As Europe moves towards low and zero-carbon housing, challenges arise in the management of building integrated renewable energy technologies. Electricity generating RES have the benefit of electrical connection and financial mechanisms allowing feed-in to the network. Thermal technologies do not have such general interconnectivity and therefore rely on sizing typically meeting 90% of summer demands in moderate climates. This approach provides little benefit in winter. Therefore an obvious approach is that of thermal energy storage that overcomes issues of heat loss, substantially increasing the overall use of RES in buildings throughout the seasons. The objective of MERITS is to develop, demonstrate and evaluate a compact seasonal storage system based on novel high-density materials that can supply required heating, cooling and DHW with up to 100% RES. Delivery of heat on different dedicated temperature levels is one of the key prerequisites of the system. Tailoring to the size of individual dwellings is a second one. The storage system must have a manageable volume comparable with the footprint of a domestic dwelling. Such a tank typically becomes between 4m3 and 8m3 and has a possibility of being incorporated under for example a garden space. We will formulate starting conditions for the dimension of storage materials and capacity, and the storage system and control system. Then we will design and develop a dedicated solar collector for the storage system for specific climate zones. We will also make an integrated design for the different components and enhance thermo chemical materials. Prototypes of the system (for three different climate zones) will be demonstrated and evaluated in a field test. To improve the market up-take we will work on business models, market strategies and other non-technical issues. Partners in the proposal are research institutes and universities as well as SME’s and industry, capable of bringing the project results to the market.