What The project aims to utilise readily available metal carbonates (minerals) as materials to store renewable energy. A simple rock like limestone (calcium carbonate), which is found in large quantities around the world and is used in multiple applications, e.g. Portland Cement, has incredible potential to store energy through its chemical breakdown to lime (calcium oxide) and carbon dioxide. This energy may be recovered when reuniting lime and carbon dioxide to form limestone. However, the process of breaking down and reuniting the compounds multiple times results in rapid degradation and the energy recovered becomes lower each time. This project embraces new ways to circumvent this degradation and improve the energy harvested from these chemical energy storage processes. Why Carbon dioxide emissions from fossil fuels and the resulting climate change are high priority topics in modern society. Thus, a general transition towards sustainable, renewable energy has been initiated. However, the intermittent nature of renewable energy sources such as wind and solar power require an energy storage solution to provide 24/7 energy availability. State-of-the-art energy storage technologies are currently too costly and have low energy densities, which prohibits their widespread utilisation in large-scale facilities. Thus, drastic improvement of current, or development of new, energy storage technologies based on abundant and cheap materials is crucial to enable the renewable energy transition. How Chemical manipulation of the metal carbonates will be performed by combining additives that assist the chemical reaction or even alter the reaction pathway of carbon dioxide release and uptake. Hence, the additives may ease the reaction conditions and prevent degradation of the process. Additives will carefully be selected based on thermodynamic calculations and their impact on the metal carbonate will be evaluated through multiple carbon dioxide release and uptake experiments. Positive effects will be further investigated through, e.g. electron microscopy and X-ray diffraction to establish reaction mechanisms and improve the metal carbonate energy storage potential. SSR A breakthrough in this materials research area could have a significant impact on our society in a global sense and promote the transition towards base-load renewable energy generation. This would lead to a paradigm shift in energy storage through the development of a low-cost thermochemical energy storage system, i.e. a ‘thermal battery’. The thermochemical energy storage approach is versatile as the heat input can be generated from a range of sources, e.g. industrial waste heat, wind mill farms, or directly from the sun. Thus, the range of applications is diverse, e.g. enabling stable power generation in remote areas outside of the electrical grid, or store excess renewable energy from, e.g. wind power for use when demand is high or when the wind is not blowing.