Sensible heat thermal energy storage (SHTES) is an important technology for waste heatrecovery and renewable energy utilization. They store the energy in form of heat and improvethe efficiency and economics of concentrated solar power (CSP) plants. In this work, thesecondary SHTES system of in-house solar air tower simulator (SATS), designed for metalsprocessing, is investigated. The system uses hot air as heat transfer fluid and magnesiumsilicate pebbles as the storage material. The function of the secondary SHTES is to storethe waste energy from the hot air after it exits the solar convective furnace (SCF). At firstthe charging and discharging of the SHTES system is studied experimentally. The resultsare compared with an unsteady two-dimensional numerical model simulating the charging aswell as discharging of the secondary energy storage. The model is developed for randomlydistributed pebbles and includes radiation heat transfer between pebble and space in between,with air as media. Further, alternative TES designs using different energy storage materialsare investigated. The main targets to achieve are : high energy density and faster charging.For using dense materials, shell-and-tube thermal storage system is considered. The system isnumerically modeled using a simplified 1-D transient model developed in MATLAB which cansimulate the charging and discharging process at low computational load. Numerical resultsare compared with available data for sand saturated with Xceltherm 600 heat transfer oil.Graphite powder and sand are also explored as low cost and locally available energy storagematerials.