauric (LA) acid at a temperature range of 50–60°C with the help of a magnetic stirrer at 200 rpm for 3–4 hrs followed by sonication for 15 minutes using Sonics Vibracell probe sonicator and get eutectic PCMs. Organic non-paraffin compounds are mixed in different compositions to get desired eutectics. A total of 20 wt % of BW mixed was with 80 wt % of SA to prepare BWSA28. Similarly, 40, 10, and 10 wt % of BW were mixed with 60, 90, and 90 wt % of PA, MA, and LA, respectively, to form BWPA46, BWMA19, and BWLA19 eutectic PCMs. Each sample is prepared in a quantity of 10 gm and acids SA, PA, MA, and LA used here were sourced from MOLYCHEM with product codes 19060, 16705, 16392, and 12520, respectively. Whereas BW was sourced from the center of Excellence on Honey Bees (Nalanda College of Horticulture, Nalanda, Bihar). The PerkinElmer DSC 4000 equipment was used for the differential scanning calorimetry (DSC) study. In order to measure this little amount (mg) of the samples, an analytical digital weighing machine with a precision of 0.00001 g was used. The weighted sample between 10 to 15 mg was filled into an aluminium pan, and the DSC procedure was carried out in a nitrogen environment at a flux of 20 ml/min at a heating rate of 2°C/min. The accuracy of the DSC device was ±2% for enthalpy measurement and ± 0.1°C for temperature measurement. The reference pan and the sample pan are heated at the same rate during the DSC analysis. The latent heat of fusion, peak melting temperature, and other thermophysical parameters was measured. The top point of the curve offers the peak melting temperature, while the area that comes under the curve explicated latent heat of fusion and crystallization, and the tangent of the highest slope explicated the onset melting point. Eutectic phase change materials (PCMs) exhibit a distinct thermal transition behaviour upon heating, which is central to their thermal energy storage (TES) performance. When heat is applied, the molecules within the eutectic PCM begin to oscillate more vigorously. This increased molecular vibration leads to a greater intermolecular distance, resulting in an expansion in volume. As temperature continues to rise, the kinetic energy of the molecules increases significantly, causing the disruption of the supramolecular interactions such as hydrogen bonding or Van der Waals forcesthat stabilize the solid-state structure. This disruption facilitates the transformation from a well-ordered crystalline solid into a disordered liquid state at a specific temperature, known as the phase transition temperature. Thermogravimetric analysis (TGA) complements this understanding by tracking the material’s weight loss as a function of temperature, revealing the onset of thermal degradation, evaporation of volatile components, and thermal stability limits. It provides critical insights into whether the PCM maintains its integrity during heating cycles. The thermogravimetric analysis (TGA) plot illustrates the thermal stability and decomposition behaviour of pure beeswax (BW) and its eutectic mixtures with stearic acid (SA), palmitic acid (PA), myristic acid (MA), and lauric acid (LA) over a temperature range from room temperature to 800 °C (shown in Figure 1). The weight percentage versus temperature profiles reveal distinct degradation patterns for each sample. Pure beeswax exhibits the highest thermal stability, with initial decomposition starting around 250 °C, major weight loss occurring between 250–450 °C, and near-complete decomposition by ~500 °C. This is attributed to the breakdown of long-chain hydrocarbons, esters, and waxy compounds present in BW. The BWSA28 sample begins degrading slightly earlier (~200 °C) and shows significant mass loss between 250–450 °C, continuing up to ~600 °C, indicating reduced stability compared to pure BW but better than pure SA, likely due to the inclusion of BW which stabilizes the blend. For BWPA46, BWMA19, and BWLA19, thermal stability decreases progressively with decreasing fatty acid chain length. BWLA19 exhibits the earliest degradation (~160 °C) and the fastest decomposition, completing by ~350 °C, highlighting its low thermal resistance due to the volatility and lower molecular weight of lauric acid. BWMA19 and BWPA46 show intermediate behaviour, with BWPA46 displaying a broader degradation range due to multistep decomposition from its mixed components. The thermal degradation proceeds via sequential breakdown of molecular constituents starting with volatilization of free fatty acids and followed by the cleavage of ester bonds and fragmentation of hydrocarbon backbones. These reactions are influenced by molecular weight, bonding type, and blend miscibility, where longer chains require higher activation energy to decompose compared to shorter ones. The near-zero residue at 800 °C confirms complete volatilization, which is advantageous for clean decomposition but may necessitate containment considerations in cyclic TES operations. All eutectic mixtures leave minimal residue (~0–5%) at 800 °C, indicating complete decomposition. The observed mass losses are primarily due to thermal evaporation and breakdown of organic constituent’s fatty acids and hydrocarbon chains into volatile products. These results confirm that beeswax improves thermal stability in eutectic formulations, and the degradation temperature systematically decreases with shorter fatty acid chain lengths. This information is essential for selecting eutectic phase change materials (PCMs) in thermal energy storage systems where both thermal stability and phase transition behaviour are crucial. Through DSC analysis, the thermal energy storage properties of BWSA28, BWPA46, BWMA19, and BWLA19 were determined. The DSC curves for BWSA28, BWPA46, BWMA19, and BWLA19 are shown in Figure 2. The DSC curves for BWSA28, BWPA46, BWMA19, and BWLA19 displayed comparable patterns and nearly equal forms. For BWSA28, BWPA46, BWMA19, and BWLA19, the onset melting points were 49.59°C, 48.85°C, 50.91°C, and 41.02°C, respectively, which are listed in Table 6. Similarly, the peak melting temperatures for these materials were 55.17°C, 56.85°C, 55.22°C, and 44.96°C, respectively. These values suggest that the materials begin to undergo phase transition within a relatively narrow and moderate temperature range, making them suitable for low-to-intermediate temperature thermal storage applications. Onset and freezing temperatures obtained from BWSA28, BWPA46, BWMA19, and BWLA19 were 50.79°C, 50.22°C, 45.44°C, 36.77°C, and 48.93°C, 49.59°C, 45.34°C, 36.08°C, respectively. The relatively small supercooling gap between the melting and freezing temperatures across all samples suggests good reversibility and stability in repeated thermal cycling, a critical requirement for TES materials. In the DSC plot, the area under the curve provides latent heat of fusion and latent heat of crystallization as shown in Figure 2 and marked with the arrow. So, the obtained latent heat of fusion and latent heat of crystallization for BWSA28, BWPA46, BWMA19, and BWLA19 were 174.52 kJ/kg, 166.03 kJ/kg, 192.85 kJ/kg, 195.73 kJ/kg, and 177.94 kJ/kg, 155.55 kJ/kg, 211.52 kJ/kg, and 201.04 kJ/kg, respectively. These results indicate that BWMA19 and BWLA19 possess superior thermal storage capacity, making them especially attractive for applications requiring higher energy density. DSC analysis confirms that all four eutectic PCMs possess favorable thermal properties, including sharp phase transition, moderate-to-high latent heat, and low supercooling. Among them, BWMA19 and BWLA19 demonstrate the most promising performance due to their higher latent heat values, making them strong candidates for efficient thermal energy storage in solar thermal systems, building climate control, or electronic cooling applications. Drying is a widely used technique in the preservation of food and agricultural products, primarily employed to reduce moisture content while maintaining the quality, nutritional value, and shelf life of the products. Among various drying techniques, solar drying has emerged as a cost-effective and environmentally friendly alternative, particularly well-suited for rural and off-grid regions. The operating temperature range typically required for drying sensitive agricultural products such as fruits and vegetables lies between 40°C and 80°C, a range that ensures adequate moisture removal without causing thermal degradation of essential nutrients. Effective solar drying requires stable temperature regulation and moisture control, which are heavily influenced by ambient solar radiation, air temperature, humidity, and airflow. To address the challenge of fluctuating environmental conditions during solar drying, phase change materials (PCMs) can be integrated into drying systems to store thermal energy during peak sunlight hours and release it when solar input diminishes (e.g., late afternoon or cloudy periods). This enhances drying consistency, improves energy efficiency, and reduces the risk of spoilage.15–17 The eutectic PCMs developed in this study BWSA28, BWPA46, BWMA19, and BWLA19 exhibited melting and freezing temperatures in the range of 36°C to 56°C, aligning well with the optimal temperature window for solar drying of food and agricultural products. Specifically, BWLA19, with a melting temperature around 44.96°C and a freezing point near 36.08°C, is particularly well suited for low-temperature drying applications where gentle heat is necessary to preserve delicate nutritional compounds. BWMA19 and BWSA28, having melting temperatures of 55.22°C and 55.17°C respectively, can support drying processes that require temperatures closer to the upper end of the safe drying range. The high latent heat capacities of these eutectics (up to 195.73 kJ/kg for BWLA19 and 192.85 kJ/kg for BWMA19) indicate that they can store and release substantial amounts of thermal energy, thus extending the effective drying period beyond peak sunlight hours. In addition to technical compatibility, the use of PCMs in solar drying systems contributes to energy conservation and sustainability. Unlike fossil-fuel-based thermal storage or continuous electrical input, eutectic PCMs offer passive energy storage with no carbon emissions, aligning with ecological and economic goals of the agricultural industry. Thus, the integration of these eutectic PCMs into solar-assisted drying units could significantly enhance the efficiency, reliability, and product quality of food drying processes, while maintaining a low operational cost and minimizing environmental impact. Compared to commercial PCMs, the thermal storage capacity of BWMA19 and BWLA19 (>190 kJ/kg) is comparable or superior to RT50 and fatty acid eutectics.18 Phase transition temperatures are finely tuned for different drying needs BWLA19 for more sensitive drying (e.g., herbs, berries), and BWMA19 for general fruits/vegetables. These eutectics likely offer better chemical compatibility, biodegradability, and cost-effectiveness for agricultural use, depending on the specific constituents. Moreover, the narrow supercooling range and consistent melting/crystallization behaviour observed in the DSC curves indicate that these PCMs maintain reversible thermal cycling with minimal thermal hysteresis, enhancing their reliability for repeated drying operations.19,20 Due to its capability to enhance system performance, energy storage is particularly alluring to a wide range of parties. Technology development is more efficient and practical when excess energy is stored for later use rather than being replaced by new power plants. The latent heat of the phase change is associated with prepared eutectic PCMs and has a crucial influence on their ability to store greater amounts of energy. A target-oriented settling temperature is also supported by PCMs due to the fixed phase change temperature. This paper deals with the development of eutectics PCM. The foremost advantages of these prepared eutectic PCMs were their low cost and eco-friendly nature. DSC analysis of this prepared eutectics BWSA28, BWPA46, BWMA19, and BWLA19 showed good thermal energy storage capacity, and it lies between 155–211 kJ/Kg and they are thermally stable around 200–250°C. These eutectics have a temperature range between 36–56°C. Figshare: Dataset, https://doi.org/10.6084/m9.figshare.23496929.v1.21 This project contains the following underlying data: Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0). - 1. Anand A, Shukla A, Sharma A: Recapitulation on latent heat hybrid buildings. Int. J. Energy Res. 2020; 44(3): 1370–1407. Publisher Full Text - 2. Nazir H, Batool M, Bolivar Osorio FJ, et al.: Recent developments in phase change materials for energy storage applications: A review. Int. J. Heat Mass Transf. 2019; 129: 491–523. Publisher Full Text - 3. Farid MM, Khudhair AM, Razack SAK, et al.: A review on phase change energy storage: Materials and applications. Energy Convers. 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PubMed Abstract | Publisher Full Text - 15. Kant K, Shukla A, Sharma A, et al.: Thermal energy storage based solar drying systems: A review. Innov. Food Sci. Emerg. Technol. 2016; 34: 86–99. Publisher Full Text - 16. Shalaby SM, Bek MA, El-Sebaii AA: Solar dryers with PCM as energy storage medium: A review. Renew. Sust. Energ. Rev. 2014; 33: 110–116. Publisher Full Text - 17. Getahun E, Delele MA, Gabbiye N, et al.: Importance of integrated CFD and product quality modeling of solar dryers for fruits and vegetables: A review. Sol. Energy. 2021; 220(March): 88–110. Publisher Full Text - 18. Wang S, Huang Q, Sun Z, et al.: Porous Carbon Network-Based Composite Phase Change Materials with Heat Storage Capacity and Thermal Management Functions. Carbon N. Y. 2024; 226: 119174. Publisher Full Text - 19. Nazir H, Batool M, Ali M, et al.: Fatty Acids Based Eutectic Phase Change System for Thermal Energy Storage Applications. Appl. Therm. Eng. 2018; 142: 466–475. Publisher Full Text - 20. Pandey S, Kumar A, Sharma A: Sustainable Solar Drying: Recent Advances in Materials, Innovative Designs, Mathematical Modeling, and Energy Storage Solutions. Energy. 2024; 308: 132725. Publisher Full Text - 21. Pandey S: DataSet. Dataset. figshare. 2023. Publisher Full Text Version 3 VERSION 3 PUBLISHED 06 Aug 2025 Revised - Reader Comment 09 Mar 2026Afrah Awad, Northern Technical University, Mosul, Iraq09 Mar 2026Reader CommentI recommend that the authors improve their manuscript as follows: - The research gap and contribution should be clearly stated at the end of the Introduction section. - Although - The research gap and contribution should be clearly stated at the end of the Introduction section. - Although the paper was submitted in 2022, the reference list needs to be updated. There are several recent studies on the development of PCM that should be included. - The Methodology section is too brief, where is the schematic of prepration of samples? - The Results section also lacks sufficient detail. More information should be provided, such as the results of Cp vs. time or Cp vs. temperature, and these results should be clearly discussed for the different PCMs. - The authors should provide a deeper analysis and discussion of the obtained results. I recommend that the authors improve their manuscript as follows:Competing Interests: There is no conflict of interest Close- The research gap and contribution should be clearly stated at the end of the Introduction section. - Although the paper was submitted in 2022, the reference list needs to be updated. There are several recent studies on the development of PCM that should be included. - The Methodology section is too brief, where is the schematic of prepration of samples? - The Results section also lacks sufficient detail. More information should be provided, such as the results of Cp vs. time or Cp vs. temperature, and these results should be clearly discussed for the different PCMs. - The authors should provide a deeper analysis and discussion of the obtained results. Author details Author details 1 Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Jais, Amethi, UP, 229304, India 2 Uttaranchal University, Dehradun, Uttarakhand, 248007, India 2 Uttaranchal University, Dehradun, Uttarakhand, 248007, India Saurabh Pandey Roles: Conceptualization, Data Curation, Formal Analysis, Methodology, Software, Writing – Original Draft Preparation Roles: Conceptualization, Data Curation, Formal Analysis, Methodology, Software, Writing – Original Draft Preparation Abhishek Anand Roles: Formal Analysis, Software Roles: Formal Analysis, Software Dharam Buddhi Roles: Investigation, Project Administration, Validation, Visualization Roles: Investigation, Project Administration, Validation, Visualization Atul Sharma Roles: Data Curation, Formal Analysis, Funding Acquisition, Project Administration, Resources, Supervision, Validation, Visualization, Writing – Review & Editing Roles: Data Curation, Formal Analysis, Funding Acquisition, Project Administration, Resources, Supervision, Validation, Visualization, Writing – Review & Editing Competing interests No competing interests were disclosed. Grant information The author (Saurabh Pandey) would like to thank the Rajiv Gandhi Institute of Petroleum Technology (RGIPT) for providing the Institute Fellowship. Article Versions (3) Copyright © 2025 Pandey S et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. metrics | Views | Downloads | | |---|---|---| | F1000Research | - | - | | PubMed Central Data from PMC are received and updated monthly. | - | - | Citations CITE how to cite this article Pandey S, Anand A, Buddhi D and Sharma A. Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.12688/f1000research.127268.3) NOTE: If applicable, it is important to ensure the information in square brackets after the title is included in all citations of this article. track receive updates on this article Track an article to receive email alerts on any updates to this article. Current Reviewer Status: ? Key to Reviewer Statuses VIEW HIDE ApprovedThe paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approvedFundamental flaws in the paper seriously undermine the findings and conclusions Version 3 VERSION 3 PUBLISHED 06 Aug 2025 Revised Views 0 How to cite this report: Atia A. Reviewer Report For: Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.5256/f1000research.183569.r412630) The direct URL for this report is: https://f1000research.com/articles/11-1277/v3#referee-response-412630 https://f1000research.com/articles/11-1277/v3#referee-response-412630 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Reviewer Report 17 Sep 2025 Aissa Atia, Higher Normal School of Laghouat, Laghouat, Laghouat, Algeria Not Approved VIEWS 0 After a thorough review of the article, several significant weaknesses were found that do not align with the journal's standards, including unclear research methodology, insufficient analysis of the results, and weak arguments to support the conclusions. The theoretical framework also ... Continue reading I confirm that I have read this submission and believe that I have an appropriate level of expertise to state that I do not consider it to be of an acceptable scientific standard, for reasons outlined above. Close After a thorough review of the article, several significant weaknesses were found that do not align with the journal's standards, including unclear research methodology, insufficient analysis of the results, and weak arguments to support the conclusions. The theoretical framework also needs to be strengthened to become more robust and convincing. - Is the work clearly and accurately presented and does it cite the current literature? No - Is the study design appropriate and is the work technically sound? No - Are sufficient details of methods and analysis provided to allow replication by others? No - If applicable, is the statistical analysis and its interpretation appropriate? No - Are all the source data underlying the results available to ensure full reproducibility? Yes - Are the conclusions drawn adequately supported by the results? Yes Competing Interests: No competing interests were disclosed. Reviewer Expertise: Renewable energy, PCM CITE HOW TO CITE THIS REPORT Atia A. Reviewer Report For: Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.5256/f1000research.183569.r412630) The direct URL for this report is: https://f1000research.com/articles/11-1277/v3#referee-response-412630 https://f1000research.com/articles/11-1277/v3#referee-response-412630 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. Views 0 How to cite this report: P. Joshi D. Reviewer Report For: Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.5256/f1000research.183569.r403164) The direct URL for this report is: https://f1000research.com/articles/11-1277/v3#referee-response-403164 https://f1000research.com/articles/11-1277/v3#referee-response-403164 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Reviewer Report 19 Aug 2025 Not Approved VIEWS 0 The revised manuscript entitled “Development and thermophysical analysis of binary eutectics phase change materials for solar drying application” has again some issues which are not clear; some points are as follows: Comments: I confirm that I have read this submission and believe that I have an appropriate level of expertise to state that I do not consider it to be of an acceptable scientific standard, for reasons outlined above. Close Comments: - Beewax PCM was The revised manuscript entitled “Development and thermophysical analysis of binary eutectics phase change materials for solar drying application” has again some issues which are not clear; some points are as follows: Comments: Comments: - Beewax PCM was mixed with other PCMs in random composition. Even in the revised version, the reason for selecting the random composition for the comparative study is not clear. It should be constant for all samples, either 20:80 or 40:60, or 10:90. - Without any characterisation, how could we know which ratio we have to choose? What are the basic properties of a sample required for the solar drying application? Competing Interests: No competing interests were disclosed. Reviewer Expertise: composite, core-shell nanomaterials , thermal energy storage CITE HOW TO CITE THIS REPORT P. Joshi D. Reviewer Report For: Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.5256/f1000research.183569.r403164) The direct URL for this report is: https://f1000research.com/articles/11-1277/v3#referee-response-403164 https://f1000research.com/articles/11-1277/v3#referee-response-403164 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. - Author Response 11 Sep 2025Abhishek Anand, Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Jais, Amethi, 229304, India11 Sep 2025Author Response - Thank you for your valuable comment. The specific compositions of BW, PA, MA, and LA were determined through experimental optimization. Several ratios, including BW:SA at 10:90, 20:80, 30:70, - Thank you for your valuable comment. The specific compositions of BW, PA, MA, and LA were determined through experimental optimization. Several ratios, including BW:SA at 10:90, 20:80, 30:70, 40:60, and 50:50, were systematically evaluated to identify the formulation with the most favorable thermal characteristics. The optimized composition was selected for its ability to provide a high latent heat and a sharp, well-defined melting point, both of which are critical for the intended application. In contrast, other tested ratios exhibited lower latent heat values and broader melting ranges, making them less suitable for achieving the desired thermal properties. (mentioned in second Reviewer first response ) - Thank you for your valuable comment. As highlighted in the title, the present work focuses on the development and thermophysical analysis of binary eutectic PCMs for solar drying applications. Accordingly, all prepared compositions were systematically characterized using DSC and TGA to determine their key thermophysical properties, including phase transition temperature, latent heat of fusion, and thermal stability. These parameters are the most critical in identifying suitable PCMs for solar drying, where high latent heat capacity, a sharp melting/solidification range close to the operating temperature, and adequate stability are essential. Based on this thermophysical analysis, the optimized composition was selected as the most appropriate candidate. Competing Interests: No competing interests were disclosed. Close- Thank you for your valuable comment. The specific compositions of BW, PA, MA, and LA were determined through experimental optimization. Several ratios, including BW:SA at 10:90, 20:80, 30:70, 40:60, and 50:50, were systematically evaluated to identify the formulation with the most favorable thermal characteristics. The optimized composition was selected for its ability to provide a high latent heat and a sharp, well-defined melting point, both of which are critical for the intended application. In contrast, other tested ratios exhibited lower latent heat values and broader melting ranges, making them less suitable for achieving the desired thermal properties. (mentioned in second Reviewer first response ) - Thank you for your valuable comment. As highlighted in the title, the present work focuses on the development and thermophysical analysis of binary eutectic PCMs for solar drying applications. Accordingly, all prepared compositions were systematically characterized using DSC and TGA to determine their key thermophysical properties, including phase transition temperature, latent heat of fusion, and thermal stability. These parameters are the most critical in identifying suitable PCMs for solar drying, where high latent heat capacity, a sharp melting/solidification range close to the operating temperature, and adequate stability are essential. Based on this thermophysical analysis, the optimized composition was selected as the most appropriate candidate. COMMENTS ON THIS REPORT - Author Response 11 Sep 2025Abhishek Anand, Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Jais, Amethi, 229304, India11 Sep 2025Author Response - Thank you for your valuable comment. The specific compositions of BW, PA, MA, and LA were determined through experimental optimization. Several ratios, including BW:SA at 10:90, 20:80, 30:70, - Thank you for your valuable comment. The specific compositions of BW, PA, MA, and LA were determined through experimental optimization. Several ratios, including BW:SA at 10:90, 20:80, 30:70, 40:60, and 50:50, were systematically evaluated to identify the formulation with the most favorable thermal characteristics. The optimized composition was selected for its ability to provide a high latent heat and a sharp, well-defined melting point, both of which are critical for the intended application. In contrast, other tested ratios exhibited lower latent heat values and broader melting ranges, making them less suitable for achieving the desired thermal properties. (mentioned in second Reviewer first response ) - Thank you for your valuable comment. As highlighted in the title, the present work focuses on the development and thermophysical analysis of binary eutectic PCMs for solar drying applications. Accordingly, all prepared compositions were systematically characterized using DSC and TGA to determine their key thermophysical properties, including phase transition temperature, latent heat of fusion, and thermal stability. These parameters are the most critical in identifying suitable PCMs for solar drying, where high latent heat capacity, a sharp melting/solidification range close to the operating temperature, and adequate stability are essential. Based on this thermophysical analysis, the optimized composition was selected as the most appropriate candidate. Competing Interests: No competing interests were disclosed. Close- Thank you for your valuable comment. The specific compositions of BW, PA, MA, and LA were determined through experimental optimization. Several ratios, including BW:SA at 10:90, 20:80, 30:70, 40:60, and 50:50, were systematically evaluated to identify the formulation with the most favorable thermal characteristics. The optimized composition was selected for its ability to provide a high latent heat and a sharp, well-defined melting point, both of which are critical for the intended application. In contrast, other tested ratios exhibited lower latent heat values and broader melting ranges, making them less suitable for achieving the desired thermal properties. (mentioned in second Reviewer first response ) - Thank you for your valuable comment. As highlighted in the title, the present work focuses on the development and thermophysical analysis of binary eutectic PCMs for solar drying applications. Accordingly, all prepared compositions were systematically characterized using DSC and TGA to determine their key thermophysical properties, including phase transition temperature, latent heat of fusion, and thermal stability. These parameters are the most critical in identifying suitable PCMs for solar drying, where high latent heat capacity, a sharp melting/solidification range close to the operating temperature, and adequate stability are essential. Based on this thermophysical analysis, the optimized composition was selected as the most appropriate candidate. Version 2 VERSION 2 PUBLISHED 20 Sep 2023 Revised Views 0 How to cite this report: Abdeen Ali Abuelnuor A. Reviewer Report For: Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.5256/f1000research.151630.r337593) The direct URL for this report is: https://f1000research.com/articles/11-1277/v2#referee-response-337593 https://f1000research.com/articles/11-1277/v2#referee-response-337593 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Reviewer Report 30 Dec 2024 Abuelnuor Abdeen Ali Abuelnuor, Al-Baha University, Al-Baha, Saudi Arabia Approved with Reservations VIEWS 0 - Was the choice of specific compositions for BW, PA, MA, and LA (e.g., 20:80 for BWSA28) based on prior experimental optimization or theoretical predictions? Could alternative ratios yield better eutectic properties, and were these tested? - Was the choice of specific compositions for BW, PA, MA, and LA (e.g., 20:80 for BWSA28) based on prior experimental optimization or theoretical predictions? Could alternative ratios yield better eutectic properties, and were these tested? - The onset and peak melting temperatures for the eutectic PCMs are close but show variations. Were these differences attributed to specific interactions between the molecular components, and how do these differences influence the practical applications of these PCMs? - The latent heat of fusion and crystallization values for the PCMs vary significantly (e.g., BWSA28 vs. BWMA19). What factors contribute to these differences, and how do they affect the efficiency of thermal energy storage in real-world scenarios? - How do the specific melting and freezing temperature ranges of the prepared eutectic PCMs (36°C to 56°C) ensure optimal performance in maintaining product quality during solar drying, particularly for sensitive nutritional characteristics of fruits and vegetables? - The discussion of the results needs to be expanded, as well as a comparison of your results with those of other studies. - Is the work clearly and accurately presented and does it cite the current literature? Yes - Is the study design appropriate and is the work technically sound? Yes - Are sufficient details of methods and analysis provided to allow replication by others? Yes - If applicable, is the statistical analysis and its interpretation appropriate? Yes - Are all the source data underlying the results available to ensure full reproducibility? Yes - Are the conclusions drawn adequately supported by the results? Yes Competing Interests: No competing interests were disclosed. Reviewer Expertise: Phase Change Materials, Solar Drying CITE HOW TO CITE THIS REPORT Abdeen Ali Abuelnuor A. Reviewer Report For: Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.5256/f1000research.151630.r337593) The direct URL for this report is: https://f1000research.com/articles/11-1277/v2#referee-response-337593 https://f1000research.com/articles/11-1277/v2#referee-response-337593 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. - Author Response 11 Sep 2025Abhishek Anand, Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Jais, Amethi, 229304, India11 Sep 2025Author ResponseReviewer Comments 2 Comment 1: Was the choice of specific compositions for BW, PA, MA, and LA (e.g., 20:80 for BWSA28) based on prior experimental optimization or theoretical predictions? ... Continue reading Reviewer Comments 2 Comment 1: Was the choice of specific compositions for BW, PA, MA, and LA (e.g., 20:80 for BWSA28) based on prior experimental optimization or theoretical predictions? Could alternative ratios yield better eutectic properties, and were these tested? Response The selection of specific compositions for BW, PA, MA, and LA was based on experimental optimization. Various ratios, such as BW:SA 10:90, 20:80, 30:70, 40:60, and 50:50, were systematically tested to identify the composition with the most favourable properties. The chosen composition was selected based on its ability to provide a higher latent heat and a sharp, well-defined melting point, which are crucial for the intended application. Compositions with alternative ratios were either found to have lower latent heat values or broader melting ranges, making them less suitable for achieving the desired thermal performance. Comment 2: The onset and peak melting temperatures for the eutectic PCMs are close but show variations. Were these differences attributed to specific interactions between the molecular components, and how do these differences influence the practical applications of these PCMs? Response The onset and peak melting temperatures for the eutectic PCMs (beewax-stearic 20:80, beewax-palmitic 40:60, beewax-myristic 10:90, and beewax-lauric 10:90) are close but exhibit variations due to specific molecular interactions between the components. These differences are primarily attributed to variations in the chain length and molecular structure of the fatty acids. Longer-chain fatty acids, such as stearic acid, tend to have stronger van der Waals interactions and higher melting points, while shorter-chain fatty acids like lauric acid exhibit weaker interactions and lower melting points. The chosen ratios also play a significant role in determining the eutectic composition, influencing the degree of miscibility and crystallization behaviour within the PCM mixture. Intermolecular forces, such as hydrogen bonding and van der Waals forces, vary depending on the proportion of beewax and fatty acids, leading to differences in thermal properties. From a practical standpoint, these variations are significant as they determine the suitability of a particular eutectic PCM for specific temperature ranges in thermal energy storage applications. For example, a narrower melting range and sharp phase transition temperature are desirable for efficient thermal regulation in applications like solar dryers, where precise heat absorption and release are critical. On the other hand, minor differences in melting temperatures allow for the tailoring of PCMs to suit diverse climatic conditions and operational requirements, enhancing the versatility of these materials. Comment 3: The latent heat of fusion and crystallization values for the PCMs vary significantly (e.g., BWSA28 vs. BWMA19). What factors contribute to these differences, and how do they affect the efficiency of thermal energy storage in real-world scenarios? Response: The significant variation in the latent heat of fusion and crystallization values for PCMs, such as BWSA28 (20:80) with 174.52 J/g and 177.94 J/g and BWMA19 (10:90) with 195.73 J/g and 201.04 J/g, is influenced by the chain length, molecular structure, and composition of the fatty acids. Myristic acid (C14) in BWMA19, with its shorter carbon chain, facilitates lower molecular packing density and more efficient phase transitions compared to stearic acid (C18) in BWSA28, leading to higher latent heat values in BWMA19. The higher proportion of myristic acid in BWMA19 optimizes crystalline phase formation and enhances energy storage capacity, whereas the lower fatty acid content in BWSA28 reduces its thermal performance. Additionally, stronger molecular interactions, such as hydrogen bonding and van der Waals forces, and better crystalline packing in BWMA19 contribute to its superior thermal properties. The higher latent heat of crystallization in BWMA19 ensures efficient energy release during cooling, making it more suitable for high-energy-demand applications like solar dryers. Conversely, BWSA28 may be more appropriate for moderate energy storage needs, depending on the operating temperature and energy requirements of the application. These variations directly affect the efficiency of thermal energy storage in real-world scenarios, with BWMA19 offering higher energy density and thermal performance. Comment 4: How do the specific melting and freezing temperature ranges of the prepared eutectic PCMs (36°C to 56°C) ensure optimal performance in maintaining product quality during solar drying, particularly for sensitive nutritional characteristics of fruits and vegetables? Response The specific melting and freezing temperature ranges of the prepared eutectic PCMs (36°C to 56°C) ensure optimal performance in solar drying by maintaining consistent thermal conditions crucial for preserving the sensitive nutritional characteristics of fruits and vegetables. These temperature ranges align with the optimal drying conditions for most agricultural products, which require moderate heat to effectively remove moisture without causing thermal degradation of vitamins, enzymes, and flavour compounds. During the drying process, the melting phase of the PCMs absorbs and stores excess heat, preventing overheating, while the freezing phase releases stored heat during cooling periods, maintaining a stable temperature. For example, BWLA19, with its lower melting range (41.02°C to 44.96°C), is suitable for drying delicate produce, such as leafy greens, where minimal thermal stress is essential. In contrast, BWSA28 and BWPA46, with higher melting peaks (up to 56.85°C), are more appropriate for drying fruits with higher moisture content or thicker peels, requiring slightly elevated drying temperatures for effective moisture removal. This thermal regulation not only improves drying efficiency but also ensures uniform drying, thereby preserving texture, colour, and nutritional value, making these PCMs highly effective for solar drying applications. Comment 5: The discussion of the results needs to be expanded, as well as a comparison of your results with those of other studies. Response: As per your instruction discussion of the results expanded and comparison of the result with other result also listed in that section.Reviewer Comments 2Competing Interests: No competing interests were disclosed. Close Comment 1: Was the choice of specific compositions for BW, PA, MA, and LA (e.g., 20:80 for BWSA28) based on prior experimental optimization or theoretical predictions? Could alternative ratios yield better eutectic properties, and were these tested? Response The selection of specific compositions for BW, PA, MA, and LA was based on experimental optimization. Various ratios, such as BW:SA 10:90, 20:80, 30:70, 40:60, and 50:50, were systematically tested to identify the composition with the most favourable properties. The chosen composition was selected based on its ability to provide a higher latent heat and a sharp, well-defined melting point, which are crucial for the intended application. Compositions with alternative ratios were either found to have lower latent heat values or broader melting ranges, making them less suitable for achieving the desired thermal performance. Comment 2: The onset and peak melting temperatures for the eutectic PCMs are close but show variations. Were these differences attributed to specific interactions between the molecular components, and how do these differences influence the practical applications of these PCMs? Response The onset and peak melting temperatures for the eutectic PCMs (beewax-stearic 20:80, beewax-palmitic 40:60, beewax-myristic 10:90, and beewax-lauric 10:90) are close but exhibit variations due to specific molecular interactions between the components. These differences are primarily attributed to variations in the chain length and molecular structure of the fatty acids. Longer-chain fatty acids, such as stearic acid, tend to have stronger van der Waals interactions and higher melting points, while shorter-chain fatty acids like lauric acid exhibit weaker interactions and lower melting points. The chosen ratios also play a significant role in determining the eutectic composition, influencing the degree of miscibility and crystallization behaviour within the PCM mixture. Intermolecular forces, such as hydrogen bonding and van der Waals forces, vary depending on the proportion of beewax and fatty acids, leading to differences in thermal properties. From a practical standpoint, these variations are significant as they determine the suitability of a particular eutectic PCM for specific temperature ranges in thermal energy storage applications. For example, a narrower melting range and sharp phase transition temperature are desirable for efficient thermal regulation in applications like solar dryers, where precise heat absorption and release are critical. On the other hand, minor differences in melting temperatures allow for the tailoring of PCMs to suit diverse climatic conditions and operational requirements, enhancing the versatility of these materials. Comment 3: The latent heat of fusion and crystallization values for the PCMs vary significantly (e.g., BWSA28 vs. BWMA19). What factors contribute to these differences, and how do they affect the efficiency of thermal energy storage in real-world scenarios? Response: The significant variation in the latent heat of fusion and crystallization values for PCMs, such as BWSA28 (20:80) with 174.52 J/g and 177.94 J/g and BWMA19 (10:90) with 195.73 J/g and 201.04 J/g, is influenced by the chain length, molecular structure, and composition of the fatty acids. Myristic acid (C14) in BWMA19, with its shorter carbon chain, facilitates lower molecular packing density and more efficient phase transitions compared to stearic acid (C18) in BWSA28, leading to higher latent heat values in BWMA19. The higher proportion of myristic acid in BWMA19 optimizes crystalline phase formation and enhances energy storage capacity, whereas the lower fatty acid content in BWSA28 reduces its thermal performance. Additionally, stronger molecular interactions, such as hydrogen bonding and van der Waals forces, and better crystalline packing in BWMA19 contribute to its superior thermal properties. The higher latent heat of crystallization in BWMA19 ensures efficient energy release during cooling, making it more suitable for high-energy-demand applications like solar dryers. Conversely, BWSA28 may be more appropriate for moderate energy storage needs, depending on the operating temperature and energy requirements of the application. These variations directly affect the efficiency of thermal energy storage in real-world scenarios, with BWMA19 offering higher energy density and thermal performance. Comment 4: How do the specific melting and freezing temperature ranges of the prepared eutectic PCMs (36°C to 56°C) ensure optimal performance in maintaining product quality during solar drying, particularly for sensitive nutritional characteristics of fruits and vegetables? Response The specific melting and freezing temperature ranges of the prepared eutectic PCMs (36°C to 56°C) ensure optimal performance in solar drying by maintaining consistent thermal conditions crucial for preserving the sensitive nutritional characteristics of fruits and vegetables. These temperature ranges align with the optimal drying conditions for most agricultural products, which require moderate heat to effectively remove moisture without causing thermal degradation of vitamins, enzymes, and flavour compounds. During the drying process, the melting phase of the PCMs absorbs and stores excess heat, preventing overheating, while the freezing phase releases stored heat during cooling periods, maintaining a stable temperature. For example, BWLA19, with its lower melting range (41.02°C to 44.96°C), is suitable for drying delicate produce, such as leafy greens, where minimal thermal stress is essential. In contrast, BWSA28 and BWPA46, with higher melting peaks (up to 56.85°C), are more appropriate for drying fruits with higher moisture content or thicker peels, requiring slightly elevated drying temperatures for effective moisture removal. This thermal regulation not only improves drying efficiency but also ensures uniform drying, thereby preserving texture, colour, and nutritional value, making these PCMs highly effective for solar drying applications. Comment 5: The discussion of the results needs to be expanded, as well as a comparison of your results with those of other studies. Response: As per your instruction discussion of the results expanded and comparison of the result with other result also listed in that section. COMMENTS ON THIS REPORT - Author Response 11 Sep 2025Abhishek Anand, Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Jais, Amethi, 229304, India11 Sep 2025Author ResponseReviewer Comments 2 Comment 1: Was the choice of specific compositions for BW, PA, MA, and LA (e.g., 20:80 for BWSA28) based on prior experimental optimization or theoretical predictions? ... Continue reading Reviewer Comments 2 Comment 1: Was the choice of specific compositions for BW, PA, MA, and LA (e.g., 20:80 for BWSA28) based on prior experimental optimization or theoretical predictions? Could alternative ratios yield better eutectic properties, and were these tested? Response The selection of specific compositions for BW, PA, MA, and LA was based on experimental optimization. Various ratios, such as BW:SA 10:90, 20:80, 30:70, 40:60, and 50:50, were systematically tested to identify the composition with the most favourable properties. The chosen composition was selected based on its ability to provide a higher latent heat and a sharp, well-defined melting point, which are crucial for the intended application. Compositions with alternative ratios were either found to have lower latent heat values or broader melting ranges, making them less suitable for achieving the desired thermal performance. Comment 2: The onset and peak melting temperatures for the eutectic PCMs are close but show variations. Were these differences attributed to specific interactions between the molecular components, and how do these differences influence the practical applications of these PCMs? Response The onset and peak melting temperatures for the eutectic PCMs (beewax-stearic 20:80, beewax-palmitic 40:60, beewax-myristic 10:90, and beewax-lauric 10:90) are close but exhibit variations due to specific molecular interactions between the components. These differences are primarily attributed to variations in the chain length and molecular structure of the fatty acids. Longer-chain fatty acids, such as stearic acid, tend to have stronger van der Waals interactions and higher melting points, while shorter-chain fatty acids like lauric acid exhibit weaker interactions and lower melting points. The chosen ratios also play a significant role in determining the eutectic composition, influencing the degree of miscibility and crystallization behaviour within the PCM mixture. Intermolecular forces, such as hydrogen bonding and van der Waals forces, vary depending on the proportion of beewax and fatty acids, leading to differences in thermal properties. From a practical standpoint, these variations are significant as they determine the suitability of a particular eutectic PCM for specific temperature ranges in thermal energy storage applications. For example, a narrower melting range and sharp phase transition temperature are desirable for efficient thermal regulation in applications like solar dryers, where precise heat absorption and release are critical. On the other hand, minor differences in melting temperatures allow for the tailoring of PCMs to suit diverse climatic conditions and operational requirements, enhancing the versatility of these materials. Comment 3: The latent heat of fusion and crystallization values for the PCMs vary significantly (e.g., BWSA28 vs. BWMA19). What factors contribute to these differences, and how do they affect the efficiency of thermal energy storage in real-world scenarios? Response: The significant variation in the latent heat of fusion and crystallization values for PCMs, such as BWSA28 (20:80) with 174.52 J/g and 177.94 J/g and BWMA19 (10:90) with 195.73 J/g and 201.04 J/g, is influenced by the chain length, molecular structure, and composition of the fatty acids. Myristic acid (C14) in BWMA19, with its shorter carbon chain, facilitates lower molecular packing density and more efficient phase transitions compared to stearic acid (C18) in BWSA28, leading to higher latent heat values in BWMA19. The higher proportion of myristic acid in BWMA19 optimizes crystalline phase formation and enhances energy storage capacity, whereas the lower fatty acid content in BWSA28 reduces its thermal performance. Additionally, stronger molecular interactions, such as hydrogen bonding and van der Waals forces, and better crystalline packing in BWMA19 contribute to its superior thermal properties. The higher latent heat of crystallization in BWMA19 ensures efficient energy release during cooling, making it more suitable for high-energy-demand applications like solar dryers. Conversely, BWSA28 may be more appropriate for moderate energy storage needs, depending on the operating temperature and energy requirements of the application. These variations directly affect the efficiency of thermal energy storage in real-world scenarios, with BWMA19 offering higher energy density and thermal performance. Comment 4: How do the specific melting and freezing temperature ranges of the prepared eutectic PCMs (36°C to 56°C) ensure optimal performance in maintaining product quality during solar drying, particularly for sensitive nutritional characteristics of fruits and vegetables? Response The specific melting and freezing temperature ranges of the prepared eutectic PCMs (36°C to 56°C) ensure optimal performance in solar drying by maintaining consistent thermal conditions crucial for preserving the sensitive nutritional characteristics of fruits and vegetables. These temperature ranges align with the optimal drying conditions for most agricultural products, which require moderate heat to effectively remove moisture without causing thermal degradation of vitamins, enzymes, and flavour compounds. During the drying process, the melting phase of the PCMs absorbs and stores excess heat, preventing overheating, while the freezing phase releases stored heat during cooling periods, maintaining a stable temperature. For example, BWLA19, with its lower melting range (41.02°C to 44.96°C), is suitable for drying delicate produce, such as leafy greens, where minimal thermal stress is essential. In contrast, BWSA28 and BWPA46, with higher melting peaks (up to 56.85°C), are more appropriate for drying fruits with higher moisture content or thicker peels, requiring slightly elevated drying temperatures for effective moisture removal. This thermal regulation not only improves drying efficiency but also ensures uniform drying, thereby preserving texture, colour, and nutritional value, making these PCMs highly effective for solar drying applications. Comment 5: The discussion of the results needs to be expanded, as well as a comparison of your results with those of other studies. Response: As per your instruction discussion of the results expanded and comparison of the result with other result also listed in that section.Reviewer Comments 2Competing Interests: No competing interests were disclosed. Close Comment 1: Was the choice of specific compositions for BW, PA, MA, and LA (e.g., 20:80 for BWSA28) based on prior experimental optimization or theoretical predictions? Could alternative ratios yield better eutectic properties, and were these tested? Response The selection of specific compositions for BW, PA, MA, and LA was based on experimental optimization. Various ratios, such as BW:SA 10:90, 20:80, 30:70, 40:60, and 50:50, were systematically tested to identify the composition with the most favourable properties. The chosen composition was selected based on its ability to provide a higher latent heat and a sharp, well-defined melting point, which are crucial for the intended application. Compositions with alternative ratios were either found to have lower latent heat values or broader melting ranges, making them less suitable for achieving the desired thermal performance. Comment 2: The onset and peak melting temperatures for the eutectic PCMs are close but show variations. Were these differences attributed to specific interactions between the molecular components, and how do these differences influence the practical applications of these PCMs? Response The onset and peak melting temperatures for the eutectic PCMs (beewax-stearic 20:80, beewax-palmitic 40:60, beewax-myristic 10:90, and beewax-lauric 10:90) are close but exhibit variations due to specific molecular interactions between the components. These differences are primarily attributed to variations in the chain length and molecular structure of the fatty acids. Longer-chain fatty acids, such as stearic acid, tend to have stronger van der Waals interactions and higher melting points, while shorter-chain fatty acids like lauric acid exhibit weaker interactions and lower melting points. The chosen ratios also play a significant role in determining the eutectic composition, influencing the degree of miscibility and crystallization behaviour within the PCM mixture. Intermolecular forces, such as hydrogen bonding and van der Waals forces, vary depending on the proportion of beewax and fatty acids, leading to differences in thermal properties. From a practical standpoint, these variations are significant as they determine the suitability of a particular eutectic PCM for specific temperature ranges in thermal energy storage applications. For example, a narrower melting range and sharp phase transition temperature are desirable for efficient thermal regulation in applications like solar dryers, where precise heat absorption and release are critical. On the other hand, minor differences in melting temperatures allow for the tailoring of PCMs to suit diverse climatic conditions and operational requirements, enhancing the versatility of these materials. Comment 3: The latent heat of fusion and crystallization values for the PCMs vary significantly (e.g., BWSA28 vs. BWMA19). What factors contribute to these differences, and how do they affect the efficiency of thermal energy storage in real-world scenarios? Response: The significant variation in the latent heat of fusion and crystallization values for PCMs, such as BWSA28 (20:80) with 174.52 J/g and 177.94 J/g and BWMA19 (10:90) with 195.73 J/g and 201.04 J/g, is influenced by the chain length, molecular structure, and composition of the fatty acids. Myristic acid (C14) in BWMA19, with its shorter carbon chain, facilitates lower molecular packing density and more efficient phase transitions compared to stearic acid (C18) in BWSA28, leading to higher latent heat values in BWMA19. The higher proportion of myristic acid in BWMA19 optimizes crystalline phase formation and enhances energy storage capacity, whereas the lower fatty acid content in BWSA28 reduces its thermal performance. Additionally, stronger molecular interactions, such as hydrogen bonding and van der Waals forces, and better crystalline packing in BWMA19 contribute to its superior thermal properties. The higher latent heat of crystallization in BWMA19 ensures efficient energy release during cooling, making it more suitable for high-energy-demand applications like solar dryers. Conversely, BWSA28 may be more appropriate for moderate energy storage needs, depending on the operating temperature and energy requirements of the application. These variations directly affect the efficiency of thermal energy storage in real-world scenarios, with BWMA19 offering higher energy density and thermal performance. Comment 4: How do the specific melting and freezing temperature ranges of the prepared eutectic PCMs (36°C to 56°C) ensure optimal performance in maintaining product quality during solar drying, particularly for sensitive nutritional characteristics of fruits and vegetables? Response The specific melting and freezing temperature ranges of the prepared eutectic PCMs (36°C to 56°C) ensure optimal performance in solar drying by maintaining consistent thermal conditions crucial for preserving the sensitive nutritional characteristics of fruits and vegetables. These temperature ranges align with the optimal drying conditions for most agricultural products, which require moderate heat to effectively remove moisture without causing thermal degradation of vitamins, enzymes, and flavour compounds. During the drying process, the melting phase of the PCMs absorbs and stores excess heat, preventing overheating, while the freezing phase releases stored heat during cooling periods, maintaining a stable temperature. For example, BWLA19, with its lower melting range (41.02°C to 44.96°C), is suitable for drying delicate produce, such as leafy greens, where minimal thermal stress is essential. In contrast, BWSA28 and BWPA46, with higher melting peaks (up to 56.85°C), are more appropriate for drying fruits with higher moisture content or thicker peels, requiring slightly elevated drying temperatures for effective moisture removal. This thermal regulation not only improves drying efficiency but also ensures uniform drying, thereby preserving texture, colour, and nutritional value, making these PCMs highly effective for solar drying applications. Comment 5: The discussion of the results needs to be expanded, as well as a comparison of your results with those of other studies. Response: As per your instruction discussion of the results expanded and comparison of the result with other result also listed in that section. Views 0 How to cite this report: P. Joshi D. Reviewer Report For: Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.5256/f1000research.151630.r346917) The direct URL for this report is: https://f1000research.com/articles/11-1277/v2#referee-response-346917 https://f1000research.com/articles/11-1277/v2#referee-response-346917 NOTE: it is important to ensure the information in square brackets after the title is included in this citation. Reviewer Report 24 Dec 2024 Not Approved VIEWS 0 Reviewer Report The manuscript presents a study on “Development and thermophysical analysis of binary eutectics phase change materials for solar drying application ” Summary of the work: In the Manuscript, I confirm that I have read this submission and believe that I have an appropriate level of expertise to state that I do not consider it to be of an acceptable scientific standard, for reasons outlined above. Close The manuscript presents a study on “Development and thermophysical analysis of binary eutectics phase change materials for solar drying application ” Summary of the work: In the Manuscript, - Non-paraffin organic PCM Reviewer Report The manuscript presents a study on “Development and thermophysical analysis of binary eutectics phase change materials for solar drying application ” Summary of the work: In the Manuscript, The article provides details only of single characterization technique (DSC). Therefore, it lacks primary information about the prepared composite. Manuscript does not provide substantial discussion and practical applications of the findings. Therefore, at its current stage, the manuscript does not provide sufficient information to draw meaningful conclusions. Significant revisions are required to draw impactful conclusions from the manuscript. The manuscript presents a study on “Development and thermophysical analysis of binary eutectics phase change materials for solar drying application ” Summary of the work: In the Manuscript, - Non-paraffin organic PCM beeswax (BW) was mixed in another non organic PCMs Palmitic (PA), Myristic (MA), and Lauric (LA) acid. - 20 wt % of BW mixed was with 80 wt % of SA to prepare BWSA28. - 40, 10, and 10 wt % of BW were mixed with 60, 90, and 90 wt % of PA, MA, and LA, respectively, to form BWPA46, BWMA19, and BWLA19 eutectic PCMs. - DSC analysis was carried out to obtain phase transition properties. - The PCMs are good candidate for solar drying applications. - Beewax PCM was mixed in other PCMs in random composition. The author didn’t provide a reason for selecting a particular composition for a particular eutectic. - In the DSC analysis only results are provided, Discussion part is missing completely. - The entire manuscript contains only a single characterization (DSC). Other characterization should be performed to get an idea about morphological, structural and thermal changes by mixing that may occurring in eutectic PCM. - TGA should be performed to get the effect on thermal stability of individual PCM. The article provides details only of single characterization technique (DSC). Therefore, it lacks primary information about the prepared composite. Manuscript does not provide substantial discussion and practical applications of the findings. Therefore, at its current stage, the manuscript does not provide sufficient information to draw meaningful conclusions. Significant revisions are required to draw impactful conclusions from the manuscript. - Is the work clearly and accurately presented and does it cite the current literature? No - Is the study design appropriate and is the work technically sound? No - Are sufficient details of methods and analysis provided to allow replication by others? Partly - If applicable, is the statistical analysis and its interpretation appropriate? Partly - Are all the source data underlying the results available to ensure full reproducibility? No - Are the conclusions drawn adequately supported by the results? No Competing Interests: No competing interests were disclosed. Reviewer Expertise: composite, core-shell nanomaterials , thermal energy storage CITE HOW TO CITE THIS REPORT P. Joshi D. Reviewer Report For: Development and thermophysical analysis of binary eutectics phase change materials for solar drying application [version 3; peer review: 1 approved with reservations, 2 not approved]. F1000Research 2025, 11:1277 (https://doi.org/10.5256/f1000research.151630.r346917) The direct URL for this report is: https://f1000research.com/articles/11-1277/v2#referee-response-346917 https://f1000research.com/articles/11-1277/v2#referee-response-346917 NOTE: it is important to ensure the information in square brackets after the title is included in all citations of this article. - Author Response 11 Sep 2025Abhishek Anand, Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Jais, Amethi, 229304, India11 Sep 2025Author ResponseReviewer Comments 1 Comment 1: Beewax PCM was mixed in other PCMs in random composition. The author didn’t provide a reason for selecting a particular composition for a particular ... Continue reading Reviewer Comments 1 Comment 1: Beewax PCM was mixed in other PCMs in random composition. The author didn’t provide a reason for selecting a particular composition for a particular eutectic. Response: As per you instruction I have added reason behind selecting a particular composition in last paragraph of Section 2 Comment 2: In the DSC analysis only results are provided, Discussion part is missing completely. Response I have discuss the DSC analysis part and highlighting it in manuscript in Result section and highlighted the changes. Comment 3: The entire manuscript contains only a single characterization (DSC). Other characterization should be performed to get an idea about morphological, structural and thermal changes by mixing that may occurring in eutectic PCM. Response : As per you instruction I have added other characterizations in manuscript. Comment 4: TGA should be performed to get the effect on the thermal stability of individual PCM. Response: Figure: Thermogravimetric analysis (TGA) curves of pure beeswax (BW) and its eutectic mixtures with stearic acid (BWSA28), palmitic acid (BWPA46), myristic acid (BWMA19), and lauric acid (BWLA19), showing weight loss (%) as a function of temperature. The thermogravimetric analysis (TGA) plot illustrates the thermal stability and decomposition behaviour of pure beeswax (BW) and its eutectic mixtures with stearic acid (SA), palmitic acid (PA), myristic acid (MA), and lauric acid (LA) over a temperature range from room temperature to 800 °C. The weight percentage versus temperature profiles reveal distinct degradation patterns for each sample. Pure beeswax exhibits the highest thermal stability, with initial decomposition starting around 250 °C, major weight loss occurring between 250–450 °C, and near-complete decomposition by ~500 °C. This is attributed to the breakdown of long-chain hydrocarbons, esters, and waxy compounds present in BW. The BWSA28 sample begins degrading slightly earlier (~200 °C) and shows significant mass loss between 250–450 °C, continuing up to ~600 °C, indicating reduced stability compared to pure BW but better than pure SA, likely due to the inclusion of BW which stabilizes the blend. For BWPA46, BWMA19, and BWLA19, thermal stability decreases progressively with decreasing fatty acid chain length. BWLA19 exhibits the earliest degradation (~160 °C) and the fastest decomposition, completing by ~350 °C, highlighting its low thermal resistance due to the volatility and lower molecular weight of lauric acid. BWMA19 and BWPA46 show intermediate behaviour, with BWPA46 displaying a broader degradation range due to multistep decomposition from its mixed components. The thermal degradation proceeds via sequential breakdown of molecular constituents starting with volatilization of free fatty acids and followed by the cleavage of ester bonds and fragmentation of hydrocarbon backbones. These reactions are influenced by molecular weight, bonding type, and blend miscibility, where longer chains require higher activation energy to decompose compared to shorter ones. The near-zero residue at 800 °C confirms complete volatilization, which is advantageous for clean decomposition but may necessitate containment considerations in cyclic TES operations. All eutectic mixtures leave minimal residue (~0–5%) at 800 °C, indicating complete decomposition. The observed mass losses are primarily due to thermal evaporation and breakdown of organic constituent’s fatty acids and hydrocarbon chains into volatile products. These results confirm that beeswax improves thermal stability in eutectic formulations, and the degradation temperature systematically decreases with shorter fatty acid chain lengths. This information is essential for selecting eutectic phase change materials (PCMs) in thermal energy storage systems where both thermal stability and phase transition behaviour are crucial.Reviewer Comments 1Competing Interests: No competing interests were disclosed. Close Comment 1: Beewax PCM was mixed in other PCMs in random composition. The author didn’t provide a reason for selecting a particular composition for a particular eutectic. Response: As per you instruction I have added reason behind selecting a particular composition in last paragraph of Section 2 Comment 2: In the DSC analysis only results are provided, Discussion part is missing completely. Response I have discuss the DSC analysis part and highlighting it in manuscript in Result section and highlighted the changes. Comment 3: The entire manuscript contains only a single characterization (DSC). Other characterization should be performed to get an idea about morphological, structural and thermal changes by mixing that may occurring in eutectic PCM. Response : As per you instruction I have added other characterizations in manuscript. Comment 4: TGA should be performed to get the effect on the thermal stability of individual PCM. Response: Figure: Thermogravimetric analysis (TGA) curves of pure beeswax (BW) and its eutectic mixtures with stearic acid (BWSA28), palmitic acid (BWPA46), myristic acid (BWMA19), and lauric acid (BWLA19), showing weight loss (%) as a function of temperature. The thermogravimetric analysis (TGA) plot illustrates the thermal stability and decomposition behaviour of pure beeswax (BW) and its eutectic mixtures with stearic acid (SA), palmitic acid (PA), myristic acid (MA), and lauric acid (LA) over a temperature range from room temperature to 800 °C. The weight percentage versus temperature profiles reveal distinct degradation patterns for each sample. Pure beeswax exhibits the highest thermal stability, with initial decomposition starting around 250 °C, major weight loss occurring between 250–450 °C, and near-complete decomposition by ~500 °C. This is attributed to the breakdown of long-chain hydrocarbons, esters, and waxy compounds present in BW. The BWSA28 sample begins degrading slightly earlier (~200 °C) and shows significant mass loss between 250–450 °C, continuing up to ~600 °C, indicating reduced stability compared to pure BW but better than pure SA, likely due to the inclusion of BW which stabilizes the blend. For BWPA46, BWMA19, and BWLA19, thermal stability decreases progressively with decreasing fatty acid chain length. BWLA19 exhibits the earliest degradation (~160 °C) and the fastest decomposition, completing by ~350 °C, highlighting its low thermal resistance due to the volatility and lower molecular weight of lauric acid. BWMA19 and BWPA46 show intermediate behaviour, with BWPA46 displaying a broader degradation range due to multistep decomposition from its mixed components. The thermal degradation proceeds via sequential breakdown of molecular constituents starting with volatilization of free fatty acids and followed by the cleavage of ester bonds and fragmentation of hydrocarbon backbones. These reactions are influenced by molecular weight, bonding type, and blend miscibility, where longer chains require higher activation energy to decompose compared to shorter ones. The near-zero residue at 800 °C confirms complete volatilization, which is advantageous for clean decomposition but may necessitate containment considerations in cyclic TES operations. All eutectic mixtures leave minimal residue (~0–5%) at 800 °C, indicating complete decomposition. The observed mass losses are primarily due to thermal evaporation and breakdown of organic constituent’s fatty acids and hydrocarbon chains into volatile products. These results confirm that beeswax improves thermal stability in eutectic formulations, and the degradation temperature systematically decreases with shorter fatty acid chain lengths. This information is essential for selecting eutectic phase change materials (PCMs) in thermal energy storage systems where both thermal stability and phase transition behaviour are crucial. COMMENTS ON THIS REPORT - Author Response 11 Sep 2025Abhishek Anand, Non-Conventional Energy Laboratory, Rajiv Gandhi Institute of Petroleum Technology, Jais, Amethi, 229304, India11 Sep 2025Author ResponseReviewer Comments 1 Comment 1: Beewax PCM was mixed in other PCMs in random composition. The author didn’t provide a reason for selecting a particular composition for a particular ... Continue reading Reviewer Comments 1 Comment 1: Beewax PCM was mixed in other PCMs in random composition. The author didn’t provide a reason for selecting a particular composition for a particular eutectic. Response: As per you instruction I have added reason behind selecting a particular composition in last paragraph of Section 2 Comment 2: In the DSC analysis only results are provided, Discussion part is missing completely. Response I have discuss the DSC analysis part and highlighting it in manuscript in Result section and highlighted the changes. Comment 3: The entire manuscript contains only a single characterization (DSC). Other characterization should be performed to get an idea about morphological, structural and thermal changes by mixing that may occurring in eutectic PCM. Response : As per you instruction I have added other characterizations in manuscript. Comment 4: TGA should be performed to get the effect on the thermal stability of individual PCM. Response: Figure: Thermogravimetric analysis (TGA) curves of pure beeswax (BW) and its eutectic mixtures with stearic acid (BWSA28), palmitic acid (BWPA46), myristic acid (BWMA19), and lauric acid (BWLA19), showing weight loss (%) as a function of temperature. The thermogravimetric analysis (TGA) plot illustrates the thermal stability and decomposition behaviour of pure beeswax (BW) and its eutectic mixtures with stearic acid (SA), palmitic acid (PA), myristic acid (MA), and lauric acid (LA) over a temperature range from room temperature to 800 °C. The weight percentage versus temperature profiles reveal distinct degradation patterns for each sample. Pure beeswax exhibits the highest thermal stability, with initial decomposition starting around 250 °C, major weight loss occurring between 250–450 °C, and near-complete decomposition by ~500 °C. This is attributed to the breakdown of long-chain hydrocarbons, esters, and waxy compounds present in BW. The BWSA28 sample begins degrading slightly earlier (~200 °C) and shows significant mass loss between 250–450 °C, continuing up to ~600 °C, indicating reduced stability compared to pure BW but better than pure SA, likely due to the inclusion of BW which stabilizes the blend. For BWPA46, BWMA19, and BWLA19, thermal stability decreases progressively with decreasing fatty acid chain length. BWLA19 exhibits the earliest degradation (~160 °C) and the fastest decomposition, completing by ~350 °C, highlighting its low thermal resistance due to the volatility and lower molecular weight of lauric acid. BWMA19 and BWPA46 show intermediate behaviour, with BWPA46 displaying a broader degradation range due to multistep decomposition from its mixed components. The thermal degradation proceeds via sequential breakdown of molecular constituents starting with volatilization of free fatty acids and followed by the cleavage of ester bonds and fragmentation of hydrocarbon backbones. These reactions are influenced by molecular weight, bonding type, and blend miscibility, where longer chains require higher activation energy to decompose compared to shorter ones. The near-zero residue at 800 °C confirms complete volatilization, which is advantageous for clean decomposition but may necessitate containment considerations in cyclic TES operations. All eutectic mixtures leave minimal residue (~0–5%) at 800 °C, indicating complete decomposition. The observed mass losses are primarily due to thermal evaporation and breakdown of organic constituent’s fatty acids and hydrocarbon chains into volatile products. These results confirm that beeswax improves thermal stability in eutectic formulations, and the degradation temperature systematically decreases with shorter fatty acid chain lengths. This information is essential for selecting eutectic phase change materials (PCMs) in thermal energy storage systems where both thermal stability and phase transition behaviour are crucial.Reviewer Comments 1Competing Interests: No competing interests were disclosed. Close Comment 1: Beewax PCM was mixed in other PCMs in random composition. The author didn’t provide a reason for selecting a particular composition for a particular eutectic. Response: As per you instruction I have added reason behind selecting a particular composition in last paragraph of Section 2 Comment 2: In the DSC analysis only results are provided, Discussion part is missing completely. Response I have discuss the DSC analysis part and highlighting it in manuscript in Result section and highlighted the changes. Comment 3: The entire manuscript contains only a single characterization (DSC). Other characterization should be performed to get an idea about morphological, structural and thermal changes by mixing that may occurring in eutectic PCM. Response : As per you instruction I have added other characterizations in manuscript. Comment 4: TGA should be performed to get the effect on the thermal stability of individual PCM. Response: Figure: Thermogravimetric analysis (TGA) curves of pure beeswax (BW) and its eutectic mixtures with stearic acid (BWSA28), palmitic acid (BWPA46), myristic acid (BWMA19), and lauric acid (BWLA19), showing weight loss (%) as a function of temperature. The thermogravimetric analysis (TGA) plot illustrates the thermal stability and decomposition behaviour of pure beeswax (BW) and its eutectic mixtures with stearic acid (SA), palmitic acid (PA), myristic acid (MA), and lauric acid (LA) over a temperature range from room temperature to 800 °C. The weight percentage versus temperature profiles reveal distinct degradation patterns for each sample. Pure beeswax exhibits the highest thermal stability, with initial decomposition starting around 250 °C, major weight loss occurring between 250–450 °C, and near-complete decomposition by ~500 °C. This is attributed to the breakdown of long-chain hydrocarbons, esters, and waxy compounds present in BW. The BWSA28 sample begins degrading slightly earlier (~200 °C) and shows significant mass loss between 250–450 °C, continuing up to ~600 °C, indicating reduced stability compared to pure BW but better than pure SA, likely due to the inclusion of BW which stabilizes the blend. For BWPA46, BWMA19, and BWLA19, thermal stability decreases progressively with decreasing fatty acid chain length. BWLA19 exhibits the earliest degradation (~160 °C) and the fastest decomposition, completing by ~350 °C, highlighting its low thermal resistance due to the volatility and lower molecular weight of lauric acid. BWMA19 and BWPA46 show intermediate behaviour, with BWPA46 displaying a broader degradation range due to multistep decomposition from its mixed components. The thermal degradation proceeds via sequential breakdown of molecular constituents starting with volatilization of free fatty acids and followed by the cleavage of ester bonds and fragmentation of hydrocarbon backbones. These reactions are influenced by molecular weight, bonding type, and blend miscibility, where longer chains require higher activation energy to decompose compared to shorter ones. The near-zero residue at 800 °C confirms complete volatilization, which is advantageous for clean decomposition but may necessitate containment considerations in cyclic TES operations. All eutectic mixtures leave minimal residue (~0–5%) at 800 °C, indicating complete decomposition. The observed mass losses are primarily due to thermal evaporation and breakdown of organic constituent’s fatty acids and hydrocarbon chains into volatile products. These results confirm that beeswax improves thermal stability in eutectic formulations, and the degradation temperature systematically decreases with shorter fatty acid chain lengths. This information is essential for selecting eutectic phase change materials (PCMs) in thermal energy storage systems where both thermal stability and phase transition behaviour are crucial. Version 3 VERSION 3 PUBLISHED 06 Aug 2025 Revised - Reader Comment 09 Mar 2026Afrah Awad, Northern Technical University, Mosul, Iraq09 Mar 2026Reader CommentI recommend that the authors improve their manuscript as follows: - The research gap and contribution should be clearly stated at the end of the Introduction section. - Although - The research gap and contribution should be clearly stated at the end of the Introduction section. - Although the paper was submitted in 2022, the reference list needs to be updated. There are several recent studies on the development of PCM that should be included. - The Methodology section is too brief, where is the schematic of prepration of samples? - The Results section also lacks sufficient detail. More information should be provided, such as the results of Cp vs. time or Cp vs. temperature, and these results should be clearly discussed for the different PCMs. - The authors should provide a deeper analysis and discussion of the obtained results. I recommend that the authors improve their manuscript as follows:Competing Interests: There is no conflict of interest Close- The research gap and contribution should be clearly stated at the end of the Introduction section. - Although the paper was submitted in 2022, the reference list needs to be updated. There are several recent studies on the development of PCM that should be included. - The Methodology section is too brief, where is the schematic of prepration of samples? - The Results section also lacks sufficient detail. More information should be provided, such as the results of Cp vs. time or Cp vs. temperature, and these results should be clearly discussed for the different PCMs. - The authors should provide a deeper analysis and discussion of the obtained results. Alongside their report, reviewers assign a status to the article: - Approved - Approved with reservations - Not approved | Invited Reviewers | ||| |---|---|---|---| | 1 | 2 | 3 | | | Version 3 (revision) 06 Aug 25 | read | read | | | Version 2 (revision) 20 Sep 23 | read | read | | | Version 1 09 Nov 22 | Sign up for content alerts You are now signed up to receive this alert Alongside their report, reviewers assign a status to the article: Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit. Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions Provide sufficient details of any financial or non-financial competing interests to enable users to assess whether your comments might lead a reasonable person to question your impartiality. Consider the following examples, but note that this is not an exhaustive list: Examples of 'Non-Financial Competing Interests' - Within the past 4 years, you have held joint grants, published or collaborated with any of the authors of the selected paper. - You have a close personal relationship (e.g. parent, spouse, sibling, or domestic partner) with any of the authors. - You are a close professional associate of any of the authors (e.g. scientific mentor, recent student). - You work at the same institute as any of the authors. - You hope/expect to benefit (e.g. favour or employment) as a result of your submission. - You are an Editor for the journal in which the article is published. 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