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Heat energy storage is pivotal in modern times. However, the technology to efficiently stored heat energy is still in the research stage. Heat energy storage is possible through phase change material, exothermic chemical reactions, and solar ponds. The latter uses a natural phenomenon that relies on solar Energy and convective heat transfer. Solar ponds can store more heat energy throughout the day than other processes and meet higher energy demands. The working principle of a typical solar pond can be adopted to develop a compact setup that can store sufficient heat energy to meet the heat energy demand of a small family. Salinity gradient solar ponds are used for heat storage to meet the demand of rural and urban communities in arid and semiarid zones around the globe. Often the solar ponds are constructed on the ground by storing a large volume of salt water. The performance of the solar pond is affected by the intensity of solar radiation. In this study, a compact solar pond is constructed using aluminum plates and a glass cover. Sea water was used to store solar radiation in this experiment. The experiment was carried out in South India during the winter season when the intensity of solar radiation was minimum. The study aims to determine the performance of the solar pond and its thermal properties under low sunshine. Heat storage mediums comprising paraffin wax and additives of nanoparticles of graphene and carbon nanotubes were used to enhance the heat storage capacity of the solar pond. It was found that compared to the simple salinity gradient solar pond, the heat storage medium with carbon nanotube nanoparticles increased the maximum temperature attained by 26.5%. The carbon nano tubes infused phase change material increased the heat transfer, heat transfer coefficient, and the heat stored in the saline water by 244%, 713%, and 83.3%, respectively. It is concluded that the carbon nano tubes and phase change material augmented the performance of the solar pond even while the intensity of solar radiation was low. [ABSTRACT FROM AUTHOR]

Phase change material (PCM) based heat sinks are the passive cooling technologies that achieve required thermal management. PCM increases the energy storage capacity, and adding nanomaterial to the PCM improves the heat sink capacity. However, there are very few studies on the effect of heat load on thermal performance in this field. This research focuses on the experimental investigation of the thermal characteristics of Nano-PCM-based heat sinks with varying base roughness and load. To enhance the heat transfer characteristics of paraffin PCM, two distinctive nanoparticles, i.e., graphene and Silver Titanium Dioxide (Ag-TiO 2), are used. Two different heat sinks containing one of the nanoparticles mixed PCM were tested. However, one more heat sink containing only PCM was also used in the study. Scanning electron microscope analysis, thermogravimetric analysis, differential scanning calorimetry, and energy dispersive X-ray analysis were performed, and the performance was measured at various heat loads (25 W, 35 W, and 45 W), and different roughness configurations (R1, R2, and R3) with PCM and Nano-PCM. The study's findings indicate that the R3 configuration containing graphene-PCM performs better than the others. It had a longer charging time (heating), a shorter discharging time (cooling), and a more constant temperature during discharging. Comparing the discharging cycles of AgTiO 2 -PCM, graphene-PCM reveals a minor difference. The cooling rate depends on the heat load and a heat load of 45 W results in a faster cooling rate. • Thermal characteristics of Nano-PCM-based heat sinks were analysed. • Graphene and Ag TiO 2 were used for nanocoating. • Experiments were carried out at different loads and roughness. • Graphene-PCM performs better for R3 configuration. • Heat load of 45 W results in a faster cooling rate. [ABSTRACT FROM AUTHOR]

Due to the increasing demand for air conditioners to maintain thermal comfort in buildings, it is necessary to search for alternatives that can reduce the soaring temperature and meet total air conditioning demands. There are several proven technologies for maintaining thermal comfort in buildings of which the use of phase change material (PCM) in buildings provides improved thermal comfort with fewer energy requirements. The present study analyzes the impact of the incorporation of PCM in roofs on the thermal behavior of buildings. The experiments were conducted in two identical model building roofs with and without the implementation of PCM. A numerical model was developed to find the effect of variation in the PCM layer thickness and month wise temperature variations. To get minimum variation in the results, the simulation was run continuously for 5 days assuming average climatic conditions. The results showed that temperature fluctuations in the room were reduced with the use of PCM, and also the average peak temperature rise was reduced by 2-4°C. The increased PCM layer thickness resulted in decreased energy demand for maintaining the required thermal comfort in buildings at an almost constant temperature. [ABSTRACT FROM AUTHOR]