Design of test rig and parametric investigation of the ratcheting effect in packed-bed thermal energy storage systems

Kurzfassung

Thermocline molten salt energy storage allows hot and cold salt to be stored in a single tank, and the use of filler material reduces molten salt inventory and cost. To investigate this concept, DLR’s test facility for thermal energy storage in molten salts (TESIS) has been equipped with basalt filler. While the thermal performance of such systems is well studied, its mechanical behavior poses challenges. Stresses between filler material and tank wall could lead to plastic deformation and trigger a catastrophic structural failure known as thermal ratcheting. These stresses must be known and accounted for in the tank design. Since existing experimental studies often do not reflect the particle-diameter-to-tank-expansion ratios, a cold test rig is developed to examine mechanical behavior of packed-beds under horizontal compressive stress. Repeatable experiments are performed to assess effects of test rig abrasion and wear during cyclic operation.