WP2 will generate the scientific base for the technology development of the PUSH-CCC concept of isobaric operation in a constant volume cavern and implementing other operational strategies adjusted to different load profiles, and circuits integration. The main research lines will be the following: 1. Large-scale membranes: i) Membrane materials; ii) Membrane fastening systems; iii) Membrane replacement systems; iv) Membrane scalability; v) Bellows and piston type systems. 2. Thermodynamic modelling: i) Air cycle optimization; ii) Auxiliary fluid selection; iii) Auxiliary fluid cycle optimization. 3. Compression alternatives: i) Single / dual stage compressors; ii) Magnetic bearing compressors; iii) Reverse compressors. 4. Heat Exchange & storage systems: i) Heat exchangers optimization; ii) Advanced air heat storage system suitable for high temperatures T (>=730℃); iii) Reverse compressors. 5. Control & grid integration systems: i) AI based hierarchical control system; ii) Plant management to follow up grid supply and demand evolution and forecast; iii) Ramps and partial loads operation; 6. CO2 DAC system: i) Direct atmospheric air CO2 capture during compression and storage process. 7. Hybridization: i) Solar power; ii) Wind power; iii) Biomass power; iv) Industrial heat excedents; v) Thermal conventional power plants. All these points will be examined considering both technical and economic aspects, and potential system scale-up.