Large-scale high-temperature solar energy storage using natural minerals

The present work is focused on thermochemical energy storage (TCES) in Concentrated Solar Power (CSP) plants by means of the Calcium-Looping (CaL) process using cheap, abundant and non-toxic natural carbonate minerals. CaL conditions for CSP storage involve calcination of CaCO3 in the solar receiver at relatively low temperature whereas carbonation of CaO is carried out at high temperature and high CO2 concentration to use the heat of reaction for power production by means of a CO2 closed power cycle. Under these conditions, large CaO particles derived from limestone to be used in industrial processes are rapidly deactivated due to pore-plugging, which limits the extent of the reaction. This is favored by the relatively small pores of the CaO skeleton generated by low temperature calcination, the large thickness of the CaCO3 layer built upon the CaO surface and the very fast carbonation kinetics. On the other hand, at CaL conditions for CSP storage does not limit carbonation of CaO derived from dolomite (dolime). Dolime is shown to exhibit a high multicycle conversion regardless of particle size, which is explained by the presence of inert MgO grains that allow the reacting gas to percolate inside the porous particles. Thermochemical Energy storage of CSP using the Calcium-Looping process [Display omitted] •CSP can be stored by means of the Calcium-Looping process in thermochemical form.•The CaL process uses cheap, abundant and non-toxic natural calcium carbonate minerals.•These materials may exhibit a high multicycle activity at CaL conditions that maximize the global plant efficiency.•Natural limestone performance is limited by particle size at practical conditions due to pore plugging.•Pore plugging does not pose a significant limitation to the performance of natural dolomite.