SoTherCo’s major objective is to install, monitor and assess an innovative modular, compact and seasonal thermo-chemical solar heat-storage system, namely the SoTherCo HSS (Heat-Storage System). The modular design, based on the proper arrangement of ~1000L heat-storage modules, is intended to offer the needed flexibility and adaptation to answer the space-heating demand of low-energy buildings, from a single family dwelling up to communities and district heating.The Demonstration WP5&WP6 will be performed semi-virtually over long periods of time and at two different locations i.e. Arlon (ULg-Belgium) and Bourget-du-Lac (CEA-INES, France)) for regional climatic particularities. The testing periods will be shifted in time (6 months) for permitting to integrate the learning from the first demonstrator into the other one.To this end, RTD activities are also scheduled according to a progressive and controlled integration of the best-in-class knowledge and improvements in the field.WP1 will select and optimize at least 3 thermo-chemical working pairs referred to as SMG (Salt-in-Matrix composites + water-vapour (G)).WP2 will test the SMGs performance in laboratory-scale heat-storage units (the mini-Modules, m-M) operating in simulated real-life conditions. At least 3 m-M will be designed, modelled, constructed, tested and iteratively improved with respect to each of the selected SMGsWP3 will up-size (model, build and test) several real-scale (rs-M) to understand their complete behaviour in terms of power response and energy balance.WP4 will design, model and engineer the complete Heat-Storage Systems (HSS) comprising several properly connected rs-M as well as all the needed additional devices (energy inlets outlets, pumps, control, ..) ready to be integrated at the demonstration sites.The main expectation from this SME strongly supported Project (ESE & Regulus, 51% of the budget) is to provide a strong basis to elaborate a roadmap for future industrial steps