Preliminary characterizations of natural rocks as storage materials for a medium range temperature TES

Abstract

Natural rocks are attractive storage materials for packed bed configuration, as they are inexpensive, available, ecologically friendly and the most important they are not limited to working range of temperatures. However, their suitability is based on various criteria, which include thermo-physical and mechanical properties, stability and compatibility with both the heat transfer fluid and the container. This work aims to investigate the potential of three natural rocks namely (leuco-gabbro, dolerite and wherlite), which were collected from the region of Kettara near to the site of Green energy park Benguerir Morocco from where the prototype of dual thermocline will be constructed. This prototype will be related to Fresnel collectors with an operating temperature from 100°C to 300°C with thermal oil as heat transfer fluid. For that, a deep literature review was summarized to determine the parameters influencing the mechanical and thermal stability of rocks. Additionally an experimental study was conducted to define the petrographic characterizations by using the optical microscopy light. Moreover, the SEM/EDX techniques were used to analyze their chemical compositions and structures. Finally, their thermo-physical properties (density, thermal conductivity, thermal diffusivity and specific heat capacity) were measured. As a conclusion, all the studied rocks are good potential candidates for this target application, yet their long-term stability and compatibility must be determined to confirm their suitability.