Enhanced energy storage density in thermal energy storage systems simultaneously heated with solar radiation and industrial waste heat

• Adsorbents charged with solar and waste heat simultaneously. • Synergistic improvement by using two heat sources is experimentally demonstrated. • Novel adsorbent bed utilizes low-grade heat sources more efficiently. Adsorbent-based thermal energy storage (ATES) systems can provide high energy storage densities for long durations. However, abundantly available thermal energy sources, such as industrial waste heat and solar energy, often do not provide enough heat to effectively charge ATES systems. Herein experiments are performed to investigate the benefits of using simulated solar radiation and waste heat simultaneously to charge zeolite 13X for ATES applications. The energy storage density (ESD) for three cases is determined: 1) the adsorption bed is heated with simulated solar radiation alone, 2) the adsorption bed is heated using simulated waste heat alone, and 3) the adsorption bed is heated using simulated solar radiation and waste heat simultaneously. When simulated solar radiation is the sole source of thermal energy, the ESD is 5.6 kWh/m 3 . When the adsorbent bed is charged using waste heat the ESD is 7.6 kWh/m 3 . However, when both solar-simulated radiation and waste heat are used simultaneously to charge the adsorbent bed the ESD is 18.9 kWh/m 3 . The results show that using both solar and waste heat at the same time to charge the adsorbent bed is a promising strategy for improving the performance of ATES systems.