A critical overview of the suitability of natural Moroccan rocks for high temperature thermal energy storage applications: Towards an effective dispatching of concentrated solar power plants

Packed-bed thermal energy storage (TES) systems are considered as the key solution to ensure the dispatchability and enhancement of the cost-effectiveness of concentrated solar power (CSP) plants. Indeed, the use of natural rocks as suitable storage materials in these systems has been proven in several experimental investigations worldwide and particularly in Morocco. This North African country has significant potential areas sites for hosting ambitious CSP projects, in addition to those already existing. Moreover, it has a large and diversified geological heritage, with a wide variety of igneous, metamorphic and sedimentary rocks abundantly available. In this context, the present overview provides global data about natural Moroccan rocks as sensible storage materials. Therefore, the data available in the literature are initially collected, treated and classified according to various criteria required for storage applications. The missing parts of highly desirable properties such as the mechanical and thermal ones are estimated for compensating the lack of data. Secondly, the comparative assessment of the three above-mentioned rock types is presented and discussed, in order to select the most potential rocks which could be used as high-temperature thermal storage materials. Thus, based on the existing experimental results in the literature of each studied rock, some empirical correlations of thermal properties such as heat capacity, volumetric thermal capacity and thermal conductivity were established. Furthermore, other new natural Moroccan rocks were identified and localized on the geological map of Morocco. Finally, the main outcomes of this study are summarized and presented in the conclusion part.