Atul Sharma

Bio-based phase change materials (PCMs) are promising candidates for sustainable thermal energy storage (TES). However, their practical application is limited by low thermal conductivity, leakage during phase transition, and limited understanding of the relationship between microstructure and flow behavior. In this study, a bio-based eutectic PCM composed of candelilla wax (CW) and stearic acid (SA) was reinforced with expanded graphite (EG) to simultaneously improve thermal transport and rheological stability. The optimized eutectic PCM (CS28) exhibited a melting temperature of 57.34 °C and a latent heat of 172.64 J g–1, making it suitable for medium-temperature TES. Incorporation of 2 wt % EG produced a porous, layered graphitic morphology, with the presence and structural characteristics of EG supported by FESEM, Raman spectroscopy, and XPS, which enhanced both heat transfer and molten-state structural stability. Rheological analysis revealed pronounced shear-thinning behavior and an increased consistency index, indicating the formation of a graphite-mediated internal network that restricted PCM mobility while maintaining flowability. Consequently, the best-performing composite PCM within the investigated EG loading range (CS28G4) achieved a thermal conductivity of 0.119 W m–1 K–1 (45.1% enhancement) while retaining 80.1% of the latent heat storage capacity (138.34 J g–1). The composite also demonstrated excellent thermal reliability after 200 thermal cycles, with negligible changes in phase transition temperatures and latent heat, together with improved leakage resistance. Practical applicability was demonstrated by integrating the composite PCM into an indirect solar dryer, resulting in prolonged heat release and improved thermal regulation during agricultural drying. Unlike previous studies that primarily target thermal conductivity enhancement in EG-reinforced PCMs, this work establishes a structure–rheology–thermal transport relationship in EG-reinforced bio-based eutectic PCMs, providing a mechanistic framework for relating EG-induced structural and rheological changes to thermal transport and leakage resistance in composite PCMs.

Flexible electronics, textile engineering, and nanomaterials have combined to transform gas sensing from rigid devices into advanced wearable platforms. The most recent developments in flexible substrate-integrated gas sensor components are examined in this review, with particular attention paid to their ability to detect hydrogen (H2), nitrogen dioxide (NO2), and ammonia (NH3). Protonation-driven charge transfer for selective NH3 detection; catalytic lattice modulation via palladium hydride formation, which regulates H2 sensing via percolation dynamics; and adsorption-induced band modulation for NO2 detection based on oxidative electron withdrawal and engineered heterointerfaces are the three distinct methods of gas sensing. Furthermore, mesoporous diffusion paths, heterojunction-based signal amplification, defect-engineered nanostructures, and mechanically robust conductive networks all contribute to the improved performance of these systems. This work integrates textile compatibility, structural design, and gas material interaction chemistry to give a unified framework for the logical development of wearable sensing platforms with many functions. Cross-selectivity, humidity sensitivity, long-term mechanical durability, and scalable production are some of the major issues that still need to be resolved despite significant advancements in room temperature operation and mechanical flexibility. The integration of IoT-enabled data analytics, machine learning to aid in signal classification, and self-powered sensing devices will probably be the main focus in the future. With the goal to assist users to develop scalable, intelligent, and self-monitoring textile-based gas sensing networks, this paper integrates all the opportunities and issues into a single platform.

Solar cooking is a sustainable and environmentally friendly alternative to conventional cooking technologies; however, conventional box-type solar cookers (BTSCs) suffer from limited thermal retention and reduced cooking capability during low solar-intensity periods and late evening hours. In addition, the thermal performance of BTSCs strongly depends on structural design parameters and phase change material (PCM) selection. Therefore, the present study aims to numerically optimize a PCM-integrated box-type solar cooker using COMSOL Multiphysics prior to experimental fabrication. A three-dimensional transient numerical model incorporating conductive, convective, and radiative heat transfer along with PCM phase change using the apparent heat-capacity method was developed. The effects of glazing thickness, absorber plate thickness, pot thickness, cooking load, and PCM selection were systematically investigated under transient solar heat-flux conditions. Thermal performance was evaluated using temperature distribution, cooking power, and BIS/ASAE performance indicators (F1 and F2). The results demonstrated that a double-glazed configuration with 3 mm glass thickness and a 1.5 mm aluminium absorber plate provided optimal thermal performance, achieving F1 = 0.15 and F2 = 0.38. The optimized cooker attained absorber temperatures of approximately 157°C and improved late-hour thermal retention. Among the investigated PCMs, acetanilide exhibited superior unloading thermal behaviour, maintaining temperatures of 66 °C at 10 h and 52 °C at 14 h. The non-PCM configuration achieved the highest peak cooking power (53.2 W), whereas PCM integration improved thermal stability and extended heat availability during the cooling period. The study demonstrates that numerical optimisation and suitable PCM selection can significantly enhance the thermal performance of PCM-assisted box-type solar cookers for sustainable cooking applications.

Thermal Energy Storage (TES) has emerged as a crucial innovation in solar cooking, addressing the major limitation of traditional solar cookers—their dependence on sunlight. This chapter explores the principles, technologies, and applications of TES in solar cookers, emphasizing its transformative role in enabling cooking during off-sunshine hours, such as evenings, nights, and cloudy days. By storing excess thermal energy collected during peak sunlight hours, TES systems extend the operational period of solar cookers, making them more practical, efficient, and reliable. While solar cookers offer an eco-friendly and cost-effective alternative to conventional cooking methods, their reliance on direct sunlight restricts their usability. TES bridges this gap by ensuring uninterrupted cooking and enhancing efficiency. The chapter categorizes TES systems into three main types: sensible heat storage, which utilizes materials like water, oil, or rocks that retain and release heat through temperature changes; latent heat storage, which leverages phase change materials (PCMs) such as paraffin wax or salt hydrates that store and release energy during phase transitions; and thermochemical storage, which employs reversible chemical reactions for long-term heat retention with minimal losses. A comparative analysis highlights their thermal properties, cost effective, and practicality for solar cooking. Effective TES integration requires high energy density, thermal stability, durability, and ease of use, and this chapter discusses how TES systems can be tailored to various solar cooker designs, from small household units to large-scale community systems. The discussion also covers key aspects such as thermal insulation, heat retention, and heat transfer mechanisms to maximize efficiency and minimize heat loss, while safety and user-friendliness are emphasized for adoption in resource-limited settings. TES significantly enhances solar cooking by extending cooking hours, reducing reliance on conventional fuels, and improving user convenience. However, challenges such as heat loss, material degradation, and inefficiencies, along with economic and accessibility barriers, must be addressed. The chapter underscores the need for continued research and innovation to improve TES-integrated solar cookers, making them more affordable, efficient, and accessible for widespread adoption.

Background 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. Methods 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. Results 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. Conclusions Due to suitable temperature and good latent heat storage range, it is a good choice as thermal energy storage, for solar drying applications.

The current study presents a novel technique incorporating Artificial Neural Network and dimensionality reduction (Principal Component Analysis) for predicting the two thermophysical properties of the binary fluoride/chloride reciprocal eutectic salt systems namely the composition and melting point (MP) temperature of the eutectic system. This model considers 12 molecular and atomic parameters to compute the composition and melting point of binary fluoride/chloride reciprocal eutectic salt systems. The Principal Component Analysis-Feed Forward Neural Network methodology demonstrated enhanced prediction accuracy, with a mean root mean squared error of 5.533 for melting point and 1.329 for eutectic composition, as assessed by the leave-one-out cross-validation method (LOOCV). Further, the R2 values of the melting point and eutectic composition, for the models with the least RMSE on test data, were 97.69 % and 97.26 % respectively. This modelling technique offers the potential to forecast the composition and melting points of multi-component reciprocal eutectic salt systems, and also to ascertain the other properties of reciprocal eutectic salt systems, such as their densities, enthalpies, conductivities, and so on.

Background: 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. Methods: 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. Results: Prepared eutectics melt and solidify in the temperature range 36–56°C and with latent heat in the range of 155–211 kJ/Kg. Conclusions: Due to suitable temperature and good latent heat storage range, it is a good choice as thermal energy storage, for solar drying applications.

Being one of the major energy consumers, cooking is a necessary part of daily life. Non renewable cooking fuel sources, such as wood or cow dung cause hazardous pollution and a poor ecosystem worldwide. Over the past few decades, solar-powered cooking has undergone numerous improvements. Solar cooking has been predominantly used as a substitute for reducing oil and gas dependence, increasing environmental sustainability, and reducing global warming threats. This paper talks about the recent development of the box-type solar cooker. The paper discusses the principles and classifications of various parameters that affect the performance, energy, and exergy related to the solar cooking system. In line with the sustainable development goals of the UN agenda 2030 and especially the heed to the accomplishment of SDG 7 and SDG 13, various economic factors, such as the payback period (PP), net present value (NPV), benefit–cost (B–C) ratios, internal rate of return (IRR), levelized cost of heat (LCOH), and levelized cost of cooking a meal (LCCM) have been discussed. The environmental analysis has also been presented to show the overall benefit of solar cooking. The review also focuses on the current development of a box-type solar cooker, its components, and its heat transfer characteristic. Various geometrical modifications, the use of reflectors, and transparent insulating materials that improve cooking have been discussed. The concept of energy storage in the form of Phase change material (Latent heat storage) with the latest studied designs improvements of solar cookers has been obtained to be efficient, which also help in late-evening cooking. It can be said that with better policy implications, the social and economic acceptability of the solar cooker can be achieved.