Abstract This work presents the results of the performance characterization for novel salt-in-silica composites, destined for seasonal energy storage. The materials were synthesized using the Davisil® silica gel to support the hygroscopic inorganic salts of calcium chloride ( C a C l 2 ), magnesium chloride ( M g C l 2 ) or strontium bromide ( S r B r 2 ). The experiments were carried out on an open sorption laboratory setup under constant hydration conditions. The sample mass was 245 g, which is representative of a prototype control volume of 0.5 l, and the nominal air flow rate was 215 l min−1. Energy storage densities between 70 and 145 k W h m - 3 of control volume were experimentally found at 30 °C (inlet air temperature) and for different inlet air relative humidity levels. Average specific thermal powers in the range between 93 and 311 W k g - 1 were measured. Based on the experimental results, the design and upscaling of the seasonal energy storage were demonstrated. The best feasible energy storage densities ranging from 50 to 90 kWh m-3 of up-scaled reactor were predicted to deliver 1000 W of rated thermal power.