Grid energy storage is viewed as a key element in the transition to sustainable and reliable energy systems. So-called thermomechanical energy storage can be a site-independent, ecofriendly and low-cost large-scale energy storage solution. Thermal energy storage units are a core technology in such systems. Favorable thermal energy storage units display high operational temperatures and thermal power densities, while being available on a large-scale and at low cost. Novel horizontal packed bed thermal energy storage units, with air as heat transfer fluid and natural rocks as storage material, can potentially meet the discussed criteria in a comprehensive manner. This work aims at investigating and evaluating this novel technology. To this end, an efficient thermo-fluid dynamic simulation model was developed. The model is capable of depicting all fundamental mass and heat transfer mechanisms at the required level of detail, while maintaining short simulation times. In particular, the influence of the buoyancy effect on the fluid flow distribution had to be incorporated. The model was validated with experimental data and computational fluid dynamic (CFD) simulations in a rated thermal power range of 10 kWth to 200 MWth. The new model predicted temperatures and pressure drops with only marginally less accuracy than a CFD model, yet required only a fraction of the simulation time. The model was further utilized to design cost-optimized large-scale horizontal packed bed thermal energy storage units. These storage units were first integrated into thermomechanical energy storage systems and then benchmarked against competing storage technologies by an energy system design simulation. Thermomechanical energy storage systems were integral part of the cost-optimized solution.weiterlesen