This paper investigates an innovative open thermochemical system dedicated to high density and long term (seasonal) storage purposes. It involves a hydrate/water reactive pair and operates with moist air. This work focuses on the design of and experimentation with a large scale prototype using SrBr2/H2O as a reactive pair (400 kg of hydrated salt, 105 kW h of storage capacity and a reactor energy density of 203 kW h/m(3)). Promising conclusions have been obtained regarding the feasibility and performance of such a storage process. Hydration specific powers from 0.75 to 2 W/kg have been reached for a bed salt energy density of 388 kW h/m(3). Moreover, two important parameters that control the storage system have been identified and investigated: the equilibrium drop and the mass flow rate of moist air. Both have a strong influence on the reaction kinetics and therefore on the reactor's thermal power. (C) 2014 Elsevier Ltd. All rights reserved.