https://orcid.org/0000-0003-2862-6294
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ABSTRACT
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.
Nomenclature
| Abbreviations | = | |
| β | = | Coefficient of thermal expansion |
| εbεcεbc | = | Emissivity |
| υ | = | Kinematic viscosity |
| σ | = | Stefan-Boltzmann constant |
| η | = | Overall efficiency |
| γ | = | Adiabatic index |
| ϕp | = | Quantity of PCM utilized during the heating and cooling processes |
| ϕip | = | Quantity of PCM melted |
| CNT | = | Carbon Nano Tubes |
| g | = | Acceleration of gravity |
| Gr | = | Grashof number |
| h, hba,hca | = | Heat transfer coefficient |
| Hp | = | Sensible heating of PCM |
| Hw | = | Sensible heating of water |
| Ir | = | Solar irradiance |
| k | = | Thermal conductivity |
| L | = | Spacing, Latent heat energy |
| LCZ | = | Lower Convective Zone |
| n | = | Number of repeated measurements |
| Ne | = | PCM – nanoparticle- integrated PCM |
| NCZ | = | Neutral Convective Zone |
| Nu | = | Nusselt number |
| PCM | = | Phase Change Material |
| PVP – polyvinylpyrrolidone | = | 40 |
| qba | = | Heat loss from the walls of the solar pond |
| qca | = | Heat loss from the glass cover |
| qabs | = | Total heat loss |
| qin | = | Inlet heat energy |
| qout | = | Outlet heat energy |
| qpcm | = | Heat storage capacity of the PCM |
| SD | = | Standard deviation |
| SGSP | = | Salinity Gradient Solar Pond |
| Ta | = | Temperature of the atmosphere |
| Tb | = | Temperature of the black plate |
| Tc | = | Temperature of the cooling plate |
| = | Uncertainty of the equipment | |
| = | Temperature measured by the thermocouple | |
| = | Repetition of the uncertainty | |
| UCZ | = | Upper Convective Zone |
| x | = | Average accuracy of the thermocouple |
Disclosure statement
No potential conflict of interest was reported by the authors.
Additional information
Notes on contributors
M. Arulprakasajothi
Dr M Arulprakasajothi has 17 years of teaching experience and 10 years of research experience. He is working in the area of energy storage, solar pond, and thermal management.
N. Poyyamozhi
Dr N. Poyyamozhi has 10 years of teaching experience. He is working in the area of solar ponds and energy storage.
P. Chandrakumar
Dr Chadrakumar has teaching experience of more than 10 years. Research interest: composite materials, innovation, and entrepreneurship.
N. Dilip Raja
Dr N. Dilip Raja is currently working on thermal energy-driven mechanisms like Solar desalination, Solar pond and heat sinks. He has also submitted patents related to Solar Energy.
Yuvarajan D
Dr Yuvarajan D has 14 years of teaching experience and 10 years of research experience. His research area includes alternate fuels, energy storage, solar pond, and thermal management.