A conceptual design study for a unique long-term energy storage system for the lunar environment based on aqueous hydrogen peroxide (H2O2) and magnesium oxide (MgO) is presented. Key technologies to enable this thermochemical regenerative energy storage system (TRESS) are investigated and risk assessments at the subsystem and system levels described. Results of parametric analysis of key performance parameters considering variations in a variety of component and system figures of merit are discussed. Design embodiments for stationary and mobile configurations and associated weight and volume predictions are provided. Additionally, connections to lunar in-situ resource utilization (ISRU) and other exploration program objectives are outlined.