The broader/commercial impact of this SBIR Phase II project is to demonstrate the durability of key subsystems of a novel long duration energy storage technology, which has the potential to increase the capacity of the electric grid. Long-duration energy storage is a key unlock for energy security to provide firm capacity by balancing supply and demand across various timescales. The Total Addressable market (TAM) for grid-scale energy storage is immense and rapidly expanding. Wood Mackenzie forecasts that the global energy storage market will grow 27-fold between 2022 and 2032, reaching a total of 1,420 gigawatt-hour (GWh) of cumulative capacity. This growth represents a $380 billion investment opportunity over the next decade. In the United States alone, the National Renewable Energy Laboratory's Storage Futures Study suggests that economic potential for energy storage could exceed 160 gigawatt (GW) by 2050 in a high renewable energy scenario. The technology's ability to provide long-duration storage (10+ hours) at an estimated capital expenditure (CapEx) of $25/kilowatt-hour(electric) (kWh-e) (class 4 estimate), positions it to play a pivotal role in enabling high renewable penetration and grid decarbonization. The intellectual merit of this project aims to demonstrate the reliability and durability of high-temperature graphite plumbing systems for liquid tin heat transfer. The proposed work will involve extensive accelerated life testing of critical components, includ