Thermal energy storage (TES) is a key factor for increasing the efficiency of concentrated solar power plants. TES using a reversible chemical reaction appears to be a promising technology for high energy density thermal storage (100-500 kW h m(-3)), at high temperature (up to 1000 degrees C) and during a long period (24 h to several months). This paper details an experimental study to carry out the reversible reaction Ca(OH)(2(s)) +Delta H double left right arrow CaO(s) + H2O(g) in a fluidized bed (FB) reactor. The 4 mu m Ca(OH)(2) powder fluidization has been performed with an appropriate proportion of inert easy-to-fluidize particles. Then, Ca(OH)(2) dehydration and CaO hydration have been implemented in a FB reactor and 50 cycles have been reached. The mean energy density obtained is 60 kW h m(-3) solid_mixture which amounts to a promising energy density of 156 kW h m(-3) Ca(OH)(2)-bulk if the reactants and the easy-to-fluidize particles are separated. The results demonstrated the feasibility of the implementation of the Ca(OH)(2)/CaO thermochemical heat storage in a fluidized bed reactor. (C) 2014 Elsevier Ltd. All rights reserved.