Thermal characterization of botswana sands for application in high-temperature thermal energy storage (TES)

This study investigates the suitability of selected Botswana sands for high-temperature thermal energy storage through thermal experiments and characterisation. The research employs thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray fluorescence (XRF) techniques to characterise different sand samples in Botswana. Exploration of alternative sustainable energy storage methods is critical to Botswana and the world, as the fraction of non-dispatchable renewable energy sources like solar keeps increasing in the energy mix. Sand-based heat storage can provide an affordable and environmentally friendly energy storage solution which can be easily scaled up. The elemental tests proved that Botswana sands are silica-rich, which contributes to the thermal stability and reaction predictability. Kgalagadi sand was identified as the overall best sand for heat storage after considering its heat capacity (1.02 kJ/kgK), thermal conductivity (0.927 W/mK), purity (94.6% silica-rich), grain size distribution (coefficient of uniformity, C u =2.1), thermal stability and many other properties. Some Botswana sand samples suffered from agglomeration when heated to 1000 °C, although the agglomerates were easily disintegrated by light vibrations. Experiments were repeated and validated using reference materials to ensure that the results presented are accurate, reliable and reproducible. Ultimately, this study proves that Botswana sands can be leveraged as a solid material for high-temperature sensible heat storage, which can be used to develop affordable and environmentally friendly energy storage systems.