Energy storage systems are essential for the deployment of renewable energy at large scale and the use of CO2 as working fluid has experienced a significant boost in recent years due to its unique thermo-physical properties. This thesis presents a conceptual large scale thermoelectrical energy storage system based on a reversible heat pump that works with CO2 in transcritical conditions. An exergo-economic analysis of the base close system is performed to determine the thermodynamic and economic feasibility of this kind of technology. Then, different possible integration scenarios for the base case are proposed and analysed; an open cycle that stores CO2 and performs a geological injection of it; low and high temperature storage integrations to maximize the performance of the base case..