The MOST project aims to develop and demonstrate a zero-emission solar energy storage system based on benign, all-renewable materials. The MOST system is based on a molecular system that can capture solar energy at room temperature and store the energy for very long periods of time without remarkable energy losses. This corresponds to a closed cycle of energy capture, storage and release. The MOST project will develop the molecular systems as well as associated catalysts and devices to beyond state-of-the-art performance and scale. Further, the MOST systems will be combined with thermal energy storage (TES) in a hybrid concept to enable efficient and on-demand utilization of solar energy. The hybrid structure of the device, combining TES and MOST, enables the operation of the system in two different modes, targeting different applications. In mode A, the objective is to reach a stable thermal output. In this operation mode, the MOST system is used to mitigate the daily variation in solar flux which consequently leads to a variable output of the TES. In operation mode B, the system is targeting larger temperature gradients under shorter durations of time. Mode A is simulating applications where a stable temperature output is needed, such as e.g. heat to power generation. Mode B is simulating operation where the system operates as a part of a larger energy system where the task is to mitigate variations in energy demand and energy production. The materials production features scalable, green chemistry production routes. Further, the project will build an innovation ecosystem around the project and engage with future users of the technology in order to ensure future development and EU capacity for future market implementation.