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This study presents a novel methodology for determining the apparent thermal diffusivity of subsoil in situ, employing two heat transfer models within the subsurface: one method is based on heat conduction caused by air temperature oscillations, while the other considers heat transmission via both conduction and convection due to groundwater flow. Differential equations were solved, and non-linear regression analysis was employed. This method has direct applications in various engineering and environmental domains, such as underground transmission lines, oil and gas pipelines, radioactive waste management, and geothermal systems, especially in the context of implementing horizontal geothermal collectors (HGC). The apparent thermal diffusivity value of 1.514 × 10−6 m2 s−1, within a 95% confidence interval spanning 1.512 × 10−6 m2 s−1 and 1.516 × 10−6 m2 s−1, was obtained from the section between 1.67 and 3.86 m depth in a research borehole located in Asturias, Northern Spain, using twenty-one temperature sensors. The method allowed for the calculation of the subsoil's apparent thermal diffusivity up to a depth of 14.55 m. [ABSTRACT FROM AUTHOR]

The use of solar energy for power generation using the innovative solar chimney concept has been explored by many researchers mostly with the help of analytical models as well as CFD simulations while experimental studies for a pilot and bench scale facilities have been carried out. The efficiencies of these chimneys, however, are less than 1% (~0.07% for 50 kW pilot plant similar to Manzanares plant in Spain). In the present study, an effort has been made to make modifications in the chimney design to improve the efficiency of the chimney in terms of power generation. CFD simulations have been carried out for this modified design and the efficiency is seen to improve to 0.12% for a 50 kW chimney. Furthermore, a techno-economic feasibility analysis has been carried out for a conventional 5 MW solar power plant which can be installed on the western part of India, which receives good solar irradiation throughout the year. Two cases with and without government subsidies have been considered. It is observed that a high rate of return (~20.4%) is obtained for a selling price of electricity of Rs 5 per kWh with government subsidy, while a rate of return of ~19% is obtained for Rs 10 per kWh without government subsidy. [ABSTRACT FROM AUTHOR]

The important topic of modelling tanks filled with phase change materials (PCMs) is discussed in this article. Due to the increasing use of heating and cooling installations, tanks containing two types of PCMs are the subject of many experimental analyses. However, there are still deficiencies in their models, which are presented in this paper. The theory model was created in order to design two tanks, each with a volume of 2 m3. They were filled with water and containers with two PCMs. The modelled tanks were meant to replace the existing water tanks that were previously used in the solar heating and cooling installation in a research building located in the southern part of Spain. After the tanks were assembled, the model was validated during the summer period when the designed storage tanks supported the operation of the solar system operating in the cooling mode. The created model consists of a 1D description of the heat transfer in the storage tank, and also a 1D description of the phase change in the containers with the PCMs. The model takes into account the front of the phase change and also discusses its impact on the thermal efficiency of the tanks. The agreement of the water output temperature is very good and validates the model, which can then be used to provide further details on the operation of the storage system—in particular, heat fluxes or a fraction of solid or liquid PCM. [ABSTRACT FROM AUTHOR]